Browse Topic: Exhaust gas recirculation (EGR)

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Medium/Heavy-Duty E/E Systems Diagnosis NomenclatureJ2403_202008 (Historical)8/3/2020
This SAE Recommended Practice is applicable to all E/E systems on MD and HD vehicles. The terms defined are largely focused on compression-ignited and spark-ignited engines. Specific applications of this document include diagnostic, service and repair manuals, bulletins and updates, training manuals, repair data bases, under-hood emission labels, and emission certification applications. This document focuses on diagnostic terms, definitions, abbreviations, and acronyms applicable to E/E systems. It also covers mechanical systems which require definition. Nothing in this document should be construed as prohibiting the introduction of a term, abbreviation, or acronym not covered by this document. The use and appropriate updating of this document is strongly encouraged. Certain terms have already been in common use and are readily understood by manufacturers and technicians, but do not follow the methodology of this document. These terms fall into three categories: a Acronyms that do not logically fit the term. b Acronyms existing at the component level (i.e., their terms contain the base word or noun that describes the generic item that is being further defined). c Acronyms for terms that appear to contain the base word, but are frequently used as a modifier to another base word. (This use may possibly be thought of as following the methodology, since the acronym is normally used as a modifier.)
Truck Bus Control and Communications Network Committee
A Calculation Methodology for Predicting Exhaust Mass Flows and Exhaust Temperature Profiles for Heavy-Duty Vehicles02-13-02-00097/20/2020
The predictive control of commercial vehicle energy management systems, such as vehicle thermal management or waste heat recovery (WHR) systems, are discussed on the basis of information sources from the field of environment recognition and in combination with the determination of the vehicle system condition. In this article, a mathematical method for predicting the exhaust gas mass flow and the exhaust gas temperature is presented based on driving data of a heavy-duty vehicle. The prediction refers to the conditions of the exhaust gas at the inlet of the exhaust gas recirculation (EGR) cooler and at the outlet of the exhaust gas aftertreatment system (EAT). The heavy-duty vehicle was operated on the motorway to investigate the characteristic operational profile. In addition to the use of road gradient profile data, an evaluation of the continuously recorded distance signal, which represents the distance between the test vehicle and the road user ahead, is included in the prediction model. Using a Fourier analysis, the trajectory of the vehicle speed is determined for a defined prediction horizon. To verify the method, a holistic simulation model consisting of several hierarchically structured submodels has been developed. A map-based submodel of a combustion engine is used to determine the EGR and EAT exhaust gas mass flows and exhaust gas temperature profiles. All simulation results are validated on the basis of the recorded vehicle and environmental data. Deviations from the predicted values are analyzed and discussed.
Kreyer, Jörg, Müller, Marvin, Esch, Thomas
Investigations of the Emissions of Fuels with different Compositions and Renewable Fuel Components in a GDI Engine2020-01-02854/14/2020
Investigations were performed, in which fuels and fuel components were compared regarding gaseous as well as particulate number (PN) emissions. The focus on the selection of the fuel components was set on the possibility of renewable production, which lead to Ethanol, as the classic bio-fuel, Isopropanol, Isobutanol and methyl tert-butyl ether (MTBE). As fuels, a Euro 6 (EU6) reference fuel, an anti-spark-fouling (ASF) fuel, a European Super Plus (RON 98) in-field fuel and a potentially completely renewable fuel, which was designed by Porsche AG (named POSYN), were chosen. The composition of the fuels differs significantly which results in large differences in the exhaust gas emissions. The fuels, except ASF, are compliant with the European fuel standard EN 228.The experiments chosen were a variation of the start of injection (SOI) at different load points at a constant engine speed of 2000 rpm, amongst others. The influence of the fuel properties like boiling characteristics, fuel composition (e. g. the content of aromatic compounds), viscosity and enthalpy of vaporization were considered for interpreting the gaseous and PN emissions and efficiencies of the fuels. The results show decreased NO emissions, when the oxygen content increases. Based on these observations, a 0D/1D model was calibrated with the engine data of the EU6 fuel. The model was used to calculate the NO emissions using the Zeldovich mechanism. For each fuel, the only difference in the model was the definition of the fuel, which includes the (theoretical) molecular formula, heat of vaporization, heating value, density and the enthalpy. In addition to that, the burn rate was determined by a three-pressure-analysis (TPA) and was put into the full engine model. The results show, that the influence of the fuel on the NO emissions can be described well by calculations performed.
Albrecht, Michael, Deeg, Hans-Peter, Schwarzenthal, Dietmar, Eilts, Peter
Development of Three-Way Catalyst with Advanced Coating Layer2020-01-06534/14/2020
Further improvements in catalyst performance are required to help protect the atmospheric environment. However, from the viewpoint of resource availability, it is also necessary to decrease the amount of precious metals used at the active sites of the catalyst. Therefore, a high-performance three-way catalyst with an advanced coating layer has been developed to lower the amount of precious metal usage. Fuel efficiency improvement technologies such as high compression ratios and a large-volume exhaust gas recirculation (EGR) generally tend to increase the ratio of hydrocarbons (HC) to nitrogen oxides (NOx) in exhaust gas. This research focused on the palladium (Pd) loading depth in the coating layer with the aim of improving the hydrocarbon (HC) conversion activity of the catalyst. Contact between Pd, which has a high degree of HC conversion activity, and the exhaust gas can be facilitated by controlling the loading depth on the surface of the coating layer, enabling efficient conversion even under high space velocity (SV) conditions. Subsequently, this research focused on the coating structure to maximize the conversion activity and oxygen storage capacity (OSC) performance and improve gas diffusivity in the coating layer. The particle size of each coating material was controlled to maximize the heat resistance and OSC performance. The coating thickness was controlled by applying finer alumina and fabricating connected pores. This coating structure ensures excellent gas diffusivity without affecting the pressure drop. As a result, the developed catalyst achieves high conversion activity with nearly 20% less precious metal usage. This catalyst will start to be introduced in vehicles from 2020.
Saito, Yoshinori, Chinzei, Isao, Morikawa, Akira, Ito, Minoru, Oishi, Shunsuke, Okuda, Takuya
Rework of an in-line two-cylinder engine for the application in Formula Student2019-32-05321/24/2020
Formula Student is an international design competition, where students all over the world develop, design and build their own race car and afterwards compete with each other at different disciplines at events worldwide. The development process includes every module of the race car and the team of joanneum racing graz has focused on the powertrain since the beginning. The following paper contains an overview of the reworking process of an in-line two-cylinder engine for the application in Formula Student. The intention was to increase the BMEP and at the same time reach a desired power/weight ratio of the engine. The process of selecting the most appropriate turbocharger by means of experimental testing on an engine dynamometer, as well as its optimization by means of numerical simulation, is outlined. Subsequently, the paper discusses the challenges regarding valve timing and finding the best trade-off between power and residual gas with the help of 1D-simulations. The necessary implementation of an intercooler and its efficiency optimization is also addressed. Finally, the calibration and optimization of the setup on the engine test bed is presented. After the selection of the most suitable turbocharger for the engine and the reworking of its compressor side, it was possible to achieve a maximum boost pressure of 2.76 bar absolute. Charge air cooling and closed loop boost control guaranteed fast boost pressure build up. Together with the optimized cam timing, which reduced residual gas, and an increased compression ratio, the overall torque output of the engine resulted in 135 Nm at 4000 rpm and a maximum power of 63 kW at 6000 to 6500 rpm. The overall target of increasing the BMEP of the selected engine and at the same time achieving a lower power/weight ratio than the previous engine (FS133) was accomplished with a final value of 0.81 kW/kg.
Feigl B.Sc, Michael, Rößmann B.Sc, Dominik, Michael Trzesniowski, FH-Prof. DI
Application of Porous Material as Heat Storage Medium to a Turbocharged Gasoline Engine2019-32-05411/24/2020
Porous materials, which have large surface areas, have been used for heat storage. However, porous Si-SiC material, as heat storage medium to be applied to a turbocharged gasoline engine has not been investigated extensively. In this study, porous Si-SiC material was used in the upstream of the turbine as heat storage medium and a model was thereby developed for further study. Substrate surface area and substrate volume of Si-SiC were calculated for structure model calibration. Following these calculations and test results, the pressure loss and thermal model were validated. Results show that the weaken exhaust gas pulsation amplitude by porous Si-SiC leads to better turbine performance and BSFC in steady engine condition for a turbocharged gasoline engine. In addition, its transient operation response needs to be improved under transient engine conditions. Hence the possibility of improving the transient response is investigated with characteristics of porous Si-SiC material. It was observed that less time was required for the engine to reach the target torque in transient conditions.
Dong, Dongsheng, Moriyoshi, Yasuo, Kuboyama, Tatsuya, Shen, Fuchao, Hasegawa, Naohiro
Calcium in Oil Effects on Pre-ignition of Two-stroke Engine2019-32-05791/24/2020
Investigations of the influence of calcium on pre-ignition in a two-stroke engine have shown that the lower the calcium concentration, the lower the frequency of pre-ignition. Pre-ignition problems can occur in small, air-cooled, two-stroke engines such as a chainsaw. In contrast, in a supercharged automobile engine, it has been reported that calcium, which is a detergent component in engine oil, causes low-speed pre-ignition. The oil for two-stroke engines also contains calcium and is mixed with the fuel and lubricated before being supplied to the combustion chamber. This makes, two-stroke engines more likely to be affected by oil components. Based on this, we investigated the influence of calcium on pre-ignition of a two-stroke engine. First, we investigated driving conditions in which pre-ignition is likely to occur, such as warming up the engine. Under this condition, oil with calcium concentrations ranging from 0 ppm to 1,500 ppm were tested at a mixing ratio of 2%. The results show that the lower the calcium concentration, the lower the incidence rate of pre-ignition. Which could also occur at 0 ppm. The incidence rate was 4.6% at 1,500 ppm and 2.3% at 0 ppm.
Eto, Kuniyoshi, Kihara, Masaki
Mahle reveals modular, scalable integrated hybrid powertrain19AUTP11_1011/1/2019
Mahle is developing a complete “fits all, off-the-shelf” modular hybrid-drive propulsion system for a wide range of automakers' models, designed to cut costs, improve packaging and provide a level of electrified-vehicle commonality not seen before in the auto industry. Designated Mahle Modular Hybrid Powertrain (MMHP), the system is modular, scalable and dual-mode (parallel and series). It could be in production within two years, ready to power anything from compact sedans to hefty SUVs. The MMHP integrates an all-new turbocharged gasoline internal-combustion engine in twin- and 3-cylinder forms, customizable gearbox (1-, 2- or 4-speed) and a compact but powerful (choice of power/torque) electric traction motor.
Birch, Stuart
Experimental and Numerical Prediction of the Pressure Drop Reduction of Catalytic Converter under Various Mass Flow Rate of Exhaust Gas for a Naturally Aspirated Diesel Engine2019-28-003010/11/2019
Nowadays, Diesel emission control strategies are stringent across the globe which caused the rise in need of diesel after treat treatment devices that are more reliable and efficient. The optimized design of the catalytic converter aids in the durability of the product as well as the improvement in efficient operation of the Indian driving cycle. By changing the convergent and divergent cone angles of the catalytic converter, the consequential decrease in pressure drop leads to efficient flow of exhaust gases. The purpose of this study is to design, test, and analyse the catalytic converter in order to reduce the pressure drop in the exhaust system of a naturally aspirated diesel engine using both experimental and CFD techniques. In this study, a Diesel Oxidation Catalyst Catalytic Converter is investigated. For numerical analysis, ANSYS Fluent is used. Validation is done on baseline Catalytic converter pressure drop results obtained both numerically and experimentally for various speeds conditions and it is found that a reasonably good agreement exists. From the analytical calculations, Catalytic converter diameter, length and Cone angle are selected so as to have maximum pressure drop reduction. The modified inlet and outlet cone angles in catalytic converter chosen are 20°, 22°, 26°, and 28° and the porosity value is 0.826 with square shaped pores in monolith. The Cone angle of 26° gives more reduction in pressure drop of 1.7499KPa, which is less than the baseline pressure drop value of 1.85699 KPa. This leads to 7% overall pressure drop as compared to the different cone angle results. It could be concluded that the inlet and outlet cone angles must be in 26° to yield best flow with reduced pressure drop across the catalytic converter for the selected engine configuration and operating conditions when the porosity is 0.826 with the shape of square monolith.
Vinodh Kumar, Kanchi Gopi, Senthilkumar, Sundararaj, Rajasingh, Edison
Exploring the Potential of Miller Cycle with and without EGR for Maximum Efficiency and Minimum Exhaust Emissions in a Heavy-Duty Diesel Engine03-12-05-00379/3/2019
Abstract In order to improve the fuel conversion efficiency and meet more stringent exhaust emissions regulations, Miller cycle and exhaust gas recirculation (EGR) have been researched as separate means to reduce carbon dioxide (CO2) and pollutant emissions from the internal combustion engines. In this article, an experimental work was carried out to explore the potential benefits of Miller cycle operation via late intake valve closing (LIVC) with and without EGR in a single-cylinder heavy-duty (HD) diesel engine equipped with a variable valve actuation (VVA) system. The overall engine-out emissions, fuel conversion efficiency, and estimated urea consumption in the selective catalytic reduction (SCR) aftertreatment were analysed and compared over the World Harmonized Stationary Cycle (WHSC) for different combustion control strategies. Additionally, the potential of Miller cycle with and without EGR based on the “SCR-only” and “SCR + EGR” technical routes to meet the Euro VI nitrogen oxides (NOx) limit of 0.4 g/kWh was assessed at different NOx aftertreatment efficiencies. When considering the urea consumption in the SCR, the results showed that the introduction of EGR allowed for an engine operation with higher corrected net indicated efficiency (NIEcorr.) or lower specific total fluid consumption than the baseline cases without EGR due to the relatively lower engine-out NOx emissions. However, the use of EGR adversely affected soot and carbon monoxide (CO) emissions when operating with constant intake pressure (Pint) of the baseline case. The application of Miller cycle with and without EGR strategies decreased the NIE and NIEcorr. when operating with the same Pint of the baseline operation. The use of higher Pint helped to improve upon the NIE and NIEcorr. of the Miller cycle cases. The WHSC cycle-averaged analysis showed that different combustion and engine control technologies can be adopted with and without EGR to meet Euro VI NOx limit. A conventional baseline engine operation without EGR would require a high SCR efficiency of 96% in order to curb a cycle-averaged NOx emissions level of 10 g/kWh. Miller cycle operation without EGR achieved the optimum NIEcorr. at the cycle-averaged NOx level of 8 g/kWh. When increasing the Pint, this strategy enabled an increase of 2.6% in the NIEcorr. and reduced the required SCR efficiency to 93.5%, but with a penalty on the NIE of 3.3% when controlling the cycle-averaged NOx level at 6.5 g/kWh. Alternatively, Miller cycle operation with EGR and higher Pint allowed for cycle-averaged NOx levels of 4.0 g/kWh, decreased the total fluid consumption by 8%, and minimised the required SCR efficiency to 90%. Therefore, this study has presented promising cost-effective emission control and fuel efficiency technologies that could be suitable for the “SCR-only” and “SCR + EGR” technical routes for the future HD diesel engines.
Guan, Wei, Pedrozo, Vinícius B., Wang, Xinyan, Zhao, Hua, Ban, Zhibo, Lin, Tiejian
Fuel Reforming and Catalyst Deactivation Investigated in Real Exhaust Environment2019-01-03154/2/2019
Increased in-cylinder hydrogen levels have been shown to improve burn durations, combustion stability, HC emissions and knock resistance which can directly translate into enhanced engine efficiency. External fuel reformation can also be used to increase the hydrogen yield. During the High-Efficiency, Dilute Gasoline Engine (HEDGE) consortium at Southwest Research Institute (SwRI), the potential of increased hydrogen production in a dedicated-exhaust gas recirculation (D-EGR) engine was evaluated exploiting the water gas shift (WGS) and steam reformation (SR) reactions. It was found that neither approach could produce sustained hydrogen enrichment in a real exhaust environment, even while utilizing a lean-rich switching regeneration strategy. Platinum group metal (PGM) and Ni WGS catalysts were tested with a focus on hydrogen production and catalyst durability. Although 4% additional hydrogen was initially produced in the EGR stream, leading to improvements in the coefficient of variation (CoV) and brake specific fuel consumption (BSFC), catalyst activity decreased within a few hours regardless of the regeneration strategy employed. With an SR catalyst, a small amount of hydrogen was produced in the EGR stream via the WGS reaction but not the SR reaction. Similar to the WGS catalyst testing, the SR catalyst deactivated quickly due to coking. While neither of these approaches displayed acceptable long-term performance, the exhaust environment still poses a significant opportunity for the production of hydrogen rich reformate to deliver improvement in engine efficiency.
Bartley, Gordon, Gukelberger, Raphael, Henderson, Robert, Henry, Cary
An Assessment of a Sensor Network Using Bayesian Analysis Demonstrated on an Inlet Manifold2019-01-01214/2/2019
Modern control strategies for internal combustion engines use increasingly complex networks of sensors and actuators to measure different physical parameters. Often indirect measurements and estimation of variables, based off sensor data, are used in the closed loop control of the engine and its subsystems. Thus, sensor fusion techniques and virtual instrumentation have become more significant to the control strategy. With the large volumes of data produced by the increasing number of sensors, the analysis of sensor networks has become more important. Understanding the value of the information they contain and how well it is extracted through uncertainty quantification will also become essential to the development of control architecture. This paper proposes a methodology to quantify how valuable a sensor is relative to the architecture. By modelling the sensor network as a Bayesian network, Bayesian analysis and control metrics were used to assess the value of the sensor. This was demonstrated on charge mass flow estimation in the inlet manifold. Four control architectures modelled using a Bayesian network were compared: balanced sensors, redundant sensors, synergistic sensors and unbalanced sensors. The assessment metrics included uncertainty propagation, area of one sigma ellipses and the relative gain in information entropy of the estimated variable. The unique uncertainty characteristics of each case were identified using these assessment metrics, allowing for direct comparison between the architectures. Multivariate analysis by Gaussian modelling of the covariance matrix of the model was also performed. These results were used to quantifiably assess how each sensor and variable affects the charge mass flow estimation.
Comissiong, Rhys, Steffen, Thomas, Shead, Leo
Modeling of Close-Coupled SCR Concepts to Meet Future Cold Start Requirements for Heavy-Duty Engines2019-01-09844/2/2019
The low-NOx standard for heavy-duty trucks proposed by the California Air Resources Board will require rapid warm-up of the aftertreatment system (ATS). Several different aftertreatment architectures and technologies, all based on selective catalytic reduction (SCR), are being considered to meet this need. One of these architectures, the close-coupled SCR (ccSCR), was evaluated in this study using two different physics-based, 1D models; the simulations focused on the first 300 seconds of the cold-start Federal Test Procedure (FTP). The first model, describing a real, EuroVI-compliant engine equipped with series turbochargers, was used to evaluate a ccSCR located either i) immediately downstream of the low-pressure turbine, ii) in between the two turbines, or iii) in a by-pass around the high pressure turbine. These simulations indicate that the location downstream of the low-pressure turbine offers nearly the best NOx conversion, and that the optimal volume of the ccSCR in this location is 25% of a conventional SCR catalyst. The second model describes a conventional heavy-duty aftertreatment system, to which a ccSCR was added. This model was used to examine the performance of the ccSCR in the context of the full ATS. Optimization of the diesel oxidation catalyst (DOC) and SCR catalyst designs in this system was considered, as well as the use of an NH3 storage-based control strategy for DEF dosing to the SCR catalysts.
Harris, Thomas Miller, Mc Pherson, Kristoffer, Rezaei, Reza, Kovacs, David, Rauch, Hendrik, Huang, Yinyan
Optimization of a Diesel Engine with Variable Exhaust Valve Phasing for Fast SCR System Warm-Up2019-01-05844/2/2019
Early exhaust valve opening (eEVO) increases the exhaust gas temperature by faster termination of the power stroke and is considered as a potential warm up strategy for diesel engines aftertreatment thermal management. In this study, first, it is shown that when eEVO is applied, the engine main variables such as the boost pressure, exhaust gas recirculation (EGR) and injection (timing and quantity) must be re-calibrated to develop the required torque, avoid exceeding the exhaust temperature limits and keep the air fuel ratio sufficiently high. Then, a two-step procedure is presented to optimize the engine operation after the eEVO system is introduced, using a validated diesel engine model. In the first step, the engine variables are optimized at a constant eEVO shift. In the second step, optimal eEVO trajectories are calculated using Dynamic Programming (DP) for a transient test cycle. The optimized results indicate that with early EVO, the boost pressure should be increased to provide enough cylinder air charge and to maintain the engine torque. External EGR can be reduced due to increased internal EGR while maintaining the same engine out NOx. An optimal zone to maximize temperature benefit with least impact to BSFC has been observed. The study also shows some of the penalties related to eEVO including increased flow pulsation at the air flow sensor location. Finally, with optimal eEVO, a 6.5% - 11% reduction is observed in the light-off time of the selective catalytic reduction (SCR) catalyst and 45% reduction in tailpipe NOx compared to the baseline operation without eEVO.
Srinivas, Pavan Kumar, Salehi, Rasoul
Generation and Oxidation of Soot due to Fuel Films Utilizing High Speed Visualization Techniques2019-01-02514/2/2019
For a better understanding of how soot is generated due to fuel films, a constant volume vessel was used together with four visualization techniques due to their high spatial (2D) and time resolution: Schlieren, natural luminosity, diffused back illumination and OH* chemiluminescence. The analysis was performed keeping the injection pressure at 30 bar and changing the plate temperature on which the spray impacts: 80, 120, 160 and 200 °C. The fuel is a mixture of iso-octane, hexane, toluene and 1-methylnaphthalene, which presents similar properties to commercial gasoline. Valuable insights were gained from the results that infer the real nature of the radiation observed during combustion events in gasoline direct injection (GDI) engines due to the presence of a fuel films which are conventionally described as “pool fires”. The results show that the highest quantity of soot is generated between plate temperatures of 80 and 120 °C. The composition of the fuel film and the flow field generated after the passage of the flame front are of paramount importance in the description of the soot generated around the impingement region. The 2D maps of KL-factor (obtained from DBI) confirm the same trend of the natural luminosity observations. The image analysis of KL-factor and OH* reveals that the radiation emitted is due to diffusion flames reacting inside a post combustion environment which consumes the fuel film that has survived to the flame. Four key moments on the soot generation are discussed and some limitations in the application of the OH* chemiluminescence are presented.
Roque, Anthony, Foucher, Fabrice, Imoehl, William, Helie, Jerome
A Simulation Research on Emission Control Technology of Low-Speed Two-Stroke Diesel Engine Based on EGR and Miller Cycle2019-01-09454/2/2019
This paper investigates the influences of EGR and Miller cycle on NOx emission of a heavy-duty two-stroke diesel engine. The NOx emission is strictly restricted by the IMO Tier III Emission Regulations, resulting in an insufficient application of the single emission reduction technology to meet the emission requirements. It is asserted that EGR is the most effective manner to reduce NOx emission, but the fuel consumption increases simultaneously. In consideration of emission reduction with fuel economy, EGR and Miller cycle were combined and studied in this paper. Parameters like in-cylinder pressure, in-cylinder temperature, mass in the chamber, emission (NOx and soot) and fuel consumption rate were investigated based on a single-cylinder 3D model. The wet condition that happens in the engine application was considered in the model development process. The model was validated and compared with the experimental data. The simulation results show the "trade-off" relationship between NOx and soot under EGR, as well as the performance of reducing NOx in different load. This paper, subsequently, used Miller cycle (achieve by delay the closing timing of the exhaust valve with intake boosting) to optimize the fuel consumption rate base on the EGR results. Finally, the combustion conditions under different EGR ratio and different Miller cycle condition were reflected by in-cylinder pressure, the contours of in-cylinder temperatures and the generating area of NOx. According to the simulation results of EGR and Miller cycle, the optimum scheme was giving out to satisfy the IMO Tier Three with better fuel economy performance.
Zhu, Zhijie, Liang, Xingyu, Wang, Yuesen, Liu, Bo
Effect of EGR and Premixed Mass Percentage on Cycle to Cycle Variation of Methanol/Diesel Dual Fuel RCCI Combustion2019-26-00901/9/2019
Reactivity controlled compression ignition has been a proven combustion strategy for better reduction of NOx and PM emissions without compromising the fuel economy. However, the combustion strategy still need more investigation to overcome its operational stability. In this study, the influence of hot/cooled exhaust gas recirculation and premixed mass percentage and there cyclic variation of Methanol/Diesel dual fuel reactivity controlled compression ignition (RCCI) combustion was investigated in a modified 3 cylinder light duty, turbocharged, CRDI diesel engine. Methanol/Diesel RCCI combustion was achieved by premixing methanol with intake air in the intake port and injecting diesel directly into the cylinder by flexible common rail direct injection system. The intake manifold was altered to adopt port fuel injection of methanol and EGR. Experiments were conducted at 3.4 bar and 5.1 bar BMEP at 1500 rpm by varying EGR and premixed mass percentage. Overall, the results shows that 26% cooled EGR resulted in less cycle to cycle variation, better reduction in NO, and smoke emissions with improved thermal efficiency at both loads with methanol mass percentage 76% and 81% respectively. At hot EGR operation the higher cyclic variation, higher pressure rise rate and higher NOx and smoke emissions observed than cooled EGR operation. It is also observed that 5.1 bar BMEP operation exhibited a lesser cycle to cycle variation and emissions compared to 3.4 bar BMEP operation.
Duraisamy, Ganesh, Rangasamy, Murugan, Nagarajan, Govindan
Medium/Heavy-Duty E/E Systems Diagnosis NomenclatureJ2403_201812 (Historical)12/19/2018
This SAE Recommended Practice is applicable to all E/E systems on MD and HD vehicles. The terms defined are largely focused on compression-ignited and spark-ignited engines. Specific applications of this document include diagnostic, service and repair manuals, bulletins and updates, training manuals, repair data bases, under-hood emission labels, and emission certification applications. This document focuses on diagnostic terms, definitions, abbreviations, and acronyms applicable to E/E systems. It also covers mechanical systems which require definition. Nothing in this document should be construed as prohibiting the introduction of a term, abbreviation, or acronym not covered by this document. The use and appropriate updating of this document is strongly encouraged. Certain terms have already been in common use and are readily understood by manufacturers and technicians, but do not follow the methodology of this document. These terms fall into three categories: a Acronyms that do not logically fit the term. b Acronyms existing at the component level (i.e., their terms contain the base word or noun that describes the generic item that is being further defined). c Acronyms for terms that appear to contain the base word, but are frequently used as a modifier to another base word. (This use may possibly be thought of as following the methodology, since the acronym is normally used as a modifier.)
Truck Bus Control and Communications Network Committee
Design Considerations for Enclosed Turboprop Engine Test CellsAIR5295A (Current)11/21/2018
This document is offered to provide state-of-the-art information about design factors that must be considered in the design of new or significantly modified engine test cells used to test propeller equipped turboprop engines in either QEC or bare engine configurations. The report does not address design considerations for test cells designed to test turboprop engines with dynamometer type load absorption devices because they are essentially tested as turboshaft engines. Design considerations for those test cells are presented in AIR4989, Reference 2.1.
EG-1E Gas Turbine Test Facilities and Equipment
Study of Discharge under Swirl Flow and Combustion Conditions2018-32-000610/30/2018
Combustion at a high EGR (Exhaust Gas Recirculation) ratio is an effective means for improving the fuel efficiency of a gasoline engine. However, there is a problem that the combustion speed decreases. So, it is necessary to intensify the in-cylinder flow to ensure the combustion speed. The spark discharge generated by the ignition coil is strongly influenced by the in-cylinder flow. It forms an arcuate discharge path along the flow, and may blow off and re-discharge under a strong gas flow. The behavior of spark discharge strongly affects the ignition, and consequently affects the stability of combustion. However, the phenomena in a combustion chamber are very complicated because of various environmental conditions, and the discharge and combustion phenomena under a strong gas flow remain unclear. In this research, in order to study these phenomena, discharge and combustion experiments under flow using a constant volume container were performed. We observed discharge channel and length from the images obtained by high-speed camera, and calculated the discharge resistance from the voltage and current waveforms of the plug, and discussed the results. Also we performed the experiments by changing the flow velocity, Air/Fuel ratio, etc., and evaluated the follow-up property of the discharge to the flow and the change of the current value due to combustion. From these experimental results, the influence of each factor on discharge characteristics was clarified. We will report on the results of the experiments and discussions obtained in these studies and introduce the future prospects.
Inoue, Takahiro, Tamida, Taichiro
A Study of the Factors Determining Knocking Intensity Based on High-Speed Observation of End-Gas Autoignition Using an Optically Accessible Engine2018-32-000310/30/2018
The purpose of this study was to investigate how autoignition leads to the occurrence of pressure oscillations. That was done on the basis of in-cylinder visualization and analysis of flame images captured with a high-speed camera using an optically accessible engine, in-cylinder pressure measurement and measurement of light emission from formaldehyde (HCHO). The results revealed that knocking intensity tended to be stronger with a faster localized growth speed of autoignition. An investigation was also made of the effect of exhaust gas recirculation (EGR) as a means of reducing knocking intensity. The results showed that the application of EGR advanced the ignition timing, thereby reducing knocking intensity under the conditions where knocking occurred.
Ishikawa, Takahiro, Takahata, Shuhei, Kudo, Hiroki, Izako, Takuya, Yamashita, Takahiro, Koga, Hibiki, Kiura, Toshiro, Iijima, Akira
Artificial Neural Network Based Predictive Real Drive Emission and Fuel Economy Simulation of Motorcycles2018-32-003010/30/2018
As the number of different engine and vehicle concepts for powered-two wheelers is very high and will even rise with hybridization, the simulation of emissions and fuel consumption is indispensable for further development towards more environmentally friendly mobility. In this work, an adaptive artificial neural network based predictive model for emission and fuel consumption simulation of motorcycles operated in real world conditions is presented. The model is developed in Matlab and Simulink and is integrated into a longitudinal vehicle dynamic simulation whereby it is possible to simulate various and not yet measured test cycles. Subsequently, it is possible to predict real drive emissions RDE and on-road fuel consumption by a minimum of previous measurement effort. The modelling approach is adaptive in terms of usability for different engine and exhaust gas treatment systems as the model does not require specific knowledge of technical vehicle parameters, which might be unknown due to manufacturers’ concealment. Backpropagation is used as supervised learning technique for training the neural networks and various learning inputs are investigated and evaluated. The paper expands on previous research of possible measurement methodologies for real drive emissions for motorcycles to minimize the effort in estimating real world effects and to serve as a tool for further improvement towards upcoming more stringent emission limits. Therefore, the applicability of the software will be shown with three examples. Moreover, tools are presented to assign emission relevant scenarios to specific driving patterns and to assess them according to the vehicles driving dynamic.
Hiesmayr, Johannes, Schmidt, Stephan, Hausberger, Stefan, Kirchberger, Roland
Study on Knocking Characteristics for High-Efficiency Operation of a Super-Lean Spark Ignition Engine2018-32-000210/30/2018
This study investigated the influence of EGR and spark advance on knocking under high compression ratio, ultra-lean mixture and supercharged condition using premium gasoline as a test fuel. A high-compression ratio, supercharged single cylinder engine was used in this experiment. As a result, the period from ignition to autoignition was prolonged. In addition, knock intensity was drastically reduced. In other words, it is inferred that by combining an appropriate amount of EGR and spark advance, high efficiency operation avoiding knocking can be realized.
Nishiyama, Takeshi, Agui, Keito, Togawa, Masaaki, Saito, Masanori, Tanabe, Mitsuaki, Iijima, Akira
Diesel CAI Combustion in Uniflow Scavenging 2-Stroke Engine Provided with Port Fuel Injection Device2018-32-001510/30/2018
We studied a simple and cost effective controlled auto ignition (CAI) combustion engine in order to achieve simultaneous reduction of NOx and soot, which are issues in diffusion combustion. The engine type was a uniflow scavenging 2-stroke engine, and the fuel used was diesel, as is common in diesel engines. We examined the position of the injector that effectively forms the premixture and realized stable operation with diesel fuel by the low pressure fuel injection device for port fuel injection (PFI), and it was found that the CAI combustion ignition timing can be controlled through setting the air/fuel ratio that obtains the optimal ignition timing per operation conditions. As a result of verifying the potential of this engine, it was confirmed that the regulation emissions level required for joint use of common rail fuel injection system (CRS), exhaust gas recirculation (EGR), diesel particulate filter (DPF), diesel oxidation catalyst (DOC), etc. in nonroad compression ignition (NRCI) engines can be achieved only by exhaust aftertreatment with a DOC. Furthermore, it was confirmed that break mean effective pressure (BMEP) equivalent to 4-stroke is about the same level as naturally aspirated NRCI engines and specific fuel consumption (SFC) has the potential to be about the same level or lower than NRCI engines with displacement of less than 2000 cm3.
Kurata, Mashu, Yamada, Yoshikazu
Subaru ‘Ascends’ to three-row crossover segment18AUTP10_1410/1/2018
Fuji Heavy Industries has needed a competitive three-row utility for its Subaru brand since its first attempt, the slow-selling Tribeca, bowed out after 2014. The 2019 Ascent, the brand's largest-ever vehicle, fills that role on a lighter, stiffer, extended version of the new Subaru Global Platform (SGP) that launched with the fifth-generation Impreza and is slated to underpin every model in the portfolio. Available with a standard second-row bench seat or available captain's chairs, Ascent is powered by an all-new 2.4-L horizontally-opposed four-cylinder gasoline engine coupled to a revised version of Subaru's TR690 ‘Lineartronic’ continuously variable transmission (CVT) produced in house, and the company's torque-vectoring AWD system.
Witzenberg, Gary
0D Modeling of Real-Driving NOx Emissions for a Diesel Passenger Vehicle2018-01-17619/10/2018
NOx emissions from diesel passenger vehicles affect the atmospheric environment. It is difficult to evaluate the NOx emissions influenced by environmental conditions such as humidity and temperature, traffic conditions, driving patterns, etc. In the authors’ previous study, real-driving experiments were performed on city and highway routes using a diesel passenger car with only an exhaust gas recirculation system. A statistical prediction model of NOx emissions was considered for simple estimations in the real world using instantaneous vehicle data measured by the portable emissions measurement system and global positioning system. The prediction model consisted of explanatory variables, such as velocity, acceleration, road gradient, and position of transmission gear. Using the explanatory variables, NOx emissions on the city and highway routes was well predicted using a diesel vehicle without NOx reduction devices. However, the prediction model had some limitations owing to the effects of NOx reduction devices. In this study, among various NOx reduction systems, a diesel vehicle with NOx storage catalyst (NSC) was chosen to predict the NOx emissions under a catalytic system. To improve the accuracy of the NOx emissions under the NSC, a catalyst model was added to the prediction model and used to predict the catalyst properties. By adding the catalyst model, the accuracy of NOx emissions of the prediction model was improved compared to the previous prediction model with individual explanatory variables. The NOx emissions were well predicted compared to the measured data.
Kim, Sangmyeong, Kuboyama, Tatsuya, Moriyoshi, Yasuo, Suzuki, Hisakazu
Dual Fuel Injection (DI + PFI) for Knock and EGR Dilution Limit Extension in a Boosted SI Engine2018-01-17359/10/2018
Combined direct and port fuel injection (i.e., dual injection) in spark ignition engines is of increasing interest due to the advantages for fuel flexibility and the individual merits of each system for improving engine performance and reducing engine-out emissions. Greater understanding of the impact of dual injection will enable deriving the maximum benefit from the two injection systems. This study investigates the effects of dual injection on combustion, especially knock propensity and tolerance to exhaust gas recirculation (EGR) dilution at different levels of EGR. A baseline for comparison with dual injection results was made using direct injection fueling only. A splash blended E20 fuel was used for the direct injection only tests. For the dual injection tests, gasoline, representing 80% by volume of the total fuel, was injected using the direct injector, and ethanol, representing 20% by volume of the total fuel, was injected using the port fuel injector. EGR mass fraction was varied from 0% to 21%, under boosted intake air pressure of 1.25 bar for both injection strategies. The results showed dual injection was beneficial to shorten the burn duration and improve combustion stability. Dual injection was more sensitive to knock than direct injection primarily due to increased unburned gas temperature. The overall thermal efficiency for the two injection types was comparable. The particulate matter emissions from dual injection showed slightly lower values, and the gaseous emissions showed lower total hydrocarbons and similar nitrogen oxides compared with only using direct injection of E20.
Han, Taehoon, Lavoie, George, Wooldridge, Margaret, Boehman, André
Investigation of Late Stage Conventional Diesel Combustion - Effect of Additives2018-01-17879/10/2018
The accepted model of conventional diesel combustion [1] assumes a rich premixed flame slightly downstream of the maximum liquid penetration. The soot generated by this rich premixed flame is burnt out by a subsequent diffusion flame at the head of the jet. Even in situations in which the centre of combustion (CA50) is phased optimally to maximize efficiency, slow late stage combustion can still have a significant detrimental impact on thermal efficiency. Data is presented on potential late-stage combustion improvers in a EURO VI compliant HD engine at a range of speed and load points. The operating conditions (e.g. injection timings, EGR levels) were based on a EURO VI calibration which targets 3 g/kWh of engine-out NOx. Rates of heat release were determined from the pressure sensor data. To investigate late stage combustion, focus was made on the position in the cycle at which 90% of the fuel had combusted (CA90). An EN590 compliant fuel was tested. To this fuel was added an organic compound, commonly encountered in sunscreen products, that was designed to absorb ultraviolet light. Such a material is postulated to speed up the late stage combustion and thereby improve the thermal efficiency. It was found that both the CA90 and the CA50 were advanced by addition of this material. There is evidence to suggest that addition of the material particularly effects the late stages of combustion, and that it works in a different way to a conventional diesel ignition improver.
Bakker, P.C., Willems, Robbert, Dam, Nico, Somers, Bart, Wakefield, Caroline, Brewer, Mark, Cracknell, Roger
Effects of Hot and Cooled EGR for HC Reduction in a Dual-Fuel Premixed Charge Compression Ignition Engine2018-01-17309/10/2018
Most internal combustion engine makers have adopted after-treatment systems, such as selective catalytic reduction (SCR), diesel particulate filter (DPF), and diesel oxidation catalyst (DOC), to meet emission regulations. However, as the emission regulations become stricter, the size of the after-treatment systems become larger. This aggravates the price competitiveness of engine systems and causes fuel efficiency to deteriorate due to the increased exhaust pressure. Dual-fuel premixed charge compression ignition (DF-PCCI) combustion, which is one of the advanced combustion technologies, makes it possible to reduce nitrogen oxides (NOx) and particulate matter (PM) during the combustion process, while keeping the combustion phase controllability as a conventional diesel combustion (CDC). However, DF-PCCI combustion produces high amounts of hydrocarbon (HC) and carbon monoxide (CO) emissions due to the bulk quenching phenomenon under low load conditions as a huddle of commercialization. In this study, the effects of exhaust gas recirculation (EGR) rate and EGR temperature were investigated to overcome the bulk quenching phenomenon under low load conditions in the DF-PCCI combustion. Natural gas (NG) and diesel were selected for low reactivity fuel (LRF) and high reactivity fuel (HRF) respectively. As experimental results, adopting the high temperature EGR could reduce the HC emission, and improve combustion efficiency (ηc) and fuel conversion efficiency (ηf), while maintaining the NOx and PM emissions under the EU-VI emission regulations. The results suggest that controlling the global equivalence ratio (∅global) and increasing the initial charge temperature by hot-EGR are quite effective way to mitigate the bulk quenching phenomenon and incomplete combustion under low load conditions in the DF-PCCI combustion.
Shim, Eui joon, Park, Hyunwook, Bae, Choongsik
A Simulation Study of Optimal Integration of a Rankine Cycle Based Waste Heat Recovery System into the Cooling System of a Long-Haul Heavy Duty Truck2018-01-17799/10/2018
As a promising solution to improve fuel efficiency of a long-haul heavy duty truck with diesel engine, organic Rankine cycle (ORC) based waste heat recovery system (WHR) by utilizing the exhaust gas from internal combustion engine has continuously drawn attention from automobile industry in recent years. The most attractive concept of ORC-based WHR system is the conversion of the thermal energy of exhaust gas recirculation (EGR) and exhaust gas from Tailpipe (EGT) to kinetic energy which is provided to the engine crankshaft. Due to a shift of the operating point of the engine by applying WHR system, the efficiency of the overall system increases and the fuel consumption reduces respectively. However, the integration of WHR system in truck is challenging by using engine cooling system as heat sink for Rankine cycle. The coolant mass flow rate influences strongly on the exhaust gas bypass which ensures a defined subcooling after condenser to avoid cavitation of pump. The coolant temperature decides the condensation pressure which impacts on the efficiency of WHR system. This paper aims to investigate the impacts of cooling conditions on WHR system by simulation. An optimal integration position of WHR condenser has been found. A complex 0D/1D-simulation model for a turbocharged production heavy duty engine with low-/high-temperature cooling circuits and a WHR system with ethanol as working fluid have been established in a conventional 1D-simulation software. A comparison between two WHR system layouts is made to determine WHR system concepts. An optimization for thermal management of the engine has been conducted to evaluate the maximal recovered energy in consideration of cooling fan engagement, thermostat operation and interactions between subsystems under transient conditions.
Yang, Kangyi, Grill, Michael, Bargende, Michael
Effects of Different Injection Strategies and EGR on Partially Premixed Combustion2018-01-17989/10/2018
Premixed Charge Compression Ignition concepts are promising to reduce NOx and soot simultaneously and keeping a high thermal efficiency. Partially premixed combustion is a single fuel variant of this new combustion concepts applying a fuel with a low cetane number to achieve the necessary long ignition delay. In this study, multiple injection strategies are studied in the partially premixed combustion approach to reach stable combustion and ultra-low NOx and soot emission at 15.5 bar gross indicated mean effective pressure. Three different injection strategies (single injection, pilot-main injection, main-post injection) are experimentally investigated on a heavy duty compression ignition engine. A fuel blend (70 vol% n-butanol and 30 vol% n-heptane) was tested. The effects of different pilot and post-injection timing, as well as Exhaust-gas Recirculation rate on different injection strategies investigated. All the measurements were performed at the same load, combustion phasing, lambda and engine speed. The results show that all three injection strategies produced ultra-low soot emission, while less NOx emission was noticed for pilot-main injection because of less diffusion combustion mode. Pilot-main injection strategy decreases the maximum pressure rise rate effectively compared to single injection. For pilot-main injection at 15.5 bar gross indicated mean effective pressure, when 24.3% (pilot/total fuel mass ratio) of fuel injected at −30 crank angle after top dead center in the pilot and the rest injected in the main with 45% EGR rate, 48.97% gross indicated efficiency is achieved. In addition, ultra-low soot (0.19 ppm) and NOx (0.327 g/kWh) emissions are achieved respectively without using after treatment.
Han, Jinlin, Wang, Shuli, Somers, Bart
Effects of EGR Constituents and Fuel Composition on DISI Engine Knock: An Experimental and Modeling Study2018-01-16779/10/2018
The use of exhaust gas recirculation (EGR) in spark ignition engines has been shown to have a number of beneficial effects under specific operating conditions. These include reducing pumping work under part load conditions, reducing NOx emissions and heat losses by lowering peak combustion temperatures, and by reducing the tendency for engine knock (caused by end-gas autoignition) under certain operating regimes. In this study, the effects of EGR addition on knocking combustion are investigated through a combined experimental and modeling approach. The problem is investigated by considering the effects of individual EGR constituents, such as CO2, N2, and H2O, on knock, both individually and combined, and with and without traces species, such as unburned hydrocarbons and NOx. The effects of engine compression ratio and fuel composition on the effectiveness of knock suppression with EGR addition were also investigated. A parametric, experimental matrix of diluents, compression ratio, and fuels was tested to measure knock-limited combustion phasing of each combination. The resulting knock limits were evaluated in the context of thermodynamic effects on the closed cycle, chemical interactions between the EGR constituents and the fuel-oxidizer mixture, and the effect of altered pressure-temperature trajectories on fuel-autoignition behavior. This paper provides an overview of the experimental results, and uses chemical-kinetic modeling to investigate the behavior of a particular fuel - diluent combination which had a strong sensitivity to compression ratio variation. The numerical results shed light on the complex interactions between fuel chemistry, the engine’s thermodynamic cycle, and the effect of residence times on the autoignition chemistry which leads to knock. An important and fuel-dependent role of thermal stratification in the end-gas is also suggested by the chemical-kinetics modeling of the experimentally observed knock limits.
Vuilleumier, David, Kim, Namho, Sjöberg, Magnus, Yokoo, Nozomi, Tomoda, Terutoshi, Nakata, Koichi
A Physical-Based Approach for Modeling the Influence of Different Operating Parameters on the Dependency of External EGR Rate and Indicated Efficiency2018-01-17369/10/2018
External Exhaust Gas Recirculation (EGR) provides an opportunity to increase the efficiency of turbocharged spark-ignition engines. Of the competing technologies and configurations, Low-Pressure EGR (LP-EGR) is the most challenging in terms of its dynamic behavior. Only some of the stationary feasible potential can be used during dynamic engine operation. To guarantee fuel consumption-optimized engine operation with no instabilities, a load point-dependent limitation of the EGR rate or alternatively an adaptation of the operating point to the actual EGR rate is crucial. For this purpose, a precise knowledge of efficiency and combustion variance is necessary. Since the operating state includes the actual EGR rate, it has an additional dimension, which usually results in an immense measuring effort. With the objective of avoiding long measuring periods, the given contribution introduces a physically based approach that models the influence of different engine operating parameters on the dependency between the external EGR rate and indicated efficiency. This also implies the dependency between the EGR rate and combustion variance. Since the model addresses vehicle applications, it only uses input parameters that can be assumed to be known during vehicle operation, such as the valve timing, engine load, engine speed, air fuel ratio, intake manifold pressure or ignition timing. Knowing the correlation of these parameters along with the EGR rate, the indicated efficiency and the EGR tolerance allows the fuel consumption to be optimized while maintaining the stability limits. As part of this publication, the measuring program that is used to set up the model is explained and presented. The mathematical formulation is described and a comparison of the model and measurement data is presented. The model quality is evaluated in terms of specific parameter variations. Finally, the results obtained are discussed under the aspect of how well the model can be used for the virtual calibration of spark-ignition engines.
Langmandel, Daniel, Orlick, Hannes, Haas, Daniel, Rottengruber, Hermann, Riegger, Franziska
Analysis of patent deposits and PROCONVE MAR – I in the development sector of agricultural machinery engines2018-36-02719/3/2018
Agriculture is directly associated with climate change issues and is a major source of Greenhouse Gas (GHG) emissions. Part of the emissions are the result of burning fossil fuels such as coal, natural gas and oil in internal combustion engines of agricultural machinery. In addition, because of negative impacts on air quality, human health and climate change, new strategies are being developed to reduce the impacts of GHG emissions. However, it is noted that there is a lack of information that instigates emissions of non-road equipment, such as emissions from agricultural machinery. Thus, in order to achieve climate policy objectives, new trends in agriculture are being adopted. They set emission standards for GHG reductions by agricultural engine engines. In Brazil, the Program for the Control of Air Pollution by Automotive Vehicles (PROCONVE) is responsible for establishing the legal regulations for admissible emissions for the different categories of motor vehicles. In order to control the emission limits of agricultural and road machinery, PROCONVE granted the MAR - I phase (Agricultural and Road Machinery), which came into force in 2015. Brazil, through the regulation of PROCONVE MAR - I, seeks to reduce GHG emissions, which among its guidelines are the improvement of the concepts of agricultural engine engines and their post - treatment technologies, resulting in improvements in the control of atmospheric emissions from exhaust gases. Thus, the article presents an analysis of the deposits in patent bases, through the Questel Orbit Platform, aiming at verifying who are the main manufacturers of the Brazilian market, what are the post-treatment systems for agricultural machinery engines and who are the countries which stand out for developing technologies linked to the reduction of the emission of pollutants. As a result, the main meta specifications structured in agricultural machines in countries with high emission standards include Selective Catalytic Reduction (SCR) for the control of NOx (Nitrogen Oxides), Exhaust Gas Recirculation (EGR) to enable cooling of the NOx formation and the Diesel Particulate Filters (DPF) in the control of PM (Particulate Material). In addition, the Electronic Fuel Injection System also allows a significant reduction in the emission of pollutant gases. As a consequence, research on these results can help to provide new conceptions of products that, besides being functional, have a legal adequacy, thus establishing a connection with PROCONVE MAR - I.
Silveira, Franco da, Ruppenthal, Janis Elisa, Farias, Marcelo Silveira de, Machado, Filipe Molinar, Costa, Marcela Avelina Bataghin, Amaral, Fernando Gonçalves
Effect of Piston Bowl Geometry on Performance and Emissions with Mahua Biodiesel Blend2018-28-00577/9/2018
The depletion of fossil fuels and environmental degradation with its emissions motivated the researchers to search for alternatives. Vegetable oils are considered as one of the productive alternative for internal combustion engines because of good combustion properties. Currently, very few commercial devices that utilize bio-diesel combustion for the production of heat, due to the economic viability and limited availability. To attain effective combustion, an effort is made in investigating the effect of change of piston geometry on the Performance & Emission characteristics of bio-diesel of mahua oil. Experiments are conducted to study the effect of varied piston bowl geometry on the performance and emission characteristics of mahua oil biodiesel on four stroke single cylinder diesel engine at constant speed of 1500 rpm for different loads. It is noticed that, at 20% blend of biodiesel of Mahua oil, the performance and emission parameters were improved compared to alone diesel operation. Hence the same optimal blend is adapted for conducting experiments by changing piston bowl geometry of toroidal shape. The experiments are conducted duly ensuring the same compression ratio as that of with standard hemispherical geometry at optimal blend of bio-diesel. It was noticed there is slight improvement in performance parameters and significant improvement in the emission parameters. At optimal blend emissions reduced by 16.4%, 11.4%, and 5.3% of unburnt hydrocarbons (UHC), Carbon monoxide (CO), Carbon dioxide respectively compared to diesel alone operation at rated load. However, there is 8% increase in oxides of Nitrogen (NOx) emission due to attainment of high combustion temperatures with biodiesel. With toroidal geometry, at optimal blend of bio-diesel the emission parameters are further reduced notably but increase in NOx emission is observed compared to standard piston due to high cylinder temperatures and pressures.
U S, Jyothi, K, Vijaya Kumar Reddy
Aging Effects of Catalytic Converters in Diesel Exhaust Gas Systems and Their Influence on Real Driving NO x Emissions for Urban Buses02-11-03-00146/18/2018
The selective catalytic reduction (SCR) of nitrogen oxides seems to be the most promising technique to meet prospective emission regulations of diesel-driven commercial vehicles. In the case of developing cost-effective catalytic converters with comparably high activity, selectivity, and resistance against aging, ion-exchanged zeolites play a major role. This study presents, firstly, a brief literature review and subsequently a discussion of an extensive conversion analysis of exemplary Cu/ and Fe/zeolites, as well as a homogeneous admixture of both. The aging stages of SCR catalysts deserve particular attention in this study. In addition, the aging condition of the diesel oxidation catalyst (DOC) was analyzed, which influences the nitrogen dioxide (NO2) formation, because the NO2/nitrogen oxides (NOx) ratio upstream from the SCR converter could be identified as a key factor for low temperature NOx conversion. Furthermore, it could be proved that a surplus of NO2 has the potential to suppress the overall efficiency in NOx conversion. In the final step of this investigation, the data gained during the conversion analysis were used as input parameters for a numerical model. This previously published simulation model was applied to predictively determine NOx emissions for one representative public bus route, for all investigated configurations of SCR catalysts and DOCs in different aging stages. It could be shown that an exhaust gas system in a moderate aging stage has the potential to deliver lower NOx emissions than its fresh equivalent. The reason for this could be a more favorable NO2/NOx ratio caused by an aged DOC compared to a fresh oxidation catalyst, which overcompensates for the losses in activity of aged SCR converters, particularly at low temperatures.
Moeltner, Lukas, Hohensinner, Michael, Schallhart, Verena
Literature Review on the Effects of Organometallic Fuel Additives in Gasoline and Diesel Fuels04-11-01-00054/18/2018
A literature review was conducted and fuel survey data were obtained to identify the use of metallic fuel additives (MFAs) within market fuels and determine their effects on engines, exhaust systems, and vehicle performance. The primary focus was on modern vehicles equipped with on-board diagnostic (OBD) systems and advanced emissions control systems. For gasoline, this includes vehicles categorized as National Low Emission Vehicles (NLEV) and Tier 2 or beyond in the U.S., and Euro-3 through Euro-6 in the EU. For diesel, this includes engines/vehicles with original equipment manufacturer (OEM)-equipped oxidation catalysts and diesel particulate filters. The literature search of peer-reviewed papers and other publicly available articles returned over 100 items relevant to the use of organometallic fuel additives, but did not provide significant evidence of widespread use of MFAs in either gasoline or diesel fuels. It is possible, however, that in specific cases, MFAs are added to fuels downstream of refinery blending. Recent fuel survey information confirmed that relatively few MFAs are found in market fuels, and they are generally present at quite low concentrations. Manganese was found most frequently, at concentrations as high as 66 mg Mn/L. Iron was detected less frequently and at lower levels, typically at concentrations ranging from 5 to 25 mg Fe/L. Silicon and other contaminants were frequently seen, albeit at very low levels. Evidence suggests that both manganese and iron, as well as other MFAs that are less frequently used, can contribute to deposits in combustion chambers and on exhaust components, resulting in poor performance and increased vehicle emissions. Although not in widespread use, the most common application of MFAs involves regeneration of diesel particulate filters (DPF). However, this is considered an aftermarket treatment, as the MFAs are not blended directly into marketplace diesel fuels.
Hoekman, S. Kent, Leland, Amber
A Comprehensive Evaluation of Diesel Engine CFD Modeling Predictions Using a Semi-Empirical Soot Model over a Broad Range of Combustion Systems2018-01-02424/3/2018
Single-cylinder engine experiments and computational fluid dynamics (CFD) modeling were used in this study to conduct a comprehensive evaluation of the accuracy of the modeling approach, with a focus on soot emissions. A semi-empirical soot model, the classic two-step Hiroyasu model with Nagle and Strickland-Constable oxidation, was used. A broad range of direct-injected (DI) combustion systems were investigated to assess the predictive accuracy of the soot model as a design tool for modern DI diesel engines. Experiments were conducted on a 2.5 liter single-cylinder engine. Combustion system combinations included three unique piston bowl shapes and seven variants of a common rail fuel injector. The pistons included a baseline “Mexican hat” piston, a reentrant piston, and a non-axisymmetric piston similar to the Volvo WAVE design. The injectors featured six or seven holes and systematically varied included angles from 120 to 150 degrees and hole sizes from 170 to 273 μm. A single nominal operating condition was studied: 100% load at 1800 rpm. Variations in the start of injection (SOI), injection pressure, intake pressure, and exhaust gas recirculation (EGR) level were also studied. These broad hardware and operational variations were modeled using Reynolds-averaged Navier-Stokes (RANS) CFD simulations with direct combustion chemistry integration. The focus of the work was to assess the ability of the model with Chalmers n-heptane combustion chemistry to predict the soot emissions from the various combustion systems. The results show that while the model predicts some general trends regarding SOI and injection pressure, it tends to fail as a comprehensive predictive simulation tool for designing DI diesel combustion systems regarding soot emissions. This suggests that further improvements in diesel engine CFD modeling for predicting soot emissions are needed.
Dempsey, Adam B., Seiler, Patrick, Svensson, Kenth, Qi, Yongli
Analysis of the Hardware Requirements for a Heavily Downsized Gasoline Engine Capable of Whole Map Lambda 1 Operation2018-01-09754/3/2018
MAHLE has developed a heavily downsized demonstrator engine to explore the limits, and potential benefits, of engine downsizing. The 1.2 litre, 3-cylinder, MAHLE downsizing (Di3) engine, in conjunction with an Aeristech 48 V electric supercharger (eSupercharger, eSC), achieves a BMEP level of 35 bar and a specific power output in excess of 160 kW/litre. The eSupercharger enables high specific power output, good low speed torque and excellent transient response. The resulting heavily downsized engine has been installed into a demonstrator vehicle that also features 48 V mild hybridization. At specific power output levels above 90 kW/litre the engine is operated with excess fuel in order to protect the turbine from excessive exhaust gas temperatures. In this analytical study, the boosting system requirements to maintain lambda 1 fuelling, via the use of EGR, across the entire engine operating map for the eSupercharged version of the MAHLE Di3 engine, have been explored. It has been found that a HP EGR system, with the eSupercharger located downstream of the main compressor, has the greatest potential to enable lambda 1 operation at maximum power output. At this point an EGR flow rate of 15 % is required, which would require about 38 kW of EGR cooling capability.
Bassett, Mike, Vogler, Christian, Hall, Jonathan, Taylor, James, Cooper, Adrian, Reader, Simon, Gray, Kevin, Wall, Richard
Reaction Kinetics Calculations and Modeling of the Laminar Flame Speeds of Gasoline Fuels2018-01-08574/3/2018
In the quasi-dimensional modeling of the spark-ignition combustion process, the burn rate calculation depends, among other influences, on the laminar flame speed. Commonly used models of laminar flame speeds are usually developed on the basis of measurement data limited to boundary conditions outside of the engine operation range. This limitation is caused by flame instabilities and forces flame speed models to be extrapolated for the application in combustion process simulation. However, for the investigation of, for example, lean burn engine concepts, reliable flame speed values are needed to improve the quality and predictive ability of burn rate models. For this purpose, a reference fuel for gasoline is defined to perform reaction kinetics calculations of laminar flame speeds for a wide range of boundary conditions. In order to define a reference fuel as representative as possible for standard gasoline, the influence of octane number and hydrogen-to-carbon ratio on the laminar flame speed of a toluene reference fuel (TRF) is investigated. Furthermore, the necessity to use a TRF instead of a primary reference fuel is shown. The reaction kinetics calculation results are then investigated to give possible explanations for the influence of boundary conditions like temperature, pressure, fuel composition, residual exhaust gas and air-fuel ratio on the laminar flame speed. Additionally, they are used to identify and illustrate the shortcomings of the widely used Heywood-approach, which belongs to the extrapolating flame speed models mentioned above. In a next step, the calibration parameters of an existing, more advanced model are adapted to match the flame speeds calculated for the TRF. This model is then expanded to cover the admixture of ethanol and finally employed in engine simulation to exemplarily show the prediction of burn rate changes due to a variation of exhaust gas recirculation rate or air-fuel equivalence ratio.
Hann, Sebastian, Grill, Michael, Bargende, Michael
Crank-Angle Resolved Real-Time Engine Modelling: A Seamless Transfer from Concept Design to HiL Testing2018-01-12454/3/2018
Virtual system integration and testing using hardware-in-the-loop (HiL) simulation enables front-loading of development tasks, provides a safer and reliable testing environment and reduces prototype hardware costs. One of the greatest challenges to overcome when performing HiL simulations is assuring a high model accuracy under stringent real-time requirements with acceptable development effort. This article represents a novel solution by deriving the plant model for HiL directly from the existing detailed models from the component layout phase using co-simulation methodology. It provides an effective and efficient model implementation and validation process followed by detailed quantitative analysis of the test results referred to the engine test bench measurements. For virtual calibration purpose, a detailed one-dimensional (1D) GT-POWER model for a state-of-the-art turbocharged diesel engine with exhaust gas recirculation (EGR) is simplified and transformed to a HiL platform connected to an engine control unit (ECU). The engine model remains semi-physical and crank angle resolved. The major pressure pulsations within the system are well captured, which is mandatory for the determination of volumetric efficiency, turbocharger operation and EGR distribution. A predictive combustion model based on injection profiles is implemented for modelling of the indicated engine efficiency and the exhaust gas temperature. After detailed investigations on steady-state and transient model performance in an offline environment, the model is integrated into the HiL testing platform. The coupling of the model to the ECU interface has been implemented using the co-simulation approach on FEV’s xMOD platform. The simulation results of the integrated HiL system, including the engine thermodynamics and the controller behaviours, have been validated with measurement data from engine test bench, and the real-time capability of the model has been proven. The work has demonstrated the capability and advantages of a seamless transfer from component design to system integration and testing within a combustion engine development process.
Xia, Feihong, Lee, Sung-Yong, Andert, Jakob, Kampmeier, Andreas, Scheel, Thomas, Ehrly lng, Markus, Tharmakulasingam, Raul, Takahashi, Yu, Kumagai, Tomohisa
Steady-State Experimental and Meanline Study of an Asymmetric Twin-Scroll Turbine at Full and Unequal and Partial Admission Conditions2018-01-09714/3/2018
The use of twin-scroll turbocharger turbines has gained popularity in recent years. The main reason is its capability of isolating and preserving pulsating exhaust flow from engine cylinders of adjacent firing order, hence enabling more efficient pulse turbocharging. Asymmetrical twin-scroll turbines have been used to realize high pressure exhaust gas recirculation (EGR) using only one scroll while designing the other scroll for optimal scavenging. This research is based on a production asymmetrical turbocharger turbine designed for a heavy duty truck engine of Daimler AG. Even though there are number of studies on symmetrical twin entry scroll performance, a comprehensive modeling tool for asymmetrical twin-scroll turbines is yet to be found. This is particularly true for a meanline model, which is often used during the turbine preliminary design stage. This study presents the development of a generalized meanline model for a twin-scroll turbine, which can be used in the early design stages, concentrating on asymmetrical scrolls. The improvements from the previous meanline model, i.e., the inlet duct and interspace model, in order to enable asymmetrical scroll prediction is described. The latter is based on the popular theory of turbomachinery wakes mixing, adopted from literature. The model is validated against experimental cold gas stand data under equal and unequal-admission conditions. Comparison between the model and experiments indicates the importance of the inlet duct and interspace model between the scrolls in obtaining satisfactory predictions across different admission conditions, due to the non-symmetrical features between the scrolls.
Palenschat, Torsten, Mueller, Markus, Rajoo, Srithar, Chiong, Meng Soon, Newton, Peter, Martinez-Botas, Ricardo, Tan, Feng Xian
Water Recovery from Gasoline Engine Exhaust for Water Injection2018-01-03694/3/2018
Water injection (WI) can improve gasoline engine performance and efficiency, and on-board water recovery technology could eliminate the need for customers to refill an on-board water reservoir. In this regard, the technical feasibility of exhaust water recovery (EWR) is described in this paper. Water injection testing was conducted at a full load condition (5000 rpm/18.1 bar BMEP) and a high load condition (3000 rpm/14.0 bar BMEP) on a turbocharged gasoline direction injection (GTDI) engine. Water recovery testing was conducted both after the exhaust gas recirculation (EGR) cooler and after the charge air cooler (CAC) at a high load (3000 rpm/14.0 bar BMEP), as well as a part load (2080 rpm/6.8 bar BMEP) condition, at temperatures ca. 10-15 °C below the dew point of the flow stream. Three types of water separation designs were tested: a passive cyclone separator (CS), a passive membrane separator (MEM), and an active separator (AS). Water injection and recovery amount was also simulated on three different drive cycles: FTP, WLTP and US06. The results showed that using water injection at full load reduced fuel enrichment requirements and reduced knock, yielding a 13% fuel economy improvement. Engine testing at high load condition showed that WI had a negligible effect on three-way catalyst (TWC) conversion efficiency under stoichiometric conditions. EWR was shown to be effective both post EGR cooler and post CAC. The CS and AS showed better performance than the MEM separator for water recovery. With the CS, up to ~100% condensate separation efficiency was achieved with very low pressure drop (~1 kPa). All the condensate samples collected with low sulfur fuel showed near neutral pH levels (6.5-8.5). From the appearance of the condensate samples, MEM-collected water had better quality than the CS and AS collected water. Water collected after the CAC showed better quality and lower pH than that collected downstream of the EGR cooler. Water recovered from post-TWC EGR showed better quality and higher pH than that collected from pre-TWC EGR. Water injection and collection simulations on three different drive cycles using GT-Drive showed that more water could be collected than was required for injection on FTP and WLTP drive cycles, while 40~70% of required water for injection could be collected on the US06 cycle.
Sun, Yong, Fischer, Michael, Bradford, Michael, Kotrba, Adam, Randolph, Eric
Thermodynamic Cycle and Working Fluid Selection for Waste Heat Recovery in a Heavy Duty Diesel Engine2018-01-13714/3/2018
Thermodynamic power cycles have been shown to provide an excellent method for waste heat recovery (WHR) in internal combustion engines. By capturing and reusing heat that would otherwise be lost to the environment, the efficiency of engines can be increased. This study evaluates the maximum power output of different cycles used for WHR in a heavy duty Diesel engine with a focus on working fluid selection. Typically, only high temperature heat sources are evaluated for WHR in engines, whereas this study also considers the potential of WHR from the coolant. To recover the heat, four types of power cycles were evaluated: the organic Rankine cycle (ORC), transcritical Rankine cycle, trilateral flash cycle, and organic flash cycle. This paper allows for a direct comparison of these cycles by simulating all cycles using the same boundary conditions and working fluids. To identify the best performing cycle, a large number of working fluids were evaluated with regards to the maximum power output of the power cycle for each heat source. Taking into account the constraints and boundary conditions, this study shows that the ORC gives the best performance with a power output of around 1.5 kW for the coolant, 2.5 kW for the exhaust gas recirculation cooler, and 5 kW for the exhaust with acetone, cyclopentane and methanol as the best performing working fluids.
Rijpkema, Jelmer, Andersson, Sven, Munch, Karin
A Fuel Sensitive Ignition Delay Model for Direct Injection Diesel Engine Operating under EGR Diluted Conditions2018-01-02314/3/2018
This empirical work investigates the impacts of thermodynamic parameters, such as pressure and temperature, and fuel properties, such as fuel Cetane number and aromatic contents on ignition delay in diesel engines. Systematic tests are conducted on a single-cylinder research engine to evaluate the ignition delay changes due to the fuel property differences at low, medium and high engine loads under different EGR dilution ratios. The test fuels offer a range of Cetane numbers from 28 to 54.2 and aromatic contents volume ratios from 19.4% to 46.6%. The experimental results of ignition delays are used to derive an ignition delay model modified from Arrhenius’ expression. Following the same format of Arrhenius’ equation, the model incorporates the pressure and temperature effects, and further includes the impacts of intake oxygen concentration, fuel Cetane number and aromatic contents volume ratio on the ignition delay. The model is verified by results obtained under different engine loads and with different fuels. It is shown from the results that the inclusion of oxygen concentration improves the accuracy in predicting the ignition delays in the EGR diluted conditions. The inclusion of Cetane number and aromatic contents in the ignition delay model improves the adaptivity of the model, so that it can be used to predict the ignition delay of different fuels with improved accuracy.
Yang, Zhenyi, Han, Xiaoye, Yu, Shui, Yu, Xiao, Wang, Meiping, Zheng, Ming, Ting, David
Exploring the NOx Reduction Potential of Miller Cycle and EGR on a HD Diesel Engine Operating at Full Load2018-01-02434/3/2018
The reduction in nitrogen oxides (NOx) emissions from heavy-duty diesel engines requires the development of more advanced combustion and control technologies to minimize the total cost of ownership (TCO), which includes both the diesel fuel consumption and the aqueous urea solution used in the selective catalytic reduction (SCR) aftertreatment system. This drives an increased need for highly efficient and clean internal combustion engines. One promising combustion strategy that can curb NOx emissions with a low fuel consumption penalty is to simultaneously reduce the in-cylinder gas temperature and pressure. This can be achieved with Miller cycle and by lowering the in-cylinder oxygen concentration via exhaust gas recirculation (EGR). The combination of Miller cycle and EGR can enable a low TCO by minimizing both the diesel fuel and urea consumptions. In this work, Miller cycle with late intake valve closing (IVC) and EGR technology were investigated on a single cylinder common rail heavy-duty diesel engine at high load operation of 24 bar net indicated mean effective pressure. The experiments were performed with a constant intake manifold pressure of 3 bar while optimizing the start of diesel injection to keep the peak in-cylinder pressure limit of 180 bar. The aqueous urea solution consumption in the SCR aftertreatment system was estimated to evaluate the effectiveness of the strategies in terms of TCO. The calculation was based on the engine-out NOx emissions and the Euro VI NOx limit. The results revealed that the use of the Miller cycle without EGR reduced NOx emissions by 35% and the net indicated efficiency by 4% when compared to the case with the baseline IVC at −178 crank angle degrees (CAD) after top dead center (ATDC). The introduction of 8%EGR decreased the levels of NOx by 54% while maintaining similar net indicated efficiency at the baseline IVC. The combination of Miller cycle with an IVC at −127 CAD ATDC and an EGR rate of 8% achieved the best trade-off between NOx and ISFC, decreasing the NOx levels by 57% and the fuel consumption by 1.6% compared to the baseline case. Soot emissions were maintained below the Euro VI limit of 0.01 g/kW h. Carbon monoxide emissions were maintained at low levels except for the combination of an IVC at −114 and an EGR rate of 8%. Unburned hydrocarbon emissions were slightly decreased with EGR and late IVCs likely due to relatively longer ignition delays and higher exhaust gas temperature. Overall, the analysis showed that the combination of Miller cycle with an IVC at −127 CAD ATDC and 8%EGR achieved the lowest total fluid consumption despite the reduction in net indicated thermal efficiency.
Guan, Wei, Pedrozo, Vinícius, Zhao, Hua, Ban, Zhibo, Lin, Tiejian
Ultra-High Fuel Injection Pressure with Massive EGR to Enable Simultaneous Reduction of Soot and NOx Emissions2018-01-02274/3/2018
In this study both double and triple injection strategies were used with fuel pressures up to 300 and 250 MPa, respectively. Tests were conducted at medium load conditions with cooled, high-pressure EGR at a ratio of 40% and higher. A four-cylinder production engine, featuring double turbochargers with one variable geometry turbocharger, was tested. The double injection strategy consisted of a 20% close-coupled pilot injection while the triple injection strategy introduced a post injection consisting of 10% the total cycle fuel. Results of this study do not indicate an advantage to extreme fuel pressure. The increased air entrainment reduces soot while increasing the premixed burn heat release, mean cylinder temperature, and NOx. Compared to the double injection scheme, triple injections achieved much lower soot for the same EGR rate with only a small NOx penalty. Under the conditions tested, triple injections could be used with high EGR as a mixing strategy, allowing for the use of fuel pressures below 200 MPa to achieve a low FSN that can be effectively cleaned by the DPF.
Ogren, Ryan M., Kong, Song-Charng
Influence of Direct-Injected Fuel Properties on Performance and Emissions from a Light-Duty Diesel Engine Running Under RCCI Combustion Mode2018-01-02504/3/2018
The dual-fuel combustion mode known as reactivity controlled compression ignition (RCCI) allows an effective control of the combustion process by means of modulating the in-cylinder fuel reactivity depending on the engine operating conditions. This strategy has been found to be able to avoid the NOx-soot trade-off appearing during conventional diesel combustion (CDC), with diesel-like or better thermal efficiency in a great part of the engine map. The role of the low reactivity fuel properties and engine settings over RCCI combustion has been widely investigated in literature, concluding that the direct-injected fuel injection timing is a key parameter for controlling the in-cylinder fuel stratification. From this, it can be inferred that the physical and chemical characteristics of the direct-injected fuel should have also an important role on the RCCI combustion process. This experimental work investigates the effects of using direct-injected fuels with different properties on RCCI engine-out emissions and performance. For this purpose, three fuels based on diesel-gasoline mixings at different ratios (D90, D70 and D50), also known as dieseline, have been tested and compared to pure diesel (D100). Gasoline used for mixing was 98 ON, which was also used as low reactivity fuel in all the cases. Methodologically, the direct-injected fuels were compared by means of a series of parametric sweeps varying EGR, gasoline fraction and direct injection timing at same levels.
Benajes, Jesus, Garcia, Antonio, Monsalve-Serrano, Javier, Boronat, Vicente
Increasing Exhaust Temperature of an Idling Light-Duty Diesel Engine through Post-Injection and Intake Throttling2018-01-02234/3/2018
Especially in crowded urban areas, light-duty vehicles often spend a great deal of time operating under idle conditions for which exhaust temperatures may be too low to maintain exhaust catalyst activity. This study investigated two methods of increasing Diesel exhaust temperature of a light-duty Diesel engine under idle conditions: post injection of fuel after TDC and intake throttling. For this particular study, EGR was not used. The engine operating parameters considered included three idle speeds of 800, 1100 and 1200 rpm, with the engine fully warmed up. Two rail pressures of 500 and 800 bar were studied with the injection strategy being the primary variable. The parameters measured included exhaust temperature, exhaust concentrations of NOx and HCs, as well as fuel consumption, IMEP and COV of IMEP. For the baseline idle conditions, manifold-out exhaust temperature was approximately 100 °C-105 °C. It was found that under idle conditions the post-injected fuel had to be injected within 30-45 degrees after TDC for the fuel to contribute to both IMEP and to higher exhaust temperatures. Without throttling, the contribution of the post-injection to increased exhaust temperature was relatively modest, about 20 °C. With heavy throttling it was possible to significantly increase idle exhaust temperature by more than 60 °C. The addition of post-injection in combination with heavy throttling allowed further temperature increases, on the order of 20-30 °C, yielding manifold-out exhaust temperatures above 200 °C. HC emissions, however, roughly doubling over the baseline idle condition. For conditions for which heavy throttling was used, it was interesting to note that the highest exhaust temperatures were found for a post-injection timing of approximately 25o –30oCA aTDC which also corresponded to a minimum in engine-out NOx emissions.
Ozel, Tayyar, Hall, Matthew J., Matthews, Ron
Early Pilot Injection Strategies for Reactivity Control in Diesel-ethanol Dual Fuel Combustion2018-01-02654/3/2018
This paper examines the diesel-ethanol dual fuel combustion at medium engine loads on a single-cylinder research diesel engine with a compression ratio of 16.5:1. The effect of exhaust gas recirculation (EGR) and ethanol energy ratio was investigated for the dual fuel combustion to achieve simultaneously ultra-low NOx and soot emissions. A medium ethanol ratio of about 0.6 was found suitable to meet the requirements for mixing enhancement and ignition control, which resulted in the lowest NOx and soot emissions among the tested ethanol ratios. A double-pilot injection strategy was found competent to lower the pressure rise rate owing to the reduced fuel quantity in the close-to-TDC injection. The advancement of pilot injection timing tended to reduce the CO and THC emissions, which is deemed beneficial for high EGR operations. The reactivity mutual-modulation between the diesel pilot and the background ethanol mixture was identified. The experiments confirmed that the background ethanol mixture could delay the ignition of the diesel pilot. The background ethanol can suppress the low-temperature heat release of the diesel pilot. With the close-to-TDC pilot as a reliable ignition source, the combustion phasing was controlled by the reactivity modulation of the cylinder charge through coordinated adjustment of the fuel quantity of the early injection diesel pilot and the port injection ethanol.
Yu, Shui, Dev, Shouvik, Yang, Zhenyi, Leblanc, Simon, Yu, Xiao, Han, Xiaoye, Li, Tie, Zheng, Ming
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