Browse Topic: Combustion and combustion processes

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Acoustic Assessment in a Small Displacement Diesel Engine2014-32-01291/30/2026
In the last years, the increasing concern for the environmental issues of IC engines has promoted the development of new strategies capable of reducing both pollutant emissions in atmosphere and noise radiation. Engines can produce different types of noise: 1) aerodynamic noise due to intake and exhaust systems and 2) surface radiated noise. Identification and analysis of noise sources are essential to evaluate the individual contribution (injection, combustion, piston slap, turbocharger, oil pump, valves) to the overall noise with the aim of selecting appropriate control strategies. Previous paper focused on the combustion related noise emission. The research activity aimed at diagnosing and controlling the combustion process via acoustic measurements. The optimal placement of the microphone was selected, where the signal was strongly correlated to the in-cylinder pressure development during the combustion process. Analysis and processing of the sound emission allowed the acoustic contribution of the combustion event to be isolated. Some indices capable of relating the combustion noise radiation back to the combustion development were defined. This paper presents an experimental activity devoted to analyze the entire noise generation process of a small displacement diesel engine. The purpose was to identify the contribution of the different sources (mechanical, combustion, fluid dynamic) to the overall emission. The methodology here proposed analyze the specific signature in the frequency domain of each source. The final objective was to use the microphone signal acquired in a proper selected location, to obtain indications about the effective strategies to achieve noise reduction. The repetitiveness of the measurements was guaranteed by a network encircling the engine. Microphones were placed in different positions and tests were performed in the complete engine operative field. In the paper, the experimental set-up is described, the methodology is presented. Results are then shown and discussed.
Chiatti, Giancarlo, Recco, Erasmo, Chiavola, Ornella, Conforto, Silvia
Aircraft Lightning Test MethodsARP5416B (Current)11/26/2025
This document is one of a set covering the whole spectrum of aircraft interaction with lightning. This document is intended to describe how to conduct lightning direct effects tests and indirect system upset effects tests. Indirect effects upset and damage tolerance tests for individual equipment items are addressed in DO-160/ED-14. Documents relating to other aspects of the certification process, including definition of the lightning environment, zoning, and indirect effects certification are listed in Section 2. This document presents test techniques for simulated lightning testing of aircraft and the associated systems. This document does not include design criteria nor does it specify which items should or should not be tested. Acceptable levels of damage and/or pass/fail criteria for the qualification tests must be approved by the cognizant certification authority for each particular case. When lightning tests are a part of a certification plan, the test methods described herein are an acceptable means, but not the only means, of meeting the test requirements of the certification plan. Each test method is set out in a uniform format, describing the test purpose, test object, test setup, test waveforms (voltage and/or current), measurements and data recording, test procedure and data interpretation. Guidance is provided on how to select the appropriate test or series of tests, and how the test results can be assessed. Natural lightning is a complex and variable phenomenon and its interaction with different types of vehicles may be manifested in many different ways. It is not intended that every test described herein be applied to every system requiring lightning verification tests. The document is written so that specific aspects of the environment can be called out for each specific program as dictated by the vehicle design, performance and mission constraints.
AE-2 Lightning Committee
TightAIR12122024A (Current)12/12/2024
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A-6 Aerospace Actuation, Control and Fluid Power Systems
ACHIEVING 44% THERMAL EFFICIENCY in TODAY’S ENGINES “More for Less”2024-01-318811/15/2024
ABSTRACT The US Army is seeking improvements in the fuel efficiency of their military vehicles.. They have initiated a number of R&D projects aimed at advancing the state-of-the-art of powertrain efficiency including demonstration in a laboratory environment. This effort will set a benchmark for the vehicle integrators, allowing them to improve future vehicle offerings. The SAIC, AVL, Badenoch, QinetiQ and Ker-Train Research team offered powertrain solutions from 7 Tons to 40 Tons that achieved the goal of 44% thermal efficiency and the stringent flexible fuel and emissions requirements. In each of these offerings the team was able to identify modifications to existing engines that allowed dramatic improvements in the thermal efficiency. These efficiency improvements were achieved through a combination of techniques, combustion cycle adjustments using in-cylinder pressure monitoring and precise control of fuel injector timing, and turbo-compounding. For the R&D project, the fuel injector timing will be controlled using commercial engine development hardware and software. The high speed hardware emulates the engine control module but allows the developer to finely tune the fuel injection to maximize the 50% Maximum Fuel Burn point (MFB50) with only limited NOx production. This will be accomplished using a variety of fuels and maintaining the output power to within 2% of the engine’s nominal rating. This paper will describe the fundamental diesel combustion process that must be controlled and techniques for usable power extraction from the waste exhaust gases to provide this performance. It will describe the engine development tools that enable these controls changes to be realized within a vehicle development cycle and retain the baseline engine maturity.
McDowell, Jim, Hunter, Gary L., Hennessy, Chris
test download manager cache issue 12/27/2023 at 9 amSAE-PP-0908512/27/2023
test download manager cache issue 12/27/2023 at 9 am
Mutagaana, Festo
Regression 11/1/23SAE-PP-0892211/1/2023
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Mutagaana, Festo
Ducted Fuel Injection Provides Consistently Lower Soot Emissions in Sweep to Full-Load Conditions03-19-01-00017/14/2023
Abstract Earlier studies have proven how ducted fuel injection (DFI) substantially reduces soot for low- and mid-load conditions in heavy-duty engines, without significant adverse effects on other emissions. Nevertheless, no comprehensive DFI study exists showing soot reductions at high- and full-load conditions. This study investigated DFI in a single-cylinder, 1.7-L, optical engine from low- to full-load conditions with a low-net-carbon fuel consisting of 80% renewable diesel and 20% biodiesel. Over the tested load range, DFI reduced engine-out soot by 38.1–63.1% compared to conventional diesel combustion (CDC). This soot reduction occurred without significant detrimental effects on other emission types. Thus, DFI reduced the severity of the soot–NOx tradeoff at all tested conditions. While DFI delivered considerable soot reductions in the present study, previous DFI studies at low- and mid-load conditions delivered larger soot reductions (>90%) compared to CDC operation at the same conditions. Therefore, the DFI configuration used here has been deemed nonoptimal (in terms of parameters such as the injector-spray and piston geometries), and several improvements are recommended for future studies with high-load DFI. These improvements include employing better spray-duct alignment, a deeper piston bowl with a smaller injector umbrella angle, and a fuel injector that opens and closes faster. The study also suggests future research to make DFI ready for commercialization, such as metal-engine tests to ensure desirable DFI performance over an engine’s complete speed/load map. Overall, this study supports the continued development and commercialization of DFI to meet upcoming emissions regulations for heavy-duty vehicles. Specifically, multicylinder engine experiments and CFD simulations should be utilized to optimize the performance and clarify the full potential of DFI.
Buurman, Noad J., Nyrenstedt, Gustav, Mueller, Charles J.
Water Injection for Combustion Phasing Control and Load Expansion on an Ethanol HCCI Engine2022-01-04513/29/2022
Homogeneous charge compression ignition (HCCI) combustion is low-temperature combustion (LTC) mode that offers an alternative to conventional combustion modes. The advantages of HCCI combustion include high conversion efficiency and low NOx emissions. On the other hand, a direct control mechanism for combustion phasing control is not attainable as in conventional SI (spark ignition) or CI (compression ignition) engines. This limits the HCCI operational range and provides one of the biggest challenges in HCCI mode commercial implementation. High heat release rates and knock initiation limit the high load operation, whereas combustion instabilities limit the low load operation. In this context, this paper explores the use of water injection technique to control the combustion phasing and expand the load of an ethanol HCCI engine. The experiments were conducted on a three-cylinder diesel engine, where all the exhaust gases from a diesel cylinder were used to achieve the HCCI combustion in another cylinder. The results showed that the water injection technique was effective in controlling the charge reactivity and consequently the combustion phasing while enabling higher engine load. The water injection reduced combustion speed and heat release rates, which led to higher combustion duration, better combustion phasing control, and a reduction of ringing intensity. It was possible to expand the initial engine load from 2.0 bar without water injection to 6.0 bar IMEP with water injection. In addition, the ethanol HCCI combustion achieved high indicated efficiencies, ranging from 34 to 39%, while maintaining good combustion stability and low emissions characteristics.
Telli, Giovani D., Rocha, Luiz A.O., Zulian, Guilherme Y., Lanzanova, Thompson D.M., Martins, Mario E.S.
Investigation of a Second Exhaust Valve Lift to Improve Combustion in a Methane - Diesel Dual-Fuel Engine2022-01-04663/29/2022
In recent years, the utilization of dual-fuel combustion has gained popularity in order to improve engine efficiency and emissions. With its high knock resistance, methane allows operation in high compression diesel engines with lower risk of knocking. With the use of diesel fuel as an ignition source, it is possible to exploit the advantages of lean combustion without facing problems to provide the high amount of ignition energy necessary to burn methane under such operating conditions. Another advantage is the variety of sources from which the primary fuel can be obtained. In addition to fossil sources, methane can also be produced from biomass or electrical energy.As the rate of substitution of diesel by methane increases, the trade-off between nitrogen oxide and soot is mitigated. However, emissions of carbon monoxide and unburned methane increase. Since carbon monoxide is toxic and methane has 25 times the global warming potential of carbon dioxide, these emission components pose a problem. Because of the stability of the molecule, methane catalysts require an exhaust gas temperature of over 500 °C in order to work effectively.In this work, the effect of conventional cooled external exhaust gas recirculation (EGR) and additional hot internal EGR are investigated for different substitution rates in a nonroad tractor engine converted to dual-fuel operation. The internal EGR rate is controlled by a variable second exhaust valve lift during the intake stroke - an approach which promises to benefit dual-fuel engines by increasing the in-cylinder gas temperature, thus favoring more complete combustion. A simulation model of the engine is used to determine the internal EGR rates and in-cylinder temperatures based on the experimental data. When internal EGR is used in combination with external EGR, the resulting emissions show additional reductions in nitrogen oxide (up to -51 %), carbon monoxide (up to -18 %) and methane (up to -28 %) with increasing internal EGR, while still maintaining low soot levels due to the substitution of diesel fuel for methane.
Mueller, Florian, Guenthner, Michael, Weigel, Alexander, Thees, Matthias
A Numerical Study on the Effect of a Pre-Chamber Initiated Turbulent Jet on Main Chamber Combustion2022-01-04693/29/2022
To elucidate the complex characteristics of pre-chamber combustion engines, the interaction of the hot gas jets initiated by an active narrow throated pre-chamber with lean premixed CH4/air in a heavy-duty engine was studied computationally. A twelve-hole KAUST proprietary pre-chamber geometry was investigated using CONVERGE software. The KAUST pre-chamber has an upper conical part with the spark plug, and fuel injector, followed by a straight narrow region called the throat and nozzles connecting the chambers. The simulations were run for an entire cycle, starting at the previous cycle's exhaust valve opening (EVO). The SAGE combustion model was used with the chemistry modeled using a reduced methane oxidation mechanism based on GRI Mech 3.0, which was validated against in-house OH chemiluminescence data from the optical engine experiments. Two different piston geometries, a flat piston geometry, and a more realistic bowl piston geometry were studied to understand the influence of jet on main chamber combustion. Varying the piston geometries results in different free jet times and hence main chamber combustion characteristics. Pre-chamber fuel ratio (PCFR) 6% of the total amount of fuel was investigated while keeping the global excess air ratios (λ) condition a constant value of 2.0. Both piston cases resulted in similar pre-chamber pressurization, with almost the same pre-chamber discharge and the equal pressure difference between pre-and main-chamber (ΔP) at the start of jet ejection. Different combustion behaviors were observed on analysis of the heat release rate in the main chamber. The importance of turbulence generated by the pre-chamber-initiated jets was further studied. It was observed that free jet time is a critical factor in developing turbulence in the main chamber. This increase in turbulence helps in increasing the burning velocity causing faster combustion. The influence of the jet-piston interaction is also analyzed as that determines the combustion behavior in the later CAD.
Sanal, Sangeeth, Echeverri Marquez, Manuel, Silva, Mickael, Cenker, Emre, Im, Hong G.
Aircraft Turbine Fuel Contamination History and Endurance Test RequirementsAIR4023C (Current)11/1/2021
This document discusses the history and development of endurance requirements, provides an analysis of test contaminant material and includes a discussion of future requirements.
AE-5B Aircraft and Engine Fuel and Lubricant Sys Components
Aircraft Flame Arrestor Installation Guidelines and Test MethodsARP5776 (Current)8/26/2021
The scope of this document is to provide pertinent information on demonstrating the performance of Flame Arrestors, also known as Fuel Vent Protectors (FVPs), in preventing the propagation of a deflagration when the arrestors are subjected to aerospace-representative flames produced by the venting of flammable gas through the arrestor. Test procedures for two separate combustion-loading profiles are presented herein: The flame hold test condition, and the flame propagation test condition. For the flame hold test condition, the applicability of two separate critical flows is discussed in which one flow results in the greatest flame arrestor temperature and a second flow results in the greatest temperature of the surrounding structure. These guidelines are necessary for OEMs and fuel/vent system designers to validate the flame arresting-performance of the subassemblies comprising of the flame arrestors and relevant surrounding structures in an installation environment representative of the actual unique aircraft installation. Flame arrestors are components of the fuel system plumbing and, as such, are subject to the same requirements of other fuel system plumbing components. This document presupposes that the flame arrestor is properly installed; note that existing documentation (refer to ARP8615) provides detailed guidance for testing a flame arrestor as a component of a system, including standard requirements for testing the installation of a flame arrestor. Flame arrestors are installed on other aircraft system installations besides fuel vent systems. These include: fuel tank inerting system (within the distribution system at the tank entrance), electrical pump inlets and external aircraft drain masts. Although only the fuel tank vent system installation is specifically addressed in this document, portions of the detailed flame test procedures may be useful to qualify flame arrestors in other applications, e.g., the flame propagation test which is applicable to flame arrestors installed in the inerting system.
AE-5A Aerospace Fuel, Inerting and Lubrication Sys Committee
Power and Torque Determination for UAS Engines Having Maximum Power Ratings at or Below 22.4 kWARP6971 (Current)4/7/2021
This recommended practice is applicable to reciprocating engines powering unmanned aerial vehicles (UAV) having rated power values less than 22.4 kW, and which are not to be used for human transport.
E-39 Unmanned Aircraft Propulsion Committee
7.0.104 - Managing Distributed Systems Development through Model-Based E/E-Architecture DesignSAE-PP-002802/4/2021
This paper sketches a model based E/E-architecture analysis and design process for the development of distributed in-vehicle systems. Together with a model based system development, the sketched analysis and design process results in a cost-effective E/E-architecture which fulfills all the requirements for the developed in-vehicle system. As an example scenario, the integration of a new feature into a car, which requires integrating a new distributed function into the existing E/E-architecture of the car, is shown.
Lname, Fname
Ignition System Measurements ProcedureJ973_202011 (Historical)11/3/2020
This SAE Recommended Practice specifies the design and/or evaluation with the specific equipment, conditions, and methods for distributorless battery ignition systems intended for use in various internal combustion engines including automotive, marine, motorcycle, and utility engine applications. The test procedures listed in this document are limited to measurements performed on a test bench only and do not include measurements made directly on engines or vehicles. This standard is not intended to supply information for battery ignition systems used in aircraft applications of any type.
Ignition Standards Committee
Lubricating Oil, Aircraft Piston Engine (Ashless Dispersant)J1899_202010 (Current)10/28/2020
This SAE Standard establishes the requirements for lubricating oils containing ashless dispersant additives to be used in four-stroke cycle, reciprocating piston aircraft engines. This document covers the same lubricating oil requirements as the former military specification MIL-L-22851. Users should consult their airframe or engine manufacturers manuals for the latest listing of acceptable lubricants.
E-38 Aviation Piston Engine Fuels and Lubricants
Test Cell InstrumentationAIR5026B (Current)10/21/2020
This document discusses, in broad general terms, typical present instrumentation practice for post-overhaul gas turbine engine testing. Production engine testing and engine development work are outside the scope of this document as they will typically use many more channels of instrumentation, and in most cases will have requirements for measurements that are never made in post-overhaul testing, such as fan airflow measurements, or strain measurements on compressor blades. The specifications for each parameter to be measured, in terms of measurement range and measurement accuracy, are established by the engine manufacturers. Each test cell instrument system should meet or exceed those requirements. Furthermore, each instrument system should be recalibrated regularly, to ensure that it is still performing correctly.
EG-1E Gas Turbine Test Facilities and Equipment
Model-Based Precise Air-Fuel Ratio Control for Gaseous Fueled Engines02-13-03-001710/9/2020
In this article, an adaptive state estimation algorithm for precise air-fuel ratio (AFR) control is presented. AFR control is a critical part of internal combustion engine (ICE) control, and tight AFR control delivers lower engine emissions, better engine fuel economy, and better engine transient performance. The proposed control algorithm significantly improves transient AFR control to eliminate and reduce the amplitude of the lean and rich spikes during transients. The new algorithm is first demonstrated in simulation (using Matlab/SimulinkTM and GT-PowerTM) and then verified on a test engine. The engine tests are conducted using the European Transient Cycle (ETC) with HoribaTM double-ended dynamometer. The developed algorithm utilizes a nonlinear physics-based engine model in the observer and advanced control principles with modifications to solve real industrial control issues. This method dramatically reduces on-engine AFR transient calibration efforts, which was one of the objectives of this research. The developed algorithm is applicable for various fuel mixer configurations including pre-turbocharger, pre-throttle, and post-throttle. It also demonstrates robustness to engine to engine inconsistency. The novel algorithm is developed by following model-led design process. WoodwardTM natural gas engines and engine control modules are used for algorithm development and validation.
Han, Yi, Young, Peter
Candidate Improvements to Dedicated Short Range Communications (DSRC) Message Set Dictionary [SAE J2735] Using Systems Engineering MethodsJ3067_202010 (Current)10/6/2020
This document is not a standard, it is a candidate for a standard being submitted to SAE for their consideration as a comment to SAE J2735. The term SAE J2735 SE candidate is used within this document to refer to this submission. This document specifies dialogs, messages, and the data frames and data elements that make up the messages specifically for use by applications intended to utilize the 5.9 GHz Dedicated Short Range Communications for Wireless Access in Vehicular Environments (DSRC/WAVE, referenced in this document simply as “DSRC"), communications systems. Although the scope of this Standard is focused on DSRC, these dialogs, messages, data frames and data elements have been designed, to the extent possible, to be of use for applications that may be deployed in conjunction with other wireless communications technologies. This standard therefore specifies the definitive message structure and provides sufficient background information to allow readers to properly interpret the message definitions from the point of view of an application developer implementing the messages according to the DSRC Standards.
V2X Communications Steering Committee
Multiposition Small Engine Exhaust System Fire Ignition SuppressionJ335_202010 (Current)10/6/2020
This SAE Recommended Practice establishes equipment and test procedures for determining the performance of spark arrester exhaust systems of multiposition small engines (<19 kW) used in portable applications, including hand-held, hand-guided, and backpack mounted devices. It is not applicable to spark arresters used in vehicles or stationary equipment.
SAE IC Powertrain Steering Committee
Tools, Inserting and Extracting Helical Coil Wire Screw Thread Inserts Inch and Spark Plug SizesAS59158A (Current)8/3/2020
This SAE Aerospace Standard (AS) describes taps, thread plug gages, inserting tools, expanding tools, offset and staking tools, tang break-off tools, extracting tools and thread repair kits.
EG-1B Hand Tools Committee
V2X Communications Message Set DictionaryJ2735_202007 (Historical)7/23/2020
This SAE standard specifies a message set, and its data frames and data elements, for use by applications that use vehicle-to-everything (V2X) communications systems. While the data dictionary was originally designed for use over DSRC, this document is intended to be independent of the underlying communications protocols used to exchange data between participants in V2X applications.
V2X Core Technical Committee
Automated Diagnosis of Engine Misfire Faults Using Combination Classifiers02-13-02-00076/26/2020
Existing on-board diagnostics vehicle systems can detect the existence of faults, but their diagnostic (fault isolation) capabilities are rather low. Extensions to on-board diagnostics are needed in order to provide a high degree of automated diagnostic support. In this context, we study in this article the problem of internal combustion engine misfires, which constitute a class of automotive faults known to be difficult to diagnose, and present a combination classifier that has excellent performance in classifying the various root causes of misfire faults. We first obtained real-life data and built a database consisting of 2,299 time instances of actual misfire and misfire-free cases. Fault data were captured on several different vehicle makes and models, with each misfire fault belonging to one of three different categories (air-intake, coil-ignition, and fuel-injection), further subdivided into a total of seven subcategories. We then developed a combination classifier (referred to as TMF, “Trees for MisFires”) and obtained its performance on the real-life misfire fault dataset. Extensive simulation results show that TMF outperforms a variety of other standard classifiers (whether single or ensemble) as well as other combination classifiers, both for “low-resolution” diagnosis (classification consisting of three misfire fault categories plus misfire-free) and “high-resolution” diagnosis (classification consisting of seven misfire fault subcategories plus misfire-free). Moreover, these results hold even when the training set is restricted to be a very small portion of the available dataset, which is a valuable asset of a realistic classifier.
Suda, Jessica L., Kagaris, Dimitri
Preignition Rating of Spark PlugsJ549_202006 (Current)6/15/2020
This SAE Recommended Practice describes the equipment and procedures used in obtaining preignition ratings of spark plugs.
Ignition Standards Committee
Environmental Control System ContaminationAIR1539C (Current)5/29/2020
This SAE Aerospace Information Report (AIR) includes a discussion of liquid and particulate contaminants which enter the aircraft through the environmental control system (ECS). Gaseous contaminants such as ozone, fuel vapors, sulphates, etc. are also covered in this AIR. This publication is concerned with contamination sources which interface with ECS and fuel tank inerting systems, and the effects of this contamination on equipment. Methods of control will be limited to the equipment and interfacing ducting which normally falls within the responsibility of the ECS designer.
AC-9 Aircraft Environmental Systems Committee
Infrared/Visible Optical Diagnostics of RCCI Combustion with Dieseline in a Compression Ignition Engine2020-01-05574/14/2020
Compression ignition engines are widely used for transport and energy generation due to their high efficiency and low fuel consumption. To minimize the environmental impact of this technology, the pollutant emissions levels at the exhaust are strictly regulated. To reduce the after-treatment needs, alternative strategies as the low temperature combustion (LTC) concepts are being investigated recently. The reactivity controlled compression ignition (RCCI) uses two fuels (direct- and port- injected) with different reactivity to control the in-cylinder mixture reactivity by adjusting the proportion of both fuels. In spite of the proportion of the port-injected fuel is typically higher than the direct-injected one, the characteristics of the latter play a main role on the combustion process. Use of gasoline for direct injection is attractive to retard the start of combustion and to improve the air-fuel mixing process. In this work, the influence of the direct-injected fuel properties on RCCI combustion mode is studied in an optical compression ignition engine. Gasoline fuel is injected in the intake manifold while a blend of gasoline and diesel (a.k.a. dieseline) is directly injected into the cylinder. Non-conventional optical diagnostics in the visible and infrared spectra are applied for the direct investigation of the in-cylinder phenomena during the injection and the combustion processes. A low-luminosity, mainly kinetically controlled combustion mode has been observed.
Sequino, Luigi, Mancaruso, Ezio, Monsalve-Serrano, Javier, Garcia, Antonio
The Use of Piezoelectric Washers for Feedback Combustion Control2020-01-11464/14/2020
The use of piezoelectric cylinder pressure sensors is very popular during engine testing, but cylinder pressure information is becoming mandatory also in several on-board applications, where Low Temperature Combustion (LTC) approaches require a feedback control of combustion, due to poor combustion stability and the risk of knock or misfire. Several manufacturers showed the capability to develop solutions for cylinder pressure sensing in on-board automotive and aeronautical applications, and some of them have been patented. The most straight-forward approach seems the application of a piezo-electric washer as a replacement of the original part equipping the spark plug; the injector could also be used to transfer the cylinder pressure information to the piezoelectric quartz, in diesel or Gasoline Direct Injections (GDI) engines. The paper describes the features of signals acquired using piezoelectric washers, discussing possible applications, highlighting the factors which impact the sensors accuracy, and proposing algorithms to compensate potential errors in the evaluation of combustion metrics. The sensors have been first tested on a press, then in two different gasoline engines: a naturally aspirated V12 and a turbocharged 2 cylinders with Variable Valve Lift system (VVL). Signals have been compared to those obtained with lab-grade cylinder pressure sensors, with particular attention to peak pressure, combustion phase and knock intensity. The main issue affecting the accuracy of cylinder pressure measurement using the piezoelectric spark plug washer is the effect of temperature variations both on the force transmitted by the thread to the washer and piezoelectricity properties.
Corti, Enrico, Abbondanza, Marco, Ponti, Fabrizio, Raggini, Lorenzo
Impact of Spark Plasma Length on Flame Kernel Development under Flow Condition2020-01-11144/14/2020
Advanced ignition systems with enhanced discharge current have been extensively investigated in research, since they are highly regarded as having the potential to overcome challenges that arise when spark-ignition engines are running under lean or EGR diluted conditions. Local flow field is also of particular importance to improve the ignitability of the air-fuel mixture in SI engines as the spark plasma channel can be stretched by the flow across the spark gap, leading to longer plasma length, thus more thermal spark energy distributed to the air-fuel mixture in the vicinity of the spark plug. Research results have shown that a constantly high discharge current is effective to maintain a stable spark plasma channel with less restrikes and longer plasma holding period. However, with the further increase in discharge current, plasma channel becomes thicker, and the stretched plasma length becomes shorter under a constant flow speed, which may suppress the advantages of the enhanced discharge current. In this work, the interaction between discharge current level and plasma length under flow conditions is investigated. Whether a thick but shorter plasma channel or a thin but stretched farther plasma channel is more effective for the flame kernel formation is discussed to provide an insight into the influence of the plasma length on flame initiation. An optical combustion chamber platform along with a cross-flow generation system was used to study the plasma channel behavior; an in-house developed spark energy management module was employed to boost the discharge current level up to 3 A; in order to decouple the effect of discharge duration on flame initiation, the total discharge process was controlled within 0.8 ms.
Zhu, Hua, Tan, Qingyuan, Yu, Xiao, Yang, Zhenyi, Liang, Li, Zheng, Ming, Reader, Graham, Qian, Jin
The Effects of Thick Thermal Barrier Coatings on Low-Temperature Combustion2020-01-02754/14/2020
An experimental study was conducted on a Ricardo Hydra single-cylinder light-duty diesel research engine. Start of Injection (SOI) timing sweeps from -350 deg aTDC to -210 deg aTDC were performed on a total number of five pistons including two baseline metal pistons and three coated pistons to investigate the effects of thick thermal barrier coatings (TBCs) on the efficiency and emissions of low-temperature combustion (LTC). A fuel with a high latent heat of vaporization, wet ethanol, was chosen to eliminate the undesired effects of thick TBCs on volumetric efficiency. Additionally, the higher surface temperatures of the TBCs can be used to help vaporize the high heat of vaporization fuel and avoid excessive wall wetting. A specialized injector with a 60° included angle was used to target the fuel spray at the surface of the coated piston. Throughout the experiments, the equivalence ratio, ϕ, was maintained constant at 0.4; the combustion phasing was consistently matched at 6.8 ± 0.4 deg aTDC. It can be concluded that the thick TBC cases achieved 1 to 2 percentage points improvement in combustion efficiency, and generally, a ~2 percentage points increase in indicated engine efficiency. It is also noticed that applying a dense top sealing layer to the TBC further improves the UHC emissions compared to the TBC coated piston with an unsealed surface. From the heat release analysis, it can be concluded that the TBCs have no significant impact on the heat release process and knock intensity while matching the combustion phasing; however, it reduces the intake temperature requirement by up to 20 K. The exhaust gas temperatures were expected to increase for the TBC cases, but the expected increase in exhaust temperature was not conclusive from the results observed in this study.
Yan, Ziming, Gainey, Brian, Gohn, James, Hariharan, Deivanayagam, Saputo, John, Schmidt, Carl, Caliari, Felipe, Sampath, Sanjay, Lawler, Benjamin
Instantaneous PLII and OH* Chemiluminescence Study on Wide Distillation Fuels, PODE n and Ethanol Blends in a Constant Volume Vessel2020-01-03404/14/2020
The combustion characteristics and soot emissions of three types of fuels were studied in a high pressure and temperature vessel. In order to achieve better volatility, proper cetane number and high oxygen content, the newly designed WDEP fuel was proposed and investigated. It is composed of wide distillation fuel (WD), PODE3-6 mixture (PODEn) and ethanol. For comparison, the test on WD and the mixture of PODEn-ethanol (EP) are also conducted. OH* chemiluminescence during the combustion was measured and instantaneous PLII was also applied to reveal the soot distribution. Abel transformation was adopted to calculate the total soot of axisymmetric flame. The results show that WDEP has similar ignition delays and flame lift-off lengths to those of WD at 870-920 K. But the initial ignition locations of WDEP flame in different cycles were more concentrated, particularly under the condition of low oxygen atmosphere. Comparing with WD, the soot amount of WDEP decreased for 55% and 27% at 870 K and 920 K. For the case of 920 K and 15.8% of ambient oxygen, the soot amount in WDEP case decreased by 44%, indicating a more significant soot reduction effect at lower temperatures and EGR conditions.
Cui, Longxi, Ma, Yue, Liu, Dong, Ma, Xiao, Xu, Hongming, Shuai, Shijin
Effect of Split Injection and Intake Air Humidification on Combustion and Emission Characteristics of a Marine Diesel Engine in Partially Premixed Low-Temperature Combustion Mode2020-01-02984/14/2020
The objective of this study was to investigate combined effects of split injection strategies and intake air humidification on combustion and emissions of a partially premixed charge compression ignition (PCCI) marine diesel engine. In this research, a three-dimensional numerical model was established by a commercial code AVL-Fire to explore in-cylinder combustion process and pollutant formation factors in a four-stoke supercharged intercooled marine diesel engine under partial load at 1350 r/min. The novelty of this study is to combine different water-fuel ratios and fuel injection parameters (pilot injection timing and main injection timing) to find the optimized way to improve engine performance as well as NOx-soot emissions, thus meeting the increasingly stringent emissions restriction. The results indicate that as the main injection timing advances (-14°CA to -20°CA aTDC), the in-cylinder peak pressure increases by about 10%, the main injection ignition delay (MI ignition delay) becomes longer, the CA50 is advanced near the top dead center (TDC), which is effective to improve the indicated thermal efficiency (ITE). Meanwhile, soot emissions are reduced by about 50% compared with the original engine at the -20°CA aTDC main injection timing. The early pilot injection timing can form relatively uniform temperature field and concentration field in the cylinder before the start of main injection (SOMI) timing, which is advantageous to fuel-air mixing. The high level of water-fuel ratio is utilized to reduce overall combustion temperatures and achieve low temperature combustion of the diesel engine. NOx emissions significantly decrease by about 75% compared with the original engine when the water-fuel mass ratio is 2.0. All in all, the technical route to improve the NOx-soot trade-off relationship is found through the coupling optimization of split injection strategies and intake air humidification. Meanwhile, the indicated specific fuel consumption (ISFC) is reduced and NOx-ISFC trade-off relationship is improved.
Cai, Yujie, Wang, Ke, Kong, Shiru, Bian, Zhishang
The Prospect and Benefits of Using the Partial-Averaged Navier-Stokes Method for Engine Flows2020-01-11074/14/2020
This paper presents calculations of engine flows by using the Partially-Averaged Navier Stokes (PANS) method (Girimaji [1]; [2]). The PANS is a scale-resolving turbulence computational approach designed to resolve large scale fluctuations and model the remainder with appropriate closures. Depending upon the prescribed cut-off length (filter width) the method adjusts seamlessly from the Reynolds-Averaged Navier-Stokes (RANS) to the Direct Numerical Solution (DNS) of the Navier-Stokes equations. The PANS method was successfully used for many applications but mainly on static geometries, e.g. Basara et al. [3]; [4]. This is due to the calculation of the cut-off control parameter which requires that the resolved kinetic energy is known and this is usually obtained by suitably averaging of the resolved field. Such averaging process is expensive and impractical for engines as it would require averaging per cycles. A recently published work on PANS (Basara et al. [5]) opens a prospect of more cost-effective engine calculations. This new PANS approach solves the additional equation for a total resolved turbulent kinetic energy which enables continuous (in situ) update of the resolution parameter fk. Thus fk. is dynamically specified in time and space depending on the flow and computational meshes. Calculation results of the IC engine will be compared with the measurements which include cycle-to-cycle variations and emission data.
Basara, Branislav, Pavlovic, Zoran, Girimaji, Sharath
Numerical Modeling of Spray Formation under Flash-boiling Conditions2020-01-03284/14/2020
Flash boiling occurs in sprays when the ambient gas pressure is lower than the saturation pressure of the injected fuel. In the present work, a numerical study was conducted to investigate solid-cone spray behaviors under various flash-boiling conditions. A new spray cone angle correlation that is a function of injection parameters was developed and used for spray initialization at the nozzle exit to capture plume interactions and the global spray shape. The spray-breakup regime control was adjusted to enable catastrophic droplet breakup, characterized by Rayleigh-Taylor (RT) breakup, near the nozzle exit. The model was validated against experimental spray data from five different injectors, including both multi-hole and single-hole injectors, with injection pressure varying from 100 to 200 bar. Different fuels, including iso-octane, n-heptane, n-pentane, ethanol, and n-butanol, were investigated under a wide range of flash-boiling conditions, in which flash boiling was induced by high injected fuel temperature, ranging from 323 to 493 K, and/or low ambient gas pressure, ranging from 0.1 bar to atmospheric. It is found that flash boiling can significantly increase the spray cone angle near the nozzle exit, causing spray spreading and obvious plume interactions, which strongly influence the global spray shape. For flash boiling induced by high fuel temperature, penetration length tends to decrease because of enhanced liquid breakup and vaporization. For flash boiling induced by low ambient gas pressure, the reduced resistance from the ambient gas and enhanced droplet breakup lead to competing effects on spray penetration. By using the modified breakup regime control and spray cone angle correlation, the model shows good agreement with experimental data in capturing spray spreading, plume interactions and global spray shape in all simulated cases. The modeling approach proposed in this paper is expected to be universally applicable to all solid-cone flash-boiling sprays.
Tao, Mingyuan, Liang, Long, Wang, Yue, Meeks, Ellen
Step by Step Conversion of ICE Motorcycle to a BEV Configuration2020-01-14364/14/2020
With the mass movement toward electrification and renewable technologies, the scope of innovation of electrification has gone beyond the automotive industry into areas such as electric motorcycle applications. This paper provides a discussion of the methodology and complexities of converting an internal combustion motorcycle to an electric motorcycle. In developing this methodology, performance goals including, speed limits, range, weight, charge times, as well as riding styles will be examined and discussed. Based on the goals of this paper, parts capable of reaching the performance targets are selected accordingly. Documentation of the build process will be presented along with the constraints, pitfalls, and difficulties associated with the process of the project. The step-by-step process that is developed can be used as a guideline for future build and should be used as necessary. During the development and conversion process, the model of the electric motorcycle was developed in Simulink to size the battery pack and the electric motor. This model was also the focus of different design experiments to choose the proper components and subsystems to minimize the development cycle time. The goal of this paper is also to provide guidelines of the conversion process for the future industry as well as the academic arena.
Lawrence, Matthew D., Siavoshani, Saeed
An Experimental Study on the Effect of Exhaust Gas Recirculation on a Natural Gas-Diesel Dual-Fuel Engine2020-01-03104/14/2020
Natural gas (NG)-diesel dual-fuel combustion can be a suitable solution to reduce the overall CO2 emissions of heavy-duty vehicles using diesel engines. One configuration of such a dual-fuel engine can be port injection of NG to form a combustible air-NG mixture in the cylinder. This mixture is then ignited by a direct injection of diesel. Other potential advantages of such an engine include the flexibility of switching back to diesel-only mode, reduced hardware development costs and lower soot emissions. However, the trade-off is lower brake thermal efficiency (BTE) and higher hydrocarbon emissions, especially methane, at low load and/or high engine speed conditions. Advancing the diesel injection timing tends to improve the BTE but may cause the NOx emissions to increase. In this study, exhaust gas recirculation (EGR) is used in combination with the diesel injection timing control to demonstrate the compromises between lowering NOx, soot, and methane emissions while maintaining diesel-like BTE. Determining such optimal operating conditions can not only reduce the consumption of diesel and NG but may also enhance the life of the exhaust after-treatment system components such as the diesel particulate filter (DPF). Tests are performed on a heavy-duty, four-stroke, NG-diesel dual-fuel single-cylinder research engine with independent and flexible air and fuel delivery systems. Two load levels corresponding to 50% and 75% of full load are investigated at a constant engine speed of 1000 rpm and NG-diesel energy ratio of 3:1. Results show that advancing the diesel injection timing at a low EGR ratio (~10% based on intake and exhaust CO2) can reduce the soot and methane emissions but cause the NOx emissions to increase. Further increase of EGR to up to 18% can reduce the NOx emissions while limiting the soot emissions to the heavy-duty regulatory limits. In general, with the use of EGR, dual-fuel combustion can provide an improved NOx-soot trade-off compared to diesel-only combustion.
Dev, Shouvik, Guo, Hongsheng, Lafrance, Simon, Liko, Brian
Characteristics of Auto-Ignition for Lubricants and Lubricant/Gasoline Based on an Innovative Single Droplet Test System2020-01-14284/14/2020
Due to the advantages of low weight, low emissions and good fuel economy, downsized turbocharged gasoline direct injection (GDI) engines are widely-applied nowadays. However, Low-Speed Pre-Ignition (LSPI) phenomenon observed in these engines restricts their improvement of performance. Some researchers have shown that auto-ignition of lubricant in the combustion chamber has a great effect on the LSPI frequency. To study the auto-ignition characteristics of lubricant, an innovative single droplet auto-ignition test system for lubricant and its mixture is designed and developed, with better accuracy and effectiveness. The experiments are carried out by hanging lubricant droplets on the thermocouple node under active thermo-atmosphere provided by a small “Dibble burner”. The auto-ignition process of lubricant droplets is recorded by a high-speed camera. Influences of different base oil types, viscosities, calcium contents, initial droplet diameters, co-flow speeds, new oil, used oil and blending ratios of lubricant and gasoline on the ignition delay time of droplets are investigated at different droplet temperatures. The background co-flow field temperature varies from 823K to 1323K. Equivalent diameters of droplets, 0.99mm, 1.24mm and 1.63mm, generated by micro-syringes are compared for their characteristics of auto-ignition. The results show that the ignition delay time of all the droplets is significantly shortened with the increase of droplet temperature. When the droplet temperature is lower than 1073K, the ignition delay of droplets from Type III base oil is shorter than that of droplets from Type IV base oil. Besides, lubricant droplets with higher viscosities or larger initial diameters have a longer ignition delay. Furthermore, increasing both the calcium content and co-flow speed can obviously promote the auto-ignition process of droplets. Moreover, there is a critical blending ratio for gasoline to lubricant, whose value is between 20% and 30%. When it is lower than the critical blending ratio, the ignition delay of lubricant droplets increases with the rising of blending ratio. When it is higher than the critical blending ratio, the rule is contrary.
Yu, Yang, Pan, Kaifeng, Deng, Jun, Hu, Zongjie, Xie, Wei, Wu, Zhijun, Li, Liguang
Experimental and Numerical Analysis of Passive Pre-Chamber Ignition with EGR and Air Dilution for Future Generation Passenger Car Engines2020-01-02384/14/2020
Nowadays the combination of strict regulations for pollutant and CO2 emissions, together with the irruption of electric vehicles in the automotive market, is arising many concerns for internal combustion engine community. For this purpose, many research efforts are being devoted to the development of a new generation of high-performance spark-ignition (SI) engines for passenger car applications. Particularly, the PC ignition concept, also known as Turbulent Jet Ignition (TJI), is the focus of several investigations for its benefits in terms of engine thermal efficiency. The passive or un-scavenged version of this ignition strategy does not require an auxiliary fuel supply inside the PC; therefore, it becomes a promising solution for passenger car applications as packaging and installation are simple and straightforward. Moreover, combining this concept with lean burn is an interesting alternative for both improving the engine efficiency and maintaining low pollutant emissions as it enables Low Temperature Combustion (LTC) which ultimately reduces NOX emissions. EGR dilution is also an attractive approach as it is compatible with the three-way catalyst for NOX control. However, previous researches focused on developing the technology rather than understanding the governing physical phenomena. Consequently, the knowledge about the characteristics and limitations of the combustion process for this ignition concept is still limited. For this purpose, an experimental campaign combined with a computational study was performed in this research work to analyze the TJI combustion features in a turbocharged passenger car-size single-cylinder SI engine, sweeping EGR and λ levels. Single-cycle RANS simulations were carried out following a suitable methodology and the results were validated against experimental data keeping the same engine configuration and operating conditions. The simulation results were used to study in detail the combustion process and jet characteristics. The analysis of the results provided a detailed insight about the key aspects limiting the passive PC ignition concept compatibility with air/EGR dilution.
Novella, Ricardo, Pastor, Jose, Gomez-Soriano, Josep, Barbery, Ibrahim, Libert, Cedric, Rampanarivo, Fano, Panagiotis, Chistou, Dabiri, Maziar
Virtual Development of Injector Spray Targeting by Coupling 3D-CFD Simulations with Optical Investigations2020-01-11574/14/2020
Further improvements of internal combustion engines to reduce fuel consumption and to face future legislation constraints are strictly related to the study of mixture formation. The reason for that is the desire to supply the engine with homogeneous charge, towards the direction of a global stoichiometric blend in the combustion chamber. Fuel evaporation and thus mixture quality mostly depend on injector atomization features and charge motion within the cylinder. 3D-CFD simulations offer great potential to study not only injector atomization quality but also the evaporation behavior. Nevertheless coupling optical measurements and simulations for injector analysis is an open discussion because of the large number of influencing parameters and interactions affecting the fuel injection’s reproducibility. For this purpose, detailed numerical investigations are used to describe the injection phenomena. These intensive calculations are not advisable considering CFD virtual engine development. It is rather reasonable to find a methodology for a numerical characterization of the fuel injection process that takes into account both macroscopic and microscopic spray properties and to integrate these models into the complete engine simulations. Based on these concepts a fast response 3D-CFD tool has been developed at IVK/FKFS Stuttgart with the purpose of reliable and time effective simulation using dedicated models for internal combustion engines. The purpose of this paper is a further development of the model and the spray simulation within the 3D-CFD-tool QuickSim, coupling optical measurements performed in a constant volume chamber and a new methodology to calibrate the simulations with a repeatable analysis of both experimental and numerical results. Axial and radial penetration curves, injection tip velocity, as well as jet angles were measured and evaluated. In addition to the investigation a PDA-system is used for detecting droplet velocities and diameters. These data were used to calibrate the injection model, enhancing the simulations’ reliability. Finally the modelled injectors were tested in a single-cylinder engine through 3D-CFD simulations, with the aim of studying the differences in the mixture formation and improving engine efficiency.
Vacca, Antonino, Hummel, Simon, Müller, Karsten, Reichenbacher, Marc, Chiodi, Marco, Bargende, Michael
Adaptive Optimal Management Strategy for Hybrid Vehicles Based on Pontryagin’s Minimum Principle2020-01-11914/14/2020
The energy management strategies (EMS) for hybrid electric vehicles (HEV) have a great impact on the fuel economy (FE). The Pontryagin's minimum principle (PMP) has been proved to be a viable control strategy for HEV. The optimal costate of the PMP control can be determined by the given information of the driving conditions. Since the full knowledge of future driving conditions is not available, this paper proposed a dynamic optimization method for PMP costate without the prediction of the driving cycle. It is known that the lower fuel consumption the method yields, the more efficiently the engine works. The selection of costate is designed to make the engine work in the high efficiency range. Compared with the rule-based control, the proposed method by the principle of Hamiltonian, can make engine working points have more opportunities locating in the middle of high efficiency range, instead of on the boundary of high efficiency range. Besides a hard and soft constraints of battery SOC are defined to balance the control of optimal costate and the working state of battery. Simulations based on the standard driving cycles are conducted to verify the FE performance. The results are compared with other control strategies to show the effect of proposed method in unknown driving condition.
Zhu, Mingliang, Wu, Xiaodong, Xu, Min
Effects on Cycle-to-Cycle Variations and Knocking Combustion of Turbulent Jet Ignition (TJI) with a Small Volume Pre-Chamber2020-01-11194/14/2020
Turbulent jet ignition (TJI) has the advantages of improving burning rates and expanding lean burn limitations of gasoline engines. Based on a single cylinder engine, combustion process with different ignition methods, including single spark ignition, twin spark ignition, one-hole TJI and seven-hole TJI, are studied in this work. Experiments are carried out under conditions with different air/fuel equivalence ratios and different engine loads. Results show that the cycle-to-cycle variations of TJI combustion, which is evaluated by coefficient of variations (CoV) of IMEP and CoV of peak pressure, are obviously reduced due to the fast burning rate induced by the jet flame, and one-hole TJI combustion has the best combustion stability, especially for reducing the CoV of peak pressure. Furthermore, under full-load conditions, pressure oscillations are observed in TJI combustion, and the intensity distribution is different from that in SI combustion, which means that the roots causing the pressure oscillations of TJI and SI are different. Pressure oscillations in TJI combustion are caused by the local fast burning rate of the hot jets, while the pressure oscillations of SI are caused by end-gas auto-ignition, which randomly happens during combustion. Under TJI knock condition, excellent combustion stability and great auto-ignition consistency can still be achieved. Considering these features of TJI combustion, a new combustion concept, jet induced compression ignition (JICI), and a different ignition method, spark combined jet ignition (SCJI), are proposed in order to organize combustion with high efficiency, stability and controllability.
Hua, Jianxiong, Zhou, Lei, Gao, Qiang, Feng, Zhonghui
Use of Butanol Blend Fuels on Diesel Engines - Effects on Combustion and Emissions2020-01-03334/14/2020
Butanol, a four-carbon alcohol, is considered in the last years as an interesting alternative fuel, both for Diesel and for gasoline application. Its advantages for engine operation are: good miscibility with gasoline and diesel fuels, higher calorific value than ethanol, lower hygroscopicity, lower corrosivity and possibility of replacing aviation fuels. Like ethanol, butanol can be produced as a biomass-based renewable fuel or from fossil sources. In the research project, DiBut (Diesel and butanol) addition of butanol to Diesel fuel was investigated from the points of view of engine combustion and of influences on exhaust aftertreatment systems and emissions. One investigated engine (E1) was with emission class “EU Stage 3A” for construction machines, another one, engine (E2) was HD Euro VI. The most important findings are: with higher butanol content, there is a lower heat value of the fuel and there is lower torque at full load. With Bu30 the conversion rates of CO and HC in the oxidation catalyst (DOC) are slightly lower, light-off temperatures are a little higher and NO2 production is lower. The PM-emissions with Bu30 are lower, so the soot loading of DPF takes a longer time. No impacts of Bu30 on NOx reduction rates of the SCR-system and on the non-legislated gaseous emission components were found. The operation of engine (E1) with Bu30 (30% vol butanol in fuel) was instable at lower part load due to the lower Cetane Number of the blend fuel. The electronic control system of the engine (E2) compensated very well the varying properties of fuels up to Bu30. For both investigated engines, the butanol rate (Bu30) can be considered as a limit for a problem-free engine starting and operation.
Engelmann, Danilo, Czerwinski, Jan, Nauroy lng, Hervé, Comte, Pierre, Hüssy lng, Andreas
CO2 Neutral Heavy-Duty Engine Concept with RCCI Combustion Using Seaweed-based Fuels2020-01-08084/14/2020
This paper focusses on the application of bioalcohols (ethanol and butanol) derived from seaweed in Heavy-Duty (HD) Compression Ignition (CI) combustion engines. Seaweed-based fuels do not claim land and are not in competition with the food chain. Currently, the application of high octane bioalcohols is limited to Spark Ignition (SI) engines. The Reactivity Controlled Compression Ignition (RCCI) combustion concept allows the use of these low carbon fuels in CI engines which have higher efficiencies associated with them than SI engines. This contributes to the reduction of tailpipe CO2 emissions as required by (future) legislation and reducing fuel consumption, i.e. Total-Cost-of-Ownership (TCO). Furthermore, it opens the HD transport market for these low carbon bioalcohol fuels from a novel sustainable biomass source. In this paper, both the production of seaweed-based fuels and the application of these fuels in CI engines is discussed. Ethanol and butanol are considered as the most viable fuels derived from seaweed. The potential of these fuels has been evaluated for the dual-fuel RCCI mode regarding efficiency and NOx emissions. The operating conditions that have been varied are mainly the fuel blend ratio (BR), fuel injection timing, and EGR rate on both a HD single-cylinder and on a HD multi-cylinder engine. The results for E85/diesel-RCCI demonstrate that CI engine-like efficiencies are feasible. The gross Indicated Thermal Efficiency (ITE) reaches up to 52% and 46.5% using E85 in a single-cylinder and a multi-cylinder engine, respectively. The first results using biomass based butanol show greater difficulty in realizing targeted efficiencies on the multi-cylinder engine due to the higher fuel reactivity and higher boiling temperature than ethanol. The gross ITE reaches up to 51.6% and 38.5% using butanol in a single-cylinder and a multi-cylinder engine, respectively. The demonstrated potential of seaweed-based fuels is an important driver for upscaling the production process of these fuels. Furthermore, future development activities will focus on improving the brake thermal efficiency of the RCCI engine running on seaweed-based fuels. Improving the low reactivity fuel-air mixture preparation will be key to achieve this.
Seykens, Xander, Bekdemir, Cemil, Han, Jinlin, Willems, Robbert, Van Hal, Jaap
Numerical Investigation of the Combustion Kinetics of Partially Premixed Combustion (PPC) Fueled with Primary Reference Fuel2020-01-05544/14/2020
This work numerically investigates the detailed combustion kinetics of partially premixed combustion (PPC) in a diesel engine under three different premixed ratio fuel conditions. A reduced Primary Reference Fuel (PRF) chemical kinetics mechanism was coupled with CONVERGE-SAGE CFD model to predict PPC combustion under various operating conditions. The experimental results showed that the increase of premixed ratio (PR) fuel resulted in advanced combustion phasing. To provide insight into the effects of PR on ignition delay time and key reaction pathways, a post-process tool was used. The ignition delay time is related to the formation of hydroxyl (OH). Thus, the validated Converge CFD code with the PRF chemistry and the post-process tool was applied to investigate how PR change the formation of OH during the low-to high-temperature reaction transition. The reaction pathway analyses of the formations of OH before ignition time were investigated. It was found that in the case of PR0%, the second isomerization from C7H14OOH2-4O2 to NC7KET24 and the decomposition of NC7KET24 contributed 27.6% and 46.46% of OH formation respectively. The contribution of AC8H16OOH-B to the formation of OH was just 12.13%. It can be concluded that the low temperature oxidation reactions of n-heptane were key steps in producing OH. While in the cases of PR30% and PR50%, because of the higher in-cylinder temperature, most of OH derived from the decomposition reaction of H2O2 that contributed 54.47% and 54.63% of OH formation respectively. Besides, in the PR30% and PR50%, the oxidation reactions of IC4H7 contributed 31.95% and 33.84% of OH formation respectively, and the oxidation reaction of IC4H6OH contributed 19.08% and 22.22% of OH formation respectively, which indicated that the oxidation of iso-octane also contributed to the production of OH. In addition, the distributions of mass fraction, production rate and representative creation reaction (RCR) of OH showed that in the case of PR30% and PR50%, the formation of OH outside the spray periphery were dominated by the reactions R394 (H2O2 (+ M) <=> 2 OH (+ M)), while that in the spray periphery were predominantly controlled by the reaction R21 (NC7KET24 => NC3H7CHO + CH3COCH2 + OH) and R125 (IC4H6OH + HO2 <=> CH2CCH2OH + CH2O + OH). Premixed fuel from port injection changed the formation pathway of OH during the oxidation of direct injection fuel through the reaction R125.
Zhao, Yuanyuan, Wang, Hu, Liu, Xinlei, Liu, Daojian, Chenchen, Wang, Zhu, Hongyan, Zheng, Zunqing, Yao, Mingfa
Potential Analysis and Virtual Development of SI Engines Operated with Synthetic Fuel DMC+2020-01-03424/14/2020
On the way to emission-free mobility, future fuels must be CO2 neutral. To achieve this, synthetic fuels are being developed. In order to better assess the effects of the new fuels on the engine process, simulation models are being developed that reproduce the chemical and physical properties of these fuels. In this paper, the fuel DMC+ is examined. DMC+ (a mixture of dimethyl carbonate (DMC) and methyl formate (MeFo) mainly, characterized by the lack of C-C Bonds and high oxygen content) offers advantages with regard to evaporation heat, demand of oxygen and knock resistance. Furthermore, its combustion is almost particle free. With the aid of modern 0D/1D simulation methods, an assessment of the potential of DMC+ can be made. It is shown that the simulative conversion of a state-of-the-art gasoline engine to DMC+ fuel offers advantages in terms of efficiency in many operating points even if the engine design is not altered. This is mainly due to the higher knock resistance and the lower temperatures in the intake stroke resulting from the higher amount of evaporated fuel. For a fixed amount of fuel energy, a lower air mass flow rate is needed, making the fuel particularly interesting for down-sizing concepts. Therefore, the engine design is adapted for the new fuel to take full advantage of the fluid properties. In a first step, the adaptions include the compression ratio, the engine displacement and the turbocharger matching. A considerable efficiency gain in the whole operating range can be demonstrated, making DMC+ a highly promising prospective for future SI engines.
Wagner, Cornelius, Grill, Michael, Keskin, Mahir-Tim, Bargende, Michael, Cai, Liming, Pitsch, Heinz
Influence of Nozzle Opening Pressure, Fuel Injection Timing and Compression Ratio on the Performance of Compression Ignition Engine Fueled with Biodiesel-Diesel-Butanol Blends2020-01-02994/14/2020
Biodiesel from vegetable waste can be utilized as fuel for compression ignition engine. This experimental study used biodiesel extracted from the cauliflower outer leaves and butanol from vegetable waste as property enhancer to fuel the diesel engine. This study consists of two stages: Solubility and properties test of various proportions of diesel biodiesel butanol blends to obtain an optimal fuel blend that possesses closer properties to that of diesel; followed by testing the optimal blend in a modified engine for nozzle opening pressure (180, 190, 200 and 210 bar), fuel injection timing (23, 26, 29 and 320 before top dead centre) and compression ratio (16: 1, 17.5:1, 19:1 and 20.5:1). The optimal level of these parameters was attained using L16 orthogonal array and Taguchi method. Test results showed that the blend containing 40% biodiesel 20% diesel and 40% butanol can be used as fuel for diesel engine. The diesel engine was operated under 210 bar of nozzle opening pressure, 260before top dead center of fuel injection timing and 19:1 of compression ratio. This optimal blend produced closer brake thermal efficiency, in-cylinder peak pressure, peak heat release rate, ignition delay, and combustion duration which were found to be similar compared to that of diesel (above 40% of rated power). The emissions produced by this blend were found lower compared to that of diesel operated at higher brake power condition (above 50% of rated power). This study enables to utilize the waste vegetables and renewable resources to fuel diesel engine and replacing the diesel to a certain extent.
B, Prabakaran
Motor Vehicle Emission Control Quality Monitoring for On-Road Driving: Dynamic Signature Recognition of NO x & NH 3 Emissions2020-01-03724/14/2020
Motor vehicle emission testing during on-road driving is important to assess a vehicle’s exhaust emission control design, its compliance with Federal regulations and its impact on air quality. The U.S. Environmental Protection Agency (EPA) has been developing new approaches to screen the characteristics of vehicle dynamic emission control behaviors (its operating signature) while driving both on-road and on-dynamometer. The so-called “signature device” used for this testing is equipped with an O2/NOx sensor, thermocouple and GPS to record dynamic exhaust NOx concentration, air fuel ratio-controlled tailpipe lambda (λ), tailpipe temperature and vehicle speed (acceleration). In the early EPA research, signature screening was used to characterize a vehicle’s PCM control behaviors (cause/effect bijectivity), which help distinguish operation in normal control state-space and abnormal state-space. Currently, signature devices are being used to recognize when ammonia (NH3) has been emitted and to estimate the presence of NOx and NH3 within on-road and on-dyno driving. The presence of NH3 is observed by the signature device’s NOx sensor at times when tailpipe lambda readings are biased rich, after the engine three-way-catalyst (TWC) has warmed up. To study the production of NH3, EPA established a vehicle test program to gather and evaluate the emissions from on-road driving conditions. The same driving conditions were then replicated on an indoor chassis dynamometer (dyno) while using a bag analyzer bench, a raw exhaust modal bench, and a signature device to measure vehicle emissions and control behaviors. EPA ascertained, under certain operating conditions, that stoichiometric engine exhaust passing through a TWC can create hydrogen (CO+H2O→H2), which is then available to produce unregulated ammonia (CO+NO+H2→NH3). These reactions can accelerate when the engine operates with slightly rich-biased lambda introduced either by control or by calibration design. Under current Light-Duty Tier 3 emission regulations, NOx and NMOG emissions are counted together, creating an “opportunity” for more of this type of engine operation.
Tang, Xiaoguo, Kargul, John, McBryde, Dan
Transition from HCCI to PPC: Investigation of the Effect of Different Injection Timing on Ignition and Combustion Characteristics in an Optical PPC Engine2020-01-05594/14/2020
The partially premixed combustion (PPC) concept is regarded as an intermediate process between the thoroughly mixed Homogeneous charge compression ignition (HCCI) combustion and compression ignition (CI) combustion. It’s a combination of auto-ignition mode, a fuel-rich premixed combustion mode, and a diffusion combustion mode. The concept has both high efficiency and low soot emission due to low heat losses and less stratified fuel and air mixtures compared to conventional diesel CI. The mechanisms behind the combustion process are not yet very well known. This work focuses on the efficiency and the in-cylinder process in terms of fuel distribution and the initial phase of the combustion. More specifically, double injection strategies are compared with single injection strategies to achieve different levels of stratification, ranging from HCCI to PPC like combustion as well as poor (43%) to good (49%) of gross indicated efficiency. The experiments were performed in an optical heavy-duty CI engine. To analyze how the efficiency was affected in a transition from HCCI to PPC, the natural luminosity (N.L.) was captured with high-speed video (HSV). To complement the HSV data, fuel, temperature, and oxygen distribution were explored by Computational fluid dynamics (CFD) simulation. The results show that the jet-jet and jet-piston interactions can be modified and can reshape the transition trends of gross indicated efficiency and ignition location compared to a single injection. In the transition region, these interactions can improve the efficiency by shaping the fuel-rich region away from cold areas, like the vertical wall of the piston and the squish region, to avoid fuel wetting and incomplete combustion. However, with double injections in the piston bowl (PPC region), jet-jet interaction can unfortunately inhibit the mixing process of the second fuel jet and oxygen due to interaction with the fuel rich region from the first injection, ending up with a lower combustion efficiency.
Zhang, Miao, Derafshzan, Saeed, Xu, Leilei, Bai, Xue-Song, Richter, Mattias, Lundgren, Marcus
Impact of the Injection Strategy on Soot Reactivity and Particle Properties of a GDI Engine2020-01-03924/14/2020
The gradual global tightening of emission legislation for particulate matter emissions requires the development of new gasoline engine exhaust aftertreatment systems. For this reason, the development of gasoline direct injection engines aims at the reduction of particulate emissions by application of a Gasoline Particulate Filter (GPF). The regeneration temperature of GPF depend on soot reactivity towards oxidation and therefore on particle properties. In this study, the soot reactivity is correlated with nanostructural characteristics of primary gasoline particles as a function of specific engine injection parameters. The investigations on particle emissions were carried out on a turbocharged 4-cylinder GDI-engine that allows the variation of injection parameters. The emitted engine soot particles have been in-situ characterized towards their number and size distribution using an engine exhaust particle sizer (EEPS). Ex-situ analytics focuses on the analysis of oxidation kinetics and the nanostructural characteristics affecting soot reactivity significantly. The oxidation kinetics were determined by temperature programmed oxidation (TPO) employing thermogravimetric analysis (TGA). The temperature at the maximum of the reaction rate is referred to Tmax, where low temperatures are linked to high reactivity. In addition, the nanostructure analysis of primary particles (graphene layer length, tortuosity and separation distance) was also investigated by using high resolution transmission microscopy (HRTEM) and an image analysis algorithm. Findings from this work show that soot reactivity relies significantly on the quality of mixture formation of a GDI engine depending on injection strategy. These findings are in very good agreement with the nanostructural parameters obtained by high-resolution transmission electron microscopy. Soot particles formed in a relatively homogeneous air/fuel mixture due to optimized injection parameters show a high soot reactivity (Tmax ≈ 525°C) and an amorphous carbon nanostructure. Such primary particles are characterized by short mean graphene layer length (Lmean ≈ 0.5 nm) and an unordered configuration resulting in an increased separation distance (Dmean ≈ 1 nm). In addition, approximately a comparable number of small (Dp ≈ 5...25 nm) and large particles (Dp ≈ 30...100 nm) are generated. Conversely, inhomogeneous mixtures result in increased formation of primary particles showing long, extended and more ordered graphene (Lmean ≈ 0.55 nm, Dmean = 0.4 nm), which in turn lead to low soot reactivity (Tmax ≈ 615°C).
Koch, Sergej, Kubach, Heiko, Velji, Amin, Koch, Thomas, Hagen, Fabian P., Bockhorn, Henning, Loukou, Alexandra, Trimis, Dimosthenis, Suntz, Rainer
Impact of Multiple Injection Strategies on Performance and Emissions of Methanol PPC under Low Load Operation2020-01-05564/14/2020
There is growing global interest in using renewable alcohols to reduce the greenhouse gases and the reliance on conventional fossil fuels. Recent studies show that methanol combined with partially premixed combustion provide clear performance and emission benefits compared to conventional diesel diffusion combustion. Nonetheless, high unburned hydrocarbon (HC) and carbon monoxide (CO) emissions can be stated as the main PPC drawback in light load condition when using high octane fuel such as Methanol with single injection strategy. Thus, the present experimental study has been carried out to investigate the influence of multiple injection strategies on the performance and emissions with methanol fuel in partially premixed combustion. Specifically, the main objective is to reduce HC, CO and simultaneously increase the gross indicated efficiency compared to single injection strategy. The work was performed with a single cylinder heavy duty engine, operated at 4 bar gross indicated mean effective pressure, and an engine speed of 1200 rpm. Double and triple injections were implemented with varying dwells, injection timings and fuel mass proportions. The experimental results were analyzed with a merit function to select the optimal injection strategy. Concerning emissions, the constraints for the merit function were based on the EURO VI limits, while the highest gross indicated efficiency for single injection was used to define the performance constraint. The results revealed that with proper dwell and mass proportion, multiple injection strategies can improve the gross indicated efficiency and reduce the emissions compare to single injection strategy.
Aziz, Amir, Garcia, Antonio, Pinto Dos Santos, Clarisse, Tuner, Martin
Control of Ignition Timing and Combustion Phase by Means of Injection Strategy for Jet-Controlled Compression Ignition Mode in a Light Duty Diesel Engine2020-01-05554/14/2020
Controllability of ignition timing and combustion phase by means of dual-fuel direct injection strategy in jet-controlled compression ignition mode were investigated in a light-duty prototype diesel engine. Blended fuel with lower reactivity was delivered in the early period of compression stroke to form the premixed charge, while diesel fuel which has higher reactivity was injected near TDC to trigger the ignition. The effects of several important injection parameters including pre-injection timing, jet-injection timing, pre- injection pressure and ratio of pre-injection in the total heat value of injected fuel were discussed. Numerical Simulation by using CFD software was also conducted under similar operating conditions. The experimental results indicate that the jet-injection timing shows robust controllability on the start of combustion under all the engine load conditions. Pre-injection timing/pressure/ratio show little impact on the start of combustion due to low reaction activity of premixed charge. Early pre-injection timing and larger pre-injection pressure lead to wall-wetting and poor vaporization of pre-injected fuel especially at light duty conditions, as a result, combustion duration increases, and CO/THC emissions enhance. Larger pre-injection ratio in the total heat value of injected fuel prolongs combustion duration and enhances CO/THC emissions at lower engine load, reduces combustion duration and CO/THC emissions at higher engine load. The numerical simulation results demonstrate the two-stage combustion process described according to the experimental results. The two-stage combustion process of diesel jet JCCI mode is featured by the evolution of intermediate species such as H2O2 and OH, and the main emission products such as CO and NOx. At last, the effects of injection parameters on JCCI combustion characteristics are summarized.
Zhu, Jingyu, Bo, Li, Long, Wuqiang
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