Browse Topic: Exhaust valves

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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
Dynamic Exhaust Valve Flow 1-D Modelling During Blowdown Conditions2019-01-00581/15/2019
To conduct system level studies on internal combustion engines reduced order models are required in order to keep the computational load below reasonable limits. By its nature a reduced order model is a simplification of reality and may introduce modeling errors. However what is of interest is the size of the error and if it is possible to reduce the error by some method. A popular system level study is gas exchange and in this paper the focus is on the exhaust valve. Generally the valve is modeled as an ideal nozzle where the flow losses are captured by reducing the flow area. As the valve moves slowly compared to the flow the process is assumed to be quasi-steady, i.e. interpolation between steady-flow measurements can be used to describe the dynamic process during valve opening. These measurements are generally done at low pressure drops, as the influence of pressure ratio is assumed to be negligible. As it is very difficult to measure time-resolved mass flow it is hard to test validity of these modeling assumptions. Experimental data indicates that the model overestimates valve flow during the blowdown event. As the blowdown pulse contains a significant portion of the energy in the cylinder at exhaust valve opening, it is therefore of importance to model this correctly. In this paper experimental results from previously published research have been compared to simulation results and the deviation from quasi-steady behavior has been quantified. The deviation appears to be a function of pressure ratio over the valve and valve opening speed. A model is proposed to compensate for the observed effects.
Holmberg, Ted, Cronhjort, Andreas, Stenlaas, Ola
Design and Development of a Roller Follower Hydraulic Lash Adjustor to Eliminate Lash Adjustment and Reduce Noise in a Serial Production Diesel Engine2018-01-17669/10/2018
Commercial vehicles require continual improvements in order to meet fuel emission standards, improve diesel aftertreatment system performance and optimize vehicle fuel economy. Aftertreatment systems require significant space claim which makes vehicle packaging a challenge. Today’s diesel engines require valvetrain lash adjustment settings at distinct intervals to ensure proper valvetrain performance. This requires removing the engine rocker cover to access the valvetrain rocker arms for setting lash. Setting lash for compact vehicle applications sometimes requires removing the aftertreatment system to provide access to the rocker cover prior to setting lash. Then, the rocker cover is reinstalled followed by the aftertreatment system making the lash setting process time consuming and complex. This paper focuses on the design, development and validation of adapting hydraulic lash adjusters (HLAs) into a type V (camshaft in block) diesel engine thus eliminating the lash adjustment process. The flat mechanical tappets were replaced with roller follower HLAs on both the intake and exhaust valves. The roller was included to reduce valvetrain friction over flat tappets. An anti-rotation design was included to maintain alignment between the roller and the camshaft. A major advantage of using the HLA was reduced engine valvetrain noise. Minor engine block changes were required to accommodate the roller follower HLAs. The HLA design ensured reliable and repeatable valve motion from engine build thru cold start and normal engine operation over the useful life of the engine. Reliability was key for the roller follower HLA as it is embedded inside the block which makes replacement impractical. This paper highlights the major design aspects for including roller follower HLAs in a type V diesel engine.
Roberts, Leighton, McCarthy, Jr., James
The Fuel Economy Improvement through the Knock Margin Expansion in a Turbocharged Gasoline Direct Injection Engine2018-01-16719/10/2018
Knocking combustion limits the downsized gasoline engines’ potential for improvement with regard to fuel economy. The high in-cylinder pressure and temperature caused by the adaptation of a turbocharger aggravates the tendency of the end-gas to autoignite. Thus, the knocking combustion does not allow for further advancing of the combustion phase. In this research, the effects of the ignition and valve timings on knocking combustion were investigated under steady-state conditions. Moreover, the optimal ignition and valve timings for the transient operations were derived with the aim of a greater fuel economy improvement, based on the steady-state analysis. A 2.0 liter turbocharged gasoline direct injection engine with continuously variable valve timing (CVVT), was utilized for this experiment. 2, 10, and 18 bar brake mean effective pressure (BMEP) load conditions were used to represent the low, medium, and high load operations, respectively. The engine speed was set at 1,500 RPM since the low speed conditions were more vulnerable to knocking combustion than the high speed conditions. Both the intake and the exhaust valve timings were controlled from the reference timings in a step of 10 crank angle degrees (CAD). The ignition timing was also controlled in a similar manner, but only with 1.5 CAD steps. The experimental result showed that reducing the exhaust backpressure by increasing the wastegate opening level was effective in expanding the knock margin. This was mainly owing to the enhanced scavenging driving force created by the increased wastegate opening. During the transient operation, increasing the wastegate opening by maximally advancing the exhaust valve timing was shown to be an effective procedure in this case. With the maximized advance, sufficient exhaust energy was supplied to the turbocharger such that less amount of exhaust flow was required. Thus, the greater wastegate opening could be achieved, which enhanced the scavenging process. As a result, the ignition timings were advanced beyond the previous knock margins. With the use of this procedure, torque output and fuel consumption were improved by a maximum of 3.3% and 2.4%, respectively.
Shin, Ji Yong, Park, Chansoo, Jung, Jinyoung, Bae, Choongsik
Divided Exhaust Period Implementation in a Light-Duty Turbocharged Dual-Fuel RCCI Engine for Improved Fuel Economy and Aftertreatment Thermal Management: A Simulation Study2018-01-02564/3/2018
Although turbocharging can extend the high load limit of low temperature combustion (LTC) strategies such as reactivity controlled compression ignition (RCCI), the low exhaust enthalpy prevalent in these strategies necessitates the use of high exhaust pressures for improving turbocharger efficiency, causing high pumping losses and poor fuel economy. To mitigate these pumping losses, the divided exhaust period (DEP) concept is proposed. In this concept, the exhaust gas is directed to two separate manifolds: the blowdown manifold which is connected to the turbocharger and the scavenging manifold that bypasses the turbocharger. By separately actuating the exhaust valves using variable valve actuation, the exhaust flow is split between two manifolds, thereby reducing the overall engine backpressure and lowering pumping losses. In this paper, results from zero-dimensional and one-dimensional simulations of a multicylinder RCCI light-duty engine equipped with DEP are presented. It is shown that while DEP helped reduce pumping penalty at medium and high loads, the pumping benefit was negated by crankshaft power consumption from a mechanical supercharger which made up for the boost deficit as the low exhaust enthalpy could not be efficiently utilized by a fixed geometry turbocharger (FGT). However, by replacing the FGT with a variable geometry turbocharger (VGT), a 1% improvement in brake-specific fuel consumption (BSFC) over the stock engine configuration was observed at high load, as the VGT allowed more efficient exhaust energy utilization through aspect ratio adjustment. In addition, by closing the blowdown valve at low load, higher exhaust gas temperatures were obtained by bypassing the turbocharger and thereby eliminating exhaust heat losses, which would be useful for aftertreatment thermal management.
Bharath, Anand Nageswaran, Reitz, Rolf, Rutland, Christopher
Divided-Exhaust Turbocharger System with Boost-Valve2018-01-08954/3/2018
In a divided-exhaust turbocharging system, 1 exhaust valve and port from each cylinder can be directed to the turbocharger turbine (referred to as the Blowdown Path) and the other can bypass the turbocharger (referred to as the Scavenge Path). The Blowdown and Scavenge valve events are determined based on the functions of the blowdown and displacement phases of the exhaust process. In our previous publications of another version of Divided Exhaust Period Turbocharging, the Valve Event Modulated Boost system (VEMB), we demonstrated significant engine efficiency and performance improvements over the base turbocharged engine. Reductions in pumping work and high-load Residual Gas Fraction are the primary reasons for efficiency and performance improvements. In this project we have evaluated through simulation and engine testing, the further advantages of the Divided-Exhaust-Boost (DEB) system version of Divided Exhaust Boosting; a version that does not require a concentric-camshaft for boost control. This system retains the previously-reported very large improvement in catalyst light-off performance, which is to be expected from a system that can completely remove the turbocharger from the exhaust pathway during the cold-start period.
Roth, David B., Chen, Wei, Ciaravino, Joseph
Cylinder Pressure Based Cylinder Charge Estimation in Diesel Engines with Dual Independent Variable Valve Timing2018-01-08624/3/2018
With stricter emission legislations and demands on low fuel consumption, new engine technologies are continuously investigated. At the same time the accuracy in the over all engine control and diagnosis and hence also the required estimation accuracy is tightened. Central for the internal combustion control is the trapped cylinder charge and composition Traditionally cylinder charge is estimated using mean intake manifold pressure and engine speed in a two dimensional lookup table. With the introduction of variable valve timing, two additional degrees of freedom are introduced that makes this approach very time consuming and therefore expensive. Especially if the cam phasers are given large enough authority to offer powerful thermal management possibilities. The paper presents a physical model for estimating in-cylinder trapped mass and residual gas fraction utilizing cylinder pressure measurements, and intake and exhaust valve lift profiles. The cylinder pressure at intake and exhaust valve opening and closing together with manifold pressures and temperatures are combined with thermodynamic and heat transfer models to calculate the trapped cylinder mass. The estimator is validated on test data from a prototype engine with dual independent cam phasers under a wide range of operating conditions, including large variations in valve timing ranging from scavenging to early exhaust cam timing for thermal management. The main contribution is the developed model, with the ability to accurately estimate the trapped cylinder charge during large independent variations in both intake and exhaust valve timing.
Thomasson, Andreas, Nikkar, Sepideh, Höckerdal, Erik
Sodium Cooling Efficiency in Hollow Valves for Heavy Duty Engines2018-01-03684/3/2018
As a consequence of the ongoing evolution of engines, where performance is continuously improving and the use of alternative fuels is being adopted by many engine manufacturers, thermal working conditions of the exhaust valves are increasingly critical. In order to better resist the higher temperature levels of the exhaust gases, current development ranges from improvement of the cooling concept for the overall system, new materials for valve set components up to the upgrade of the exhaust manifold material. Change in the design of several valvetrain components due to the increased thermal loads is a logical consequence of this technical evolution process. Hollow exhaust valves filled with Sodium (Na) are a known technology that is widely used in passenger car engines to improve thermal behavior and to avoid the need to change to expensive materials (Ni-base alloys). Nevertheless, shaker-cooling effect of Na for engine speeds below 3.000 [rpm] has been questioned in the past and this technology has not been fully explored in heavy duty (HD) applications [1]. In order to investigate the thermal efficiency or effectiveness and to confirm Na-filled valves as a potential technical solution for thermal issues in HD engines, back-to-back analyses (FEA) and tests (temperature measurements and endurance) were performed, mainly focused on heavy duty spark ignition (SI) engines (gas fueled) and on severe applications of diesel engines.
Zenklusen, Fernando, Coenca, Marcio, Puck, Alexander
Variable Valve Actuation Strategies for Better Efficiency Load Range and Thermal Management in an RCCI Engine2018-01-02544/3/2018
The Reactivity Controlled Compression Ignition concept for dual-fuel engines has multiple challenges of which some can be overcome using Variable Valve Actuation approaches. For various fuel combinations, the engine research community has shown that running dual-fuel engines in RCCI mode, improves thermal efficiency and results in ultra-low engine-out nitrous oxides and soot. However, stable RCCI combustion is limited to a certain load range, depending on available hardware. At low loads, the combustion efficiency can drop significantly, whereas at high loads, the maximum in-cylinder pressure can easily exceed the engine design limit. In this paper, three VVA measures to increase load range, improve combustion efficiency, and perform thermal management are presented. Simulation results are used to demonstrate the potential of these VVA measures for a heavy-duty engine running on natural gas and diesel. First, TNO’s multi-zonal combustion model is introduced and validated using experimental data from a multi-cylinder heavy-duty engine operated in RCCI mode with variable intake timing. This combustion model is used in conjunction with a commercial zero-dimensional engine simulation tool to examine three different VVA strategies, each with its own advantage: 1 Early intake valve closing for extending high load range 2 Late intake valve opening for improved combustion efficiency at low load 3 Exhaust valve double lift for improved combustion efficiency and thermal management (better after-treatment efficiency). The latter two are especially important for dual-fuel engines using natural gas since they offer an effective means for CH4 slip reduction. It is shown that thanks to these measures, a heavy-duty engine can run with natural gas - diesel RCCI in the full load range and that significant CH4 reduction towards Euro VI limits is possible. The paper is concluded with an outlook on options to achieve these goals successfully on a real engine.
Mikulski, Maciej, Balakrishnan, Praveen Ramanujam, Doosje, Erik, Bekdemir, Cemil
Eaton goes internal with its next-generation EGR solution18AUTP08_051/1/2018
Eaton's Internal Exhaust Gas Recirculation (iEGR) solution production-debuts in the 2020MY as a next-generation technology providing near-instantaneous heating of the selective catalytic reduction system to reduce diesel exhaust emissions. “The iEGR technology is controlled by an electro-mechanical actuator, so operation can occur in cold conditions,” Nicola Andrisani, Eaton's Engineering Manager of the Valvetrain Advanced Engineering Vehicle Group based in Torino, Italy, said in an Automotive Engineering interview.
Buchholz, Kami
Numerical Analysis of Scavenging Process in a Large Marine Two-Stroke Diesel Engine2017-01-220110/8/2017
For uniflow scavenged two-stroke marine diesel engines, the main function of scavenging process is to replace the burned gas with fresh charge. The end state of scavenging process is integral to the subsequent compression and combustion, thereby affecting the engine’s fuel economy, power output and emissions. In this paper, a complete working cycle of a large marine diesel engine was simulated by using the 3D-CFD software CONVERGE. The model was validated by mesh sensitivity test and experiment data. Based on this calibrated model, the influences of swirl ratio and exhaust valve closing (EVC) timing on the scavenging process were investigated. The parameters evaluating the performance of scavenging process were introduced. The results show that, by adjusting the swirl orientation angle(SOA) from SOA=10° to SOA=30°, different swirl ratios are generated and have obvious differences in flow characteristics and scavenging performance. Advancing or delaying the EVC has limited effects on scavenging efficiency, but have obvious effects on the retaining and charging efficiency. In addition, adjusting the EVC timings also have obvious effects on the in-cylinder pressure and temperature, thus affecting the engine’s fuel economy and emission.
Cao, Zhongye, Wang, Tianyou, Sun, Kai, Cui, Lei, Gui, Yong
Modeling of Phase Change within a Wax Element Thermostat Embedded in an Automotive Cooling System2017-01-01313/28/2017
In an automotive cooling circuit, the wax melting process determines the net and time history of the energy transfer between the engine and its environment. A numerical process that gives insight into the mixing process outside the wax chamber, the wax melting process inside the wax chamber, and the effect on the poppet valve displacement will be advantageous to both the engine and automotive system design. A fully three dimensional, transient, system level simulation of an inlet controlled thermostat inside an automotive cooling circuit is undertaken in this paper. A proprietary CFD algorithm, Simerics-Sys®/PumpLinx®, is used to solve this complex problem. A two-phase model is developed in PumpLinx® to simulate the wax melting process. The hysteresis effect of the wax melting process is also considered in the simulation. The physics captured in the simulation includes the turbulent flow out of the coolant pump, turbulent mixing, heat transport, and rigorous treatment of Fluid Structure Interaction (FSI) of the circuit with the dynamic valves in the system. Two different operating sets of data are used for the analysis, case A, lower engine speed and case B, higher engine speed. The details of the model setup and the comparisons of the simulation results with experimental data are discussed in the paper.
Srinivasan, Chiranth, Zhang, Chonglin, Gao, Haiyang, Wang, De Ming, Slike, Jody
Simulation of Subcooled Flow Boiling on Engine Cooling Jacket with a Bubble Waiting Time Coefficient Model2017-01-01393/28/2017
The objective of this present research is to investigate the influence of bubble waiting time coefficient on subcooled flow boiling heat transfer in internal combustion engines and propose an approach to predict its value. The three-dimension simulated cooling jacket structure of valve bridges for forced water-cooling system was developed respectively. The numerical model for subcooled flow boiling based on two-fluid approach was established and calculated. Numerical results suggest that the bubble departure diameter increases with the increasing wall superheat or decreasing inlet subcooling. And the proportion of the quenching heat flux gradually rises and its peak value is delayed along the direction of the higher wall superheat when the subcooling degree increases. The bubble waiting time coefficient has been found to have a significant impact upon the boiling heat transfer. A prediction model of bubble waiting time coefficient was presented with the verification of Abou-Ziyan’s experimental results. The two-phase subcooled flow boiling model with considering bubble waiting time coefficient may be well applicable to boiling simulation on engine cooling jacket. Finally, the modified boiling model can be used in the calculation of the boiling heat transfer of actual cylinder head. It clearly shows that the calculated temperature is more close to the experimental value with correction in boiling heat transfer area such as bridge zone of exhaust valve and injector nozzle. The maximum deviation of the experimental temperature decreases by 4.61%. While in the areas without boiling, the deviation changes a little with correction.
Dong, Fei, Hou, Liuwendi, Xu, Zhenlong, Cao, TaoTao
Pressure Ratio Influence on Exhaust Valve Flow Coefficients2017-01-05303/28/2017
In one dimensional engine simulation software, flow losses over complex geometries such as valves and ports are described using flow coefficients. It is generally assumed that the pressure ratio over the valve has a negligible influence on the flow coefficient. However during the exhaust valve opening the pressure difference between cylinder and port is large which questions the accuracy of this assumption. In this work the influence of pressure ratio on the exhaust valve flow coefficient has been investigated experimentally in a steady-flow test bench. Two cylinder heads, designated A and B, from a Heavy-Duty engine with different valve shapes and valve seat angles have been investigated. The tests were performed with both exhaust valves open and with only one of the two exhaust valves open. The pressure ratio over the exhaust port was varied from 1.1:1 to 5:1. For case A1 with a single exhaust valve open, the flow coefficient decreased significantly with pressure ratio. This trend was not replicated for the other single valve case B1, as pressure ratio only had a small influence on the flow coefficient. For the twin valve case A2, the pressure ratio influence was confined to the lower range of valve lifts as the limiting factor was the exhaust port outlet at higher valve lifts. The flow coefficient for the twin valve case B2 increased with pressure ratio in the mid-range of valve lifts.
Holmberg, Ted, Cronhjort, Andreas, Stenlaas, Ola
DigitalAir ™ Camless FVVA System - Part 2, Gasoline Engine Performance Opportunities2017-01-06413/28/2017
The paper describes a completely new approach to fully variable valve actuation (FVVA), which allows almost unlimited continuously variable control of intake and exhaust valve opening and closing events, and duration without the use of a camshaft. DigitalAir replaces conventional poppet valves with horizontally actuated valves located directly above the combustion deck of the cylinder head, which open and close a number of slots connecting the cylinder with the intake and exhaust ports, Figure 1. The stroke of the valves to provide the full flow area is approximately 25% of the stroke of the equivalent poppet valve, thus allowing direct electrical actuation with very low power consumption. This design arrangement also avoids the risk of poppet valve to piston collision, or the need for cut-outs in the piston crown, since the valves do not open into the cylinder. The paper will present analytical and experimental data which confirms that the proposed FVVA system can meet the basic performance requirements of modern GDI engines with respect to breathing characteristics across the speed range, throttleless operation at and above idle, opening and closing event optimization, cylinder deactivation, control of residual gas fraction / scavenging and exhaust thermal management. Analytical results were developed using GT-POWER Cycle Simulation and CONVERGE computational fluid dynamics (CFD). Cycle simulation was used to study the system level performance, such as full load capability and transient response, and in particular to quantify the fuel consumption benefits of throttleless operation. CFD was used to better understand the opportunities for in-cylinder charge motion - tumble, swirl and turbulence. JP SCOPE Inc. has been running experimental engines with DigitalAir for several years and has successfully completed performance and durability tests. The mechanical and thermal design of the cylinder head, and the design of the actuator will be covered in Part 1 of this paper [1].
Charlton, Stephen J., Price, Charles E., Rogers, Jeff, Turner, James W.G., Wijetunge, Roshan S., Anderson, William
DigitalAir™ Camless FVVA System – Part 1, Valve Train Design, Capability and Performance2017-01-06353/28/2017
This paper provides an overview of the analysis and design of the DigitalAir™ camless valve train including the architecture and design of the valve and head; the details of the electric valve actuator, and the flow characteristics of the valves and resulting charge motion in a motoring engine. This valve train is a completely new approach to fully variable valve actuation (FVVA), which allows almost unlimited continuously variable control of intake and exhaust valve timing and duration without the use of a camshaft. This valve train replaces conventional poppet valves with horizontally actuated valves located above the combustion deck. As the valves move, they open and close a number of slots connecting the cylinder with the intake and exhaust ports. The valve stroke necessary to provide the full flow area is approximately 25% of the stroke of the equivalent poppet valve, thus allowing direct electrical actuation with very low power consumption. This design arrangement avoids the risk of poppet valve to piston collision, or the need for cut-outs in the piston crown, since the valves do not open into the cylinder. The results from the analytical models used to predict the performance of the valve train are presented and compared with experimental data (when available). JP SCOPE Inc. has been running engines with this valve train for several years and has successfully completed preliminary performance and durability tests. Part 2 of this paper [1] will present analytical and experimental data which confirms that the proposed FVVA system can meet the basic performance requirements of modern GTDI engines.
Babbitt, Guy, Rogers, Jeff, Weyer, Kristina, Cohen, Drew, Charlton, Stephen
Development of Heat Resistant Titanium Alloy for Exhaust Valves Applicable for Motorcycles2016-32-002311/8/2016
Amidst of the recent concerns on depletion of natural resources, a new heat resistant titanium alloy has been developed using the minimum amount of rare metals. Using Ti-811 as a basis and modifying the alloy composition to Ti-7Al-2Mo-0.2Si-0.15C-0.2Nb, the mechanical property, the creep resistance and the oxidation resistance at high temperatures are improved. At the same time, with the β transformation point shifted to a higher temperature, the hot formability is also improved. The newly developed alloy has made it possible to expand the application of titanium material to exhaust valves in reciprocating engines.
Kasatori, Shinji, Marui, Yuji, Oyama, Hideto, Ono, Kosuke
A Numerical Study on Combustion and Emission Characteristics of Marine Engine through Miller Cycle Coupled with EGR and Water Emulsified Fuel2016-01-218710/17/2016
The combustion in low-speed two-stroke marine diesel engines can be characterized as large spatial and temporal scales combustion. One of the most effective measures to reduce NOx emissions is to reduce the local maximum combustion temperature. In the current study, multi-dimensional numerical simulations have been conducted to explore the potential of Miller cycle, high compression ratio coupled with EGR (Exhaust Gas Recirculation) and WEF (water emulsified fuel) to improve the trade-off relationship of NOx-ISFC (indicated specific fuel consumption) in a low-speed two-stroke marine engine. The results show that the EGR ratio could be reduced combined with WEF to meet the Tier III emission regulation. The penalty on fuel consumption with EGR and WEF could be offset by Miller cycle and high geometric compression ratio. NOx can be reduced by 81.1% without penalty on fuel economy by using retarded exhaust valve closing timing (20°CA later) combined with 20% EGR and 40% W/F (the ratio of water and fuel), which can meet the Tier III emission regulation.
Liu, Haifeng, Zhang, Huixiang, Wang, Hu, Zou, Xian, Yao, Mingfa
Development of Combustion System for a 1-Liter Advanced Turbocharged Gasoline Direct Injection 3-Cylinder Engine2016-01-224310/17/2016
In recent years, more attention has been focused on environment pollution and energy source issues. As a result, increasingly stringent fuel consumption and emission legislations have been implemented all over the world. For automakers, enhancing engine’s efficiency as a must contributes to lower vehicle fuel consumption. To reach this goal, Geely auto started the development of a 3-cylinder 1.0L turbocharged direct injection (TGDI) gasoline engine to achieve a challenging fuel economy target while maintaining fun-to-drive and NVH performance. Demanding development targets for performance (specific torque 205Nm/L and specific power 100kW/L) and excellent part-load BSFC were defined, which lead to a major challenge for the design of the combustion system. Considering air/fuel mixture, fuel wall impingement and even future potential for lean burn combustion, a symmetrical layout and a central position for the injector with 200bar injection pressure was determined. For the injector, several spray pattern proposals were investigated using CFD. The top-3 best ones were extensively tested on engine dyno, taking injector aging into account. Comparing pre-ignition events, oil dilution, combustion stability and especially particulate number (PN) emission, a 5-hole injector was finally selected. Dual cam phasers were introduced to optimize intake and exhaust valve timing to reduce pumping losses and consequently improve fuel economy. To ensure performance output and responsiveness, an efficient but with very low inertia turbocharger was well mated. As a result, thanks to superior combustion system design and low friction optimization, excellent fuel economy was realized. For instance, BSFC at 2000rpm/2bar BMEP was only around 360g/kWh, which represents new benchmark in the database. Compared to the predecessor a 1.3L TC PFI engine, 13.7% fuel consumption reduction was achieved in the NEDC cycle.
Yang, Chen, Cheng, Haiyuan, Fan, Zizhu, Yin, Jiandong, Shen, Yuan, Haubner, Frank, Slotman, Jeroen, Seibel, Joerg, Baer, Stephan
Fast Exhaust Nephelometer (FEN): A New Instrument for Measuring Cycle-Resolved Engine Particulate Emission2016-01-232910/17/2016
Soot emissions from direct-injection engines are sensitive to the fuel-air mixing process, and may vary between combustion cycles due to turbulence and injector variability. Conventional exhaust emissions measurements cannot resolve inter- or intra-cycle variations in particle emissions, which can be important during transient engine operations where a few cycles can disproportionately affect the total exhaust soot. The Fast Exhaust Nephelometer (FEN) is introduced here to use light scattering to measure particulate matter concentration and size near the exhaust port of an engine with a time resolution of better than one millisecond. The FEN operates at atmospheric pressure, sampling near the engine exhaust port and uses a laser diode to illuminate a small measurement volume. The scattered light is focused on two amplified photodiodes. Proof-of-concept tests were conducted on a heavy-duty single-cylinder research engine using a Westport high-pressure direct-injection (HPDI) natural gas fuel system. For this engine, the particulate emissions are dominated by soot at high loads, as they would be for a conventional diesel engine. When tested on the diluted exhaust, the FEN shows a close linear correlation with a commercial light-scattering instrument (DustTrakTM DRX 8533). Undiluted PM measurements close to the exhaust port show a spike (several times the average) after the exhaust valve opens; the signal then drops to a plateau for the remainder of the cycle. The magnitudes of the peak and the plateau vary by a factor of two or more from cycle to cycle, depending on the engine operating mode. Analysis of the ratio of the forward-to-backward light scattering signal indicates the emission of larger particles soon after the opening of the exhaust valve. On average, the diameter of the freshly emitted soot aggregates sampled after the exhaust valve is smaller than the diluted soot. Particle coagulation in the exhaust pipes and surge tank may explain this. Using the ratio of signals at two angles, the mass concentration at the exhaust port can be adjusted according to the Rayleigh-Debye-Gans (RDG) light scattering theory, and brought closer to the average concentrations in the diluted exhaust.
Kheirkhah, Pooyan, Kirchen, Patrick, Rogak, Steven
Internal Exhaust Gas Recirculation for Efficiency and Emissions in a 4-Cylinder Diesel Engine2016-01-218410/17/2016
The application of stringent requirements on emission reduction and higher fuel economy in diesel engines has led to the need for efficient energy extraction in the cylinders and reductions in exhaust gas temperatures, as well as posing challenges for energy availability for emission control systems. Internal exhaust gas recirculation (I-EGR) can increase the exhaust gas temperature and reduce engine-out gaseous emissions. The secondary opening of exhaust valves in a diesel engine produces an efficient recirculation of exhaust gases from the previous engine cycle to the cylinder mass charge during the intake stroke. However, I-EGR alone can increase exhaust gas temperature only up to a limit determined by the resulting increase in soot emissions. To obtain higher exhaust gas temperatures, I-EGR can be combined with multiple injections after the main injection event, thereby altering the heat release rate and the exothermic reactions in the exhaust stroke. Based on experimental observations, it is feasible to maintain or reduce engine-out emissions of nitrogen oxides while achieving simultaneous reductions in hydrocarbons and carbon monoxide. In this paper, one-dimensional computational methods combined with experimental bench tests are applied to analyze the performance of a four-cylinder diesel engine using I-EGR. The impact of I-EGR on transient test cycles is determined for different valve event configurations. One, two, or continuously selectable exhaust valve profiles are applied for phasing and lift variation in the recirculation flow area.
Gonzalez D, Manuel A., Di Nunno, Davide
Investigation of the Gas Exchange (Scavenging) on a Single-Scroll Turbocharged Four Cylinder GDI Engine2016-01-10244/5/2016
For scavenging the combustion chamber during the gas exchange, a temporary positive pressure gradient between the intake and the exhaust is required. On a single-scroll turbocharged four cylinder engine, the positive pressure gradient is not realized by the spatial separation of the exhaust manifold (twin-scroll), but by the use of suitable short exhaust valve opening times. In order to avoid any influence of the following firing cylinder onto the ongoing scavenging process, the valve opening time has to be shorter than 180 °CA. Such a short valve opening time has both, a strong influence on the gas exchange at the low-end torque and at the maximum engine power. This paper analyzes a phenomenon, which occurs due to short exhaust valve opening durations and late valve timings: A repeated compression of the burned cylinder charge after the bottom dead center, referred to as “recompression” in this paper. By means of a new energetic analysis (available technical work capacity) the energetic contribution of the recompression to the boost pressure generation has been examined and is presented in this paper. Furthermore two different variable exhaust valve train systems in combination with a part-scroll-separation exhaust manifold are compared in this paper. The aim is to reduce fuel consumption at the nominal power. The two exhaust valve train systems increase the valve opening duration by either a two step system or by a system with the ability to offset the valve timing. It is shown in simulation results how both systems in combination with a prolonged part-scroll-separation in the exhaust manifold reach a potential to reduce fuel consumption up to 10 %.
Wolany, Adalbert, Glahn, Claus, Berner, Hans-Juergen, Bargende, Michael
Development of a New 1.5L I4 Turbocharged Gasoline Direct Injection Engine2016-01-10204/5/2016
A 1.5 L downsizing turbocharged engine was developed to achieve both driving and environmental performance. The engine is intended to replace 1.8 - 2.4 L class NA engines. In downsizing turbocharged engines, mixture homogeneity is important for suppressing knocking and emission reduction. Particularly under high load, creating rapid combustion and a homogeneous mixture are key technologies. The authors used a long-stroke direct injection engine, which has outstanding rapid combustion and thermal efficiency, as a base engine meeting these requirements. They combined this with a high-tumble port and shallow-dish piston intended to support tumble flow. The combination enhanced flow within the cylinder. The combustion system was built to include a sodium-filled exhaust valve to reduce knocking and a multi-hole injector (six holes) for mixture homogeneity and to reduce the fuel wall wetting. The above combustion system is able to achieve high rates of in-cylinder pressure rise with its rapid combustion and therefore improves IMEP, even with a retard ignition timing setting at 1500 rpm full load. Dual VTC makes it possible to set the optimal intake and exhaust valve overlap and valve timing for the engine speed and load. The use of this in combination with the above-described combustion system achieved a minimum BSFC of 220 g/kWh and maximum thermal efficiency of 38%. This paper will also introduce the engine’s output, fuel economy, its technologies for achieving lower emissions, reducing vibration and noise, and achieving light weight, and the performance of the finished vehicle.
Wada, Yusuke, Nakano, Koji, Mochizuki, Kei, Hata, Ryuichi
Development of a New 2.0L I4 Turbocharged Gasoline Direct Injection Engine2016-01-10174/5/2016
It is important to take action regarding environmental issues on a global scale, and automakers are adding downsized turbocharged engines to their line-ups as a means of reducing CO2 emissions, particularly in Europe. Honda has recently announced a next-generation powertrain series that realizes a good balance between environmental performance and driving pleasure. As part of this series, the company has developed a downsized and turbocharged 2.0L gasoline direct injection engine. This is a high-powered sports car engine positioned in the European “hot hatch” category. The development balanced engine power with good environmental performance. The new powertrain featured a range of technologies to enable these demands to be satisfied, including a high-tumble port, a dual VTC(Valve Timing Control),variable exhaust valve lift mechanism, a two-piece water jacket for the exhaust manifold, which has been integrated with the cylinder head, a mono-scroll turbocharger, pistons equipped with cooling channels and lightweight crankshaft. The engine realizes a maximum torque of 400Nm and a maximum output of 228kW, while achieving CO2 emissions of 170g/km in the EU fuel economy test cycle (36.6% maximum thermal efficiency) and clearing the Euro 6b standards. This paper will report on the technologies employed in the new powertrain.
Jono, Mitsutaka, Taguchi, Masayuki, Shonohara, Toshimitsu, Narihiro, Shigeru
Local Gaussian Process Regression in Order to Model Air Charge of Turbocharged Gasoline SI Engines2016-01-06244/5/2016
A local Gaussian process regression approach is presented, which allows to model nonlinearities of internal combustion engines more accurate than global Gaussian process regression. By building smaller models, the prediction of local system behavior improves significantly. In order to predict a value, the algorithm chooses the nearest training points. The number of chosen training points depends on the intensity of estimated nonlinearity. After determining the training points, a model is built, the prediction performed and the model discarded. The approach is demonstrated with a benchmark system and air charge test bed measurements. The measurements are taken from a turbocharged SI gasoline engine with both variable inlet valve lift and variable inlet and exhaust valve opening angle. The results show how local Gaussian process regression outmatches global Gaussian process regression concerning model quality and nonlinearities in particular.
Raidt, Benedikt
Development of New High-Efficiency Kappa 1.6L GDI Engine2016-01-06674/5/2016
Hyundai/Kia Motor Company will introduce new Kappa 1.6L GDI engine dedicated for hybrid vehicles, starting production for Korean market in the early 2016. It has achieved the challenging level of 40% maximum thermal efficiency as a gasoline engine. Even though it has the highest fuel efficiency, it can generate sufficient power to provide vehicle's dynamic driving performance. The new Kappa 1.6L GDI engine has been developed focusing on the fuel efficiency. To maximize fuel efficiency, compact combustion chamber is designed with 1.35 stroke-bore ratio. And other key technologies such as Atkinson cycle with high compression ratio, cooled EGR system with high energy ignition coil and high tumble intake ports are applied. The knock has been suppressed significantly to improve fuel efficiency by split cooling system with two thermostats and block insert, the piston cooling jet and the sodium-filled exhaust valve. Friction of Kappa 1.6GDI engine is minimized by the two-stage pressure control oil pump, low viscosity engine oil and low friction coating on moving parts. Also the OCV integrated CVVT has the faster response speed to cover the wider phasing angle of CVVT in Atkinson cycle. Also, to meet SULEV emission regulation, the spray pattern of the laser drilled-injector is optimized for the combustion chamber consisting of high tumble and flat piston with 200 bar fuel pressure system.
Hwang, Kookjin, Hwang, Iljoong, Lee, Hwangbok, Park, Hyunil, Choi, Hoyeon, Lee, Kwanwoo, Kim, Wootae, Kim, Heungchul, Han, Bonghoon, Lee, Jongsub, Shin, Bosung, Chae, Dongsuk
A Sectoral Approach to Modelling Wall Heat Transfer in Exhaust Ports and Manifolds for Turbocharged Gasoline Engines2016-01-02024/5/2016
A new approach is presented to modelling wall heat transfer in the exhaust port and manifold within 1D gas exchange simulation to ensure a precise calculation of thermal exhaust enthalpy. One of the principal characteristics of this approach is the partition of the exhaust process in a blow-down and a push-out phase. In addition to the split in two phases, the exhaust system is divided into several sections to consider changes in heat transfer characteristics downstream the exhaust valves. Principally, the convective heat transfer is described by the characteristic numbers of Nusselt, Reynolds and Prandtl. However, the phase individual correlation coefficients are derived from 3D CFD investigations of the flow in the exhaust system combined with Low-Re turbulence modelling. Furthermore, heat losses on the valve and the seat ring surfaces are considered by an empirical model approach. Since the comparison between measured and simulated exhaust temperature at turbine inlet serves as an evaluation criterion, a detailed 1D thermocouple model is implemented. Exothermic exhaust after-reactions are represented by a reduced reaction kinetics mechanism. The investigations were carried out for four TC-DI gasoline engines. The low scattering of the correlation coefficients as well as the high agreement between simulated and measured exhaust temperature verify the model quality. Overall, the new sectoral approach shows a significant improvement of wall heat flux calculation in comparison to conventional single-phase approaches from literature.
Franzke, Bjoern, Pischinger, Stefan, Adomeit, Philipp, Schernus, Christof, Scharf, Johannes, Uhlmann, Tolga
Modelling Analysis of Aftertreatment Inlet Temperature Dependence on Exhaust Valve and Ports Design Parameters2016-01-06704/5/2016
Upcoming emissions regulations will force to optimize aftertreatment system to reduce emissions looking for lack of fuel penalty. Despite advances in purely aftertreatment aspects, the performance of the diverse aftertreatment devices is very dependent on the operating temperature. This makes them rely on the engine design and calibration because of the imposed turbine outlet temperature. The need to reach target conversion efficiency and to complete regeneration processes requires controlling additional parameters during the engine setup. For that reason, exploring the potential of different solutions to increase inlet aftertreatment temperature is becoming a critical topic. Nevertheless, such studies cannot be tackled without considering concerns on the engine fuel consumption. In this paper, the influence of several design parameters is studied by modelling approach under steady state operating conditions in a Diesel engine. An engine model has been setup with experimental data using GT-Power software coupled to an external heat transfer and friction losses turbocharger model to predict correctly turbine outlet temperature. The analysis covers parametric studies focused on the exhaust and intake valves diameter, valves timing as well as the use of multi-step openings. The exhaust ports total length and distribution into several branches are also explored. Differences in the potential of every proposal are also considered as a function of the engine operating range. Finally, discussions on the influence on turbine outlet temperature and fuel consumption are conducted to define general guideline criteria. These are affected by the need to look for solutions providing a suitable balance between exhaust temperature increase and minimized impact on engine fuel economy.
Serrano, José Ramón, Piqueras, Pedro, Navarro, Roberto, Gómez, Javier, Michel, Marc, Thomas, Bénédicte
Extending the Dilution Limit of Spark Ignition Combustion via Fuel Injection during Negative Valve Overlap2016-01-06714/5/2016
Using exhaust gas recirculation (EGR) as a diluent instead of air allows the use of a conventional three-way catalyst for effective emissions reduction. Cooled EGR can also reduce fuel consumption and NOx emissions, but too much cool EGR leads to combustion instability and misfire. Negative valve overlap (NVO) is explored in the current work as an alternative method of dilution in which early exhaust valve closing causes combustion products to be retained in the cylinder and recompressed near top dead center, before being mixed with fresh charge during the intake stroke. The potential for fuel injection during NVO to extend the dilution limit of spark ignition combustion is evaluated in this work using experiments conducted on a 4-cylinder 2.0 L gasoline direct injection engine with variable intake and exhaust valve timing. The results demonstrate fuel injection during NVO can extend the dilution limit, improve brake specific fuel consumption (BSFC), and reduce CO and NOx emissions. Specifically, 80 CAD of NVO with start of fuel injection at top dead center allowed the use of 32% total EGR (internal and external) and resulted in the best BSFC of 278.7 g/ kWh; an improvement of 22% compared with the BSFC of 358.3 g/kWh for the production version of this engine at the same speed and load condition (1800 RPM and 3 bar BMEP) without EGR. The optimized case of SOI = 360 CAD bTDC and NVO = 80 CAD, resulted in slightly higher CO emissions of 3865 ppm and significantly lower NOx emissions of 281 ppm, compared with the CO and NOx emissions for the stock production version of the engine of 3230 ppm and 986 ppm, respectively.
Chang, Yan, Wooldridge, Margaret, Bohac, Stanislav V.
Exhaust and Muffler Aeroacoustics Predictions using Lattice Boltzmann Method2015-01-23146/15/2015
Exhaust and muffler noise is a challenging problem in the transport industry. While the main purpose of the system is to reduce the intensity of the acoustic pulses originating from the engine exhaust valves, the back pressure induced by these systems must be kept to a minimum to guarantee maximum performance of the engine. Emitted noise levels have to ensure comfort of the passengers and must respect community noise regulations. In addition, the exhaust noise plays an important role in the brand image of vehicles, especially with sports car where it must be tuned to be “musical”. However, to achieve such performances, muffler and exhaust designs have become quite complex, often leading to the rise of undesired self-induced noise. Traditional purely acoustic solvers, like Boundary Element Methods (BEM), have been applied quite successfully to achieve the required acoustic tuning. However, they fail at predicting all of flow-induced noise, as well as non-linear noise dissipation mechanisms. A natural candidate for this type of problem is the use of a Lattice-Boltzmann Method (LBM) solver as a CFD tool. It has already been successfully applied and validated to quantify self-induced noise of mufflers as well as complex acoustic devices performance like acoustic liners. In this paper, a muffler baseline geometry self-induced noise is assessed using the commercial LBM solver PowerFLOW. Noise generation mechanisms are identified and design modifications are proposed to atone it. The given baseline and iterations designs noise mechanisms are analyzed and the obtained noise reductions are compared and discussed.
Mann, Adrien, Kim, Min-Suk, Neuhierl, Barbara, Perot, Franck, Powell, Robert, Rose, Thomas, Krueger, Jan
Investigation of Low-Speed Pre-Ignition in Boosted Spark Ignition Engine2015-01-07514/14/2015
This paper presents the results of study low-speed Pre-ignition (LSPI) on highly supercharged spark ignition engines. It was investigated on both a gasoline direct injection (GDI) engine with turbo and a port fuel injection (PFI) engine with turbo to find the individual characteristics of LSPI. In terms of the PFI engine, influence of different parameters control strategy such as air-fuel ratio and injection timing on pre-ignition was investigated. In terms of the GDI engine, influence of different control strategies such as injection quantity, first and second injection timing, the second injection ratio, coolant temperature, exhaust valve closing (EVC) and intake manifold temperature (MAT) were investigated. In addition, CFD analysis was extensively used to understand test results including wall film, air-fuel ratio distribution and temperature distribution at top dead centre (TDC). For GDI engine in this paper, pre-ignition (PI) results from the combine action of wall film, temperature distribution at TDC and air- fuel ratio distribution at TDC. Enrich air-fuel rate have effective suppression of low-speed Pre-ignition on the GDI engine and the PFI engine.
Han, Liwei, Zhu, Tao, Qiao, Haibo, Zhang, Desheng, Fu, Dingyuan, Zhang, Jing
Synergy between Boost and Valve Timings in a Highly Boosted Direct Injection Gasoline Engine Operating with Miller Cycle2015-01-12624/14/2015
Gasoline engine downsizing has become a popular and effective approach to reduce CO2 emissions from passenger cars. This is typically achieved in the form of a boosted direct injection gasoline engine, which are typically equipped with variable valve timing (VVT) devices on the intake and/or exhaust valves. This paper describes the synergies between valve timings and boost based on experimental investigations in a single cylinder gasoline direct injection spark ignited (DISI) engine with variable cam phasing on both the intake and exhaust cams. Two cam profiles have been tested to realize Miller cycle and compared with the standard camshaft. One cam features a long opening duration and standard valve lift for Late Intake Valve Closing (LIVC) and the other cam has a short opening duration and low valve lift for Early Intake Valve Closing (EIVC). An external boost rig was used to provide adjustable pressurized air charge, allowing conditions of up to 4000rpm and 25.6 bar NIMEP to be studied. Results have shown that the EIVC cam produced the best net Indicated Specific Fuel Consumption (ISFC) among the three cam profiles, with up to 11% improvement in net ISFC relative to the standard cam profile. The benefits of late split injections have also been studied to overcome the issue of low combustion speed when using low valve lift.
Li, Yuanping, Zhao, Hua, Stansfield, Phil, Freeland, Paul
Comparison of Variable Valve Actuation, Cylinder Deactivation and Injection Strategies for Low-Load RCCI Operation of a Light Duty Engine2015-01-08434/14/2015
While Low Temperature Combustion (LTC) strategies such as Reactivity Controlled Compression Ignition (RCCI) exhibit high thermal efficiency and produce low NOx and soot emissions, low load operation is still a significant challenge due to high unburnt hydrocarbon (UHC) and carbon monoxide (CO) emissions, which occur as a result of poor combustion efficiencies at these operating points. Furthermore, the exhaust gas temperatures are insufficient to light-off the Diesel Oxidation Catalyst (DOC), thereby resulting in poor UHC and CO conversion efficiencies by the aftertreatment system. To achieve exhaust gas temperature values sufficient for DOC light-off, combustion can be appropriately phased by changing the ratio of gasoline to diesel in the cylinder, or by burning additional fuel injected during the expansion stroke through post-injection. Alternatively, variable valve actuation (VVA) strategies such as Early Exhaust Valve Opening (EEVO) and cylinder deactivation may be implemented to raise the exhaust gas temperatures for DOC activation, and/or improve fuel economy by firing fewer cylinders at operating points with higher combustion efficiencies. Since each of these strategies has benefits and drawbacks, it is of interest to compare them in terms of engine performance, emissions and catalyst efficiency for low load operation. In this work, coupled GT-Power and KIVA simulations of a multi-cylinder light duty engine operating on RCCI are performed at a near-idle operating point of 1 Bar BMEP at 1,500 rev/min. Five operating strategies are considered: 1. Varying combustion phasing via the gasoline-diesel ratio, 2. Using late fuel injection during the expansion stroke to activate the catalyst, 3. EEVO using a cam phaser, 4. EEVO using a fully flexible variable valvetrain, and 5. Cylinder deactivation. The cylinder-out emissions are compared and explained for each strategy. The effects of exhaust gas temperature on DOC performance, and the impact of each strategy on fuel economy are also studied to determine the most suitable strategy for low load operation.
Bharath, Anand Nageswaran, Yang, Yangdongfang, Reitz, Rolf D., Rutland, Christopher
Evaluation of the Potential Benefits of an Automotive, Gasoline, 2-Stroke Engine2015-01-12614/14/2015
In the present paper, the use of a 2-stroke (2S) concept in an automotive gasoline engine is evaluated. In a first stage, the engine architecture chosen is discussed. Taking into account the requirements in gas exchange processes, a uniflow scavenging design was retained (intake ports in the cylinder, controlled by the piston; exhaust valves in the cylinder head, controlled by a Variable Valve Timing, VVT, system), performed by an external blower driven by the crankshaft. To avoid any fuel short-circuiting and to keep an acceptable cost, a direct injection (DI) air-assisted fuel injection system was selected. Since the engine behavior is much more complex compared to a classical 4-stroke engine, some complexity in the engine design needs to be added to allow engine optimization at the different operating conditions. This is the main reason why a VVT system, as well as a flexible fuel injection system were selected. In a second stage, the chosen engine concept is evaluated. At high loads, because of the high quality of the scavenging process, the combustion initiation is controlled by a spark as in any standard spark ignition (SI) engine. However, at low load, the scavenging process is incomplete, and the high amount of residual gases leads, in some cases, to a controlled autoignition (CAI) combustion process. These two completely different scenarios are analyzed in the paper. In summary, on the one hand, the operation under SI conditions is basically similar to that of any classical 4-stroke, SI engine, but with higher knock risk. On the other hand, the operation in CAI leads to a faster combustion process, which might lead to higher fuel efficiency. However the control of the combustion process is more complex, since it is more sensitive to the operating parameters (air temperature, combustion chamber walls temperature…), and not fully controlled by the spark anymore. A significant effort has been carried out in the paper to understand how the combustion process can be controlled, and some ideas for such control are proposed and discussed.
Lopez, J. Javier, Novella, Ricardo, Valero-Marco, Jorge, Coma, Gilles, Justet, Frederic
Design of 65 degree V4 Moto GP Engines with Pneumatic Poppet Valves or Rotary Valves2015-26-01761/14/2015
Moto GP engines have since the year 2012 4 cylinders in V or inline layout for a total capacity of up to 1,000cc. With pneumatic valve spring but wet sump, and with the maximum bore limited to 81mm, the maximum speed these engines may have is about 18,000 rpm, with power outputs 250-260 HP. The paper presents the design of a 65 degree V4 Moto GP engine further optimizing the pneumatic poppet valve design, as well as a novel rotary valve design. The rotary valve permits up to extremely sharp opening or closing and very large gas exchange areas. The two engines are then modeled by using a 1D engine & gas dynamics simulation software package to assess the potentials of the solution. The improved design produces much larger power densities than the version of the engines with traditional poppet valves revving at higher speeds.
Boretti, Alberto, Scalzo, Joseph
Investigation of Cylinder Deactivation (CDA) Strategies on Part Load Conditions2014-01-254910/13/2014
Many efforts have been invested to improve the fuel efficiency of vehicles mainly for the local consumers. One of the main techniques to have better fuel efficiency is cylinder deactivation system. In this paper, the main research area is focus on the investigation of cylinder deactivation (CDA) technology on common engine part load conditions within common Malaysian driving condition. CDA mostly being applied on multi cylinders engines. It has the advantage in improving fuel consumption by reducing pumping losses at part load engine conditions. Here, the application of CDA on 1.6 liter four cylinders gasoline engine is studied. One-dimensional (1-D) engine modeling is performed to investigate the effect of intake and exhaust valve strategy on engine performance with CDA. The 1-D engine model is constructed starts from the air-box cleaner up to exhaust system according to the 1.6 liter actual engine geometries. The model is simulated at various engine speeds with full load condition. The simulated results show that the constructed model is well correlated to measured data. This correlated model is then used to investigate the effect of valves timing configurations on engine performance. The model is then used to determine the optimum intake and exhaust valve lift and timing for CDA application at part load conditions. Also, the effects on the in-cylinder combustion as well as pumping losses are presented. The study shows that the effects of valves strategies are very significant on the engine performance. Pumping losses is found to be reduced, thus improving fuel consumption and engine thermal efficiency.
Muhamad Said, Mohd Farid, Abdul Aziz, Azhar Bin, Abdul Latiff, Zulkanain, Mahmoudzadeh Andwari, Amin, Mohamed Soid, Shahril Nizam
Development of New Cam-Shower for Oil Flow Optimization2014-01-285110/13/2014
On internal combustion engines, the intake and exhaust valves are reciprocated by the cam mechanism. ‘Cam-shower’ is oil supplying device for each cam of a camshaft. The conventional cam-shower is simple pipe shape with several same size outlets for each cam. Oil from cylinder head is supplied in the middle point of cam-shower pipe. The oil flow of outlets near the oil supplied point is large amount, and outlet far from supplied point is small. The distribution of oil flow from each outlet is uneven. A new structure of cam-shower has been developed, and it has two important features. First, it has branched oil passage like cereoid cactus. Second, supplied oil flow from cylinder head to a cam-shower is intermittent by using throughhole passage in a camshaft journal. The new developed cam-shower properly distributes oil flow to each cam evenly and reduces wasted oil flow, so that total amount of oil flow of the cam-shower can be remarkably reduced by 90%. Then small discharge rate of the oil pump for engine can be set up and its driving torque gets lower. Eventually, that achieves low fuel consumption of engine.
Hikita, Yasuhiro, Kawahara, Masahiro, Noguchi, Naoto
Performance Sensitivity to Exhaust Valves and Turbine Parameters on a Turbocompound Engine with Divided Exhaust Period2014-01-259710/13/2014
Turbocompound can utilize part of the exhaust energy on internal combustion engines; however, it increases exhaust back pressure, and pumping loss. To avoid such drawbacks, divided exhaust period (DEP) technology is combined with the turbocompound engine. In the DEP concept the exhaust flow is divided between two different exhaust manifolds, blowdown and scavenging, with different valve timings. This leads to lower exhaust back pressure and improves engine performance. Combining turbocompound engine with DEP has been theoretically investigated previously and shown that this reduces the fuel consumption and there is a compromise between the turbine energy recovery and the pumping work in the engine optimization. However, the sensitivity of the engine performance has not been investigated for all relevant parameters. The main aim of this study is to analyze the sensitivity of this engine architecture in terms of break specific fuel consumption to different parameters concerning the gas exchange such as blowdown valve timing, scavenging valve timing, blowdown valve size, scavenging valve size, discharge coefficients of blowdown and scavenging ports, turbine efficiency, turbine size and power transmission efficiency. This study presents the sensitivity analysis of the turbocompound DEP engine to these parameters and defines a set of important parameters that should be examined in experimental studies.
Aghaali, Habib, Angstrom, Hans-Erik
Simulation Study of Divided Exhaust Period for a Regulated Two-stage Downsized SI Engine2014-01-255010/13/2014
The Divided Exhaust Period (DEP) concept is an approach which has been proved to significantly reduce the averaged back pressure of turbocharged engines whilst still improving its combustion phasing. The standard layout of the DEP system comprises of two separately-functioned exhaust valves with one valve feeding the blow-down pulse to the turbine whilst the other valve targeting the scavenging behaviour by bypassing the turbine. Via combining the characteristics of both turbocharged engines and naturally aspirated engines, this method can provide large BSFC improvement. The DEP concept has only been applied to single-stage turbocharged engines so far. However, it in its basic form is in no way restricted to a single-stage system. This paper, for the first time, will apply DEP concept to a regulated two-stage (R2S) downsized SI engine. By controlling the timing of the exhaust valves separately to feed the exhaust mass flow to the high-pressure turbine or the low-pressure turbine or the exhaust pipe, it is anticipated that such system could achieve even better breathing characteristics than the standard one-stage turbocharged engine. The simulation was carried out on a heavily downsized R2S turbocharged SI engine model. As the major objective of this project is to explore the gas exchange process for the DEP-based R2S downsized engine, the knock model in the system is ignored. The results showed that PMEP is significantly improved over the entire engine speed and BSFC was decreased by up to 3% with minimum modification of the original system. The system also showed the potential benefit for knock sensitivity and it is considered that by adding the knock model, there will be some more BSFC improvement.
Hu, Bo, Brace, Chris, Akehurst, Sam, Copeland, Colin, Turner, J.W.G.
Investigation of Ethanol-Gasoline Dual Fuel Combustion on the Performance and Exhaust Emissions of a Small SI Engine2014-01-262010/13/2014
The growing concerns over the pollutant emissions as well as the depletion of fossil fuel led to the research of advanced combustion mode and alternative fuels for the reduction both of fuel consumption and exhaust emissions. The dual-fuel injection system can be used to improve the engine performance and reduce the fossil fuel consumption performing simultaneously a direct-injection (DI) and a port-fuel-injection (PFI) of different fuels. Ethanol is one of the most promising alternative fuels for SI engines. It offers high anti-knock quality because of the high octane number; moreover, being an oxygenated fuel is very effective in particle emissions reduction. On the other hand, it is characterized by lower energy density mainly because of the low lower heating value (LHV). The aim of the paper is the investigation of the ethanol-gasoline dual fuel combustion on engine performance and emissions. The experimental activity was carried out in a single cylinder engine for two wheel vehicles with a displacement of 250 cc. It was equipped with a prototype gasoline direct injection (GDI) head and with an injector in the intake manifold. This makes it possible to run in dual fuel mode performing a direct injection of ethanol and a port fuel injection of gasoline. This configuration was chosen in order to reduce the particle emissions typical of GDI engines. The tests were carried out at engine operating points representative of the typical urban driving conditions: 2000 rpm, 4000 rpm and 5000 rpm full load. The in-cylinder pressure was measured by means of a quartz pressure transducer flush-mounted in the region between intake and exhaust valves. The gaseous emissions and particle concentration were measured at the exhaust by means of a gas analyzer and a smoke meter. Particle size distribution function was measured in the range from 5.6 nm to 560 nm by means of an Engine Exhaust Particle Sizer (EEPS).
Catapano, Francesco, Di Iorio, Silvana, Sementa, Paolo, Vaglieco, Bianca Maria
Modelling and Experimental Study of Internal EGR System for NOx Control on an Off-Road Diesel Engine2014-01-264510/13/2014
This study deals with the development of an internal EGR (Exhaust Gas Recirculation) system for NOx reduction on a six cylinder, turbocharged intercooled, off-road diesel engine based on a modified cam with secondary lift. One dimensional thermodynamic simulation model was developed using a commercially available code. MCC heat release model was refined in the present work by considering wall impingement of the fuel as given by Lakshminarayanan et al. The NOx prediction accuracy was improved to a level of 90% by a generic polynomial fit between air excess ratio and prediction constants. Simulation results of base model were correlating to more than 95% with experimental results for ISO 8178 C1 test cycle. Parametric study of intake and exhaust valve events was conducted with 2IVO (Secondary Intake Valve Opening) and 2EVO (Secondary Exhaust Valve Opening) methods. Combinations of different opening angles and lifts were chosen in both 2IVO and 2EVO methods for the study. Residual gas content has been estimated for each combination along with performance parameters and NOx emission. Simulation results showed 2IVO with 12 - 13% of main lift closing at 60°CA prior to main lift was found to be meeting the target internal EGR rates. Experimental set up was developed with instrumentations for performance, emission and internal EGR residual measurement along with temperatures and pressures. Experimental results showed a NOx emission reduction upto 27% with secondary lift of 12% to the main lift which is producing 10% iEGR rate. Experimental results of modified cam correlated to simulation results to a higher degree.
Balaji, J., M. V., Ganesh Prasad, Rao, L. Navaneetha, Bandaru, Balaji, Ramesh, A.
Combustion and Emission Characteristics of a HCCI Engine Fuelled with Different n-Butanol-Gasoline Blends2014-01-266810/13/2014
Biobutanol, i.e. n-butanol, as a second generation bio-derived alternative fuel of internal combustion engines, can facilitate the energy diversification in transportation and reduce carbon dioxide (CO2) emissions from engines and vehicles. However, the majority of research was conducted on spark-ignition engines fuelled with n-butanol and its blend with gasoline. A few investigations were focused on the combustion and exhaust emission characteristics of homogeneous charge compression ignition (HCCI) engines fuelled with n-butanol-gasoline blends. In this study, experiments were conducted in a single cylinder four stroke port fuel injection HCCI engine with fully variable valve lift and timing mechanisms on both the intake and exhaust valves. HCCI combustion was achieved by employing the negative valve overlap (NVO) strategy while being fueled with gasoline (Bu0), n-butanol (Bu100) and their blends containing 30% n-butanol by volume (Bu30). The results indicate that, with the increase of n-butanol volume fraction in the blend, the autoignition timing advances and the combustion duration shortens, but indicated mean effective pressure (IMEP) decreases at the same conditions. The addition of n-butanol to gasoline can expand the low load boundary in HCCI combustion mode. But it decreases high load boundary in HCCI combustion mode. In addition, oxides of nitrogen (NOx) emissions sharply decrease with advanced exhaust valve closing timing. The addition of n-butanol results in a reduction in NOx emissions.
Liu, Maobin, He, Bang-Quan, Zhao, Hua
Engine Parameter Optimization for Improved Engine and Drive Cycle Efficiency for Boosted, GDI Engines with Different Boosting System Architecture2014-01-12044/1/2014
As boosted, direct injected gasoline engines become more prevalent in the automotive market, the boosting system architecture and efficiency are intimately entwined with the efficiency and performance of the engine. Single-stage as well as two-stage boosting systems, comprising of either two turbochargers or a supercharger in combination with a turbocharger, are potential configurations. When combining an internal combustion engine with boosting hardware, a mechanical, fluid-dynamic and thermodynamic coupling is created and the system as a whole will need to be treated as such. For the initial selection of the boost system, it is important to match all of the engine design features, such as the engine's compression ratio, valve profiles and intake and exhaust components as well as to adjust and optimize all engine controls' calibration parameters. 1-D engine cycle simulations in combination with engine experimental testing were utilized to explore optimum engine configurations and calibration settings when using a variety of boosting systems. A total of five different engine and boosting configurations where configured for this project, including two 4-cylinder, 1.6 liter GDI gasoline engines with single stage boosting (turbocharging and supercharging) and three downsized, 3-cylinder, 1.2 liter GDI gasoline engines with two-stage boosting configurations (series-sequential twin-turbo, super-turbo and turbo-super). Design-of-Experiment routines were carried out to optimize both fixed engine hardware specifications, e.g. compression ratio, as well as variable parameters, e.g. intake and exhaust valve phasing, combustion phasing, for a given boost system architecture on the target engine. Fuel economy and performance comparison were conducted between the different engine and boost system architectures for steady-state operating conditions as well as for common vehicle drive cycles. For light load operating conditions and lightly loaded test cycles e.g. NEDC), the downsized engines with two-stage boosting systems, particularly the 3-cylinder engine with super-turbo configuration, offered the greatest fuel economy potentials. For mid and high load operating conditions and more highly loaded test cycles (e.g. US06), the 4-cylinder, supercharged arrangement offered best fuel economy potentials. For steady-state, high load operating conditions, the 4-cylinder, turbocharged arrangement yielded best fuel consumption values.
Amann, Manfred, Ouwenga, Daniel
Characterization of Ethanol-Gasoline Blends Combustion processes and Particle Emissions in a GDI/PFI Small Engine2014-01-13824/1/2014
The objective of this paper is the evaluation of the effect of the fuel properties and the comparison of a PFI and GDI injection system on the performances and on particle emission in a Spark Ignition engine. Experimental investigation was carried out in a small single cylinder engine for two wheel vehicles. The engine displacement was 250 cc. It was equipped with a prototype GDI head and also with an injector in the intake manifold. This makes it possible to run the engine both in GDI and PFI configurations. The engine was fuelled with neat gasoline and ethanol, and ethanol/gasoline blends at 10% v/v, 50% v/v and 85% v/v. The engine was equipped of a quartz pressure transducer that was flush-mounted in the region between intake and exhaust valves. Tests were carried out at 3000 rpm and 4000 rpm full load and two different lambda conditions. These engine points were chosen as representative of urban driving conditions. The gaseous emissions and particle concentration were measured at the exhaust by means of conventional instruments. Particle size distribution function was measured in the range from 5.6 nm to 560 nm by means of an Engine Exhaust Particle Sizer (EEPS). The effect of ethanol blending on particle emission depends on engine configuration and ethanol percentage. A strong increase of particle emission for E50 was observed in PFI configuration. For GDI configuration a larger particle emissions with respect to gasoline fuel was measured for E10. Moreover, for blends fuelling, particle emissions decrease with the ethanol percentage.
Catapano, Francesco, Di Iorio, Silvana, Sementa, Paolo, Vaglieco, Bianca Maria
1-D Simulation Study of Divided Exhaust Period for a Highly Downsized Turbocharged SI Engine - Scavenge Valve Optimization2014-01-16564/1/2014
Fuel efficiency and torque performance are two major challenges for highly downsized turbocharged engines. However, the inherent characteristics of the turbocharged SI engine such as negative PMEP, knock sensitivity and poor transient performance significantly limit its maximum potential. Conventional ways of improving the problems above normally concentrate solely on the engine side or turbocharger side leaving the exhaust manifold in between ignored. This paper investigates this neglected area by highlighting a novel means of gas exchange process. Divided Exhaust Period (DEP) is an alternative way of accomplishing the gas exchange process in turbocharged engines. The DEP concept engine features two exhaust valves but with separated function. The blow-down valve acts like a traditional turbocharged exhaust valve to evacuate the first portion of the exhaust gas to the turbine. While the scavenge valve feeding the latter portion of the exhaust gas directly into the low resistant exhaust pipe behaves similarly to valves in a naturally aspirated engine. By combining the characteristics of both turbocharged and naturally aspirated engines, high backpressure between the turbine inlet and the exhaust port is maintained in the blowdown phase while significant reduction of the backpressure could be achieved in the latter displacement phase. This is directly beneficial for pumping work and residual gas scavenging. Combustion phasing & stability and turbocharger efficiency could also benefit from such concept. This simulation study was carried out using a validated 1D model of a highly downsized SI engine. Two degrees of freedom including the lift and the duration of the scavenge valve were optimized to achieve minimum BSFC. The potential for higher attainable BMEP was also briefly investigated at low engine speed.
Hu, Bo, Akehurst, Sam, Brace, Chris, Copeland, Colin, Turner, James
Ultra Boost for Economy: Extending the Limits of Extreme Engine Downsizing2014-01-11854/1/2014
The paper discusses the concept, design and final results from the ‘Ultra Boost for Economy’ collaborative project, which was part-funded by the Technology Strategy Board, the UK's innovation agency. The project comprised industry- and academia-wide expertise to demonstrate that it is possible to reduce engine capacity by 60% and still achieve the torque curve of a modern, large-capacity naturally-aspirated engine, while encompassing the attributes necessary to employ such a concept in premium vehicles. In addition to achieving the torque curve of the Jaguar Land Rover naturally-aspirated 5.0 litre V8 engine (which included generating 25 bar BMEP at 1000 rpm), the main project target was to show that such a downsized engine could, in itself, provide a major proportion of a route towards a 35% reduction in vehicle tailpipe CO2 on the New European Drive Cycle, together with some vehicle-based modifications and the assumption of stop-start technology being used instead of hybridization. In order to do this vehicle modelling was employed to set part-load operating points representative of a target vehicle and to provide weighting factors for those points. The engine was sized by using the fuel consumption improvement targets and a series of specification steps designed to ensure that the required full-load performance and driveability could be achieved. The engine was designed in parallel with 1-D modelling which helped to combine the various technology packages of the project, including the specification of an advanced charging system and the provision of the necessary variability in the valvetrain system. An advanced intake port was designed in order to ensure the necessary flow rate and the charge motion to provide fuel mixing and help suppress knock, and was subjected to a full transient CFD analysis. A new engine management system was provided which necessarily had to be capable of controlling many functions, including a supercharger engagement clutch and full bypass system, direct injection system, port-fuel injection system, separately-switchable cam profiles for the intake and exhaust valves and wide-range fast-acting camshaft phasing devices. Testing of the engine was split into two phases. The first usied a test bed Combustion Air Handling Unit to enable development of the combustion system without the complication of a new charging system being fitted to the engine. To set boundary conditions during this part of the programme, heavy reliance was placed on the 1-D simulation. The second phase tested the full engine. The ramifications of realizing the engine design from a V8 basis in terms of residual friction versus the fuel consumption results achieved are also discussed. The final improvement in vehicle fuel economy is demonstrated using a proprietary fuel consumption code, and is presented for the New European Drive Cycle, the FTP-75 cycle and a 120 km/h (75 mph) cruise condition.
Turner, J.W.G., Popplewell, A., Patel, R., Johnson, T.R., Darnton, N.J., Richardson, S., Bredda, S.W., Tudor, R.J., Bithell, C.I., Jackson, R., Remmert, S.M., Cracknell, R.F., Fernandes, J.X., Lewis, A.G.J., Akehurst, S., Brace, C.J., Copeland, C., Martinez-Botas, R., Romagnoli, A., Burluka, A.A.
Development of Valvetrain System to Improve Knock Characteristics for Gasoline Engine Fuel Economy2014-01-16394/1/2014
It is difficult to reach higher compression ratios of the gasoline engine even though higher compression ratios improve thermal efficiency. One of the barriers is large torque drop led by knocking. Extensive researches to suppress knocking of the gasoline engine have been conducted. It is focused on lowering the temperature of fuel mixture in combustion chamber at compression top dead center (TDC). This paper covers the new valvetrain system to decrease the temperature of exhaust valve bottom (combustion) side. Hollow head and stem sodium filled valve (HHSV) have shown more heat transfer from combustion chamber to valve seat insert and valve guide, and higher thermal conductivity valve seat insert (HVSI) and valve guide (HVG) help to decrease valve temperature lower by higher heat transfer. This combination generates a synergy effect to decrease exhaust valve bottom temperature much lower and improve knock behavior, which contributes to improve engine fuel consumption and valvetrain durability.
Baek, Hong-Kil, Lee, Seung Woo, Han, Donghee, Kim, Jiho, Lee, Juhun, Aino, Hiroshi
Particle Image Velocimetry Measurements of Swirl and Scavenging in a Large Marine Two-Stroke Diesel Engine2014-01-11734/1/2014
In-cylinder flow velocity measurements using particle image velocimetry (PIV) have been performed for the first time in a full-size marine Diesel engine. The engine was a four cylinder two-stroke engine with a bore diameter of 0.5 meter and a stroke of 2.2 meter. For such engines uniflow scavenging is used, with fresh air entering through angled ports at the bottom of the cylinder to generate a swirling flow and burnt gases exiting through a centrally located exhaust valve at the top. For efficient design of this process and for validation of CFD models it is essential to obtain an experimental characterization of the flow inside a fully operational engine. Optical access was obtained through a custom designed engine cover, fitted with a number of optical ports into which sapphire windows were mounted. Both the laser and camera used for PIV were mounted directly onto the engine in order to minimize effects of vibrations on optical alignment. Laser sheet generation and relay imaging modules were then positioned inside the optical ports, in order to achieve efficient illumination and detection. Zirconium oxide particles, introduced through the scavenging box, were employed for seeding. Velocity measurements could thus be performed over the entire engine cycle, except during peak combustion. Tangential and axial velocity components were measured at two different radial locations and for two different scavenging port configurations. The results obtained provide the first quantitative experimental information on swirl velocities in this type of engine.
Hult, Johan, Matlok, Simon, Mayer, Stefan
Demonstration of Air-Fuel Ratio Role in One-Stage Turbocompound Diesel Engines2013-01-270310/14/2013
A large portion of fuel energy is wasted through the exhaust of internal combustion engines. Turbocompound can, however, recover part of this wasted heat. The energy recovery depends on the turbine efficiency and mass flow as well as the exhaust gas state and properties such as pressure, temperature and specific heat capacity. The main parameter influencing the turbocompound energy recovery is the exhaust gas pressure which leads to higher pumping loss of the engine and consequently lower engine crankshaft power. Each air-fuel equivalence ratio (λ) gives different engine power, exhaust gas temperature and pressure. Decreasing λ toward 1 in a Diesel engine results in higher exhaust gas temperatures of the engine. λ can be varied by changing the intake air pressure or the amount of injected fuel which changes the available energy into the turbine. Thus, there is a compromise between gross engine power, created pumping power, recovered turbocompound power and consumed compressor power. In this study, the effects of different λ values and exhaust back-pressure have been investigated on the efficiency of a heavy-duty Diesel engine equipped with a single-stage electric turbocompounding. A one-dimensional gas dynamics model of a turbocharged engine was utilized that was validated against measurements at different load points. Two configurations of turbocompound engine were made. In one configuration an electric turbocharger was used and the amount of fuel was varied with constant intake air pressure. In another configuration the turbocharger turbine and compressor were disconnected to be able to control the turbine speed and the compressor speed independently; then the compressor pressure ratio was varied with constant engine fuelling and the exhaust back-pressure was optimized for each compressor pressure ratio. At each constant turbine efficiency there is a linear relation between the optimum exhaust back-pressure and ideally expanded cylinder pressure until bottom dead center with closed exhaust valves. There is an optimum λ for the turbocharged engine with regard to the fuel consumption. In the turbocompound engine, this will be moved to a richer λ that gives the best total specific fuel consumption; however, the results of this study indicates that turbocompound engine efficiency is relatively insensitive to the air-fuel ratio.
Aghaali, Habib, Angstrom, Hans-Erik
Using Valve Timing and Exhaust Back Pressure to Improve Catalyst Warm-Up Time2013-01-265610/14/2013
This work examines the effects of valve timing and back pressure on the engine out enthalpy flow which is critical to the light off of the catalyst. The engine behavior is observed under fast-idle condition using a turbocharged production direct injection spark ignition engine with variable cam phasing that could shift both the intake and exhaust valve timing by 50 deg. crank angle. The back pressure is adjusted by throttling the exhaust. The engine operates at a constant net indicated mean effective pressure of 2 bar. The valve timing effect is largely governed by the residual gas trapped. With increasing valve overlap, the exhaust enthalpy flow increases because of the increase in exhaust temperature due to a slower combustion, and of the increase in air and fuel flow to compensate for the lower efficiency due to the slower combustion. When the back pressure is increased, the engine through flow has to increase to compensate for the larger pumping loss. The exhaust temperature also increases because there is less expansion for the charge in the blow-down process. Both effects contribute to a higher enthalpy flow to the catalyst and facilitate the light off process.
Cedrone, Kevin, Cheng, Wai K.
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