Browse Topic: Exhaust valves

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A CFD Investigation Comparing the Performance of an Alternative Valvetrain Design Against a Traditional Poppet Valvetrain 2022-01-076003/29/2022
The poppet valve is by far the most widely used cylinder head design in internal combustion engines; however, poppet valves themselves create significant flow restrictions during both the intake and exhaust strokes, thus causing a reduction in overall engine efficiency. By removing the restrictive poppet valve from the flow path of air into and out of the cylinder head and allowing air to flow unobstructed, any given ICE engine can achieve higher specific output and greater volumetric efficiency. A new alternative valvetrain design, the flow through barrel valve (FTBV) cylinder head, utilizes straight-cut flow passages that reduce such restrictions. The FTBV, designed by Vaztec, LLC., is a rotary valve system that is designed to be belt driven by the crankshaft, thereby replacing the camshaft and poppet valve system altogether. This paper will primarily explore the differences in flow characteristics between the FTBV and conventional poppet valve cylinder heads using both CFD and flow
Robinson, Austin Clay, Garrett, Norman, Vaseleniuck, Darrick, Uddin, Mesbah
Improvement of Transient Response on a Downsized 4 Cylinder Engine for Automobile Application2021-28-028010/01/2021
The automobile industry is one among the fastest in terms of adapting the technological advancements and evolving based on changing customer requirements. Researchers are focusing on making the automobiles better by means of making the vehicles more efficient, powerful and less polluting. In this study, venues of improving low end torque via improvement in volumetric efficiency as well as proper selection of turbochargers. An in-depth analysis of gas dynamics with respect to valve timing is studied along with the AVL boost simulation. It was found that volumetric efficiency starts to improve when there is a reduction in exhaust – exhaust valve overlap. There is an improvement found in the fresh air ratio (lambda) as the residual gas content is reduced. After the selection of valve timing, turbocharger optimization is done with comparison between two turbine sizes. Along with turbocharger comparison, technology comparison is also done namely between normal electronic VGT (Variable
Jain, Praveer Kirtimohan, Chendil, Chellapandi, Asthana, Shivam, Sanjay, Nehal, Meda, Venkata Saikumar, R, Sivasubramamanian, Daithankar, Parag, Ramadandi, Padmavathi, RS, Ranganathan, A, Guru Sankar
Investigations into the Effects of Spark Plug Location on Knock Initiation by using Multiple Pressure Transducers2021-01-115909/21/2021
Despite a long history of development, modern spark-ignition engines are still restricted in obtaining higher thermal efficiency and better performance by knock. Knocking combustion is an unnatural combustion phenomenon caused by the autoignition of unburned air-fuel mixture ahead of the propagating flame front. This work describes investigations into the significance of spark plug location (with respect to inlet and exhaust valve position) on the knock formation mechanism. To facilitate the investigation, four spark plugs were installed in a specialized liner at four equispaced distinct locations to propagate flames from those locations, which provoked a distinct flame travel from each and thus individual autoignition profiles. Six pressure transducers were arranged to precisely record the pressure oscillations, knock intensities, and combustion characteristics. Four of the six transducers were mounted on the circumference of the liner (each next to one of the spark plugs), one was
Uddeen, Kalim, Shi, Hao, Tang, Qinglong, Turner, James
Automated Diagnostic System for Engine Cylinder-Piston Group2020-01-202209/15/2020
The work is aimed at increasing the reliability, accuracy, information content and depth of the process of diagnosing the cylinder-piston engine group. For this, an automated diagnostic system has been developed, which includes a system unit with a monitor, special software for measuring and processing information, a measuring analog-to-digital module, adapters for connecting to the engine. The diagnostic system allows you to record the change in pressure of the cylinder for every degree of rotation of the crankshaft with an error that does not exceed 1.7%. Measurements are performed in test mode, when the crankshaft of the engine is scrolled with a starter, and strain gauges are screwed in place of spark plugs. The measurement results are presented in the form of diagrams, text and digital values. The system also allows you to save, reproduce and transmit diagnostic information in digital, graphic and text form. Using the developed diagnostic system, the engines of automobiles of
Saraiev, Olexii, Saraieva, Iryna, Gritsuk, Igor V., Volkov, Vladimir, Litikova, Oleksandra, Belousov, Evgen, Savchuk, Volodymyr, Samarin, Oleksandr, Ahieiev, Maksym, Volodarets, Mykyta, Vrublevskyi, Roman, Kurnosenko, Daria
On the Effects of Urea and Water Injection on Particles across the SCR Catalyst in a Heavy - Duty Euro VI Diesel Engine2020-01-219609/15/2020
Particle emissions from heavy-duty engines are regulated both by mass and number by Euro VI regulation. Understanding the evolution of particle size and number from the exhaust valve to the tail pipe is of vital importance to expand the possibilities of particle reduction. In this study, experiments were carried out on a heavy-duty Euro VI engine after-treatment system consisting of diesel oxidation catalyst, diesel particulate filter and selective catalytic reduction (SCR) unit with AdBlue injection followed by ammonia slip catalyst. The present work focusses on the SCR unit with regard to total particle number with and without nucleation particles both. Experiments were conducted by varying the AdBlue injection quantity, SCR inlet temperature [to vary the reaction temperature], exhaust mass flow rate [to vary the residence time in SCR], and fuel injection pressures [to vary inlet particle number and inlet NOx]. Sampling for particle measurements was performed at the inlet, upstream
K, Arun Prasath, Bernemyr, Hanna, Erlandsson, Anders
Lean-Burn Stratified Alcohol Fuels Engines of Power Density up to 475 kW/Liter Featuring Super-Turbocharging, Rotary Valves, Direct Injection, and Jet Ignition2020-01-203609/15/2020
Direct injection (DI) and jet ignition (JI), plus assisted turbocharging, have been demonstrated to deliver high efficiency, high power density positive ignition (PI) internal combustion engines (ICEs) with gasoline. Peak efficiency above 50% and power density of 340 kW/liter at the 15,000 rpm revolution limiter working overall λ=1.45 have been report-ed. Here we explore the further improvement in power density that may be obtained by replacing gasoline with ethanol or methanol, thanks to the higher octane number and the larger latent heat of vaporization, which translates in an increased resistance to knock, and permits to have larger compression ratios. Results of simulations are proposed for a numerical engine that uses rotary valves rather than poppet valves, while also using mechanical, rather than electric, assisted turbocharging. While with gasoline, the power density is 410-420 kW/liter, the use of oxygenates permits to achieve up to 475 kW/liter working with methanol.
Boretti, Alberto
Analysis of the Boost System for a High Performance 2-Stroke Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) Engine2020-01-200709/15/2020
A 2-stroke boosted uniflow scavenged direct injection gasoline (BUSDIG) engine was researched and developed at Brunel University London to achieve higher power-to-mass ratio and thermal efficiency. In the BUSDIG engine concept, the intake scavenge ports are integrated to the cylinder liner and controlled by the movement of piston top while exhaust valves are placed in the cylinder head. Systematic studies on scavenging ports, intake plenum, piston design, valve opening profiles and fuel injection strategies have been performed to investigate and optimise the scavenging performance and in-cylinder fuel/air mixing process for optimised combustion process. In order to achieve superior power performance with higher thermal efficiency, the evaluation and optimisation of the boost system for a 1.0 L 2-cylinder 2-stroke BUSDIG engine were performed in this study using one dimensional (1D) engine simulations. The results show that the engine exhaust valve opening (EVO) timing and exhaust
Wang, Xinyan, Zhao, Hua
Numerical Study of the Scavenging Process in a Large Two-Stroke Marine Engine Using URANS and LES Turbulence Models2020-01-201209/15/2020
A computational fluid dynamics study of the scavenging process in a large two-stroke marine engine is presented in this work. Scavenging which is one of the key processes in the two-stroke marine engines, has a direct effect on fuel economy and emissions. This process is responsible for fresh air delivery, removing the combustion products from the cylinder, cooling the combustion chamber surfaces and providing a swirling flow for better air-fuel mixing. Therefore, having a better understanding of this process and the associated flow pattern is crucial. This is not achievable solely by experimental tests for large engines during engine operation due to the difficulties of measuring the flow field inside the cylinder. In this study, the axial and tangential velocities are compared and validated with the experimental results obtained from Particle Image Velocimetry (PIV) tests [1]. The simulations are conducted using both Unsteady Reynolds Averaged Navier Stokes (URANS) and Large Eddy
Nemati, Arash, Ong, Jiun Cai, Jensen, Michael Vincent, Pang, Kar Mun, Mayer, Stefan, Walther, Jens Honore
The Study on the Characteristics of Different Intake Port Structures in Scavenging and Combustion Processes on a Two-Stroke Poppet Valve Diesel Engine2020-01-048604/14/2020
Two-stroke engines have to face the problems of insufficient charge for short intake time and the loss of intake air caused by long valve overlap. In order to promote the power of a two-stroke poppet valve diesel engine, measures are taken to help optimize intake port structure. In this work, the scavenging and combustion processes of three common types of intake ports including horizontal intake port (HIP), combined swirl intake port (CSIP) and reversed tumble intake port (RTIP) were studied and their characteristics are summarized based on three-dimensional simulation. Results show that the RTIP has better performance in scavenging process for larger intake air trapped in the cylinder. Its scavenging efficiency reaches 84.7%, which is 1.7% higher than the HIP and the trapping ratio of the RTIP reaches 72.3% due to less short-circuiting loss, 11.2% higher than the HIP. The RTIP also behaves better in mixture formation and combustion performance with higher air utilization and superior
Dong, Mengmeng, Pei, Yiqiang, Qin, Jing, Wang, Chenxi, Zhang, Yan, Liu, Wei, Zhang, Shuyong
Optimization of a Diesel Engine with Variable Exhaust Valve Phasing for Fast SCR System Warm-Up2019-01-058404/02/2019
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
Srinivas, Pavan Kumar, Salehi, Rasoul
Simulation of System Brake Efficiency in a Double Compression-Expansion Engine-Concept (DCEE) Based on Experimental Combustion Data2019-01-007301/15/2019
The double compression-expansion engine concepts (DCEE) are split-cycle concepts where the compression, combustion, expansion and gas exchange strokes occur in two or more different cylinders. Previous simulation studies reveal there is a potential to improve brake efficiency with these engine concepts due to improved thermodynamic and mechanical efficiencies. As a continuation of this project this paper studies an alternative layout of the DCEE-concept. The concept studied in this paper has three different cylinders, a compression, a combustion and an expansion cylinder. Overall system indicated and brake efficiency estimations were based on both engine experiments and simulations. The engine experiments were carried out at 10 different operating points and 5 fuelling rates (between 98.2 and 310.4 mg/cycle injection mass) at an engine speed of 1200 rpm. The inlet manifold pressure was varied between 3 and 5 bar. Due to concerns with structural stability the peak cylinder pressure
Lam, Nhut, Tunestal, Per, Andersson, Arne
Methods of Improving Combustion Efficiency in a High-Efficiency, Lean Burn Dual-Fuel Heavy-Duty Engine2019-01-003201/15/2019
Combustion losses are one of the largest areas on inefficiency in natural gas/diesel dual-fuel engines, especially when compared to the traditional diesel engines on which they are based. These losses can vary from 1-2% at high load, to more than 6% of the total fuel energy at part load conditions. For diesel/natural gas dual-fuel engines, the three main sources of combustion losses are: bulk losses (increasing air-fuel ratio, AFR, to the premixed fuel’s lean flammability limit), crevice losses (premixed fuel trapped near valve pockets and top ring lands unable to oxidize), and blow-through losses (fumigated fuel/air intake charge passes through the cylinder and out the exhaust valve during valve overlap). In order to improve overall engine efficiency and decrease greenhouse gas emissions, these losses must be minimized. In this paper, various mitigation techniques are explored experimentally on a 13 L, 2010-class on-highway diesel engine that has been modified for fumigated natural
Nieman, Derek E., Morris, Andrew P., Miwa, Jason T., Denton, Bradley D.
Dynamic Exhaust Valve Flow 1-D Modelling During Blowdown Conditions2019-01-005801/15/2019
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
Holmberg, Ted, Cronhjort, Andreas, Stenlaas, Ola
A Study of Cycle-to-Cycle Flow Variations in a Small Spark-Ignition Engine at Low Throttle Opening2018-32-003510/30/2018
Cycle-to-cycle flow variations significantly influence the combustion variations from one cycle to the next, particularly at low operating loads in small spark-ignition engines. Hence in the present work, cycle-to-cycle flow variations are analyzed at low throttle opening of 25% in a small spark-ignition engine using particle image velocimetry (PIV) technique. Experiments are conducted in an optically accessible single-cylinder, port-fuel-injection engine (volume: 110 cm3) at 1200 rpm engine speed. Images are captured at different crank angle positions during both intake and compression strokes over a tumble measurement plane bisecting the intake and exhaust valves, and processed using cross-correlation method to obtain the instantaneous velocity fields considering 200 image pairs at each crank angle position considered. Turbulent kinetic energy and probability density functions of vorticity are then calculated from measured instantaneous velocity fields at different crank angle
Shinde, Gaurav, Mittal, Mayank, Lakshminarasimhan, V
The Fuel Economy Improvement through the Knock Margin Expansion in a Turbocharged Gasoline Direct Injection Engine2018-01-167109/10/2018
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
Shin, Ji Yong, Park, Chansoo, Jung, Jinyoung, Bae, Choongsik
Design and Development of a Roller Follower Hydraulic Lash Adjustor to Eliminate Lash Adjustment and Reduce Noise in a Serial Production Diesel Engine2018-01-176609/10/2018
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
Roberts, Leighton, McCarthy, Jr., James
Divided Exhaust Period Implementation in a Light-Duty Turbocharged Dual-Fuel RCCI Engine for Improved Fuel Economy and Aftertreatment Thermal Management: A Simulation Study2018-01-025604/03/2018
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
Bharath, Anand Nageswaran, Reitz, Rolf, Rutland, Christopher
Sodium Cooling Efficiency in Hollow Valves for Heavy Duty Engines2018-01-036804/03/2018
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
Zenklusen, Fernando, Coenca, Marcio, Puck, Alexander
Divided-Exhaust Turbocharger System with Boost-Valve2018-01-089504/03/2018
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
Roth, David B., Chen, Wei, Ciaravino, Joseph
Cylinder Pressure Based Cylinder Charge Estimation in Diesel Engines with Dual Independent Variable Valve Timing2018-01-086204/03/2018
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
Thomasson, Andreas, Nikkar, Sepideh, Höckerdal, Erik
Variable Valve Actuation Strategies for Better Efficiency Load Range and Thermal Management in an RCCI Engine2018-01-025404/03/2018
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
Mikulski, Maciej, Balakrishnan, Praveen Ramanujam, Doosje, Erik, Bekdemir, Cemil
Eaton goes internal with its next-generation EGR solution18AUTP08_0501/01/2018
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 Engine2017-01-220110/08/2017
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
Cao, Zhongye, Wang, Tianyou, Sun, Kai, Cui, Lei, Gui, Yong
Scavenge Ports Ooptimization of a 2-Stroke Opposed Piston Diesel Engine2017-24-016709/04/2017
This work reports a CFD study on a 2-stroke (2-S) opposed piston high speed direct injection (HSDI) Diesel engine. The engine main features (bore, stroke, port timings, et cetera) are defined in a previous stage of the project, while the current analysis is focused on the assembly made up of scavenge ports, manifold and cylinder. The first step of the study consists in the construction of a parametric mesh on a simplified geometry. Two geometric parameters and three different operating conditions are considered. A CFD-3D simulation by using a customized version of the KIVA-4 code is performed on a set of 243 different cases, sweeping all the most interesting combinations of geometric parameters and operating conditions. The post-processing of this huge amount of data allow us to define the most effective geometric configuration, named baseline. In the second step of the study, the baseline is further optimized, keeping into account some fundamental design constraints, such as the
Mattarelli, Enrico, Rinaldini, Carlo, Savioli, Tommaso, Cantore, Giuseppe, Warey, Alok, Potter, Michael, Gopalakrishnan, Venkatesh, Balestrino, Sandro
Modeling of Phase Change within a Wax Element Thermostat Embedded in an Automotive Cooling System2017-01-013103/28/2017
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
Srinivasan, Chiranth, Zhang, Chonglin, Gao, Haiyang, Wang, De Ming, Slike, Jody
DigitalAir™ Camless FVVA System – Part 1, Valve Train Design, Capability and Performance2017-01-063503/28/2017
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
Babbitt, Guy, Rogers, Jeff, Weyer, Kristina, Cohen, Drew, Charlton, Stephen
DigitalAir ™ Camless FVVA System - Part 2, Gasoline Engine Performance Opportunities2017-01-064103/28/2017
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
Charlton, Stephen J., Price, Charles E., Rogers, Jeff, Turner, James W.G., Wijetunge, Roshan S., Anderson, William
Development of a 1-Liter Advanced Turbocharged Gasoline Direct Injection 3-Cylinder Engine2017-01-063203/28/2017
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 engine systems, especially for 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
Yang, Chen, Cheng, Haiyuan, fan, Zizhu, Yin, Jiandong, Shen, Yuan
Analysis of the Effect of Intake Plenum Design on the Scavenging Process in a 2-Stroke Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) Engine2017-01-103103/28/2017
In this study, the effect of the intake plenum design on the scavenging process in a newly proposed 2-stroke Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) engine was studied in detail by three dimensional (3D) computational fluid dynamics (CFD) simulations. In the BUSDIG engine, the intake scavenge ports are integrated into the cylinder liner and their opening and closure are controlled by the movement of piston top while exhaust valves are placed in the cylinder head. In order to accommodate the optimized scavenge ports in the real engine application, the intake plenum with an inlet pipe and a scavenge chamber was designed and connected to the 12 evenly distributed scavenge ports in a single cylinder BUSDIG engine. In order to achieve optimal scavenge performances and sufficient in-cylinder flow motions to enhance the fuel/air mixing, five design parameters of the intake plenum were investigated, including the ratio of the inlet area relative to the scavenge port area
Wang, Xinyan, Ma, Jun, Zhao, Hua
Pressure Ratio Influence on Exhaust Valve Flow Coefficients2017-01-053003/28/2017
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
Holmberg, Ted, Cronhjort, Andreas, Stenlaas, Ola
Simulation of Subcooled Flow Boiling on Engine Cooling Jacket with a Bubble Waiting Time Coefficient Model2017-01-013903/28/2017
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
Dong, Fei, Hou, Liuwendi, Xu, Zhenlong, Cao, TaoTao
Development of Heat Resistant Titanium Alloy for Exhaust Valves Applicable for Motorcycles2016-32-002311/08/2016
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
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
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
Gonzalez D, Manuel A., Di Nunno, Davide
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
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
Yang, Chen, Cheng, Haiyuan, Fan, Zizhu, Yin, Jiandong, Shen, Yuan, Haubner, Frank, Slotman, Jeroen, Seibel, Joerg, Baer, Stephan
A Sectoral Approach to Modelling Wall Heat Transfer in Exhaust Ports and Manifolds for Turbocharged Gasoline Engines2016-01-020204/05/2016
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
Franzke, Bjoern, Pischinger, Stefan, Adomeit, Philipp, Schernus, Christof, Scharf, Johannes, Uhlmann, Tolga
Development of a New 1.5L I4 Turbocharged Gasoline Direct Injection Engine2016-01-102004/05/2016
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
Wada, Yusuke, Nakano, Koji, Mochizuki, Kei, Hata, Ryuichi
Development of a New 2.0L I4 Turbocharged Gasoline Direct Injection Engine2016-01-101704/05/2016
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
Jono, Mitsutaka, Taguchi, Masayuki, Shonohara, Toshimitsu, Narihiro, Shigeru
A Virtual Residual Gas Sensor to Enable Modeling of the Air Charge2016-01-062604/05/2016
Air charge calibration of turbocharged SI gasoline engines with both variable inlet valve lift and variable inlet and exhaust valve opening angle has to be very accurate and needs a high number of measurements. In particular, the modeling of the transition area from unthrottled, inlet valve controlled resp. throttled mode to turbocharged mode, suffers from small number of measurements (e.g. when applying Design of Experiments (DoE)). This is due to the strong impact of residual gas respectively scavenging dominating locally in this area. In this article, a virtual residual gas sensor in order to enable black-box-modeling of the air charge is presented. The sensor is a multilayer perceptron artificial neural network. Amongst others, the physically calculated air mass is used as training data for the artificial neural network. The air mass calculation is performed by taking into account valve timing, effective valve cross-sectional area and low-pressure indication at intake and exhaust
Raidt, Benedikt
Extending the Dilution Limit of Spark Ignition Combustion via Fuel Injection during Negative Valve Overlap2016-01-067104/05/2016
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
Chang, Yan, Wooldridge, Margaret, Bohac, Stanislav V.
Development of New High-Efficiency Kappa 1.6L GDI Engine2016-01-066704/05/2016
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
Hwang, Kookjin, Hwang, Iljoong, Lee, Hwangbok, Park, Hyunil, Choi, Hoyeon, Lee, Kwanwoo, Kim, Wootae, Kim, Heungchul, Han, Bonghoon, Lee, Jongsub, Shin, Bosung, Chae, Dongsuk
Investigation of the Gas Exchange (Scavenging) on a Single-Scroll Turbocharged Four Cylinder GDI Engine2016-01-102404/05/2016
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
Wolany, Adalbert, Glahn, Claus, Berner, Hans-Juergen, Bargende, Michael
Modelling Analysis of Aftertreatment Inlet Temperature Dependence on Exhaust Valve and Ports Design Parameters2016-01-067004/05/2016
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
Serrano, José Ramón, Piqueras, Pedro, Navarro, Roberto, Gómez, Javier, Michel, Marc, Thomas, Bénédicte
Local Gaussian Process Regression in Order to Model Air Charge of Turbocharged Gasoline SI Engines2016-01-062404/05/2016
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
Exhaust and Muffler Aeroacoustics Predictions using Lattice Boltzmann Method2015-01-231406/15/2015
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
Mann, Adrien, Kim, Min-Suk, Neuhierl, Barbara, Perot, Franck, Powell, Robert, Rose, Thomas, Krueger, Jan
Comparison of Variable Valve Actuation, Cylinder Deactivation and Injection Strategies for Low-Load RCCI Operation of a Light Duty Engine2015-01-084304/14/2015
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
Bharath, Anand Nageswaran, Yang, Yangdongfang, Reitz, Rolf D., Rutland, Christopher
Investigation of Low-Speed Pre-Ignition in Boosted Spark Ignition Engine2015-01-075104/14/2015
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
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 Cycle2015-01-126204/14/2015
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
Li, Yuanping, Zhao, Hua, Stansfield, Phil, Freeland, Paul
Evaluation of the Potential Benefits of an Automotive, Gasoline, 2-Stroke Engine2015-01-126104/14/2015
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
Lopez, J. Javier, Novella, Ricardo, Valero-Marco, Jorge, Coma, Gilles, Justet, Frederic
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