The Experts below are selected from a list of 18621 Experts worldwide ranked by ideXlab platform
J W G Turner - One of the best experts on this subject based on the ideXlab platform.
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1 d simulation study of divided exhaust period for a highly downsized turbocharged si engine scavenge valve optimization
SAE International journal of engines, 2014Co-Authors: Sam Akehurst, Chris Brace, Colin Copeland, J W G TurnerAbstract: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.
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influence of the variable valve timing strategy on the control of a homogeneous charge compression hcci engine
2004 SAE Fuels & Lubricants Meeting & Exhibition, 2004Co-Authors: Nebojsa Milovanovic, Rui Chen, J W G TurnerAbstract:Homogeneous Charge Compression Ignition (HCCI) engine concept has the potential to be high efficient and to produce low NOx and particulate matter emissions. However, the problem of controlling the combustion over the entire load/speed range limits its practical application. The HCCI combustion is controlled by chemical kinetics of the charge mixture, with no influence of the flame diffusion or turbulent propagation. Therefore, to achieve a successful control of the HCCI Process, the composition, temperature and pressure of the charge mixture at IVC point have to be controlled. The use of the variable valve timing strategy that enables quick changes in the amount of trapped hot exhaust Gases shows the potential for the control of the HCCI combustion. The aim of this paper is to analyse influence of the variable valve timing strategy on the Gas Exchange Process, the Process between the first valve open event (EVO) and the last valve closing event (IVC), in a HCCI engine fuelled with standard Gasoline fuel (95RON). The Gas Exchange Process affects the engine parameters and charge properties and therefore plays a crucial role in determining the control of the HCCI Process. Analysis is performed by the experimental and modelling approaches. The single-cylinder research engine equipped with the fully variable valve train (FVVT) system was used for the experimental study. A combined code consisting of a detailed chemical kinetics code and one-dimensional fluid dynamics code was used for the modelling study. The results obtained indicate that the variable valve timing strategy has a strong influence on the Gas Exchange Process, which in turn influences the engine parameters and the cylinder charge properties, hence the control of the HCCI Process. The EVC timing has the strongest effect followed by the IVO timing, while the EVO and IVC timings have the minor effects.
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Influence of variable valve timings on the Gas Exchange Process in a controlled auto-ignition engine
Proceedings of the Institution of Mechanical Engineers Part D: Journal of Automobile Engineering, 2004Co-Authors: Nesa Milovanovic, Rui Chen, J W G TurnerAbstract:The controlled auto-ignition (CAI) engine concept has the potential to be highly effcient and to produce low NOx and particulate matter emissions. However, the problem of controlling the combustion over the entire load/speed range limits its practical application. The CAI combustion is controlled by the chemical kinetics of the charge mixture, with no influence of the flame diffusion or turbulent propagation. Therefore, to achieve successful control of the CAI Process, the composition, temperature and pressure of the charge mixture at the inlet valve closure (IC ) point have to be controlled. The use of the variable valve timing strategy, which enables quick changes in the amount of trapped hot exchaust Gases, shows the potential for control of CAI combustion. The aim of this paper is to analyse the influence of the variable valve timing strategy on the Gas Exchange Process, the Process between the first valve open event (EO) and the last valve closing event (IC ), in a CAI engine fuelled with standard Gasoline fuel (95RON). The Gas Exchange Process affects the engine parameters and charge properties and therefore plays a crucial role in determining the control of the CAI Process. Analysis is performed by experimental and modelling approaches. A single-cylinder research engine equipped with a fully variable valvetrain (FVVT) system was used for the experimental study. A combined code consisting of a detailed chemical kinetics code and one-dimensional fluid dynamics code was used for the modelling study. The results obtained indicate that the variable valve timing strategy has a strong influence on the Gas Exchange Process, which in turn influences the engine parameters and the cylinder charge properties, and hence the control of the CAI Process. The EC timing has the strongest effect, followed by the IO timing, while the EO and IC timings have minor effects.
P. Luszcz - One of the best experts on this subject based on the ideXlab platform.
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A modelling study into the effects of variable valve timing on the Gas Exchange Process and performance of a 4-valve DI homogeneous charge compression ignition (HCCI) engine
Energy Conversion and Management, 2009Co-Authors: A-f.m. Mahrous, A. Potrzebowski, H M Xu, Athanasios Tsolakis, Miroslaw L. Wyszynski, P. LuszczAbstract:Homogeneous charge compression ignition (HCCI) combustion mode is a relatively new combustion technology that can be achieved by using specially designed cams with reduced lift and duration. The auto-ignition in HCCI engine can be facilitated by adjusting the timing of the exhaust-valve-closing and, to some extent, the timing of the intake-valve-opening so as to capture a proportion of the hot exhaust Gases in the engine cylinder during the Gas Exchange Process. The effects of variable valve timing strategy on the Gas Exchange Process and performance of a 4-valve direct injection HCCI engine were computationally investigated using a 1D fluid-dynamic engine cycle simulation code. A non-typical intake valve strategy was examined; whereby the intake valves were assumed to be independently actuated with the same valve-lift profile but at different timings. Using such an intake valves strategy, the obtained results showed that the operating range of the exhaust-valve-timing within which the HCCI combustion can be facilitated and maintained becomes much wider than that of the typical intake-valve-timing case. Also it was found that the engine parameters such as load and volumetric efficiency are significantly modified with the use of the non-typical intake-valve-timing. Additionally, the results demonstrated the potential of the non-typical intake-valve strategy in achieving and maintaining the HCCI combustion at much lower loads within a wide range of valve timings. Minimizing the pumping work penalty, and consequently improving the fuel economy, was shown as an advantage of using the non-typical intake-valve-timing with the timing of the early intake valve coupled with a symmetric degree of exhaust-valve-closing timing.
Hua Zhao - One of the best experts on this subject based on the ideXlab platform.
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High load performance and combustion analysis of a four-valve direct injection Gasoline engine running in the two-stroke cycle
Applied Energy, 2015Co-Authors: Macklini Dalla Nora, Hua ZhaoAbstract:With the introduction of CO2 emissions legislation or fuel economy standards in Europe and many countries, significant effort is being made to improve spark ignition Gasoline engines because of their dominant market share in passenger cars and potential for better fuel economy. Amongst several approaches, the engine downsizing technology has been adopted by the automotive companies as one of the most effective methods to reduce fuel consumption of Gasoline engines. However, aggressive engine downsizing is constrained by excessive thermal and mechanical loads as well as knocking combustion and low speed pre-ignition (also known as super-knock). In order to overcome such difficulties, a Gasoline direct injection single cylinder engine was modified to run under the two-stroke cycle by operating the intake and exhaust valves around bottom dead centre (BDC) at every crankshaft revolution. The combustion products were scavenged by means of a reversed tumble flow of compressed air during the positive valve overlap period at BDC. The engine output was determined by the charging and trapping efficiencies, which were directly influenced by the intake and exhaust valve timings and boost pressures. In this research a valve timing optimisation study was performed using a fully flexible valve train unit, where the intake and exhaust valve timings were advanced and retarded independently at several speeds and loads. A supercharger was used to vary the load by increasing the intake pressure. The effects of valve timing and boost pressure in this two-stroke poppet valve engine were investigated by a detailed analysis of the Gas Exchange Process and combustion heat release. Gaseous and smoke emissions were measured and analysed. The results confirmed that the two-stroke cycle operation enabled the indicated mean effective pressure to reach 1.2MPa (equivalent to 2.4MPa in a four-stroke cycle) with an in-cylinder pressure below 7MPa at an engine speed as low as 800rpm. The engine operation was limited by scavenging inefficiencies and short time available for proper air–fuel mixing at high speeds using the current fuel injector. The large amounts of hot residual Gas trapped induced controlled auto-ignition combustion at high speeds, and thus the abrupt heat release limited higher loads.
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Understanding the infiuence of valve timings on controlled autoignition combustion in a four-stroke port fuel injection engine
Proceedings of the Institution of Mechanical Engineers Part D: Journal of Automobile Engineering, 2005Co-Authors: Li Cao, Hua Zhao, Xi Jiang, Navin KalianAbstract:Controlled autoignition (CAI) combustion, also known as homogeneous charge compression ignition (HCCI), was achieved through the negative valve overlap approach by using small-lift camshafts. Three-dimensional multicycle engine simulations were carried out in order better to understand the effects of variable intake valve timings on the Gas Exchange Process, mixing quality, CAI combustion, and pollutant formation in a four-stroke port fuel injection (PFI) Gasoline engine. Full engine cycle simulation, including complete Gas Exchange and combustion Processes, was carried out over several cycles in order to obtain the stable cycle for analysis. The combustion models used in the present study are a modified shell ignition model and a laminar and turbulent characteristic time model, which can take high residual Gas fraction into account. After the validation of the model against experimental data, investigations of the effects of variable intake valve timing strategies on the CAI combustion Process were carried out. These analyses show that the intake valve opening (WO) and intake valve closing (IVC) timings have a strong influence on the Gas Exchange and mixing Processes in the cylinder, which in turn affect the engine performance and emissions. Symmetric IVO timing relative to exhaust valve closing (EVC) timing tends to produce a more stratified mixture, earlier ignition timing, and localized combustion, and hence higher NO, and lower unburned HC and CO emissions, whereas retarded WO leads to faster mixing, a more homogeneous mixture, and uniform temperature distribution.
M V Panchenko - One of the best experts on this subject based on the ideXlab platform.
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seasonal behavior of the co2 Gas Exchange Process in the atmosphere water system of littoral zone of southern baikal 3 autumn
Atmospheric and Oceanic Optics, 2013Co-Authors: V M Domysheva, M V Sakirko, D A Pestunov, M V PanchenkoAbstract:This paper is the next in a series of publications dealing with the analysis of seasonal features of the carbon dioxide Exchange Process in the littoral of the Southern Baikal during the open-water period, and devoted to results obtained during the fall period. It is shown that variations in the concentrations of dissolved Gases and biogenic elements in the surface waters of the Lake Baikal littoral during fall are opposite in character to the Process observed during the spring-summer period. The concentrations of carbon dioxide, oxygen, nitrates, and phosphates increase from the second half of September toward December. The sink of CO2 from the atmosphere into the water surface is still observed during early October in the Baikal littoral, with its diurnal budget being comparable in value to the daily average sink during the period of hydrological summer. The daily average CO2 flux reverses sign in November, and the lake surface becomes a source supplying carbon dioxide to the near-water atmosphere; the CO2 supply rate keeps increasing and reaches a maximum level during December, i.e., until the beginning of freezing-over period. At the beginning of this period, an additional small CO2 amount can be expected to be supplied to the atmosphere of the littoral zone due to the Process of premorning freezing and a subsequent ice melt.
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seasonal behavior of the co2 Gas Exchange Process in the atmosphere water system of the littoral zone of southern baikal 1 hydrological spring
Atmospheric and Oceanic Optics, 2011Co-Authors: V M Domysheva, M V Sakirko, D A Pestunov, M V PanchenkoAbstract:Analysis of the mechanisms determining the direction and intensity of CO2 fluxes in the “atmosphere-water” system seems to be important in the context of studying the problem of present-day increase in the content of one of the greenhouse Gases (carbon dioxide) in the atmosphere. This paper starts a series of publications devoted to the analysis of seasonal features of the CO2 Gas Exchange Process in the littoral zone of southern Baikal and presents the results obtained in the spring period.
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seasonal behavior of the co2 Gas Exchange Process in the atmosphere water system of the littoral zone of southern baikal 1 hydrological spring
Atmospheric and Oceanic Optics, 2011Co-Authors: V M Domysheva, M V Sakirko, D A Pestunov, M V PanchenkoAbstract:This is the next in the series of publications devoted to the analysis of seasonal features of the carbon dioxide Exchange Process in the littoral zone of Southern Baikal.
A-f.m. Mahrous - One of the best experts on this subject based on the ideXlab platform.
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A modelling study into the effects of variable valve timing on the Gas Exchange Process and performance of a 4-valve DI homogeneous charge compression ignition (HCCI) engine
Energy Conversion and Management, 2009Co-Authors: A-f.m. Mahrous, A. Potrzebowski, H M Xu, Athanasios Tsolakis, Miroslaw L. Wyszynski, P. LuszczAbstract:Homogeneous charge compression ignition (HCCI) combustion mode is a relatively new combustion technology that can be achieved by using specially designed cams with reduced lift and duration. The auto-ignition in HCCI engine can be facilitated by adjusting the timing of the exhaust-valve-closing and, to some extent, the timing of the intake-valve-opening so as to capture a proportion of the hot exhaust Gases in the engine cylinder during the Gas Exchange Process. The effects of variable valve timing strategy on the Gas Exchange Process and performance of a 4-valve direct injection HCCI engine were computationally investigated using a 1D fluid-dynamic engine cycle simulation code. A non-typical intake valve strategy was examined; whereby the intake valves were assumed to be independently actuated with the same valve-lift profile but at different timings. Using such an intake valves strategy, the obtained results showed that the operating range of the exhaust-valve-timing within which the HCCI combustion can be facilitated and maintained becomes much wider than that of the typical intake-valve-timing case. Also it was found that the engine parameters such as load and volumetric efficiency are significantly modified with the use of the non-typical intake-valve-timing. Additionally, the results demonstrated the potential of the non-typical intake-valve strategy in achieving and maintaining the HCCI combustion at much lower loads within a wide range of valve timings. Minimizing the pumping work penalty, and consequently improving the fuel economy, was shown as an advantage of using the non-typical intake-valve-timing with the timing of the early intake valve coupled with a symmetric degree of exhaust-valve-closing timing.
