Numerical Study to Achieve Stratified EGR in Engines

2002 ◽  
Author(s):  
Bassem H. Ramadan ◽  
Charles L. Gray ◽  
Harold J. Schock ◽  
Fakhri J. Hamady ◽  
Karl H. Hellman
Keyword(s):  
Numerical Study ◽  
Direct Injection ◽  
Fuel Mixture ◽  
Combustion Engines ◽  
Lean Burn ◽  
Complete Combustion ◽  
Stratified Charge ◽  
Automotive Emissions ◽  
Si Engines ◽  
Inlet Manifold

Exhaust Gas Re-circulation (EGR) has been used in intemal combustion engines to control automotive emissions. EGR is usually used to dilute the inlet charge, which consists of air, by redirecting part of the exhaust into the inlet manifold of the engine. This results in a reduction of the oxygen mass fraction in the inlet charge. However, dilution of the air-fuel mixture in an engine using stratified EGR could offer significant fuel economy saving comparable to lean burn or stratified charge direct-injection SI engines. The most critical challenge is to keep the EGR and air-fuel mixture separated, or to minimize the mixing between the two zones to an acceptable level for stable and complete combustion. Swirl-type stratified EGR and fuel-air flow structure is considered desirable for this purpose, because the circular shape of the cylinder tends to preserve the swirl motion. Moreover, the axial piston motion has minimal effect on the swirling motion of the fluid in the cylinder. In this study, we consider intake system design in order to generate a two-zone combustion system, where EGR is maintained in a layer on the periphery of the cylinder, and the fuel-air mixture is maintained in the center of the cylinder. KIVA-3V was used to perform numerical simulations on different EGR systems. The simulations were performed to determine if the two-zones can be generated in the cylinder, and to what extent mixing between the two zones occurs. For the engine geometries considered in this study, the results showed that it is possible to generate the two zones, but mixing is difficult to control.

Numerical Studies of Glow Plug Shield on Natural Gas Ignition Characteristics in a CI Engine

2016 ◽  
Author(s):  
Kang Pan ◽  
James S. Wallace
Keyword(s):  
Natural Gas ◽  
Ignition Delay ◽  
Fuel Injection ◽  
Numerical Study ◽  
Direct Injection ◽  
Fuel Mixture ◽  
Injection Angle ◽  
Glow Plug ◽  
Gas Ignition ◽  
Ignition And Combustion

This paper presents a numerical study on fuel injection, ignition and combustion in a direct-injection natural gas (DING) engine with ignition assisted by a shielded glow plug (GP). The shield geometry is investigated by employing different sizes of elliptical shield opening and changing the position of the shield opening. The results simulated by KIVA-3V indicated that fuel ignition and combustion is very sensitive to the relative angle between the fuel injection and the shield opening, and the use of an elliptical opening for the glow plug shield can reduce ignition delay by 0.1∼0.2ms for several specific combinations of the injection angle and shield opening size, compared to a circular shield opening. In addition, the numerical results also revealed that the natural gas ignition and flame propagation will be delayed by lowering a circular shield opening from the fuel jet center plane, due to the blocking effect of the shield to the fuel mixture, and hence it will reduce the DING performance by causing a longer ignition delay.

Simulation-Aided Development of Prechamber Ignition System for a Lean-Burn Gasoline Direct Injection Motor-Sport Engine

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Muhammed Fayaz Palakunnummal ◽  
Priyadarshi Sahu ◽  
Mark Ellis ◽  
Marouan Nazha
Keyword(s):  
Thermal Efficiency ◽  
Direct Injection ◽  
Fuel Mixture ◽  
Gasoline Direct Injection ◽  
Lean Burn ◽  
Ignition System ◽  
Motor Sport ◽  
Auto Ignition ◽  
Computational Fluid Dynamics Cfd ◽  
Sport Events

Abstract Due to recent regulation changes to restricted fuel usage in various motor-sport events, motor-sport engine manufacturers have started to focus on improving the thermal efficiency and often claim thermal efficiency figures well above equivalent road car engines. With limited fuel allowance, motor-sport engines are operated with a lean air–fuel mixture to benefit from higher cycle efficiency, requiring an ignition system that is suitable for the lean mixture. Prechamber ignition is identified as a promising method to improve lean limit and has the potential to reduce end gas auto-ignition. This paper analyses the full-load performance of a motor-sport lean-burn gasoline direct injection (GDI) engine and a passive prechamber is developed with the aid of a computational fluid dynamics (CFD) tool. The finalized prechamber design benefited in a significant reduction in burn duration, reduced cyclic variation, knock limit extension, and higher performance.

Four Stroke Engine Geometry for Stratified Charge Combustion

2005 ◽  
Author(s):  
E. Musu ◽  
S. Zanforlin ◽  
R. Gentili
Keyword(s):  
Combustion Chamber ◽  
Numerical Study ◽  
Direct Injection ◽  
Combustion Efficiency ◽  
Loss Reduction ◽  
Stratified Charge ◽  
Conventional Combustion ◽  
Gas Expansion ◽  
Partial Loads ◽  
Stroke Engine

In four-stroke engines direct injection increases power and fuel economy, which is further improved by charge stratification, due to pumping loss reduction and better combustion efficiency at partial loads. Charge stratification can be obtained by different techniques and injector designs. In every case late injection is necessary for stratification, which however is impaired by fuel dilution and spreading in consequence of burnt gas expansion, leading to incomplete combustion at very light loads. A numerical study has been carried out modifying KIVA code to handle new piston shapes. An innovative combustion chamber that is split in two volumes and allows fuel confinement during combustion has been conceived. CFD comparison has been made between a conventional combustion chamber and the proposed new one in term of combustion efficiency. Combustion is enhanced by the new design and unburnt emissions are reduced.

Lean Burn Combustion Influence on Stratified Charge Ethanol Direct Injection Engine

2016 ◽  
Author(s):  
Rafael Lara Franco ◽  
Roberto Berlini da Costa ◽  
Carlos Alberto Gomes Júnior ◽  
Fernando Antonio Rodrigues Filho ◽  
Ramon Molina Valle
Keyword(s):  
Direct Injection ◽  
Lean Burn ◽  
Stratified Charge ◽  
Direct Injection Engine

Effect of Injection Timing on Fuel-Air Mixing and Combustion in a Direct Injection Stratified Charge SI Engine

2007 ◽  
Author(s):  
T. Anand Kumar ◽  
J. M. Mallikarjuna ◽  
V. Ganesan
Keyword(s):  
Numerical Study ◽  
Direct Injection ◽  
Combustion Characteristics ◽  
Spark Ignition Engine ◽  
Injection Timing ◽  
Flame Surface ◽  
Si Engine ◽  
Stratified Charge ◽  
Spark Plug ◽  
Air Mixing

This paper describes a numerical study on fuel-air mixing and combustion in a direct injection stratified charge spark ignition engine. The in-cylinder flow, fuel-air mixing and combustion characteristics are investigated in a single cylinder, four-valve, four stoke, direct injection SI engine with pent-roof head and reverse tumble ports. The engine combustion chamber had the side mounted injector and spark plug at the center of pent-roof. Wall guided fuel-air mixing scheme has been adopted. The pre processor code Es-ice, used for dynamic grid generation preparation including description of piston and valve motion. Commercial computational fluid dynamics code Star-CD is used for solving governing equations and post processing of results. Combustion in the present study is simulated using Extended Coherent Flame Model-3z (ECFM-3Z). This model is based on a flame surface density transport equation that can describe inhomogeneous turbulent premixed combustion. In the present study, engine simulations has been carried out from 370 CAD before TDC and upto 90 CAD aTDC. The process includes the closing of the exhaust valves, the whole intake stroke, injection, combustion, and part of expansion. Three different injection timings are simulated viz. 55, 60 and 65 CAD bTDC. For validation of the code predicted results are compared with experimental results available in the literature. It is observed that, injection timing has an important role in mixture preparation and distribution around the spark plug. Hence, for the better combustion characteristics start of injection timing should be optimized.

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