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Technical Paper

Simulation of the Effect of Intake Pressure and Split Injection on Lean Combustion Characteristics of a Poppet-Valve Two-Stroke Direct Injection Gasoline Engine at High Loads

Poppet-valve two-stroke gasoline engines can increase the specific power of their four-stroke counterparts with the same displacement and hence decrease fuel consumption. However, knock may occur at high loads. Therefore, the combustion with stratified lean mixture was proposed to decrease knock tendency and improve combustion stability in a poppet-valve two-stroke direct injection gasoline engine. The effect of intake pressure and split injection on fuel distribution, combustion and knock intensity in lean mixture conditions at high loads was simulated with a three-dimensional computational fluid dynamic software. Simulation results show that with the increase of intake pressure, the average fuel-air equivalent ratio in the cylinder decreases when the second injection ratio was fixed at 70% at a given amount of fuel in a cycle.
Technical Paper

Experimental investigation of combustion and emissions characteristics of stoichiometric stratified flame ignited (SFI) hybrid combustion in a 4-stroke PFI/DI gasoline engine

Controlled Auto-Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), has the potential to improve the fuel economy of gasoline engines and simultaneously achieve ultra-low NOx emissions. However, lack control of combustion phasing and violent combustion at high loads limit the commercial application of CAI combustion. To overcome above problems, stratified fuel, which is rich mixture around the central spark plug and lean mixture around the cylinder wall, is formed with port fuel injection and direct injection strategies, and rich mixture consumed by flame propagation triggered by spark ignition increases the temperature of unburned mixture and achieve, i.e. stratified flame ignited (SFI) hybrid combustion.
Technical Paper

The application of Controlled Auto-Ignition Gasoline Engines -The challenges and solutions

Controlled auto-ignition (CAI) combustion, also known as homogeneous charge compression ignition (HCCI), has the potential to simultaneously reduce the fuel consumption and nitrogen oxides (NOx) emissions of gasoline engines. However, narrow operating region in loads and speeds is one of the challenges for the commercial application of CAI combustion to gasoline engines. Therefore, the extension of loads and speeds is an important prerequisite for the application of CAI combustion to gasoline engines. The effect of intake charge boosting, charge stratification and spark-assisted ignition on the operating range in CAI mode was reviewed. Stratified flame ignition (SFI) hybrid combustion is one form to achieve CAI combustion under the conditions of highly diluted mixture caused by the flame in the stratified mixture with the help of spark plug.