Effect of Fuel Injection Timing on the Mixture Preparation in a Small GDI Engine(see the link below)

https://www.researchgate.net/publication/328890783_Effect_of_Fuel_Injection_Timing_on_the_Mixture_Preparation_in_a_Small_Gasoline_Direct-Injection_Engine
GDI engines have evolved as a solution to meet the current demands of the automotive industry. Benefits include good fuel economy, good transient response, and low cold start emissions. However, they suffer from problems, like combustion instability, misfire, and impingement of fuel on in-cylinder surfaces. Therefore, to highlight the influence of fuel injection timing on in-cylinder flow, turbulence, mixture distribution and wall impingement, a computational study is conducted on a small-bore GDI engine. Results showed that air motion inside the engine cylinder is influenced by direct-injection of fuel, with considerable variation in turbulent kinetic energy at the time of injection. Due to charge cooling effect, mixture density and trapped mass were increased by about 10.8% and 9.5%, respectively. A significant drop in mean in-cylinder temperature was observed with direct-injection near the spark plug and fuel impingement on in-cylinder surfaces are carefully evaluated. An early injection at 80 crank angle degree after top dead center of intake provided the best fuel distribution and minimum wall impingement. At the time of spark, in-cylinder turbulence was also found to be higher for this injection timing. Experimental results also indicated relatively higher BTE and lower emissions with early fuel injection timings.

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