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Combustion is known to be affected by variations in the air-fuel mixture concentration, residual gas concentration, turbulent kinetic energy, ignition, etc. However, because each of these factors is related to cycle-to-cycle variations, their effects on combustion variation are unclear. The purpose of this study was to clarify the influences of the air-fuel mixture distribution near the spark plug and variation in the relative position of the ignition on the combustion variation. A 4-cylinder port injection gasoline engine was used as the test engine, and the combustion variation was investigated by measuring the cylinder pressure and air-fuel ratio (A/F) near the spark plug for each cycle using a micro-Cassegrain sensor for each cylinder. The air-fuel mixture distribution was calculated using a Reynolds averaged Navier-Stokes simulation, and the spatial region of the high ignition probability was determined from the gas flow velocity.

Powertrain development requires an efficient development process with no rework and model-based development (MBD). In addition, to performance design that achieves low CO2 emissions is also required. Furthermore, it also demands fuel economy performance considering real-world usage conditions, and in North America, the EPA (U.S. Environmental Protection Agency) 5-cycle, which evaluates performance in a combination of various environments, is applied. This evaluation mode necessitates predicting performance while considering engine heat flow. Particularly, simulation technology that considers behavior based on engine temperature for Hybrid Electric Vehicle (HEV) is necessary. Additionally, in the development trend of vehicle aerodynamic improvement, variable devices like Active Grille Shutter (AGS) are utilized to contribute to reducing CO2 emissions.