Numerical Simulation Study of Spray Wall Impingement Combustion

Abstract

Fuel spray wall impingement is a common phenomenon in small high-pressure direct injection diesel engines. Fuel spray wall impingement influences the in-cylinder combustion process, and significantly impacts the engine’s dynamics, fuel economy, and emissions. To better understand the combustion characteristics of fuel spray wall impingement, the numerical simulation was applied to calculate the process and explore this process. The results show that, during the 2-stage combustion process of spray wall impingement, the impingement promotes the radial development radius and the vortex height of the spray, enhances oil-gas mixing near the wall, and forms favorable conditions for low-temperature ignition near the wall. Low-temperature combustion reactions start in the near-wall region, where the mixture is relatively dilute, and then develop into the dense mixed gas area in the center of the impinging spray. As low-temperature oxidation combustion continues to release heat, the maximum temperature in the center of the impinging spray will gradually increase, and a large amount of CH₂O will accumulate. Meanwhile, the impinging spray can cause the formation of a more concentrated mixture in the center of the impinging spray, and low-temperature combustion would release less heat, resulting in the incomplete combustion of some carbon, and increasing the amount of soot generated. Additionally, as high-temperature combustion proceeds, the temperature will continue rising, and the impinging spray will draw more oxygen, generating a large amount of NO_x through oxidation reactions.