Secondary Influence Factors of Combustion Noise Mechanism under Transient Conditions of DI-Diesel Engine

This paper concerns the secondary influence factors of combustion noise under transient conditions of DI-Diesel engines. By designing combustion noise test in transient and steady conditions, the secondary influence factors of combustion noise are measured. At the same load and rotational speed, the secondary influence mechanism of combustion noise is studied by analyzing indirect influence factors of combustion noise, such as the temperature of combustion chamber wall, the pressure of fuel injection and the needle lift between transient and steady conditions. The difference of the secondary influence factors in two conditions affects the aerodynamic load and the high-frequency oscillation, which will further influence the combustion noise of steady and transient conditions. The secondary influence mechanism of combustion under transient conditions is also studied at different fuel supply advance angles. The results show that, the temperature of combustion chamber wall, the pressure of fuel injection, the maximum needle lift and the unsealing standing time of needle lift in transient conditions are higher than those of steady conditions under the same load and rotation speed. This will result in the gaps of ignition delay, ignition point and fuel injection quantity under transient conditions. Therefore, the aerodynamic load and high-frequency oscillation of combustion pressure are influenced, which results in difference of combustion noise between two conditions.