Abstract: Study the effect of combustion chamber’s temperature in transient conditions on combustion noise mechanism of DI-Diesel engines. By developing testing technique and method of transient conditions and studying the difference of combustion chamber’s wall temperature between transient conditions and steady conditions, the different combustion noise mechanism between transient conditions and steady conditions is analyzed from the point of aerodynamic load and high-frequency oscillation of combustion pressure. The combustion chamber’s wall temperature in transient conditions is higher than steady conditions in the same load and at the same rotation speed. It results in the changing of ignition delay in two conditions and affects the combustion pressure, rate of pressure rise, frequency and amplitude of the high-frequency oscillation of combustion pressure. The result shows that the difference of combustion chamber’s wall temperature between transient and steady conditions in the same load and at the same rotation speed affects the dynamic load and high-frequency oscillation of combustion noise. It is one of the important second level factors resulting in the difference of combustion noise in two conditions.

Key words: Transient conditionCombustion chamber’s wall temperatureCombustion noise, DI-diesel engine