The Transfer Function of Combustion Noise in DI-Diesel Engine

A single cylinder DI-diesel engine is chosen as the research object, to study the relationship between the cylinder pressure and surface vibration and the combustion noise. In order to separate the noise of piston slapping from the combustion noise and identify the combustion noise, a new experimental method is designed to obtain the transfer function of combustion noise by setting off a small explosive charge in the cylinder with the crankshaft locked in a fixed position. The spectrum of cylinder pressure created by the explosive charge is measured, along with the spectrum of radiated noise. The transfer function of the combustion noise which reflects the structure attenuation of engine can be obtained. The transfer functions gained from different shape of the combustion chamber and different exploding pressures are compared and analyzed. The measurement of noise is carried out in a practical DI-diesel. The combustion noise that includes the piston slapping noise is gained by time window and compared with the combustion noise that is gained by combustion noise's transfer function and combustion pressure. The character of the noise of piston slapping is analyzed. The method of obtaining the theoretical combustion noise is provided.