Combustion Induced Noise of Engine by Single Explosion Excitation : 1st Report, Combustion Noise for Stationary Engine

Abstract

This paper exemplifies an attempt to clarify the characteristics of combustion noise generation of an engine. The transmission-radiation coefficients which are defined as a conversion ratio of the combustion impact to the acoustic power generated noise are examined for the transmission paths and the noise radiating surfaces of the engine. Experiments are carried out generating a single combustion impact by exploding an electric igniter with explosive or a fire cracker in the combustion chamber of a stationary engine. The calculation procedures of the transmission-radiation coefficient of the combustion noise are discussed. Using modified structures of a test engine, the characteristics of these coefficients are separately obtained for engine surfaces and for three transmission paths each, i.e. the gas excitation path, the piston-cylinder path and the piston-crankshaft path. For an air-cooled single-cylinder spark ignition engine, it was found that the combustion noise through the piston-cylinder path is most strongly radiated from the cylinder head and the cylinder block.