Origin of Low-Frequency Mechanical Noise from Diesel Engines

Abstract

In his book, Noise of Marine Diesel Engines, V. I. Zinchenko distinguishes between aerodynamic-noise sources, such as the intake blowers and the exhaust, and mechanical sources associated with the reciprocating mechanism. Zinchenko proposes that the dominant source of mechanical engine noise is the lateral slap of the piston against the cylinder wall which occurs close to the time of peak cylinder pressure, and he develops an expression for the impulse of such an impact. From this expression, using some simplifying assumptions, one can derive an expression for the radiated sound associated with piston impact. The results are of the right order of magnitude; and the resultant dependence on rpm, horsepower, cylinder pressure, number of cylinders, and engine-design parameters are all in reasonable agreement with experimental trends.