The Use of Coherence Techniques to Predict the Effect of Engine Operating Parameters on Diesel Engine Noise

Abstract

A technique is presented in which the effects on noise of changing diesel engine operating parameters can be predicted. Traditionally, the effects have been determined by experiment. The technique presented in this paper utilizes experimentally determined frequency response functions between each cylinder pressure input and the engine noise. Once the frequency responses are measured, the engine noise can be calculated for an arbitrary cylinder pressure input. The effect of injection timing, engine load, and engine speed are predicted using cylinder pressure histories obtained from a single cylinder research engine. Experimental results are presented, showing good agreement with predicted data. It has been found that the measured frequency responses are independent of the cylinder pressure level. Also presented here is the multiple coherence between the cylinder pressures and the engine noise and the ordinary coherence between two typical cylinder pressures.