Analysis of Vibration on an Engine Block Caused by Combustion in a Diesel Engine

An accelerometer replaced an in-cylinder pressure sensor to detect the combustion status. The correlation between the vibration on an engine block caused by direct combustion as well as the combustion status was analyzed. The direct combustion vibration was determined. The direct combustion vibration on an engine block was blended with indirect combustion vibrations and other accessories. In addition, the combustion status was specified among several combustion status parameters, namely, RoHR, MPRR, and the peak pressure. There were two distinct vibrations in the motoring state. The frequency range of 2.5–8 kHz and 0–10°CA aTDC was assumed to be a crankshaft vibration. The other vibration, 1–3 kHz and 20–30°CA aTDC, was estimated as a slap motion of the piston. The combustion vibration frequency was 0.1–8 kHz after combustion. As an injector vibration (3–8 kHz) disrupted the search for combustion noise, a 0.1–2 kHz vibration range was appropriate for finding the correlation with the direct combustion state and the peak of the RoHR. As the peak of the RoHR was proportional to the combustion noise, the estimated peak of the RoHR can be used to control the diesel engine’s combustion noise. Estimation was possible in the transient and steady states.