Analysis of variations in diesel engine idle vibration

Abstract

The variations in diesel engine idle vibration caused by fuels of different composition and their contributions to the variations in the steering wheel vibrations were assessed. The time-varying covariance method (TV-AutoCov) and time-frequency continuous wavelet transform (CWT) techniques were used to obtain the cyclic and instantaneous characteristics of the vibration data acquired from two turbocharged four-cylinder, 4-stroke diesel engine vehicles at idle under twelve different fuel conditions. The analysis revealed that TV-AutoCov analysis was the most effective for detecting changes in cycle-to-cycle combustion energy (22.61%) whereas changes in the instantaneous values of the combustion peaks were best measured using the CWT method (2.47%). On the other hand both methods showed that diesel idle vibration was more affected by amplitude modulation (12.54%) than frequency modulation (4.46%). The results of this work suggest the use of amplitude modulated signals for studying the human subjective response to diesel idle vibration at the steering wheel in passenger cars.