Fault detection in a diesel engine by analysing the instantaneous angular speed

Instantaneous angular speed of a diesel engine contains a lot of informatio n about gas pressure in cylinders, which can be used to diagnose combustion -related faults and other faults affecting the gas pressure, such as fuel l eakage in fuel system, valve leakage, etc. In this paper, a dynamic model f or simulating the instantaneous angular speed is presented, and the instant aneous angular speed waveforms on a small four-cylinder diesel engine are s imulated. The tangential forces induced by the gas pressure and the vertica l imbalance inertial force are calculated and analysed based on the propose d dynamic model, respectively. It is concluded that the gas pressure and th e vertical imbalance inertial force have a great influence on the instantan eous angular speed. The simulated results of the instantaneous angular spee d fluctuation ratio based on the dynamic model are confirmed by the experim ental results. The instantaneous angular speed waveforms both in the fuel l eakage condition and in the nor mal condition are measured under various en gine speeds and loads in laboratory condition. The characteristic parameter s for detecting the faults relating to the gas pressure in the cylinder are obtained successfully. It is promising, therefore, to develop and to apply the diagnosis technique further using the instantaneous angular speeds to detect the faults relating to the gas pressure in the cylinder. (C) 2001 Ac ademic Press.