Diesel injector dynamic modelling and estimation of injection parameters from impact response .2. Prediction of injection parameters from monitored vibration

Part 2 of this paper presents the experimental and analytical procedures used in the estimation of injection parameters from monitored vibration. The mechanical and flow-induced sources of vibration in a fuel injector are detailed and the features of the resulting vibration response of the injector body are discussed. Experimental engine test and data acquisition procedures are described, and the use of an out-of-the-engine test facility to confirm injection dependent vibration response is outlined. Wigner-Ville distribution (WVD) analysis of non-stationary vibration signals monitored on the injector body is used to locate regions of vibration in the time-frequency plane which are responsive to injection parameters. From the data in these regions, estimates of injection timing and fuel pressure are obtained. Accurate estimation of injection parameters from externally monitored vibration is shown to pave the way for the detection and diagnosis of injection system faults. Moreover, it is demonstrated that the technique provides an alternative method for the set-up, checking and adjustment of fuel injection timing.