Diesel injector dynamic modelling and estimation of injection parameters from impact response part 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.

Table 1 caption: Test engine specification

Fig. 1 caption: Injector vibration versus cylinder pressure, line pressure and needle lift

Fig. 2 caption: Bench‐top test rig layout and data acquisition system

Fig. 3 caption: Injector vibration and needle motion from bench‐top testing

Fig. 4 caption: Engine test layout and data acquisition system

Fig. 5 caption: Time‐frequency analysis of injector vibration

Fig. 6 caption: Time‐frequency analysis of injector vibration at 3000 r/min

Fig. 7 caption: Timing of the fuel injection process

Fig. 8 caption: Comparison of needle lift and vibration derived injection timing

Fig. 9 caption: Comparison between injection line pressure and injector vibration

Fig. 10 caption: Relationship between injector vibrtation and line pressure