Compensation Strategies for Aging Effects of Common-Rail Injector Nozzles 2019-01-0944
The diesel combustion process is mainly driven by the fuel injection process. Over engine lifetime injection rate and quality will change due to adverse aging effects like coking or cavitation. In this paper we investigated indicators for nozzle aging effects and discuss the influences of these effects on injector and engine parameters.
The injection rates of previously unused nozzles and nozzles that had been operated for hundreds of thousands kilometers in a vehicle engine were compared in order to clarify the impact of aging effects. The key to the detection of alterations of injection nozzles is the identification of strongly correlating parameters. As a first step an instrumented injector had been set up that enabled to measure fuel pressure inside the feed line of the injector and the lift of the control piston. These parameters were measured for the different nozzles mounted onto the instrumented injector and were contrasted to each other.
In a second step engine simulations were performed to investigate the impact of nozzle aging on heat release rate and engine performance of a single-cylinder engine. A predictive combustion model used the measured injection rates as input for calculating the heat release rates. We assessed the kind and magnitude of aging effects impacting on engine performance and emissions. Different compensating strategies for these effects were compared regarding their emissions potential. This study closes the knowledge gap between the effects of nozzle aging and the best method to compensate for them.
Sebastian Schuckert, Mark Huthmacher, Georg Wachtmeister