Optimization of the Injection Behavior in Common Rail Systems under the Influence of Aging of the Injector

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Modern diesel engine vehicles are commonly equipped with the common rail (CR) injection technology. Higher injection pressures, faster response times and flexible adaptation of the injection contribute to meeting the requirements of current emission standards. In addition to determining pollutant emissions during diesel vehicle registration, the emission behavior over lifetime is becoming increasingly important and therefore needs to be considered in engine development. With regard to the injectors in diesel engines, aging phenomena like coking, wear and cavitation result in a different injection behavior. Since these changes might deteriorate pollutant emissions, the long-term consequences of aging are subject of state-of-the-art research. Controlling the combustion process and the resulting pollutant emissions is achieved by suitable adjustment of the CR injection system. Model-based optimization during engine operation is a promising approach to improve injection behavior.The objective of this project is to develop identification and adaptation methods to compensate for aging phenomena in the injector nozzle. These methods are used in an adaptive control scheme in order to comply with emission legislations over engine lifetime. In order to detect the effects of aging phenomena on the injection process, additional signals such as injection pressure and control piston lift are measured and then used to validate a high-fidelity simulation model of the injector. The injection rate of the altered injector is estimated with the injector model and then used to compensate aging effects and nozzle wear.In the application period so far, the improvement of emission behavior was achieved by optimizing the injection rate with an adaptive controller. The previous results reveal the following points that will be topic of the requested project extension of one year:1) Analysis of the effects of aging phenomena on the overall engine behavior ;2) Adjustment of the identification and adaption methods ;3) Feasibility study on an extended, model-based controller to optimize engine parameters using multiple injection strategies.The adaptive control researched in this project is applied to a solenoid valve injector and tested on a single-cylinder research engine. The methods are easily applicable to injection systems with different injector types and engines and improvement of long-term injection behavior can be expected.