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

现代柴油发动机车辆普遍采用共轨（CR）喷射技术。更高的喷射压力、更快的响应时间和灵活的喷射适应性有助于满足当前排放标准的要求。除了确定柴油车登记期间的污染物排放外，整个使用寿命期间的排放行为也变得越来越重要，因此需要在发动机开发中加以考虑。对于柴油机喷油器来说，焦化、磨损、空化等老化现象会导致喷油器的喷射行为发生变化。由于这些变化可能会使污染物排放恶化，因此老化的长期后果是最先进的研究课题。控制燃烧过程和由此产生的污染物排放是通过适当调整CR喷射系统来实现的。发动机运行过程中基于模型的优化是一种很有前途的改善喷射行为的方法。该项目的目的是开发识别和适应方法，以补偿喷油器喷嘴的老化现象。这些方法用于自适应控制方案，以符合排放法规的发动机寿命。为了检测老化现象对喷射过程的影响，测量了额外的信号，如喷射压力和控制活塞升程，然后用于验证喷油器的高保真仿真模型。利用喷油器模型对改变后的喷油器的喷射速度进行估计，并对老化效应和喷油器磨损进行补偿。在目前的应用期内，通过自适应控制器优化喷射速率，实现了排放行为的改善。之前的研究结果揭示了以下几点，这将是该项目延期一年的主题：1)分析老化现象对发动机整体性能的影响；2)识别和适应方法的调整；3)基于模型的扩展控制器在多种喷射策略下优化发动机参数的可行性研究。本课题研究的自适应控制方法应用于电磁阀喷油器，并在单缸研究发动机上进行了试验。这些方法很容易适用于不同喷油器类型和发动机的喷射系统，并有望改善长期喷射行为。

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.