Thermodynamic operating indicators of an SI engine with a rate-shaping type direct injection

The authors proposed a rate-shaping injection consisting of a time-controlled fuel dosing to allow better control of the injection process and also of the combustion process as a final result. The effects evaluation of applying such fuel injection control method should be based on the obtained engine operating indicators improvement analysis, especially the thermodynamic indicators. Selected injection strategies were implemented in an experimental engine model – a rapid compression machine (RCM). The observations of the processes inside the cylinder were carried out at the frequency of 10 kHz using the high speed camera. Indicator tests (AVL IndiModul) were performed with the same data acquisition frequency for further synchronization with the optical tests results. Comparative analyses of the effects of the direct injection system with a single fuel dose and rate-shaping system were performed. Combustion rates influencing the process thermodynamic indexes and resulting in differences in the results of optical tests were experimentally determined. The comparative assessment of the obtained results and analyses lead to the conclusion that the use of the rate-shaping system enables a significant increase in the combustion process control and enables the injection process control methods to be correlated with the operational indices of the model engine. (paper)