Prediction of In-cylinder Pressure for Light-duty Diesel Engines 2019-01-0943
In recent years, emission regulations are getting stricter than ever. To develop engines that comply with these regulations, in-cylinder pressure plays a fundamental role as it is necessary to analyze combustion characteristics and to control combustion-related parameters. The analysis of the in-cylinder pressure data enables the modelling of exhaust emissions where characteristic temperature can be derived from the in-cylinder pressure and the pressure can be used for other researches, such as optimizing efficiency and emissions through controlling combustion.
Therefore, piezoelectric pressure sensor is an essential element in engine research field to measure in-cylinder pressure. However, it is practically difficult to install this pressure sensor on all engines and on-road vehicles due to cost issues. Therefore, there have been a lot of studies to estimate the in-cylinder pressure using data available only from the Engine Control Unit (ECU) without additional pressure sensor.
In-cylinder pressure prediction model for conventional light-duty diesel engines is described in this paper. Firstly, pressure during compression stroke could be estimated with variable polytropic index. Next, Wiebe function was applied for describing pressure during pilot and main combustion. This prediction of in-cylinder pressure was established for real-time estimation.
Entire pressure prediction model consists of subordinate models, where physical phenomena are simplified for real-time application of the model. The accuracy of the sub-models directly has an influence on error of parent model, pressure prediction. Therefore, sensitivity analysis was conducted in this study to verify the effect of the sub-models such as polytropic index model, ignition delay model, heat loss model and combustion duration model on entire pressure prediction model. This study will contribute to establishing more accurate pressure prediction through the sensitivity analysis and many researches that require the in-cylinder pressure information.
Youngbok Lee, Seungha Lee, Kyoungchan Han, Kyoungdoug Min
Seoul National Univ., Hyundai Motor Co.