Development of a Start of Combustion Estimation Algorithm using Modified Heat Release Equation for Diesel Engines

Abstract

In diesel engines, the start of combustion (SOC) is an important engine control indicator due to its effects on to engine noise, emission, and engine performance. The SOC is calculated as a location of one percent of total heat release which can be calculated using cylinder pressure. However the calculation of heat release requires a large amount of cylinder pressure data and enormous computation time. In this study, we proposed a simplified SOC estimation algorithm using an initial heat release (IHR). The IHR is modified heat release equation which eliminates negligible terms of the heat release equation at the start phase of combustion. The IHR has the similar tendency near the combustion start range. Especially the location of two percent of the IHR has a high linear correlation with the SOC under various engine operating conditions, such as varying the fuel rail pressure, injection timing, injection quantity, boost pressure, and EGR rate. We defined the location of two percent of IHR as IHR2. Furthermore, the proposed method reduces 55% of computational load and 50% of required number of cylinder pressure data compared to one percent of heat release detection method.