Development and Validation of a Modeling and Calibration Method for Diesel-Like Multistage Combustion Based On a Modified Multi-Wiebe Function.

The stringent regulations of fuel consumption and exhaust emission require further refinement of the control strategy for diesel engines. In the future, the prediction of the in-cylinder combustion process will become necessary to achieve a more dedicated control performance. Hence, a more precise model able to run in a real-time application is required to predict the nature of multiphase Diesel combustion. This paper presents a modified multi-Wiebe function with a concise parameter structure, which is governed by the center point of the combustion process and the form factor of each stage. The modified function captures the typical characteristics of the measured heat release rate and avoids the ambiguous determination of several parameters, therefore improving the calibration efficiency. A novel calibration method called "backward-stepwise recursion" is introduced that decomposes the nature of the measured heat release rate and fits the function from the tail stage to the precombustion stage. This method is suitable for large-quantity diesel fuel combustion and dual-fuel combustion cases in which the adjacent combustion stages superimpose one another. The proposed method is applied in the measured heat release rate of a single-cylinder prototype diesel engine from 15% to 100% load conditions. The modified multi-Wiebe function suggests good accordance in heat release prediction at all the load conditions, which demonstrates its ability to be embedded in the control unit for crank-angle-resolved real-time combustion prediction.