Ammonia-diesel Engines Segmented Modeling approach and Simplified Combustion model Research

Ammonia-diesel dual-fuel engines can effectively reduce greenhouse gas (GHG) emissions. Aiming at the real-time control requirements of ammonia/diesel dual-fuel engines, this study proposes a segmented real-time modeling method and a heat release rate model simplification strategy by linearized heat release rate curves. First, the engine working cycle is divided into three parts: intake and exhaust stage, compression and expansion stage, and combustion process. Different simulation steps and modeling strategies are designed to optimize computational efficiency while maintaining the necessary level of accuracy at each stage. Secondly, based on the calibrated heat release rate (HRR) curves, feature points are extracted to construct a simplified linear heat release model. In the absence of calibration data, the characteristic points of the HRR curves are obtained through interpolation. Compared with the commonly used combustion model, the Wiebe model, the proposed simplified model can more easily obtain the parameters required for calibration while maintaining accuracy. Finally, the effectiveness of the model was verified experimentally under various cases. The results showed that the real-time modeling method can keep single-cycle simulation time in 2ms, the prediction deviations of the indicated mean effective pressure (IMEP) under 4% and the peak pressure in the cylinder (pmax) deviations are less than 2%, and the deviations of specific combustion angle (CA10, CA50, CA90) are controlled within 1°crankshaft angle (CA). It provides a model basis for the real-time control of ammonia diesel engines and is of great value in promoting the engineering application of ammonia fuel in transportation fields such as ship power systems.