Measuring pressure in the combustion chamber of internal combustion engines is crucial for 0D thermodynamic analysis. However, piezoelectric sensors only detect relative pressure changes, not absolute values. In addition, due to piston kinematics—which depend, among other things, on the operating point of the engine—a shift may occur between the measured and actual top dead center (TDC) position of the piston. For accurate combustion analysis, it is therefore necessary to appropriately adjust the pressure trace before using it in thermodynamic analyses. In this work, we reviewed existing methods and, for further development, selected the rate of heat release (ROHR) analysis to determine the pressure offset and the polytropic method to determine the TDC offset. Both methods were implemented in Python and validated on pressure traces of a diesel engine. An iterative model was developed that enables the determination of both offsets. The results show that the model achieves high accuracy after 2-3 iterations for small offsets of absolute pressure and TDC, while a higher number of iterations is required for larger offsets.
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