This paper presents an application of in-cylinder pressure for the compression heat transfer estimation. Based on some assumptions and the first law of thermodynamics, the state-space model for the compression process can be derived. This model consists of two state variables, namely, in-cylinder pressure and temperature. During the compression stroke, the heat transfer to, or from, the cylinder walls can be computed using the least squares regression. The identification results show that the proposed method can estimate the amount heat transfer and its direction. However, the proposed method should be improved for increasing the accuracy of the heat transfer estimation. For instance, the specific heat ratio for the in-cylinder pressure offset compensation varies with temperature and the in-cylinder temperature during compression is calculated precisely. Therefore, in the last section, we then also discuss the analysis methodology and possible ways for improvement of the heat transfer estimation method.
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