Improvement of Quasi-Steady State Heat Transfer Model for Intake System of IC Engines with Considering Backflow Gas Effect Using 1-D Engine Simulation

For improving the thermal efficiency and the reduction of hazardous gas emission from IC engines, it is crucial to model the heat transfer phenomenon starting from the intake system and predict the intake air’s mass and temperature as precise as possible. Previously, an empirical equation was constructed using an experimental setup of an intake port model of an ICE, in order to be implemented into an engine control unit and numerical simulation software for heat transfer calculations. The empirical equation was based on the conventional Colburn analogy with the addition of Graetz and Strouhal numbers. Introduced dimensionless numbers were used to characterize the entrance region, and intermittent flow effects, respectively. In this study, further improvement of the model was done by characterizing the effect of backflow gas on intake air temperature by the introduction of the Euler number. 1-D engine simulations were done to analyze the valve-overlap and displacement backflow gas phases’ effect on the intake air temperature. Additionally, engine test-bench experiments were conducted to validate the in-house built model and its applicability into engine control unit algorithm. The outlet temperature of the intake manifold was measured and results were compared to the various correlations. The in-house built equation showed the best accuracy when compared with the conventional approach, Colburn analogy. Maximum and average errors between the measured and estimated outlet temperatures were found to be 2.7% and 0.8%, respectively. The coefficient of variation for the in-house built equation was found to be 6.2%, which is considered to be a strong correlation. The average calculation time for the model is found to be 32 microseconds which satisfies the requirement for the current engine control unit technology.