Instantaneous heat flux simulation of S.I. engines: comparison of unsteady thermal boundary layer modelling with experimental data

Due to the inherently unsteady environment of the internal combustion engine, unsteady thermal boundary layer modelling could make a useful contribution. Instantaneous heat flux measurements in three different spark ignition internal combustion engines were simulated using a quasi-one dimensional engine simulation program developed in Matlab. Simulation parameters were tuned within reasonable limits until good agreement between the simulated and measured pressure was achieved. The heat flux simulated using Annand´s model agreed with the experimental data to some degree, particularly when an averaging process was applied over the simulated unburned and burned zones. However, the agreement between the measured heat flux and the unsteady thermal boundary layer model was less satisfactory. Implementing a model for turbulent thermal conductivity in the unsteady thermal boundary layer is expected to improve the simulated heat flux results.