A Method of Evaluation for Skin Friction and Heat Transfer in the Cylinder of an Internal Combustion Engine Using a Boundary Layer Resolution

Our intention is to present an alternative method for the determination of skin friction and heat transfer in the cylinder of an internal combustion engine. It is based on the resolution of the boundary layer equations, from the knowledge of the main flow used as external conditions.

The detailed description of the complex structure of the flow field has been obtained by means of LDA measurements of the three components of the velocity, and more particularly in the vicinity of the wall. To complete this work, wall streamlines visualizations have been performed in order to improve the knowledge of the wall flow. The results are achieved in the simpler case of the intake stroke which can be assumed to be steady and incompressible.

According to the experimental results, it has been shown that the wall flow is quasi two-dimensional. Therefore, we can carry out a complete calculation of the boundary layer, using a curvilinear system of coordinates based on the streamlines of the external flow. At first, the thermal approach remains simple. The temperatures of the cylinder wall and of the main flow are assumed to be both constant, but different. We can then obtain estimations of the local skin friction and heat transfer coefficients on each streamline as well as their distribution on the whole cylinder surface.