Coupled Approach to Perform Thermal Analysis of a Heavy Duty Diesel Engine

CFD simulations of an engine cooling system needs to resolve two aspects of the system; in-cylinder combustion and engine cooling. Underlying physics of an in-cylinder combustion process and heat transfer through engine cooling system requires very different time scales for resolution. This puts a limitation on practicality of solving the two problems simultaneously for any industrial case. Instead of solving the problem simultaneously, solution for an engine cooling system operating at a constant load can be derived using the coupled approach. This involves running two different CFD simulations: a transient in-cylinder simulation to model combustion in the engine, and a steady state CHT simulation using engine cooling system for heat transfer. These simulations are thermally coupled through boundary conditions and are performed in cyclic manner one after the other. Simulations are continued till the change in temperature with coupled cycles becomes insignificant.

This paper reports the process development and validation study of such an analysis for engine head system. A script based approach was developed as a part of this work to accommodate the effect of valve motion on conduction heat transfer between vale and valve seat, within the steady state CHT simulation. Paper also includes discussion on spray model calibration and wall function comparative studies, which were performed for transient IC engine simulations during the process development.