Cooling system simulation for an off-road machine under transient conditions

Abstract

Traditionally, the design of cooling systems for off-road machines has relied on steady-state and quasi steady-state cooling system models. Performance characteristics of cooling modules are obtained from tests under steady-state conditions, and analysis methods assume worst-case heat loads, which leads to cooling package over-design. Solutions to recent emissions regulations involve increased space claim of aftertreatment systems, and a significant increase in underhood heat rejection. Consequently, tighter constraints on cooling package size, cost, and performance, have led to a need to operate much closer to the optimum; this requires transient cooling system simulation. A simple transient heat exchanger component has been developed for Dynasty, Caterpillar’s proprietary 1D simulation tool. Different heat exchanger types were tested using a specially developed transient flow rig, and new test procedures. The Dynasty component was validated and then configured to represent heat exchangers in a model of a heavy-duty, off-road machine. Numerical optimisation methods were used to tune transient parameters, to minimise the deviation between simulated and measured fluid temperature responses in a representative work cycle. Through the use of this baseline, optimised model, it has been demonstrated that a considerable improvement in simulated fluid temperature accuracy can be achieved by moving from quasi-steady to transient cooling system simulation.