Test The Limits

How to Predict Overheating on the Track

By Zhongzhou Yang

November 29 2016

Overheating could cause permanent damages to engines. Oversized radiators are usually used to ensure that engines could be cooled down in time, on the track. On the other hand, we want to minimize the size of radiators for reducing production costs. In order to meet these conflicted objectives, we need to accurately predict coolant temperatures in the track such that we could accurately evaluate the performance of different radiators and choose a radiator with an appropriate size before vehicle prototypes are built.

 

It was difficult to predict coolant temperatures in the track due to complex airflow in a vehicle’s underhood and fast changing operating conditions including vehicle speed, fan speed, engine speed and coolant flow rate et al. This issue was resolved in the SAE paper (SAE 2014-01-0654) by use of accurate PowerFLOW flow solver and a fast system model.

 

At first, the unique transient solver in PowerFLOW accurately captured non-uniform air velocity and temperature before radiators at stabilized operating conditions. Then, non-uniform airflow velocity and temperature in stabilized operating conditions were interpolated at different vehicle speeds and fan speeds. Finally, a system model, with time-varying non-uniform velocity and temperature imposed as boundary conditions, was used to accurately predict coolant temperatures in the track.

 

Underhood airflow, non-uniform airflow at radiator inlet, non-uniform air temperature at radiator inlet and validation of temperature drop through a radiator are shown in the following figures, respectively.

 

 

 

 

 

 

 

 

 

 

This simulation methodology provides accurate early evaluation of cooling packages’ performance in the track before vehicle prototypes are built. Overheating in the track could be accurately predicted. The performance of cooling packages could be easily re-evaluated in different drive cycles and the related engineering cost is much lower than that in vehicle prototype testing. This methodology has been used by several OEMs in their vehicle programs.

 

Reference:

Jansen, W., Amodeo, J., Tate, E., and Yang, Z., "Drive Cycle Simulation of A Tiered Cooling Pack Using Non-Uniform Boundary Conditions," SAE Technical Paper 2014-01-0654, 2014, doi:10.4271/2014-01-0654.