Modeling and Control Strategy of Engine Cooling System for a Light Weight Commercial Vehicle

The engine cooling fan, water pump and thermostat are key controllable components of the engine cooling system. In order to investigate the effects on the engine cooling system under different control strategies, a simulation model for a light weight commercial vehicle's engine cooling system is established. The simulation model takes into account the performance parameters for each component of the engine cooling system and the impact of vehicle operating conditions on the engine cooling system, with the goal of achieving the highest possible fidelity of the simulation model. The engine outlet coolant temperature and the power consumption of the engine cooling fan, water pump and thermostat are calculated at various vehicle speeds and engine loads. Comparing the simulation results with the data read from the Electric Control Unit (ECU) in the engine road tests, the simulation model’s accuracy is validated. Based on the validated model, the engine cooling system is then optimized by replacing mechanically actuated key controllable components with electrically actuated equivalents: an electronically controlled silicone oil clutch fan, an electric water pump and an electric bypass valve. Considering the working characteristics of the key controllable components in the engine cooling system, a nonlinear control strategy is proposed for the combined control of the engine cooling fan, water pump and thermostat. The simulation results show that, under the China heavy-duty commercial vehicle test cycle for light trucks of GVW≤5500 kg (CHTC-LT), the optimized engine cooling system under the nonlinear combined control strategy can maintain optimal engine performance and reduce energy consumption of the engine cooling system.