Optimization Study on Coolant-Flow for Heavy-Duty Vehicle Diesel Engine by Experiment Study and Numerical Simulation

摘要

Problems such as higher heat load in the diesel engine and the occurrence of crazes within the valve bridge of heavy-duty vehicle diesel engine should be solved, with the increase of the power density of heavy-duty vehicle diesel engine. In this paper, the heat load experiment of complete machine, temperature-measuring of bottom part of cylinder head and the three-dimension numerical simulation on coolant flow and heat transfer in the water jacket have been performed. The result shows that the main reasons of higher heat load of the engine are insufficiency of heat-sinking capability of the water radiator and shortage of coolant flux; and the unsuitable flow field in water jacket in cylinder head, where only a little of the coolant can cool the bottom of cylinder head, is the main cause of cylinder head bottom overheating and thermal crack in the valve-bridge region. Then, optimized protocols for coolant pump and water radiator, and 7 optimized protocols for the structure of water jacket have been proposed. It shows that the flow field in the water jacket of the 7 optimized protocols could be improved significantly, by way of the numerical simulation for the flow and heat transfer in these protocols. At last, in this paper, temperature-measuring experiment of bottom part of cylinder head is performed to validate the optimizing effect of these protocols, and the results show that the optimized protocols proposed in this paper can solve these problems encountered by the heavy-duty vehicle diesel engine properly.