The Study Of Improving Cooling System In Yuchai 6M Diesel Engine

The development orientation of YUCHAI 6M diesel engine is a heavy duty commercial vehicle engine targeting on deluxe coach and heavy duty truck markets.There were some problems with cooling system when it was launched,such as over-high coolant temperature in summer and over-low coolant temperature in winter,and over-high lub oil temperature,etc.This paper studied the problems in cooling system,inproved the constructions of the system parts via simulation and optimization,finally validated the optimized results by bench tests.To solve the problem,some methods,i.e.,1D cooling system simulation and 3D CFD simulation,design calculation and structural layout configuration were applied.1D simulation revealed that the main reason of over-high coolant temperature was the insufficient water flow.The water pump blade impeller was replaced by a vortex impeller,and the balde numbers were increased from six to nine.By the means of special test and CFD,the reason of over-low coolant temperature was found caused by the unreasonable thermostat structure.The author proposed solutions by added seal ring to the thermostat and retrofitted the flow pass smooth and with consistent cross-section.Also with CFD,the reason of over-high luv oil temperaturewas figured out,which was due to the non-uniform flow around the lub oil cooler.As a result,some turbulence bars were added to solve this problem.Finally,the improvements and optimizations were verified by cooling system bench test and vehicle heat balance test.