Improvements And Studies On The Overheat For The Rear-Mounted Diesel Engine On The Large Bus

The thesis firstly simply introduces the cooling system's composes, classifies and its importance. Then the cause of overheat for the rear -mounted and the effect on engine performance are discussed. Next, in the process of looking for the method solving the overheat, coolant is proposed. This way is very theoretical and practical. Ethylene glycol that is a glycol matter with high boiling point character is selected to carry out the experiment. Thus, the experiment of contrasting the liquid cooled with water cooled is carried out on N485Q diesel engine. The research shows adopting the liquid cooled can improve the cooling strength and give the engine more flexibility in accommodating temperature ranges. At the same time, the regular pattern that the fluid cooled effects the power, economy and emission of the engine is obtained. The conclusion that the optimal coolant concentration would be different under different rev and load is also drew.Following, on the base of the performance experiment, the design method of orthogonal regression rotation experiment is put to be used. The experiment of four adjusting parameters (coolant boiling point, environment tempreture, rotation speed, load rate) is designed. The influence of power, oil consumption rate, smoke emission are researched under the different matching of four parameters. The corresponding mathematical models have been established. Finally, with computer looking for the best patameter, the six regressionequations at maximum torque and maximun power are optimized. The best values of each performance index is measured in theory and the corresponding values of adjusting parameters are concluded. The result is in good accord with experiment date.The research result shows that the problem of overheating of rear-mounted is surely resolved by adopting ethylene glycol aqueous solution with a certain concentration as coolant. The power and economic performance are improved . The emission is reduced. The energy and oil saving and pollution reducing are reached. To a certain extent, this conclusion have an affect on the reseach and appliance of ethylene glycol on the high tempreture cooling .