Engine Cooling Control System Design And Thermostat Diagnosis

The amending of national environmental regulations makes the emissions and fuel consumption become urgent problems to be solved.Recently,more and more innovative technologies in engine cooling system are used to improve engines performance.Electronic thermostat is one of them.It reduces fuel consumption via increasing the water temperature of running engines and decreasing the loss of heat and mechanical simultaneously.This paper studies the cooling system which uses electronic thermostat,and the main contents are shown below.(1)Comparing domestic and overseas researches of cooling control system technology,the cooling control system is mainly used in electronic thermostat and fan.Thus,this study treat electronic thermostat and fan as control targets of cooling system.(2)A bench test based on water temperature change of engine: we take 1.8 T supercharged engine as the research object,water temperature of engine as a control variable,and the brake specific fuel consumption(BSFC)as an evaluation index.Then we observe how different loads in engines effect fuel consumption when water temperature increases.According to the results,the fuel consumption decrease 4.87% at most with increasing water temperature for the small load,while fuel consumption changes little with increasing water temperature for heavy load.(3)We establish an engine cooling control system,taking a certain type Chang'an car as our research object.There exists an applicable situation in control system when people replace the mechanical thermostat for the electronic thermostat.Aiming at this problem,we analyze the characteristic and structure of components in cooling control system and build an updated system which the target temperature is the kernel and the control target is the electronic thermostat and fan.This control system also includes modules such as thermocouple full judgment,fan running,sensor fault operation and so on.Based on MATLAB/Simulink simulation platform,the feasibility and practicability of the control system are verified.(4)We establish a thermostat diagnostic system.Based on the requirements of the latest national VI regulations for the diagnosis of thermostats,we analyze the heat transfer process of high temperature gas engines,build a water temperature model during normally working,and compare the difference value between the water temperature in model and the actual water temperature.In addition,we diagnose whether thermostat is malfunction or not,and verify the precision of water temperature model under MATLAB/Simulink.Our results show that the error between water temperature in model and actual water temperature is 1? under idling,while the error is 4? under driving model.It indicates that water temperature model satisfies the requirements of thermostat according to the smaller error.(5)We verify the control system via using actual vehicles.After carrying our cooling control system for the test car,the result shows that our system is able to control cooling water temperature for engines effectively.At the same time,all functions of our system meet the design requirements.