Research On High Efficiency Cooling System For Hybrid Engine

With the rapid development of the economy and society,the energy problem has become increasingly prominent.And the energy conservation and emission reduction of automobiles has become a major concern of various companies and countries.In order to improve energy efficiency and reduce engine emissions,the development of hybrid vehicles is an effective method.At the same time with the development of engine technology,the definition of the function of the cooling system has gradually changed.The cooling system not only needs to meet the engine heat dissipation requirements under various working conditions,its performance will also profoundly affect the engine's emissions and economy.In order to improve engine efficiency and reduce engine emissions,it is necessary to do some research on high-efficiency cooling systems.In this paper,the engine cooling system test bench is designed and built,and the engine coolant flow distribution test is carried out to analyze the flow resistance characteristics of various components in the engine cooling system.The cavitation limit experiment of cooling system is carried out to study the cavitation margin of cooling system under different working conditions.The heat balance experiment of the engine was carried out to study the heat transfer from the engine to the coolant under different working conditions.The characteristic curves of the fan,water pump and radiator are studied through the single specimen test.The power of fans,pumps and the radiation efficiency of radiators are fitted by formulas.The fmincon function of MATLAB is used to solve the optimal matching combination of the rotational speed of electronic fans and electronic pumps.According to the obtained test data,one-dimensional simulation model of the cooling system is built using Flowmaster.What's more one-dimensional simulation model of the high-efficiency cooling systems is also built based on the original one.The dimension simulation model of high-efficiency cooling system is constructed by using electronic water pump,electronic fan and electronic thermostat instead of mechanical water pump,two-stage adjustable fan and wax thermostat.The overall control strategy of the cooling system is designed based on the simulation model of the high-efficient cooling system.The control of the high efficient cooling system is divided into three parts: start control,travel control,and post-cooling control.The advantages of high-efficiency cooling system in coolant outlet temperature,warm-up time,post-cooling and the energy-saving under NEDC cycle is studies in this paper.The results are as follows:Coolant outlet temperature: In the process of warming up,if the outlet temperature does not reaches 108 ? the thermostat will not open,because the high-efficiency cooling system adopts the electronic thermostat.What's more using electronic will reduces the oscillation of the engine coolant outlet temperature in the process of warming up.When the engine is working under normally condition,the oscillation range of coolant outlet temperature is also changed from [-5,5] ? to [-1,1] ? by using electronic controlled thermostat.Warming-up: The power consumption of the pump during the warm-up process is greatly reduced by 78.2% and the warm up time is reduced by 40 s,because the pump speed is controlled at a lower speed in high-efficiency cooling systems;It not only reduces pump power consumption,but also helps to reduce engine emissions.Energy-saving under NEDC cycle: The research results show that under the NEDC cycle,the energy consumption of the high-efficiency cooling system is 40.85% lower than that of the original cooling system.And the energy consumption of pump is reduced by 61.18%,the energy consumption of fan is reduced by 32.24%.At the same time,the oscillation amplitude of the outlet coolant temperature is also greatly reduced,because the PID-controlled electronic thermostat is adopted in the high-efficiency cooling system.What's more when the vehicle is running at high speed,the coolant outlet temperature is maintained at a large value,which will reduce the heat loss of the engine.Post-cooling: The result shows that the coolant temperature will increase significantly(up to 121?)after the engine is stopped if the engine has no post-cooling.Two ways about post-cooling is proposed in this paper: the pump works only or the pump and the fan work at the same time.The results show that the post-cooling time will reduced by 80.1% and power consumption will be saved by 50.3% if the second method is used.