| As the altitude increases,the air density decreases,and the oxygen content in the cylinder decreases.The diesel fuel injected into the cylinder cannot be fully burned due to lack of oxygen;and the air quality of the cold side that can enter the vehicle cooling system is significantly reduced due to the decrease in atmospheric density,resulting in a decrease in the amount of heat that can be transferred from the radiator,and the boiling point of the cooling water is lowered,it is easy to boil after being heated.On the other hand,altitude changes place higher demands on the robustness of the cooling system’s control strategy,which poses great challenges to the design and control of the cooling system.This paper takes a diesel engine cooling system as the research object,designs and simulates the high and low temperature cooling system,analyzes the influence of external conditions on the cooling system,and establishes the optimal pump and fan map under different external environments based on the principle of minimum power consumption.Finally designed a variable domain fuzzy controller,this control form can effectively solve the fluctuation of engine coolant outlet temperature under different altitude and variable altitude conditions,and combined with the optimal pump and fan MAP map,can greatly reduce the power consumption under different working conditions.The main research contents and conclusions of this paper are as follows:1.Taking a certain engine cooling system as the research object,the high and low temperature double circuit cooling form of the cooling system was designed and developed.The one-dimensional simulation model of the engine cooling system was established and checked by GT-COOL software.The heat balance bench test obtained the heat dissipation of the cooling system under full working conditions.2.The effects of external environment such as inlet air temperature,inlet air flow rate,pump flow rate and altitude on the thermal balance of the cooling system are studied.At the same time,a 3-factor orthogonal test is designed to obtain the influence of different inlet flow,coolant flow,and inlet air temperature on the engine outlet coolant temperature and the radiator inlet and outlet temperature difference.3.Based on the principle of minimum power consumption,establish the optimal pump and fan MAP map under different external environments.The control system can use the optimal MAP map to realize the control of pump and fan speed under different working conditions,at the same time,the influence of optimal MAP at different altitudes,ambient temperature and vehicle speed is studied,and the power reduction effect was verified.4.Aiming at the high and complex control requirements of a diesel lowtemperature cooling system in the highland area,a variable-domain fuzzy controller was designed.The joint simulation of GT-cool and SIMULINK simulated the cooling system under high altitude and variable altitude conditions.The control process verifies that the control mode can effectively control the fluctuation of the engine coolant outlet temperature under different altitudes and variable altitude conditions,and has good temperature followability and low power consumption. |
