Study Of Electronic Control Cooling System In LNG Engine Based On Coolant Temperature Map

Cooling system is an important part of the engine, whose performance has strong influences on the dynamics, economical efficiency and reliability of the engine. Modern engine adopts more compact design and has greater power per liter and higher degree of enhancement, which sets a higher requirement for the cooling system. The application of electronic control technology improves the overall performance of the engine, which could save energy and protect the environment. Under the increasing constraints on environment and energy policy, the engine control is developing fast in an electrification and intelligent trend, and the traditional mechanical cooling system is also being converted to electronic controlled. Therefore, the study on optimal control of engine cooling system is meaningful.This thesis took EQRN375 LNG (Liquefied Natural Gas) engine as the research object and a comprehensive properties optimal design of LNG engine based on coolant temperature had been done. Performance of the LNG engine was tested on overall conditions with different coolant temperatures. By tests, the engine's optimum coolant temperature MAP was obtained, which will be taked as the control basis for its electronic control cooling system. Based on the structure and working process of engine cooling system, a mathematic model of this system base on Lumped Parameter Method was established and a new type of electronic control cooling system without thermostat was designed. Then the engine starting process was simulated in mechanical cooling system model and electronic control cooling system model separately. The simulation results were compared with the Flowmaster simulation results and demonstrated by warm-up tests.A test device was built for the electric control cooling system. For the non-linearity of this system's mathematical model, linearization process has been done by the method of feedback-linearization. Then, simulation and experiment of two-input-two-output control system were carried out based on mathematical model. Considering the fuzzy control technique does not rely on the accurate mathematical model of controlled object, which makes it could overcome the influence of nonlinear factors. Thus, a basic fuzzy controller and a variable universe fuzzy controller were designed separately to carry out experimental study on engine coolant temperature.Feasibility of optimization design reducing the overall energy consumption of engine electronic control cooling system in the case of heat transfer steady state was proposed. By the means of heat exchanger calculation, energy consumption optimization design and test were developed to the electronic control cooling system. Thermal balance tests were developed to compare the performance among mechanical driving cooling system, silicone oil fan clutch cooling system and electronic control cooling system, and the results showed that engine equipped with electronic control cooling system has the best economical efficiency and the one equipped with mechanical cooling system has the worst economical efficiency.