Research On Energy Flow Of XL6SD Natural Gas Engine For Heavy Duty Truck

With the implementation of the sixth stage emission regulations in China,the limits of various harmful emissions of heavy truck engines are becoming more and more stringent,so it is particularly important to optimize the thermal efficiency of engines.The energy flow analysis method can reveal the distribution law of various energy balance terms in different subsystems of the engine,and evaluate the performance of the engine under different working conditions,which is of great significance to the analysis and study of the engine energy flow system.In this paper,we construct and calibrate the engine performance simulation model as well as the cooling system simulation model based on GT-Power for the tin coupled XL6SD natural gas engine,including the engine intake and exhaust system,cooling system,cylinder,crankcase and so on.According to the simulation results,the influence of engine speed,load and cooling water temperature on engine energy flow is studied.At the same time,the effective work,the loss of cooling water,the loss of exhaust gas and the uncalculated loss of energy flow distribution and the law of change are analyzed,and the energy distribution proportion map and the energy change curve are drawn.At the same time,the engine bench energy flow test research will be carried out,and the simulation will be carried out the results were compared with the test results.The results are as follows:(1)The calculation method of engine energy flow is put forward,and the simulation modeling theory of cylinder working process,intake and exhaust system and cooling system is analyzed based on GT-Power,and the simulation model of engine performance and cooling system is established and calibrated.The variation law of the external characteristic energy flow distribution of the engine under full load is analyzed by simulation.At the same time,the energy flow distribution characteristics of the engine varying with the load at different speeds are analyzed.The influence of the cooling water temperature on the engine performance parameters and the change trend of each energy balance term with the engine operation parameters are studied.The values of energy loss,cooling water energy loss and other energy loss also increase with the increase of rotation speed.With the increase of the engine load,the proportion of the engine effective work to the total energy increases slowly;the proportion of the cooling water loss of the energy decreases with the increase of the load;the proportion of the exhaust loss and other energy loss varies in a small range under each load;and the proportion of the exhaust loss energy to the conversion to effective work is approximately the same.(2)Carrying out the engine bench test,The results of engine bench test show that the torque,power,specific gas consumption and other performance parameters of natural gas engine are basically consistent with the simulation results.The energy flow experiments under different working conditions are carried out to compare and analyze the external characteristics,load characteristics and the energy flow distribution law based on the cooling water temperature.Through the test and simulation analysis,it is concluded that the cooling water temperature at about 87? under small load can make the engine work in the best condition.The temperature of cooling water is about 84??87? under medium load,which can make the engine work in the best condition.Under high load,the temperature of cooling water at low speed should be controlled at about 78?,and the temperature of cooling water at medium speed will decrease with the increase of load,and it is reasonable to basically stabilize at 78??87?.The research results are helpful to improve the utilization ratio of engine gas and increase its economy.So we should try our best to control the temperature of cooling water at the most suitable point.The research results mainly reveal the distribution law of energy flow of natural gas engine under different working conditions,provide theoretical support for improving engine energy use efficiency,and have important significance for engine to improve fuel utilization.