Optimization Of Intake System Of Natural Gas Engine Based On Numerical Simulation

The problems of energy scarcity and environmental pollution are becoming more and more serious,and natural gas as an alternative fuel for engines is becoming more and more popular.The intake system has a great influence on the performance parameters of natural gas engine.In this paper,the intake system of a certain type of natural gas engine is optimized.The main work accomplished and the results achieved in the full text are summarized as follows:In this paper,according to the specific technical parameters of the original natural gas engine,the required simulation model is established by using the engine simulation software GT-POWER.The full load simulation is carried out under a total of 14 rotating speed conditions in the 800r/min-2100r/min interval,and the performance parameters such as torque,gas consumption rate,intake flow rate and power are carried out,and the engine bench is built and tested under the same working conditions as the simulation.The above model is verified and calibrated by using the experimental data.The diameter and length of intake Manifold are optimized by numerical simulation method.It is concluded that the optimal length of intake Manifold is to increase the length of intake Manifold by 20%on the basis of the original machine,and the diameter of intake Manifold is 70mm.The performance parameters of the engine are greatly improved.The structure of the pressure stabilizing cavity of intake pipe is optimized by using one-dimensional and three-dimensional coupling method,and the inhomogeneity and inlet flow rate of each cylinder are taken as the optimization goal.The evaluation function is established by using the multi-objective optimization algorithm of linear weighted sum method,and the results are calculated that the comprehensive intake capacity of the intake pipe is the best when the inclination angle of the steady pressure cavity is 15°.Finally,the results are verified by the velocity vector distribution map and the pressure cloud diagram.The influence of each performance parameter of valve distribution phase on engine performance is analyzed.The gas distribution phase is optimized,and the full load performance is simulated under three different speed conditions:low speed,medium speed and high speed.Taking the parameters such as engine output torque,gas consumption rate and charging efficiency as evaluation indexes,different exhaust advance angles and intake late closing angles are simulated and calculated.It is found that the intake late closure angle and exhaust advance angle of the original machine should be reduced by 15℃A and 10℃A.respectively on the basis of the original machine.The intake advance angle and exhaust late closure angle should be increased by 10℃A and 5℃A.respectively on the basis of the original machine.The performance parameters of the engine before and after optimization are compared,among which the output torque of the optimized engine is 7.1%higher than that of the original engine,the intake flow rate is 6.21%higher than that of the original engine,and the gas consumption rate is 3.67%lower than that of the original engine.After optimization,the power and economy of the original machine are improved to a certain extent.