Improvement Of WP7 Natural Gas Engine Intake System

A large area of haze and fog weather in China caused by automobile exhaust,already have serious influence on the health of people.Environmental pollution has become the price of the rapid development of Chinese economy,and it produce a lot of trouble to the Chinese government.The main component of natural gas is methane,which is generated by the combustion process,and the greenhouse gas emission is low,which is the ideal fuel for vehicle engine.In this paper,focused on WP7 NG natural gas engine.In the first,the influence of combustion chamber on the combustion velocity is established,and the influence of the flow ratio on the ignition,the turbulent kinetic energy and the combustion process is analyzed.On the basis of the original WP7 NG intake port,a new model of intake port design is proposed,and the simulation of the steady state of the intake port is established,and the influence of the different combinations of the helical and tangential ports on the roll forming ability is analyzed.A comparative computational model is established including the intake port and combustion chamber.The influence of the two kinds of structures on the mixing gas concentration,turbulent kinetic energy,air velocity and flame propagation in the cylinder is analyzed.A one-dimensional engine working process model is established,the use of the test results of the calibration of the model parameters,optimization of valve timing and turbocharger match calculation.The calculation results of three-dimensional combustion process show that the original machine will help improve the in-cylinder combustion chamber turbulent kinetic energy,heat release rate and tumble ratio that can effectively improve the combustion rate,but too high tumble ratio easily lead to ignition difficulties,tumble ratio should be controlled within 1.4.Intake port steady simulation results show that: two tangential intake port and intake port head diversion combinations can form a larger tumble ratio in the cylinder.The new case made mixed gas ignition flame develop to the piston top surface more easily than the original machine,increased the burning rate.Analyzed the influence of valve timing volumetric efficiency,exhaust gas flow backwards,fuel consumption rate,power and other parameterson engine,determined the WP7 engine the optimal gas distribution phase is to maintain the original valve overlap angle,intake lag closed angle decreased 10 DEG crank angle.The results show that the engine is used as the engine for the bus to improve the low speed torque and can be matched with the small flow turbocharger.Finally,the paper compared the original case and new case torque and other parameters,and analysis of the engineindicator diagram,heat release rate and emission,the new case is more suitable tocity buses than the original program.