Research On Intake System Of Multi-point EFI Gas Engine

The air intake system is an important part of the engine.A good air intake system can not only increase the efficiency of the engine charge,improve the miscibility of air and fuel but also reduce fuel consumption and emissions.With the rapid development of industry,the demanding levels of vehicle emissions and fuel consumption get higher and higher.The research on air intake system is also becoming one of the approaches to improve engine performance and it has never stopped.The air intake system of gas engine consists of the air supply system and the gas fuel supply system.The traditional researching method of the intake system relies on the experience of the engine researchers,which will make heavy workload,long cycle,high cost.In the wake of the development of computer technology,computer-aided software is widely used in simulating the air intake system which greatly improves the research efficiency and reduces the research cost.This paper is based on the project "Research On High Power Multi-point EFI Engine Injector and Control Technology ".The project team used a multi-point EFI engine instead of a basis single point EFI engine in order to meet the demand.Then the air intake system has been improved accordingly to satisfy the improved engine performance.First of all,the design of the natural gas rail pipe was predesigned,and the rail from the one side to the natural gas was adopted and the engine bench test was carried out.After comparing and analyzing external characteristic data of single engine(original engine)with multi-engine,it was found that the power of multi-engine natural gas engine was better than that of single-engine natural gas engine at the same speed.Among 1300 rpm to 1700 rpm,the maximum increased power was 10%,and multi-point engine was overall better than a single engine on the fuel consumption.Per hour fuel consumption could be reduced by nearly 1kg of the partial load characteristics.Although the multi-point EFI engine had some advantages over the original engine in terms of power and fuel consumption,unstable speed and abnormal work would happen during the high-speed and heavy load inthe course of the test of the engine bench.It was estimated that the structure of the intake system was deficient,so the research of the intake system was begun.The CFD method is used to all various parts of the system modeling,the model discretization and simulation calculation.Firstly,one-sided the natural gas rail pipe was simulated.According to the simulation results,it was found that there was a lack of structure in the natural gas rail pipe.This structure would cause inconsistencies of the pressure near the outlet of each injector during the opening time.The average pressure in the vicinity of the outlet of the injector 1 was significantly lower while the injector 5 was significantly higher than the other positions.Then the pressure loss of the intake manifold was calculated,the pressure loss of the two conditions were about 550 Pa and 440 Pa.It could be found that the pressure loss of the intake manifold was not large.After that,the flow characteristics of the injector were simulated and verified.A middle dual natural gas rail pipe was redesigned,and the modeling and simulation calculation were made,it was found from the data analysis that injector opening time pressure distribution was more uniform,the average pressure was higher,which could prove the feasibility of the natural gas pipe structure.Finally,the transient simulation of the intake port-cylinder section under three operating conditions was carried out,and the pressure distribution,velocity vector distribution,turbulent kinetic energy distribution and miscibility of the mixture air in the cylinder were analyzed.It can be concluded that the intake port-cylinder structure was reasonable and the pressure distribution of the mixture distributed relatively uniform.The vortex and turbulent kinetic energy produced by the intake could promote the mixing of the mixture and the mixture mixed well at the end of the intake.In this paper,the intake system of gas engine was studied by using the CFD method,and the rationality of the multi-point EFI engine intake system was analyzed,which had certain theoretical significance for the design of the engine intake system.