Study In The Effects Of Integrated Exhaust Manifold On Performance For A Gasoline Engine

With the gradual reduction of traditional energy sources and increasingly serious environmental problems,China is expected to fully implement the CN 6b standard in2023,and impose stricter requirements on engine emissions.In recent years,integrated exhaust manifold(IEM)technology has received widespread attention in the automotive industry as a low-cost and good-efficiency technology for reducing emissions and fuel consumption.However,compared with foreign companies,domestic car companies still lack research in this area.Based on this background,the application of integrated exhaust manifold on the engine based on a 1.5L gasoline engine has been simulated and tested in this paper.The influence of integrated exhaust manifold on engine power performance is revealed,and the causes are analyzed.Data support and theoretical guidance can be provided for subsequent integrated exhaust manifold applications to existing engine platforms.By studying simulation schemes and evaluation methods of outlet ports and exhaust manifolds,a steady-state simulation scheme and evaluation method of integrated exhaust manifolds is proposed.According to this scheme,the influence of the exhaust outlet position of the 4-1 integrated exhaust manifold structure on the flow performance and uniformity was studied.The results show that the fourth cylinder of the engine with side-mounted integrated exhaust manifold has the best flow performance,the first cylinder has the worst flow performance,and the largest deviation in flow uniformity is 17.1 %.The center-mounted integrated exhaust manifold has better flow performance than the side-mounted one,with a maximum deviation in flow uniformity of 9.8 %.Placing the exhaust outlet in the middle position can conduct good exhaust flow,increase the exhaust flow rate,and reduce the unevenness of the exhaust.Then,the effects of the integrated exhaust manifold on the engine’s power performance and the causes of this effect has been researched.The simulation results show that the power performance is reduced at low speed and slightly increased at high speed after the adoption of integrated exhaust manifold.By comparing the combined operation line of turbocharger between the original engine and the engine with integrated exhaust manifold,it is found that the combined operation line moves to the left.As a result,the efficiency of supercharger is reduced at low speeds,which affects the intake mass flow.Then taken 1200 r/min as an example,the cause of the engine’s low speed torque drop was studied.After using the integrated exhaust manifold,the peak pressure before turbo is increased and the peak time is advanced.the pressure state before the turbo changes the turbine and compressor operating conditions.Overall,the area of the efficiency increase is smaller than the area of the efficiency reduction,thus reducing the total efficiency of the supercharger.The peak pressure rises and comes ahead to make the exhaust interference phenomenon worse,the exhaust gas reflux increases,and the residual exhaust gas in the cylinder compared with the original engine increases.Then a 4-2-1 integrated exhaust manifold was designed to investigate its improvement in low-speed power performance.At 1200r/min,the torque is higher than that of the 4-1 type,and the exhaust gas reflux phenomenon is significantly reduced.The engine with 4-1 integrated exhaust manifold was prototyped and tested.The test show that: at 1000 ～ 1200 r / min,the dynamic performance of the 4-1 prototype is slightly reduced,and the dynamic performance of other speeds is improved.Fuel enrichment area is reduced.HC and CO emissions are also significantly reduced.