Analysis Of Effects Of Variable Intake And Exhaust System On Engine Power Performance

Gas exchange process directly influences the engine power performance. Inorder to obtain good power per liter, further improve the engine power output, theintake process and valve timing of engine should be optimumed under differentoperating conditions. The traditional engine’s intake process and valve timing arefixed and are a compromise under high-low load conditions of engine. It can’t meetthe requirements of different operating conditions of engine. At present, besides theturbocharger technology, variable intake and variable valve timing technology are themost rapidly developing technology. It solves the problem which the traditionalengine’s intake process and valve timing are fixed effectively and makes the engineperformance best under different working conditions.The engine power and performance of a2.0liter natural aspirated gasolineengine was simulated by GT-Power, and the reliability was verified by experimentaldata. Variable air intake and variable valve timing technology was researched basedon this simulation model, to find out the effects on the engine power and performanceaccordingly.This article has conducted research on the influence of variable intake system onengine power performance. It mainly researches intake manifold length, intakemanifold diameter and the volume of the steady pressure box. For the best poweroutput of engine, appropriate improvements to the engine intake system have beenfulfilled. First, the effects of the length of intake manifolds on engine powerperformance are researched. Research has shown that the longer length of intakemanifold has a positive effect on gas fluctuations of intake pipes in low-speedconditions. The gas fluctuations which are used effectively will improve the gasexchange process obviously and enhance the power output of the engine finaly. While,the shorter length of intake manifold has a positive effect on gas exchange process inhigh-speed conditions. Summing up the above rules, the intake manifold is improvedinto two levels structure of variable length and the switching speed of the length of the intake manifold is determined. The simulation results prove that the engine powerperformance is greatly improved. After that, the effects of different diameter of intakemanifolds on engine power performance are analysed. Research has shown that thethinner intake manifolds have better gas fluctuations and will get more fresh air inlow-speed conditions. While the ruder intake manifolds have a better performance inhigh-speed conditions. The diameter of intake manifolds is choosed by integrating theengine power performance in high and low speed condition. At last, the steadypressure box is discussed. Summing up the above rules, variable intake system hasgreatly improved the engine power performance.This article has conducted research on the influence of variable valve timing onengine power performance. Based on the engine indicator diagram, the effects of inletvalve timing or outlet valve timing on engine power performance are researched.After that, the valve timing is reseached in full-load condition. The valve timing havebeen optimized based on the optimization tool of GT-Power software. Research hasshown that variable valve timing has greatly improved the engine power performance.In summary, the engine power performance has been markedly enhanced byvariable intake and valve timing system. In particular, the engine power output hasincreased signally in the medium-speed condition. The maximum torque reaches195N·m, while original engine is180N·m, the maximum torque is improved by8.3%.