Study Of Effects Of Valve TrainOptimization For Engine Performance

The valve train is one of the most important mechanisms in an engine, whetherthe performances are good or bad, that affecting the power performance, economicperformance, emissions performance of the engine, as well as affecting the reliabilityand wear performance of the whole engine. With the requires of performances ofengine are improved, and in order to make engine more stable at high speed, whichdemand that the valve train system should have a high performance. Cam is the hardcore of the valve train, which design is one of the important ways to carry out valvetrain optimal design. Simulation calculation and experimentation are two importantways to carry out research and development on valve train of engine.In this paper, the kinematics and dynamics model on valve train of one engineare built up with AVL TYCON, the performances on the valve train are calculated,some problems on the valve train are made certain, then combine the paper'srequirements of the engine performance, adjusted the valve timing, the cam profilewas redesigned, via computer simulation optimization with BOOST software, whichnot only solved the primary problems and improved the engine performance duringlow-medium speed phases comparing to the prototype engine, and this fulfilled theexpectant intention. Finally, the new optimized valve train was manufactured, and thesimulation conclusions were confirmed by the engine experiments. The main researchworks include:(l)The kinematics and dynamics model on valve train of the engine were built upwith TYCON. The Simulation analysis calculation of the valve train indicated that thefullness ratios of valve curves are on the low side, and the maximum contact stressbetween cam and tappets are higher, and the minimum curvature radius of cam islower. In response to these questions, the improvement design measure and method ofthe cam profile has been brought up.(2)A new optimized cam profile was redesigned by use of model for cam designin TYCON software. Through redesign of the cam profile, the kinematic and dynamiccharacteristics have improved, and solved the problems of the original valve train.(3)Via computer simulation optimization with BOOST software, and theconclusions indicated that the engine performance during low-medium speed phases was improved comparing to the prototype engine. The new optimized cam profileachieved the purpose.(4)The new optimized valve train was manufactured, and the simulationconclusions were confirmed by the engine experiments.