Optimal Design Of Cam Profile For Diesel Engine And Optimization Of Valve Timing

Energy and environmental protection have become two main themes of the the contemporary world. As society and economy developing, the problem caused by non-road diesel engine emission has been widely drawing people's attention, and lots of countries have established non-road diesel emission regulation. For small non-road diesel engine, optimization of cam profile, improving performance of intake and exhaust, rational valve timing are main methods of preventing pollution.Firstly, the kinematics and dynamics models on valve train of the TY3100 diesel engine were set up by AVL-Tycon software, and the performances of kinematics and dynamics were simulated. Two methods of High Order Polynomial Dynamic Cam(POLYDYNE) and Constant Acceleration Cam(STAC) were used to optimize original cam profile with the goal of fullness coefficient. The rationality of the cam profile was judged by the contact stress between cam and tappet, lubrication function, valve acceleration, the bounce of the valve when it seat down, and combination of the valve spring. The results showed POLYDYNE not only increased the fullness coefficient, but also ensured good dynamic performances. Confirming the max valve lift according to the rule that the valve could not meet piston, the design of cam profile of variable maximal valve lift was done by the method of POLYDYNE for diesel engine.Secondly, the intake valve closing and exhaust valve opening were optimized through establishing TY3100 integrated system model by GT-Power software for the cam profile of variable maximal valve lift. According to the performances comparison, the optimized valve timing not only improved the performances in the high speed, but also in the low speed, which provided important theoretical basis to the comprehensive performances on TY3100 non road diesel engine.Finally, according to the new process technology of and actual needs, put forward two methods of transforming the data of the lift of cam follower to the data of the cam profile with the change of the angle of the camshaft. One was AVL-Tycon Recalc, which was based on the kinematics model of valve train by AVL-Tycon software. The other was mathematical method of pure geometry relation.