Turbocharged And Intercooled Diesel Valve Train Dynamics And Influencing Factors Research

Valve train, which controlled engine intake and exhanst process should have a high aerated efficiency, the small pump gas loss, precise valve timing,running smoothly, the smaller vibration and noise.It has important impact on engine's performance and service life. Therefore, with increasing of the engine's performance demand, it is very meaningful for the engine's valve train to research the kinematics and dynamics.The kinematics and dynamics model on valve train of the engine are built up with AVL EXCITE TD. On the plane,we simulated for the orignal vavle train and analysis on the features for the engine. Against the original of the cam profile that jumped degrees changed so much question, the cam profiles were about to optimized.AVL BOOST software was applied on engineperformance simulation,and valve timing of the diesel engine were optimized.Meanwhile, the engine in actual operation of the valve seat badly worn, which are designed to adopt the method for conducting qualitative research on the valve seat of the impact of excessive wear.(1) after the calculation for the original cam profile, the kinematics lift and velocity curves of intake and exhaust valves were smooth and continuous. but the jumped degree was relatively larger.The smallest spring margin and lubrication characteristics met what the kinematics required;the contacting stress of intake and exhaust cam with tappet was between the kinetics of the material during the kinematics simulation, but the phenomenon of flying off exists about intake valve during dynamic calculation; the valve spring worked naturally, there was no phenomenon that springs were merged; but there was great impact in the acceleration when the intake valve was on and off,and this resulted in the impact when it was seated.Besides,the sitted-foce is so lager that needs to be optimized.(2) By means of optimizing the cam profile, intake valve and exhaust valve's fullness coefficient enhanced 1.9%and1.2%;the jerk diagrams decreased 63% and 73%;the tappet force also decreased 20% and 4%; spring margin was inceased to 1.954 and 1.88 from 1.572 and 1.413; Though dynamics calculation, the phenomenon of flying off and lager seating force were improved.The maximum tappet force decreased from 440.8 N/mm2 to 798.3 N/mm2. the seating force dropped from 1835N to 1117N. the valve spring also worked naturally, there was no phenomenon that springs were merged or spring force larged.(3) through optimization of the valve timing,comparing with the original valve timing and,the engine's power and torque improved compared with the oirginal engine; For fuel consumption rate,it reduced 2.5% in 2000r/min, But the exhaust gas temperature was just increased lightly; when the engine speed is at 3200r/min, it increased by 20.5℃, and the increasing range was 3.1%. Therefore, optimizing increased engine's power and economy to a certain extent.(4) we analysed the valve seat wearing factors at the base of orthogonal experiment method. After analysis, we can informed that the engine speed of changing was the key factor of valve seating speed; In addition, stiffness of rocker arm and push rod were also the important factors for high valve seating speed.