What is the function of the valve train?
1 Answers
The function of the valve train is to open and close the intake and exhaust valves of each cylinder in accordance with the working cycle and firing order of the engine, ensuring that fresh charge enters the cylinder in a timely manner and exhaust gases are expelled promptly. During the compression and expansion strokes, it ensures the sealing of the combustion chamber. For gasoline engines, the fresh charge is a mixture of gasoline and air, while for diesel engines, it is pure air. The degree to which the fresh mixture or air fills the cylinder is indicated by the volumetric efficiency. The higher the volumetric efficiency, the greater the mass of fresh air or combustible mixture entering the cylinder, the more heat the combustion mixture can generate, and the greater the engine's power output. For an engine of a given displacement, the mass of the charge is related to the temperature (T) and pressure (P) at the end of the intake stroke. The lower the intake temperature and pressure, the greater the mass of the intake charge and the higher the volumetric efficiency.