Discharge from the Cylinder of a Piston Engine

Consideration is given to problems of calculating the exhaust from the engine cylinder through a “valve–valve pipe” system at all flow modes. It has been shown that there is a need to determine the exhaust parameters precisely in the cross section of the valve pipe outlet and also to clarify the moment of blocking the flow in the valve and at the valve pipe outlet. Based on the idea of analogy with a sudden expansion of the passage section of a conditional channel, relations have been obtained for determining the flow coefficient of the valve system. The results of calculations using these relations are in good agreement with the results of blowdowns of the valve system of a real engine. To simplify flow calculations and visualize the flow modes in the system using the criteria of the similarity theory and gas-dynamic functions, a method has been developed for constructing a universal two-parameter gas-dynamic characteristic (map) of a valve system similar to maps of compressors and turbines. In this case, the values of flow coefficients in all the modes represented by the maps will be almost the same for systems of various scale and having identical parameters of geometric expansion.