Effect of Valve Port Gas Inertia on Valve Dynamics - Part II: Flow of Retardation at Valve Opening

T.J. Trella, U.S. Department of Tr~nsportation, Transportation Systems Center, Cambridge, Massachusetts 02142 and A mathematical model of non-linear reciprocating air-compressor discharge valve . system unsteady response was presented :n Part I. As a first step, to demonstrate the application of the unsteady modeling approach, a comparison of discharge discvalve response was made with a more popular quasi-steady modeling technique. For unsteady disc-valve response, contraction coefficients in the vicinity of the valve and ori~ice sections were determined from static measurements of discharge and liftforce coefficients. Under the assumptions that the contraction coefficients do not change appreciably from the static flow pattern during the dynamic response of the disc-valve, it is shown by comparing results of both modelin~ techniques that the inertia of the fluid, which initially retards tre flow between the disc-valve and seat, has a dominant effect on valve response for suction to pressure ratioscommo~ ly used in most air compressor designs. Lastly some calculated time histories are shown which illustrate the effects of mechanical disc-valve systems natural frequency, ~ass and stiffness, damping and valve diameter on unsteady flow and valve response.