EFFECT OF VALVE PORT GAS INERTIA ON VALVE DYNAMICS - PART II: FLOW RETARDATION AT VALVE OPENING

摘要

A mathematical model of non-linear reciprocating air-compressor discharge valve system unsteady response was presented in Part I. As a first step, to demonstrate the application of the unsteady modeling approach, a comparison of discharge disc-valve 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 orifice sections were determined from static measurements of discharge and lift-force 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 modeling techniques that the inertia of the fluid, which initially retards the flow between the disc-valve and seat, has a dominant effect on valve response for suction to pressure ratios commonly used in most air compressor designs. Lastly some calculated time histories are shown which illustrate the effects of mechanical disc-valve systems natural frequency, mass and stiffness, damping and valve diameter on unsteady flow and valve response.