Effect of Valve Port Gas Inertia on Valve Dynamics - Part I: Simulation of a Poppet Valve

T. J. Trella, U.S. Department of Transportation, Transportation Systems Center, Cambridge, Massachusetts 02142 and A theoretical model was developed of the nonlinear dynamic response of a reciprocating air compressor discharge valve system considering unsteady flow. It constitutes an extension of previous modeling procedures where the flow was considered in a quasi steady manner. The most simplified valve system was used which coDsists of a mechanical spring loaded circular disc valve centered over a single circular orifice. Cotipled unsteady nonlinear flow and disc valve motion equations were developed by treating the flow by a sequence of finite control volumes. Unsteady contimity and momentum equations were written for each control volume. The flow in the orifice, valve passage and piston cylinder was modeled as compressible. Contraction coefficients were incorporated to account for s~reamllne effects. The Kirchoff contraction coefficient was assumed in the orifice area, while the entrance and exit discharge coefficients in the disc valve passage are assumed from experimental flowforce data. Viscosity was included between the disc valve and seat.