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Abstract
Differing from the traditional method of treating the motion of ring valve plates as translational or inclined motions of rigid bodies, this paper originated from the concept on deformations involved in the motion processes. Emphasis of research is centred on flexural warping vibrations during opening and closing. Mechanical modelling and mathematical interpretations of plate motion with variously positioned spring systems are established, enabling theoretical solutions of model shape functions, stresses and strains. Numerical computer results of dynamic analyses can be used as basis for improvement of compressor design with regard to reliability. A set of diagramatic representation of the computed circumferential distribution of the instantaneous displacements, dynamic stresses and velocities of some ring valve plates of an actual air compressor are hereby presented. (A)
Zugl.: Braunschweig, Techn. Universiẗat, Diss., 2004.
Experimental records of the displacement during opening of a ring plate suction valve in an air compressor showed that the plate did not lift symmetrically. Values of velocity at the centre of gravity of the plate were compared to those calculated using three mathematical models (a), (b) and (c). The simplest, model (a), assumed that a uniformly increasing pressure difference (ramp function) existed across the valve. Model (b) accounted for the change of the pressure difference due to variation of the interrelated valve displacement and piston motion but assumed that the pressure in the plenum chamber remained constant. Model (c) described the complex physical situation in greater detail, accounting for the variation of the pressure difference across the valve due to the interacting effects of valve displacement, piston velocity and pressure changes in the finite volume plenum chamber caused by the wave action in the pipework of the system in addition to the pressure changes in the cylinder. Models (a) and (b) predicted valve velocities during suction valve opening greatly in excess of those measured. While model (c) predicted values of maximum valve velocity close to those observed, much more computer time was required by this model. (A)
Inserting a cushion between the valve plate and the seat or plating the seat on the impact stresses generated in the valve as well as the plate was discussed. The analysis is based on the assumption of colinear impact between all the three materials. An example case of a soft cushion of twice the thickness of the valve plate was analyzed. The results indicate that the impact stresses are reduced both in the valve plate as well as in the seat. The amount of reduction in stress level will depend upon the softness of the cushion material relative to the plate and seat materials, as well as possibly on the thickness of the cushion. (from paper)
Hypothesis on the Failure of Spring Loaded Compressor Valve Plates
- L Btlswirth
L.Btlswirth, "Hypothesis on the Failure
of Spring Loaded Compressor Valve
Plates." Proceedings of the 1980 Purdue
Compressor Technology Conference.