ANALYSIS OF BENDING STRESSES IN CANTILEVER TYPE SUCTION VALVE REEDS

摘要

Design techniques are described which allow prediction of bending stresses in reed valves from theoretical and experimental data. Their application is to aid the development of more durable valves. A relatively simple analysis is described which permits valve stresses and impact velocities to be estimated from the initial pressure drop across a valve reed. (Conversely, experimental measurement of valve stresses allowed prediction of the initial pressure drop at valve opening and hence impact velocities). The simplifying assumptions in the analysis are enumerated; these simplifications provided a model which was economical of computer resources. The finite element method was then applied to check the simple model and predict both static and dynamic reed displacements. The resultant finite element model yielded static and dynamic stresses, together with natural frequencies and mode shapes of reeds. It was found that dynamic stress predictions allowed estimates to be made of the valve reed life in relation to the fatigue limit of the valve reed. Comparison between the results from the simple model and the more detailed finite element models justified the use of the simpler analysis. Hence the shape of a valve reed could be economically studied with a view to reducing bending stresses and impact velocities.