Improved Dynamic Valve Analysis for Mass Damping and Moving Frame of Reference

This paper presents investigations of two special cases of dynamic valve analysis. These special cases arose in the development of a new type of gas field reciprocating compressor. These special cases were for a moving frame of reference (since the discharge valves were integral with the piston) , and for independent mass damping {sealing/damping elements are modelled separately instead of as "lumped" masses). NOMENCLATURE. gas damping force sealing element spring force damping element spring force sealing element mass damping element mass valve lift F=ma constant time valve lift for fixed coordinates piston position piston acceleration gas pressure gas constant cylinder swept volume X KE D m vp cp d p v Ag p r N z T A eq INTRODUCTION distance kinetic energy drag force mass of element piston speed drag coefficient gas density gas speed plan area of element crank radius machine speed gas compressibility gas temperature equivalent flow area The dynamic valve analysis or "DVA" is used to predict the motion of the moving elements (plates, poppets, etc. ) in reciprocating compressor valves. This valve motion prediction is valuable for the proper design and selection of these valves, and this motion prediction represents a significant contribution to reciprocating compressor performance prediction. Computer programs based on Woollatt [1] have proven quite useful in this regard. In order to assist in the design and analysis of a new type of reciprocating compressor, new demands were placed on the dynamic valve analysis. The first demand was to predict the motion of sealing and damping elements as separate masses. This problem arose since damping elements were failing in field tests, and no acceptable explanation could be determined based on existing dynamic valve analysis methods. The second demand involved predicting the motion of the valve elements {sealing and/or damping plates) in a moving frame reference (since the valve basically comprised the compressor piston in the new design). It was not known what effect this was having on the motion of the damping and sealing plates. .