Measurements & Predictions of Valve Plate Motion and Strain in a High-Speed Compressor
This paper describes measurements of valve plate motion and strain in the GMRC's Reciprocating Compressor Test Facility (RCTF). Under a project co-funded by GMRC, PRCI, and BP, a metal plate valve in an operating compressor was modified to incorporate three displacement sensors (to measure plate motion) and three strain gages (to measure plate deformation). Data from all six transducers were recorded as a function of crank angle (512 points per revolution), together with cylinder pressure, for a number of pressure ratios and speed combinations. The displacement data was differentiated with respect to time and give plate velocity, and the relative motion between sensors was interpreted to give angle of the plate relative to the aligned condition. Using linear regression, the relationship between maximum measured strain and maximum impact velocity was investigated, in terms of slope and regression coefficient. The paper also describes a finite element model used to predict strain response of the valve plate to specified impact velocity for different values of impact angle. The paper presents predictions of stress propagation through the plate following impact and shows that aligned impact yields the highest plate stresses. The strain predicted at the strain gages agrees satisfactorily with the measured data. However, the maximum strain predicted at any point in the plate substantially exceeds the strain predicted at the strain gages. These results represent the first year of a project designed to develop knowledge and tools which support enhanced application engineering for plate valves in high-speed compressors.