Vortex shedding-free strainers

The subject of the periodic vortex shedding behind bluff bodies, which exhibits oscillatory behaviour, is of direct relevance to many practical applications, e.g. pipelines and heat exchangers. Repetitive failures were occurring in associated piping components on the suction of a sales gas compressor. Available experimental investigations indicated the occurrences of vibrations at the predominant frequencies of 1500 and 3000 Hz in the compressor strainer pipes. Hence, this study is aimed at identifying the source of such high vibration levels. The study investigated the flow-induced vibrations in the compressor strainer pipe through numerical simulation of the flow in the pipe including the strainer, as well as structural modal analysis calculations for the strainer at steady-state conditions. Three different geometrical configurations were considered. The first strainer has a truncated-cone geometry with uniform size holes. The second is witch-hat geometry with uniform holes, while the third is a modified witch-hat configuration with non-uniform holes. The results obtained from the frequency analysis of the flow field downstream of strainers with the first two geometries indicated dominant amplitudes at 1500 Hz and appreciable excitations at its second harmonic. However, the results demonstrated that the dominant vibration amplitudes have been appreciably reduced for the third case of the modified witch-hat configuration with non-uniform holes.