Passive pressure pulsation damping using shaped nozzles

Abstract

Pressure pulsations in intake and outlet systems of positive-displacement compressors are one of the most important problems in compressed gas pipelines. This problem occurs not only in huge compressed systems, such as the natural gas piping in gas mines or national gas transport systems, but also in small refrigeration compressors in domestic applications. Nowadays systems require new approach since in all applications the variable rotational speed compressors are introduced. The mufflers designed in a conventional way on the basis of the Helmholtz theory are effective only for specific frequency range. In case of variable rotational speed the reaction of such damper may be insufficient. Therefore, any innovative ideas for pressure pulsating damping are welcomed by the compressor industry. One of the possible solutions to attenuate pressure pulsation over a wide range of frequencies is the introduction of shaped nozzles just after the compressor outlet chamber. It is obvious that the nozzle attenuates pressure pulsation, but simultaneously the requirement for the driving power of the compressor rises. The main subject of this paper is to show that using properly shaped nozzles one can achieve pressure pulsation damping, with insignificant influence on the compressor power consumption. The results of experimental investigations and some results of CFD analyses are shown in the paper, with indication for the best construction of the nozzle shape.