Centrifugal compressors installed for natural gas transmission produce significant noise. Many of these compressors have a single impeller with high power input. Large diameter pipes are typically connected to the inlet and discharge of the compressors. As a result, a single stage pipeline compressor not only has a strong noise source but also has a large structure to radiate noise to the ambient. As pipeline compressors are installed close to residential areas, community noise complaints become a concern to pipeline companies and compressor manufacturers. To make compressors more environmentally friendly, duct resonator acoustic arrays have been developed to lower the acoustic energy emanating to the environment. This paper focuses on acoustic technology applied to a single stage pipeline direct-inlet compressor with a 28-inch diameter impeller. The effectiveness of the duct resonator acoustic array is described in this paper with field noise data from three different tests — one test before the compressor was retrofitted with the resonator arrays and two tests afterwards. A baseline noise test was first conducted in January 2002 to obtain the compressor noise signature and to establish the baseline noise data. Using the baseline noise data, duct resonator arrays were designed, manufactured, and retrofitted into the compressor to reduce noise. A second test was performed in October 2002, just after the upgrade, to check the effectiveness of the resonator arrays. The compressor was tested under six different operating points (two speed lines at three points per speed line) from overload to surge during both the first and the second tests. In February 2004, fifteen months after the second test, a third noise test of the same unit was performed to assess the effectiveness of the resonator array over time. The purpose of this third test was to identify if there was any degradation of noise attenuation due to fouling. A comparison of the data taken on the third noise survey with those measured on the second noise survey indicated there was no change in noise levels. After the third test, the unit was disassembled for an aerodynamic retrofit. At this point, the array was inspected and found to be clean. This indicates that the duct resonator array has been performing well since its installation. Fouling has not been detected and the array performance did not degrade over time. This paper provides acoustic data for all three field tests conducted with a focus on the technology applied to reduce the acoustic energy of this centrifugal compressor.

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