Noise reduction of a multistage export / reinjection - Dresser-Rand

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Because sound intensity data are generally more accurate than sound pressure data for the given acoustic environment of a compressor installation site, the sound intensity measurement was used in this study. Before the start of the measurement, surface segments need to be predefined around the compressor. Sound intensity levels were obtained by scanning the specified surface segments with sound intensity equipment. Noise Signature Measurement of Compressor B Both compressors are installed in a room on the weather deck of the platform and both are driven by a gas turbine through a gearbox. Because compressor B was not equipped with duct resonator arrays, its acoustic measurement provides the baseline noise data. The compressor system was divided into several segments for sound intensity measurement. The surface segments defined prior to the measurement are shown as white blocks in Figure 8. Two 20-inch long (50-cm) quarter pipe segments represent the sound emitted from the suction and discharge pipes. A portion of the compressor casing surface represents another segment of measurement. Each segment was scanned individually according to ISO 9614-2 [8]. Using the multiple analysis capability of the B&K pulse system, the following quantities were obtained simultaneously: (1) Sound intensity level in both narrow band (FFT) and 1/3 octave band, (2) mean sound pressure averaged between the phase-match microphone pair of the intensity probe, and (3) the p-I (pressure-intensity) index that gives an indication of the quality of the measurement. The p-I index of 2 to 8 dB was observed for all intensity data measured in the
critical frequency range. This indicates the sound intensity measurement is of good quality since the p-I index does not exceed 10 dB (ISO 9416-2 Engineering grade). Figures 9-11 present the baseline noise data measured from compressor B for the operating conditions listed in Table 1. The compressor noise signature shows that the blade passing frequency (BPF) dominates the overall noise. The noise peak at the second harmonic is also relatively strong. Both peaks are sharp and have a relatively narrow bandwidth. Extending the noise attenuation range of the duct resonator arrays to cover both peaks will help reduce the overall noise level. Comparing the sound intensity levels of the suction and discharge pipes at the high speed (8900 rpm), i.e., Figure 9 versus Figure 10, shows that the discharge pipe radiates higher noise than the suction pipe. This reveals that the last stage of the compressor is the first priority in noise reduction efforts. The duct resonator arrays installed in the last stage diffuser of Compressor A were intended to reduce the dominant discharge pipe noise level. Figure 11 shows sound intensity levels of the discharge pipe of compressor B while running at a slower speed. Comparing figures 9 and 11 indicates the higher noise level occurs at the higher speed. As expected, the compressor casing (cylinder) did a good job containing the noise. The sound intensity level from the casing is much lower than that of the suction and discharge pipes, as shown by Figure 12. The compressor casing is typically a thicker structure and, therefore, provides higher noise transmission loss than the thinner suction and discharge piping. The noise level emitted from the casing is more than 10 dBA lower than the suction and discharge pipes. As a result, the ambient noise is controlled by the noise emitted from the suction and discharge pipes. Because the dominate noise source is the discharge pipe, the majority of the remaining data presented will be focused on this pipe.
Page 1 and 2: NOISE REDUCTION OF A MULTISTAGE EXP
Page 3 and 4: evamped. The revamped configuration
Page 5 and 6: more than sixty-one multistage and
Page 7 and 8: The measured compressor noise data
Page 9 and 10: highest velocity. High gas velocity
Page 11: In 2002, two compressors installed
Page 15 and 16: compressor B and lists the noise at
Page 17 and 18: References 1. Liu, Z. and Hill, D.
Page 19 and 20: Table 1 - Operating Conditions duri
Page 21: Figure 5 - Close-up of One of the S
Page 24 and 25: Figure 4 - Photograph of the Compre
Page 26 and 27: Array Location Figure 6 - Multistag
Page 28 and 29: V1 Z Y X Suction pipe Casing Figure
Page 30 and 31: [dB(A)/1.00p W/m²] Calc. Intensity
Page 32 and 33: [dB(A)/1.00p W/m²] Calc. Intensity
Page 34 and 35: [dB(A)/1.000p W/m²] Calc. Intensit
Page 36: Sound Intensity Level [dB] 100 95 9

Noise reduction of a multistage export / reinjection - Dresser-Rand

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