twin screw compressors, noise, vibration, one-third octave band, narrow band, receiver test.
The tonal noise or vibration of air-cooled or water-cooled chillers with rotary twin screw compressors is crucial for environmental concerns. This work aims to perform the receiver tests regarding the radiated noise and structural vibration due to the compressor in different operating conditions. The sound pressure near the compressor is recorded by the one-third octave and narrow band frequency analyzers, respectively. For environmental concern, the one-third octave band spectrum is frequently adopted to evaluate the radiated noise, while the narrow band spectrum can be used to characterize the noise sources. The axial, vertical and horizontal accelerations on the compressor shell at the motor and oil-injection locations are also monitored to correlate the structure-borne noise. Other than the comparison of spectral content between radiated noise and compressor shell vibration, the frequency response functions and the coherence functions are examined to further characterize the relation between noise and vibration. This work lays out the general steps and measurement procedures for noise and vibration evaluation in primary stage for receiver tests considering different load capacities. The vibration energy transmission path tests as well as the refrigerant pulsation effects on the compressor noise and vibration can then be carried out accordingly.