Screw compressors for bus air conditioning (A/C) have many advantages: low noise, reduced vibration eliminating the need for isolation mounts, a large operating speed range, and quiet unloading. However, sometimes interesting resonance situations can occur. The opportunity for this to happen is largely increased for roof-mounted A/C systems, where the discharge tubing can become quite long, given that the compressor is situated in the engine compartment. This paper discusses different features, such as unloading, volume ratio, oil viscosity, oil flow and bracket design, etc. from sound and vibration perspectives.
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