PD compressors, gas pulsation control, shunt pulsation trap, parallel dampening
This paper is a continuing work from the same authors on the same topic of gas pulsation control using a shunt pulsation trap method by Huang (2012a, 2014). Traditionally, a serial pulsation dampener/muffler, often a reactive type, is connected AFTER the discharge of a positive displacement compressor or engine. It is capable of reducing pressure pulsation level up to 10-20 folds or 20-40 dB but is bulky and suffers sizable back pressure losses. It has been demonstrated in the previous theoretical and experimental investigations by Huang (2012a, 2014) that gas pulsations can be as effectively controlled by an alternative method, shunt pulsation trap (SPT) of a parallel configuration, which is more compact and tackles the gas pulsations BEFORE the compressor or engine discharge, hence not suffering any back pressure losses. However, it is observed that the dampening element inside SPT by a perforated plate (p-plate) induces a severe â€œdrum effectâ€ with enhanced vibration and noise. This paper investigates experimentally the effect of a new dampening element inside the SPT by using circular perforated tubes (p-tubes) with minimum trap volume. It is found that p-tubes can effectively resolve the adverse â€œdrum effectâ€ of p-plate with improved pulsation/vibration/noise reduction. Furthermore, the use of an absorption type silencer is beneficial to further reduce noise level by 10-15 dB in addition to the p-tubes under Exhauster and Blower modes. However, this type of silencer will not have the sizable back pressure drop associated with reaction type silencers and therefore will not affect system efficiency. The integration of absorptive silencer into a p-tube based SPT would provide an optimal design choice for size/weight and pulsation/noise reduction, energy saving and for improving equipment fatigue life. The potentials for applying the SPT to screw and scroll compressors are enormous in the future since a significant portion of their operation is under off-design conditions of either an under-compression (UC) or over-compression (OC).