Pump Noise (Part 1) – How it Generated

Previously on iHydrostatics N10~N12, latest academic researches on hydraulic piston pump at Maha Fluid Power Center has been illustrated. iEditor hopes you can get the picture of the most frontier researches on piston pump from these three posts. If you missed these interesting posts, please reply N10/N11/N12 in Wechat iHydrostatics. Any questions are always welcomed, iHydrostatics encourages you to leave your comments in iHydrostatics QQ Group: 426372753.


In the coming posts, iEditor would like to discuss something about noise in piston pump. We all hate noise generated in piston pump, but do we know how the noise is generated? Where is the noise born?

1Where is the Noise From?
The noise in axial piston pump originates from many different sources. The main sources which have high impact on noise are:

Fluid Borne Noise (FBN) Source1Kinematic Flow Ripple & Compressibility Effects

The effective discharge is the resultant of flow rates from all the individual chambers which result in kinematic flow ripple. Kinematic ripples are superimposed by compressibility effect due to fluid bulk modulus. Kinematic ripple and compressibility effect result in flow ripples at both discharge and suction ports. The flow ripple, main cause of FBN, is transferred to the entire system through hydraulic lines connected to the pump.

2Cavitation

Localized collapse of air bubbles formed in the fluid due to cavitation can be heard distinctly as high frequency noise. Cavitation mainly occurs in the suction port due to insufficient suction but also in the gaps between the rotating groups whenever the fluid pressure falls below the vapor pressure or below air desorption.

Structure Borne Noise (SBN) Source1Forces on the Swash Plate

The pressure inside each displacement chamber rapidly rises and falls between discharge and suction pressure during each revolution. This pressure dynamics imparts a varying force on the swash plate through each piston. The resultant is an oscillating force of high magnitude and frequency causing the swash plate to vibrate. Swash plate vibration is the main source of SBN in axial piston pumps.

2Structural Vibration
The vibrations of the swash plate are transferred to pump casing and further to the structure on which the pump is mounted to. Also, the pressure ripples, as mentioned earlier, make the system components such as pipes, hoses and valve elements to vibrate. All mechanical vibrations dissipate the mechanical energy as acoustic pressure variations which finally result in air borne noise (ABN). Vibrations sources external to the pump such as the prime mover, shaft bearings, and vibration induced due to pressure ripple in system components such as relief valves and throttling orifices also contribute to overall system noise.

Of these mentioned sources above, the Flow Ripple and Forces on the Swash Plate are the major contributors to the piston pump noise.

2What to Do Next?
By summarizing the noise sources above, iEditor believes you have got the whole picture of how axial piston pump noise comes. We are engineers, we pursue the quiet world. What can we do to reduce the noise level generated in piston pump?
In the next episode – Pump Noise (Part 2), iEditor will show you what research work have been done during the past decades to achieve the engineer’s desiring world.
Don’t go away, keep following up with iHydrostatics! See you in next week!

REFERENCES

[1]. Maha Fluid Power Research Center. 2014 Annual Report.
[2]. Ganesh Kumar SEENIRAJ. NOISE REDUCTION IN AXIAL PISTON MACHINES BASED ON MULTI-PARAMETER OPTIMIZATION. Proc. of 4th FPNI-PhD Symp.
[3]. Zhang Junhui. Study on Valve Plate Design and Insensitive Flow-Distribution Method of Axial Piston Pump. Ph.D thesis. University of Zhejiang University.
[4]. Monika IVANTYSYNOVA. Hydrostatic Pumps and Motors. Academic Books International.
[5]. MATTEO PELOSI. AN INVESTIGATION ON THE FLUID-STRUCTURE INTERACTION OF PISTON/CYLINDER INTERFACE. Dissertation Purdue, US.
[6]. Simerics Technology Website. Http://www.simerics.com/.

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