Pump Noise (Part 4) – How PCFV Works

Previously on iHydrostatics N15, piston pump products with PCFV solution were summarized. By introducing this technique, flow ripple and noise are significantly decreased in this kind of pumps. If you want to review this topic again, please reply N15 in Wechat iHydrostatics to get the detailed information. Any questions are always welcomed, iEditor encourages you to leave your comments in iHydrostatics QQ Group: 426372753.


In Pump Noise (Part 4), iEditor will do a little further research on PCFV technique. Practical experience has proven the validity of this solution, but how does PCFV influence pump performance? What can we do with PCFV to achieve high performance during operation? Secrets will be revealed in this episode.

1How PCFV Works?PCFV (Pre-Compression Filter Volume) is located between the delivery port and suction port to reduce the flow ripple during the piston chamber transferring between the two ports. Here is the working process of PCFV during pump operation.
When the piston locates at the BDC as shown in (a), the piston speed in y direction is zero, and the pressure in delivery port and PCFV are larger than in the cylinder chamber, so the fluid flows from the delivery port and PCFV into the cylinder chamber.
As the piston moving, the piston moves in y direction as shown in (b). Because the pressure in PCFV is larger than that in the cylinder chamber, the fluid flows from PCV into the cylinder chamber. The pump delivery pressure is higher than that in the cylinder chamber, so the fluid flows into the cylinder chamber. In other words, the reverse flow rate occurs.
The piston rotates around y axis as shown in (c), the piston continues moving in y direction. When the pressure in cylinder chamber is larger than or equal to that in PCFV and delivery port, the fluid flows out of the cylinder chamber into the delivery port and PCFV.
When the piston leaves away the suction port as shown in (d), the piston moves in the opposite y direction, and the fluid flows from suction port to cylinder chamber.
As the piston connecting to the PCFV and suction port as shown in (e), the piston moves at opposite y direction, so the fluid flows from suction port to cylinder chamber. In addition, when the pressure in PCFV is larger than that in cylinder chamber, the fluid flows from the PCFV into the cylinder chamber
According to the depiction mentioned above, it can be seen that the reverse flow rate from the delivery port is reduced, because additional fluid flows into the cylinder chamber from the PCFV. Therefore, it is reasonable to infer that the pump discharge flow ripple is reduced.

2PCFV DesignBased on the description of PCFV working cycle and relevant researches, the main parameters of PCFV are size (VPCFV), port diameter (DPCFV) and placement (φPCFV) as shown below.

1Size of PCFV
The size of PCFV is determined mainly by the discharge pressure, total piston volume (including dead volume) at ODC and pressure drop inside PCFV during pre-compression. Of the three, pressure drop inside PCFV and total piston volume have more influence on the size of PCFV.

Researcher suggested that a PCFV three times the size of the displacement chamber was sufficient.

2Port Diameter of PCFV
Port diameter determines rate of flow transfer between PCFV and displacement chamber, which in turn affects the rate of pre-compression.

3Placement of PCFV
The location of PCFV determines whether pre-compression starts before or after the piston reaches its ODC and affects the force applied on the swash plate.
3PCFV Next LevelPCFV does have positive effect on the flow ripple reduction, but the researching results also show its own disadvantages. Thus, a new idea has been proposed to use the combination of relief groove and PCFV, simulation results have shown the improved performance compared to traditional PCFV technique.

iEditor will not detail this in the post, if you are interesting in this new technique, you can check the paper [3] listed in REFERENCES.

REFERENCES

[1]. XU Bing, SONG Yuechao. Pre-Compression Volume on Flow Ripple Reduction of a Piston Pump. CHINESE JOURNAL OF MECHANICAL ENGINEERING, Vol. 26, No. 6, 2013.
[2]. Ganesh Kumar SEENIRAJ. NOISE REDUCTION IN AXIAL PISTON MACHINES BASED ON MULTI-PARAMETER OPTIMIZATION. Proc. of 4th FPNI-PhD Symp.
[3]. Ganesh Kumar Seeniraj. EFFECT OF COMBINING PRECOMPRESSION GROOVES, PCFV AND DCFV ON PUMP NOISE GENERATION. International Journal of Fluid Power 12 (2011) No. 3.

STATEMENTS

[1]. Copyright of the pictures, videos and paragraphs quoted in this post belong to the original author.
[2]. iHydrostatics is only the platform to share but not create information, iHydrostatics post is NOT intended for academic research.
[3]. This post reprint should be noted with “iHydrostatics Original”.