Floating Cup Pump (Part 4) — FC Performance

Previously on iHydrostatics N20, the interesting topic of “Floating Cup” – how to float, was discussed. iEditor is pretty sure that you may have got all the idea of “Floating” principles. If you missed this post, please reply N20 in Wechat iHydrostatics to get the previous episode. Any questions are always welcomed, iEditor encourages you to leave your comments in iHydrostatics QQ Group: 426372753.


Deformation of Piston and Cup [1]
You have known “Floating” principle, but does this “Floating” do good to pumps? In this episode, iEditor will summarize the advantages of this kind of “Floating”, we’ll see how “Floating” influence the performance of pumps.


1Floating Cup EfficiencyAs for displacement machine, efficiency is an important parameter of its performance, which includes volumetric efficiency and mechanical efficiency. Volumetric efficiency is highly related to the internal leakage, while mechanial efficiency is greatly influenced by friction forces.
In order to figure out difference of volumetric efficiency, we should know the different leakage paths in the three typical displacement pumps: slipper type, bent axis type and floating cup type.


Leakage Paths of Three Different Types [1]
In order to figure out if the real performance matches the theoretical analysis, various testings were done in IFAS. The three types of pumps were compared.


Testing Circuit and Conditions [1]




Efficiency Comparison Testing Result [2]
Based on the testing results, floating cup has on average about the same efficiency as bent axis pump, although at 500 rpm the overall efficiency is up to 4% higher; compared to the slipper type pump the floating cup pump offers an efficiency improvement of around 3% on average and up to 7% at 500 rpm. [2]



Torque Losses for Three Types at Different Pressures [1]

We can conclude from this results that the torque losses of slipper type and bent axis pump are strongly related to the pump pressure, while the floating cup pump is almost completely independent of the pressure. [2]



2Floating Cup Low Speed BehaviorLow speed testing results have also confirmed the excellent low friction behavior of floating cup principle.


Low Speed Test Circuit and Conditions [1]


Low Speed Output Torque [1]
Figure above shows that the torque of the bent axis type varies strongly during one revolution, while the floating cup type is much more flat. [2]
The torque losses figure indicates that in the bent axis machine, torque losses increase linearly with the pressure, whereas in the floating cup machine, it is almost constant. As a result the low-speed hydraulic mechanical efficiency of the floating cup pump is much higher than of the bent axis machine as shown below. [2]


Starting-up Efficiency [1]






REFERENCES[1] INNAS. Efficiency and Start-up Torque. www.innas.com.
[2] Peter A. J. Achten. Efficiency and Low Speed Behavior of the Floating Cup Pump. SAE 2004-01-2053.

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[3]. This post reprint should be noted with “iHydrostatics Original”.