<p>The valve plate/cylinder block interface in an axial piston
pump is often subject to extreme pressures, which can cause wear of the valve
plate and ultimately, failure of the pump. The purposes of this study were to:
a) experimentally investigate the film thickness generated between a floating
valve plate and cylinder block in situ using proximity probes, b) develop a
model which can predict the motion, film thickness and pressures of the
floating valve plate and corroborate with experimental results, c) investigate
surface pockets to provide additional lubricant at the valve plate interface by
measuring the flow velocities and cavitation areas in a thrust washer bearing,
d) numerically investigate surface modifications of the floating valve plate to
observe any changes in lubricant pressure, temperature, cavitation, or valve
plate deformation. Two different test rigs were designed, developed and used to
investigate the performance of axial piston pumps and surface pockets. The
axial piston pump test rig (APTR) was designed to operate and measure the
steady state conditions of an axial piston pump. The APTR utilizes three
non-contact proximity probes to measure the valve plate motion and film
thickness between the cylinder block at various speeds and pressures. A thrust
washer test rig (TWTR) was developed to measure the cavitation areas and flow
velocities of lubricant in a pocketed thrust washer using μPIV. Through a novel interpolation approach, the depths
of the micro-particles in the bearing pocket were determined using an
analytical model. Using this approach, the μPIV measured 2D velocity field was employed
to develop a 3D velocity field, which illustrates the fluid motion inside a
pocketed thrust bearing at various speeds and viscosities. A dynamic
lubrication model was developed using the thermal Reynolds equation augmented
with the JFO boundary condition and the energy equation to determine the pressure,
cavitation regions and temperature of the lubricant at the valve plate cylinder
block interface. The lubricating pressures were then coupled with the equations
of motion of the floating valve plate to develop a dynamic lubrication model.
The stiffness and damping coefficients of the floating valve plate system used
in the dynamic lubrication model were determined using a parametric study. The
elastic deformation of the valve plate was also considered using the influence coefficient
matrix approach. The
experimental and analytical motion of the valve plate were then corroborated
and found to be in good agreement. 4
and 8 pocket designs were then added as surface modifications to the
floating valve plate in the dynamic lubrication model. The addition of surface
modifications improved the lubricating conditions at the valve plate/cylinder
block interface and resulted in increased minimum film thicknesses and lowered
lubricant temperatures at the same operating conditions.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/7999322 |
| Date | 10 June 2019 |
| Creators | David W Richardson (6593138) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Hydrodynamic_Lubrication_of_Floating_Valve_Plate_in_an_Axial_Piston_Pump/7999322 |
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