Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
(OP)
I am measuring a gear pump's suction pressure at different speeds (500, 1000, 2000, and 3000 RPM) using SAE 30 lube oil in ambient conditions. Comparing the results between the initial set-up (bended tubes) and putting a plugged T-fitting on the suction side (see TFittingSetUp.JPG) to gauge the effect of one 90 degree elbow, I noticed that at 500, 1000, and 2000 RPM the set-up with the T-fitting resulted in a suction pressure rise of 56%. But at 3000 RPM the suction pressure rose only 15% from 9.6 psi to 11.1 psi. What would cause the much lower rate of increase at 3000 RPM?





RE: Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
Good luck,
Latexman
RE: Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
RE: Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
RPM psi psi
500 1.7 2.7
1000 3.2 4.9
2000 6.3 9.8
3000 9.6 11.1
Attached is an image of the "base" set-up to complement the previous image. I hope that helps better explain what I am comparing.
RE: Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
RE: Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
RE: Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
Good luck,
Latexman
RE: Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
Speed Base T-Fitting
RPM in Hg in Hg
500 3.5 5.5
1000 6.5 10.0
2000 12.8 20.0
3000 19.5 22.5
RE: Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
RE: Effect of 90-Degree Fitting on Lube Oil Flow at Different Speeds
At 3000 rpm you may be right at or close to a choked flow condition with the t-fitting (which is more restrictive that your smooth transition setup), at which point the fluid can move no faster.
With the t-fitting set-up, if you begin to hear a noisy, rumbling sound from the pump, then it may cavitating, which would signify that the fluid flow is becoming "choked".
At some higher rpm and flow rate, the tubing will also become choked as well.