Flow around a reducing bend - effect on pumping work

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The discussion focuses on optimizing a race vehicle's modified oil lubrication system, specifically addressing a 120-degree bend in the pipe that has been reduced in diameter from 16mm to 13mm. The participant is concerned about potential cavitation issues due to the change in pipe diameter and the transition to a larger pump housing. They are exploring the relationship between flow rate and pressure using the equation Q = (Pi*(R^4)*P)/8*L*n, suggesting that a significant increase in input energy may be required to maintain pump efficiency. The participant seeks clarification on the implications of these changes and their impact on pumping work. Input from others, particularly a user named AK_NC, is requested to further analyze the situation.
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Hi all,

On my race vehicle, one part I am looking at is reducing the pipe losses within the modified oil lubrication system (now dry sump). The main area in question is a 120 degree bend that the engines lubrication pump is pulling oil into the oil storage tank. This has been reduced in ID from 16mm (-12JIC) to 13mm (-10JIC). Naturally I aim keen to reduce the radii difference, however I am struggling to put to words the reasoning for why.

In short, could cavitation be an issue? Since for around 0.5m the pipework is 16mm then round the inlet to the pump 13mm and expanding into a larger pump housing (around 20mm inlet)?

Could I characterise this issue using Q = (Pi*(R^4)*P)/8*L*n, since Q is the same (positive displacement pump), as are L/n/Pi we are left with:

R1^4*(P1)=R2^4*(P2) ---->>> (16E-3)^4*P1=(13E-3)^4*P2 ------>>> 2.3P1=P2, meaning that a 2.3 x greater input energy would be required to turn the pump specific to this situation?

Any input appreciated!
 
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ping @AK_NC can you help with this old post?
 
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