How to calculate the required length of an axial pump piston

In summary, the required length of a piston inside the cylinder block of an axial piston pump is determined by the maximum angle between the connecting rod and the bore centerline, the peak force on the piston, the location of the wrist pin, and the allowable bearing stress on the side of the piston. There is no single equation for this calculation, as it is an optimization problem that requires engineering judgement. Factors such as rod length ratio, bearing stress, and overall size must be considered in the calculations. The number of piston rings, diameter of the wrist pin, and cooling mechanism for the piston are also important factors to consider.
  • #1
ENGBIO
19
1
Based on other parameters how do you calculate the required length of a piston inside the cylinder block of an axial piston pump?

What are the relevant equations? I've found many for the required diameter but not the length.
 
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  • #2
How about the required difference in volume, piston up and piston down?
 
  • #3
The piston length is determined by the maximum angle between the connecting rod and the bore centerline, the peak force on the piston, the location of the wrist pin, and the allowable bearing stress on the side of the piston. There is no single equation that I am aware of. You need to use engineering judgement to determine the rod length ratio and allowable bearing stress, then calculate from there. The calculations are straight from Statics 101.
 
  • #4
Do you mean length or stroke?
 
  • #5
CWatters said:
Do you mean length or stroke?
No i meant length
 
  • #6
Then I agree with post #3.
 
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Likes jrmichler
  • #7
This is not a typical academic problem with a single exact solution. It is an optimization problem with many solutions, none of which are "the best". You can optimize for least overall size, lowest friction, least number of parts, lowest cost, highest reliability, etc, etc. You choose how you weight the various factors using engineering judgement, then do the calculations. It's an iterative process.
 
  • #8
ENGBIO said:
how do you calculate the required length of a piston inside the cylinder block
How many piston rings are there?
What is the diameter of the wrist pin?
What keeps the piston axially aligned with the cylinder?
What are you pumping? The heat of compressed air will expand the piston unless the skirt/sides can cool by radiating heat into the block.
Skirt of piston must be clear of crankshaft so connecting rod and bore must be longer for longer skirted pistons.
 

1. How do you calculate the required length of an axial pump piston?

To calculate the required length of an axial pump piston, you will need to know the pump's flow rate, the rotational speed, and the pressure drop across the pump. This information can then be used in the following formula: Piston Length = (Flow Rate x 60) / (π x Rotational Speed x Pressure Drop).

2. What units should be used for the flow rate, rotational speed, and pressure drop in the formula?

The flow rate should be in liters per minute (L/min), the rotational speed in revolutions per minute (RPM), and the pressure drop in kilopascals (kPa). It is important to use consistent units in the formula to get an accurate result.

3. How does the required length of the piston affect the performance of the axial pump?

The required length of the piston plays a crucial role in the performance of the axial pump. If the piston is too short, it can cause cavitation and decrease the pump's efficiency. On the other hand, if the piston is too long, it can increase the wear and tear on the pump and decrease its lifespan.

4. Are there any other factors to consider when calculating the required length of an axial pump piston?

Yes, there are other factors that may affect the required length of the piston, such as the viscosity of the fluid being pumped, the type of fluid, and the design of the pump. These factors may require adjustments to be made to the formula to get a more accurate result.

5. Can the required length of the piston be determined experimentally?

While it is possible to determine the required length of the piston experimentally, it is not recommended. This method can be time-consuming and costly, and the results may not be as accurate as using the formula. It is best to use the formula as a starting point and make any necessary adjustments based on the specific conditions of the pump.

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