Question

I have a 50cc of hydraulic motor, accumulator pressure at 40MPa at max, with 10MPa at precharge. How can i determine what pump sizing will i use for hydraulic hybrid purpose.

Answer 1

First of all the required flow for the system (hydraulic motor) is around 3 litres per minute and accumulator maximum pressure will be 40+10=50 MPA ( because the fluid should overcome the precharge pressure of bladder or spring). The accumulator's maximum allowable working pressure should meet or exceed the system's maximum pressure. Therefore systems required pressure will be more or equal to 50MPA depends on the systems required pressure.

If the system safe pressure is 50MPA then u must choose a pump whose capacity is greater than system requirements in both head(pressure) and flow. Since the flow is less and pressure is more we must obviously go the positive displacement pumps like vane pump,radial piston pump , axial piston pump etc.........

The selection of the pump is also depends on the viscosity of the fluid you use, which in turn depends upon the type of application.In this case the type of fluid is not mentioned and it is difficult to choose a pump.Because the frictional losses in pipe will also count . After choosing the type of pump you must use a pump manufacturers catalogue to choose the pump model whose specifications meets your demand.

The basic procedure of the pump selection is as follows:

1. Determine the flow rate

To size and select a pump, first determine the flow rate. Selecting the right flow rate may be as simple as determining that it takes 100 gpm (6.3 L/s) to fill a tank in a reasonable amount of time or the flow rate may depend on some interaction between processes that needs to be carefully analyzed.

2. Determine the static head

This a matter of taking measurements of the height between the suction tank fluid surface and the discharge pipe end height or the discharge tank fluid surface elevation.

3. Determine the friction head

The friction head depends on the flow rate, the pipe size and the pipe length.

4. Calculate the total head

The total head is the sum of the static head (remember that the static head can be positive or negative) and the friction head.

5. Select the pump

You can select the pump based on the pump manufacturer’s catalogue information using the total head and flow required as well as suitability to the application.