aafuni
Mechanical
- Dec 29, 2009
- 188
I have a nozzle with complex geometry that has a specified flow condition that must be met. The specification gives a flow rate (lb/hr) at a given test stand pressure (psig) using MIL C7024 type 2 fluid (commonly sold as stoddard solvent or white spirit).
I would like to be able to flow test the nozzle using water in our test stand rather than the solvent. I was hoping to find an accurate way to correlate the flow rates of water and oil through the nozzle. Ideally I would like to be able to run the test at a different test pressure to compensate for the fluid's density and viscosity change, and be able to get the same flow rate, and therefor be able to verify the nozzle's geometry in this way.
I have experimented with similitude, but am not that familiar with this method. Using similitude it seemes that I must match both the Re and Cp values given the variables. Using the equations for both, I get an equation dP*rho/mu^2=constant between the flows. This equation makes no sense physically as it suggests that the more viscous fluid requires less total pressure drop to result in a matched flow rate.
I have been experimenting with ALGOR on simpler nozzle geometry as the nozzle I am working with requires a fine mesh and long processing times. With a simple conic nozzle, by trying different inlet pressures I seem to get a match of flow at 100psi of solvent compared to at 130psi with water. These values make more sense to me. This value is also congruent with a cv approach (flow coefficient which I think is only valid for isenthalpic valves). By calculating a cv for oil, then solving for the dP term, I get flow matching at 130psi water to 100psi oil.
Using these values (130psi for water and 100psi for the oil) in ALGOR with my more complicated geometry, I am unable to obtain equal flow rates.
Anyone have any suggestions?
I would like to be able to flow test the nozzle using water in our test stand rather than the solvent. I was hoping to find an accurate way to correlate the flow rates of water and oil through the nozzle. Ideally I would like to be able to run the test at a different test pressure to compensate for the fluid's density and viscosity change, and be able to get the same flow rate, and therefor be able to verify the nozzle's geometry in this way.
I have experimented with similitude, but am not that familiar with this method. Using similitude it seemes that I must match both the Re and Cp values given the variables. Using the equations for both, I get an equation dP*rho/mu^2=constant between the flows. This equation makes no sense physically as it suggests that the more viscous fluid requires less total pressure drop to result in a matched flow rate.
I have been experimenting with ALGOR on simpler nozzle geometry as the nozzle I am working with requires a fine mesh and long processing times. With a simple conic nozzle, by trying different inlet pressures I seem to get a match of flow at 100psi of solvent compared to at 130psi with water. These values make more sense to me. This value is also congruent with a cv approach (flow coefficient which I think is only valid for isenthalpic valves). By calculating a cv for oil, then solving for the dP term, I get flow matching at 130psi water to 100psi oil.
Using these values (130psi for water and 100psi for the oil) in ALGOR with my more complicated geometry, I am unable to obtain equal flow rates.
Anyone have any suggestions?