20 May 03 15:27
I need to calculate the pressure drop across a section of pipe to be inserted into an eninge lube oil system. The section of pipe will be inserted in-line in the common discharge from the scavenge pump where the flow has an air to oil ratio of about 10. The flow has quite alot of air and we therefore have neither a pure fluid flow nor a pure air flow situation.
What is the proper method for calculating pressure drop for these air/oil flow conditions? Does anybody know of any reference or technical paper where pressure drop data for pipe flow of this sort has been published?
I would prefer to only do a quick hand calculation and don't want to expend the effort that would be involved with doing a detailed analysis with a CFD package. We may rig up an experiment too but I would like to quickly put together some expected data from a suitable calculation.
The details of the problem are as follows:
Scavenge system pipe inner diameter = 1.375 inch
Pipe section insert inner diameter = 0.7 inch
Pipe section insert length = 6 inches
Oil flow = 1200 gal/hr
Total flow (air + oil) = 13,000 gal/hr
scavenge dishcarge pressure = 40 psi
temperature = 440 K
Note that there will be a sudden contraction from the system pipe to the insert and then a sudden expansion back from the insert back to the system pipe. (The insert will actually be a passive sensing device but from the point of view the flow it will look just like a section of straight pipe).