flow coefficient and loss coefficient relationship???
flow coefficient and loss coefficient relationship???
(OP)
Hello, I have searched all over and have not been able to find the answer to this question so I decided to post it here in hopes of getting some help.
First let me explain my situation. We are using an Engine Cycle and Gas Exchange Simulation program called BOOST that is made by AVL to model the effects of the intake manifolds for our 4 cylinder engine. This is a very rough sketch of what the plenum looks like.

The arrow shows the direction of air flow and the entrances enclosed in the red oval are sharp corners (NOT bellmouthed) for each of the 4 intake runners (round pipe). My problem is, the program is asking for a flow coefficient for those entrances and I have not been able to find any source that gives flow coefficients for something like this. I have a source that gives a loss coefficient of 0.5 for a sharp corner like this
but i'm not certain if it is acceptable to assume my situation is the same since the flow is entering the plenum and then turning (can I assume a loss coefficient of 0.5?)?
If it is ok to assume a loss coefficient of 0.5 (if not could you suggest some references to look at for appropriate K values?) is there a direct relationship between the loss coefficient and flow coefficient? I looked in my old fluids text books and found equations for both the loss and flow coefficients and I could manipulate those equations to get a relationship with the loss coefficient being equal to 1 over flow coefficient squared. This is the manipulations I performed to get this.

I am sorry for making such a long post especially since this is my first one here but I wanted to make sure I fully explained what it is i'm looking for. If anyone can give me some help or point me to a reference to look at that would answer this I would greatly appreciate it.
Thanks,
Nick
First let me explain my situation. We are using an Engine Cycle and Gas Exchange Simulation program called BOOST that is made by AVL to model the effects of the intake manifolds for our 4 cylinder engine. This is a very rough sketch of what the plenum looks like.

The arrow shows the direction of air flow and the entrances enclosed in the red oval are sharp corners (NOT bellmouthed) for each of the 4 intake runners (round pipe). My problem is, the program is asking for a flow coefficient for those entrances and I have not been able to find any source that gives flow coefficients for something like this. I have a source that gives a loss coefficient of 0.5 for a sharp corner like this
but i'm not certain if it is acceptable to assume my situation is the same since the flow is entering the plenum and then turning (can I assume a loss coefficient of 0.5?)?If it is ok to assume a loss coefficient of 0.5 (if not could you suggest some references to look at for appropriate K values?) is there a direct relationship between the loss coefficient and flow coefficient? I looked in my old fluids text books and found equations for both the loss and flow coefficients and I could manipulate those equations to get a relationship with the loss coefficient being equal to 1 over flow coefficient squared. This is the manipulations I performed to get this.

I am sorry for making such a long post especially since this is my first one here but I wanted to make sure I fully explained what it is i'm looking for. If anyone can give me some help or point me to a reference to look at that would answer this I would greatly appreciate it.
Thanks,
Nick





RE: flow coefficient and loss coefficient relationship???
Good luck,
Latexman
RE: flow coefficient and loss coefficient relationship???
One of my advising professors for my thesis research is actually the person who is doing the AVL modeling since he is the only person with the software. I asked him last week if he had a phone number for AVL so I could talk to them about it but he said that the last time he tried calling them for help they were not very helpfull because they also sell tutorials and such. Thanks for the suggestion though.
If anyone else has any input i'd greatly appreciate hearing it.
Thanks
RE: flow coefficient and loss coefficient relationship???
Mike Halloran
Pembroke Pines, FL, USA
RE: flow coefficient and loss coefficient relationship???
Thanks
RE: flow coefficient and loss coefficient relationship???
Q = Cv x sqrt( press drop / SG )
where
Q is in USgpm
press drop is in psi
SG is relative to water
If this is the flow coefficient that AVL are using then the relationship to the loss coefficient is given by
Cv = 29.9 x d^2 / sqrt(K)
where d is the inside diameter in inches.
A good reference to these conversions is the Crane Technical Publication 410, specifically Equation 3-16 on page 3-4. This is probably the most referenced book on fluid flow in the English language.
Harvey
Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com
RE: flow coefficient and loss coefficient relationship???
To account for the change of direction for flow I used loss coefficient of a tee with flow thru branch.
I also had to account for the sharp edge entrance. I used the sharp edge coefficient. I added the two pressure losses together.
I may have over compensated but I wanted to ensure that exhaust fan could handle the system pressure loss.
RE: flow coefficient and loss coefficient relationship???
Good luck,
Latexman
RE: flow coefficient and loss coefficient relationship???
Thanks to everyone who gave references to look at. I'm going to try to make it to the library today to check these sources out and hopefully I can learn something today. :D