Ideal radius for a bellmouth inlet
Ideal radius for a bellmouth inlet
(OP)
Surely this is basic, I want to calculate the ideal bellmouth radius (and lenght?) for a 2" opening where the flow rate is about 900 cfm of air (assumed 28" H2O presure drop).
Thanks in advance,





RE: Ideal radius for a bellmouth inlet
I think the length of the intake tube depends on what you want the response of the engine to be, the longer you go the better the mid-range torque.
The leading edge radius is required to allow the airflow entrained from the sides of the air intake to turn smoothly down the intake without overshooting the turn or becoming turbulent, which can cause effective airflow "narrowing" in the first part of the inlet tube. I don't know if there is a method of calculating this but I would have thought that a radius of 1/4" would be sufficient provided that you use an edge that is fully turned back on itself. I have seen some so-called performance inlet trumpets that don't have this and have a perforated metal screen as a "filter". I think these are probably worse for airflow than an open intake would be, the only advantage would perhaps be to stop small children falling in.
David Vizard has written a good section on intake tubes/ rampipes in his book "Tuning the A series engine". It is primarily for that articular engine (Leyland Mini) but it is full of useful stuff for general consumption. David uses airflow benches to prove his ideas.
Hope this is of some use, I noticed that folks aren't exactly rushing to give advice on this one.
RE: Ideal radius for a bellmouth inlet
Regards
RE: Ideal radius for a bellmouth inlet
Have you considered using an elliptical edge rather than a round one? I understand that this form prevents the build up of resonance in the airflow, the last thing you want in a flowmeter.
RE: Ideal radius for a bellmouth inlet
If you have 28"w.g. to pull the flow, you won't make it because the fluid when set in motion required energy to do it (fluid is at rest initially because you want a bell mouth inlet). Mean velocity is approx 41,300 fpm and the velocity head (energy in the fluid flowing, not static head) is about 106"w.g. So you gotta have about over 106"w.g. + fittings and meter loss to get the 900cfm. And keep in mind sonic is about 1138fps at 80F (kgRT)^0.5
RE: Ideal radius for a bellmouth inlet
jimkden is right, you are not going to be able to reach your target flow and pressure drop.
RE: Ideal radius for a bellmouth inlet
RE: Ideal radius for a bellmouth inlet
source unknown.
I figure unless I'm at full throttle >>I<< am the limit to airlflow and power.
http://www.spannerfodder.com/the_works_escorts-generic-...
RE: Ideal radius for a bellmouth inlet