Flow bench efficiency

[Scott]

I'm trying to make my latest bench as efficient as possible, but using sharp edged o's it takes alot of motor horsepower, so I thought about making some short flow elements averaging pitot style. Now I'm thinking on making radiused orifice's for it. What do you think the Cd would be on a 1.402 diameter orifice being fed with a .7 dia. radius.(Using T.o.o's R=.5D formula for Ideal inlet radius). What can you guys see as potential problems? I dont see why it couldnt be calibrated using an SE Orifice. It would be great if it would work, more flow using less motor. If you can go from a .62Cd to a .95Cd thats a big improvement........

RRBD

[Thomas Vaught]

I have investigated buying Flow Nozzles for a flow bench. Our carb lab benches had the flow nozzles. As you mentioned very high cd.

Tom V.

[Scott]

Heres a pic of the the Radius'd Orifice, orifice holder and velocity pickup......

[Scott]

Heres the exhaust side, both orifice holders are the same, and both will accept 1/8" thick orifice's if the Quadrant Orifice gives me trouble........

[Scott]

Heres the velocity pickup for the exhaust. I would have made them both the same, but the quadrant orifice is about .900 thick and to space the holes 1 inch from each side of the orifice I would need a drill about 3.5" long, so I only machined the exhaust pickup so it feeds from the end....

Scott

[Scott]

Heres another pic of just the orifice, it 1.440 Dia. with a .72 Dia. entry Radius (T.o.o's R=.5D formula), I ball milled the entry in 2-degree increments and polished it. The program had only two cuts that were only two axis moves, the rest were three axis simultaneous cuts. Thank GOD for programming software, I dont have the brains to write the code by hand.......

Where should I start with the Cd now? I'm guessing .90?
Give me some thoughts and a design review on the rest of the crap, thats how we learn. Thanks guys

Scott

[Thomas Vaught]

Looks very nice.

The place I was looking at Nozzles at had I think 5 of them in a dice pattern much like my orifice flow plate is but the plate was round on the edges.

They had a clamshell deal where the flow plate could be turned around for exhaust testing. I liked some parts of the set-up really well but there was the aggravation of trying to get to the stoppers if the range was off.

The carb flow nozzles benches have special stopper actuators that either plug the nozzle or retract out of the flow path. One direction only though.

Keep us informed, it looks like a great project.

Tom V.

[Scott]

C'mon, 50 some views and nobody has an opinion on whether or not, it'll work????

Scott

[86rocco]

I can't think of any reason it shouldn't work. I think the only reason that sharp edged orifices are most often used is because they are relatively easy to construct, are bi-directional and have a cd falls within a fairly narrow, predictable range. I have no idea what cd you could expect to get with your nozzle although it's probably safe to assume it'll be considerably higher than a sharp edge.

BTW, very nice looking pieces, good work!

[Nick]

Alrite I'll post. Where did you get the T.O.O's formula? I guess what your doing is over my head. What is the purpose of using a velocity probe?

I like the Idea of building a more efficient measurement orifice.

Why not make a flow nozzle in a pipe? You get the best of every thing, repeatability, high CD numbers, and accuracy.

The next bench I build will ether be se orifices, or nozzles in a pipe.


Nick

[larrycavan]

[Mouse]

Hi Scott,

I am not too familiar with flow characteristics of a nozzel of venturi, which seems to be what you have leaned toward, so I am just watching. It will be interesting to see how this works for you. Keep posting, inquiring minds are watching.

I like your mounting method, a few screws with washers clamping the piece down. You could cut one side off the washers then you just need to loosen the screw and turn the washer to remove venturi.

Oh, one more thing, I did try to post a responce several times to this thread a while ago, but it never took for some reason. I think the server was hic-upping or something. I gave up.

John

[bruce]

[Scott]

The probe things are just to measure the pressure drop across the orifice, just like we traditionally do, but I just thought I'd see how it works putting them in a piece of round stock to make this nice and clean. The exhaust one has two holes drilled from the end, one deep, one short and then I drilled intersecting holes into those passages for the actual taps. I'm trying this having the pressure ports 1" fore and aft the orifice, I dont know how it'll work yet but we'll see.

Mouse, I have to finish off the orifice mounting set up yet, the screws are just for the time being, when I finish it, I'll post more pics.

Bruce, as for the entry radius, I used my CNC and a ball mill, started with a 1.440 dia. hole and then programmed it to mill the radius I wanted starting on the outside the machine basically moves over and down to form the radius.

I have some plans around here for a ball cutting set up for a manual lathe I think a guy could modify to cut your inlet radius' other wise I have a super simple way to make a tool using your mill to do the same thing.

Scott

[Scott]

Oh,yeah, the (R=.5D) comes from Larry Widmer(The Old One) of Endyn fame. Its in his archive section under "inlet design".
Larry has contributed alot to the Engine industry, with some very controversial designs, he was shunned by most with his designs in the 70's-80's, but alot of his stuff is very common now, you can thank him and a few others for leading the industry into small, high velocity ports and fast burn combuston chambers we all love today. His understanding of Thermaldynamics is second to none.

Scott