Ratiometric Benches

[bnoji]

It seems as though most flow benches operate at roughly 1psi. I have a specific need to test flow at pressures of at least 20psi, up to and possibly beyond 30psi. Specifically, I'm looking at measuring flow from the outlet of a turbo compressor through various types of piping and fittings. Is there any bench capable of producing the necessary PSI?

Thanks.

[Mouse]

I don't know where you could get that much air, but I can supply you with an electronic processor and possibly a flow element that will handle those rates.

Email me at Sales@FlowPerformance.com

John

[bnoji]

Mouse,

Thanks for the offer.

I want to test flow through several pieces connected to a turbos compressor outlet. I would like to test as close to operating conditions as possible, which will be in the range of 12-30 PSI from the turbo.

I don't see a problem measuring and scaling results based on a 1psi test pressure. I am worried about change in airflow characteristics at higher pressures/velocities and whether the general sqaure root of the pressure ratio method will be accurate enough without accounting for these changes.

As for the PSI problem, I am looking at a way to run a cheap turbo from a compressor or driven directly from an electric motor and actually use the turbo on the bench.

[Thomas Vaught]

I do boosting for a living for The Ford Motor Company.

A Industry "rule of thumb" is that you would need at 15 psi, (2.0 pressure ratio), ONE HP to move ONE LB of air.

ONE LB of AIR will make TEN HP in a gasoline engine.

Say that you want to make 500 hp. You would need at least 50 lb
of air capability on your turbo compressor (at 2.0 pressure ratio).

This means your test stand would have to have a 50 hp electric motor to test the turbo compressor at that pressure ratio, not counting the losses in the bearings and belt drive of of your set-up to spin the compressor to the correct compressor rpm.

A Vortech Supercharger (a belt driven turbo compressor device)
will need 37 additional engine hp to make 400 hp just for the air
flow plus an additional 20% (about 8 hp) for the mechanical losses,
as an example.

I do centrifugal supercharging testing on a stand that has a 160
hp electric motor and you would not believe the wiring required.

Most Turbos are testing on what they call "Turbine" stands where
a complete turbo assembly is tested using a high heat/ volume gas
burner arrangement to vary the speed of the turbo (much like an
engine changes the exhaust volume based on engine load). The
turbo is also shielded by explosion plates as turbo compressor and
turbo turbing housing have come apart during testing. Food for thought.

Most quality turbo companies like Turbonetics have compressor
maps for most any turbocharger housing. My suggestions would be to save the expense for buying a very large hp electric motor and use the money to buy several matched sets of turbos for your project from Turbonetics as the motor will be quite expensive and
the power company will love you as a customer.

Sorry for the levity.

Tom V.

[bnoji]

We're not working on the turbo itself. We're mainly working on the piping and intercooling. What I meant by actually using the turbo on the bench was to replace the vacuum motors with a small turbo to generate the desired pressure. I can test flow on the parts at 1psi and scale it based on the square of the pressure ratio...but my main question is whether flow characteristics change between the 1psi test pressure and the 30psi operating pressure. So I'm stuck deciding on trying to build a bench that can operate at as close to 30psi as possible or build one to work at 1psi and scale the results.

[Mouse]

What size pipe will you be working with?

[bnoji]

Mouse,

The majority of the piping is 2.5 and 3 inch diameter.

I don't really need to test at 30psi unless airflow characterstics change at higher velocities/pressures. My big concern is that a test piece will flow fine at 1-2psi but not at 20-30psi and when adjusting the ratio for the higher psi I would not see that change.

I think what I'm heading towards is if there is a terminal velocity of a fluid through a certain diamter pipe and whether that limit occurs within the operating range of the turbo. I wouldn't hit that boundary at 2psi but I may at 30psi...

[Mouse]

Yeah, hard to say. The pressure would increase the air density which may amplify any phenomenas or turbulance, or maybe not. Anyway, Flow Performance could build you a 2.5" or 3" flow element to place in front of your plumbing, or at the end (in front works best) and a processor to give you real time flow rates as you tinker with it. You can test at low pressures to give you an idea of how much restriction your design has and if any changes improve or degrade the flow rates.

John

[Thomas Vaught]

See this link:



The units there WILL be capable of 20+ psi through a 3 inch pipe.

Tom V.

[2seater]

Do you know how much air flow is needed? The volume of air through the system is what generates the turbulence. The backpressure inside the engine, which causes the need for high boost, will reduce the air flow well below what an open pipe will flow at that same pressure. My relatively small diameter, about 2.25", throttle body and MAF combination will flow almost 500 cfm @ 28" of water. The flow velocity through the 3" i.d. flow tube is about 9800 fpm or 111 mph to flow that much air.