my first bench

[jason pohlman]

here is my first attempt at a bench.it is powered by a 5 hp motor turning a pro-charger.depression is controlled by a flow performance pwm valve.i'm using the fp-1 w/ a 100" sensor and the 3rd sensor for using a velocity probe, which i need to get from bruce.it has a 2.5 flow element and 4 rv valves to controll air flow through the bench. the valves are controlled by small air cylinders.it needs to be wired and the cylinders plumbed so i can try this thing out.

[jason pohlman]

try again!!!!!!

[jason pohlman]

and again!!!

[jason pohlman]

i'm having trouble w/ these pictures, here is another.

[bruce]

Looks good!

Took me a few minutes looking at the pics to follow the flow path (to early in the AM). First bench I've seen with air actuated valves for flow control. I like the blower!! Get'er up and running and lets hear how it works out for you

[Thomas Vaught]

I have posted in the past about the Vortron type stationary (Vortech)
superchargers being used for flow benches. What supercharger did you use? I assume one of the smaller units like a P1SC (self contained oil supply) units.

Would be really interested in the motor rpm you used, pulley ratios, amount of flow depression, and overall maximum air flow through the bench. Sorry for all of the questions. Last time I saw one of these deals was in a Circle Track magazine some years ago using a Vortech S-trim
blower.

Tom V.

[jason pohlman]

the blower is a p1sc-2.it is self contained so there is no oil lines to run!it will move 1200 cfm and build up to 30 psi so i "think" it will work!the motor is 3450 rpm with a 7.5" pulley.the blower has a 4.75 pulley with a 4.10:1 step up ratio.the max impeller speed is 60,000.i can't find the formula to see what rpm the blower will be turning with these pulleys,it's around here some where in my pro-charger book.i think i will need to pulley it up to reach my goals but won't know until i start testing.

[Thomas Vaught]

Formula is:

(Large drive pulley/smaller driven pulley) times
blower step-up ratio times motor speed

(7.5"/4.75") X 4.10 X 3450 = rpm

(1.5789) X 4.10 X 3450 = 22,334 rpm.

You will have lots of cfm (1200 at 60,000) available and the Vac for the test pressure will be pretty high. In reality with the lower blower rpm the PSI will be about 1/4th what they claim but will still be quite high for a flow bench.

Normal rule of thumb is that if the blower makes 30 psi at 60,000 rpm it will make 1/4th the pressure at 1/2 the speed. Your 22,334 rpm is about 75% of the 30,000 rpm. if the rpm was 30,000 the blower would be making 7.5 psi.
28" H20 is about 2" Hg or 1 psi.
Say your deal actually made 5.6 psi, that is
over 156 inches of water delta P.

In reality you will have a lot of cfm available and a lot of test pressure available.

JMO

Tom V.

ps Every centrifugal flow bench I have seen in operation had an adjustable throttle blade valve on the discharge of the blower to keep the blower out of surge. Test pressure was set with that butterfly valve.

[blownalcohol]

Nice job Jason!!!

Your bench looks great. Like Tom V., I am very interested in the numbers you come up with when you get it operational. I am considering converting my bench to a centrifugal blower style at a later date, so please keep us posted!!!

Again, good job.

[blownalcohol]

Nice job Jason!!!

Your bench looks great. Like Tom V., I am very interested in the numbers you come up with when you get it operational. I am considering converting my bench to a centrifugal blower style at a later date, so please keep us posted!!!

Again, good job.

[jason pohlman]

will the pwm valve work for controlling the depression or will i need somthing else to help with this?maybe plumb in another small bleed valve that will be manually operated?the pwm says not to exeed 2psi? how will the rv valves hold up to this psi? i am wanting to test at 40".can i just tap the settling chamber with a small barbed fitting to measure the depression? if so where would be the best place for it? i'm using 28" of 6" pipe for the chamber. i guess i don't understand what you are saying about the blower surging, can you explain this further?

[jason pohlman]

thanks jeff.your bench looks very good as well.i only hope mine turns out as nice as yours! once i have the bugs worked out i will inclose it and doll it up a little to make it look like something :p you know how this stuff goes i am not even done with this and am already looking forward to adding a wet flow system to it.

[Thomas Vaught]

Quote:

"i guess i don't understand what you are saying about the blower surging, can you explain this further?"

Centrifugal superchargers are designed to work with-in a given flow range (typically labeled as lb/min) of air movement and with-in a given Pressure Ratio.

More info on these terms and many more can be found here:



to see how the engine and the turbo relate to each other play around with the program shown here.



Hope this helps. A centrifugal blower is just a "turbo" that is driven by a belt vs by exhaust gases (like a turbo is).

Tom V.

[jason pohlman]

got to play with the bench tonight. i think i need a bigger motor! it will only run for about 10 seconds and trip the reset button on the motor.with my short testing time i got a flow reading of 340.3 @ 26.4" with a crude orfice plate.a piece of 1/8" mdf with 1 5/8" hole.this is not even close to where i want to be, so i will have to speed up the blower. question is will a 7.5 hp mtor be enough after i change pulleys? maybe i should just step up to a 10 hp?any thoughts would be great. thanks jason

[Thomas Vaught]

You speed up the blower, the blower will move more air but the hp to drive the blower will go up too. The old Paxton blowers used in the really old flow bench articles Jim McFarland did in the early 70s used a 10 hp electric motor that was 3 phase.

The rule is that up to 100 lbs of air moved by the blower, it basically takes 1 HP to move one lb of air. So you move 10 lb of air you need a 10 hp electric motor minimum.

n(lbs/min)= P(psia) x V(cu.ft./min) x 29
-------------------------------------
(10.73 x T(deg R))

This should get you a good approximation of the motor you need.

Tom V.