Eaton M62

[Scott]

I have a really nice Eaton M62 Supercharger, how well do you guys think it would work powering a flow bench?

RRBD

[bruce]

Ah . . . send it to me and I'll findout for you and let you know :laugh:

[Tony]

I have never tried a roots blower myself in a flow bench, but I have read that the late Smokey Yunick once used a GM 6-71 blower driven by a 35HP electric motor in one of his flow benches. So that is certainly encouraging.

Roots blowers are actually very efficient at low pressures. The Eaton with it's three twisted rotors should have hardly any pulsing.

If I was planning this, I would definitely fit a pressure safety release valve directly around the blower. If the flow ever accidentally became totally blocked, the massive developed pressure spike, could easily burst or implode your bench in a split second. Another worry would be if a small object suddenly disappeared down the test hole and tried to pass through the blower carried along by the airflow. Also easily prevented.

A very interesting idea indeed, let us know how it goes.

[Scott]

This is a future project. I don't know how big of a motor to drive it with, there is some info on it on the CAPA site, but its all given at a Dp of 5psi and greater. Any Ideas how to figure out motor size and what speed to turn it?

RRBD

[Thomas Vaught]

I have two friends who have used 6-71 superchargers turning at very low speeds to act as vacuum/ pressure sources for a flow bench.

Both would up using a three phase motor to spin the blower.

A M-62 would draw a lot less hp as it is 62 cubic inchs of volume per revolution vs the 6-71 which was 420 cubic inchs per revolution.

I do supercharging and turbocharging for a living for the Ford Motor Company so I know superchargers.

I say go for it!

Tom V.

[Scott]

Thomas, if my rudementary calcuations are correct then this thing will pull about 720 CFM at 1725 rpm?

Scott

[Thomas Vaught]

I would say, give it a try.

Tom V.

ps Paxton superchargers have been used for years as flow bench sources. They typically required a 10 hp three phase motor.

[Tony]

Scott, assume 62 cubic inches flow per rev at zero back pressure.

So we need 27.9 revolutions to reach one cubic foot. Let's assume 2,790 Rpm would give us 100 CFM flow, assuming no losses.

As soon as you begin loading it with some back pressure, flow falls, but not by much at the very low pressures we are talking about here. For example 28" of water is almost exactly 1 psi, say we design for a 1.5 psi working pressure.

Theoretical power required to thermodynamically compress the air: 100 CFM x 1.5psi divided by 229 = 0.655 Hp In practice it may end up closer to about 1 horsepower to do that.

If we start speeding up the action (keeping the pressure at 1.5 psi) we may be able to very roughly guess at the airflow and power required as they will both be roughly proportional to blower Rpm.

My wild off the top of my head guess, is you are going to need about 1Hp for every 100 CFM, and about 3,000 blower Rpm for every 100 CFM.

A much larger blower turning more slowly might be more convenient, but it is possible.

[Thomas Vaught]

Another comment, all of the roots style Eaton blowers have a max rpm limit of 14,000 Blower rpm. If you need to go higher than 14,000 using Tony's calculation then you need a larger volume supercharger.

Tom V.