Electric forced air induction?

[Hypsi87]

Originally Posted by Alastor187

Maybe this is a circular argument but I thought a fan, compressor, and pump created pressure. For example in a centrifugal fan the pressure difference across the blades causes the working fluid to move from the inlet to the outlet. The pressure or flow after the outlet is function of the restriction.

Nope all a true pump does is create flow, I just looked it up in my fluid dynamics book.

[gmatov]

"Once the fan encounters pressurized air backing up towards it, it loses its effectiveness and stops pumping air."

By this reasoning, you seem to imply that, if you take your old bicycle pump, plug the hose, push as hard as you can, till the piston stops, you are not making pressure, because no air is moving, just "choking" the piston.

No, I don't think you mean that.

Where, except in the rebuts to the OP, did we start to discuss axial flow fans?

I think most of the posters know ( I hope they do, anyway ) that leaf blowers and vacuums are centrifugal, therefore, radial flow.

A turbocharger is a radial flow device.

A leaf blower is a radial flow device, as is any vacuum cleaner you can name, whether it be Shop Vac or Hoover, or Orek.

Radial flow COMPRESSORS have been built for a 100+ years.

Your shop Vac may not make the pressure you desire, due to limitations of speed, design of the impellor, clearances in the compressor, itself, but that does not mean it does not compress air.

Good grief, just try to squeeze the Hoover bag, after you turn it on!!!

And, that is from the COMPRESSOR trying to compress the air into a container (the filter bag and the containment vessel, the outer bag ) that are designed to let filtered air escape, so it can continue sweeping up more dust. It would work the same, for about 2 feet of travel, if you had a hose attached to a 100 gallon drum outside the house. Except, you would have to go outside, release the pressure, dump the dust, reseal it, then go inside and clean 2 more feet of the carpet.

I wrote elsewhere, that a well designed centrifugal, radial flow, compressor ( much stricter tolerances, and much higher rotational speeds ) will double the input pressure. ie, atmospheric, after 1 stage, 30 PSI, 2 stages, 60 PSI, 3 stages, 120 PSI, up to as many stages as you need.

One company I worked at built centrifugal compressors that produced 10,000 PSI, for use in floating oil rigs, drilling deep. That will push oil up a 25,000 foot oil well casing.

Fans and centrifugal compressors, if you want to call a leaf blower or a shop vac OR a supercharger, such, DO NOT choke when the flow is restricted. They MAINTAIN the pressure. So long as the air can't escape elsewhere, the pressure is held. Lift your hand a little bit, air comes out, instantly. It IS compressed.


Curtis,

"There is almost no pressure behind that wind, but it will rip a roof off a house."

It has been scientifically proven that 60 MPH winds do not blow roofs off houses. The vacuum caused by those winds cause a house to explode, due to the difference in pressure, inside to outside. Tornados, for instance, cause a low pressure area to develop over their path. Houses blow apart. Warnings in all tornado prone areas advise you to open your windows to allow pressure to equalize. Minimal damage results.

Even axial flow fans, like your typical 4 bladed air circulator,you know, that 10 buck thing that oscillates in your den, creates pressure. Put it up against the wall and turn it on. It can't move the wall, so it tries to knock itself over from the force.

They use axial flow air turbines, read really big powerful fans, in wind tunnels. Not supersized superchargers, ie, centrifugal compressors. These babies can blow some air. They can tear the skin off an improperly designed aircraft fuselage.

If any fluid dynamics savvy people are here, they could tell you what the potential pressures these devices would be capable of are.

1 mm Mercury differential means a hell of a lot more over a couple thousand square miles than in an engine manifold. It means cubic miles of air rushing in to fill that void. The amount of work, or of havoc, is stupendous.

Hypsi,

Correct. I have had this problem with hydraulic metal working machinery. Pumps putting out plenty of flow, but no work being done.

Bad pump, still moves the oil, but so much slip, due to bad vanes, the machine wouldn't run, change the pump, all's well.

Same with air, only easier to "stall" the "pump", after all, it's air. You get to the max pressure it is capable of, it just lies there in wait, you bleed off a little air, toe the throttle, take the piece of paper off the discharge hose, it recharges to the max pressure it is capable of.

Why this is so difficult to understand, I don't know. How can anyone say "No flow, no pressure."?

You take a 3" leaf blower wand, flatten the end to a 1x3 nozzle, you have a restriction, you have pressure, you have speed.

You stick it in your intake, without the nozzle, you have more air than an NA engine.
I give up,

Gotta go to bed.

Cheers,

George

[Hit_N_Run-player]

we need to test it, but what kind of blower would you use? It has to be alot better than a leafblower though..SOMEBODY TEST IT!!

[Hypsi87]

A bicycle pump is a piston pump. Your trying to compare apples to grapefruit.

[gmatov]

Doesn't matter.

A centrifugal "stalls" because the pressure in the outlet is at the highest it is capable of. The pressure is still there, but, whereas, a centrifugal can slip, it will hold the pressure, and when you bleed off a little, it rebuilds.

A piston pump will stall by coming to a stop, period, maintaining the pressure, and when you bleed off a little, will advance to its stall point.

The efficiency of the centrifugals you guys are talking about is low, so naturally the pressure developed and held is low. But, it IS there.

Why you cannot understand this is beyond me.

Cheers,

George

[nissanfanatic]

But when the pump stalls, it isn't flowing anything. When it "stalls" on a centrifugal, the air just backs up in the housing while the impeller spins. Pressure+no flow=no more power. Flow+no pressure=no power. Exactly the same as the HP vs Torque arguement.

[Alastor187]

Originally Posted by nissanfanatic

But when the pump stalls, it isn't flowing anything. When it "stalls" on a centrifugal, the air just backs up in the housing while the impeller spins. Pressure+no flow=no more power. Flow+no pressure=no power. Exactly the same as the HP vs Torque arguement.

I think the point that gmatov is trying to make is that the total pressure created by the fan is sum of the dynamic and static pressures. So when the flow is restricted to the point that it stops, the dynamic pressure will go to zero and the total pressure will equal the static pressure (and be non-zero).

Below is a typical fan curve for a centrifugal fan with forward curved blades. It shows static pressure on the vertical axis plotted again flow rate on the horizontal axis.

[Jet-Lee]

I understand gmatov 100%. He's just more persistent at explaining than I am.

[gmatov]

Now why did the term "static pressure" slip my mind? Thank you.

I think, instead of just saying "It ain't so!", just doing a little experiment would be enlightening.

Start your ShopVac and cover the exhaust hole. Harder to hold back the pressure than you might think. The motor slows. It's trying to force more air out the volute, is compressing denser air, but slipping.

Now cover the intake. Sucks your hand tight, and, no air to move, motor spins faster, as it's no longer doing any more work than trying to build vacuum in the tank. Again, not efficient, due to slip from clearances and impellor design.

Have to revise a post on another board, same subject but different application. Posted results there with 1 1/4 hose attached. Corrugations in the hose change things tremendously from open port.

Cheers,

George

[Sluttypatton]

I have always agreed that some pressure will be created. What I have been arguing about is the magnitude of that pressure.

Now that my finals are finished I will have some time to do a little experimentation and hopefully get some answers a little more definative than my speculation. I will try to find time to do it within a week or so, but if it turns out to be more work than a couple of hours I might not do an experiment at all. I don't care enough about the argument to spend more than a couple of free hours on it. When I do the experiment I'll document everything as fully as possible and take as many pictures as I can of the whole thing to lend some credibility to whatever I find. Whatever I find I will post, even if that means disproving my argument.

The experiment is going to also be limited by what materials I have on hand; I'm not going to go buy an industrial leaf blower just to test an argument.

[gmatov]

Slut,
When they put 100,000 bushels of grainn in a silo, they do not use turbochargers to push air through it to prevent spontaneous combustion, they use axial flow fans, granted, with a little larger motors than you have in your home. 50 to 100 HP? And, they will force cooling and drying air through all that grain, 100, 200, 300 foot tall silo.

But you still insist you can put your hand over it and it's all gone. The blades do NOT cause a pressure rise, just a volume rise.

Come with me to a steel mill and walk close to one of the fans. It will blow your hard hat off, and, if you are not prepared, will blow you over. You'll be leaning into, a 60 or more MPH wind, and you will think differently.

I wouldn't ask you to go buy a leaf blower, though I may, If I do, I'll post my results, here.

I think those results will surprise all of you, also.

Cheers,

George

[Sluttypatton]

I know nothing of grain silos so it is pretty hard for me to respond to that, however I never argued that the pressure simply disappears when you cover the outlet. What I have been arguing all along is that the fan will stop pumping air when the static pressure builds as a result of the blockage and that the resulting static pressure will be small. I think we have misunderstood each other, because the more you elaborate on what you mean, the more it sounds to me like what I am trying to argue.

Originally Posted by gmatov

the pressure developed and held is low. But, it IS there.

Originally Posted by Sluttypatton

I'm not saying that no pressure at all will be created, just that the amount created is not very large.

I have a leaf blower, and that is what I will be doing the experiment with. The leaf blower I have is electric and capable of approximately 300CFM (one of the things I will do is find out more precisely what the airflow is), which is shy of the 400CFM you have been talking about and is why I said I would be limited by the equipment I have. I feel however that it is close enough to give us a general idea as to what kind of pressure can be built by a leaf blower.

[C.Jackson]

Hey,

I just read this whole topic (Hense my eyes hurt). I want to see if it does make any difference! Even if it's just a little, for the hell of it. A 1G Mitsubishi turbo produces 405 CFM, but at 14 PSI, pressure matters alot in the game of turbo's so I don't think the blower will add much. Just a little, because it is giving more air than the engine requires........

_C.Jackson

[rguenthner]

I just finished reading this entire thing and now my head hurts. What George is saying is simple physics if you just stop to think about what happens in your turbo. Now I don't have years of experience working with turbos, compressors, turbines, fans or anything close, but I do have a good understanding of physics (without all the fancy lingo ).

First off George is in no way saying that your run of the mill electric (or gas for that matter) leaf blower is going to come anywhere close to doing what your low end/cheap/stock/high end/whatever turbo you've got on your car will do. He is simply saying that increasing the airflow (and therefore the manifold pressure) will help no matter how small it might be.

Now lets cover some of the arguments that have been made here. We need to keep in mind that we are comparing apples to oranges here, so when trying to make a comparison it helps to try and equalize the equation. Realize that your turbo has been designed to do everything much better than the leaf blower. It is much more powerful, built with much higher tolerances, built to last much longer and therefore it also costs much more.

Could an electric turbo be made that makes the power that your current turbo does? Sure it could be. Replace the impeller that sits in the path of your exhaust gases with a big electric motor and bingo, you're golden, right? I suppose advantages would be that you have more control over the speed of the compressor and you could locate it in a more convenient place. The downside is it's FAR less efficient than your traditional turbo. You need a larger alternator to supply the current needed (weight and energy loss via heat), larger wiring to carry the current (more weight + heat + energy loss), and then the large electric motor on the turbo (even more weight and energy loss via heat). The question is why would you want to do that when we already have a better alternative?

Now for a new way of thinking about the solution that George is offering with the leaf blower. We have a 350 that flows ~500 cfm at 5k rpm. That puts the manifold pressure at some negative number. Instead of putting the 400cfm leaf blower in the already existing intake, lets just add another hole right on top of the intake manifold. Now the leaf blower isn't going to get in the way. Hey I have a better idea! How about instead of your normal intake, we change it to ram-air! Now you have your extra pressure at low rpm and at high speeds. ghetto rigged? Well yes, maybe =) But we don't want to spend the money on a turbo to do it right now do we?

It's late so forgive my rambling. One more thing to address though.

Lets talk about pressure. What is pressure? Everyone here seems to be thinking of pressure as something bottled up. Pressure in a hose, pressure in a tank, pressure in a bottle, pressure in the intake manifold... Well, when a fan is spinning, why does the air move? Because as the vanes move through the air on one side the air is compressed, while on the other side there is a slight decrease in pressure. The weight of the air in the atmosphere pushes air in to replace the air behind the fan blades, while the higher pressure air in front of them expands to equalize, creating that nice breeze you feel. Sailboats use pressure from the wind to move. Extremely low pressure over a very large surface area equals a very large force. See what that low pressure difference making a 60 mph wind does to a sailboat.

Centrifugal fans work differently, they spin the air and use centrifugal force to move it. As the air is 'slung' outwards a negative pressure is created in the void where the air used to be. Again, atmospheric pressure forces air to replace it, which is then slug outwards and the process repeats itself, creating the airflow you feel.

There was a lot of talk about 'stalling' blowers and turbos. I think covering the outlet of your turbo with your hand is a bad example. You've got a lot of force driving the turbine that is pushing the air out and I don't think anyone is going to be strong enough to stop that. I think it would be better to imagine what would happen if you COULD stop it. For the sake of the argument, lets forget that we want to use the air coming out of the turbo to make our engine perform better. Lets just say the engine makes 200 hp without the turbo, and we just hooked one up to it to see if we could stop it. Without a waste gate (that also messes with my theory) if the engine has enough power the same thing would happen with your turbo as happens to the leaf blower when you put your hand over the outlet. It will reach a maximum pressure and then fail to make any more pressure. If your engine isn't strong enough to continue to drive the turbine at this point it's likely you'll stall it due to the lack of a place for the exhaust gases to go. I imagine having that happen depends on many different factors such as engine speed, angle of the turbine blades, and some other things I can't think of right now - but it would be an interesting experiment!

And finally, for the original poster - Why not just invest in Nitrous for the power on demand application your looking for? Cheap, lightweight, fairly safe and big horsepower gains.

If anyone has made it this far I commend you! I will end my ramblings here. Good night all!

-Randy

[gmatov]

rquenthner,

Welcome to the forum, and thanks for the backup, although I did not think up the leaf blower, simply tried to argue that they WILL put out pressure, even when "stalled".

I don't really think it would be hard to "stall" a detached real turbo. How you do this, considering that it assists the engine to make more HP, I won't speculate.

They are still going to put out 14.7 psi at max. If you can't stop that pressure, from a small nozzle, you're rather weak.

If it is a rather large nozzle, and those are the technical terms, whether they be 1 inch, or 36 inch diameter, excuse me, say 4 inch diameter, now it takes some effort to hold back, as it is 185 pounds of "force" pressing against your hand. If it's a blowgun on the end of the hose from your 125 psi compressor, all you need do is force your thumb down over the 1/16 exit, and you will, if not stop it, severely restrict it.

Try it. Some air tools actually work this way, particularly cutters, like pneumatic bolt cutters, which are used to cut rod to length for fabs such as grates. Finger on the trigger, plug the exit, the pressure works on the piston, lift your finger, the exhaust flows from the trigger.

Ah, well, no one is going to suggest that anyone throw away their 10 grand blower to put a 100 buch leaf blower in the intake, instead. That was not the point, to begin with. The point was that, when you raise the presure of ANY compressor, compressor, mind you, it is still maintaining, as you say. Pressure does not drop to zero as some of the prior posters said.

Thanks, but I doubt that any of the other posters will admit such.

Cheers,

George