Designing a Centrifugal compressor and plenum.

[airmcn_3]

Thanks for the help guys.

[Speed is Life]

:eek: :eek: :eek:
Looks like you want to try to make your "rice rocket" run faster or maybe turbo charge your toilet?
:rolleyes:

[corsair nut]

im curious as to why it has 2 exhaust exits, rather than a single larger one. this would work if you could spin it up to about 100,000 rpm. below that, even if its 60,000 you may only get a couple pounds of boost at best. ive had a couple turbo cars, even designed and built an entire turbo system, from intake/intercooler piping to the exuast, like i said, your going to need atleast 100,000 rpm, or it wont be doing much, if your intension is for auto use.

[airmcn_3]

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[airmcn_3]

im curious as to why it has 2 exhaust exits, rather than a single larger one. this would work if you could spin it up to about 100,000 rpm. below that, even if its 60,000 you may only get a couple pounds of boost at best. ive had a couple turbo cars, even designed and built an entire turbo system, from intake/intercooler piping to the exuast, like i said, your going to need atleast 100,000 rpm, or it wont be doing much, if your intension is for auto use.


No auto use here, but does anybody know of a BL motor capable of producing 100,000+ RPM?

[bmiller]

No auto use here, but does anybody know of a BL motor capable of producing 100,000+ RPM?
None that I'm aware of could turn that impeller at 100K. You're looking at alot of horsepower to do it and 750watts=only 1 HP
A dentists drill motor does that but obviously too small for your project.
Possibly Bob at Astro Motors might know or actually could make one.
His company seems (to me at least)to be moving away from this hobby and does or did aerospace projects all the time.(IIRC highest altitude prop-driven UAV)
The small(no autostart) turbine guys use compressed air to turn theirs near that speed to start the motor. Another company is/was Aveox. They had some really specialized stuff back in 2003.

Bruce

[John Wright]

Chris

You need to buy
Model Jet Engines by Thomas Kamps
and Gas Turbines for Model airacraft by Kurt Screckling
from Traplet publications.

https://sslrelay.com/s119033911.oneandoneshop.co.uk/sess/utn;jsessionid=1547074cab5e39f/shopdata/index.shopscript

They will give you all the answers you need on compressor and diffuser design, or at least start you on the right road.

John

[raptor22]

I don't think that there are any commercially available motors that are rated to 100K at any wattage.

Most commercial inrunners are rated to 50-60K max.

[dalbert02]

100k is really not that hard, a gear drive in revearse can get you there. But, how much torque do you need? As you probably know, turbos consume some serious power before they return the favor. I read once that a stock chevy big block does not have enough power to drive the turbos on a top fuel dragster. :eek: Google electric super chargers and you will see where the currently available technology stands. When I researched it about a year ago, it was kinda ho-hum, only 2-5psi boost, but maybe that is all you need.
-dave

[eman2]

Which dimension do you mean by 'exit slot'? Can you show on one of your pictures?

Small automotive turbochargers do run around 100,000 rpm, but they also have a pressure ratio of about 3. That means they have a pressure rise of about 30 psi. If you only need a few psi you should be able to get that at much lower speed. The efficiency will also be lower.

If you can give me an idea of the dimenions of your impeller (hub and tip diameter of the blade at the inlet, and overall diameter of the impeller at the exit) I can give you a rough idea of how fast you have to turn to make whatever pressure rise you need.

[airmcn_3]

Which dimension do you mean by 'exit slot'? Can you show on one of your pictures?

Small automotive turbochargers do run around 100,000 rpm, but they also have a pressure ratio of about 3. That means they have a pressure rise of about 30 psi. If you only need a few psi you should be able to get that at much lower speed. The efficiency will also be lower.

If you can give me an idea of the dimenions of your impeller (hub and tip diameter of the blade at the inlet, and overall diameter of the impeller at the exit) I can give you a rough idea of how fast you have to turn to make whatever pressure rise you need.


Excellent info guys! I can not disclose too much info here but if you could send me your E-mail via PM I will get you all the info you need.

Thanks again for all the help! Keep up the good work.

Chris

[Joe 1320]

The problem might be with the starting point itself. Turbochargers are designed boost, but with an enormous amount of heat interaction. It's the burning exhaust gases that are really driving the hot side of the impeller. The fuel is burning as it passes thought the turbo! Wastegates are usually incorporated to bleed off the excess pressure so that things don't destruct from overboost. This design looks like effeciency might not be very good. It may be better with a single outlet that shares a common plenum where the exhaust is then split downstream of the compressor outlet.

[monkamarm2000]

2-4 at up to .18, wouldnt a simple gerator type setup do that? offset wheel rubbing along nylon tube like a blood pump? and if bl cant do 100k what about 50k with a 2 to 1 up box? bearing could do it since turbines can.

Barry

[airmcn_3]

2-4 at up to .18, wouldnt a simple gerator type setup do that? offset wheel rubbing along nylon tube like a blood pump? and if bl cant do 100k what about 50k with a 2 to 1 up box? bearing could do it since turbines can.

Barry

There may be some merit to that, I am easily getting 4psi now, I am just trying to find the most efficient way to get there.

Gear box does not sound too bad though i imagine it would have to be one stout piece of machinery.

Chris

[Tophinater]

Is this a mobile or stationary set up? If its stationary I would just drive the thing off of compressed air. You will not find a motor that can spin that fast as most fly apart around that range. Gear reduction wont get you up to 100k either, you cant mount a gear strait enough to take that kind of force and vibration without ridiculous wear. Most bearings wont even take that speed with out self destructing. I would just go with a fluid bearing and drive it with a air driven turbine mounted on the shaft, simple, practical, and it will work.

[pmackenzie]

Are you sure that is a compressor blade? It looks more like the turbine end to me.
The compressor usually has a smaller diameter leading in to it.
http://www.thesaabsite.com/turbophoto4.jpg
http://www.thesaabsite.com/turbophoto3.jpg

Pat MacKenzie

[Accu157]

Considering the pressure you're trying to attain, and the exit slot you're asking for, I'd say you just want to use a piston based air pump with a small reservoir to smooth the airflow. It would be easy to get that level of pressure out of that small of an area. I think the centrifugal compressor will not be able to handle that pressure without going to extreme lengths in power and extremely high levels of wasted energy. The piston is sure to be sealed. Even a small airbrush compressor could accomplish what you want. Maybe even a GWS brushed motor hooked up to a modified cox engine. BTW, 2-4 psi on that thin of a strip isn't much airflow. I've got a feeling I know exactly what you're doing. If not oh well, I'll act like I do and be general about it. :D Try to get uniform airflow across the whole 30" strip. You need a decent amount of airflow, and you might want more than one strip. A different commercial model airplane did this in the past, I don't think anyone who flew it noticed anything, then again it wasn't forced airflow.

BTW, your models kinda remind me of a Romulan D'deridex class starship. :D Maybe I could make a flying model of one.

[airmcn_3]

Considering the pressure you're trying to attain, and the exit slot you're asking for, I'd say you just want to use a piston based air pump with a small reservoir to smooth the airflow. It would be easy to get that level of pressure out of that small of an area. I think the centrifugal compressor will not be able to handle that pressure without going to extreme lengths in power and extremely high levels of wasted energy. The piston is sure to be sealed. Even a small airbrush compressor could accomplish what you want. Maybe even a GWS brushed motor hooked up to a modified cox engine. BTW, 2-4 psi on that thin of a strip isn't much airflow. I've got a feeling I know exactly what you're doing. If not oh well, I'll act like I do and be general about it. :D Try to get uniform airflow across the whole 30" strip. You need a decent amount of airflow, and you might want more than one strip. A different commercial model airplane did this in the past, I don't think anyone who flew it noticed anything, then again it wasn't forced airflow.

BTW, your models kinda remind me of a Romulan D'deridex class starship. :D Maybe I could make a flying model of one.


Thank you for all the great info and reading, I am going to try and figure out all of it now.

Only time will tell.

Thanks
Chris