Comparing Turbine Rotors
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- Опубліковано 26 кві 2022
- NOTE: There's an error in the graphs where i label 20.1W as the max power on a data point below 20W. This was because i accidently clipped the Y-axis at 20W, but the maximum power was in fact 20.1W
This is the second part of my video on building a 3d printed compressed air turbine, which you can find here:
• 3d Printed Compressed ...
In this video I'll be experimenting to find the best rotor and casing geometry for a 2D-flow turbine. I'm focusing on 2D flow because of the relative ease of machining parts, since I eventually plan to build one of these out of aluminum or brass to power with steam.
All the tests are conducted at 50 PSI with a 1/16" nozzle.
Another goal of this project is to see if it's feasible to use a 3d-printed turbine for Brayton cycle refrigeration (like the ACM on an airliner does). This requires extracting energy from the compressed air in the form of mechanical work to drop its temperature, so a more efficient turbine will have more cooling power (and provide more mechanical output to drive auxiliary devices like a secondary compressor).
Overall, my best configuration achieved a ~20% improvement over my last video, but there's a relatively large amount of scatter in my data, probably due to vibration and temperature dependance. Some further improvements I still haven't looked at are:
-Tighter tolerances between the turbine rotor and casing
-A convergent/divergent nozzle to convert more of the pressure energy to kinetic energy
-Better seals to prevent pressure leakage between stages (or to the outside).
Music Used:
Kevin MacLeod - Groove Groove
One of the things million dollar, multistage gas turbines have in common is that each stage has a different geometry. I think maybe when you put a lot of back pressure on one stage and reduced pressure on the next stage, you alter their power bands so severely that they're actually fighting each other through the whole range of flow. (i.e. one or the other isn't acting as a turbine at all, but a really bad impeller)
It might be interesting to artificially restrict the output flow on a single stage turbine to see how that affects the power curve.
I know you've moved on to the pulse tube cooler and that does seem more promising for LOX/LN2 production, but these turbines are interesting too.
Agree. Look at the old double and triple expansion steam engines. The piston diameter and ducting increases with each stage. So with this setup the second and subsequent turbines and ducting should all be larger by the 1.6 ratio.
The design seems to be struggling between being a pelton wheel (where the energy is transferred from the inflow by the change in momentum of the inflow water stream reversing as it hits the wheel) and an expansion engine.
The turbine stages are for expansion, and should be sized accordingly.
All the present 'cog' design does is carry pockets of air at constant pressure around the wheel. The intermediate pockets do no work at all. The only pressure differential in each stage is between the first pocket at the inlet and last pocket by the outlet - so 90 degrees or 180 degrees to the exit may not make any difference. The ostensible purpose of a longer rotation to the exit is simply to reduce the air losses around the cog's sides by increasing the area of surface friction in the gap between the cog and the casing. May as well try a Telsa turbine in that case. Good luck with that!
@@nigelwilliams7920 Well, and with a steam locomotive you have the advantages of it genuinely being a positive displacement pump and being relatively slow. Even if you didn't make the cylinders larger and the ducting wider, you probably at least wouldn't get something *worse* than the power and torque you would have with the first cylinder by itself.
With an expansion turbine (which this is kind of in halfway between land) you can have one turbine that wants to go at 10k rpm and another that wants to go at 8k, and because they're not positive displacement and you're doubling (like you said) ALL of the drag and fluid shear surface areas, the 8k turbine might actually being powered by the 10k turbing and you'll get 9k total (or whatever).
I need to watch his first video, but I think he might have wanted to go with something like a turbocharger turbine vane design with an axial inlet and radial outlet. I think this design does choke off the ability for expansion to do work. There were a few wheel designs we didn't see in this video that looked like simplifications of a pelton wheel. I'm assuming they did worse or he'd be using them. It would probably be hard to print an actual pelton wheel and not have it self-destruct at the rpms he wants though.
@@nigelwilliams7920 I went back and watched his other video. His first video was an impulse turbine (basically half a stage of what you'd find in an axial flow gas turbine).
It was ultimately less efficient than the 2d scoop things he used, but I think if he'd had a series of flow bending rotors and stators, the impulse turbine may have been much more applicable to multiple stages.
He also has what looks to be several meters of 1/4 inch copper tubing to act as a cooler for the compressed air. I know from working in a shop that small diameter air hoses (like the plastic springy coil ones) totally destroy airflow. I have to wonder how much of the 50psi he's actually getting at the nozzle. Its fine for airing up a tire, but an air drill or impact wrench would probably barely work with that copper pipe in the path.
(if you're reading these comments, just try breathing through it. You'll be surprised just how much resistance something like 10 feet of 1/4 inch pipe has)
@@htomerif Yes he would be better off using a turbo heat exchanger as the cooler as it has ample flow capacity, or at least several 1/4" pipes in parallel.
@@htomerif Indeed. Matching the design of each subsequent stage to the gas flow is a hard part of overall multi-stage expansion designs, otherwise you get back pressure/compressor stall etc. Frank Whittle no doubt went through this agony using the radial then axial compressor and the axial multi-stage turbine.
Its a fun intellectual exercise for the tinkerer, but as they say 'Space (and aeronautics generally) is Hard'!!
the fact that you use a song/songs that i've heard numerous times when building stuff in KSP makes your videos even better
One interesting thing to not is that all of these designs seems to be of impulse type. Meaning the pressure is being converted into velocity in the nozzle and the turbine simply redirect the already expanded gas. Not that its bad or anything. I just wanted to point that out since its a different beast than reaction turbines, where the gas continue to expand in the turbine. Keeping in mind this fact brings to light the fact that the nozzle where the air is accelerated is part of the design system if not as important as the turbine itself.
Also, I can't help but notice that all these new designs are just 2D profiles spinning around. Beware that these geometry causes your exit gas to still have a very high angular momentum a.k.a energy left on the table. Might I suggest experimenting with 2 additionnal parameters to try and make up for this :
1. Add an helix angle to a scoop design (like an helical gear) to straighten up the exit vector. It could be progressive, like first half staright then it helixes.
2. Or, reduce the radius of the turbine on the side where the gas is exiting. That way the spiraling down of the gas into a smaller radius naturrally imparts its momentum to the turbine wheel and the tangential component of the output vector gets minimized. This is literraly how a radial turbine works now that I think about it. Yeah, just do a radial tubine basically XD. They just work really great and aren't as finicky to tune perfectly as axial turbines.
Thank you for covering this project so thoroughly. It has reignited my interest in learning about turbine application for mechanical designing
Thanks for the update.
This one got me even more interested, since I also always looked for a way to make an air liquifier.
In Europe, it is even more impossible to find a sterling cooler for anything remotely close to a reasonable price.
I'm looking forward to what you come up with.
very cool!
I think at 8:36, the tube there being kinked means that no air can flow between stages, causing added resistance with no benefit, which may be the reason for the efficiency / power loss.
I didnt even see that. Good catch!
I was thinking of doing the same thing about turbines and their settings for a compressed air engine. And you show me your video with so much detail and incredible video editing.
You saved me a lot of money. Thanks.
Really cool project, your videos are so well made, offer great visuals and knowlage. Thank you!
That last part with the Brayton cycle sounds very interesting. I also looked into that cycle, but more to use it as a heat pump / heat engine alternative to a stirling cycle, to use as a bidirectional heat storage system.
Your Videos are amazing i was looking for this kind of content just engineering and optimating while explaining the whole thing very understandable but on such a high level
Looking forward to the next installment
Very nice experiments! Thanks for posting.
Great video! Thanks for sharing you research and test results.
Fascinating man. Keep up the work.
I would love to see you test out a Tesla Turbine in Part 3.
Glad to have found your channel. You do great work 😊❤️
When adding a second stage to your turbine, would it be more efficient to use less blades on the primary stage? Then it may allow more airflow into the second stage thus more power.
Maybe also slightly bigger diameter on the later stage?
@@xmysef4920 actually a smaller ènt stage
@@charadremur333 A smaller entry stage? Well that’s essentially just the same thing. Either you make the later bigger, or the one before smaller
@@xmysef4920 longer, so he can save some printer time and reuse the bigger rotor he printed earlier, while keeping nice design :)
Awesome Project!
I just found this channel, Thanks for edutaining me!
"0% efficient" xD
6:09 ohhhh, now I finally understand why those turbine stacks always look the way they do. I was wondering about that already, and now it clicked, thanks to the explaination and correlation.
THIS IS MY NEW FAVORITE UA-cam CHANNEL
Awesome build brotha!
Catia ,rc boats , cnc 3d print thang this channel have it all , just suscribed 💪👍
youre the kind of person i would focus on a party and sink into an hour long discussion about "why you cant shoot a potato above Mach 3" xD
Excellent video.
I'd like to see comparisons to ...
1: Results from smaller radii ...
2: A pelton turbine
.. using the same housing you've already got.
Nice video, thank you for sharing it with us :)
awesome vid rally enjoyed it!
I am pretty sure your air velocity would be slower in the second stage. So you probably need the second stage to either be on its own shaft or a smaller diameter to make up for the lower flow rate so it doesn't create drag on the first stage. And yes I know this is an older video now but I wouldn't mind seeing more turbine stuff.
I just watched both videos and liked the project.
As with engeneering background I would like to suggest improvements.
- balancing the rotors: do it like the RCcommunity does it: 2 cones on a horizontal steel axis on two horizontal rails.
- how about a pelton turbine? Maybe one-sided blades? You could add more conventional stages by making the outlet in a spiral way. More nozzles?
- reducing vibrations by using only prime numbers like they do in the industrial designs
- reduce friction by making spiral grooves on the sides of the rotor
Good luck!
I just learned one can get argon from fractional distillation of liquid air. That's super sick and now I can't wait for the cryo stuff.
Great content; love the way you go thru subsequent iterations; the CAD software you were using for the modeling of parts was FreeCAD?
"I guess real life is more complicated than theory."
You FINALLY learned something!!!
You're getting close to 10,000 subscribers! I've always liked how you do your projects so it's rather neat to see your audience grow to this point!
*They have over 80K subscribers*
@@phreeesubz Yep. Lots have joined in the last 8 months.
really good video, thanks a lot
I've never seen any of your videos before, and now I'm hooked. I love your tests and step by step isolation of different elements so you can increase efficiency with each factor. I have some thoughts for further testing if you are interested. I love how you tested 0° bend, 90° bend and 180° bend. Is there any way you could go just a tad further? what about a 200° or 240° bend? How many more watts do you get? What efficiency does that add?
So I've been wandering around the internet looking at air and water compressors and turbines and such and I'm really curious how well a scroll expander would work as a turbine. Do you thing there is a way you could test that?
Also, have you tried different angles of entry? Is there a reason you always enter and leave the turbine tangentially? The angle of entry may offer more or less efficiency base on the angle of the fins. So that's easily another test you could do.
I agree nozzle shapes could change your efficiency a lot as well.
I believe the largest issue with your 2 stage design is the complete redirect of flow. Throwing 2 90° bends abruptly like that would cause a ton of friction and slow down the air considerably. In the interest of science and no so much practicality, You may try creating 2 exactly the same turbines and instead of mounting them side by side like you did, just make the inlet of one, the outlet of the other. Then try capturing the watts of the 2 separate shafts to see if there is any true gain.
Loved the video. Keep up the fun work.
One major trick to compressor / gas pump efficiency is tolerances, like thousands kinda tolerances...
The tighter your tolerances, the lower the losses to leakage around the turbine (within the casing), downside being cooling coefficient, compressing gas creates heat which you have to dissipate to avoid lock up under general usage conditions
70-80% Efficient
0% Efficient
😂😂 Subscribed.
If you could polish internal side of blade notches, it could make air to escape with less resistance and thus increase the speed.
I think the issue with the wider rotor is the increase in mass. I would try out a slimmer rotor to see what happens. The power probably goes down a bit, but I expect the RPM to go up. This way you could use multiple stages with slimmer rotors to keep the RPM and boost the power.
My friend. I had a similar problem with a hydraulic motor that I wanted to build. On my design I found that when I placed the rotor in the center I had to deal with the negative force of the rotor. I do hope you would look at a much closer or almost sealing rotor-casing entrance and a expanding casing with a much larger exit. Hope this can solve your problem. Great presentation thanks.
What do you mean by "dwell time" ? Yeah, the high pressure air stays confined longer inside the turbine, but that does not add energy - it stays at the same exact size so it does not add any energy to the rotation. It will however (by chance) reduce some of the parasitic effects like when the air pushing backwards when exiting the turbine. With the later release more air will leak around and there will be a more consistent outstream of air.
Hello,
FDM prints are not air-tight and you are using with very high pressure. It might be causing the pressure on the blades to decrease very fastly since you must be losing pressure on the chasis walls. If you can buy a SLA printer you can rule out pressure leak problem and have a lot better accuracy on your prints.
I might not imagined this correctly but lets say you put screws on the both walls and sealed them with o-rings. it might help you gain the heat while you are decreasing pressure on the blades.
As far as I remember, the formula you are using is used for closed systems such as piston systems. However, you have kinetic energy at the outlet. I might be wrong wanted to remind it :).
I also wanted to experiment on the turbines but did not have enough courage to spin them that fast :).
Very nice videos, thank you.
Buen trabajo excelente explicación! Gracias
Quizás si puedes unir los escapes de las turbinas consigas más W?
Dude please keep up with this...
Hey nice work, have you tried a pelton wheel as a turbine. and probably have a look at the nozzle on the input size how the air is put into the case the angel and nozzle type seems to have a factor here. more seen in other videos than own experience but could help
I think part of your problem with the multi-stage setup is that your turbine blades are designed such that the high-pressure air is just instantly captured and halted relative to the turbine, as opposed to being deflected and expanded via an airfoil like a gas turbine normally uses. I think you should try designing some "normal" looking turbines in a snail housing just like car turbos use. That's more in line with how the turbopumps in i.e. rocket engines work anyways, or they use annular combustion chambers pointed through a jet-engine-looking turbine. The annular design might be easy enough to 3d print.
love the vid, and I envy your CAD skill... 1st stage 20mm second stage 40mm?
I am currently working on something similar and for me, eddy current brakes as torque-givers work great. Would you mind elaborating on what you mean by "Vibration issues"? Also maybe try printing your turbine casings with more walls, less infill. I print with 8 walls and leakage (which was a big problem) virtually disappeared altogether.
This whole video, I was thinking hmm, being able to create a mostly 3d printed turbine could be used for air liquification! As I'd previously also delved down this path previously, ended up attempting a Hampson linde instead similar to Tesla500 on UA-cam, he has since created the chronos high speed camera and air liquification is probably the last thing on his mind these days hah. I see you ended up going with the pulse generator later down the track which seems to be going much better!
Keep in mind the in and out air pressure needs to be outside of the chamber so here coming in to power it's already contained the exit air needs to exit the chamber of vacuum
I'm very interested have you considered different material for the flaps in the air drill motor like maybe 3d printered ones pla/abs?
How do you think having the rotors on independent shafts would affect the output?
fences and thicker rotor means more drag and increases moment of inertia, cupping the scoops like pelton wheels do wil increase power yield
I personally preferred your scooped notched design . However , I would have integrated a streamlining feature by adding a "dorsal fin" or tail on the back of each notch as an air foil In a shape much like a cross section of a freighter ship with the keel representing the dorsal fin. My logic suggests to me that it will help by causing the air to comply or conform , if you will , much faster as it tends to want to fill in the voids as it moves attempting pressure equilibrium. I also think it will help in reducing rotational resistance substantially.
I think the problem with second stage was that you left the same mass as with double size. I think you should need to cut the thickness of double stage turbines by half
First and second stage nozzles have to be perfectly matched to ensure proper pressure drop in each stage. That is critical since they are on the same shaft. And first stage has to be sealed. More interesting would be to test one stage only with air outlet in the centre of rotation. And another interesting test is Pelton turbine. The first wheel design most likely needs higher reaction for better performance but more importantly blades should be oriented in a different plane so exit would be oriented towards the centre of rotation of the wheel to take advantages of better flow kinetic energy conversion. The idea is to take high speed flow and convert it to as low speed flow as possible. Only the first design attempted to do that.
Have you looked in to a Spiral jet turbine with 12 blades In a Vortex like design That would allow it to get faster as it went down the vortex quite like a Whirl pool or black hole Or tornado
There is a geometry called a Pelton wheel where the shape of each blade imparts a 180 degree turn on the impinging stream and should double the energy transferred.
Look at the previous video in the series, he did that and it was much less efficient
Put a cap across the pickup coil to smooth your waveform
I don't think the different stages should be the same size. You loose pressure in the following stages so you probably need a smaller wheel in the next stage to keep the angular speed the same. Otherwise I just think each extra stage will act as a break for the first stage.
or maybe it's larger wheel. My brain can't decide right now but I still think the break logic is valid.
@@dbtest117 larger - and you need stators between each section to straighten the airflow if you're using axial turbines
For centrifugual turbines, you need an inlet volute of some sort (this is what the delaval nozzle is about)
There's a lot to be said for running separate shafts for the lower pressure stages, else they spin so fast they can disintegrate, whilst the high pressure stages aren't spinning fast enough to be efficient
Very interesting.
my heart sank when i saw the kink in the hose
what if you added a vacuum stage to the second rotor to help pull the air through ? and maybe some check valves the would open when the vacuum is below 15 psi.
what if you printed a cross tube that connects the two rotors together, the hose looked like it was being choked.
Thx 🙂
At 4:52, couldn't the housing be almost 360 degree spin for the air (in practice a bit less of coursE), if the inlet and outlet are angled correctly and are positioned very close to each other?
if you want to talk about some ideas and methods to optimize the design send me a message.
i work with compressors and turbines.
“In theory, there’s no difference between theory and practice but in practice, there is.”
I just started the video but I am pretty sure that I've learned that large turbines are more efficient with less fins and as you get smaller more things are more efficient. It has to do with mass of each fin and I believe production costs. That's why large windmills only have three fins and Automotive turbos have lots
Enjoyed the statistical comparisons. Wondering how a tesla would compare .
In recent gas turbine engine such as cfm56 it has 2 stage hp turbine and 4 lp turbine
And more than one nozzle with working chosen tested design parameters in effect? Then add multi-nozzle stages?
What if you took the 180 degree and loop it back into the system at an angle that is less direct than it's primary power source?
A feedback loop. I assume it kills some lagg, but not give more power necessarily.
However, you're using exhaust pressurised air back into the system, so efficiency goes up in theory. However, it shouldn't be interfering with the primary power input as that could abuse some flow and makes it less efficient, so there's some play.
Fun video.
How did the input area & output area compare between the 20mm & 40mm wide turbines?
Have you considered using the "disk format" of a Tesla rotary pump in place of bladed rotors. I believe the Tesla pump is up to 97% efficient. I don't know if scale causes variations in efficiency, but I know it is pretty high anyway. I wish I had a 3D printer, it's a great asset. Nice job.
That was my instant thought, Tesla turbine.
Does the mass of the turbine effect the power?
Consider a bladed turbine like those used industry with inlet along the axis of the shaft and stators between stages instead of perpendicular to the shaft
Another design is possible, but requires a hard polished inner housing and compresses wheel with hard steel polished blades that fling out by the centrifugal forces, like in the Wankel engine roters.
Can't remember where i saw it but that's how they do in industrial things.
check the scoop with the final box
hey is there any place where we can buy all the materials?
Try making the air inlet as a convergent nozzle
god damn you do some dope shit.
how did you even learn about this whole turbine thing? I get thinking turbines are cool and wanting to make them, but the maths? how do you come across that?
also you never really mentioned friction, which I think may be causing you issues. and I would bet is why the big one and the one with the sides didn't work so well. even just not having them balanced might be putting a lot of extra force on the bearings, which at that speed might create some considerable friction. greased bearings will be problematic too at those high rpms.
can't wait for the cryogenic stuff. I have never really been super curious about it because I've never had any use, but now I am. and by the time you're done I'll probably be wanting to do it too.
last thing, you seem to know what you're doing with building CNCs, why not make yours a little more chunky and add an extra axis? seems like it would certainly make this whole endeavor much easier.
thank you
Hi, what about an air exit as close as possible to the injection nozzle ? Logically, you should gain a bit of power.
Can you install separate pressure sensors to monitor the pressure behind each vane as the turbine spins?
My idea is the pressure difference between the vane high side & vane low side is the same as torque output.
Wider vane = more torque
larger diameter vane = more torque
More vanes doesn't mean more torque.
I'm guessing that your ports were too small, so the (larger/double capacity) vane cavities were not filling and/or exhausting sufficiently. Monitoring the pressures inside the vane cavities will tell you which is the problem.
IE: several psi remain after the exhaust port = exhaust flow is restricted /&/ several psi short of supply after the intake port = inlet flow is restricted
what about water turbines? there is only 1 stage but they still are very efficient, is that because of that extracting energy from liquid is easyier?
3:55 Why add more thicknes instead of make blade moredeep. What i mean is the R5 go more close to the center, more deep so you have more surface at same thiknes.
@Hyperspace Pirate i have a question maybe unrelated to what you are trying to do but would it be possible to build a air motor where you imput the air through the middle of the shaft and then have a it enter into a thin cylinder with a spiral channel/flute going from the middle and out to the edge making something like 2 complete turns around the axle before exiting the centrifugal force would help speed up the air flow and pull more air, in a sense the engine would help power it self. But maybe im am wrong and it is the opposite it well help pull air through faster and easier so the same amout of air produce less rotational energy of course it could be a matter os getting it right maybe the channel should be wider at the centere and get thinner further out or having crazy many rotations around the axle before it exits or having dual channels.
I dont know alot about these things just something that popped up in my head when watching this and i would like to hear what you think about it? would make for an intresting project
And please correct me if this just a stupid idea that wont work
I think that's how a centrifugal turbine works. Like the impeller on a turbocharger in reverse
@@HyperspacePirate can you please make more advancements for you turbine rotors please
what does the spray on the glue do?
What you are making is an impulse turbin that is not very efficent with stages.
So per stage you will be able to get a 1/3 of the power
I think a lot of people have already done all these types of experiments with water turbines.
Hi Hyperspace Pirate, can I find these pieces in STL or STEP somewhere?
The reason your fenced designs and the 40 mm thick blade had a drop in peak torque is bc the added mass increases the moment of inertia, which will decrease the angular acceleration
you don't have to drill the laval nozzle but instead you can 3d print it flat, like your rotors.
concerning your Mach number calculations: isn't the p2/p1 relation you use only valid for quasi-1D flows performing no shaft work? my understanding is that turboexpanders often operate at p2/p1 of 4 or above
I think your issue is RPM matching. Imagine your first stage wants to spin at 5000rpm at the given pressure and the second stage 4000. Because their shafts are linked the first turbine is going to be bogged down by the slower revolution rate and the second stage acting like a pump at higher rpm and wasting precious work. Similar concept in reverse. I think if you tried to get them within a few hundred rpm you could massively improve dual stage performance
Check out “Turbo Billet Compressor Wheels”
Do you have a link for that radiator?
get an SLA for the nozel
Part 3!
👍
Hello, why don't you use the pelton turbine design?
Why not try a tesla turbine? You could cnc the discs out of sheet aluminium to get them crazy thin.
So can i do this on my cars turbo diesel?