Sciencemadness Discussion Board

Direct Gas Fired Tesla Turbine

3DTOPO - 3-12-2016 at 20:29

I understand that if Tesla had modern material science, we would all be driving Tesla's today. But since the internal combustion engine was in-vogue, people frowned on the steam requirement (not to mention the phase conversion inefficiencies ). He tried direct fired turbines, but steel just couldn't live up to the direct exhaust spinning at 30,000+ RPMs. :D

I have yet to find a direct-fired tesla turbine, and would very much like to build one. I am thinking single-crystal Inconel would be a good fit - but I can't find anyone selling sheets of it (in single-crystal form). Any ideas if single-crystal would even be required with say a propane flame for the working fluid? What type of Iconel would be best? Or, any other super-alloy suggestions?

Any idea how they coat super alloys with ceramics for added protection? Perhaps SiC or alumina?

I thought of using SiC or Alumina cutting wheels for the turbine blades - they do live up to the insane forces of cutting though steel after all. But I fear the phenol resin just wouldn't live up to the continuous hot exhaust.

RogueRose - 4-12-2016 at 17:39

The cutting wheel idea is interesting especially with some of the thinner ones I would think may be ideal for this or it may need more mass for heat dissipation.

I've wondered about using Tesla turbines on the exhaust side as it could greatly reduce the cost of manufacture from what I have seen. I'm not sure if greater compression can be reached on the intake side with a Tesla turbine or if it can, whether it would be more or less efficient. I looked into turbine efficiency as steam being the working medium and it looked like current turbine technology is pretty tough to beat but when scaled to turbo size and with exhaust as the driving force, that may change a lot of factors.

I've had a few thoughts on automobile turbos and using various "fuels" as to create additional boost during the spool-up period where turbo lag is a major issue.

I've considered compressed air, CO2, N2 and water (steam) could be injected into the exhaust stage of the turbo after being run through a pre-heating cycle - such as tubing running inside the length of the exhaust and possibly into the exhaust headers, exiting headers (or down-pipe) and ported into the exhaust side of the turbo. All of the "fuels" would expand greatly with the high temps. The turbo could even be cooled with these "fuels" as a pre-heat before entering the exhaust to heat - or through/around the turbo for final stage heating (although the headers/downpipe/cat would probably be hotter than turbo).

If water was used for steam, the mass of the fluid would provide more torque from a much smaller turbo

With water at high temps, I've read that it can split to H2 and O2 at 800-1,200C (Water splitting via solar thermal plant) which the exhaust may reach this temp - thus igniting the split water.. IDK if that would be good with a normal turbo setup but could possibly be utilized for injecting into the combustion chamber.

[Edited on 5-12-2016 by RogueRose]

3DTOPO - 4-12-2016 at 17:47

Quote: Originally posted by RogueRose  
The cutting wheel idea is interesting especially with some of the thinner ones I would think may be ideal for this or it may need more mass for heat dissipation.


I just wonder if the phenol resin would make the idea useless.
Quote: Originally posted by RogueRose  
I'm not sure if greater compression can be reached on the intake side with a Tesla turbine


My understanding is that tesla turbines are poor at generating compression. If I were to have a direct fired tesla turbine, my thought is to use a turbo compressor to feed the firebox but then send the working exhaust to a tesla instead of a conventional turbine.

RogueRose - 4-12-2016 at 21:33

Quote: Originally posted by 3DTOPO  
Quote: Originally posted by RogueRose  
The cutting wheel idea is interesting especially with some of the thinner ones I would think may be ideal for this or it may need more mass for heat dissipation.


I just wonder if the phenol resin would make the idea useless.
Quote: Originally posted by RogueRose  
I'm not sure if greater compression can be reached on the intake side with a Tesla turbine


My understanding is that tesla turbines are poor at generating compression. If I were to have a direct fired tesla turbine, my thought is to use a turbo compressor to feed the firebox but then send the working exhaust to a tesla instead of a conventional turbine.


I would suspect the "glue" on those discs won't hold up to the temps. If you use them enough, you'll find that when used for cutting for extended periods they heat the edge and can start wearing down incredibly quick (like right before your eyes in seconds). It's like they hit a critical point and start to disintegrate with the heat, speed and pressure.

When you mention firebox, are you talking about some kind of furnace or boiler or is this for motive means.


I would like to find a way to drive a compressor with exhaust and or heat from a furnace/boiler/stove. The compressed air could be for a venturi aspirator for fuel/oil injection possibly along with additional forced air for combustion in the burn box. Do you think a tesla turbine could be used for this application?

3DTOPO - 4-12-2016 at 22:23

Quote: Originally posted by RogueRose  

I would suspect the "glue" on those discs won't hold up to the temps. If you use them enough, you'll find that when used for cutting for extended periods they heat the edge and can start wearing down incredibly quick (like right before your eyes in seconds). It's like they hit a critical point and start to disintegrate with the heat, speed and pressure.


Yeah, I kind of suspect the same thing, thus my question about super-alloys.
Quote: Originally posted by RogueRose  

When you mention firebox, are you talking about some kind of furnace or boiler or is this for motive means.


I would like to build a direct-fired tesla - that means no boiler. I would feed the fire exhaust as input to the tesla turbine.
Quote: Originally posted by RogueRose  

I would like to find a way to drive a compressor with exhaust and or heat from a furnace/boiler/stove. The compressed air could be for a venturi aspirator for fuel/oil injection possibly along with additional forced air for combustion in the burn box. Do you think a tesla turbine could be used for this application?


Its pretty straight forward to build a tesla that uses steam for the working fluid (search for Steam Tesla Turbine on youtube to see some examples). You could just use stainless steel for the blades and aluminum for the case.

As I mentioned, the Tesla turbine doesn’t generate any appreciable compression. So you would have essentially two choices:

1. run a compressor through a mechanical linkage using a drive shaft connected to the tesla. You might need to gear it down as the Tesla works most effectively at quite high fixed RPMs.

2. have the tesla spin an alternator and power the compressor with electricity produced from the tesla turbine.

My understanding is that you can get about 40% efficiency from your working fluid with a single stage, and about 70% efficiency with multiple stages. The stage for the input stream would be designed for highest pressure working fluid (eg small discs tightly spaced) and the last stage would have larger discs more loosely spaced. So just for conversation purposes, if you had 10 horsepower of steam, you could hope to get 4 useable horsepower out with a single stage and 7 horse with 3 stages.

RogueRose - 5-12-2016 at 06:12

Quote: Originally posted by 3DTOPO  
Quote: Originally posted by RogueRose  

I would suspect the "glue" on those discs won't hold up to the temps. If you use them enough, you'll find that when used for cutting for extended periods they heat the edge and can start wearing down incredibly quick (like right before your eyes in seconds). It's like they hit a critical point and start to disintegrate with the heat, speed and pressure.


Yeah, I kind of suspect the same thing, thus my question about super-alloys.
Quote: Originally posted by RogueRose  

When you mention firebox, are you talking about some kind of furnace or boiler or is this for motive means.


I would like to build a direct-fired tesla - that means no boiler. I would feed the fire exhaust as input to the tesla turbine.
Quote: Originally posted by RogueRose  

I would like to find a way to drive a compressor with exhaust and or heat from a furnace/boiler/stove. The compressed air could be for a venturi aspirator for fuel/oil injection possibly along with additional forced air for combustion in the burn box. Do you think a tesla turbine could be used for this application?


Its pretty straight forward to build a tesla that uses steam for the working fluid (search for Steam Tesla Turbine on youtube to see some examples). You could just use stainless steel for the blades and aluminum for the case.

As I mentioned, the Tesla turbine doesn’t generate any appreciable compression. So you would have essentially two choices:

1. run a compressor through a mechanical linkage using a drive shaft connected to the tesla. You might need to gear it down as the Tesla works most effectively at quite high fixed RPMs.

2. have the tesla spin an alternator and power the compressor with electricity produced from the tesla turbine.

My understanding is that you can get about 40% efficiency from your working fluid with a single stage, and about 70% efficiency with multiple stages. The stage for the input stream would be designed for highest pressure working fluid (eg small discs tightly spaced) and the last stage would have larger discs more loosely spaced. So just for conversation purposes, if you had 10 horsepower of steam, you could hope to get 4 useable horsepower out with a single stage and 7 horse with 3 stages.


Running the turbine from the exhaust is what I thought you meant. When I said furnace or boiler, I wasn't meaning using steam as the working fluid, I simply meant a stationary "burn box" not like the exhaust from a internal combustion engine. I've actually heard them called "fireboxes" before... (though very rarely).

So you want to combust something in say "a stove" (wood, coal, whatever), or an oil burner, or fuel oil/kerosene burner/furnace - then use the exhaust to run the turbine? Is that correct? If that is the case I'm thinking that it might be kind of difficult to do so as I would guess it would require forced air aspiration for the combustion chamber and then although the gases will expand a turbine is going to severely restrict exhaust flow to the point of working directly against the inflow of air for combustion. Something like this works much better in an IC b/c it has valves that block back-flow and a totally separated air intake that doesn't compete against the outflow of the exhaust.

3DTOPO - 5-12-2016 at 14:48

Quote: Originally posted by RogueRose  

Running the turbine from the exhaust is what I thought you meant. When I said furnace or boiler, I wasn't meaning using steam as the working fluid, I simply meant a stationary "burn box" not like the exhaust from a internal combustion engine. I've actually heard them called "fireboxes" before... (though very rarely).


I guess your term “boiler” threw me off. ;)
Quote: Originally posted by RogueRose  

So you want to combust something in say "a stove" (wood, coal, whatever), or an oil burner, or fuel oil/kerosene burner/furnace - then use the exhaust to run the turbine? Is that correct?


Correct.
Quote: Originally posted by RogueRose  

If that is the case I'm thinking that it might be kind of difficult to do so as I would guess it would require forced air aspiration for the combustion chamber


Correct, like I said, I envision a regular turbo-charger forcing the air into the combustion chamber.
Quote: Originally posted by RogueRose  

and then although the gases will expand a turbine is going to severely restrict exhaust flow to the point of working directly against the inflow of air for combustion. Something like this works much better in an IC b/c it has valves that block back-flow and a totally separated air intake that doesn't compete against the outflow of the exhaust.


Well I know it works because even Tesla made them direct fired, but they just did not last very long because mild steel quickly oxidized and warped.

I have also made a oil-fired burner before, and I use a squirrel fan to force air into a combustion chamber, and the exhaust jet shot out 5+ feet long. Never had the problem of having a back flash. The exhaust will want to leave the path of least resistance, and if air is being forced in, that leaves the path through the turbine as the path of least resistance. I suppose it is just a matter of properly sizing things (the exhaust holes/vent/disc spacing etc.).

I suppose the same thing happens to internal combustion engines - the expansion is adequate to raise the piston so that it may be exhausted. The difference with a tesla is it is a continuous process.

3DTOPO - 5-12-2016 at 16:01

I neglected to mention that Tesla invented a valve, called appropriately the Tesla Valve. It has a flow ratio of 15:1 - up to 200:1 that I suspect was invented for this very purpose.

If the compressed intake was ran through a Tesla Valve, I think it would solve the back pressure issue:

https://en.wikipedia.org/wiki/Tesla_valve

officescape - 30-4-2018 at 00:13

Quote: Originally posted by 3DTOPO  
I neglected to mention that Tesla invented a valve, called appropriately the Tesla Valve. It has a flow ratio of 15:1 - up to 200:1 that I suspect was invented for this very purpose.

If the compressed intake was ran through a Tesla Valve, I think it would solve the back pressure issue:

https://en.wikipedia.org/wiki/Tesla_valve


Tesla also designed a very specific nozzle for the injection of steam between the disks of the turbine which drastically increased fluid velocity. Its amazing he made all these fluid dynamic inventions before computer modeling or rapid prototyping, or even solid materials science.