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 Post subject: Re: Low cost turbine....
PostPosted: 29 Dec 2019, 12:37 
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Think of the energy you recover from the exhaust (waste) heat as fuel that you won't have to burn in order to make the already compressed air, when it goes into the turbine section, as hot as you need it to get to make the desired horsepower.

That's not a thermodynamically precise way to explain it but it's close enough.


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 Post subject: Re: Low cost turbine....
PostPosted: 29 Dec 2019, 16:14 
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This device, according to that description heats the air prior to combustion... which means you are basically making this engine “more efficient” by reducing the horsepower... by using hot air... I can’t think of a good reason I would want that in a GA aircraft.



No, you don't understand thermodynamics. (not trying to be demeaning, but that's the truth).

It makes the engine stronger, believe it or not, and greatly improves its efficiency at the same time.


You want the inlet air to the compressor section as cold and dense as possible, so the compressor is as effective as possible and gets the most mass of air into the engine.

However, once the air exits the compressor, you want to make it as hot as possible, up to the point that the turbine section can withstand.

The recuperator takes waste heat from the exhaust and uses that to increase the heat of the compressed air, ahead of the combustor and the turbine section.

The combustor then adds heat by burning fuel.

All that hot gas goes through the turbine section, turns the turbine wheel(s) which convert that heat into kinetic energy.

Gas turbine engines are thermally limited by the turbine in the amount of power that they can make. Literally, when the turbine inlet temperature reaches the limit where the turbine section can be damaged, is the horsepower limit.

But a lot of heat exits the turbine section as hot exhaust gas, which is nothing but wasted energy. If it were completely efficient, then the exhaust temperature would be the same as the ambient temperature.

So every bit of heat ahead of the turbine is valuable to creating kinetic energy. If we can recover some of the exhaust heat, that's fuel that doesn't need to be burned.

The gas turbine is different than a reciprocating engine, as it is a continuous flow, and there's a physical opportunity to insert a heat increase after the compression cycle.

In a reciprocating engine, even a turbocharged one, the compression cycle happens within the cylinder and there's no convenient way to increase the heat of the compressed air or air-fuel mixture within.

We use intercoolers on turbo-charged piston engines because the turbo discharges ahead of the compression cycle in the cylinder. You want that air dense and cool. Also, there's a danger of detonation in gasoline engines, which increases as the heat in the cylinder increases. That's why there's a limit to compression.

Turbines of course, don't have a detonation problem. There's only the thermal limit of the turbine to worry about.


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 Post subject: Re: Low cost turbine....
PostPosted: 30 Dec 2019, 22:23 
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Username Protected wrote:
This device, according to that description heats the air prior to combustion... which means you are basically making this engine “more efficient” by reducing the horsepower... by using hot air... I can’t think of a good reason I would want that in a GA aircraft.



No, you don't understand thermodynamics. (not trying to be demeaning, but that's the truth).

It makes the engine stronger, believe it or not, and greatly improves its efficiency at the same time.


You want the inlet air to the compressor section as cold and dense as possible, so the compressor is as effective as possible and gets the most mass of air into the engine.

However, once the air exits the compressor, you want to make it as hot as possible, up to the point that the turbine section can withstand.

The recuperator takes waste heat from the exhaust and uses that to increase the heat of the compressed air, ahead of the combustor and the turbine section.

The combustor then adds heat by burning fuel.

All that hot gas goes through the turbine section, turns the turbine wheel(s) which convert that heat into kinetic energy.

Gas turbine engines are thermally limited by the turbine in the amount of power that they can make. Literally, when the turbine inlet temperature reaches the limit where the turbine section can be damaged, is the horsepower limit.

But a lot of heat exits the turbine section as hot exhaust gas, which is nothing but wasted energy. If it were completely efficient, then the exhaust temperature would be the same as the ambient temperature.

So every bit of heat ahead of the turbine is valuable to creating kinetic energy. If we can recover some of the exhaust heat, that's fuel that doesn't need to be burned.

The gas turbine is different than a reciprocating engine, as it is a continuous flow, and there's a physical opportunity to insert a heat increase after the compression cycle.

In a reciprocating engine, even a turbocharged one, the compression cycle happens within the cylinder and there's no convenient way to increase the heat of the compressed air or air-fuel mixture within.

We use intercoolers on turbo-charged piston engines because the turbo discharges ahead of the compression cycle in the cylinder. You want that air dense and cool. Also, there's a danger of detonation in gasoline engines, which increases as the heat in the cylinder increases. That's why there's a limit to compression.

Turbines of course, don't have a detonation problem. There's only the thermal limit of the turbine to worry about.


A Rolls m250-b17f2 engine is rated to 92 psi/ 752 degrees Celsius continuous at 380hp at sea level..burning 23gph at 18-21k’... how would a recouperation system effect those numbers?

D

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 Post subject: Re: Low cost turbine....
PostPosted: 30 Dec 2019, 23:26 
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I had a book on industrial and automotive turbines from the 60s, and I recall that the greatest gains are at partial power but it helped across the board.

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 Post subject: Re: Low cost turbine....
PostPosted: 31 Dec 2019, 04:37 
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Username Protected wrote:

A Rolls m250-b17f2 engine is rated to 92 psi/ 752 degrees Celsius continuous at 380hp at sea level..burning 23gph at 18-21k’... how would a recouperation system effect those numbers?

D


I don't have full data on the 250-B17F/2. I'd love to see it.

The engine is flat-rated to 450hp. It's kind of complicated getting your head around the concept. Pretty much, you get a smaller maximum output, which is good to a certain altitude, above which the engine can't produce that much power anymore.

Rolls only claims a 0.613 bsfc in their marketing, so 380hp would show a fuel flow of 233 pph or 35 gph. The bsfc probably not as good at high altitude, as the M250 is not real good at altitude. If you dial in the numbers, 23gph is 154pph, and using an optimistic bsfc of 0.67, you arrive at 230hp. ( I think that's optimistic, I'd wager closer to only 200-210hp for that fuel/altitude)

A recuperator might lower the bsfc into the 0.50-ish range or perhaps lower. The same cruise performance of 230hp at 20k, would be a lot closer to piston numbers, 17-18gph, instead of 23gph. That's pretty darn good.

The downside is the added weight, complexity, and of course, cost.

Just for comparison, my TSIO550C produces 310hp at 215pph takeoff power (36 gph), and 230hp, 90pph or 15.3 gph (best economy mixture) (all data directly from Continental's published data).


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 Post subject: Re: Low cost turbine....
PostPosted: 31 Dec 2019, 12:10 
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Username Protected wrote:

A Rolls m250-b17f2 engine is rated to 92 psi/ 752 degrees Celsius continuous at 380hp at sea level..burning 23gph at 18-21k’... how would a recouperation system effect those numbers?

D


I don't have full data on the 250-B17F/2. I'd love to see it.

The engine is flat-rated to 450hp. It's kind of complicated getting your head around the concept. Pretty much, you get a smaller maximum output, which is good to a certain altitude, above which the engine can't produce that much power anymore.

Rolls only claims a 0.613 bsfc in their marketing, so 380hp would show a fuel flow of 233 pph or 35 gph. The bsfc probably not as good at high altitude, as the M250 is not real good at altitude. If you dial in the numbers, 23gph is 154pph, and using an optimistic bsfc of 0.67, you arrive at 230hp. ( I think that's optimistic, I'd wager closer to only 200-210hp for that fuel/altitude)

A recuperator might lower the bsfc into the 0.50-ish range or perhaps lower. The same cruise performance of 230hp at 20k, would be a lot closer to piston numbers, 17-18gph, instead of 23gph. That's pretty darn good.

The downside is the added weight, complexity, and of course, cost.

Just for comparison, my TSIO550C produces 310hp at 215pph takeoff power (36 gph), and 230hp, 90pph or 15.3 gph (best economy mixture) (all data directly from Continental's published data).


Does the power remain the same and only gph is improved? Or is there a cost in the power dept?

And how much weight are we talking about?

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 Post subject: Re: Low cost turbine....
PostPosted: 31 Dec 2019, 15:13 
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Username Protected wrote:

Does the power remain the same and only gph is improved? Or is there a cost in the power dept?

And how much weight are we talking about?



The power output would stay the same and the amount of fuel burned to get that power is significantly reduced.

I don't know how much the recuperator (aka regenerator) weighs or costs. No published data. It's a significantly-sized heat exchanger.

Rolls-Royce (nee' Allison) tried it on the M250 series, third parties have tried it on the M250, but so far, I haven't seen any for sale.

There's the French company making their own ~120hp small turbine with a recuperator, but again, not yet for sale and no data.

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 Post subject: Re: Low cost turbine....
PostPosted: 01 Jan 2020, 02:23 
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Ok, well, I look forward to reality when it exists...


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 Post subject: Re: Low cost turbine....
PostPosted: 13 Feb 2020, 20:30 
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dunno if posted
https://www.turb.aero/

https://www.homebuiltairplanes.com/foru ... nes.27527/

something else
http://www.bd5.com/CouguarSurgery.htm

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 Post subject: Re: Low cost turbine....
PostPosted: 14 Feb 2020, 03:46 
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The Australian "Turb Aero" is a straight gas turbine, sans recuperation, so the BSFC is like all other non-recuperated TPs, about double that of pistons.

Also, the discussion was from 2017 - does'nt seem like any progress since...

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 Post subject: Re: Low cost turbine....
PostPosted: 14 Feb 2020, 04:10 
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... Meanwhile, TurboTech ( https://www.turbotech-aero.com/solution ... ogenerator ) is running the TP-R90 on the test stand just about everyday !

I expect to see one flying this Spring, possibly for Friedrichshafen 2020 .

Here's a quik vid of the TP running in it's test cell :

[youtube]https://youtu.be/c91YNU12QXU[/youtube]

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 Post subject: Re: Low cost turbine....
PostPosted: 14 Feb 2020, 04:27 
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Weird, video not available.


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 Post subject: Re: Low cost turbine....
PostPosted: 18 Feb 2020, 19:53 
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I can see the video, although there's not a direct view of it.

We need something the equivalent HP for the Duke in a footprint that doesn't cost $1 Million to retrofit, or essentially $400k per engine new.

Not sure what the pricing on this is planned to be but at least they're running it.


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 Post subject: Re: Low cost turbine....
PostPosted: 22 Feb 2020, 18:03 
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- General Jet and Turbine Discussion

https://jetandturbineowners.proboards.c ... discussion

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 Post subject: Re: Low cost turbine....
PostPosted: 23 Feb 2020, 08:15 
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Username Protected wrote:
I can see the video, although there's not a direct view of it.

We need something the equivalent HP for the Duke in a footprint that doesn't cost $1 Million to retrofit, or essentially $400k per engine new.

Not sure what the pricing on this is planned to be but at least they're running it.


The guys asked me not to film, hence why you can't really see the unit.

The turboprop TP-R90 which produces 90kW ( 120 hp ) is priced @ less than $50K , in-line with the Rotax 914 110 Hp turbo'd piston.

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