Get that up to Duke power at that price and you'd have some serious competition for Walter.

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.

I know about the physics behind them, and their implementation from an engineering standpoint, maybe even some of the math if I can remember, though engineering school was a few decades ago.

Recuperators or regenerators are essentially unheard of in aero turbine applications, no doubt due to the weight, size and complexity added. But they are used in other stationary gas turbine applications and even the Chrysler turbine cars of the 1960's had them.

This is a schematic that Chrysler provided in the 1960's:



And here's a cut-away drawing of the actual turbine engine:




This is the thermodynamic diagram:

Doesn’t that rob you of power since there is less air mass going into the combustion section?

Yes, but the gains are great than the losses. You are recovering and using energy that would otherwise be lost.

No the air mass is the same. Same mass of air, just hotter.

Heat doesn’t reduce the mass.

Recuperators have been used on ground based turbines for decades. The problem for aircraft engines is getting the heat exchanger small enough and light enough to not cause a negative impact to aircraft performance. Additive manufacturing has enabled some gains to be made in those areas. Recuperated engines typically provide the largest gains with low pressure ratio engines, modern engines use high pressure ratios and high turbine temperatures to achieve thermodynamic efficiencies greater than can be accomplished with recuperated engines.

Pretty much sums it up, excepting the additive manufacturing, of which I've seen none.

So why am I betting on this French start-up ?

Because the real driver behind this initiative is an Industrial that has developed the technology for a very efficient, light and cost effective heat exchanger - Le Guellec is their name.

Oh, and besides having this important partner, there's Airbus and $3.5M on the table.

they just posted a video of the engine running in a test cell no real data but it appears to be running

cool

https://youtu.be/kmWJB-gTP5A

the real question is can they run it for 100 hours or so continuous at specified power and it is still in good shape

Is this for proof of concept ? For a fleet of cessna 150s?

What do you do with a 122hp engine?

Wouldn’t see any reason why not. Lubrication and cooling being the only two factors and those aren’t exactly new technologies to add to this.

The bigger question is can they do it at much higher power outputs, say the 200+ HP range where we start being able to apply it to anything other than the sport category? 120HP isn’t where we need it to be but the idea is very interesting.

I hope they can do it. We need some innovation. The idea of using an electric generator as a captured energy source that adds more than it takes away is pretty intriguing.

There's data:

I compute 0.577 lbs/hp/hr from the figures on the screen, which is about as good as a PT6 gets but it is a much higher power engine (TPE331 is under 0.500). That's quite an achievement in this size class.

It is producing 97 HP at 8.4 GPH. This may be SHP (shaft horsepower) and not EHP (effective horsepower) which adds the effect of the jet exhaust thrust, which would raise the power somewhat (7.5% for a TPE331, less for a PT6). I presumed it was Jet-A fuel.

A 300 hp class engine would find a lot more utility, IMO, but it is still impressive.

The video obscured what the exhaust routing was. I surmise it is straight back which is efficient but sometimes hard to integrate with a single engine airplane.

Mike C.

These guys are my neighbors and this is happening just 300 meters from my hangar.

I've posted about TurboTech before and they are indeed moving steadily forward, I fully expect to see one flying on a LSA this Spring.

It burns just about anything you can throw at it: diesel fuel, bio-ethanol, JetA1, etc., etc.

The exhaust routing is indeed straight out the back but I would think that the thrust is somewhat attenuated by the recuperator's heat exchanger.

I see this puppy running in it's test cell for hours on end, day after day, for the last 18 months or so. I'll ask them how many hours they've racked up soo far and revert.

I see this puppy running in it's test cell for hours on end, day after day, for the last 18 months or so. I'll ask them how many hours they've racked up soo far and revert.