New Aussie Turboprop engine (200 HP) introduced at Sun 'n Fun

[Geoff_H]

I don't know about this GT, they are not even considered in power generation, but weight is a big factor with recupetators.  The bigger they are the less fluid flow penalties, the smaller they are the higher the gas flow, and consequent efficiency loss. Gas and air losses square as the velocity increased.  So a designer, I guess, would pictch recupetators size at cruise power. 

[Garfly]

1 hour ago, Ian said:

Back to the topic at hand, I'd be interested to know what the ballpark price is for this engine and it would be great if someone could really upset the current status quo in the current market.

 

In the AvWeb video (original post) the TurbAero CEO mentioned a target price of 80-85K USD for the 200HP version.  He also said the were planning a 120HP model. 

[Ian]

Going small with turbines is hard work without the support of deep pockets realise high compression and turbine temperatures.

Looking at this I came across NASA's analysis of rotaries where the power to weight and low vibration were seen as being very attractive. 

While rotaries are thirsty they're still better than small turbines.

 

 

 

[RossK]

8 minutes ago, Ian said:

While rotaries are thirsty they're still better than small turbines.

Rotaries are typically high wear, short TBO engines though.

[turboplanner]

Turbines are now quite common in RC aircraft now, so someone has found a way to make them economically.

 

Since most RC flights are less than 10 mins and you might get three sessions in a day at city fields, hours would be low, but I haven't seen any figures.

 

I just plucked one, Jetcat with 2.4 kg thrust 2255 Euro incl starter motor

14 kg thrust $US1780

 

Turbine record speed in RC aircraft currently 465.44 mph.

 

There's not going to be many sales in Recreational Aviation if you start in the aero market discussed so far, but starting with the RC products it would be interesting to see price/total life/fuel consumption compared to 80 and 100 hp, or even lower for single seat recreational, all with around 100 kts cruise.

[Geoff_H]

I looked into using the jet engines that are used in the cri cri for my cri cri like project.  I can't remember the exact endurance either the dual two stroke engine tank.  It endurance was less than the monomum.  The guy in WA that has put the engines into his cri cri has added significant fuel storage.  The engines were designed for model aircraft and had very high fuel consumption. 

[Ian]

7 hours ago, turboplanner said:

Turbines are now quite common in RC aircraft now, so someone has found a way to make them economically.

Their fuel consumption is pretty poor even by turbine standards. There is an paper on how they might be made more efficient. I think that this one states that JetCat overstates their thrust figures significantly as well.

 

[turboplanner]

11 hours ago, Ian said:

Their fuel consumption is pretty poor even by turbine standards. There is an paper on how they might be made more efficient. I think that this one states that JetCat overstates their thrust figures significantly as well.

 

Don't worry about Jetcat; I just plucked a random set of figures to make the point that GT are relatively common now in RC, and affordable, and it may be possible to upscale them to the current RA thrust range. 

 

For anyone interested in basing a GT on these units, I'd recommend going to a field to see them in action, and talking to the owners to find out the current popular suppliers and the design techniques they use.

 

The key factor in RA flying is keeping the cost down to affordable flying.

[Geoff_H]

Maybe afforfable flying is an oxymoron.  I have been trying to make an aircraft design that can be built for under $10k, with access to good metal machines.  Not sure that I have enough years left to get it done.  I have been using the twin small two strokes a brilliant idea, but as it will never get capable of being RAA it maybe a fruitless effort.  

[onetrack]

This is affordable flying - and even this costs vastly more than it did, when I was a youngster, 65 years ago!

 

https://www.fishpond.com.au/Toys/RAF-USAAF-Mustang-P-51D-complete-vintage-model-rubber-powered-balsa-wood-aircraft-plane-kit-that-flies-Farm-Garden/9999861742348

[turboplanner]

10 minutes ago, onetrack said:

This is affordable flying - and even this costs vastly more than it did, when I was a youngster, 65 years ago!

 

https://www.fishpond.com.au/Toys/RAF-USAAF-Mustang-P-51D-complete-vintage-model-rubber-powered-balsa-wood-aircraft-plane-kit-that-flies-Farm-Garden/9999861742348

The principle was good for the first two seconds but no matter how much you wound them the rubber never seemed to produce enough torque after that.

[BrendAn]

On 12/04/2022 at 2:40 PM, turboplanner said:

Ceramics failed in the 1980s/90s in both clutch discs and engine components, primarily combustion chamber parts such as piston tops valve tops, valve seals. We've had many discussions on this site about combustion chambers getting too hot and damaging components as a result, and ceramics were going to break through this barrier, but the failure was in installation and servicing; there were just too many hours and broken ceramics during installation. The clutches failed for a different reason; they were designed for almost instant engagement, but the drivers just couldn't adapt to an instant start; they wanted to slip the clutches. In those circumstances the ceramics acted like machine tools and tore up the flywheel face, shortening the life. Today there may be a chance with robotic assembly etc.

One of my Isuzu trucks has a ceramic clutch and it is a horrible thing to operate smoothly

[ClintonB]

On 10/04/2022 at 9:47 AM, Bruce Tuncks said:

Last time I bought a new auto start battery, it was more than $100!

I asked the guy, and he said "world price of lead mate".

So I said that my old battery weighed the same, so I reckon I hadn't used any lead. The recycling center offered $2 for the old battery.

Getting $500 per 1000kg at moment.

Saving dead ones is worth it at the moment.

[Ian]

There's a nexus of cost issues when flying, the initial buying price, airframe maintenance costs, engine maintenance costs, fuel costs and then storage airfield costs. Everyone needs to make their own choices in this space. While turbine engines have wonderful TBO maintenance and virbration characteristics unless their efficiency improves radically I can't see one really appealing unless I decide that I must use a turbine. 

Fuel from both a greenhouse gas and political instability point of view is likely to stay high so that's going to be on peoples minds.

I came across the PDF "Stratified Charge Rotary Engine", where they achieved a BSFC .375 running on turbine fuel, the progress that NASA made with stratified charge Rotary engines was significant. The engine weight was 480lbs for 400HP dry.

While rotaries have never had enormous lifetimes they don't have many moving parts and their motion is closer to a turbine than a reciprocating engine.

[onetrack]

The need to inject oil into the rotary rotor and seals is where the greatest weakness lies in the Wankel design. Mazda still see life in the design, and they have a very small rotary planned as a generator power unit in a Mazda Hybrid car in the near future.

RotaryAviation.com was a site started by a bloke named Tracy Crook who managed to convert the RX-7 engine to aviation use - but tellingly, Crook left the aviation scene in 2013, and now simply deals in rotary components to "hot up" Mazda rotaries for car owners.

 

https://www.rotaryaviation.com/store/c1/Featured_Products.html

 

Edited April 16, 2022 by onetrack

[Ian]

The idea of running on turbine fuel or diesel appeals to me. More easily available in both the short and long term.

[facthunter]

Rotaries (Wankels) have seals and the easiest thing to seal is  a round hole, not one with  square corners. Also the combustion chamber is a crook shape and always will be. Too much surface area for a given volume so thermally bad. Nev.

[Ian]

On 17/04/2022 at 12:18 PM, facthunter said:

Too much surface area for a given volume so thermally bad.

Yes not as thermally good as a cylinder however if you read the NASA paper on their engine they achieved fuel consumption better than any of the current turbines or reciprocating engines in a lighter package, yes a cylinder is better however it's overall efficiency that counts.

All engine design is a compromise, look at the valves in a cylinder head. The sleeve valve engine was used by the British in ww2, it provides better volumetric efficiency at the expense of complexity. Standard reciprocating aircraft engines are a bit shitty and don't seal particularly well either, just look at the amount of oil they burn and the amount of piston slap that is deeded acceptable.

Actually the seals on the rotary operate best at higher RPM, it's the low throttle times where the engines typically struggle so constant high throttle should be a boon for them. One of the reasons to the poor efficiency of turbines is that they have no seals.

 

In a nutshell, the power to weight of a rotary is significantly better than a normal piston engine, even with the  efficiency compromise of a flat combustion chamber, NASA managed to get fuel economy out of the engine that significantly beats any of the existing reciprocating or turbine engines (0.375). If you read their analysis they compared diesel, turbine and rotary engine for their potential as a next generation engine design for aircraft and from an engineering perspective decided that the rotary showed the best promise from a weight, vibration, cost and fuel consumption perspective. That's why they spent money on it development. However development pretty much stopped when some of the associated military contracts were cancelled and the commercial sponsors changed tack.

[Student Pilot]

Rotary as in Clerget or Le Rhone? 😁 

[turboplanner]

38 minutes ago, Ian said:

Actually the seals on the rotary operate best at higher RPM, it's the low throttle times where the engines typically struggle so constant high throttle should be a boon for them. 

 

In the Mazda RX2 I owned, the engine was very poor in urban traffic under 4000 rpm, gutless in fact, but at around that rpm became a fire breather, so expensive on fuel around town, and difficult to mix with conventional traffic.

 

On the highway it would spin the wheels at 5500 rpm and 160 km/r, so very good for fast highway travel before speed cameras.

 

It was happy to cuise at 209 km/hr for several hundred kilometres, again, before speed limits; faster point to point than a light aircraft with preflights and taxi at the end.

 

With all of this, I didn't notice any seal issues or excessive oil consumption; just excessive fuel consumption and inflexibility in the city.

 

However............if there was a constant head wind on a country trip, even at a cruise of 110 km/hr, the silicone seals (not the tip seals) would burn out, requiring a pull down and replacement, which I could do in a weekend.

 

In a light aircraft application it would be a juggling act to set cruise rpm just under that beautiful high power threshold that burns silicon seals and uses a lot of fuel.

[Garfly]

 

[Bruce Tuncks]

Geoff-h, if you ever build that cri-cri, you are welcome to bring it to the farm here to test fly.  I guarantee you will be free from bureaucracy.

[Garfly]

6 minutes ago, Bruce Tuncks said:

Geoff-h, if you ever build that cri-cri, you are welcome to bring it to the farm here to test fly.  I guarantee you will be free from bureaucracy.

Can we all come to watch, Bruce?

[Geoff_H]

19 minutes ago, Bruce Tuncks said:

Geoff-h, if you ever build that cri-cri, you are welcome to bring it to the farm here to test fly.  I guarantee you will be free from bureaucracy.

I would like to do that.  Looks like Garfly  wants to get the crash pictures 😁

[Bruce Tuncks]

Anybody is welcome to come and watch as long as they don't start spouting bureaucratic stuff. Actually, I have no doubt at all that it will be safe and sound. It is an amazing bit of nonsense that 2 engines like the cri-cri are banned.

What about drones and electric planes with multiple engines?  More independent engines = more safety obviously.