Alternative engines

[hais]

Spawning from EV thread :

do you think alternative engines like Free Piston Linear Generators will be the answer before batteries become viable? 

Ignore for the moment certification challenges : would a 30% increase in efficiency motivate anyone to even attempt? 

 

[carusoam]

From the imaginary engines department….

Let’s go turbine…

Then increase its efficiency….

And Make it low cost….

For fun… make it electric powered…

With a magic battery….

and a silent propellor….

900nm range, 185kt cruise….

Opening the next can of worms….

Bring back the pressurization….

And full Fiki…..with air conditioning…

Why not?

-a-

[McMooney]

I'd be super happy with a diesel.  Certified Jet-A Engines (continental.aero)

 

Edited May 26, 2022 by McMooney

[carusoam]

23 minutes ago, McMooney said:

I'd be super happy a diesel.  Certified Jet-A Engines (continental.aero)

 

Would we expect to get even better fuel economy similar to a diesel car with that?

The 300hp diesel continental engine doesn’t weigh much more than an IO550…

-a-

[A64Pilot]

The Diesels have real problems as yet unsolved, like torsional vibrations so strong a metal prop will fatigue and break, then they aren’t usually that much more efficient, for some reason they are throwaways, with the 300 HP one going for about $100K, you don’t overhaul them, my guess is fatigue from those torsional vibrations, to build strong enough that they don’t fatigue means heavy, but just guessing.

As they are compression engines restarts at altitude are problematic at best.

The only thing they have going from them is they burn Jet, but Both Lycoming and Mercury marine have built spark ignition engines that run on Jet. Military has gone to one fuel long ago, so Mercury built an outboard and Lycoming a small drone motor, for the military so it’s possible. Both I think are two strokes.

https://www.lycoming.com/engines/el-005

https://www.mercurymarine.com/en/us/engines/outboard/diesel-outboard/diesel-outboard/

The Merc uses the Australian orbital engine compressed air fuel injection system to atomize the fuel, it was first used back in the day to make two strokes burn clean enough to pass emissions.

https://www.greencarcongress.com/2007/10/orbital-introdu.html

I suspect however that our existing engines, the IO-550 as an example which can run well at a BSFC of .39 is pretty close to the limit efficiency wise that you can get without significant increases in complexity and probably weight/size. The issue is lead, which has been solved in a couple of ways, water injection which I’m a proponent of and apparently Gami’s fuel. I hope both are offered so we are allowed to decide, but I don’t think we need or want Diesels, the cost alone takes me out of the picture, and it would ground all of the classic aircraft, then Diesels have issues from an emissions standpoint, largely particulates, gasoline motors just run cleaner, and if we are made to go away from lead from an emissions standpoint, those making it happen may look at the replacements emissions, and if you start trying to clean up a Diesel weight and cost would essentially get out of control, it’s do-able of course, look at todays Diesel pickups, but compare one of their engines from one 20 years ago.

I’ve flown the Diesel Maule they built years ago to have the engine company go out of business, one problem was a go-around, it had a prop governor but it was fixed to one RPM for some reason and if you wanted power now it wasn’t happening, you had to wait for boost to build, it’s delay was very similar to a larger PT-6. It was heavier and compared to the 540 and underpowered. I wasn’t impressed, but if no 100 LL is available it’s pretty much your only option.

https://www.aviationconsumer.com/aircraftreviews/engines/maules-m-9-aero-diesel/

Maule built the turbine Maule with the little Allison too, but due to cost it was a flop, it’s Certified though and a few were sold.

http://www.pilotfriend.com/aircraft performance/Maule/28.htm

We had a dealer (Africair) that was doing a lot of 172 conversions for Africa, but I think that dried up, apparently according to them there is no  100LL in Africa, which I doubt, but maybe true for certain parts?

Edited May 26, 2022 by A64Pilot

[hais]

12 hours ago, A64Pilot said:

The Diesels have real problems as yet unsolved, like torsional vibrations so strong a metal prop will fatigue and break, then they aren’t usually that much more efficient, for some reason they are throwaways, with the 300 HP one going for about $100K, you don’t overhaul them, my guess is fatigue from those torsional vibrations, to build strong enough that they don’t fatigue means heavy, but just guessing.

As they are compression engines restarts at altitude are problematic at best.

The only thing they have going from them is they burn Jet, but Both Lycoming and Mercury marine have built spark ignition engines that run on Jet. Military has gone to one fuel long ago, so Mercury built an outboard and Lycoming a small drone motor, for the military so it’s possible. Both I think are two strokes.

https://www.lycoming.com/engines/el-005

https://www.mercurymarine.com/en/us/engines/outboard/diesel-outboard/diesel-outboard/

The Merc uses the Australian orbital engine compressed air fuel injection system to atomize the fuel, it was first used back in the day to make two strokes burn clean enough to pass emissions.

https://www.greencarcongress.com/2007/10/orbital-introdu.html

I suspect however that our existing engines, the IO-550 as an example which can run well at a BSFC of .39 is pretty close to the limit efficiency wise that you can get without significant increases in complexity and probably weight/size. The issue is lead, which has been solved in a couple of ways, water injection which I’m a proponent of and apparently Gami’s fuel. I hope both are offered so we are allowed to decide, but I don’t think we need or want Diesels, the cost alone takes me out of the picture, and it would ground all of the classic aircraft, then Diesels have issues from an emissions standpoint, largely particulates, gasoline motors just run cleaner, and if we are made to go away from lead from an emissions standpoint, those making it happen may look at the replacements emissions, and if you start trying to clean up a Diesel weight and cost would essentially get out of control, it’s do-able of course, look at todays Diesel pickups, but compare one of their engines from one 20 years ago.

I’ve flown the Diesel Maule they built years ago to have the engine company go out of business, one problem was a go-around, it had a prop governor but it was fixed to one RPM for some reason and if you wanted power now it wasn’t happening, you had to wait for boost to build, it’s delay was very similar to a larger PT-6. It was heavier and compared to the 540 and underpowered. I wasn’t impressed, but if no 100 LL is available it’s pretty much your only option.

https://www.aviationconsumer.com/aircraftreviews/engines/maules-m-9-aero-diesel/

Maule built the turbine Maule with the little Allison too, but due to cost it was a flop, it’s Certified though and a few were sold.

http://www.pilotfriend.com/aircraft performance/Maule/28.htm

We had a dealer (Africair) that was doing a lot of 172 conversions for Africa, but I think that dried up, apparently according to them there is no  100LL in Africa, which I doubt, but maybe true for certain parts?

Kinda depressing to think that we can't expect exciting news firewall forward. 

[A64Pilot]

24 minutes ago, hais said:

Kinda depressing to think that we can't expect exciting news firewall forward. 

I think you can, maybe. But above my price point. Just as a Swag I’d think a Diesel conversion would run as much as my airplane is worth or more.

While water injection would cover me to run Premium auto gas, that stuff stinks and doesn’t store well, but I’d run it if I could and 100LL wasn’t available. If nothing else the Gami fuel should cover the Turbo guys. Water injection may too but would have to be on continuously.

So it would seem between the Gami fuel and water injection we don’t have to have Diesel

Of course this is my beliefs, time will tell

Edited May 27, 2022 by A64Pilot

[A64Pilot]

17 hours ago, carusoam said:

Would we expect to get even better fuel economy similar to a diesel car with that?

The 300hp diesel continental engine doesn’t weigh much more than an IO550…

-a-

You should get better fuel consumption likely as much from the turbo as the Diesel, but the Diesel will most likely be heavier, and the fuel is heavier too.

6.8 lbs per gallon seems to ring a bell

[Shadrach]

I know of no NA or turbo gasoline engine (Aircraft or GV) that approaches the thermal efficiency of of a modern turbo diesel.  Torsional Vibration issues are nothing new to engine designers, but are far easier to solve at a constant RPM than in variable speed applications.  The military has been using a 205hp Lycoming Diesel in UAVs for the better part of a decade.  It's fuel specifics exceed the IO360s by quite a bit and trounce any of the current TSIO engines.

Continuous power ratings:

.360lbs/hr @ 180hp (90%) = 9.53 GPH of Jet A

.345lbs/hr @ 120hp (60%) = 6.08 GPH of Jet A

By comparison ,if you were able to run an IO360 at 90%, at best BFC of .397lbs/hr, 180HP (which you can't) it would take nearly 12gph. At 60%, 120hp, which is doable, it takes ~8gph 

This diesel is based on a FIAT 4cyl aluminum block and has a C/R of 16.5:1. With Turbo, Reduction gear and intercooler, the Diesel is ~60lbs heavier than an IO360 but that does not include coolant nor radiator. These engines have been flying since at least 2013 but maybe longer.  If any one knows any active military that works with UAVs, it would be interesting to get opinions from actual users about dispatch reliability.

I don't know what the critical altitude is for the engine, but it would be an interesting engine upgrade for a mid or short body.

It will likely never get certified but it's an intriguing idea.

 

[A64Pilot]

There is a reason why Lycoming hasn’t sought Certification of their Diesels, it may be financial as in they expect no sales, or it may be that it’s not Certifiable as in can’t pass the regs. It would seem to be in their interest to Certify it if it could be.

A lot is done with UAV’s simply because they are a UAV and a Military aircraft, for instance the -10 powered Reaper has only the one Starter Generator and a small battery, if it loses the Starter Generator as many have, they pick a spot on the ground and lawn dart the thing as they only have control for a short time. It’s considered an acceptable loss. The SG problem was resolved before my Retirement Four or Five years ago, I only found out because we were losing SG’s too. One would expect to see a RAT or a second generator, but it’s unmanned, so just lawn dart it.

‘Forever we as in GA lived off of Military money being spent to develop and Certify engines, props etc. Look at all our fuel, oil, parts standards, but long ago the Military dropped piston engines and progress essentially ground to a halt because no more sugar Daddy to pay for things.

Even when I was in the Military we went to a single fuel for logistics, the cooks stove was the last gasoline consumer in the Army so the Military needs Diesels, it’s telling that Lycoming isn’t using Government money to develop a Certified Diesel.

I wonder why? 

[A64Pilot]

This is the guys who used to be our dealer down in Miami, four things killed the Diesel 172 conversion in the US, primarily it had the useful load of a 152, but also the price delta between Avgas and Jet-A wasn’t high enough to make it work, plus Avgas is available and the big chunk of money to convert.

https://www.aviationconsumer.com/industry-news/diesel-conversion-whats-involved/

Diesel could work in a Mooney, maybe but it would surely be way out of my price range as I expect it would be for the majority of J model owners. I’d expect to see them in a new airplane, Cirrus first maybe because the price delta surely wouldn’t be so big

Edited May 27, 2022 by A64Pilot

[carusoam]

There is a lot of drone activity using the Rotax 912…

Kind of lower UL than a Mooney….

Not sure if they get many hours on each one because of the environment they fly into…

They may not get the luxury of a return trip…

Turkey has an interesting drone business…

Does Rotax have a Diesel engine?

https://en.wikipedia.org/wiki/Baykar_Bayraktar_TB2

The next step TB3 is expecting a larger engine for typical long body MGLWs….

Best regards,

-a-