# Using RC Model Turboprop Engine



## skullbearer (Jul 9, 2008)

Ok, here's an example of what I'm talking about. It produces up to 6kW, this is designed for a helicopter application, there are a lot of different options among models, however its is like $4000.


Just thinking, though I can't seem to find any fuel usage right off the site, turboprops are way way more efficient than ICEs, is there any really efficient micro-turbines out there we can use to replace an ICE in a parallel/series system or as a range extending generator?

This is 6kW with a 90mm diameter motor and not that long either... VERY TINY, HUGE POWER!!!


I didn't realize these little ones made that kind of power. Someone pointed out to me that the military surplus ones I suggested in a thread are like 8gph, which is massive fuel consumption (though power output is also massive).


A lower rpm high efficiency low maintenance turboprop that made up to say, 14-18kW at max rpm would be ideal in my mind.

:EDIT:

This is another from the same company here, that's the detailed stats page they provide on that one.

5.62kW max at 6300rpm for this guy, 8.52Nm @6300rpm of torque, 165ml/min fuel use at full consumption... lets see, in an hour that's 9.9L that's 2.5 gallons about per hour at max power... damn, not that great. What we need is something bigger with better efficiency, unless these get really good efficiency at less than full power, in which case you could connect up a few of them I'd think.


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## aeroscott (Jan 5, 2008)

skullbearer said:


> Ok, here's an example of what I'm talking about. It produces up to 6kW, this is designed for a helicopter application, there are a lot of different options among models, however its is like $4000.
> 
> 
> Just thinking, though I can't seem to find any fuel usage right off the site, turboprops are way way more efficient than ICEs, is there any really efficient micro-turbines out there we can use to replace an ICE in a parallel/series system or as a range extending generator?
> ...


the only turbines that are big , small ones are simple low compression (3 or 4 to 1 ) single stage compressors and turbines . I have an apu turbine about 25 to 35 kw and 17 gph from what I read . still would be very cool for a hot rod hybrid . Volvo did a ceramic turbine generator for a hybrid . along with high temps you need high compression to max efficiency . but thinking about it turbochargers are going ceramic and compression ratios and air flows are increasing all the time . i heard about a s r generator for direct drive on a small turbine . no cooling system , small , light and smooth .


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## skullbearer (Jul 9, 2008)

I think I followed that, and you make a good suggestion, high quality turbos are moving into high compression turbine level build elements.

I have read instructions and found you-tube videos of people driving go-karts on 50hp turboshafts made with two turbos pulled from a junkyard and started with compressed air.

The cool thing about turbines is they can run nearly any fuel, often without modification.


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## Jeremy (Jul 12, 2008)

> turboprops are way way more efficient than ICEs


Unfortunately they aren't. They are more efficient than an ICE at high altitude, but that's because ICE efficiency at altitude is very poor. At ground level a turbine engine sucks fuel like it's going out of fashion.

I flew a twin turboprop years ago, it burnt a ridiculous amount of fuel when just turning and burning on the ground, yet was pretty good once you got up to about 20,000ft.

The key thing here is the Specific Fuel Consumption (or Brake Specific Fuel Consumption) as this tells you how much fuel an engine needs to burn for a specific amount of power delivered in a specific time. Top of the league are big marine diesels, as they can use only around 0.25lbs/hp/hr, normal car diesel engines can use around 0.33lbs/hp/hr, normal car gasoline engines use around 0.5lbs/hp/hr, the Toyota Prius gasoline engine uses about 0.39lbs/hp/hr whilst a turboprop at ground level uses around 1.2lbs/hp/hr.

(lower numbers are good)

Jeremy


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## aeroscott (Jan 5, 2008)

do a google on rotary V engine , you will get a lot of Mazda stuff not that . you will find Sport Aviation article from about 1986 it's a 2 stroke engine developed in the 50's or 60's was planned for the Bricklin sports car later . NASA did a study on the efficiency came up with a .25 spf ( .35 is very good ) on diesel (can be gas ) . this engine has no crankshaft no reciprocating parts is as light or lighter then turbines with much better fuel numbers . So these guys build this thing and show it off at EAA international air show in 86 or 88 . they had 2 engines one running one for display ,smooth ,everyone was impressed.what the lightest simplest best fuel eff. going not a another word ! I did not make it to see this wonder engine but made it the flowing year . No updates no booth nothing . So I start asking around , I was told Bowing aircraft bought them out . any patents would have expired by now .


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## TX_Dj (Jul 25, 2008)

Exactly what the others have said... turboprop/fan/jet engines are not more efficient in a fuel consumption sense. But they are more efficient at producing power at altitude than an ICE.

I've seen fuel consumption figures for the small-to-mid-size turbines used for RC applications, and the rate of thirst is still beyond reasonable. I had considered whether it would be feasible to use one or two of the larger turbojet engines to power a Part 103 ultralight, but in remaining Part 103 compliant you cannot carry more than 5 gallons of fuel, which if I remember correctly would have powered two of the 150-lbs thrust turbojets for about 12 minutes... just about enough time, if you were lucky, to taxi, take off, and circle back around the pattern for landing and roll back to the gas pump. 

Not to mention... they are INCREDIBLY loud. Even those TINY ones! 

GM, Chrysler, and others tinkered with gas turbine powered cars throughout the 50's/60's and some in the 70's, and just overall scrapped the idea. They just eat too much fuel, are too loud, and really don't provide any torque- all their shaft horsepower is created at 10's of thousands of RPM. It also takes a good long while to spool up the compressor stage before it's got enough air in the combustion chamber to ignite enough fuel for it to self-sustain.

They sure are cool engines though! Jay Leno has a custom motorcycle that has a 550 SHP turbine engine from a helicopter.


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## Schmism (Aug 16, 2008)

skullbearer said:


> A lower rpm high efficiency low maintenance turboprop that made up to say, 14-18kW at max rpm would be ideal in my mind.
> 
> :EDIT:
> 
> ...



I think your missing an important part. they all use some sort of planetary or harmonic gear box to reduce the massive 100K rpm down to ONLY 10K rpm

most small scale turbines have to run in the 100K rpm... your fuel consumption is based on turbine RPM, not output shaft rpm.

for the ultra cool setup in the ultra big boy price check out the Allison Rolls-Royce turbine that leno put into a custom bike. with a 320 to 350 hp and a hefty 450 ft.-lb in a 130lb weight package, just what you want right?

http://www.popularmechanics.com/automotive/jay_leno_garage/1302876.html?nav=hpPrint


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## TX_Dj (Jul 25, 2008)

skullbearer said:


> 2.5 gallons about per hour at max power... damn, not that great.


Exactly. What do they run on? how much does it cost in quantity? If it's anything like what my RC10 GT runs on, it's about $24/gallon 

Sure is a cool thought though. I like the idea of natural gas turbines in a stationary generator configuration, though in some locations the same thing that takes out your power can take out your gas, I reckon.


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## aktill (Jun 18, 2008)

TX_Dj said:


> Exactly. What do they run on? how much does it cost in quantity? If it's anything like what my RC10 GT runs on, it's about $24/gallon
> 
> Sure is a cool thought though. I like the idea of natural gas turbines in a stationary generator configuration, though in some locations the same thing that takes out your power can take out your gas, I reckon.


Your RC10 will be running on nitromethane, most likely.

Most of these seem to run on what the big guys do - aviation kerosene I believe. Very thirsty little critters, as has been said before...most of the birds come home weighing 1/2-1/3 less then what they did taking off.

Cheers,
Adam


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## skullbearer (Jul 9, 2008)

Yet Volvo is still putting turbines in those wacky hybrid trucks they've been testing over the last couple years. They had them on that Futurecar show on Science Channel (and Discovery). I looked it up after seeing it on the show and Volvo's claim was nearly double fuel efficiency of piston engines.


What about a Toroidal engine, I know the guys that were re-developing said they were sending out some test units, anyone heard anything beyond that? I can only find websites talking about the concept.


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## Nodd (Jun 6, 2008)

Jeremy said:


> Unfortunately they aren't. They are more efficient than an ICE at high altitude, but that's because ICE efficiency at altitude is very poor. At ground level a turbine engine sucks fuel like it's going out of fashion.


I don't know much about turbines but is it possible that most are simply "tuned" for high altitude & that's why they guzzle gas sitting on the tarmac? Is it possible to tweak them for optimal efficiency at sea level instead? I know the military uses them in tanks & what-not so there must be some merit to using them in a surface vehicle.

Maybe they guzzle more gas than an ICE but I hear they're also way lighter. That's gotta be a factor also.

Installing an afterburner might be a great way to cut down on folks tailgating you too.


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## 1clue (Jul 21, 2008)

I'll try not to say too much that others already have.

The Wren turbojet I saw used a 2-liter fuel tank and got maybe 8-10 minutes of flight, which is probably more than enough, since the pilot has to turn the plane constantly in order to keep it in range of the transmitter AND in range of his sight. Not sure where the weak link is on that, but for me it would be sight.

The other thing I can say from direct observation is that you DO NOT WANT THIS THING IN YOUR CAR! The noise is stupendous, and it's not so much in your ears as in the roots of your teeth.

Not sure why small turbines suck so much fuel. It could be what the other posters have said, or it could be that the engineering that makes them efficient for a 747 are worthwhile on a large scale but not on a small scale.

I looked into a turbine engine for a racing hovercraft a few years ago, and nothing was even remotely interesting at that time. The APU's weighed as much as a good two stroke of equivalent power, they drank 4x as much gas, they couldn't be muffled and they couldn't be filtered -- at least not in any way that a racing hovercraft could carry.


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## aeroscott (Jan 5, 2008)

Nodd said:


> I don't know much about turbines but is it possible that most are simply "tuned" for high altitude & that's why they guzzle gas sitting on the tarmac? Is it possible to tweak them for optimal efficiency at sea level instead? I know the military uses them in tanks & what-not so there must be some merit to using them in a surface vehicle.
> 
> Maybe they guzzle more gas than an ICE but I hear they're also way lighter. That's gotta be a factor also.
> 
> Installing an afterburner might be a great way to cut down on folks tailgating you too.


turbines inlet temp determines the efficiency and to a lesser extent low exhaust pressure helps . did some reading on the net about Volvo turbine sounded like it used a exhaust heat exchanger to preheat combustion air . this has been done before to good effect . Jon Goodwin is said to be working a gpu hybrid . so I checked his site H-line and SAE Engineering didn't see anything on the apu . I have a 30 kw turbine gen set and some stainless steel air to air heat exchangers . If you could get the fuel burn down to something like .40 or .50 which sounds doable we might have something . then there's the sound .


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## skullbearer (Jul 9, 2008)

There's always the Tesla turbine route too. I've seen youtube videos where they had some Teslas running with gas combustion that were _encased_ by a muffling housing, and both intake and exhaust were muffled. Package was still pretty small and not any louder (you could hear their voices) than most poorly muffled 2-strokes.


Turbos are turbines sans the combustion phase, they aren't super loud and work just fine with a muffled automotive exhaust. Always possible to muffle things.


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## aeroscott (Jan 5, 2008)

skullbearer said:


> There's always the Tesla turbine route too. I've seen youtube videos where they had some Teslas running with gas combustion that were _encased_ by a muffling housing, and both intake and exhaust were muffled. Package was still pretty small and not any louder (you could hear their voices) than most poorly muffled 2-strokes.
> 
> 
> Turbos are turbines sans the combustion phase, they aren't super loud and work just fine with a muffled automotive exhaust. Always possible to muffle things.


Tesla's have a lot going for them . It's high frequency sound essayer to deaden but there's a lot of it . the heat exchanger will cut down a lot of it on the exhaust side and the glass packs( also called the Swiss muffler ) work good on high frequency


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