JAM747
Topic Author
Posts: 524
Joined: Thu Feb 03, 2005 12:17 am

Hybrid Or Ethanol Jet Engines?

Sun Apr 03, 2005 1:38 am

With fuel prices rising and oil supply dwindling has any jet engine maker embarked on a hybrid jet engine in a similar way that car manufacturers have done for hybrid cars. I am not an engineer but could the high rotation speeds of the turbine fans be used as a type of 'alternator' which generates electricity which in turn is used to spin the turbine to create thrust. I am sure there would be weight concerns of this and some type of batteries that would be needed to store the current and redirect it. It would probably be very expensive and certain high tech materials would be needed. May be this would be more practical for prop and turbo prop engines? In addition could it be possible for a jet type engine to run on ethanol?
 
DfwRevolution
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Joined: Sat Jan 09, 2010 7:31 pm

RE: Hybrid Or Ethanol Jet Engines?

Sun Apr 03, 2005 2:22 am

Quoting JAM747 (Thread starter):
With fuel prices rising and oil supply dwindling has any jet engine maker embarked on a hybrid jet engine in a similar way that car manufacturers have done for hybrid cars.

Airplane systems can be made eletric, as we are seeing with the 787, but I doubt a hybrid propulsion system will ever work.
 
MD11Engineer
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RE: Hybrid Or Ethanol Jet Engines?

Sun Apr 03, 2005 3:59 am

Quoting JAM747 (Thread starter):
With fuel prices rising and oil supply dwindling has any jet engine maker embarked on a hybrid jet engine in a similar way that car manufacturers have done for hybrid cars. I am not an engineer but could the high rotation speeds of the turbine fans be used as a type of 'alternator' which generates electricity which in turn is used to spin the turbine to create thrust.

This sounds like a bootstrap perpetuum mobile, which is not possible in accordnce with the laws of thermodynamics. You can´t create energy out of nothing.

Then concerning ethanol. Ethanol has a much lower specific energy content than kerosene. You would need to burn lots more of ethanol to get the same energy output.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
JAM747
Topic Author
Posts: 524
Joined: Thu Feb 03, 2005 12:17 am

RE: Hybrid Or Ethanol Jet Engines?

Sun Apr 03, 2005 5:12 am

Quoting MD11Engineer (Reply 2):
This sounds like a bootstrap perpetuum mobile, which is not possible in accordnce with the laws of thermodynamics. You can´t create energy out of nothing.

The thought is that the energy would not be created from nothing as I know that is not possible. The idea is that the engine would run the normal way using fuel .Some of the energy from the spinning fans would be harnessed in a hybrid system which would in turn assist the conventional turbine and thus reducing it's workload. The ultimate idea is that less fuel would be used . This is just a theory maybe in 20yrs there might be away to make it feasible. In a hybrid car a smaller than normal ( for that particular car) conventional engine is complemented by a hybrid electric motor. Some of the energy from gas or diesel engine is to propel the hybrid system which also generates energy. Power from both the conventional and hybrid turns the wheels of the car. Hence energy is not created from nothing , it is just that there is a better and efficient utilization of energy from the primary conventional because it is complemented by a hybrid. On some Hybrid cars the rotation of the wheels or braking is used to generate electricity.
 
FredT
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RE: Hybrid Or Ethanol Jet Engines?

Sun Apr 03, 2005 8:15 am

The fans and compressors put energy into the air. You then burn fuel to add more energy. To extract that energy and turn it into torque, which normally turns the compressor and fan, propeller or output shaft but also could turn e g a generator, you need a turbine.

Here's a good starting point if you want to learn more about gas turbine engines.

All the energy used for moving a hybrid car comes from the fuel. The saving is in not wasting energy by idling and by letting a smaller engine run at a higher percentage of its maximum power output, i e more efficiently, when it is running, storing energy in batteries which is then used to supplement the engine when lots of power is needed. Not a good explanation, but I have to hit the sack. I'm sure someone else will fill in.

Not a winner this time I think, but keep thinking! Having ideas is the first part of having great ideas - and very few people get even the first part right.  Smile

Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
Fly2HMO
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RE: Hybrid Or Ethanol Jet Engines?

Sun Apr 03, 2005 4:04 pm

Completely off topic, but the way hybrids charge their batteries is only when the car is coasting, or when you slow down by downshifting (the electric motor switches to generator mode) using the car's momentum to power the generator. So, when you touch brakes or throttle, or at the stop light, you just aren't producing electricity.

 twocents 
 
LeanOfPeak
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Joined: Thu Oct 21, 2004 2:18 am

RE: Hybrid Or Ethanol Jet Engines?

Mon Apr 04, 2005 12:22 am

Most hybrids also have some provision for regenerative braking.

As for a hybrid jet, the reason the hybrid car is effective is that, by its nature, the power required of a car is peaky. You have to start from a stop (With a lot of power), then cruise for a while (With little power), then brake to a stop (With no power). Hybrids work chiefly by recovering energy during the braking phase and reusing it during the acceleration phase. There are also those that use the availability of an electric motor to allow the use of a smaller gas motor, and those glean a further benefit from that. However, if you just moderately accelerate to speed on the highway, drive until you run out of gas, and coast to a stop (Which is about the profile aircraft use), a hybrid car is likely to often actually get WORSE mileage than a comparable conventionally-powered one due to the weight of the batteries, motors, and controllers, because it is the speed-up/slow-down where hybrids thrive (This is why their city rated MPG is often higher than their highway rated MPG).
 
Thrust
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RE: Hybrid Or Ethanol Jet Engines?

Mon Apr 04, 2005 6:28 am

Hybrid systems are terrible. I have a friend who owns a Hybrid car...he says he would much rather own a gasoline car because the Hybrids are lacking in power. Nuclear powered aircraft could be the better solution.
Fly one thing; Fly it well
 
727EMflyer
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Joined: Wed Mar 09, 2005 3:22 am

RE: Hybrid Or Ethanol Jet Engines?

Mon Apr 04, 2005 11:45 am

Quoting MD11Engineer (Reply 2):
Then concerning ethanol. Ethanol has a much lower specific energy content than kerosene. You would need to burn lots more of ethanol to get the same energy output.

What about a blended fuel? Give it just the right amount of ethanol, or some other viable alternative fuel, to strech the cocktail to the limit of power and cost efficiency? For instance (bogus numbers used for easy math) say 1 gallon of Jet A cost 1 dollar and had a power output of 1 unit while an 80%/20% blend of Jet A and ethanol cost 85 cents per gallon with power output of .9 units... if a flight took 1000 units of energy output to complete, you would burn 1000 gallons of Jet A at a cost of $1000 while the requisite 1111 gallons of cocktail cost only $944 plus any weight penalty.
Eventually the cost benefits could outweigh the R&D money you'd have to put into it, could they not?
 
LeanOfPeak
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Joined: Thu Oct 21, 2004 2:18 am

RE: Hybrid Or Ethanol Jet Engines?

Mon Apr 04, 2005 12:05 pm

Unfortunately, it doesn't work that way. What fuel you need to consume, you need to carry. So you need to consume more fuel to carry the fuel, so you need to consume more fuel to carry the fuel, .... Eventually you hit a point that works, but there is a snowball effect to it that makes any penalty you accept more severe.
 
727EMflyer
Posts: 538
Joined: Wed Mar 09, 2005 3:22 am

RE: Hybrid Or Ethanol Jet Engines?

Tue Apr 05, 2005 11:12 am

Quoting LeanOfPeak (Reply 9):
Unfortunately, it doesn't work that way. What fuel you need to consume, you need to carry.



Quoting 727EMflyer (Reply 8):
1111 gallons of cocktail cost only $944 plus any weight penalty.

Even though I included a disclaimer for the unknown: Sorry I am not an engineer, and further sorry that I didn't figure out exatly how much my imaginary fuel would weigh and how much my imaginary airplane would be bogged down by what couldn't be more than a whole 800 pounds.
 
LeanOfPeak
Posts: 496
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RE: Hybrid Or Ethanol Jet Engines?

Tue Apr 05, 2005 12:04 pm

Sorry, the first time I read it, I missed the, "Plus any weight penalty," part. I merely intended to indicate that weight penalties upon weight penalties can become substantial.

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