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Thread: Gas Turbine engine price,efficiency

  1. #1 Gas Turbine engine price,efficiency 
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    I know that some automakers such as Volvo and GM experimented with gas turbine engines in their series hybrid vehicles and even made some cars with it.
    What is efficiency of gas turbine engine installed on a passenge car? I read that turboprop engines in planes acheive 70% efficiency.But wikipedia article about gas turbines mentiones that they in general are less eficient than ICE.What is truth?And what is price of efficient turboshaft for a car?As I understend this is the main obstacle for such engines.But I really wander if it is so expensive to make two or three small blades made out of heat resistant materials? For example price of Tungsten is so high? Or some kind of quartz fiberglass? Or graphite fiber?
    As I know currently even some parts of skies are made of graphite fiber.So it should be in range of tens of dollars not a thousands.Because size of turboshaft could be relatively small.But there would be great fuel economy and much less maintnance.No fuel changes,no coolant or radiator etc.


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  3. #2 Re: Gas Turbine engine price,efficiency 
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    Quote Originally Posted by Stanley514
    I know that some automakers such as Volvo and GM experimented with gas turbine engines in their series hybrid vehicles and even made some cars with it.
    What is efficiency of gas turbine engine installed on a passenge car? I read that turboprop engines in planes acheive 70% efficiency.But wikipedia article about gas turbines mentiones that they in general are less eficient than ICE.What is truth?And what is price of efficient turboshaft for a car?As I understend this is the main obstacle for such engines.But I really wander if it is so expensive to make two or three small blades made out of heat resistant materials? For example price of Tungsten is so high? Or some kind of quartz fiberglass? Or graphite fiber?
    As I know currently even some parts of skies are made of graphite fiber.So it should be in range of tens of dollars not a thousands.Because size of turboshaft could be relatively small.But there would be great fuel economy and much less maintnance.No fuel changes,no coolant or radiator etc.
    IC engines are more efficient. Roughly, the efficiency will follow the temperature difference between the intake and exhaust. The closer the difference is to zero the greater the efficiency. Of course you must also subtract any energy loss from external cooling like the radiator or air cooling fins in an IC engine. Gas turbines have really really hot exhaust and thus low efficiency.

    The advantage of gas turbine is power to weight ratio. Since the combustion temperature and pressure is so high they get lots of power for their size. Gas turbines are great when you need waste heat. Then the heat is recovered (cogen facilities use the waste heat) and they are clearly the way to go.

    Small gas turbines are expensive ($20-30k) only because they are not mass produced.

    I can't speak to your questions about blade material.


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    Is there some difference between turboshaft/turboprop and gas turbine?
    For example this guy states that turboprop could provide three to four times
    more efficiency then ICE.

    http://forums.spacebattles.com/showthread.php?t=46667

    Is it not the same as gas turbine?

    I know that scientists experimented with ceramic engine which didn't require
    cooling and thus been much more efficient.But ceramics is not very good for reciprocating engine because it is too brittle.For those who know something about
    materials I have a question: is fused silica or some quartz glass so bad for engine
    parts or such expensive?I know that there are even flywheels made of fused silica
    and it seems to be much stronger then steel.Also quartz glass is very heat resistant and have very low thermal expansion.And what about rotary engine such as Wankel? It contains much less reciprocating parts and whould be easier to
    do from unconventional material.
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  5. #4  
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    Quote Originally Posted by Stanley514
    Is there some difference between turboshaft/turboprop and gas turbine?
    For example this guy states that turboprop could provide three to four times
    more efficiency then ICE.

    http://forums.spacebattles.com/showthread.php?t=46667

    Is it not the same as gas turbine?
    The engine is a turbine engine but it drives a propeller. They are efficient because most of the exhaust stream contributes to thrust rather than waste heat in an airplane .... You can't have hot high speed exhaust blasting out of the back of a car, it will kinda ruin the nice Beamer paint job or flame a pedestrian.

    I know that scientists experimented with ceramic engine which didn't require
    cooling and thus been much more efficient.But ceramics is not very good for reciprocating engine because it is too brittle.For those who know something about
    materials I have a question: is fused silica or some quartz glass so bad for engine
    parts or such expensive?I know that there are even flywheels made of fused silica
    and it seems to be much stronger then steel.Also quartz glass is very heat resistant and have very low thermal expansion.And what about rotary engine such as Wankel? It contains much less reciprocating parts and whould be easier to
    do from unconventional material.
    As you suspected I can't help here.
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  6. #5  
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    Quote Originally Posted by Stanley514
    I know that scientists experimented with ceramic engine which didn't require
    cooling and thus been much more efficient.But ceramics is not very good for reciprocating engine because it is too brittle.For those who know something about
    materials I have a question: is fused silica or some quartz glass so bad for engine
    parts or such expensive?I know that there are even flywheels made of fused silica
    and it seems to be much stronger then steel.Also quartz glass is very heat resistant and have very low thermal expansion.And what about rotary engine such as Wankel? It contains much less reciprocating parts and whould be easier to
    do from unconventional material.
    Very simple: it's currently either impossible or extremely expensive to give ceramics a complicated shape. You can make disks and blocks, and even tubes out of quartz, but that's where it stops. Someone in our department is doing research to mill glass and ceramics with ultrasound machining, but that's pretty much in its infancy.

    Some cermats (ceramics in a metal matrix: e.g. Tungsten Carbide) can be machined with EDM (electro discharge machining), but at the moment it costs easily several thousands of dollars to make one small turbine (only the rotor) with it.

    As you mention yourself, the brittleness is also a big issue, as is the thermal shock resistance: you can have very high temperature differences. Some ceramics are better suited than others. There are for example already cars driving around with the valves made of Silicium Nitride.
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    I'd like a turbine car. The only problem I see, the expensive cost; but technologically, it's possible. The efficiency is not high, and the price of a turbine of this size is so much more than Otto engine, but at a time when gasoline threatens scarce, perhaps alternative cars would decrease demand and therefore the price of gasoline.
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    The thing about turbines to consider are the high RPMs that you need to achieve in order to have something that you can extract energy from. So even though you could use less expensive materials, they would have to be very strong (and light). Consider the centripetal forces (or centrifugal if you like) at the tip of a blade that is going at 10,000 rpm. If the blade is only a few inches long, the forces will likely rip the blade apart if it weights only a bit too much. Hence most turbines are made from titanium since it has a high strength to weight ratio. Now you could consider a carbon fibercomposite blade but the issue comes up due to thermal growth. If the blade touches the fan shroud "a bit" it will generate a lot of heat (and this seal needs to be very tight in order to produce the pressures required). The heat will propagate through the blades far better in a metal than a composite. In the composite the blade tips will get glowing hot and delaminate (the resin) and therefore lose a lot of performance very quickly. As to ceramics, you have a similar situation with the added difficulty of manufacturing. So metals like titanium are stil the most economical alternative (weird but true). For the hot side, only metals and ceramics are an option since the temperature will get into the 1000F quite easily (depending on the type of engine).
    So the real reason that turbine engines are expensive is because they require high performance materials.
    Last point: the efficiency of a turbine engine will never be as high as that of a reciprocating engine (turbine engines are really internal combustion engines too). Consider the effect of taking the energy off an expanding volume (piston/cylinder) vs. the energy taken off of blowing over a propeller.
    The only way of getting higher energy out of a combustion process is to increase the pressures (as in a Diesel engine) and increase the temperature differential between the hot and cold side (see Carnot efficiency).
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  9. #8  
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    Currently, I don't see a great sense to use gas turbine because if we need something ceramic and working without cooling we could use ceramic Wankel engine.
    Drivers say Wankel engine is not less efficient than usual reciprocating engine.
    And it seems to me less complicated than turbine and hence easier to manufacture.I don't know if it's possible to make some engine which would be even simplier than Wankel,maybe a simplest reaction drive.(If we could enforce it to rotate around an axle and thus generate electricity.)
    Generally, I agree that increase of working temperature is unavoidable in engine development.Fortunately, there is bunch of materials which could sustain heat of burning hydrocarbons (1600 C).But probably we'll need to avoid lot of reciprocating parts to make it suiteable for ceramics.
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    I'm on board with the view that a turbine will never make it in to the automobile again. ICE's are positive displacement, which enable them to convert more of the heat (pressure) into usable force and power. Any type of turbine is a sacrifice in efficiency.
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    What do you think about pyroelectric engine?
    Some researchers promis 50% efficiency and even up to Carnot limit.
    http://www.ikhebeenvraag.be/mediasto...harvesting.pdf

    I think it could be good a supplement for hybride vehicles.High efficiency and low maintnance.
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  12. #11  
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    Quote Originally Posted by Gen1GT
    I'm on board with the view that a turbine will never make it in to the automobile again. ICE's are positive displacement, which enable them to convert more of the heat (pressure) into usable force and power. Any type of turbine is a sacrifice in efficiency.
    I hope this will change your mind...Hello I'm Big Mike and I'm new to this forum. I built and own a gas turbine powered Porsche 928 (2nd built/version). Aside from the noise form the turbine intake, my car gets 17 miles per gallon on the highway. I use Jet-A fuel to keep my fuel system from gumming up. I could always switch to diesel if needed. I have logged over 1,000 miles on this vehicle and love the reaction of pedestrians when I drive by (they always look skyward and never at the car).
    Here is a link to my videos. The first was filmed during the first start up after the build: http://www.youtube.com/user/BIGMIKES.../2/z6wdxlIYizk
    The secont video is the first drive: http://www.youtube.com/user/BIGMIKES.../0/Pf2NUd1E3U8
    At the moment the car is not complete yet. I am currently building a roll cage and will install light weight race seats. The vehicle would also be custom painted to look like a U.S. Air Force jet in Camo pattern.

    Thanks,
    Big Mike
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    my car gets 17 miles per gallon on the highway
    It doesn't look pretty efficient yet...
    Close to 14 L/100 km.
    What do yo think about trying ceramic Wankel engine instead of gas turbine?
    Maybe it will have even greater efficiency?
    I think that rotors may be made out of such material as carbon fiber reinforced
    Titanium Nitride or similar.
    Antislavery
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    I also have a car that I race in SCCA Solo 2 events that is powered by a Wankel engine (a 13B mazda engine). This engine is not that much more efficient than my Turbine engine.
    Here's the link to my Wankel racer:
    http://www.youtube.com/user/BIGMIKES.../1/gKkFL-AzWLM
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    You may also consider prototype rotay pulse engine:
    http://conceptengine.tripod.com/conceptengine/id2.html
    and nutating disc engine:
    http://en.wikipedia.org/wiki/Nutating_disc_engine

    Both are promised to deliever very great power and I think could be made of
    heat resistant materials to encrease efficiency.
    Antislavery
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    Hi to all I know that scientists experimented with ceramic engine which didn't require
    cooling and thus been much more efficient.But ceramics is not very good for reciprocating engine because it is too brittle.For those who know something about
    materials I have a question: is fused silica or some quartz glass so bad for engine.


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    There is a Jaguar C-X75 concept car which features 2 micro gas turbine engines connected to electric generator.
    Jaguar C-X75 - Wikipedia, the free encyclopedia

    I have a questions to those who is proficient in gas turbine engines about micro turbines similar to those used in this one car.
    1) What is peak efficiency of a modern microturbine?
    2) Does it work completely without oil and liquid cooling? What is lubrication mechanism used?
    3) Why thermal efficiency of a microturbine is lower than in Otto engine and exhaust is hotter? Why its heat to work conversion efficiency is worse?
    4) Why does it require giant amounts of air?
    5) Why peak efficiency of gas turbine is achieved at huge rotational speeds only?

    Hence most turbines are made from titanium since it has a high strength to weight ratio. Now you could consider a carbon fibercomposite blade but the issue comes up due to thermal growth. If the blade touches the fan shroud "a bit" it will generate a lot of heat (and this seal needs to be very tight in order to produce the pressures required). The heat will propagate through the blades far better in a metal than a composite. In the composite the blade tips will get glowing hot and delaminate (the resin) and therefore lose a lot of performance very quickly. As to ceramics, you have a similar situation with the added difficulty of manufacturing. So metals like titanium are stil the most economical alternative (weird but true).
    What about tungsten or tungsten carbide? It suppose to have even higher melting point and strength than titanium.
    Last edited by Stanley514; July 25th, 2014 at 09:00 PM.
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