Why are gas turbine engines not used in automobiles?

[chhitiz]

barring a few exceptions
i read that it is because they aren't effecient at small scale. can someone elaborate on that?
also, would even smaller turbines need some time to start up?

 

[UltrafastPED]

See http://en.wikipedia.org/wiki/Chrysler_Turbine_Car

 

[chhitiz]

barring a few exceptions

as far as i have read, coz they need to be at very high rpms, and no effective throttle response
but can anyone provide me more figures? more literature?

 

[UltrafastPED]

They also had a problem with cooking the asphalt roadways behind them ...

There are many "great ideas" that don't work out because of (1) cost (2) lack of suitable materials (3) unachievable tolerances (4) unanticipated problems.

A good example is the Wankel engine - my father was a draftsman for an engineering company that worked on the Wankel engine in Detroit ... in the 1930s. Decades later it hit the road ... but was never a great success.

It is very easy to research any of these; you will find lots of opinions if you go to a site devoted to automotive stuff.

 

[chhitiz]

can u name these sites?

 

[SteamKing]

Gas turbines are most efficient when the turbine operates at high speed. Cars, on the other hand, operate at relatively low speed, even on the highway. I think the big drawback with a practical turbine car was coming up with a practical transmission design which could accommodate the two radically different operating speeds.

Small gas turbines are efficient and powerful. They are ideal for producing thrust, but ground vehicles operate using torque rather than thrust. The turbofan engine in the Tomahawk cruise missile is 12" in diameter and about 48" long, and it weighs less than 150 pounds. This engine can produce 600-700 pounds of thrust. In the missile, this amount of thrust is equivalent to about 1000 horsepower.

Williams International, which produces these engines, was founded by one of the engineers who worked on the Chrysler turbine cars in the 1950s.

http://en.wikipedia.org/wiki/Williams_International

http://en.wikipedia.org/wiki/Williams_F107

 

[chhitiz]

what about radial turbines? wouldn't they generate more torque than thrust? also read somewhere that radial turbines are better at lower speeds.
can anyone give more details on transmission design of turbine powered cars and motorcycles?

 

[MisterDynamics]

Back in the 1950's, Chrysler implemented a Turboshaft driven car which used a powerplant similar to the Allison 250 C-30 Turboshaft Engine.

Like with any heat-of-air-compression engine whether piston (diesel) or turbine (kerosene) there needs to be an external oil cooler since the extreme internal cylinder (or burner can) pressures & temperatures would literally congeal oil in closed engine lubrication system.

The advantages of a Turboshaft powerplant to power a car is the top speed and overall power-to-weight ratio is much higher than it would be with any type of piston driven car. At continual high speeds a Turboshaft driven car would also operate much more efficiently than a piston driven car. There is an enormous amount of torque in a Turboshaft Engine and its peak torque curve RPM range is quite wide at its gear reduction final drive output. Also a Turboshaft driven car would have a much higher top speed than a piston driven car.

The disadvantages of a Turboshaft powered car would be that the throttle response would not be as instant as it would be with a piston driven car. It also would probably would be more noisier than a piston driven car unless some type of acoustic cancellation structure was implemented to minimize noise output. The time it would take to accelerate to speed also would take longer than with a piston engine.

There are many reasons why Gas Turbine Turboshaft Engines have been used and not used in automobile applications. In the present day (2014) there have been a great many advances in computer controlled machinery, advanced materials, an increase in practical efficiency and reliable management of highly complex mechanical & electronic systems.

Because of this, it might not be a bad idea to re-implement Gas Turbine Turboshaft Engines back into automobile applications.

Fast start up time, throttle response, advanced materials to handle heat & pressure and practical light-off with few if not any flame-outs all could be achieved in this day and age. Also the thermal efficiency is far greater in a Turbine Engine Core due to the extremely high compression ratio and heat-of-air-compression pressures which would maximize fuel efficiency and permit more miles to a US gallon of Kerosene than with much lower compression higher volatility Gasoline Piston Engines.

Some think that Gas Turbine Engines and many other more thermally-efficiency powerplant technologies have not made a come-back into automobile applications due to the oil companies suppression of such technologies. Since most if not all major manufacturers have a majority of their stocks owned by oil company investors. So why wouldn't the oil companies suppress or stop funding any type of fuel-efficient (or fuel-less) transportation technology that would not allow them to sell more oil?

Although others disagree and posit that gas turbine engines just operate at way too high temperatures and aside from on aircraft, commercial ships and isolated electric power generation they are a potential safety liability for automobile applications to operate within the general public.

Whether or not Turboshaft Engines on automobile applications were suppressed by oil companies ownership of all major manufacturer's corporation stock or that they are safety hazards when implemented on cars is subject to debate and deep analysis.

But one thing that is certain about Gas Turbine Engines is that they are far more thermally-efficient than Four-Stroke Diesel Piston Engines and Four-Stroke Gasoline Piston Engines due to their extremely high compression ratios. Most of the (Kerosene) fuel injected into a Gas Turbine Engine or around 68% is returned back into usable power.

Gas Turbine Engines are between 68% to 70% Thermally Efficient usually powered on Kerosene (JP4 Jet Fuel).

Gasoline Four-Stroke Piston Engines are 33% (or less) Thermally Efficient.

Diesel Four-Stroke Piston Engines are 42% (or less) Thermally Efficient.


Regards,

- MisterDynamics -

January 08, 2014

 

[kevindeschamp]

The Abrams military tank is a practical application of the turbine engine. The roots of the Abrams tank started with the Chrysler turbine car. The biggest drawbacks are fuel economy, cost, and emissions.

 

[Shaun_W]

There is also a safety issue here. What happens if a fan disk fails? We tolerate this with aircraft because the risk of it happening is low, there aren't many flights per day relative to car journeys, and planes spend most of their flight away from other planes and people. This means that the event of a fan disk escape is very small, and if it does happen then it's not likely to be near other people.

But it's a different story with cars, which are used much more frequently and in much closer proximity to others.

 

[MisterDynamics]

Correction: The Thermal Efficiency of Gas Turbine Engines is between 30% to 40% at the most. Right around the same for Gas Piston Engines. The larger Gas Turbine Engine cores are closer to 40% Thermal Efficiency.

Most of the heat energy of any combustion engine extracting heat energy from the BTU/Lbs heat energy content of hydrocarbons and fossil fuels plus the heat of air compression converted into mechanical and electrical power is lost out of the exhaust making their thermal efficiency quite low.

Thermal efficiency decreases even more regarding heat engines especially when they move vehicles requiring more power to overcome aerodynamic drag and rolling resistance & planar resistance (land vehicles & watercraft).Regards,

- MisterDynamics -

April 10, 2014

 

[dmsasso]

What about using a small turbine set at a constant speed as a generator and the propulsion of the car was done by electric motors. Like the Chevy Volt only a small turbine would be way more efficient than a piston engine.

 

[elbrownos]

I don't know where you're getting the idea that gas turbines are efficient, they're not.
Small ones are especially inefficient.
Gas turbines have several advantages:
- Very high reliability / low maintenance
- Very high power to weight ratio
- Very high maximum power
- Low capital cost per MW output
The main uses for gas turbines are in aviation and power generation.
Aviation uses gas turbines for their high power to weight ratio.
Power generation uses gas turbines for their high reliability / low maintenance, high maximum power and low capital cost.
There is absolutely no reason to use gas turbines in cars. Piston engines are cheaper, more efficient, have better throttle response... basically everything that matters.

 

[dmsasso]

Thank you for your reply. I was always under the impression that once you had a turbine spun up and running at steady rpm that they were very efficient source of power. I appreciate the explanation.

 

[elbrownos]

No problem.
Gas turbines have their niche. For power generation, they can't be beaten when run at high load (max effienciency) in combined cycle (with a steam turbine utilising the exhaust heat). Overall efficiencies can now exceed 60%.
A small gas turbine in simple cycle (no steam turbine) run at varying load will have much poorer efficiency than an ordinary car engine.
I don't believe we will ever see gas turbines in production cars. Pure electric cars have too many advantages.

 

[dmsasso]

Thank you for your explanation. I appreciate the insight.

 

[rcgldr]

A company called marine turbine technologies converts "retired" turbine engines for usage on boats and during 2000 to 2005, for motorcycles (the bike being called the MTT or Y2K), running the turbines on diesel or jet fuel A instead of kerosene. It makes more sense for performance boats which are often run at near constant high speed, where the turbines are running more efficiently.

 

[dmsasso]

thank you for the info.

 

[jlefevre76]

First, let me just point out that tanks actually use turbines as powerplants ( the ones that don't use Diesel cycles).

However, for your average commuter car, that would be impractical for a number of reasons.

1. Scaling down turbines changes the Re number, among other things, they don't scale down very well. The efficiency advantage they yield is usually lost when they are scaled down.
2. Turbo machinery required complex parts. For instance, as many on this forum can attest, turbine and compressor geometries can get very complicated. More moving parts, throttling is a problem (in terms of controlling power output), higher powered fuel pumps (to offset combustion chamber pressures), and probably a whole lot of other things related to the increased complexity. This also increases cost (both for purchase and maintenance), which is typically the driving force behind consumer and society's habits.
3. Probably the biggest problem would be this: air intakes would scoop up small animals and shred them to pieces. They would then come out the exhaust system and splatter on the windshields of following cars. This is much more objectionable to simply flattening them on the road, as conventional automobiles currently do.

 

[dmsasso]

Thank you for your concise and humorous answer

 

[dmsasso]

I appreciate the reply but I was not thinking of the turbine being the direct drive train for the car. I was wondering if a small turbine would be a better generator of electricity than an internal combustion engine. My thought was to use it in an extended range electric car. The turbine would provide the electricity for an electric motor. Does that make sense or would it be less efficient than a piston driven generator?

 

[thiru]

^^ In the recent times, based on the electric - turbine hybrid concept, Jaguar made a prototype super-car called C-X75.

Introduced in 2010 Paris motor show, it was touted to go into production in 2015ish but it was canceled later.

 

[Aerodave]

The main reasons turboshaft engines aren't used are as follows:They are crazy loudThere is relatively slow throttle responseThe difference between engine shaft rpm and wheel rpm is quite large.Due to advances in technology since it was tried decades ago, it is more possible and these factors can be mitigated. However, Lockheed Martin have a sort of prototype that kinda works.Noise can be reduced but it would still be quite loud.Modern electronics and control systems would allow the throttle lag to be reduced.The difference in rpm can be mitigated with either a free power turbine or hydraulic coupling. The use of reduction gears could also reduce rpm and increase torque (this is why a turboshaft engine was used in the m1 Abrams, tanks need lots of torque).I fully believe it is possible in regards to a practical solution. However the automotive industry has been built around piston engines. Changing doesn't give enough advantage to completely rethink the industry. For now gas turbine engines will have to remain in tanks, boats and aircraft.

 

[abledoc]

With the rise of hybrid cars, the small size and weight of gas turbines and the ability to accommodate diverse fuels such as CNG or liquid fuel, gas turbines should be reconsidered. Throttling is no longer needed when all you are doing is run a generator.

 

[newbie science geek]

What if, radial gas turbine with advance material and 3d printing to lower the weight and more strength to accommodate higher compression, coupled with torque converter to directly deliver the output (much simpler and lightweight than reduction gears) and an electric motor to mitigate throttle lag and make hybrid system.

I think with more recent technologies, the use of gas turbine is more possible.

 

[anorlunda]

It is certainly true that 3D printing and materials science can lead to higher performance turbines. General Electric is doing that for aircraft turbines as in the GE90 engine.

https://www.ge.com/additive/additive-manufacturing/industries/aviation-aerospace

However, GE has deep pockets and a multibillion dollar market to sell into. I suspect that the high development costs may put it out of economic reach for automotive uses. I also suspect that the technology of the GE90 can not be scaled down simply.

But the really big factor is that turbines require fuel. Hydrogen is not easy to do on a car. Fossil fuels are very much out of favor (to understate it). Development dollars are attracted to electric vehicles.