Why not a turbine powered hybrid car similar to an aircraft APU?

Question

Ok so with all of the inefficiencies of the reciprocating internal combustion engine why don’t they make a hybrid car powered by a small centrifugal turbine that would work like an aircraft APU. The car would have an all electric drive system and the turbine would produce electricity for the electric motor. The FADEC computer would control fuel flow to the turbine as more power was needed. Trains have been doing this for decades so why not cars? A plus would be that you could use any liquid or flammable gas for fuel.

Ok you missed the piont it is an electric car not driven directly by the turbine but buy the electricity produced by a generator connected to the turbine

A single stage centrifugal flow turbine could be machined from a single piece of metal using computerized tools so it would be less complicated to manufacture than an internal combustion engine

I would not consider using and actual aircraft APU I was thinking of something about the size of a turbocharger or maybe a little larger but similar in function to an APU

Get the car moving using battery power then use ram air to help spin up the turbine

Answer 1

As turbines get smaller, they get less efficient.
A 500hp PT6 turbine used .58 lbs of fuel per horsepower per hour, and the engine of an SUV gets about .55.
A 300hp turbine uses about 1lb for ever hp per hour, and a 130hp turbine uses about 3lbs per hp per hour.
There are some cheap turbine engines out there that use parts from turbochargers, but they use nearly 10lbs of fuel for every horsepower they produce per hour.
Those little jet engines in models use a ridiculous amount of fuel for the power they produce, some consume 15 gallons and hour to make 0.8 hp.

Answer 2

Turbines are not any more efficient than a reciprocating engine. They are just much lighter for the power they produce. Weight is not as much of a factor in a car as it is in an airplane. Turbines are also much more expensive, so you'd need a huge increase in performance or economy to justify the cost. Trains may be using them but a train has a fairly constant power demand. A hybrid car is shutting off the engine on a regular basis. This leads to the other problem with using a turbine, they take a fair amount of time to start and stop. They run at very high RPM and temperatures, so you can't just turn it on instantly, you have to spend time and fuel getting it running. There is also a lag of up to one second between power demand and power delivery on a turbine.

The reason large aircraft use turbine APU's is because they already have jet fuel on board and just need enough juice to get the big turbines going. After that the APU is no longer needed.

In the case of a hybrid system a reciprocating engine is actually better, it plays to the strengths of the engine.

Answer 3

Might be a good idea but it would have to be a lot of changes to work in a car.

First is the high pitched whine of a turbine and the loud rocket noise. You would need more than a regular muffler to suppress the noise. Regular cars now days are almost as quiet as electric cars so they would have to make it at least as quiet.

The piston engine in a hybrid isn't on all the time, it starts and stops as needed to charge the batteries and they start in less than a second and using very little electrical power. Turbines started by electric starter take a long time to spool up fast enough to start, then they have to power up a glow plug or igniter to light the compressed fuel. It'll probably take up to 30 seconds to start it and bring it up to speed. This takes a lot of electrical power that the turbine powered generator has to replenish.

If they overcome these things turbines could be a good alternative to the piston engine. The initial cost would be higher but the maintenance would probably be a lot lower because there's less moving parts, it's air cooled, so no radiator or coolant, the oil lubricates only the bearings not the cylinder walls where the viscosity break down and contamination come from.

Piston engines are easier to make because of the bigger tolerances they can get away with and therefore will be cheaper to make which is the bottom line. Money.

Answer 4

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Personally, I think that is a pretty good idea. The Rover turbine car was made in 1950 and was merely experimental. Chrysler also made almost 100 turbine cars and actually had some of them in use by the general public. The problems that were experienced all had to do with the fact that they were directly coupled to the drivetrain (low starting torque, idling problems, etc.). The idea posted here is to use the turbine merely as the generator to produce electricity for the electrical motors that would run the car. There would also have to be some batteries, like in current hybrids, to handle the transient starting conditions, but mostly the electricity required would be sent straight to the motors. This would solve all of the problems of the initial prototypes. The reason that I think this is not really being pursued is because it is still a combustion process. Everyone is focusing on hydrogen or an all electric solution because these are perceived to be cleaner.

Answer 5

I remember hearing about a turbine powered car I think it was Ford in the 60's or 70's tried it out. As memory serves there was a problem with the turbine blades being TOO fragile because of the size and the materials being used. Also there was a big problem with foreign object damage (FOD) being that it was a car sized vacuum cleaner, I guess the roads would be VERY clean if we used that type of tech.

I've think it was VW that used the electric drive you suggested but with a diesel engine driving the genset on a concept car. As far as I know the system worked well but was never put into production. I've heard that the Toyota prius uses the gas engine to power the electric motor but I haven't looked at the tech.

Answer 6

A car being driven by the power generated by a small turbine would not have the acceleration problems like a purely turbine powered vehicle, and it could use the traction motors for dynamic braking and power recovery, however....

While the gas turbine has excellent power to weight ratio, it is NOT as efficient as a piston plant (it is nowhere even close). A turbine burns way more fuel for the power it produces. It also costs more to produce and creates much more noise.

As far as I know there were only a few turbine powered trains and none were very successful. The major obstacles to turbine trains were high fuel costs and high maintenance costs. These would be even greater obstacles to overcome for cars.

Answer 7

An APU would be far too powerful to waste driving a generator. Probably use more fuel than a petrol engine anyway.......
But, those small jet engines which are now found on Radio Controlled model A/c could work, driving a generator....... which would also need some form of capacitor to store power that is needed rapidly.
There must be a reason why, otherwise somebody would have done it by now.
If it were to charge batteries, then they need to be as big as the car to be any good. Present electric cars are a sham, and are unsafe (The G Whiz for example).

Answer 8

Turbine engines scale awfully towards the low power end. From a physics point of view I would guess that it all comes down to combustion time, adiabatic expansion time vs. speed of gas going through the turbine and physical size of the turbine. It is also extremely hard to make efficient axial (and even radial) compressors because the losses at the rim of the fans dominate. Not to mention the nightmare of changing load and/or rpm on a gas turbine. So unless you are planning on a hybrid car that can go at close to the speed of sound, just forget about it. Not to mention your difficulties to survive the NOX test... gas turbines are not nearly as clean as modern ICEs and a catalytic converter for 10MW power output is still rather large (the size of a bus, I would think). Nothing that can go into a normal garage, for sure. Like many ideas which sound great in the shower, this one stinks as soon as you look at reality.

Answer 9

Turbines get very inefficient when small, and they tend to be narrower range of power at which they are efficient, and they have very high RPMs....

On plus they are very light and in aircraft light is big deal as it takes energy to resist gravity. Aircraft also have more steady power demands and larger engines.

For a hybrid car they are being considered as "range extender" for a mostly electric car... eg have a system that mostly works off battery and occasionally uses battery and the light weight is more important than the efficiency.

Answer 10

Aircraft Apu For Sale

Answer 11

They have used it in the M-1 Abrams and works reasonably well in its role.

However in civillian use, it wouldnt be of much benefits. To start with, the fuel efficiency will be hit, GTs are usually run at operating speeds, not much scope for idling. Starting up will be a long process (starting the M1's GTs takes more than 10 gallons of fuel), diffusion of the jet efflux and sound control would be engineering nightmares.

In return what you get is high reliability, flexible fuel and good power to weight ratio. As of now reliability is pretty good in reciprocating engines and benefits of power to weight ratio is not so pronounced in a road vehicle. Economy, sound control and exhaust control are the ones that makes the GT quite unsuitable for a car.