Cars Gas Turbine

You will find HERE some dope on gas turbine cars.

Added weight and the need to seal both ends of the tube are two drawbacks I see.

Hitting a bump in the road could hause the whole tamale to expolde.

Thanks

I thought about some general explanation like you explained, but wasn't sure about it!

Actually it has nothing to do with sealing issues. Most turbine engines use a "fir-tree" design to attached the blades onto the turbine disc. The blades cannot be connected with a tube because they expand and contract with changes in temperature. The "fir-tree" design allows for expansion and contraction of the individual blades but also keeps them in place when subjected to high centrifugal forces.

There's more to it but those are the basics.

We've built a few machines to assembly some of these turbine discs and blades. You would be surprised as to how "loose" the blades really are when installed on the disc and in their free state. They "tighten up" during high speed rotation.

Actually that is not the reason that they are not used in cars.

They have been used in some experimental cars, Rover for example many years ago developed over many years street and racing cars.

Look here for more details:-

http://www.rover.org.nz/pages/jet/jet5.htm

The Rover Jet 1 from 1950, set a world land speed record of 150MPH for a Turbine car.

The main reasons were that the power band of a turbine is a) a bit tight and b) power turbine revs exceedingly high c) Fuel consumption was also relatively high as well........

How did these cars behave? Graham Robson describes his first (and only) drive in a T4...

"Starting drill is simple but drawn out - turning the key actuates the special Lucas starter motor which winds away for several seconds. A faint, distant whine rises in pitch and intensity before light-up occurs and the engine settles down to 'idle' at 35,000rpm. This is enough to cause the car to creep along the road if the brakes are not applied, as there is about 4bhp residual at idle. To get moving engage forward gear and depress 'loud pedal' - after a jet lag of about 3 seconds, the engine speed rises rapidly to 50,000rpm and the car whooshes off up the road leaving engine noise behind (although this is quite acceptable to passers-by). 60mph is reached in 8 secs (a la 3500S) with very civilized handling"

The RN used a modified Rover Turbine in an extremely efficient emergency fire water pump that could be carried around the ship by 4 men and supplied huge amounts of water at a very good pressure. We used to clean them using powdered walnut shells if I remember correctly, while running!! I was fascinated......

This was a similar engine to the various cars described above....

RN Turbine Fire Pump Starting Sequence

Again Starting One!!

http://www.youtube.com/watch?v=nMZvTLcwy0c&feature=endscreen

I hope this was of interest to all concerned, sorry if it was not!

Interesting, but I fails to address the question at hand. It's not about why aren't they used, it's about altering the design of the turbine to incorporate a tubular ring into the fan.

That has already been answered, not by me directly, its a completely bad idea, which is why nobody has done it....

I answered with the real reasons why they were never popular, not to do with the tip clearance.....and a bit of pertinent extra info....

You don't have to like it.....

Az Native directly asked the question,

"...what is the reason that the rotor blades tips are not attached to a tube that will rotate with the rotors [there will be no gap between the rotors and this tube!]..."

How did the use of gas turbines in cars ever become part of this thread?

........as an interesting aside by showing that a large motor corporation invested around 15 years of development, before giving up the idea completely....

Showing that the idea of a turbine driven car is not new.....and providing for some some interesting reading. There is no requirement for everyone to read it though. If you don't like it, don't read it!!!

Here is the OP's original post slightly shortened:-

I know that utilizing gas turbines for cars, or even trucks is inefficient, mostly because of hot gas leakage in the gap between the rotor blades tips and the housing. [the inner tube] of the turbine, what is the reason that the rotor blades tips are not attached to a tube that will rotate with the rotors [there will be no gap between the rotors and this tube!],to avoid gas leakage?

This demonstrates clearly that the OP is of the wrong opinion as to why car gas turbines are seldom used.....the tube idea is also as inefficient/impractical as many have shown here, including yourself!

Note that you are the only "complainer" as well.......does that not tell you something too?

Have a great day anyway....

I get it Andy. No need get your panties in a bunch. Your posts corrected the OP's incorrect assumption as to why turbines are not used in cars, while Lyn and I responded directly to his question about the design of the turbine.

I'm not complaining about anything. I really don't give s!%@ if the threads go off topic or not. I was just asking the question as to why?

Typically a poster will ask a question so I will try to respond to the question and not elaborate on the back story.

It's the weekend Andy...chill out!

You may be upset, but I am the Cool-Man himself......

I can swear on the Bible, that nobody from CR4 has ever upset me, none are clever enough!!! and I would not allow myself to react badly anyway.......

Don't ever judge others by yourself.......

Oh, by the way, you do not make the rules about what we write, ADMIN does to a degree.....do not forget that!!!

1- "You may be upset" - No I'm not. Did you see the happy face ??

2- "...nobody from CR4 has ever upset me, none are clever enough!!!" - Congratulations, I'm happy for you.

3- "Don't ever judge others by yourself" - I never do.

4- "you do not make the rules about what we write" - Write whatever the f%!* you want Andy !! Like I said, I don't give a s%!*. I never did!

Cheers. _{(let's move on shall we?)}

I agree, we should:- _{(let's move on shall we?).}

_{But why did you stop there in the first place?}

Cleverly, you have pointed out the real problem, you see CR4 posting as a contest to win or lose. (you are not alone, sadly! There are a few others around).

But most here are here for the humor, to help others and to learn from them as well. No contests.

I am one of those, I don't see it as a contest either. I also believe we are here to help each other with our knowledge and experience.

If English is your primary language, then its worth while in getting the grammar and spelling correct to help others not so lucky, to understand you fully. We are truly international.

If you decide to change your viewpoint on it being a "contest", then things get far better here for everyone, especially you yourself.

Have a great day and "see" you soon I hope, as I don't bear grudges either.....

I think the reason they would not attach turbine blades at their outer most parts would be because then there would be no room for the blades to expand lengthwise when they heat up. They would buckle and distort. Also, the shape of the blade changes a bit depending on the load, and this engineered change (as small as it is) would be negated, possibly resulting in catastrophic failure at the outboard root.

Now I will go out on a limb, and make an oversimplified statement which was used to me when I asked why the gaseous fluid doesn't simply go around the outside edges...."The tips of the turbine blades rotate within the boundary layer of the gaseous fluid, and this boundary layer prevents gasses from finding their way around the end". I personally think this explanation is a crock, but hey...its what they told me. I think the air doesn't leak around the turbine tips because it is dragged around in an eddy by the blades....

Which come to think of it they would both be a form of secondary flow.(google that!) (boundary flow in turbines is funny stuff....I don't THINK it is black magic. But I also don't think a lot of people really understand it. My old Sergeant's eyes would glaze over as I explained about how foil bearings in the APU worked. Probably because I would confidently state a line like the one above as if I understood what I was talking about.)

And we are now moving out of my area of expertise....grin! Anybody with a better explanation?

With modern, much more sophisticated gas turbines available now, there should be no good reason for not using them in hybrid vehicles.... so AZ, there is still hope!

Your explanation is as good as any that I have heard or read.

The distance between the blade tips and the sides of the turbine are kept tiny in proportion to the size of the blades, surely at worst, only a tiny, minor drop in efficiency?

It would be great if there is a Gas Turbine Engineer some where here to help us.

I can't buy into the thermal expansion theory. If made from the same material, and exposed to the same heat, there's no reason that the outer ring would not expand outward in proportion to the rest of the turbine blade.

It would grow at the same rate.

Just my opinion.

I think that what Yusef is refering to, is that the inner tube will be not exposed to the heat levels of the blades.

So-I think that the question is what temperature differences will there be?

Are not the blades now ceramic on some engines at least in the "hot" bit?

Of course, and that's what make the turbines so expensive!

Millions upon millions of dollars in research and development are what make gas turbines expensive. It's not because of the blades. Just to be a little more precise...the blades are coated with ceramics. The blade itself is still a metal alloy. There are no solid ceramic blades in production yet that I know of. Do you know of any companies who succeeded in developing a solid ceramic turbine blade?You seem very confident about it. It would interesting to know.

The hot and cold zones in a turbine are carefully created....there will be differential heating. I don't know how you could avoid that. But maybe it could be corrected for in the design.

More to the point, I suppose, is that the outer ring would either need a huge bearing of its own, (a foil bearing would be best) or there would be clearance between the outer shaft and the wall which would result in the same "leakage" around it that blade tips would have. Such a ring would result in some odd gyroscopic effects, would provide a different balancing problem, and there would be something else to catastrophically collapse explode in the event of a bump or collision. Flywheel effects would also need to be considered. And it would be the very devil to mill. OTOH, it is perfectly do-able.

The honeywell wind turbine uses an outer ring...in which they mount magnets. It might be a stretch to apply the same engineering to a gas turbine or a steam turbine, or even a multi stage wind turbine (something else I have never seen but this link shows some promise.)

On a tangent (which I always seem to end up on) idea, aircraft control surfaces created by jets of air coming out of slots are used now with some success....I wonder if you could make "virtual" turbine blades out of slotted jets of ram air. No upper speed limit...no dangerous flying blades...no birds blowing up engines. Half the weight or less. Gravel runways and hail/ice not a problem. Downside? Nobody I know has ever done any research on the topic and I don't know if the idea has legs. But...could you imagine!!!!!!

We live in an incredible age!