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[beelsebob]

No it's not constant at all – increased thrust means more mass is going backwards to generate that thrust. If thrust wasn't involved I would agree.

Mass conservation anyone?
You can't have more mass, you can have more impulse.

But you certainly can move more mass... Or are you trying to assert that a jet engine that's off moves as much mass as a jet engine that's on?

[timbo]

No it's not constant at all – increased thrust means more mass is going backwards to generate that thrust. If thrust wasn't involved I would agree.

Mass conservation anyone?
You can't have more mass, you can have more impulse.

But you certainly can move more mass... Or are you trying to assert that a jet engine that's off moves as much mass as a jet engine that's on?

You suppose to inject fuel in radiators?

[gridwalker]

The expansion ratio of jet fuel as it combusts is MASSIVE when compared to the expansion ratio of hot air alone. The heat produced through the combustion process is not solely responsible for the expansion, but the fuel's change of state (liquid-gas) and the subsequent chemical reaction as the fuel ignites is what creates most of the thrust : heat is just a happy byproduct.

Expanding air by using radiated heat will certainly increase the volume, but there is no state change that will produce the violent expansion required to produce any significant thrust or through-flow induction (at least, not within the turbulent environment experienced on-track).

Comparing the thrust potential of these two processes is like comparing a hand grenade to a molotov cocktail.

[beelsebob]

But you certainly can move more mass... Or are you trying to assert that a jet engine that's off moves as much mass as a jet engine that's on?

You suppose to inject fuel in radiators?

No, there are more ways of heating the air than burning something in it.

[beelsebob]

The expansion ratio of jet fuel as it combusts is MASSIVE when compared to the expansion ratio of hot air alone. The heat produced through the combustion process is not solely responsible for the expansion, but the fuel's change of state (liquid-gas) and the subsequent chemical reaction as the fuel ignites is what creates most of the thrust : heat is just a happy byproduct.

Expanding air by using radiated heat will certainly increase the volume, but there is no state change that will produce the violent expansion required to produce any significant thrust or through-flow induction (at least, not within the turbulent environment experienced on-track).

Comparing the thrust potential of these two processes is like comparing a hand grenade to a molotov cocktail.

Yes, but as you will see from the discussion a few pages back, this process can and does create (limited) thrust. And once thrust is involved, more mass is moving, which is what ringo was commenting on.

[raymondu999]

But you certainly can move more mass... Or are you trying to assert that a jet engine that's off moves as much mass as a jet engine that's on?

You suppose to inject fuel in radiators?

No, there are more ways of heating the air than burning something in it.

beelsebob; I think the point Timbo was trying to drive across is that you can't introduce more mass into the air - what you take into the intake will still equal the mass of the exhausted gas; rather than a change in temperature.

[beelsebob]

No, there are more ways of heating the air than burning something in it.

beelsebob; I think the point Timbo was trying to drive across is that you can't introduce more mass into the air - what you take into the intake will still equal the mass of the exhausted gas; rather than a change in temperature.

Yes – which was my point – by generating thrust, you will not only chuck more out the back, but also suck more in the front – which will allow you to shrink radiators potentially.

And... we're back to where this discussion started.

[raymondu999]

I kind of see where you're going there. If you can accelerate the thrust; you'll create a vacuum which *should* suck more in. Is that what you're getting at?

[beelsebob]

I kind of see where you're going there. If you can accelerate the thrust; you'll create a vacuum which *should* suck more in. Is that what you're getting at?

Yes.

[gridwalker]

Beelsebob, the important word (which I should perhaps have put in bold) is significant : we would be looking at thrust being produced which is proportional to the expansion ratio and total mass of air that is expanding.

How much air will be drawn through the radiator and how much will it expand? I don't know the maths, but I floated the idea past a contact at British Aerospace last night and they found it more than slightly amusing.

The temperatures required to produce significant thrust from air expansion alone are simply ludicrous, and are such that they could never be reached in a formula one car.

I think that the best example of a heat-induced jet engine (which operates without introducing additional expansion material into the air stream) is the little-known and ill-fated nuclear ramjet : http://en.wikipedia.org/wiki/Project_Pluto

This type of propulsion is still being experimented with on a smaller scale (for use in unmanned drones) but I doubt similar effects can be achieved using waste heat from a simple combustion engine.

[timbo]

I kind of see where you're going there. If you can accelerate the thrust; you'll create a vacuum which *should* suck more in. Is that what you're getting at?

Yes.

You gotta drain energy somewhere or it's a perpetuum mobile description

[Shakeman]

Anyone know where the air from the radiators is exiting?

The exit at the back of the engine cover was, or appeared to be, sealed off yesterday.

I can't believe there would be any thrust from radiator heating and there is more to be gained by making the exit of this air as easy as possible, hence MW's comments re: internal aerodynamics.

But where is the exit for this air?

[raymondu999]

Maybe they integrated that into the exhaust bulges?

[beelsebob]

Beelsebob, the important word (which I should perhaps have put in bold) is significant : we would be looking at thrust being produced which is proportional to the expansion ratio and total mass of air that is expanding.

How much air will be drawn through the radiator and how much will it expand? I don't know the maths, but I floated the idea past a contact at British Aerospace last night and they found it more than slightly amusing.

As you can see from earlier in the thread, this effect can generate reasonably significant amounts of thrust – enough to increase plane top speeds by a good chunk... There does seem to be some debate over whether it will have a significant effect at low speeds though. I'm not certain, and haven't claimed to be certain, but it sure is an interesting avenue of discussion.

The temperatures required to produce significant thrust from air expansion alone are simply ludicrous, and are such that they could never be reached in a formula one car.

Again – there are planes that do this simply with the radiators from their engines, not even using the temperature of the exhaust manifold.

[kalinka]

You gotta drain energy somewhere or it's a perpetuum mobile description

I think they (including me ) think that air from the radioators is heated by circulating it around hot exhaust pipes, and there is your added energy. Where it exits is another question. Personally I'm not convinced that this energy is enough for their purposes, but who knows...

@belsebob > exactly ! - still not convinced. If you get it wrong, the heated air could form a high pressure zone behind the radiators, thus preventing the proper cooling. The exit route of the haetad air must be cleverly designed to be to least resistive exit.