31 replies to this topic

[Amadeus]

Hi - This was inspired by an earlier thread and Xmas spirits so please ignore it if it's a totally stupid idea ;)

There is a lot of talk about how much drag is generated by radiators. But isn't aero downforce just controled drag? In other words if you shaped the cooling fins etc corectly in the radiators could you generate downforce?

[perfectelise]

Nice idea
Don't know how fast the air flow is through the radiators as a percentage of the cars air speed.
I still think that some of the advertising on the car's body should make way for a radiating surface (exposed smooth surfaces of water circuit painted matt black) even if this represents only a few % of normal radiator surface area.
perfectelise

[Ali_G]

Perfectelise: While a black surface may give off heat faster it also attrats it better. On a warm day it would cause some serious overheating problems. THe best colour that an F1 car can be is white.

I can't see how a radiator can transfer drag into downforce.

For a start there needs to be suficient space of low area for any bit of downforce to be created.

The only reason a wing creates downforce is that its creates low downforce between the car and the ground. But creating low downforce between two parts of the car is useless.

Niall

[perfectelise]

OK so it would need to be something more sofisticated than black paint.
There are coatings used on solar water heating collectors that absorb much more than they emit; we need the reverse.
A wing in clear air can create downforce without any ground effects - Amadeus is talking about shaping the elements of the heat exchangers (radiators) to act in a similar way to wing elements.
The air flow would force the radiatiors, hence the car, downwards.

perfectelise

[Ali_G]

Perfectelise: Yes but you would need a certain distance beneath the wing.

Take for example a wing postitioned directly above a sidepod. Wouldn't a low pressure area between the wing and side pod just suck the sidepod cover towards the wing and the wing to the sidepod cover.

Can anyone clear this up.

Niall

[Amadeus]

Quote

Originally posted by Ali_G
Perfectelise: Yes but you would need a certain distance beneath the wing.

Take for example a wing postitioned directly above a sidepod. Wouldn't a low pressure area between the wing and side pod just suck the sidepod cover towards the wing and the wing to the sidepod cover.

Can anyone clear this up.

Niall

Q: If a truck is full of caged birds is the truck lighter or heavier if the birds are flying as opposed to on the perch?
A: There is no difference - the downthrust of thier wings is equal to thier body weight, so the truck weight remains identical.

Now transfer that to the rads - a low pressure area may create downforce on, for example, the sidepod, bot that still foces the car down onto the track because pressure is pressure. You have a point about the elements sucking each other together but it's not an issue at the mo, when a rear wing element is over the rear body it doesn't pull the rear to it after all.

[colejk]

Quote

Originally posted by Ali_G
Perfectelise: Yes but you would need a certain distance beneath the wing.

Take for example a wing postitioned directly above a sidepod. Wouldn't a low pressure area between the wing and side pod just suck the sidepod cover towards the wing and the wing to the sidepod cover.

Can anyone clear this up.

Niall

Well, we're talking about downforce, not ground effects.
Any curved (concave) surface facing upwards (you all know what I mean) will be pushed lower and also create a certain amount of drag and downforce. This is actually quite a smart idea. It makes good use of another exposed surface. (the rad fins) with all the recent talk and new regs restricting wing size and numbers this idea is a good way of compensating for the lost wing space. But I think the teams have already figured this one out as a few have air exits out the tops of the sidepods if I'm not mistaken so I'm sure the air gets channelled in some form.
Now along the lines of another thread regarding exposed areas on the sidepods to dissapate heat, if this idea was to be implemented with the upper surface of the sidepods being shaped with a smaller rad opening this could make better use of the whole sidepod.

[Ali_G]

Aren't those vents to help with the cooling of the engine in the car.

Niall

[Jhope]

Patrik Head once used on-board Venturis, but realized that they were a packaging nightmare. The rads and other computer peices were just too hard to place anywhere else. Head did ay that they created a significant improvement, but in the end, not enough to further research.

[Yelnats]

A few calculations (on the palm of my hand) indicate that a single F1 radiator has about 75,000 cm sq of surface area. This is about the same as the entire entire top surface of an F1 car so in effect the entire surface of the car would have to become a radiator. This of couse is impossible with any reasonable weight limit so perhaps this is why Brabham failed miserably when they tried this a few decades ago.

A better solution would be to use a heat pump to raise a specialised cooling fluid to about 400 degees celcius. This would reduce the radiator area requrements to a managable size and perhaps allow a hot wing to do the job. But internally a large rad/heat exchanger and pump would be required so I can't see this being a practical solution either.

If lubricants were improved or eliminated by the use of low friction surfaces in piston, bore and valves then coolant temps could be raised by several hundred degees celcius. This would allow surface cooling to function with much smaller areas. But with F1 regulations clamping down on innovative technologies, I can't see this solution coming to the fore either.

[Ali_G]

Yelnats: As Desmo pointed out to me before some parts of the engine rely on lubrication for both lubrication and for cooling it. Try the thread
http://www.atlasf1.c...?threadid=12136

It deals with the problems of removing a lubrication system.

Niall

[desmo]

It occurred to me that this very issue had been addressed in an old Racetech mag I had.

Now assuming that our 800bhp F1 engine is one third efficient at transforming the fuel's energy into torque, then we have something like 1600bhp of energy that must be lost as heat. That's quite a lot! This energy can, apparently, be tapped into as thrust, likely vectored as downforce.

I refer you to page 55 of issue 17 of Racetech for the maths, but the author Mike McDermott calculates that roughly 1.6% of the heat energy is available as thrust. That being 3.2% of the mechanical energy we are looking at ~25.6bhp available as thrust at 135mph which would more than double at 200mph.

McDermott from Racetech:

"You deserve to get some downforce in exchange for the inevitable drag caused by decelerating the air in the first place, and then not recovering the pressure. The duct must be designed to slow the air efficiently to a very low velocity (with correspondingly raised pressure determined by Bernoulli's equation) at the radiator- as it usually is for minimum drag. The air must be turned upwards and by careful duct design the pressure gain, after being further increased by radiator heating, is recovered by being converted to velocity."

He goes on to state that potentially more thrust is available if you can energise the flow through the duct with the addition of heat from the exhaust.

"Arranging the exhaust system to heat the air would help. If the exhaust gases are cooled in the process that is no bad thing. The viscocity of a gas falls with temperature so, the cooler the exhaust gases, the lower the back pressure- but not that much lower. The ramjet effect shouldn't be confused with pointing the exhaust pipe exit backwards to get thrust. That mass flow, being only the air breathed for it's combustion needs by the engine, is much smaller, typically no more than 5% of the radiator airflow."

Now the numbers are admittedly not huge but given the difficulty of getting even tiny incremental gains in lift/drag ratio, any little bit could be worth persuing.

[Richard Border]

Quote

Now assuming that our 800bhp F1 engine is one third efficient at transforming the fuel's energy into torque, then we have something like 1600bhp of energy that must be lost as heat.

About 800bhp will be loss in exhast heat, only about 800bhp of the energy stays as heat in the engine.

The radiator all over the body work won't work in practice for one reason. If MS knows all he has to do to get you out of the race is bump your bodywork enough to make it spring a leak, how long do you think it will be until you get that bump?

[desmo]

"About 800bhp will be loss in exhaust heat, only about 800bhp of the energy stays as heat in the engine."

I'm not sure what you are getting at here. Yes, assuming 1/3rd efficiency ~800bhp converted to torque, ~800bhp lost to the cooling system, and another ~800 out the exhaust. My post indicates a potential way to derive some benefit from this energy. An illustration for the article shows a bit of ductwork similar to the Mac's "chimney" outlets as an illustration of how one might go about getting downforce from this energy. This was published well before the intro of the MP4/15.

[Amadeus]

Quote

A few calculations (on the palm of my hand) indicate that a single F1 radiator has about 75,000 cm sq of surface area. This is about the same as the entire entire top surface of an F1 car so in effect the entire surface of the car would have to become a radiator. This of couse is impossible with any reasonable weight limit so perhaps this is why Brabham failed miserably when they tried this a few decades ago.

posted by Yelnats

You wouldn't need to have the radiators outside - they could be inboard but with each cooling surface shaped as a 'mini-wing'. Imagine the downforce generated by 75,000 cm sq of wing equivalent! Big problem may be the turbulence generated by hundreds of ting wings, but if, as suggested, that can be translated into thrust of some form.....

[Richard Border]

"About 800bhp will be loss in exhaust heat, only about 800bhp of the energy stays as heat in the engine."

desmo wrote:[qoute]I'm not sure what you are getting at here.[/quote]

It seemed to me that you had the 1600bhp going into the cooling system, which would throw off your numbers.


The only way other than jet effect to get thrust out of the exhaust that I can see is to run it through a turbine. Then with a fluid coupling connect them to the crankshaft making a compound engine. That surely must have be banned.

The exhaust could be used to "blow the wing." By using the exhaust in this way you could in effect have a variable wing without having to physically move the wing. You would want to blow the wing at corners when you wanted max downforce and then not on straights when you don't need all the downforce.

[bugeye]

Being a bit out of my league here in Fluid Dynamics, but if as the Racetech article contends there is benefit to using the exhaust to energise the ariflow, is that why Mac has switched to having the exhaust in the diffuser? Not sure I completely "get it" though. I couldn't find those nice airflow diagrams someone posted, but as I understand it, the air is accelerated somewhat under the car (on the flat bottom) to produce downforce and then decelerated in the diffuser to hopefully be near the ambient pressure to reduce the drag. How does adding hot exhaust gases moving at what I would guess are high speeds help matters here? Does the Exhaust come in at an early part of the diffuser and as such create an additional low pressure force to accelerate the air under the car further?

Boy this stuff gets complicated quickly... can somebody help me out here?


Dave

[desmo]

Amadeus, the low velocity flow through a radiator would not allow for the efficient creation of downforce in the way you descibe. Nice try, though!

Richard, you have very nearly described the incredible Napier Nomad compound diesel/turbine aircraft engine. I recommend doing a web search on that name for details of that thermodynamic masterpiece.

It has been suggested that "periscope" exhausts might "blow the wing" in reverse contaminating the airflow to the rear wing with disorganised hot exhaust flow at open throttle reducing the efficiency of the wing, thus downforce and drag simultaneously. Downforce when you need it with minimal drag penalty at WFO throttle when you don't!

Here's a repost of some info I put up on the Napier Nomad months ago here:





Here's some stuff on the incredible Nomad engine. I found a snippet of text from LJK Setright's book which I have included in this post. The first time I saw this cutaway illustration in a book from the local library, I'm pretty sure my jaw literally dropped.

From 'Some Unusual Engines', LJK Setright, ISBN 0852982089
>
>
> On the other hand, a far more thorough (if not to say brilliant)
> exploitation of compounding principles by Napier enjoyed no
> success at all: their Nomad engine, conceived at a time when
> propellors were expected to be the normal means of airliner
> propulsion, did not mature until the aviation world had gone over to
> jets. Like so many unusual engines, it arrived too late ; and to be
> truthful it may be argued that it never really matured anyway, since
> it was by all accounts a pig to start.
>
> Looking at its specification, this hardly seems surprising. The
> Nomad was a 12 cylinder horizontally-opposed liqid cooled two-
> stroke compression-ignition engine cmpounded with an exhaust
> gas turbine, both of these units driving a single propellor shaft
> through reduction gears. Even the basic construction was
> satisfying: the crankcase was a two-piece structure of magnesium
> alloy castings, the two cylinder blocks were of aluminium alloy with
> dry liners fitted in each cylinder bore. Each of the cylinders had its
> own aluminium cylinder head, elegant and simple in shape
> because the 8 inlet and three exhaust ports of each cylinder were
> of course in the walls.
>
> As appropriate to a 2-stroke the the ratio of bore to stroke was
> unfashionably low, resulting in measurements of 6 and 7.375
> inches respectively. This yielded a displacement of 2505 cubic
> inches, (41.2 litres), making a fairly big engine thet weighed
> 3580lb. Beneath and behind the crankcase was the turbine
> department, where a three-stage axial flow turbine rotor was
> mounted on a shaft which drove through a variable-ratio Bair fluid
> coupling and gearing which connected it to the propellor shaft -
> which in turn conected through reduction gears to the crankshaft.
> Coupled ot the turbine shaft was the compressor, a twelve stage
> axial flow affair delivering air to the cylinders at very high pressure
> (8.25 atmospheres) and in enormous quantities (13 lb/sec at
> maximum speed)
>
> Many an engine of much less complication has been debased by
> some want of efficiency in one of more of its component elements.
> It is a tribute to the design of the Nomad that,
> with so many constituent sections that could
> have let it down , it was in fact of
> extraordinary efficiency. The whole operating
> cycle was designed to extract every possible
> quantum of energy: nothing was allowed to to be
> wasted at any stage. After combustion was
> initiated by the injection of diesel fuel into
> the cylinders, the initial expansion of the charge would deliver
> power through the pistons to the crankshaft. As soon as the
> exhaust ports were uncovered expansion would continue through
> the exhaust manifold to the turbine, where the gasses and residual
> hot air produced by combustion would liberate more power for
> transmission through the hydraulic coupling to the propellor shaft.
> The total power from the crankshaft and turbine was considerable,
> and with water injection the take-off rating was 3476hp at 2050
> rev/min. But there was more to come: there as still a little energy
> left in the exhaust gasses even after negotiating the turbine, and
> this was squirted out as a jet at the back to produce a further
> 250lbs of thrust, maing a total equivalent horspower of 3570.
>
> This was equivalent to a BMEP of 205 psi, a very high figure for a 2-
> stroke. The other specific performance factors were no less
> impressive: the engine weighed virtually one pound per horsepower
> and developed 10.5 hp for every square inch of piston area - which
> provides a revealing comparison with the 6.58 hp.in^2 of the Wright
> Turbo Compound. At maximum continuous rating the Nomad
> developed 2248 equivalent horsepower, ; but looming overall was an
> incomparably mean specific fuel consumption. The engine had after
> all been concieved as the propulsive unit for a really long range
> aircraft, intended to realise the most outstanding economy. Napier
> claimed 0.33 lb/hp.hour, although Air Vice Marshal Banks has
> hinted that it never quite achieved that.
>
> It was nevertheless a most satisfying performance. Napier were not
> to be satisfied though, for thay argued that it ought to be possible
> to do something with the unburned air in the exhaust system. A
> diesel can only burn 70% of the air it breathes: they therefore
> inserted an afterburner nozzle in the exhaust manifold, injecting
> extra fuel to burn the remaining oxygen and thus allow the the
> turbine to make a much greater contribution to engine output.
>
> This and an intercooler betwen the the compressor and the
> cylinders added a mere 170lb to the total weight of the engine; but
> the result of this slight investment was a fantastic profit of no less
> than 530hp. On this basis the specific weight fell to 0.83 lb/hp -
> and who would have though that any diesel would have proved to be
> relatively lighter than the majority of spark-ignition engines gulping
> relatively larger quantitis of the best quality petrol?
[p][Edited by desmo on 01-02-2001]

[Ali_G]

Guys I think I have come up with a great idea on how to reduce a coolant system in the cars.

How about putting some sort of chemical in with the petrol so that when it burns it soaks up a lot of the heat and therefore goes out with the exhaust.

I know that there are some chemicals that could be used which are very good at taking in heat. Except this chemical would want to be found in an oxidsed form. So the chemical to put in at the start would be reduced and therefore could be burned to create a certain heat robbing chemical.

Having a chemical whic would rob heat before combustion would be useless as the gases inside the cylender would just be less. But for this chemical to kick in after combustion it would be great.

Niall

[bugeye]

Like Lead perhaps?

[Ali_G]

Not a bad idea. But I beleive that PB + Oxegyn would be an exothermic reaction. That would just raise the tempreature in there.

Something more like water.

A few drops would do the trick. At very high tempreatures and pressures like after combustion the water would turn into hydrogen peroxide. This reaction would soak up a lot of the heat.

Niall

[bugeye]

Actually had a water injection system (aftermarket) on a 1970 Chevrolet.

Also, I believe the Germans (and probably others) used a similar system on WW2 airplanes.

So I guess you had a good idea there, but like most of my good ideas somebody else got there first.

Dave

PS: I was being facetious about the Lead, as it was available in pump gas until recently, not meant in a bad way, more with a wink....

[marion5drsn]

Reference: Napier Nomad engine. This engine has been a thorn in my side ever since I heard of its usage in WW-1! We must remember that at this time Britain and the Allies were in a great struggle for survival of their philosophies. Would it not have been of more help to have used their energies to support the development of the Jet engine than a dead end approach to the piston engine which as an aircraft power source was absolutely at the end of its era! Not that the Brits were any more at fault than the U.S.A. Only Westinghouse and Lockheed working on Axial Flow Jet engines. This without much U.S.A. government help! But this is a result of war and all of its byproducts of waste. Yours, M. L. Anderson

[Richard Border]

marion5drsn wrote:

Quote

Would it not have been of more help to have used their energies to support the development of the Jet engine than a dead end approach to the piston engine which as an aircraft power source was absolutely at the end of its era!

20/20 hindsight. The jet engine wasn't really a sure thing even at the end of the war. The jet had terrible throttle response, fuel consumption, reliability,low power, TBO, and slow acceleration. All but TBO were very important in a dogfight.

A compound engine such as the Napier can be thought of as a turboprop that is using pistons instead of compressor blades for the first stage of the engine. You could say it WAS the logical next step, jumping to jets was a radical move. The allies did not need to do anything radical to win, the Germans did. The turboprop was good for 560 mph in the Bear bomber, the jet was only good for 550 mph in the Me-262.

[desmo]

Without referring to the tech regs for F1, I cannot say for certain that a compound engine of this sort wouldn't be legal. I think adding fuel to the turbine or using it to drive a supe (turbocharging) are expressly forbidden but to simply use the heat energy of the exhaust to add torque mechanically might, in fact, be legal. I'm too lazy right now to look it up. Anyone?

[Ali_G]

Just wondering but would the torque gained from the flow of the exhaust be of any real significance.

Niall

[desmo]

Read the Nomad description above. Combustion was completed in the exhaust manifold, thus the pressure to run the turbine. Doesn't sound like it would work does it? But it did!

[Yelnats]

With modern ECU and Fuel injection I would think the waste oxygen in the exhaust would be reduced to vanishing levels in an F1 car. Lost oxygen means lost power so a modern race tuned ECU would enrichen the mixture to avoid this power robbing situation.

[GunStar]

One note about using water/water injection into the fuel mixture. This was used during the turbo era to increase cooling. It has since been banned. As far as I read into the rules you can't have ANY energy reclamation devices. No super/turbocharging, electric generators (set up like turbos) to create a petrol/electric engine, or whatever. Talk about restricting development.

The P-51's radiator was used sort of like a jet engine. They just ran the radiator in a passage that, properly formed, produced extra thrust. Now create this (lenght permitting), and angle it upwards. And pray you don't wind up doing wheellies due to the enormous rear downforce when starting off the line.

[Bluehair]

Question for Desmo: Your description of the Napier Nomad makes me wonder if driving a turbine with exhaust takes more energy than it can give back to the crankshaft if fuel is not added in the exhaust. Would a regular 4-stroke benefit by having a turbo fan mechanically linked to the crankshaft? At low engine speeds, the fan would actually be driven by the crank to help pull out exhaust (forced extraction, rather than induction), while at high engine speeds, the exhaust would push on the turbine (which is now spinning to slowly for the exhaust) and helps turn the crankshaft like the Nomad.

[desmo]

My gut feeling is that it wouldn't be worth the added weight, friction and complication. But when one looks at the quantity of energy given up as waste heat in an IC engine, particularly that which flows out the tailpipes, one can't help but wonder if there isn't some way to get some useful work from all that energy. Of course if it was easy, it would have already been done!

[marion5drsn]

Desmo;
The only compound engine that I know of that actually worked was the Curtis-Wright R-3350 Turbo Compound.This engine was used in the Lockheed Constellation passenger plane.At first it was a very troublesome engine. Used in the B-29 bomber in twin Turbo supercharger version.Maybe you could find picture of it somewhere Yours Marion L. Anderson