22 replies to this topic

[perfectelise]

"F1 cars rely on the flow of air through the car to keep water and oil temperatures at a working level. Because size and weight matter, radiator dimensions are reduced to the absolute minimum, the precise calculations working on the theory that the car will be at a standstill for a maximum of 12 seconds during a pit stop and half a minute before the start." Maurice Hamilton in The Observer (UK)

Cooling fans set low in the side pods could be used in the hotest moments, perhaps adding up to only a very small proportion of the total race time, allowing radiator dimensions to be further reduced with associated benefits for aerodynamics. Y/N?

[Pilla]

It would add wait, size, and complexity to a Formula One car. The current system seems to run fine.

[lustigson]

The teams already use portable cooling fans on the grid and dry ice and so on. Like pilla said: fans like in any road car don't have any function whatsoever on a Formula 1 car.

[perfectelise]

Originally posted by lustigson
...fans like in any road car don't have any function whatsoever on a Formula 1 car.

Except possibly to force air through radiators when forward speed is low. Whatever the size threshold is that radiators are built down to now I think they could be made even smaller if fans took care of the hottest moments - pre start, pit stops, whenever.

[YKTS]

As far as i know, you cannot run fans on a modern day f1 car. they come under a movable aerodynamic devide, think back to the brabham fan car, that was argued as a cooling device.........

Also in the book, Formula 1: The Turbo Era - Alan Henry 'He had elected to use a fan assisted intercooler, but recalled Brabham designer Gordon Murray coming into the garage at one race and saying "It's a good idea boys, but I'm afraid it's illegal." However as he (Brian Hart) explains, "We were so far back on the grid that nobody bothered with us. In those days you didnt screw your mates!"'

[Aubwi]

Hmm, here's a question... was the Brabham fan car the only F1 car that ever had a fan?

[desmo]

[Wuzak]

No radiators on that one.

That is the Porsche? There was also an air-cooled Honda.

[desmo]

Yes, I believe thats the 804 from 1962. I can't find anything more specific that the rather vague "no moving aerodynamic devices" rule that would preclude fan cooling either the coolant radiators or an air-cooled engine. Would a fan cooled engine such as the Porsche necessarily be illegal today?

[Wuzak]

I think a fan would be allowed, just so long as it didn't add to aerodynamic effects - ie doesn't help downforce (such as running a powerful fan, and blowing the radiator air through the diffuser, like the exhausts once were, or over the rear wing).

How it was driven might be another issue - the rules ban secondary motive devices.

[YKTS]

Originally posted by YKTS
As far as i know, you cannot run fans on a modern day f1 car. they come under a movable aerodynamic devide, think back to the brabham fan car, that was argued as a cooling device.........

Also in the book, Formula 1: The Turbo Era - Alan Henry 'He had elected to use a fan assisted intercooler, but recalled Brabham designer Gordon Murray coming into the garage at one race and saying "It's a good idea boys, but I'm afraid it's illegal." However as he (Brian Hart) explains, "We were so far back on the grid that nobody bothered with us. In those days you didnt screw your mates!"'

woops! forgot to mention that this quote was regarding the 1982 Toleman Hart, the other turbocharged car at the time when only Brabham, Ferrari and Renault were running them.

This also answers up Aubwi and Wuzaks questions

[RDV]

...back to fundamental equations of engine heat rejection and radiator dissipation=

ram driver cooler matrixes are efficient by themselves, usual track velocity profile means you have full power for `70% of lap time (commonly used to size cooling systems), and heat rejection is directly linked to power output ( realy amount of fuel burnt and thermal efficiency), there is also the heat buffer effect of mass to be heated (IE engine block , quantity of water in system etc)

excess heat rejected from engine in low gear(hence hi RPM), slow corner (hence low rad core velocity) periods has to heat the bulk of water and block by several degrees , as cooling availiable at lower air speed is below required ( figure it out yourself , to raise 90kg of metal and assorted 10 lts of water plus 8lts of oil by 2 degrees ..)

by the same token when at full speed going down straights ram airspeed on ducts is over required cooling , now bringing down entire system temperatures , and we cycle through this during lap, remember even going down a straight , as you shift through gears, power output & consequent heat rejection is following a saw-tooth pattern whilst duct spead is smoothly increasing

power produced can drop a bit as ignition mapping and fuel injection mapping compensates for temperature , but in a well balanced cooling system it all blends in and gives you maximum availiable power to accelerate vehicle (engine power -(aero drag loss+rolling resistance+mechanical losses). All systems are designed using compromise to have biggest total efficiency (you always have mechanical losses in system... no free lunch!)

Fundamentally mechanical and aero cost of ram driven system (at this moment of development and with these regs) is cheaper and lighter than an additional power drain on engine required to drive fan whereas ram losses and duct losses are there whether you have a fan or not)

Control systems as thermostat regulated fan drives or vanes in rad intakes are required for road cars as drive cycle profile has to take in account idling in traffic jams to full power on motorway with a very high variety of climactic conditions.

Race cooling systems can easily be trimmed by opening or closing intake s , and when changing track profiles using different radiator packs.. IE Monaco requirements are quite different to Monza

The use of dry ice for intercoolers on turbos and smaller rad ducting packed full of dry ice (in earlier days ice cubes until banned after people spun on their own ice as it shot out of ducts under braking for first corner..) for qualyfing laps used to be very common... different usage conditions dictate configuration.

Nascar cars on qualifying queue have almost completely closed ducting to radiators and separate unit plugged in on quick connectors to maintain high oil temperatures and minimum coolant temperatures (thus building up size of thermal buffer) ready to go out for short stint. For race ducts are opened to required size.

same reasioning applies to brake cooling ... ducts are working full time , whilst discs and pads just heat-up during braking cycle... sum under integral of power in (through braking ) and power out (through cooling) balance out...

[RDV]

...whoops , got so sidetracked with sequence of though that didn`t add point of question... pit stops and grid=

same reasoning applies , the adding of a separate system to cope with these short (albeit important) parts of race ends up being too expensive , briefly ends up being

energy used fan * say 1 hour 40 mins =(fan drive loss(or cost in weight ,complexity and reliability of control system for intermitent use)+fan system weight cost (X kgs to accelerate and brake ) > energy used increased size water capacity or heat buffer

...of course if you dawdle too long in pits or grid procedure gets held up will give you trouble inversely proportional to your safety margin...

[desmo]

Excellent RDV. The primary potential advantage I see for a blown radiator would be simply to free up the location of the air intake and rads. Intakes would no longer need to necessarily be facing frontally anymore. I have no idea what the aero ramifications might potentially be, there must be a hundred ways of looking at it. If it were an intrisically good idea I'd imagine aircraft would have adopted the practice ages ago, but aircraft don't as far as I know have arbitrary and arcane bodywork regulations.

[Yelnats]

I'm not sure that there would be a significan improvement in overall performance with side facing fan driven radiators. Of course there would be a reduction in localized drag without the frontal openings but this would be offset having to draw a similar quantity of air laterally into the rads which which then would undergo the same decelerative process as the "free" air supplied by frontal rads. There would be additional energy losses caused by accelerating and braking the weight of the fan's energy source and it's mechanisims around the track which I believe would result in a net performance loss for the side facing rads.

[Aubwi]

Need some kind of device that can recover excess heat and use it to power the car, instead of just expelling it into the air like a radiator does.

[Engineguy]

If fans with their inlets underneath the car or their outlets on the top surface of the bodywork are moving aerodynamic devices... what does that make the pistons in a car with its exhaust outlets pointing upward? Hmmm...

Back on topic... As for pit stop and extended grid delay engine cooling... under drivetrain disengagement (i.e. clutch disengaed and/or trans in neutral) conditions, I would monitor the coolant temp and randomly fire fewer and fewer cylinders per crank revolution, with richer and richer fuel mixture as needed to keep temps out of the red zone.... it doesn't take much power to keep revs up without load, and the special map can be instantly abandoned upon detection of drivetrain status change. Cadillac boasted of total coolant loss limp home capability for their Northstar engines a few years ago... and that was while generating enough power to drive the car.

[desmo]

Originally posted by Engineguy
If fans with their inlets underneath the car or their outlets on the top surface of the bodywork are moving aerodynamic devices... what does that make the pistons in a car with its exhaust outlets pointing upward? Hmmm...

Back on topic... As for pit stop and extended grid delay engine cooling... under drivetrain disengagement (i.e. clutch disengaed and/or trans in neutral) conditions, I would monitor the coolant temp and randomly fire fewer and fewer cylinders per crank revolution, with richer and richer fuel mixture as needed to keep temps out of the red zone.... it doesn't take much power to keep revs up without load, and the special map can be instantly abandoned upon detection of drivetrain status change. Cadillac boasted of total coolant loss limp home capability for their Northstar engines a few years ago... and that was while generating enough power to drive the car.

And if not the pistons, surely the valves are. And I thought of the Cadillac Northstar limp-home cylinder disablement while reading the top of the 2nd paragraph as well!

[RDV]

And if not the pistons, surely the valves are

...pistons valves , turbos and all ancillaries connected to engine plus vented discs were all accepted as outside moveable device definition after Ken Tyrrel brought this up on a Foca meeting... at that point common sense prevailed as we were going more and more into legalese, not so much technical as semantic... as I ve said before ACOs LeMans rules are interpreted on spirit rather than letter of regulations, as Berthaud (ex-chief scrutineer and race director) used to say " You and I know what the rule intends to specify... "

[JwS]

An interesting note along these lines, the radiator outlet on P-51 mustangs was designed to generate thrust from the expanding air as it exited, I forget the amount, but it was a significant percent of the planes thrust (20%????) I remember being impressed with the amount. I can only imagine that if it were possible that someone would use it. Dealing with the heat must be integral with the aero package.
JwS

[desmo]

I suspect the P-51 Mustang "thrust ducting" story is apocryphal or an exaggeration at best. Here's a snippet I posted last year from a Mike McDermott article in the April/May '98 issue of RaceTech. I'll quote a little, though I won't attempt to write out the maths referred to in the sidebar.

"Assuming that an engine is a typical one-third efficient in converting the fuel's chemical energy into mechanical energy at the flywheel, then two-thirds of the the fuel energy has to be rejected as heat. A 700BHP engine has to lose 1400BHP as heat either via the the coolant or out of the exhaust pipe. Can any of this energy be recovered and put to good use? Probably with careful attention to detail."

"The crude calculations in the sidebar show up to 1.6% of the heat energy being available as thrust at 135 mph. This is 3.2% of the mechanical power and for a 700BHP car could be as much as 22BHP; at 200 mph it's more than twice as much. You just can't ignore the possibility of more than 40BHP at the top end. A major advantage of this additional power is that it creates a thrust directly on the car, specifically on the radiators and ducting, from the air, not between the tires and the track, so it by-passes grip limitations. To achieve this the duct has to be carefully designed to ensure effective pressure/velocity recovery both before and after the radiator. Not for nothing was the ramjet originally called the 'aero-thermo-dynamic duct'."

"It is not clear to me if, or where, this effect is currently being exploited in racing. In general, great care is taken to coax the right amount of air into the radiator but, provided the exit is in a low pressure region which extracts the air, that seems sufficient. In single-seaters, space to achieve the optimum exit is undoubtedly limited, particularly with the new narrow F1 format. Judging from press photographs, the ducting on most of the 1998 F1 cars is typified by the Williams F20. This terminates inboard of the rear wheel and ahead of the rear axle line and the exit air then has to find its way through the suspension, exhausy and diffuser assemblies. The design probably at least provides effective pressure recovery and so minimises drag. But for maximum thrust the exhaust stream has to exit as a parallel jetand to react on the surrounding air. The airflow in the space immediately behind a race car is famously disturbed. So extending the radiator exit duct to form a nozzle at the extreme rear of the car is unlikely to create a jet effect. A significantly different exit duct is to be seen on the 1998 F1 Arrows A19. The exits on te Arrows are relatively large and they feed into an area directly ahead of the rear tyres."

"Arranging for the exhaust system to heat the air in the duct would help. If the exhaust gasses are cooled in the process, this is no bad thing. The viscocity of a gas falls with temperature, so the cooler the exhaust gasses, the lower the exhaust back pressure- but not 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 its combustion needs by the engine, is much smaller, typically no more than 5% of radiator airflow."

"Manufacturers in F1 are already producing engines capable of operating at higher coolant temperatures. This is said to allow car designers to use smaller radiators, which require smaller ducts, creating less drag, to improve the car's aerodynamic performance. By raising the exit air temperature, the same developmentenhances the thrust available from the ramjet effect. Thermodynamicas, as always, tells us that nothing is for nothing. Raising the coolant temperature in an engine reduces the working temperature difference and so, in principle, reduces the thermodynamic efficiency although, in a practical engine, other temperature-dependant effects can reduce or overcome this drawback. At the least, the ramjet effect could be, or maybe already is, for those who know, a way of recovering some of this lost efficiency."

One of the accompanying illustrations shows a radiator duct forcing the airflow upwards 90 degrees to provide downforce. This seems to presage the Mac "chimany" rad exits, at least superficially. Also, the reference to the A19's at the time rather novel rad exits in front of the rear tires seems as well to presage a lot of obvious later aero development in this very area. I wonder if the exhaust airflow- being much a smaller mass flow, but containing comparable heat to the rad outflow might make a more promising heat source for aero energizing. No untidy coolant plumbing and mass either- granted this has been done in the diffusers already certainly.

The use of all the 'wasted' heat energy produced by the IC engine is like gold to the thermodynamic alchemist seeking to turn this into useful work. From the P-51 to the Napier Nomad compound CI aircraft engine, to the turbocharger, it makes a shimmering and elusive target to pursue. The allure of the 'lost' two-thirds is well-nigh irresistable!

[hydra]

Funny I should happen to run into this thread, I had a similar idea lately...

Let's forget about F1 and single seater race car design for a moment, and concentrate on road car design and packaging. While I realize this idea isn't very practical for your average mass-produced saloon car, I like to think that it is of some merit for a low-volume high-end sports car design.
I figured why not have two radiators, one placed in the usual upright frontal position, sized for high-speed operation,and ducted to exit in the hood. And another radiator flat on the underbody of the car, with a ducted fan to cater for idling/low-speed operation, in addition to providing some measure of downforce at high speed. Let's assume for the sake of discussion that the said vehicle is low to the ground, with a flat-underbody with a well-designed venturi/tunnel out back...

The system would be specified such that the fan runs constantly, and the the frontal radiator would be sized (smaller) to take advantage of this for a reduction in drag and an increase in downforce. I also envision the use of a computer controlled water pump/cooling system, to keep coolant temps in the right place at the right time. Other than a slight increase in weight, on the order of half a radiator or so, and of course an increase in costs, this system is all good. What do you guys think?

[ckkl]

Sounds like leaves are the enemy of such a setup

The JGTC NSX does use a horizontally mounted radiator with air flowing from under the car through a vent in the bonnet. I never thought the heat dissipated from the radiator/oil cooler would be used to "charge" the air to great downforce. Ingenious.