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Off the wall cooling idea

airguy

airguy

Unrepentant fanboy
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I hope to buy my 9A kit soon and get started, I'm still in the process of researching all the particular parts and pieces associated with building my first aircraft before writing the check - including engine choices. I was talking the other day with a friend about the Thielert turbodiesel, and possibly using it in my aircraft. We started talking about the liquid cooling loop, and he had an idea about using a liquid-liquid heat exchanger to dump the heat from the coolant into the diesel fuel in the tanks, instead of using a draggy radiator. Then the fuel can dissipate the heat through the wet wing.

Initially, I see several issues with this, all of which could be dealt with by using some good analysis and careful engineering, and a couple real nice benefits. Coolant leaks, increased vapor pressure of the fuel, CG changes, failure modes and heat exchanger design jump up real big in my mind, but the more I think about it the more I can see design changes that could handle these issues. The loss of the radiator would mean a nice decrease in drag with a redesigned cowl, and it would look pretty cool to boot. I'm not too sure about this being thermodynamically feasible, though, so I'm asking for some additional input from some guys with more engineering knowledge than me before I waste any more dreamtime on this.

The coolant loop and oil cooler on this engine will need to dump roughly 160,000 btu/hr at full power. The fuel (pump diesel or Jet A) will be stable to about 300 F, so no issue there. The coolant is thermostatically controlled to 210F nominal, 250 max,and pressurized to 25 psig. A minimum quantity of fuel would obviously be required for adequate heat removal. Assuming a high flow, low pressure fuel pump drawing from the inboard end of the tank through a heat exchanger and returning to the far outboard point of a properly baffled tank, you can assume fairly decent thermal mixing and complete bottom tank skin exposure to the slipstream. The issue then becomes twofold. Can the tank skin dump that much heat in a worst-case-scenario of a hot day with a full-power climb (think extended touch and go session here, in summertime West Texas heat) and what kind of heat exchanger/pump setup would be needed to handle that heat flow?

For takeoff/climbout on a hot day, you can safely assume (especially with cool tanks) that you'll be effectively "storing" heat for the first 10 minutes or so in the fuel, to be dumped once you climb into cool air. What would be the equilibrium temp of the fuel at common cruise conditions, say 75% power(120,000 btu/hr heat rejection), 140ish kias, and 40F OAT?

At first blush, I thought this was a pretty cool idea. Then I started seeing the problems associated with it, and thought it was a disaster looking for place to happen. Then, the more I thought about it, I starting seeing solutions to the problems posed, and now I'm back to the point of thinking it just might be feasible from a design/engineering standpoint, if the heat flows work out. Any suggestions?
 
Think about what happens to the mass of your heat sink and to the effective radiator area of the fuel tanks as you burn off fuel.
 
Considered that - hence the need to establish a minimum quantity of fuel in the tanks for cooling. As long as your pumping it to the far end of the baffled tank, it should cover all the surface area of the tank on the way back to the pump, and you are still dumping the same amount of heat through the same number of square feet of wing, just with a smaller quantity of fuel over a shorter period of time. The fuel will not care about the rate of it's thermal cycle. The key will be ensuring that you're still covering enough square inches of tank surface to dump that same quantity of heat.
 
It's a neat idea, but there's definitely a lot of challenges. You would need to design the system to make it impossible to run the fuel tanks below that minimum quantity required to keep the engine cool on a worst case hot day. That means you're probably going to carry around more weight than a traditional radiator setup would have added.

Also, wouldn't your operating limitations have to require that you not start the plane unless it's been stored in the shade and the fuel temperature is below a certain point to ensure you have enough cooling mass for your engine to survive a hot summer day taxi when the tower decides you have to go 2 miles to the far runway and wait in line for 20 minutes?

PJ
RV-10 #40032
 
Wings as radiators

I recall that the amount of heat disapated by a surface levels out at about 40 mph, so your "radiator" would always be working at full capacity. Area would be a factor, and as noted, it would diminish as fuel level dropped. As a precaution, you might consider a cowled and vented aux radiator that would open (or be opened by the pilot) at higher temps. This would limit added drag to these times. Considering the power wasted in cooling an engine, I would think this would be worth investigating, although I have no idea of how well it could be made to work. It sure could make one "hot" plane, though!

Bob Kelly, Taxi testing
 
Remember a commerical jet blowing up over New England a few years ago????

If you do this, just DONT have anything in the way of an ignition source in the tank--------capactance fuel guage comes to mind.

Mike
 
One issue I can see that would largely affect this wonderful concept is once the aircraft has landed, if the fuel was cooler than ambient air, condensation would be a certain factor.
 
A related suggestion

What about cooling vanes on the wing, aligned with the airflow? They might have the additional advantage of acting like fences to inhibit spanwise motion of the air. Maybe get a winglet effect? There might be a slight weight penalty which might be offset by the reduced cooling drag. What kind of lightweight fluid coolant could be used?
 
Wouldn't it be great if someone would just build a simple, lightweight, direct drive, air-cooled engine for these little planes? Hopefully, one designed for, and capable of running at high, or full power for a couple thousand hours? Lemme see, at 150 MPH, that would mean you could travel and explore new places for, golly, 300,000 miles! No complex systems or cooling leaks to worry about? An engine you wouldn't have to think twice about when your wife, or son or daughter wanted to go for a ride with you? I sure hope someone invents one soon!
 
captainron said:
Wouldn't it be great if someone would just build a simple, lightweight, direct drive, air-cooled engine for these little planes? Hopefully, one designed for, and capable of running at high, or full power for a couple thousand hours? Lemme see, at 150 MPH, that would mean you could travel and explore new places for, golly, 300,000 miles! No complex systems or cooling leaks to worry about? An engine you wouldn't have to think twice about when your wife, or son or daughter wanted to go for a ride with you? I sure hope someone invents one soon!
Click to expand...

I know what you mean! I'm in the heating and cooling business, and have seen home grown heat extraction systems that seemed to take half the basement, as well as a wall full of pumps, valves, relays, etc.

And then I just throw in these little 90+ efficient heating systems, that are an example of compactness & symplicity, & most of all, reliability.

And that's exactly what we're comparing here. A plane weighed down by plumbing, pumps, and probable headaches; when something as simple as a four cylinder air cooled engine would solve all problems.

L.Adamson RV6A 180 Lyc
 
Sounds like a LOT of complexity for very little gain.

The other issue is you have to run steam pipe in the fuselage, which if it burst would cause you and your passenger a LOT of discomfort.

I seem to remember some early airplanes (WWII German vintage?) that used the wings for cooling and they dropped the idea. You might wish to research that.

Just my $.02
 
captainron said:
Wouldn't it be great if someone would just build a simple, lightweight, direct drive, air-cooled engine for these little planes? Hopefully, one designed for, and capable of running at high, or full power for a couple thousand hours? Lemme see, at 150 MPH, that would mean you could travel and explore new places for, golly, 300,000 miles! No complex systems or cooling leaks to worry about? An engine you wouldn't have to think twice about when your wife, or son or daughter wanted to go for a ride with you? I sure hope someone invents one soon!
Click to expand...

LOL

You trying to kiss up to George or sumptin'

Mike
 
George...???
No, I'm serious here. I'm building a -7 and will be looking for something to turn the propeller (and keep it turning)!
 
Centurion = certified, not available for experimental !

Hello Airguy,

Forget about the Thielert diesel: they do not sell to experimental builders!

If you want this engine in your plane (I would love one), get Van?s to design a FWF-kit and set up an agreement with Thielert. That is the only way you will be able to buy a new Centurion engine.

(Or you could buy a recently converted Cessna?s and strip the engine out of that, of course)

By the way, why don?t you make a double-wall leading edge that is filled with coolant? It only needs to be a couple of mm?s thick No need to mess with the fuel system and no need for an additional heat exchanger. I don?t know if the surface would be enough, but if the tank surface is, the leading edge surface should certainly be enough, because it is cooling all around and not only at the bottom, right? It would also double as permanent de-icing of the outboard part of the wing!

Regards, PilotTonny
 
ROFLMBO!!

captainron said:
George...???
No, I'm serious here. I'm building a -7 and will be looking for something to turn the propeller (and keep it turning)!
Click to expand...


Ron, Ron, we think alike, bro!!

I've been toying in my mind about the 6 cyl subaru engine Jan has developed but remove those ugly, draggy radiators up front, close the cowl inlets into a really nice radius like Rivets (The F-1 racer from the 70's did) and mount the radiator behind the baggage area and make a neat scoop, ala P-51. The water lines could go through the spar web (on a 7) and through an inclined radiator. With a little work, the exit door could be either manually or thermostatically controlled.

I think there is a similar setup being developed on a -10 in Canada.

Regards,
Pierre
 
Surface conduction cooling was utilized on various speed record aircraft in the 1930s (Maachi, Heinkel, Supermarine) with some success however is is heavy and complicated. The wing leading edge area on an RV would not offer anywhere near enough area to cool a 180hp engine in the climb especially. Couple this to the fuel tank location on RVs which halves the leading edge length available and seriously complicates running cooling lines outboard, not to mention the structural challenges of building an efficient heat exchanger structure into the leading edge which can withstand the coolant system pressure with no leaks and light weight.

In designing the belly rad configuration for our RV10, I examined all placements of radiators from wing root, cowling, baggage bay, inner wing and belly, fed by boundary layer and NACA ducts. Structural challenges, piping concerns, duct efficiency, and exhaust/ oil cooling heat contamination of the inlet air finally showed that the belly location offered the least compromises with a flat six engine. The moveable exit door should offer enough mass flow reduction through the rad in cruise to offset the drag of the scoop.

The packaging of efficient oil cooling, cabin heating and intercooling systems precluded having space for cowling mounted rads in our case. In flow bench studies on rad sections and ducts, oblique mounted rad setups showed considerably higher flow losses than traditional rads mounted with finning parallel to the airstream even with guide vanes incorporated. The louvered exits usually required also indicated higher boundary layer disturbance and plume drag.

There is a balancing act here between complexity, weight and performance. In the end, my extensive study into the problem showed that the engineers in the WW2 era had already figured out the most efficient solutions although some are difficult to implement on an RV.
 
RV_7A said:
One issue I can see that would largely affect this wonderful concept is once the aircraft has landed, if the fuel was cooler than ambient air, condensation would be a certain factor.
Click to expand...

That's true for any aircraft using any fuel, and we know how to deal with this.
 
Mike S said:
Remember a commerical jet blowing up over New England a few years ago????

If you do this, just DONT have anything in the way of an ignition source in the tank--------capactance fuel guage comes to mind.

Mike
Click to expand...

Covered - I've already got design changes for ram-air fed positive pressure ventilation of the tanks to keep the vapor levels below explosive levels.
 
captainron said:
Wouldn't it be great if someone would just build a simple, lightweight, direct drive, air-cooled engine for these little planes? Hopefully, one designed for, and capable of running at high, or full power for a couple thousand hours? Lemme see, at 150 MPH, that would mean you could travel and explore new places for, golly, 300,000 miles! No complex systems or cooling leaks to worry about? An engine you wouldn't have to think twice about when your wife, or son or daughter wanted to go for a ride with you? I sure hope someone invents one soon!
Click to expand...

Good point - there are several good options available - but I want a turbo and cheap fuel. The Thielert will produce sea-level power to 10,000 ft and runs on pump road diesel, Jet A, or any mixture of the two.
 
Pilottonny said:
Hello Airguy,

Forget about the Thielert diesel: they do not sell to experimental builders!

If you want this engine in your plane (I would love one), get Van?s to design a FWF-kit and set up an agreement with Thielert. That is the only way you will be able to buy a new Centurion engine.

(Or you could buy a recently converted Cessna?s and strip the engine out of that, of course)

By the way, why don?t you make a double-wall leading edge that is filled with coolant? It only needs to be a couple of mm?s thick No need to mess with the fuel system and no need for an additional heat exchanger. I don?t know if the surface would be enough, but if the tank surface is, the leading edge surface should certainly be enough, because it is cooling all around and not only at the bottom, right? It would also double as permanent de-icing of the outboard part of the wing!

Regards, PilotTonny
Click to expand...

Thought about that too - but the second wing skin and additional coolant mass to fill it would outweigh the benefits of losing the radiator, and I'm not too crazy about the idea of screwing around with a proven airfoil design. I'm certainly not an aerodynamic engineer, and I have no intention of becoming a test pilot.
 
rv6ejguy said:
Surface conduction cooling was utilized on various speed record aircraft in the 1930s (Maachi, Heinkel, Supermarine) with some success however is is heavy and complicated. The wing leading edge area on an RV would not offer anywhere near enough area to cool a 180hp engine in the climb especially. Couple this to the fuel tank location on RVs which halves the leading edge length available and seriously complicates running cooling lines outboard, not to mention the structural challenges of building an efficient heat exchanger structure into the leading edge which can withstand the coolant system pressure with no leaks and light weight.
Click to expand...

The speed record aircraft you speak of were all running much higher horsepower engines, and as such dissipating (or trying to) much larger quantities of heat than I would be looking at. You have a valid point about the restrictions of the tank surface area - you're only cooling fuel at the wet skin areas, that's the leading edge and bottom, and top when full. It was not my intention to put cooling lines in the tanks - rather I had a design change for a small, sealed header tank with a single heat exchanger in it, cool fuel pumped into it from the inboard edge of the tank and hot fuel out to the outboard edge of the tank. This requires only one full-tank-length piece of tubing to be added to each wing, and it doesn't need to be heavy since it will essentially carry no pressure.
The possibility of explosive blowdown of the coolant through a catastrophic heat exchanger failure would have to be dealt with, though. Large-diameter return lines would transfer the load to the tanks, where you would have to deal with it via relatively large exit vents which would be in place anyway for the ram-air venting system. Alternatively, you could make the header tank strong enough to take the pressure hit, use normal size lines for the return flow to restrict the pressure buildup rate in the tanks, and put a high-flow pressure relief on your header tank. The engine will probably ingest coolant in the fuel flow and shut down before it roasts itself, either way you're deadstick.
 
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captainron said:
George...???
No, I'm serious here. I'm building a -7 and will be looking for something to turn the propeller (and keep it turning)!
Click to expand...

Well, your prior post described a Lyc O320 about as well as I can think of.

Mike
 
pierre smith said:
Ron, Ron, we think alike, bro!!

I've been toying in my mind about the 6 cyl subaru engine Jan has developed but remove those ugly, draggy radiators up front, close the cowl inlets into a really nice radius like Rivets (The F-1 racer from the 70's did) and mount the radiator behind the baggage area and make a neat scoop, ala P-51. The water lines could go through the spar web (on a 7) and through an inclined radiator. With a little work, the exit door could be either manually or thermostatically controlled.

I think there is a similar setup being developed on a -10 in Canada.

Regards,
Pierre
Click to expand...

Hi Pierre, nice to know that great minds really DO think alike. While I was posting this in a joking manner, I can see the dilemma that faces so many builders. We drive cars that have engines that couldn't have been built in a Formula-1 engine shop fifteen years ago. We have avionics that surpass most airliner's panels. We talk about our atomic-time syncronized watches that are accurate to fractions of seconds per year.
Then we look at an engine that looks like it was hammered-out in Fred Flintstone's garage. Can it be any more crude? But really take a good look. It reaches its maximum rated horsepower at the same RPM as the maximum propeller RPM. No reduction required. It is cooled the same way as all engines are ultimately cooled- by AIR! No extra water jackets, no water or coolant, pumps, hoses, fittings, radiators, etc..
On the Flintstone engine, the propeller even doubles as a cooling fan!
On the Flintstone engine, it can produce its own energy for ignition completely independent of any outside source.
On the Flintstone engine, it is made to be lightweight, but robust. It is designed and manufactured to run its entire life at full throttle, after warm-up. It is easy to install, and designed flat to fit under a nice-looking cowl.
With the proliferation of Flintstone clones, look at the prices becoming competitive.
Not all mechanical devices produced in past generations are obsolete today.
One of my hobbies (not to start anything here, please) is collecting military .45 auto pistols. A design that was perfected in 1911, and still being produced virtually unchanged today! The choice of many professionals and SWAT teams, etc..
My point here is we are trying to fix things that aren't broken, and trying to re-invent the wheel, when we could by flying instead.
As for our European counterparts, I realize that it's almost imperative for you to find a suitable Jet-A burning engine and wish you absolute success in your search. I looked with interest and optimism at the oil-burning alternative engines at OSH this year, but for now have to go with the un-impressive but totally proven Flintstone.
 
Cooling through fuel mass on an RV is not practical with only a max of 252 lbs. of fuel when you start out. If you run the math even quickly it is clear that starting out with 90F fuel and the BTUs having to be dissipated into the fuel with the declining fuel mass and increasing fuel temperature, thus decreasing delta T between the fuel and coolant as the flight progresses, you rapidly run out of heat sink capability. It might work for a short flight. The radiator can be much smaller on a diesel due to its higher thermal efficiency. The drag penalty on a well designed rad setup would be minimal to nil.

The surface conduction systems used on the Schneider Cup racers involved many square feet of exposed copper cladding and tubing even over the float surfaces. Coolant temps on the Maachi would rise over each full throttle run to near critical until pulling back power to start the next timed pass in the opposite direction. It is very impressive that they went 440 mph with a float plane, a record still unbeaten today.

For the RV7/ Sube, a James type cowling with the chin scoop as offered for rotary powered RVs might be a good compromise. This would give a straight airflow path, the possibility of a cowl flap, short and light plumbing, decent length for a proper diverging/ converging duct under the oil pan for proper pressure recovery. The twin batteries for the Sube could be located behind the baggage bay to correct the C of G.
 
rv6ejguy said:
Cooling through fuel mass on an RV is not practical with only a max of 252 lbs. of fuel when you start out. If you run the math even quickly it is clear that starting out with 90F fuel and the BTUs having to be dissipated into the fuel with the declining fuel mass and increasing fuel temperature, thus decreasing delta T between the fuel and coolant as the flight progresses, you rapidly run out of heat sink capability. It might work for a short flight. The radiator can be much smaller on a diesel due to its higher thermal efficiency. The drag penalty on a well designed rad setup would be minimal to nil.
Click to expand...

Agreed - the only way to make this work is to dump the heat as fast as you can make it - not rely on the fuel to contain it till the end of the flight. As fuel temp rises, it will dump heat faster into the slipstream. At some point it will dump it as fast as you're producing it, thus making a stable thermal equilibrium. The $64,000 question (and maybe more than that) is this - at what temperature will it be equilibrated? At what temp can the fuel dump that amount of heat (120,000 btu/hr for cruise power) to the slipstream - and can a heat exchanger be built to dump that same 120,000 btu/hr from 210F coolant into the fuel at the equilibrium fuel return temp?
Once that equilibrium temp is known (and it will vary according to OAT), you'll know how much heat you can inject into the fuel before the fuel reaches that temp, thus giving you the amount of time you have available for startup, taxi, and climb before fuel temps get ugly.
 
The taxi, takeoff and climb would not be a problem with this setup but there is no way on a warm day that with the tank area on a RV presented to the slipstream that you would reach a cruise power BTU rejection rate even with the fuel at the same temperature as the coolant. The thermal rejection rates on massive sheet type conduction systems especially without agitation is quite low as would be the gradient around the heat exchanger.

Pumping the hot fuel to the engine then becomes a scary proposition with altitude and vapor lock possibilities on the suction side of the pump.

You are certainly thinking outside the box here and if you are really set on trying your idea out, I say go for it! I'm not one to discourage experimentation. Please let us know what you learn if you do. :)
 
Supermarine used radiators/heat echangers embedded in the skins of pontoons for its speed setting seaplane racers. The high horsepower was used only for short periods and the concept worked well. Military applications were not successfull due in large part to the VULNERABILITY of large-area radiators to enemy fire. The concepts worked fine but were not feasible in combat applications.

Jekyll
 
Jekyll said:
Supermarine used radiators/heat echangers embedded in the skins of pontoons for its speed setting seaplane racers. The high horsepower was used only for short periods and the concept worked well. Military applications were not successfull due in large part to the VULNERABILITY of large-area radiators to enemy fire. The concepts worked fine but were not feasible in combat applications.

Jekyll
Click to expand...

Yes, and of course no floats for heat exchangers either in something like a Spitfire. It should be stressed that these aircraft were designed around the cooling system, a luxury we don't have with the RV airframe.

Rolls Royce and DB also tried a steam/ expansion type cooling systems. It looked great on paper but was a disaster in practice. Maybe this concept has merit however. The state change makes for some interesting possibilities if you can build a good condensor system within the airframe.

A P51 at Reno years back had the rad and scoop removed entirely and a loss type system with about 200 gallons of water to flash off to steam out wing tip vents. It proved no faster than the scooped Mustangs lending some credance to the Merideth Effect theory. Certainly with the massive amounts of spray bar water and 500 mph speeds used on Reno P51 racers, there is likely a net thrust being developed. The revised shape, composite rad ducts on Strega and Voodoo are clearly designed to reduce frontal area and converge flow more efficienty.

The #33 Lancair and the new Algie LP1 racer have exhaust augmentation and tunneled eixts. This technology is well proven on both air and liquid cooled installations. The added mass from the spray bars can be shown to produce measurable thrust and signicantly better cooling in the climb which is the critical condition on most aircraft. Another new design is implementing this concept to a much greater degree with water being injected into a large surface area exhaust system and variable geometry exit duct. They are trying to capture some of that 35% wasted energy going out the exhaust. Facinating stuff and I hope it makes it to Reno sometime soon.
 
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What did I say.

Mike S said:
captainron said:
Wouldn't it be great if someone would just build a simple, lightweight, direct drive, air-cooled engine for these little planes? Hopefully, one designed for, and capable of running at high, or full power for a couple thousand hours? Lemme see, at 150 MPH, that would mean you could travel and explore new places for, golly, 300,000 miles! No complex systems or cooling leaks to worry about? An engine you wouldn't have to think twice about when your wife, or son or daughter wanted to go for a ride with you? I sure hope someone invents one soon!
Click to expand...
LOL

You trying to kiss up to George or sumptin'

Mike
Click to expand...
Geee I am not even participating or planned to and I get dragged in to it. Don't worry Captainiron, I don't know what Mike is talking about either, I am the king of KISS, that is keep it simple stupid.


Like RV6ejguy, go for it, however I would use the engineering approach first and research how much heat rejection you need, and than determine the heat transfer capacity of the heat exchanger you are thinking of. I sounds like you started to run some numbers and identify some possible reasons it might not work. If you are thinking of a diesel and this elaborate liquid cooling system, you may want to look into weight. That could be a killer.

The discreet radiator is still the most compact and practical approach, but the adaptation of automotive liquid cooling has some major drawbacks which limits its efficiency, which I address below. As far as the diesel you mention it will have to WORK WITH the cooling system. The pump and pressure must be matched to the plumbing and heat exchanger. If they did it properly you could get away with a fairly small radiator that will fit inside the cowl of a RV. Of course you will need to modify the cowl extensively and make ducts and plenums to route the air to and from the heat exchanger.

I have flown planes with all kinds of liquid to liquid, air to air, liquid to air heat exchangers, as you might have as well. There's a lot of research and engineering data out there in these areas. If you like off line I can guide you to some data to get you started, just you, not Mike. :rolleyes:

Now the bad news, with out running spacific number's my SWAG is the weight and efficency will be prohibitive.

The good news is there are solutions; the big problem with many water cooled engines on planes (aka, Subaru, Mazda) is they are cooling systems for use on car's. Although you are talking about an aircraft diesel, which is still a bit of a unknown, I'll address auto engines which have there own challenge. It would be of benifit if you got a hold of the company and ask them what kind or pressures and flow their pump is capable. They may have a pump which could help or hurt and the following may apply.


COOLING IN CAR ENGINES USED IN PLANES
To get the efficency up you need to run the glycol-water at higher pressures as well as flow rates. Also the radiator used for cars are ideally for 35 mph not 230 mph, but it not just the radiator its the whole cooling system.

Off the shelf care radiators really don't work properly. Now what size will work? Well that is the key, it has to work with the pressure drop (air pressure differential across the radiator) and the liquid's flow and pressure. Regardless, you are talking about expensive stuff, up to $2,000 for a proper radiator. If you do it right you can get away with a very small radiator and still get excellent cooling. To get the proper pressure and flow with a stock car pump is a problem. Builders try to adapt the car engine and its car cooling which is already at a disadvantage. If you are talking about long pipe runs you will need a MONSTER pump to make that work.

The other down side of car water cooling system's, they are serial, the water jackets flow one into the next, so the subsequent cylinders get hotter and hotter liquid. If done properly each cylinder or each rotor would have its own cooling supply. What happens with serial heating is lower pressures, steam pockets and lower efficency. The more efficient the cooling system (internal to the engine) the smaller the radiator.

It's a complex topic and no offense to the experts, the answer takes a lot of math and testing. It's a daunting task for even an experienced engineering team with dynos and test facilities. The research is out there and the existing status quo of water cooling for experimental aircraft has plenty room for improvement. Unfortunately a lot of the weakness is in the basic car engine design. Works fine in a car but not so good for a plane. A car does not suffer too much having to push a radiator the size of a big screen TV thru the air at 80 mph. A plane on the other hand going 200 mph is a different story.

The P-51 is often held up as an ideal but for many reasons it's not scalable or transferable to the RV. Besides the water cooled P-51 was not really that great. People wax poetic but it had its limits as well. Suburu powered RV's have cooling problems as well. All I am saying is there is room for improvement, but guessing and just going for it will not work.

Be glad to help you off line, so I can put all those years of Grad school and heat transfer knowledge to work I have not used in decades. I think the solution may be just an aircraft spacific liquid cooling not fuselage, fuel tank or skin heat exchangers. The experts like Mike are on their own. :D

BTW, part of full disclosure I am in the air cooled camp. It's simple and works well. There are no heat exchangers, hoses, liquid, pumps, reservoirs and thermostats to deal with. It is also lighter and lower drag. However if you made an engine designed for liquid cooling in a plane, the drag in theory could be less.

That reminds me. I talked to the guys at Liquid Cool Jugs have been re-grouping and are coming out with an all new design for the experimental market and retro fit cylinders on Lyc 360's and 540's. Their original approach was to copy the Lyc cylinder design and water cool it to get FAA approval on certified planes, based on it being a minor modification. Those plans where squashed by the FAA who said it was a major change. Now their new design goal's are aimed only towards experimentals. This allows them to make and all new design with high tech combustion chambers and up to 12:1 CR pistons, that can run detonation free on 92 octane, full power, 36 deg timing advance and 110F air temps. The HP is much higher than the stock cylinders and pistons. The radiator takes up only 150 sq-inch by 3 inch deep because of the pressures and parallel cooling system. They're something to look out for, but it will not be cheap. Plan on a full system installation $15,000 over the cost of 4 stock air cooled cylinder assemblies. The weight gain should only be about 25 lbs best I can tell, and reduction in cooling drag by up to 50% is possible. This all remains to be seen and there is no firm date to get parts, due to supply and vendor problems. However they should be flying within a year from now. As a self proclaimed "air head" and KISS guy I was scheptical and the fact they appeared to not be acctive the last two years confirmend my suspecisons, but after talking to them I think they may have a nice product. The question is will it be for everyone or replace air cooling. IMHO no, but for some that want the best or just want liquid cooling and can afford it, it may be a great thing. They claim TBO of the top end could go 3000 hrs. They also will recommend a composite prop because of harmonics with a Hartzell. As we know if you change something the prop and engine combo needs to be tested. (See the Kit Plane article on testing a Harzell this month.)

P.S., what is LOL?, Oh yea I saw that on TV yesterday. That's what former Senator Foley puts on his emails and IM's to his friends. :rolleyes:
 
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What did I say

YOU must be the "George"! Sorry, I haven't been around here long enough to know everybody. I am a fan of KISS, mainly 'cause I'm not smart enough to figure out all the complexities of the tougher road to travel. I saw someone here write about the yet un-seen Honda aircraft piston engine, and how it would probably look a lot like a Lycoming. Maybe this is the reason we haven't seen one yet!

P.S. As an old-time biker, I can tell you that Honda once proclaimed "that they would NEVER build a V-Twin!"
 
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gmcjetpilot said:
Geee I am not even participating or planned to and I get dragged in to it. Don't worry Captainiron, I don't know what Mike is talking about either, I am the king of KISS, that is keep it simple stupid.


George--------you missed the humor here.

His description fitted a Lyc to a "T"-------and I was waiting for you to say so. ----You do have a bit of a track record of being a bit of a fan of them.

LOL= Laugh out loud---------also can be used for other things, but that is the one I meant, as I was seeing the "Bait" dangling out there in Ron's post.

Mike
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Contrary to speculation from some here, the cooling layout on modern engines is very well researched and engineered. The development papers on engines like the EJ series Subaru and Chev LS series outline the pains gone to in this area. Efficient coolant flow is critical to shorten warmup cycles for emissions and reduce parasitic losses not to mention reliability at WOT on a hot day.

The Subaru does not have a series coolant flow path. The LS engines have a carefully designed system to ensure even temperatures throughout the engine by controlling flow rates between areas of the block and heads. CFA and thermocouple validation is currently used by most manufacturers in this area. Coolant flow through the cylinders is relatively unimportant, it is head flow that is critical, especially in the exhaust seat and chamber areas. On the EJ series engines, max deviation temperature at the head gasket is less than 20C from coldest to hottest region.

The stock water pumps on the EJ series 4 cylinder is quite capable of cooling the engine at 560hp continuously with a 28 gpm flow rate at 6000 rpm.

Plumbing over long distances does not require different water pumps nor huge plumbing. Certainly at the 200hp level, 1.25 inch plumbing will easily handle the flow even with 20 foot coolant runs. .75 inch plumbing is flight proven to do the job with shorter runs at this hp level.

Custom rads run around $500-$700 using the latest core designs and our testing has shown that the often used GM evap cores have very high pressure losses for air and coolant flow. Custom rads are the way to go for better performance and lower drag.

The basic coolant flow design is very sound on most modern engines, the main trick in aircraft is a proper rad design enclosed in a proper duct design placed in an aerodynamically favorable location.
 
cool day dreaming

Im a day dreamer too. Beats working and so were the wright brothers too. I really like to build and wish I could afford to experiment. I strongly considered an auto conversion but found that there are nice O/IO 360s to be had for resonable prices if you look hard enough. research watch ebay and pray to the lycoming fairy and you'll find a good air cooled engine. I like your idea though sounds cool and all but youll have to carry extra fuel always... its your cooling media.... thats weight. I dont think its practical but is possible...
and is a very inovative Idea...
nathan
 
I'm not giving up on the idea, but I am going to build my first one with a standard Lyc air cooled mill. My second one will likely be an experimental model in the true sense of the word. All you guys will be in on the drama via this forum as it happens.
 
The wet wing

has been tried before in the early Schneider cup seaplane races I seem to remember.

Now you can easily remove the cooling drag of air cooling and water cooling...

Just buy an Innodyn Turbine.....OK i'm running for cover now...:)

I have a friend at CVO who's got a Walter 601 (about 700HP)in a stretched (2+2) Glassair...It idles at 25GPH!!!!!!

Frank
 
Rocket-like performance?

rv6ejguy said:
Plumbing over long distances does not require different water pumps nor huge plumbing. Certainly at the 200hp level, 1.25 inch plumbing will easily handle the flow even with 20 foot coolant runs. .75 inch plumbing is flight proven to do the job with shorter runs at this hp level.

.
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Hi Ross,
My idea of a -7 with the six cyl Sube and water lines running to the baggage area with a radiator there, very similar to your -10 setup, is what I've considered.

If that engine were pushed to the 250 HP region, would you not expect Rocket-like climbs and cruise speeds? Especially since the cowling air intakes would be closed and faired neatly.

The coolant runs would be less than 20 feet and you mention that .75" lines would do the job. Your opinions on a -7 's performance (increase?) given the above.
Regards,
 
Pierre,

I'd run 1.25 inch lines for this length of run and the 250 hp target. It is important to have the correct redrive ratio to allow the engine to spin up to its rated hp rpm with the propeller at its design max rpm. The 2005-2006 JDM engines are rated at 247 hp @6600 rpm and 224 ft./ lbs.@ 4200. The 2007 domestic engines are rated at 250hp at 6600 and 219 ft./lbs at 4200.

The EZ30 naturally aspirated engine is much lighter than an IO-540 installation but short about 15 hp. I would expect near Rocket performance in a -7. Longblock weight is around 245 lbs. without intake, exhaust or accessories.

With the rear mounted rad, it is important to consider exhaust intrusion to the rad inlet air. In the RV10, I'm using a horizontal splitter between the stock cowling air exit and the rad intake. Exhaust pipes are angled away from the rad duct and on top of the splitter.

You will probably need some "clearance air" for the redrive, alternator, oil pan and oil cooler and some exit for this air to escape. This air needs to be kept from entering the rad inlet downstream also. A coolant to oil heat exchanger would negate the need for the oil cooler airflow. A Modine unit can probably be adapted here.
 
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