Air Cooled VS. Water Cooled

[Rotary10-RV]

Originally Posted by gmcjetpilot

Great post. The pressures where much greater in many aircraft coolant systems. I remember in the 80's the early V6 and V8 auto conversions (no particular) had problems with hot spots, steam pockets and cavitation. So how to get a REAL HIGH PRESSURE pump radiator system? The stock pump will not due, will it?

The "cool jug" guys (water cooled cylinder/heads for Lycs) ran a separate mechanical pump off the accessory case at very high pressures. I talked to them once and the pressures I think where 15-20 psi (typical) but the flow is very high. They don't say much on their site but this might be worth a quick read:
It will be great to read about you twin turbo Subaru RV-10 with a P-51 belly scoop set-up, when you get flying Ross. You have to go with a streamlined P-51 cowl to match the belly radiator. Long coolant lines are begging for higher pressures. If the radiator size, thickness and fins/tube spacing if carefully selected should cool very nicely. Will the stock water pump be up to it? Will you have redundant or supplemental electric water pump?

George,
I did some snipping here but I think you missed what Ross was talking about the 50 PSI comment. He was talking about pressurizing the SYSTEM to 50 PSI then the boiling point is sagnifigantly raised. They were also running a high level of EG mix which raises the boiling point even more. The 50 PSI system wouldn't change the power required to flow the mix through the system, which IS a factor. A good 50-60 GPH pump will consume 5 HP at design RPM. I'm sure the designers of the engine were trying to raise the normal operating temperature so there would be less of the delta T difference we were talking about at the beginning. So it isn't the stock water pump that is inadaquate, rather it is the radiator and radiator pressure cap. Cooling can be improved, usually by increasing the water flow, but there are limits and the pumps needed consume ever more HP.
Bill Jepson

[Rotary10-RV]

Originally Posted by Mike S

This thread is shaping up to generate a headache almost as bad as the torsional vibration thread

Why, oh why do I keep reading this stuff??

Sorry Mike! If it's any consolation the TV thread hurts my head too. I need to look up too much stuff and it makes my hair hurt
Bill Jepson

[rv6ejguy]

Originally Posted by RV8RIVETER

Don't forget the Jumo powered FW190D/TA-152. They used an annular radiator arrangement and were plenty fast. That type of arrangement may work well in a -10 provided the LS engines are thin enough, as they appear to be in photos.

It doesn't hurt that at a distance people will think you have a radial.

I've always admired these aircraft and have a big painting of a D10 in my hangar. You just need to find someone who will build you a round rad.

[rv6ejguy]

The OE water pumps on any modern engine that I've played with are more than adequate for very high sustained power levels. The Sube ones are driven off the cam belt on the EJ/EG series so if that breaks, you have other things to worry about- like a suitable field! Modern water pumps are super reliable and with aircraft maintenance procedures, I would never expect a failure on ones of these. I have not seen a failures in about 20 years and they give plenty of warning with seals or bearings. I've seen totally roasted pumps go many more months before getting replaced. They might seep a bit and grumble but they are tough.

Higher pressure just needs a higher cap pressure as Bill stated

The oblique rad setups probably show high drag compared to traditional layouts. No WW2 aircraft used these setups and these guys were pretty smart. Turning airflow 180 degrees is usually a recipe for high pressure loss.

My RV10 will retain the stock cowling for intercooler and oil cooler placement and airflow. Without the turbos, I could go with a more streamlined cowling- but I hate glass work anyway.

I use good old Prestone glycol- same as the P38.

[TSwezey]

This is my set-up with two large radiators which I think will be highly effective on the ground and will probably create significant drag at 200mph. Once I get everything running I will start working on some type of cowl flap system. Baby steps. Since it is pretty hot/warm down here 2/3's of the year I need to insure that my engine stays cool on the hots days.

[Rotary10-RV]

Originally Posted by rv6ejguy

I've always admired these aircraft and have a big painting of a D10 in my hangar. You just need to find someone who will build you an round rad.

Ross I'm sure you are tongue-in-cheek about the round rad. I should mention that the tapered curved radiator available for the Yamaha 750cc road racer was a great piece of aluminum sculpture, for a mere $10,000.00! I'd really hate to crash one of those!
Bill Jepson

[RV8RIVETER]

I didn't say it would be cheap.

Just listing it as another example of an aerodynamic and efficient radiator install. Minimal if any turns, close to the engine, nice exit distance to work with, and a good low pressure point to exit.

Would need custom radiators for sure, but may not be that expensive if on each side use half circles (I use that description loosely), or tapered ones with creative inlet ducting.

Originally Posted by Rotary10-RV

Ross I'm sure you are tongue-in-cheek about the round rad. I should mention that the tapered curved radiator available for the Yamaha 750cc road racer was a great piece of aluminum sculpture, for a mere $10,000.00! I'd really hate to crash one of those!
Bill Jepson

[rv6ejguy]

Originally Posted by Rotary10-RV

Ross I'm sure you are tongue-in-cheek about the round rad. I should mention that the tapered curved radiator available for the Yamaha 750cc road racer was a great piece of aluminum sculpture, for a mere $10,000.00! I'd really hate to crash one of those!
Bill Jepson

I was looking at a curved rad for a 250 GP bike a couple weeks ago. Very cool. I did not ask what it would cost.

The ground cooling thing is a bit of a bear with some installations. I've measured the pressure at various parts of the prop disc and it is pretty minimal near the prop shank. For decent ground cooling it seems that inlets outboard of 1/3 prop span give the best chance of success.

Getting good ground cooling, good climb cooling and no excessive drag in cruise where massflow is high and power is somewhat lower really demands some sort of cowl flap especially if you are not using a thermostat. The WW2 stuff generally did not use 'stats to restrict water flow. In flight, we are at odds with the shape of the radiator as well for what works well on the ground with low Delta P and high area probably hurts for drag in cruise. Flow bench tests show that pressure drop is not proportional to depth which is good but a thick rad is essentially useless on the ground as no air penetrates the core at the low Delta Ps available from the prop at idle. It is all a big compromise.

I did some other tests on the rad exit duct with 3 big centrifugal blowers and wool tufts. My thought was that turbulence could be reduced in this area using a double hinged flap to fill in the area aft of the flap at partially closed settings. The tufts showed this was not the case at all. The straight flap had less turbulence than the complicated solution I dreamed up. Easier to build too.

[Rotary10-RV]

Ross and Wade,
Didn't the round radiator system have a forced air fan? Kind of a slotted ducted fan? perhaps that was the FW190 oil cooler. I'm not right up on those radiators. The ability to change shape of the heat exchanger is one of the advantages listed in the WC plus column. An air cooled radial does fit this area better though, and that is without a very expensive radiator.
Keeping to the topic the ability to remote locate the radiators in an area that would normally be wasted space is a water cooled plus. The P-51 is an excellent example. The ME-109 had a good in-wing radiator as well. The 109 also had a interesting ability to split the inboard flap for good ground cooling.
Bill Jepson

[TSwezey]

Originally Posted by Rotary10-RV

Ross and Wade,
Didn't the round radiator system have a forced air fan? Kind of a slotted ducted fan? perhaps that was the FW190 oil cooler. I'm not right up on those radiators. The ability to change shape of the heat exchanger is one of the advantages listed in the WC plus column. An air cooled radial does fit this area better though, and that is without a very expensive radiator.
Keeping to the topic the ability to remote locate the radiators in an area that would normally be wasted space is a water cooled plus. The P-51 is an excellent example. The ME-109 had a good in-wing radiator as well. The 109 also had a interesting ability to split the inboard flap for good ground cooling.
Bill Jepson

I have thought about this many times. They make this tubing for installing under tile floors to keep them warm. It would be great if you could bond these to the wing skins. You could cool the engine and heat the wings (great against icing). Downside is a very complex piping network and added weight.