Really interesting
rv6ejguy said:
He did offer these treats for free however:
?.layed over radiators work just fine and rarely need turning vanes if designed right
All piston powered retractable general aviation planes have 1/3 of their drag due to cooling
P51 does NOT have low cooling drag
Internal turning never exhibits any losses for my cowls?I trust my measurements ZERO LOSS
Both air and liquid cooled??
Air cooled engines use much less air and have much lower drag by definition?.
Core face area or core volume is meaningless info?
As far as augmentors, have you ever seen one installed that exhibited any reduction in required pressure cooling? I did not think so..they all have full size inlets and exits so the augmentors are only ornamental?
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Turbo Subaru RV6A flying
Twin Turbo Subaru RV10 building
Race engine builder, fabricator, turbo junkie, technical writer, mad scientist since 1978
I have not got a chance to see the book. I gather the info you mention was in conversation? Is this what Jim LoPresti said? I don't get some of the comments? Can you explain them?
I do want to talk about water cooling since you are way more experienced with water cooled engines in planes, Subaru in particular, than I think anyone on these here forums.
" P51 does NOT have low cooling drag"
Really I have always heard how low the drag was? I have no strong opinion. I do think an air cooled Lyc in a RV is lower drag than any water cooled installation to date. That may change but not yet. Do you have some facts or can you elaborate on what he was saying? I know the P51 was not perfect and they can and do overheat. What do you think he was talking about?
" Air cooled engines use much less air and have much lower drag by definition?."
I can't believe that is true in general, but I do think it's true with today's small water cooled engine installations, which by default are Subaru and Mazda alternative engines. I don't know about Rotax's water cooling. Since they are 115hp max we'll forget them for now. Adapting water cooling to an airframe optimized for air cooled engines is always going to be a compromise. I know you are working on that. How is it going?
I would like your opinion on COOL JUGS in California. I talked to them the other day. They got their Piper/O360 cooled with 3.5 inches of water (air pressure). An air cooled Lyc needs up to 9 inches of H2O across the fins to cool.
I like the KISS method of air cooling, which is lighter (no glycol-water to carry around, pumps, hoses radiators), simpler and cheaper. However with that said, water cooling should allow a Lyc to run super high compression (12:1 CR) and get better efficiency (lower fuel burn) and/or power. The "NEW" Cool Jugs may be out in about a year for $17,000. We shall see.
If "Cool Jugs" ARE SUCCESFUL, it changes the equation around, where a small radiator with lower pressure requirements than a stock air cooled Lyc, would make the water cooling drag less. They have only one plane flying with the original designed COOL JUGS. They claimed they picked up speed even with an over-sized scoop and radiator. I recall 7 mph. The new design cylinders will have better combustion chambers and HC pistons (12:1 CR) which can run on 92 octan and not detonate. We shall see.
I am pro air cooling, but this may change if water cooled Lycomings show their full promise. On the other hand at $17,000, plus $1000 for a custom radiator/houses, I'll probably stay with air cooling. I think there is room for both, but it will take some changes in the methods and design used in a typical Subaru and Mazda. I think Cool Jugs may have a good design. We shall see, when there are 20 planes flying with the cool jugs for a few years.
"Core face area or core volume is meaningless info?"
Don't get it. I think if you have a smaller radiator, requiring less air than a larger one, the smaller radiator would have less drag? But it brings up a question about the relation of the cooling system as a whole and the radiator size.
"Cool Jugs" I think have better water flow and pumping which allows the use of a smaller radiator. You might disagree, but Subaru's and Mazda's both have cooling problems in planes. The recent Eggenfellner RV-9A test Van showed water temp was an issue. We can digress into how terriable Lycoming cooling is, but if it's baffled properly with an oil cooler sized and installed properly, cooling is not a big deal. However the Lyc driver does need CHT awareness and may have to lower the nose climbing out heavy on a very hot day. Since we all know 400F is the real max CHT for long engine life.
I speculate that the Cool Jug, with the higher pressure, high flow water pump, along with good water passage design, in parallel, allows it to be very efficient. This allows it to run a smaller radiator. Now you tell me is a 12" by 9" core, by 3" deep not a small radiator? I don't know, but I can see how to hide that inside the cowl with some ducting.
Do you reject the idea that a car cooling systems are not ideal for aircraft? I know the Mazda guys do have serial flow thru the case and do have steam pocket issues.
Here are some Cool Jug pictures. Look at the size of the water pump:
Just one of those big hoses can be $150!
"As far as augmentors, have you ever seen one installed that exhibited any reduction in required pressure cooling?"...." I did not think so..they all have full size inlets and exits so the augmentors are only ornamental?"
I am going to disagree (a lot), and I think AJ and others (the entire aerospace industry) have found that exhaust augmentors work great. I agree that if you increase the exit air velocity and efficiency and don't reduce the inlets or modulate the size of the exit, e.g., cowl flaps, using exhaust augmentation is not gaining you much, but augmentor exhaust nozzles are used on every thing from a C-310 to low-bypass turbofan engines to increase thrust or cooling.
There are stacks of studies and books showing the principles of exhaust augmentation, nozzles and
Coandă effect. This is based in physics and Bernoulli's principles, to dismiss it as useless is just "W", wrong, but it does have to be done properly. "Augmentation" is how modern jet engines work, high velocity air in a core of low flow air, promoting greater flow. Its also used in rockets. This area is well understood as is lift on a wing, it works.
Exhaust augmentation has been used in many plans, two GA planes that come to mind are C-310 and P-23 twins, commercial piston planes (military, airliners) many.
So may be his book is over priced? You think?