I believe it's safe to say Muller has no idea at all of the complexities involved in converting his throwaway statement into reality. He blithely speaks of the design change as if it is no more challenging than cobbling another heat exchanger on the aircraft, ignoring the fact that executing the same idea on the Starship overwhelmed Burt Rutan and Beechcraft while consuming a good portion of its billion dollar development costs.
10/23 Raptor Video
- Thread starter Volzalum
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Dont know the effect of the prop stream, but having the cooling outlet right at the end of the fuselage were the perimeter of the fueselage is shortest, makes up for the highest pressure location. On top, as the outlet is at the prop root where minimal suction takes place i suspect that the prop stream doesnt help to reduce pressure. He needs to radically overthink the cooling configuration and get rid of criteria based on aestetics in order to make the cooling work.
Maybe an aestetically atractive location would be to place two cooling units at each armpit, right after the door and below the wing.
Maybe an aestetically atractive location would be to place two cooling units at each armpit, right after the door and below the wing.
What do they know? They fitted an expensive and underpowered aircraft engine instead of a lightweight and efficient out of production car engine.
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Watched this video again after a long time. It seem like the bird climbs really slow. Can this be fixed in the current design? Seems like he added a lot of weight for the pressure cabin and other shenanigans.
rv6ejguy
Well-Known Member
Not without losing 1200 pounds of weight and redesigning the cooling system completely, so I guess the answer is no, not with the current design.
Induction/Exhaust systems have two main problem areas: Inappropriate sizing and inadequate intercooling. The results are less power than expected from the fuel flow and higher temperatures than are wise on everything from the compressors through the combustion chamber and turbines. Then there is the interactive issue of intercoolers being part of managed air for cooling.
Cooling has two main problem areas: Poor air management and inappropriately sized heat exchangers. The result is having to trade performance against overheat risk. Then there is the interactive issue of heat exchangers being part of managed air for cooling.
The two issues are mostly independent, but share in the air management to do the cooling.
Billski
rv6ejguy
Well-Known Member
I just uploaded Part 2 of my vids on liquid cooling last night:
Maybe Peter could watch these and see how others have done it successfully.
Maybe Peter could watch these and see how others have done it successfully.
New video, and the most efficient thing in his cooling system is the heater. I was surprised he’s still opening it as that is distorting his numbers and performance.
I’m really not clear on why his heater works so well to drop coolant temps...something really doesn’t seem right there.
I’m really not clear on why his heater works so well to drop coolant temps...something really doesn’t seem right there.
As I understand it, this also opens the big coolant tank in the nose, so he's flowing unheated coolant into the system, thus dropping the temps temporarily.
Thanks, Ross, great video.
1) Some aspects of achieving low-drag liquid cooling may not be obvious
2) The above has been known, and solid approaches have already been researched and widely promulgated for at least 75 years. But, first a person needs to know that they might not know everything already.
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rv6ejguy
Well-Known Member
A lot of cooling research was done in the 1940s and forgotten by many with the introduction of jets but if you dig, it's available. Several NACA papers exist online.
However many people don't know or don't care about cooling drag and slap some dreadful things together, just as we see on Raptor. There are very few good examples of low drag liquid cooling on new aircraft which is why I made these 2 vids. Also very little applicable data on small aircraft radiator design available, period.
However many people don't know or don't care about cooling drag and slap some dreadful things together, just as we see on Raptor. There are very few good examples of low drag liquid cooling on new aircraft which is why I made these 2 vids. Also very little applicable data on small aircraft radiator design available, period.
TarDevil
Well-Known Member
Watched the video last night, informative as always. Diametric contrast to the Raptor approach.
rv6ejguy
Well-Known Member
Frontal area is the killer at 480 knots... Voodoo is strictly a race/ record aircraft. 4000hp, heavily cooled with spray bars and ADI. Ingesting the boundary layer didn't seem to harm the speed of this aircraft. The builders know a lot more about this aspect than I do.
On my aircraft, the rad was placed against the belly skin so I had X frontal area to contend with. The inlet didn't need to be very big so the rest of the duct was just shaped for minimum drag.
The heater is most likely thin enough to be able to drive significant air through it, and thus reject a significant dose of heat. It does seem to be rejecting as much or more heat than the base radiator and duct scheme.
Early on temperature vs time data was being shared, but flight conditions were constantly changing, so estimating delta T's and time constants were impossible to determine. Now thermal performance data is not being shared, so we are in the dark.
The coolant temperature drops we have seen have been largely a matter of having the heater loop cold, and suddenly opening the loop, so that dose of cold coolant is dumped on the system, giving a quick cool. After the heater loop has been on for a bit, temps do climb again.
Billski
Ross has also shared elsewhere with us that his splitter has another function, that of preventing the radiator duct from ingesting a plume of hot air coming out of the cowling and coming out of the exhaust pipe. Russell achieved that goal by having his cowling exit to one side of the airplane while the radiator is to the other side...
Outstanding video and so much guidance on how to do this correctly. Qudos to Ross!
Billski
Billski
SuperSpinach
Active Member
Thank you very much for those two videos ! I watched the first one and was waiting for the second to come out. They are both very interesting !
rv6ejguy
Well-Known Member
Thanks guys. I see lots of people struggling with cooling auto engines. Hopefully these vids will lead them down a better path with less do-overs. I probably have 50+ hours into making these 2 vids so I hope some folks find them useful... I know I had very little to go on when I redid my setup.
I'm going to relax on the next few vids and do some easy ones.
I'm going to relax on the next few vids and do some easy ones.
