High-end V-12 engines in Ki-84/Ki-61 (1 Viewer)
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Shortround6
Lieutenant General
You might be able to change a Ki-84. There is a lot more work to changing a Ki-61. Good work instead of poor work (design) involves a good /low drag cooling system.
Stuffing in engines that weight hundreds of pounds of pounds more and their larger propellers requires a lot of work to get the CGs right.
Spit XII gained about 1000lbs (?) over a Spit V. Spit XII used the single stage, two speed Griffon.
Stuffing in engines that weight hundreds of pounds of pounds more and their larger propellers requires a lot of work to get the CGs right.
Spit XII gained about 1000lbs (?) over a Spit V. Spit XII used the single stage, two speed Griffon.
cherry blossom
Senior Airman
- 555
- Apr 23, 2007
Fully agree that there would be a great deal of work to be done especially on the cooling system but the Ki-61-II has a performance not too different from a Spitfire V with about the same power, so I would suspect that going to a Merlin 60 series would give performance similar to a Spitfire IX and changing to a Griffon 65 might give something like a Spitfire XIV. However, if the Japanese designer had looked at the radiator from a Mustang, he might have been able to do rather better.
For a minimal change, fitting a DB 605 DB might give 1600 PS output at 6,0 km (Kurfürst - Performance of 8 - 109 K4 and K6 with DB 605 ASCM/DCM) which would be notleistung compared to a military power of 1250 ps at 5.7 km for a Ha 140.
For a minimal change, fitting a DB 605 DB might give 1600 PS output at 6,0 km (Kurfürst - Performance of 8 - 109 K4 and K6 with DB 605 ASCM/DCM) which would be notleistung compared to a military power of 1250 ps at 5.7 km for a Ha 140.
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- #4
The Ki-61 had dimensions and radiator arrangement similar to some of the Italian Series-5 fighters. I suspect it would be similar to the Fiat G.56 outfitted with DB 603.
And the Ki-61 featured kind of a licensed DB 601 in the Ha-40 engine already.
Maybe most of the fighters with underslung radiators could be refitted with Mustang-style radiators.
The Ki-84 fuselage, sleek as it is, was designed to house a radial engine right from the start, so the diameter was likely larger compared to one designed for inline engines. So drag might be a bit higher for it.
And the Ki-61 featured kind of a licensed DB 601 in the Ha-40 engine already.
Maybe most of the fighters with underslung radiators could be refitted with Mustang-style radiators.
The Ki-84 fuselage, sleek as it is, was designed to house a radial engine right from the start, so the diameter was likely larger compared to one designed for inline engines. So drag might be a bit higher for it.
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Depends on the engine version.
A 1-stage supercharged Griffon, DB 603 or the Jumo 213 might put these aircraft to real 400+ mph/650+ km/h? The 2-stage supercharged versions might've put them close to 430-440 mph/700 km/h?
Ki-61/-100 series was not with some fancy airfoil - 2R14 (same series like on the Bf 109 & 110) with the 16% t-t-c at root is behind the curve when compared with the laminar-flow wings or vs. the 13% t-t-c at root Spitfire's NACA 2200 series. The thickness to chord ratio of the Ki-84 was supposedly at 18% - again, not good when compressibility awakens. Neither aircraft was with a small wing, either.
A 1-stage supercharged Griffon, DB 603 or the Jumo 213 might put these aircraft to real 400+ mph/650+ km/h? The 2-stage supercharged versions might've put them close to 430-440 mph/700 km/h?
Ki-61/-100 series was not with some fancy airfoil - 2R14 (same series like on the Bf 109 & 110) with the 16% t-t-c at root is behind the curve when compared with the laminar-flow wings or vs. the 13% t-t-c at root Spitfire's NACA 2200 series. The thickness to chord ratio of the Ki-84 was supposedly at 18% - again, not good when compressibility awakens. Neither aircraft was with a small wing, either.
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- #6
Wing area of both (20/21 sqm) was less than a Spitfire's (22,5 sqm/ 23.5 sqm for 20 series) though.
Are the drag properties of the wing profile of the NACA 2415 (Fiat G.56) and NACA 0015 (Re.2006) known?
Ki-61/100 is said to have very good dive characteristics, something I couldn't quite get behind, getting close to 850 or 900 km/h iirc.
A very high figure especially when seeing its wing shape and single-spar construction.
We can take the Fw 190 as a measuring stick.
18.3 sqm wing area, more modern and a bit thinner profile than what the Ki 61 had (and much thinner than what the Ki-84 had). Speed - book values - for the 190D-9 was 685 km/h with the Jumo 213A on 87 oct, without MW 50. Loose 10 km/h on account of the bigger wing, and 10km/h on account of the worse wing profile that is also a bit thicker?
FWIW, the Ki-61 with the Ha-140 engine (1250 HP at 5700m) did 610 km/h (per the Bunrin-Do book about the Ki 61), vs. 628 km/h Re.2005 prototype, or 626 km/h G.55 prototype (same power vs. altitude; late 1942 Italian data per this). Does not point to some great streamlining of the Ki-61.
Probably our best bet is to page
Aeroweanie and
drgondog .ThomasP
Chief Master Sergeant
re
From what I have read the Ki-61 series had a very rugged 3-spar wing structure. I do not have the post-war US analysis of the Ki-61, but it commented on the rugged structure. AFAIK the US did not do maximum dive speed tests, but the Japanese Ki-61 pilot's manual states the VNE as 435 mph IAS which works out to M0.85 (960 km/h) at 20,000 ft, M0.77 (890 km/h) at 15,000 ft, and M0.69 (820 km/h) at 10,000 ft - the altitudes at which most airframes were tested for VNE in a dive.
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From what I have read the Ki-61 series had a very rugged 3-spar wing structure. I do not have the post-war US analysis of the Ki-61, but it commented on the rugged structure. AFAIK the US did not do maximum dive speed tests, but the Japanese Ki-61 pilot's manual states the VNE as 435 mph IAS which works out to M0.85 (960 km/h) at 20,000 ft, M0.77 (890 km/h) at 15,000 ft, and M0.69 (820 km/h) at 10,000 ft - the altitudes at which most airframes were tested for VNE in a dive.
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- #9
The D-9 was less draggy than the Spitfire XIV.We can take the Fw 190 as a measuring stick.
18.3 sqm wing area, more modern and a bit thinner profile than what the Ki 61 had (and much thinner than what the Ki-84 had). Speed - book values - for the 190D-9 was 685 km/h with the Jumo 213A on 87 oct, without MW 50. Loose 10 km/h on account of the bigger wing, and 10km/h on account of the worse wing profile that is also a bit thicker?
FWIW, the Ki-61 with the Ha-140 engine (1250 HP at 5700m) did 610 km/h (per the Bunrin-Do book about the Ki 61), vs. 628 km/h Re.2005 prototype, or 626 km/h G.55 prototype (same power vs. altitude; late 1942 Italian data per this). Does not point to some great streamlining of the Ki-61.
Probably our best bet is to page
Seeing the figures of the Italian fighters, I assume that the Spit was still less draggy than the Japanese fighters.
True.
These radiators on the Spits with 2-stage engines, especially with the 2-stage Griffons, cost an arm and a leg wrt. the drag.
As above - depends on the engine, plus on the bits & pieces, like the BP glass, exhausts, type of carb, presence or absence of wheel well covers, type of tailwheel, and on the fit & finish.
Choice of the wing thickness on the Spit was a masterpiece, though. Too bad it didn't received the next-gen radiators' layout by some time of 1942-ish.
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- #11
If given all the contenders an improvement on all bits and pieces while keeping the original shapes.
Performance boost with implementation of Spiteful radiator arrangement would be interesting. Wonder why it wasn't used.
Are there estimates of expected performance improvement for the Spitfire airframe with those?
Shortround6
Lieutenant General
Sometimes they couldn't do much to radiators without rebuilding half the aircraft.
Many radiators go up into the aircraft quite a ways, as boxy as the Ki-61 radiator looks the actual radiator is about double in height and goes up into the fuselage just about as much as it comes down. On the 109s and Spitfires the radiators go up into the wing and fit between ribs. If you want to fit wider radiators you have extend the radiator bay/s and restress/redirect the forces that act on that area of the wing. You do need to use about the same area of radiator assuming you use the same radiator construction. Deep like the Spitfire XIV or shallow but much wider?
A lot less frontal area but it is kissing goodbye to any Meredith effect. To have any Meredith effect they have to have a sizable change in the cross section of the duct. AND the change in cross section has to not be abrupt in the inlet or the exhaust side.
Spiteful used short and wide, also used a new wing that would hold it.
Many radiators go up into the aircraft quite a ways, as boxy as the Ki-61 radiator looks the actual radiator is about double in height and goes up into the fuselage just about as much as it comes down. On the 109s and Spitfires the radiators go up into the wing and fit between ribs. If you want to fit wider radiators you have extend the radiator bay/s and restress/redirect the forces that act on that area of the wing. You do need to use about the same area of radiator assuming you use the same radiator construction. Deep like the Spitfire XIV or shallow but much wider?
A lot less frontal area but it is kissing goodbye to any Meredith effect. To have any Meredith effect they have to have a sizable change in the cross section of the duct. AND the change in cross section has to not be abrupt in the inlet or the exhaust side.
Spiteful used short and wide, also used a new wing that would hold it.
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- #13
Performance-wise the Spiteful (2375 hp) was on par to or even a few mphs faster than the P-51H (2218 hp).
There was a Spitfire concept which featured Mustang-style radiator.
They should have gone with that which would have propelled the Spiteful to even greater speeds.
drgondog
Major
Page 480-490 for Lift and Drag Coefficients for the NACA 2415 in Theory of Wing Sections. Page 324 for pressure distribution and wing thickness form for NACA 0015. Both A/c ~ 0.239 to 0.241. Both at Cd minimum of ~ 0.010 at RN 6x10^6.We can take the Fw 190 as a measuring stick.
18.3 sqm wing area, more modern and a bit thinner profile than what the Ki 61 had (and much thinner than what the Ki-84 had). Speed - book values - for the 190D-9 was 685 km/h with the Jumo 213A on 87 oct, without MW 50. Loose 10 km/h on account of the bigger wing, and 10km/h on account of the worse wing profile that is also a bit thicker?
FWIW, the Ki-61 with the Ha-140 engine (1250 HP at 5700m) did 610 km/h (per the Bunrin-Do book about the Ki 61), vs. 628 km/h Re.2005 prototype, or 626 km/h G.55 prototype (same power vs. altitude; late 1942 Italian data per this). Does not point to some great streamlining of the Ki-61.
Probably our best bet is to page
Once the 2-stage engines were in the play, and especially the 2-stage Griffons, Spitfire was scoring bad grades both in the extra frontal area of the radiators, as well as in the Meredith effect usage. Having a lot less of extra frontal area via the LE radiators set-up reverts one bad grade into a good grade.
For the Japanese fighters, they can also benefit with the improvement of the ttc ratio with the leading edge extensions that house the radiators, in the same fashion many British aircraft benefited, as well as what the NACA suggested for the P-38. Or, they can go in the German fashion and use the annular radiators.
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- #16
Please excuse my layman's question but what does it mean wrt to the comparative drag values of the other fighters? Could you elaborate?
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- #17
How was the Meredith effect with leading edge and annular/drum radiators?
Depends on the specific installation?
IMO - if the postulates of the Meredith idea (basically, smooth expansion towards the radiator, then the radiator itself, followed by the smooth reduction of the area towards exit; no structural members to mess with the airflow) are followed, coupled with no boundary layer problems - easy to do with both LE and annular installation - and continuous control of the exit, the reduction of cooling drag should be notable.
FWIW, the Meredith effect oil cooler was one of the things mooted for the BMW 801F installation for 1945.
drgondog
Major
Well, the P-51wing based on NAA/NACA 45-100 which was loosely speaking a derivative of the NACA 45-125 laminar flow airfoil, had a CDp of 0.0070 @ RN=2.0x10^6. The P-51H wing based on NACA 66,2 (18155) airfoil had a CDp of 0.0054
Builder 2010 The Spitfire wing based on NACA 2213, IIRC was in CDp=0.009 @RN=2.0x10^6.
While the drag of the Mustang wing was lower due to not only the airfoil features, the production processes of very fine tolerances for surface flatness and 'smoothness' due to the putty/prime/sand/paint processes were also a major factor on reducing drag. When paint chipped, drag increased.
The major factor in high speed drag reduction was the Meredith effect obtained by the near unique NAA approach, namely a well designed intake and exhaust plenum which encouraged boundary layer attachment nearly to the radiator matrices (Oil and Coolant). That is critical to achieve nearly equal pressure distribution across the radiator face.
The second critical design feature, missed by nearly all competitors, was the lengthy exit plenum to achieve retention of energy (heat and velocity) of the exit of heated air from the radiator coils. If you look at the changes from P-51B/D to F/G/H you will notice dramatic change in aft plenum length - nearly all the way back to the tail wheel doors. The higher the exit temp, given same cross section of scoop, the higher the velocity of the exit gases.
The P-51H actually achieved net positive thrust at 90"MP speed runs, but also quickly overheated at low altitudes.
The P-51H also had a better designed intake plenum by removing the oil cooler from the lower plenum and placing it in the engine bay where it share heat transfer system with the engine return coolant. In that move the intake plenum was nearly symmetrical on top and lower surface, making it easier to delay boundary layer separation during expansion to the radiator face.
David Lednicer (Aeroweenie) performed excellent theoretical models and internal pressure and temp profiles for the P-51D. Offhand I don't recall the Paper but I uploaded it into the Tech section here many moons ago. In comparison Lednicer is a giant of applied aerodynamics compared to me.
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- #20
I thought it to be a construction with a single main spar and two auxiliary spar fore and aft.
I wonder how it compares two the, also very rugged, two-spar design of the Fw 190 with its massive front main spar.
You have VNEs for other fighters as well for comparison (especially Fw190, Spitfire, Mustang, Corsair etc.)?
