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It may have been possible.
Trying to figure exhaust thrust with any accuracy is just about impossible without a lot more data than we have for most planes. The only really good figures I have seen are for a Merlin XX in a Hurricane under test by RR.
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The RR data included the mass air flow, the exhaust gas velocity, the atmospheric pressure at altitude (and temperatures) some this was calculated. They had also rigged an engine in a test house/cell where they could but instruments on one cylinder bank to measure some this stuff while controlling the air pressure/temp. They then checked flight performace vs calculations.
Just saying engine X picked up 100hp due to exhaust thrust actually doesn't tell us much
photos for the earlier mentioned DB 601 exhausts
Now how much thrust do you get from a DB 601 engine??????
Or rather how much useful thrust if the axis of the thrust is 45 degrees from the aircraft's line of flight?
Kind of depends on the exhaust pipes doesn't it?
DB 605 on a Bf 110 night fighter.
Not only more drag but what is the velocity of the exiting exhaust gas at the rear after it is mixed with the cool/cold ambient air? Lowering the temperature of the exhaust gases lowes the volume and thus the pressure in the pipe. Lower pressure means lower velocity.
Perhaps the RR data was also for best-case scenario (exhausts as used on Spitfire IX, or P-51, not for the early type of exhausts as used on Hurricane I/II, Spitfire I/II/V, nor for the type used on Lancasters or Beaufighters)?
My sympathies for your loss. I saw your announcement but don't know you well enough to have anything more meaningful to say.
You accused me of being a "proponent of the Zero's virtues"
The "Normal Rated" Power for Hellcat isn't really the same thing as what was called "Normal Maximum" for the A6M series.
If you look at the closest engine settings to the "Normal Maximum" for Sakae engines and meet the criteria of Boost Pressure barely above Sea Level ambient and RPM about 250 below maximum, what you get for an equivalent for the Hellcat is "Maximum Cruise"
Interesting someone calculated Zero.21 as less drag than Zero.52. I suspect the smaller diameter cowling on 21 flowed better along fuselage cigar profile, Zero.21 is the efficiency peak of the design. The apparently similar speeds for A6M2 vs A6M3/5 is only valid for the A6M2's single speed supercharger rated altitude 14,000ft, above and below that the two speed A6M3/5 is faster peaking at 9,000/20,000ft.Speeds Zero 21/22/52
Thrust exhausts , jet thrust effect?
ANd we are talking about exhaust thrust and not exhaust Horsepower which is inversely proportional to the speed of the aircraft.
The closer the plane's speed matches the speed of escaping gases the more "power" you get from the same thrust.
Exhaust (or jet thrust) with the plane parked on the runway with brakes set is zero thrust horsepower.
Sorry, it wasn't meant as something demeaning. You seemed to be providing me with a point/counterpoint situation. I find it's more fun to have a little healthy competiveness while exchanging information (must be the military guy in me). I was taking the pessimistic approach concerning maximum level speeds attained, while you seemed to be more optimistic IMHO. This obviously didn't turn out for the best though...
So let me see if I have this straight. The speed listed in the A6M5 manual is for "Normal Maximum", which is basically like a high cruise setting for the airplane, correct? But doesn't 338 mph at altitude seem rather excessive to you in this setting, especially with boost running barely above normal S/L pressure? There has to be more to this that I'm honestly not getting at that moment. Does the manual happen to give the altitude for that particular speed?
we just avoided them when possible
Interesting someone calculated Zero.21 as less drag than Zero.52. I suspect the smaller diameter cowling on 21 flowed better along fuselage cigar profile, Zero.21 is the efficiency peak of the design. The apparently similar speeds for A6M2 vs A6M3/5 is only valid for the A6M2's single speed supercharger rated altitude 14,000ft, above and below that the two speed A6M3/5 is faster peaking at 9,000/20,000ft.
Quotes for the Zero.22 been faster than the Zero.32 are an example of a test anomaly as the 32 was originally made because the long 2x series wings were felt to slow the A6M3 too much! Given the data sources we have on other Japanese planes I suspect the often quoted 351mph speed for A6M5 was a pre-production test machine.
Interesting someone calculated Zero.21 as less drag than Zero.52. I suspect the smaller diameter cowling on 21 flowed better along fuselage cigar profile, Zero.21 is the efficiency peak of the design. The apparently similar speeds for A6M2 vs A6M3/5 is only valid for the A6M2's single speed supercharger rated altitude 14,000ft, above and below that the two speed A6M3/5 is faster peaking at 9,000/20,000ft.
Quotes for the Zero.22 been faster than the Zero.32 are an example of a test anomaly as the 32 was originally made because the long 2x series wings were felt to slow the A6M3 too much! Given the data sources we have on other Japanese planes I suspect the often quoted 351mph speed for A6M5 was a pre-production test machine.
I also would have expected Model 32 to be slightly faster, but that is not how it is listed in the manual.
The difference is very small and the altitudes are not quite the same even for the same engine, so perhaps that affected the results.
What I don't see is how it would reduce the heat load on the exhaust valves and how the engine's RPM limit would be raised.
Regarding pre-production A6M5, there appear to have been quite a few service test examples with different configurations. Are you suggesting that the definitive production variant was faster or slower?
Yes we are looking at a <2% difference in speeds, not statistically significant unless they tested 10 of each plane, which i doubt! Logically the short wing Model.32 should be faster but perhaps at around the 20,000ft top speed height the longer winged Model.22 has some advantage.
I found some papers about metallurgy of aircraft exhaust steels by Roll Royce where they say collector rings run at 800'C and straight exhausts run at 400'C. My piston engine experience is in street racing car engines, and a free flowing exhaust does improve throttle response, and alone they can improve power by ~10% over simple "log" manifolds even on a common engine. Its not really a higher RPM limit, but as more power now comes at higher RPM that makes that high RPM usable. If the exhaust is very restrictive all the 1000'C exhaust gases will not be expelled and some remain in the cylinder, and gases in the exhaust pipe may even flow back to the closed exhaust valve after it closes due to back pressures!
I was shocked when I first saw a typical radial engine exhaust collector, its about as bad a design for efficiency as you could make. There is no doubt a free flow exhaust on a radial would increase HP, I am surprised there is no test data on this?
I think 351mph is the speed for a good A6M5, The 1944 US tests A6M5 was part of a batch of ~12 they brought from Saipan, so I give them credit that they built a decent one out of that and they got 335mph which is only <5% slower.
Quoted Aircraft Speeds
exhausts & A6M2 vs A6M3/5 performance
I agree there would be some test basis, but I bring up the Me109G-2 tests the Germans did in 1942, from memory they tested some 20 planes coming of the production line and the speeds varied 390-410mph!
I may overemphasise the exhaust valve issue but straight through thrust-pipes would remove some heat from that region. I would love to see some HP test data on the change from collector ring to thrust-pipes for the Sakae engine, stating 1130hp for all definately is an example of book figures rather than tested figures.
I was just giving an example of production variation, a complex machine like an aircraft assembled by several different shifts from different production batches will not all be +/-1% to book values.I don't actually know much about the production of the Me 109G-2,
Ask HiromachiIs this the book "Eagles of Mitsubishi"? If so, what page is the description on? (I just want to read about it for myself.)
My own belief is that the actual power increase of the Sakae 21 over Sakae 12 turned out to be much less than expected.
The Ki-43-I had a huge wing and apparently not as smooth riveted skin as Zero, also the fuselage design was not a high speed cigar, and Army used worse fuel than Navy before 1942! Its interesting that the Ki-43 followed much the same development path, but improved much more over its development than Zero to catch up and even slightly overtake it. The Ki-43 with 2 speed ha-115 "Sakae.21" did 1 major cowl redesign to taper it better and 3 redesigns of air intake to enlarge it and move into air stream more.Note that the Ki 43-I had the same intake configuration as A6M2 and was a LOT slower with basically the same engine.
The water-injected Sakae.31 is a bit of a mystery, it apparently needed a larger cowling, but the Ki-43-III's water-injected ha-115-II did not? Perhaps the Navy used direct manifold injection ?!?The typically listed power output for the Ki 43-III is over 1200 HP and apparently the Army managed to get a Water Methanol injection system working on it while the Navy didn't with the A6M5.
yes the Sakae.21 only got some 200rpm more and +2psi extra boost, the 2 speed supercharger helped low alt and high alt. The 980 vs 1130hp is misleading as its a low altitude peak. But it was ~50kg heavier and needed a larger cowling. I find the A6M3/5 cowl ugly
The Ki-43-I had a huge wing and apparently not as smooth riveted skin as Zero, also the fuselage design was not a high speed cigar, and Army used worse fuel than Navy before 1942! Its interesting that the Ki-43 followed much the same development path, but improved much more over its development than Zero to catch up and even slightly overtake it. The Ki-43 with 2 speed ha-115 "Sakae.21" did 1 major cowl redesign to taper it better and 3 redesigns of air intake to enlarge it and move into air stream more.
Although they say air ram effect only really matters over rated altitude of supercharger speeds, so maybe thats why zero did not get a better one.
The water-injected Sakae.31 is a bit of a mystery, it apparently needed a larger cowling, but the Ki-43-III's water-injected ha-115-II did not? Perhaps the Navy used direct manifold injection ?!?
The later cowl is undoubtedly higher because of the relocated intake, but is it also wider?
Ki-43-I.... and there was enough of an engine power increase that its speed advantage may be attributed to that rather than aerodynamic improvements.
Did the changes in intake configuration actually improve performance of the Ki 43-II and if so, by how much?
I believe the photographs I have seen of Sakae 31 aircraft have had more of a gap between cowl flaps and fuselage but otherwise look the same
The A6M3/5 cowl is higher as the cowl MG openings get covered by it, where in the A6M2 they are open channels. Whether the cowl is a perfect circle though?
In comparison the Ki-43-I -> II cowl did not get wider, just longer and MG tubes appear same.
Apparently early IJ army fuel was only 87 octane up to 1942. The two blade propeller may be a case of cheapness rather than performance like using old tubular gunsights on Ki-43-IBut the Ki-43-I was a "bad" plane, Nakajima got free contract from Army without competition, (and this at around time they said Zero was impossible to build but Horikoshi did it!) Zero should have replaced Ki-43 by Pearl Harbour if they made honest appraisal and no Army vs Navy rivalry!
I rechecked my references and some do state the Army Ha-115 (Sakae.21) take off HP increased from 1120 -> 1130 -> 1150 -> 1190 during the different Ki-43 series. The 1130 -> 1190hp increase actually matches my guess-estimated 5% increase from straight pipes vs collector ring!
With a series of constant refinements during 1943 the Ki-43-II went from around 320 to 335mph on the same power, the Ki-43-III may have tested 358mph in clean configuration but all came with bomb racks (see above) that cost ~15mph, so it also was around 340mph true speeds.
Well spotted, its just an optical illusion from slightly shorter cowl flaps? Maybe this was a way to get some more cowling without drag?
I think also Sakae.31 was a case of why bother....it would not have been enough help and their were other more promising projects to do in 1945.
AeroDetail states that the cowl was larger for Sakae 31 and seems to indicate that Model 62 would have had Water Methanol injection but Model 63 had Sakae 31 without Water Methanol. I take it that for more promising, you are referring to A6M8 with Kinsei engine?
I am actually a bit surprised that there was such a great loss in speed with the wing racks on Ki 43-III. That would actually make the factory Ki 43-III slower than a factory new A6M5.