Technical developments of a Luftwaffe vs. VVS only war

[Koopernic]

An intercooler, in the case of the Jumo 211J or Merlin 60, is an liquid air heat exchanger that uses the cooling water from the standard radiator. It does not increase frontal area, its a surprisingly small device. Cooling requirements might go up somewhat which would require a slightly larger radiator or wider open settings for the cooling gills.

This admittedly turned into a problem for the Fw 190D12 and D13 as they used a Jumo 213F (same as Jumo 213E but without intercooler). The more powerful C3 fuelled two stage supercharged engine generated more heat and so the radiator gills had to be kept open which increased drag. As a result the aircraft had after about a minute the same speed as the Fw 190D9. This was forced as result of an economy measure, using the same radiator as the Fw 190D9. The aircraft had better acceleration, climb and power to weight ratio as well as service ceiling. They decided to wait till the Jumo 213EB came out with the compact intercooler and enlarged radiator.

A 1 minute take-off rating for a Jumo 211J intended to get a bomber in overload condition off the ground before it ran out of runway might turn into a 3 minute WEP rating for a fighter at speed, since the airflow provides more cooling effect.

 

[tomo pauk]

An intercooler, in the case of the Jumo 211J or Merlin 60, is an liquid air heat exchanger that uses the cooling water from the standard radiator.
It does not increase frontal area, its a surprisingly small device. Cooling requirements might go up somewhat which would require a slightly larger radiator or wider open settings for the cooling gills.

Intercooler is indeed a heat exchanger. The liquid-to-air system will need a radiator, pump, coolant fluid, tubing, regulation. Air-to-air intercooler is the radiator in the same time - simpler lighter, but might be not that flexible to install it.
The Jumo 211J used the air-to-air heat exchanger, the air was 1st compressed by the S/C, then routed down to the intercooler, then routed in the intake manifold. The intercooler used separate air stream vs. coolant and oil radiators.
Please note the bulge due to the intercooler, would it be worth to shoehorn it on the tightly packed Bf-109?

Air-to-air intercoolers were used in P&W turboed and 2-stage supercharged engines, as well as in turbo V-1710s. Once better intercoolers were installed in the P-38J, it gained a good deal of power, but some of the gain was consumed by increased drag.
2-stage Merlin used separate system to provide the coolant for its liquid-to-air intercooler, with, eg. in a Spitfire, a rectangular radiator slung under left wing, sharing the housing with the oil cooler. Cd0 went from 0.0213 (Spit V with 2 cannons + 4 LMGs) to 0.0229 (Spit IX with same armament). Sure enough, with hundreds of HP gained, intercooler it's radiators were low price to pay - not so much with proposed Jumo-211J installation on the Bf 109.

This admittedly turned into a problem for the Fw 190D12 and D13 as they used a Jumo 213F (same as Jumo 213E but without intercooler). The more powerful C3 fuelled two stage supercharged engine generated more heat and so the radiator gills had to be kept open which increased drag. As a result the aircraft had after about a minute the same speed as the Fw 190D9. This was forced as result of an economy measure, using the same radiator as the Fw 190D9. The aircraft had better acceleration, climb and power to weight ratio as well as service ceiling. They decided to wait till the Jumo 213EB came out with the compact intercooler and enlarged radiator.

What would be the source for the claim that Jumo 213F used the same radiator as the Jumo 213A? Source for the Jumo 213F using C3 fuel?
The Jumo 213EB was to use the 'unitary' cooling system, with single barreled-shaped radiator. Main flow cooled the engine coolant, heat exchangers served the oil cooler and intercooler. Germany was in no position to wait for anything in late 1944/early 1945.

A 1 minute take-off rating for a Jumo 211J intended to get a bomber in overload condition off the ground before it ran out of runway might turn into a 3 minute WEP rating for a fighter at speed, since the airflow provides more cooling effect.

Let's say it is happens so. With all the pros cons of that installation, what is the gain vs. the Bf 109F4 with fully rated DB 601E or the Bf 109G2 with restricted DB 605A?

 

[Koopernic]

Intercooler is indeed a heat exchanger. The liquid-to-air system will need a radiator, pump, coolant fluid, tubing, regulation. Air-to-air intercooler is the radiator in the same time - simpler lighter, but might be not that flexible to install it.
The Jumo 211J used the air-to-air heat exchanger, the air was 1st compressed by the S/C, then routed down to the intercooler, then routed in the intake manifold. The intercooler used separate air stream vs. coolant and oil radiators.
Please note the bulge due to the intercooler, would it be worth to shoehorn it on the tightly packed Bf-109?

View attachment 290835

Air-to-air intercoolers were used in P&W turboed and 2-stage supercharged engines, as well as in turbo V-1710s. Once better intercoolers were installed in the P-38J, it gained a good deal of power, but some of the gain was consumed by increased drag.
2-stage Merlin used separate system to provide the coolant for its liquid-to-air intercooler, with, eg. in a Spitfire, a rectangular radiator slung under left wing, sharing the housing with the oil cooler. Cd0 went from 0.0213 (Spit V with 2 cannons + 4 LMGs) to 0.0229 (Spit IX with same armament). Sure enough, with hundreds of HP gained, intercooler it's radiators were low price to pay - not so much with proposed Jumo-211J installation on the Bf 109.



What would be the source for the claim that Jumo 213F used the same radiator as the Jumo 213A? Source for the Jumo 213F using C3 fuel?
The Jumo 213EB was to use the 'unitary' cooling system, with single barreled-shaped radiator. Main flow cooled the engine coolant, heat exchangers served the oil cooler and intercooler. Germany was in no position to wait for anything in late 1944/early 1945.



Let's say it is happens so. With all the pros cons of that installation, what is the gain vs. the Bf 109F4 with fully rated DB 601E or the Bf 109G2 with restricted DB 605A?

The source I believe is: Focke-Wulf Fw 190, Vol. 3: 1944-1945Jan 26, 2015 by Eddie Creek and J. Smith. Sorry I can't provide a photograph. I think you'll find it in Dietmar Hermann book long nose as well. I am overseas on 'site' and don't have access to my library to check.

Its my assumption that the Intercooler on the Jumo 213E1, as used on the Ta 152H was already a liquid air type, the so called "warmtauscher" but the fact that the Jumo 211F was exactly the same engine without the heat exchanger might explain why the Fw 190D12/13 didn't receive the Jumo 213E1 and had to take the Jumo 213F but was expected to take the Jumo 213EB. I can't see air to air intercooler on the Ta 152H, there are no structures for it. The use of C3 fuel would have compensated for the lack of heat exchanger.

The use of an air to air intercooler creates a problem for Me 109 integration, I believe Avia succeeded in part. Stanley Hooker chose a water based unit its said because the Spitfire was already being considered, that may be wrong given the Merlin 60's roots in the high altitude Wellington.

 

[tomo pauk]

In this post there is a diagram depicting different radiators for the Fw/Ta fighters (taken from the JaPo book about the Ta 152). The 213F inherited radiator set-up from 213E, not the 213A.

Its my assumption that the Intercooler on the Jumo 213E1, as used on the Ta 152H was already a liquid air type, the so called "warmtauscher" but the fact that the Jumo 211F was exactly the same engine without the heat exchanger might explain why the Fw 190D12/13 didn't receive the Jumo 213E1 and had to take the Jumo 213F but was expected to take the Jumo 213EB.

Von Ghersdorff et al list the 213E1 as without intercooler (1750 PS for TO, with MW 50 2050 PS per same source); the 213E0 was with intercooler.
Agreed that C3 fuel would help without an intercooler installed, though the 213F (merely a renamed 213E1?) was to use MW 50 to help out. Both D9 and D12 (single stage engines) have smaller cooling and fuselage drag than Ta 152 fighters (2-stage engines); D12 was to be quite a performer, along the lines of world's best of 1944/45.

The use of an air to air intercooler creates a problem for Me 109 integration, I believe Avia succeeded in part.

Avia installed the Jumo 211F in the late Bf-109G airframe, not the intercooled 211J.

edit: you're right that 213E used the heat exchanger (Waermetauscher), not just for needs of the intecooler, but also for coling the oil - per Von Ghersdorff et al. The annular cooler provided the cool liquid for all 3 cooling needs.

 

[kool kitty89]

I would not be so sharp, e.g. Operation Blau had sensible roots, Germany needed Causasian oil, Volga was an essential waterway to the SU and Stalingrad was an important industrial and transport center. Problems were Hitler's demand to try to conquer Stalingrad and Caucasus simultaneusly not one after another and the logistics. Did germany have capacity to reach Baku in 1942?

The issue of oil/fuel resources and logistics came up here:
http://www.ww2aircraft.net/forum/av...ofessionals-study-oil-production-43043-5.html

A lot was discussed but one big point was there were many alternate solutions for expanding German fuel production outside of greater access to crude oil. The shale oil reserves mentioned early on in the thread weren't all that viable to expand in the short term, but the synthetic fuel production using a variety of coal types and potentially biomass (wood waste, agricultural waste, any sort of plant waste able to be amassed and transported effeciently, potentially domestic and industrial waste/recycling programs as well -but the coal reserves was the main/immediate interest). A much broader array of synthetic fuel plants could have been dispersed and the infrastructure shifted more and more towards the much more efficient to produce fractions of the products from Fischer–Tropsch fuel plants -particularly methanol, ethanol, butanol, acetone and a few others. (ideally they should have made the shift starting pre-war, but the earlier the better -and in the interim, focus on producing the most efficient fuels still acceptable in the existing infrastructure; along with that, drop further investment in the far more costly hydrogenation based fuel plants, maintain the ones in service, and use the limited oil and liquid coal fractions to supplement synthetic liquid fuel production)
Germany had a great deal of coal reserves to work with and lots of options for fuel production and power generation based on that alone. (Italy and Japan had other problems though ... and Italy was just starting to exploit their natural gas reserves and potential synthetic fuel production based on that)


But the overall logistics and fuel situation are another topic anyway, and managing efficient transportation/allocation of what resource they DID have historically was as big of a problem as the limited quantities of resources themselves.


But on the issue of the Caucasus oil fields ... with more sane military planning, attempted capture/occupation could have made sense along with contingencies in the event of failure or potential destruction of the entire infrastructure in a scorched earth campaign. (destroying that source of oil for Russia would at least be a more minor strategic gain, though the question of risk vs reward and opportunity costs for expending those resources trying to capture Caucasus is still important)

The governments in exile are likely going to cut deals with Hitler if Britain drops out, so they bring back their merchant shipping, while the end of the war and blockade means German shipping can come home from the neutral ports they were trapped in during the early war. Plus the Axis captured a fair amount of foreign shipping in the invasion of Norway and Western Europe. Britain didn't control all the waters of Europe, so its not as if they could legally inspect German shipping for contraband; they could cut sales of contraband once Germany invades the USSR, but not stop Germany trading with other neutrals. Britain didn't have the finances to give the USSR unlimited anything for free, plus its not as if the British conservative party, which had a visceral class hatred of the USSR, would supply the USSR with anything for free, rather they were more likely to sell them whatever they could afford and bank on Germany getting stuck in an endless occupation and low/medium level conflict in the East as the rump USSR continued to resist from Central Russia even if it wasn't able to drive out the Germans.

What if Germany had focused on securing the coastal regions more aggressively than deep penetration into Russia? Focus on securing/maintaining alliances/neutrality with Scandinavian states and invading/capturing the Baltic region, creating a land blockade on Russia?

The DB605A didn't get released for 1.42 ata boost till somewhere between june-October 1943. Thus for nearly a year the Jumo 211J produced more power, mainly down low.

This is only comparing the existing DB-601E and 605A (the latter possibly not even existing in this scenario -or developing differently due to different resource limits), not potential models turned with lower FTH in mind, less charge heating, and less power consumed by the supercharger.

Granted, it's also ignoring potential developments like WM/50 use (on either DB or Jumo engines) or possible Jumo 211s tuned for C2 or C3 fuel. (or not even tuned for it per se, but cleared for higher power levels and boost limits with such fuel)

Not to drift the topic too much, but higher octane fuel might have become the norm if a shift in synthetic fuel manufacturing was being undertaken.

Aside from that, the lack of provisions for mounting hub cannon on the Jumo 211 would be a problem, unless this too changed.

Ju 288A was to weigh 11 tons, have 3 crew and required 2000hp of the Jumo 222A2/B2. The first two Ju 288A prototypes flew on BMW801 but the V3 and V4 flew on 2000hp Jumo 222A2/B2 before December 1941.

Requirements changed and the Ju 288B was speced to be a 4 man 14 tons aircraft, this required the 2500hp Jumo 222A2/B2, in fact it now required the Jumo 222E/F which had an two stage supercharger and intercooler.

Had the DB-603 been focused on during this period (over the 604 and possibly 605 as well -and 606/610 abandoned outright) might it have not been ready for mass production even sooner than any possible variant of the 222?

And without confusing/problematic politics muddying the waters, would the 222 be on the whole a competitive design to invest in purchasing compared to the competing 603? (I suppose for Junkers the answer is obvious ... with the possible exception of the 213 arriving earlier, using their own engine would be more appealing than a competitor's)

But there in lies the problem as well ... would the Ju 288 even be attractive to a more focused military strategy minded regime? Might they settle more for DB 603 powered Do 217s over 222 powered 288s? Would the 1941/42 era 222 be more appealing for Do 217 variants as well? Might a 4 engined He 177 be seriously reconsidered sooner?

The Avia copy was burdened with every draggy item from the late Bf-109s: HMG bulges, fixed tailwheel, bigger main wheels wing bulges to acomodate them, gondola cannons. Add the low power of the Jumo (211F?) and in 1946 you have a a fighter that is not even as good as Spitfire V.

I believe they were 211Fs salvaged from He 111s, the Heinkel nacelles being close enough to somewhat adequately adapt to the 109 airframe and there'd be no intercooler so not even a factor in this comparison. The broad chord prop and lower speed, higher torque reduction gearing made it a poor fit for both handling and high speed performance.

Had the Jumo 211N been adopted along with proper propellers and gear ratios more suited to a high speed fighter ... and had overall weight and drag additions elsewhere been compromised better (perhaps eliminating the nose armament entirely, and adopting internal cannon bays in the wings similar to how Adolf Galland's 109G had been modified, then perhaps they'd have ended up with a more adequately performing aircraft. (or, for that matter, if there was to be a Jumo 211 powered 109 in war-time German service, the configuration probably should have been closer to that ... though possibly including 211F powered variants -with proper prop/gearing- earlier on as well ... maybe retaining the MG-17 nose guns as well)

Or for that matter, with a better military/government in power, perhaps the 109T and carrier program wouldn't have been canceled (or would have been revived) and jumo powered variants of the 109T may have developed. (particularly if somewhat lower priority still went towards the Naval air support and refinements of the 109F perhaps didn't extend to the 109T to the same levels ... or simplifying development by retaining the existing wing structure and cannon armament, but upgrading the MG-FFs to MG-FF/Ms and then to MG 151s)

 

[tomo pauk]

...
Had the Jumo 211N been adopted along with proper propellers and gear ratios more suited to a high speed fighter ... and had overall weight and drag additions elsewhere been compromised better (perhaps eliminating the nose armament entirely, and adopting internal cannon bays in the wings similar to how Adolf Galland's 109G had been modified, then perhaps they'd have ended up with a more adequately performing aircraft. (or, for that matter, if there was to be a Jumo 211 powered 109 in war-time German service, the configuration probably should have been closer to that ... though possibly including 211F powered variants -with proper prop/gearing- earlier on as well ... maybe retaining the MG-17 nose guns as well)

Quirk with the Jumo 211N is that it was available from about the time the DB 605A is fully rated (2800 rpm, 1.42 ata). The power levels are in the ballpark under ~3 km, above that the 605A reigns supreme. I'm not that sure that Bf 109, from F0 until G4, needed any drag or weight reduction.
Galland's 109 was 'F' variant, feturing the MG FFM as wing armament, along with MG 131 as cowl guns. I'd propose also a deletion of cowl guns, installing the MG FFM in series (with apropriate strengthening of the wing) and use of 90-rd drum as used on mid-series Fw 190s, along with MG 151/20 as engine cannon; all for the historical Bf 109.

Or for that matter, with a better military/government in power, perhaps the 109T and carrier program wouldn't have been canceled (or would have been revived) and jumo powered variants of the 109T may have developed. (particularly if somewhat lower priority still went towards the Naval air support and refinements of the 109F perhaps didn't extend to the 109T to the same levels ... or simplifying development by retaining the existing wing structure and cannon armament, but upgrading the MG-FFs to MG-FF/Ms and then to MG 151s)

The 'big wing' Bf 109 should have had better rough strip take off and landing abilities, and/or should be able to take off with more payload, not just as a fighter, but also as a fighter-bomber. It would be also interesting as a hi-alt variant, not so 'drastic' as the Bf 109H.
The swap from MG FF to MG FFM was easy job, since those were basically the same as far as airframe is concerned. The next swap (from MG FFM to MG 151) will mean substantial change in the wing structure: for example, the Spanish redesigned the wing internals for their Buchon, that included going from 1-spar to 2 spars, in order to acomodate a 20 mm cannon more powerful than MG FFM.

 

[Juha]

The issue of oil/fuel resources and logistics came up here:
http://www.ww2aircraft.net/forum/av...ofessionals-study-oil-production-43043-5.html

A lot was discussed but one big point was there were many alternate solutions for expanding German fuel production outside of greater access to crude oil. The shale oil reserves mentioned early on in the thread weren't all that viable to expand in the short term, but the synthetic fuel production using a variety of coal types and potentially biomass (wood waste, agricultural waste, any sort of plant waste able to be amassed and transported effeciently, potentially domestic and industrial waste/recycling programs as well -but the coal reserves was the main/immediate interest). A much broader array of synthetic fuel plants could have been dispersed and the infrastructure shifted more and more towards the much more efficient to produce fractions of the products from Fischer–Tropsch fuel plants -particularly methanol, ethanol, butanol, acetone and a few others. (ideally they should have made the shift starting pre-war, but the earlier the better -and in the interim, focus on producing the most efficient fuels still acceptable in the existing infrastructure; along with that, drop further investment in the far more costly hydrogenation based fuel plants, maintain the ones in service, and use the limited oil and liquid coal fractions to supplement synthetic liquid fuel production)...

Before the war Göring initiated very ambitios synthetic fuel program but it was over-ambitious. The shortage of both steel and manpower had delayed the completion of the full construction program of hydrogenation plants most planned plants were not built also some of the planned Fischer-Tropsch plants were never completed and those completed were badly overdue. It doesn't matter how big heap of coal one has if one has only a limited processing capacity.

 

[Shortround6]

AS an example one writer has claimed that going from 3cc of lead per gallon to 4cc lead per gallon (US gallons) saved the allies tens of thousands of tons of steel for refinery construction.

Being able to technically do something doesn't always mean it is either economical or even practical.

 

[tomo pauk]

The reasons why Jumo 211 series lagged a bit vs. the DB 601/605 in altitude performance might be two-fold: the DB usually turned greater RPM, while also having a bigger supercharger. Eg. the diameter of the impeller of the Jumo 211F/J was at 225 mm (8.897 in per this NACA report), while the DB 601E was at 260 mm. The DB 605A received a bit bigger S/C, and turned another 100 rpm more than DB 601E (for equivalent settings), and in 1944 an even bigger S/C from the DB 603A, 295 mm.
The production Jumo engines featured 3 valves per cylinder, vs. 4 valves of the DB engines.

I'm not sure whether the Jumo 211N/P/R received a better/bigger S/C, however the RPM was increased to 2700; the N and P should be able to match the DB 601E, though a year or two too late. The 211R should be able to match the fully rated DB 605A at altitude, but that is already 1944 we're talking about. The 211R sacrificed the take off power vs. the 211N (1350 vs. 1450 PS; probably a different S/C gearing was used, tailored more towards high altitudes). The DB 605A was at 1475 PS for take off.

 

[kool kitty89]

I'd propose also a deletion of cowl guns, installing the MG FFM in series (with apropriate strengthening of the wing) and use of 90-rd drum as used on mid-series Fw 190s, along with MG 151/20 as engine cannon; all for the historical Bf 109.

No existing 211 allowed an engine cannon to be fitted, but that may have been more due to lack of demand than difficulties in mounting. (then again, the demand should have been there from the start with the 213, competing with the DB-603, and a motor cannon mounting lagged in production there as well)

The 'big wing' Bf 109 should have had better rough strip take off and landing abilities, and/or should be able to take off with more payload, not just as a fighter, but also as a fighter-bomber. It would be also interesting as a hi-alt variant, not so 'drastic' as the Bf 109H.

Improved take-off/landing performance (and reduction in accidents) may have been even more worthwhile, though the landing gear legs didn't get a wider track as the 109H did. (better climb and turn performance might also make the compromise in drag worthwhile)

The swap from MG FF to MG FFM was easy job, since those were basically the same as far as airframe is concerned. The next swap (from MG FFM to MG 151) will mean substantial change in the wing structure: for example, the Spanish redesigned the wing internals for their Buchon, that included going from 1-spar to 2 spars, in order to acomodate a 20 mm cannon more powerful than MG FFM.

The hispano cannons were far heavier and more powerful guns than the MG 151/20, the latter only moderately more powerful than the rounds used by the MG-FF/M, plus the 109F and G had already been able to carry 151s in gun pods underwing. Being able to physically fir the 151 and its ammunition into the 109's wings might be more the problem.

That said, the MG FF/M with 90 round drums seems a reasonable enough weapon and (regardless of structural issues) the lower recoil of the API blowback weapons should make aiming at least slightly more consistent. (plus the velocity isn't too much lower than the 151/20 -lower rate of fire is a bigger drawback) Still, in the case of the jumo 211, assuming no ability to fit a nose cannon, the sole armament of 2 MG FF/M cannons would be useful enough. Pilots might prefer retaining the cowl guns too, but practically speaking, learning to not rely on those for ranging (or the few light targets they were effective against) might be preferable, especially with the differing ballistics of the guns. (well ... with the MG 131, ballistics would be closer and the HMG would be more useful in its own right)

Before the war Göring initiated very ambitios synthetic fuel program but it was over-ambitious. The shortage of both steel and manpower had delayed the completion of the full construction program of hydrogenation plants most planned plants were not built also some of the planned Fischer-Tropsch plants were never completed and those completed were badly overdue. It doesn't matter how big heap of coal one has if one has only a limited processing capacity.

That too was discussed in this thread http://www.ww2aircraft.net/forum/av...study-oil-production-43043-4.html#post1195777

The problem was the hugely expensive hydrogenation synthetic fuel plants and intention to produce fuel totally equivalent to existing gasoline and diesel rather than considering more efficient alternatives.

Smaller, cheaper, quicker/easier to construct/repair/replace and disperse Fischer–Tropsch plants with more flexible feed stocks would have been extremely useful for producing a variety of synthetic fuels. The main reason they were less attractive than hydrogenation being they were much less efficient at producing conventional gasoline and diesel grade hydrocarbons (but could produce alcohols -especially simple methanol- far, far more efficiently -including a number of fuels very similar in energy density and combustion properties to aviation gasoline).

But a great deal was already discussed in that thread, so I won't repeat it all here.

The production Jumo engines featured 3 valves per cylinder, vs. 4 valves of the DB engines.

I'm not sure whether the Jumo 211N/P/R received a better/bigger S/C, however the RPM was increased to 2700; the N and P should be able to match the DB 601E, though a year or two too late. The 211R should be able to match the fully rated DB 605A at altitude, but that is already 1944 we're talking about. The 211R sacrificed the take off power vs. the 211N (1350 vs. 1450 PS; probably a different S/C gearing was used, tailored more towards high altitudes). The DB 605A was at 1475 PS for take off.

Higher altitude supercharger gearing is less relevant for the Eastern front, but if it had been in greater demand as a fighter engine alongside the 601/605, higher alt supercharger gearing may have been introduced sooner. (or maybe even earlier emphasis on a 2-stage supercharger, or water injection for that matter -the latter also useful for omitting intercooling and for allowing increased boost at low level on takeoff with higher speed single stage units) Without the strength increases and other changes in the valves and crankshaft of the 213, you still wouldn't be seeing higher power levels, but better power at a wider range of altitudes would be significant, and possibly better power sooner. (aside from WM/50, having increased boost ratings with C2/3 fuel would be notable -including potentially pushing 211F power levels closer to 211N)


All that said, with existing engines early-war and the 211F might at least have been a useful supplemental engine to the 601E and N, and better than the older 601A. (plus, didn't the 601E initially have boost restrictions that lessened its advantages over the 211F?)

 

[Shortround6]

No existing 211 allowed an engine cannon to be fitted, but that may have been more due to lack of demand than difficulties in mounting. (then again, the demand should have been there from the start with the 213, competing with the DB-603, and a motor cannon mounting lagged in production there as well)

It may have been lack of "demand". The Jumo 210 allowed for a gun through the prop. The BMW 116 is described in one book as having a hollow propshaft for a shell gun and the same book says the Jumo 211 allowed for one.
Since the Jumo 211 was used (aside from the Ju 87) in multi-engine aircraft there may have been no need to use this feature in the planes that used it. Why stick a gun through the props of a He 111 or Ju-88? Bf 110s didn't use though the prop guns even though their DB 601 engines would allow it.
Luftwaffe may have had the hollow shaft through the engine for a gun barrel as a requirement for ALL V-12s after around 1933/34. Jumo would be rather negligent if they didn't make allowance for it. perhaps on some of the bomber engines they mounted some of the accessories (generators/pumps) to block the tube so trying to use them as is on the Avia didn't work very well.

That said, the MG FF/M with 90 round drums seems a reasonable enough weapon and (regardless of structural issues) the lower recoil of the API blowback weapons should make aiming at least slightly more consistent. (plus the velocity isn't too much lower than the 151/20 -lower rate of fire is a bigger drawback) Still, in the case of the jumo 211, assuming no ability to fit a nose cannon, the sole armament of 2 MG FF/M cannons would be useful enough. Pilots might prefer retaining the cowl guns too, but practically speaking, learning to not rely on those for ranging (or the few light targets they were effective against) might be preferable, especially with the differing ballistics of the guns. (well ... with the MG 131, ballistics would be closer and the HMG would be more useful in its own right)

The MV was around 100m/s different between the guns using the same projectiles. Unfortunately the Germans were forced to use mixed ammo loads (different projectiles) which screwed things up a bit for long range fire.

The Mine-Geschoss which is everybody's favorite for it's HE content had no tracer version and due to it's light weight (92 grams) had a much higher MV than the other 20mm projectiles used. Around 100m/s depending on gun. So you can have a variation of from around 585-600ms for a MG-FFM firing 115gram conventional shells to 800m/s for a MG 151 firing 92 gram shells.

The idea that pilots used the cowl MGs for "ranging" needs to be gotten rid of unless people can find multiple references in pilots memoirs, at least for "long range". Long range being much in excess of 300 meters. Time of flight for a 7.9 mm MG round to 300 meters was 0.453 seconds. Time of flight for a M-Geschoss shell fired from a MG/FFM was 0.551 seconds. The tracers will tell you where you should have been aiming 1/2 second ago but since the 20 mm shells are arriving 1/10 of second after the the MG tracers and a 300mph airplane is covering 44 ft per second the technique may work against a bomber. It isn't much good against a fighter. It also wastes about 3/4-1 second of possible firing time. Again, against bombers not so important. Against fighters unless, like many, they are taken by surprise? Our hero has to get the enemy plane in his sight with a good firing solution (proper range set in sight and proper lead, or at least close so initial rounds aren't hosing the sky), you then have pilots reaction time to seeing a good (or usable) sight picture, hitting the trigger, time of flight to target, reaction time to seeing bullet strikes (tracer or incendiary/marker ammo) and hitting the trigger for the cannon. If he has to manipulate a selector switch to get the cannon to fire off the same trigger so much the worse.

The German 13mm was actually a pretty good match for the 7.9mm. time of flight to 300 meters was only 0.037 different with the 7.9 being better. Even at 600 meters they are close enough to make little practical difference.

Higher altitude supercharger gearing is less relevant for the Eastern front, but if it had been in greater demand as a fighter engine alongside the 601/605, higher alt supercharger gearing may have been introduced sooner. (or maybe even earlier emphasis on a 2-stage supercharger, or water injection for that matter -the latter also useful for omitting intercooling and for allowing increased boost at low level on takeoff with higher speed single stage units) Without the strength increases and other changes in the valves and crankshaft of the 213, you still wouldn't be seeing higher power levels, but better power at a wider range of altitudes would be significant, and possibly better power sooner. (aside from WM/50, having increased boost ratings with C2/3 fuel would be notable -including potentially pushing 211F power levels closer to 211N)

It is not the "gearing" in the supercharger you have to worry about. It is if the compressor (intake/impeller/diffuser) can make the pressure (and volume) needed at the altitude desired. Changing gears is relatively simple.

Hooker greatly improved the Merlin supercharger (added several thousand feet of full throttle height) by changing the inlet shape and keeping the same impeller/diffuser and pretty much the same gearing. The late 30s German superchargers were pretty crappy, but then so were most other peoples. speeding up the impeller with a gear change doesn't do much good if the intake shape is bad, or if the impeller is bad ( and the Junkers ones were very far from good). see fig | spiral volute | flight january | 1942 | 0144 | Flight Archive

Supercharger design was far from static and most countries and companies made significant improvements from 1938/39 to 1945. P&W managed to pull 1600hp from an "E" series R-2800 at 22,000ft at 2800rpm and a single stage supercharger compared to 1650hp at 2700rpm at 22500ft from the two stage supercharger in the early F4Us and F6Fs.

development by company was often in fits and starts rather than an even progression.

 

[tomo pauk]

No existing 211 allowed an engine cannon to be fitted, but that may have been more due to lack of demand than difficulties in mounting. (then again, the demand should have been there from the start with the 213, competing with the DB-603, and a motor cannon mounting lagged in production there as well)

Getting rid of cowl guns in the V-12 powered Fw 190 and installing a cannon to fire through the prop not only increases the firepower, it cuts a bit of drag.

That said, the MG FF/M with 90 round drums seems a reasonable enough weapon and (regardless of structural issues) the lower recoil of the API blowback weapons should make aiming at least slightly more consistent. (plus the velocity isn't too much lower than the 151/20 -lower rate of fire is a bigger drawback) Still, in the case of the jumo 211, assuming no ability to fit a nose cannon, the sole armament of 2 MG FF/M cannons would be useful enough.

Having not to worry about Western airforces in this scenario, the LW has even less pressure to insist with Jumo Bf 109. They can start trickling the Fw 190 in the East by at least early 1942, instead in late 1942. Bf 109G-2 (even when with restricted engine) was anyway better regarded than any fighter by Soviets in mid-42 to late 1943.
The MG FFM was firing the M-geschoss at 700 m/s, the MG 151/20 was at ~800 m/s, the discrepancy would be far smaller than with, say, what Bf-109s with old MG FF and LMGs had. Or the MG 151/20 and MK 108 combo. As SR6 noted, the LW practice of mixing different ammo types in a single belt/drum will probably bring greater problems for the pilot.
The Fw 190A was using the proposed combo (less one MG 151/20) for quite some time.

Higher altitude supercharger gearing is less relevant for the Eastern front, but if it had been in greater demand as a fighter engine alongside the 601/605, higher alt supercharger gearing may have been introduced sooner. (or maybe even earlier emphasis on a 2-stage supercharger, or water injection for that matter -the latter also useful for omitting intercooling and for allowing increased boost at low level on takeoff with higher speed single stage units) Without the strength increases and other changes in the valves and crankshaft of the 213, you still wouldn't be seeing higher power levels, but better power at a wider range of altitudes would be significant, and possibly better power sooner. (aside from WM/50, having increased boost ratings with C2/3 fuel would be notable -including potentially pushing 211F power levels closer to 211N)

An earlier introduction of MW 50, or rating the V-12 engines for C3 engines would've made the LW fighters extracting an even greater toll on Soviet aircraft. The Jumo 211 series might've been perhaps better users of C3 fuel, with their compression ratio of 6.5:1 (the DB 601E at 7.2:1, the 605A at 7.5/7.3:1) allowing for greater boost.
Granted, many times the German engine designers upped the compression ratio when tailoring the engine for hi-oct fuel, hence negating the chances for greatly increased boost levels.

All that said, with existing engines early-war and the 211F might at least have been a useful supplemental engine to the 601E and N, and better than the older 601A. (plus, didn't the 601E initially have boost restrictions that lessened its advantages over the 211F?)

The DB 601E have had both boost and RPM restrictions (ban on 'Start- Notleistung' until New 1942 Year), however it was still producing more HP on aggregate than Jumo 211F. On Kampfleistung (30 min rating), it was making ~50 PS more at lower and higher altitudes, and up to 200 PS more at medium altitudes (due to the hydraulic drive S/C - no 'kink' between two rated altitudes). The Jumo 211F was also not rated for Notleistung; the take off power (Startleistung) was greater, and allowed for 1 min only.
By the time the 211F is introduced, the DB 601A is old news, but when over-revved at 2600 or 2800 rpm will give any Jumo 211 (bar 211R of 1944) a good run for their money at high altitudes.
But, as above - with no war in West and Med, Germany does not need to have Jumo 211s supplementing DB and BMW 801 engines in fighters.

It may have been lack of "demand". The Jumo 210 allowed for a gun through the prop. The BMW 116 is described in one book as having a hollow propshaft for a shell gun and the same book says the Jumo 211 allowed for one.

Might be for the early Jumo 211 models, but the Jumo 211F/J have had the prop governing items (item group 55 on the pic) at the rear part of what would otherwise be gun barrel tube?

The pic of Jumo 211B/D does not have those items there, it shows an open rear part of the tube.

Hooker greatly improved the Merlin supercharger (added several thousand feet of full throttle height) by changing the inlet shape and keeping the same impeller/diffuser and pretty much the same gearing. The late 30s German superchargers were pretty crappy, but then so were most other peoples. speeding up the impeller with a gear change doesn't do much good if the intake shape is bad, or if the impeller is bad ( and the Junkers ones were very far from good). see fig | spiral volute | flight january | 1942 | 0144 | Flight Archive

The 'box-wheel' supercharger of the Jumo 210 to 211B/D was judged by NACA not to be that efficient, with 59% peak efficiency on the 211A. The DVL designed S/C, installed on the Jumo 211F/J, have had the peak adiabatic efficiency of 76.6% and peak impeller efficiency of 82.3%.

 

[Shortround6]

Might be for the early Jumo 211 models, but the Jumo 211F/J have had the prop governing items (item group 55 on the pic) at the rear part of what would otherwise be gun barrel tube?

View attachment 291145

The pic of Jumo 211B/D does not have those items there, it shows an open rear part of the tube.


The 'box-wheel' supercharger of the Jumo 210 to 211B/D was judged by NACA not to be that efficient, with 59% peak efficiency on the 211A. The DVL designed S/C, installed on the Jumo 211F/J, have had the peak adiabatic efficiency of 76.6% and peak impeller efficiency of 82.3%.

Thank you. The basic engine had the tube/space. The Avia fighters were using parts on hand. A contract for several hundred engines place at the factory for delivery later could very well have had the prop governor items moved to a different location.

And thank you for the efficiency figures for the 'box-wheel'. If only 59% (at best) of the power going into the supercharger is going to actually compress the air that means that 41% (minus friction loss in the gear drive) is going into heating the air over and above the heat of compression. Spinning the impeller faster is going to lower the efficiency even more putting you in the land of diminishing returns. The more efficient impeller requires less power to turn ( leaving more for the prop) heats the air less for the same manifold pressure, meaning the charge is denser for more power to begin with, and the lower temp might allow even higher boost to be used before hitting the detonation limit. Changing the supercharger gearing gets you none of those advantages and instead takes more power from the crank (at the square of the rpm, 10% faster impeller needs 21% more power to turn) lowers the efficiency a bit and increases the charge temperature and reducing the charge density for the same manifold pressure. The hotter air also means more danger from detonation at the same manifold pressure so the upper manifold pressure limit might have to be restricted. And that may apply at ALL altitudes and not just at the upper end of the FTH.

 

[tomo pauk]

Thank you. The basic engine had the tube/space. The Avia fighters were using parts on hand. A contract for several hundred engines place at the factory for delivery later could very well have had the prop governor items moved to a different location.

The Avia S-199 (Jumo 211F engine) have had no prop cannon, 2 cannons were in gondolas. Two HMGs were installed as cowl guns, as in plain vanilla Bf 109G-6

Pic for the 211B/D; the item 60 is "flange for motor-cannon or prop governor":

 

[kool kitty89]

It is not the "gearing" in the supercharger you have to worry about. It is if the compressor (intake/impeller/diffuser) can make the pressure (and volume) needed at the altitude desired. Changing gears is relatively simple.

Hooker greatly improved the Merlin supercharger (added several thousand feet of full throttle height) by changing the inlet shape and keeping the same impeller/diffuser and pretty much the same gearing. The late 30s German superchargers were pretty crappy, but then so were most other peoples. speeding up the impeller with a gear change doesn't do much good if the intake shape is bad, or if the impeller is bad ( and the Junkers ones were very far from good). see fig | spiral volute | flight january | 1942 | 0144 | Flight Archive

Previous times I've seen Junker's box-wheel impeller design, I'd assumed those outlets were static channels not part of the rotor ... that seems like an awful arrangement that would needlessly increase drag. I'd thought DB's partially shrouded arrangement was a bit unusual, but I hadn't realized it was in fact one of the better designs around.

The fully or nearly fully shrouded base/hub arrangement is what I thought had already been adopted universally (with a few odd ball experimental cases aside) well before the late 1930s. Things like straight vs curved blades, the number of blades, taper and height of the blades, perpendicular radial blade placement vs tangential/diagonal (or helical/spiral bladed) are more the sorts of differences I expected, that and diffuser designs. I mostly expected straight, flat blades due to simplicity of manufacturing.
( Coanda aeroplane -Henri Coanada's compressor for his ducted fan 'air reaction engine' of 1910 seems to have implemented a fully shrouded helical bladed impeller)

In fact, I'd assumed Ohain's use of fairly basic, simple flat radial compressor blading with a tapered shroud/hub was rather spartan and aimed more at ease of assembly and testing than aerodynamic efficiency. (particularly as it was made from sheet metal blades mounted to a steel hub -avoiding forging or machining -particularly compared to the intricate single-piece machined impellers used by Rolls Royce and several american companies) But in this light, Ohain's design actually seems rather efficient and perhaps a good deal better than what Jumo may have come up with for a turbojet in 1938.

The inlet design issues are something I already understood and a more common design problem than the impeller/diffuser. (the more significant change on both the V-1710 and especially Merlin in as far as aerodynamic supercharger alterations -the V-1710's revision was delayed though -2 stage developments aside) Allison's supercharger seems pretty damn decent compared to Jumo's.

I wonder if a superior supercharger design was one of the factors contributing to the Bramo 323's power output and altitude performance compared to other late 30s engines and especially given its displacement, and if so whether they considered applying that experience to their jet engine developments alongside the axial ones. (Also makes me wonder what the impeller on Kurt Loehner's P.3303 centrifugal engine at BMW looked like, though given what the 801 managed, they appear to have had fairly efficient supercharger design)

And thank you for the efficiency figures for the 'box-wheel'. If only 59% (at best) of the power going into the supercharger is going to actually compress the air that means that 41% (minus friction loss in the gear drive) is going into heating the air over and above the heat of compression. Spinning the impeller faster is going to lower the efficiency even more putting you in the land of diminishing returns.

With the drag from the air impacting the outside of the box-wheel impeller's channels and (as near as I can tell) swirling around pointlessly in the compressor housing, it seems like there'd be a lot of wasted power without necessarily resulting in charge heating. (or would that swirl and -my understanding of fluid dynamics is limited, but- what seems to me would be pockets of high and low pressure or pressure and partial vacuum left in the wake of those box channels result in all that wasted power going into heating the charge?)

Regardless of charge heating, the sheer drag of that arrangement seems very likely to have very diminishing returns well short of the more typical supersonic tip-speed limits. But with the DVL compressor used on the 211F and later models, that poor efficiency wouldn't be relevant.

Getting rid of cowl guns in the V-12 powered Fw 190 and installing a cannon to fire through the prop not only increases the firepower, it cuts a bit of drag.

Indeed, it seems the obvious choice and strange that 3x MG 151/20s wasn't the standard Fw 190D armament. (aside from the potential to carry an MK 108 in the nose instead)

An earlier introduction of MW 50, or rating the V-12 engines for C3 engines would've made the LW fighters extracting an even greater toll on Soviet aircraft. The Jumo 211 series might've been perhaps better users of C3 fuel, with their compression ratio of 6.5:1 (the DB 601E at 7.2:1, the 605A at 7.5/7.3:1) allowing for greater boost.
Granted, many times the German engine designers upped the compression ratio when tailoring the engine for hi-oct fuel, hence negating the chances for greatly increased boost levels.

Yes, though with the poor Jumo supercharger design holding things back, the benefits from high compressor may have outweighed those of limited boost considerably more than they did on the DB engines. (with DB's relatively decent superchargers, using lower compression ratios and higher supercharger speeds -or adopting the DB 603's supercharger earlier would seem much more appealing -particularly as applying boost limits could potentially allow such engines to switch between using higher and lower octane fuels)

The 'box-wheel' supercharger of the Jumo 210 to 211B/D was judged by NACA not to be that efficient, with 59% peak efficiency on the 211A. The DVL designed S/C, installed on the Jumo 211F/J, have had the peak adiabatic efficiency of 76.6% and peak impeller efficiency of 82.3%.

With the introduction of that rather vastly superior supercharger design (though I'd imagine inlet design would still be a significant limiting factor apart from the compressor itself), the prospect of pushing the impeller speed to higher altitude ratings at the expense of take-off power seems more feasible, especially on models using the intercooler. (or had they adopted water injection earlier)

Of course, at some point, a larger supercharger is going to be needed to manage increased mass flow and compression at reasonable efficiency.

I'm still curious to how a Jumo 211 with Jumo 213 derived supercharger may have fared, more so if it could have entered volume production earlier than the 213 itself.

 

[tomo pauk]

...
I wonder if a superior supercharger design was one of the factors contributing to the Bramo 323's power output and altitude performance compared to other late 30s engines and especially given its displacement, and if so whether they considered applying that experience to their jet engine developments alongside the axial ones.
...

Can't agree that Bramo engines have had that good altitude performance, were looking at maybe 700-750 HP at altitude? The Bristol Mercury have had 840 HP, and it was a bit smaller engine.

Indeed, it seems the obvious choice and strange that 3x MG 151/20s wasn't the standard Fw 190D armament. (aside from the potential to carry an MK 108 in the nose instead)

Jumo 213A was not suitable to engine cannon, being more or less a 'bomber engine' slapped on a fighter; the engine accessories went into the way of the gun. The 213C was suitably modified for engine cannon, but I'm not sure that was ever installed in the Fw 190, the 2-stage 213E went to serve in Ta 152.

I'm still curious to how a Jumo 211 with Jumo 213 derived supercharger may have fared, more so if it could have entered volume production earlier than the 213 itself.

The S/C of the Jumo 213A featured the inlet guide vanes, so, if the transplantation is without problems, the power under the rated heights should be high even without inter-coolers installed. I don't know any dimensions of the S/C of the Jumo 213, but it should be tailored for greater outputs of the compressed air, so it's installation on the Jumo 211 should've produced a capable hi-alt engine.

OTOH, Jumo might want to remember, early enough, of it's inter-war engines, the L 55 and L 88a, that were employing 2-stage superchargers, the L 55 even the 3-stage. All of those were hydraulically coupled to the crankcase.

 

[kool kitty89]

Can't agree that Bramo engines have had that good altitude performance, were looking at maybe 700-750 HP at altitude? The Bristol Mercury have had 840 HP, and it was a bit smaller engine.

I was speaking more in terms of comparing things to other German superchargers, but 1000 PS at 10,200 ft for the 323A, and I believe the low-alt gearing allowed 1,100 ps at a reduced critical altitude. The 2-speed models managed 940 ps at 13,000 ft which would be only slightly less than the 2-speed pegasus managed.

But more notable is the boost pressures being managed without detonation problems on 87 octane fuel, implying relatively low charge heating.

OTOH, Jumo might want to remember, early enough, of it's inter-war engines, the L 55 and L 88a, that were employing 2-stage superchargers, the L 55 even the 3-stage. All of those were hydraulically coupled to the crankcase.

I wonder how those early supercharger designs compared to what Jumo was using immediately pre-war on the 210, 211, and diesel engines. With the sort of pressures/volumes needed on the L55, it seems a bit odd to resort to multi-stage designs, though.

 

[Shortround6]

I wonder how those early supercharger designs compared to what Jumo was using immediately pre-war on the 210, 211, and diesel engines. With the sort of pressures/volumes needed on the L55, it seems a bit odd to resort to multi-stage designs, though.

Not so odd. the multi stage versions or more properly, examples as they were hardly production engines, were used for research flights.

Fixed pitch 4 blade prop (or two two blade props combined) , Pressure cabin and a ceiling (eventually) of over 40,000ft. It needed a pretty good pressure ratio to fly at that altitude.

 

[tomo pauk]

I was speaking more in terms of comparing things to other German superchargers, but 1000 PS at 10,200 ft for the 323A, and I believe the low-alt gearing allowed 1,100 ps at a reduced critical altitude. The 2-speed models managed 940 ps at 13,000 ft which would be only slightly less than the 2-speed pegasus managed.
...

I'd like to politely ask for sources for such power values vs. altitude

I wonder how those early supercharger designs compared to what Jumo was using immediately pre-war on the 210, 211, and diesel engines. With the sort of pressures/volumes needed on the L55, it seems a bit odd to resort to multi-stage designs, though.

The rated height of those early 2-stage supercharged engines was at 5000m or 5800m (y. 1928 L55 and y. 1932 L88a respectively), compared with ~3800m for the Jumo 210 (2-speed S/C, high gear, in 1936). Jumo 211B was at ~5000m, not sure the 211A.
Once could wonder how much trickier it would've been for the Allies to win with the air war with Germans pushing a concerted effort with 2-stage superchargers they knew to work for years before (European) ww2 started.