Me-262 performance

Please explain where I was wrong Davparlr.

You know as-well as I do that 25 kg isn't going to have any noticable effect on the performance of the Me-262, not even climb is affected and speed is completely the same.

That kind of weight certainly would have no noticable effect on such a large a/c, plus overall thrust/weight would increase, and fuel economy of the 004D (and especially 004E) was significantly improved over the 004B (particularly over the early models, although similar to the 004-3/4 iirc) plus it could overrev to 10,000 rpm to produce 1000-1050 kp. (due to elimination of the vibration problems)

As the 004D was esentially the same in overall weight to the 004B, the point in argument of 25kg seems even more moot. (the 004C being lighter than the other two)


Now a Me 262 powered by HeS 30 engines (He 109-006) would be a whole other story: with at least as much thrust as the 004B, but with much better fuel consumption under 400 kg in weight and with a diameter of only 0.61 m and much shorter as well. Unfortunately the 004 and 003 seemed to be nearing production quality in early 1942 (which was untrue, except for the 004A, with problems converting to the 004B) and the Heinkel design may have seen production first as well as being technically superior and easier to build in most respects.

(only 5 compressor stages, small design required less materials, although the advanced reaction-type compressor required the use of thrust bearings and machining of the compressor blades -opposed to stampping used to produce the 004's impulse blading-, this same type of compressor was used in the 1200 kp 003D with only a slight increase in nominal fuel consumplion -and much lower SFC- , which acheived a compression ratio of 1.25 per stage)

The thrust performance compared to weight, frontal area, length, and the SFC figures were not exceeded by any engine tested in the war with the possible exception of the very compact Westinghouse J30 which flew in the FH Phantom prototype in early 1945. (originally part of the NACA jet initiative spurred by Whittle's sucess, and was the first indigenous American design to run, although originally only designed for JATO with ~1000 lbf and 6 compressor stages, 2 more stages were added, weight was reduced to ~650 lbs and a diameter of only 19 in with a thrust of 1600 lbf and a SFC of under 1.2 lb/lbf/hr.)

But I digress, and Delcyros has mentioned several times the promise and misfortunate decision to cancel this best (and most promising) class I engine of the war.

PS: A good read on the Me 262 engine: http://www.enginehistory.org/German/Me-262/Me262_Engine_2.pdf

That was a good read.

I have that PDF on file, in the pictures you can see the impulse blading of the stators where there is no pitch on the blades except prior to the first stage and after the last. This type of axial compressor is inefficient but simple with the rotors acheiving ~80% of compression and stators just acting to guid the air flow.(reaction blading used on the HeS 30 and BMW 003D acheived roughly half of the compression at the stators) Only ~1.155:1 compresson per stage was produced, opposed to ~1.25:1 with a reaction compressor of the same time period (while centrifugal compressors could manage 2.8-4.0:1), this way the HeS-30 acheived the same compresson in 5 stages that the 004 did in 8 with resulting savings in weight, length, materials, and greater energy efficiency. The reaction compressor blades had to be machined and used thrust bearings, while the impulse blading of the 004 could be stamped, a rather inexpensive and efficient method.

I'm not sure what type of axial compressor the 003A/E used though, it seems to have been slightly more efficient (~1.18:1) than the Jumo but not by much, so possibly an impulse type as well. Encorporating a reaction type compressor (with the same number of stages) in the 003D raised thrust from 800 kp to 1,200 kp (a 50% increase!) and increased compression from ~3.2:1 to ~4.7:1 with little increase in fuel consumption or weight. (thus much better specicic fuel consumption) Just think, if the 004 had similar improvments 1300+ kp with nearly 6:1 compression should be possible!

There's also the "textbook" example of an axial compressor where most of the compression occurs at the stators: the rotors accelerating the air and the stators slowing it down, compressing in the process, and guiding it into the next stage. (like a difuser of a centrifugal compressor) I'm not sue of the name of this type of compresser though...

From Soren, 02-21-2008 04:27 AM:

Me-262 performance chart, showing the difference in climb rate from a starting weight of 6,897 kg and 5,700 kg. (5,700 kg time to climb is calculated!) Enjoy!

Is this chart still available anywhere?

kool kitty89 said:

I have that PDF on file, in the pictures you can see the impulse blading of the stators where there is no pitch on the blades except prior to the first stage and after the last. This type of axial compressor is inefficient but simple with the rotors acheiving ~80% of compression and stators just acting to guid the air flow.(reaction blading used on the HeS 30 and BMW 003D acheived roughly half of the compression at the stators) Only ~1.155:1 compresson per stage was produced, opposed to ~1.25:1 with a reaction compressor of the same time period (while centrifugal compressors could manage 2.8-4.0:1), this way the HeS-30 acheived the same compresson in 5 stages that the 004 did in 8 with resulting savings in weight, length, materials, and greater energy efficiency. The reaction compressor blades had to be machined and used thrust bearings, while the impulse blading of the 004 could be stamped, a rather inexpensive and efficient method.

I'm not sure what type of axial compressor the 003A/E used though, it seems to have been slightly more efficient (~1.18:1) than the Jumo but not by much, so possibly an impulse type as well. Encorporating a reaction type compressor (with the same number of stages) in the 003D raised thrust from 800 kp to 1,200 kp (a 50% increase!) and increased compression from ~3.2:1 to ~4.7:1 with little increase in fuel consumption or weight. (thus much better specicic fuel consumption) Just think, if the 004 had similar improvments 1300+ kp with nearly 6:1 compression should be possible!

There's also the "textbook" example of an axial compressor where most of the compression occurs at the stators: the rotors accelerating the air and the stators slowing it down, compressing in the process, and guiding it into the next stage. (like a difuser of a centrifugal compressor) I'm not sue of the name of this type of compresser though...

Click to expand...

The BMW 003A and E did indeed use simple impulse type axial compressors. A set of compressors of the reaction type was on the Bench at subcontractor ABB Cie the Hermaso I and II.

These would have produced the BMW 003C with 900kg thrust instead of 800kg but with better fuel consumption and also the BMW 003D with 1100kg thrust BMW were also working on one of these compressors. The inpulse type has lower tollerance requirements and so the blades can be pressed rather than machined furthermore there is less axial thrust which simplifies the bearing arrangment. Production costs were totally critical to the Germans who resorted to every trick and compromise to pull out more production.

Designation of the end of war engines is rather collapsed roughly the engines were
Jumo 004A, experimental version using a high proportion of refractory metals.
Jumo 004B-1 with tinidur blades; first production version. The pre production Jumo 004B-0 was actually more reliable due to the greater skill level.
Jumo 004B-4 with hollow aircooled tunidur blades, from Oct/Nov 44 onwards, more reliable.
Jumo 004B-4 with hollow aircooled cromidur blafes, from Feb 45, an inferior alloy but more reliable in practice due to easier fabrication.
The Jumo 004B2 seems to have had a more advanced compressor that however had problems
There may or may not have been a jumo 004B-3.

The Jumo 004C was a developed Jumo 004B as was the Jumo 004D with higher thrust levels. Exact improvments are hard to discern but they would have included
1/ Better fuel control to measure the air flow rate and stop under and over dosing of fuel thus preventing flameouts or temperature excursions.
2/ Duplex injector nozzles to switch to a second nozzle at low flow rates seen at idling or high altitude to ensure proper vapurisation and complete combustion. This reduces flameout issues and improves economy.
3/ Improved compressors with better altitude performance
4 Electronoics to monitor engine temperature and adjust fuel flow accordingly, thermocouple mountings were available but no electronics was yet ready.

The fuel control mod would have reached opperational service in the begining of April, I pressume as an upgrade to the Jumo 004B however the KTB I have seen doesn't specify which engine.

The Jumo 004E was a sightly scaled up and improved Jumo 004D. However it was decided to produce the Jumo 004H instead, this was a scaled down Jumo 012 which had a much higher compression ratio and blow out valves to handle this extra ratio.

Soren is no longer a member and this thread is 3 years old - the posters may not be around anymore.

We picked that issue apart awhile back.

The Jumo004A did not use significantly more strategic metals then existing DB605 piston engines. There had to be other reasons for not producing the engine during 1943.