What if BMW and Bramo merged in 1936?

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Might help Fw-190 day fighter but I doubt it would make Ju-88 night fighter perform better then historical. Nor did it need to. By 1943 Me-110 and Ju-88 night fighter aircraft performed just fine vs RAF Bomber Command.
 


You're right about the flame front limitation in practice but in theory this limitation could be avoided. Av engines pretty much used the hemispherical combustion chamber. This design induced little turbulence in the fuel charge and limited flame travel to conduction speeds. However, combustion chambers that induce turbulence through squish or intake geometries that produce swirl or tumble in the charge can speed up combustion by 12 to 15 fold. This was doable but not on the engine designers radar at the time.
 
Turbo was 801Q, probably based on the 801 D-2 for the other mechanical systems.

Even if BMW and Bramo merged earlier I doubt we could have the 801 much earlier + have far better reliability thant it had from the start. Both BMW and Bramo had problems with their own attempts to develop the requested engine but they learned from it. AFAIR (read in a book somewhere) both entered a cooperation for this project in late 38 which led to the 801. The 139 was shelved shortly after building some working prototypes for the Fw 190 development (not easy to develop and aircraft without an engine on hand).
Much less is known about the 329 - I have never heard of it being installed in any aircraft.

Both 801S and 801F wer specified for 2000PS engine power with 1940/1930PS available at the shaft, the 801F was supposed to reach 2400PS with MW50 boost, the 801S 2200PS (probably using a lower-powered MW50 system).
 

By the late 1930s, it was widely recognized that the R-1820 and R-1830 were significantly superior to the Hornet and related engines, such as the BMW 132. Bramo seems to have made a decent job of the Bramo 323 by progressively improving earlier and mostly rather unsatisfactory designs, though it still fell short of the US designs.
 

My impression is that the BMW 801 was basically an improved BMW 139 with refinements such as a two speed supercharger. The publications that claim it was an 18 cylinder engine are almost certainly mistaken.

I have seen claims that the Bramo 329 achieved 2,000 hp on the test bench, but am in no position to evaluate them. It is quite unclear to what extent the BMW 801 reflects Bram influence.

Although the BMW 801 enjoyed a high reputation, particularly in the FW 190, I have some reservations about it - one issue is that it was difficult to adequately cool even with a cooling fan. It would be of interest if anyone could provide informed comments on the reasons for this behavior.
 
wiking85 said:
Any clue why the German radials still used 2 valves per cylinder?
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The provision of a satisfactory 4 valve/cylinder implementation is supposed to have presented practical difficulties radial engines having 2 or more rows - as far as I know, this idea was only seriously attempted by a few mostly unsuccessful Italian and Japanese designs.

Even for single row engines, 2 valve cylinders were the norm - Bristol and its licensees was about the only exception and Bristol went to sleeve valves with its later designs. Wikipedia is very misleading on this issue.
 
wiking85 said:
Any clue why the German radials still used 2 valves per cylinder?
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Almost all radial engines only used two valves per cylinder, including the allied ones. The reason was that push rods keep the diameter of the engine down, as well as weight, this rules out Over Head Cams. In the absence of OHC one can only use a huge and complicated array of pushods not only at the end of the cylinder banks but between as well. Gunston ("development of piston aero engines") says that the Japanese built some. It's not worth the effort. I one wishes to increase throughput of air to overcome the increased resistance of the slightly smaller area provided by single inlet and exhaust valves one can simply increase supercharging pressure slightly. Also as the specific volumetric output of air cooled cylinders was slightly less anyway so the valve area per unit mass of air processed was about the same anyway I suspect. The British got around it with their "sleeve valve" technology.

There is more than one way to skin a cat as they say. German engines used a very specific type of fuel injection called direct in port multi point injection whereby a variable stroke pump injected fuel directly into the cylinder. This is more sophisticated than throttle body injection or mufti point injection into the plenum behind the intake valve during the intake stroke. It came out of Robert Bosch's and Oscar L'Orange's (He was German Huguenot like Marseilles not French) work on high speed diesels and was also helpful in bypassing carburetor patents.

The result is that the German aero engines could have a large valve overlap where the intake and exhaust would be simultaneously open. This allowed the last 15% of air to be purged and scavenged out without fear of blowing out already mixed in fuel. It wasn't just the supercharger pressure that did this but the technique of tuning the inlet/exhaust ports like a trumpet so that an actual compression was achieved. Though this did work across all RPM ranges the maximum allowable overlap was still not optimal so from the DB601E onwards DB added a variable length inlet port that operated during starting and low RPM econ cruising to tune the engine.

The option of variable inlet ports was probably too mechanically complicated to be attractive for a radial which is why BMW on the BMW 802 wanted to use variable exhaust valve timing to "tune" the system.

There is more than one way to skin a cat.

The use of sleeve valves potentially gave the British an advantage in high RPM and power (eg 4000RPM Napier Sabre) but once Junkers decided to increase the power of the Jumo 213 they seemed to just set about fixing the limitations of the poppet valve to the point the Jumo 213J could do 3700RPM.

Apart from evolutionary developments of the BMW 801 with its two speed single stage supercharger there are perhaps three noteworthy variants:

1 The BMW 801TJ (possibly correctly called the BMW 801 J) which is a turbo charged development of the BMW801D-2 rated to 1600hp 40000ft
2 The BMW 801TQ (possibly correctly called the BMW 801 Q which is a turbo charged development of the BMW801E rated to 1750hp to 40000ft.

It's worth noting that these engines were rated to about 11500m (nearly 40,000ft) which is much more than the 25,000ft of the R-3350-23 and R-2800 which were flat rated to an impressive 25,000ft.

This partially explains why German high altitude engines were somewhat belated: The German high altitude program was aiming very very high. For instance the Ju 488 with 4 x BMW 801J was expected to have an service ceiling of 50500ft.

The engine saw a little service on the Ju 88S-2 (in which case the GM-1 system used on the Ju 88S-1 wasn't required) and also the Ju 388L-1.

3 There was also the BMW 801R which added an inter-cooled two stage 4 speed mechanical supercharger. The engine was as long as a inline V12 such as the Jumo 213E and would have been used on Ta 152 and Ta 154.

BMW designations could get complicated because the designation changes when delivered as a unitary "power egg". Stops confusion on the production line but certainly confuses historians.
 
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Enjoyed the post. Some remarks:


The Jumo 213J introduced increased strokeand 4 valve head, in order to increase RPM. The latest versions of the Db 603 were also to have increased RPM, up to 3000.


Those power figures at altitudes and designations are at odds at the ones from this report. The contemporary R-2800 C series with turbo were sea level rated up to 33000 ft, both for 2100 and 2800 HP.

This partially explains why German high altitude engines were somewhat belated: The German high altitude program was aiming very very high. For instance the Ju 488 with 4 x BMW 801J was expected to have an service ceiling of 50500ft.
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The hi-alt derivatives of the BMW 801 never received such resources as the USN-supported development ofthe 2-stage radials, let alone the resources devoted for development of turbos favoured bz USAC/USAF.

The engine saw a little service on the Ju 88S-2 (in which case the GM-1 system used on the Ju 88S-1 wasn't required) and also the Ju 388L-1.
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That's interesting. Care to share more info about turboed BMWs on Ju-88?

3 There was also the BMW 801R which added an inter-cooled two stage 4 speed mechanical supercharger. The engine was as long as a inline V12 such as the Jumo 213E and would have been used on Ta 152 and Ta 154.
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Although the table posted above mentions such a layout of supercharger, I wonder whether is that a misunderstanding like it was a case for the fairey 24 cylinder engine.
 
The sleeve valve had little to do with the Sabre's ability to run at 3750-4000rpm. The small cylinders (121mm stroke) had a lot more to do with it.

The 4 valve head involves a number of trade-offs. 4 smaller valves can have more area than 2 large ones for better breathing, they may be easier to control with valve springs of the same quality and strength.
However the valve train will be more complicated (especially using push rods) as will the intake and exhaust ports. The Bristol engines used a pent roof chamber with the angle of the head running front to rear but the intake valves were in the rear and the exhaust valves in the front. One exhaust and one intake valve on each side of the pent roof. This makes it harder to use exhaust thrust as the exhaust ports were in the front and and the exhaust has to do a 180 degree turn to go to the rear. Anything that reduces the velocity of the exhaust gases reduces the thrust.
One of the Achilles heel's of the air cooled engine is cooling the cylinder head (especially the exhaust valve area) and introducing more ports into the head cuts into the area or volume available for the cooling fins or extends the distance from the combustion chamber to the fin area. It does no good to increase the breathing ability if it comes at the cost decreased cooling ability. The increases in power of the Allied radial engines ( R-1820, R-2600, R-2800, R-3350 and Hercules) involved large increases in the fin areas of the cylinder heads and some increase in fins on the cylinder barrels rather than any increase in valve area.
The other limitation of radial engine RPM was the stress on the crankpins, crankshaft and crank bearings. No sense in designing a 3500rpm top end if the bottom end is going to fail at 2800-2900rpm.
 
There is definetly no mistake in regards to the BMW 801R. It is described in detail in Thomas Hitchcocks "The Focke Wulf Ta 152" on page 81. It is a BMW 801E but with a two stage 4 speed supercharger but with both a inter-cooler and after cooler. Photo of that page is attached.

The figures for the turbo charged BMW801J are from janes and are here repeated from 3 separate sources:
http://www.ww2aircraft.net/forum/aviation/bmw-801s-what-were-power-values-34279.html
BMW 801 TJ-0

Aeronautical Research in Germany: From Lilienthal Until Today - Ernst Heinrich Hirschel, Horst Prem, Gero Madelung - Google Books

The engines features of the TJ-0 were as follows:
At a critical altitude of 12300m, that's 40,700ft a power of 1430 hp was available. The critical altitude is where 1 atmosphere of pressure can be maintained in the manifold.
There was also a TJ-1 which gave slightly more power but at a lower critical altitude. These figures are likely all being read of a graph, hence the slight variations.

If you have any links for power versus altitude of the R-3350-23 (B-29 power plant) It has always been rated at 2000-2200-hp at 25000ft in the B-29 pilots manual.

 


1600 PS is not 1500 PS, and that value (1500 PS) was stated in both Janes and Allied post war report. The critical altitude is NOT an altitude where 1 ata can be mantained, but differs from engine to engine.


Thanks. I've checked it out in the 'Flugmotoren und strahltriebwerke', they also list the 801R as 4-speed, 2-stage engine.

If you have any links for power versus altitude of the R-3350-23 (B-29 power plant) It has always been rated at 2000-2200-hp at 25000ft in the B-29 pilots manual.
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No quarrels about that. The 2200 HP was military power, 2000 was max continuous. I've looked at the values for the C series R-28000 with turbo - it is 2100 HP military, at 30000 ft; 2800HP WER.
 
Now that we're discussing the turboed BMW 801 and US 18-cylinders: the BMW engines still used gear changing of the engine-stage compressor, that feature gave some 250 PS above 9.5 km (for 801J engine) and above 12 km (for the 801Q engine; called TM/TN at the Allied report). The take off powers, without ADI used, were better for the US engines, 2000-2200 HP vs. 1800-1880 HP.

The BMW-801J was lacking ADI (MW-50) capability. For that engine, that was actually used in service (unlike the 801Q) the 'Flugmotoren und strahltriebwerke' gives the power of 1485 PS (1464 HP) at 11500 m (37730 ft). At 2400 rpm and 1.32 ata, it was good for ~1440 PS at 8.5 km (1st S/C gear, rated altitude) and ~1270 PS at 11700 m (2nd S/C gear, rated altitude).

The data tables for the BMW 801 engines in most cases give power without deduction of the fan power needs, and that can be eg. 70 PS for the 2000 PS of the 801S.
 
wiking85 said:
Do you mean the 801F? How was it able to achieve a 2400hp take off rating? Could it enter widespread service by 1944?
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The "F" had a strengthened crankcase. It could achieve 2580hp with MW50. One advance was precision vacuum caste cylinder heads for better cooling. The rating was in fact raised from 2400 to 2580.
engine | piston-engine development | air-cooled radial | 1945 | 2394 | Flight Archive
The "E" in fact used the heads and pistons developed for the "F" but lacked other improvements. The E was actually a bomber engine and was known as the TS when supplied to the Fw 190A rating was initially 2000 but then raised to 2200hp.
BMW 801 ? Wikipedia, I'll let you use translate on that yourself.

MW50 didn't become common on German aircraft till 1944. The basic systems used supercharger pressure to pressurize and blow in the MEW50, the more advanced versions pumped it in at higher rates and presumably better atomization. That's why there is a range of speeds quoted for the Fw 190D-9, they actually had 3 different power boost systems added within as many months. I've read that MW50 on another forum was used with some Fw 190A5 with the BMW801D2 engine but that it tended to split the cylinder heads hence it was more common to use rich mixture to boost power. At some point the problem was solved with the BMW801E or TS and it was standard for the Fw 190A9 of which about 1000 were produced.

Development of the 2580hp 801F was complete, the only thing that kept it out of production was tooling shortages, possibly related to the supercharger and most likely due to the bombing campaign.
 
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Just some comments:
1 I accept that the term critical or full throttle altitude refers to the point at which the base engine can accept the full pressure of the supercharger. It obviously would vary with RPM. It does seem to have been used as meaning 1 ata manifold pressure at some point historically and in some contexts. Thanks for inducing me to clear that up.

2 BMW801TJ came in two models: BMW 801TJ-0 was based on the BMW801D2 while the BMW801TJ-1 was based on the BMW801E core engine. The "E" was considerably improved with better cylinder heads and packaged in the form of the BMW801TS (for the Fw 190A-9 fighter) could produced 2200hp when using MW50 though it was initially rated at 2000hp.

3 The BMW801TQ used the BMW801E core engines as per the BMW801TJ-1 above but seems to have been refined and had MW50 added, this makes sense as it is rated at 2200hp as per the BMW801TS(modified E for use in fighters) which of course had the same core.

4 There was no need to deduct 70hp fan power once the aircraft is in flight since once the aircraft was moving at speed it no longer drew power: it was effectively windmilling. It only lost power during the slow part of the takeoff run.

5 R-2800 that is producing 2800hp is using ADI ie water/alcohol plus 100/150 fuel.

You seem to be quoting some odd projected engine, the TN, optimized for lower altitudes when you refer to 1270hp above. This also is the max cruise power. Maximum long term power (ie military power or combat power) which is still not war emergency power but is greater than max cruise speed that would thus not involve using rich mixtures or ADI is quoted at around 1470-1500hp for these engines and over 1725hp for the TQ.


These BMW 801 turbo engines are effectively an R-2600 (due to 2600 cubic inch displacement) do seem to have higher critical altitudes than the R-2800 and R-3350 and likely reflects larger turbo chargers and more importantly inter coolers. Its likely they would've offered around the same power at 40,000ft despite their smaller size.

The BMW801F was capable of offering 2580hp WEP and takeoff. I seems likely that this engine, in the course of development, would've made itself into the turbo version of the BMW801Tx series and offered at least that level of power at takeoff. It had a stronger crankshaft so may have been able to operate at higher power when at altitude by running faster so long as the turbo could keep up the airflow.

Since Junkers estimated the Ju 488 as capable of opperating at 50500ft using the BMW801TJ I woould assume a model with the 801TQ would be even more impressive.
 
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1) Please don't mix up hp and PS, there's enough of a difference to make it problematic.
2) Please do not mix up bare engine designations and M/T engine system designations, the same letter engine designation was not always the same letter in engine system designation. Although the TS contained the S-1 engine in this case, the 801TU had the Q-2 engine.
3) At takeoff-power with 2700 rpm it was almost always 70PS to drive the fan, lower rpm/boost and lower need to drive the fan (~45 PS at ~2500, ~30 at 2300). RAM effects are not given in BMW docs but it's indeed posible it reduced the power loss.

BMW has the F-1/H-1 AKA TH-1 at 2000 PS but with reduced fan losses at high rpm settings with 10/10/5 PS less required in the first three powersettings (without boost system). Both S-1 and F-1 got either fuel or MW-50 boost kits to achieve at least 2200 PS, the F-1 was most likely suitable for higher boost pressures to achieve the claimed 2400 PS.
 

The 2000 PS take-offrating for the 801TS was available, against the 801D, through use of greater boost as standard (1.65 ata vs. 1.42) and lower supercharger gearing. The 2200 PS was available through over-boosting ("Erhohte Notleistung' power setting, equivalent of American term 'WER (dry)' ) at 1.82 ata, not via use of MW-50. That is still not the power available for the prop, that was 1930 PS for 'regular' take off power at 1.65 ata.


You're probably right about this.

4 There was no need to deduct 70hp fan power once the aircraft is in flight since once the aircraft was moving at speed it no longer drew power: it was effectively windmilling. It only lost power during the slow part of the takeoff run.
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I'm afraid you're wrong about this. Eg. the BMW-801D was rated, without fan, at 1490 PS at 5.7 km on Noitleistung. With fan, it was 1440 PS. At lower engine output, less power was used for the fan.

5 R-2800 that is producing 2800hp is using ADI ie water/alcohol plus 100/150 fuel.
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Nope, the turbo R-2800 C was never cleared for 100/150 fuel. It was using 100/130 grade: the extra power vs. R-2800 B + turbo was available due to greater both engine and turbo RPM.


I was simply typing out the data from the chart that can be found in the book 'Flugmotoren und strahltriebwerke'. The 2400 rpm and 1.30 ata was the 'Steig und Kampfleistung' (30 miutes rating), ie. one step under the 'Notleistung'' (2700 rpm and 1.42 ata here), and one step above maximum continuous power. The book also states the power of 1485 PS at 11700 m. When I get home, I'll post the data for the 801E + turbo.


The American engines did not used second supercharger gear of the engine-stage S/C, that detail probably cost them a good deal of power at really high altitudes. BMW turbo powerplants were far more compact and lighter, due to use of air-cooled blades for the turbines. On the other hand, US turbo engines were a timely executed thing, that managed to beused in great quantityin the ww2 - that's the greatest difference here.


Beit as it was, IIRC the 801F never entered service use.

Since Junkers estimated the Ju 488 as capable of opperating at 50500ft using the BMW801TJ I woould assume a model with the 801TQ would be even more impressive.
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I'd be rather careful with manufacturer's estimates. Hawker estimated that Typhoon would've been capable for 450-460 mph, Bell estimated 400 mph for the XP-39, Focke Wulf was hoping for 700 kim/h for the Fw-190A-3 (in combat trim).
 
The peculiar shape of the power curves is evident for the BMW-801J (red) - the 1st speed (or 1st gear) of the engine-stage S/C is active until ~8800 m (FTH being at ~8300 m), and then the 2nd speed (or second gear) is clutched in. FTH for 2nd speed is at ~11700 ft. The lines are for 2400 rpm and 1.32 ata power setting. The red square at SL is for 2650 RPM and 1.55 ata, where 1810 PS is available for take off. The red square, "<- 2" is power at 2425 rpm and 1.45 ata (1385 PS). Red square, "<- 1" is the greatest power at altitude, given by 'Flugmotoren und strahltriebwerke' - 1485 PS at 11500 m.
All data is from that book.
The line, violet color, is for the 'P.8035', the project involving the turbo system of the 801J and the 801E engine. The book states that development of that powerplant was 'soon canceled'. Power setting is: 2500 rpm, 1.45 ata. The 801E was capable for 2700 rpm and 1.65-1.82 ata, without ADI.
Looking at the graph posted at the book, my best guess is that lines are with deduction made for power used for the cooling fan.
People can also note that, for conditions without ram, the lines for the BMW-801D do not make allowance for the power used up by the fan.

 
Coloured lines and English text in an old German document, really credible indeed….
cimmex
 
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