Fast bomber for USAAC: how would've you done it?

[cimmex]

MW-50 should enable good high altitude performance even on the B4 fuel.

MW50 only works below FTH
cimmex

 

[tomo pauk]

The benefits are most pronounced below FTH.
The MW-50, or similar ADI system, adds some intercooling/aftercooling effect. Eg. above 21000 ft, the 2-stage R-2800-10W gave almost 100 HP more with ADI, and the -18W gave more than 150 HP above 25000 ft.

 

[cimmex]

The benefits are most pronounced below FTH.
The MW-50, or similar ADI system, adds some intercooling/aftercooling effect. Eg. above 21000 ft, the 2-stage R-2800-10W gave almost 100 HP more with ADI, and the -18W gave more than 150 HP above 25000 ft.

According to "Flugmotoren und Strahltriebwerke" the use of the MW50 system allows higher Boost without detonation. Above FTH the supercharger could not deliver higher boost anymore.
cimmex

 

[tomo pauk]

According to "Flugmotoren und Strahltriebwerke" the use of the MW50 system allows higher Boost without detonation.

Of course, but that is not all what it does.

Above FTH the supercharger could not deliver higher boost anymore.

In case intercooling/afterooling is used, there is more air (or mixture) admitted in cylinders at a same boost, since cooler air is also denser. Please note the speed loss (graph) of some 7-8 km/h when the MW-50 system is disengaged ('MW abschaltung') once the Bf-109 with DB-605DB/ASB is above 7.5 km. The FTH being at 7.1 km; all altitudes with ram, of course. The MW-50 system acts as an intercooler there.

added: the benefits of the ADI systems were probably more pronounced with superchargers capable for boost (=2 stage), than with single stage ones?

 

[cimmex]

I'm sure you are wrong in this case but I'm too lazy to search the source now. Your original statement was "MW-50 should enable good high altitude performance even on the B4 fuel." For this the Germans uses the GM1 system not MW50.
cimmex

 

[tomo pauk]

No, that was not my statement.

 

[cimmex]

Helo, Koopernic,



I too do feel that the B-26 would do better with greater power. The 2 turbos per A/C would add quite a bit of weight, however - around 2 x 800 lbs, judging by weight distribution of the P-47. The B-26 was already at the limits of the weight loading. Some weight should be cut by reducing armament and crew, but not all 1600 lbs?
The 2-stage R-2800 should offer better performance than turbo up to 20000 ft, and comparable between 20-25000 ft? Much smaller weight penalty, circa 2 x 300 to 2 x 400 lbs - easier to balance out with reduction of guns and crew.



The early B-26s were good for 325 mph, admittedly at not max weights?



Maybe install some fuel tanks in the aft bomb bay, or use some space where the navigator and radioman were?



The single stage engines in the Mossie were not specially tailored for low altitude. The Merlins XX, 21, 23, 31 and 32 were 'normal' Merlins, that gave better power at altitude than single stage V-1710s. The WER (over boosting due to ever better fuel) was only available at altitudes 'under' the FTH, though.



Interestingly enough, the single stage R-2800 did not received water-alcohol injection (ADI) until the 'C' series of engines, ie. too late for ww2. The turbo and 2-stagers were equipped with ADI from late 1943/early 1944. No ADI = no WER for US radials.
The V-1710s were allowed for WER without ADI (= WER dry), officially from mid 1942 on. Depending on version, altitude and time, the WER was between 1400 and 1600 HP.



Seems like the Germans embarked into the 2-stage bandwagon too late. Big engines, decent RPM, intercoolers and MW-50 should enable good high altitude performance even on the B4 fuel.

not? see last two lines.

 

[tomo pauk]

Indeed, and not just "MW-50 should enable good high altitude performance even on the B4 fuel."

 

[cimmex]

well,our discussion started with post 161