German 2-stage engines

[Shortround6]

Two stage superchargers did not exist for aircraft when the 109 was selected, it had nothing to do with cost or expense.

Adding them at a latter date to an existing design was difficult as not only is there a weight penalty but there is a considerable cost in volume and a drag penalty for the intercooler airflow. The P-39 was too small to house an effective intercooler and the 2 ft longer P-63 also might have had problems. The 109 may have been too small to house the needed intercooler without major redesign.

[davebender]

That was a design choice.

Auto Union race cars used two stage superchargers during 1936. Dr. Porsche could have applied the same technology to the new DB601 aircraft engine.

[Shortround6]

Using what for fuel?

Edit: There is also some doubt that the 1936 Auto union used a two stage supercharger. Or at least when in 1936 it showed up. The 1934 and 35 cars used a single stage supercharger and they started 1936 with a single stage. At some point in 1937 they had the two stage which was continued on in 1938.

Using the latest Formula I Grand Prix technology on a service aircraft may not be the brightest idea either. Considering that Formula I cars don't have to worry much about elevation changes makes things a lot easier for them too.

[tomo pauk]

The DB-628 was not an intercooled engine, the frontal compressor feeding the engine compressor via a simple tube. Image by jerryw.

[Shortround6]

Thank you Tomo,

I can just picture this on the front of a 109, and the prop spinner to go with it

Does the pipe connecting the two superchargers go inside or outside the cowl?

Put it on the outside with a bunch of fins and you have a 1930s Era race car intercooler

[tomo pauk]

I'd like to see the DB-628 on some Fw-190, though, with plenty of cannons aboard. If the Allied report is right, the high altitude power is as good as of Jumo-213A with GM-1.
IIRC the ducting was under cowling; the idea to leave it out, with fins attached, seem so straightforward

[rank amateur]

That was a design choice.

Auto Union race cars used two stage superchargers during 1936. Dr. Porsche could have applied the same technology to the new DB601 aircraft engine.

I might be mistaken but Ferdinand Porsche wasn't working for Daimler Benz at the time, Auto Union was direct competitor. Furthermore Porsche was putting too much time in tankdesigning to be involved in aero engines designing.

[wuzak]

The Daimler Benz series progressively increase compression ratio to 8.5:1 whereas the Merlin and almost all other engines stayed at 6.2:1. The higher compression ration produces both more power and better fuel efficiency but clearly would also limit maximum manifold boost. The DB series used an usual head attachement system; using the cylinder sleave as a giant bolt which had a giant nut applied, this allowed a larger volume with no increase in size and weight.

Merlins and Griffons used 6.0:1. Early Allisons were about 6.5:1, but some later went to 6.0:1.

While the higher CR allowed better fuel economy, because the supecharger had to do less work, I dispute that it gave more power. In fact, the evidence is the opposite - low CRs and high boost gave more power.

Hence while the DB produced about the same amount of power as the Merlin and needed to process about the same amount of air this air was required at lower pressure which meant that a single stage supercharger could do.

To a point.

And you are comparing an engine with 33% greater capacity with the Merlin. That no doubt helped in matching the power at lower boost pressures.

Very few two stage supercharger engines came on line. The few I think of are
Jumo 213E1 of the Ta 152H
DB603LA of the Ta 152C3
Jumo 213F of the FW 190D-13

one reason for the introduction of the intercooled two stage supercharged engines was not their altitude performance but their abillity to opperate at high power levels on lower octane levels. The DB603EM was likely never built because its 2260hp needed C3+MW50 whereas the DB603LA could do the same job on B4.

Intercooling definitely helped maintain high boost levels with lower grade fuels. It is the same job that MW50 did.

But it was also vital for high supercharger pressure ratios - which were required at high altitudes.

[wuzak]

I might be mistaken but Ferdinand Porsche wasn't working for Daimler Benz at the time, Auto Union was direct competitor. Furthermore Porsche was putting too much time in tankdesigning to be involved in aero engines designing.

That is correct.

Mercedes-Benz's 1938 GP car (the W154) had a V12 with two superchargers, but these were not in series - they were in parallel (ie not 2 stage). They were both the same size. For 1939 the W154's M154 engine was replaced with the M163 which did have a 2stage engine (superchargers in series, one smaller than the other).

It may be that the Auto Union had two parallel superchargers, and not a 2 stage system. I will have to look that up.

[Tante Ju]

Thank you Tomo,

I can just picture this on the front of a 109, and the prop spinner to go with it

Does the pipe connecting the two superchargers go inside or outside the cowl?

Put it on the outside with a bunch of fins and you have a 1930s Era race car intercooler

Did not look that awful - Me 209H V5



Me 109V-54

[tomo pauk]

I don't know if some members remember the cartoon featuring the ant and ant-eater; the Me 109V-54 reminds me to the ant-eater The fairing for the tube connecting two stages is clearly seen there.

The 209-II was not equipped with DB-628 IIRC?

[rank amateur]

Did not look that awful - Me 209H V5



Me 109V-54

Totaly of topic but the tail of the me109v-54 reminds me of the me 262 tail
Makes me realise that my data on the me/bf 109 is somewhat lacking

[wuzak]

Two stage superchargers did not exist for aircraft when the 109 was selected, it had nothing to do with cost or expense.

Wasn't one of Bristol's early 1930s altitude records set with a 2 stage supercharger?

[wuzak]

Thank you Tomo,

I can just picture this on the front of a 109, and the prop spinner to go with it

Does the pipe connecting the two superchargers go inside or outside the cowl?

Put it on the outside with a bunch of fins and you have a 1930s Era race car intercooler

The 109's fuselage was very narrow. Other aircraft which used annular radiators it probably would fit in without an issue.

Tresilian proposed, for Rolls-Royce, a small X-16 using the Griffon (two stage) supercharger mounted in front, with a turbine to the rear for turbocompounding, with an annular radiator around the front of the supercharger. The supercharger housing would have been the widest part of the unit.

The DB628 probably woudl have worked well with an annular radiator.

[Shortround6]

Here is the Wiki entry for the Bristol 138a with the two stage supercharger.

Bristol Type 138 - Wikipedia, the free encyclopedia

Is it just me or does the the Me 209V5 look like a 109 with an annular radiator and a standard supercharger?

Looks like a standard air intake on the port side in the right position and no radiators under the wing?

The Me 209V54 does look like it has a fairing for the intake pipe from the front of the engine to the rear.