Jumo 213 Boost Pressure in Winter Months?

[CBSKY]

Could the Jumo-213 reach it's full boost pressure 1.8 ata in cold winter months? I can't read technical German (or any German at all!) so it is very difficult for me to understand the operation and boost pressure of this motor and it's unique mass air flow regulator.

Since the engine had a mass flow regulator and you have greater air density in cold/winter months - does this limit the motor to something like 1.6 ata? Flight tests are showing 1.8ata in chart dated Dec. 15, 1944:

 

[Deleted member 68059]

Could the Jumo-213 reach it's full boost pressure 1.8 ata in cold winter months? I can't read technical German (or any German at all!) so it is very difficult for me to understand the operation and boost pressure of this motor and it's unique mass air flow regulator.

Since the engine had a mass flow regulator and you have greater air density in cold/winter months - does this limit the motor to something like 1.6 ata? Flight tests are showing 1.8ata in chart dated Dec. 15, 1944:

View attachment 692595

Doesn't matter what the boost is at various times of year, the control unit has a temperature sensor which is always at work anyway because temp at high altitude might be minus 30 C or worse. A far bigger change on every flight than between summer and winter. The density will be maintained and thus power will be unchanged.

 

[CBSKY]

Doesn't matter what the boost is at various times of year, the control unit has a temperature sensor which is always at work anyway because temp at high altitude might be minus 30 C or worse. A far bigger change on every flight than between summer and winter. The density will be maintained and thus power will be unchanged.

Thank you. I just finished your book by the way...outstanding!

I was confused and stuck on the lower ata and wrongly thought it meant lower power. That regulator then is quite fascinating.

 

[Deleted member 68059]

Thank you. I just finished your book by the way...outstanding!

I was confused and stuck on the lower ata and wrongly thought it meant lower power. That regulator then is quite fascinating.

I have the Jumo213 control unit operational description in English, I will try to upload it to my website one day, but the diagrams need a lot of image processing to make clear so it will take me a while.

There are a LOT of "qualifiers" on that chart. The text on the top left says "With half fuel load!" (and some different prop reduction gear ratio) - pointin at the Ta152C curves.

The top right says:

"Speeds with consideration of the increase in resistance due to compressibility, without ETC, with movable landing gear doors, sealed engine panel gaps, surfaces smoothed and painted!"

Glad you liked the book!

 

[BiffF15]

Doesn't matter what the boost is at various times of year, the control unit has a temperature sensor which is always at work anyway because temp at high altitude might be minus 30 C or worse. A far bigger change on every flight than between summer and winter. The density will be maintained and thus power will be unchanged.

Calum,

With turbo props and pure jets, the more you push the throttles up, the more power you get. In cold weather you get more power sooner (throttle further aft). With a piston engine, like the Jumo (or any of piston for that matter), would the same apply particularly with differences between summer and winter temps?

Cheers,
Biff

 

[Farky]

You are right, you get more power in winter than in summer temperatures.
Simple formula is saying that for each 6°C decrease from standard altitude temp. you need to ad 1% hp and subtract 1% hp for each 6°C increase from standard altitude temperature.

So for example - power of Jumo 213A at S.L. on 1.8 ata is 2 100 PS in standard temperature (15°C). Same engine will give you in -15°C on 1.8 ata 2 205 PS.

 

[Daggerr]

[...............]
Simple formula is saying that for each 6°C decrease from standard altitude temp. you need to ad 1% hp and subtract 1% hp for each 6°C increase from standard altitude temperature.
[...............]

I would expect more impact. Where did you find that simple formula?

 

[Deleted member 68059]

Dont forget you`ll get dramatic differences depending on the forward speed of the aircraft too...

 

[Farky]

I would expect more impact. Where did you find that simple formula?

It can be found on various power charts, for example here (top left corner) - http://www.wwiiaircraftperformance.org/mustang/V-1650-7-High-Blower-power-chart.jpg

Little bit hard to read, so here is detail from another source -

 

[Denniss]

In the chart all 3 Ta 152 weights are with half fuel load, the reduction gear info is for the DB 603LA powered Ta 152C, the cooling fan info is for the BMW 801S powered Fw 190A-9 which also does not use any special boost system (A-8 with C3-injection, all others with MW-50 and the top right curves with NOx injection (GM1)).

 

[Daggerr]

It can be found on various power charts, for example here (top left corner) - http://www.wwiiaircraftperformance.org/mustang/V-1650-7-High-Blower-power-chart.jpg

Little bit hard to read, so here is detail from another source -
View attachment 692998

That makes no sense to me.

6 oC is 2 % (or more, depending on altitude) on absolute ambient temperature.

I would then expect that for a given boost and rpm:
As a consequence supercharger outlet temperature will change about 2 %.
As a consequence of that the manifold temperature will also change roughly 2 %, resulting in roughly 2 % change in density, resulting in roughly 2 % change in power.

Maybe the original rule of thumb was that 6 degrees (meaning degrees Fahrenheit) has an impact of 1 % on power, but somebody else assumed that degrees meant degrees Celsius and published that, which then started a life of its own.

 

[Farky]

That makes no sense to me.

...

Maybe the original rule of thumb was that 6 degrees (meaning degrees Fahrenheit) has an impact of 1 % on power, but somebody else assumed that degrees meant degrees Celsius and published that, which then started a life of its own.

And nobody catch that error? Very unlikely.

Anyway, it was used to make quick correction, nothing absolutely accurate. We can take a look at RAAF instructions how to correct power vs temperature -

(from RAAF instructions for R-1340 power curves, 1944)

Little bit different from US instructions, 10°F is not 6°C but 5.6°C. Also, US standard S.L. temperature was 15°C, in RAAF it was 60°F (15.5°C ) at this point.

 

[CBSKY]

You are right, you get more power in winter than in summer temperatures.
Simple formula is saying that for each 6°C decrease from standard altitude temp. you need to ad 1% hp and subtract 1% hp for each 6°C increase from standard altitude temperature.

So for example - power of Jumo 213A at S.L. on 1.8 ata is 2 100 PS in standard temperature (15°C). Same engine will give you in -15°C on 1.8 ata 2 205 PS.

Could the Jumo-213A be adjusted to develop 1.8ata in cold winter months, or was this not done?

Would the top speed of the D-9 suffer in comparison to say a Mustang since the Mustang get's a % boost in winter, but the Dora-9 stays the same? The Mustang adds say 85 (?) hp in winter, how much additional speed would it get from that?

Sorry if these are dumb questions, I am but a simple layman.

 

[Deleted member 68059]

Could the Jumo-213A be adjusted to develop 1.8ata in cold winter months, or was this not done?

Would the top speed of the D-9 suffer in comparison to say a Mustang since the Mustang get's a % boost in winter, but the Dora-9 stays the same? The Mustang adds say 85 (?) hp in winter, how much additional speed would it get from that?

Sorry if these are dumb questions, I am but a simple layman.

The 213 controller knows how much fuel to inject, for given temperatures etc. The boost pressure itself is not actually very relevant.
Remember these are injected engines, the incoming air conditions have to be matched by the controller
actually changing the fuel injection pump fuel mass flow output and the swirl throttle guide vane angle. The
controller "knows" what the external conditions are, otherwise it cant inject the right volume of fuel, and
whatever the temperature is outside, if you inject more than there is air available to burn, its essentially wasted,
(there is a benefit to running too rich for max power, but that too is a known value, so it comes out in the wash)
and if you inject too little you are losing potential power (depening of course on if you`re running on
rich or lean power settings of course). Above rated altitude, all thats happening is that the supercharger is
maxed out, and so the engine power just decreases on an ALMOST identical curve to that of atmospheric
pressure, so the swirl throttle remains at full open above rated, and the controller just keeps the
mixture correct by adjusting the fuel mass flow by reducing pump output.

It might be a lot more useful if you explain what exactly the underlying question IS you`re trying to get at ?

 

[CBSKY]

It might be a lot more useful if you explain what exactly the underlying question IS you`re trying to get at ?

Thanks - I was trying to estimate from standard atmosphere the top speeds for the major late war fighters in cold winter months.

For the underlying reason: I was trying to see if D-9 was suffering in performance in cold relative to say P-51 because of the way the engines are boosted.