WWII Inline engines: Daimler Benz vs Rolls Royce vs Allison vs Klimov vs Jumo

[gripen]

Originally posted by Charge
GJ+FX? You mean this? http://kurfurst.allaboutwarfare.com/Performance_tests/109G_DB-G6AS_wMW/DB_109G6_ASM.html

How much below specification is it?

The spec at 2600rpm 1,3ata is 8900m -200m while the GJ+FX did 8600m at that rating, other data gives lower values.

Originally posted by Charge

There is no sense in using a specific oil pump to feed the clutch but to use the  oil pressure from pump that feeds the engine and just do what ever you do to regulate the pressure after the clutch and thus control the rotation speed.

There is two pumps feeding clutch; the first one does constant flow and another controlled by barometric valve does variable flow between the 1st and 2nd FTH. Below 1st FTH the flow of the second pump is used to increase oil cooling flow.

For further information see Von Gersdorf&co, Raunio's article and DB 605A manual (can be found from FAF museum).

Originally posted by Charge

I don't see such thing. The system maintains steady ATA and delivers good power at low FTH and high FTH without large fluctuations in power output.

Please look the picture here.

At the left side of the graph you can see the curves of the MAP (ladedruck) and the pressure between the impeller and the throttle valve (gebläsedruck). These are close each other only above 2nd FTH, as an example at 4000m the supercharger does about 1,55ata pressure which is throttled down to 1,3ata at intake manifolds using the throttle valve.

Originally posted by Charge

What kind of problems? Blown engines because of over pressure or just no pressure?

Mainly oil cooling problems, that was the reason why the size of the oil cooler was increased in the AS Bf 109Gs. And cooling problems set the limits for the max slip.

[gripen]

Originally posted by joeblogs

No I don't have the same confusion as Charge. I know the clutch works off external atmoshperic pressure - I've seen the engineer's drawings. I am simply asking for some precision about the source of power increases above the 1st Full Throttle Height as altitude is increased.

Sorry if I understood you wrong, you wrote that "I thought all the action was done by the clutch" which led me to think that you are not aware about throttle use to fine tune the MAP.

Originally posted by joeblogs

Up to the 1st FTH, increased power with altitude can only come from increases in RPM and opening the throttle. I understand the German controls choose the combination of RPM and throttle automatically.

Below 1st FTH power increases with altitude mainly for the same reason as it increases in the any fixed speed supercharger ie when the throttle valve opens and the altitude increases, the supercharger works more efficiently and the engine gets cooler air. In addition the losses due to clutch are highest at max slip.

Originally posted by joeblogs

Now, at the 1st FTH, is it the case the engine is at maximum RPM with the throttle open or not? If the answer is yes, the only gain in power at altitudes above the 1st FTH must come from spinning the supercharger at ever increasing multiples of crankshaft speed. Tthis seems entirely possible.

At given engine setting the engine RPM is constant at whole altitude range and the MAP is constant up to the 2nd FTH. The speed of the impeller is constant below the 1st FTH (at max slip) and above 2nd FTH (at min slip). The opening of the throttle valve follows closely the difference between the MAP and "Gebläsedruck; when these are close each other, the throttle valve is open and when the differerence is large, then the throttle valve more or less shut.

If there is power increase with altitude between 1st and 2nd FTH, it's probably caused by large difference between MAP and "gebläsedruck" ie the min slip is reached before FTH. This is probably the reason why the shape of the power curves of the DBs is quite bit different than in the case of the ideal DVL variable speed supercharger.

[joeblogs]

If I understand the second part of your description it sounds like above the 1st FTH, there is the effect of (1) the clutch tightening up so that the supercharger is spinning faster and faster relative to crankshaft speed AND (2) continued opening up of the throttle as altitude rises (assuming the pilot is looking for maximum power).

Now does that mean there is a discrete change in the throttle around the 1st FTH, or perhaps the throttle is not wide open there in the first place?

Full Throttle height is probably the wrong term to use here. We are stealing it from the vocabulary used for superchargers with constant gearing. Here there is no necessity for the engine to be wide open at the point where the second pump begins to operate; that is if I understand you correctly.

Also if I understand what you are saying, the pilot's throttle/RPM controller acts as a governer on MAP, but the controller does not have any influence on the supercharger gearing. So it takes whatever pressure the supercharger delivers and adjusts engine RPM and the throttle to attain the MAP the pilot wants, subject to some maximum limit on MAP set by the controller?

-Blogs

Originally posted by gripen
Sorry if I understood you wrong, you wrote that "I thought all the action was done by the clutch" which led me to think that you are not aware about throttle use to fine tune the MAP.



Below 1st FTH power increases with altitude mainly for the same reason as it increases in the any fixed speed supercharger ie when the throttle valve opens and the altitude increases, the supercharger works more efficiently and the engine gets cooler air. In addition the losses due to clutch are highest at max slip.

 

At given engine setting the engine RPM is constant at whole altitude range and the MAP is constant up to the 2nd FTH. The speed of the impeller is constant below the 1st FTH (at max slip) and above 2nd FTH (at min slip). The opening of the throttle valve follows closely the difference between the MAP and "Gebläsedruck; when these are close each other, the throttle valve is open and when the differerence is large, then the throttle valve more or less shut.

If there is power increase with altitude between 1st and 2nd FTH, it's probably caused by large difference between MAP and "gebläsedruck" ie the min slip is reached before FTH. This is probably the reason why the shape of the power curves of the DBs is quite bit different than in the case of the ideal DVL variable speed supercharger.

[Knegel]

Hi,

GJ + FX is a G14AS, with DB605ASM, with the more weight due to the MW50 installation, this plain will have a disadvantage with combat climb to the 109G6AS.

The more weight will limit the speed of this plane in this high altitude, this minimize the RAM effect and power.

In the DB605ASM, the max power could get used rather long, although above rated alt the power is the similar to the normal Start/Not, the MW50 could get used as "Ladeluftkühlung" to increase the time of usage.

Therefor the GJ + FX had around 1,5 ata in 10000m alt for 2 x 10min combat.

If i compare the Speeds of the GJ + FX with the Spitfire IX BS. 551 (Merlin 70
 ( http://www.spitfireperformance.com/bs543.html , the other HF Spits show a rather similar result), the Vmax performences seems to be very similar.
The 109G14AS is better with Sondernot, but less good with combat climb, the RAM FTH of this Spit is a bit below that of the DB605ASM with combat climb, at 8350m.

If we take the time of usage into account, both engines seems to be rather similar in high alt.

Greetings,

Knegel

[llama]

Slightly off-topic question:

At first I thought it was a mistake: we're all talking about "V configuration" engines when the topic calls for the best "inline engine." In the car world, a V-6 and an Inline-6 are two very different types of configurations (that is, pistons arranged in a single row versus arranged in two rows canted 60 or 90 degrees toward each other.)

Yet as I look online and in my books, it seems that no distinction is made in classifying these two different configurations.

The usual distinction is simply "Radial" (and thereby aircooled) and "Inline" (meaning water-cooled.)

Anyone care to say why things are categorized this way?

-Llama

[MiloMorai]

llama, it all has to do with the position of the cylinders with respect to the crankshaft.

A V-6, V-8, V-10, V-12, V-16 are still inline engines but with a V configurartion.

[joeblogs]

Actually a great point. Continental's Hyper engine was a straight 12 - two banks of six cylinders in the same plane. Junkers had a diesel like that.

There are a number of air-cooled inlines, typically straight sixes. The tend to have smaller displacement.

-Blogs

Originally posted by llama
Slightly off-topic question:

At first I thought it was a mistake: we're all talking about "V configuration" engines when the topic calls for the best "inline engine." In the car world, a V-6 and an Inline-6 are two very different types of configurations (that is, pistons arranged in a single row versus arranged in two rows canted 60 or 90 degrees toward each other.)

Yet as I look online and in my books, it seems that no distinction is made in classifying these two different configurations.

The usual distinction is simply "Radial" (and thereby aircooled) and "Inline" (meaning water-cooled.)

Anyone care to say why things are categorized this way?

-Llama

[Viking]

Originally posted by Angus
Could you tell me why I find NO SOURCE for this??????????????????????
I have been begging for 109 tests for years, yet half of what I have just popped up in this thread. While the Spitfire climbing tests give me some data and not nearly enough, they are vastly more that all combined as a good reliable source of the Db & 109.

On page 6 of the „Kennblatt für das Flugzeugmuster Bf 109 Baureihe F1 und F2 Motor DB 601 N“ there is a speed and climb table that states time to various altitudes as well as rate of climb in m/sec. Under this table there is noted: “Die Werte die Flugleistungstabelle sind mit ‚Steig- und Kampfleistung‘,  d. b. n. = 2400 U/min., P-lade= 1,3 ata (bis Fülldruckhöhe) erflogen.“ And „Die geklammerten Werte beziehen  sich auf ‚Start- und Notleistung‘, d. b. n. = 2800 U/min., P-lade= 1,42 ata (bis Fülldruckhöhe).

Now, if my German serves me well this means that the rates of speed and climb in the table is flown at “climb and combat” setting with the number in parenthesis being flown at “Start and emergency” power. So the German Kennblatt of Messerschmitt aircraft lists both numbers.

If we compare this to The Aircraft Evaluation Report, U. S. Army Air Forces, German Messerschmitt 109F; the “Climb to 15,000 feet” table states 5 minutes for the 109F-1 and 109F-2. 15,000 feet is 4,572 metres and the Kennblatt states a time to altitude in “Climb and Combat” to 4 km at 4.3 minutes and 5 km at 5.4 minutes. Using “Start and Emergency” power the Kennblatt states 3.6 and 4.5 minutes respectively. It is pretty clear that the US evaluation is flying at “Climb and Combat”. It also states a time of 4.8 minutes for the 109F-4 (DB 601 E), which fits nicely with the F-4’s Climb and Combat. It is also interesting that the engine specifications listed only lists “military” and “normal cruise” power. Emergency power is not mentioned at all.

For allied documents on the performance of the Spitfire and other aircraft I can only assume that they test time to altitude in MIL power setting given the usual 5 min restriction on WEP. Also a time to altitude in WEP is of little practical value since you wouldn’t be climbing on WEP unless there was an emergency. Normal climbs to interception or air station was done at MIL. At least in this evaluation of captured 109F’s the climb tests seem to have been made at Climb and Combat.

[joeblogs]

1k3 asked for some comparisons of water cooled engines.

Knegel pointed out (correctly) that we should look at performance at different altitudes.

Below are some charts for several manufacturers and different models of their engines.

What I plot are take-off and military (or emergency) powers at different altitudes. Other than take-off, I believe the points correspond to full throttle heights, but I can be corrected there.

There are two important disclaimers on the axis engines. First, note that the powers are not based on the best fuels, an important part of the discussion in this thread. Second, the powers at altitude are "rated" powers. Now in the allied nomenclature these are not necessarily military powers. I don't know if that is also true for the axis engines, but we have experts here that can tell the difference.

I should add that a more even handed comparison of the engines would be by specific weight or specific displacement, i.e. dividing output by the weight or size of the engine.

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/allison.pdf

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/packard_merlin.pdf

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/rr_merlin.pdf

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/rr_griffon.pdf

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/daimler_benz.pdf

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/junkers.pdf

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/klimov.pdf

-Blogs

Originally posted by 1K3
In the radial department, nothing beats the Pratt & Whitney series.  Not even the BMW radials can beat P&W.

When it comes to Inline liquid-cooled engine, which company made THE best inline engine


[ EDIT:  Jumo is added to the list ]

[Viking]

Also those charts do not factor in the use of water injection (MW50) on any axis engine, and the only DB 605 listed is the 1942 model A1.

[gripen]

Originally posted by joeblogs
If I understand the second part of your description it sounds like above the 1st FTH, there is the effect of (1) the clutch tightening up so that the supercharger is spinning faster and faster relative to crankshaft speed

Yes.

Originally posted by joeblogs

AND (2) continued opening up of the throttle as altitude rises (assuming the pilot is looking for maximum power).

At 1st FTH the throttle valve is nearly all open because "Gebläsedruck" is near same as MAP. Once the second oil pump starts to increase the speed of the impeller, the difference between the "gebläsedruck" and MAP increase again ie the throttle valve is closing a bit gain.

Originally posted by joeblogs

Now does that mean there is a discrete change in the throttle around the 1st FTH, or perhaps the throttle is not wide open there in the first place?

The only change at 1st FTH is that the speed of the supercharger starts to increase, the throttle system itself works similarly above and below the 1st FTH. In the ideal case, the throttle is wide open above 1st FTH because the speed of the supercharger is adjusted to give exactly needed MAP.

Originally posted by joeblogs

Full Throttle height is probably the wrong term to use here. We are stealing it from the vocabulary used for superchargers with constant gearing. Here there is no necessity for the engine to be wide open at the point where the second pump begins to operate; that is if I understand you correctly.

The term is confusing but in the ideal case it is correct. In Finnish language we say "ahtimen ensimmäinen määräkorkeus" which can be translated something like 1st rated altitude but also that is confusing as well.

Originally posted by joeblogs
Also if I understand what you are saying, the pilot's throttle/RPM controller acts as a governer on MAP, but the controller does not have any influence on the supercharger gearing. So it takes whatever pressure the supercharger delivers and adjusts engine RPM and the throttle to attain the MAP the pilot wants, subject to some maximum limit on MAP set by the controller?

Basicly the pilot has only one lever which is used to choose wanted RPM/MAP combination. The automatic system itself is quite complicated but shortly it adjusts the propeller to keep wanted RPM and the throttle valve to keep wanted MAP. Note that the engine RPM is constant at any given setting.

[joeblogs]

Actually they do, when its available on the particualr engine tested. -

Well at least for the allied engines I am sure. But I think the numbers for the German engines should be treated cautiously. I think people have posted some better numbers than I think Wilkinson had available.

-blogs

Originally posted by Viking
Also those charts do not factor in the use of water injection (MW50) on any axis engine, and the only DB 605 listed is the 1942 model A1.

[joeblogs]

Gripen

Thanks, I learned a lot from your posts.

-blogs

[Viking]

Originally posted by joeblogs
Actually they do, when its available on the particualr engine tested.  

That's the point. None of the Daimler-Benz or Junkers engines in those charts have MW50. There are no DB 605 AM, DB 605D or Junkers Jumo 213 (190D/Ta 152) engines. Only pre-1943 DB engines and Junkers bomber engines, none with MW50.

[joeblogs]

This is true.

I do have numbers on the Jumo 213-A, but they are at normal, not military powers, so that does not help.

Wilkinson is very good with the allied engines, not so good with German engine developments after about 1941. His coverage of postwar piston engines is good, but for the German engines he jumps immediately to the jets.

-Blogs

Originally posted by Viking
That's the point. None of the Daimler-Benz or Junkers engines in those charts have MW50. There are no DB 605 AM, DB 605D or Junkers Jumo 213 (190D/Ta 152) engines. Only pre-1943 DB engines and Junkers bomber engines, none with MW50.