On superchargers, Mikulins, Klimovs, Jumos, etc

[GregP]

Thanks Tomo,

What a useful site! Appreciate it.

- Greg

 

[tomo pauk]

Useful site, indeed. I've just registered there, the forum is devoted to dig out the USSR stuff, among other stuff

Mikulin's design bureau was further experimenting with high-altitude engines. The AM-39 was something a mix of AM-37 and AM-38, performance-wise. It received a 2-speed supercharger drive, thus it was well suited for all altitudes, unlike the mass produced AM-35A and AM-38/38F. Further experiments included combining the AM-39, and, later, AM-42, with turbo supercharger. Table and graph are not from same source, the graph showing lower power values than the table:

 

[tomo pauk]

NACA translation of the captured Mikulin engines, with emphasis to the Polikovsky's guide vanes:

NASA Technical Reports Server (NTRS) - Description of Russian Aircraft Engines "AM 35" and "AM 38"

German researchers admit that the invention is a Soviet one.

 

[tomo pauk]

The French have also introduced the supercharger with adjustable vanes, known as Szydlowski-Planiol supercharger. It was substantially better than previous superchargers used on Hispano Suiza V-12 engines, and was installed on the HS 12Y-45 engine, used on D.520 fighters. More reading:
-war-time US article, with comment: link
-article (French language, can be translated) with graphs illustrations: link
-NACA docments, pertaining to the S-P supercharger (it also talks about variable speed DLV superchargers): link

 

[razor1uk]

Some very interesting and useful info diagrams etc guys, thanks, ...adjustable stator/inlet guide vanes to the chargers intake, seems such a common sence idea nowadays, not that most ground vehicle superchargers or turbo-superchargers use similar devices at all even now though, this concept only really got utilised in jet engines; and then mostly on 60's era and later jet/turbines engines.

 

[Shortround6]

Good work Tomo.

I would note that for production cars the extra moving parts, sensors and actuators might not be worth the gain, that and basic impeller and housing dressings have gotten a bit better.

 

[tomo pauk]

Thanks

The basic design certainly got better, and the adjustable vanes are nowadays present at the turbine side of the car's compressors. IIRC VW started that 1st on large scale some 20 years ago (1.9 TDI with 110 PS), today most of the turbos (at least when attached to diesel engines) feature that. Was driving one (KIA 1.5 CRDI, ~100 HP), wonderful for everyday use and then some more

added: gentlemen Szydlowski and Planiol founded their company in 1938. Company's name was Turbomeca (now part of SAFRAN, along with SNECMA).

 

[unix_nerd]

Hallo all,

Thats an interessting discussion going on here.
With a more in deep engineering background I would like to add the following thoughts:
The shape of the power curve is ( in my understanding) given by the designer - which of tries to meet the demands of the customer. So if the customer wishes a "Volldruckhöhe" (altitude were the power starts to drop of) of lets say 2000m or so the designer tries to match supercharger gear ration in that way. Here we have a more complex situation were the supercharges has a two stage gear or even a fliud coupling like in some DB-60x engines. These things will give (the engine) or take (supercharger) power non linear with varring rpm speed. On top of this with altitude pressure and temperature will drop (also non linear). On the BMW 801 the work of fuel management, supercharger gear speed and so on was orchestered by an computer. Ok, not a computer as we know them today but a mechanical analog calculating one. Have a look:
http://www.focke-wulf190.com/images/bmwkommandogeraet.jpg
Pretty complex aye?
I guess that the power at low altitude was lower because due to the higher intake temperature the engine would start knocking(detonating). Only a guess....
Best regards

 

[tomo pauk]

Hallo all,

Thats an interessting discussion going on here.
With a more in deep engineering background I would like to add the following thoughts:
The shape of the power curve is ( in my understanding) given by the designer - which of tries to meet the demands of the customer. So if the customer wishes a "Volldruckhöhe" (altitude were the power starts to drop of) of lets say 2000m or so the designer tries to match supercharger gear ration in that way.

For ww2 engines, most of the engines with single speed superchargers have had similar shape of power curve: raising up to the rated altitude, then falling down. Distinctive 'kink', or angle was to be observed by the rated altitude. With AM-34FRN and later Mikulin engines, the inlet guide vanes were employed just before supercharger's impeller. How those benefited the engine, can be read in the report that I've posted the link in post #23. The power curve did not have the distinctive kink, but of a more smooth shape. Jumo copied the device for their Jumo 213 series of engines, ditched the throttle plate(s) all together, and, at least it does seem to me like that, 'earned' even more power at ~2 km under each rated height. I was trying to describe all of those workings in this 2-page long thread
In the picture, one can note the differences in power with and without 'swirl throttle' (ie. intake guide vanes). In case the maifold pressure is 1.35 ata, and 1900 rpm, the difference is more than 160 PS at sea level (red vs. green line). For 1.415 ata and 2050 rpm, the difference is lower, just better than 50 PS between SL and 6.5 km (full black line vs. blue line):

Here we have a more complex situation were the supercharges has a two stage gear or even a fliud coupling like in some DB-60x engines.

There was no 2 stage gear in ww2 piston engines' superchargers - maybe you think of two speed gear?

These things will give (the engine) or take (supercharger) power non linear with varring rpm speed. On top of this with altitude pressure and temperature will drop (also non linear). On the BMW 801 the work of fuel management, supercharger gear speed and so on was orchestered by an computer. Ok, not a computer as we know them today but a mechanical analog calculating one. Have a look:
http://www.focke-wulf190.com/images/bmwkommandogeraet.jpg
Pretty complex aye?

Not sure what to say here - in most of clutched multi-speed supercharged engines, the power curves were similar. The power curves of the Jumo 213s and AM-39 were different that those majority.

I guess that the power at low altitude was lower because due to the higher intake temperature the engine would start knocking(detonating). Only a guess....
Best regards

Guess you're right. The use of Polikovsky's device on the AM-35A reduced the temperature of compressed air, eg. from 165°C to 125°C, for 1.415 ata and 2050 rpm at sea level.

 

[Algernon]

Posted by unix_nerd

I guess that the power at low altitude was lower because due to the higher intake temperature the engine would start knocking(detonating). Only a guess....

Below FTH (Full Throttle Height, i.e. Critical Altitude or Volldruckhöhe), at constant boost pressure, power (at propeller shaft) decreased for higher backpressure (i.e. more power consumed for scavenging).

 

[tomo pauk]

Ever decreasing intake air temperature (from lower altitude up) should also help to increase brake horse power, as engine gains altitude. The Polikovsky's device was managing to cool the intake air temperature, so the power loss at lower altitudes was smaller that when engines were without it.

Greg, the chart about Klimov V-12s is posted here.

added: sure enough, looking at the shape of VK-107A power curve, the suspicion is that it was also employing the inlet guide vanes. Picture at this post is not a proof, but it seems that they were installed.

added 2: per this site, one of the improvements vs. VK-105 engine was:
новый ПЦН с лопатками Поликовского на входе.

or:

new compressor with Polikovsky's vanes in the inlet

That entry is from the TsAGI book, in article about Klimov engines.