Twin Screw supercharger on an aircraft?

[prabesh]

As I'm writing my paper about superchargers in aviation, I'm explaining different types of superchargers. For every type, I'm mentioning how it works, advantages, disadvantages of the kind, and if possible application in aviation industry. For Roots type, Vane type and centrifugal type, this has not been a problem. But when it comes to twin screw type, it seems the application of this is really limited to the automotive industry or large diesel engine industry. Anyone aware of aircraft (either from WW or modern days) which uses this kind of supercharger? One that i found was a modified one "Thomas Shapkow's Lysholm Screw supercharged Acroduster". Thank you in Advance!

 

[wuzak]

As I'm writing my paper about superchargers in aviation, I'm explaining different types of superchargers. For every type, I'm mentioning how it works, advantages, disadvantages of the kind, and if possible application in aviation industry. For Roots type, Vane type and centrifugal type, this has not been a problem. But when it comes to twin screw type, it seems the application of this is really limited to the automotive industry or large diesel engine industry. Anyone aware of aircraft (either from WW or modern days) which uses this kind of supercharger? One that i found was a modified one "Thomas Shapkow's Lysholm Screw supercharged Acroduster". Thank you in Advance!

D Deleted member 68059 may be able to help with this.

I know that Roots type superchargers were in use prior to the war, in road cars like the Bugatti Type 57SC and Mercedes-Benz SSK and in racing cars like the Mercedes-Benz W125, Auto Union Type C. The Mercedes-Benz W154 had two Roots type superchargers, running parallel in 1938 and as a two stage system in 1939.

But when it came to aero engines, centrifugal types were preferred. I think mainly because they were more efficient.

 

[Simon Thomas]

I had a Lancia Volumex with a Roots blower for a few years. The Roots is good for small flows and low dPs.
The twin screw compressors I am familiar with are designed for one pressure ratio, and their efficiency and reliability drops off as it moves away from that ratio.

 

[Deleted member 68059]

D Deleted member 68059 may be able to help with this.

I know that Roots type superchargers were in use prior to the war, in road cars like the Bugatti Type 57SC and Mercedes-Benz SSK and in racing cars like the Mercedes-Benz W125, Auto Union Type C. The Mercedes-Benz W154 had two Roots type superchargers, running parallel in 1938 and as a two stage system in 1939.

But when it came to aero engines, centrifugal types were preferred. I think mainly because they were more efficient.

Roots blowers are horribly inefficient, and the racing cars which "sucessfully" employ/ed them usually use/d fuels with extremely high cooling properties like methanol.

Methanol is worthless as an aviation fuel as the calorific value is pitiful, requiring collosal fuel flow rates and hence monstrous fuel consumption.

Roots, being "positive displacement" also give fairly quick "pick up" in transient situations, important around a racing car track. (these days technology has advanced to the stage where this advantage is basically gone, if you have some money to spend...)

Aero engines are basically constant speed, and require minimum fuel consumption with maximum efficiency, so roots blowers were abandoned in serious aviation very quickly.

For a given size, the roots blower is also at a dramatic disadvantage relative to a centrifugal compressor - with respect to flow rate - which only becomes more serious
a drawback the as you climb.

Archaic things, which only survive in popular conciousness due to dragsters, which, thanks to regulations have kept them low-(er) cost, entertaining, but technologically backwards.

FIA regs, TOP FUEL, pg 71.

https://www.fia.com/sites/default/files/2021_fia_drag_racing_technical_regulations_and_race_procedures_v.05.03.2021_marked_up.pdf

"Restricted to Roots-type supercharger, rotor helix angle not to exceed that of a standard 71-series GM-type rotor. Turbocharger and/or centrifugal supercharger prohibited."

Roots-rotors are sometimes used in top level racing as oil mist scavenge pumps, which is about all they are good for in an engine in this age. You can get some with complex helical geometry which are a bit better, but they`re very expensive to manufacture, and are still basically obsolecent.

 

[Shortround6]

Don't hold back, tell us how you really feel

 

[Simon Thomas]

From "Aircraft engines; theory, analysis, design, and operation" by Domonoske and Finch. Catalog Record: Aircraft engines; theory, analysis, design, and operation
p213

 

[Shortround6]

I believe that chart and study were made in the 1920s, which basically showed why only very few people were trying to use roots superchargers on aircraft even by the 1930s

I believe the US (and perhaps others) had tried to use roots superchargers on experimental engines during the 1920s.

 

[vikingBerserker]

Getting back to the original question, I cannot find anything about twin screw type superchargers being installed in aircraft. I think Simon hit the nail on the head about their efficiency dropping off.

 

[Deleted member 68059]

That graph above is in fact originally from NACA report #384 by Oscar Schey, in Jan 1931.

Its a slightly dubious report in the context of the discussion here, as they "assumed" that all the compressors had a 70 % efficiency because
they were more comparing the drive methods and throttling systems than the inate tendancies of the compressors themselves.

Which is *cough* doubtful, but they do admit in the intro page that:

"The Roots type gives the lowest net engine power of all at high critical altitudes,
because it has the least efficient type of compression"

 

[vikingBerserker]

So..................... is it safe to assume then that you are not aware of a twin screw type supercharger being fitted to an aircraft?

 

[Deleted member 68059]

I`m not no, but my field of historical expertise drops off radically before about 1928, which is to be honest the sort of early period when these would have been used (IF they were),
so I can only say that as far as I know, after abouyt 1930, I cannot think of any applications in aircraft.

Before that date, I cannot say they were NOT, just that I`m not aware of any (yet)

 

[GrauGeist]

NACA tested a Roots system on both a Liberty L-12 and a Wright J-4 back in the mid 1920's (I believe around 1926 or 27) geared for performance up to around 18,000 feet.
While the results were satisfactory, the weight and size of the Roots system negated any real advantage.

The Radial did perform better than the Inline and I believe that was due to the Liberty's valve timing.

 

[XBe02Drvr]

I can only say that as far as I know, after abouyt 1930, I cannot think of any applications in aircraft.

Admittedly this is a curveball, but the Fokker F27, other Dart powered planes (Viscount? YS11? CV600?) and, I believe some late era recip airliners, used roots blowers for cabin pressurization. The blowers were a major contributor to the ear-piercing shriek those Dart powered planes emitted. The F27 was a particular offender, as the intake duct to the blower was quite short and very direct, a veritable megaphone. Changing a blower is a painful job, especially outdoors at night in wintertime. (Ask me how I know.)

 

[SaparotRob]

Admittedly this is a curveball, but the Fokker F27, other Dart powered planes (Viscount? YS11? CV600?) and, I believe some late era recip airliners, used roots blowers for cabin pressurization. The blowers were a major contributor to the ear-piercing shriek those Dart powered planes emitted. The F27 was a particular offender, as the intake duct to the blower was quite short and very direct, a veritable megaphone. Changing a blower is a painful job, especially outdoors at night in wintertime. (Ask me how I know.)

How you know?

 

[eljefe]

Modern twin screw superchargers are the old Lysholm design realized with CNC machining. As such, they are a fairly recent innovation, going back to the 1990s (the Lysholm design goes back to the 19th century). They are more efficient than Roots-type superchargers. One manufacturer claims 85% for twin-screw vs. 65% for Roots. Manufacturers of twin-screw (Lysholm) superchargers for automobile applications are Whipple and PSE.

They still have the drawbacks of the Roots compared to the centrifugal type. Centrifugal superchargers are easily driven by waste energy in the exhaust, meaning that you get "free" boost without stealing torque from the crankshaft. Even when they aren't, centrifugals can still reach 90% efficiency when matched for flow and speed...which are exactly the conditions in aviation...cruise speed and rpm are nearly constant (close enough to be near the sweet spot for centrifugal supercharger efficiency).

If there was no such thing as turbo lag, and if GM had not put Roots-type superchargers in mass production on diesel truck engines, the automotive world would have abandoned positive-displacement superchargers years ago. The hottest new development in automotive forced induction is the e-turbo, which incorporates a high speed (75,000 rpm) electric motor/generator on the shaft between the turbine and the centrifugal compressor. The motor can steal power from a battery to maintain shaft speed (and boost) off-idle, and can act as a generator, braking the shaft speed at high engine rpm and returning excess energy to the battery rather than dumping exhaust through a waste gate. You might think of it as electrical rather than mechanical turbo-compounding, with a computer rather than the mechanical design setting turbocharger rpm over the engine rpm range.

 

[brianwnz]

The below excerpt is from a June 1943 SAE paper titled "The ELLIOTT-LYSHOLM SUPERCHARGER" by Alf Lysholm, Ronald Smith & W A Wilson. Unfortunately, it doesn't state who or exactly where the 'experiments' were taking place.

Other than this, I've only heard of Allison making roots blowers for aircraft engines, including NACA experiments, as per below (book excerpt is from Rick Leye's book on North American Gas turbines; although I can't confirm the P&W engines, I'm happy to trust Mr. Leyes on this):

Moss wrote a small book on Superchargers in aviation, but only mentions Roots blowers in passing; the book is mostly on turbochargers and centrifugal superchargers..... There may well be other engines out there that have tried the screw-type supercharger (they seem to have tried every conceivable other sort of device over the years), but it is hard to search by that reference alone, as most authors did not reference them by type of supercharger....... Good luck with your paper

 

[GrauGeist]

Found the abstract to the technical paper for the 1926 NACA test:

A ROOTS-TYPE AIRCRAFT-ENGINE SUPERCHARGER

Development of the aircraft powerplant has been the greatest single contributing factor to the progress of aviation. A logical field for future development seems to be the improvement of its altitude performance, and the best of the several proposed methods for doing this. Consequently, the Sub-Comm

www.sae.org

 

[prabesh]

I would like to thank you all for your contributions. As some of you guys have been refering to the NACA technical notes, yes I've read almost all of those which include anything about the superchargers. If anyone is interested, the lysholm type indeed had no applications in the aviation due to its bulky size and complexity. they did try to make a light version out of it (1943 SAE paper titled "The ELLIOTT-LYSHOLM SUPERCHARGER") but unfortunately the arrival of godly efficient turbosuperchargers and the already existing centrifugal supercharger were far more superior to compete so the researches were stopped (this is what my hypothesis says after analysing the reports). Also good to know, the centrifugal superchargers became better and better by adding features like multi stages for more boost, variable speed technologies using mechanical or hydraulic clutches or even fluid clutches (see Fottinger Coupling if interested) which made it possible to vary the impeller speed infinitely so not just two speed. The effficiency hereby skyrocketed and people never looked back to any other types. As mentioned in the thread, the next step would probably be the electric turbos but the history has shown very disappointing results everytime someone comes up with electric version.

 

[prabesh]

So..................... is it safe to assume then that you are not aware of a twin screw type supercharger being fitted to an aircraft?

yup, our beloved aircrafts didn't get screwed.

 

[mikemike]

I think twin-screw compressors were used to produce high-pressure compressed air, for instance in submarines. There is also a faint recollection of them being used as stationary compressors for gas pipelines.