'Increasing the Charge' - how piston engine technology provided the power to fly

[J.A.W.]

Here is a recent Lotus 2-stroke effort..

http://www.lotuscars.com/gb/omnivore-interactive-animation

 

[Trident]

Very cool video - there are actually shock diamonds visible in the exhaust flames if you look closely!

 

[tartle]

JAW, Trident...
Is that good?

 

[J.A.W.]

Not good for night flying, glare disrupts pilot vision & attracts the view of enemies..

As a matter of contrast - the sleeve valve engines were noted to produce much less - exhaust flame.

 

[tartle]

Which sleeve-valve engine compared to what?
I only ask this after a 'hard day at the office' which reminded me of over simplifying our comparisons e.g. musing here.

 

[J.A.W.]

Compared to poppet valve, T.

The Fury in the vid has had its Centaurus replaced by a Wright mill.
From Tempest II (Centaurus) flight trials, re night flying..

"The almost total absence of exhaust glare is a particularly pleasant feature of this aircraft."

& also - refer: paragraph 4, in this Sabre article..

http://www.flightglobal.com/pdfarchive/view/1946/1946%20-%201455.html

 

[J.A.W.]

over simplifying our comparisons... here.
[/quote]



Well T, at the risk of appearing over-simple..

..Don't just about all engines that work by gas transfer - essentially seek efficiency in inertia management of
the working medium, by means of best maintaining flow over time, via low-loss ducts & pressure/velocity control?

Some, like most piston engines will transfer primary power mechanically,with maybe, a bit of extra heat re-use..

 

[tartle]

I have nothing to add on simplistic... but adopting a different technology i.e. sleeve valves had a beneficial effect on exhaust flames; but of course there was a bmep trade-off to achieve that if I might be over simplistic... as they say we rarely get something for nothing,,, but it is very interesting how ten years of development changes the balance of outcomes.

 

[J.A.W.]

True T, & while from 1935-1945 sleeve valves had got to demonstrate their considerable advantages,
these were rendered less so by the ready availability of high octane fuel, then swept aside by turbines..

 

[tartle]

The fuel and the sodium filled valves, Fedden told me in 1965, were the two technologies that closed the gap and reduced the competitive advantage of the sleeve valve over conventional valves. It took so long to 'crack' the manufacturing technology required to produce the reliability of the sleeve in opertaion that valves had closed the gap and the gas turbine swept it all away!

 

[J.A.W.]

Here is a relatively recent appraisal of the sleeve valve VS poppet valve aero-engine debate.

http://www.enginehistory.org/members/articles/Sleeve.pdf

I note that the NASA article on the modern application of a turbo-compound 2-stroke Diesel aero-engine
also reiterated the potential advantages of the sleeve valve in their considerations.

I did enjoy working the smooth operating cycle of the Bristol Hercules sleeve valve cylinder on public
display at the RNZAF museum.

 

[tartle]

JAW,
The sleeve valve text is a great example of a thoroughly researched paper; the cost comparison figures he wrote that Rod Banks said are in fact really reliable figures from the work of Devons who was the planning guru at the Ministry through the last half of WW2.

 

[J.A.W.]

I'd reckon T, that while interesting, it could've done with a good technical editing..

One example, the weak comparison of relative compactness - in liquid cooled engines.

It is not too difficult to measure the difference between them per complexity above the piston,
- since cylinder-head-wise, poppet valve mills are significantly more dimensionally massive there,
with having to carry camshaft, rockers, valves, springs, ports, manifolding & etc..

& again costs-wise, how many quid would you put on stopping the Focke-Wulf attacks & 800+ V1s
crashing on London, or not knowing if the likes of the Jumo 222 would show up in numbers?

Len Setright wrote that the Centaurus was good for a 3,000hr TBO..

 

[tartle]

Who will do the 'improvement' then?

 

[J.A.W.]

Who will do the 'improvement' then?

If you mean via actual flying of piston engines T,

I guess that is up to the contractor/tender winner of a defence specification program?

Or - if it is simply an academic thesis matter, well, then his supervisor needs a kick up the jacksey..

 

[J.A.W.]

Unless.. Ricardo has a Crecy test unit in storage - that they can do a 21st century make-over on?

 

[J.A.W.]

R.J. Raymond in his report (post #90) appears to have little hands on experience with engines..

His analysis is a bit lacking in parts..

Obviously an H engine with 2 crankshafts & 24 cylinders (Sabre) is likely to weigh more than a V12 (Griffon)
of ~the same cubic capacity - but the output potential in power to weight terms - more than compensated.

 

[tartle]

R.J. Raymond in his report (post #90) appears to have little hands on experience with engines..

His analysis is a bit lacking in parts..

Obviously an H engine with 2 crankshafts & 24 cylinders (Sabre) is likely to weigh more than a V12 (Griffon)
of ~the same cubic capacity - but the output potential in power to weight terms - more than compensated.

I suggest that you email him and ask what his experience given all the technical papers he has written his email is
robertjraymond@gmail.com
P.S. what is the protocol for this forum?

 

[J.A.W.]

Thanks T, & I did note that he indicated that he would welcome comments on his work.

But given that it was published almost 10 years ago, somehow I doubt that any critique at this point
- would be novel - to RJR..

As for this forum, a discussion of the cogent issues ought to be of interest..

 

[J.A.W.]

R.J. Raymond also makes a bit of an incorrect assumption - as he put it - "...one would suspect..."

Re: the ports cut into sleeves being less effective than the "nozzle"-like poppet valve porting.

Of course poppet valves are limited in allowable lift by cam/spring matters,
- or before damaging contact possibly occurs with piston, or opposing valve/s..
& the "nozzle" is largely restricted into an annular orifice by the obtunding poppet head..

As an example, the final 2-stroke 125cc Aprilia G.P. single cylinder motorcycle engine was capable of flowing through its sleeve ports what the final 4-stroke OHC 500cc Norton G.P. single cylinder poppet engine could, yet to greater max power output..

 

[J.A.W.]

This well researched & written P&W R-2800 development article..
..includes reference to poppet valve gear inertia contributing to NVH issues..

http://www.enginehistory.org/NoShortDays/Development%20of%20the%20R-2800%20Crankshaft.pdf

 

[Artie Bob]

I do not know if Kimble is still alive, but if one does a little research, they will probably find he was the R-2800 test stand engineer that lived with that engine from the time he joined P&W shortly before WWII and stayed with it all the way through the war. Thus, his "well researched" article could actually have been written in the first person. What he does not say in this article are some of his test stand achievements with the R-2800, including a 100 hour test at 3000hp rating and a final peak output test at 3800hp. He reported that all of that test stand development had been accomplished with a single "stock" R-2800 except for the outsize supercharger and water injection (Hartford city water with no alcohol).

Best Regards,

Artie Bob

 

[J.A.W.]

Thanks A-B, the article does mention a 'moment' in the dyno room when a test engine failed catastrophically..

Alcohol was added to ADI primarily as an anti-freeze agent for flying at low temperature altitudes,
- so for ground/laboratory testing - it was not needed.

& cooling/supercharging constraints were likewise absent, so a mill could be really wrung out on lab test.

 

[Artie Bob]

After posting my note on the R-2800, I realized that I had done this from memory of a phone conversation with the P&W engineer some years ago and I couldn't lay my hands on either my phone notes or other back-up material. The information is I believe correct as told to me but it is not certain if Kimble was the P&W engineer or whether it was Kimble who had put me in contact with him. I will go through my material and post a correction if needed.
Relative to the use of alcohol added to the water injection fluid, the point here is that in addition to acting as antifreeze, IIRC, it can also further enhance the power output, so the power increases in actual service with the R-2800 were possibly more than predicted at any given boost pressure using water injection. The point made by the high output testing was that mechanically, the R-2800 was very difficult to break and had the ability to run reliably after heavy overboost (which saved many pilots during that period).
I began to fly and spend most of my waking hours at airfields in the early 1950s, earning my keep fueling, moving aircraft and starting engines with dead batteries (a 420hp Wright was the largest I hand propped). Some of my most vivid memories are of WWII surplus transports taking off overloaded on hot days nearing the end of the runway, trailing blue flame visible 20 to 30 feet behind the wing. One can only wonder what manifold pressure produced this effect. I never saw an accident, but often the aircraft could be seen a mile or more beyond the runway, just beginning to climb out of ground effect.

Best regards,

Artie Bob

 

[WJPearce]

I think we are talking about two different articles here. Kimble D. McCutcheon is the president of the Aircraft Engine Historical Society and I am fairly certain he never worked for P&W. However, he did write the article mentioned above and also the article below that involves Frank Walker. Walker was the P&W test engineer who ran up an R-2800 to 3,800 hp, in competition with the R-4360, and never blew an engine.

http://www.enginehistory.org/Frank%20WalkerWeb1.pdf

Regards,

 

[J.A.W.]

Great article B, - & wow, those R-2800 were real thirsty - 275 gallons per hour WFO!
.. no wonder those series production P-47s had to keep adding fuel tankage.

Interesting too, how they only wanted the alcohol in the ADI as anti-freeze
& avoided the isopropyl-type which did upset the fuel mixture ratio.

Although BMW ran a direct fuel injection system that discretely fed each cylinder on their radial,
they also used an extra injector squirting high-test C3-type fuel into the supercharger eye - as ADI..

 

[J.A.W.]

`40s period American book on aero-engines..

http://babel.hathitrust.org/cgi/pt?id=mdp.39015002094285;view=1up;seq=698

 

[tartle]

This is the bible on piston aero engine and fuels development written by Schlaiffer and Heron, frequently quoted on this board.
I obtained my CD copy from weak force press.
It is pretty accurate overall and is a good starting point but its assertions should be tested as there can be other interpretations now we have more government papers in the public domain... Heron graduated and researched at Manchester University before moving to the Royal Aircraft Factory at Farnborough. In the twenties he may have been keen on attracted Jimmy Ellor away from RAE (also a Manchester grad and researcher)
but Fell arranged for RR to make him a good offer with consequent benefits to increasing the charge' in RR engines.

 

[tartle]

Following up on digging into Kew in order to chart the history of supercharging in more detail than Schlaifer and Heron and on another website I started the journey through WW1 to just post-war. Extending the timeline has taken me to an interesting RAE turbocharger design circa 1934 for the 'High Altitude Kestrel'. This is shown in section below. An installation drawing of that turbocharged Kestrel is also shown below. The aeroplane is a high-altitude monoplane... but I am unsure what that is.... anyone have an idea what it could be?

 

[JFC Fuller]

Tartle,

The only thing that comes to mind is the Bristol Type 138B, it was a follow on to the original Type 138 and was to be fitted with the Kestrel in supercharged form though I can see a turbocharger being considered for obvious reasons.

 

[J.A.W.]

This is the bible on piston aero engine and fuels development written by Schlaiffer and Heron, frequently quoted on this board.
I obtained my CD copy from weak force press.
It is pretty accurate overall and is a good starting point but its assertions should be tested as there can be other interpretations now we have more government papers in the public domain... Heron graduated and researched at Manchester University before moving to the Royal Aircraft Factory at Farnborough. In the twenties he may have been keen on attracted Jimmy Ellor away from RAE (also a Manchester grad and researcher)
but Fell arranged for RR to make him a good offer with consequent benefits to increasing the charge' in RR engines.

Too right - 'assertions should be tested' - T.

& while I couldn't possibly comment on who was 'keen on' who, or 'attracted/arranged/offer/benefits'-wise..
..by odd coincidence, the Kevin Cameron TDC column in the April 2014 issue of Cycle World mentions this..

Kevin Cameron is a veteran engine tuner & gifted technical writer, & relates..

"I don't want to put out nonsense, so I try hard to speak the truth. My friend Graham White, author of
'Allied Aircraft Piston Engines of WW 2' & two other wonderful, thick engine books, was dismayed when
prickly, retired, & very experienced engine men crabbed over the inevitable few small errors in his 1st book.

I asked him to consider the statistics. The more you say, the more rubbish you must inevitably utter.
Every manufacturing process has a scrap rate, & writing is no exception.

So, over the long haul, you must accept fallibility & criticism.
& resolve each time to do better."

 

[tartle]

As Samuel Becket the playwright expressed it:

Ever tried. Ever failed. No matter. Try again. Fail again. Fail better.
​

"A second machine was ordered as the Type 138B in 1935. This was to be a two-seater powered by a Rolls-Royce Kestrel S engine fitted with a similar two-stage supercharger installation and generating 500 hp (370 kW). The airframe was delivered to Farnborough Airfield in 1937 for completion but the engine installation was never completed."

 

[J.A.W.]

Early aero-engine turbochargers were tested on Liberty V12s in America, 1918 at Pikes Peak altitude..

http://www.enginehistory.org/superchargers.shtml

& a little later - on the Napier Lion in Blighty, but metallurgy/pressure control issues were problematic..

Here is an interesting view of the innards of a (Napier) Lion..

http://www.apss.org.uk/projects/completed_projects/lion/index.htm

 

[J.A.W.]

Interesting that P&W developed their R-2800 as a fighter mill for both USAAF & USN, (turbo'd for Army use).

This article claims the R-2800 installation in the USN Corsair provided significant exhaust jet benefits..

Viz, thrust worth ~190lbs/210hp & ~20mph to Vmax..

http://legendsintheirowntime.com/F4U/F4U_IA_4508_DA.html

 

[J.A.W.]

Chrysler Corp turned down the British request to build Napier Sabres - in favour of the Curtiss-Wright R-3350,
-for the B-29 program.

This was a huge undertaking ( ~$100,000 for engines per plane) & by hard engineering toil the Mopar guys
got the TBO to rise above ~200 hours.. ..see the exploded view of the troublesome radial here..


http://www.allpar.com/corporate/factories/chicago.html

 

[tartle]

Jimmy Ellor was looking at turbos during WW1 . Towards or just after the end of the war RAE schemed several generic gear and turbo driven superchargers and these designs were adapted to fit various engines such as Lion and Liberty ... lack of test beds meant these then took to the skies.

 

[J.A.W.]

T, were the pioneering efforts at supercharging directed at increasing service ceilings?

Or as out & out power enhancement?

Obviously the racing Schneider Trophy/air-speed record planes wanted max sea-level power..

.. But the turbo-charged service engines were noted for maintaining a steady boost pressure to a primary mechanical supercharger so as to maintain performance over a fairly high altitude range - due to the turbo's ability to compensate by 'spooling up' (to the rpm limit) - as atmospheric pressure dropped, but were not known for high performance on the deck, & the US turbo fighters (P-38 & P-47) could not make enough low level speed to effectively run down V1 cruise missiles..

 

[tartle]

I believe the first superchargers for boosting sea level performance were the Schneider trophy machines.... before that it was really about restoring sea level ratings higher up in altitude. I am accessing performance reports on the turbo lion in a day or two so that I hope will enlighten us both!

 

[JFC Fuller]

Chrysler Corp turned down the British request to build Napier Sabres - in favour of the Curtiss-Wright R-3350,
-for the B-29 program.

Said Chrysler Sabres would have been for 750 Bell manufactured Hawker Typhoons. Was anywhere else ever considered for Sabre manufacture?

 

[J.A.W.]

Sabres built in Acton, & Liverpool.
Maybe the Beaverbrook memoirs would have some more info on the matter?

Perhaps the US deal fell through on proposed US Sabre usage?
(Albeit - there may have been some trust issues with Bell, after the RAF Airacobra debacle).

Certainly the USAAF were impressed by the Typhoon/Tempest.
- & are responsible for the saving the sole intact surviving Typhoon..