Turbo-Fans Générique !

Bonjour !
J'ouvre ce fil pour caser une belle compil concernant la genése des gros moteurs, reçue de Airinsight
Auteur :

Big Aero Engines Addison Schonland | September 12, 2010 at 10:13 am

--------------- L'article de AirInsight ------------

http://airinsight.wordpress.com/2010/09/13/big-aero-engines/
Big Aero Engines

The engines that power the widebody planes had a difficult start. PW’s JT9D had some teething troubles as did Rolls-Royce’s RB211. General Electric developed its CF6 based on an earlier design, the TF39, and the CF6 also had some teething troubles. (An interesting tidbit - the TF39 was developed for the C-5 Galaxy, which recently has been re-engined with the CF6) These engines and their subsequent generations and derivatives went on to serve with distinction – and still do to this day.The JT9D went to be replaced by the PW4000, while Rolls-Royce kept its RB211 name and GE kept the CF6 name. What started out as a ~50,000 lb engine thrust class is what we are discussing here.These engines are important from the perspective that they power airline icons in terms of large aircraft. If you have been flying for years and on a long haul flight, one of these three engines got you from point A to point b, likely without any mishap at all. These engines set the standard for all future engines as being among the most reliable ever made. The lessons learned from the early versions were relentlessly refined into what we see on aircraft today.The category is a three horse race. It was this class of engine that powered the 747, 767, A300/310/330, DC10/MD11 and TriStar. So as you can imagine, this was, and still is, a big market for the three engine OEMs. The chart illustrates how the original engine designs were refined and grew in power over the time period.The purpose of the chart is to show readers how the power evolved for each firm. Note how each firm saw thrust development over time – the thrust choices are particularly varied for Pratt & Whitney.Rolls-Royce offered its first RB211 in 1972 on the Lockheed TriStar (L1011-1) and this engine offered 41,030 lb of thrust. This engine went on to power a fair number of Boeing 747-400s as well as a much smaller selection of Boeing 767s (Basically those at British Airways). Of course, the engine saw a number of improvements with later generations. The final version offered in 1991 (RB211-524H-T) came with 60,600 lb thrust. The chart shows Rolls-Royce had a stable program with power rising by 47.7% over 19 years on nine versions of the original engine.General Electric first offered its CF6 in 1978 with 45,600 lb thrust on the 747-100B. This engine also saw numerous tweaks and by 2004 was offering 72,000 lb thrust for the A330. This is a power growth of 57.9% over 26 year period. There are 33 versions of this engine, which shows GE’s relentless tweaking to extract improvements from the original design.Pratt & Whitney offered its first PW4000 in 1987 with 50,000 lbs thrust. Previously PW offered the JT9D in 1972 at 46,300 lbs thrust on the DC-10-40, and the final JT9D was offered in 1983. Like GE, it tweaked the design relentlessly, seeking higher power as the chart illustrates. The engine has gone through 23 versions and by 2009 was offering 70,000 lb thrust on the A330. Over 22 years the engine saw thrust rise by 40%. But note that there is a version of the engine (PW4098) that was offered for the 777-300ER that came with 99,040 lb thrust. (The 777-300ER is offered with the GE90 exclusively)Interestingly the original Rolls-Royce RB211 had a thrust to weight ratio of 4.5 and ended up at 6.4. GE’s CF6 started off with a thrust to weight ratio of 5.1 and is now at 6.4. The PW4000 started off with a thrust to weight ratio of 5.4 and is now at 5.7.Finally, a key number for any engine is weight – lighter is always better. The Rolls-Royce engine weighs 9,470 lbs, the GE weighs 11,225 lbs and the PW weighs 9,332 lbs.These “big fans” were the forerunners of what we see coming out today on the latest airplanes. These were the first of the high power high bypass engines. Their influence will be felt for a long time yet.
JPRS

Bonjour !

AirInsight me re tombe dessus !
Suite, la genèse des GTF etc ... belle anthologie, des conclusions déterminantes, ! J'ai aéré le texte !
Par:
Addison Schonland | September 21, 2010 at 3:59 am

--------- Airinsight l'article ----------

http://airinsight.wordpress.com/2010/09/21/propfans-limitations-for-re-engine-programs/#more-408
Propfans – Limitations for Re-Engine Programs

The last time the aviation industry saw tremendous growth and evolution in aero engines was the 1980s. This was the time when GE joined forces with SNECMA to create CFM. P&W joined with Rolls-Royce, MTU and other to create IAE. Those were heady days.

The CFM engine took to exclusive spot on the 737, and never looked back. P&W had success with their PW2000 on the 757, GE left that segment, though Rolls-Royce stayed to compete for every 757 sale. It was the time when the engines saw rapid progress.Meanwhile P&W and GE started working on new ultra high bypass engines with sweeping open fans.

The race was on to radically lower fuel burn and these “propfans” were thought to be the answer. These engines offered lower power and speed, but they burned 50% less fuel. During the first oil crisis, saving fuel costs was paramount.There were two primary options, a GE solution and an P&W/Allison solution.

Both engines were tested on a McDonnell Douglas MD-80. Boeing also tested the GE engine on a 727. Take a look at this video from GE explaining the influence the GE36 had on today’s GE engines. Because of their design, the engines were all rear mounted. Rolls-Royce was working on a shrouded engine called Contrafan – and of the offerings, this was the only design that could fit under a wing.
As this image clearly shows, the rear mounted engines may have been small but the blade sweep was very large. In other words, these engines, even if they saved lots of fuel, were limited. At the time only McDonnell Douglas was developing more rear engine designs. Boeing was focused on under wing engine layouts as was the nascent Airbus.As the image illustrates, propfans don’t work well under a wing. But they can, and do, work well on high wing designs like the Antonov AN70. These engines, while being great on fuel burn still have to overcome a big issue – noise. Take a look at this video of the AN70 in action and note the noise it makes. For a military aircraft this is simply not an issue. But for commercial airplanes, this is a growing and serious matter. Particularly as residential areas crowd airports.

Besides the airplane design limitations, oil prices spiked when the PW/Allison and GE programs were being tested and prices were on their way down. Financial pressure dissipated and airlines went after growth and less concerned with fuel costs.

Airlines are now once again sensitive to oil shocks. The recent flirtation with $140/bbl oil was a rude reminder that airlines need to maintain focus on ensuring the lowest fuel burn possible. This is one of the prime drivers behind the current fervor in thinking about re-engine programs. But as we have shown, even if unducted fans (UDF) were to make a comeback, their usefulness is limited since the current designs are all under wing powered. They simply have no place in any re-engine program.

Of the big engine makers, only Rolls-Royce is talking about a UDF solution. No surprise then that they pooh-pooh the LEAP-X and GTF. Especially the latter, since they could have been a part of that program under the guise of IAE. P&W felt strongly that the geared solution was the right one, it took the risk and went ahead without IAE.

P&W’s wilderness days are coming to an end as its GTF technology is proven appropriate and GE races to develop its own new generation engine, the LEAP-X. A recent demonstration of how quiet the GTF is going to be means that it will be a good neighbor engine too.

Rolls-Royce bet wrong with the Contrafan during the previous round (but got other programs like Trent exactly right) and might be well advised to rapidly update that idea now. Otherwise it will have to wait out another cycle and then have to try sell an idea which remains limited even with new airplane designs planned for 2020 or later.


JPRS

Ouaip...

Je complète avec le lien vers la video GE / UDF

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