Open rotor générique

R-R and Snecma emphasise that TERA's results to date have been based on existing public domain data and not confidential commercial engine and airline operation data.......

The TERA 2020 tool also showed that a bypass ratio of 12 was optimal for fuel burn, not 14, which only improved noise. The TERA 2020 tool also showed that a bypass ratio of 12 was optimal for fuel burn, not 14, which only improved noise......

Beyond a ratio of 12, drag and wing integration issues were found to reduce specific fuel consumption......

"Beyond a ratio of 12, drag and wing integration issues were found to reduce specific fuel consumption efficiency-performance......"

-- The project technology themes include advanced technologies mainly devoted to fuel consumption / CO2 reduction pollution reduction, whilst retaining acceptable noise levels

-- Develop and validate novel engine systems providing potential advances for traditional turbofan -- engines and open rotor engines.

-- An open rotor engine has been shown to produce significant benefits in terms of a fuel burn reduction.
-- The aim of this sub-project is to demonstrate this benefit whilst maintaining acceptable noise levels (better than ICAO Stage 4 regulation).

Aero and Acoustic
• The development of a preliminary design for the optimisation of aerodynamic and noise characteristics

-- Open Rotor engine brings significant fuel burn and CO2 reduction.
--Thechallenge is to reach a noise level better than ICAO Stage 4 regulation, and in any case as quiet as nowadays turbofans.
- Important progress in aerodynamic and acoustic modelling done since the earlier 1990’s
should allow us to achieve this goal.

Aero/noise
• Making an advanced design of the direct drive contra rotating open rotor
• Validating its acoustic and aero behaviour by wind tunnel model tests

Integrated Acoustic Liners
• Several alternative design concepts will be developed based on aerodynamic and noise optimization, structural and manufacturing aspects.

.."Qui a évité d'être mouton de mode, ... et qui n'a pas suivi la pensée unique des peu perspicaces, des Adeptes du DPO,... et qui a décidé de ne pas faire partie du troupeau des moutons de mode " ?

-- Open Rotor engine brings significant fuel burn and CO2 reduction.
--Thechallenge is to reach a noise level better than ICAO Stage 4 regulation, and in any case as quiet as nowadays turbofans.
- Important progress in aerodynamic and acoustic modelling done since the earlier 1990’s
should allow us to achieve this goal.

Engines are front and centre once more as the driving force behind advances in aviation as the industry struggles with soaring fuel costs and mounting environmental concerns.
....
CFM and R-R believe advanced turbofans can deliver a 15% lower sfc than today's CFM56 and V2500 by 2015, enough to achieve a 20% reduction in fuel burn when combined with airframe advances. P&W says the same for GTF. But if airlines want deeper cuts, open rotors may be the only option.

sevrien a écrit: Un voyage de 2 heures avec le turbo-réacteur deviendrait 2h20 / 2h25 minutes avec "open rotor"...

Aujourd'hui, un turbo-réacteur capable de donner une vitesse maxi de 800 kph,
-- tel, par exemple, un Embraer RJ-145 de 50 sièges,
-- n'est pas plus performant qu'un Saab 2000 ou un Bombardier Dash --- (données SAS, & SWISS / Ex-Crossair à l'appui, et expérience personnelle sur des dizaines de trajets pertinents ),
-- en terme de temps "point -to-pont",
-- sur une distance allant jusqu'à 700 / 750 kms.

Les open rotors (moins bruyantst, aussi, que les turbo-props rapides, comme les excellents P&W sur les Bombardier Dash-- et les SAAB 2000 ... ),
-- permettent des vitesses plus élevées que les turbo-props.

Les chiffres comparatifs, des 700-750 kms. ci-dessus pour les distances, deviennnent, avec les "open rotors" 850 à 900 kms..

Au delà de ces distances, le turbo-réacteur permet de voler plus rapidement de bout en bout, mais la facture carburant se fait sentir. Les Passagers peuvent (selon étude de marché) supporter 10 à 35 minutes de durée de vol supplémentaire. Car cela serait la réalité !

Ici, l'avantage est qu'on peut parler d'avions transportant 150 à 180 passagers !

Est-il réellement certains que le open-rotor rendent autant de temps que ça "point to point"...

Pratt & Whitney's rivals have been content to mostly watch from the sidelines during the past year as the geared turbofan concept garnered headlines and its first two customers.

But the General Electric/Snecma joint venture, CFM International, is poised to break a year-long silence on its two-pronged response to the emerging need for a next-generation engine to serve the narrowbody market.

Duelling press conferences hosted by P&W and CFM at the Farnborough air show this month will set the stage for a decade-long debate within the industry about the future of narrowbody propulsion.

CFM's strategy, last updated in May 2007, is to introduce the LEAP56 advanced turbofan in 2015 and perhaps follow up with open-rotor technology after 2017.

The LEAP56 has a 15% higher-loaded single high-pressure turbine stage and an eight-stage high-pressure compressor, with 10-15% lower specific fuel consumption, up to 15dB less noise and 25% longer life on wing.

Both the GTF and LEAP56 technology would essentially transfer the ultra-high bypass ratio technology already powering widebody jets to the narrowbody market. Narrowbody engines have remained stuck in the same bypass range since turbofans were introduced in the 1970s.

A 1.8m (70in) class blade was scheduled to enter stress tests by the end of 2007, and should run on a CFM56-5C some time this year.
Meanwhile, CFM's more radical open-rotor concept still faces the same questions that appeared when the concept was reintroduced by CFM last year.
It will be at least another 18 months before GE can validate that the noise generated by unshrouded, counter-rotating blades can be counteracted by other design techniques, such as blade design.

Rolls-Royce, meanwhile, is continuing to pursue both advanced turbofans and open-rotor technology, but have yet to clarify their strategy.

P&W's strategy is now well-known and focused on the GTF, but also faces questions.
The PW6000 is being adapted for the GTF demonstrator engine, which is scheduled to fly in July.

But P&W plans to introduce an all-new core for the production GTF engine - the company's first new centreline project in more than a decade.

Le problème des "open rotors", ... c'est que les acteurs sont déjà figés dans un calendrier qui leur a été imposé, dans un jeu de circonstances qui a changé, ....et dont le motoristes sont devenus prisonniers !

Il est déjà un peu trop tard pour modifier le rythme !

Et le gros du travail sera davantage sur la réduction du bruit, que sur les économies de carburant / consommation, plus faciles à réaliser !

D'où, chez RR, l'accord de principe, de se laisser tenter par les possibilités en Russie, si les contraintes de bruit sont moindres qu'en Europe occidentale ! Cela permettrait à RR de faire un bond en avant, avec son moteur, sans la contrainte immédiate de la limitation draconienne du bruit "à l'Ouest" ! Mais RR pourrait aussi travailler très fort les économies de consommation, et faire des expériences avec les techniques d'attenuer de mieux en mieux les émissions de bruit !

Designing engines that require more frequent overhauls is one option being looked at by Rolls-Royce as it accelerates efforts to deliver efficiency savings of up to 50% for the next generation of Airbus and Boeing 150-seat airliner families.

Fuel savings could be achieved by using lighter components and operating the engine at higher combustion temperatures, in return for a reduction in time between overhauls.

"One per cent of fuel now is probably the same as about 10-15% of maintenance costs, depending on whether you're short range or long range," says King.

Getting the company's strategy for the 150-seat market right is so critical that R-R has assembled a 25-strong team to study the emerging requirements of the airlines and airframers, and the manufacturer has visited more than 50 customers to "understand how they use their aircraft, and how they will in the future", says King.

"We think there could be some quite fundamental changes going on in the market," he says.

Although 150-seaters today serve as workhorses on short- and medium-haul routes, "we're not quite sure what it is those people are going to fly around in in 10 or 15 years time".

In terms of pure technology R-R is looking at two- and three-shaft engine architectures, as well as a potential open-rotor solution.

But King says there are many more factors at play, such as the relative inefficiency of ultra-long-haul flying (given the large amount of fuel that must be carried over long distances), the relatively high operating speeds of current airliners and the fact that engines are being maintained in the same way that they were when oil cost $20 per barrel.

"We think there's a range of options we can pursue here, starting with something that is of the order of 15% efficiency improvement on the next aeroplane, through to something that could be as big as 50%," says King.

"The trade between maintenance cost, time-on-wing and fuel is very different from what it was. You really have to go right back and look at first principles about how should you be operating an engine in service.

What should you be doing in terms of the balance between, for example, time-on-wing and fuel?"

"There is 20-25% worth of decision making that can be done within the aircraft design," says King.

Option 15 - denoting a 15% efficiency gain - would essentially comprise an advanced but conventional turbofan incorporating the latest technology being incorporated into the three-shaft Trent XWB and two-shaft RB282. This could be available by the middle of the next decade.

"If you were prepared to wait a bit longer, wrap in some of these service approaches, maybe move the aeroplane design to something a bit bigger, then we come up with something that is more than 15%, a little bit later in that decade, still based on an advanced turbofan," says King.

Achieving "Option 50" would require making the leap to 3open rotor3, optimising airframe design, accepting reduced time on wing and possibly the adoption of alternative fuels.

Earlier this month R-R ran a one-sixth scale model of an open-rotor engine in the Netherlands to investigate noise characteristics, and the company plans to eventually run a full demonstrator based on a BR700-series core.

"We don't think that 50% efficiency improvement for the next generation is ridiculous, given the number of options we have," says King.

"We are essentially saying to the aircraft manufacturers that we are ready to go, as long as we understand the timeframe and exactly what this aircraft looks like."

R-R's partner in the International Aero Engines consortium, Pratt & Whitney, believes its geared-fan PW1000G-series engines can deliver significantly reduced fuel consumption without compromising durability.

"Cash operating cost is something that we always work to, and that balances fuel cost versus maintenance cost," says P&W senior vice-president engineering Paul Adams.

"We are seeing a trend towards much higher performance engines and better fuel consumption, which typically does have to run hotter," says Adams. "We have built this into our baseline engine and we honestly don't think that we need to substantially drive maintenance cost up to be able to get lower fuel burn."

Robert Saia, P&W commercial engines vice-president next-generation product family, adds that the PW1000G has around 1,500 fewer aerofoils as a result of the geared architecture, the majority of which have been removed from the relatively maintenance-intensive low-pressure turbine.

sevrien a écrit:-- " NB : Les choses se sont améliorées pendant les 2 derniers mois ! En juillet, RR parlait de 15%, en terme de gain de "fuel efficiency" ! C'est le minimum pour lancer un "step-change engine". Mon "contact" m'avait dit qu'ils pouvaient affirmer, avec facteur prudence incorporé, "16%".
Aujourd'hui, RR est prêt à parler ouvertement en terme de 15% à 20% ! Ce n'est pas l'habitude de la maison d'exagérer, de se vanter".

vertol a écrit: Bonjour à tous,
Bonjour cher Alain,

En complément des messages instructifs de Sevrien, mais dont les circonstances font qu’il ne s’agit que de reprises d’éléments déjà diffusés dans votre gare de départ…

vertol a écrit: ......je me permets d’apporter quelques éléments historiques.
Mes données sont malheureusement un peu anciennes,

"Entrée en matière sans parti pris" ? Non ! Avec parti pris "par omission " !

On reconnaît !

When can we expect to see open rotors?
Engine manufacturers such as Rolls-Royce have begun work on open rotor engine designs for the next generation single aisle aircraft. It predicts that by 2013 the open-rotor concept will be sufficiently mature for the anticipated performance benefits to be confirmed and that engines will be available between 2015 and 2020.

Pratt & Whitney claim their GTF engine offers a 12% reduction in fuel burn over current engines with a further potential improvement of 5-7% available by 2020. Although this fuel burn reduction is less than that predicted for an open rotor engine, GTF technology offers the benefit of enhanced maturity and hence reduced time for entry into service, is likely to be slightly quieter than an open rotor engine and is exempt from some of the challenges associated with open rotor technology (e.g. fan blade off and some integration issues).

Et sans parti pris !

The flight speed of an open rotor powered aircraft is limited by the propeller speed – propellers experience a dramatic loss in efficiency at high speeds, reducing the fuel burn benefit associated with the design.

While open rotors could operate at today’s cruise speeds, (Mach Number of about 0.8 for short-haul flights) for optimum fuel
efficiency they should fly at a Mach Number of about 0.75.

Although this means that open rotor powered aircraft will fly slightly more slowly than aircraft powered by equivalent turbofan engines,
the impact on flight time on a short-haul journey is likely to be minimal (under 5 minutes on a onehour journey and 5-10 minutes on a two-hour journey).

Different flight profiles, which are currently being considered for open rotor powered aircraft, may help to reduce this time
difference.However given that a high proportion of the total journey time for a short-haul flight is spent travelling to the airport, checking in, going
through security, collecting baggage, etc it is anticipated that any small increase in flight time will be acceptable to passengers once they are aware of the environmental benefit offered by open rotors.

Oui ! Il me semble que nous avons vraiment fait une entrée en matière sans parti pêis ! C'est comme si Carrie LAMBERT avait lu & étudié nos écrits !
Juste une impression personnelle !

Whether open rotor, GTF or novel three-shaft engines are selected for the new single aisle aircraft, it is clear that the opportunity to implement radical environmental improvements on a grand scale must not be missed.

The next generation single aisle aircraft market represents a rare and exciting opportunity that the aviation industry is determined to seize to make a significant difference to the future of the environment.

Effectivement, je ne vois rien de fondamentalement différent de ce que nous écrivons depuis déjà pas mal de temps ! L'auteur a dû nous lire, en effet !

Je suis de plus en plus convaincu, cher alain57, que nous avons proposé une entrée en matière vraiment sans parti pris !