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The next steps for Airbus' big bet on open rotor engines
- inhumantsar 9mo ago> Airbus is also assessing shielding the area of the fuselage closest to the engines to minimize the risk of a blade off — one or more composite blades breaking, which could dent or puncture the fuselage and, in the worst-case scenario, strike a passenger. sightly terrifying
- KolmogorovComp 9mo agonot more terrifying than sitting in any turboprop airplane.
- roboror 9mo agoYeah I'd think you'd need some serious shielding to prevent a puncture
- in_a_hole 9mo agoI had a sharp intake of breath after reading this and then clicking through to see the header image of the article.
- mapt 9mo agoThe cowling of the current turbines serves the same purpose, but needs to cover 360 degrees of rotation, so it's heavier and draggier. The blades have a bit more angular momentum in the propfan than in a high bypass turbofan, but there's fewer of them.
- dameyawn 9mo agoInstead of reinforcing the fuselage, I wonder if just having a 1/4 nacelle that shields the passenger side would work.
- fsckboy 9mo ago>The cowling of the current turbines serves the same purpose, but needs to cover 360 degrees of rotation this doesn't make sense. if you are not worried about fan blades flying off in directions other than the fuselage, why cover 360 degrees? (and if you are worried 360, then why open rotor?)
- somewhereoutth 9mo agoThe cowling is its own structural support, so needs to be strong all around, otherwise it would fail on the other side and you'd get blade+cowling approaching the fuselage at high velocity.
- pavon 9mo agoThe impact area of the fuselage looks much larger than an unrolled cowling, and thus significantly heavier to reinforce. The smaller cowling will save drag through.
- ahartmetz 9mo agoIt might hit the fuselage at a flatter angle than it would hit a nacelle, which would help.
- csours 9mo agoHigh bypass turbo fans do this as well, it's just in the fan/engine housing, not the fuselage.
- danparsonson 9mo agoReminded me of this: https://youtu.be/j973645y5AA?si=QJrNJe0gT-zwpElD https://youtu.be/j973645y5AA?si=QJrNJe0gT-zwpElD Seems like quite an engineering challenge with this new design...
- drivebyhooting 9mo agoWon’t this be absurdly loud?
- Etheryte 9mo agoThis is discussed in the article, was there a specific part that was ambiguous?
- drivebyhooting 9mo agoIt was glossed over and buried.
- xattt 9mo agoTFW does say there is an opportunity for reduced noise. However, conventional turboprops are very loud compared to their jet counterparts. Each revolution of a prop blade sends out a shockwave of air against the airframe. The strength of the shockwave is likely proportional to the instantaneous thrust of the engine, and more blades are likely to weaken or smooth it. A turbofan has a nacelle to contain the shockwave, and avoid the whole noisy mess.
- ufmace 9mo agoIt's only discussed in a similarly ambiguous way - like that they know noise is a potential problem that they're working on. Though to be fair, the designers probably have no idea themselves, since apparently nobody has built a prototype engine that could be run at the rated thrust level in a way they could check the real-world noise and vibration on.
- rgmerk 9mo agoI would assume that these days you can simulate that increasingly accurately before you need a full-scale prototype. They could also use active noise cancellation, which is already used in some turboprops like the Q400.
- xattt 9mo agoJust an opportunity to sell premium quiet seats at the back, and pleb seats at the front. With all seriousness, I am thinking whether there are parallels between this proposed plane and the Q400.
- bob1029 9mo agoI am assuming the target market for this is European short haul flights? On something like a New York <-> Los Angeles flight I cannot imagine the turboprop beats a 737 in any performance or comfort category.
- micwag 9mo agoThe article is not about turboprop but about open-rotor engines which are a modern variation of propfan engines.
- ricksunny 9mo agoSince you've undertaken the effort of distinguishing, please elucidate the difference in your own understanding of it, (and not whose brand or publication name is validating the terminology) in more detail.
- 4fterd4rk 9mo agoEverything old is new again... McDonnell Douglas looked into the propfan thing. Boeing looked into the propfan thing. Now it's Airbus' turn. IIRC the technology has been ready for years but the passengers are freaked out by it.
- cherryteastain 9mo agoReal problem was noise, not passengers. Immense advances in aeroacoustics over the past 40 years thanks to CFD is the main enabler here.
- dcrazy 9mo agoI think it’s a cool idea but I also know that the nacelles have a safety function of containing the rotor blades in the event of disintegration (e.g. from a bird strike). If these fans have blades with anywhere near the same kinetic energy, I would be nervous.
- txru 9mo agoSouthwest 1380[0] is a case where the cowling didn't quite contain the thrown rotor blade. They were very lucky that only one person died. [0] https://en.wikipedia.org/wiki/Southwest_Airlines_Flight_1380 https://en.wikipedia.org/wiki/Southwest_Airlines_Flight_1380
- filleduchaos 9mo agoTurboprops have already existed for decades, so perhaps you should already be nervous.
- AnotherGoodName 9mo agoIt's part of the tradeoff between momentum and energy that you should aim to move as high of a mass of air at as low of a speed as possible for efficiency. When you put energy into a mass of air you impart energy of 1/2 MV^2, the kinetic energy equation, which you can think of as the energy you're leaving in the air as it's accelerated to a given velocity on exhaust from the engine. The V^2 part is a killer. This does not translate directly into momentum at all and the most energy efficient way to gain momentum is with a large mass that's accelerated to a low velocity. You can actually see this with the wings which keep the plane itself up. The wings impart enough momentum to hold the weight of the aircraft up by moving a lot of air at relatively low velocity which sacrifices very little energy for the upwards momentum gained. So engines in aircraft have been getting bigger and bigger as well as slower and slower. It's basic physics, aiming to move as high of a mass at as low of a practical velocity as possible. The 737 max issues were an example of adding giant engines to an airframe not originally built for them due to the drive to move as much air at as low of a velocity as possible while still keeping the plane moving forwards. Passenger aircraft have been getting slower over the years, the 747 was faster than the newer 787's because we're looking for efficiency above all else these days. Going open bladed makes a lot of sense as we go further down this path.
- Gibbon1 9mo agoI'm curious about using a hybrid system where you have multiple electric fans. For instance 2 turbines and 4 fans. Advantage is smaller diameter for the same mass flow. And more redundancy. A negative is the weight of the electric motors and generators. If you added a battery you have some other advantages. Less pucker when you lose an engine. And better throttle response.
- pedrocr 9mo agoAnother advantage is you can place the fans all along the wing getting you better stall resistance as the flow doesn't detach as easily. There's already a prototype of a hybrid plane that does this: https://www.electra.aero/ https://www.electra.aero/
- zabzonk 9mo agoIsn't this like turboprops (already very efficient) with bigger propellors? I couldn't tell from the article, but quite possibly missed something.
- nickff 9mo agoThis website has some nice explanations and GIFs: https://s2.smu.edu/propulsion/Pages/variations.htm https://s2.smu.edu/propulsion/Pages/variations.htm
- game_the0ry 9mo agoThe inner nerd in me is so satisfied. Thanks for the link.
- jiehong 9mo agoThat website it gold!
- Ajedi32 9mo agoSo the "open rotor" engine is actually a propfan engine?
- nickff 9mo agoEssentially yes, different engine companies have used different nomenclature over time. It seems that the "open rotor" terminology is being used to emphasize the improvements which have been made to blade design, noise, and general efficiency.
- somewhereoutth 9mo agoI think it is the stators fixed to the engine nacelle, judging by the article image.
- Stevvo 9mo agoThe Antonov An-70 has been in service with "open rotor" engines for 30+ years. It's superior to its western counterparts in every way. i.e. greater speed and payload with less fuel consumption than a C-130 or A400M.
- nradov 9mo agoHuh? Only two An-70 prototypes were ever built so it's not really "in service". The early propfan designs, while efficient, were too loud for widespread civil use. Newer open rotor designs are much quieter.
- vel0city 9mo agoYou know what makes the C-130 or the A400M superior? The fact there's more than one operational today.
- cpursley 9mo agoRussia has also just modernized their IL-114s and got an order from India.
- direwolf20 9mo agoIs this not... a propeller? A turboprop engine?
- idontwantthis 9mo agoI’m not an expert but I think the distinction is that the blade tips in these reach supersonic speeds like in turbofans. That is a hard problem to fix because you don’t have the duct to contain the noise and catch the blades if one were to break.
- JumpCrisscross 9mo ago> the distinction is that the blade tips in these reach supersonic speeds like in turbofans Commercial engines are not designed to have anything to supersonic.
- idontwantthis 9mo agohttps://aviation.stackexchange.com/questions/22316/why-do-turbofan-blade-tips-exceed-the-speed-of-sound-while-prop-tips-should-not https://aviation.stackexchange.com/questions/22316/why-do-tu...
- JumpCrisscross 9mo agoSorry, you’re correct. You want to avoid supersonic tips as much as possible. Modern turbofans permit supersonic tips during high-thrust regimes. (Part of the work in these new designs is releasing that constraint since those supersonic tips are a bastard.) It’s something sought to be avoided. But not at all costs at all times.
- Galxeagle 9mo agoNot clear to me from the article - what's the different between an 'open rotor' engine and a turboprop (https://en.wikipedia.org/wiki/Turboprop https://en.wikipedia.org/wiki/Turboprop)? At face value, both seem to be jet engines with propellers used on single-aisle planes?
- kdaker 9mo agoThere is still a jet stream coming out of the engine propelling the aircraft. Unlike a turboprop where only the propellor generates thrust.
- JumpCrisscross 9mo ago> Unlike a turboprop where only the propellor generates thrust Each of turbojets, turboprops and turbofans generate thrust with exhaust.
- ggm 9mo agoLike a lot of people I think I hold a mental image of "jet" which is actually not helpful for a modern engine. All modern jets seem to have this massive rotational component, the turbine, and the fan outside the turbine chamber. so does a turboprop. And the basic propeller before that. Oh, the "fan" has more blades. Pshaw! a spitfire went from 3 blades to 5 across it's lifetime. post-spitfire engines had contra rotating props with many more blades. It can't just be about the NUMBER of blades can it? So, there is the turbine. Is that directly coupled to the "fan" bit? If not, it's probably a turboprop, but even then I am unsure all visible fans on modern jets on the spool couple directly to the turbine. The "jet" part is the combustion chamber. Everything else, you might as well consider turbines and propellers as "the same kind of thing" but then you're in a pub arguing which details make one a prop and the other a fan. If you like Roger ramjet you're in the other kind of Jet: the one which is more like a rocket. Also, if you work in government service how are you passing the drug test with those proton energy pills? Frank Whittle's biography is a great read. He had some hair raising moments. things OSHA would not be happy about.
- joleyj 9mo agoMost modern engines have two turbines. A low pressure turbine and a high pressure turbine. The low pressure turbine is connected directly to the fan.
- JumpCrisscross 9mo ago> I am unsure all visible fans on modern jets on the spool couple directly to the turbine They exist now [1][2]. The general term is geared turbofans. If you want to mentally unfuck it a bit, the major variables are: combustion type (internal or turbine), gearing or not, ducting or not and bypass ratio. (Compression ratio and number of blades can come too.) When one of these changes substantially, you get a change in engine type. When it changes a little bit, you get a blur. [1] https://en.wikipedia.org/wiki/Pratt_%26_Whitney_PW1000G https://en.wikipedia.org/wiki/Pratt_%26_Whitney_PW1000G [2] https://en.wikipedia.org/wiki/Rolls-Royce_Trent#UltraFan https://en.wikipedia.org/wiki/Rolls-Royce_Trent#UltraFan
- CGMthrowaway 9mo agoWhich bio?
- JumpCrisscross 9mo agoThen we can duct it.
- philip1209 9mo agoInteresting - I'm curious to learn how ETOPS ratings apply to open rotor engines. Any experts can chime in?
- havaloc 9mo agoI knew I had seen this before growing up as a child, Popular Science, 1985: https://books.google.com/books?id=rgAAAAAAMBAJ&lpg=PA69&dq=turbofan&pg=PA66#v=onepage&q=turbofan&f=false https://books.google.com/books?id=rgAAAAAAMBAJ&lpg=PA69&dq=t...
- whatever1 9mo agoI cannot stop thinking about the fact that air travel wastes so much energy, just to float. Buoyancy is free. It is insane that we are not doing materials research on how to capture vacuum in thin cavities.
- SPICLK2 9mo agoModern jetliners get a higher miles per gallon per seat than most US (ICE) cars. They easily beat any ICE car with a single occupant in miles per gallon equivalent. If you want to minimise fuel usage and can't find someone to share with, it's better to fly! The issue is almost entirely the distance travelled.
- whatever1 9mo agoCars also waste energy just to overcome friction while most of the times they do not change momentum (go straight at constant speed). But this is a discussion for another tire.
- SPICLK2 9mo agoAerodynamic drag accounts for more energy losses than tyre friction (and tyre friction can be relatively easily changed with tyre pressure or tyre type).
- riirifneo 9mo agonow do high speed rail..
- SPICLK2 9mo agoIt varies so much depending on passenger occupancy rates. Planes tend to run near 100%, and cars (at least in the US, although I'm sure other countries aren't much better) at near 20%. Assuming 1mpg for the entire train, it needs at least 100 passengers to compare to a fully-occupied passenger plane.
- ErroneousBosh 9mo agoMaking aircraft slower would make it more efficient. Big slow props, biplane wings, take twice as long, serve better coffee, give me somewhere to plug in my laptop charger. I'll even wear a nice suit. Make flying An Occasion again.
- api 9mo agoThe extreme of this is airships, but also trains.
- ErroneousBosh 9mo agoIt's quite difficult to make trains work over water.