MIT-Led Team Designs Two Airplanes That Would Use 70% Less Fuel Than Current Models
15 May 2010
An MIT-led team has designed an airplane that is estimated to use 70% less fuel than current planes while also reducing noise and emission of NOx. The design was one of two that the team, led by faculty from the Department of Aeronautics and Astronautics, presented to NASA last month as part of a $2.1 million research contract to develop environmental and performance concepts that will help guide the agency’s aeronautics research over the next 25 years.
Known as “N+3” to denote three generations beyond today’s commercial transport fleet, the research program is aimed at identifying key technologies, such as advanced airframe configurations and propulsion systems, that will enable greener airplanes to take flight around 2035.
|
|
| |
| The D “double bubble” series design concept is based on a modified “tube-and-wing” structure that has a very wide fuselage to provide extra lift. The aircraft would be used for domestic flights to carry 180 passengers in a coach cabin roomier than that of a Boeing 737-800. Click to enlarge. | The H “hybrid wing body” series would replace the 777 class aircraft now used for international flights. The design features a triangular-shaped hybrid wing body aircraft that blends a wider fuselage with the wings for improved aerodyanmics. The large center body creates a forward lift that eliminates the need for a tail to balance the aircraft. The plane is designed to carry 350 passengers. Click to enlarge. | |
| Images: MIT/Aurora Flight Sciences. | ||
MIT was the only university to lead one of the six US teams that won contracts from NASA in October 2008. Four teams—led by MIT, Boeing, GE Aviation and Northrop Grumman, respectively—studied concepts for subsonic commercial planes, while teams led by Boeing and Lockheed-Martin studied concepts for supersonic commercial aircraft. MIT team members include Aurora Flight Sciences Corporation and Pratt & Whitney.
The objective was to develop concepts for, and evaluate the potential of, quieter subsonic commercial planes that would burn 70% less fuel and emit 75% less NOx than today’s commercial planes. NASA also wanted an aircraft that could take off from shorter runways.
The MIT team met NASA’s challenge by developing two designs: the 180-passenger D “double bubble” series to replace the Boeing 737 class aircraft, currently used for domestic flights, and the 350 passenger H “hybrid wing body” series to replace the 777 class aircraft now used for international flights.
The engineers conceived of the D series by reconfiguring the conventional tube-and-wing structure. Instead of using a single fuselage cylinder, they used two partial cylinders placed side by side to create a wider structure whose cross-section resembles two soap bubbles joined together. They also moved the engines from the usual wing-mounted locations to the rear of the fuselage.
Unlike the engines on most transport aircraft that take in the high-speed, undisturbed air flow, the D-series engines take in slower moving air that is present in the wake of the fuselage. Known as the Boundary Layer Ingestion (BLI), this technique allows the engines to use less fuel for the same amount of thrust, although the design has several practical drawbacks, such as creating more engine stress.
According to Mark Drela, the Terry L. Kohler Professor of Fluid Dynamics and lead designer of the D series, the design mitigates some of the drawbacks of the BLI technique by traveling about 10% slower than a 737. To further reduce the drag and amount of fuel that the plane burns, the D series features longer, skinnier wings and a smaller tail.
Not only does the D series meet NASA’s long-term fuel burn, emissions reduction and runway length objectives, but it could also offer large benefits in the near future because the MIT team designed two versions: a higher technology version with 70% fuel-burn reduction, and a version that could be built with conventional aluminum and current jet technology that would burn 50% less fuel and might be more attractive as a lower risk, near-term alternative.
Carl Burleson, the director of the Federal Aviation Agency’s Office of Environment and Energy, said that in addition to its “really good environmental performance,” the D series is impressive because its bubble design is similar enough to the tube-and-wing structure of current planes that it should be easier to integrate into airport infrastructure than more radical designs. “You have to think about how an airport structure can support it,” he said. “For some other designs, you could have to fundamentally reshape the gates at airports because the planes are configured so differently.”
Although the H series utilizes much of the same technology as the D series, including BLI, a larger design is needed for this plane to carry more passengers over longer distances. The MIT team designed a triangular-shaped hybrid wing body aircraft that blends a wider fuselage with the wings for improved aerodyanmics. The large center body creates a forward lift that eliminates the need for a tail to balance the aircraft.
The large structure also allows engineers to explore different propulsion architectures for the plane, such as a distributed system of multiple smaller engines. Although the H series meets NASA’s emissions-reduction and runway-length goals, the researchers said they will continue to improve the design to meet more of NASA’s objectives.
The MIT team expects to hear from NASA within the next several months about whether it has been selected for the second phase of the program, which will provide additional funds to one or two of the subsonic teams in 2011 to research and develop the technologies identified during the first phase. The researchers acknowledge that some propulsion system technology still needs to be explored. They have proposed evaluating the interactions between the propulsion system and the new aircraft using a large-scale NASA wind tunnel. Even if the MIT designs are not chosen for the second phase, the researchers hope to continue to develop them.
This is great news. With the money saved on fuel they will be able to make the seats 10% wider and have two full arm rests! Oh I forgot, these are private, unregulated companies, so they will cram as many people in as possible to maximize their profits.
Posted by: Zhukova | 15 May 2010 at 06:09 AM
This is new? I saw designs like these 20 years ago.
Posted by: ai_vin | 15 May 2010 at 08:08 AM
That was the old way, comrade Z.
But I can tell you are a visionary.
By 2035 we will have liberated ourselves from this materialistic culture to a socially conscious one.
Workers will receive the same high pay that executives get - whoops, it is so easy to slip back to the old ways - we will all be given adequate money to survive by a benign government (like so many that are increasingly common throughout the world).
The aircraft will be comfortable, super-high-tech with free food and frequent flights on all routes (however unprofitable) and many wide seats and some empty seats.
Tickets will be exorbitant, of course - but we will have learned that money is not the real measure of wealth - and if you do not have an important government job and still want to go somewhere and cannot afford to fly, you can walk or stay home (= more empty seats; see how this all works out?) .
The idea that they can cram enough people in to offset the cost, which they don't mention, and make it affordable is the old paradigm – flight affordable for the masses is a bankrupt concept that only make flight affordable and fills the sky with low cost aircraft.
Soon there will only the occasional aircraft (the NEW minimalism, which will be resisted by evil BIG aviation) and then we can then do the same with autos. There is absolutely no excuse for us to visit friends or relatives more than 2 miles away.
Cuba is WAY ahead of us on this, but it is never too late to start.
Posted by: ToppaTom | 15 May 2010 at 08:10 AM
Exactly ai_vin. I'm very skeptical of these designs. Boeing and Airbus have been building and designing planes for how long? Decades. And only now these "breakthrough" fuel saving designs are coming out? As if all the aeronautical engineers at Boeing and Airbus haven't explored virtually every possible conceiveable design to gain a competitive edge and secure more orders for planes. I think before ANY more tax dollars are spent, Boeing and Airbus need to be consulted regularly for what's been researched, what hasn't, what's practicable & safe, what's realistic in the marketplace & regulatory environment, etc.
Posted by: ejj | 15 May 2010 at 08:18 AM
I agree.
But I am also sure the typical, technically naive politician is convinced that, since breakthroughs by “new” organizations can occur, all it takes is giving some of our money (here they are NOT naïve) to some visionary and voila, another easy breakthrough.
Posted by: ToppaTom | 15 May 2010 at 09:04 AM
Boeing was one of the investigators. The MIT team design outperformed theirs. Maybe they did add something to the current state of knowledge on efficient large aircraft design.
Not that studies aren't commisioned by our government when it does not make sense.
Posted by: mds | 15 May 2010 at 09:32 AM
eji
Your naive thought always amaze me...yes in the 80s Boeing and other were working on Propfan and blended wing/body concept, but the airlines companies told them they were longer interested in innovations to save fuel because oil prices fell sharply in 1986 the aircraft makers dropped all this fuel saving programs at the time. These concepts are coming back because CO2 emissions and oil dependencies have to be slashed aggressively, air trips are the fastest growing segment of transportation as well as the more energy intensive. If you have missed this then you are poorly informed.
Another tendency is the use of diesel engines for helicopter or fan ducted aircraft for short range flight, the saving of fuel can be up 40% because of the better efficiency of diesel engines compared to jet engines
Posted by: Treehugger | 15 May 2010 at 09:35 AM
Another issue is the materials science. The H-series requires advanced composite construction, and the airline industry just wasn't ready for it. The 787 is getting to the required techniques.
An aluminum "double-bubble" is an advance nobody seems to have considered. The question is, could anyone sell enough of them to make money on the effort?
Posted by: Engineer-Poet | 15 May 2010 at 10:15 AM
Many of the near future aircraft will make use of lighter materials to get up to 15% fuel consumption reduction. Would these more effective designs cost that much more to manufacture? It may be what is required for USA to regain the leadership in passenger planes manufacturing. It may be a worthwhile long term investment if military procurement steps in to offset the initial cost.
Posted by: HarveyD | 15 May 2010 at 10:33 AM
More efficient aircraft and biofuels like Branson is investing in can mean that we will have air travel in the future even after peak oil. This is encouraging.
Posted by: SJC | 15 May 2010 at 12:28 PM
Over the last decades Boeing and other US air framers investigated Propfans, blended wing/body concepts etc, but the overall cost of ownership was too high (whether due to GM patents or oil prices or whatever - does not matter).
Foreign airframers reached the same conclusions.
These concepts keep coming back because conditions change, such as CO2 emissions and oil dependencies etc.
If you missed this then you are poorly informed.
The use of diesel engines for helicopter or fan ducted aircraft for short range aircraft, makes little sense because the engine weight is huge and fuel weight is of little inconsequence.
ICEs have long been on the fringes for long range (slow) aircraft where the saving of fuel might offset the poor hp/lb of diesels and gas engines.
Posted by: ToppaTom | 15 May 2010 at 01:32 PM
This sort of achievement reminds me of another vehicle universities have been designing for decades: sleek one seater that can give you 1000+ mpg.
If the technology is practical, either Boeing or Airbus would build it and wipe the other from the market, forever.
Posted by: Peace Hugger | 15 May 2010 at 04:49 PM
Boeing did research on a double-stack flying wing that could hold ~800 passengers. The fuel economy was great. The wingspan required was too big for too many airports, though, so they dropped it.
Posted by: HealthyBreeze | 15 May 2010 at 06:57 PM
TT, you seem to have zero knowledge of current diesel aircraft engines.
Posted by: Engineer-Poet | 15 May 2010 at 08:13 PM
For an aircraft, the weight of a diesel engine plus fuel will be less than the weight of a turbine engine plus fuel, if the range is similar in both cases. This was shown already in 1948 by Napier and in studies later. Weight is not the issuse. Cheap jet fuel killed the Napier diesel engine. Presumably, it is still too cheap. An aero-diesel would have nothing in common with an automotive diesel, so there is much development to be done. In addition, the propeller would also have to be developed from the status of the propfan in the 80's.
Why make the seats 10% wider. It would make much more sense to make the americans 10% less wide. A mutual benefit for both health and climate.
Posted by: Peter_XX | 16 May 2010 at 01:39 AM
70% fuel saving would make an aircraft more efficient than a bus (per passenger mile) - which appears implausible regardless of the aircraft design.
Posted by: globi | 16 May 2010 at 04:52 AM
The "zero knowledge of..." link compares small power reciprocating gasoline engines with small power reciprocating diesel engines. Both engines deliver roughly 1 kW/kg.
The GE 90 gasturbine currently applied on the Boeing 777 delivers up to 512 kN of thrust, which corresponds to roughly 100 MW at 200 m/s. With a weight of 7550 kg this is over one order of magnitude more power per weight than the reciprocating engines above.
Posted by: globi | 16 May 2010 at 05:15 AM
Anyway one has to wonder:
When there's a reciprocating engine generator powered by chicken manure, people say: "Why don't they just use gas turbines?" and when there's a gas turbine powering an aircraft, people say: "Why don't they just use reciprocating engines?"
Posted by: globi | 16 May 2010 at 05:27 AM
globi
It is out of the table to make diesel engine to replace GE90. But to replace turbine of 2000kW on ATR72 is quite possible and with huge benefit in term of consumption.
Posted by: Treehugger | 16 May 2010 at 07:54 AM
What does "out of the table" even mean treebooger? Where do you get all your bizarre expressions?
Posted by: ejj | 16 May 2010 at 09:01 AM
Besides that the ATR72 is less efficient than a Boeing 777 per passenger mile. The ATR72 can only carry 7 tons. 2 x 2000 kW Diesel engines already weigh 4 tons while the turboprop engines weigh only 1 ton.
http://cobweb.ecn.purdue.edu/~propulsi/propulsion/jets/tprops/pw100.html
It's doubtful that the more efficient diesel engines can offset the higher energy needs due to the increased aircraft weight and increased air resistance (Diesel engines incl. auxiliaries also require more space than turboprop engines).
Posted by: globi | 16 May 2010 at 09:02 AM
Turbines rule at high speed. The growth of power requirements makes piston engines of any kind too heavy. But turbines pay in fuel requirements.
At the speeds and power levels of light aircraft, turbines are less and less efficient due to losses at small sizes. The BSFC advantage of diesel produces a lower cost than either Otto-cycle or turbine, and often a lower total mission weight. That's where we are going to see them.
Posted by: Engineer-Poet | 16 May 2010 at 12:08 PM
Many of you are probably comparing apples and pears. Frist, an aero diesel would not look like a tractor engine. Old pictures of the Napier engine (see link below) gives some hints about what such an engine would look like. The diesel engine would be the (very) high pressure combustion chamber sitting piggy back on a turbine engine. Then, just imagine what more we could do with downsizing since this 60-year example. So, it is quite plausible that engine+fuel weight would be less for the diesel engine compared to the jet engine. The engine itself will, of course, be heavier.
http://en.wikipedia.org/wiki/Napier_Nomad
Posted by: Peter_XX | 16 May 2010 at 01:39 PM
Aerodynamic is a well understood science. There is nothing shown in these two designs that would justify their superior efficiency over the Boeing 787, nor the latest super-jumbo Airbus.
Profan is 30% more efficient than ducted-fan, but with the penalty of higher noise and lower reliability.
The most efficient form of long-distance high-speed transportation is the electric train, either the TGV or the Maglev. Renewable electricity can be fed directly to the electric trains without wasteful conversion to jetfuel.
Posted by: Roger Pham | 16 May 2010 at 06:55 PM
This "Double Bubble" lifting-body design was done over 80 years ago. It seems as if the designs of Vincent Burnelli have finally been vindicated. Check out www.burnelli.com
Posted by: planeguy | 16 May 2010 at 06:57 PM