Blended Wing Bodies
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Transcript of Blended Wing Bodies
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By Bh.Phanindra Kumar
07521A0335
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The goal of aircraft design is to achieve safe andefficient flight. In the world of commercial airtransport, efficient, economically attractiveconfigurations are needed.
New technologies are being implemented in everysector now-a-days.Like ways, the aero sector has been
seeing vast changes in its development due to theadvancements in technology over the years.
One of such technologies is the Blended Wing Bodydesign for the modern aircrafts.
The evolution of the BWB dates
back to the medieval of the
19th century.
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1) Conventional Configuration: "Tube and Wing" or "Tail Aft"2) Blended Wing Body (BWB)3) Hybrid Flying Wing4) Flying Wing5) The Boeing C wing
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What is a Blended wing body concept ?
Blended Wing Body, or BWB,
designates an alternative airframedesign which incorporates designfeatures from both a futuristicfuselage and flying wing design. Thepurported advantages of the BWB
approach are efficient high-liftwings and a wide airfoil-shapedbody. This enables the entire craftto contribute to lift generation withthe result ofpotentially increasedfuel economy.
The airplane concept blends thefuselage, wing, and the engines intoa single lifting surface, allowing theaerodynamic efficiency to be
maximized
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History of BWB:
A flying wing is a type of tail-less aircraft design and has been
known since the early days of aviation. Since a wing is necessary for any
aircraft, removing everything else, like the tail and the fuselage, results ina design with the lowest possible drag. Successful applications of this
configuration are for example the H-09 and latter H-0229 developed by
the Horton brothers for Nazis during 1942. Latter Northrop started
designing flying such as NIM in 1942 then latter XB-35 bomber that
flew first in 1946, and the stealthy B-2 bomber that flew first in 1989.
H09 1939
H0229
1942
1946 XB-35
bomber
YB-49 1949 B-2 bomber 1989
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In modern era after B-2 bomber blended wing
body was used for stealth operations. The
unmanned combat aerial vehicle (UCAV) in the year
2003 X-47 was subjected to test flights. Flight testsbegan on July 20, 2007 - the first flight reached an
altitude of 7,500 feet MSL (2,286 m) and lasted 31
minutes.. NASA and Boeing successfully completed
initial flight testing of the Boeing X-48B on March
19 2010.
The Blended Wing Body (BWB) is a relatively
new aircraft concept that has potential use as a
commercial or military transport aircraft, cargo
delivery or as fuel tanker
X-47A (UCAV) 2003
X-48 B 2007
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Basic configuration and nomenclature of
Boeing BWB 450
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BWB-450 specifications:
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BWB advantages compared to today's
advanced aircraft
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B-2 bomber specifications
Crew: 2
Length: 69 ft (21.0 m)
Wingspan : 172 ft (52.4 m)
Height: 17 ft (5.18 m)
Wing area: 5,140 ft (478 m)
Empty weight: 158,000 lb (71,700 kg)
Loaded weight: 336,500 lb (152,200kg)
Max take off weight : 376,000 lb(170,600 kg)
Powerplant: 4 general electricf111-GE100 non-afterburning turbaofans, 17,300 lbf (77 kN) each
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What makes B-2 bomber a stealth configuration:
It continuously changes shape when looked from different toconfuse radar
Whatever beams are locked onto it are either get reflected in
outer space or reduced or dissipated into nothing
Coated with special RAM (radar absorbing material ) such as
carbon fiber composite and top secret reflective paint to reduce
detection from enemy.
Electronic counter measure for jamming radar makes it
undetectable aircraft.
RCS (radar cross section ) is 1000 times less then B-52 bomber
It has special exhaust vents on top of which when hot gases are
mixed with cooler air make it almost undetectable to heat
seeking SAM(surface to air missile )
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Design cycle:
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This is the wind tunnel for performing all the tests for a BWB.
Analysts from NASA and Boeing will be testing the flights
and analyze its results.
This is the NASA Langleys Aeronautics Research Mission
Directorate where the tests for BWB ships are being done for
several years.
The effort has been funded primarily by Boeing, with some
money to support the flight test program coming from the Air
Force Research Lab (AFRL) at Wright Patterson AFB, Ohio.
Dryden is providing facilities and support for the flight test
under contract, as Langley did for the wind tunnel portion
of the prototype program.
Similar tests for noise, efficiency, other criteria are performed
for the BWBs.
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Alternate Fuels:Necessity to look for alternate fuels is one of the
major criterion for the futuristic models of any type. Therefore alternate
fuels like Synthetic fuels, Bioorganic fuels and Cryogenic fuels are to be
used according to the suitability.
Fossil fuels used in the aviation industry like Jet-A
produce carbon emissions, which contribute to roughly 2% of the global
carbon emissions. There is widespread call to reduce these emissions.
Synthetic fuels is not suitable due to the fact that the emission of the
extraction process themself are creating pollution. Although they can
be subsidized by other processes it is harmful.
Bioorganic fuel fuels are best for use in this type. Bio-fuels need to be
developed and have to be especially tailored for jet aircraft
applications, which are termed as biojet. Another major challenge of
pure biojet fuel is its poor high temperature stability characteristics in
the engine. The alternative to this problem is to use a mixture of
biofuels and jet fuel.
Cryogenic fuels are to be tested for their usability in usage by various
researches.
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There are certain causes for the noise in a conventional
aircraft. Some of them are below and the remedies for such
problems too
Noise by engine position: Engine noise reduces as by pass
ratio increases. The mixing of high energy hot air with
surrounding air is uniform and not sudden, exhaust noise
reduces to a great extent. The solution is to place engine halfabove and half below the wings to enhance the BLI.
Airframe: there is reduction in noise since
there are no tail aft, fuselage, or hanging
engines which are main contribution ofnoise.
Landing Gear Fairings: Fairings are
produce smooth outline and reduce drag.
Fairings when used in landing gear resiult
in reduction in noise.
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Other Features: tabs are small protrusions
at nozzle exit. There are delta wing like
structures like stream vortex generators
that increase mixing of jet & surrounding
air. Other devices are Chevrons which are
saw toothed structures enabling free
mixing of exhaust & air. They are larger
than tabs with same principle.
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Clearly the BWB shows a significant
advantage over a conventional aircraft
in terms of performance and weight.
However, the BWB is a revolutionaryaircraft concept and will require a
large and expensive engineering effort
to become a reality. Most likely, before
being used as a transport aircraft, it
will be utilized for military
applications. In fact, Boeing and the US
military are designing the BWB to be
used as an advanced tactical transport
and as an air refuel tanker The BWB
has a large fuselage and can carry
massive amounts of fuel. Also, it canprovide two permanent refueling
boom stations, rather than one as in
the KC-135, KC-10 or KC-767.A Boeing BWB tanker with pylon-mounted engines (picture fromBoeing).
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Flying wing challenges:
1. Cabin pressurization is one of several design challenges facing the BWB.
2. The BWB, however, has a unique shape that requires a novel approach to
satisfy pressurization and structural needs.
3. The design uses ten intermediate chord-wise (front-to-back) ribs to connect
the upper and lower wing skins. These ribs separate the interior into ten
passenger bays.
4. Advanced composite material will be required to minimize the amount of
structure needed to withstand the pressurization loads and deflections in
the skins.
5. Open certification problems : unstable configuration , ditching
6. Open design problems : rotation on take-off, landing gear integration,
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Recommendations for further study: The BWB concept incorporates features that are pretty much new to the
present aircraft technology. Extensive research is needed in the areas of
manufacturing technology, structures ad materials. Issues like cabin pressurization are very crucial, which if does not satisfy
the basic requirements of a passenger will make it unsuitable as a
passenger aircraft. Therefore it demands a very keen attention.
The control of a BWB is not as easy as controlling the aircrafts of today.
Also the BWB maneuvers cause undesirable reactions on passengers
affecting their comfort level greatly. This needs to be catered while
devising the control laws.
Airport infrastructure has to be revolutionized, to accommodate the wide
BWBs and also, the large flow of passengers expected with an
exponentially increasing air-traffic. Runway width has to necessarily
increase for the wide body BWBs. Safety is a significant criterion that has to be ensured. Design and
positioning of emergency exit doors needs careful attention keeping in
mind the crowd behavior in a cabin layout that does not favor easy crowd
control.
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The BWB is a revolutionary, but viable concept that has a
great potential to cater to the needs of the future. In a timeafter fifty years, when fuel costs would be intolerably high,
even with a blend of alternative fuels, BWBs lesser fuel
consumption will be a very great boon. The environmental
restrictions in terms of emissions and noise would be even
more stringent, which might completely rule out theoperation of the present aircrafts, in which case, a radical
design like that of a BWB with its reduced noise and
emissions would save the era.
CONCLUSION: