Study of Blended Wing Body Design (BWB

STUDY OF BLENDED WING BODY DESIGN (BWB)

Presented by :Chirag.D.Soni 1MJ09MAE03

Contents 1.

Introduction to BWB aircraft configuration

2.

History of BWB

3.

How is it different from flying wing designs

4.

Square-Cube-Law

5.

Basic configuration and nomenclature of Boeing BWB 450

6.

Flying wing challenges

7.

What Does the Future Hold for the BWB?

8.

Preliminary sizing

9.

Aero disciplines:

Structures Aerodynamics Flight mechanics Ground handling

10.

BWB advantages compared to today's advanced aircraft

11.

Stealth configuration in military aircrafts

Introduction to BWB aircraft configuration

MVJ College department of Aeronautics

Classification

1) Conventional Configuration: "Tube and Wing" or "Tail Aft" 2) Blended Wing Body (BWB) 3) Hybrid Flying Wing 4) Flying Wing MVJ College department of Aeronautics 5) The Boeing C wing

BWB Definition The Blended Wing Body aircraft is a blend of the tail aft and the flying wing configurations.

A wide lift producing centre body housing the payload blends into conventional outer wings


What is a Blended wing body concept ? Blended Wing Body, or BWB, designates an alternative airframe design which incorporates design features from both a futuristic fuselage and flying wing design. The purported advantages of the BWB approach are efficient high-lift wings and a wide airfoilshaped body. This enables the entire craft to contribute to lift generation with the result of potentially increased fuel economy. The airplane concept blends the fuselage, wing, and the engines into a single lifting surface, allowing the aerodynamic efficiency to be maximized MVJ College department of Aeronautics

How is it different from flying wing designs 

Flying wing designs are defined as having two separate bodies and only a single wing, though there may be structures protruding from the wing.



Blended wing/body aircraft have a flattened and airfoil shaped body, which produces most of the lift to keep itself aloft, and distinct and separate wing structures, though the wings are smoothly blended in with the body.


History of BWB The following provides an insight into the aircraft design evolution. 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 in a 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 Nazi’s 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. 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 tests began on July 20, 2007 - the first flight reached an altitude of 7,500 feet MSL (2,286 m) and lasted 31 minutes. The remotely-piloted aircraft was successfully stalled for the first time on 4 September, with fixed leading edge slats, a forward center of gravity, and 23degree angle of attack (2° beyond the maximum coefficient of lift ). Stall testing was repeated on 11 September with a NASA pilot at the console. 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


H229 1942 1946 XB-35 bomber

H09 1939

YB-49 1949

X-48 B 2007

B-2 bomber 1989

X-47A (UCAV) 2003

Team members studying the Blended-WingBody (BWB) design 

McDonnell Douglas,



Stanford University,



The University of Southern California,



Clark Atlanta University,



The University of Florida,



NASA Langley and Lewis Research Centers.



Boeing Phantom Works



Air Force Research Laboratory



NASA's Dryden Flight Research Center



Institute of Aircraft Design and Lightweight Structures, TU Braunschweig


Square-Cube-Law When a physical object maintains the same density and is scaled up, its mass is increased by the cube of the multiplier while its surface area only increases by the square of said multiplier. This would mean that when the larger version of the object is accelerated at the same rate as the original, more pressure would be exerted on the surface of the larger object.



Basic configuration and nomenclature of Boeing BWB 450


BWB-450 specifications Seating capacity

478 passengers in three class interior arrangement

Design Range

7750 nautical miles

No: of engines

The BWB-450 uses three upper surface pylon mounted turbofan engines, located at the trailing edge of the wing, for propulsion

Type of engines

3 UEET direct drive turbofan engines (Ultra-Efficient Engine Technology)

Cruise mach no:

A recent Boeing optimization study1 indicated that a cruise Mach number of 0.90 is optimal for a range of 7,750 nm.

Maximum gross weight

823,000 lb

Cruise speed

0.85 mach (560 mph)


Flying wing challenges 1.

Cabin pressurization is one of several design challenges facing the BWB.

2.

Current airliners have a cigar-shaped fuselage ideal for maintaining cabin pressurization.

3.

The BWB, however, has a unique shape that requires a novel approach to satisfy pressurization and structural needs.

4.

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.

5.

Advanced composite material will be required to minimize the amount of structure needed to withstand the pressurization loads and deflections in the skins.

6.

Open certification problems : unstable configuration , ditching

7.

Open design problems : rotation on take-off, landing gear integration,


What Does the Future Hold for the BWB?


Clearly the BWB shows a significant advantage over a conventional aircraft in terms of performance and weight. However, the BWB is a revolutionary aircraft 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 (Figure 10). The BWB has a large fuselage and can carry massive amounts of fuel. Also, it can provide two permanent refueling boom stations, rather than one as in the KC-135, KC-10 or KC767.

Figure 10: A Boeing BWB tanker with pylon-mounted engines (picture from Boeing).


Other BWB projects 5th Framework Program of the European Commission: VELA and MOB Very Efficient Large Aircraft (VELA) from 1999 to 2002

VELA 1

VELA 2 MVJ College department of Aeronautics

6th Framework Program of the European Commission:

)

(VELA follow on

Vela 3 (2003-2006)


X48-b first flight July 20, 2007

Flight tests began on July 20, 2007 - the first flight reached an altitude of 7,500 feet MSL (2,286 m) and lasted 31 minutes. The remotely-piloted aircraft was successfully stalled for the first time on 4 September, with fixed leading edge slats, a forward center of gravity, and

23-degree angle of attack (2 beyond the maximum coefficient of lift). Stall testing was repeated on 11 September with a NASA pilot at the console . NASA and Boeing successfully completed initial flight testing of the Boeing X-48B on March 19 2010.

Design cycle In order to investigate potential improvements and to predict major design challenges of this new class of aircraft the modeling and analysis capabilities of the in-house aircraft design tool of the Institute of Aircraft Design and Lightweight Structures, TU Braunschweig (IFL), PrADO, have been adapted to the BWB requirements The methods used and the modeling and analysis capabilities of the improved, BWB-specific PrADOsystem are described.


Preliminary sizing • Data collection • Preliminary Weight estimation • Optimization of wing loading and thrust loading • Wing design • C.G calculation • Control surface design • Features of designed airplane • Details of performance estimation


Preliminary multidisciplinary aircraft design with the tool PrADO 1. Design requirements of the configuration are summarized and completed. 2. Aircraft geometry is calculated based on the parametric aircraft description (see Section 3.2). 3. An aerodynamic panel model of the airplane is created, and maps of aerodynamic coefficients are generated for the whole flight regime 4. A propulsion sizing and engine characteristics calculation is performed. A thermodynamic cycle model is used to size the turbo-fan engines including a geometry and mass estimation—based on the latest thrust requirements 5. Flight mission simulations are undertaken to create performance data and to determine the required fuel masses for prescribed missions 6. The structural sizing module (SSM) includes a multi-model generator (MMG) that creates a structural model (finite element model) and an aerodynamic surface panel model simultaneously. 7. Component masses for systems and primary and secondary structures are calculated. Structural mass is based on the sized finite element model with additional corrections to account for sealants, paints, and other omitted details of the FE mode 8. Direct operational costs (DOC) are calculated for the life-cycle of the aircraft based on economical data, aircraft masses, and performance data 9. Satisfaction of design boundaries (e.g., compliance with take-off and landing distances) is controlled, and the consistency of the database is checked


Structures



Aerodynamics One of the beauties inherent in a BWB airliner is it strength. It readily absorbs both cabin pressure and wing bending loads, and in recent tests in the Stanford University wind tunnel, a 6% scale model easily passed all extreme flight envelope tests. The BWB concept reduces the load on the outboard wing section airfoils, while the large centerbody chord provides enormous strength, requiring a much low sectional lift coefficient. This reduced lift demand allows the large thick profile of the centerbody to hold passengers and cargo, without exacting a high compressibility drag penalty. Due to its shape and structure, typical shocks evident on the thinner outboard wing panels become very weak on the centerbody. Ahead of this shock, airflow is supersonic; behind it, the air slows and that sub-sonic area is highly suitable for engine installation. The low effective wing loading of the BWB and its beneficial trim effect means that no exotic high lift system is necessary; only leading edge slats are necessary on the outboard wing, with all trailing edge devices made up of simple hinged flaps which double as elevons. MVJ College department of Aeronautics

Wake Turbulence


Flight Mechanics


Placing the engine The BWB program is examining a new method for engine installation that promises to increase safety and fuel efficiency. Three advanced “high-bypass ratio” engines will be buried in the trailing edge of the center section of the BWB wing. While conventional aircraft engines only take in “free-stream air,” both the air on and near the surface of the wing will flow through the BWB’s curved inlets and into its engines. Taking in the layer of air on the wing surface reduces drag. While this technology will require validation before becoming a reality, researchers are initiating tests to determine acceptable levels of turbulence in the engine inlet.


Ground Handling (vela 3) A cargo loading vehicle drives in between. Cargo loading from below with lifting system. Catering from the right. Water / waste servicing on trailing edge left side. Ground Handling


BWB advantages compared to today's advanced aircraft

better L/D

10 to 15% better

reduction in emissions

yes

reduction in noise

only with engines on top (reduction in noise to 42db below stage 4)

increase of airport capacity

yes, more than 750 pax per A/C (probably no problems with wake turbulence)

Fuel burnt when compared to conventional aircraft

20% less


Stealth configuration in B2 bomber Jack Northrop who established the northrop corporation along with Donald Douglas to develop first the YB-49 and latter the B-2 stealth Bomber

There is no point in considering military aerodynamic configuration development without including stealth. It plays a key role in the configuration layout.. Although the details are classified, certain basic principles have been described. Stealth is usually considered to consist of several elements (often referred to as signatures): • radar cross section, rcs • infrared • visual • aural MVJ College department of Aeronautics

How rcs works (1) A radar site transmits a signal and measures the signal that is returned from the target (in this case an airplane). When the sending and receiving antennas are co-located, the radar is known as monostatic. This is the usual case. If the receiving antenna is located somewhere else, the radar is bistatic. Bistatic systems may be able to detect aircraft designed to operate stealthily against monostatic systems. This is a fundamental consideration in stealth. MVJ College department of Aeronautics

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 ft² (478 m²)

Empty weight: 158,000 lb (71,700 kg) Loaded weight: 336,500 lb (152,200 kg) Max take off weight : 376,000 lb (170,600 kg) Powerplant: 4× general electric f111-GE100 nonafterburning turbaofans , 17,300 lbf (77 kN) each


What makes B-2 bomber a stealth configuration 

It continuously changes shape when looked from different to confuse 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 )


Thank you


Study of Blended Wing Body Design (BWB

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