10-01-2011, 10:50 PM
ABSTRA CT
Concorde
Concorde is the world’s only supersonic passenger aircraft. This aircraft flies at more than two times the speed of sound. In 1962, the British and French governments signed an agreement to develop a supersonic transport aircraft (SST) and the plane was built jointly by British Aerospace (Bae) and Aerspatiale. The first flight took place in 1969 and began passenger service in 1976.The Concorde holds many records, including fastest crossing of the Atlantic from New York to London in 2 hours 54 minutes and45 seconds as opposed to about 8 hours for a subsonic flight. A total of 20 Concordes were made, of which 13 are still in service. British Airways and Air France fly the planes. Each Concorde is young in "aeroplane years" having completed about the same number of take-offs and landings as a 3-4 year old 737 and the same number of hours as a 4-5 year old 747.
This paper includes the special features of the Concorde from the ordinary airplane, which enables supersonic flight.
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HISTORY
Supersonic airline research in Europe began in 1956 and resulted in the British and French Governments signing an international treaty for the joint design, development and manufacture of a supersonic airliner in 1962.The first prototype was rolled out at Toulouse in 1967. First flight of Concorde 001 was from Toulouse France on 9th March 1969.Concorde's first supersonic flight was on 1st October 1969.The Russians built an SST similar in design to the Concorde, called the Tupolev Tu -144, nicknamed the "Konkordski."
The Concorde vs. Other Passenger Jets
The Concorde flies faster and higher than most commercial jets. For example, a Boeing 747 aircraft cruises at about 560 mph (901 kph, or Mach 0.84) at an altitude of 35,000 ft (10,675 m). In contrast, the Concorde cruises at 1,350 mph (2,172 kph, or Mach 2) at an altitude of 60,000 ft (18,300 m). Because the Concorde travels faster than the speed of sound and almost twice as high as other commercial jets, it has several features that set it apart from other aircraft:
• Streamlined design
Needle-like fuselage
Swept-back delta wing
Moveable nose
Vertical tail design
• Engine design
Engines built into the wing
Afterburners
• Main and auxiliary fuel tanks
• High-reflectivity paint
Streamlined Design
As any aircraft approaches the speed of sound (1100 ft/s, 343 m/s), the air pressure builds up in front of the aircraft, forming a "wall" of air. To punch through that wall of air, planes must be streamlined. To streamline the Concorde, the following designs have been implented:
• Needle-like fuselage
• Swept-back delta wing
• Moveable nose
• Vertical tail design
Fuselage
The fuselage (body) of the Concorde is only 9.5 ft (2.7 m) wide (for comparison, a 747 is 20 ft (6.1 m) wide). The length of the Concorde is about 202 ft (61.7 m), just slightly shorter than a 747. The designers of Concorde had to elongate the aircraft's silhouette, assuring it maximum atmospheric penetration, even with a full load of 186 tons. The long, narrow shape of the Concorde reduces the drag on the plane as it moves through the air.
Delta wing
A delta shape is the most appropriate for supersonic flight, which requires a combination of sufficient length and sweep, minimum relative thickness, and a low aspect ratio. This design meets these requirements as well as those of subsonic flight, takeoff and landing, while offering sufficient structural rigidity and an extremely solid system of aerodynamic lift. Its stability is such that Concorde is the only commercial aircraft that requires no stabilizing rudders.
The Concorde's wings are thin and swept back at an angle. Thin wings reduce drag and help delay the formation of shock waves. But wings can be made only so thin. The angling back of the wings, which further reduces drag, makes them act as if they are thinner in the air stream.
The big ogival wing is unique as is the fact that Concorde has no ailerons, speed brakes, spoilers or leading edge flaps/slats. Concorde has six elevons, grouped in three pairs, for pitch and roll. Concorde also has no trailing edge flaps, but the elevons droop on takeoff and for landing to create increased wing camber. The six elevons are hydraulically powered and electrically controlled.
A Concorde in flight
(Wide, triangular wing structure and lack of horizontal tail)
A Boeing 747 in flight
(Thin, rectangular wing structure and horizontal stabilizer on the tail)
Nose
The Concorde has a longer, needle-shaped nose compared to most commercial jets. The nose helps penetrate the air, and can be tilted down upon takeoff and landing (13 degrees) so that the pilots can see the runway. (Delta-winged aircraft have a steeper angle of attack during takeoff and landing than other types of aircraft.) Also, the Concorde's nose has a visor to protect the windshield when flying at supersonic speeds and which maintains the aerodynamic profile of the aircraft in flight.
Position of Nose at different stages of flight
Takeoff and subsonic cruising
(Nose at 5° - Visor down)
Supersonic flight
(Nose up - Visor up)
Subsonic cruising
(Nose up - Visor down)
Approach, landing and taxiing
(Nose Down - Visor down)
Engines
The engines on the Concorde provide the thrust necessary for takeoff, cruising and landing. The Concorde has four Rolls Royce/Snecma Olympus 593 turbo jet engines. Each engine generates 18.7 tons (180 kN) of thrust. Together, the four engines burn 6,771 gallons (25,629 liters) of fuel per hour.
The location and type of engines on the Concorde's are different from on other
Concorde in flight
(The engines are attached directly underneath the wing without struts)
Airbus 320 in-flight
(The engines are attached underneath the wing with struts)
The Concorde's engines are attached directly to the underside of the wing without engine struts. This design reduces air turbulence and makes for a more stable engine. At supersonic speeds, engine struts would be overstressed and likely to break.
TURBO JET ENGINE
The main components of a turbo jet engine are
1. Inlet diffuser 2.Compressor 3.Combustion chamber
4. Turbine 5.Tail pipe
The compressor through an inlet diffuser sucks ambient air and the pressure of air is raised by the compressor besides a small rise through the diffuser. After adiabatic compression the high pressure air supports combustion in the combustion chamber which occur at constant pressure in the ideal cycle. The air is supplied in three streams- (a) primary air, which is about 15% of the total, initiates the combustion of atomized fuel entering the combustion chamber. About 30% of air (secondary air) is introduced to complete the combustion; the remaining quantity of air (about 55%)known a tertiary air is used to dilute the high fuel-air ratio mixture and lowering down its temperature to safe limits for the turbine. The fuel-air mixture is ignited by means of a high voltage device at the time of starting the engine.
The hot gases from combustion chamber at designed pressure and temperature expand adiabatically through one or more turbine stages.
Expanded gases from turbine enter the exhaust pipe (tail pipe). This is provided with a convergent type exhaust or propelling nozzle where the gases expand further to the ambient pressure. The velocity at exit is very high corresponding to high values of pressure ratio across the nozzle.
AFTER BURNER
Exhaust gases from the last turbine stage have a large quantity of oxygen, which can support the combustion chamber of additional fuel. If the thrust of the engine is desired to be increased without changing the physical dimension of the compressor, turbine etc; additional quantity can be burnt in a section of the jet pipe to increase the velocity of jet. This process is known as reheating, which is done by an After Burner. Reheating can also be used for a short time to obtain increased thrust.
STABILITY
In common with any aircraft the Concorde design has to ensure the stability of the aircraft over the complete speed range.
It is well known that, as an aircraft accelerates, its aerodynamic center of pressure moves backwards. On a lot of subsonic aircraft the tendency of the plane to pitch down is corrected by trimming the elevators, but there is an aerodynamic drag penalty associated with this gain in stability
For Concorde at Mach 2.2 a rearward shift of two meters in the center of aerodynamic pressure occurs.
The kerosene fuel is primarily contained in the wings, but two supplementary tanks are located in the fuselage, one in the front and the other in the back. They contain approximately a third of the fuel. In the climb and acceleration, fuel is pumped rearward into the tanks of the wing and tail. The centre of gravity will thus move back at the same time as the center of pressure.
In subsonic equilibrium (1)
In supersonic flight the aircraft "TENDS TO PIQUER" as the centre of gravity moves back (2)
Classic solution is to rebalance the aircraft using the elevons but this increases the drag (3)
On Concorde the rebalancing is achieved by a system of fuel transfer, which makes it possible to readjust the centre of gravity of the aircraft to match the aerodynamic center of pressure both during acceleration when the c.g. moves back(4) and,
during deceleration, when the center of gravity moves forward again (5),
to move at the same time the centre of gravity (6)
Other Special Components
There are several components that enable and support the speed and power achieved by the Concorde.
Fuel Tanks
The Concorde has 17 fuel tanks that can hold a total of 31,569 gallons (119,500 liters) of kerosene fuel. The main tanks are located in each wing (five on each side) and fuselage (four).
The Concorde also has three auxiliary or trim fuel tanks (two in front and one in the tail). Here is what the trim tanks are used for:
• As the Concorde reaches supersonic speeds, its aerodynamic center of lift shifts backward.
• This shift drives the nose of the aircraft downward.
• To maintain balance, fuel is pumped backward into the trim tanks.
• The redistribution of fuel balances the aircraft by making its center of gravity match the center of lift.
• When the plane slows down, the center of lift shifts forward.
• Fuel is then pumped forward into the trim tanks to compensate
So, unlike other jets, the Concorde uses fuel not only for the engines, but also for aerodynamic stability.
High-reflectivity Paint
Because the Concorde moves faster than sound, the air pressure and friction (collision with air molecules) really heat up the plane. The temperature of the aircraft's skin varies from 261 degrees Fahrenheit (127 degrees Celsius) at the nose to 196 F (91 C) at the tail. The walls of the cabin are warm to the touch. To help reflect and radiate this heat, the Concorde has a high-reflectivity white paint that is about twice as reflective as the white paint on other jets.
The heat encountered by the Concorde causes the airframe to expand 7 inches (17.8 cm) in flight. To minimize the stress on the aircraft, the Concorde is made of a special aluminum alloy (AU2GN) that is lightweight and more heat-tolerant than titanium.
NOISE
Concorde is not as noisy as that (in normal use).
Curve showing the level of noise produced by various jets at the moment of takeoff and approach
It will be noticed that concordes it less noisy than some subsonic aircraft.
The red feature represents the limit of the noise
Even comparison measured in approach, to 1852 meters of the runway entry.
HEAT BARRIER
CONCORDE, employ lot of ingenuity in order to overcome the difficulties of a supersonic flight.
Indeed, CONCORDE is large (62,19 meters - 202.61 feet), rapid (Mach 2.02) transports approximately a hundred and twenty people , this involves the deformations of structure and the rises in consequent temperatures.
127° =260°F | 91° =196°F
To 11 miles of altitude and 1364 miles/hours,
Concorde grows of 9.44 inch
For a plane of 202 feet length and 84 feet scale, with an area of 3856 sq ft, the surface of the meters being deducted, the estimate of weight is185 tons. Approximately 50% of the mass will be devoted to the fuel. It is seen that the remainder will have to be very light. On this point, the engineers count on material chosen for the structure and the coating: a refractory aluminium alloy named AU2GN. It has only one defect: that to age a little quickly. But it fights much better the ' heat barrier '. A Mach 2.2, friction will heat the point of the nose with 356° F, the leading edge with 311°F, the fuselage and the trailing edge of the aircraft between 284°F and 302°F. Taking into account the ambient cold at high altitude (-122°F/ -131°F), the temperature of surface will be about 257°F/ 266°F, high for traditional alloys. In the absence of AU2GN, it would be necessary to employ titanium, but this metal is heavier and also more difficult to work.
The AU2GN is not a ' prototype ' alloy. It is used already for the paddles of engines at considerable motor mechanics.
FUTURE SSTs
The Concordes are undergoing modifications. These modifications include installing Kevlar linings to the fuel tanks, to prevent them from rupturing in the event that the wing is punctured, and strengthening the wiring in the undercarriage
Several plans are going on research to improve the Concorde in terms of safety and comfort. New seats and cabin lighting are being installed to improve the passenger's experience onboard the plane. In addition to the Concorde, other supersonic planes are currently under design. President Ronald Reagan called for a program to develop a hyperspace transport or National Aerospace Plane capable of going from New York to Tokyo in two hours.
One concept of the National Aerospace Plane
Another concept of the National Aerospace Plane
. They would have to develop the air-breathing rocket engines necessary to achieve the appropriate speeds and deal with the intense heat of re-entry, much like the space shuttle.
CONCLUSION
Concorde will retire in 2005/2010/2015 (hard to say) but what we know is that her successor will not be there to take place. US say they are not working anymore on that project. French government has initiated in May 2001 a second call for supersonic studies but sums allocated are far from what they should be.
As for hypersonic planes, they still belong to science fiction. All the points (noise, fuel consumption, heating…) must be multiplied by X. First test of experimental plane without pilot X 43 has failed on 2nd June 2001. Rocket Pegasus XL, launched from a B 52 bomber above Pacific ocean and was supposed to haul X 43 in high altitude for an historic flight at Mach 7 (4,800 mph) had to be destroyed in flight due to erratic comportment
After more than five years of testing in wind tunnel, this real test should have checked overall performances in flight of the first scramjet, a revolutionary engine able to propel X 43 at speeds up to Mach 10 (6,875 mph).X 43 is the result of 20 years of research in the technology called scramjet (Supersonic Combustible Ramjet) based on the principle of propelling by a supersonic combustion ramjet engine
