07-04-2011, 11:58 AM
PRESENTED BY
SUBHSANKAR DWIBEDI
[attachment=11837]
AIR-CUSHION VEHICLE
WHAT IS A.C.V ???
Air cushion vehicles are also known as Hovercrafts
A hovercraft is a vehicle that floats slightly above surface either land or water it is over, on a cushion of air
A hovercraft relies on air pressure to lift it off the ground, as opposed to aerodynamic lift
A hovercraft can attain higher speeds than either ships or most land vehicles and use much less power than helicopters of the same weight.
MODEL OF HOVERCRAFT
LIFT MECHANISM
The lift mechanism for a hovercraft must supply enough air to:
1. pressurize the air under the hovercraft enough to lift the vehicle off the surface
2. replace the air that leaks out from under the hovercraft so as to maintain the desired air pressure.
PROPULSION
Propulsion is that which makes the craft move
The source of this effect is the fan, which is used to move the air for propulsion
the propulsion of the craft requires a fan but a normal fan is not sufficient
because a normal fan does not blow air straight
PARTS OF HOVERCRAFT
Lifting Fan
It is a centrifugal fan which operate efficiently in an environment when backpressure is high and they will move larger volumes of air for a given rotation speed than a propeller with the same speed and power input
It forces air into the chamber below the craft so creating a specific pressure under the craft.
Thrust Propellers
1. These are four-bladed and nineteen feet in diameter.
2. These are mounted on the pylon.
3. Pylons rotated to change the direction of thrust.
Hovercraft Skirt
1. The skirt is a shaped, flexible strip fitted below the bottom edges of the plenum chamber slot.
2. skirt enables a hovercraft to maintain its normal operating speed
3. The skirt material has to be light flexible
The Engine
1. The engine has a main shaft on which a compressor and a turbine is mounted.
2. A starter motor is connected to one end of the shaft and the other end is connected to the lift fan and propeller gearboxes.
3. When the engine is started, the compressor compresses air from the engine intakes and pushes it into combustion chambers. Fuel is squirted into the combustion chambers and ignited.
4. The compressed air then rapidly expands as it is heated and forces its way out through the turbine to the exhaust
Air box
1. The box-like structure at the rear of the hovercraft is called an air box.
2. The air box takes about 10% of the air being pushed backward by the propeller and forces it downward.
ADVANTAGES
1. Operate over water, land, sandbanks, mudflats ice, rocks and rapids.
2. High Speed: Cruise at fill payload at speeds of 25 –36 knots.
3. A hovercraft over other vehicles is its ability to cross a wide variety of surfaces.
SUBHSANKAR DWIBEDI
[attachment=11837]
AIR-CUSHION VEHICLE
WHAT IS A.C.V ???
Air cushion vehicles are also known as Hovercrafts
A hovercraft is a vehicle that floats slightly above surface either land or water it is over, on a cushion of air
A hovercraft relies on air pressure to lift it off the ground, as opposed to aerodynamic lift
A hovercraft can attain higher speeds than either ships or most land vehicles and use much less power than helicopters of the same weight.
MODEL OF HOVERCRAFT
LIFT MECHANISM
The lift mechanism for a hovercraft must supply enough air to:
1. pressurize the air under the hovercraft enough to lift the vehicle off the surface
2. replace the air that leaks out from under the hovercraft so as to maintain the desired air pressure.
PROPULSION
Propulsion is that which makes the craft move
The source of this effect is the fan, which is used to move the air for propulsion
the propulsion of the craft requires a fan but a normal fan is not sufficient
because a normal fan does not blow air straight
PARTS OF HOVERCRAFT
Lifting Fan
It is a centrifugal fan which operate efficiently in an environment when backpressure is high and they will move larger volumes of air for a given rotation speed than a propeller with the same speed and power input
It forces air into the chamber below the craft so creating a specific pressure under the craft.
Thrust Propellers
1. These are four-bladed and nineteen feet in diameter.
2. These are mounted on the pylon.
3. Pylons rotated to change the direction of thrust.
Hovercraft Skirt
1. The skirt is a shaped, flexible strip fitted below the bottom edges of the plenum chamber slot.
2. skirt enables a hovercraft to maintain its normal operating speed
3. The skirt material has to be light flexible
The Engine
1. The engine has a main shaft on which a compressor and a turbine is mounted.
2. A starter motor is connected to one end of the shaft and the other end is connected to the lift fan and propeller gearboxes.
3. When the engine is started, the compressor compresses air from the engine intakes and pushes it into combustion chambers. Fuel is squirted into the combustion chambers and ignited.
4. The compressed air then rapidly expands as it is heated and forces its way out through the turbine to the exhaust
Air box
1. The box-like structure at the rear of the hovercraft is called an air box.
2. The air box takes about 10% of the air being pushed backward by the propeller and forces it downward.
ADVANTAGES
1. Operate over water, land, sandbanks, mudflats ice, rocks and rapids.
2. High Speed: Cruise at fill payload at speeds of 25 –36 knots.
3. A hovercraft over other vehicles is its ability to cross a wide variety of surfaces.
