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Cutaway view of an air-start motor of a General Electric J79 turbojet. With air-start systems, gas turbine engine compressor spools are rotated by the action of a large volume of compressed air acting directly on the compressor blades or driving the engine through a small, geared turbine motor. These motors can weigh up to 75% less than an ...
The compressed air is heated in the combustor and passes through the turbine, then expands in the nozzle to produce a high speed propelling jet [3] Turbojets have a low propulsive efficiency below about Mach 2 [ citation needed ] and produce a lot of jet noise, both a result of the very high velocity of the exhaust.
The increased thrust from the C-D nozzle (2,000 lb, 910 kg at sea-level take-off) on this engine raised the speed from Mach 1.6 to almost 2.0 enabling the Air Force to set a world's speed record of 1,207.6 mph (1,943.4 km/h) which was just below Mach 2 for the temperature on that day. The true worth of the C-D nozzle was not realised on the F ...
The propelling nozzle converts a gas turbine or gas generator into a jet engine. Power available in the gas turbine exhaust is converted into a high speed propelling jet by the nozzle. The power is defined by typical gauge pressure and temperature values for a turbojet of 20 psi (140 kPa) and 1,000 °F (538 °C). [18]
In this state, lowering the back pressure increases the flow speed everywhere in the nozzle. [13] When the back pressure, p b, is lowered enough, the flow speed is Mach 1 at the throat, as in figure 1b. The flow pattern is exactly the same as in subsonic flow, except that the flow speed at the throat has just reached Mach 1.
Its function is the same, using a vacuum at the intake to trigger a valve that pulses atmospheric air into the exhaust. The original "iron barrel" style engine did this with a hose from the PAV going to the exhaust pipe, the newer (2003–2009) AVL aluminum engine pulses the gas directly into the exhaust port on the head of the engine itself.
The Pratt & Whitney JT8D is a low-bypass (0.96 to 1) turbofan engine introduced by Pratt & Whitney in February 1963 with the inaugural flight of the Boeing 727.It was a modification of the Pratt & Whitney J52 turbojet engine which powered the US Navy A-6 Intruder and A-4 Skyhawk attack aircraft.
While research into this nozzle continues, it could be used before all its advantages are developed. As an upper stage, where it would be used in a low ambient pressure/vacuum environment specifically in closed wake mode, an E-D nozzle would offer weight reductions, length reductions and a potential increase to the specific impulse over bell nozzles (depending on engine cycle) allowing ...