Shape
The inlet cone is shaped so that the shock wave that forms on its apex is directed to the lip of the intake; this allows the engine to operate properly in supersonic flight. As speed increases, the shock wave becomes increasingly more oblique (the cone gets narrower). As a result, some inlet cones (for example, on the SR-71) are designed to move axially to maintain the shock-on-lip and allow efficient operation over a wider range of flight speeds. On MiG-21 this movement also makes the opening between the intake (diffusor) lip and the cone smaller, preventing the inside of the intake section from bursting open from dynamic air overpressure at the aircraft's highest speeds above Mach 2.
Read more about this topic: Inlet Cone
Famous quotes containing the word shape:
“The structure was designed by an old sea captain who believed that the world would end in a flood. He built a home in the traditional shape of the Ark, inverted, with the roof forming the hull of the proposed vessel. The builder expected that the deluge would cause the house to topple and then reverse itself, floating away on its roof until it should land on some new Ararat.”
—For the State of New Jersey, U.S. public relief program (1935-1943)
““Must a name mean something?” Alice asked doubtfully.
“Of course it must,” Humpty Dumpty said with a short laugh: “my name means the shape I am—and a good handsome shape it is, too. With a name like yours, you might be any shape, almost.””
—Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)
“The shape of a rat?
It’s bigger than that.
It’s less than a leg
And more than a nose,
Just under the water
It usually goes.”
—Theodore Roethke (1908–1963)