航空術(shù)語詞典 Dictionary of Aeronautical Terms 上

時(shí)間：2011-03-11 23:11來源：藍(lán)天飛行翻譯 作者：admin 點(diǎn)擊：次

Chokes are used with capacitors to make filter circuits to smooth out the voltage variations and change pulsating DC into smooth DC.
choked nozzle (gas turbine exhaust system). A nozzle in a gas turbine engine that limits the speed of the gases flowing through it. The gases speed up until they reach the speed of sound. At this point, a normal shock wave forms that prevents further acceleration.
choke-ground cylinder (reciprocating engine cylinder). A cylinder of a reciprocating engine ground in such a way that its diameter at the top of the barrel is slightly smaller than the diameter in the center of the barrel.
The large mass of metal in the cylinder head absorbs enough heat to cause the top end of the barrel to expand enough more than the remainder of the barrel that, at the normal operating temperature, the diameter of choke-ground cylinders becomes uniform throughout.
choke-input filter (electronic filter). A form of filter used with an electronic power supply to change pulsating direct current into smooth DC.
A choke, or inductor, is the first element in the filter, and one or more capacitors are installed in parallel with the output of the power supply following the choke.
choke of a cylinder. The difference between the bore diameter of a reciprocating engine cylinder in the area of the head and in the center of the barrel.
choo-choo (gas turbine engine operating condition). A mild compressor surge caused by an obstruction of the airflow through the compressor. The name comes from the sound made by the engine.
chopper (electrical component). An electronic or electromagnetic device used to interrupt DC or low-frequency AC at regular intervals to produce a pulsating voltage whose frequency is high enough that it can be amplified by an AC amplifier.
chord of a circle. A straight line across a circle that touches the circumference at two points. The chord passing through the center of a circle is called the diameter.

chord of an airfoil. An imaginary line drawn through an airfoil from its leading edge to its trailing edge. The chord, or chord line, is used as a reference, or datum, for laying out the curve of the airfoil.

chromel. An alloy of nickel and chromium. Chromel is highly resistant to oxidation and has a high electrical resistance. It is one of the metals used in a thermocouple to measure the exhaust gas temperature in both reciprocating and gas turbine engines.
chromel-alumel thermocouple. A thermocouple used to measure the temperature of the exhaust gas in either reciprocating or gas turbine engines. It can be used for measuring temperatures up to 1,000°C.
Chromel is the positive lead, and it is normally enclosed in a white insulation for color coding. Alumel is the negative lead, and it is normally enclosed in a green insulation. The alumel lead can also be distinguished from the chromel lead because alumel is magnetic.
chrome molybdenum steel. A high-strength alloy steel in which chromium and molybdenum are the chief alloying agents. It is easy to machine and weld, and has high strength for its weight. Most welded tubular steel aircraft structure is made of chrome molybdenum tubing. Chrome molybdenum steels are the SAE 41xx series.

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