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

時(shí)間：2011-03-11 23:13來源：藍(lán)天飛行翻譯 作者：admin 點(diǎn)擊：次

hydraulic system. A fluid power system that transmits power or force through an incompressible fluid, such as oil. A complete hydraulic system contains a reservoir to hold the fluid, a pump to move the fluid, valves to control the flow of fluid, and actuators to produce the mechanical force. All of the components are connected together with either rigid or flexible fluid lines.
hydraulic valve lifter (reciprocating engine component). A hydraulic device in the valve train of certain aircraft reciprocating engines. When the cam follower is on top of a cam lobe, the intake or exhaust valve is held open by a cushion of oil inside the valve lifter. A specific amount of this oil leaks out while the valve is open, and when the valve closes, a spring pushes the piston up and oil is pulled into the lifter to replace that which was lost.
The continual leakage and replenishment of the oil in the hydraulic valve lifter keeps all clearance out of the valve operating system.
hydrocarbon. An organic compound which contains only carbon and hydrogen. The vast majority of fossil fuels such as gasoline and turbine-engine fuel are hydrocarbons.
hydrodynamics. The branch of science or technology that deals with forces produced by incompressible fluids in motion.
hydrofoils. Flat or airfoil-shaped plates attached to struts below the hull of a hydrofoil watercraft.
hydrofoil vessel. A watercraft with a conventional hull which supports it when it is still or moving at a slow speed, but when traveling at a high speed, hydrodynamic lift produced by hydrofoils below the hull lifts the vessel out of the water, greatly decreasing the drag and allowing the vessel to travel at a higher speed.
hydrogen. A colorless, highly flammable, lighter-than-air, gaseous chemical element. Hydrogen’s symbol is H, its atomic number is 1, and its atomic weight is 1.00797. Hydrogen is the lightest of all of the chemical elements.
An atom of hydrogen has one proton and no neutrons in its nucleus, and spinning around this nucleus is only one electron. A molecule of hydrogen gas is made up of two atoms of hydrogen (H2). Hydrogen gas is colorless, tasteless and lighter than air. It is used as a fuel gas for welding.
hydrogen bomb. A nuclear weapon in which two light elements such as deuterium and tritium are forced together under extreme conditions of heat and pressure. When two of the light nuclei join together to form a heavier nucleus (this is called atomic, or nuclear, fusion), a tremendous amount of heat is released. A hydrogen bomb is far more powerful than the original atomic bomb.
hydrogen brazing. A form of brazing in which hydrogen is used as the fuel gas.
hydrogen embrittlement. A condition in which certain types of metal become brittle from absorbing hydrogen while they are being electroplated.
hydrogen peroxide. A heavy, colorless, unstable liquid used as a bleaching agent, an antiseptic, and a fuel for liquid-propellant rocket engines.
hydrolysis. The change in a chemical substance caused by water.

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