时间：2011-03-11 23:18来源：蓝天飞行翻译 作者：航空 点击：次
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valve-timing clearance (reciprocating engine specification). A specified clearance between the end of the valve stem and the rocker arm of an air-cooled aircraft engine equipped with solid valve lifters. The valves in one cylinder, usually cylinder number one, are adjusted to the valve-timing clearance, and the valve operating cam mechanism is adjusted so the valves in this cylinder open and close when the crankshaft is in the correct position. After the cam mechanism is adjusted, the valves are reset to the correct cold clearance. Valve-timing clearance is also called the hot, or operating, valve clearance of the engine. vanadium. A silvery-white, ductile, metallic chemical element. Vanadium’s symbol is V, its atomic number is 23, and its atomic weight is 50.942. Vanadium is used as an alloying element for steel to increase its hardness and toughness. Vanadium steel alloyed with chromium is used to make mechanics’ hand tools. vane-type pump (fluid pump). A constant-displacement fluid pump that uses sliding vanes to move fluid through the pump. An eccentrically mounted shaft is turned inside a circular housing that has an intake port on one side and an outlet port on the other. Flat vanes are free to slide back and forth through slots in the shaft as it turns. As the shaft turns, the volume of the chamber connected to the intake port increases and pulls fluid into the pump. This fluid is carried around the inside of the pump until it reaches a point connected to the outlet port. At this point, the vanes sliding through the shaft decrease the volume of the chamber, and fluid is forced out of the pump. Vane-type pumps move a comparatively large volume of fluid, but produce a relatively low pressure and are used as fuel pumps and low-pressure air pumps. vanishing point (mechanical drawing). The point in a linear perspective drawing at which the lines forming parallel sides of an object meet. Drawings made in linear perspective cause the object to appear to have depth. vapor. The gaseous state of a material. Water is normally a liquid, but when it evaporates, it turns into invisible water vapor. Certain metals can be turned into a vapor in the intense heat of an electric arc and the low pressure of a vacuum. vapor-cycle air cooling system. A sealed mechanical refrigeration system used to lower the temperature of the air in an aircraft cabin. A liquid refrigerant, such as R-12 or R-134a, is sprayed into the evaporator coils, and as it evaporates, it absorbs heat from the cabin air blown across the evaporator. The refrigerant, now in its vapor form, flows from the evaporator into a mechanical compressor where it is compressed, increasing both its temperature and pressure. The hot, high-pressure vapor flows from the compressor through the coils of a radiator-like condenser. Air from outside the aircraft blowing across the condenser coils absorbs heat from the refrigerant vapor, causing it to change back into a liquid. The liquid refrigerant now repeats its cycle through the evaporator and picks up more heat. |
