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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velocity turbine. A turbine designed in such a way that it is driven by forces produced by the velocity, rather than the pressure, of the gases flowing through the vanes. Velocity turbines are used on turbocompound engines as the power recovery turbines (PRTs). vendor. A person or business that sells something. veneer (wood product). A thin sheet of wood “peeled” from a log with a knife held against the log as it is rotated in the cutter. Veneer is used for making plywood. Several sheets of veneer are glued together, with the grain of each sheet placed at 45° or 90° to the grain of the sheets next to it. V-engine (reciprocating engine). A form of reciprocating engine in which the cylinders are arranged in two banks, separated by an angle of between 45° and 90°. Pistons in two cylinders, one in each bank, are connected to each of the crankshaft throws. vent. An orifice, or hole, in a container that maintains the air pressure inside the container the same as the pressure on the outside. ventilate. To allow fresh air to circulate through a room or compartment. A compartment is ventilated to remove fumes and make it more comfortable for the occupants. ventral fin (aircraft structural component). A fixed vertical surface on an airplane that extends below the aft end of the fuselage. Ventral fins are used to increase the directional stability of an airplane. venturi. A specially shaped restriction in a tube designed to speed up the flow of fluid passing through it. According to Bernoulli’s principle, any time a fluid is speeded up without losing or gaining any energy from the outside, the pressure of the fluid decreases. Venturis are used in carburetors and in many types of fluid control devices to produce a pressure drop proportional to the speed of the fluid passing through them. See Bernoulli’s principle. verdigris. A green or a greenish-blue deposit that forms on the surface of copper when it is acted on by certain acids or other contaminants. vernier. A device used to allow very fine adjustments or very small measurements to be made. A vernier coupling, for example, has two sets of splines, or teeth. One set has 35 teeth and the other set has 36 teeth. When the coupling is moved ahead one tooth on the 35-tooth side, it moves ahead 10.285 degrees (360 ÷ 35 = 10.285). When it is moved back one tooth on the 36-tooth side, it moves back 10 degrees (360 ÷ 36 = 10). By moving the coupling ahead one tooth on the 35-tooth side and back one tooth on the 36-tooth side, the shafts joined by the coupling have been moved by an amount of only 0.285 degree. vernier caliper. A precision measuring instrument used to make inside or outside measurements with an accuracy in the range of 1/1000 inch, or 1/50 millimeter. The movable jaw of the vernier caliper moves a vernier scale next to the main scale. The distance between the end marks on the vernier scale is divided into one more space than the same distance on the main scale. |
