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1、【精品文档】如有侵权，请联系网站删除，仅供学习与交流能源与动力工程专业英语.精品文档.For practical reasons,most impulse turbines mount their buckets on the rims of disks (wheels),and nozzles feed steam from one side (Fig.6.9),Pressurized steam from the nozzle box flows through parallel converging nozzles formed by vane or foils.Steam leaves
2、 as a broad high-speed jet to flow through the slower moving-bucket passages,which turn the steam flow to an axial direction as they absorb its kinetic energy.The steam leaves with lower internal energy and speed.由于实用性的原因，大部分冲击式汽轮机把他们的叶片安装在轮缘，并且喷嘴从一边提供蒸汽。高压蒸汽从喷嘴室流过由叶片或翼形成的平行的渐缩喷嘴。蒸汽离开的时候是一个宽阔的高速气流，它
3、流过较慢的动叶片通道，把蒸汽换向流到一个轴线方向，在那里吸收他们的动能。蒸汽带着较低的内能和速度离开。Steam pressure and speed vary through the true impulse stage.When the impulse stage are pressure-compouned,which are called Rateau stages,pressure drop occurs in steps and exhausted steam from one-stage folws through following similar impulse stages
4、,where it expands to a lower pressure.If the impulse stages are velocity-compounded,which are called Curtiss stages,steam velocity is absorbed in a series of constant-pressure steps.流过一个完全的冲击级时，蒸汽压力和速度是不同的。当冲击级是压力复合的，这样的就被称做压力级，在过程中发生压降，并且乏汽从一级流过相似的冲击级，在那里它膨胀成低压。如果冲击级是复速的，那就被称作复速级，在一系列压力不变的过程中蒸汽速度被吸
5、收。In the reaction stage (Fig6.10),steam enters the fixed-blade passage;it leaves as a steam jet that fills the entire rotor periphery.Steam flows between moving blades that form moving nozzles.There it drops in pressure,and its speed rises relative to the blades,which creates the reactive force that
6、 does work.Despite the rising relative speed,the overall effect reduces the absolute steam speed through one stage.When the enthalpy drop is about equal in moving and stationary blades,it is called a 50 percent reaction stage.在反应级中，蒸汽进入静叶片通道，它作为一种蒸汽气流而离开，并且充满整个边缘。蒸汽流经形成动的喷嘴的动叶片。在这里，压力下降，速度随着叶片而上升，这样
7、就导致反冲击力工作。尽管速度上升，通过一级的时候，总的影响是减少绝对速度。在动叶片和静叶片中焓降是相同的，那就被称作一个50的反冲击级Fig.6.11 shows a velocity-compounded control stage followed by two reaction stages.The high speed steam jet gives up only part of its kinetic energy in the first row of moving buckets. The come reversing blades that redirect the slow
8、ed-up steam into the second row of moving buckets,where most of its remaining kinetic energy is absorbed.Steam then enters the series of reaction stages.图6.11展示了一个复速控制级随着反冲击级流动。在动叶片的第一行中，高速蒸汽气流仅释放一部分动能。转向式叶片改变方向进入动叶片第二行，在那里他保留的动能被吸收。蒸汽进入一系列反冲击级。In practice,so-called impulse-stage turbine use about 5
9、 to 10 reaction in their design.This means there is a small steam pressure drop through the moving-blade passages.These buckets,instead of taking the symmetrical shape, have a longer tail to form a slightly coverging passage at the exit.在实际中，这种被称作冲击级式的汽轮机在设计中有5到10的都使用反冲击式。这就是说通过动叶片通道时会有一个小的蒸汽压降。这些叶片代替采用对称的形状，有一个较长的尾巴为了在出口形成一个小的渐缩的通道。