说New words

•        Distribution 分配

•        Obscure 模糊的、不清楚的

•        Momentum 动量

•        Opposing 对立的

•        Rearward 向后

•        Rated 额定

•        Origin 起源、源头

•        Induced 诱导、诱发

•        Resultant 合成的

•        Exert 施加、运用

•        Consequent 随之而来的

•        Deflect 偏转、偏离

•        Magnitude 巨大、重大

•        Inner cone 内锥

•        Bullet 子弹、尾锥

•        Calculate 计算

•        Section 部门、部分、切开、剖面图

•        Area 面积

•        Mass flow 质量流量

•        Particular 特别的、不寻常的

•        Pressure difference 压力差

•        Overall thrust 总推力

•        Formula 公式

•        Gravitational constant 重力常数

•        Individual thrust 单个推力

•        Various 各种各样的

•        Assume 假定

•        Static 静止的、静态的

•        Illustrate 举例说明

•        Casing 机匣

•        Given 给定的、指定的

•        Duct 管道

•        Assembly 装配

•        Wheel 车轮、轮盘

•        Unit 单位、单元

•        Jet pipe 喷管

•        Propelling nozzle 推进喷管

•        Emphasized 强调的

•        Ignore 忽略

•        Gross thrust 总推力

•        Total thrust 总推力

•        Choke 阻塞、堵塞的

•        Algebraically 用代数、用代数的方法

•        Axial 轴向的

•        Inclined 倾斜的

•        Cosine 余弦

•        Hypotenuse 斜边

•        Axis 轴线

读Sentence

•        3. Atthe start of the cycle, air is induced into the engine and is compressed. Therearward accelerations through the compressor stages and the resultant pressurerise produces a large reactive force in a forward direction. On the next stageof its journey the air passes through the diffuser where it exerts a smallreactive force, also in a forward direction.

•        4.From the diffuser the air passes into the combustion chambers (Part 4) where itis heated, and in the consequent expansion and acceleration of the gas largeforward forces are exerted on the chamber walls.

•        5.When the expanding gases leave the combustion chambers and flow through thenozzle guide vanes they are accelerated and deflected on to the blades of theturbine (Part 5). Due to the acceleration and deflection, together with thesubsequent straightening of the gas flow as it enters the jet pipe,considerable 'drag' results; thus the vanes and blades are subjected to largerearward forces, the magnitude of which may be seen on the diagram. As the gasflow passes through the exhaust system (Part 6), small forward forces may acton the inner cone or bullet, but generally only rearward forces are producedand these are due to the 'drag' of the gas flow at the propelling nozzle.

•        7. Thethrust forces or gas loads can be calculated for the engine, or for any flowsection of the engine, provided that the areas, pressures, velocities and massflow are known for both the inlet and outlet of the particular flow section.

•        8. Thedistribution of thrust forces shown in fig. 20-1 can be calculated byconsidering each component in turn and applying some simple calculations. Thethrust produced by the engine is mainly the product of the mass of air passingthrough the engine and the velocity increase imparted to it (i.e. NewtonsSecond Law of Motion), however, the pressure difference between the inlet toand the outlet from the particular flow section will have an effect on theoverall thrust of the engine and must be included in the calculation.

•        20.Although the momentum change of the gas stream produces most of the thrustdeveloped by the engine (momentum thrust =                             ), anadditional thrust is produced when the engine operates with the propellingnozzle in a 'choked' condition (Part 6). This thrust results from theaerodynamic forces which are created by the gas stream and exert a pressureacross the exit area of the propelling nozzle (pressure thrust).

读全文并回答以下问题：

•        Define the rated thrust.

•        What is the applicable scope of divergent and convergentpassage？

•        When does the thrust results only from the gas streammomentum change?

•        How to calculate the thrust of an engine with inclined combustionchambers.

作业收看收听以下资源的21：55至最后，并用英文回答问题，同时请将答案翻译成中文。