说New words
• Essentially 本质上、根本上
• Accelerate 加速
• Velocity 速度
• To obtain 获得
• Addition 加法
• Heat energy 热能
• Conversion 转换
• Jet efflux 射流
• Working cycle 工作循环
• Four-stroke piston engine 四冲程活塞式发动机
• Combustion 燃烧
• Constant 常数
• Pressure 压力
• Whereas 然而、尽管
• Volume 容积、体积
• Instance 例子、事例
• Induction 归纳、入门、进气
• Compression 压缩、浓缩
• Exhaust 排气
• Processes 过程
• Whilst 同时
• Continuously 连续不断地
• Utilized 利用
• Eliminate 消除
• Idle 闲置的、懒惰的
• Enabling 有可能
• Hence 因此、由此
• Output 输出
• Given 规定的、指定的
• Enclosed 封闭的、围住的
• Peak 峰值、高峰
• Fluctuating 波动
• Withstand 抵抗、经受
• Cylinder 圆柱、圆筒
• Construction 施工、建造
• Octane 辛烷值
• In contrast 相反
• Fabricated 编造、装配式
• Represented 代表
• Pressure volume diagram 压容图
• Expand 展开
• Mechanical power 机械功率
• Ambient air 大气、环境空气
• Remainder 其余的
• Propulsive 推进的、推进
• Turbo-jet 涡轮喷气发动机
• Value 价值
• Turbine assembly 涡轮组件
• Air-cooled blade 气冷叶片
• Permit 许可证
• Thermal efficiency 热效率
• Working fluid 工质、工作介质
• Embodied 具体化
• Briefly 短暂地、简要地
• Proportional 比例
• Absolute 绝对的
• Principle 原则、法则、原理
• Typical 典型
• Axial flow 轴向流动
• Casing 机匣
• Rotation 旋转
• Nozzle guide vanes 导向器叶片
• Stage 阶段、时期、舞台、级
• State 状态、情况
• Corresponding 对应
• Diagram 简图、图解
• Conversely 相反地
• Adiabatic 绝热的
• Losses 损失
• Friction 摩擦
• Conduction 传导
• Turbulence 湍流、紊流
• In practice 在实践中、实际上
• Passage 通道、管路
• Aerodynamic 空气动力学
• Demand 需求
• Internal 内部
• Rotate 旋转
• Momentum 动量
• Local 本地、局部
• Flame 火焰
• Stored 存储
• Subsonic 亚音速
• Sonic 音速、声波
• Supersonic 超音速
• Encountered 遭遇、遇到
• Venturi 文丘里管
• Maximum 最大值
• Effected 影响
• Interference 干扰、干预
• Smooth 平滑的、平坦的
• Component 组成部分
• Eddy 涡流
• By-pass ratio 涵道比
• Intermediate 中介的、中间的
• Contra-rotating 反向旋转
• Path 路径、路线
• Straight-through 直通
• Relatively 相对地
• Frontal 正面
• Reverse 反转
• Overall 总体的、全面的、全部
• Operation 操作
• Variation 变化、变更
• Subsequent 后续的、随后的
• Majority 大部分、大多数
• Absorbed 被……吸引住、专心致志
• Shaft 轴
• Division 分开、分隔
• Initial 最初的、开始的
• Percentage 百分比
• Manner 态度、方式、方法
• Conducive 有利于
• Propulsive efficiency 推进效率
• Specific fuel consumption 燃油消耗率、耗油率
• Feature 特色
• Order 顺序、订单、条理
• Regarded 将……认为、把……视为
• Configuration 布局、结构、配置
• Capable 能干的
• Seldom 很少、罕见
• Aft fan 后置风扇
• 1. Thegas turbine engine is essentially a heat engine using air as a working fluid toprovide thrust. To achieve this, the air passing through the engine has to beaccelerated; this means that the velocity or kinetic energy of the air isincreased. To obtain this increase, the pressure energy is first of allincreased, followed by the addition of heat energy, before final conversionback to kinetic Energy in the form of a high velocity jet efflux.
• 2. Theworking cycle of the gas turbine engine is similar to that of the four-strokepiston engine. However, in the gas turbine engine, combustion occurs at aconstant pressure, whereas in the piston engine it occurs at a constant volume.Both engine cycles (fig. 2-1) show that in each instance there is induction,compression, combustion and exhaust. These processes are intermittent in thecase of the piston engine whilst they occur continuously in the gas turbine. Inthe piston engine only one stroke is utilized in the production of power, theothers being involved in the charging, compressing and exhausting of theworking fluid. In contrast, the turbine engine eliminates the three 'idle'strokes, thus enabling more fuel to be burnt in a shorter time; hence itproduces a greater power output for a given size of engine.
• 4. Theworking cycle upon which the gas turbine engine functions is, in its simplestform, represented by the cycle shown on the pressure volume diagram in fig.2-2. Point A represents air at atmospheric pressure that is compressed alongthe line AB. From B to C heat is added to the air by introducing and burningfuel at constant pressure, thereby considerably increasing the volume of air.Pressure losses in the combustion chambers (Part 4) are indicated by the dropbetween B and C. From C to D the gases resulting from combustion expand throughthe turbine and jet pipe back to atmosphere. During this part of the cycle,some of the energy in the expanding gases is turned into mechanical power bythe turbine; the remainder, on its discharge to atmosphere, provides apropulsive jet.
• 5.Because the turbo-jet engine is a heat engine, the higher the temperature ofcombustion the greater is the expansion of the gases. The combustiontemperature, however, must not exceed a value that gives a turbine gas entrytemperature suitable for the design and materials of the turbine assembly.
• 8.Thereare three main conditions in the engine working cycle during which these changesoccur. During compression, when work is done to increase the pressure anddecrease the volume of the air, there is a corresponding rise in thetemperature. During combustion, when fuel is added to the air and burnt toincrease the temperature, there is a corresponding increase in volume whilstthe pressure remains almost constant. During expansion, when work is taken fromthe gas stream by the turbine assembly, there is a decrease in temperature andpressure with a corresponding increase in volume.
• 10.The efficiency with which these changes are made will determine to what extentthe desired relations between the pressure, volume and temperature areattained. For the more efficient the compressor, the higher the pressuregenerated for a given work input; that is, for a given temperature rise of theair. Conversely, the more efficiently the turbine uses the expanding gas, thegreater the output of work for a given pressure drop in the gas.
• 11.When the air is compressed or expanded at 100 percent efficiency, the processis said to be adiabatic. Since such a change means there is no energy losses inthe process, either by friction, conduction or turbulence, it is obviouslyimpossible to achieve in practice; 90 per cent is a good adiabatic efficiencyfor the compressor and turbine.
• 13.These various changes are effected by means of the size and shape of the ductsthrough which the air passes on its way through the engine. Where a conversionfrom velocity (kinetic) energy to pressure is required, the passages aredivergent in shape. Conversely, where it is required to convert the energystored in the combustion gases to velocity energy, a convergent passage ornozzle (fig. 2-3) is used. These shapes apply to the gas turbine engine wherethe airflow velocity is subsonic or sonic, i.e. at the local speed of sound.Where supersonic speeds are encountered, such as in the propelling nozzle ofthe rocket, athodyd and some jet engines (Part 6), a convergent-divergentnozzle or venturi (fig. 2-4) is used to obtain the maximum conversion of theenergy in the combustion gases to kinetic energy.
• 16.The major difference of a turbo-propeller engine is the conversion of gasenergy into mechanical power to drive the propeller. Only a small amount of'jet thrust' is available from the exhaust system. The majority of the energyin the gas stream is absorbed by additional turbine stages, which drive thepropeller through internal shafts (Part 5).
18. An important design feature of the by-pass engine is the by-passratio; that is, the ratio of cool air by-passed through the duct to the flow ofair passed through the high pressure system. With low by-pass ratios, i.e. inthe order of 1:1, the two streams are usually mixed before being exhausted fromthe engine. The fan engine may be regarded as an extension of the by-passprinciple, and the requirement for high by-pass ratios of up to 5:1 is largelymet by using the front fan in a twin or triple- spool configuration (on whichthe fan is, in fact, the low pressure compressor) both with and without mixingof the airflows. Very high by-pass ratios, in the order of 15:1, are achievedusing propfans. These are a variation on the turbo-propeller theme but withadvanced technology propellers capable of operating with high efficiency athigh aircraft speeds.
读全文并回答以下问题：
• Describe ‘heating atconstant pressure’.
• How to obtain a higher thermal efficiency for turbine engine?
• Describe the laws of Boyle and Charles.
• Why the design of the passages and nozzles is of greatimportance?
• Explain the advantages of the by-pass design.
作业收看收听以下资源的11：30-21：55，并用英文回答问题，同时请将答案翻译成中文。
