Single stage steam turbine components

Содержание

Введение …………………………………………………………………..3

PART I. TEXTS FOR CLASS-READING...................................................5

Text 1. Steam Turbine History....................................................................... 5

Text 2. Steam Turbine Principle of Operation............................................... 6

Text 3. Steam Turbine Components ..............................................................8

Text 4. Reactiona nd Impulse Steam Turbines ............................................11

Text 5. Types of Steam Turbines .................................................................13

Text 6. Steam Turbines: Condensing vs Noncondensing ...........................15

Text 7. Multistage Steam Turbines ..............................................................17

Text 8. Single-valve vs Multivalve Construction ………………………....19

Text 9. Steam Turbine Performance Characteristics………………...….... 21

Text 10. Steam Turbine Design Characteristics ..........................................22

Text 11. Steam Turbines Application ..........................................................24

PART II. TEXTS FOR SUPPLEMENTARY READING .......................25

Text 1. Steam Turbine: History of Development ........................................25

Text 2. Theory of Steam Turbine .................................................................26

Text 3. The operation of Single Stage Steam Turbine .................................26

Text 4. Coppus Model RLHB24 Single Stage Turbine................................27

Text 5. Reaction and Impulse Steam Turbine .............................................29

Text 6. Steam Turbine Capacity ................................................................. 29

Text 7. Steam Turbine Operating Characteristics ....................................... 30

Text 8. Steam Turbine Maintenance ............................................................31

Text 9. Steam Turbine Operation and Maintenance ....................................31

Text 10. Steam Turbine Speed Regulation ..................................................32

VOCABULARY ......................................................................................... 33

Список литературы ………………………………………………………

Введение

Учебный практикум «Паровые турбины» предназначен для студентов специальности 141100 «Энергетическое машиностроение», изучающих английский язык как иностранный.

Целью данного учебного практикума является совершенствование навыков изучающего и ознакомительного чтения аутентичных англоязычных текстов по специальности студентов, повторение лексических единиц и грамматических конструкций, характерных для научного стиля речи, а также формирование умений реферирования и аннотирования.

Включенные в данный учебный практикум тексты представляют собою статьи из оригинальной англоязычной литературы, английской энциклопедии «Britannica», а также ряда Интернет сайтов.

Тематика пособия охватывает разнообразные вопросы в области турбиностроения, а именно: история развития паровых турбин, основные компоненты паровой турбины и принципы их работы, классификация паровых турбин, использование паровых турбин и т.д.

Задания, представленные в данном учебном практикуме, позволяют совершенствовать следующие умения и навыки:

∙ перевод специальной технической литературы;

∙ говорение на основе прочитанного текста;

∙ составление реферата и аннотации текстов по специальности;

∙ работа с электронными словарями по специальности, тезаурусами англоязычной лексики.

Работа с первой частью данного учебного практикума предполагает аудиторную работу студентов под контролем преподавателя, что дает возможность коррекции результатов выполнения заданий. Режим работы с каждым заданием также определяется преподавателем, который также может рекомендовать студентам выполнение того или иного задания в аудитории или дома.

Вторая часть учебного практикума предназначена для внеаудиторной работы студентов с обязательной последующей проверкой преподавателем. Тексты, представленные во второй части учебного практикума предназначены для перевода, реферирования и аннотирования. Порядок работы с каждым конкретным текстом определяется преподавателем.

PART I. TEXTS FOR CLASS-READING

TEXT 1. Steam Turbine History

I.Memorize the meaning of the following new words:

A jet – струя

Rotation – вращение

A shaft - вал

A chamber – камера

A blade (a vane) – лопатка турбины

To impinge – ударяться, сталкиваться

To impel – приводить в движение

An internal combustion engine – двигатель внутреннего сгорания

To pump – выкачивать

A coal mine – угольная шахта

A sprinkler – пульверизатор

A bottom valve – донный клапан

A piston – поршень

II.Read and translate TEXT 1 paying attention to the new words from Ex.I:

The turbine is a machine which applies the energy of a jet of water or steam to produce the rotation of a shaft. It consists essentially of a wheel or chamber provided with a number of blades or vanes upon which the fluid jet impinges; the impelled fluid causes the blades to rotate and also the shaft to which they are attached.

Early examples of the use of steam engines were the steam locomotive trains, and steamships that relied on these steam engines for movement. The Industrial Revolution came about primarily because of the steam engine. The thirty seconds or so required to develop pressure made steam less favored for automobiles, which are generally powered by internal combustion engines.

The first steam device was developed by Hero of Alexandria, a Greek, before 300 BC, but was never utilized as anything other than a toy.

Thomas Savery (1650 – 1715) was an English military engineer and inventor who in 1698 patented the first crude steam engine. Thomas Savery had been working on solving the problem of pumping water out of coal mines. His machine consisted of a closed vessel filled with water into which steam under pressure was introduced. This forced the water upwards and out of the mine shaft. Then a cold water sprinkler was used to condense the steam. This created a vacuum which sucked more water out of the mine shaft through a bottom valve.

Thomas Newcomen (1663 – 1729) was an English blacksmith, who invented the atmospheric steam engine, an improvement over Thomas Slavery’s previous design. The Newcomen steam engine used the force of atmospheric pressure to do the work. Thomas Newcomen'sengine pumped steam into a cylinder. The steam was then condensed by cold water which created a vacuum on the inside of the cylinder. The resulting atmospheric pressure operated a piston, creating downward strokes. In Newcomen's engine the intensity of pressure was not limited by the pressure of the steam, unlike what Thomas Savery had patented in 1698.

James Watt (1736 – 1819) was a Scottish inventor and mechanical engineer who was renowned for his improvements of the steam engine. Most notable was Watt's 1769 patent for a separate condenser connected to a cylinder by a valve. Unlike Newcomen's engine, Watt's design had a condenser that could be cool while the cylinder was hot. Watt's engine soon became the dominant design for all modern steam engines and helped bring about the Industrial Revolution.

The modern steam turbine was invented in 1884 by the Englishman Sir Charles Parsons. Since that time a number of other variations of turbines have been developed that work effectively with steam.

II.Translate the following word combinations into English using TEXT 1:

Энергия струи воды или пара, вращение вала, приводить в действие с помощью двигателя внутреннего сгорания, сила атмосферного давления, усовершенствование парового двигателя, откачивать воду из угольных шахт, закачивать пар в цилиндр, давление пара, наполнить водой закрытый сосуд, работать эффективно.

III.Answer the questions to TEXT 1:

1. What is a turbine?

2. Which parts does a turbine consist of?

3. What were the early examples of the use of steam engines?

4. Who was the first to develop the steam device?

5. What kind of problem did Thomas Savery try to solve? Which parts did his machine consist of?

6. What kind of improvements did Thomas Newcomen introduce in his atmospheric steam engine compared to Savery’s one?

7. What was different in Watt’s steam engine design compared to Newcomen’s steam engine?

8. When and by whom was the modern steam turbine developed?

IV.Remember the functions of Participle II and analyze the underlined cases of its use in TEXT 1.

TEXT 2. Steam Turbine Principle of Operation

I.Memorize the meaning of the following new words:

Thermal efficiency –тепловой КПД

To convert - преобразовывать

Rotational energy – энергия вращения

A stage – ступень турбины

A nozzle – сопло

Velocity – скорость

Pressure drop – падение давления

Co-generation – комбинированное производство тепловой и электрической энергии

Process steam – технологический пар

II.Read and translate TEXT 2 paying attention to the new words from Ex.I:

In order to efficiently and reliably drive compressors and other fluid movers, every industry depends on steam turbine drivers. A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884. It has almost completely replaced the reciprocating piston steam engine primarily because of its greater thermal efficiency and higher power-to-weight ratio. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator – about 80% of all electricity generation in the world is by use of steam turbines. Modern steam turbines use essentially the same concept but many detailed improvements have been made in the intervening years mainly to improve turbine efficiency.

Energy in the steam after it leaves the boiler is convertedinto rotational energy as it passes through the turbine. The turbine normally consists of several stages with each stage consisting of a stationary blade (or nozzle) and a rotating blade. Stationary blades convert the potential energy of the steam (temperature and pressure) into kinetic energy (velocity) and direct the flow onto the rotating blades. The rotating blades convert the kinetic energy into forces, caused by pressure drop, which results in the rotation of the turbine shaft. The turbine shaft is connected to a generator, which produces the electrical energy.

In a typical larger power station, the steam turbines are split into three separate stages, the first being the High Pressure (HP), the second the Intermediate Pressure (IP) and the third the Low Pressure (LP) stage, where high, intermediate and low describe the pressure of the steam.

After the steam has passes through the HP stage, it is returned to the boiler to be re-heated to its original temperature although the pressure remains greatly reduced. The reheated steam then passes through the IP stage and finally to the LP stage of the turbine.

Steam turbines can be configurated in many different ways. Several IP or Lp stages can be incorporated into the one steam turbine. A single shaft or several shafts coupled together may be used. Either way, the principles are the same for all steam turbines. The configuration is decided by the use to which the steam turbine is put, co-generation or pure electricity production. For co-generation, the steam pressure is highest when used as process steam and at a lower pressure when used for the secondary function of electricity production.

II.Translate the following word combinations into English using TEXT 2:

Управлять компрессором, различные виды гидродвигателей, вращающаяся лопатка, неподвижная лопатка, направить струю, отдельная ступень, преобразовывать потенциальную энергию пара, привести к движению вала турбины, несколько соединенных вместе валов, повысить эффективность работы турбины, пройти через турбину.

III.Answer the questions to TEXT 2:

1. Why does every industry depend on steam turbine drivers?

2. How many stages does a turbine usually consist of?

3. What is the function of stationary blades?

4. What do rotating blades do?

5. How many stages is the steam turbine split into in a typical larger power station? What are these stages?

6. Describe the way the steam goes through in a turbine.

7. What does the configuration of the steam turbine depend on?

IV.Remember the functions and forms of Participle I and analyze the underlined cases of its use in TEXT 2. Pay attention to the Independent Participial Construction.

TEXT 3. Steam Turbine Components.

I.Memorize the meaning of the following new words:

Mechanical drive – механический привод

Horsepower – лошадиная сила

Rating – параметры

A casing – корпус

A bucket – лопатка турбины

A drum – барабан

A bearing journal – опорная шейка

To capture – брать, захватывать

To spin – крутить, вращать

To attach – прикреплять, присоединять

Alloy steel – легированная сталь

A bearing – подшипник

A governor – регулятор, управляющее устройство

Lubrication – смазывание

A control valve – контрольный клапан

A relay system – релейная система

A coupling – соединительная муфта

Pipe connection – трубопровод, трубное соединение

An exhaust system – система выпуска

II.Read and translate TEXT 3 paying attention to the new words from Ex.I:

All steam turbines have the same basic parts, though there is a lot of variation in how they are arranged.

The illustration shows a small simple mechanical-drive turbine of a few horsepower. It illustrates the essential parts for all steam turbines regardless of rating or complexity:

(1) a casing, or shell, usually divided at the horizontal center line, with the halves bolted together for ease of assembly and disassembly; it contains the stationary blade system;

(2) a rotor carrying the moving buckets (blades or vanes) either on wheels or drums, with bearing journals on the ends of the rotor; it takes power from the turbine to an electricity generator (or whatever else the turbine is driving);

(3) blades - the most important part of a turbine: their design is crucial in capturing as much energy from the steam as possible and converting it into rotational energy by spinning the rotor round. All turbines have a set of rotating blades attached to the rotor and spin it around as steam hits them. The blades and the rotor are completely enclosed in a very sturdy, alloy steel outer case;

(4) a set of bearings attached to the casing to support the shaft;

(5) a governorand valve system for regulating the speed and power of the turbine by controlling the steam flow, and an oil system for lubrication of the bearings and, on all but the smallest machines, for operating the control valves by a relay system connected with the governor;

(6) a coupling to connect with the driven machine;

(7) pipe connections to the steam supply at the inlet and to an exhaust system at the outlet of the casing or shell.

Components of a single-stage steam turbine

II.Translate the following word combinations into English using TEXT 3:

Турбина с механическим приводом, основные части паровой турбины, лопатки, прикрепленные к ротору, система клапанов, заключенный в корпус из легированной стали, подача пара, преобразовывать энергию, трубные соединения, контролировать поток пара, монтаж и демонтаж.

III.Answer the questions to TEXT 3:

1. Why are the halves of the turbine casig bolted together?

2. What is the function of the rotor?

3. Why is the design of the blades important? What kind of blades does a turbine usually have?

4. Which casing are the rotor and blades enclosed into?

5. What is the function of the bearings?

6. What does the governor do?

IV.Using the picture describe the main components of the steam turbine and comment on their functions.

V.In TEXT 3 find Participle I and Participle II and analyze their functions.

TEXT 4. Reaction and Impulse Steam Turbines

I.Memorize the meaning of the following new words:

A reaction turbine – реактивная турбина

An impulse turbine – активная турбина

A convergent nozzle – сужающееся сопло

To accelerate – ускоряться, разгоняться

Circumference – окружность, круг, периферия

To decelerate – замедляться

Net change – чистое изменение

Leakage – протечка, утечка

A clearance – зазор

A balance piston – уравновешивающий поршень

A thrust load – осевая нагрузка

Exit pressure– давление на выходе

Expansion – расширение

II.Read and translate TEXT 4paying attention to the new words from Ex.I:

There are two principal turbine types: reaction and impulse. A distinction made between "impulse" and "reaction" turbine designs is based on the relative pressure drop across the stage.

In the reaction turbine (Fig.1), the rotor blades are arranged to form convergent nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor. To operate efficiently the reaction turbine must be designed to minimize leakagearound the moving blades. This is done by making most internal clearances relatively small. The reaction turbine also usually requires a balance piston(similar to those used in large centrifugal compressors) because of the large thrust loads generated.

Fig.1 Reaction turbine

The impulse turbine (Fig.2) has little or no pressure drop across its moving blades. Steam energy is transferred to the rotor entirely by the steam jets striking the moving blades. An impulse turbine has fixed nozzles that orient the steam flow into high speed jets. These jets contain significant kinetic energy, which the rotor blades, shaped like buckets, convert into shaft rotation as the steam jet changes direction. A pressure drop occurs across only the stationary blades, with a net increase in steam velocity across the stage. As the steam flows through the nozzle its pressure falls from inlet pressure to the exit pressure (atmospheric pressure, or more usually, the condenser vacuum). Due to this higher ratio of expansion of steam in the nozzle the steam leaves the nozzle with a very high velocity. The steam leaving the moving blades has a large portion of the maximum velocity of the steam when leaving the nozzle.

Fig.2Impulse turbine

Most steam turbines use a mixture of the reaction and impulse designs: each stage behaves as either one or the other, but the overall turbine uses both. Typically, higher pressure sections are impulse type and lower pressure stages are reaction type.

II.Translate the following word combinations into English using TEXT 4:

Различие между активной и реактивной турбиной, увеличение скорости пара, расширение пара в соплах, струи пара ударяются о движущиеся лопатки, преобразовать кинетическую энергию в энергию вращения вала, пар ускоряется при прохождении через статор, снижение давления и температуры, давление на входе, работать эффективно, пар меняет направление.

III.Answer the questions to TEXT 4:

1. What are the two basic types of the steam turbine?

2. In what way are the blades of the reaction turbine arranged?

3. What happens to the steam in the reaction turbine? Describe the process.

4. In what way should the reaction turbine be designed to operate efficiently?

5. Is there any pressure drop across the moving blades in the impulse turbine? Where does it occur?

6. What kind of nozzles does the impulse turbine have?

7. Why does the steam leave the nozzle with a very high velocity?

8. What kind are modern turbines?

IV.Summarize the differences between the reaction and impulse turbine.

TEXT 5. Types of Steam Turbines

I.Memorize the meaning of the following new words:

An impeller – лопастное колесо

A power station – электростанция

A marine propeller – гребной винт

A free-jet turbine – активная гидротурбина

Spoon-shaped – ложкообразный

A runner (a wheel) – рабочее колесо

To transmit – передавать, сообщать

Head – напор

Low flow – слабый поток

To emerge – появляться

To adjust – регулировать

To shut off– выключать

A water passage – водовод, канал

An output – мощность

MW (megawatt) – МВт (мегаватт)

To resemble – иметь сходство

A gate – затвор, клапан

An angle – угол

Discharge– расход

Partial load – неполная нагрузка

II.Read and translate TEXT 5 paying attention to the new words from Ex.I:

When people began to use water power to win mechanical work, they looked first for the best forms of impellers. Three types were established thereby and variations of them are used today in various applications, among other in steam turbines in power stations, as marine propellers, as compressors in gas turbines etc. These types are the following:

Pelton turbine is also called a free-jet turbine or Pelton wheel. It is a type of impulse turbine, named after L.A. Pelton who invented it in 1880. Water passes through nozzles and strikes spoon-shaped buckets or cups arranged on the periphery of a runner, or wheel, which causes the runner to rotate, producing mechanical energy. The runner is fixed on a shaft, and the rotational motion of the turbine is transmitted by the shaft to a generator. Pelton turbines are suited to high head, low flow applications. Typically, to work this type of turbine, water is piped down a hillside so that at the lower end of the pipe it emerges from a narrow nozzle as a jet with very high velocity. The Pelton turbine can be controlled by adjusting the flow of water to the buckets. In order to stop the wheel, a valve is used to shut off the water completely.

Francis turbine is a type of hydropower reaction turbine that contains a runner that has water passages through it formed by curved vanes or blades. The runner blades, typically 9 to 19 in number, cannot be adjusted. As the water passes through the runner and over the curved surfaces, it causes rotation of the runner. The rotation motion is trasmitted by a shaft to a generator. The Francis turbine has a wide range of applications and can be used for full heights of 2 – 800 meters. The largests Francis turbines have an output of 750 MW.

Kaplan turbine is a type of turbine developed around 1915 by an Austrian engineer Viktor Kaplan. The turbine has two or more blades, which are adjustable, and resembles a marine propeller. The turbine may have gatesto control the angle of the fluid flow into the blades. Kaplan turbines are well suited to the situations in which there is a low head and a large amount of discharge. The adjustable runner blades enable high efficiency even in the range of partial load, and there is little drop in efficiency due to head variation and load. As a result of recent developments, the range of Kaplan turbine apllications has been greatly increased.

II.Translate the following word combinations into English using TEXT 5:

Различные применения, мощностью 750 МВт, напоминать гребной винт, струя очень высокой скорости, ударять по ложкообразным ковшам, снижение эффективности, из-за изменения напора и нагрузки, ротационное движение передается генератору, производить механическую энергию, рабочее колесо крепится к валу.

III.Answer the questions to TEXT 5:

1. When were the three basic types of turbines established? What are they?

2. What is the principle of operation of Pelton turbine?

3. What kind of applications is Pelton turbine suited to?

4. In what way is Pelton turbine controlled?

5. Describe the principle of operation of Francis turbine.

6. When is Francis turbine used? What is its output?

7. When and by whom was Kaplan turbine developed?

8. How many baldes does Kaplan turbine have?

9. What situations is Kaplan turbine suited to?

IV.Summarize the main features of Pelton turbine, Francis turbine and Kaplan turbine.

V.Remember the functions and forms of Infinitive and analyze the underlined cases of its use in TEXT 5.

TEXT 6. Steam Turbines: Condensing vs Noncondensing

I.Memorize the meaning of the following new words:

A condensing turbine – конденсационная турбина

A noncondensing (back-pressure) turbine – турбина с противодавлением

An extraction turbine – турбина с регулируемым отбором пара

To expand – расширяться

An outlet – выход, выпускное отверстие

Surplus – избыток, излишек, остаток

Exhaust steam – отработанный пар

Reheating – повторный нагрев

To extract – извлекать

Intermediate pressure– среднее давление

An admission turbine – всасывающая турбина

II.Read and translate TEXT 6 paying attention to the new words from Ex.I:

There are three types of steam turbines: condensing, noncondensing, and extraction.

Inside the condensing steam turbine the steam expands below the atmospheric pressure and then condenses while heating the cooling water in a condenser. After the steam exits the outlet of the condensing turbine, the pressure of the steam is so low that it is no longer available for providing power for industrial applications. Condensing steam turbines can be used in industrial power plants as condensing tails connected to back-pressure turbines. In cases of low demand for process steam the steam surplus is run through the condensing tail to generate more power.

Noncondensing steam turbines are also referred to as “back-pressure” steam turbines. Here, steam is expanded over a turbine and the exhaust steam is used for to meet a facilities steam needs. The steam is expanded until it reaches a pressure that the facility can use. Fig.1 shows the process of a back-pressure steam turbine:

Fig.1 Noncondensing steam cycle

So, a condensing turbine uses all the energy from the steam going from high pressure turbine to secondary turbine to condensing turbine then sends the condensate back for reheating, while a noncondensing turbine just uses the high pressure aspect of the steam then returns the low pressure stream back to be reheated.

Another type of the steam turbine is called an extraction turbine. In these turbines steam is extracted from the turbine at some intermediate pressure. This steam can be used to meet the facilities steam need. The remaining steam is expanded further and condensed. Extraction turbines can also act as admission turbines. In admission turbines, additional steam is added to the turbine at some intermediate point. Fig.2 shows the process in an extraction steam turbine:

Fig.2 Extraction steam cycle

II.Translate the following word combinations into English using TEXT 6:

Паровая турбина с противодавлением, паровая турбина с регулируемым отбором пара, конденсационная паровая турбина, всасывающая паровая турбина, излишек пара, извлечь пар из турбины, при среднем давлении, отправить конденсат на повторный нагрев, отработанный пар, обеспечить энергией, нагреть охлаждающуюся жидкость, производить энергию.

III.Answer the questions to TEXT 6:

1. What are the three types of steam turbines?

2. What is the principle of opertaion of the condensing turbine? Why is the steam is no longer available for providing power when it exits the outlet?

3. In what way can condensing turbines be used?

4. What is the principle of operation of a noncondensing turbine?

5. At what pressure is steam extracted from the extraction turbine? What happens to the remaining steam?

6. What is an admission turbine?

IV.Summarize the differences between condensing, noncondensing and extraction turbines.

V.Remember the functions and forms of Gerund and analyze the cases of its use in TEXT 6. Find Participle I in the text. Pay attention to the difference between Gerund and Participle I.

TEXT 7. Multistage Steam Turbine

I.Memorize the meaning of the following new words:

A multistage turbine – многоступенчатая турбина

Multistaging – многоступенчатость

To obtain – получать, приобретать

Constant – постоянный

To issue – выходить, выпускать

To exert – оказывать, вызывать

Turning effort – вращающее усилие

A torque – вращающий момент

Standstill – остановка, пауза

To seek – стремиться

A speed governor – регулятор скорости

A limitation – ограничение

To give up – отдавать

Succeeding – последующий

II.Read and translate TEXT 7 paying attention to the new words from Ex.I:

Turbinemultistaging does not change the principle of the steam turbine operation. The only reason for adding stages is to increase the efficiency of the turbine at any given speed, and as any stage has its best efficiency under certain conditions of speed and pressures, it is usually necessary to multistage the turbine to obtain the high efficiency required today.

Why a single turbine wheel has its best efficiency under one set of operating conditions may be understood from a study of the elemental turbine if it is assumed that this simple turbine has a fixed pressure in the boiler, it follows that a constant flow of steam will issue from its nozzle and this steam will be traveling at a constant velocity. When the wheel (turbine rotor) is held stationary, the steam issuing from the nozzle strikes it with its full force and exerts its greatest possible turning effort. In any turbine the maximum torque occurs at standstill when the steam issuing from the nozzles strikes stationary buckets. But under this condition the rotor is not moving and hence no work can be done. It is the condition of maximum torque, zero speed, and zero work.

At the other extreme consider the case where the speed of the rotor is the same as the speed of the steam. With equal bucket and steam speeds, the steam has no velocity relative to the bucket and can exertno turning effort. This condition, then, is one of maximum speed, zero torque and zero work. In between these two extremes work can be done, for there will always be the force exerted by the steam and the rotor will always be in motion. But, as the speed is increased from zero to the maximum, there will be a point where the product of turning effort and speed will result in the greatest work being done. This will be the point of best efficiency for that stage.

In actual practice turbines are seldom applied to loads where the turbine can seek its most efficient speed. Usually the turbine speed must be held constant, and this is done by a speed governor which adjusts the steam flow to the load to be carried. Structural limitations prevent turbines from being built for usual commercial speeds with a single wheel large enough and efficient enough to use the energy available from most conditions of steam pressures.

In a true multistage turbine steam is generated in the boiler at a high pressure, issues from the first-stage nozzle, and gives up a portion of its energy to the first-stage wheel. The steam in the first-stage shell is at a pressure less than boiler pressure, and this pressure will be reduced in each succeeding stage until finally the steam is exhausted.

II.Translate the following word combinations into English using TEXT 7:

Пар, исходящий из сопел, продукт вращающего усилия, отдавать часть энергии, структурные ограничения, стремиться к наиболее оптимальной скорости, достигнуть наибольшей производительности, рабочие условия, скорость возрастает от нуля до максимума, ротор находится в движении, точка самой высокой производительности.

III.Answer the questions to TEXT 7:

1. Does multistaging change the principle of the steam turbine operation?

2. What is the reason for adding stages?

3. When does the steam exert the greatest possible effort?

4. When does the maximum torque occur? Can work be done under this condition? Why?

5. Describe the condition of maximum speed, zero torque and zero work.

6. When can work be done?

7. What is the point of the best efficiency for each stage?

8. In what way is the turbine speed held constant?

9. What happens to the steam in a multistage turbine?

IV.Find Participle I, Participle II, Gerund and Infinitive in TEXT 7. Analyze their functions. Pay attention to the translation.

TEXT 8. Single-valve vs Multivalve Construction

I.Memorize the meaning of the following new words:

Single-valve – одноклапанный

A shutoff valve – запорный клапан

Steam consumption – расход пара

Part load – неполная нагрузка

Overload – перегрузка

Design load – расчетная нагрузка

Manually – вручную

Multivalve – многоклапанный

A governing valve – управляющий клапан

Throttling loss – потери на дросселирование

An arc – дуга

To feed (fed, fed) – питать, подавать

A valve gear – клапанный механизм

Subsequent – последующий

To anticipate – ожидать

Cast iron – чугун

To exceed - превышать

Psig (pound-force per square inch gauge)– фунт на квадратный дюйм

Bar – бар (единица давления)

Carbon steel – углеродистая сталь

F (Fahrenheit) – температура по шкале Фаренгейта

Respectively – соответственно

To utilize - использовать

Carbon-moly steel – молибденоуглеродистая сталь

Chrome-moly steel – хромомолибденовая сталь

Appropriate – соответствующий, подходящий

II.Read and translate TEXT 8paying attention to the new words from Ex.I:

Single-valve units are available when justified by plant economics. When used, individual nozzle ring segments are controlled by hand-operated shutoff valves. Hand valves may be specified for reduced steam consumption at part load or overload, or for design load with reduced steam pressures. Hand valves are not automatic and are only of value when manually operated as needed.

Multivalveturbines automatically limit pressure drop across the governing valves, thereby minimizing throttling loss. The prime benefit of a multivalve turbine is the fact that the nozzles forming a short arc are fed by a single valve, which will allow a better velocity ratio than would result if all available nozzles were fed with the same amount of steam. Valve gear designs will sequence valve opening so that subsequent valves will only open when the previous valve is wide open. Multivalve turbines are the wise choice if frequent load changes or varying outputs are anticipatedor when inlet volume flows will be high. The multivalve arrangement usually improves efficiency over the full operating range of a steam turbine.

Single-stage turbines are available in six classes of construction. Class 1 (cast iron) is suitable for pressures not exceeding 250 psig (17.2 bar) and for temperatures not exceeding 500°F (260°C). If either one of these limits is exceeded, steel construction is required. Classes 2 and 3 (carbon steel) incorporate construction features suitable for a maximum pressure of 700 psig (48.3 bar). Temperature limit for Class 2 is 650°F, 750°F for Class 3 (343 and 399°C, respectively). For pressures exceeding 700 psig (48.3 bar), the casting is formed from a different pattern and otherwise utilizes construction features suitable up to a maximum pressure of 900 psig (62 bar). Class 4, 5, or 6 is required, depending on temperature. Class 4 (carbon steel) is suitable to a maximum temperature of 750°F (399°C). Alloy steels are required for temperatures exceeding 750°F, or 399°C. Class 5 (carbon-moly steel) can be used to 825°F (440°C), Class 6 (chrome-moly steel) to 900°F (482°C).

Note that these material classes do not define the situation in which the operating pressure is 700 psig (48.3 bar) or less, with an operating temperature exceeding 750°F (399°C). For this combination of operating limits, Class 3 construction, with the appropriate material, is utilized. In other words, 700 psig (48.3 bar) construction is utilized with the parts cast in the appropriate steel alloy (carbon-moly steel to825°F, chrome-moly steel to 900°F (440 and 482°C, respectively).

II.Translate the following word combinations into English using TEXT 8:

Многоклапанная турбина, температура не выше 500°F, повышать производительность, частые изменения нагрузки, использовать подходящий материал, требуется стальная конструкция, основное достоинство, конструкция клапанного механизма, последующие клапаны, снизить потери на дросселирование.

III.Answer the questions to TEXT 8:

1. When are single-valve units usually used?

2. What are the chief advantages of a multivalve turbine?

3. Speak of the principle of a multivalve turbine operation.

4. Which conditions are multivalve turbines suitable to?

5. How many classes of construction are single-valve turbines available?

6. Describe each class of construction (material, pressure, temperature).

TEXT 9. Steam Turbine Performance Characteristics

I.Memorize the meaning of the following new words:

HHV (higher heating value) – теплопроизводительность

A capacity factor – коэффициент мощности

Annual– ежегодный

A byproduct – побочный продукт

A process – технологический процесс

A heating system – система отопления

A ratio – коэффициент, соотношение

Net power – полезная мощность

To measure – измерять

CHP (combined heat and power)– a system in which steam produced in a power station as a byproduct of electricity generation is used to heat nearby buildings)

Thermal load – тепловая нагрузка

II.Read and translate TEXT 9paying attention to the new words from Ex.I:

The electrical generating efficiency of standard steam turbine power plants varies from a high of 37% HHV for large, electric utility plants designed for the highest practical annual capacity factor, to under 10% HHV for small, simple plants which make electricity as a byproduct of delivering steam to processes or district heating systems.

Steam turbine thermodynamic efficiency refers to the ratio of power actually generated from the turbine to what would be generated by a perfect turbine with no internal losses using steam at the same inlet conditions and discharging to the same downstream pressure. Turbine thermodynamic efficiency is not to be confused with electrical generating efficiency, which is the ratio of net power generated to total fuel input to the cycle. Steam turbine thermodynamic efficiency measures how efficiently the turbine extracts power from the steam itself. Multistage (moderate to high-pressure ratio) steam turbines have thermodynamic efficiencies that vary from 65% for small (under 1,000 kW) units to over 90% for large industrial and utility sized units. Small, single-stage steam turbines can have efficiencies as low as 50%.

When a steam turbine exhausts to a CHP application, the turbine efficiency is not as critical as in a power only condensing mode. The majority of the energy not extracted by the steam turbine satisfies the thermal load.

II.Translate the following word combinations into English using TEXT 9:

Термодинамический кпд, большая часть энергии, коэффициент полезной мощности, ежегодный коэффициент мощности, местная отопительная система, внутренние потери, условия на входе, не следует путать, расход топлива, варьироваться от 65% до 90%.

III.Answer the questions to TEXT 9:

1. What is the electrical generating efficiency of standard steam turbine power plants?

2. What does steam turbine thermodynamic efficiency refer to?

3. Which two terms are not to be confused?

4. What is electrical generating efficiency?

5. What does steam turbine thermodynamic efficiency measure?

6. What is the thermodynamic efficiency of a multistage turbine?

7. What is the thermodynamic efficiency of a single-stage turbine?

8. When is the turbine efficiency not crictical? Why?

TEXT 10. Steam turbine Design Characteristics

I.Memorize the meaning of the following new words:

A custom design – типовой проект

To match the requirements – соответствовать требованиям

Thermal output – теплопроизводительность, тепловая мощность

A utility – коммунальное сооружение

An inch - дюйм

Hg (mercury) – ртуть

Backpressure – противодавление

Flexibility – гибкость

A heat source – источник тепла

Reliability – надежность

To maintain – обслуживать

An overhaul – капитальный ремонт

Differential expansion –дифференциальное расширение

A transient– переходный процесс

Emissions – выбросы

A boiler furnace – топка котла

A exhaust cleanup system – выпускная очистительная система

II.Read and translate TEXT 10 paying attention to the new words from Ex.I:

Custom design: Steam turbines are designed to matchCHP design pressure and temperature requirements and to maximize electric efficiency while providing the desired thermal output.

Thermal output: Steam turbines are capable of operating over a broad range of steam pressures. Utility steam turbines operate with inlet steam pressures up to 3,500 psig and exhaust vacuum conditions as low as one inch of Hg. Steam turbines are custom designed to deliver the thermal requirements of the CHP applications through use of backpressure or extraction steam at appropriate pressures and temperatures.

Fuel flexibility: Steam turbines offer a wide range of fuel flexibility using a variety of fuel sources in the associated boiler or other heat source, including coal, oil, natural gas, wood and waste products.

Reliability and life: Steam turbine life is extremely long. When properly operated and maintained, steam turbines are extremely reliable, only requiring overhauls every several years. They require controlled thermal transients to minimize differential expansion of the parts as the massive casing slowly heats up.

Size range: Steam turbines are available in sizes from under 100 kW to over

250 MW. In the multi-megawatt size range, industrial and utility steam turbine designations merge, with the same turbine (highpressure section) able to serve both industrial and small utility applications.

Emissions: Emissions are dependent upon the fuel used by the boiler or other steam source, boiler furnace combustion section design and operation, and built-in and add-on boiler exhaust cleanup systems.

II.Translate the following word combinations into English using TEXT 10:

Соответствовать температурным требованиям, надежная паровая турбина, требовать капитального ремонта, нагрев массивного корпуса, при соответствующем давлении и температуре, отходы, снизить до минимума дифференциальное расширение, обеспечить желаемый тепловой кпд, использовать различные источники топлива, выброс зависит от используемого топлива.

III.Answer the questions to TEXT 10:

1. What are steam turbine design requirements?

2. What pressures are steam turbines are capable of operating over?

3. Which heat sources do steam turbines use?

4. Is steam turbines life long? Which rules should be followed to keep a steam turbine in a good condition?

5. What is the size of steam turbines?

6. What does emissions depend upon? What can help to minimize emissions?

TEXT 11. Steam Turbines Application

I.Memorize the meaning of the following new words:

Versatile – универсальный

A prime mover – первичный двигатель

A reciprocating engine – поршневой двигатель

Solid fuel – твердое топливо

Waste fuel – отходы используемые в качестве топлива

A feedwater pump – питательный насос

A refrigeration chiller – морозильная камера, холодильная установка

A refrigeration compressor – холодильный компрессор

Sufficient – достаточный

Bottoming – насыщение, работа в режиме насыщения

Heat recovery – регенерация тепла, использование вторичного тепла

To yield – извлекать

A distribution system – система распределения

Moderate – средний

To discharge – выпускать

II.Read and translate TEXT 11 paying attention to the new words from Ex.I:

Steam turbines are one of the most versatile and oldest prime mover technologies still in general production. Power generation using steam turbines has been in use for about 100 years, when they replaced reciprocating steam engines due to their higher efficiencies and lower costs. Conventional steam turbine power plants generate most of the electricity produced all over the world. The capacity of steam turbines can range from 50 kW to several hundred MWs for large utility power plants. Steam turbines are widely used for combined heat and power (CHP) applications.

Industrial and CHP applications.

The primary locations of steam turbine based CHP systems is industrial processes where solid or waste fuels are readily available for boiler use. In CHP applications, steam extracted from the steam turbine directly feeds into a process or is converted to another form of thermal energy. The turbine may drive an electric generator or equipment such as boiler feedwater pumps, air compressors, and refrigeration chillers. Turbines as industrial drivers are usually a single casing machine, either single stage or multistage, condensing or non-condensing depending on steam conditions and the value of the steam. Steam turbines operate at a single speed when driving an electric generator and operate over a speed range when driving a refrigeration compressor. For non-condensing applications, steam exhausted from the turbine is at a pressure and temperature sufficient for the CHP heating application.

Combined Cycle Power Plants.

The trend in power plant design is the combined cycle, which incorporates a steam turbine in a bottomingcycle with a gas turbine. Steam generated in the heat recoverysteam generator (HRSG) of the gas turbine is used to drive a steam turbine to yield additional electricity and improve cycle efficiency. Combined cycle CHP applications use an extraction-condensing type of steam turbine.

District Heating Systems.

There are many cities that have steam district heating systems where adding a steam turbine between the boiler and the distribution system may be an attractive application. Often the boiler is capable of producing moderate-pressure steam but the distribution system needs only low-pressure steam. In these cases, the steam turbine generates electricity using the higher-pressure steam, and discharges low-pressure steam into the distribution system.

II.Translate the following word combinations using TEXT 11:

Морозильная камера, турбина с регулируемым отбором пара, пар среднего давления, вырабатывать электричество, отопительная система, промышленный процесс, заменить поршневой двигатель, выходящий пар, энергоснабжение, преобразовываться в другую форму тепловой энергии, повысить тепловой КПД.

III.Answer the questions to TEXT 11:

1. How long has power generation using steam turbines been in use?

2. Why did steam turbines replace reciprocating steam engines?

3. What is the capacity of a steam turbine?

4. What are steam turbines used for?

5. What can a steam turbine drive when apllied industrially?

6. What are turbines as industrial drivers like?

7. In what way are steam turbines used in combined cycle power plants?

8. What kind of a turbine do combined cycle CHP applications use?

9. What is the third attractive application of steam turbines?

Part II. TEXTS FOR SUPPLEMENTARY READING

TEXT 1. Steam Turbine: History of Development

The first device that may be classified as a reaction steam turbine was little more than a toy, described in the 1st century by Greek mathematician Hero of Alexandria in Roman Egypt. More than a thousand years later, in 1543, Spanish naval officer Blasco de Garay used a primitive steam machine to move a ship in the port of Barcelona. In 1551, Taqi al-Din in Ottoman Egypt described a steam turbine with the practical application of rotating a spit. Steam turbines were also described by the Italian Giovanni Branca (1629) and John Wilkins in England (1648).