IV. Answer the following questions.

1. What is a stage in a steam turbine?

2. What are four types of turbine seals?

3. What are the two basic types of steam turbines?

4. What is the operating principle of an impulse turbine?

5. What is the operating principle of a reaction turbine?

 

V. Translate into English.

1. Турбина состоит из следующих основных частей: корпуса (цилиндра) с направляющими (сопловыми) аппаратами, обоймами, диафрагмами и уплотнениями; ротора; подшипников; соединительных муфт; валоповоротного устройства; системы смазки, регулирования и защиты.

2. К статору турбину относятся корпус, обоймы для установки и крепления диафрагм и диафрагмы.

3. Для размещения направляющих лопаток, образующих сопловые каналы и обеспечивающих эффективный вход пара на рабочие лопатки служат диафрагмы.

4. В современных мощных турбинах используют два типа диафрагм: литые и сварные.

5. Одним из самых ответственных элементов корпуса является паровпуск, через который поступает пар.

ВАРИАНТ 3

I. Translate into Russian.

REDUCTION GEARS AND COUPLINGS

Steam turbines must operate in a relatively high rpm range for greatest efficiency while propellers operate most efficiently in a relatively low rpm range. One means of accomplishing the necessary step down from high turbine shaft rpm to lower propeller shaft rpm is by use of an electric drive. The most common means of obtaining the required propeller rpm for ship propulsion is by use of reduction gears.

The use of reduction gears is by no means limited to ship propulsion. Other steam turbine-driven machinery such as ship’s service generators, air compressors, and various pumps also have reduction gears. In these, as in ship propulsion units, turbine operating efficiency requires a higher rpm range than that suitable for the driven unit.

Reduction gears are classified by the number of steps used to bring about the speed reduction and the arrangement of the gearing. There are single and double reduction gears, although double reduction is more usual.

Since the shaft (rotor) is made in small parts due to forging limitations and other technological and economic reasons, the couplings are required between any two rotors. This coupling permits angular misalignment, transmits axial thrust and ensures axial location.

The types of couplings generally employed in power plants are:

· Flexible coupling

· Solid shaft coupling

II. Read the following definitions in column A and find the corresponding terms which they explain. Translate the completed sentences into Russian.

1. This is a system of gears where one or more wheels travel around the outside or inside of another wheel whose axis is fixed. 2. It is an arrangement by which an input speed can be lowered for a requirement of slower output speed, with same or more output torque. 3. This unit is usually known as reduction gear box. 4. This arrangement consists of only one pair of gears. 5. This arrangement is generally used in applications involving very high speeds. In this arrangement the pinion is connected to the input shaft using a flexible coupling.

A.The reduction gear assembly   B. Double Reduction gear   C. Reduction Gear   D.Single Reduction gear   E. Epicyclical gearing.

 

III. Fill in the following diagram.

Coupling	Function	Application	Advantage(s)	Disadvantage(s)
Solid
Flexible

 

IV. Rearrange the following words to make up the sentences.

Example: Placed ports are exhaust the cylinder on side.

Answer: Exhaust ports are placed on the cylinder side.

1. The speed turbine reduced to is that of the propeller the use by of a gearing system.

2. Gears used to are transmit motion rotary to another from shaft one.

3. A flexible is coupling always between fitted rotor the turbine and the pinion gearbox.

4. A flexible permits coupling rotor slight and misalignment pinion.

5. In the flexible most installations couplings are of the gear type.

 

V. Translate from Russian into English.

1. Соединительные муфты предназначены для соединения роторов турбин с шестернями редуктора, валом генератора или вспомогательным механизмом.

2. По конструкции муфты могут быть жесткие, подвижные и эластичные.

3. Жесткие муфты чаще всего применяют в турбинах небольшой и средней мощности, а также для соединения большого зубчатого колеса с валопроводом.

4. Жесткие муфты не допускают в условиях работы ни радиальной, ни угловой расцентровки.

5. Достоинством жестких муфт является их простота и надежность, но они требуют большой точности изготовления и высококачественного монтажа.

ВАРИАНТ 4

I. Translate into Russian.

Impulse and Reaction Turbines

The heat energy contained within the steam that passes through a turbine must be converted into mechanical energy. How this is achieved depends on the shape of the turbine blades. The two basic blade designs are: 1. Impulse 2. Reaction. Therefore there are two main types of turbine, the 'impulse' and the 'reaction'. The names refer to the type of force which acts on the blades to turn the turbine wheel.

An impulse turbine is a type of steam turbine where the rotor derives its rotational force from the impact force, or the direct push of steam on the blades.

In the impulse turbine the steam is expanded within the nozzle and there is no any change in the steam pressure as it passes over the blades.

A reaction turbine is a type of steam turbine that works on the principle that the rotor spins, as the name suggests, from a reaction force rather than an impact or impulse force.

In this type of turbine, there is a gradual pressure drop and takes place continuously over the fixed and moving blades. The rotation of the shaft and drum, which carrying the blades is the result of both impulse and reactive force in the steam. The reaction turbine consists of a row of stationary blades and the following row of moving blades. The fixed blades act as a nozzle which are attached inside the cylinder and the moving blades are fixed with the rotor.

II. Read the following definitions and find the corresponding terms, which they explain. Translate the completed sentences into Russian.

1. … is obtained when the steam enters at or near the shaft and flows substantially radially outward among blades which are placed parallel to the axis of rotation. 2. … signifies steam flow substantially parallel to the axis of rotation, among blades which are set radially. 3. … is the term applied when the steam enters through a nozzle placed approximately tangent to the periphery and directed into semicircular buckets milled obliquely into the edge of the wheel. 4. In an …. steam is withdrawn from one or more stages, at one or more pressures, for heating, plant process, or feedwater heater needs. 5. In the …. the expansion and consequent change in pressure of the steam occurs entirely in the blading where the steam is directed against the moving buckets or blading by guide valves or orifices.

Reaction turbine   Extraction turbine   Tangential flow   Radial flow   Axial flow

III. Delete the phrase, which is not applicable in the following statements.

1. Velocity-Compounded impulse turbines consists of a nozzle or sets of nozzles and a wheel fitted with two or more rows of moving/fixed blades.

2. Steam entering/leaving the nozzle expands from the initial pressure down to the exhaust pressure.

3. On passing through the first ring of moving blades, the steam gives up only a part of its kinetic/potential energy.

4. It then enters the stationary blades and is redirected by them into the second ring of moving blades/nozzles.

5. There is a slight drop in velocity/pressure in the fixed guide blades due to friction.

 

IV. Answer the following questions.

1. What is the difference between an impulse and a reaction turbine?

2. How does steam impart energy to a turbine to develop work?

3. Describe the turbine stage design, and identify the major components.

4. What are the major components of a turbine?

5. What prevents steam from leaking at the point where the rotating shaft penetrates through the casing?

V. Translate into English.

1. По принципу действия в зависимости от характера сил, вызывающих вращение вала, турбины подразделяют на активные и реактивные.

2. Турбины, работающие по активному принципу, имеют симметричную форму лопаток и лопаточный канал почти постоянного сечения.

3. Особенностью реактивных турбин является несимметричная форма лопаток, образующих криволинейные суживающиеся каналы.

4. При движении по таким каналам пар на выходе из сопла продолжает расширяться, повышая свою относительную скорость.

5. К основным недостаткам активных турбин относятся: большая частота вращения, низкий КПД (0, 5—0, 6) при значительных перепадах тепла и невозможность получения больших мощностей.

ВАРИАНТ 5

I. Translate into Russian.

CASING

The turbine casing completely surrounds the rotor and provides the inlet and exhaust passages for the steam. The casings of turbine cylinders are of simple construction to minimize any distortion due to temperature changes. Casings are usually split horizontally to permit easier access for inspection and repair. 

The flanges are accurately machined to ensure a steam-tight metal-to-metal fit, and the flanges are strongly bolted together. Flange seals, except for corrective maintenance measures, are not normally used. In some (high temperature) units, both top and bottom casing halves are made of two vertical casings bolted together and seal-welded. The inlet end is made of alloy steel (Cr-Ni), while the exhaust end is made of carbon steel. The flanges in the casing are bolted together.

One method of joining the top and bottom halves of the cylinder casing is by using flanges with machined holes. Bolts or studs are insertion into these machined holes to hold the top and bottom halves together. To prevent leakage from the joint between the top flange and the bottom flange the joint faces are accurately machined.

Another method of joining the top and bottom cylinder flanges is by clamps bolted radially around the outer of the cylinder.

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