Text b Steam Turbines

The success of the water turbine led to developing the turbine principle for extracting power by utilizing the kinetic energy of steam flow. A modern modification of a steam turbine which extracts thermal energy from steam and converts it into rotary motion was invented by Sir Charles Parsons in 1884. It was fortunate for Parsons to see his invention adopted for all major world power stations, and the size of generators had increased by about 10,000 times, from his first 7.5 kW set up to units of 50,000 kW capacity.

Besides, Parsons was the first who offered the so-called principle of staging. According this principle steam was permitted to expand in a number of stages, a small amount of thermal energy converted to kinetic energy and performing useful work at each stage.

Steam turbines are considered to be rather simple machines. There are two types of steam turbines: reaction turbines and impulse turbines. In an impulse turbine there are 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.

In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine uses the reaction force produced as the steam accelerates through the nozzles formed by the rotor.

Although these turbines are built according to two different principles, the essential parts of all steam turbines are similar. They have only one major moving part, the rotor; however, auxiliary equipment is necessary for their operation. Journal bearings support the shaft. A thrust bearing positions the shaft axially. An oil system provides lubrication to the bearings. Seals minimize steam leakage within the steam path. The speed of rotation is controlled by valves at the inlet(s) of the machine.

The action of the steam turbine is based on the thermodynamic principle that when a vapor is allowed to expand, its temperature drops, and its internal energy is thereby decreased. This reduction in internal energy is transformed into mechanical energy in the form of an acceleration of the particles of the vapor. This transformation makes a large amount of work energy directly available to drive machines, pumps, compressors, and electrical generators.

Задания к тексту B:

I. Найдите в тексте английские эквиваленты следующим русским выражениям:

вспомогательное оборудование; ряд ступеней; впускное устройство установки; современная модификация паровой турбины; в виде ускорения частиц пара; непосредственно доступной для приводных устройств, насосов, компрессоров и электрических генераторов; так называемый принцип ступенчатости; только одна главная движущаяся часть; согласно этому принципу; подшипник скольжения; принцип турбины по извлечению энергии за счет использования кинетической энергии потока пара; термодинамический принцип; главные электростанции в мире; в форме ковша; жесткозакрепленные сопла; скорость вращения; высокоскоростные струи; упорный подшипник; лопасти ротора.

II. Сформулируйте в нескольких словах содержание каждого абзаца.

III. Напишите резюме к тексту.

IV. Ответьте на вопросы:

1. What did lead to developing the steam turbines?

2. Whom was a modern modification of a steam turbine invented and when?

3. What does the so-called principle of staging mean?

4. How many types of steam turbines are there?

5. How does an impulse turbine work?

6. What does the reaction turbine use?

7. What are the essential parts of steam turbines?

8. On what principle is the action of the steam turbine based?

9. What is the work energy directly available to?

V. Перескажите текст, используя в качестве плана вопросы предыдущего упражнения.