Steam Turbine

The most widely used source of power in large power plants is a steam turbine. A steam turbine is driven by steam, the heat of steam being converted into mechanical work. Any apparatus converting heat into mechanical work is called a heat engine. Thus, the steam turbine may also be considered a kind of heat engine.

Such steam turbines can be of very large size so they have completely replaced the reciprocating piston steam engines primarily because of their greater thermal efficiency (to 1,500,000 kw). Also, because the turbine generates rotary motion, it is used to drive an electrical generator - it doesn't require a linkage mechanism to convert reciprocating to rotary motion.

The steam turbine was the first form of heat engine developed. It’s interesting to note that the history of heat engine goes back to ancient times. The first steam engine was little more than a toy. It was made by Hero of Alexandria in about 150 B.C. … almost two thousand years before it was re-invented. Sadly, the device didn’t receive any serious recognition during Hero's lifetime.

In Russia steam turbine production started in 1907 when a 200-kW steam turbine was first produced at a Petersburg plant and installed at the power station of that very plant. However, large capacity turbines have been developed only over the last 90 years or so.

Nowadays steam turbines may be broadly grouped into three types, the classification being made in accordance with the conditions of the steam exploitation. The groups are as follows: 1) impulse, 2) reaction, 3) impulse-and-reaction (combination of 1 and 2). 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. In the reaction turbine, the rotor blades themselves 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.

• Transcribe the following words, practice reading them, give Russian equivalents:

Steam, engine, reciprocating, issue, stationary, cause, transfer, arrangement, efficient, wheel, mention, impulse, mechanism, convert

• Are the following sentences true or false? Correct the false sentences.

1. Both steam turbine and reciprocating heat engine convert heat into mechanical work in the same manner.

2. Any apparatus converting heat into mechanical work is considered to be a steam turbine.

3. The steam turbine drives the generator.

4. Steam turbines are as efficient as reciprocating steam engines.

5. An impulse turbine was first mentioned more than 2000 years ago.

6. Steam turbines are divided into three types according to the size and capacity.

• Answer these questions:

1. What is the most widely used source of power in large power plants?

2. How does a steam turbine work?

3. Why is a steam turbine considered to be a heat engine?

4. What are the main parts of a steam turbine?

5. Which is more efficient – a steam turbine or an ordinary reciprocating steam engine?

6. When was the first heat engine made?

7. When and where did steam turbine production start in Russia?

8. What types of steam turbines are there?

9. What does the type of turbine depend on?

10. Where are the steam turbines used?