Modern high-pressure steam engines

Although Watt understood the advantages of utilizing the expansive power of steam within a cylinder, he refused to use steam under high pressure for reasons of safety. The pressures in his engines were not much greater than normal atmospheric pressure, or about 15 pounds per square inch (p. s. i.), or 103 kilopascals. This limited the application of steam engines. By 1815, Oliver Evans, an American, had built an engine that used 200 p. s. i. (1,379 kilopascals) of pressure. _ 1 _ Within a few years Evans designed lighter-weight high-pressure steam engines that could do various other tasks, such as drive sawmills, sow grain, and power a dredge. From 1806 to about 1816 he produced more than 100 steam engines that were employed with screw presses for processing paper, cotton, and tobacco. Today, many engines use steam under a pressure of more than 1,000 p. s. i. (6,895 kilopascals).

Other major advances in the use of high-pressure steam were achieved by Richard Trevithick in England during the early years of the 19th century. One of his first engines operated under 30 p. s. i. (207 kilopascals) of pressure. Trevithick built the world's first steam-powered railway locomotive in 1803. Two years later he adapted his high-pressure steam engine to drive an iron-rolling mill and to propel a barge with the help of paddle wheels.

Watt’s engine was able to convert only a little more than 2 percent of the thermal energy in steam to work. The improvements introduced by Evans, Trevithick, and others (e.g., three separate expansion cycles and higher steam temperatures) increased the efficiency of the steam engine to roughly 17 percent by 1900. Yet, within the next decade the steam engine was supplanted for various important applications by the more efficient steam turbine. _ 2 _

At about the same time, the first compound steam engines were built by the British engineer and inventor Arthur Woolf. In the compound engine, steam at high pressure is used in one cylinder and then, after it has expanded and consequently lessened in pressure, is piped to another cylinder, in which it expands still further. Woolf’s original engines were of the two-cylinder type, but later types of compound engines used triple and even quadruple expansion. The advantage of compounding two or more cylinders is that less energy is lost in the heating of the cylinder walls; as a result, the engine is more efficient.

_ 3 _ In this engine, steam moves in only one direction while entering the cylinder of the engine, expanding, and then leaving the cylinder. The flow of steam into the two sets of inlet ports is controlled by separate valves. The inherent advantages of the uniflow system are such that engines of this type were usually chosen for use in large installations, although the initial cost of the engines is considerably higher than that of conventional steam engines. One virtue of the uniflow engine is that it permits the efficient use of high-pressure steam in a single cylinder engine without the necessity of compounding.

From Encyclopædia Britannica

 

LANGUAGE DEVELOPMENT

Match the words in column A with the words in column B to form meaningful phrases. Translate them into Ukrainian.

Column A Column B

1) separate a) temperature

2) high b) wheel

3) steam c) expansion

4) quadruple d) energy

5) inherent e) applications

6) thermal f) port

7) various g) valve

8) paddle h) cylinder

9) inlet i) pressure

10) single j) advantages

11) high k) system

12) uniflow l) engine

 

Fill in the words from the list below. Use each word only once.

steam-powered, heating, applications, high-pressure, high, expansion, steam, turbine, pressure, mill, engine, thermal

1) cylinder walls …..

2) to convert ….. energy

3) normal atmospheric …..

4) ….. steam temperature

5) single cylinder …..

6) separate ….. cycles

7) efficient steam …..

8) iron-rolling …..

9) ….. railway locomotive

10) various important …..

11) conventional ….. engine

12) ….. steam engine