HARNESSING ENERGY 



165 



raising the other side of the beam and making it pos- 

 sible to do work. As more steam was let into the cylin- 

 der, the counter balance weight helped raise the pis- 

 ton and lower the other end of the beam. 



To James Watt we 

 owe the development of 

 the modern steam en- 

 gine. In 1763 he was 

 working as an instru- 

 ment maker at the 

 University of Glasgow 

 in Scotland. A model 

 of Newcomen's engine 

 was brought to him for 

 repair and he became 

 greatly interested in it. 

 He was quick to see 

 FIG. 273. NEWCOMEN'S ENGINE that a large amount of 



heat energy was lost 



each time the cylinder walls had to be warmed by the 

 new steam which was admitted. Watt suggested that 

 it would be more efficient if the cylinder were also 

 closed at the other end and if steam instead of air 

 pressure were made to push the piston to and fro in 

 the cylinder. In Watt's engine, by means of a slide 



Courtesy Hoover, Owens, Renischler 



FIG. 274. A MODERN STEAM ENGINE 



valve, the steam is admitted first to one side of the 

 piston and then to the other. This keeps the cylinder 

 always hot and thus saves much heat energy form- 

 erly wasted in the Newcomen engine. If you do not 

 now understand how the modern steam engine works, 

 turn to page 163 and review the experiment. While 

 Watt greatly improved the steam engine, he realized 

 that not all of the heat energy of the steam was 

 being used. Much of it escaped with the exhaust 

 steam which was still very warm. Modern steam en- 

 gines, called compound engines, are now used and get 

 more useful work out of the steam and thus are more 

 efficient. Figure 274 is a picture of a modern steam 

 engine. 



Modern steam turbines differ from the one made 



Courtesy General Electric Company 



FIG. 275. ROTOR 



by Branca in 1629 chiefly in their efficiency ; that is, in 

 getting more useful work out of the heat energy of 

 the steam. The basic principle is still causing a jet 

 of steam to push against a wheel (Fig. 276). Figure 

 275 shows one of these rotors, as they are called. Some 

 modern steam turbines make the steam run past sev- 

 eral rotors until most of its push has been used. 



How is the energy of 

 gas and oil made avail- 

 able? Crude oil, or pe- 

 troleum, is found in 

 many parts of the Unit- 

 ed States and in other 

 countries. The crude oil 

 is used in some places 

 as a fuel, but finds its 

 energy in the form of 

 gasoline for automo- 

 biles, airplanes, and 

 tractors. From crude 

 oil, by various refining 

 processes, man gets 



naphtha, benzine, kero- FIG 276 STEAM PUSH ING ON 

 sene, gasoline and vase- TURBINE ROTOR 



