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Introduction to the Study of Science 



137. Waste in simple engine. In the case of a simple steam 

 or heat engine the steam is conducted from the steam chest 

 on the boiler to the cylinder, where it expands, utilizing heat 



FIG. 97. A boiler setting to secure complete combustion, with a superheater. 

 Trace out the course of gases formed in combustion and explain possible use of 

 them. 



and driving the piston from one end to the other. The used 

 steam is forced through the exhaust port and allowed to escape. 

 138. Multiple engines and compound engines. Such an 

 engine fails to make use of anything like the total quantity of 

 heat energy of steam. To overcome this waste, many improve- 

 ments have been made, among which are the compound, 

 triple and quadruple expansion types of engines, and steam 

 turbines for ocean steamships and stationary power plants. The 

 steam turbine, for instance, is adapted to a range of pressure 

 from two hundred fifty or more pounds absolute pressure 

 (which is gage pressure plus ordinary atmospheric pressure) to 

 one pound absolute, or a partial vacuum. Consult the table 



