Oil Engines. 



437 



A further convenience arises from the difference between the 

 work of handling the petroleum and handling coal or coke, 

 The small steam engine, with the ordinary small vertical boi'er 

 used with most of them, will require from 5 to 8 tons of coal for 

 every ton of oil used by the oil engine. This requires handling 

 on receipt and handling by shovelsfull into a fire grate by hand. 



The oil is not only so many times less in weight, but in most 

 cases the engine supplies itself from the casks, or the casks in 

 properly arranged engine houses are so placed that the oil runs 

 without any attention to the supply reservoir. 



The oil engine or most oil engines require occasional cleaning 

 out, but this does not take so long as the occasional cleaning out 

 of a boiler, and even if it did the saving in labour in other ways is 

 so great that the cleaning out work time is over and over again 

 saved. Some engines require more frequent attention to the 

 cleaning of the vapouriser and passages, in which carbon may 

 be deposited, than others, but regular attention avoids difficulties. 



Oil engines, like gas engines, are the modern development of 

 the hot-air engine. The oil is simply used as a means of 

 rapidly heating the air, compressed in the engine cylinder, to a 

 high temperature almost instantaneously. It is convenient from 

 a mechanical point of view, and for heat economy reasons, to 

 burn the oil thus rapidly in the working cylinder, directly with 

 the air to be heated and used as the working medium, rather 

 than to burn the oil as a fuel for indirectly heating the air. The 

 engines are thus known as internal combustion engines, as 

 distinguished from steam engines, for which the steam as the 

 working medium is generated by combustion of oil or other 

 fuel in a boiler and not in the engine cylinder. 



The oil is prepared for its ready combustion in the oil engine 

 cylinder by several different forms of vapourisers. In some, the 

 vapouriser consists simply of a chamber at the end of the 

 cylinder, into which the oil is injected in the form of a fine 

 spray under considerable pressure. 



The vapouriser chamber is at first heated by an exterior 

 heating lamp so as to convert the spray into a vapour, which 

 will ignite when the engine, by turning the fly-wheel, compresses 

 and heats a charge of air and vapour. Explosive combustion of 

 the hydrocarbon vapour taken up by the air then occurs, and 



