DURAND— MECHANICAL ASPECTS. 179 



tion, the importance of this phase of the problem is apparent with- 

 out further emphasis. 



The best of present carburetors reahze these conditions in high 

 degree. The principal points still open for improvement are perhaps 

 the following : 



1. Improved means for atomizing the liquid fuel, looking espe- 

 cially toward the finest attainable degree of subdivision. This will 

 aid both economy and reliability. 



2. Improved means for covering a wide range of atmospheric 

 conditions as regards density, temperature and humidity, and with 

 a wide range of power developed under any combination of these 

 conditions. 



3. Improved means for atomizing the gasoline with the minimum 

 drop in pressure through the carburetor. This will aid in decreas- 

 ing the back pressure and will increase the net power developed per 

 cycle. 



Improvement in the carburetor is primarily dependant on experi- 

 ence. The interaction of the various controlling factors is so com- 

 plex in character that cut and try methods based on the intelligent 

 application of underlying principles seem to promise the most 

 fruitful results in the improvement of this element of the internal 

 combustion prime mover. The field is open and we may look con- 

 fidently to the future to provide a standard form of carburetor 

 which will secure the highest practicable results over the widest 

 range of operating conditions. 



We turn next to the thermodynamic aspect of the problem. 



Under this head I shall only refer briefly to the character of 

 thermodynamic cycle employed. As well known, the cycle at present 

 universally employed is that based on the constant volume — adia- 

 batic ideal. There remain open the constant pressure-adiabatic 

 cycle and the constant temperature-adiabatic or Carnot cycle, or 

 some combination of these. 



The Diesel engine uses a cycle more or less intermediate between 

 the latter two. 



The constant pressure-adiabatic cycle has long been the ideal 

 of engineers with special reference to sustained crank efifort and 

 the elimination of the explosive shock characteristic of the constant 



