1907.] 



on Flame in Gas and Petrol Motors. 



513 



indicator diagrams reseml)ling the coiisttmt volume diagram shown 

 upon the wall. I show an actual diagram from an enghie like this 

 upon the screen. These diagrams give information as to the time of 

 ignition, the work done, and the compression and expansion lines 

 followed by the charge within the cylinder. Such diagrams, how- 

 ever, do not give any information as to the rate of heat loss through 

 the sides of the cylinder, or the specific heat of the high temperature 

 charge undergoing expansion. By modifying the action of the 

 engine, however, it is possible to get information of this nature. 

 By altering the valve arrangements, so that w^hen desired both charge 

 inlet valve and exhaust valve can be held closed, I was able to get 

 diagrams from which a cooling curve could be calculated. One 

 of these diagrams is shown at Fig. 6. It will be seen that when 



Fig. 6. 



the exhaust period approaches, instead of exhaust discharge at the 

 proper point, no gases escape from the cylinder. The piston 

 accordingly compresses the whole contents of the cyKnder into the 

 compression space, and the temperature which has fallen by expan- 

 sion, rises by compression. A point is touched on a vertical line from 

 the end of the card. On expanding, a line below the first compres- 

 sion line is traced, then another compression line is obtained, and so 

 on, a series of compression and expansion lines are obtained, each 

 terminating under compression at certain specific points. It Avill be 

 observed that before the ordinary compression line of the engine is 

 reached in the diagram shown, there are six of those points. If no 

 cooling existed in the cylinder, obviously whenever the volume was 

 restored to the original point, no fall of temperature would be visible. 

 YOL. XYIII. (No. 101) 2 L 



