28 



Prof. W. M. Thornton on the 



to the decrease in the number of combustible units from their 

 maximum at P, the point o£ perfect combustion. 



Fig. 5. 



PQ represents to a certain scale the maximum velocity of 

 explosion ; the ordinates of LQ, QU the velocities of 

 explosion as the percentage of gas is increased from 

 the lower to the upper limit of inflammability. 



(6) Influence of initial compression on the efficiency 

 of explosion. 



The expression for the efficiency may be also used to show 

 how compression improves the efficiency of combustion. 



Other conditions remaining the same, doubling the 

 pressure doubles the number of combustible units in a given 

 volume. This is represented in fig. 6 by extending the 

 upper limit. OUi is the upper limit at atmospheric pressure, 

 OU 2 at two atmospheres, OU 3 at three, and so on. The 

 lines corresponding to CD in fig. 2 are CUi, CU 2 , CUs.... 



It is well known that mixtures which are so weak that they 

 cannot be ignited at atmospheric pressure are inflammable 

 when compressed, so that N at the lower limit does not 



