﻿104 Messrs. H. T. Tizard and D. R. Pye on the 



XL If the value for the temperature coefficient so deduced 

 is correct, it should be possible to use it to calculate the 

 higher ignition temperature when the fan is used, and also 

 the shape of the new delay curve. 



Now, the mean cooling factor with the fan has been shown 

 to be 1*4-2. The ignition temperature under these conditions 

 is evidently about 310° C. (see Table V.), the temperature 

 of the walls being 60° C. Hence the ratio of the rate of 

 loss of heat with and without fan at the respective ignition 

 temperatures is — 



Qo' _ 1'42 (310-60) 

 Qo" 



= 2-90. 



0-51(280-40) 



Hence the new (theoretical) ignition temperature T ' (with 

 fan) should be given by (see equation (8)) — 



lo g ^ = lo g 2-90=|- o (l-|) = 

 = 10 ( 1 -|) 



e. 0-462 



or 



Jr = 0-954. 



T ' = 580 = 307° C. 

 This is close to the observed value. 



tv, , J 6 .„ . 5530 



Ine new value ot ™ will be "~^J7T 



9' 5 ; while the value 



of 



(T o '-0\ 1*42x247 



\ T ' ) 



= 0-60. 



T ' / ~ 580 

 The corresponding theoretical values of the delay are 

 shown in the following table. 



Table VII. 



Ignition of heptane by air. Fan full speed. 



Ignition temperature calculated from previous results, 580° C. 



b_ 



To' 



= 9-5. 



T/T . 



T. 



*°C. 



« 1 m , ) t (theor.). 



t fcalc.). 



1-004 



582 



309 



012 



0-20 sec. 



1-01 



586 



313 



008 



0-13 



1-03 



597 



324 



0-04 



0-07 



1-07 



621 



348 



0-016 



0027 



111 



644 



371 



0-0076 



0-013 



