1015] 



on Gaseous Explosions 



287 



trip gear was operated, keeping the engine running at the same 

 speed and taking exactly the same charge, and the ignition was 

 arranged to take place on the third compression instead of the first. 

 Two complete additional revolutions thus intervened between the 

 state of turbulence during ordinary ignition and the state at the 

 experimental ignition. It was then found that the diagrams showed 

 the time of rise of temperature from the beginning of the rise leaving 

 the compression line to the maximum temperature was from 2*2 

 to 2*8 times that of the ordinary temperature rise in the usual 

 running of the engine. The appearance of the indicator cards show 

 in a marked manner the great difference in ignition rate caused 

 by allowing the turbulence of ignition to die down. 



Fig. 17. — Tuebulence. 



Mixture of one volume of coal gas and 9 • 3 volume of air and other 

 gases ignited by side igniter of engine. Line A to B indicates ignition 

 of charge fired upon first compression stroke, which takes 0-033 second. 

 Line A' to B' indicates ignition of charge fired upon third compression 

 stroke, which takes 0'078 second. 



Figs. 16 and 17 show diagrams taken in this manner, and it is 

 very clear that in this engine, were it not for the increased rate of 

 flame propagation due to charge turbulence, economical running at 

 the usual speed of 180 to 200 revolutions would be impossible. In 

 these turbulence experiments the time taken is not what has been 

 previously called the time of explosion as determined by maximum 

 pressure within the engine, but the time to attain maximum tempera- 

 ture, which in the case of the trapped charges, as will be seen, occurs 

 well on in the stroke. In ordinary engine running it is better to 



u 2 



