28G 



Mr. Dugald Clerk 



[Jan. i^U, 



admission and compression under full load with the engine hot, in the 

 ordinary manner of working a four-cycle engine, with the rate of 

 inflammation after the charge had l)een compressed and expanded 

 several times before ignition. The idea was that turbulence was 

 caused within the cylinder by admission of the charge at a high 

 velocity through the inlet valve, and that this turbulence persisted 

 during the compression stroke, so that in the ordinary running of the 

 engine the flame was projected into a moving mass of gas, and so the 

 flame velocity was much more rapid than if the charge had been 

 still. The alternate compression and expansion before ignition was 

 intended to allow the turbulence to subside, so that ignition started 

 in a still mass of gaseous mixture and not in a moving one. The 



Fig. 16. — Turbulence. 



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

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

 of charge, fired upon first compression stroke, which takes "037 second. 

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

 stroke, which takes 0*092 second. 



experiments prove that inflammation at the end of the third com- 

 pression stroke took 2 • 5 times the period of the ordinary Otto cycle 

 explosion. From Fig. 13 it will be seen that the engine was fitted 

 with two electrical igniters, one in the cover above the charge inlet 

 valve and the other in the side of the combustion space near the 

 piston. Tests were made using these igniters alternately. To try 

 the experiment the engine was first run at full load till the water 

 jacket, piston, and other parts had become hot. Diagrams were then 

 taken under load of the ordinary Otto cycle explosions. Then the 



