HUMPHREY INTERNAL-COMBUSTION PUMP 267 



through the valve a or such scavenging air and combustible 

 mixture may with advantage be supplied under sufficient 

 pressure so that some of the burnt products may be positively 

 scavenged out from the combustion chamber ; the remain- 

 ing products may be swept out when the liquid returns under 

 the head or pressure to which it has been raised and rising 

 from the level gg reaches the exhaust valves e, shuts them 

 and by the virtue of its momentum continues its movement 

 upwards and compresses the combustible charge contained 

 in b ready for a fresh ignition to start a new cycle. We 

 have thus only one out-stroke and one in-stroke of the liquid 

 column for each cycle of operations. 



A 



I G 



1L 



Fig. 4. 



We will now take the simplest case of a pump having a suction 

 lift, as illustrated in fig. 4, in which the cycle is as follows : 



1. Explosion of compressed combustible charge in a, driving 

 water to high level tank k, continuation of expansion stroke 

 below atmospheric pressure owing to the existence of non-return 

 valve in exhaust pipe ; consequent lowering of pressure till 

 water is raised from low level tank h, past valve g, until water 

 comes to rest and valve g shuts. 



2. Return movement of water column towards chamber a, 

 giving exhaust and cushion stroke. 



3. Cushion expansion and intake of a measured combustible 

 charge into a and expansion of this charge below atmospheric 

 pressure. 



