﻿Ignition of Gases by Sudden Compression. 85 



Experiments on Air Leakage from the Cylinder. 



Observations were made of the rate of fall of pressure 

 beginning 10 seconds after compression had occurred. By 

 this time all pressure-fall due to heat-loss has ceased, and the 

 observed fall represents leakage only. 



Experiments were made — 



(a) With fan stationary. Compression ratio 9 : 1. 



Contents of cylinder were the products of com- 

 bustion of a benzene and air mixture. 



rp. Deflexion on Indicator 

 e * Screen. 



10 sees, after compression and combustion 063 inches. 



20 „ „ „ 0-61 „ 



30 „ „ „ 0-57 „ 



45 „ „ „ 0-56 „ 



60 „ „ „ 0-53 „ 



The indicator calibration was 1 inch deflexion = 188 lb. 

 per sq. in., so that the above gives a rate of fall of 



0-1 X 188 >aftll 



— = -5b lb. per sq. in. per sec. 



(b) With fan rotating at full speed, 2000 r.p.m. Com- 



pression ratio 10 : 1. Contents of cylinder pure 

 hydrogen. 



m . Deflexion on Indicator 



Time. c 



Screen. 



10 sees, after compression 066 inches. 



20 „ „ 053 „ 



30 „ „ 0-40 „ 



This, owing to the low viscosity of hydrogen and the high 

 compression ratio, was a very severe test. The rate of fall was 



'26 x 188 AK „ . xt ■ .u- 



— r = 2*45 lb. per sq. in. per sec. JNow in this expe- 



riment the rate of fall of pressure due to cooling was as high 

 as 600 lb. per sq. inch per second immediately after com- 

 pression, so that the effect of. gas leakage on the apparent 

 rate of cooling was clearly negligible. 



The Indicator. 



It will be convenient at this point, before going on to 

 describe the timing apparatus, to give some further data as 

 to the indicator used. As stated above, this was of the 



