A sehlieren system for photographing the inner cone in bunsen flames used in burning t'elocily mea.~uremerits is described. A useful matjnification factor of 20 to 25 times measured from the b~trning co~e to its photograph is obtainable : so the system can be used with the small b~trner.~" needed for s.ch fast burning flames as those of hydrogen-oxygen mixtures. Some resalts for b!Idrogele oxygen and hydrogen-air flames are given which accord will+ John's values at the lean end, though tire res~dt.~' for the richer hydrogen-ox!lgen mixtures agree with the higher vab.tes determil+ed by B,irthotom~ ~.
A SEARCH through the literature for burning w,locity measurements of hydrogen, carbon mc,noxide, methane, ethylene and propane mix,.d with air or oxygen gave 67 separate determinations (see ref. 1). Of these only 14 rcl;,ted to mixtures containing oxygen and only 8 rdated to mixtures containing hydrogen. The reason for the scarcity of measurements on mixtures containing oxygen or hydrogen derives in part from their high burning velocity which lt'ads to experimental difficulty whatever method at measurement is used.
In measurements based on the inner cones in bu~sen flames, for example, the difficulty lies in the need to use burning tubes of a very small di:~meter in order to preserve laminar flow at th,. high flow rates required to prevent flash-b~,k. Thus, for hydrogen-oxygen mixtures ar ~und stoichiometric, the tube diameter cannot e.~,,~ed 1 mm, though E. BAR'I'LtOLOMa z has su 'ceeded in increasing this somewhat by means ,~t , specially shaped nozzle. With such small bt ~wrs, accurate measurement of the burning c~: ,. is impossible unless very good optical ar :,ngements are employed.
,I,, need was clear, however, for further data o~ ~ydrogen-air and particularly on hydrogen-c~:_.~,,en ttames and attention was therefore given to producing an optical system which would "F, ~mcrl~, of Admiralty