easily ionizable gas should speed op the movement of flame. The proton is practically a point molecule and on this nccount collisions between it and other niolecules will present unusn:il features. One of these feihres may be tire more ready conversion of molecular vibrational energy into kinetic energy.
Acknowledgment
The autlior is very much indebted to C. W. Johnson for collaboration in the esrlier experimental work on the carbon monoxide flame, iind to I?. Roffey for the experimental work roSerred to in this paper and for calculations of the composition of the gases a t the temperature of the flame.
Bunsen Flames of Unusual Structure' F r a n c i s A. Smith and Samuel F. Pickering 201 CHEIIISII(VDIVISION, BVRBAU011 STANDABDS, WASRINCTON, D.C .
An absh-act of a description, illustrated by laniern slides and autochromes, of unusualjame structures, the causes ,for which haw not yet been investigated.
A
MIXTURE of air or oxygen Tvith $1 coinl>nstiblc gas is forced through a burner tube, arid tlie fiiiint? is ohserved as it hums in secondary air.
Some examples of coniglcx structure observed
iii
acetyleiie-
:tir flirtnes are: four distinct zoiies oS coml?ustiou. the inter-
section of two zones: and n holluv dark curt' &ending up nard from tile tip of the priinary anile. When secondary air is excluded, tlie Iwiinwy combustion surface of some hydrocarbon-:iir flames 1m:omes polyhedral. F1:imes having three, four, five, six, and seven sides have been observed, which will rotate or remain stationary. The
primary zone or combustion'sarface presents t h e appearance shown inPigure 1 (5.31 per cent CaH,). It is perfectly stable and reproducible. The figure can be made t o rotate rapidly, slowly, or to remain stationary, depending upon the composition of the pa'; mixturc, to which it is very sensitive. Figure 2 (5.08 per cent C2H1in air) shows the primary cone with very little mantle. The mixture is almost as lean as it can
Figure 4 (13.23 peicent) shows thchollow mantle, most of the light cuming from its surface. Figure 5 (15.58 per cent) shows a second inner non-luminous zone. This zone has no well-defined bomdary except near the basc. It is larger at the base than the primary cone, the base of
~~
Figure I-Propane-Alr
number of sides is a funct,ion of the size OS t.lre hunrer tube and of the composition of the gas rnixtore. Burning in secondary air, the primary zone uf some propane-oxygeu flanlos heconies polyhedral, and luminous streamers rise from tlie t,ip and corners of the fignre, whicli can be made to rntate slowly, rapidly7 or remain stationary. Accurate and reproducible control of tile composition and rate of fiorv of the gas mixtures, and very steady stream line flow in the burner tubes have been attained. l'iiot,ograplu of t,he above flames are presented herewith. Using propane and air, when secondary air is excluded the L
the
Publicaliuii aimroved 1'y the IJirecto: oi i h c i i u r r i i o: St:tsdarrls d cominrrce.
u. s. 1,er>artinr,tt Of
2
a
4
5
~~.
In eigure 7 (l(i.GOper cent) thc third zone is distinct. Starting at the base of the primary cone, it occupics most of the second zone, intersects it, and extends outsidc it. The primary cone and the second and third inner zones are cach surroundcd by a sheath from which no light is comiug. These join a t their tips in a continuous dark streak which extends from the tip of the primary cone upward through the center of thc flame. Viewed from above, as shown in 1:igure 8, the streak is obviously a holiow, dark center and the slleaths appear as circler of darkness surrounding and separating the zones of light. In Figure 9 (17.73 per cent) the luminosity of zones 2 and 3 has increased, and the line of separation bas disappeared except at the base, where that portion of zom 2 not occupied by zone 3 is still noo-luminous. The dark core and the sheath surroundine mile 3 arc still prescnt. Zones 2 and 3 in Figure 10 (24.00 per cent) have increased in size and brilliance until they occupy nearly the entire volume of the Aame arid havc almost obscured the primary cone, but a scarcely perccptihie bluc mantle still envclops them completely. Figure 11 (44.75 per ctmt) shows the luminosity of all parts of the Rame greatiy rcduccd for lack of primary air. That which was the ijrimarv cone is now merely a iegioii OS brighter luminosity. Tbc blue maiitlr whicii
6 7 8 Figures 2 t o ~ t - ~ c e t y i e n e - ~ i r
I
D
10
11
Ih'D USTRIAL B N D BNGINEERING CHBMISTR Y
October, 1928
1013
can:be plainly seen at the sides is no longer continuous, and unburned carbon is escaping freely a t the top. Figure 12 is a luminous Rame of propane and oxygen (33.75
In Pig& 13 (33.40 per cent) the cone has.become a foursided figme, and the luminous zone has separated into four streams which rise from the dark ridges of t h e non-luminous miman zone. This view. fscinr one side. shows t h e dark iidges -from which no 1iaht is &in%, the figure cdsisting mcrely of four disconnected sides.
13
15
14
C16
Figures 12 to 17-Ropane-OrY*en
17
smaller, forming an apparently continuous nng at the base and extending upward like the sides of a cup.
The Flicker of Luminous Flames D. S . C b m b e r l i n a n d A. Rose' LES~OH
u~rvsnszrv.8 e m L * m s m . PA.
The vibratory motion of luminous flames has been studied by t h e photographic method. The rate of vibration, speed of flame, movement, and amplitude of vibration have been determined for various gases under differe n t conditions. The data show t h a t the upper portion of the luminous zone rises to a maximum height ten times per second. This rate of vibration is not greatly affected by change in conditions. T h e lower portion of the flame has a continuous existence, b u t periodically gives off another flame, which rises above the main flame during its short period of existence.
ditions are quite dificrent from those of a free flame burning from an orifice of any kind, and it is questionable whether the two sets of phenomena are related. Since no explanation of this behavior of free flames wm evident, a closer study was made. The photographic method was used, by means of which pictures were taken at the rate of 32 per second and developed and studied by projecting the image of the film. The results sliorved that the flicker CODsisted of a regular upand-down movement of the middle and upper portions of tlie flame while the lower portion remsined quite steady, and that the downward movement is extremely rapid if the flame exists at all during this stage. The upward movement is approximately that of the Bane speed of the gas mixture probably present iU the flame, and the rate of vibration for tlie flames of all t.he gases investigated is of the order of 10 per second. This rate is not greatly affected by the at,mosphere in which the flame bums or by the tip from which the gas issues, or by the rate of flow of the gas. Furthermore, there is only one way in wllich the flicker can be stopped and that is by inserting a plate or similar object into tlie flame a t or below 9 definite point in the flame structure. This destroys the upper part of the flame structure snd, therefore, eliminates the flicker.
BSERVATIOS of a luminous Bunsen flanie shows that the flame is not in a steady state at any time, but that there is considerable motion, especially in the upper part. This is apparently true of all flames burning w-ithout primary air, from any tip or opening. Although a large amount of work has been done on the phenomena of flames in general, there has been almost 110 study of this vibratory nature of most flames.z It has been noted in flame-speed studies that the flame does not travel wit21 uniform motion but with periodic increases and decreases of speed.s In some cases the flame travels alternately forward and backward, the backward Materials movement being the slower. However, all such observations have been made in tubes having one end closed and which The gases whose flames were studied were natural gas, were completely filled with a mixture of combustible gas and oxygen or air a t tlie start of the experiment. These con- hydrogen, carbm monoxide, ethylene, methyl chloride, hutane, ethane, and hydrogen sulfide. All cxcept carhon monI Columbian Carbon Fdioa. oxide were obtained in cylinders under pressure and were prac9 Cos Agr-KeCord. 67 (1926). tieally pure. The carbon monoxide was prepared by dropping *Bone nnd Tobwoeod, "Plame and Combustion ill Gases," Longmanr. Gr& company. formic acid into hot sulfuric acid, The natural gas had the
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