INDUSTRIAL AND ENGINEERING CHEMISTRY
672
TABLE
LEAD RESPONSE OF
V.
SYNTHETIC CRACKED
Comooaition. 00.: Stmight-run gaaoline Crcloherene Trimethylethylene 2-Pente"e
2700
inn
200 200 IOU 2w
Eeene
Triisobutene n-Heptane
1W 250
Sp. ai. a t OOo F. (15.6' C . ) Sulfur. %. Bromine ' i o . Distillstion.
'C.
nietiiintion, 0
GASOLINE
0.718 Tieas than 0.01 34
c.
Diatlllation,
* C.
VOL. 28, NO. 6
Attempts to prepare sulfur-free cracked gasoline were not successful, and it was decided to employ instead a synthetic product. This was obtained by blending various olefins which happened to be avaaable in the laboratory with desulfurized straight-run gasoline. The octane number of the blend was 68.5 and it was therefore reduced to 65 by the addition of n-heptane, thus making direct comparison with straight-run fuels possible. The composition and characteristics of this synthetic cracked gasoline are given in Table V and Figure 7. The figuresfor a typical refined cracked Iranian gasoline and Venezuelan straight-run gasoline are included for comparison.
Acknowledgment The autliors are indebted to the chairman of the AngloIranian Oil Company Limited for permission to publish this paper. Sulfur Treatment Synthetic orsoked gesoiine Same 0.1 8 ae EtSH same 0 . 1 8 s =s E ~ S *
+ +
Irsnian craoked gaeoline
0
C 06 64.8
04.8
I 74.370.9
69.5
64.5 71 Vsneiuelanatraight-run w m l i n e 04.4 73.8 1.5 CC. tetraethylled produced &a octane numbcr of 76.4.
3 80.2 76.8 74.8
77 82.3
Literature Cited (1) Birch and Norria, IND.ENG.Camx., 21, 1089 (1929). (2) Hebl, Rendel, and Gsrton. Ihid.; 25, 191 (1933). (3) Norria and Joubert. J . Am. Chem. Soc.. 49, 873 (1927). (4) Tonpborg, C . O.,Pickens, J. D.. Fenske, M. R., and Whitmore, F. C..Ibid., 54. 3706 (1932). HecEmEn January 10, 1930
High-speed Motion Pictures of Engine Flames M. RASSWEILER AND LLOYD WITHROW General Motom Corporation, Detroit, Mich.
S A PART of a general investigation of the physical and chemical aspects of the combustion process within a gasoline engine, previous results of which have appeared from time to Oime in the pages of INDUS%>RIAL AND ENGINEERING CHEMISTEY, a high-speed motion picture camera was constructed which photographs the ignition spark, the subsequent flanie propagation throughout the combustion chamber, and the hehavior of the luminous gases during the early part of the expansion stroke. This equipnient is now being used to study the velocity of flame motion, the changing shape and sfructure of the flame fronts, the mass movements of the gases, the relationship between flame travel and pressure rise, and the beliavior of the flame a t the time of knock. Some information ahout these characteristics of the combustion process has already been obtained in gasoline engines by other methods, such as the analysis of gas samples removed from the cornbustion chamher by special quick acting sampling valves (3, f5), the photography of tiedisplacement records of Aaine motion together with pressure-time diagrams of single explosions (8, 10, fS, 14, 16), visual and photographic observations through small windows in the top of an engine (4,6, ?'), and observations of the ionization a t various pointsin thecombustion chamber (8, 9, 18). But the present apparatus yields information not obtainable by other methods, particularly with regard
JUNE, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
to the shape and structureof the flame fronts a n d t h e n a t u r e of knock. This paper describes the engine and camera and illustrates the nature of the data o b t a i n e d with them.
The Engine
across the c o m b u s t i o n chamber, a distance of 5 inches, in about 0.004 second with the engine running at 2000 r. p. m. Since at least twenty pictures are desired during this 0.004second interval, it is necessary to make exposures at a minimum rate of five thousand per second at this engine speed. However, the flame speed decreases with the engine speed with the result that lower picture frequencies are acceptable at lower engine speeds. With the engine running 400 r. p. m., for example approximately twenty pictures o! the flame propagation can be obtained with a p i c t u r e f r e q u e n c y of one t h o u s a n d per second. For such picture speeds the tensile strength of the film does not permit intermittent film motion; thus, the film must be moved continuously. It is obvious that, if s h a r p p i c t u r e s a r e t o be obtained with continuous film movement, either the time of exposure must be very short or the ima e to be recorded must be moved with the film. The choice between theae two alternatives is determined by the intensity of the light emitted by the engine flames. 3. The available light is fixed b the engine conditions and the fuel and cannot be i n c r e a s e d a t will. Earfier experiments showed that a well-exposed negative results if each point on a typical time-displacement record is exposed for approximately 0.0002 second with a n F 1.6 lens using h persensitive panchromatic film. dnsequently, the light emitted by. the engine flames sufEces for five t h o u s a n d pictures per second provided the duration of the exposure can be made comparable to the time interval between pictures and prov i d e d t h e l e n s s p e e d is F 1.5 or greater during all or during the major portion of the exposure. If the duration of the exposure is to be comparable to the time between pictures, and the film is to be moved continuously, it is necessary to move the image with the film durin the exposure. Various means o f “0 tical equalization” have been use$ (IC, d, g, h, i, 3, 0, 9, r, t, u, VI, but the method suggested by Wedmore (10) seemed most readilv adaDtable to the - present problem. 4 The optical system should produce the maximum photographic effect with a minimum exposure time. Since the luminosity of the flames is fixed by engine conditions, the photo raphic exposure (exposure time multi lied by li ht intensity falfing on the a m ) can be controlled onfy by the fens speed and the exposure time. As the exposure time increases, the blurring of the image caused by gas and flame movements increases; hence, it is necessary to use minimum exposure times. It follows then that the lens speed should be kept at its maximum value during the entire exposure of each frame. This type of operation is a p proximated with a focal-plane shutter. Furthermore, the duration of the exposure should be adjustable because of the fact that the luminosity of the flames varies with engine conditions. 5 . The picture should not be so small that details of flame structure are lost. A standard 16-mm. frame was chosen as the minimum desirable picture size. Using this picture size and photographing five thousand pictures per second means that the minimum film speed must be approximately 38 meters per second. When a film is wound from one spool to another at this speed, difficulties arise from friction, breakage, scratching, and static, but fortunately these difficulties may be largely avoided by mounting the film inside a drum. 6. To make full use of the flame pictures, it is necessary to know the angular position of the crankshaft while each picture is being taken, as well as the gas pressure in the combustion chamber at that same angle and in the same explosion. For this
To record the phenomena occurring within the combustion space of an operating gasoline e n g i n e , a special m o t i o n picture camera was constructed which utilizes continuous film and image motion synchronized by m e a n s of thirty lenses carried in a disk mounted on t h e engine crankshaft. Pictures which present an unobstructed view of the entire combustion chamber were obtained by solving the problem of mounting a large quartz plate in the cylinder head. The camera photographs thirty pictures of a single explosion at rates up to five t h o u s a n d pictures per second. At the same time a pressure-time curve of the explosion is recorded. A set of flame pictures photographed with this apparatus and presented here shows the i g n i t i o n spark, the spread of the flame through the combustion chamber, gas movements behind the flame front, and an increase in luminosity of the burned gases near the spark plug as the explosion process proceeds and the pressure rises.
The camera was built around a specially designed, single-cylinder, ell-head engine with a 2 ‘/s-inch bore, a 43/4-inch stroke, and a compression ratio of 4.6 to 1. The unique feature of this engine (Figure 1) is a window which allows a n unobstructed view of the whole combustion chamber. Through the window can be seen the edge of the cylinder barrel, the two valves, and the spark plug terminals which are incorporated in a carbon stack indicator developed by Martin and Caris (6). The window is a fused quartz plate, 51/4 X 4 X 8/4inch, and is cemented into an invar frame clamped to the top of the cylinder block. Although the two clamps facilitate the removal of the window for cleaning, the engine can be operated for a day or more under proper conditions without an appreciable deposit collecting on the quartz. Even under conditions of moderate knock the window withstands gas pressures which rise to a maximum of about 400 pounds per square inch (a total force on the unsupported area of the window of approximately 5000 pounds) and instantaneous gas temperatures of a p p r o x i m a t e l y 4500” F. (11). Two years of experimentation witah this engine have not been entirely free from casualties to windows, but most of the difficulty can be attributed to strains introduced in clamping the windows and to warping of the cylinder block as the engine heats and cools.
Camera Requisites I n planning the camera, the known characteristics of the engine combustion process, as determined from visual and photographic observations in a somewhat similar engine, were considered in connection with the design and operation of some of the high-speed motion picture equipment described in the literature (1). Careful consideration of 6he following aspects of the photographic problem showed that many of these cameras would be wholly unsuited for the photography of engine flames and pointed the way to the design finally adopted : 1. The object t o be photographed is self-luminous; that is, the light is emitted by the flames themselves. This fact imposes a severe limitation in the camera design. It is obvious that any camera which depends for its action on intermittent illumination of the object by sparks (la, b, d, n, s), discharge tubes ( l e , f ) ,or other means is not suitable. 2. Owing to the rapid motion of the flame, the picture frequency must be extremely high. After ignition, the flame moves
673
614
Ignition breaker B . Intske port C. Exhauvt port D. Combustion oharnhi E. Spark plqg hole F . Quarts windor C. Invai window frhine N. steliite mirror r. stationary fieid tenc J. LPlrr atop A.
INDUSTRIAL AND ENGINEERING CHEMISTRY
K . Shutter L. Rotatinv diak M. M0"l"p: lene N. m i m 0. Food plane siiuttei P. Film '2. noor in light-tight housing R. Cam ioilowei sctusting shutter S. Shutter czwn T. Crankshsit
VOI.. ?R. NO. 6
The moving lenses are F 2 iuot.ion picture camera ohjectives purchased from the Eastman Kodak Company. The focal lengths are closely matched, but slight differences can be compensated by individual adjustment of the position of each lens in the large disk. The lenses are spaced 2.4 crankshaft degrees apart; hence, five thousand pictures per second are secured with the engine running a t 2wO r. p. m. The disk carrying the lenses is fastened to the crankshaft by means of two heavy flanges which form a hub for the large disk. The flanges are keyed to the shaft and are clamped together with a nut as shown in Figure 2. This direct connection between the crankshaft and disk permits accurate measurement of the crankshaft angle a t which each picture is exposed and a t the same time permits adjustment so that any desired portion of the cycle can be photographed. The pictures are taken on regular 16mm. moving picture film which is threaded through a guide just inside the nverhanging rim of the disk. The film is held against this rim by centrifugal force when the disk is in motion. In order to facilitate the replacing of exposed with unexposed film, the disk is equipped with a take-up spool, Rr (Figure 3), a supply spool (not visible in the photograph), and a metering device, V , which allows only the length of film equal to the distance between spools to be pulled through a t one time. The spacing of the leuses on the disk gives image spacings very different from the conventional. Renee, in order to prnject the flame photographs as motion pictures, i t is necessary to copy the negatives in a special print.ing device by means of which each image can be framed separately. Such a printer has becu built and will be described in another paper. IIIorder that a series of snapshot pictures and a pressure record can be obtained simultaneously during a single engine explosion, a shut,ter, K , is provided, which can be opened for one engine cycle hy means of a cylindrical cam, S. Shutter R is connected electrically in series with the shutter of the nscillograph which records the pressure. Thus, when the mechanical shutter in the camera is tripped, a series of pictures of the flame movements is obtained, and a record of the pres-
reason it neeined dcsictble to attitoh the moving parts of the camera. directly to the crankshaft of the engine. 7. Simplicity of construction is an important consideration and need not be dwelled upon at length.
Description of Camera Figures 2 and 3 illustrate the essential parts of the camera mounted in position on the engine. These two views of the apparatus are from opposite sides of the engine, but corresponding parts are readily recognizable. Light from the combustion chamber, D,passes through t~hewindow, F , and is reflected by the stellite mirror, H , into a stationary field lens, I (a Zeiss Tessar). The principal plane of lens I lies in the combustion chamber. The beam of parallel rays formed by stationary lens I passes through each of a series of small lenscs, M ,as they are moved through this beam by a large circular disk attached to the crankshaft and rotated in a plane perpendicu1a.r to that of the paper. Light from the series of lenses, M ,is rcflected by a corresponding series of right-angled prisms, N , also mounted upon the disk and located one behind each lens as shown in Figure 2. Images of the flames inside combustion chamber D are formed upon a film, P , which is held against the inside surface of a rim on the disk. With such a system, the image of a stationary object in the combustion chamber remains a t rest with respect to the film (except for a slight relative twisting motion) despite the motion of the small lenws. As each of the thirty small lens= in turn passes the field lens, a separate picture of the flame is secured. The duration of the exposure of each picture is controlled by varying the width of a stationary aperture a t 0 which is close to the film and acts as a focal-plane shutter.
FIQWRE 3. CAMBRA ASSEMBLEDnx THE ENGINE (i.
IT.
I.
0.
R.
W i d o w retainer Mirror
Field leas Focsl plane slnrtter Shutter
'W.
xoving lem
V.
Metenng syrooket
L. Rotatpg disk
R.
Tnke-up s ~ o o i
INDUSTRIAL AND ENGINEEHIYC CHEMISYR \i
JUNE. 1936
sures is registered during one and the same explosion. By means of two reference marks, automatically placed upon the pressure card a t the time of ignition and GO" after ignit.ion, each individual snapshot can be correlated with the corresponding time interval on the pressure record. There are several merits in the camera just described from the viewpoint of simplicity of construction: (1) The lenses and film are moved together and may therefore be attached rigidly to the same moving member. (2) During exposure, the film does not have to he moved with a high velocity from one spool to another. (3) The quality of the focus is controlled, first, by the distance between the stationary field lens and the object and, secondly, by the distance between the moving lenses and film. As a result, small displacements of the moving parts with respect to the stationary parts do not throw the system out of focus. (4) There is no possibility for lost mot,ion in the mechanical linkage between the engine and camera.
Camera Performance OPTICAL EQUALIZATION. Wedmore ( I v ) pointed out that although his method gives accurate synchronization of linear film and image motions, there is a rotation, about the optic axis, of the film with respect to the image as each picture is taken. The blurring due to this rotation varies from zero at the center of the picture to a maximum at the comers, and the magnitude of the effect depends upon the angle through which the disk turns during the exposure of the picture. T o study this phenomenon experimentally with the camera just d e scribed, a piece of cross-section paper was placed in the combustion chamber and four sets of pictures were taken, three sets with different focal-plane shutter openinm, and one set with the shutter removed-and the exposuie limited to approdmately 7" by the diameter of the field lens. While the pictures were being taken, the engine was driven by the dynamometer a t 800 r. p. m. so that the camera action was precisely the same as when photographing flame pictures a t a rate of two thousand per second. One picture from each set is shown in Figure 4. The opening of the focal-plane shutter is given in terms of the approximate angle subtended a t the center of the crankshaft by the opening. The picture taken with a l o shutter shows no appreciable blurring due to rotation and illustrates the character of the focus and the freedom from relative linear motion of film and image. With a 2" shutter the blurring is still slight even though this shutter opening is comparable to the angular interval between pictures (2.4'). The remaining two photographs in Figure 4 show the increased blurring due to rotation as the duration of the exposure is further increased. SHUTTERACTION. When the separate photographs o f a sequence of motion pictures are to be examined individually, data showing the operation of the shutter and the time of exposure of each portion of every frame are necessary, particularly if values of velocities and accelerations of moving park3 of the subject are desired. Information of this type based on an engine speed of 2000 r. p. m., a picture frequency of five thousand per second, and a focal-plane shutter opening of 2.2 cra.nkshaft degrees follows: Time Crankshaft Factor
Mil& seconds
Ti"
Degrees 2.4
T8
2.2
0.18
TP
2.0
0.17
0.20
Time Crankshaft Faotor Decess T+d 0.17 Z'# 0.8
* Time from the beginning of the eapoeure of
Milliseconds 0.0014 0.06
a given point on one pioture until the beginning of the exposure of the asme point on the next picture. * Time from the beginning of the exposure of a point at the oenter of the picture to the end of the expo~umof that point. This value is controlled by the opening in the focal-plane shutter. a Time thst a point st the oenter of tho picture would have to be
FIQIJRE 4. IMAQESOF WITH
EXPOSUHE
CROSS-SECTION PAPER OBTAINED 1, 2, 3, AND 7 CRANKSRAPT
TIMES OB'
DEQREES
-____
sawsed at full aperture in order to obtain t.ho same photographic effect as is obtained during time 'Ts (aasuruine that the reeiprooity law holds for the photogrsphio emulsion). Under ideal oonditions, if tho lens eystem were working at full apert,ure during tho whole exposure. T2would egud Tz, This condition is closely approaohed. Time required for the light intensity at B given point on the film to drop from its full d u e to zero 88 that point on the film move* past tho edge of the focal-plane shut,tor. In 0.17" the flame moves only about 0.02 inch. *Time between the completion of the cxpo~ureof a point at one end of the oomhuustiun ohsinbor and the completion of the exposure of B point nt the other end. If Ts is large. there will be distortion in the curvature of the flame fronts. In 0.So, however, the flarnsa m n ~ only e about 0.1 inch; hence with the present camera the dietartion offlame ehapes from this c m 8 e is not appreciable.
SAMPLE FLAMEP I ~ U R E Figure . 5 show a complete set of flame pictures obtained a t a rate of five thousand per second while the engine was operated at 2000 r. p. m. Enough light was thrown down on top of the enginc to outline the oombustion chamber and to show dimly the valves and piston. The spark appears in frames 2 to 5. On the original negative the flame can first be discerned in frame 4. Thereafter the progress of the flame and the changing shapo of its envelope can readily be followed to the end of flame propagation in frames 21 to 25. Figure G shows a pressure record of the same explosion pertrayed in Figure 5. Each vertical line denotes the time at which the frame of corresponding number was exposed. The significance of these and other pictures will be discussed in another paper. Summary A transparent quartz plate mounted on a gasoline engine affords an unobstructed piew of the whole combustion chamher. To study the combustion process in this engine, a special
INDUSTRIAL AND ENGINEERING CHEMISTRY
676
VOL. 28, NO. 6
1 to
5
6 10
10
11 10
16
18
to 20
ai 10
26
20
to
30
FIonaE 5.
F t A M E PICTURES OF A SINGLE ENOINE
EXFLOSSON PHOI'OGF.APHED
AT TUE R4TE OF FWE
ma SECOND
camera photographs about thirty pictures of a single explosion a t rates up to five thousand per second. The high picture frequency and the limited light intensity of the flames make it necessary to move the film continuously and to synchronizethe film and image motions during the exposure of each picture. The method adapted to this purpose, originally suggested by Wedmore ( f v ) , has the following merits: (1) The synchrouil;atiou of linear 6hn and image motions is accurate and the relative twisting is slight for exposure times required for engine flame photography. (2) The method lends itself to a simde and mazed mechanical arrangement mhich is easilv bnik into the engine. The incorporation of a focal-plane shutter gives the camera characteristics which are particularly snitable for the problem a t hand: (1) The duration of the exposure can he adjusted from zero to three times the interval between pictures without decreasing the effective speed of the optical system. (2) The moving lenses work a t full aperture during most of the exponure, giving a maximum photographic effect in a given exposure time. When flame pictures photographed with this camera a t a rate of five thousand per second are projected as ordmary moving pictures, the flame motions are slowed down over two hundred times.
THOUSAND
~
Acknowledgment Many members of the staff of General Motors Research Lahoratory participated in the construction and development of the camera described. To them the writers take this o g portunity to express their sincere thanks. In particular they acknowledge the valuable contributions to the design of the
1
0
11
10
'rims
21
26
FIQUEE6. Pa~asnarmRSCORD OP TEE EXPLOSION SHOWN IN FIouaE 5
engine, camera, and printer, respectively, by H. H. Love, C. J. Kinsey, and V. C. Smith.
Literature Cited (1)
(0)
Abraham. E., Bloch. E., and Bloch. L., Corn@. rend.. 169, 1031 (1919); (b) Beardsley, E. G.. Tram. Am. Soo. Me&. Ewrs.. oil Gas Power. SO, 3 (1927); NaW. Advisory Comm. Aeronaut., Rep Jenkins, C. F., Trans. SOC. Motion Picture Engrs., No. 17. 77 (1923); No.25,25 (1926); J . SOC.Automotive Eng., 22, 200 (1928); (j) Klemin, A., Mech. Eng., 50. 217 (1928); (IC) Legg, J. W., Elec. J., 16,509 (1919); (2) Lindner, W., 2. Ver. deut. Ing., 74, 186 (1930); (m) Linke, H.. Filmtech., 8, 2 (1932); (n) Magnan, A,, and Magnan, C., Compt. rend., 198, 635 (1934); ( 0 ) Ohnesorge, W. V., 2. tech. Physik, 13, No. 7, 299; 13,No. 8,345 (1932); ( p ) Sass, F., “Knmpressorlose Dieselmachinen,” p. 64, Berlin, Julius Springer, 1929; (Q) Suhara, T., Proc. Imp. Acud. (Tokyo), 9, 334 (1929); ( r ) Suhare, T., Sato, N., and Kamei, S., Rept. Aeronaut. Research fnst. Tokw Imp. Univ.. No. 60, 187 (1930); ( 8 ) Terazawa, K.. Yamazaki, K., and Akishino, Y., Ibid., No. 8, 213 (1924); (t) Thun, R., Z . Ver. deut. Ing., 70, 1355 (1926); (u) Tuttle, F. E., J . SOC. Motion Picture Engrs., 21, 474 (1933); ( v ) Wedmore, E. B., J. Sci. Instruments, 4,345 (1927).
(2) Draper, Natl. Advisory Comm. Aeronaut., Rept. 493 (1934). (3) Egerton, Smith, and Ubbelohde, Trans. Roy. SOC.(London), 234, 433 (1935). (4) Glyde, J . Inst. Petroleum Tech., 16,756 (1930). (5) Martin and Caris, Elec. J . , 27,87 (1930). (6) Marvin. J . SOC.Automotive Eng., 35,391(Nov., 1934). (7) Marvin and Best, Natl. Advisory Comm. Aeronaut., Rept. 399 (1931). (8) Mason and Brown, AvtomotiveInd., 72,583 (1935). (9) Rabezzana and Kalmar, Ibid.. 72,324,354,394(1930). (10) Rassweiler and Withrow, Automobile Engr., 24.385 (1934). (11) Rassweilcr and Withrow, J . SOC.Automotive Eng., 36,125 (1936). (12) Schnauffer, Ibid., 34,17(1934). (13) Taylor, Draper, Taylor, and Williams, Ibid., 34,59(1934). 23,539 (1931). (14) Witbrow and Boyd, IND.ENG.CHEIM., (15) Withrow, Lovell, and Boyd, Ibid., 22,946(1930). (16) Withrow and Rassweiler, Automobile Engr., 24,281 (1934). R~CBIVE February D 17, 1936.
DISTILLATION The first comprehensive treatise on distilling is the famous “Liber de arte Distillandi de Cornpositis” of Hieronymus Brunswig, printed by Johannus Grueninger in Strassburg early in the XVI Century. It appeared in numerous editions, starting with the f i s t in 1500, which can be distinguished by the illustrations (wood-cuts) on the title pages. Our reproduction, No. 66 in the Berolzheimer Series of Alchemical and Historical Reproductions, is from the title page of Volume 2 of the 1507 edition. This shows a column still being used for the production of Aqua vite (schnaps, brandy, or the like). Undoubtedly this is the first still in column form, being the forerunner of the famous Derosne still of 1804. Incidentally, it is not generally known that John French’s “Art of Distillation,” London, 1651, is merely a translation from medieval German into Elizabethan English of selected purtions of Brunswig’s treatise, and be it noted, without the usual acknowledgment of the indebtedness.
9.3
-
A detailed list of the first sixty reproductions, together with full particulars for obtaining photographio copies of the originals, a peared in our issue for January, 1936 grtge 129, where also will {e found Reproduction No. ,131. Reprd uction No. 82 a pears on page 241 of our February issue N o 63 on page 280 of g a r o h , No. 84 on page 413 of April, and No. ‘e60; page 672 of May.
