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22 AIRCRAFT ENGINEERIN G January, 1942 (summarized in AIKCKAVT ENGINEERING, Vol. XI, thickness ratio of th e aerofoil, taking the air as th e FRANCE April, 1939, p . 162), designed to measure the co iluid. The result s arc shown graphically in Figs. PUBLICATIONS SCIENTIFIQUES ET efficient of friction between two metals in a stat e of 7-11, where th e ordinat e gives the value s of Af rit TECHNIQUES DU SECRETARIAT boundar y lubrication is used in th e present study t o an d the abscissa gives the thickness ratio, t, of th e measure the quality of oiliness between several aerofoil. One of th e interesting results obtained is D'ETAT A L'AVIATION metals and under various conditions of temperature tha t when the angl e of incidence takes any value (Blondel la Rougcry and Gauthiey-Villars, Paris) an d pressure—the oiliness qualities a t hig h tempera different from 0°, th e curve of th e critical Mach tures being of grea t importance. Oiliness is accept numbe r plotted against the thicknes s ratio t ha s a B.S.T. No. 93. La Fonderie dans la Con ed as th e reciprocal of th e co-eilicicnt of friction. maximu m at a certain definite value of t. This struction Acronautique. R. de Flcury. After some preliminary notes on oiliness an d a short feature seems to b e worthy of special notice. description of th e apparatus the author deals with Th e first part of thi s report is devote d to a study Th e lift acting on the symmetrical Joukowski variations in th e co-efficient of friction with pressure, of th e characteristic s of aluminium foundry work aerofoil has also been calculated, and b y making on the basis of a comparison with the better-known th e continuous and fluctuating types of sliding , th e various numerical calculations the effect of com technique for casting iron and steel. The author influence of th e metals and the effect of temperature . pressibility of th e air upo n the lift of th e aerofoil is conducts the reader , in theory , through the work Tables show the co-efficient of friction between a discussed. It is found that when the valu e of th e shops of a n aluminiu m foundry so tha t he ma y be silver chain and a stainless steel cylinder in th e angle of incidence is fixed, the valu e of th e ratio come familiar with all th e practica l aspects of th e following oils a t temperatures between 20 deg. and L jL for a definite symmetrical Joukowski aerofoil c t problem. It is shown tha t the casting of aluminium 300 deg. a t intervals of 25 deg.—Castro l Aero CH, increases as th e Mach number increases and also frequently entails the use of patterns, feeding Yacco AK-425DE, Texaco 12 deg. F, Aero Shell 100, tha t the value of LJL for a definite Mach number castor , oil and olive oil. At 240 deg. th e co method s and arrangements different from those increases slightly with increasing angle of incidence, efficient of friction of olive oil is very much less adopted for the casting of iron owing to th e absence where L denotes, in general , the lift which a sym tha n that of an y of th e othe r oils, being less than of contraction on solidification of th e latter material. metrical Joukowski aerofoil with a certain definite 0'05. Among the conclusions are th e following : Th e technique is also widely different from the thickness ratio experiences when placed in a stream with ordinary steel an oxide layer is formed which method s usually employed in th e bronze foundry of a compressible fluid and L the lift which th e causes bad friction characteristics—this layer is no t makin g extensive use of long channels, clusters and same aerofoil would experience when placed, a t th e local sprues. Long channels and runner s are best present with the stainless steels and the lubrication same angle of incidence as before, in th e incom avoided in castin g th e light metals. Aluminium is a t high temperature is muc h superior. When oil is pressible fluid flow. very much more iluid than steel, which facilitates heate d its viscosity decreases, bu t the oiliness quali Further , th e validity of Glauert-Prandtl' s approxi th e production of thi n part s and owing t o it s higher ties improve and reach their maximum at about mat e formula for the ratio LJL is briclly discussed. therma l conductivity the application of chills is very 200 deg. One of th e best pairs of metal s is stainless much extended, compared with the use of heat steel on silver, pure silver, jewellers' silver alloy or a silver bronze containing 12 pe r cen t tin all giving retainin g devices and sprues used with steels. Report No. 206, April, 1941. The Vibration similar results and all being better than the usual Th e study of th e complexit y of th e phenomen a and Sound of a Revolving Thin Plate. (Acous anti-friction metals. examined in th e secon d part is bes t summarised in tical Model of Airscrew Flutter.) (Investiga th e two principal ideas : (a) th e " polymorphous " natur e of certai n defects due t o a single cause or t o a tions of Airscrew Flutter. Part III.) By combination of causes , and (b) th e similarity of th e JAPAN Juichi Obata, Yahei Yosida and Yasuo Makita. forms and " habit s " of certain defects under th e (In English.) TH E AERONAUTICAL RESEARCH influence of a single cause or of many causes in complex equilibria. INSTITUTE : TOKYO IMPERIAL Th e properties of th e airscrew llutter were studied I n the third part, the author deals similarly with an d described in detail in Parts I and I I of this UNIVERSITY magnesium, but dispenses with a full description series of papers . (Reports Nos. 187 an d 202.) (Kogyo Tosho Kabushihi Kaisha, Tokyo) owing t o th e number of paper s previously published. These experiments on airscrew flutter were all car Compared with aluminium the casting of magne ried out with actual airscrews, which naturally Report No. 204, February, 1941. Numerical sium is more simple owing to th e shorter solidi required large equipment and constituted experi Calculation of Power Variation with Altitude fication interval, bu t th e higher viscosity and surface ment s on a n unusuall y large scale. It was desired, tension of magnesium make pouring less easy and it s in a Naturally Aspirated Engine by Means of consequently, to carr y out the study of flutter with chemical reactivity make i t necessar y t o tak e certain some kind of model airscrew which however, was J.S. Diagrams. By Keikichi Tanaka, Osamu practica l precautions. Special attention must be almost impracticable for the following reasons. Tamura and Osamu Konisi. (In English.) pai d to th e sand since deterioration of magnesiu m is As already described in previous papers, llutter caused by enrichmen t in silicon due to decomposi This paper deals with th e changes in th e theoret is merely a phenomenon in which certain kinds of tion of the sand. The troubles caused by th e ical I. M. E . P . of a naturall y aspirated engine with vibratio n modes of th e airscre w blade arc strongly sudden release of gas bubbles are loss marked than altitude , from sea level t o 15,000 m. In calculatin g excited. However, it is well known in connexion in the cas e of aluminium when the necessary pre th e I. M. E . P. , th e J.S . diagrams of ai r an d com with the vibratio n of a thin uniform rod tha t th e cautions have been taken. bustion gases, constructed by one of th e writers and frequencies of it s natural vibration, flexural as well S. Awano, was used. In these calculations th e as torsional, increase in inverse proportion to the Th e fourth part deals witli production troubles changes in specific heat of both air an d ga s wit h length itself or t o th e squar e of th e lengt h of th e an d their remedies and with various instability th e temperature, as well as th e degree of dissociation rod. By diminishing, therefore, the size of a n factors. of the combustio n gas wit h th e temperatur e an d airscrew, that is, b y using a model airscrew, th e pressure, were duly taken into consideration. frequencies of natural vibrations are increased B.S.T. No. 92. Controle de la Temperature considerably, with the result that an extraordinary de Couleur de Lampcs a Incandescence high revolution is needed in order to produce th e Report No. 205, March, 1941. On the Destinces a des Feux de Signalisation. Maurice flutter, which evidently is a matte r of considerable difficulty. Subsonic Flow of a Compressible Fluid past Roulleau. I n the cours e of th e experiment s on flutter with a Symmetrical Joukowski Aerofoil. By Susumu Th e author considers various methods of measur an actual airscrew, it was realized that a revolving ing colour temperatures, such a measurement con Tomotika and Hazimu Umcmoto. (In English.) thi n metal plate exhibits a phenomenon greatly stitutin g a useful method for classifying the colour Th e two-dimensional irrotational subsonic flow resembling, a t leas t acoustically, the actual airscrew ratin g of incandescent, position and signalling lamps. of a compressible lluid past a symmetrical Joukow llutter. Th e method selected, by elimination , is tha t based ski aerofoil placed a t a n arbitrary inclination to th e A set-up was therefore devised in which a thin on the red/blu e ratio and requiring the use of a direction of th e undisturbe d stream has been re duralumi n plate (20 cm. long, 2-0 cm. wide, an d 0-5 photoelectric cell, two-colour filters and apparatu s investigated in detail , with th e special intention of mm . thick) is attache d to a small electric motor. lor measuring the current delivered by th e cell. studyin g the manner in which the valu e of th e so- This plate, which is of simple rectangular form, Th e principle on which the red/blue ratio method is called critical Mach number for th e symmetrical havin g initially no angle of attac k (i.e. withou t any based is explained. The apparatu s developed on Joukowski aerofoil varies with the angle of incidence twist) rotates at first very smoothly without these lines and know n as th e chromopyromete r is a s well as wit h the thicknes s ratio of th e aerofoil. emittin g any appreciable sound ; but upo n attain the n described in detail and illustrated. It con Th e critical Mach number is, a s is well known, th e ing a certain number of revolutions a peculiar sists externally of a box 1 metr e in length , 45 cm . value of th e Mach number a t which the local speed sound is abruptl y emitted, indicating tha t some sort wide and 40 cm . deep with th e voltmete r and th e of sound is first attained in th e field of flow, and, of vibration is excited. Upon increasing the revo microammetc r graduated in degree s of temperature , according to th e results of recent experimental lution further, the vibration-sound soon ceases, mounte d on th e outside . The metho d of calibra investigations, it has a close connexion with th e followed by smoot h and noiseless revolution. With tion of th e microammeter is explained . The maxi importan t phenomenon called the compressibility still higher revolution, a peculiar sound, which mu m error of measuremen t is claimed not t o exceed burble . seems t o differ in natur e somewhat from the previous 5 per cen t and a lam p can b e teste d in 30 seconds one, is heard. These phenomena arc repealed Poggi's method is used, as in Kaplan's papers. withou t requiring any calculation. The apparatus alternately , th e intensity of th e emitted sound being Although Kaplan has confined his attention chiefly is sufficiently robust to withstand industrial usage increased with increase in revolution. t o th e state of affairs on th e surface of th e aerofoil, an d has been proved satisfactory while in continu th e analysis has bee n generalized to some extent, This extremely simple experiment, besides seem ous use in France over a period of approximately b y obtaining first the velocity potential at an y ing t o furnish useful hints on th e nature of airscrew two years. poin t in th e field of flow and then proceeding t o th e flutter, also presents interesting problems in th e discussion of th e stat e of affairs on th e surface of th e theor y relating to the vibration of a revolving body . thi n plate. The phenomenon-wa s therefore care P.Sc.T. No. 169. Etude sur L'Onctuosite fully studied in th e hope that it would throw some Very laborious numerical calculations have been des Lubrifiants (Second Part). Fernand light on th e mechanis m of actual airscrew flutter, carried out in detail and thu s the values of th e Charron. an d the results are described in the present critical Mach number, ilfcrit. have been found as paper. Apparatu s described in a previou s report, No. 131, functions of both the angle of incidence and the
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Jan 1, 1942
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