February, 1931 AIRCRAFT ENGINEERING 47 Aer o Engines and Airscrews and a Symposium in Honour of Aachen's New Building Automobil e and Aircraft Engines . By A . W . an indicator card without a pressure scale is really propeller Wades for the purpose of stressing. The Judge, A.R.C.S. , A.M.I.A.E. (Second Edition) quit e valueless except as a picture. metho d is relatively simple and would have made [Pitman 42s. net.] Th e description of the Beardmore fuel pump th e chapter on strength of real value. (Fig. 307) can hardly be correct. If the metering Th e book finishes with a chapter on design pro The ground covered by the original edition of was done by the flash-valve C an entirely uncon cedure. The design procedure consists in copying to this book was so wide that it should have proved trolled factor of plunger leakage would be present— suitabl e scale existing propellers tested at full scale of great value, both to the engineer and to the occurring after the fuel had been metered—and an d full speed. It is a melancholy implied confes student. also the rat e of injection would vary throughout the sion tha t confidence in an y theory was so small tha t However, owing to the very large number of injection period. Actually in this system injection recourse to the expense of full-scale full-speed errors and mistakes appearing throughout, it is at constant pressure and the fuel metering is propeller trials was considered justified. But proved to be practically useless as a work of refer done by the pump plunger. havin g carried such trials through one feels that ence and quite unsuitable for a text-book. Th e results obtained in America about three th e author has missed a great chance of producing It was, then, wit h pleasure tha t the preliminary year s ago on an early type of experimental single- a great book in which the results obtained are com announcement of the second edition was received; cylinder compression-ignition unit (p. 505) seem pare d with the results to be predicted by use of, since, if only the various mistakes were corrected, no t worth quoting at this date ; a maximum fuel say, the Vortex theory. As the book stands the the book would fill a real need. load b.m.e.p. of 76 lb./sq . in., with a fuel consump instruction s for design are only of very limited use, Mention must be made of the fact that the tion at this load of 0·7 lb. b.h.p./hour can be of being applicable to propellers geometrically similar publishers refer t o the book as being th e "standard no possible interest. to a set of thin solid duralumin propellers, and work on th e internal-combustion engine" as such I t is needless to quote further examples—enough therefore cannot have the same international a claim clearly entails a definite obligation of ha s been said to demonstrate that wherever one interes t as a checked and confirmed theory on a accuracy. looks in the book the most glaring inaccuracies are metho d of design applicable to all and every form However, it is found that this new edition, encountered. of airscrew (propeller or windmill). The data and although covering even more ground than the We have considered it necessary to deal severely opportunit y are still there, however, for anyone original book, still suffers from the defects that wit h Mr. Judge's book, in part because it has been wh o wishes to use them. But although the book made its predecessor so disappointing. falls so far short of what it could have been when definitely announced as the standard work on the There are two main pitfalls to be avoided in com one realises the magnificent data available to the internal-combustion engine, and also because the piling a book of this description; actual mis author , yet because it contains this data, and, to author , in writing a book of this type, has accepted statement of fact and the expression of matter of aircraft designers particularly, because of the certain responsibilities which unfortunately he has opinion as facts without qualification. chapte r on body interference, it is well worth treate d very lightly. Surely it is far better—when describing phe reading . Perhaps one day the author will finish If only more care had been taken to ensure nomena for which a t present there is no satisfactory his work. H. C. W. accurac y we would have welcomed the book or generally-accepted explanation—simply to say whole-heartedly. T. that the explanation is not known, rather than to attempt to cloud th e issue wit h meaningless phrases. Vorträg e aus de m Gebiete der Aerodynamik An example of this method of treatment occurs un d verwandter Gebiete. [Julius Springer, Aircraf t Propeller Design . By F. E. Weick. very early in th e book when the theory of explosion Berlin, 1930, 18·50 Marks.] is being discussed. The author says tha t the flame, [McGraw-Hill, £1.] after ignition, spreads "throug h the mixture from I t is now about ten years since the publication of Th e Aerodynamic Department of the Technical particle to particle until the whole volume is com an y treatise devoted solely to aircraft propeller Institut e of Aachen was considerably enlarged in busted [disgusting word!], thi s process being called 1927-29 by a new building furnished with facilities design. In that period changes in theories have inflammation." He adds tha t "whe n the mixture for research. The Principal of the Institute issued been evolved, research in all countries has been is completely inflamed, explosion follows." All this an invitation to the best-known workers in the persisten t and full-scale experience considerable. means nothing and conveys no understanding of department s of aerodynamics and allied sciences Moreover, changes in materials of construction have what happens in the cylinder after the spark has to give an account of their latest researches a t the also taken place. There is, therefore, room for passed. inauguration . This resulting volume docs not suc h a work as tha t now under review. In the same section, in discussing detonation, it preten d to handle the problems in the given sciences Th e first five chapters deal wit h theories from the is unfortunate that a mixture of carbon-monoxide systematically, since each lecturer dealt with the simple blade elemen t theor y u p to th e Glauer t Vortex was selected as an example, since it is well known particula r problem with which he was interested; Theory, which the autho r accepts and uses. So far that C O never detonates. bu t it is hoped by the editors that it will awaken th e book is merely a recapitulation of existing When discussing the value of the index in the interes t and response in scientific circles. The knowledge, but serves a useful purpose in collecting equation PV" = constant for expansion the author Paper s are given in their original language; hence an d editing it. states tha t "th e constant (!) n varies from 1·30 to thei r value is not lessened by translation. Th e next two chapters relate to aerodynamic 1·10, a good average value being 1·32." This value Th e results quoted in many of the Papers have test s and deductions therefrom of effects of changes is obviously too high—1·22 is very much nearer to alread y appeared elsewhere, but the volume forms of shape. As the author admits, most of these take as an average value. For the compression a handy compendium which gives the reader a good could be deduced from the basic theory. One's curve, it is said tha t the values of "n lie between insight into the present state of aerodynamic interes t begins, however, to be powerfully aroused 1·25 and 1·30 as a rule," and then in an example research, both theoretical and practical. Papers a t the chapter which deals with the effect of tip immediately afterwards the author uses the value speed. Due reference is given to the large amount in German, French and English are presented, but of 1·35. Actually, of course, these values are of work done on this subject in England by the th e majority of the thirty-three are in German. altogether too low, 1·33 being about right for R.A.E. , bu t to the English reader thi s is well known. Th e Papers printed in English are as follows:— normal conditions, falling to about 1·31. His interest will at once centre on Wind Tunnel "Som e studies of the flow past cylinders," by A large section dealing with the compression- Test s on full-scale propellers at tip speeds from A. Thom. ignition engine has been added to the book, but 400 to 1,300 ft. per sec. Here he will find data of "Recen t investigations into the Kármán street here again the information is equally unreliable. greate r valu e tha n an y we, with our limite d resources of vortices in a channel of finite breadth," by In discussing the weight of engines the author says an d equipment, can ever hope to obtain here. L. Rosenhead. that "th e best results obtained in this respect are "Th e force and moment on an oscillating aero Th e chapter on body and propeller interference those of the Packard C.I. engine and the Beardmore foil," by H. Glauert. is of even greater interest: more, perhaps, for the airship engine which give an approximate figure of "Note s on th e effect of high tip speed on airscrew aircraft designer than the propeller design. Here 7 lb. to 8 lb. per b.h.p." In the description of the performance, " by G. P. Douglas. again the author has the inestimable advantage of Packard Diesel engine published in this journal* wind tunnel tests at full scale and full speed. "Modu s operandi of the air-jet pulsator," by it is definitely stated that the specific weight is J . Hartmann. Fro m this point onwards interest flags. Variable 2·26 lb./b.h.p . Prandt l contributes an important Paper, in which pitc h propellers, gearing, tandem arrangements, It is, of course, incorrect to say (p. 586) tha t the strength , and materials of construction are dealt th e effect of stabilising forces on turbulence is jerk-pump system of injection suffers from the wit h in the usual way. One is disappointed in the considered, firstly, in regard to the system studied defect tha t the injection pressure is low, both a t the chapte r on "Strength" to find the subject of experimentall y by W. Schmidt in which air flows beginning an d the end of the injection period. The flutter dismissed with a mere paragraph. One had between a hot. an d a cold plate, and secondly, the indicator card of injection pressure (Fig. 318) makes hope d that with the experience gained on the syste m of concentric cylinders investigated by G. I. this quite clear, although it must be mentioned that magnificent U.S.A. spinning plants the author Taylor . Kármán has a theoretical Paper on the origin of the lift of an aerofoil. Altogether, this could have thrown real light on this important mus t have been an interesting congress in aero subject . It is also a matter of surprise that no dynamics . E. G. R. metho d is given of calculating the deflection of * AIRCRAFT ENGINEERING, Vol. II, July, 1930, p. 164.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Feb 1, 1931
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