Search results

Mr. Pye's book sets a high standard for those who are to follow him in this series. It consists of seven chapters and some 250 pages admirably printed on excellent paper. It has an adequate list of references, well arranged tables of relevant physical constants, and a good index. It abounds in numerical illustrations, but has no “examples.” It contains no enigmatic “working drawings.” It sticks to the point, which is to present a logical account of the principles which underlie the design and operation of the internal combustion engine.

This paper was read before the World Petroleum Congress on July 19, 1933. Mr. Pye acted as chairman of a committee set up by the Institution of Petroleum Technologists to investigate the corelation of knock‐rating as determined in a test engine with the results obtained using aero‐engine cylinders. This paper prepared by him summarises the results of the committee's investigations

WE conclude in this issue Mr. D. R. Pye's admirable Akroyd‐Stuart Lecture surveying the position in regard to the compression‐ignition engine, which, read in conjunction with Mr. Ricardo's able Wilbur Wright lecture published in AIRCRAFT ENGINEERING last July, gives a complete picture of where the Diesel engine stands to‐day, with fruitful suggestions of what may be expected from it tommorrow. In passing, we feel bound to call attention to the fact that the appearance of both these papers is due to funds administered by the Royal Aeronautical Society, and the standard of them affords its own tribute to the value of this branch of the Society's activities.

THE second volume of Mr. Pye's work fulfils completely all the hopes the reviewer had based upon a study of and constant reference to the first volume.

AMONG the less well‐known activities of the Royal Aeronautical Society is the administration of a number of funds which endow prizes to encourage the production of technical papers on various subjects. One of the most important of these prizes is that initiated in commemoration of the early pioneer work in heavy‐oil engines of Herbert Akroyd Stuart. Regular readers of AIRCRAFT ENGINEERING may remember that in our issues of February and March, 1931, we published the paper by Mr. D. R. Pye, which was awarded the first Akroyd Stuart Prize.

THE title of this article requires a few words of explanation. In a study of the principles of air cooling, theory by itself takes us only a very little way. On the other hand, the offspring of a happy marriage of theory and practice is capable of taking us very much further than cither of his parents unaided. Theory, like a wise mother, must accept the limitations of her more practical partner, and rest content in the knowledge that he will turn to her for wise and deep counsel when in doubt.

RECENT researches by Withrow and Boyd (reference 1) and by Schnauffer (reference 2) each using a different technique, have shown that the phenomenon of knocking is accompanied by an apparently simultaneous reaction of the last part of the charge to burn. Whether the reaction of this part of the charge is actually simultaneous or whether the reaction zone travels with a very high velocity, has not yet been determined. In any case, it will be conceded that the progress of the reaction zone is too rapid to be dependent upon the transfer of heat energy by conduction from the flame front as in normal combustion. In the light of these researches and others, some of which have been carried out in the Aeronautical Engine Laboratory of the Massachusetts Institute of Technology, I believe it is possible to postulate a very simple and reasonable theory of knocking, which fulfils all present requirements and which may in some degree help to remove the veil of mystery which has surrounded the subject.

The high‐speed engine cannot compete with these fuel consumptions on a b.h.p. basis, but on a basis of indicated power there is little to choose, under optimum conditions, as is seen by comparison of the data in Figs. 7 and 8.

IT has been stated above that the rate of heat transfer is closely proportional to the temperature difference between the plate and the free air stream, and over the laminar portion it will also be proportional to the conductivity of the air. It remains to consider to what extent the actual temperature of the air in the boundary layer will influence the rate of heat transfer. The conductivity of air increases with temperature by reason of the increased molecular velocities, and we might expect, therefore, that the hotter the surface the greater will be the rate of heat transfer per unit of temperature difference above that of the air. This is, in fact, found to be the case.

The Nature of the Boundary Layer The changes of velocity in an air stream at points close to a surface past which it is flowing have been calculated by Blasius and von Karman for the surfaces of a thin plate placed edgewise to the stream; and they have also been directly measured by Fage and Falkner close to the surfaces of an aerofoil, by means of an arrangement of minute pitot tubes, down to distances of a few thousands of an inch from the surface.