bluuebunny/crossref_metadata_2025 huggingface dataset:
The Corrosion of Heating Surfaces in Boiler Plants: Further Studies in Deposit Formation
Authors: Rylands J. R. , Jenkinson J. R.
Published: October 2007

Corrosion is an important factor in the formation of deposits on the gas-swept heating surface of steam generating plant. The paper compares the behaviour of cast iron and steel under the corrosive attack of the sulphur acids occurring in boiler gases.

Preliminary laboratory tests show a pronounced difference in behaviour of the two metals. Further investigation shows that cast iron has inherent properties which increase its resistance to corrosion over a wide range of conditions. These properties are shown to be linked with the silicon content of cast iron.

Consideration is given to the influence of corrosion products, and of sulphurous acid. An explanation is offered of a number of observed phenomena in practice, including the puzzling “band corrosion” in air-heaters. This is shown to be a temperature and acid-concentration phenomenon.

The paper ends with some comments on the modern practice of cleaning economizers and air-heaters by washing, and makes suggestions for the future guidance of designers.
The Motion of a Railway Axle
Authors: Davies R. D. , Cook A. F.
Published: October 2007

The authors investigated the motion of a single axle and pair of wheels by means of a model, paying particular attention to the action of the flanges and to their influence on the development of “hunting”. In justification of the use of a single axle, evidence is produced that, owing to the various clearances, the axles of a bogie are in fact largely free to follow their individual paths. The effects of unsprung mass, wear of tyres and rails, flange clearance, lateral stiffness of the track, and other variables were studied. It is shown from considerations of dynamical similarity that the speed at which oscillation of a given violence occurs varies approximately inversely as the square root of the unsprung mass, and that a reduction of this mass would therefore be beneficial. Possible changes in tyre profile are discussed.
The Theory and Practical Application of Vertical Log Frame-Saws
Authors: Topham-Bruckmann H. C.
Published: October 2007

Wood is one of the most important of raw materials; it can be used in various ways to meet demand, and can also be grown as required. In spite of its extensive use throughout the ages, and the wastage caused by fire and axe, there still exist huge virgin forests, covering partly unexplored regions of the world, whilst scientific forest management gains increased scope in keeping the timber resources in line with the constantly growing demand.

Saw-milling is one of the main methods employed in wood conversion, producing sawn timber such as boards, planks, battens, and cants. Three types of saw-mill head rigs are used, i.e. circular, band, and frame. This paper deals with certain particulars related to the reciprocating type—the frame- or gang-saw. The circular- and band-saw-mills use continuously moving saw-blades, but frame-saws have to be sufficiently powered and strong enough to take up the great force developed by the reciprocating motion of the saw-gate, blades, and all accessories.

The first patents and other technical literature relating to almost any type of woodworking and saw-mill machinery are of British origin. At the beginning of the Industrial Revolution Britain was leading for many years in the manufacture of these machines, but more recently frame-saws and other types were developed in many parts of the world, where a growing saw-mill industry has had to satisfy its needs for such machines, well suited to local demands.

It should be a matter of topical interest to give some details here of the close relationship between theory and practice in their application to the frame-saws, due to the fact that enormous damage was done during the recent war years, not only to all kinds of property which requires urgent replacement, but also to the fact that numerous saw-mills have first to be put in order, before they can again produce the timber needed for urgent repair work.
The Mobile Locomotive Testing Plant of the London, Midland and Scottish Railway
Authors: Andrews H. I.
Published: October 2007

To measure the performance and efficiency characteristics of any type of locomotive under service conditions, it is necessary for the locomotive to be worked at different rates of speed and loading, and for the conditions of working to be maintained constant for sufficient time for the necessary observations to be made. Such conditions have been achieved on certain continental railways, over long stretches of straight and level track, by the use of various forms of loading capable of adjustment to maintain constant speed and to absorb the power of the locomotive. This method of testing has hitherto been impossible on the L.M.S. Railway, as no suitable section of line was available. A special testing train has now been constructed in which the power of the locomotive is absorbed by a number of electrically-braked vehicles, the loading of which is controlled by an electronic regulator so that constant speed is automatically maintained and the effects of gradients, curves, etc., are immediately compensated. The train consists of three braking units, having different gear ratios, which may be used in any combination, a dynamometer car which records the performance of the locomotive and from which the braking units are controlled, and a special tender for measuring the fuel and water consumption of steam locomotives.
The Dynamic Yield Strength of Steel at an Intermediate Rate of Loading
Authors: Brown A. F. C. , Edmonds R.
Published: October 2007

A comparison has been made between the dynamic and static tensile yield strengths of eight steels varying from mild steel to a heat-treated low-alloy steel, the rate of loading in the dynamic tests being such as would occur in a ship under the action of an underwater explosion.

The dynamic yield strength of the steels with low static strength was 20–30 per cent greater than their static yield strength but, for the stronger steels, the increase was less, being negligible in the case of the heat-treated low-alloy steel. This result conforms with the findings of other investigators, and shows that any increase in strength under the dynamic loading considered is too small to be of importance in design.
The Criterion of ‘Yield’ of Gun Steels
Authors: Morrison J. L. M.
Published: October 2007

This paper describes tests carried out on standard nickel-chromium-molybdenum gun steel in the form of bar material and in the form of gun-barrel forgings, and on seven alternative gun steels in the form of forgings produced experimentally during the 1939–45 war, with the object of determining the criterion of “yield” of these materials.

The standard gun steel in the form of bar material gives a drop in stress at yield: the same steel in the form of forgings does not, nor do any of the alternative steels.

In the first case, the criterion for the occurrence of the initial yielding is found to be the existence of a critical maximum shear stress; plastic flow continues in accordance with the Mises-Hencky criterion. In all the other steels the plastic flow occurs and continues in accordance with predictions based on the Mises-Hencky criterion.

A brief additional note compares these results with those of earlier work, and draws attention to an earlier theoretical analysis which offers an explanation of them.

The following paper is an abridgement of a monograph written for the Permanent Records of Research and Development of the Ministry of Supply.
Factors Influencing the Weldability of High Tensile Alloy Steels, and a New Weld Cracking Test
Authors: Leder P. L. J.
Published: October 2007

The paper consists of a short review of the factors controlling the weldability of steel, together with an account of certain work carried out in connexion with the welding of armour type steel. After referring to the basic principles governing the weldability of steel, and describing the influences of alloying additions, the paper discusses the problems peculiar to deep-hardening steels, and summarizes current views on the causes of hardened-zone cracking. A detailed description is given of an improved welding test, and of some of the work carried out with it. The results of this work are then related to the theories already described.
The Fuel Problem in Gas Turbines
Authors: Lloyd Peter
Published: October 2007

Accepting the principle that the gas turbine is potentially capable of consuming all fuels, the author proceeds to investigate the range of possible liquid fuels and the fuel characteristics of greatest practical significance. Whilst certain properties of liquid fuels—as for example, ignition characteristics and molecular structure—are so complex that no correlation with gas-turbine combustion behaviour has been possible, yet other properties, mainly but not exclusively physical in nature, do exist for which the reverse is the case. Properties falling in the latter category are those which show relatively little variation as between hydrocarbon types or as between isomers, and include carbon/hydrogen ratio, density, vapour pressure, viscosity, and inflammability limits. The influence of these properties on the combustion process is discussed in detail under the two main heads, ( a) fuel injection and stabilization of flame, and ( b) the burning of the droplets after ignition, and the nature of the exhaust products. A number of new and interesting generalizations emerge from this discussion, and are presented in graphical form. Though no hard and fast conclusions may be drawn, the author indicates that the main fuel characteristics affecting gas turbine operation are viscosity, initial and final volatility, elementary analysis of the organic constituents and physical characteristics of the ash.
Performance of Axial-Flow Turbines
Authors: Ainley D. G.
Published: October 2007

The advent of the gas-turbine engine, with its absolute dependence on high component efficiencies for reasonable economic operation, and the necessity for new materials which will withstand high stresses at much greater temperatures than encountered on steam turbines, has led engineers to review the design of turbines closely both from an aerodynamic and a mechanical standpoint: there is still a great deal to be learnt. Reeman† has outlined the present mathematical approach to the design of turbines and surveyed very comprehensively the mechanical problems that are involved. This paper is intended to indicate the manner in which the aerodynamic design of a turbine has developed from that of its steam predecessor and, in particular, surveys some recent experimental work relating to turbine performance. The general aims of the experimental work are to explore the gas-flow processes within a turbine stage, to determine the associate aerodynamic efficiencies, and to gain some understanding of the limitations imposed upon the aerodynamic design of a stage by the necessity for the high efficiency which is required for economic operation of a gas-turbine engine. The data that have so far come to light, though incomplete, illustrate the general overall characteristics of high- and low-reaction turbines, and also the effect that high Mach number or low Reynolds number may have on turbine performance. To conclude the paper, a brief description of the technique adopted for adequate full-scale testing of turbines is presented. This covers the essential points of, power absorption, instrumentation, and safety precaution. The effects of errors in measurements are also discussed.
Three-Dimensional-Flow Theories for Axial Compressors and Turbines
Authors: Carter A. D. S.
Published: October 2007

It has long been known that the energy losses occurring in an axial compressor or turbine cannot be fully accounted for by the skin-friction losses on the blades and annulus walls. The difference, usually termed secondary loss, is attributed to miscellaneous secondary flows which take place in the blade row. These flows both cause losses in themselves and modify the operating conditions of the individual blade sections, to the detriment of the overall performance. This lecture analyses the three-dimensional flow in axial compressors and turbines, so that, by appreciation of the factors involved, possible methods of improving the performance can readily be investigated.

The origin of secondary flow is first examined for the simple case of a straight cascade. The physical nature of the flow, and theories which enable quantitative estimates to be made, are discussed at some length. Following this, the three-dimensional flow in an annulus with a stationary blade row is examined, and, among other things, the influence of radial equilibrium on the flow pattern is noted. All physical restrictions are then removed, and the major factors governing the three-dimensional flow in an actual machine are investigated as far as is possible with existing information, particular attention being paid to the influence of a non-uniform velocity profile, tip clearance, shrouding, and boundary layer displacement. Finally the various empirical factors used in design are discussed, and the relationships between them established.
Wave Action following Sudden Release of Compressed Gas from a Cylinder
Authors: Bannister F. K. , Mucklow G. F.
Published: October 2007

The limitations of sound wave theory, and the work of Earnshaw and Riemann are first examined in relation to the propagation, under frictionless conditions, of waves of finite amplitude. The theory of pressure equalization in a semi-infinite pipe, due to Aschenbrenner, is extended to cover discharge from a cylinder into a pipe of the same bore, or to atmosphere. The effects of friction are examined and the accepted mathematical solution of the analogous electrical transmission-line problem is applied to the case of small-amplitude waves. Friction in relation to waves of finite amplitude is examined, and a hyperbolic law defining the effects of friction is deduced. The arguments developed are applied to discharge from a cylinder through an orifice of smaller diameter.

The experimental apparatus consisted of a number of cylinders of 2-inch bore, and of lengths from 1 foot to 40 ft. 6 in., from which air, at gauge pressures from 140 lb. per sq. in. to minus 25 inches of mercury, was discharged either directly to atmosphere or through a pipe of 2-inch bore and up to 81 feet in length. Indicator diagrams were recorded at points spaced along the cylinder and pipe, and corresponding diagrams were also obtained, using a cylinder 4 feet long and 4 inches in diameter in conjunction with a pipe of 2-inch bore.

From the general agreement between the experimental and the theoretical investigation, it is concluded that the processes of discharge, under the conditions considered, are capable of full explanation on the basis of accepted physical laws. Experimental confirmation is obtained for the theoretical treatment put forward by Giffen for discharge from a cylinder through an orifice of smaller diameter, and quantitative data are given in regard to velocities of propagation, pressure amplitudes, attenuation, etc., for the range of conditions covered.
The Design of Contra-Flow Heat Exchangers
Authors: Schmidt Ernst
Published: October 2007

The problem of contra-flow heat exchangers, for gases at turbulent flow, is treated in a general way, using the analogy between heat transfer and friction. For making this analogy more evident, another non-dimensional heat transfer coefficient is introduced. This number may be used profitably instead of the Nusselt number for describing heat transfer in tubes, and in similar problems. Thus the main dimensions of the apparatus are given in formulae based on the intended heat exchange, the total drop of temperature, the total loss of energy, and the properties of the fluid. It is shown that weight and total volume of the heat exchanger depend on the ratio of temperature drop and loss of energy on both sides of the heat exchanging surface. The conditions of minimum weight and minimum volume are derived.
Thermal Analysis of the Contra-Flow Regenerative Heat Exchanger
Authors: Iliffe C. E.
Published: October 2007

The regenerative heat exchanger was first proposed and constructed by Dr. Robert Stirling in 1816, in connexion with a regenerative hot-air engine. Since then its use has been mainly confined to furnace air preheaters. With the advent of the gas turbine, however, the need has arisen for a compact heat exchanger of high thermal ratio and low pressure loss. This, of “necessity, tends to the use of gas passages of small hydraulic diameter. In the recuperator, a limit to the size of the gas passages is imposed by the difficulties of producing and supporting in position long thin passages which must perform the dual function of transferring heat from one gas to another and of keeping separate the two gases at different pressures. Small gas passages in a recuperator also tend to become blocked with the deposits from the hot gases of a gas-turbine unit.

The renewed interest recently taken in the regenerative heat exchanger is due to the promise which it shows of meeting these objections. The requirement that the gas passages must keep the gases separate is removed, so that these passages may, for instance, be merely the voids in any porous material or in any aggregate of elements. The manufacture and task of supporting in position such a “matrix” is comparatively simple. Information to date suggests that the tendency to blockage of the gas passages in a gas-turbine regenerator should be very much reduced because of the blasts of clean air which alternate with every gas discharge. So far as the author is aware, however, no regenerative heat exchanger has yet been set to work in conjunction with a gas-turbine installation.

Little appears to have been written in the English language on the subject of regenerator design, but the converse is true of the German language. This paper has been written after a fairly extensive research into German publications.

The paper makes no attempt to deal with pressure losses or the application of the regenerator to the gas turbine. The treatment of these aspects of the problem follows fairly conventional lines, once the thermal behaviour of the regenerator has been investigated.
Tensile Fillet Stresses in Loaded Projections
Authors: Heywood R. B.
Published: October 2007

The loaded projection is an essential feature of practically every machine and structure—the screw thread, gear tooth, and simple cantilever are examples. The strength frequently depends on the fillets connecting the projection to its base, and hence the maximum tensile fillet stress may be a critical factor. Existing fillet stress formulae give accurate results over only a narrow range of projection shapes. In this paper an empirical formula is advanced which agrees well with experiment over a wide range of projection shapes, and which provides a powerful method of determining the strongest shape of projection for any given purpose, the procedure being demonstrated for the derivation of a series of screw thread forms having greatest strength.
Mechanical Engineering Aspects of Naval Mining
Authors: Wadlow E. C.
Published: October 2007

The paper outlines some of the engineering problems which arise in connexion with naval mining, and describes some of the weapons and devices used by Britain and Germany in the war of 1939–45.

Although naval mining has a long history, its development is necessarily conducted under conditions of secrecy, and publication of information concerning it is possible only after a major war in which there has been a general disclosure of methods and materials employed by both sides.

The popular conception of a mine is a spherical buoyant object which will explode if hit by a ship. The buoyant contact type is, however, only one of many forms now available. A number of these are illustrated here, and the variety may surprise those not familiar with the subject. Methods of laying, general principles of operation, and safety requirements are described, and the mechanical details of design of mineshells, fittings, components for control and firing circuits, and other features are mentioned.

Naval mines have reached a state of considerable complexity and many fields of scientific knowledge are now called upon in making them effective weapons.
Some Mechanical Features in Anti-Submarine Weapons
Authors: Kirkby J. M.
Published: October 2007

The paper describes—by reference to anti-submarine weapons used in the 1939–45 war—some of the features in the design of underwater armaments that are peculiar to this class of mechanical engineering. A brief description is given of how an attack on a submarine by a ship is carried out either with depth charges dropped from the stern or with projectiles discharged ahead (“Hedgehog”). Features of the weapons of mechanical interest are described under the headings of weapon discharge gear, effect of explosions, safety requirements, and aircraft depth charges. Rails and throwers, including the method of their remote control, for the discharge of depth charges, and the mounting for the Hedgehog, are described. The importance of preventing the explosion of one charge in a pattern having an adverse effect on the remaining charges is discussed. Safety requirements which must be taken to prevent weapons exploding prematurely are described and illustrated. Finally, the method of investigating the behaviour of the form of depth charge dropped from aircraft is described, illustrating an aspect of hydro-ballistics.
Mechanical Engineering in the Chemical Industry
Authors: Bramwell F. H.
Published: October 2007

The author reviews briefly the close connexion of an important section of the chemical industry with the Liverpool and the Merseyside areas, from the early years of the nineteenth century, and then discusses the changes that have taken place in these industries due largely to the development of engineering technique and materials of construction. Owing to the wide range of products and processes covered by the chemical industry, the paper has been limited in scope to those branches of the heavy chemical industry that are established and flourishing on Merseyside. Modern methods of performing various operations are compared with methods used in the early days of the industry, the comparison being illustrated by photographs. Prime movers, pumps, packages, materials of construction, instrumentation, and workshop facilities are then considered, and finally emphasis is placed on the scope and opportunities that exist in the industry for mechanical engineers.
Causes of Flue Gas Deposits and Corrosion in Modern Boiler Plants
Authors: Harlow W. F.
Published: October 2007

This paper is intended to be an amplification and continuation of the author's previous paper entitled “Causes of High Dew-point Temperatures in Boiler Flue Gases” read before the Institution in 1943, in which attention was drawn to the phenomenon of the catalytic production of sulphuric acid in flue gases by their passage over heated iron surfaces.

At that time the full importance of these findings was not apparent, but evidence is now submitted to show that, in addition to causing deposits and corrosion by the deposition of acid in air heaters and economizers, this phenomenon is primarily responsible for the flue-gas deposits and corrosion in all parts of boiler plants.

Experiments are described which show that when flue gases are passed over sand-blasted steel-surfaces which are maintained at the gradation in metal temperatures which can occur through a modern boiler plant, sulphur trioxide is produced at the high temperature surfaces, causing sulphuric acid to condense on the cooler surfaces. When the maximum surface temperature is moderated no appreciable formation of acid occurs.

It is believed that the interaction of the sulphur trioxide in the generation zone, and the condensed acid in the cooler zone, with the various constituents of the fuel ash and the metal of the heating surface, can explain all the numerous deposit and corrosion effects which have been the subject of research work both here and abroad during recent years.

The high surface temperatures which are necessary for the catalytic action to occur are largely due to the general advances in operating temperatures and pressures, and in some measure to “surface combustion” taking place on the tube surfaces, elevating their temperature above that which they would acquire if swept only by inert gases.

Although the advance in steam and water temperatures is considered to be a primary factor in these difficulties, many other contributory factors, particularly the nature of the fuel, play an important part.

Pulverized-fuel boiler-plants are least affected and, at the present time, the adoption of pulverized fuel appears to be the most effective way of dealing with the problem. Further research is necessary to devise practical means of prevention or alleviation in stoker and oil-fired plants, and it is thought that full consideration of the factors outlined in the paper may materially assist in this object.
The Measurement of Kinetic Boundary Friction, or the Experimental Investigation of “Oiliness”
Authors: Bristow J. R.
Published: October 2007

Considerations concerning the nature of sliding in friction-measuring instruments, in which friction is measured by the deflexion produced in an elastic system which presses one surface against another moving surface, have led to the design of an instrument which allows the variation of boundary friction with velocity to be determined at very low velocities.

It is suggested that curves of the coefficient of boundary friction versus velocity constitute the correct form in which the results of measurements of kinetic boundary friction should be stated. Results are presented illustrating the influence of temperature, material nature of the surfaces, and surface finish on kinetic boundary friction for a variety of lubricants. These allow the boundary lubricating quality, or “oiliness”, of lubricants to be assessed in some measure. The results lend support to the original ideas of Sir William Hardy on boundary friction and lubrication.
On the Accuracy of Gear-Hobbing-Machine Tables
Authors: Newton J. M.
Published: October 2007

This paper deals with experiences on two gear-hobbing machines originally fitted with creep work tables. The flanks of the teeth cut on these machines were so irregular that it was decided to abandon the creep mechanism.

A non-creep table was purchased. The flanks of the teeth cut on this table were much smoother: but the gears cut on this table, when run, produced an objectionable dominant note having a pitch equal to the number of teeth in the master wheel multiplied by the revolutions per second of the running gearwheel.

The steps taken to correct the errors in the master wheel and worm of the non-creep table, and the manufacture of a non-creep table having a greater number of teeth, are described. This latter table was completed in 1931 and gears cut on it were free from the worm-table note.

In 1944, the manufacture of another master wheel of higher accuracy was undertaken, making use of the improved gauging apparatus invented by the late Dr. Tomlinson about 1940. The manufacture of this table is described.

In appendices are discussed the problem of the measurement of pitch errors on large wormwheels; the theory and a special application of the Tomlinson Undulation Recorder; and the principles which should govern the choice of the number of teeth in a non-creep master wheel.
The Surface-Roughness of Bearing-Surfaces and its Relation to Oil Film Thickness at Breakdown
Authors: Cameron A.
Published: October 2007

In this paper the relation of surface roughness of bearing surfaces to allowable film thickness is studied quantitatively with a simple Michell pad apparatus. The pads used were faced with white metal and ran against mild steel collars. The lubricants studied were water, soap solution, paraffin, and light oil. There was little difference in the frictional behaviour of any of the lubricants, except that the aqueous lubricants would not run with very finely finished steel surfaces. The onset of metal to metal contact was detected by an increase in the frictional drag, and also by the change in electrical conductivity between the pad and collar—an extremely sensitive method.

The paper shows that there is, at any rate for this system, a quantitative relation between the total surface roughness of the rubbing surfaces and the calculated oil film thickness both at the initial metal to metal contact and seizure. Initial contact occurs when the outlet film thickness, calculated from normal hydrodynamic theory, falls to three times the maximum surface roughness and seizure occurs when it is double the average roughness.
The Yield Phenomena of a Medium Carbon Steel under Dynamic Loading
Authors: Warnock F. V. , Taylor D. B. C.
Published: October 2007

The paper describes dynamic tensile tests carried out on a medium carbon steel to determine the true shape of the stress-permanent strain curve for rapid straining. The variation of this curve with change in strain rate, and the progressive deformation of the steel are also studied.

An impact testing machine was used, straining being carried out as a series of dynamic loadings, and the stress was measured by means of electrical resistance strain gauges attached directly to the specimens.

Comparison is effected between dynamic and static stress-strain curves, the existence of a “dynamic upper yield stress” and a “dynamic lower yield stress” being shown, together with a difference in the rate of strain hardening for the two straining conditions.

Non-uniform yielding of the metal is shown to be more pronounced for dynamic straining and, like static yielding, to be an integral part of the lower yield stress phenomenon.

The manner in which all these factors are affected by normalizing the steel is shown.

A special form of deformation of the steel peculiar to rapid straining is indicated.

Theoretical and experimental facts are used to deduce a theory for the observed increases in stress, and the use of these dynamic stresses for design purposes is discussed.
The Behaviour of a Nominally Isotropic 0.17 per cent Carbon Cast Steel under Complex Stress Systems at Elevated Temperatures
Authors: Johnson A. E.
Published: October 2007

The work described in this paper is part of an approved programme, undertaken to investigate the behaviour of an isotropic 0·17 per cent carbon steel under general stress systems at elevated temperatures. It relates to an experimental study, and analysis of the time independent plastic strain properties in short-time tensile and torsion tests at temperatures between 20 and 550 deg. C. (68 and 1,022 deg. F.).

The object of the investigation is to obtain relations between stress, strain, time, and temperature, to afford a basis of design in cases where steels are subjected to plastic deformation under general stress systems at elevated temperatures.

Pure tensile and torsion tests have been made at temperatures of 20, 150, 350, 450, and 550 deg. C. (68, 302, 662, 842, and 1,022 deg. F.), and at various rates of stressing. The results of these tests have been analysed, and information derived concerning the nature of the criterion of elastic failure for this material, and the nature of the stress-plastic strain relations after plastic strain has been established. The effect of rate of stressing on these latter relations has been examined.
Some Properties of the Compression Shock as in Turbine and Compressor Blade Passages
Authors: Davidson I. M.
Published: October 2007

The generalized theory of the plane compression shock has been widely known for some forty years, but only recently has appreciable progress been made in its application to everyday engineering practice. In the fields of ballistics and aircraft engineering, the shock is still generally regarded as a most undesirable phenomenon to be avoided whenever possible. However, in the fluid dynamics of gas-turbine power plant a stage has now been reached at which the shock, far from being regarded as a nuisance, must be considered as a potential aerodynamic tool of considerable consequence.

Starting with a brief mention of the isentropic expansion of a compressible fluid and the classical compression-shock theory, the paper introduces some practical definitions and conceptions concerning the description and classification of the various forms of the single shock. The phenomena associated with shock wave reflection and boundary layer interaction are then considered, and finally four examples are given of the occurrence of shocks in practice. Of these examples, two are from the aircraft and two from the gas-turbine field, and in all they demonstrate most of the phenomena considered.
An Approximate Investigation of the Off-Design Performance of a Turbo-Compressor Stage
Authors: Merchant W.
Published: October 2007

Turbine or compressor stages are often designed by comparison with a mathematical model with a perfect fluid and a particular flow quantity.

Empirical correction factors are required for the various sources of discrepancy between the mathematical model and an actual stage, such as wall and blade friction losses and tip clearance losses, but such models are of considerable use as a basis of comparisons.

In multistage compressors or turbines that are required to operate over a wide range of speeds and flow quantities, the individual stages are required to operate over a wide range of velocity ratios. So far no satisfactory model has been proposed for the effect of variation of flow quantity from the design conditions.

This paper considers the simple problem of an isolated stage working in a long, parallel annulus with a perfect incompressible fluid.
The Provision of Technological Courses in Universities, Technical Colleges, and National Colleges
Authors: Anderson D. S.
Published: October 2007

At the last two meetings of the British Association the view was expressed, without dissent, that the most urgent need today is not for further scientific discovery but for a more intensive application in industry of discoveries already made. The achievement of the highest rate of industrial development, and the highest level of industrial efficiency, depends primarily on an adequate supply of technologists, and the present supply appears to be inadequate both in quantity and quality. The provision of courses in technology has not hitherto been planned; many courses have come into being as the result of private generosity and not as the result of deliberate educational policy. At this critical juncture in our economic life, the whole question of technological courses merits the most careful examination.

The principal aspects of the problem appear to be: (1) In the case of full-time degree and diploma courses, is the provision adequate; should the number of students in the existing courses be increased? Are there other branches of technology for which courses should be provided? (2) Is the general structure of degree and diploma courses satisfactory? If not, what modifications are desirable? (3) Should there be far more provision of post-graduate courses of various types? (4) What modifications, if any, are desirable in part-time courses of the National Certificate type? (5) Do courses in technology need liberalizing, and how can this best be done? (6) Good management is an essential factor in securing the highest standard of industrial efficiency; how can management studies best be incorporated in technological courses?

Subsidiary questions arise, but if answers can be obtained to the principal questions it will be simpler to plan further developments in technological education.
The Application of Gas-Turbine Technique to Steam Power
Authors: Field J. F.
Published: October 2007

Early attempts to adapt the mechanism of the turbine to the air- or gas-engine were frustrated by the losses in the compressor, but in the last twenty years improvements in the efficiency of the latter, together with better high-temperature metals for the turbine, have enabled the gas turbine to approach the efficiency of the steam turbine. The gas turbine has to operate from a much higher temperature and with more effective high-temperature regeneration to achieve this. On the other hand it cannot utilize heat down to anything like the same lower temperature as steam power. Most regenerative gas-turbine cycles are therefore more efficient than the steam cycle at the upper temperature range, and less efficient at the lower temperature range. Now that the Rankine steam cycle has reached 1,000 deg. F., a given increment of temperature has much less effect on the steam turbine than on the gas turbine.

The paper describes a condensing gas-turbine† cycle with external combustion, which utilizes orthodox gas-turbine and steam-turbine components in such a manner that the thermodynamic advantages of the two in the respective temperature ranges mentioned above are combined to give a higher thermal efficiency than either the steam or the gas turbine is capable of alone, and with the prospective ability to utilize almost any fuel.

A great improvement may thus be made possible in the fuel economy of condensing steam power stations, steamship propulsion, and steam locomotives, and in the ratio of mechanical power to heat in combined power and process or district heat production. It may become commercially worth while, apart from the saving in coal, to eliminate a large proportion of condensing operation on land in the winter months. By integrating the fuel-using industries in this manner it should be possible to save at least fifty-million tons of coal per annum on the present aggregate output of power and heat, with a further saving of eleven-million tons of locomotive coal. This should enable the nation to afford much more liberal use of power and heat and thus achieve much greater production in transport and industry.
The Full Application of Motion Study
Authors: Shaw Anne G.
Published: October 2007

The paper outlines the full scope of the application of motion study to an industrial organization. The successful use of motion study is not confined to any one industry: it has been applied in recent years to an increasingly large number of different industries. There are great advantages to be gained from making detailed investigations into single specific problems, using all the detailed motion study techniques; but there is also a need for training large numbers of supervisors, technical specialists, and even operators to use simplified techniques in their daily work, so as to make numerous small improvements over a wide field. The first type of application gives high percentage savings over a small area of work, and the second, low percentage savings over a large area of work. The best and most profitable results are obtained by combining the two types of application, the fully trained motion study investigator dividing his time between making major investigations and teaching and supervising others in the use of simplified techniques.

Of the detailed techniques, micromotion study, process charting, and the study of the path of movement, the latter is the least well known. Although Gilbreth originated the chronocyclegraph it has been neglected since his time, but recent work has shown its value, and it is now taking its place as an essential technique. It is the only technique that can put on to paper the subtle difference between a good and a bad movement. It is, therefore, of great value in teaching students of motion study to discriminate between one type of movement and another and to see the path of a movement as it is made.

In its broader applications, motion study can be used in some way by everyone in an organization. It is most effective where it is applied as team work, each man playing the part that best suits him and that best fits in with his normal work. In planning the general use of motion study, the programme should begin with a campaign of lectures, exhibitions, and general propaganda to rouse interest. Courses should then be planned for all groups: managers, supervisors, technical specialists, and operators. Since each will apply motion study differently, each will need a different syllabus and different illustrations. There can be no ready-made scheme applicable to all. Courses of training should be followed up by a long-term plan of progress reports, meetings, and supervision, to maintain interest and stimulate individual work.
The Aviation Engine
Authors: Banks F. R.
Published: October 2007

This lecture is an attempt to give a cross-section of aviation engine development and progress during the last two decades.

Such a lecture is now opportune, since great progress has been made during the last ten years—mainly due to the 1939–45 war and the advent of the aviation gas turbine. The rapid development of this prime-mover has started a new era in aviation and the well-tried piston engine is already being relegated to second place and even eliminated in the more important aircraft applications.

The lecture is divided into two parts. The first deals with the piston engine and the second with the gas turbine. In the first part, the development of the piston engine is discussed; with emphasis upon those factors, such as supercharging and improved fuel, which have particularly contributed to its present high performance.

Cooling developments of both the air- and the liquid-cooled engine are discussed, and also the influence of such detail refinements as the sodium-cooled valve and sparking plugs having sintered aluminium oxide insulators.

The second part of the lecture describes the present forms of aviation gas turbine, with some details of its specific performance and the author's views concerning the future development and application of this new engine.

At the request of the Council, and where relevant, the author has shown how the development of the aviation engine has influenced that of the automobile engine and he has also given—in Appendix I—a summary of his views on the application of the gas turbine to road-vehicle propulsion.

This lecture would not be complete without reference to the great part played, in the 1939–45 war, by the aviation engine and automobile industries of Britain, in combining to produce large numbers of aviation engines for the Royal Air Force. In this particular connexion, the author is of the opinion that the experience and the production methods of the automobile industry, as a whole, contributed largely to the uniform excellence and economical production of the aviation engine, and fully vindicated the faith of those who originated the “Shadow” scheme in the rearmament period before the war.
Caustic Cracking: Stress-Corrosion Tests in Sodium Hydroxide Solutions at Elevated Temperatures
Authors: Weir C. D.
Published: October 2007

The paper describes a series of tests carried out using an apparatus specially designed for stress-corrosion investigations at high temperatures. The specimens, which were of hollow form, were inserted into the base of an autoclave and loaded by means of a lever system, through a push rod inserted in the specimen. This arrangement permitted the production of accurate notch-forms on the external surface in contact with the sodium hydroxide solutions.

It was found possible to produce failure of notched specimens rapidly and consistently, but homogeneously stressed specimens were immune. The fractures were intercrystalline and typical of those occurring in practice. Dilute solutions, though not entirely impotent, were found to be very much less effective than those of high concentration. The presence (or absence) of silica in the solutions exerted no appreciable influence. Neither the addition of tannin nor the use of fine-grain steels was completely effective in preventing intercrystalline failure, though in the case of the latter, increased resistance was noted in some cases. Cathodic polarization was found to be protective while anodic polarization did not prevent, and possibly hastened, failure.
Recent Developments of the Mechanism of the Hydraulic Variable-pitch Aircraft Propeller
Authors: Milner H. L.
Published: October 2007

After briefly outlining the main features of the variable-pitch propeller, this paper proceeds to describe the development of the piston-engined hydraulically operated propeller as a brake, both in the air and on the ground. Examples are given of the magnitude of the braking effort of a propeller when windmilling under controlled conditions and when in reverse pitch under power. The advent of the gas turbine, originally intended as a means of jet propulsion, opened up a new field of application for the variable-pitch propeller and this application with its attendant problems and their solution is discussed. Three types of gas-turbine power plant, together with the appropriate propeller arrangements are reviewed. These are: (1) the direct-connected turbine; (2) the compound-compressor turbine; and (3) the free-propeller turbine.

Each engine requires a plurality of controllable pitch stops peculiar to the engine type, and these are described.

The necessity for powerful controlling forces in maintaining the blades at any given pitch angle is made clear by consideration of the centrifugal action of a blade element, and an example of the magnitude of these forces is given for a specific case. Brief reference is made to developments in blade bearings, followed by an illustrated description of a contra-rotating propeller.
A Theoretical Investigation of Roll Flattening
Authors: Bland D. R.
Published: October 2007

A method of finding the distortion of the roll surface when subject to a known pressure distribution is described. This method is then combined with a plastic-flow theory of rolling to determine the shape of the arc-of-contact and the pressure distribution over it when neither of these are known beforehand. Apart from the assumptions inherent in the theory of plastic flow, two assumptions only have been made: that the roll is in a state of plane strain and that the shape of the arc-of-contact is independent of the distribution of the balancing forces. The accuracy of the results is estimated to be 20 per cent.

This paper shows that: first, it is not necessary to assume a parabolic pressure distribution to obtain a quantitative result; secondly, Hitchcock's solution (Hitchcock 1935)† is within the limits of error of the more fundamental solution and remains the most suitable method, for practical purposes, of allowing for roll flattening; thirdly, the main feature of the arc-of-contact is the depression in the region of peak pressure and the compensating greater curvature at both ends. This is a theoretical confirmation of Orowan's experiments (Orowan 1943).