bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.