bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Application of Cyclone Theories to Centrifugal Spray Nozzles
Authors: Doble S. M. , Halton E. M. 
Published: October 2007

The problem of designing centrifugal spray nozzles has been attacked by applying well-established cyclone formulae; these provide a theoretical explanation for empirical relationships (which have been obtained previously‡) between nozzle output, spray cone angle, and pressure drop. The nozzle is designed by first selecting suitable values of the following quantities:— [Formula: see text] Both the above quantities should be greater than 1 in order that the subsequent prediction of design data may be as accurate as possible. Apart from this limitation, the values assigned to those quantities are largely arbitrary in that they are not dependent upon the final spray characteristics required, but, as they affect the dimensions of the nozzle, the original selection may have to be adjusted after preliminary calculations if the estimated nozzle shape is in any way unsuitable. They may also have to be adjusted if they result in the calculated value of the quantity t/RE, i.e. (orifice film thickness)/(exit radius), being much greater than 00·5, as this will involve loss of accuracy in applying the theoretical equations. Having finally selected suitable values of Φ and Ri/ Re, the dimensions of the nozzle can be calculated by substituting the required values of the spray characteristics in the various formulae.
An Investigation of the Airbox Method of Measuring the Air Consumption of Internal Combustion Engines
Authors: Kastner L. J. 
Published: October 2007

The mass of air taken in per unit time by an internal combustion engine is a quantity of considerable importance in any analysis of engine performance, and a convenient means of measuring this quantity will often be required by the research worker or development engineer. Where reciprocating engines are concerned, the problem of measurement is not easy, since the flow is of a pulsating nature, for which “constant flow” types of measuring apparatus will, in general, be unreliable. A few suitable methods for measuring pulsating flows have, however, been devised, and what is generally known as the “airbox method”—consisting of the use of a measuring orifice in conjunction with a smoothing capacity—has often been employed, mainly because of its simplicity and the ease with which the necessary apparatus can be constructed. The work of Watson and Schofield (Proc. I.Mech.E., 1912, p. 517) has been of great value to users of the airbox method, but, though it has to some extent been supplemented by later investigations, several important questions still remain unanswered. The experiments described in the present paper represent an attempt to furnish additional information, in particular as regards the amplitude of the pressure fluctuations occurring in boxes of inadequate size and the errors in measurement produced thereby, a simple theory being given to account for these latter. The various factors governing the design of a reliable airbox meter are discussed, and it is shown that they can be related to the value of a dimensionless criterion which may be determined for any given engine.
Progress in Turbine Gear Manufacture in Recent Years
Authors: Sykes A. 
Published: October 2007

The problem of producing accurately cut gears for high-speed work has received a great deal of attention, which commenced with the work done by Sir Charles Parsons introducing geared turbines for marine purposes. During the 1914–18 war, a considerable impetus was given to the production of geared turbines, which resulted in an abnormal rate of development. Soon after the war there was an outbreak of gear failures—particularly in double-reduction gears for merchant ships—and investigation showed that the most important requirement was improved accuracy in gear cutting. Between 1920 and 1940 the search for accuracy continued, but there was a backward tendency in demand. An important incentive to improvement during the recent war came from Admiralty requirements for lighter and quieter running gears, and the subject was referred to the British Standards Institution. After the outbreak of war with Japan, marked progress was made in America, both in quantity and quality of production, and there was a regular interchange of information between British and American naval authorities. The hobbing machine still remains the accepted means of cutting high-speed gears, but there has been considerable difference of opinion as to whether creep or non-creep machines were to be preferred. A particular feature of improvement in non-creep machines has been the use of master index wheels having a much finer pitch than was at one time thought suitable, and this, combined with greater accuracy in construction, has led to a decided improvement in gear cutting. Problems associated with the cutting of accurate turbine gears are the production of accurate lead screws and profile-ground hobs for finishing teeth. The process of crossed axis shaving is a relatively new development which has resulted in a higher grade of finish and has been responsible for reducing certain types of error. Reference is made to experiments with carbide-tipped hobs and an indication is given of the use of materials having higher tensile strength and greater hardness as possible future developments.
The Life of Carbide-Tipped Turning Tools
Authors: Bisacre F. F. P. , Bisacre G. H. 
Published: October 2007

The paper is a contribution towards a rational quantitative theory of the tool-life problem. In the first part of the paper, the authors discuss an adiabatic theory of high-speed metal cutting, with no coolant. In machining medium-carbon steel with dry tungsten-carbide, cutting takes place under two widely different physical conditions, depending on the speed of cutting. Plastic deformation of the metal takes place as the chip crosses the tool face, and a higher temperature is developed most intensely at or near the surface of the cutting in contact with the tool face. Consequently the temperatures generated are higher—perhaps much higher—in the lower layers of the chip than elsewhere. If the speed of cutting is high, there is not sufficient time for effective diffusion of heat to take place into the colder parts of the cutting; the heat in fact stays where it is generated. The conditions are adiabatic. On the other hand, when cutting is slow enough, there is time for complete diffusion of heat to take place, whereby the temperature becomes uniform through the thickness of the chip. This is the isothermal case. It is found that these extremes occur when Reynolds thermal number (speed × thickness of chip ÷ thermal diffusivity) is large or small, respectively. In the second part of the paper, a series of experiments made by M. F. Judkins and W. E. Uecker in 1933 on tool life is examined, and a rule is given that embodies the results of these tests with unexpected accuracy. In the third and last part of the paper, a study is made of those properties of the metal cut and of the tool that affect the life of the tool. The method of dimensional analysis is applied to deduce a general form for the life-law. Judkins and Uecker's experimental result conforms to this law within the limits of the tests. But further experiment alone can confirm the general form—in its wider application.
The Development of an Axial Flow Gas Turbine for Jet Propulsion
Authors: Smith D. M. 
Published: October 2007

The paper reviews the technical development of the F2 jet propulsion engine, an axial flow gas turbine designed and manufactured by the Metropolitan-Vickers Electrical Company, Limited, under contract from the Ministry of Aircraft Production. An account is given of the preliminary work in 1938–9, in collaboration with the Royal Aircraft Establishment, on gas turbines for aircraft propulsion. The development of a simple jet engine of the axial flow type was started in July 1940. The first engine ran on bench test in December 1941. The first flights took place in June 1943 on a flying testbed, and in November 1943 on a jet-propelled aircraft. The evolution of engines of this type, leading up to the current F2/4 jet propulsion engine, is described. Each main component of the engine—the axial flow compressor, the annular combustion chamber and the high temperature turbine—necessitated extensive development work in fields previously unexplored; the methods used in the development of these and other components are explained. The F2 engine was the first British jet propulsion engine of axial flow type, and it is also unique amongst British engines in the straight-through design and annular combustion chamber that gives an exceptionally low frontal area.
The Air Cycle Heat Pump
Authors: Thomas T. F. 
Published: October 2007

The air cycle heat pump, using air both as working medium and as heat carrier, and suggested by Lord Kelvin nearly 100 years ago, has advantages as a means of combined heating and ventilating, on account of its simplicity and the recovery of ventilation heat losses. The paper briefly examines the theoretical possibilities of the air cycle for space heating and air drying. While the ideal air cycle is highly efficient with perfect machines, the inefficiency of actual machines and the temperature difference and air pressure drop across the heat exchanger reduce the performance considerably; but the power consumption for the net heat load is appreciably less than that for direct electric heating, whilst ventilation—for which electric heating is less suited—is provided in addition. Thus for certain applications such as hospitals, hotels, and restaurants where the number of air changes is greater, the air cycle heat pump might have economic advantages. The need for the improvement of heat exchangers is indicated, and the possibility of replacing separate compression and expansion machines by a “pressure exchanger” is discussed.
The Measurement of the Temperature of Sliding Surfaces, with Particular Reference to Railway Brake Blocks
Authors: Parker R. C. , Marshall P. R. 
Published: October 2007

A pyrometer, which covers the temperature range 200 to 900 deg. C. (390 to 1,650 deg. F.) with a response time of 10−3 seconds, has been developed for studying the temperature of stationary and moving surfaces. The values of the emissivities of bright and oxidized steel surfaces, determined by this method, agreed with other published work. The pyrometer has been used to determine the temperature of the surface of a railway tyre, during brake applications under various conditions, just as it emerged from beneath the brake block. Evidence is adduced to prove that the temperatures measured are not very different from those actually under the block. It is shown that the possible change in emissivity of the tyre steel is insufficient to invalidate the results. The variation and extent of the area of contact between brake block and tyre were investigated simultaneously with the temperature measurement. It was shown that high tyre surface temperatures (over 800 deg. C.; 1,470 deg. F.) are an inevitable result of “strip braking”. The preferred formation of heat spots between the spokes of the wheel, and the unequal growth of heat spots across and along the tread due to tyre distortion, were examined. An attempt to eliminate strip braking by reducing the length of the standard brake block to three-quarters, one-half, and one-quarter of its original length was made. It was found that reducing the brake block to one-quarter of its original length completely inhibited heat spot formation, reduced by a factor of 2 the standard deviation of the stopping times under standard conditions, and reduced the maximum temperature attained during brake application from over 800 deg. C. (1,470 deg. F.) to under 400 deg. C. (750 deg. F.). The deleterious formation of martensite was thus eliminated. It was found that the wear of the half-length brake blocks, expressed on a thickness basis, was not twice but maybe equal to that of a full-length block. Since the cost of a brake block is somewhat proportional to its size it follows that a shorter block may be more economical than a full-length block. It is concluded that the optimum size of a railway brake block must be determined separately for each material and set of operating conditions.
Basic Physical Properties Relied upon in the Frozen Stress Technique
Authors: Fisher W. A. P. 
Published: October 2007

The “Stress Freezing” method is a useful means of solving problems of three-dimensional stress by photo-elasticity. The method makes use of the fact that some thermo-setting resins having photo-elastic properties possess considerable residual thermo-plasticity. When softened by heat they obey Hooke's law, though the Young's modulus is, of course, very much reduced. At a given temperature, the birefringence, as well as the strain, has been shown to be proportional to the stress. Both strain and birefringence persist after cooling and unloading, and even after slicing the model. This behaviour is illustrated by means of a simplified concept. In the U.S.A., Glyptal resin is used (Bakelite B.T. 61 893), but this material cannot be had in thicknesses greater than 1 inch. Glass-clear phenol-formaldehyde resin (Catalin 800), which gives a higher stress-optical coefficient, can be had in larger sizes. The properties of both materials are compared, and troubles such as “rind effect” are discussed. Some experimental results obtained with Catalin 800 are given by way of illustration. The suitability of this material has been under investigation for some time at the Royal Aircraft Establishment, Farnborough, and careful tests have shown that, when suitably cured, Catalin 800 can give reliable results, but that “rind effect” is still a serious drawback.
Erosion Due to Incipient Cavitation
Authors: Bottomley W. T. 
Published: October 2007

Van Iterson's experiments show that cavitation erosion is produced by the collapse of minute air bubbles in water in a state of air supersaturation. This is contrary to the usual conception that cavitation erosion is due to the collapse of vapour bubbles. The author gives results of experiments which indicate that the bubbles which form and collapse at the stage of incipient cavitation in aerated water are air bubbles in a supersaturated state. The experiments also show that vapour bubbles which collapse in de-aerated water are in thermal equilibrium. It is shown that the collapse of bubbles in thermal equilibrium cannot cause erosion because the vapour pressure inside and the hydrostatic pressure surrounding the bubbles are balanced during collapse. The energy producing cavitation erosion is the free surface energy liberated by the collapse of the air bubbles. The final collapse velocity is the velocity of sound in water and the magnitude of the blow produced is of the order of 120 tons per sq. in. or more. The effect of these views on the interpretation of the model tests in cavitation tunnels and on the cavitation number is discussed.
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 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 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.
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.