bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Critical Examination of Procedures Used in Britain and the United States to Determine Creep Stresses for the Design of Power Plant for Long Life at High Temperatures
Authors: Bailey R. W. 
Published: October 2007

The operating life of land power plant being far longer than allowable testing times for the constructional metals, the selection of a material, or the determination of its appropriate working stress, is dependent in an important degree upon the procedure followed in utilizing the creep test results obtained. Different procedures practised both in Britain and in the United States can result in different views regarding the potentialities of a material, and also about the working stress allowable. The paper examines the more commonly used procedures and focuses attention upon the factors present which would operate to introduce uncertainty and error as between the probable behaviour in the long time of actual service, and as yielded by a test procedure. The principal disturbing factor in altering the resistance to creep of the material is thermal action. In some procedures, especially where the creep tests are made at working temperatures, the influence of this factor may be small or negligible in the procedure, compared with its magnitude in service. The need is emphasized for thermal action to be taken adequately into account by the test procedure. Next in importance as a possible source of error is the method of extrapolation beyond the test times to the time of the operating life. The factor of thermal action and of its representation in the several procedures examined is considered. The circumstances of extrapolation are similarly investigated, especially in regard to whether the result would over-estimate or underestimate the safe working stress. Satisfying comparisons of working stresses using different procedures cannot at present be made. The position is therefore disappointing, and one which it is very desirable should be rectified.
The Observation and Control of Dust at Portable Abrasive Wheels and Pneumatic Chisels
Authors: Holman A. T. , James E. B. , Lawrie W. B. 
Published: October 2007

A new form of dust control has been devised for portable grinders. The method has been developed on a study of the aerodynamics of the system, as shown by cine-photographs of the moving dust clouds produced when grinding. It was known from earlier work that the dust of respirable size range did not follow the sparks thrown off by a grinding wheel. In consequence, the present work, which represents the first attempt to control dust through the portable wheel-guard, was directed to the control of dust of the respirable size range. Still photographs of the dust clouds are included in the paper. For many years pneumatic chisels have been used without any method of dust control, although an increasing volume of medical evidence has shown that these tools produce dangerous dust in certain industries. In some cases stone masons have fitted small local exhaust ventilation hoods in front of the chisel, and a recent paper described an exhausted dressing bench for use in steel foundries. There are, however, many instances where the work cannot easily be placed on such a bench, and so a new dust-control system has been fitted to a pneumatic chisel. In this design local exhaust ventilation is applied through a hollow chisel, and the dust is extracted through the pneumatic hammer. The main effort has been directed to the control of dust within the respirable size range, and the whole system was evolved as a result of the observation of the paths taken by the airborne dust produced by chipping. The moving dust clouds observed during the development stages have been photographed by a cine-camera, and the paper includes still photographs taken from the 35-mm. film negative.
A New Frontier: Air-pollution Control
Authors: Mallette Frederick S. 
Published: October 2007

Activity in the field of air pollution in the United States has reached tremendous proportions. Any attempt to summarize this effort, even superficially, would require space beyond the present limits. As an illustration, the proceedings of only one three-day meeting (United States Technical Conference on Air Pollution, 1950) at which ninety-seven technical papers were presented occupies a book of almost 850 pages. Since that meeting, the amount of technical thought and effort devoted to the problem of air pollution has grown apace, so that the developments and accomplishments in the field occupy the complete attention of several special publications, as well as resulting in frequent articles in the general technical Press. Therefore, the present discussion will attempt to cover only those areas in the United States and Canada where definite accomplishment or significant developments have been made in air-pollution control. In addition, its scope is limited by the special interests and opportunities of the author. The legislative developments of the important areas are treated rather fully, because in most instances of reduced air pollution it was an effective ordinance backed by public opinion which brought about the result. The influence of meteorological factors upon the dispersion or accumulation of air pollutants has long been apparent, but an understanding of the fundamental factors, other than wind, is just being reached. These principles are discussed generally, and in specific application. The highlights of the Donora (Pennsylvania) smog of 1948 are covered, primarily to illustrate how the present warning system has been developed. A description of the control procedures and equipment presently in use there is given, together with a statistical analysis of the air sampling and meteorological data which had been collected. In the light of recent findings on the synergic effect upon laboratory animals of sulphur dioxide and sulphuric acid mist, both of which are believed to be frequent air pollutants, some speculative thoughts are presented. If further research bears out these findings, there will then be available the basis for an explanation of the physiological mechanisms acting in acute smog episodes such as Donora and London. Controls to prevent the emission of sulphur gases would then become necessary. The current air-pollution activity has stimulated the development of instrumental methods for the detection, determination, analysis and recording of atmospheric contaminants, and factors influencing their accumulation or dispersal, many of which are described or illustrated. A corresponding stimulation in the control-equipment field has resulted from stringent local demands. Specific examples of successful application are given, but emphasis is placed upon the enormous cost and technical difficulties which such installations present. A concluding section deals with the socio-economic aspects of the air-pollution problem in which an attempt is made to visualize the future of the air-pollution control movement.
Component Losses in Kaplan Turbines and the Prediction of Efficiency from Model Tests
Authors: Hutton S. P. 
Published: October 2007

This paper has been written in an attempt to provide an improved scale formula for Kaplan turbines, which has theoretical justification as well as offering reasonable results in practice. A survey is made of all the important water turbine scale formulae since 1909 and their merits are compared. The Ackeret formula is one of the most interesting because it considers the kinetic and friction losses separately, and it is widely used on the Continent. By means of a simplified theory the formula was made to apply to both Francis and Kaplan turbines. It is now shown that the theoretical basis can be improved if the argument is restricted to the Kaplan turbine. A more comprehensive analysis suggests a modified formula offering better agreement with full-scale results and, moreover, a useful guide to efficiency away from the optimum. At optimum efficiency it is suggested that about 70 per cent of the losses are frictional, and therefore affected by Reynolds number, instead of 50 per cent as in the original Ackeret formula. The actual proportion will depend on the design and operating conditions of the machine, but the need for dividing the losses into frictional and kinetic parts and the method of calculating their proportions is demonstrated. The theory also shows that between 0.5 and 1.5 times the normal flow the proportion of runner to total losses may decrease from 90 to 50 per cent, and due allowance should be made for this when scaling-up performance away from the optimum. The value of the theory and the formula can be assessed only after comparison with reliable experimental data, but in the light of the limited evidence quoted here it seems worthy of further examination.
Heat Transfer by Convection from a Hot Gas Jet to a Plane Surface
Authors: Perry K. P. 
Published: October 2007

Measurements have been made of the heat transfer from air jets, with temperature differences of up to 400 deg. C. (750 deg. F.) and velocities of up to 250 ft. per sec., impinging on a plane surface at various angles. It has been found, that for flow parallel to the surface, the recommended mean formula Nu =0.036(Re)0.8(Pr)0.33 is still valid over this extended range of velocity and temperature. For flow perpendicular to the surface, the formula Nu =0.1810(Re)0.7(Pr)0.33 expresses the results if the velocity and temperature are calculated from free jet formulae. A series of multiplying factors has been obtained for this formula for angles of gas impingement down to 15 deg., at which angle the heat transfer is approximately half that at 90 deg. Where a gas jet impinges on a relatively large plane surface, it has been found that the heat-transfer contours for any one angle are identical for all jet sizes at all cross-sections situated more than ten nozzle diameters downstream. This result holds even where the temperature of the gas at the orifice exceeds that of the ambient air by more than 500 deg. C. (930 deg. F.). This extension of the jet similarity theory to impinging gas jets provides a simple method of calculating the total convective heat transfer from such a jet.
A Method of Defining Availability, Service and Output Factors of Steam Boilers
Authors: Houghton T. E. , Nonhebel G. 
Published: October 2007

The availability of a boiler is an indication of its reliability and effective performance, and may have as important an influence on the total cost of steam and power (including capital charges) as the efficiency. There are, however, no generally accepted definitions of availability and, in consequence, many of the figures quoted in the literature are useless for comparative purposes. The paper, therefore, puts forward definitions of availability on both gross and net bases. In addition, two other factors are required completely to evaluate boiler performance, and definitions of these, which are called ‘service’ and ‘output’ factors, are also put forward. All these factors have been used with advantage in an industrial concern for some years now and, after discussing them, it is suggested that they should be adopted generally.
The Effect of Fluid Pressure on the Shear Properties of Metals
Authors: Crossland B. 
Published: October 2007

This paper describes an investigation undertaken to determine whether fluid pressure has any effect on the shear properties of several metals. An apparatus is described in which it is possible to carry out torsion tests under fluid pressure of up to 20 tons per sq. in., and up to 40 tons per sq. in. if another torque bar is used. A simple high-pressure intensifier and secondary pressure gauge are also described. The results show that pressure has no significant effect on the shape of the stress-strain curves of the metals tested, though it does increase the strain-to-failure in some instances. The strain-to-failure appears to increase linearly with pressure, except with zinc and Mazak which give no increase in ductility with pressure. Numerous cracks, which formed in the specimens during test, were found to be inclined to the transverse plane of the specimen and at an angle slightly greater than 45 deg. to the direction of the tensile component of the shear stress.
Bending Stresses in Spur Gear Teeth: Proposed New Design Factors Based on a Photo-elastic Investigation
Authors: Jacobson M. A. 
Published: October 2007

The paper embraces three related subjects: Photo-elastic measurement of stresses in spur gear teeth; interpretation of stresses so found to give revised strength factors for B.S. specification on the design of spur gears; and a tentative attempt to correlate the stresses found with fatigue-test results which have been reported by various investigators. The object of this paper is to propose maximum safe bending loads which involute spur gears can be allowed to carry. The gears investigated are confined to those which can be generated by standard cutters conforming to the 20-deg. pressure-angle, B.S. basic rack, without either causing undercutting near the root or undue pointing of the teeth. The values proposed are based on a photo-elastic investigation carried out by the author under the guidance of Professor W. A. Tuplin, at the Post Graduate School of Applied Mechanics, Sheffield University. Strength factors for spur gears are given in the form of charts. These factors embrace the whole possible range of spur-gear combinations, both with and without addendum corrections. To enable a rational assessment of strength to be made, a list of service factors, as well as a graph correlating bending-fatigue data for three classes of surface finish (ground and polished, shaved, hobbed) are given.
Promotion of Fluid Lubrication in Wire Drawing
Authors: Christopherson D. G. , Naylor H. 
Published: October 2007

One of the factors limiting the rate at which wire can be drawn through tungsten-carbide or diamond dies is the severe die wear which may occur at high speed. If true hydrodynamic (fluid-film) lubrication could be provided in the die, wear would probably be much reduced. It is suggested that this can be done by supplying oil to the entry of the die at a pressure comparable with the yield stress of the wire. The necessary pressure can be conveniently generated by causing the wire to approach the die through a tube of diameter slightly larger than the wire diameter, sealed on to the inlet side of the die. Experimental work shows that the friction in the die itself can then be so reduced that, even when the drag in the tube is allowed for, the total drawing force is less than with the existing method of soap lubrication; and tests with steel dies have shown large reductions in wear. A theory of the behaviour of the inlet tube and of temperature distribution in the system is included.
Fuel Consumption and the Speed of Railway Transport
Authors: Gilmour A. 
Published: October 2007

One of the major factors affecting the fuel consumption of transport is speed. This paper describes an analytical method by which the effect of variations in speed on fuel consumption can be calculated. The calculation is based on the fuel-power characteristics of the power unit and the resistance to motion of the vehicle obtained from testing plant or bench-test results. The applications of this method are described, with particular reference to steam-railway traction, and the problems of operating trains so that fuel is used as economically as possible, or so that costs are minimized, are discussed, as well as associated design problems. A mathematical solution of the problem of running a train from point A to point B so that the fuel used is a minimum is given in Appendix I.
Experiments on a Small Pump Suction Well, with Particular Reference to Vortex Formations
Authors: Markland E. , Pope J. A. 
Published: October 2007

To investigate the incidence of air-entraining vortices in suction wells, experiments have been made with a suction tube of 2 1/2 inches diameter, fitted with a bellmouth intake, mounted in a series of wells of different shapes. With the tube set on the axis of a cylindrical sump into which water flowed radially between baffles at the bottom, only slight and transient air entrainment was noted, and this is ascribed to temporary irregularities in the flow near the water surface. Air entrainment was completely prevented by imparting a swirl to the flow at entry to the cylinder, and this swirl was found to pass into the suction tube with only slight reduction except near the axis. With the tube drawing from a rectangular well, air-entraining vortices formed at the edge of the wake of the external surface of the tube in the general flow in the well. The critical submergence (submergence of the bellmouth required to prevent air entrainment) is greatly affected by non-uniformity of the flow along the well. Any measure which reduces or diffuses the vorticity shed from the outer surface of the tube into the well has a beneficial effect; reducing the clearance between the rear wall of the sump and the suction tube reduces the streaming flow past it and so reduces the critical submergence, while a streamlined fairing fixed round the tube, or a cylindrical shroud placed within the well and coaxial with the tube, have both been found virtually to eliminate air entrainment.
A Standard Gas Turbine to Burn a Variety of Fuels
Authors: Feilden G. B. R. , Thorn J. D. , Kemper M. J. 
Published: October 2007

In this paper two aspects of gas-turbine design and operation are dealt with. First, an account is given of the development of special types of ‘kinematic’ construction suitable for accommodating the very large temperature changes encountered when a gas turbine is started and put on load rapidly. Examples are given of the application of this type of construction to representative components of a 750-1,000 kW. gas turbine. Secondly, a description is given of the development of combustion chambers to burn fuels ranging from natural gas and gas oil to residual fuels, coal tar fuel and peat. A range of chambers to burn these fuels has been designed to fit interchangeably on the basic components of the standard turbine. A detailed account is given of the development of a combustion chamber of elbow type which takes advantage of the fact that a number of changes of direction through 90 deg. or more are necessary in the ducting of nearly all industrial gas turbines. Development of this chamber is described from early atmospheric test models to the final pressurized combustion chambers which have been fitted to production gas turbines. With only slight adjustments, this type of chamber has shown itself capable of burning hydrocarbon fuels, ranging from natural gas to residual fuel oils, and a modified form of chamber has also successfully burnt low calorific value gases.
Three-Dimensional Motion in Axial-Flow Impellers
Authors: Hutton S. P. 
Published: October 2007

Detailed surveys have been made of the flow through a low-pressure-rise axial-flow impeller (hub/tip diameter ratio 0·33), which did not produce ‘free vortex’ whirl distribution. It was found that (1) at all flows, centrifugal forces caused large variations in axial velocity component through the rotor; (2) the angular direction of the flow varied considerably within a short distance of the rotor, and the flow did not stabilize until about two blade chords downstream; (3) as the tip clearance was increased, secondary motion was induced opposite to the motion caused by centrifugal effects and, for clearances greater than 1 per cent of the blade height, seriously restricted the use of radial equilibrium theory. The measured head-flow characteristics for various sections along the impeller blades did not agree well with those calculated by the following two-dimensional design methods: (1) ‘slip’ theory, (2) ‘cascade’ theory, (3) ‘aerofoil’ theory. Better results were given by the use of a new method which consisted of two steps: (1) calculating the change in axial velocity by the radial equilibrium theory, involving the use of cascade data; and (2) calculating the head-flow characteristics, using the aerofoil theory based on the mean axial velocity obtained from (1). By this compromise the calculated local performance over most of the blade agreed within 4 per cent of experiment for a wide range of flows between design point and the stall. The new method may be generally applicable to low-pressure-rise fans and pumps, but further experimental evidence will be required to confirm this.
The Influence of the Gas-Turbine Axial-Flow Aero-Engine on Blade Manufacturing Methods
Authors: Whyte R. R. 
Published: October 2007

In this paper, it is proposed, very briefly, to review the traditional methods of manufacture of steam-turbine blades, to comment on the different technical requirements of blades for gas turbines and then survey the history of some of the developments in manufacturing methods of blades for gas turbines with particular reference to the methods developed for the production of blades for an early series of axial-flow jet engines. As by far the larger proportion of blades in an axial-flow aero-engine are compressor blades, this paper is largely concerned with the development of compressor blade manufacturing methods. The paper concludes with a short appreciation of the past and future competitive positions of the precision forged and machined stainless-steel compressor blade.
Comparative Studies of Methane and Propane as Engine Fuels
Authors: Moore N. P. W. , Roy B. N. 
Published: October 2007

The performance of a single-cylinder, high-speed, spark-ignition engine has been studied with gaseous methane and propane as fuels. The power output and thermal efficiencies have been determined at two compression ratios, 5·5/1 and 10/1. A comparison for the same engine using liquid fuels is given in Appendix I. Both fuels will knock at high compression ratios; the limits have been determined for all ignitable mixture ratios, and also the effect of inlet temperatures has been studied. Both fuels are ‘temperature sensitive’, the effect being most marked with methane. An experimental comparison has been made of the auto-ignition limits of both fuels by the motored-engine method. Both fuels have been shown to give a stable region of visible cool-flame-type pre-reaction below the temperature for complete ignition. Despite the differing ignition temperature and pressure relationship determined by static experiments, a close similarity is revealed by auto-ignition experiments in the engine. Possible explanations of the differing effects are considered. Infra-red absorption gas analysis has been used to detect the small quantities of methane in the exhaust gas surviving combustion. A very low and constant concentration of methane is present with fast-burning mixtures, owing, it is believed, to valve overlap and scavenge effects. As the rich and weak mixture limits for steady running are approached unburnt methane increases in the exhaust, the effect being most marked near the weak limit. These effects are relevant to problems of atmospheric pollution from engine exhausts, and also assist in assigning the fall in engine efficiency at weak mixtures primarily to combustion inefficiency. Both methane and propane are shown to be suitable fuels for high-compression-ratio gas engines. Consideration of the combustion properties of these two pure hydrocarbons of simple structure is also of interest in extending the understanding of the general problem of engine knock.