bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
Transmission of Water-hammer Pressures through Surge Tanks
Authors: Zienkiewicz O. C. , Hawkins P.
Published: October 2007

This paper presents results of an experimental investigation into the way in which water-hammer pressures are transmitted through various types of surge tank. Orifice and differential surge tanks are subject to special scrutiny as in those instances the validity of the assumptions of the plane-fronted wave theory has frequently been subjected to doubt. Experimental results, however, confirm with good accuracy that the simplest and obvious assumptions are correct, and an adaptation of the Schnyder-Bergeron method is presented which allows transmitted pressures to be accurately estimated for most surge tanks. Some general formulae together with solutions of particular examples are included.
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.
The Instability of Testing Machines
Authors: Chilver A. H.
Published: October 2007

The paper is concerned with the stability of compression- and tension-testing machines. It is demonstrated that the buckling of a simple testing machine may be treated as an elementary problem in elastic stability. The case of a simple compression machine is first studied; it is found that machines of this type may be highly unstable if the length of a ball-ended compression specimen is short in relation to the length of the connecting ties. This adverse feature of compression machines is confirmed by general experience in compression testing. The theory of instability presented is in good agreement with the results of tests on both model and full-size compression-testing machines. In the case of tension-testing machines it is found that for most practical test conditions the length of the tension specimen is not a critical factor.
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.
On the Flow of a Compressible Fluid through Orifices
Authors: Jobson D. A.
Published: October 2007

By making certain basic assumptions, the author has determined a theoretical expression for the contraction coefficient, C, appropriate to an orifice when transmitting a compressible fluid, either above or below the critical pressure ratio, provided that the corresponding value for incompressible flow, Ci, be known.
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.
Heat-Transfer Problems of Liquid-cooled Gas-turbine Blades
Authors: Cohen Henry , Bayley F. J.
Published: October 2007

In this paper the authors briefly survey the possible methods of cooling gas-turbine rotor blades, and suggest that the most attractive is the thermo-syphon system, in which a quantity of liquid is enclosed within each blade to act as a conveyor of heat to the more easily cooled root. Two experimental investigations of this system are described, the first being that in which a rotating apparatus was used to give qualitative indications of the effectiveness of the system, and the second being one using a static rig with which a more detailed study of the heat-transfer mechanism was made. Provisional suggestions are made for applying the data to the design of cooled turbines, but the urgent need for data obtained under more realistic conditions is emphasized.
Behaviour of Rubber in Compression under Dynamic Conditions
Authors: McCallion H. , Davies D. M.
Published: October 2007

Experimental data are given in this paper showing the variation of stiffness, hysteresis energy absorbed per cycle, and resilience, with frequency, amplitude of deformation, and temperature. The data have been taken from the results of a series of tests covering the following ranges: Frequency 1.33–1,200 cycles per min., amplitude 0–10 per cent of the free length of the test-piece, and temperature from 125 deg. C. to −60 deg. C. (257 deg. F. to −76 deg. F.). In the latter part of the paper an attempt has been made to develop expressions to agree with the dynamic behaviour of rubberlike materials.
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.
A Servo-Controlled Continuous Feeder
Authors: Heydenrych J. C. R. , Luoto U. A.
Published: October 2007

An electronically controlled automatic feeder is described. Servo techniques are used to keep a weighing machine in continuous balance. The operation is discussed and circuit details are described.
The Vibration of Frames
Authors: Bishop R. E. D.
Published: October 2007

A method is presented of calculating the natural frequencies of plane frames. The technique is a numerical one and is based upon tables which were presented by the author (Bishop 1955)† in a recent article. The present paper is a sequel to the previous one and illustrates a way of using the data given in it. The frequency calculations are not restricted to the fundamental and they are such that a given frame may be checked for possible resonances over a prescribed frequency range without calculation of all lower natural frequencies. When a natural frequency has been found the appropriate principal mode may be calculated. The natural frequencies of the systems which are used for the purposes of explanation were checked experimentally.
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.
A Review of Applications of Radioisotopes to Engineering
Authors: Putman J. L.
Published: October 2007

Radioisotopes are radioactive versions of the natural chemical elements, differing from these only in their nuclear mass and in their ability to emit radiations. They are produced mainly by neutron bombardment of ordinary materials in a nuclear reactor.

The most important radiations are beta particles (fast electrons of nuclear origin) and gamma rays (penetrating electromagnetic radiations). These are detected with ionization chambers, Geiger counters or scintillation counters. In production control, the absorption or scattering of radiations is used as a measure of material thickness, and in some cases, of its atomic number.

Radioactive tracers aid in production research in rapid determination of mixing efficiencies and hold-up times. Tracers are also used in the non-destructive testing of materials and components and in more basic research into alloy structure. In this latter research, photographic films are used to produce autoradiographs which show the microscopic distribution of radioactively labelled constituents. Radioactivation by neutron irradiation enables certain impurities to be assayed at sub-microgram levels without chemical separation.

The wear of engine parts can be measured, in a fraction of the time taken for orthodox methods, by making the parts in question radioactive and measuring the worn radioactive debris in circulating lubricant. Cutting tools can be measured similarly by assaying radioactive debris attached to the swarf.

For many purposes gamma radiography supplements X-radiography or replaces it as a cheaper alternative. The greater manoeuvrability of gamma-ray sources is of especial advantage in the radiography of assembled engines.
Principles and Applications of Hydrodynamic-Type Gas Bearings
Authors: Ford G. W. K. , Harris D. M. , Pantall D.
Published: October 2007

In this paper is described an experimental investigation of properties and some developments in the utilization of hydrodynamic-type gas-lubricated bearings, of both journal and thrust types, as distinct from hydrostatic bearings. Two specific developments are described, the one a pump for circulating carbon dioxide gas at 100 lb. per sq. in. gauge and 150 deg. C. through a loop in a nuclear reactor, the other a gas-bearing motor driving a pump for molten radioactive bismuth, the whole within a hermetically-sealed container. The simple machining requirements and special design principles are described. The performance of gas bearings may be predicted from normal liquid bearing theory if the loading is so small that the pressure rise within the bearing is a small fraction (for example, 10 percent) of the ambient pressure. For higher pressure ratios compressibility effects must be taken into account. The experimental results and techniques used are reported, those for plain journal bearings embracing a wide range of working conditions and absolute size including compressible flow operation. An explanation of the physical reasons for the change in performance in compressible flow bearings is given. The dynamic instability sometimes encountered in journal bearings and methods of avoiding it is also discussed.
Stress and Deflexion Studies of Pipeline Expansion Bellows
Authors: Turner C. E. , Ford Hugh
Published: October 2007

In the design of pipelines for high-temperature service, allowance has to be made for the thermal expansion of the heated pipe. One particular aspect of this problem is the use of bellows expansion joints which, particularly on board ship, can transmit the pipe movements through bulkheads whilst providing a watertight flexible anchorage.

An approximate theory has been developed for the compression of a bellows, the convolutions of which have a cross-section formed by circular arcs subtending any semi-angle α. Numerical results have been calculated for the two cases α = π/2 and α = 3π/4.

Experiments have been carried out on six bellows, four corrugated-pipe type α = π/2, one S-type α = 3π/4, and one flat-plate type which was not analysed theoretically. Deflexion and resistance strain-gauge readings were taken on each bellows, and reasonable agreement was found between the theoretical and experimental results for the five bellows in which these could be compared.

It has been found that for certain design conditions optimum relationships exist between bore, wall thickness, and radius of convolution for the maximum flexibility. Stress intensification and flexibility factors have been calculated to cover a range of bellows proportions.
The Influence of Dynamical Imperfection on the Vibration of Rotating Disks
Authors: Tobias S. A. , Arnold R. N.
Published: October 2007

This paper is concerned with the vibration of disks particularly the form known as the ‘stationary wave’ which can develop in a rotating disk by the application of a stationary axial force at the periphery. The forms of vibration involving n nodal diameters are considered, and phenomena associated with linear and non-linear free and forced vibration are discussed in detail. Thereafter, attention is focused on the behaviour of real disks which, owing to inevitable imperfection, possess two independent modes of vibration, and thus two natural frequencies, for each value of n. It is shown that the stationary wave is greatly influenced by the degree of imperfection present. Experimental studies with stationary and rotating disks are presented covering forced vibration in the linear and nonlinear zones. The results show that a non-linear stationary wave may exist in a rotating disk over a wide speed range depending on the magnitude of the applied force. As speed increases this wave finally collapses and in doing so becomes a travelling wave which accelerates slowly in the direction of disk rotation as its amplitude subsides. Experiments conducted with large artificial imperfection show that the stationary wave may be transformed into two modes of vibration which are fixed in position in the disk. These modes resonate separately at their respective frequencies and apparently suffer a high degree of aerodynamic damping due to rotation. The magnitude of disk vibration is thus greatly reduced by the introduction of imperfection. Short mathematical appendices are included which contain the main theoretical results.
Effect of Heating and Cooling on the Mechanical Properties of an Alloy Steel
Authors: Kenneford A. S. , Williams T.
Published: October 2007

An investigation has been made of the effect of heating to, and cooling from, a temperature above the critical range on the mechanical properties of an alloy steel to specification B.S. En 29.

It has been shown that, on rapid cooling from a temperature above the critical range, the steel possessed poor mechanical properties (low yield and tensile strengths) at all temperatures down to the commencement of martensite formation at about 300 deg. C. (572 deg. F.). Below this temperature, there was a sudden increase in yield and tensile strengths, accompanied by a marked decrease in ductility.

The relation between these mechanical properties and the incidence of cracking after repeated heating and rapid cooling is briefly discussed.
Flow Measurement by Square-Edged Orifice Plates: Pipe Roughness Effects
Authors: Clark W. J. , Stephens R. C.
Published: October 2007

This paper presents the results of experimental work carried out recently to determine the effects on the discharge coefficient of various degrees of pipe roughness adjacent to and at different distances from an orifice plate. Experiments were carried out for air flow in 12-, 6-, and 3-inch pipes and water flow in 3-inch pipes.

Downstream, severe incrustation has no significant effect. Upstream, the effects vary with degree of roughness, pipe diameter, m value, and Reynolds number. For an m value of 0·5 and severe conditions of roughness, the combined effects of roughness and pipe diminution produce disturbance factors of the order of 1·40, 1·17, and 1·08 respectively for 3-, 6-, and 12-inch pipes. A length of two diameters of rough pipe immediately upstream from an orifice plate gives an effect close to that which would be obtained for a very long rough pipe. It has been found possible to extrapolate the results to very large pipes.

One of the most important findings is that cleaning a rough upstream pipe adjacent to an orifice plate for a relatively short distance reduces errors which may be otherwise very considerable to within known small limits. A table detailing the extent of such cleaning for various pipe sizes, mvalues, and degrees of roughness is given.

It is recommended that, where reasonable accuracy is required in the flow measurement of dirty fluids, installations should be designed for easy periodic inspection and cleaning of the upstream pipe adjacent to the orifice plate.
Vacuum Techniques in the Atomic Energy Industry
Authors: Kronberger H.
Published: October 2007

Vacuum techniques are used in two distinct fields: (1) applications where a vacuum is required as an essential part of the process, and (2) applications in which vacuum techniques are merely used to ensure the tightness of plant (which may not finally be required to operate under high-vacuum conditions). Advances in vacuum technology have made the construction and testing of plant to vacuum standards a relatively simple matter. Examples are given showing how vacuum techniques are used in the uranium 235 diffusion plant, in plant handling liquid metals at high temperature, in experimental work for pressurized water reactors, and in the testing of the Calder Hall heat exchangers.

The success of vacuum techniques in large-scale applications depends on three factors: correct design of plant, the availability of simple and reliable testing methods, and on efficient managerial control of construction and test work.

Basic design rules are given and illustrated by examples of flanges, valves, and other components used in the applications mentioned above. Vacuum testing methods are discussed. The charcoal-Pirani technique of testing is favoured for most applications; tests can be carried out on components before they are degassed and ‘clean’; equipment and operation are simple. The management of vacuum work is discussed and a method of quality control by means of binomial distribution charts is described which has been useful in improving systematically the vacuum tightness of manufactured components.
Statistical Methods Applied to Engine Testing
Authors: Buckland W. R.
Published: October 2007

In presenting the application of some statistical methods to problems in the field of research and development testing of internal-combustion engines, this paper attempts to stimulate interest in the use of modern statistical techniques in this important area of engineering practice. Owing to the wide range of possible applications the paper is selective and, besides saying little or nothing about many worth-while statistical methods, it also has to pass over the statistical approach to the control of quality and the inspection of the finished product.

After an introduction in which the need for the statistical approach is outlined, the paper considers an engineer faced with the problem of making an estimation from a few test observations. The outlying observation is dealt with followed by the desirability and value of ‘Confidence Limits’, ‘Tolerance Limits’ and the use of statistical inequalities. The third section moves one step further and considers two sets of observations. This deals with relationships, the scatter chart, and differences which must be tested for statistical significance: some attention is paid to the risks associated with drawing inferences from small samples of observations. The final section generalizes the position to many groups of data leading directly to the statistical technique of analysis of variance and the principles of statistical design of experiments. Some examples are given suitable for laboratory and bench tests as well as controlled trials and service tests. A brief glossary of statistical terms is given together with references to guide further reading.
Design and Development of Four Light-Weight High-Speed Marine Gas Turbines for Electric Generator Drive
Authors: Pope A. W.
Published: October 2007

During the last eight years, four high-speed marine gas turbines for driving generators have been designed, developed and put into operation. Two were base-load machines designed for operating at full tropical ambient temperature (100°F), and two were simple emergency and stand-by sets. The two base-load sets and one emergency were built under contract for the Admiralty while the other emergency set was built for the Merchant Navy.

A brief description of the most important features of these engines is followed by the main body of the paper which deals with the six most outstanding problems that were encountered during their design and development.
Developments in Methods of Measuring Stresses in Compressor and Turbine Blades on Test Bed and in Flight
Authors: Drew D. A.
Published: October 2007

An organization is described that has been operating for some years in connection with investigating vibratory and transient stresses in aero-engines. A large proportion of the work is being done on compressors and turbines and information is given upon some of the factors controlling the life of high-temperature gauges on them both.

Some techniques are described that are being currently used for a very big volume of testing at the Rolls-Royce works in Derby and are generally those which have been developed since the author's paper on turbine measurements read in America in 1951 (Drew 1952)†.

The system used at Rolls-Royce for a large proportion of tests of vibratory stresses is viewed by having one, and more recently two, recording rooms connected to all experimental test beds and a number of rigs by permanently installed cables.

Particular reference is made to the various forms of slip-rings in general use. The relative advantages of telemetering signals from aircraft to the ground and of obtaining flight measurements with an airborne multi-channel recorder are discussed.

Reproductions of records of rotating stall bands with their associated bands of high stress in the compressor are given, together with a brief description of the nature of rotating stall and the methods available for reducing troubles caused by it.

A small change in the running conditions to move the working point of the compressor has a very marked effect upon compressor blade stresses and in studying this either on the test bed or in flight it is vital to have a very precise knowledge indeed of the instantaneous fuel flow, rev/min and blower pressure at the instant of high compressor blade stress during a rapid acceleration.

A brief note on the results of the numerous tests which are being made is given, with a reference to a much fuller paper (Pearson 1953).
Nuclear Reactor Dynamic Analysis
Authors: Parr R. , Wordsworth D. V.
Published: October 2007

To investigate aspects of safety of control of a nuclear reactor system requires a method of analysis of the dynamic behaviour of the system following postulated disturbances or during particular operating conditions.

The paper derives equations which indicate the dependence of reactor power dynamics on fundamental design parameters, the ‘reactivity’, and the delayed neutrons, for a static fuel thermal reactor, a static fuel fast reactor, and a circulating fuel thermal reactor.

A method of analysis of component temperature variations is presented, with particular reference to a solid-fuel element, clad in a sheathing material, cooled on the outer surface by a flowing coolant. The coolant channel is formed in a solid moderator.

A comparison of theory and experiment for the BEPO reactor shows a fair agreement, there being a maximum difference of 10 per cent at maximum power during a transient resulting from a sudden increase in reactivity of 200 × 10−5.
A Study of Shrink-Fitted Assemblies Loaded in Torsion with Special Reference to Damping Capacity
Authors: Ørbeck Finn
Published: October 2007

Damping in shrink-fitted assemblies has been investigated and found to be of considerable practical importance.

It has been possible to give this damping a fundamental explanation related to elastic deflections and conditions of the mating surfaces of the assemblies.

Thus, the study of damping also yielded information about other characteristics, such as differential slip and stiffness.
Some Bearing Tests Made with a Machine Producing Impulsive Loading
Authors: Russell A. E.
Published: October 2007

It was considered that an assessment of the comparative performance of plain bearings subject to the impulsive type of load produced in compression-ignition engines would be a useful contribution to bearing knowledge. A machine for testing bearings under these conditions of loading was developed. The use of such a machine obviates the disadvantages that the use of an engine entails in respect of accurate measurement of the actual load on the test bearing, replacement of damaged journals, facility for changing journal materials and ease of examination of bearings. The use of a machine also allows the bearing to be assessed on its own merit by freeing the bearing from the influence of deleterious factors which are introduced when a bearing is housed in an engine, for example, indeterminate and variable misalignment, contaminated oil.

A description of the development of a prototype machine and of the machine in its final form is given.

The procedure for assessing the load capacity of bearings is described and the relative load-carrying capacities of various kinds of bearing material are given. The effects of changes in the lubrication conditions and also the effects of a certain amount of misalignment were determined. The changes of the running surface with increasing load and the effects of increased speed and of rate of loading (applied separately) were examined.
Some Factors Influencing the Stability of Piston-Type Control Valves
Authors: Noton G. J. , Turnbull D. E.
Published: October 2007

The reaction force on an open, spool-type, control valve acts in such a direction as to close the valve. For this reason a four-way valve, having its closed position at the centre of its stroke, can overshoot if the reaction force imparts sufficient energy to it during closure. If there is insufficient damping on the spool a continuous oscillation may arise and the present work investigates the dynamic behaviour of a common type of hydraulic position-control system in which such an oscillation has been found to occur.

Good agreement is obtained between the predicted and experimental minimum amplitudes and frequencies of oscillation and also between the theoretical and measured pressure fluctuations in the system. A graphical solution of the equation of motion of the system is included in the results and with the aid of ‘Describing Functions’ the approximate dynamic behaviour of the system considered may be derived.
Experimental Investigation into the Effects of Cross Flow with Condensation of Steam and Steam-Gas Mixtures on a Vertical Tube
Authors: Furman T. , Hampson H.
Published: October 2007

As part of a programme of comparison of filmwise and dropwise condensation of steam, it was required to know the effect of a cross flow of steam, with some non-condensable gas present, over the condenser tube. A 'steam tunnel' was developed in order to produce the required steam velocity with a limited steam supply at atmospheric pressure. Details of the apparatus are given together with the results of tests on a vertical tube.
A Large-Range Pneumatic Extensometer
Authors: Svensson N. L.
Published: October 2007

This paper describes the design and development of a pneumatic extensometer suitable for the measurement of axial strains of the order 10-5 over a range of ±20 per cent, using a 1-in. gauge length.

The pneumatic gauge is capable of measuring strains less than 10˜-5 over a range of approximately 4 times 10-3 thus ensuring adequate measurement of elastic and initial plastic strains. A micrometer screw is used for adjustment to cover the large range and is suitable for measurement of gross plastic strains. The mechanism of the instrument was designed to comply with the following requirements:

(1) magnification linear with strain, (2) nozzle and micrometer spindle to be maintained parallel, (3) insensitive to bending strains, and (4) accommodate changes in specimen diameter without adjustment.

Consideration of these requirements led to the choice of a parallel-motion mechanism made in two halves to allow for changes in specimen diameter. The measuring units were so placed as to measure the mean strain between the gauge points.

The method of calibration is described and also the method for analysing the results for comparison with the theoretical expression derived. This calibration and subsequent use of the instrument have shown that all the requirements listed above have been adequately satisfied.
Stress and Deformation Studies for Sandwich Rolling Hard Metals
Authors: Arnold R. R. , Whitton P. W.
Published: October 2007

The cold working of high-strength metals and alloys into sheet and strip form at the thinner gauges allows the metal manufacturer two alternatives: (1) high capital expenditure on a specialized mill of the Sendzimir or planetary type or (2) where demand does not justify the capital outlay, the application of new techniques utilizing existing equipment. In the latter class, the method of sandwich rolling is examined by theory and by experiment and it is shown that reductions in load up to 60 per cent can be achieved for rolling thin hard strip. The method allows greater reductions than for rolling the metal alone and decrease in finished thickness is obtained.

A method of adapting current cold-rolling theory for the calculation of loads involved in planning production schedules is set out, based upon a criterion of simultaneous yielding in the hard and soft metal layers. Optimum conditions of metal thickness ratio and hardness ratio for the sandwich metals are discussed.
Inherent Non-Linear Effects in Hydraulic Control Systems with Inertia Loading
Authors: Royle J. K.
Published: October 2007

The paper considers the inherent non-linear effects of inertia load on the performance of a pilot valve and ram system. Such a system may be considered as a model for many valve and ram or valve and motor combinations which are found in hydraulic control systems, and the results are therefore expressed in generalized form. It is shown that cavitation can occur dynamically when linear analysis would predict that only l/√2 of the static stalled effort is being utilized. Prior to cavitation there is surprisingly little distortion and attenuation of the velocity wave form of the ram when the valve is moved sinusoidally. The beneficial effects of exhaust lap are discussed and the paper goes on to develop and qualify the analysis when compressibility, friction, leakage, symmetrical lap and dither are introduced. Experimental results are compared with the theoretical predictions and the paper includes a note on the validity of small perturbation theory for this type of problem.