bluuebunny/crossref_metadata_2025 huggingface dataset:
An Investigation of the Performance and Design of the Air Ejector Employing Low-Pressure Air as the Driving Fluid
Authors: Kastner L. J. , Spooner J. R.
Published: October 2007

The air ejector, in its various forms, is a device which has many applications in engineering practice, and several attempts have been made to analyse its mode of action, some of these having been supported by experimental work. Most of the experimental results available are related to ejectors in which relatively high-pressure steam is utilized as the driving fluid, but even in these cases the information provided is restricted to a narrow field.

The investigation described relates to an air ejector employing as the driving fluid air at a relatively low pressure, not exceeding 40 lb. per sq. in. (abs.), and covering a wide range of operating conditions by means of interchangeable nozzles. Two distinct experimental arrangements were built—one for the set of conditions in which the ejector draws in a relatively small quantity of suction fluid and pumps it through a relatively high pressure-ratio, and the other covering conditions in which the quantity of suction fluid is much larger, but the pressure ratio is quite small. For a given initial pressure and quantity of driving fluid, the rate of mass flow of suction fluid depends chiefly on the diameter of the combining tube, in which the driving and suction fluids mix; in the experiments, the ratio of com-bining-tube area to driving-nozzle area was varied in twelve steps, covering a range of area ratios from 1·44 to 1,110·0, and compression ratios ranging from about 3 to about 1·001.

Efforts were made to find the best proportions of those parts of the ejector which exert a major influence on performance, and certain conclusions are drawn from the results of the experiments. Theoretical aspects of the problem are briefly discussed.
Some Factors in the Use of High Temperatures in Gas Turbines
Authors: Brown T. W. F.
Published: October 2007

A comparison is made between gas-turbine cycles with inlet temperatures of 1,250 and 2,200 deg. F. The use of high inlet temperatures necessitates cooling; the effect of air and water cooling in turbines is examined, and equations are given and used to show the factors controlling cooling loss. A cooling-loss factor is also derived which gives the turbine efficiency obtainable with various degrees of cooling. A cycle with an inlet temperature of 2,200 deg. F. is examined to show the effect of air or water cooling. With water cooling the steam generated is then considered either to provide an increase in useful power or to pre-cool the inlet air. For greater efficiency the steam should be used to increase the power delivered. Practical considerations and a proposed marine layout are given, together with a series of conclusions. Appendices are also included giving the assumptions made and derivations of the equations.
The Effect of Tapered Treads on the Motion of Overhead Travelling Cranes
Authors: Diamond E. L. , Frankau A. M.
Published: October 2007

The well-known theory of the motion of a four-wheeled vehicle having pairs of tapered tread wheels joined by an axle is applied to cranes, and is extended to the important case of a four-wheeled crane with only one axle and to eight-wheeled cranes with two pairs of wheels driven by a common shaft. Observations of the actual motion of a number of cranes with parallel and tapered tread wheels are recorded. The tapered tread cranes give sinusoidal curves of motion in good agreement with theory, and design rules for the width of both parallel and tapered treads are suggested.
Dust Deposition from Chimney Stacks
Authors: Bosanquet C. H. , Carey W. F. , Halton E. M.
Published: October 2007

Economic competition compels many firms to operate processes which emit gases carrying a dust burden many thousand times that of atmospheric air. Even after treatment in the most expensive deduster this effluent will still hold some 5 per cent of its original dust, so that it must be discharged up a tall chimney. Wind eddies then dilute the chimney gases until they can be tolerated at ground level; however, during dilution the coarser dust is liable to settle and cause objectional deposits in the vicinity. The problem of designing an installation to avoid nuisance is therefore to remove the coarser grits in a deduster and to arrange the stack to dilute the finer residue so that deposits will not be noticed.

The authors have developed a set of reasonably simple formulae and charts for predicting the path of particles emitted from a stack and spread by the wind. Experimental checks have been applied to the predictions, but the subject is complex, and at this stage it is unlikely that it will be possible to predict the rate of deposit within a factor of 2.

In order to illustrate the implications of the paper a worked example is given on a powdered-coal boiler installation. This shows that with properly designed cyclones and a moderately high stack there will be no noticeable deposits. The implication is that it should be possible in time to extend the treatment given in the paper to specify a deduster exit which will avoid nuisance with fair certainty and at a relatively moderate cost.
The Use of Mild Steel for Service at Sub-zero Temperatures
Authors: Keating F. H. , Mathias E. V.
Published: October 2007

The paper describes an investigation undertaken to determine the limiting sub-zero temperature at which mild steel may safely be used, in relation to notch brittleness.

After a brief discussion of the literature on the subject, experimental work is described on the effects of variation in notch dimensions on impact value at sub-zero temperatures. Further work determines the effect on impact values of the surface cold-working resulting from grinding and machining, and indicates the beneficial effect of stress-relieving in removing the harmful effects of cold work on the surface. Practical experiments on small welded vessels in mild steel are then described, the vessels being tested to destruction at −80 deg. C. This work indicates that, while such vessels ultimately fail in a brittle manner, actual rupture is preceded by a considerable amount of plastic flow. It is argued, from these results, that the observed plastic flow gives adequate assurance that properly constructed mild-steel welded vessels will be able to absorb local overstressing to an appreciable extent without rupture, and this conclusion is supported by stress-strain diagrams taken at sub-zero temperatures.

The results of the investigation are the basis for the conclusion that, provided the recommended precautions as to quality of material and care in fabrication are taken, mild-steel welded equipment may safely be used at sub-zero temperatures down to −50 deg. C.
A Contribution to the Theory of Natural Draught Cooling Towers
Authors: Wood B. , Betts P.
Published: October 2007

In recent years the mechanical draught cooling tower has had the benefit of theoretical analysis developed in Germany and in the United States, resulting in the evolution of the “total heat method” of heat transfer calculation which together with empirical data provides a sound background for thermal design.

The natural draught tower contains the same elements with the difference that its performance is also dependent on the atmospheric dry bulb temperature, which introduces a fourth variable in addition to the wet bulb, the load and the water rate which apply in mechanical draught towers. Because of the greater complication it has hitherto resisted a theoretical approach.

The present paper offers an extension of the theory to cope with varying air rate, establishes the relevant equations and shows how these can be solved. After deriving the basic characteristics of a tower and fill from analysis of the test data, it is possible to predict the performance of a similar tower under other conditions. Though the analysis may be rather involved for routine design work it offers a basis for the formation of logical ideas as to how the various factors influence performance and enables the effects to be visualized with the aid of diagrams.

An explanation is offered to account for the observed effect of wind in increasing the draught. The issues of water loss by evaporation and carryover, the formation of the visible plume, and the avoidance of nuisance are discussed from physical principles.
Thin Aerofoil Theory and the Application of Analogous Methods to the Design of Kaplan Turbine Blades
Authors: Hutton S. P.
Published: October 2007

In order to increase the power and working heads of Kaplan turbines it is necessary to avoid any low local pressures round the blades. The problem is similar to that encountered in high-speed aerofoil design, and the possibility of using similar methods to evolve blade sections for Kaplan turbines is explored in the paper.

A general survey for those unacquainted with recent developments in aerofoil design is given, which is intended to demonstrate the advantages of the use of profiles with specific velocity distributions and to illustrate the general methods by which they may be derived.

A brief summary is made of methods of designing aerofoils in cascade to allow for blade interference and a few examples are quoted from British and American practice.
The Friction of Flexible Packings
Authors: Denny D. F.
Published: October 2007

At any time there are anomalies and difficulties in the prediction of friction, and these are accentuated if one of the surfaces is deformable, as in flexible piston seals, since the surface strain introduces an additional variable. Such surfaces, although exhibiting the three usual kinds of friction—dry, boundary, and film—show peculiar characteristics at low speeds, when the friction is usually less than that at higher speeds. The static friction itself depends on the time during which the surfaces have been in contact, and preliminary work indicates that there is a law connecting these two quantities, the probable form of which is given in the paper.

The experiments suggest that the total friction force need be no greater than 1 per cent of the force on a 3-inch diameter piston at pressures of the order of 2,000 lb. per sq. in. (and may be much less in the case of specially shaped seals) though the accuracy of prediction is unlikely to be better than ± 10 per cent.
The Problem of Burning Residual Oils in Gas Turbines
Authors: Lloyd P. , Probert R. P.
Published: October 2007

The burning of residual oil fuels in gas turbines raises some special problems: the efficient combustion of the solid particles to which these fuels give rise, the avoidance of ash deposits, and the protection of turbine blades and other components from corrosion effects peculiar to these fuels.

This lecture discusses these problems and the methods which are being considered for solving them. It is shown that the burning of these heavy oils is not the greatest of the difficulties, since with suitably designed equipment this process can be quite efficiently performed. What is difficult is the avoidance of ash deposition and of the secondary effects, notably blade corrosion, to which this deposition gives rise. These effects are considered in some detail.
Some Problems in the Manufacture of Experimental Gas Turbines
Authors: Leedham L. H.
Published: October 2007

The gas turbine has created new workshop problems arising from the use of special materials and from the complexity of some of its component parts. The construction of experimental sets calls for much improvisation to avoid heavy expenditure on special tools and machines, and the paper gives examples of methods which meet this requirement.

Blading for axial turbines and compressors when required only in small numbers, as in the manufacture of experimental sets, is probably the major problem and cannot be met without the provision of some special facilities, the basis of which is usually copy machining.

One of the most notable developments has been the use of sheet metal in the gas turbine, not only for the combustion system but also for structural parts, many of which are subject to severe conditions imposed by high temperatures, and fatigue stressing. The highest grade workmanship is essential in this connexion, to ensure reasonable life, free from failure.

The special demands of gas-turbine design are constantly giving rise to new manufacturing techniques and the paper deals briefly with some of these, such as those associated with welded rotors and precision forged blading.
Investigations Concerning Flow Conditions in a Centrifugal Pump, and the Effect of Blade Loading on Head Slip
Authors: Peck J. F.
Published: October 2007

The object of the paper is to examine the flow conditions observed in a specially designed 6-inch centrifugal pump; firstly, when the directions and magnitudes of velocities of flow were obtained by means of Pitot tubes, and secondly, when the flow was examined with an electronic stroboscope, through an inspection window of “Armourplate” glass in the casing.

To provide uniform entry conditions a single-entry pump was chosen, preceded by a long length of straight suction-piping, but at small discharges a powerful forced vortex was found to exist with a spiral flow extending backwards for some distance from the pump inlet. This phenomenon was investigated by traverses with a direction vane and Pitot tubes, and an explanation of its cause is offered.

The direction and magnitude of the absolute velocity at the impeller outlet were measured by cylindrical Pitot-tube traverses across the passage at two positions, and at small discharges a component of flow from the casing towards the suction side was found to occur through a portion of the impeller on the side nearest to the suction pipe. Similar traverses were made at two positions around the volute casing. These indicated a symmetrical, double spiral-flow at the best-efficiency point, and at other discharges this was modified to a single-direction vortex having a core at a much lower pressure than that on the outside of the casing.

Pressure tappings on the casing, with an open-sided impeller and diffuser, showed the effect of shock on the inlet tips of the diffuser vanes, and inspection through the window confirmed a flow surging to and fro at small discharges.

The effect of impeller blade loading on “head slip” is also investigated—two impellers showed a direct relationship—and values of the resulting “slip constant” are given. A graphical analysis shows the head slip, and head losses in the impeller and casing for the full range of discharge.

Finally the performance curves of the pump, operating in reverse as a turbine, are given, from which the “runaway” speed under any head and any resisting torque may be estimated.
Pipe Joints for Hydraulic Power Transmission
Authors: Cooke B.
Published: October 2007

Hydraulic machinery suffers from the disadvantage of leakage of the fluid. Faulty pipe joints are one of the main offenders in this respect. In this paper the author describes some tests, carried out on a variety of pipe joints, to find a satisfactory one. In the absence of quantitative data, a joint and joint-ring were designed from the results of the tests. It is hoped that this paper will stimulate interest in this subject and so lead eventually to a wider knowledge and greater efficiency.
Contribution to Improved Accuracy in the Calculation and Measurement of Torsional Vibration Stresses in Marine Propeller Shafting
Authors: Archer S.
Published: October 2007

Methods of calculating torsional vibration stresses in marine propeller shafting have differed mainly in the apportionment of damping energy between engine and propeller, and for this purpose a propeller damping constant of average value has commonly been assumed.

The author has long considered this simplifying approximation unjustified, since no account is taken of variations in geometrical design factors as affecting propeller damping properties. As the propeller is usually by far the major damping influence in the single-node mode, the accuracy of stress prediction must often suffer correspondingly.

The paper details a convenient method of deriving damping coefficients for modern three- and four-bladed bronze propellers. Curves are plotted, for a series of pitch ratios, against a non-dimensional power coefficient involving only quantities usually known in the design stage, namely, horse-power, propeller revolutions and diameter. Allowance for disk area ratio is by interpolation between limiting values.

Attention is also drawn to possible serious errors in interpreting torsiograph records taken from the crankshaft end of marine heavy-oil engine systems, arising from the phase difference between engine and propeller vibration at resonance—a consequence of heavy propeller damping. Here again improved knowledge of propeller damping characteristics is desirable if maximum accuracy is to be achieved.

The paper concludes with a worked example from practice, indicating the order of magnitude of errors involved, with details of a simple vector method of allowing for the phase effect in any given instance.
New Formulae for Water Flow in Pipes
Authors: Blair J. S.
Published: October 2007

As a result of extensive investigation of water flow formulae and test data on water mains and experimental test pipes, four new formulae for water flow in pipes have been evolved. These apply to pipes in new condition using water at normal temperatures, and cover all classes and sizes of pipes and a very wide range of velocities. The constants in the formulae do not require to be varied to suit the condition or the size of pipe. It is only necessary to choose the appropriate formula to suit the material of which the internal surface of the pipe is made. These four formulae are:—

(1) For smooth non-ferrous pipes: V = 47 m***0·71 i0·57. (2) For bare steel, wrought iron, asbestos cement, or bitumen lined pipes: V = 40 m0·69 i0·555. (3) For bitumen coated steel pipes or concrete pipes: V = 36 m0·68 i0·54. (4) For galvanized cast iron, or other coated cast iron pipes: V = 300·67 i0·52.

An approximate estimate of the conditions arising when fluids other than water are used can be obtained by plotting these formulae on a Reynolds number diagram, and taking the value of F at the appropriate Reynolds number, but this is not recommended, since these formulae have not been compared with practical test results for fluids other than water.

The use of these formulae will give the discharge to be expected from any class and size of pipe to an error of not more than about ±10 per cent. Such accuracy is adequate for all ordinary water flow calculations, and is better, over the whole range of pipe surfaces, sizes, and velocities, than has been previously possible by the use of any other formula.
The Size Effect in Fatigue of Plain and Notched Steel Specimens Loaded under Reversed Direct Stress
Authors: Phillips C. E. , Heywood R. B.
Published: October 2007

The fatigue strength under reversed direct stress was ascertained for specimens of various diameters in the range from 0·19 inch to 2·4 inches, the largest diameter being determined by the capacity of the machines available. Two steels were used in this investigation—a 25-ton mild steel and a 65-ton, per cent nickel-chromium steel. The specimens were either plain or notched (transverse hole) and, as far as possible, geometrical similarity was preserved with regard to the transition radii and the diameter of the transverse hole. A few fatigue tests on other types of notch, such as a circumferential V-groove and a shoulder, were also carried out.

No intrinsic size effect with either material was observed with the plain specimens.

With transverse-hole specimens in mild steel, the fatigue limit was ±8·4 tons per sq. in. for specimens of 0·33 inch diameter, and 6·1 tons per sq. in. for specimens of 1·7 inches diameter, thus showing that an appreciable size effect was present. A similar size effect was found with the alloy steel specimens containing a transverse hole, and fatigue limits of ±17·1 and ±13·9 tons per sq. in. respectively were obtained for these two sizes of specimen.

It is suggested that the low values of fatigue-strength reduction factors usually associated with mild steel as a result of laboratory tests do not apply to the larger sections of this material commonly employed in engineering practice.
Low Pressure Reciprocating Seals for Hydraulic Control Valves
Authors: Cooke B.
Published: October 2007

In tests on low-pressure oil seals the technique of designing a synthetic rubber lip type of rotary seal so that it is “run-in” on the shaft was applied to finishing the lip of a seal for reciprocating duty. The performance of a seal so treated is shown to be greatly superior to that of untreated seals. A new method of measuring the inward load was devised and is described in detail. Interesting data on friction were noted and are shown graphically.
Plastic Flexure of Mild Steel Beams of Rectangular Cross-section
Authors: Shackell K. K. , Welsh J. H.
Published: October 2007

The paper describes tests on a 0–28 per cent carbon steel in tension and compression, and in flexure of beams of rectangular cross-section, to a maximum strain about three times that at the initial yield. The object of these tests-was to investigate the shape of the stress-strain curve immediately after the initial yielding, and to determine whether in a case such as flexure the upper yield stress could be relied upon as a criterion of design. The results from this material indicate that the stress-strain curve falls rapidly but not immediately from the upper to the lower yield value, and that a beam is capable of withstanding a slightly greater bending moment than would be predicted by calculations based on the direct stress tests including the upper yield stress.
Gear-tooth Stresses and Rating Formulae
Authors: Merritt H. E.
Published: October 2007

The state of knowledge about stress conditions in gear teeth is briefly reviewed, and directions in which further research is required are indicated. The assumptions underlying methods of stress-comparison, and the chosen load-points, are considered in relation to profile-modification, leading to revised conceptions of “precision” and “commercial” classes of gear. The present (British standard) basis for the design of “commercial” teeth is stated and a new basis for the design of precision, high-duty gears is offered.

Criteria of surface stress are re-examined and current British standard rating formulae for wear are shown to be equivalent to the use of an unmodified criterion Sc = Fc/ Rr in conjunction with a speed factor which is a function of pitch circle velocity and gear ratio. New values for zone factors and strength factors for spur gears have been determined on the revised assumptions, and it is shown how the factors for helical teeth may be derived from those for the virtual spur gears. The assumptions underlying rating formulae for variable load-cycles are also examined, and a revised formula is suggested whereby present inconsistencies are removed.
Use of Heavy Fuels for Medium-sized Marine and Stationary Diesel Engines
Authors: Smith J. R. P.
Published: October 2007

Problems are discussed associated with the burning of heavy fuels in medium-speed, two-cycle, trunk-piston types of engine. Tests with a stationary engine are described, and performances, rates of cylinder-bore wear, and degrees of fouling are compared, when five classes of fuel are burnt.

Pre-treatment of fuels in the centrifuge is considered, and the results from practical experience show how certain fuels with high ash content, probably in an oil-soluble form, promote rapid cylinder-bore wear, even after being subjected to thorough treatment.

Comparative rates of deterioration of the lubricating oil are recorded when different classes of fuel are burnt, and figures are given which show how fuels with a high sulphur content promote the formation of sulphuric acid in the crank chamber.

Findings with the stationary engine are correlated to marine requirements, and the economy aspect is presented of bunkering a lower grade of fuel in a coastwise vessel of 2,500 tons dead weight. The conclusion is reached that a marine Diesel fuel, preferably a distillate, instead of gas oil could be bunkered with financial advantage, but that in the light of present knowledge the use of a boiler-grade fuel could not be recommended.
Nodal Pattern Analysis
Authors: Grinsted B.
Published: October 2007

The paper elucidates the manner in which impeller blades, turbine and axial compressor blades, aircraft and marine propeller blades or similar bodies, vibrate in their higher modes. It is demonstrated that complex nodal patterns derive from consistent series of simpler modes and that the frequencies of the latter may be plotted in families of curves.

Classical work of Chladni, together with more recent investigations on free square and circular plates, is first reviewed. The similarity of the manner of vibration of the cantilevered plate is then described with a note on the relation of the torsional series of modes to the simple flexural “bar” type modes. The vibration nodal patterns of impeller blades are discussed and diagrams illustrate how “complex” modes were resolved into their constituent “basic” modes, each having an ordered place in the families of modes and frequencies. Similar analysis, with examples, is shown to be applicable to turbine blades, and aircraft and marine propeller blades.
Wind Tunnel Investigations on Rotating Blades of Aerofoil Section
Authors: Khalil K. H.
Published: October 2007

The results are presented in this paper of investigations on the pressure distributions around aerofoil section blades while rotating in a wind tunnel. The experimental difficulty of obtaining pressures during rotation was overcome by the use of a special gauge attached to the hubs and illuminated by “Strobo-flood” for direct observation. Pressure diagrams and lift coefficients were obtained along the radius of a double-blade set, arranged as a windmill, for various angles of incidence.

Static tests were conducted also in all cases to find values for comparison. As the purpose of the work was to contrast rotating and static conditions, two main facts are emphasized: the similarity in the pressure diagram shapes and the significance of the spin factor. It therefore becomes possible to correct ordinary test results obtained when using stationary aerofoil blades in wind tunnels by adding the effect of a vortex of rotation of uniform strength.
Machine Tool Simplification, Especially as Applied to Horizontal Boring Machines
Authors: Sparkes C. A.
Published: October 2007

The author believes that simplification, while it must not be regarded as the panacea for all the ills of our industry, can if correctly applied be of immense benefit and that, though much has been said and written on the subject, few practical examples of its application in design and manufacture have been made available.

The early history of machine tools is reviewed in this paper, and as the horizontal boring machine incorporates the general features of most machine tools it is used as a typical example.

Some suggestions are made on the subject of simplification from the aspect of design, and practical examples are given of its application to patterns, castings, machining, lubrication, controls, measuring systems, and electrical equipment. Single-purpose machines, tool equipment, and accessories are also examined.

It is proposed that the maximum advantage cannot be gained from a process of simplification unless a high degree of standardization is accepted, and therefore in reviewing the design of a complete range of horizontal boring machines a new principle of unit construction is explored in theory and practice. Examples are given of the application of this unit system to all sizes of horizontal boring machines, including the universal type. The paper concludes with a description of a new slideway grinding machine generally constructed from standard units.
Welding in Marine Engineering
Authors: Pemberton H. N.
Published: October 2007

This lecture comprises a survey and commentary on the use of welding for the construction and repair of marine machinery for main propelling and ancillary purposes. The history of welding in relation to marine engineering is traced from the hammer welding of boiler seams in 1870 up to the present day, when welds made by modern processes are accepted for highly stressed components.

Descriptions of welding processes are omitted since the lecture deals with welding applications rather than welding technique. Numerous examples are given and illustrated, and many of them relate to design details which are typical of good practice and are accepted by ship classification authorities.

The lecture is divided under two main heads, namely, “New Construction” and “Repairs”. A further subdivision is made under “New Construction”, so that boilers, pipe-work, machinery components, turbines, gearing, electrical propulsion, refrigerating plant, and dredging craft are dealt with in that order. Also included in this section are some remarks of general interest on the subject of residual stresses and their relief by thermal treatment.

Problems concerning the welding of alloy steels for gas turbines are discussed. There is need for research into the weldability of these steels, bearing in mind that not only the welds should be free from micro-cracks to start with, but they should also be equivalent to the parent metal in resistance to metallurgical and physical deterioration whilst operating at high temperatures over long periods.

A field of welding which is always of interest to marine engineers is in repair work. Unlike land plant for which complete resources for repairs are usually available, marine machinery may be involved in mishaps and breakdown on the high seas and in remote parts of the world when repair facilities might be primitive, or even non-existent. Many ships now carry electric welding equipment, and sea-going marine engineers include welding in their many manual accomplishments.

Several interesting examples of weld repairs are described, which in some cases have enabled ships to complete their voyages carrying valuable cargoes with a minimum of delay. Other examples are given which emphasize the discrimination that is necessary in deciding whether or not a welded repair is desirable. Unfortunate consequences have followed the ill-advised use of welding in some cases.
Some Practical Aspects of Cutting Tool Nomenclature Arising from Recent Research
Authors: Galloway D. F.
Published: October 2007

In recent years a considerable volume of research has been carried out to improve the techniques employed in the most widely used metal machining processes. An essential preliminary to all these experiments in turning, milling, drilling, tapping, etc., was accurate control of tool shapes. This necessitated the development of adequate tool-measuring equipment and a comprehensive nomenclature. The nomenclature has resulted from an analysis of tool geometry, and an examination of applicable tool grinding methods and inspection equipment. The nomenclature has been extended to take account of factors which were proved by research to be of considerable practical significance in the ultimate tool performance.

Nomenclatures for the most commonly used types of tool are presented as a basis for discussion together with typical examples of tool geometry, tool grinding methods, and tool inspection equipment which should be taken into account when developing improved nomenclatures. Reference is also made to some of the British, European, and American standards, which have an important place in these discussions. Some of the problems involved in the workshop application of cutting tool nomenclatures are also considered.

Recently, significant advances have been made in tool nomenclature as a result of the increasing co-operation between manufacturers and users of tools, but the nomenclature used for development work in research stations, colleges, universities, and industrial research laboratories, needs to be more comprehensive and precise than that at present used in general engineering practice.
Present Trends in Surge Tank Design
Authors: Jaeger C.
Published: October 2007

The author summarizes the well-known theory of surges in surge tanks, dealing chiefly with the fundamental equations and introducing some preliminary remarks on the stability of surges. He then describes the different types of surge tanks, ordinary cylindrical tanks, tanks with variable section and expansion or reservoir chambers, tanks with restricted orifices, and differential surge tanks, with special mention of surge tanks in conjunction with underground power stations.

The loading conditions to be adopted are discussed and the reason why load changes on the electrical grid are the prime cause of surges is explained. The basic assumptions adopted for surge calculations by Italian, Swiss, French, and British engineers are reviewed, and it is shown that, in spite of many apparent disparitiés on special points, there is widespread agreement on fundamental questions. The interaction of surges, water hammer, and turbine governing is discussed in the light of the most recent tests on large power stations and of the results of modern theories, and the importance of the influence of water hammer on surge tank design is considered together with the special case of surge tanks connected to feeder canals.
Fuel Systems and Controls for Marine Gas Turbines
Authors: Darling R. F.
Published: October 2007

It is emphasized that reliability is by far the most important requirement in the control system of a marine power plant. The controls of the Pametrada 3,500-h.p. gas turbine, which is taken as a typical marine unit, are then discussed. The sprayers, control blocks, fuel system, transmission, reversing mechanism, and governors are described in turn, and the reasons are given why various features were adopted in preference to the possible alternatives. There is an account of test-bed experience concerning these items.

Probable future developments in the field of controls are then considered, but these are found to depend mainly on the way in which the gas turbine itself is developed for marine purposes. The paper therefore concludes with a discussion of the type of gas turbine most likely to be installed in merchant vessels, and the means whereby it will be controlled.
The Calculation of Roll Force and Torque in Hot Rolling Mills
Authors: Sims R. B.
Published: October 2007

Equations are derived for the normal roll pressure, specific roll load and torque in hot rolling mills, using the condition for plastic deformation in rolling derived by Orowan, together with von Kármán's equation of equilibrium. Although applying strictly to the rolling of ideal plastic-rigid materials, these equations may be applied to the rolling of materials which strain-harden by using a mean value of the yield stress in the pass.

The equations have been checked against measurements made when rolling pure lead at room temperatures, and against the results of the experiments on steel at elevated temperatures carried out at Holfors. There is close agreement between the calculated and measured roll loads, but the roll torque is over-estimated slightly by the theory, above reductions of about 30 per cent in thickness.
Practical Training in Industry for the Graduate in Mechanical Engineering: Part II
Authors: Fulton H. W.
Published: October 2007

Essentially, Part II of this paper recommends planned interweaving of theoretical and workshop practice throughout the period of training.

A plea is made for industry's side of training to include some experience in non-engineering, but essential and ancillary branches of the industry, e.g. production and stock control, costing, sales, and general office work.

It is emphasized that the larger the organization, the more need there will be specifically to provide this external experience.
Practical Training in Industry for the Graduate in Mechanical Engineering: Part III
Authors: Medlock R. S. , Lant D. P.
Published: October 2007

The potentialities of a graduate spring from the theoretical and fundamental nature of an academic training. This develops power of analysis, judgement, and initiative, which should be remembered when planning the complementary training course which is mainly practical and technological.

The course should not attempt to make the graduate a skilled craftsman but rather to train him in the application of machine tools to production processes. The fully-trained graduate is expected to fill a vacancy in the production, sales, or research and development departments, and although the training can be slightly biased for those apprentices expressing a wish for a particular branch of engineering, early specialization should be avoided.

The training programme should be flexible to suit the needs and progress of the graduate, always provided that sufficient time is spent in each department for him to make a useful contribution to output, but without wasting time on needless repetition. In every department, the period of instruction should be as intensive as possible, leaving more time for responsible duties.

He is expected to add to his store of experience by analysing the bad things he notices as well as the good. These should not, of course, be reported, but he should be expected to make a weekly report on progress in order to help him crystallize his thoughts.

The works training should be supplemented by post-graduate courses in technology and management studies. At the end of the training period, the next phase should rest with a high-ranking committee responsible for executive development.
The Effect of Auxiliary Fuels on the Smoke-limited Power Output of Diesel Engines
Authors: Derry L. D. , Dodds E. M. , Evans E. B. , Royle D.
Published: October 2007

It is well known that one of the factors Limiting the power output from Diesel engines is the tendency to produce exhaust smoke. In consequence only some 65–70 per cent of the available air can be burnt. By reducing the full-load quantity of Diesel fuel injected and aspirating a volatile fuel, such as gasoline, into the intake air, power outputs of 20 per cent or more above the maximum rated load can be obtained without producing more smoke than when the engine is operated at full load under normal conditions. About 80 per cent of the available air can then be utilized.

The effect of octane number of the auxiliary fuel is important, maximum smoke-limited powers being obtained with the higher octane number fuels, while with fuels of low octane number, power increase may be limited by the occurrence of knocking when the air-fuel ratio is too low. By limiting the power on Diesel fuel alone to about 80 per cent of the normal maximum and aspirating gasoline into the intake, it is possible to obtain a power increase of about 12 per cent at all speeds between that of maximum torque and maximum power without increased smoking or the occurrence of knock.

Owing to improved economy, the fuel cost per brake horsepower per hour using gasoline aspiration, is not increased. Modifications required to the engine are slight and the fuels required to operate are readily obtainable; even if the auxiliary fuel should run out no damage would be done to the engine.
Some Model Experiments on Special Control Valves
Authors: Firth D. , Young Leslie
Published: October 2007

A description is given of some model experiments undertaken to resolve problems occurring in the design of special control valves for use in the Hydraulic Machinery Laboratory of the Mechanical Engineering Research Laboratory.

Four types are dealt with: (1) a valve to control flows varying from 1 to 30 cu. ft. per sec. in a flow-meter calibrating system; (2) a valve to control flows of up to 30 cu. ft. per sec. in an open pump testing rig with a maximum input of 350 h.p.; (3) a valve to control flows varying from 1 to 20 cu. ft. per sec. in a closed pump research rig with a maximum power input of 350 h.p.; and (4) a hydraulically-balanced in-line valve to control flows varying from 1 to 15 cu. ft. per sec. in a service supply.
Pipe Flanges Research Committee—Third Report
Authors: Johnson A. E. , Bailey R. W.
Published: October 2007

The Third Report of the Pipe Flanges Research Committee is concerned, with the exception of elastic resistance strain gauge measurement of stresses of two standard flange rings, with the results of a programme of investigation, projected by the Committee in being when the Second Report was made, into the elastic and plastic (creep relaxation) behaviour of flanges, drilled and undrilled, by means of model flanges, and of certain bolt materials.

Execution and completion of the programme and attention to its results, was interrupted and delayed by the 1939–45 war. Subsequently examination of the creep relaxation data showed that the phenomenon, and the interpretation of the results, involved difficulties unknown at the time the tests were made, and the need for further investigation became evident. The results, however, have important bearing upon the behaviour of flanged joints and also as a contribution to the subject providing a base for further advances.

An Addendum to the Report refers to matters which arise in connexion with utilization of its results for engineering needs.

The Committee wishes to record its indebtedness to the Reporter, Dr. A. E. Johnson, now of M.E.R.L., East Kilbride, and formerly of the N.P.L. Engineering Division, who has been chiefly concerned with the investigations at elevated temperatures, and to Mr. H. L. Cox, now of the N.P.L. Engineering Physics Section, and formerly of the N.P.L. Engineering Division, who has been principally interested in the investigation of elastic properties, and who was responsible for the automatic strain control equipment of the relaxation unit.
Comparative High-temperature Properties of British and American Steels
Authors: Bardgett W. E. , Clark C. L.
Published: October 2007

Some rather substantial differences are found in creep data on similar steels published in various countries. In view of the importance of these differences in relation to design stresses, arrangements were made for an exchange of specimens between The Timken Roller Bearing Co., of Ohio, and The United Steel Companies in order to determine whether the results from the two laboratories, on the same steel, would be in agreement, and to compare the creep resistance of selected steels.

Five representative high-temperature steels were chosen comprising three commonly used ferritic steels and two austenitic steels. For each composition, four creep curves were obtained, two by each laboratory. Stress, temperature, and time adopted in the tests in the two laboratories were the same and no attempt was made at standardization of test procedure. A high degree of reproducibility was shown by the test results for the two laboratories on the ferritic steels but those on the austenitic steels showed generally substantial differences.

Only two British steels, both of ferritic type, showed similar creep behaviour compared with the corresponding American steels, the remaining three steels showing appreciable differences, which are discussed.
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.