bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Problems of the Singing Propeller
Authors: Kerr W. , Shannon J. F. , Arnold R. N. 
Published: October 2007

The unusual noise emanating from what is known as a “singing” propeller is the direct result of the vibration of the blades. These are disturbed by the irregular hydrodynamic actions of cavitation and vortex shedding and induced by the extreme variations in the wake. It is demonstrated experimentally that a blade with a sweeping plan form and sharp edge, suppresses cavitation and vortex action within the working range of the propellers. Sharpening the blade edges round the periphery, in a wedge-shaped manner, has been applied successfully as a cure to many singing propellers. In addition to suppressing the disturbing forces, experiments show that the sharp edge provides considerable increase in hydrodynamic damping. The response of the blade to tip and edge excitation is considered. Blade flutter is examined, but it is concluded that such a condition is unlikely. Notes emitted by singing propellers suggest that many modes of flexural, torsional, and lateral vibration are present. It is shown that the lateral types respond easily and their importance is indicated by a number of noisy propellers which have exhibited fatigue cracks conforming to the lateral modes of vibration. It is recommended that the process of sharpening the blade edges be adopted, as this suppresses the exciting forces and damps the response of the blade.
Investigation of Steam Turbine Nozzle and Blading Efficiency
Authors: Dollin F. 
Published: October 2007

The paper describes the essential characteristics of the passages forming the fixed and moving elements of multistage high-efficiency turbines, whether impulse or reaction. The problems of nozzle investigations by static and dynamic methods are discussed, and a new nozzle tester is described. Reference is made to the Reynolds number; its physical significance is explained, and experimental results are used to demonstrate its effectiveness as a correlative factor. The significance of the static (nozzle) efficiency and the dynamic (turbine) efficiency is discussed, and the essentially different way in which they are affected by the discharge angle is pointed out. A mathematical expression is derived for the relation between static and dynamic efficiency for 50 per cent reaction blading as a function of the discharge angle. This, in conjunction with the Reynolds number, is used to demonstrate the unity and consistency of static and dynamic test results which at first sight seem to be conflicting or unrelated.
The Stresses in, and the Deflexion of, Circular Flat Plates, with a Central Hole, under Normal Forces
Authors: Labrow S. 
Published: October 2007

Solutions are given, and presented in graphical form, for the stresses in, and the deflexion of, a thin circular plate when loaded by normal (transverse) forces only, with various prescribed conditions of supporting or fixing the edges. The method used in deriving these results is an application of a general method for obtaining the direct and, or alternatively, the bending stresses in a thin circular plate under any type of loading. Because of the ease with which it can be applied to problems in which the loading on the plate is quite complex, this general method, due to Professor William Kerr, Ph.D., M.I.Mech.E., deserves to be more widely known, and a brief account of it is given by the author as an introduction to the special problem with which the paper is primarily concerned.
The Relationship between Stress and Strain in the Tensile Impact Test
Authors: Brown A. F. C. , Vincent N. D. G. 
Published: October 2007

Apparatus has been devised for the measurement of the relationship between stress and strain on metallic specimens broken in tensile impact. The stress was measured piezo-electrically and the strain photo-electrically. Five ferrous materials have been examined at rates of extensional strain ranging up to 800 inches per inch per second, with the following results. With wrought iron there was an increase in tensile strength and considerable increase in yield point as the rate of strain was raised. With medium-carbon steel there was some increase in the yield point. With low-carbon manganese steel, nickel-chromium steel and “Vibrac” steel there was little difference between the impact and static stress-strain diagrams. The energy absorbed in fracture of the specimens in the impact tests was only slightly greater than that absorbed in the static tests.
Wave Action in Gun Run-up Springs
Authors: Taylor H. G. Woodhouse 
Published: October 2007

A number of articles and pamphlets have appeared on the waves and oscillations that occur in springs used for commercial purposes, notably the valve springs for internal combustion engines, and it has been shown that the forces experienced, and other results obtained, are very different from what would have been expected from calculations which assumed that the load is applied slowly through the amount of compression available. No such publications, so far as is known to the author, have appeared regarding springs for military use, such as those employed to run the gun up after firing. Textbooks have tacitly assumed that the load is so slowly applied that static considerations meet the case, so they have given the corresponding theory. That a wave action does occur is observable by eye in some instances. In the 18-pounder Mark II field carriage, so well known during the war of 1914–18, the run-up springs were telescopically arranged so that the inner spring case was carried as a float between the outer and inner springs. That there was a wave action could readily be seen by carefully watching this inner spring case during the recoil of the gun on firing. There also have been several instances in which a column of identical springs have been employed, and it has been found in use that the spring in one particular position is liable to take a permanent set or to fracture. This indicates that there is a wave action and that it is accentuated at the point concerned. It was a result of this sort that led the author to work out the theory of recuperator springs, taking the time factor into consideration. Their behaviour is shown to be quite different from that calculated on static considerations.
Fans—Their Types, Characteristics, and Application
Authors: Ferguson C. G. 
Published: October 2007

A fan is defined by the British Standards Institution as “a machine which propels air continuously, the total fan head never exceeding 1 lb. per sq. in.” When the pressure is above this limit the field of blowers is entered. The paper deals descriptively with modern fans and their applications under the following three main types: ( a) propeller fans, ( b) centrifugal fans, ( c) axial flow fans. The differences in their characteristics and construction appear to justify the classification of ( a) and ( c) as different types. After recapitulation of the fundamental formulae used in assessing the output, power requirements, and efficiencies of centrifugal fans, the author discusses various test results on actual installations, with some of which he was personally concerned. Axial-flow fans are considered both from manufacturing and from aerodynamical viewpoints, and test results are given, together with curves showing the power absorbed and the efficiency achieved. In the latter part of the paper the author deals with various applications of fans: to the ventilation of buildings, ships, and mines; as a method of supplying draught to boiler installations by mechanical means; and in the operation of dust extraction plant. The control of fan speed and output by hydraulic couplings is compared with methods of adjusting the inlet vanes, in order to achieve the same result.
Tests on Transport Producer-Gas Units
Authors: Heywood Harold 
Published: October 2007

The experimental plant installed by the British Coal Utilisation Research Association for testing gas-producers, filters, and engines is described in detail. The results of tests on the engine bench show that a petrol engine converted to use producer gas will only develop about one-half of the normal brake horse-power; moreover, the peak power with gas occurs at a lower speed than with petrol, due to the decrease in volumetric efficiency at high speeds. The effect of increasing the compression ratio was not investigated by the author, but tests by other workers have shown that the gain in power obtained by this means is proportional to the increase in the air standard efficiency. Producer gas-driven engines are very sensitive to mixture strength, and maximum power is obtained with mixtures of gas and air in the proportions theoretically required for the combustion of the gas. Maximum efficiency is obtained with a mixture containing 10 per cent of excess air. Engine tests have also been made to investigate the effect of gas calorific value, of the pressure drop through the producer system, and of petrol addition. Special tests were made to determine the flexibility characteristics of the engine and producer, and the effect of running with various throttle openings, as in actual road operation. Fuel consumption under the latter conditions is about 35 per cent greater than that determined under full-throttle and constant-speed conditions.
The Design Office Problem in the Estimation of the Torsional Resonance Characteristics of Small Marine Diesel-Propulsion Units
Authors: Mitchell R. W. Stuart 
Published: October 2007

The problem of the accurate estimation of resonant amplitudes of torsional vibration in small marine Diesel-engined propulsion sets is considered from the viewpoint of the design engineer. A short discussion on torsiographs is followed by the basic theory of the energy method of calculation, with particular reference to the calculation of vibration amplitudes assuming linear damping proportional to the phase velocity of the vibration. Harmonic input torque diagrams are given for a small marine two-stroke engine. The methods put forward by different investigators are considered by comparing the calculated results with those obtained by torsiograph from a number of marine Diesel units investigated by the author. Both the one- and the two-noded forms are considered. In the former, propeller damping is shown to be the main influence and a method of computation put forward by Dorey is shown to be satisfactory after slight modification. For the two-noded form the position is not so satisfactory. Hysteresis damping in the crankshaft, viscous damping at the bearings, overall velocity damping, etc., are considered in turn and rejected as unsatisfactory. The importance of apparent damping effects—particularly cyclic fluctuations of speed or cyclic irregularity—is stressed, and a method is evolved in which this consideration is utilized in conjunction with results published by Major Carter which the author has found fairly satisfactory to date. It is concluded that much has still to be learnt on the subject before empirical methods can be dispensed with.
The Position and Development of the Gas Engine
Authors: Jones J. 
Published: October 2007

The gas engine as developed during the early years of the present century reached its zenith about the year 1914; after the post-war boom of 1918–20 production gradually declined, in the face of its rivals, the compression-ignition engine, and the national grid. In steel works, however, gas engines running on blast furnace gas continued to be a useful source of power and some of these installations reached very large sizes. The paper, after an historical introduction, provides some useful comparative data of the performance of gas engines and other prime movers, and traces the development of the dual fuel engine (in which oil fuel adds to the power developed by the gas fuel) and refers in particular to some valuable experiments carried out in the works of the Birmingham Tame and Rea Drainage Board. Eventually a type of engine was arrived at in which, by suitable atomizer design, and by modifying the cylinder head and governing gear, the proportion of oil fuel to gas fuel could be varied over a wide range whilst the engine was running on load. The dual fuel engine should go far to reinstate the gas engine as a natural type of prime mover in this country, where rich coal resources exist. In the U.S.A., some important work has been done by the Nordberg Company on a large 3,000 h.p. unit at Coolidge, Arizona, where the engine uses a very rich natural gas for six months in the year, and oil fuel for the remainder of the time. Finally the author outlines possible directions of development for the dual fuel engine, and suggests two main types employing high-pressure and low-pressure injection respectively. He also points out that in the future, some improvement in gas producers will be necessary, and makes a plea for further development of the bituminous gas producer, in order that its present disadvantages may be overcome.
Drawing Office Practice in Relation to Interchangeable Components
Authors: Gladman C A. 
Published: October 2007

The paper describes some features of the work of a special Service Committee set up by the Admiralty, for the purpose of standardizing drawing office practice in certain of their design departments. Basic principles are established for the guidance of designers and draughtsmen when preparing drawings for interchangeable components, and logical methods of approaching solutions to dimensional problems and of stating these on drawings are discussed. Particular attention has been paid to such problems as the best method of analysing, and dimensioning and applying tolerances to interchangeable components which involve tapered, concentric, or positional features such as holes and studs. Stress is laid upon the need for foreseeing, and avoiding as far as possible in the design stage, any special difficulties which may arise in practice in the construction of manufacturing equipment or of practical gauges for controlling the dimensions of components. It is understood that the British Standards Institution have in contemplation the preparation of a handbook dealing with the subject of the dimensioning of production drawings and of indicating the tolerances on them. Such a handbook, when completed, not only would be of great use to industry at large, but wouldal so form a valuable textbook for courses of instruction to engineering students in technical colleges and universities. It is hoped that this paper may be the means of stimulating thought on this aspect of interchangeable manufacture and that it will provoke discussion which may lead to the development of a uniform system suitable for use both by Service Departments and by industry in general.
Protective Air Vessels for Rising Pipe Lines
Authors: Binnie A. M. 
Published: October 2007

A long rising pipe line should be protected against the damage due to shock (or “water hammer”) which might ensue if the pumps suddenly failed. The most satisfactory method is to fit an air vessel on the delivery side of the pumps. The connexion between the air vessel and the pipe line should be constricted so that the oscillations of the water-level in the air vessel are damped. An approximate method is described in the paper for calculating the maximum expansion and pressure of the air, and its predictions are shown to be in satisfactory accord with experiment. The onset of water hammer, observed when damping was carried too far, was found to occur at velocities somewhat greater than theory suggests.
Design, Construction, and Use of Some Inspection Gauges
Authors: Leedham L. H. 
Published: October 2007

The paper begins with a reference to the necessity of regarding inspection as part of the manufacturing programme. The provision of equipment for this purpose is just as important as the use of jigs and fixtures, and in all cases where “set-ups” would have to be made for inspection purposes, the provision of specially designed gauging fixtures is advised. Some fundamental principles of such equipment are next discussed, the weak features in some and the advantages of adopting the good points of others being stressed. The use of the crossed-strip mounting, developed at the National Physical Laboratory, for indicating-arms is discussed, and the use of dial and signal indicators receives attention. Descriptions are then given of varied applications to gauging apparatus for different components, each of which presents a problem in inspection. The possibility of utilizing the component itself, in such a way as to make it amplify variations in the feature being inspected, also receives some consideration. The multiple gauging of mass-produced components, using an ingenious indicator unit, concludes the descriptions of the practical applications. In studying the examples, a mental comparison should be made with the problem which each case would present to the inspector, in the absence of the special equipment.
The Isothermal Flow of Gases through Beds of Granular Materials
Authors: Rose H. E. 
Published: October 2007

In this paper it is shown that the equation of flow of liquids through beds of granular material, developed in a previous research, may be used as a basis for calculation of the rate of flow of gases through granular beds under isothermal conditions of expansion. The equation covering the isothermal flow of gases through a granular bed is developed from an expression evolved by Unwin for the motion of a gas in a pipe, by the substitution of the equation for the flow of a liquid through a bed in place of the equation of flow of a liquid through a pipe. The equation is verified by several experimental determinations and is shown to be in accordance with the experimental results of a number of different workers. Examination of the equation developed shows that for beds of extremely open packing the pressure drop to maintain an assigned rate of flow is not a linear function of the depth of bed but for beds of the normal densities of packing the deviation from linearity is negligible.
A Comparison of Some Carbon Steels on the Basis of Various Creep Limits
Authors: Johnson A. E. , Tapsell H. J. 
Published: October 2007

The present report has been prepared with a view to determining whether any relationship exists between the results of the various short-time and long-time creep tests, which will permit the use of short-time tests, not merely as a means of separating good from bad steels, but also as the basis of design stresses intended to give satisfactory performance of the steel over working periods of considerable duration. Indications are given of some of the difficulties and limitations concerned in the use of short-time creep results in the case of carbon steels, and suggestions are made for some rational basis for steps which might be taken to offset these difficulties and limitations in applying the results of short-time tests to estimation of design stresses.
The Generation and Utilization of Steam in the Heavy Industries
Authors: Hider G. E. 
Published: October 2007

The author has for many years considered that it should be possible to design a diagram for the graphical analysis of problems arising in the transmission of heat in boilers. It became clear that such a diagram, comparable with the ideal indicator diagram or the temperature-entropy chart, could easily be designed if reliable and explicit data relative to transmission of heat by radiation were available. The position seemed to be this: the simple efficiency formula ( T1 — T2)/ T1 could be used if the correct temperature T1 could be determined, assuming also that the variation in the specific heat of the gases at widely varying temperatures was relatively unimportant. This T1 temperature is not, of course, the temperature measured over the furnace bed, but the temperature which would be observed if the coal were burned in a highly refractory chamber instead of being subject to more or less rapid cooling by the adjacent heating surfaces of a boiler. Thus this so-called theoretical temperature may be calculated for any given coal and CO2 content, provided the latter is not influenced by air leaks. The temperature of rejection T2 is, of course, easy to ascertain with accuracy. The author expresses the hope that such a diagram may be of some value to lecturers, and examples of its use are given. Arising from the design of the diagram, the author proposes a method of investigating the heat transmission by radiation and convection through the plates of Lancashire boilers: other matters of importance to the heavy industries were dealt with in detail in the original paper, and the salient features are discussed in this abridgement.
Boiler Installations on the Continent, and Future Problems
Authors: Bock J. H. 
Published: October 2007

On account of the diverse fuel situation on the Continent, boiler development since the 1914–18 war has been very different from that of Great Britain. The paper shows how combustion appliances such as travelling-grate stokers, grates for inferior coal, for lignites, and for pulverized fuel combustion, have been designed. It became necessary for boiler installations to be designed for higher pressures and, over a comparatively short period, extensive experiments were carried out which led to various new designs in boilers, superheaters, economizers, air heaters, etc. A possible line of future development is covered by reference to a scheme put into operation in 1930 by the West Moravian Electricity Works, Ltd., and the author concludes that two types of power station, i.e. the low pressure pit-head station for the burning of inferior fuel, and the high-pressure power station with district heating in towns, using fuels of low ash and water content, would form the ideal combination for the future.
An Experiment in the Use of a Standard Limit System
Authors: Loxham John 
Published: October 2007

The limit system recommended by the British Standards Institution (B.S.I.) was issued first in 1906 and again in 1924, under the title of British Standard Specification No. 164, “Limits and Fits for Engineering”. The engineering industry of this country, it is contended, has found it impracticable to use the tables contained in these publications, and it would appear desirable to ascertain the reason for this striking neglect of so important a publication. There are numerous instances where certain limits have been taken from these publications, but the author is not aware of a single instance where the B.S.I, system is the only system used, and it is claimed that it supplies all the reasonable requirements of a designing draughtsman engaged on ordinary commercial engineering work. This state of affairs cannot be considered as satisfactory and the present paper is put forward in the hope that it will form the basis of a discussion, the findings of which will assist the appropriate committee in making suitable revisions to this British Standard publication. The paper shows how a genuine attempt was made to use the B.S.I, system for every problem of design and manufacture for which standard limits seemed desirable, and how the system was modified only when it was found impracticable to use it in its original form.
The Development of Ultra High-Pressure Hydraulic Systems
Authors: Parker S. M. 
Published: October 2007

Most engineers seek to reduce weight and bulk by the use of higher specific loading of their material. The hydraulic engineer is no exception to this; but his choice of working pressure determines to an unusually large extent the detail construction of most parts of the system. The purpose of this paper is to examine briefly the reasons which lie behind this choice of pressure, with particular reference to the possibility of using a higher working pressure than is in common use at present for the lighter forms of equipment in aircraft, automobile, and industrial design. Within the scope of this paper it will only be possible to examine the essentials of the problem, and to suggest likely solutions, with the knowledge that time and experience will probably provide other and better answers.