bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative Analysis of Single- and Multiple-Capacity Plants
Authors: Kaufmann Paul G. 
Published: October 2007

In order to predict the performance of an automatic regulator, it is necessary to know the characteristic of the plant to which the regulator will be applied. A plant may consist of one or more capacities separated by resistances, and is characterized by its plant constants. The behaviour of an uncontrolled plant can be described by a non-homogeneous differential equation of the same order as the number of capacities forming the plant. The independent variable in this equation is the time; the dependent variable is the deviation of the plant from equilibrium; and the disturbance function is a function of the disturbance applied to the plant. This disturbance function and the resulting deviation will, in general, be different for disturbances created at the supply and discharge side of the plant. The use of hydraulic plants as models demonstrates clearly the physical meaning of the terms involved which can easily be translated into terms of thermal, flow, electrical, or other problems. Assuming a viscous medium with linear resistance to flow, linear differential equations are obtained and the deviations from equilibrium due to different forms of disturbances are examined for single- and multiple-capacity plants. Inversely, it is demonstrated how the plant constants can be determined from observed deviations when definite disturbances are applied to the plant. It is also shown why, for the control of multiple-capacity plants, it may be of advantage to use regulators that respond not only to the deviation from equilibrium but also to the speed and the higher derivatives of the deviation. The relative merits of placing the regulator at the discharge or supply end of the plant are also discussed. Finally, it is indicated how the equations of a regulator and of the plant can be combined to describe the behaviour of the regulating system and the interaction of regulator and plant, and how its stability criteria can be established.
Boiler Draught Production by Means of the Jet Air-Pump
Authors: Benson S. F. 
Published: October 2007

One of the most extensive applications of the jet air-pump in industry is its employment for the production of draught for the furnaces of Lancashire type boilers. The purpose of the work described in the paper was to investigate the conditions under which the requisite quantity of air can be supplied to the furnace of a boiler with minimum consumption of steam, and to examine the performance of a number of well-known and widely used furnace bars designed for this purpose. Two well-defined stages can be discerned in the process: (1) the induction of air by the jet; and (2) the transfer and distribution of the air to the furnace grids and the fuel bed. These two stages, which to some extent are interdependent, nevertheless lend themselves to individual treatment, a method which was followed in this work. With the induction process, guidance can be obtained from a theoretical analysis of the problem; and such an analysis was in fact used. For the transfer and distribution of the air to the grids and fuel bed, experiment alone can provide the required information. The question of the “efficiency” of the system in the normally accepted sense of the term is discussed, and is shown to be irrelevant to this method of operation. Some such term as “coefficient of performance” is more useful, and better suited for the purpose.
Industrial Fans: Their Practical Evaluated Rating, Performance, and Control
Authors: Kice M. S. 
Published: October 2007

The purpose of the paper is to draw attention to the situation which obtains when fan equipment forms part of the plant used to manufacture a product. Considerable detail is given in support of the points advanced, which deal mainly with the economics of production and include fan development, rating, design, application and control. Particular attention is devoted to the practical side in order to show how to obtain maximum financial profit from investment in fan equipment. As the theory of fan characteristics has, mainly, been evident in the literature on the subject, such theory has been avoided, excepting in connexion with the classic argument about the parallel operation of forward-curved bladed fans, concerning which, four premises have been cited in an attempt to inspire a mathematically qualified reader to develop a theory agreeing with observed phenomena—a theory which has not yet been produced. In the section of the paper dealing with the control of fans, the economic aspect is again stressed, particularly in connexion with the relationship between overall boiler efficiency and the method of controlling boiler house fans, the problem being resolved into terms of control of the carbon dioxide content of the flue gases.
Cutting Tools Research: Report of Subcommittee on Carbide Tools: The Mechanism of Tool Vibration in the Cutting of Steel
Authors: Arnold R. N. 
Published: October 2007

The report deals with some fundamental investigations of vibration in cutting tools. It is shown that this phenomenon may be the result of both self-induced and forced vibration. The former is a function of the cutting properties of the metal and the sharpness of the tool, while the latter depends on the interference of the tool with the surface cut during previous revolutions. Certain limitations of speed, tool frequency, and tool sharpness exist, vibration being rarely observed at low cutting speeds, at high tool frequencies, or with a freshly lapped tool. The amplitude of vibration appears to be independent of the depth of cut and seems to be limited to a value slightly in excess of that which makes the maximum vibrational velocity at the tool point equal to the speed of the work. It is governed to some extent, however, by the internal damping characteristics of the tool shank. The self-inductive influence originates from the decrease in the cutting force which occurs as speed is increased, and becomes more powerful as the wear of the tool progresses. Failure of carbide tools under vibratory cutting conditions occurs in the form of a fatigue crack which spreads inwards parallel to the top face of the tool. Photographs and profile records are given of surfaces cut under various conditions of vibration, together with a theoretical analysis of the manner in which the surfaces are formed. With small feeds, forced vibration occurs and phasing normally results. This is demonstrated by the resulting patterns on the surface, which show an orderly arrangement of the waves. A few practical examples are described.
Some Notes on the “Merchant Navy” Class Locomotives of the Southern Railway
Authors: Bulleid O. V. S. 
Published: October 2007

The operating requirements in respect of weights of trains and speeds determined the main dimensions of these new locomotives, and the paper refers to the limitations on the development of powerful locomotives imposed by the loading gauge and weight restrictions. The Merchant Navy class locomotives embody many innovations in British locomotive practice, and the reasons for these changes from orthodox practice are fully explained, and the way in which the changes were carried out described. Some difficulties were naturally experienced in service as a result of these departures, and they are fully related, together with the modifications which successfully overcame them. Some of the improved results obtained as a result of the innovations are reported.
The Loop Scavenge Diesel Engine
Authors: Carter H. Desmond 
Published: October 2007

The main theme of this paper concerns loop scavenge two-cycle engines as a type, but most of the examples refer to trunk-piston engines of powers up to 2,000 b.h.p. The characteristics of such engines are enumerated and a comparison is made with other established types of engines—both two-cycle and four-cycle—in marine, stationary and locomotive applications. Details of performance are given. Exhausting, scavenging and charging processes of loop scavenge two-cycle engines are dealt with and in particular a new method of filling the engine cylinder (“exhaust pulse pressure charging”) is described. There then follow data regarding scavenge efficiency and design of ports.
The Evolution of a Tank Transmission
Authors: Merritt H. E. 
Published: October 2007

This paper describes, substantially in chronological order, the stages of an investigation into the theory and design of steering mechanisms for armoured fighting vehicles. The first step was an inquiry, partly by simple experiment and partly by analysis, into the mechanics of a skidding track; the application of the conclusions to a complete vehicle led to unexpected results in regard to the forces and powers involved, and explained the unsatisfactory behaviour of earlier transmissions designed on a purely empirical basis. This was followed by review and analysis (although not necessarily in the classified order given in the paper) of existing or known types of mechanisms applicable to tank steering. An experimental mechanism of the coupled-differential type was then constructed in order to verify the conclusions drawn. Before it could be completed, the necessity arose for a rapid increase in the production of tanks beyond the limit of size and weight at which existing steering mechanisms could be expected to be satisfactory, at a time when limited production resources put a premium upon economical design. There were grounds for believing that the triple-differential mechanism, devised at that time, would combine the desired technical performance with comparative economy in production; this expectation was confirmed, although only after a period (outside that covered by the paper) of development of detail reliability. The problem of testing tank transmissions was also studied and the plant finally devised and constructed for this purpose has a number of interesting technical features. The technical elaboration of the internal mechanics of tank transmissions, accumulated in the course of the study, has been omitted from the paper as lacking in general interest. It reached its maximum of complexity in the case of the test plant and is left as an exercise for the student. The problem of the effect of centrifugal force still awaits a complete solution.
On the Stresses in Hooks, and Their Determination by Relaxation Methods
Authors: Fox L. , Southwell R. V. 
Published: October 2007

The “semi-inverse” method of Saint Venant has been applied to hooks by Golovin (1881)‡ and by Southwell (1942). The actual hook is replaced in calculation by a half-tore sustaining shear stresses appropriately distributed over its terminal sections, and having a cross-section identical with the principal section of the hook (shaded in Fig. 1). Golovin's solution was for a narrow rectangular hook; Southwell's is a formal solution applicable to any shape of section, and involves two stress-functions related by three conditions at the boundary. In the present paper, stress distributions are determined on the basis of Southwell's solution for two B.S.I. standard hooks, the first of “trapezoidal” and the second of circular cross-section. The results are exhibited in Figs. 3–6.
An Exploratory Study of Oil Grooves in Plain Bearings
Authors: Clayton D. 
Published: October 2007

A preliminary investigation has been made of the influence of oil holes and grooves on journal bearing performance to provide, in addition to fundamental information on fluid films in bearings, preliminary data for an ultimate analysis of the behaviour of internal combustion engine bearings. In the first part of the paper the effects of supplying oil to holes and grooves in the unloaded part of the bearing are investigated, the quantity of oil flowing through the bearing, the running temperature and the coefficient of friction being recorded. Amongst the results are shown the important part the clearance space at the point of supply plays in the quantity delivered; the surprising drop of feed as a 90 deg. circumferential groove is extended to 360 deg.; the marked effect of quantity of oil on bearing temperature for small flows and the rapid drop in efficiency of oil cooling as the quantity rises; and the absence of a groove arrangement giving more efficient cooling than the others. Change of supply temperature and pressure have a much less than proportionate effect on bearing temperature and flow. Increase of clearance leads to a disproportionate increase of oil flow. In the second part of the paper the effect of holes and grooves in the pressure film is explored. In this case measurements were made of the pressure at the crown of the bush when the hole there was closed, and of the flow when open, in addition to the previous observations. Amongst the results may be noted the relatively small initial flow through the crown hole in spite of the high pressure there when it is closed; the increase of the crown hole flow at the expense of side flow as the groove is cut into the inlet film; and the relatively small changes in bearing temperature and coefficient of friction. Again changes of oil supply pressure and temperature had less than proportionate effects on flow and temperature of the bearing. A preliminary note is made of the decrease of load-line film pressure which was found as the temperature was increased. The temperature was also raised to cause incipient failure of the bush, and it was found that the final temperature was independent of whether the crown hole was open or closed, and yet there were indications of diminished film thickness for small grooves at natural running temperatures. The safety was decreased as grooves were cut in the loaded part of the bearing; some indications of the magnitudes of the changes are given.
The Calculation of the Stresses in a Turbine Wheel by the Method of Superposition
Authors: Kearton W. J. 
Published: October 2007

The wheels of steam turbines are subjected to three separate forces, namely (1) the body forces due to the inertia of the wheel itself, (2) the force applied radially to the rim due to the inertia of such attached masses as blades, spacers, etc., and (3) the force applied to the bore of the wheel due to force fitting or shrinking the wheel on the shaft. The method of calculating the stresses in turbine wheels which is usually explained in textbooks and published papers takes account of these forces simultaneously. The calculations are tedious, and if it is desired to analyse the effects of changing the speed of rotation of the wheel, or of changing the magnitude of the attached masses, or of varying the degree of force fit on the shaft, then the calculations must be repeated for each combination of conditions. In the method given in the paper, the stresses in the wheel are calculated (1) for a rotating wheel free from rim loading and radial stress in the bore due to force fitting, (2) for a stationary wheel subjected only to the rim load, and (3) for a stationary wheel subjected only to the force fit pressure. The resultant stress in the wheel is then simply the sum of the three stresses so obtained. Since the wheel inertia stress varies directly as the square of the speed, and since the stresses in the stationary wheel are directly proportional to the boundary stresses, the effects of (1) varying the speed of rotation, (2) varying the magnitude of the attached masses, and (3) varying the degree of force fit may be analysed with very little effort. The paper shows how the method of superposition may be employed in the calculation of (1) the stresses in a turbine wheel, (2) the amount of force fit necessary to satisfy specified conditions, (3) the effect of varying force fits on the maximum stress in the rotating wheel and in the stationary wheel, and (4) the distribution of stress in the stationary wheel. The paper concludes with an estimation of the localized stresses in the neighbourhood of pressure-balancing holes.
The Thrust of a Marine Screw Propeller
Authors: Baker G. S. 
Published: October 2007

Part 1 of the paper puts forward the proposition that since the phenomenon of development of thrust is much the same in all screws, there should be a common basis by which it can be represented. The characteristics of aerofoils are considered, first in flight singly, and then the general effects which arise from the interference of adjacent blades. It is concluded from this work that for any blade there are two essentials to be fixed, the slip angle, and the slope of the lift curve as affected by aspect ratio and, or alternatively, cascade. This should afford a basis for plotting screw data. Part 2 of the paper is an examination of the results obtained with over 100 model screws. The data are given in the form of the thrust constant kT/ sp to a base representing blade width. All the results plot reasonably well together, and mean curves for screws with various numbers of blades are given. These curves enable the designer of any screw of normal type to form an estimate of its thrust for any speed of advance and revolutions per minute. Methods are given in the paper for detecting eddymaking in the screw, and it is shown that a little roughness of blade surface, although having a material effect on efficiency, does not affect the thrust prediction.
The Variable-pitch Marine Propeller
Authors: Taylor J. Lockwood 
Published: October 2007

The author first discusses propeller performance, dealing in turn with the order of the possible gain in efficiency to be expected by adopting the variable-pitch type for different classes of ships working within a range of operating speeds. The maintenance of speed in heavy weather and with a foul hull is then considered, and reference is made to the possibility of feathering for economical cruising, to the special application of variable-pitch propellers to tugs and trawlers, and to engine fuel consumption characteristics at part load and varying propeller r.p.m. Details of manoeuvring and control are discussed, from the viewpoint of exploring the possibility of eliminating the engine reversing gear and the direct manipulation of the prime mover generally. Ship speed control from the bridge is considered, and an estimation is made of astern performance, followed by a comparison with the normal reversing of a fixed-pitch screw. Factors influencing blade design are then reviewed, e.g. type of root and size of boss, the effect of the type and number of blades on the efficiency; and reference is made to the calculation of pitch-changing moments and the possibility of balancing hydrodynamic and centrifugal components by suitable design and tilt of the blades. Various types of operating mechanism are then examined—hydraulic, electric, mechanical, and combinations of these—and mention is made of the sealing of the hub against sea water. The author also refers to the need for indicating the pitch at the control station. Lastly a comparison is made with aeronautical applications. The author shows that the range of operating conditions as affecting engine r.p.m., with a fixed pitch, is in general much less for marine screws; blade widths are much greater. In the author's conclusions it is suggested that full-scale determination of the optimum pitch setting may be valuable; consideration is also given to possible size and limitations of blade width, and to the effect of the costs involved.
Some Notes on the Mechanical Factors Affecting Ring Gumming in Petrol Engines with Particular Reference to the Rating of Lubricating Oils
Authors: Pugh B. 
Published: October 2007

The phenomenon of piston ring gumming in petrol engines is well known. It is of importance not only because it is the cause of considerable trouble in service, but it has also formed the chief criterion in the majority of attempts to rate or classify lubricating oils according to their deterioration characteristics in an engine cylinder. Existing standard chemical tests on lubricating oils form no guide to the behaviour of oils from the point of view of ring gumming in a petrol engine, and the only reliable method of grading oils at present is by tests in an actual engine. The next logical step is to develop a simple chemical test or series of tests which will give the same grading as that obtained in an actual engine. Before this can be done it is necessary to have a knowledge of the nature of ring groove deposits, the mechanism of ring gumming, and the relative effects of the various factors which affect the rate and degree of ring gumming. Mechanical factors can be of sufficient magnitude not only to affect, but possibly reverse, the relative rating of oils on a ring gumming basis. Various mechanical factors which affect the degree of ring gumming obtained are discussed in detail in the paper. Those mechanical variables which cannot be eliminated must either (1) be taken into account when sifting available engine data, or (2) must be a consideration when formulating a laboratory test or series of tests simulating engine conditions. Correlation between engine tests and laboratory tests is best based on the time to give incipient gumming in the engine. To do this it is necessary to have a reliable indicator to show when ring gumming commences. Preliminary experiments have indicated that piston-crown temperature is probably the best control temperature in oil rating tests; and the temperature at the back of the ring groove, taken in conjunction with the piston crown temperature, is probably the best indicator of incipient ring sticking capable of application to any engine.
The Flow of Gases at Sonic and Supersonic Speeds
Authors: Hankins G. A. , Cope W. F. 
Published: October 2007

Problems involving the flow of gases at velocities near to or exceeding that of sound have been familiar to mechanical engineers for many years in connexion with the design of steam nozzles, and much valuable information has been accumulated from experience and from specific researches such as the classical work of Stodola (1927)‡ and of the Steam Nozzles Research Committee of the Institution (1923, etc.). The flow of steam through a converging-diverging nozzle, however, is only one instance of the flow of a gas in circumstances in which changes in density and pressure are produced or accompanied by changes in velocity. Behaviour of this kind is frequently referred to as compressible flow and arises in the design of gas turbines, in the jet propulsion of aircraft, in some high speed compressors, in diffusers, in flow through valves and measuring nozzles, in high speed aircraft and in the flight of projectiles. The subject of compressible flow is thus of great importance in a wide range of problems of practical engineering and as it has not yet reached a stage at which the essential features are treated in textbooks readily available to engineers, the present paper has been written to cover as wide a field as practicable. The authors' main experience of the subject has been in the field of external ballistics and in the design, development, and use of supersonic wind tunnels; and the illustrations are taken largely from such work. The principles are of universal application, and it is hoped that the discussion will be on general lines and range over a wide field of applications from various branches of engineering practice.