bluuebunny/crossref_metadata_2025_split huggingface dataset:
Autofrettage of Cylinders: Prediction of Pressure/External Expansion Curves and Calculation of Residual Stresses
Authors: Franklin G. J. , Morrison J. L. M. 
Published: October 2007

The shear stress-strain relationship for an initially stress-free 2 1/2 per cent nickel-chromium-molybdenum steel under reversed stress has been determined by twisting thin tubes. The effect of a low-temperature heat treatment given to this material after various amounts of overstrain has been similarly determined. The information so obtained has been used to calculate by methods outlined in Appendixes I and II the behaviour of thick cylinders of the same material when subjected to one or two cycles of internal pressure, with or without an intervening low-temperature heat treatment, and to calculate the stresses throughout the material of these cylinders at any stage in the processes. Such cylinders have been made and subjected to the treatment described, the pressure and dimensional changes being measured at all stages. They have then been bored out in steps until all the overstrained material has been removed, the corresponding dimensional changes being again measured. One of the assumptions used in the calculations has an important effect on the values of the residual axial stresses; moreover the axial dimensional changes during the boring-out process are so small that great accuracy cannot be claimed for the values measured. To this extent the results are inconclusive. It is, however, shown that both the dimensional changes and the shear stress distribution (from which the radial and hoop stress distribution can, of course, be deduced) at any stage in the process can be calculated with satisfactory accuracy by the relatively simple approximate methods described.
Inspection of Primary Circuits and Reactor Pressure Vessels of Nuclear Power Plant
Authors: Pemberton H. N. , Crossley E. 
Published: October 2007

In this context inspection relates to the acceptance of design and construction, and of components that have been in service. Inspection details of the pressure parts of British gas-cooled power reactors is outlined and discussed. Reference is also made to steel containment pressure vessels. The main problems presented by reactor pressure parts are associated with the large size and also site fabrication. Periodic inspection of plant is restricted to date to those parts that do not emit dangerous radiations. While contamination of the other parts by radioactive dusts introduces another limitation, experience over four years at Calder Hall has shown that components on the heat-exchanger side of the stop valve can be efficiently examined. The need for extension of periodic inspection to the remaining circuit components of gas-cooled nuclear-power plants is emphasized. Reference is made to the need for radical improvement in leak tightness of circuits. Also of the desirability of maintaining simplicity and including essentials only in new specifications or codes of practice for reactor pressure-vessels and circuit components.
A Comparison of Materials for Use as Unlubricated Journal Bearings
Authors:   Lubrication and Wear Group, Simpson F. F. 
Published: October 2007

A number of materials have been run as unlubricated plain journal bearings, against mild-steel journals, at a number of combinations of load P and speed v sufficient to cause failure within 100 hours. For each material the bearing life for various values of P and v giving the same product were similar, but the materials differed greatly in the P and v value which resulted in similar bearing lives. Polytetrafluoroethylene (P.T.F.E.)-lead-bronze appeared to be outstanding, supporting Pv values as much as 30 times greater than those that resulted in a similar life for other materials and surface treatments commonly used as unlubricated bearings. The performance characteristics of the various materials are commented on.
Blade Profiles for Axial-Flow Fans, Pumps, Compressors, Etc.
Authors:   Applied Mechanics Group, Carter A. D. S. 
Published: October 2007

In this paper the basic factors controlling blade-section performance are first examined. It is shown that substantial differences in performance may be expected from profiles having different fluid surface velocity distributions. Thus some distributions favour a wide working range while another may be more suitable for very high-speed operation, and so on. A desired velocity distribution may be achieved by appropriately selecting the various physical parameters, such as maximum thickness, position of maximum thickness, position of maximum camber, etc. which define the blade profile. Thus if a particular performance in terms of inlet angle, deflection, Mach number, and incidence and Mach number range, is specified, there will be a particular blade profile to do the job. These conditions will have been determined by the overall design considerations, and the various features which the profile designer can then choose to meet them are fully discussed in the second part of the paper. In the final section the requirements of some illustrative applications are discussed. It is shown that, on the basis of the earlier parts of this paper, certain applications demand significantly different blade profiles. Evidence is given that substantial gains have been achieved by using the appropriate blade profile for some duties, from which it is concluded that proper attention to the selection of profiles for all duties must lead to an all-round improvement in the performance of these machines.
Effects of Impeller Design and Surface Roughness on the Performance of Centrifugal Pumps
Authors: Varley F. A. 
Published: October 2007

Conventional methods of designing centrifugal pump impellers are based on the ideal velocity triangles and the Euler head equation. Empirical modifications derived from the performance of previous successful designs are used to correct for departures from these ideals, and design procedure becomes a matter of extrapolating from past experience. More fundamental studies of the flow conditions inside a centrifugal pump have been made, but these have generally required simplifications of the impeller geometry or other expedients in order to render the problem amenable to analysis. In consequence, the results have found only limited application for the complex pumps and real fluids met in practice. In the paper the author attempts to reconcile these different approaches by presenting data on the effects of the various impeller design elements on the performance of a 2-in. double-entry pump. The decisive parameters determining the performance of the impeller are shown to be the number of blades and their outlet angle. The inlet angle and the blade profile are of relatively minor importance. Roughness of the impeller surfaces, both internally and on the outside of the shrouds, decreases the pump's efficiency but increases its output. Analysis of the test results with artificially roughened impellers demonstrates that current conceptions of disc friction and the energy balance sheet for a pump are untenable.
A New Apparatus for the Precise Location of an Inaccessible Point, with Applications to Deep Surgery
Authors: Harrison J. Y. , Willis A. H. 
Published: October 2007

A stereotactic apparatus is a device used to guide a needle to a chosen point in the brain. The position of the point, relative to the skull or to any artificial reference system fastened to the skull, is determined by radiographic means. Many types of stereotax exist and are in present-day use; several of these are referred to in the text. Certain disadvantages are associated with existing instruments, and in developing the stereotax under discussion, specific design objectives were kept in mind, the more important of these being the elimination of excessive weight, the elimination of any form of calculation, and the need for reasonable accuracy. The basic theory and a general description of the apparatus are given, together with photographs of X-ray films taken during the course of an operation.
Behaviour of Compound Steel Cylinders Subjected to Internal Pressure
Authors:   Applied Mechanics Group, Crossland B. , Burns D. J. 
Published: October 2007

In this paper the literature on the strength of compound cylinders subjected to internal pressure is reviewed. The theoretical treatment is briefly discussed and a theory for the pressure-expansion curve for a partially plastic duplex or two-component vessel is given. Pressure tests on two duplex vessels are reported, one made of Vibrac steel and having an overall diameter ratio of 2, and the other made of 0.15 per cent carbon steel and having an overall diameter ratio of 5.86. It is concluded that considerable and unpredictable axial stresses are set up when the two-component cylinders are shrunk together. Apparently, however, these do not seriously influence the yield pressure computed on the assumption that no axial stresses are induced during shrinking. In the partially plastic region there is good agreement between the experimental values and the theoretical pressure-expansion curve. The ultimate pressure and experimental pressure-expansion curves at large strains are in good agreement with values predicted for monobloc cylinders of the same overall diameter ratio.
Some Aspects of Feed Heater Design
Authors: Finlay L. C. 
Published: October 2007

Thermodynamics dictate that ideally the process of heat transfer obtaining within a feed heater should be reversible. Modern high-pressure feed heaters are, however, costly units and so it is also important that they should be economically efficient heat exchangers. These demands are in conflict and, in an effort to achieve highest thermal efficiency with lowest capital cost, the conditions for optimum design, the heat transfer and thermodynamic aspects must be a matter of compromise. It is essential, therefore, that the designer should have to hand means of readily determining the effects that changes in operating conditions, in processes within the system, will have on the efficiency and cost of the proposed plant. First, the thermodynamic aspects are dealt with; the ideals of regenerative feed-heating systems are briefly outlined. The ‘availability’ concept is suggested as a means of readily determining the effects that changes in operating conditions have on the efficiency of the plant as a whole. Generalized equations governing the heat-transfer processes obtaining within a desuperheating-type feed heater are next formulated. The large number of dependent variables operating in these equations, together with the range of possible boundary conditions, render any optimization process an exceedingly laborious task, involving as it must much repetitive computation. This is the type of problem most advantageous for solution on a digital computer and, without entering into the field of computer programming, an effort has been made in the paper to present the problem and its solution in generalized terms.
Lubricants for Nuclear Reactors
Authors:   Lubrication and Wear Group, Vaile P. E. B. 
Published: October 2007

The earlier British carbon-dioxide-cooled, graphite-moderated power reactors were designed to operate without lubrication. This was necessitated by lack of knowledge of the effects of radiation and other reactor operating conditions on lubricants, and of the degree of compatibility of lubricants with reactor materials Investigations carried out over the past few years of the effects of nuclear radiation on many types of lubricant have shown that it is possible to produce materials capable of lubricating some reactor components. In order to further the development of such lubricants the U.K.A.E.A. and the nuclear manufacturing groups have co-operated in providing lubricant manufacturers with details of design and operating conditions of reactor components which it is desirable to lubricate In this paper is described the range of operating conditions which lubricants are expected to encounter in different reactors, with particular emphasis on the C02-cooled, graphite-moderated reactor. Nuclear lubricant requirements proposed by the U.K.A.E.A. to cater for many applications are also discussed With this information available it is now possible to assess realistically the types of test facility necessary for the evaluation of nuclear lubricants. Such test facilities are described. They include irradiation sources, a test rig for running under irradiation conditions, various test rigs to simulate reactor operating conditions for testing products both before and after static irradiation, and other specialized equipment The effect of radiation on both conventional and nuclear lubricants is described and the use of ‘anti-rads’ illustrated. Attention is drawn to other desirable properties of nuclear lubricants such as temperature stability, low volatility and compatibility with reactor and fuel-can materials Designers of reactor machinery have taken, and will increasingly continue to take, advantage of the developments in lubricants but, while still further advances in lubricant quality will be made, some components, particularly of the more advanced types of reactor, will probably continue of necessity to be operated without lubrication
Applications of Automatic Control to Pressurized Oil Film Bearings
Authors:   Lubrication and Wear Group, Royle J. K. , Howarth R. B. , Caseley-Hayford A. L. 
Published: October 2007

Expressions for the load-carrying capacity, stiffness and damping rate of pressurized oil film bearings are derived and expressed in terms of the variables available to the designer By adding a simple automatic flow valve, operated by pressure feed-back, the pressurized oil film exhibits infinite stiffness to steady normal loads. The method can be adapted for a system, embodying pilot pad control of a main bearing pad, in which the pilot pad slides on a flat strip and the film thickness of the main pad is varied to compensate for undulations in the main slideway A further experimental and theoretical investigation is described in which feed-back control is used to support concentrically the shaft of a journal bearing. With a shaft diameter of 2 in. and a radial clearance of 0002 in. the eccentricity is generally not greater than 2 × 10-5 in., as inferred from the pressure measurements, for loads exceeding 300 lb and rotational speeds up to 1200 rev/min. It is argued that much greater loads and higher rotational speeds can be attained with virtually no eccentricity
Design and Operation of a Once-Through Supercritical Steam Pressure Boiler Installation
Authors:   Steam Plant Group, Cooke G. 
Published: October 2007

The paper describes the first super-critical once-through boiler to be installed in Great Britain. The unit is designed as a topping installation working in conjunction with a back pressure turbine exhausting into a medium pressure steam system Reasons for the choice of critical pressure are given, followed by a note on the fuels used and their effect on design. The boiler and its auxiliary plant are then described together with the control system; a note is included on feed water The operation of the boiler, including the method of starting up and shutting down, as well as some difficulties with tube faults, is described The paper concludes with a statement that the boiler has fulfilled its purpose since it is extremely flexible in response to load changes, and is also capable of operation below the designed pressure and temperature, if required to do so.
Performance of Two-Stroke Compression Ignition Engines in Combination with Compressors and Turbines
Authors:   Internal Combustion Engines Group, Wallace F. J. 
Published: October 2007

Several papers (1)-(5)† have been written in recent years dealing with various aspects of the performance of turbocharged two-stroke compression ignition engines. None of these, however, provides a general method of performance prediction for a given engine-turbocharger combination over the complete range of load and speed, in terms of given design operating conditions and given compressor and turbine characteristics. Such calculations are complicated further by the inclusion in the system of a mechanically driven scavenge blower, usually in series with the turbocompressor. The paper provides a complete solution of this complex problem on the basis of certain necessary simplifying assumptions relating primarily to the engine cycle. Since the gas generator and compound engine have been recognized in recent years as, in certain circumstances, superior alternatives to the turbocharged engine, the method is extended to cover also these two cases. In all three cases the engine is assumed to be of the opposed-piston type, which is now recognized as being particularly suitable for high-pressure supercharging (6). The paper may be considered supplementary to a recent paper by Chatterton (6), in which the turbocharged, gas generator and compound cycles are compared purely on a basis of design point operating conditions.
Contact Stress Distributions on Elliptical Contact Surfaces Subjected to Radial and Tangential Forces
Authors:   Lubrication and Wear Group, Haines D. J. , Ollerton E. 
Published: October 2007

The problem of Hertzian bodies in rolling contact and supporting radial and shearing forces in the rolling direction is considered. A modified form of the conventional photoelastic frozen stress technique has been used to study the particular case of flat elliptical contact surfaces. Existing theories are reviewed and new theories are presented which permit the analysis of the frozen stress results. The dependence of the measured stresses on the hysteresis of rolling is studied.
Turbocharged Loop Scavenge Diesel Engine
Authors:   Internal Combustion Engines Group, Henshall S. H. 
Published: October 2007

This paper describes the application of turbocharging to the loop scavenge diesel engine. The first part is concerned with the important effects on the practicability of the cycle of the turbocharger efficiency, scavenge air pressure and temperature, exhaust pressure and temperature, and the pulses in the exhaust, the allowable maximum pressure in the cylinders, the pressure drop across them in relation to the air flow and the air utilization of the engine. It then goes on to a discussion of the way in which these many factors may be arranged to result in a practical engine of high efficiency and utmost reliability. Reasons are given for preferring, in the present state of knowledge, to retain the crankshaft-driven scavenge pump and the merits of series and parallel arrangements are discussed together with the possibilities of cooling during the compression stages. The application of these considerations to the development of a range of engines is described. Results of tests on the berth and in service are given together with some details of the mechanical design and construction.
Nominated Lecture: The Mechanics of Instrumentation
Authors: Boiten R. G. 
Published: October 2007

In this lecture instrumentation will be interpreted as the ways and means to transport and modify signals so as to make them suitable for the input channels of human beings and automatic controllers. A difference may be made between measuring and control systems; the first present the value of the measured quantity in an appropriate way, the second also formulate and execute command signals. Modern control theory and techniques have an increasing influence on the arts of instrumentation. An important part of all instrumentation systems is the transducers, which convert the value of the signal to be measured to another physical dimension, more suited for transport or evaluation. Typical are the conversions to electric voltages, pneumatic or hydraulic pressures. The main requirements for the design of a transducer are a low energy consumption from the measuring source, fast response and low susceptibility to disturbing signals and noise. At the input there exist besides the value of the signal to be measured xm an associate signal ym, such that xmym has the dimension of energy W (watt). The generalized impedance Z is defined as Z = xm/ym, so that W = xm2/ Z. In general W should be small, requiring Z being large, sometimes approaching infinity. On the other hand, examples will be given where Z must have a certain specified value. A low value of W can be obtained either by using a very sensitive primary sensor and applying sufficient signal amplification afterwards or by using feedback techniques. Most of the primary sensors transfer the measured quantity into a displacement or elongation of the measuring element. A fast response requires small moving parts and a high stiffness. This lowers the sensitivity and efficiency of the signal conversion. Feedback techniques make it possible to increase the high-frequency response without undue miniaturization of the mechanical parts. The shape and the way of loading of the measuring elements have great influence on the efficiency of signal conversion and a figure of merit will be defined and applied to a number of common elements. An instrumentation system should be insensitive to disturbing signals and noise. This requires no, or a non-changing, interaction between adjacent components. Further the design should be such that such disturbances as temperature and barometric changes, accelerations, vibrations and gravity have no influence on the output. The first step is to make the design as insensitive as possible for these errors and thereafter by means of series—or parallel-compensation techniques—the remaining effects can be reduced to the required values.
Lubrication and Wear Group: Oil-Whirl Characteristics of a Rigid Rotor in 360° Journal Bearings
Authors: Holmes R. 
Published: October 2007

An insight into the mechanism of oil whirl is obtained by investigating theoretically and experimentally its two main characteristics, frequency and amplitude. It is shown that the ratio of steady oil-whirl vibrational frequency to shaft speed may be predicted qualitatively by a linear treatment and some conclusions of a nonlinear treatment are also given. It is also concluded that oil-whirl amplitude can be restricted by the oil supply pressure. Experiments involving the use of a rigid rotor supported on two fully lubricated 360° journal bearings are described and ratios of steady oil-whirl frequency to shaft speed as low as 0.37 reported.
Some Problems in the Design and Operation of Jet Ejectors
Authors:   Steam Plant Group Thermodynamics and Fluid Mechanics Group, Engel M. O. 
Published: October 2007

The author presents some of the more recent ejector design theories and compares them with experimental data, and he describes the operation of a few different types of ejector used at present in industry. He also gives a short survey of the relevant literature. The design theory developed in the first part of the paper is based on the momentum exchange between motive and suction fluid and the assumption that entrainment occurs at constant pressure and mixing at constant area. The equations in which the use of experimental coefficients is kept to a minimum give the motive-to-suction mass-flow ratio in terms of the pressure ratio and certain velocity ratios, as well as the required entry and mixing tube lengths and profiles. Optimization of the ejector for fixed pressure levels enabled the best ejector geometry to be determined with regard to nozzle position, mixing tube entry profile, and mixing tube length. The nozzle was in its optimum position when it reached up to the mixing tube. For this condition the optimum mixing tube length was seven tube diameters and the entry profile did not affect the operation. Although the theory is developed in more detail for an ejector using liquids the methods necessary for calculating gas ejectors and multi-phase and multi-component ejectors are outlined. The operating characteristics given in the second part of the paper emphasize the limitations of the jet pump but it is pointed out that both efficiency and compression ratio can be improved by the use of multistage designs. A particular application for a turbine condenser is discussed.