bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of High-Temperature Strain Gauges
Authors: Bertodo R. 
Published: October 2007

This paper is restricted to a review of the work carried out in order to develop a strain gauge capable of operating at temperatures up to 1000°C with an inherent accuracy of ±5 per cent. A large number of resistance alloys were tested as unbonded long wires at room temperature and, from the results obtained, a small number were selected for further investigation, in the form of gauges, at high temperatures. The effects of factors such as metallurgical changes, geometric shape and long-term exposure on the behaviour of the gauges were investigated. A number of bonding mediums, some commercially available, were examined with particular reference to creep under load, shear strength and resistance to erosion and thermal shock. Finally some preliminary tests in conjunction with the measurement of steady strains at elevated temperatures were undertaken. It is concluded that the gauge factor is a function of the lattice imperfections of the element wire and, as such, will be temperature-conscious only if the imperfections themselves are affected by temperature variations. In general, any factor affecting the resistivity will affect the sensitivity. The most significant result obtained during the work described is that the gauge factor may be predicted within ±5 per cent at any given temperature, provided certain precautions are observed. Some typical failures under field conditions are discussed as also are the possibilities of operating for protracted periods under steady stress conditions. More stringent requirements for future applications suggest that the wire gauge will be unsuitable, in view of its low resistance in very small sizes, and a possible alternative is briefly outlined.
Hunting of Water Level in Float-Controlled Deaerators
Authors: Morton A. J. 
Published: October 2007

Operating difficulties encountered with a deaerating feed heater during full-scale test-bed trials of a complete prototype main propulsion machinery installation are described, together with the eventual successful remedy. The water level control system of the deaerator is analysed mathematically and a criterion for stable operation established. Comparison of the theoretical and observed behaviour of the deaerator shows reasonable agreement. Practical factors affecting the validity of the theory are examined and suggestions made for improvements in design. Some remarks on common deaerator design practices are made in the light of test-bed experience. The example of this deaerator is used to illustrate an introduction to more general analytical methods. The need for these in modern steam-plant design work is explained, together with the obstacle to their use imposed by our current ignorance of the kinetic characteristics of common plant items.
On Turbulent Lubrication
Authors: Constantinescu V. N. 
Published: October 2007

The paper concerns the hydrodynamic turbulent motion in the lubricant layer. Proceeding from the Reynolds equations and introducing the approximations currently used in lubrication problems, owing to the lubricant film thickness, the general motion equations for turbulent lubrication are written. Using the Prandtl mixing length hypothesis, exact and approximate solutions are obtained for the velocity distribution into the lubricant layer. The results are discussed by pointing out the pressure gradient and the Reynolds number influence on the velocity distributions, as well as the differences with respect to the laminar flow. In order to obtain simple formulae, the exact dependence of the rate of flow on the pressure gradient into a dimensionless form is replaced by a linear relation, the slope of which depends on the Reynolds number. This approximation allows the obtainment of the pressure differential equation under a simple form. The pressure equation is integrated in case of journal bearings, by assuming a constant or a variable viscosity of the lubricant. The results are compared to the experimental data obtained by M. I. Smith and D. D. Fuller and the good qualitative agreement is pointed out.
The Diesel Engine in Association with the Gas Turbine
Authors: Chatterton Ernest 
Published: October 2007

On the basis that the future development of the diesel engine is inevitably dependent upon its association with a gas turbine, this paper explores three known methods by which the association between the engine and the gas turbine may be achieved, namely, turbocharging, compounding, and the gas generator. Potential performances attainable from these three arrangements for both 2-cycle and 4-cycle engines with and without charge cooling are derived by methods which are explained, and it is demonstrated that high specific power outputs become possible at high air-manifold pressures without exceeding established limitations for maximum cylinder pressure, piston temperature, or turbine inlet temperature. The characteristics and limitations of the three alternative arrangements are compared and the conclusion is drawn that a highly supercharged 2-cycle engine used as a gas generator feeding a power turbine would provide an efficient and versatile power unit.
Development of Some Unconventional Centrifugal Pumps
Authors: Barske U. M. 
Published: October 2007

A centrifugal pump of a simplified and unorthodox design has been developed for the immediate satisfaction of special urgent requirements. The experiences gained were encouraging, and this type of pump has been successfully applied to a number of different purposes. Results of tests and recent investigations are given which suggest that some aspects of common centrifugal pump design practice are of lesser importance than are generally considered. A few more items developed in connection with this pump are described, such as shaft seals especially suitable for high rotational speeds, means to reduce hydraulic friction losses of pump impellers, and a novel pump impeller designed to overcome cavitation difficulties.
Effect of Piston/Bore Clearance in Small Refrigeration Compressors
Authors:   Internal Combustion Engines Group, Smith H. J. 
Published: October 2007

This investigation into the effect of piston diametral clearance on the performance of a small refrigeration compressor was made to determine the limiting conditions for satisfactory performance. Six pistons of standard ringless design were used in the same compressor giving clearances ranging from 00004 to 00041 in. The tests were carried out on a refrigerator with a calorimeter-type evaporator using dichlorodifluoromethane. Particular attention was given to the effects on volumetric efficiency and specific power consumption. These quantities were plotted against pressure ratio over a wide range of operating conditions and an analysis of the losses involved was made and related to the diametral clearance. Both volumetric efficiency and specific power were found to vary greatly with the clearance, the former being greatest with the minimum clearance but the latter showing a tendency under some conditions to a minimum value for a diametral clearance of 0.0022 in. Honed cylinders and ground pistons are considered essential for good performance. It is suggested that in addition to piston leakage, entry heating plays an important part in the reduction of volumetric efficiency.
Influence of Plain Journal Bearings on the Whirling Action of an Elastic Rotor
Authors:   Lubrication and Wear Group, Morrison D. 
Published: October 2007

An analysis is made of the whirling performance of an elastic rotor supported in fluid lubricated journal bearings, taking account of both the displacement and velocity-dependent components of dynamic bearing action. It is shown that two distinct modes of vibration occur corresponding roughly to half-speed whirling, oil whip, etc., and to reduced elastic whirling speed respectively. Typical bearing coefficients are given for short journal bearings. Using these, examples are given illustrating the calculation of the natural frequencies of a rotor running at a fixed speed and the calculation of the response curve of a rotor running through a range of speeds. Experimental evidence confirming these results is given The inherent stability of an elastic rotor bearing system is also investigated and a chart presented showing the limits of stable operation of an elastic rotor
Some Aspects of the Performance of High-Speed Lightly Loaded Cylindrical Roller Bearings
Authors:   Lubrication and Wear Group, Smith C. F. 
Published: October 2007

The paper deals with the wear problems which are sometimes experienced when operating parallel cylindrical roller bearings at high speed, with jet lubrication, in turbine mainshaft bearing practice Tests show that considerable cage slip often takes place, as reported by previous investigators, the cage and roller assembly travelling at speeds lower than that predicted from the epicyclic relationship It is concluded that hydrodynamic lubrication normally occurs between the rollers and races when appreciable cage slip takes place. If the radial load on the bearing suddenly increases under these conditions, the hydrodynamic film is not always able entirely to prevent metallic contact and wear of the rollers and races Further experimental work is required before complete understanding of the problem can be obtained. Tentative recommendations, however, are made for minimizing the incidence of this type of wear in practice
Methods of Load Verification of Tension and Compression Testing Machines
Authors:   Applied Mechanics Group, Swindells B. , Debnam R. C. 
Published: October 2007

A brief review is given of the early methods used for the load verification of material-testing machines. Demands for greater accuracy led to the development of elastic proving devices, followed by deadweight standards of sufficient accuracy to calibrate these devices. The methods resulting from these developments are also described. The definition of the technical unit of force is given, followed by a consideration of the minimum accuracies required of deadweight standards, proving devices and testing machines verified by proving devices. These considerations of accuracy bear particular reference to the British Standard covering the load verification of testing machines. A deadweight standard machine and many of the more common types of proving devices are briefly described. General guidance is given of the range of loads covered and the performance which may be expected of the various types of proving devices.
The Rigidity of RIB-Reinforced Cover Plates
Authors:   Applied Mechanics Group, Harvey J. , Duncan J. P. 
Published: October 2007

An experimental approach to the problem of rib-reinforced cover plate design is outlined. Exact tractable methods for calculating the deflections of radially ribbed plates are not available. Outlines of formal mathematical treatment which use several approximations are presented to highlight the theoretical difficulties. The technique of Fizeau interferometry was employed to study the deflections of a series of laterally loaded ribbed plates of varying proportions. From the results, values of the rigidity of the plates were found together with the best combination of parameters to ensure optimum stiffening with a minimum of localized curvature for plates of fixed total weight. The nature and character of the localized curvatures developed in an over-stiffened ribbed plate was revealed by photographic records obtained by means of the Salet-Ikeda slope-contouring technique. It was concluded that, for optimum design on a basis of rigidity of plates of given total weight, 40 per cent of the total weight of a ribbed plate should be in the ribs or webs and 60 per cent in the basic plate or flange. Localized curvature with attendant stress concentrations were found not to be serious under such a degree of stiffening. Frozen stress photoelastic studies have been initiated to elucidate stress distributions in the vicinity of the ribs.
Burst Cartridge Detection in British Gas-Cooled Reactors
Authors:   Nuclear Energy Group, Dent K. H. , Williams D. W. 
Published: October 2007

A burst cartridge remaining in a reactor may eventually release such quantities of radioactive fission products into the coolant circuit as to cause a potential health hazard or maintenance difficulty. It is important, therefore, to be able to detect and locate a burst so that the reactor operator can discharge the cartridge concerned. Of all the possible methods, only detection by the released fission products is satisfactory. Gaseous fission products diffuse through the leak in the can wall against a coolant inflow induced by oxidation of the fuel, and their presence in the coolant has to be detected against an unavoidable background count. The leak size at the threshold of detection can be estimated from the operating conditions, and the manner in which b.c.d. (burst cartridge detection) signals arise from a developing burst merits special study. To discriminate against the radioactive decay of the coolant gas itself the precipitation system of monitoring is used. From each fuel channel in the reactor a sample of gas is drawn periodically. This is passed through a precipitation chamber where particular fission product nuclides decay to give ionized daughter products which are collected on a charged wire. The wire is moved to a shielded scintillation counter and the fission product nuclides, which undergo a second radioactive transition, are measured to the exclusion of the active nuclides in the coolant which do not. The performance and sensitivity of the system can be calculated and optimized by considering the expression for the count from the wire. The mechanical design of the equipment varies in detail from station to station. In later designs the mechanical equipment is simpler and easier to maintain, and greater use is being made of automatic processing and presentation of the signal.
Turbine-Blading Development Using a Transonic Variable-Density Cascade Wind Tunnel
Authors: Forster V. T. 
Published: October 2007

The thermal development of the modern steam and gas turbine over the past two decades has been greatly assisted by a much better understanding of the fluid behaviour as it passes through the machine. This has been brought about by the increasing amount of aerodynamic research and development being carried out on the many components of these turbines. This paper concentrates on the fixed and moving-blade elements of the large steam turbine, and describes the design and operation of a transonic variable-density wind tunnel for static cascade testing of turbine blading. The importance of Reynolds number and Mach number is emphasized, and the manner in which these parameters influence the blading losses. The origin of the trailing edge shock waves on blades discharging obliquely, and their effect on performance, is discussed in some detail, drawing on both experimental and theoretical techniques. A large proportion of the flow section of long last 1.p. stages is operating in the supersonic region, and possible future blades may have relative discharge tip Mach numbers approaching 20.
Free Convective Cooling of Cabinets Containing Heat Dissipating Components
Authors: Noronha R. I. 
Published: October 2007

A theory has been developed based on the accepted heat transfer theories of Fishenden, Saunders, Weise and others, together with the results of the author's experiments. From this theory it is possible to evolve a design sheet which can be used to predict ambient temperatures within cabinets for predetermined areas of ventilation. Hence, design curves of temperature, in relation to areas of ventilation, can be obtained for specific cabinets and methods of cooling. From these curves, it should be possible to select the method of ventilation and the optimum cooling area and hence ensure that the maximum tolerable ambient temperature in which the components are required to operate shall not be exceeded. The effects on the hottest component, when the methods of ventilation are altered, the ventilating area is varied and the main heat source is progressively raised, are studied. The results of these experiments and the comparisons between predicted and observed ambient temperatures are discussed. Recommendations for positioning components within cabinets for maximum cooling effects are made.
Chemical Commissioning at West Thurrock Power Station
Authors: Sherry A. , Gill E. R. 
Published: October 2007

The chemical techniques adopted in the pre- and post-commissioning phases at West Thurrock power station are described. Apart from the detailed account of the chemical cleaning operations, types of cleaning processes, acids and strengths, sampling arrangements, circulation rates and method of final inspection are also considered. Mention is made of the desirability of sections of the plant arriving on site in a clean sealed state. The cleaning methods bring about a rapid reduction in boiler water silica so that full load can be achieved quickly. A new technique, involving nitrogen sealing, to reduce metal pick-up during start-ups has been evolved, whilst the early control of both feed and boiler water conditions is stressed and an optimum hydrazine level determined.
Chatter in Horizontal Milling
Authors: Andrew C. 
Published: October 2007

An analytical and experimental investigation into the chatter behaviour of a horizontal milling machine is described in this paper. The experimental results were used to check the basic assumptions involved in the analysis. The machine structure and the cutting force characteristics of the workpiece material were initially tested separately. The vibration behaviour during machining was then investigated for a range of machining conditions. These included different values of cutter speed, workpiece width, depth of cut and number of cutter teeth, different directions of cutter rotation, and plain and climb milling. The results are presented in the form of stability charts, describing conditions when chatter was present or absent. Chatter was found to be of the regenerative type, occurring in bands of cutter speed. For all conditions tested, the machining stability defined by the envelope of the chatter bands improved as cutting speed was reduced. The dependence of the chatter bands on cutter speed, the chatter frequency, and the qualitative changes in the chatter-free machining capacity were predicted successfully at all but low speeds. Quantitatively, the chatter-free machining capacity was predicted to be slightly less than half that found by experiment. The conventional assumptions for dynamic cutting force characteristics were shown to be in error. More accurate assumptions based on recent fundamental work only partly explained experimental observations, indicating that an additional, and as yet unstudied, dynamic force component exists.
Third Paper: Servo Reliability in the ‘Seacat’ Missile
Authors: Foreman P. F. , Carrington J. E. 
Published: October 2007

The ‘Seacat’ missile has been adopted by the Royal Navy as the standard close-range ship-to-air weapon of the 1960's. When the specification was drawn up reliability requirements were nebulous in the extreme, but it was appreciated that with such a missile a ‘high’ reliability had to be achieved in spite of intense pressure to reduce weight, space, and cost to absolute minima, and in spite of some unusual operational requirements. This paper reviews in retrospect some of the methods adopted both in the servo actuator design and in production procedures to meet these requirements. In addition the systematic reporting of tests carried out in depots of ships enables an assessment to be given of the reliability achieved in service. It is concluded that, in the mechanical sphere, the cost of a full scale statistical exercise aimed at a prediction of reliability may well be exorbitant, and whilst assurance will be obtained, the contribution to the degrees of reliability may only be marginal. However, the systematic recording and analysis of experience in the field will enable maximum benefit to be derived for future projects.
Design and Development of a Compressed-Air Driven, Counterblow High Energy-Rate Forming Machine
Authors: Marland I. , Organ A. J. , Tobias S. A. 
Published: October 2007

As a first stage in the development of a large, double-acting, petrol combustion actuated, high energy-rate forming machine, a compressed-air driven device was designed and constructed. This was intended to be a research vehicle for establishing general design principles, particularly as far as the structural configurations and the method of platen synchronization were concerned. The characteristic design features of this machine are discussed and an appraisal of the design is given. Experiments were carried out with the aim of (1) determining the net energy output of the machine and (2) finding the maximum platen approach velocity for a range of values of the initial charge pressure. For the determination of the energy output of the machine, calibrated crush-gauges were used, the results being cross-checked by measuring the maximum relative velocity between the platens, and from this and the weight of the moving masses finding the maximum kinetic energy. For the determination of the maximum platen approach velocity, electric velocity transducers were used, the results being checked with the aid of a high-speed ciné camera. The maximum energy output of the machine was found to be 75 000 ft lb, which was attained with a maximum impact velocity of 80 ft/s, as aimed at in the design of the machine. Some typical examples of hot forgings produced with the machine are also presented.
Gear Conformity and Load Capacity
Authors: French M. J. 
Published: October 2007

A measure, M, of the conformity or closeness of fit of gears is proposed and it is shown that there is a limit on its value; this limit is a function of the material properties and is about 2.5 times the value for involutes for gears of case hardened steel. It is shown that no very large improvement in M can be had above that obtainable in known non-involute forms, specifically Wildhaber-Novikov gears.