bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fatigue under Triaxial Stress: Development of a Testing Machine and Preliminary Results
Authors: Morrison J. L. M. , Crossland B. , Parry J. S. C. 
Published: October 2007

In this paper the reasons for attempting to investigate the effect of repeated triaxial stresses are discussed briefly. In particular the case of the thick cylinder subjected to repeated internal pressure, which is of some practical importance, is considered. The design and development of a machine capable of repeatedly applying to cylinders internal pressures of the order 20 tons per sq. in. (3,000 atm.) are described in some detail. Results are presented for such tests on one particular material and these are regarded as presenting an interim statement, but they are compared with detailed information about the properties of this material under a single and repeated application of uniaxial and biaxial stress. In all cases some attention has been paid to the effect of anisotropy. The thick cylinder tests give results much lower than might be expected from a knowledge of the properties of the material. A number of tentative explanations are put forward: some of these are at present being investigated.
An Approach to the Techniques of Graduate Training
Authors: Marples D. L. , Radford J. F. A. , Reddaway J. L. 
Published: October 2007

The initial practical training of the graduate apprentice has been largely a matter of workshop experience and training in craft skills. Such activities do not continue the training of the graduate in the way to which he is accustomed and by which he could best absorb the new knowledge required in industry. The paper describes experiments in methods of instruction for the topics which could be included in the initial three months' graduate training period in any works of which a machine shop is a dominant feature. The methods used followed the typical university teaching pattern of lectures, exercises, and preparation of reports. The topics included the study of the machine shop technology and the study of the machine shop as an operating unit together with the office work, or pre-production activities, concerned with its operation. The experimental methods have been tried out in a factory with a group of twelve undergraduates during a total period of twelve weeks. It is concluded that training which gives the graduate an opportunity to exercise the special learning abilities he has developed at the university is not only possible but the quickest way to give him the basic knowledge of the technology and organization of production necessary for any mechanical engineering career.
Crankcase Explosions: An Investigation into Some Factors Governing the Selection of Protective Devices
Authors: Freeston H. G. , Roberts J. D. , Thomas A. 
Published: October 2007

Remedies which have been suggested for crankcase explosions include the use of warning devices to detect over-heating in the crankcase, and the provision of relief vents to limit the explosion pressure to a safe value. Data were obtained experimentally at the Thornton Research Centre for the conditions necessary for the ignition of mists of lubricating oil in air in order that the margin of safety offered by a detector of overheating might be more fully assessed. The venting of explosions was also studied both on a rig scale and in the crankcase of a Diesel engine of 1,100 h.p. The results indicated that it would not be practical to provide sufficient venting area on an engine of this size, to limit the maximum explosion pressures to a safe value for the more violent explosions which might occur. For venting to provide complete protection, it would seem necessary to take measures to prevent the flame from spreading throughout the whole crankcase.
Crankcase Explosions: Development of New Protective Devices
Authors: Mansfield W. P. 
Published: October 2007

Tests of a crankcase explosion relief-valve 6 inches in diameter, provided with various wire-gauze flame traps showed such flame traps to be ineffective when ***severe explosions were made with mixtures of town gas and air. It was discovered that coating the wire gauze with lubricating oil greatly increased the effectiveness. of the flame trap. An internal, oil-wetted flame trap of less ***than half the original size was fully effective with the most severe explosion that could be produced. An oil-wetted flame trap, covering an aperture in a dividing partition of a cylindrical explosion vessel fully charged with gas-air mixture, was found to limit combustion to the chamber in which the mixture was ignited, and to limit the maximum pressure to one quarter of the value reached without the partition flame trap. Internal oil-wetted relief-valve flame traps and partition flame traps were then successfully tested on a ***three-cylinder engine of 9 inches bore. From the results obtained, the requirements of a large engine are estimated and it is concluded that the use of the two new devices would provide adequate protection at acceptable cost.
The Performance of an Axial-Flow Pump
Authors: Spencer E. A. 
Published: October 2007

Tests were made on an 11-inch diameter axial-flow propeller pump with impeller and guide blades designed for free vortex conditions, using as a basis the modified aerofoil theory. The best overall efficiency obtained was 82 per cent. Apart from head-flow and efficiency characteristics, measurements were made of velocities and yaw angles within the pump at the design flow of 6 cusecs. and these showed where departures from the theoretical assumptions occurred. Head-flow characteristics were obtained for various impeller blade-tip clearances from 0·015 to 0·060 inch (0·6 to 2·4 per cent blade height) and it was deduced that secondary flows were not confined to the tip region alone, but extended across the whole annulus. The pump was on an open circuit, so that cavitation tests were limited. Nevertheless, methods of increasing the resistance to cavitation susceptibility are considered. It was concluded that despite the fact that some of the assumptions made in the theory are invalid, this method of design may be used with confidence for pumps in the specific speed range of approximately 8,000.
The Development of a Mechanical-Draught Water-Cooling Tower
Authors: Smith L. Gilling , Williamson G. J. 
Published: October 2007

The paper describes the development of a mechanical-draught water-cooling tower containing a number of novel features. The packing is composed of serrated timber laths down which the water flow is film-wise to avoid splash formation. An earlier paper (Carey and Williamson 1950)§ gave the results of small-scale tests which indicated the theoretical advantage of grid film-flow packings in that the ratio of heat transfer to pressure drop is greater in this type of packing than in any other. A non-splash multi-trough water distributor is used to avoid the carry-over of splash droplets and hence to prevent a local deposition nuisance. Special attention has been given to the even distribution of water and air. Induced draught effects this better than forced draught and, since the fans exhaust heated air, there is no danger of ice formation upon them in frosty weather. The fans are large slow-running and aerofoil bladed, designed to give the highest possible static efficiency and to reduce the loss of velocity head at exit. The main design variables of air velocity and air/water ratio are determined from a balance of capital charges, packing, and power cost. Several examples, showing the methods of construction, are given of these towers. The main structure and shell is usually in reinforced concrete because of its rigidity in supporting the fans and drives and its permanence and fire resistance, but timber is quite satisfactory and cheaper. The pond is in concrete in all large towers. Timber is the usual material for the packing and distribution troughs, and the water flow is controlled by orifice tubes now made in glass. Methods have been developed for supporting the laths and troughs so that they remain level and in proper relation to each other after wetting. The packing is usually built on reinforced concrete beams across the main structure. Running experience obtained during six years is given together with the results of a comprehensive programme of tests. The good small-scale packing performance has been confirmed on the large scale. The tests have shown deficiencies in gear-driven fan installations, established the harmful effect on cooling efficiency of recirculation of the warm exit air and, in general, put on record performance details for critical assessment of this new development.
Education of Engineers in European Countries
Authors: Davies S. J. 
Published: October 2007

Systems of education in certain European countries are surveyed in detail in relation to the special circumstances of each country. Reference is also made to the numbers of those trained in allied branches of science. In addition to this provision, it was found that in these countries technical schools and colleges exist which cater for ‘technicians’ and in which considerable numbers of students attend full-time courses and reach standards roughly comparable to Higher National Certificate (H.N.C.) Among other matters, the survey reveals that, in spite of the fact that Great Britain is the most industrialized country of those considered, in the relative numbers of engineers educated to degree level it shares with Austria and Belgium the lowest positions. The lack of qualified engineers to fill posts abroad is mentioned, a lack which, in the long-term, must lead to loss of trade. On the other hand, Britain's position with respect to higher degrees is relatively better. Notwithstanding Britain's need for engineers, there are vacancies in some of her universities. The ‘bottle-neck’ in the supply is in the restricted numbers studying science in the sixth forms of schools; to make use of the increasing provision now being made for high-level engineering studies, these are the numbers most in need of attention.
An Investigation into the Mechanism of Oil Loss past Pistons
Authors: Dykes P. de K. 
Published: October 2007

The mechanism of oil loss past pistons was investigated in a laboratory test rig in which a piston was both reciprocated and subjected to gas pressures. The investigation brought to light the following facts and it is believed that this is the first time that they have been demonstrated: (1) Oil control is a two-way and not a one-way problem. The only reason why the rate of oil consumption is reasonably small in most engines is that, although a large amount of oil flows towards the combustion chamber past the rings during part of the engine cycle, nearly all of it returns to the sump during the remainder of the cycle. (2) The various routes permit surprisingly large rates of oil flow in both directions past rings. This applies even with good rings. (3) If oil is added to the combustion chamber, a good ring arrangement will pass it to the sump at a rate up to many thousand times larger than the normal rate of oil consumption with the same arrangement. (4) The piston lands, and the top land in particular, play an important role in deciding the rate of oil consumption. If some oil has passed the rings it may be thrown into the combustion chamber and be lost; alternatively, an effective top land may retain this oil until by one method or another it is returned to the sump.
Compressible Gas-Flow in Commercial Pipes
Authors: Mills Brian , Cole B. N. 
Published: October 2007

The main object has been to facilitate economic design of pipework for compressible flow; it being recollected that the cost of pipework in a given installation may not infrequently exceed the cost of compressor plant. It is found that the conclusion reached by Keenan and Neumann, namely, that compressible, subsonic flow in ‘smooth’ pipes is independent of Mach number and depends upon Reynolds number exactly as for incompressible flow, may be extended to commercial pipes of appreciable wall-surface roughness. While non-adiabatic flow is also examined, attention is mainly given to adiabatic flow; and various devices, tabular, graphical, and nomographical, are proposed to assist rapid estimation of such quantities as flow rate, pressure drop, maximum power transmitting capacity, etc. Encouraging correlation is found to exist between directly measured wall-surface roughness, as represented by the British Standard centre-line average index, and roughness as expressed hydrodynamically by the equation of Colebrook and White. This points to the practicability of predicting the flow characteristics of large pipes, for which flow tests may be difficult until in situ, by surface measurement alone.
Photo-Elastic Investigation of Stresses in the Heads of Thick Pressure-Vessels
Authors: Fessler H. , Rose R. T. 
Published: October 2007

The frozen stress photo-elastic technique is used to study the stresses in four different shapes of full drumheads and in five drumheads with circular or elliptical manholes. Circumferential and meridional stresses on inside and outside surfaces are presented, and some of these are compared with stresses calculated from different thin shell theories. These theories were modified to be more realistic for thick shells by considering the pressure to act on the inside instead of the middle surface of the shell. The wall thickness of every drum was one-tenth of the mean diameter of the drum. The effect of large elastic strains was studied by means of two identical models tested at different pressures. Calculations showed that the stresses were slightly decreased when Poisson's ratio was changed from 1/2 to 1/4. The effect of a reduction of the wall thickness of hemispherical heads was calculated and was found to be in good agreement with experimental results. The stress distribution in the walls of the shells was also determined for some critical sections.
Diesel Engine Lubricants: Their Selection and Utilization with Particular Reference to Oil Alkalinity
Authors: Dyson A. , Richards L. J. , Williams K. R. 
Published: October 2007

The main functions of heavy-duty lubricating-oil additives are to control engine fouling, bearing corrosion, and wear of liners and piston rings. Alkalinity is desirable for the control of wear and is one of the major requirements for the avoidance of piston fouling when conventional organo-metallic additives are used. In a well-balanced oil, sufficient dispersive power and oxidation stability may be incorporated to ensure adequate piston cleanliness and freedom from bearing corrosion provided that the alkalinity level is satisfactory. The alkalinity level falls during service, and for satisfactory performance with certain types of additive in common use it must be kept above a minimum value. For these additives equations are given which enable the variation of the alkalinity level with time in given circumstances to be predicted approximately. The most satisfactory arrangement is to use an oil containing sufficient alkalinity so that the concentration never falls below the critical value. The oil-change period is then determined by other considerations, for example, contamination with abrasives. If an oil of lower alkalinity-concentration is used, then the equations developed permit an approximate estimate of the oil-change period, determined solely from the aspect of additive effectiveness. The application of these results to engines with separate cylinder lubrication is discussed. Thus oils, and, where appropriate, oil-change periods, may be selected on a rational basis instead of by trial and error.
Journal Bearing Performance for Combinations of Steady, Fundamental and Harmonic Components of Load
Authors: Shawki G. S. A. 
Published: October 2007

The performance of a complete journal bearing is obtained for a vertical cyclic load of the form It has already been established that the ratio of the rate of load application to that of journal rotation (ω1/ω) is a prime factor in the bearing behaviour, and for the case where Pn = 0, values of this ratio slightly less than 0·5 were found to give rise to critical changes in the bearing performance depending on the ratio P1/ P0. Present test results show that the superposition of the harmonic load component Pn would, in general, bring some changes to the performance characteristics at the ω1/ω value corresponding to this harmonic, that is, at nω1/ω ⋍ 0·5, and some simultaneous related changes (in the opposite sense) at the ω1/ω value corresponding to the fundamental component P1, that is, at ω1/ω ⋍ 0·5, the extent of these changes being a function of the amplitude ratio Pn/P1. The phenomenon is explained in the light of the theory of vibrations, and the analysis is extended to include the case of a variable load on a uniformly rotating journal.
Unsteady-State Heat Transfer to and from Gases in Laminar Flow
Authors: Patten T. D. 
Published: October 2007

In this investigation of the problem of unsteady-state heat transfer to and from gas, experiments have been carried out with the flow of air through a passage of circular cross-section. Heat transfer takes place within a single vertical tube, around which is an annular guard space. Because of the magnitude of heat losses at lower values, the investigation is confined to values of Reynolds number between 1,000 and 2,500. Within this range, at moderate temperature differences, the processes of heating and cooling of gases reveal similar heat-transfer properties. When the tube wall-temperature is either constant or has a uniform temperature gradient, it is shown that the Nusselt number is in agreement with that predicted for steady-state heat transfer for the same wall-temperature distribution. The investigation deals with single-cycle operation referred to as ‘single blow’, in which the supply is either hot or cold, and with cyclic operation as a parallel flow regenerator. Heat-transfer coefficients obtained from the cyclic operation tests are of the same order as those from the single-blow tests. An analytical expression for the prediction of outlet temperatures, assuming a varying supply inlet-temperature and non-uniform initial wall-temperature, is presented and this is used in the calculation of the single-blow results.
Stress-Relaxation Behaviour of Chromium-Molybdenum and Chromium-Molybdenum-Vanadium Bolting Materials
Authors: Stafford J. A. , Gemmill M. G. 
Published: October 2007

The object of this paper is to illustrate by means of a series of tests made on two steels, the essential differences between testing under constant load, constant total strain, and a commonly used ‘weighbar’ method that is intermediate between these two. It shows that the constant strain results do not entirely support the strain-hardening and time-hardening theories suggested by other authors. An empirical relationship, which gives reasonable correlation in the ranges of stress, temperature, and time examined, is given as an aid to analysing the results, but no correlation of this with a theoretical approach has been found, though it is hoped that it will contribute to the eventual solution of this problem. Suggestions are finally made as to how relaxation data may be used for design purposes with reference particularly to the choice of an initial stress and the value of retightening.
Recent Developments in the Manufacture of Castings
Authors: Rice J. L. , Ruddle R. W. , Russell P. A. 
Published: October 2007

Developments which have taken place in the last decade in foundry practice and in the alloys used to make castings are described. The main emphasis is on the effect of these developments on the soundness, mechanical properties, dimensional accuracy, and the cost of the finished casting, and less on the way the improvements have been brought about. The topics discussed are: (1) the development of new and established processes; (2) alloy development; (3) inspection; (4) future trends. The paper is confined to cast iron and non-ferrous alloys; advances in the production of steel castings have not been covered. Many of the techniques referred to, though, are of general applicability.
Test Bed Installations and Engine Test Equipment
Authors: Freeston H. G. 
Published: October 2007

As well as meeting the functional needs of the tests required, an installation for testing engines should, also provide a satisfactory environment for operating personnel. Nuisance or disturbance to persons or apparatus in the vicinity must be avoided. Consideration is given to the requirements of heating, ventilation and acoustic treatment of the test room and the provision of services. The test bed arrangements are dependent on the kind of work to be undertaken. The test bed equipment required includes dynamometers and instrumentation for the various phenomena to be measured. Many tests can be made without personnel in attendance by the use of automatic operating equipment and recorders, provided safety devices are fitted. The simulation of service conditions gives rise to interesting problems for the equipment engineer.
Experimental Studies of the Mixing Processes and Flow Configurations in Two-Cycle Engine Scavenging
Authors: Rizk W. 
Published: October 2007

The paper describes work carried out at various stages during the period 1944–54 and indicates the need for a new approach in the study of the scavenging process in two-stroke engines. Its main object is to outline various ways of studying the main features of the scavenge flow within the cylinder as distinct from the gas dynamics of the charging process. By using a special photo-electric cell probe in a scale model and determining the change in purity of the stream at any point it was possible to examine the basic characteristics of scavenging flow and consider the process as taking place in broadly three phases. The first of these, entailing the formation and development of the inlet jets, has been studied in a preliminary way with the aid of a colour reacting technique to show the mixing region together with the undiluted core of a jet starting from rest. This has thrown light on the rate of mixing in the initial phases of scavenge flow and has indicated the possibility of achieving higher efficiencies by a reduction in the size of inlet ports and an increase in their number. An experimental study carried out on a loop-type system has shown that the flow configuration can be substantially different from that usually assumed and that flow instabilities could occur leading to partial short-circuiting of the flow. Photographic records of the flow and the major axis of rotation under various conditions have been obtained and assist in showing qualitatively the effect of altering the angles of entry of the jets. It is further shown that under certain conditions an increase in the inlet air flow could nullify any gains in scavenging efficiency. End-to-end scavenge systems are also discussed, indicating the need for further study of some of the major parameters governing the flow.
The Application of Servo-Mechanism Analysis to Fuel Control Problems
Authors: Lawrence J. O. N. , Powell R. D. 
Published: October 2007

The paper gives details of the way in which servo-mechanism techniques have been applied to accessory control problems. The emphasis has been on the correlation of theory with practice and typical results are given from tests on some 15 British gas-turbine engines. For completeness a brief introduction to the basic concepts is first dealt with, then examples are given of linear and non-linear theories applied to typical working systems. It is pointed out that though the examples refer to hydraulic, mechanical, and thermodynamic processes the ideas may be carried forward into widely differing fields.