bluuebunny/crossref_metadata_2025_split huggingface dataset:
Paper 27: On the Two-Dimensional Unsteady Flow of Compressible Fluids
Authors: Daneshyar H. , Pearson R. D. 
Published: June 2010

A numerical method which was developed in a previous report is applied to the prediction of two-dimensional non-steady homentropic flow of air in a specially shaped duct. Previous methods for performing such calculations have not been practical owing to their inherent lack of stability when applied to non-steady flow cases. These methods have therefore only found application in problems concerning supersonic steady flow. The present method is sufficiently rapid to allow of its use in the solution of real problems. It is also demonstrated to be free from instability, so that computation of non-steady flows is now possible. Only subsonic homentropic flow free from shock effects is considered, but these limitations are not fundamental. The method relies on the finite difference relations along bicharacteristics and particle path lines. A comparison with experiment is presented which appears to indicate that errors introduced by the assumptions are acceptable for practical application, at least to those shapes for which boundary layers do not separate.
Paper 7: An Investigation of Steady Compressible Flow through Thick Orifices
Authors: Deckker B. E. L. , Chang Y. F. 
Published: June 2010

A thick orifice of a given diameter is one in which the length-diameter ratio exceeds that of a British Standard sharp-edge orifice of the same diameter. Thick orifices are important technically but little systematic work appears to have been performed on them. Sharp-edge orifices are treated as limiting cases of thick orifices. This paper describes a carefully controlled investigation into the behaviour of the steady flow of air through thirty-eight orifices ranging in diameter from 3/32 to 1/2 in and of length-diameter ratios, l/d, of 2.0, 1.0, and 0.5 and of sharp-edge orifices. These orifices have been calibrated against a range of sharp-edge orifices according to the British Standards code. The maximum possible instrument error over the experimental range (maximum pressure 150 lb/in2 absolute, maximum temperature 940°R) is estimated to be less than 0.1 per cent. The greater part of the overall error is attributed to the use of the code and may be as high as 1.6 per cent in some cases. About seven hundred experimental measurements have been made during the course of this investigation from which new relationships between the geometrical and physical parameters have been derived. The existence of a hysteresis phenomenon in a compressible flow through an orifice has also been measured for the first time. The main conclusions are: (1) When the ratio of the orifice diameter, d, to that of the cylinder cross-section is small the air expands from a state of virtual stagnation at a distance of one orifice-diameter from the plane of entry to the orifice. The ambient pressure is attained at the plane of exit only in the case of orifices for which l/d ≥ 2. (2) In the range of Reynolds numbers between 104 and 105 the dimensionless mass flow, G = m( T0)1/2 /d2 po, and the coefficient of discharge, Cd, are independent of the Reynolds number. (3) For a given l/d ratio G, or Cd, is a function only of the overall pressure ratio. (4) The l/d ratio is an important parameter in thick orifices because of the possibility of jet attachment. The observed behaviour of thick orifices may be explained on this basis. (5) For l/d = 0.5 there is a clearly delineated hysteresis in the flow near the threshold of choking, the lower branch corresponding roughly to the behaviour of a sharp-edge orifice and the upper branch attaining a value of Cd of nearly 0.9 for the choked regime. (6) Within the limits of accuracy of measurement, eccentric location of the orifice has no effect upon either G or Cd. Finally, the experimental results are compared with published theoretical and experimental work on compressible steady flow through orifices.
Paper 13: Abrasive Wear of Journal Bearings by Particles in the Oil (Apparatus, Experiments, and Observations)
Authors: Broeder J. J. , Heijnekamp J. W. 
Published: June 2010

Abrasion is generally defined as wear caused by fine solid particles. In this paper the term abrasion will refer only to wear caused by hard particles introduced into and entrained by a fluid flowing between two solid surfaces, the particles possibly becoming embedded in one of these surfaces. For the study of this type of wear a plain journal bearing was considered suitable. Arguments for this choice and a description of the apparatus are given. The use of an aerostatic bearing for the application of load to the plain journal bearing has made friction torque measurement feasible. The abrasives used were silicon carbide particles of very narrow size distributions; the carrier fluid was a mixture of a straight mineral oil and n-hexadecane. The wear of the shaft was determined by measuring its surface profile, the wear of the bush by measuring its deviation from roundness. Various combinations of materials were investigated. In most cases hardened steel shafts and soft bronze bushes were used. In addition, some plastic materials served for the bushes; steel, bronze, and aluminium were applied both as bush and as shaft material. Embedding of particles was observed at various places in the bushes, which were usually softer than the shaft. Additional information on the wear processes was obtained by microscopical inspection of the worn surfaces. Results of the experiments are discussed.
Paper 4: Induction System Development for High-Performance Direct-Injection Diesel Engines
Authors: Jones P. E. 
Published: June 2010

This paper describes some of the techniques employed by the author's company in the development of induction systems for direct-injection engines. Emphasis is placed upon those methods amenable to use during the day-to-day performance development of several engine types simultaneously. The induction system has two functions to perform: ( a) to provide maximum gravimetric aspiration, and ( b) to generate optimum and consistent swirl. These requirements are investigated using digital computers, air flow and swirl rigs, and engine experimental results. The effects of port size, port shape, valve timing, engine speed, and heat transfer on volumetric efficiency are presented in simplified theoretical and experimental forms. The behaviour of ports is discussed and a method of correlation of air swirl rig and engine results is presented. Experimental data is included, demonstrating the importance of correct swirl match. Fully machined inlet ports are discussed together with reasons for their adoption. The principles of induction pulse tuning are briefly enumerated and typical results included. Iso-fuel consumption curves are included to show the present level of d.i. engine performance. The paper concludes with a tentative hypothesis to explain engine swirl response, and suggests the general level of performance improvement likely during the next few years.
Paper 25: Size Sampling of Steam-Borne Water Droplets
Authors: Ryley D. J. , Fallon J. B. 
Published: June 2010

The results are briefly reported of a detailed study undertaken to assess the most promising method of sampling steam-borne water droplets for size. The ‘impressions’ method based upon a standard microscope glass slide smoked with the aerosol magnesium oxide was chosen for experimental development. A supporting probe was designed which exposed the slide in novel manner that avoided the ‘cut-off’ of smaller droplet sizes associated with conventional impaction techniques, without the necessity of accelerating the steam. The assembly was tested in a steam tunnel in which the wet steam mixture is prepared by introducing water droplets from a spinning disc atomizer into dry steam. The droplet size is varied by adjusting the disc speed and the tests were conducted at steam conditions up to 6 per cent wet with velocities up to 30 ft/s at pressures from 17 inHg vacuum to atmospheric. The paper explores the corrections which must be applied to the observed crater size frequency distribution to allow for the collection efficiency of the probe, penetration of the stagnant layer inside it, as well as sedimentation and transient phase changes. Results suggest that the sampling method can be employed successfully at relatively low velocities of flow, but the corrections and processing of data are tedious. The advantages and limitations of the method are discussed at some length and a numerical example is appended to illustrate the application of the corrections.
Paper 10: The Influence of Moisture on the Efficiency of a One-Third Scale Model Low Pressure Steam Turbine
Authors: Smith A. 
Published: June 2010

The rapid increase in blade-tip diameters and peripheral speeds of low pressure turbines in large 3000 rev/min turbo-generators has presented the designer with many difficult mechanical and aerodynamic problems. To assist in the aerodynamic development of such blading, design studies on an experimental low pressure (l.p.) turbine were started early in 1959. Economic and technical considerations limited the choice to a one-third scale model steam turbine capable of running at three times the normal rotational speed to preserve full-scale working Mach numbers on the blading. Overall output and steam consumption were measured on a hydraulic dynamometer and by volumetric tanking respectively. The inlet steam temperature was controlled by a direct injection desuperheater so that the expansion could be kept dry for traversing or reduced to design inlet temperatures for normal wet running. Three multi-stage sets with last row blade diameters corresponding to 90-in, 120-in, and 136-in full-scale turbines have now been tested in the experimental turbine and the wet performance of the largest forms the subject of this paper. The overall wetness losses on the model 136-in diameter turbine have been assessed from a series of seven tests in which the inlet superheat and rotational speed were varied whilst maintaining fixed inlet and outlet pressure levels. To isolate the stage moisture correction factor (α), however, where a stage-by-stage approach was adopted, in which the dry stage efficiencies were initially established from interstage traverses under dry steam conditions. Two wet steam analyses were made, the first assuming equilibrium and the second supersaturated expansion, but the choice seemed immaterial since the moisture correction factor was almost the same for both. In the case of the supersaturated expansion calculation, it was necessary to establish the point of reversion from supersaturated to near equilibrium expansion (the Wilson point) and supplementary water extraction results were used to establish the maximum supersaturation ratio. These suggest that the maximum level is nearer to 3 in the model turbine than to the value of 4–6 quoted for convergent-divergent nozzles.
Paper 26: Erosion Control in the Wet Steam Turbine
Authors: Todd K. W. , Fallon J. B. 
Published: June 2010

The general problem of erosion of turbine blading under wet steam operating conditions is reviewed and remedial methods available to the design engineer are considered. Of these, direct attack on the source of erosion, steam-borne water drops, is most attractive and is examined in some detail. Five stages may be distinguished in the process culminating in erosion. They are: formation of droplets, their deposition on diaphragm blading, subsequent detachment, acceleration towards the moving blades and final impact with them. The possibilities of interrupting this process at any stage are discussed and the paper primarily deals with the experimental investigation of these possibilities for the three intermediate stages using a full sized cascade of hollow last stage diaphragm blades. This enabled various configurations of extraction slots to be investigated as well as the effects of energizing the blade wakes and heating the blades. The construction and operation of the cascade and associated instrumentation are discussed and results are presented in terms of blading efficiencies for the various processes.
Paper 31: Measuring Steam Wetness and the Operation of Drainage in a 50 Mw Condensation Turbine
Authors: Christ A. 
Published: June 2010

After a short recapitulation of the main problems in wet steam turbines, the goal of the measurements is outlined, namely to determine experimentally as accurately as possible the real expansion line in the wet steam region of a 50 MW condensation turbine. These experiments embraced measurement of the steam and water flow withdrawn from the turbine in the water draining system and measurement of the steam wetness after the last runner stage. For this purpose a special probe was built in which a small amount of steam was tapped from the main flow and heated up to saturation. The probe was movable over the blade length of the last runner stage and results are given as local steam wetness as a function of the probe position. A comparison of the results with the findings of modern theory gives some explanation of the experimental facts.
Paper 2: Pressure Oscillations in Francis Turbines
Authors: Oftebro I. , Lønning A. 
Published: June 2010

In this paper the theoretical investigation of five plants, and the results of measurements obtained during testing, are presented to explain and describe pressure oscillations in Francis turbines of the critical frequency fs = nrzr/60, where nr is the runner speed (rev/min) and zr is the number of runner vanes. The oscillations, although causing no damage to the machinery or its foundations, are intolerable owing to the intense sound produced. This is an interference phenomenon, caused by the interaction of guide vanes, runner vanes, and the pressure propagating velocity in water, and may be avoided by careful construction.
Paper 10: Unsteady Incompressible Flow through Hydraulic Systems
Authors: Roberts B. W. 
Published: June 2010

The unsteady Bernoulli equation applied to an incompressible fluid may be used to calculate the unsteady pressures and velocities in a hydraulic system involving pipework and hydraulic machines. The effects of changes in the dynamic pressure, fluid friction, and the quasi-steady pump or turbine characteristics can be included. The results are applicable to situations in which the time describing the system disturbances is very much slower than the characteristic length of the system divided by the wave speed. In other words, the approach is similar to a rigid water-column theory used in water-hammer analysis. A worked example is also included.
Paper 7: Control of Variable-Discharge Pumps and Dangers of Pipeline Resonance
Authors: Cooper B. J. , Hartland D. , Lawson R. , Stone A. M. , Tyler R. D. 
Published: June 2010

The discharge and power input of Deriaz mixed-flow pumps and pump turbines can be controlled over a wide range without significant loss in efficiency by movement of the blades. The attainment of the highest pump efficiency involves a small region of positive slope in the head discharge graph. This paper examines the limitations of designing pumps which do not exhibit positive slope and the problems of governing if a positive-slope region is accepted. It is shown that operation in the positive-slope region can introduce a serious organ-pipe resonant instability in the pipeline. A simple criterion to determine whether or not such oscillations will occur is given. This stability criterion involves the dynamic characteristics of both the pump and the pipeline. Finally, computer studies of a particular Deriaz pump installation are presented. These underline the severity of the situation should resonance develop and show how it can be avoided by the use of an air bottle of appropriate design.
Paper 7: An Investigation into the Performance of Dynamically Loaded Journal Bearings: Experiment
Authors: Middleton V. , Dudley B. R. , McCallion H. 
Published: June 2010

The design of a rig to determine the load and attitude relationships of a hydrodynamically lubricated bearing under steady and dynamic loading is described. The bearing is nominally of 3 in diameter with a diametral clearance of 0·0075 in. Two bearing lands of length-diameter ratio of 0·282 are fed by a central circumferential oil groove. It has been designed on these model conditions to minimize bearing distortion and temperature gradients in order to provide a basis for comparison with the results of the computer program reported in Paper 6. Two perpendicular load components are applied mechanically through spring levers displaced by cams. The load components are measured by strain gauges and the displacement of the bearing is detected by four inductive pick-ups. The arrangement of these permits the relative linear and angular displacements of the journal and bearing axes to be determined. Inlet and outlet oil temperatures are measured for viscosity determination. Both steady and dynamic loads are applied by the loading system. Load diagrams of approximately circular and elliptical form may be obtained directly by adjusting the magnitude and phase of the eccentrics serving as cams, while more complex load patterns may be obtained by special cams. The polar load diagrams recorded are used as data for the computer program of Paper 6. Theoretical and practical results are then compared.
Paper 12: Hydrodynamic Theory of Dynamically Loaded Bearings and its Application to Engine Bearing Design
Authors: Hahn H. W. , Radermacher K. 
Published: June 2010

In recent years the hydrodynamic theory of dynamically loaded engine bearings has been developed to such an extent that calculations of bearing behaviour under all kinds of loads can be made with good correlation to experimental results and field experience. In addition to these calculations, experiments have been performed to determine the influence of variables in practical bearings such as oil-inlet pressure or temperature, the shape of the oil inlet, and the quantity of the lubricant. At the engine-design stage, engine-bearing behaviour can be predicted by using calculations based on hydrodynamic theory. Some examples are given to show that the load-carrying capacity and consequently the reliability of engine bearings can be increased by using these calculation methods on a digital computer and with a variation of bearing characteristics, such as dimensions, clearance, oil pressure, temperature, and viscosity, or with a variation of load characteristics such as magnitude or direction of counterweight-mass forces, gas pressure, and firing order. Very good correlation is obtained between these predictions and real engine-bearing behaviour in fast-running diesel engines, as measured by radioactive tracer methods. Many German diesel-engine producers are using these calculations in an early stage of engine design.
Paper 5: The Effect of Journal Misalignment on the Performance of a Journal Bearing under Steady Running Conditions
Authors: Smalley A. J. , McCallion H. 
Published: June 2010

A method of solution is described in which the governing equation is modified to account for variations in the oil-film thickness in the axial direction owing to journal misalignment. The position of the journal is specified by means of its eccentricity at its mid-length and by two parameters defining the extent and direction of the misalignment. The pressure distribution is evaluated numerically, and the direct load, friction torque, oil flow, and couple arising from the misalignment of the journal are obtained by numerical integration. A full range of journal misalignment conditions is examined for two length-diameter ratios. Results are presented in the form of non-dimensionalized graphs, showing the variation of direct load and misalignment couple with the journal misalignment parameters described. The angle between the line of action of the misalignment couple and the load line is evaluated in each instance, and graphs are presented to show the variation of the performance parameters for a particular degree of misalignment with the direction of application of the couple. Results for the particular instances in which the couple is in line with or at right angles to the load line are extracted, and these are compared with published experimental results of other workers. Good agreement is obtained, and moreover it is shown that, in general, these are not the two extremes of misalignment. For these two conditions design charts are presented, whereby, from knowledge of the applied couple and direct load, the degree of misalignment and the resultant peak pressure parameter may be determined. Charts which illustrate the reduction in load capacity for a particular journal misalignment in the plane of the load are also presented. General validity is claimed for this method of exploring a relatively unexamined subject, and the results are considered by the authors to be a useful improvement on those obtained by previous analytical workers.
Paper 11: Anti-Vibration Journal Bearings
Authors: Pope A. W. , Healy S. P. 
Published: June 2010

An experimental rig has been constructed to establish the vibration characteristics of plain, dammed groove, and tilting pad bearings having a variety of clearances. The rig is perhaps unusual in not being a small piece of laboratory equipment, but consisting of a naval anti-submarine frigate turbo rotor (15 000 rev/min) running in two journal bearings each supported by an isotropic cantilever system of variable stiffness. Two pairs of induction probes mounted close to the test bearing monitored the shaft movement and provided an oscilloscope display of the movement of the bearing centre. Detailed information about the shaft oscillations was obtained from a wave analyser and vibration meter. The static rig natural frequencies with various bearing housing support stiffnesses were primarily determined. From preliminary running tests a fairly stiff bearing housing support, which gave a strong vibration of approxi-mately half rotational speed, was chosen for all subsequent work. With the rotor wheel balanced the tilting pad bearing tested was found to be free from serious vibration. The dammed groove type of bearing tested was also stable at low speeds but was not capable of stable operation at 15 000 rev/min and above. The plain bearing tested produced serious vibration above 9000 rev/min. The frequencies and amplitudes of vibration which occurred in different bearings with a deliberate rotor unbalance were also measured. Increase of the clearance lowered the onset speed of serious vibration. The locus of the mean position of the journal centre of the tilting pad bearing was almost a vertical straight line whereas all the other bearings showed the usual approximate semi-circle. Instantaneous oil film pressures up to 900 lb/in2 were measured using a pressure transducer in the bearing. As the design particulars of the bearings tested differed somewhat the results were not strictly comparable but nevertheless an approximate design rule has been suggested. Practical data provided about the vibration behaviour of the different journal bearing designs can be used by the many theoretical investigators in this field. This is important in view of the lack of practical attested results to substantiate or otherwise the many theories advanced.
Research Report 3: Performance of Large Journal Bearings for Steam Turbo-Generators
Authors: Watson H. , Morton P. G. 
Published: June 2010

the well-known Growth of turbo-generator size has meant using very large bearings, in which the flow is turbulent. To help in their development, two large bearing research rigs have been operated by the English Electric Company, one for 20 in diameter bearings at 3000 rev/ min which has been in use since 1959 and, more recently, one for 28 in bearings. This brief report gives some of our findings. Most of the bearings in a modern steam turbine for power generation are turbulent. Sizes currently reach up to 20 in diameter at 3000 rev/min and are likely to grow further. Gradual increase in size through the years showed a marked increase in power loss as diameters of about 14 in were exceeded.