bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measuring the Oscillating Flow from an Electro-Hydraulic Servo-Valve Using an Indirect Method
Authors: Burrows C. R. , Martin D. J. 
Published: October 2007

Recently published work concerning the dynamic flow-rate through servo-valves is discussed. It is shown that there is some disagreement amongst workers concerning the effects that fluid inertia and valve discharge coefficients have on the dynamic performance of these devices. The problem of measuring pulsating flow is discussed and the various commercially available transducers are shown to have shortcomings when used in conjunction with servo-valves. An alternative indirect dynamic flow measurement technique is described. The technique is evaluated using an analogue model. It is concluded that the method is capable of determining the dynamic volumetric flow-rate. The difficulties involved in identifying the valve dynamics from these measurements are discussed. The method is applied to determine the volumetric flow-rate in an experimental rig consisting of a servo-valve controlling a rectilinear motor used to position an inertial load.
Cold Consolidation of Powder by Hydrostatic Extrusion
Authors: Hewitt R. L. , Wallace W. , Demalherbe M. C. 
Published: October 2007

The isostatic compaction and hydrostatic extrusion of two atomized powders, namely Alcoa grade 1202 aluminium and Atomet 28 iron, are described and it is shown that the extrusion pressures for these powders may be 50-100 per cent greater than for an equivalent wrought material. Results of mechanical testing and metallographic and fractographic examinations of the extruded aluminium compacts are presented which show that good bonding can be developed by hydrostatic extrusion at ratios of 6·25 and that the resultant strengths can be higher than that of wrought material of a similar composition. This strength improvement is attributed to the strain hardening undergone by the materials during compaction. An interpretation of the bonding mechanism is also given. Although it has been shown that isostatic compaction and hydrostatic extrusion can be combined to produce well-bonded bar material from metal powder at room temperature, it is suggested that the method is limited by the very high pressures that would be required to produce materials of commercial interest.
The All-British High-Powered Marine Diesel Engine
Authors: Butler J. F. 
Published: October 2007

Over the past quarter of a century, British-designed marine propulsion diesel engines have more than doubled their power output per cylinder. During the same period weight per kilowatt, and engine length per kilowatt, have both been reduced by nearly 75 per cent, specific fuel consumption has been reduced, and reliability has improved. This progress has been achieved by detail design improvements to even out stresses in components and to reduce temperature differences between hot and cold surfaces, combined with the application of the results of advanced computer methods to air flow, fuel distribution, and separation of rubbing surfaces by oil films. At the present stage of development the marine diesel engine is in many ways more advanced than the small automotive engine and can also compete in economic power production with prime movers at the opposite end of the scale such as super-large high-pressure steam turbines.
Experimental and Theoretical Investigations into Chimney Emissions
Authors: Moore D. J. 
Published: October 2007

The simple ‘conical’ model of plume dispersion from an elevated source of effective height H (m) which indicates that the maximum ground-level concentration Cm (units m-3) is proportional to Q (rate of emission, units s-1) (σZ/ày)/ U (wind speed, ms-1) X H2 assumes that the vertical (σz) and cross-wind (σ y) spreads of plume material are similar functions of distance downwind For time average values of Cm of duration about 1 h, the length scale of the turbulence responsible for the cross-wind spread is, in general, much greater than that responsible for the vertical spread. This length *** l is restricted either by the depth h of the boundary layer or the height above the ground. In this case (σz /σy) in the expression for Cm must be replaced by (Some representative vertical turbulent velocity * l)/(Some representative cross-wind turbulent velocity X H) ’*** In conditions of strong thermal convection and light winds the turbulent vertical velocities are effectively independent of the wind speed and so the form of the first expression for Cm will change both with wind speed, atmospheric stability and the height of the plume in relation to the top of the boundary layer. Simple boundary-layer models for ‘convective’ and ‘windy’ conditions are shown to lead to equations for predicting Cm which are similar to those previously shown by the author to give a good representation of the ground-level concentrations in all categories of wind speed and stability observed on 2500 separate occasions in the Tilbury-Northfleet plume rise and dispersion experiment. The application of these expressions to other locations and sizes of plant is discussed.
Some Experiences of Fuel Dilution of Lubricating Oils in Small Diesel Engines
Authors: Thornber J. C. P. 
Published: October 2007

Fuel dilution of lubricating oils in small diesel engines is normally attributed to fuel leaking past seals, pumping elements or feed pump diaphragms. Some authorities advise that dilution greater than 10 to 15 per cent is inadvisable; others advocate an oil change if the viscosity is more than an S.A.E. grade. Another possible cause of dilution depends on fuel properties, nozzle design and aspects of air-How into a cylinder. The fuel introduced in this way plays some part in the combustion process and influences engine smoke levels. The dilution so caused is speed and temperature dependant. The paper describes tests to establish the basic characteristics, the mechanism at work and modifications to minimize this cause of oil dilution. Some tests are included to show that some fractions of fuel that is diluting lubricating oil can evaporate during engine operation; heavier fractions, however, are more likely to persist.
Investigations on the Pumping Effect of Rotating Discs
Authors: Barske U. M. 
Published: October 2007

The mathematical and experimental work described in this paper were carried out in the pump laboratory of the Rocket Propulsion Establishment (RPE) Westcott in 1955. In 1956 test runs took place with a ‘disc pump’ the impeller of which was described in the author's paper (l)t (Figs 19, 20 and 21)† The information in the present paper was not made widely available by the RPE, at that time. Since the author's view the treatment used differs widely from that described in later publications (see References in Appendix 3); the results can be readily applied to practical design work.
Effect of Gas-Side Physical-Property Variations on the Heat Transfer to a Bank of Tubes in Cross-Flow
Authors: Preece R. J. , Lis J. , Hitchcock J. A. 
Published: October 2007

The paper describes a study of the effect of variations in the physical properties of a gas caused by large gas-to-wall temperature differences on the convective heat transfer to plain tubes in cross-flow. The experiments were carried out in air at bulk air-to-wall temperature differences ranging from 109 K to 397 K with two levels of tube-wall temperature, 40°C or 120°C. The bulk Reynolds number ranged from 104 to 2.65 times 104. It was found that the variation in physical properties could be accommodated by evaluating all of these properties in the dimensionless groups of the conventional type of correlation at the air bulk temperature.
Measurement of Coarse Water Distribution in the L.P. Cylinders of Operating Steam Turbines
Authors: Williams G. J. , Lord M. J. 
Published: October 2007

SYNOPSIS The development of a ‘catchpot’ probe to measure coarse water flows (formed by deposition and re-entrainment, or agglomeration, of fog droplets) in the low pressure stages of a steam turbine is described. Theoretical considerations and laboratory calibration showed acceptable performance and accuracy limits. Results taken in three operating turbines at measuring stations situated downstream of the unshrouded penultimate and last row rotors are presented. These results show a peak in the radial distribution of the coarse water flow coinciding with the steam tip leakage region. The measured yaw angles of the coarse water flow agreed with the respective steam yaw angles except near the outer casing. The results are interpreted to give a simple model for the coarse water flows downstream of an unshrouded rotor and its implications for turbine design are discussed.
A Cost Minimization Approach to the Design of Fluid Power Circuits
Authors: Burrows C. R. , Jones N. B. , Shields R.J. 
Published: October 2007

A technique is described for selecting the operating: pressure and pipe sizes in fluid power circuits. The method is based upon the formulation and minimization of a cost function which quantifies the capital and running costs of the circuit. (The running costs are broadly defined in order to include the cost penalty due to the weight of the system, as well as the cost of lost power.) The limitation imposed upon design by the commercial availability of only a limited range of stock sizes of pipe is taken into account to ensure that the design is realizable from stock components. An example is given which compares the results of a design based upon the cost criterion with a design arising from the use of empirical flow velocities to select pipe sizes.
Some Problems in Diesel Engine Research with Special Reference to Computer Control and Data Acquisition
Authors: Marzouk M. , Watson N. 
Published: October 2007

SYNOPSIS A versatile computer-based testing and data acquisition facility developed to improve the speed and accuracy of engine research work is described. The role of computer-aided technology is illustrated through the discussion of two quite separate problems. Fuel burning rates (heat release diagrams) are the most basic measurement of combustion, yet highly sophisticated equipment and techniques are required to obtain accurate rate diagrams. The problem is illustrated through the derivation of heat release data by analysis of averaged and smoothed cylinder pressure diagrams from naturally aspirated and turbocharged diesel engines. Techniques developed for transducer mounting, choice of sampling interval, data-logging, processing, smoothing, etc. are presented. During transient conditions (e.g. sudden load chnages) a turbocharged diesel engine moves through operating regimes not normally encountered in steady state operation. Although empirical models have been used to prodict the transient response of these engines, only high-speed data-logging of many engine parameters during a transient will permit the development of more basic models. A fully instrumented turbocharged diesel engine has been run (under computer control) through a series of dynamic tests comprising load and speed demand changes, plus combinations of the two. The use of a computer controlled system allowed transients to be re-enacted with a very high order of accuracy following engine design changes. The high-speed data logging system enabled basic data, such as fuel burning rates, to be obtained for each cycle during the transient.
The Pad and Quad Resistors - Two New Methods of Fluid Flow Measurements
Authors: Morsi S. A. 
Published: October 2007

This paper describes two methods of fluid flow measurements of the differential pressure type. The first method uses a new type of linear resistor in which the flow rate is linearly proportional to the pressure drop. This linear resistor, called a pad-resistor, may be used in a single configuration when the flow rate is limited to small values. For a flowmeter of high capacity and low resistance a multi-pad multi-stage configuration, where several pad-resistors are connected in parallel, has been adopted. The second method uses a non-linear resistor called a quad-resistor. This type of resistor has a flow characteristic proportional to the fourth order of the pressure drop. By combining the quad-resistor with an orifice, the relationship between the pressure drop and the flow rate becomes approximately linear. The quad-resistor has been used in conjunction with a fluidic analogue amplifier to give a linearized output pressure proportional to the flow rate in a fluid duct.
Component Interactions and their Influence on the Pressure Losses in Internal Flow Systems
Authors: Smith A. I. Ward 
Published: October 2007

SYNOPSIS The pressure losses arising from the flow through internal flow systems are usually estimated by subdividing the system into elementary components, assigning a loss to each component, and then summing these individual contributions. This approach can lead to appreciable errors when the components are sufficiently close to one another for interactions to occur. As a contribution to the discussion of this complicated subject, this paper is concerned with the steady, turbulent flow through combinations of bends and diffusers. Under some circumstances the combined losses of the interacting components are greater than the sum of the individual losses in interference free flow. In other circumstances the reverse is the case. However, as this paper demonstrates, in all cases it is possible to produce sound physical reasons for the variations and, as a consequence, it is possible to generalise the results to interactions involving other components in combination. The paper concludes with a list of broad design principles which have wide application to systems in which interaction effects are important.
The Application of Mechanism Theory to a Textile Machinery Innovation
Authors: Wray G. R. 
Published: October 2007

The design of mechanisms for use in practical machinery applications is often of a trial-and-error nature based on traditional practice. Much emphasis has been given to the theory of mechanisms in recent years but this has yet to find wide practical application. This paper is a case study of how a basic idea, conceived by University-based inventors and intended to improve a slow method of making a textile pile fabric, became a reality in the form of a completely new type of high-speed textile machine for making an improved textile product, all within a time scale of four years. It also shows how recent University researches are further advancing its potential from both the machinery manufacturing and textile technology aspects. Step-by-step from the early experimental stages, it illustrates how the challenges of developing the novel mechanisms required for this unconventional machine and process were met by combining practical experience of traditional machinery design with theoretical investigations based on the new techniques of mechanism analysis and synthesis.
Structural Analysis of Ladder Frames under Torsion
Authors: Megson T. H. G. , Alade G. A. 
Published: October 2007

SYNOPSIS The determination of the torsional stiffness of a ladder frame is investigated and a comparison made between the assumptions of infinite and finite bending stiffness of the members. A method is proposed for the estimation of the torsion constants of the members of a ladder frame and is shown to give good agreement with measured values. Stress distributions in the cross-members of a ladder frame are also determined. Finally charts are presented to enable the torsional stiffness and stress distributions to be calculated for ladder frames comprised of channel and I-Section members.
A Mechanical Torque Converter, and Its Use as an Automobile Transmission
Authors: Williams Frederic , Tipping D. 
Published: October 2007

SYNOPSIS A torque converter is described in which the prime mover is directly coupled to a pulsator unit which produces an alternating torque. Sprag-type clutches are used to rectify this torque and to transmit it to the converter output shaft. A developed version of this basic design for use as an automobile automatic transmission is described and theoretical and experimental performance curves are given which show that an automobile drive is possible which approaches a manual transmission for fuel consumption and performance.
The Mechanics of Flash in Drop Forging-Temperature and Speed Effects
Authors: Dean T. A. 
Published: October 2007

SYNOPSIS Forging tests have been made using axisymmetric cavity dies with various flash geometries. For a particular flash geometry greater ‘rise’ was obtained with thinner flash. Also greater rise was obtained on a hammer than on a press, the load requirements being greater on the higher speed machine. Modes of metal flow were similar at all preheat temperatures. Theoretical treatment of the later stages of die filling, considering metal flow to be significant only in the region of the flash land, is able to describe the main features of the experimental results.
Treatment of Separated Flow in Cascades by a Source Distribution
Authors: Railly J. W. 
Published: October 2007

Provided that separation on the blades of a cascade takes place aft of the leading edge, the hypothesis that suction side velocity outside of an enlarged boundary layer remains constant is used as the starting point in a potential flow solution assuming that blades and enlarged bounary layers are thin compared with chord. Representing thickness, boundary layers and wake by a source distribution, an integral equation for the latter is deduced and numerical solutions are found for a nearly two-dimensional rotating radial impeller for various diffusion ratios on the suction side of the blades. The method is valid, incompressible flow for any blade-to-blade surface that is a surface of revolution and in the presence of stream sheet thickness variation. The theory is compared with experiments conducted on a radial impeller and good agreement with velocity distribution and impeller tip pressure rise is shown. Predictions of blade work may be obtained using a shape factor found from the experiment but loss coefficient predictions are too low. The conclusion is drawn that a three-dimensional influence is involved in the displacement growth on the impeller blades.
The Simulation of Air Fuel Mixing in High Swirl Open Chamber Diesel Engines
Authors: Morris C. J. , Dent J. C. 
Published: October 2007

SYNOPSIS The air fuel mixing process in the high swirl open chamber diesel engine is simulated by a steady state gas jet injected into a steady air swirl flow. The results from the simulation show good agreement with engine studies using high speed photography. An attempt to quantify fuel dispersion has been made through the introduction of a mixing parameter, which allows for combustion system geometry in addition to fuel jet and air swirl momenta.
Energy Recovery by the Incineration of Solid Waste Development, Present Status, and Experiences in Germany
Authors: Thömen K. H. 
Published: October 2007

Starting with a review of the development of incinerator plants from simple destruction units to installations for heat recovery, the author surveys different aspects of a complex theme. Using the concept of ‘heat production’, the composition of the refuse and the operating conditions which are important in the planning and construction of an incinerator are considered. The paper then discusses the choice of furnace equipment and the conditions to be imposed on it, using as an example the ‘Düsseldorf roller grate system’. The configuration of the furnaces is also dealt with in the light of experience in the construction of the boilers. Finally, under the heading ‘Operating Experiences’, facts are given about the reliability of incinerators, with special emphasis upon the problem of corrosion of the boiler-tubes.
The Influence of Oil Lubricated Journal Bearings on the Dynamics of Rotating Systems
Authors: McCallion H. , Wales D. R. 
Published: October 2007

SYNOPSIS A computer program representing a shaft and rotor whirling in bearings which allows for realistic oil film boundary conditions and non-circular bearing profiles has been developed. It gave good agreement with experimental results published by Brown and France. With the aim of increasing understanding of the influence of bearing profile on system instability, the program calculates the timewise variation of the energy in translational motion supplied to the rotor by oil film forces. One case is illustrated.
Experimental and Theoretical Identification of Air Ingestion Regimes in Pump Sumps
Authors: Swainston M. J. C. 
Published: October 2007

SYNOPSIS Results are presented of experimental observations made during investigation of the basic causes of vortex formation which show that air ingestion and vortex formation phenomena can be divided into three regimes corresponding to three ranges of submergence. Simple theoretical modelling of the flow in which the suction pipe is replaced by a point sink, shows that the occurrence of vortex formation is associated with the behaviour of the surface stagnation point. The theoretical results are compared with the extensive experimental data of Denny (4).
Performance and Emission Predictions for a Multi-Cylinder Spark Ignition Engine
Authors: Benson R. S. , Baruah P. C. 
Published: October 2007

A comparison is made of experimental results and predictions of performance and emissions from a multi-cylinder spark ignition engine over a range of air-fuel ratios and two throttle settings. The results showed that a simplified two zone combustion model, a seven reaction scheme for nitric oxide formation, a partial freezing model for carbon monoxide and the inclusion of chemical reactions and variable specific heat along the pathlines in the wave equations gave good agreement with the measurements at the common pipe junction and exhaust outlet, but due to cyclic dispersion and maldistribution of fuel between cylinders the predictions of the emissions in the exhaust manifold adjacent to the cylinder were not so good. The predicted air flow and indicated power agreed well with experiment.
Prevention of Steam Turbine Blade Erosion Using Stator Blade Heating
Authors: Akhtar M.S. , Black J. , Swainston M.J.C. 
Published: October 2007

Previous work on the phenomenon of the erosion of the moving blades in steam turbines is reviewed, which has shown that this is due to the accumulation of coarse water on the stationary blades. The basic physics of the accumulation is considered and the conclusion is drawn that this is due to condensation. This can occur even on adiabatic blading, but is expected to be particularly prevalent on blades whose interior is at a reduced pressure (and hence temperature) for suction purposes. Tests are reported on the heating of a single blade mounted in a steam tunnel downstream of a small steam turbine. The turbine exhaust could be arranged to be either wet or superheated. These tests showed that condensation on the blade could be prevented using only small amounts of heating. Methods of applying this system to full size turbines are considered and preliminary economic effects estimated, with encouraging results.
Comparison of Stochastic Identification Techniques for Dynamic Modelling of Plastics Extrusion Processes
Authors: Kochhar A. K. , Parnaby J. 
Published: October 2007

The important plastics extrusion process is briefly described and the difficulties of modelling the process from physical considerations are outlined. A number of stochastic process identification techniques, i.e. correlation, spectral analysis, generalized least squares, instrumental variable, correlation matching, maximum likelihood and Box-Jenkins algorithms are briefly reviewed. The results of experimental work carried out on a laboratory plastics extruder, using random perturbations in screw speed, are presented. From a comparison of the results of different identification methods, it is suggested that although correlation and spectral analysis techniques can help in improving the understanding of the process mechanisms, the type of models best suited for high level feed-forward computer control are of the Box-Jenkins and maximum likelihood structural forms.