bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Analysis of the Control Mechanism Used in Variable-Delivery Hydraulic Pumps
Authors: Green W. L. , Crossley T. R. 
Published: October 2007

Variable-delivery high-pressure hydraulic pumps are usually controlled by a small servo actuator fed from the pump-generated pressure. The actuator consists of a three-way valve and differential-area jack or a four-way valve and equal-area jack. This paper analyses the effect of perturbations of the generated pressure when the pump is part of a system incorporating a relief valve. It is demonstrated that, because the load on the servo jack can be a function of the generated pressure, the ‘closed loop’ formed can be unstable. In particular, the three-way-valve actuator is shown to be sensitive to perturbations in its supply pressure even when the load is independent of pressure. Frequency-response diagrams are presented, the assumptions made in the analysis are clearly discussed, and design recommendations are made in the light of the analytical results.
The Dynamic Transfer Characteristics of Reciprocating Engines
Authors: Bowns D. E. 
Published: October 2007

The methods of sampled data analysis and small perturbation techniques are used to predict the dynamic characteristics of reciprocating engines. Extensive frequency response tests have been carried out on a compression ignition engine to determine the engine dynamic characteristics and the results agree well with the theoretical predictions. A method of plotting the results is suggested which has the advantage of generality and takes into account engine speed changes and load torque-speed characteristics. The experimental methods used involve the use of electro-hydraulic systems. These have great advantages for providing the appropriate input and loading conditions. Whilst the main body of the report is concerned with the theory and testing of compression ignition engines, the methods suggested can be applied equally well to petrol engines.
Pre-Service Component Testing of Steam Power and Process Plant
Authors: Morton A. J. 
Published: October 2007

The high performance increasingly required of modern plant leaves smaller margins for error in design and makes the plant more sensitive to unforeseen phenomena. This shows itself in many industries in a high incidence of teething trouble, bringing heavy financial loss to the purchaser and discouraging further innovation. The remedy is more thorough design and development and, wherever possible, the full-scale on-load prototype testing of complete plant items before delivery, so as to expose and eliminate teething troubles and to provide the designer with an accurate record of the behaviour of the plant. It is in the purchaser's interest to make such testing a requirement of the contract. Adequate test facilities are at present lacking and can seldom be provided by individual manufacturers. A permanent fully equipped test facility has great advantages compared with ad hoc testing arrangements in various locations, and the paper proposes the establishment of publicly operated testing and development stations to serve various industries. The equipment and procedure of such a station to serve the steam power and allied industries are examined.
The Effect of Extraneous Factors on the Development of Test Methods
Authors: Hall M. A. W. 
Published: October 2007

Comparative testing of cars for a quarterly consumer magazine poses a particular set of problems. The main ones are time and the designing of apparatus to produce objective comparisons between cars. A subsidiary, but important, problem is the need to produce information which is technically valid and yet readily interpretable by a non-technical public. A test unit is described, and a typical test programme is outlined. Examples are given of the way in which particular problems have been overcome: in particular, the evolution of equipment for measuring acceleration, which has reduced the time necessary for testing by 75 per cent, is described. The development of comparative tests for handling is discussed, and the difficulty of defining a simple measurement of the noise inside a car is used as an example of the difficulty of producing objective measurements which correlate with subjective impressions. It is concluded that, whilst rationalization of test methods is often both desirable and practicable, it is sometimes necessary for individual organizations to retain their own particular methods.
The Effect of the Method of Gas Admission on Performance of a Spark-Ignition Gas Engine
Authors: Mitchell G. P. , Whitehouse N. D. 
Published: October 2007

This paper reports on the effect of position and timing of gas admission on the performance of a spark-ignition engine using methane. The investigation was aimed at exploring the effect of design limitations experienced with turbocharged medium-speed engines. Performance was judged on the criteria of optimum specific fuel consumption combined with minimum cyclic dispersion. Results were obtained at a fixed fuel consumption and mostly at fixed air/gas ratios and are not, therefore, necessarily directly applicable to commercial engines. For near stoichiometric air/gas ratios, optimum performance was obtained most easily by early and prolonged gas admission. Better thermal efficiency was obtained with weak mixtures, about 80 per cent of stoichiometric, and optimum gas admission was generally less obvious. Performance patterns did not vary consistently with gas admission timing; they improved or deteriorated with late gas admission, depending on the type of air inlet valve—presumably owing to air motion and gas/air mixing in the cylinder. From the results obtained, it seems probable that cyclic dispersion was minimal when the mixture around the spark was at, or near, stoichiometric and was most easily achieved by perfect mixing when the overall mixture was near stoichiometric.
Mechanical Handling Aspects of the Tilbury Grain Terminal
Authors: Griffith J. B. , Addicott D. W. R. 
Published: October 2007

The grain terminal for the Port of London Authority (P.L.A.) began commercial operation in April 1969. It is designed for discharge of ships up to about 45 000 ton dead weight (d.w.) at rates up to a maximum of 2000 ton/h. The installation provides two discharging machines of the marine tower type, 105 000 ton of silo storage capacity and an ability to handle from ships to silo, rail, road, coaster or to adjacent flour mills. It also permits loading out to coaster or barge either by direct trans-shipment or from silo. Many alternative handling routes are provided and a very large degree of remote control has been incorporated. The majority of the routes are capable of handling up to 1000 ton/h over a single conveyor. The marine towers are unique in Europe and probably incorporate a greater degree of sophistication than exists in any similar equipment in the world. This paper describes briefly the background leading to the construction of the terminal and the layout of the whole installation. Some of the more interesting points in the mechanical handling control system employed with particular reference to the marine towers, methods of routing, tripper control and dust suppression are described in detail. Comparisons are made between the installation at Tilbury and the installation at present under construction for the Mersey Docks and Harbour Company at Seaforth.
The Design of Alaskan North Slope Production Wells
Authors: Koch R. D. 
Published: October 2007

In 1970, three senior members of BP's Exploration Department received the MacRobert award for their outstandingly successful Alaskan North Slope exploration, which led to BP's acquisition of the leases to over half of the great Prudhoe Bay oilfield, estimated to contain in excess of 1000m tons of recoverable high quality crude oil. Their determination of the distribution of the permafrost, permanently frozen ground, and the effect that permafrost had on seismic reflections, significantly contributed to their successes. While a great deal of information on operating under Arctic conditions and providing livable working conditions for hundreds of men was available, nothing was known of the effects of producing hot oil from wells completed through up to 2000 feet of permafrost. The paper traces the events leading to the discovery of oil on the North Slope and outlines some of the design problems which BP had to resolve to exploit this discovery.
Unsteady Heat Transfer in a Motored I.C. Engine Cylinder
Authors: Hassan H. 
Published: October 2007

After a brief review of the existing formulae for the unsteady heat transfer in I.C. engine cylinders, a new approach is described. It is shown that the existing empirical heat transfer data of forced convective case for the flat plates or pipes can be used to predict the heat transfer. Experimental results obtained on a motored engine are presented which include the measurement of gas velocity, temperature, pressure and metal surface temperature to obtain the convective unsteady heat transfer through the engine cycle. The experimental results are compared with the empirical data on a flat plate and it is concluded that the agreement is within 20 per cent.
The Starved Lubrication of Cylinders in Line Contact
Authors: Wolveridge P. E. , Baglin K. P. , Archard J. F. 
Published: October 2007

A semi-analytical solution is presented showing the effect of variations in the position of the inlet boundary of the lubricant film upon the load capacity of cylinders in line contact. Firstly, isoviscous conditions and undeformed surfaces are assumed; by the use of appropriate non-dimensional parameters, the results of the theory can be exhibited as a single function applicable to all possible experimental conditions. This can then be transformed to deduce a similar unique expression showing the proportional reduction in the minimum film thickness for variations in the position of the inlet boundary, all other conditions being maintained constant. A similar analytical solution is presented showing the effect of the position of the inlet boundary upon the film thickness under heavy loads. This assumes full elastohydrodynamic conditions and is based upon an analysis similar to the familiar theoretical treatment of Grubin. Comparisons show that published computer solutions of these problems, for specific sets of conditions, are in good agreement with the more general analytical solutions presented here.
The Development of the Porsche Type 917 Car
Authors: Mezger Hans 
Published: October 2007

For approximately twenty years Porsche has participated in motor racing. The development of Porsche production cars takes advantage of a major part of the experience accumulated during these performance-oriented activities. This paper deals with the development of the Porsche 917 racing car which is powered by an air-cooled 12-cylinder engine producing about 630 DIN hp. The application of lightweight materials like titanium, aluminium, magnesium, fibreglass, etc. is also described. The Porsche 917 racing car which obtained its Fédération Internationale de l'Automobile homologation by a series of 25 in April 1969 has now become the most successful car in motor racing throughout the world. In 1970 the 917 car was the overall winner at the 24 hours race at Le Mans.
Gas Turbimes for High-Specific-Output Industrial Heat-Transfer Equipment
Authors: Kellett E. 
Published: October 2007

The incompatibility of the dual role of air as a combustion and heat-transfer fluid is apparent in the unbalance of convective heat transfer in a water boiler. Pressurized combustion has, since the middle of the nineteenth century, been postulated as a means of increasing the gas-side convective heat transfer to more nearly correspond with the water-side rate. Gas turbines, in the form of turbine-driven supercharged boilers, have been made, but without significant commercial success, in Europe and America. Modern gas turbines are employed in total-energy systems but because of the premium value of their shaft power output, additional heat exchangers must have the minimum pressure loss and therefore conventional heat-transfer criteria apply. Small turbine-driven superchargers are now mass produced for automotive diesel engines and particularly with the availability of natural gas the feasibility of pressurized combustion by their use justifies re-appraisal. Although these turbochargers have little value as gas-turbine power units the margin of turbine output over compressor power absorption can be employed to improve heat-exchanger convective heat-transfer rates significantly. The provision of a second compressor in the rotor system enables a stoichiometric air and gaseous fuel charge to be induced into a simple pre-mixed combustor thus preserving the low-cost aspect of the turbocharger and providing improved control and safety in a very durable gas-turbine device. The addition of a simple after-burner allows total combustion at relatively low excess air rates. The arguments leading to the foregoing design are presented and some of the more important product developments are described. Examination of the wider application potential of such low-cost turbomachinery indicates prospects for their employment in diverse uses particularly where high heat-transfer rates are desirable.
Impact Behaviour of Small Scale Model Motor Coaches
Authors: Lowe W. T. , Al-Hassani S. T. S. , Johnson W. 
Published: October 2007

Simplified small scale model motor coaches were designed and tested under both static and dynamic loading and attempts are made to relate the results to a full scale collision. Two theoretical approaches for the modelling of a motor vehicle collision are discussed and generally developed using dimensionless analysis and a technique of relating the actual vehicle and models to tubular structures.
Numerically Controlled Machines
Authors: Chadbund J. E. , Parker M. N. 
Published: October 2007

The paper describes the preparation of machine control tapes using a computer programme package, and the B.S.R.A. (British Ship Research Association) part-programming processor system. The comprehensive nature of the system, the development of a modular basis and the modification of the general engineering 2CL to provide a shipbuilding version are described. N.C. (Numerical Control) machines in use in shipbuilding include automatic draughting machines, several varieties of N.C. flame-cutting machines and their associated computer programmes, and a N.C. frame bending machine. The advantages of Numerical Control are listed and the importance of considering the system as a whole is emphasized.
Hydraulic and Thermal Hydraulic Instability in Condensate Feed Systems for Large Thermal Power Stations
Authors: Dartnell Lawrence 
Published: October 2007

Hydraulic shocks and instabilities occurring in condensate feed systems associated with large steam turbine generating plants have been investigated and found to be diverse in origin and character. In service instabilities are attributed, inter alia, to powerful interstage cavitation in centrifugal condensate pumps, to the penetration of unstable zones of pump suction water level, to swiftly stroking valves, to inventory shifts and the placing of pressurized systems in communication with voided systems. Shock is attributed to pumping into evacuated systems. Sustained heat transfer in steam-water and water-water heat exchangers has caused system over-pressurization during off-service conditions. Some difficulties encountered during operations are described and discussed. Recommendations are made for the elimination or minimization of trouble in existing systems and for the avoidance of trouble in future systems.
An Assessment of Diesel Engine Poppet Valves
Authors: Bertodo R. , Sivakumaran S. 
Published: October 2007

The paper reviews an assessment of the factors affecting the reliability and durability of poppet valves of highly rated medium speed diesels burning standard or residual oils. Detailed analysis demonstrated that an undercut (tuliped) profile is preferable. Optimum dimensional proportions are derived. The valve behaviour under operating conditions was such as to suggest that it plays a passive part in the phenomenon of ‘valve sinkage’. The adoption of ‘differentially angled seats’ appears to have little meaning in practice. Cylinder head deflection was a governing feature of seat ‘guttering’. A review of material properties suggested that the often quoted Eichelberg quality factor is inadequate and an alternative parameter for assessing the suitability of materials is derived. All materials suitable for valve manufacture possess poor resistance to corrosion attack. A number of possible palliatives are examined.
Natural Frequencies and Modeshapes of Systems of Generally Interconnected Shafts
Authors: Palmer N. S. , McCallion H. 
Published: October 2007

This paper describes a method for the evaluation of natural frequencies and modeshapes of a general system of shafts linked by general interconnections. A detailed description is given of the particular case where a connection is made by two meshing spur gears; transverse displacement of gear centres as well as torsional displacement being taken into account. The method which has been developed can be applied to any type of connection in which a linear relation exists between the displacements. A gearbox rig is described which has been designed and constructed for experimental testing of the spur gear interconnection. The measured natural frequencies of the rig and its casing separately are given and evaluated in terms of the predicted values. Satisfactory identification is obtained for the lower frequency modes.
Random Load Fatigue Damage Accumulation in Mild Steel
Authors: Fisher B. C. , Sherratt F. 
Published: October 2007

Using high-sensitivity eddy-current crack detection, quantitative division of fatigue life into two stages has been achieved for a variety of random and constant amplitude loading conditions. The divisions adopted were: Stage A, microcrack initiation and propagation, and Stage B, macrocrack propagation. The results of specimen sectioning and optical microscope work show that this behaviour is physically compatible with the observations of Forsyth (1)‡. It is established under random loading that for a given specimen configuration, the proportion of time spent in stage A behaviour for a given fatigue life remains unaltered for changes in the waveform irregularity factor. This statement applies to two series of tests for loading waveforms of unaltered fundamental p.s.d. (power spectral density) shapes and Gaussian amplitude probability density distributions. It is suggested that the signal maximum peak/r.m.s. ratio is a significant factor in determining the proportion of life spent in crack initiation. Cumulative damage predictions are made using Miner's hypothesis on a basis of positive peak stresses to failure for stage A and stage B lives, and overall fatigue life. The results confirm that Miner seriously underestimates the damage contribution at low stresses on fatigue life as a whole, and also for the crack initiation phase of life.
The Supercavitating Pump
Authors: Pearsall I. S. 
Published: October 2007

Cavitation in conventional pumps can cause loss of efficiency and erosion damage. For these reasons speeds and suction pressure are limited to avoid these effects. There are, however, applications where, for technical or economic reasons, these limitations are not acceptable. For these, the supercavitating pump has been developed. Basically it comprises an axial-type impeller with cavities forming over the suction side of the blade and collapsing downstream where they cause no damage. For duties requiring higher pressures, it can be staged in front of a conventional centrifugal pump. The complete development of the supercavitating pump, the theoretical optimization of the geometric parameters to get good or best performance and the theoretical design method based on potential flow cascade data are described. Experimental results are given for a series of impellers of different size, speed, stagger angle and blade shape. Comparison of the experimental results with the design method gives good agreement on the whole. Data are also given on the effects of secondary losses, tip clearance losses, blade thickness and blade rake. Some of the applications and uses of such pumps in the process industry, as boiler feed and aircraft fuel pumps and for water jet propulsion, are discussed.
Developments in Computer Control Systems for Machine Tools
Authors: Wightman E. J. 
Published: October 2007

This lecture sets out to review developments in numerical-control machine-tool technology with particular reference to the application of general-purpose digital computers to the control of individual machine tools or groups of machine tools, to meet the requirements of the end user. The subject matter embraces very broad-based technology, ranging from factors which directly contribute to machine utilization to the application of advanced digital-control techniques which directly contribute to the versatility of modern numerical-control machine tools. Thus, the lecture begins with a review of worldwide growth in numerical-control machine business and a discussion on the technological evolution of numerical-control systems with particular reference to the fast growing utilization of mini-computers. The subject is illustrated by a practical case history in the United Kingdom based on a computer control system developed by the author's firm for turning, milling, and boring machines. The lecture concludes with a review of operational benefits to be derived from the application of modern numerical-control machines to production processes and makes predictions concerning future developments in the application of general-purpose digital computers.
Design and Evaluation of Flight Control Systems
Authors: Gill F. R. 
Published: October 2007

Studies at the Royal Aircraft Establishment are aimed at the in-flight demonstration of improved control systems and policies in a fighter-attack and/or a transport aircraft. The systems being flight evaluated at the present time employ conventional linear-control policies, the design being based on a parameter-optimization technique. Two important modes are discussed briefly in the paper: a pitch-rate manoeuvre-demand system for the fighter-attack aircraft and an ILS glide path and flare system for the transport aircraft. The design studies of these and other modes have yielded quantitative data on conflicts between different performance requirements which cannot be avoided when linear-control policies are used. Studies are being made therefore to replace linear control by variable-gain policies in selected parts of the control system in order to reduce the extent of these conflicts. The reasons for and principles of the variable-gain control policies are outlined in the paper; in addition certain system improvements are discussed (e.g. trim problems) which result from the application of these non-linear control policies.
First Paper: Rotary Engines: Operation, Pre-Ignition and Wear
Authors: Brandone B. , Jeu Jh. Du 
Published: October 2007

This paper shows firstly how the choice of base stock reduces apex-seal wear. Results emphasize the influence of volatility, and particularly of the quantity and viscosity of the residue after heating. The second part (section 3) concerns pre-ignition. Testing was difficult, but a connection was found between the ash content of the oil and severity of pre-ignition. Testing of anti-wear formulations for pre-ignition was found to be necessary. The third part (section 4) is devoted to engine smoothness, which must not be confused with pre-ignition. Spark plugs and mixture strengths are the most important factors, fuel probably having only a secondary effect.