bluuebunny/crossref_metadata_2025_split huggingface dataset:
Knock Limits and Performance of Some Gaseous Fuels in a Supercharged Spark-Ignition Engine
Authors: Annand W. J. D. , Sulaiman S. J. 
Published: October 2007

Observations of knock limits, in terms of ignition time for borderline knock, are presented for methane and propane at a range of supercharge conditions up to 9 ***lbf/in2boost, in a spark-ignition engine of 105 mm bore running at speeds of 600 and 920 rev/min, with compression ratios of 7·7/1 and 9·5/1. Associated measurements of output and economy are given. Less extensive observations on a butane fuel, and on methane-propane and propane-butane mixtures, are also included. From an examination of computed temperature-pressure histories in the unburned portion of the mixture, it is found that the knock limited ignition advance on the propane fuel at chemically-correct mixture can be closely predicted over the full range of operating conditions covered, by the attainment of a certain critical value of a simple parameter.
Gas Turbines with Heat Exchanger and Water Injection in the Compressed Air
Authors: Gašparović N , Hellemans J. G. 
Published: October 2007

Water injection into the compressed air between the compressor and the heat exchanger of a gas turbine plant represents only one of various possible methods of introducing water into a gas turbine cycle. With this process, it is advantageous to inject just sufficient water to produce saturation of the compressed air with water vapour. Assuming that the same size of heat exchanger is used, the following changes are introduced as compared with a gas turbine cycle without water injection. The efficiency is increased to an extent equivalent to raising the temperature at the turbine inlet by 100 degC. The gain in specific work is still greater. It attains values which can only be achieved with about 140 degC higher temperature at the turbine inlet. With a normal size of heat exchanger, the water consumption is about 6–8 per cent of the mass flow of air. This rate of consumption is not high enough to introduce any detrimental side effects in the cycle. Special water treatment is not necessary. The performance of existing designs or installations without a heat exchanger can be improved by adding a heat exchanger and water injection without necessitating any change in pressure ratio.
Engineering Aspects of Tyre Testing
Authors: Turley J. A. 
Published: October 2007

The engineering performance expected of tyres is analysed in the context of the machines they fit—saloon cars, racing cars, lorries, earthmoving equipment, aircraft, motor cycles and pedal cycles. As the performance of vehicles depends on the reaction of their tyres to speed, braking, driving and steering forces, ways of measuring these forces and their effects using sophisticated tyre testing machinery are essential to both tyre and vehicle manufacturers. The tyre testing facilities at Fort Dunlop are described with specific reference to the circulating power machine. This machine enables the study of the effects of both high speed and driving and braking torques on tyres. One of the effects of large torques applied to tyres is the cracking and ‘chunking’ of the tread rubber and evaluation of this is described. Various measurement techniques are employed and associated calibration methods have been developed which are applicable to many types of test machines.
Some Calculations to Assess the Effect of Spin on the Tractive Capacity of Rolling Contact Drives
Authors: Poon S. Y. 
Published: October 2007

The tractive capacity of rolling with superimposed spinning motion in elastohydrodynamic lubrication is analysed on the basis of a simplification, that the contact area can be divided into strips in the direction of rolling and that the total traction carried by the contact can be obtained from the sum of these strips. For the contact conditions considered here, the slide (or creep) occurs in the rolling direction. It is shown that the traction versus slide relationship for this situation can be constructed from the basic traction data of the lubricant provided by a two-disc machine. The results can be used to assess the performance of a rolling contact drive design. The analysis also highlights the essential ***rheological properties of a good transmission fluid.
A Study of the Performance of a Non-Linear Resonant Vibratory Conveyor
Authors: Leckie G. G. , Barr A. D. S. 
Published: October 2007

The paper considers the performance of a resonant vibratory conveyor which incorporates a relatively stiff buffer spring in addition to the normal linear spring constraint. This form of non-linear spring characteristic has the advantage over its linear counterpart of being less critical in its requirement for accurate tuning and in providing less performance variation with load. Vibratory conveying with purely horizontal table motion is also possible with such a form of non-linear conveyor, and this could be of application in the transportation of particulate media having a wide range of particle size, in situations where segregation of the particles is undesirable. Experimental results for a conveyor model transporting a single mass are found to be in good agreement with the performance predicted by analogue and digital computer studies.
The Effect of Dwell Time on Die Wear in High Speed Hot Forging
Authors: Ali S. M. J. , Rooks B. W. , Tobias S. A. 
Published: October 2007

This paper describes an automatic high energy-rate forging system, consisting of a Petro-forge machine linked to an induction furnace with an automatic billet transfer mechanism. The system contains also automatic die lubrication, as well as pyrometric and other safety interlocks, permitting the feeding and forging of hot billets at a rate of one every 5 s. Hot upsetting tests carried out with this automatic forging system, aiming at the determination of the effect of dwell time on die wear, are discussed. Two series of experiments were carried out, with dwell times of 40 and 250 ms respectively. In the shorter dwell time tests, five different die materials were evaluated with the aim of establishing their relative wear resistance. It was found that the higher alloyed die steels offer improved performance over the conventional low alloy steels, ‘good value for money’ being obtained by WEX 779. An analysis of the dwell time, performed by taking a high speed cine film of the whole forging operation, showed that it consisted of forging, bouncing and after-forging phases. In both the short and the long dwell time tests the forging phase and the bouncing phase were 4 and 30 ms, respectively. However, the after-forge phase was 6 ms for the short dwell time and 216 ms for the long dwell time experiments. During the after-forge phase, the dies, with the upset workpiece between them, are pressed together by a relatively small force and in view of this heat transfer is poor. Nevertheless, the increase of the dwell time has a very large effect on die wear, doubling the rate of wear in some cases, depending on the type of die material used.
Higher Technological Education: The Other Half
Authors: Osborne-Moss J. 
Published: October 2007

Early in its life the Council of Engineering Institutions (C.E.I.) set the standard for the academic qualifications of future Chartered Engineers at the level of United Kingdom university degrees in engineering. At that time the Council for National Academic Awards (C.N.A.A.) had not long obtained its charter. In recent years the rapid growth of the numbers of undergraduates on C.N.A.A. courses, i.e. undergraduates outside the university system, has justified the allegation that many members of C.E.I, who believe university degrees provide the only route to a Chartered Engineer status are sadly unaware of the very large advanced further education system. Polytechnics and colleges of technology wishing to establish C.N.A.A. degree courses have a number of hurdles to surmount: the Department of Education and Science, regional advisory councils and local education authorities are all concerned with the approval of courses. The seeking of support from industry for the industrial training part of a sandwich course, the approval of C.E.I. constituent institutions in respect of exemptions and so on are just a few of the additional obstacles to approval. Last, but not least, the C.N.A.A. itself will vigorously examine the proposed degree scheme, following this up by a visit in which the college staff, resources, equipment, teaching, philosophies and general environment come under the microscope.
A Simple Technique for Calculating Shakedown Loads in Pressure Vessels
Authors: Macfarlane W. A. , Findlay G. E. 
Published: October 2007

A fundamental examination has been made of the post-yield behaviour at discontinuities in pressure vessels with a view to determining shakedown loads. The results of this indicate that a simple graphical construction can be devised whereby such loads are easily determined with only a knowledge of the elastic stresses and a yield criterion; in particular, a ‘five line construction’ method is suggested which can be applied to a wide range of engineering stress problems. The method is exemplified by a study of shakedown loads for both flush cylinder-sphere and cylinder-cylinder intersections under internal pressure, and the implications of the results in terms of current design philosophies are discussed.
Governing: An Examination of a Torque Feedforward Loop
Authors: Blair J. R. 
Published: October 2007

The inclusion of a load sensing loop in a governor is known to counteract the effects on engine speed of changes in the external load. To derive the maximum benefit from load sensing, it is necessary to possess a detailed mathematical representation of the individual elements within the governing loops. In this paper, a method of identifying the dynamic behaviour of a small generating set is described. A governor is designed on the basis of this dynamic model, and results are presented of tests performed on the generating set controlled by the governor. The governing action is a combination of the feedforward of a load signal, and the feedback of a speed signal. Careful selection of the gain of the feedforward path results in improved governing with only proportional action in the feedback loop. A simple criterion, derived from the mathematical model, predicts a range within which the feedforward gain should lie. The feedback loop is designed by standard control techniques. The experimental results compare favourably with the theoretical predictions. In the tests on the rig, a steady-state droop of ±1 per cent was held over the full-load range. A 100 per cent step change in the load produced a transient overshoot of less than 1·5 per cent, and a settling time of 1·5 s.
Systematic Approach to the Analysis of a Solenoid-Actuated Hydraulic Valve
Authors: Korn J. , Simpson K. 
Published: October 2007

A spool-type, hydraulic, directional-control valve is considered. The valve has four ports; it is actuated by a solenoid, and its spool overlaps the ports. The valve is looked upon as a system consisting of electrical, mechanical and hydraulic sub-systems. The sub-systems are represented as networks, which are then interconnected to form the network of the complete valve system. Hence a set of independent equations are derived which describe the dynamic behaviour of the valve between no flow and full flow states of the spool. The equations are simulated on an analogue computer to provide comparison with experimental results.
A Finite Element Method for the Calculation of Locus Paths in Dynamically Loaded Bearings
Authors: Shelly P. D. , Ettles C. 
Published: October 2007

A method using finite elements for the solution of journal bearings is outlined. The special properties of an exponentially shaped element are used together with a satisfactory approximation for the axial pressure profile. This approach is one hundred times faster than a conventional finite difference solution of equivalent accuracy. The method can be applied to the solution of locus paths for journal bearings under external dynamic load or under whirl conditions. The predictor-corrector method used to march out a locus path is briefly outlined and several typical loci are presented as examples.
Condensation Phenomena in High Speed Flow of Steam—Experimental Apparatus
Authors: Campbell B. A. , Bakhtar F. 
Published: October 2007

The paper describes a steam circuit for studies of nucleation and behaviour of wet steam. The test section is a duct of rectangular cross-section in which particular geometries are produced by fitting shaped profiles to its sides. To deliver steam to the test section, at required conditions, a turbine, cooler and superheater are included in the circuit. The experimental results presented are concerned with the variations of Wilson point as a function of pressure. Comparisons are made with the results of a theoretical treatment already published (1)‡ and agreement is shown to be good.
Recent Developments in B.S. 806: Ferrous Pipes for and in Connection with Boilers
Authors: Popplewell P. L. , Hammill J. 
Published: October 2007

The paper deals in general terms with certain aspects of B.S. 806 such as design pressure, design temperature and design stresses. These are discussed and those areas where the requirements of this standard differ from others are highlighted. There is also some discussion on the welding, inspection and testing requirements of the revised standard. The bulk of the paper is concerned with an explanation of the sections of the standard dealing with branch design and with flexibility which have been extensively revised. The paper does not claim to submit any new research work but indicates the way in which the results of such work can be incorporated into the requirements of a national standard.
Second Paper: Experiments on a Transpiration Cooled Combustion Chamber
Authors: Bayley F. J. , Cornforth J. W. , Turner A. B. 
Published: October 2007

The first part of an experimental and theoretical investigation into the feasibility of transpiration cooled combustion chambers is discussed, as well as the design and testing of two Rolls-Royce ‘Dart’ porous flame tubes. The theory of heat transfer in porous materials is briefly described and correlations for heat transfer and pressure drop-mass flow are presented for selected samples of porous metal. Experimental results are presented in which the cooling efficiency of the original ‘Dart’ splash-cooled flame tube is compared with two porous replacements constructed from sintered woven wire porous metal compacts having different permeabilities. Tests were conducted at 1 and 4 atm pressure and some selected results are compared with theoretical predictions made with and without account being taken of the effect of coolant injection on the convective heat flux. The high effectiveness of transpiration cooling is clearly demonstrated but it is also shown that the distribution of static pressure in the annulus formed between the flame tube and the casing, both longitudinally and circumferentially, plays a very important part in the design of a porous flame tube.
Forming and Shaping Operations for Iron and Steel
Authors: Ford Hugh 
Published: October 2007

Although many years of research have gone into the present knowledge of the forming and shaping of metals, most of our capability of making components in ferrous materials goes back to the days of craft and skill. The major expenditure on fundamental studies in metal working has been effective only in refining existing processes rather than leading to new ways of manufacture. A better understanding of the relationship of material properties to stress and deformation modes has had some influence on process developments. Much more is owed to developments in the size of plant units, economic, production engineering, marketing and managerial factors. The more recent developments and trends in secondary manufacturing processes are reviewed.
Dynamic Chip Formation and its Significance to Machining Stability
Authors: Pearce D. F. , MacManus B. R. 
Published: October 2007

The physical processes of dynamic chip formation were examined experimentally using direct photographic techniques; motion in the cutting zone was frozen by synchronizing an intense stroboscopic flash to particular positions in the waveform of the cutting force. Measurements obtained under conditions of controlled vibratory machining gave instantaneous values of the uncut chip thickness, tool-chip contact length, effective shear angle and cutting force. At a given amplitude of uncut chip thickness the peak-to-peak variation of contact length was seen to attenuate with increasing frequency, an effect which was shown to be significant in causing relatively high amplitude shear angle oscillations. Amplitude and phase measurements of the tangential component of the cutting force on wave removal were directly related to the deduced waveform of specific contact length, a process yielding considerable predictability. Measurements were made of the damping inherent in the cutting process; results obtained by applying the techniques of impulse response testing showed the sensitivity of this damping to both the amplitude and the frequency of the variation of the uncut chip thickness. Internal damping resulting from the process of chip formation is not uniquely positive or negative but may vary, depending upon the combination of these parameters.
High Temperature Stress-Strain Properties of a Low-Carbon Steel from Hot Machining Tests
Authors: Stevenson M. G. , Oxley P. L. B. 
Published: October 2007

Machining tests are described in which the cutting speed is kept constant and the primary shear zone temperature varied through a wide range by preheating the workpiece. Variations of the constants σ1 and n of the assumed stress-strain equation σ = σ1 εn with temperature, for an estimated strain rate of 900/s, are obtained. These show a range of temperature in which dynamic strain ageing takes place. This is consistent with results of conventional machining tests on the same material in which dynamic strain ageing takes place in the secondary zone in a certain speed range. Implications of the results for the machining process are discussed and explanations suggested for variation of force with speed in conventional machining and force with temperature in hot machining.
Block-Programme Fatigue Testing of Automobile Wheel Spindles
Authors: Tedford J. D. , Crossland B. 
Published: October 2007

The paper reports the results of fatigue tests carried out on Ford Capri wheel spindle bodies. The first three programmes were aimed at investigating the effect of the sequence in which the loads were applied in a multilevel constant-frequency block programme. A further programme was carried out to investigate the effect on the fatigue life of removing the low-load cycles from the test sequence. The first three programmes demonstrated that the sequence in which individual blocks were applied had no significant effect on the fatigue life. From the fourth programme it was concluded that the removal of stress levels equal to and less than 1·75 times the r.m.s. (root mean square) value of the normal load frequency distribution had no effect on the fatigue damage. If these stress levels are removed there is an 87 1/2 per cent reduction in testing time. The slopes of the life function curves for all four programmes were nearly identical, and gave a mean value of 6·9 which is in agreement with other workers. Lastly it was concluded that tests on small notched cantilever specimens led to very similar conclusions, and that such specimens could be used for proving and developing testing programmes.
Flank-Wear Model and Optimization of Machining Process and its Control in Turning
Authors: Koren Y. , Ben-Uri J. 
Published: October 2007

Designing the optimal control for a machine tool necessitates a mathematical model of the cutting process. In the present paper, a flank-wear model was developed for a carbide tool used in steel turning. It yields the relation between the process parameters (cutting speed, feed and depth of cut) on the one hand, and the width of the wear land on the other. In the second stage—the optimization proper—the problem consists of optimizing a non-linear system with the initial, and part of the final, conditions known, and the terminal time not given explicitly. Complexity was reduced by converting from time- to path-derivatives, and the problem was solved using the gradient method, yielding cost differences which are negligible compared with the conventional method. To complete the picture, a motor control system was sought minimizing the error in obeying the speed change command on the one hand, and the path error during simultaneous operation of several feed spindles on the other.
Effect of Contact Geometry and Elastic Deformations on the Torque Characteristics of a Drum Brake
Authors: Millner N. , Parsons B. 
Published: October 2007

Existing torque analyses of drum brakes, based on the assumption that the shoe and drum are rigid, fail to predict torques accurately, especially when the lining makes non-uniform contact with the drum. An analysis has been made therefore of a floating shoe brake in which the elastic deflections of the shoe and the drum have been included. The analysis has been verified by measuring the torque developed by a standard two-leading shoe brake on an inertia dynamometer under different contact conditions. The agreement between the theoretical and observed torques was found to be better than ± 10 per cent even under extreme contact conditions and much better under more moderate conditions. Some consequences of the theory are discussed because of their practical importance.
Stresses in Centrifugal Fan Impellers
Authors: Patton R. G. 
Published: October 2007

The conventional, theoretical method for estimating impeller stresses combined with large factors of safety is unsatisfactory for the design of the high-pressure fans being demanded today. For economic design, a more precise knowledge of the stresses involved in high-speed impellers is essential and this has been made possible by the considerable developments which have taken place over recent years in the field of strain measurement. This paper describes an experimental programme of stress analysis using brittle-lacquer and strain-gauge techniques, carried out on a range of centrifugal fan impellers. The actual stresses in the various components of these impellers are compared with those predicted by elementary theory.