The pressure ripple in a hydraulic circuit is commonly a major source of noise. A computer program has been written to simulate the pressure ripple characteristics of hydraulic circuits and to aid in the design of low noise circuits. Mathematical models of flexible hose and of pump flow ripple and source impedance have been developed. Validation tests on various circuits show that the program produces good correlation with experimental measurements. A simple silencer consisting of an asymmetric pipe loop, known as a Quincke tube, was analysed. Its performance was shown to be limited, providing attenuation over very narrow bandwidths.
When one looks at the twenty-first century it is clear that the extrapolation of high technology must lead to disaster. The factors are arms escalation, increase of the gap between rich and poor countries, growth of deserts, exhaustion of easily won raw materials, especially hydrocarbons, the cumulative effects of pollution, and increasing unemployment. Necessary steps towards a stable world are for the rich countries to accept a considerable reduction in their use of resources, to provide everyone with an interesting and well paid job and to shift a steadily increasing fraction of their engineering R & D resources from weaponry to co-operative production of equipment for the poor countries.
Results are presented of tests conducted on a 150 mm pad thrust bearing over the speed range 1000–4000 rev/min. Heat transfer to pads and runner is estimated from pad and runner temperatures. Pad heat transfer proved to be of minor importance. The runner is shown to approximate to an infinite heat sink. Heat transfer to the runner is dominated by the film thermal resistance and ranged from 0.1 to 0.8 of film energy dissipation. The dependence of film convective heat transport upon the film Peclet number is demonstrated and an improved method for the prediction of bearing performance is outlined.
Vibration measurements on gas turbine engines are normally made using accelerometers. The environment to which engine accessories would be subject has been evaluated by comparing ‘g’ peaks in the frequency spectrum, individually, with empirical yardsticks of severity. Endurance approval testing of accessories to withstand the environment so characterized is normally conducted by applying unidirectional single frequency excitation to simulate engine conditions at a particular shaft speed. These procedures have proved inadequate in predicting failure or verifying corrective measures where accessory problems due to wear phenomena are concerned. This paper analyses reasons for this inadequacy in terms of measurement practice, engine severity assessment, environmental simulation and approval procedures. By recognizing the effect of multi-frequency vibration in three planes it further aims to provide a unified approach to accessory design and development by which service accessory reliability might be improved. Although at first sight more expensive, the approach described will in many cases reduce to previous practice. In cases where greater test expenditure is necessary, loopholes will have been plugged by which many expensive service problems previously escaped.
The design of process plant must incorporate noise control since retro-fitting is impractical on both technical and economic grounds. Whilst the method of approach depends on particular circumstances, key factors common to all projects are: setting of realistic specifications; establishing working procedures which ensure full co-operation by all members of the design team; early identification of the most difficult problems so that the most economic solutions can be generated; utilization of good and bad experience from previous projects to minimize noise control costs, this forms the basic work load in most projects; evaluation of the completed plant so that the degrees of success can be determined and lessons can be learned for future projects. These, and some technical aspects, are covered in the paper and whilst they are based on experience with large process plants they are equally applicable to smaller plants. The need for ‘in house’ knowhow is essential to the whole exercise since the noise sources are a function of the process and much of the data is of an empirical and practical nature.
The development and performance of British Railways' three prototype Advanced Passenger Trains (APT-Ps) are discussed. The progression from design concept to construction, commissioning and testing prior to entry into passenger service is described. Performance aspects of the train and its sub-systems are assessed in relation to technical objectives.The commissioning programme and highlights of the track proving trials are described. Important test results are discussed, including those relating to body tilt systems, ride quality, lateral track forces, braking performance, current collection, and thyristor interference. Account is given of various development problems which arose during commissioning trials and endurance running.The paper concludes with a brief description of the design of the production train (APT-S), which is planned for fleet operation on BR's electrified West Coast routes.
A technique for the numerical optimization of a finite element model of a high energy rate forming machine is introduced. Both the nature of the impulsive loading and selected structural dimensions are optimized with respect to a simple measure of the noise created during a forging operation. The authors conclude that the technique could be applied to other structures or could be based on a more sophisticated noise criterion although dynamic finite element analyses demand considerable computing power.
Plug check valves are frequently used in high pressure systems where parallel pump operations are envisaged, in order to prevent flow recirculation through the out-of-service pump. Serious operational problems are sometimes encountered with these valves during pump changeovers. Full equations of the dynamic behaviour of the plug check valves are derived and results are obtained for their performance in a typical power plant system. Criteria for the design of the plug check valves are also developed.
This paper reviews a number of methods of improving railway vehicle suspensions in order to overcome problems of excessive wheel flange and rail wear in sharp curves. Means of implementing such ideas are discussed for a variety of railway operations, including freight and rapid transit systems. It is shown that this approach is an attractive alternative to the traditional remedy of flange/rail lubrication in a wide range of practical situations.
Substandard performance and failure to meet objectives in capital investment has been a major contribution to the catastrophic decline in the profitability of industry in the UK. The structure of a project is described and the differences between a project and ongoing operations are discussed. An approach to capital investment analysis is described which is based on rate of cashflow and which relates closely to the actual events that occur. The nature and character of the risks involved are examined and a variety of problems discussed. The inevitability of the learning process is pointed out together with the benefits of structuring this learning. Some of the human and organizational imperatives required for success are defined and the need for a knowledge-based approach to the main project disciplines is advocated. These disciplines are outlined together with some discussion of their inter-relations. The operational techniques which ensure a total, and avoid a fragmented, approach to managing a project are briefly described and the importance of top management involvement is emphasized. By taking the steps advocated in the paper the risks inherent in capital investment projects can be reduced to an acceptable level.
This paper describes the theoretical and practical aspects of a simple and rapid method of elastically hoop stressing materials in tubular form using elastomeric inserts. The method can be used for stressing to required limits, for testing to fracture or for obtaining yield points. It is extremely suitable for the testing of brittle materials. Stress equations and insert/test specimen coefficients of friction are given in appendices.
The desire to conserve mineral oil reserves has resulted in drastic increases in the cost of fuel which has become the predominant factor in operating cost criteria. Thus intensive efforts are being made throughout the automotive industry to reduce fuel consumption. Next to minimizing resistance forces, the optimization of engine and transmission offers the greatest potential for achieving this goal. For spark ignition engines this is best achieved by adapting the most efficient engine parameters to coincide with the general operating conditions. The BMW Eta engine concept when compared with current engine characteristics gives a comparable vehicle performance at considerably lower engine speeds with higher torque output. In general operating conditions this results in fuel savings of up to 15 per cent.
A method is described for calculating the chip flow direction in terms of the tool cutting edge geometry and the cutting conditions, namely feed and depth of cut. By defining an equivalent cutting edge based on the chip flow direction it is then shown how cutting forces can be predicted given the work material's flow stress and thermal properties. A comparison between experimental results obtained from bar turning tests and predicted values for a wide range of tool geometries and cutting conditions shows good agreement.
The structure of the armoured flexible conveyor (AFC) is here modelled as a continuous elastic beam resting on a bed of compressed fine coal. Such a model is shown, analytically and by simulation, to stabilize the vertical steering process for the coal-face provided the beam stiffness is sufficiently large. The discrepancy between this prediction and that of the piecewise rigid model of the preceding companion paper (1) is noted and it is concluded that the elastic beam model may be more appropriate for larger undulations which take up all the free-play in the AFC joints. Because of the potentially powerful stabilizing influence provided by the elastic model, it is proposed that the existing loose joints between AFC trays should be replaced by resilient couplings.
