bluuebunny/crossref_metadata_2025_split huggingface dataset:
Feasibility study on a composite material construction technique for highly stressed components in reciprocal walking orthoses for paraplegic patients
Authors: Woollam P J , Dominy J , McCleod N , Stallard J , Major R E 
Published: October 2002

Reciprocal walking for thoracic level paraplegic patients using reciprocal walking orthoses has become a routine treatment option. Two general design options are currently deployed within an overall treatment regime. Research has shown that one has better walking efficiency but is cosmetically less acceptable to the patient. Design analysis and experimental data have shown that a major factor in improved walking efficiency is the lateral stiffness of the body brace section of the orthosis. This is the area where problems of cosmesis in the more efficient orthosis are perceived because of the employment of metallic structures. The use of composite material structures to achieve shapes which are more closely conforming to the patient is an attractive option. However the brittle nature of these materials makes it unlikely that the requirement for the ductile failure mode will be achieved from a straightforward moulding. A new construction technique has been devised which has the potential to provide a safe failure mode with greater stiffness and lighter weight. This feasibility study has been undertaken to demonstrate its potential so that further work can be justified which will provide sufficient evidence to support a patent application. The successful outcome of the study, in which stiffness was increased by 60 per cent with a weight reduction of 50 per cent and a failure mode comparable with the original metal structure, suggests that further work will enable the dilemma in the choice of orthosis to be resolved.
Development of a novel gas turbine driven centrifugal compressor
Authors: Turner A. B. , Davies S. J. , Childs P. R N. , Harvey C. G. , Millward J. A. 
Published: October 2002

The purpose of the paper is to provide design and operational information for the conversion of small turboprop engines into land-based shaft power drives. These can provide economical solutions to individual power requirements such as standby electrical generators, combined heat and power units, fan drives or centrifugal compressor drives. Considerable numbers of ex-military engines are currently becoming available at economical prices. One such engine is the Rolls-Royce Dart turboprop gas turbine which, although there are over 2000 still in civil and military service worldwide, is now being phased out of Royal Air Force operation. This paper describes the modification of a Dart RDa 12 engine to drive a centrifugal compressor from a smaller RDa 7, Mk 552, engine for a compressed air facility on a university campus. The modified engine has a power of over 2400 hp (1790 kW) at 15000 r/min and the compressor was driven directly from the engine output shaft supplying 10.5 kg/s of air at a pressure ration of 3.3:1. To achieve this, the turboprop's main reduction gearbox was removed, the teeth on the engine drive pinion ground down and a flexible coupling fitted to it to drive the RDa 7 compressor which was flange mounted on the engine gearbox-air intake casing. The removal of the main gearbox removed the drives to the lubricating oil pumps the fuel pump and the engine control system. The manner in which these problems were overcome and the method of operating the system are described. One of the most important considerations in starting such a direct drive system is the complete closing off of the air intake to the driven compressor and the design of an annular valve to perform this duty is described. The operating parameters including the flow, pressure ratio and engine turbine entry temperatures for this system are given.
Computational studies of unsteady flows in a centrifugal compressor stage
Authors: Koumoutsos A , Tourlidakis A , Elder R L 
Published: October 2002

This paper describes the flow analysis in a centrifugal compressor stage using a three-dimensional computational fluid dynamics (CFD) algorithm. The flow unsteadiness arising from the interaction between the impeller and the diffuser has also been analysed using an algorithm suitable for equal or multiple numbers of rotor and diffuser blades. The multi-block, structured grid CFD code TASCflow which provides an approximate solution to the Reynolds-averaged Navier-Stokes equations was used as a basis and algorithm development was undertaken to provide the required capability of modelling the unsteady interactions of the impeller and the diffuser. The centrifugal compressor stage under investigation consists of 28 radial blades (of which 14 are splitter blades) in the impeller and 27 vanes in the diffuser. The presented results and analysis are for off-design flow conditions where experimental results were available for comparison. The results obtained for the steady-state model show a reasonable agreement with the measurements. In general the unsteady flow field obtained shows a reasonable agreement with experimental data and exhibits considerable differences when compared with the steady-state results.
Development of novel intermetallic compounds and solid solution systems as hydrogen storage devices
Authors: Esayed A Y 
Published: October 2002

One of the limitations surrounding the exploitation of hydrogen as a fuel is the difficulty in storing it economically and conveniently. At present, hydrogen is typically stored as a compressed gas or as a cryogenic liquid. However, neither method is very appealing. Gaseous storage requires a large volume and/or weight of storage vessels, while liquid hydrogen requires a rather expensive liquification process and some energy as well. Another possibility for storage that is currently being studied and utilized is metal hydrides. The hydrogen reacts with the metals and forms metal hydrides. Storing hydrogen as a metal hydride has many advantages. Firstly, hydrogen can be stored in metal hydrides more efficiently (in terms of volume) than as liquid, or even solid, hydrogen. Secondly, the formation reaction is easily reversible. The formation of the hydride is an exothermic and usually spontaneous reaction, but the hydrogen can easily be recovered by heating the hydride. Therefore, the metal hydride can be classified as a safe method of storing hydrogen since the hydrides are generally stable below their dissociation temperatures. Moreover, the self-cooling effect will slow down and eventually stop any loss of hydrogen if a leak is developed in the storage system. Several metal hydrides have been developed, but none of them satisfies all these requirements. Some of the more common drawbacks of the currently available materials are that (a) hydrogen-metal ratios are too low, (b) metals involved are too costly, (c) the absorption or release of hydrogen is difficult, slow or sensitive to poisoning phenomena and (d) significant hysteresis is exhibited. The available materials for hydrogen storage are briefly reviewed and a more detailed overview is given of two classes of materials that are being developed in the author's laboratory, namely zirconium-based Laves phase intermetallic compound and body-centred cubic solid solutions based on niobium.
Emissions characteristics of higher alcohol/gasoline blends
Authors: Gautam M , Martin D W , Carder D 
Published: October 2002

An experimental investigation was conducted to determine the emissions characteristics of higher alcohols and gasoline (UTG96) blends. While lower alcohols (methanol and ethanol) have been used in blends with gasoline, very little work has been done or reported on higher alcohols (propanol, butanol and pentanol). Comparisons of emissions and fuel characteristics between higher alcohol/gasoline blends and neat gasoline were made to determine the advantages and disadvantages of blending higher alcohols with gasoline. All tests were conducted on a single-cylinder Waukesha Cooperative Fuel Research engine operating at steady state conditions and stoichiometric air-fuel (A/F) ratio. Emissions tests were conducted at the optimum spark timing-knock limiting compression ratio combination for the particular blend being tested. The cycle emissions [mass per unit time (g/h)] of CO, CO2 and organic matter hydrocarbon equivalent (OMHCE) from the higher alcohol/gasoline blends were very similar to those from neat gasoline. Cycle emissions of NOx from the blends were higher than those from neat gasoline. However, for all the emissions species considered, the brake specific emissions (g/kW h) were significantly lower for the higher alcohol/gasoline blends than for neat gasoline. This was because the blends had greater resistance to knock and allowed higher compression ratios, which increased engine power output. The contribution of alcohols and aldehydes to the overall OMHCE emissions was found to be minimal. Cycle fuel consumption (g/h) of higher alcohol/gasoline blends was slightly higher than with neat gasoline due to the lower stoichiometric A/F ratios required by the blends. However, the brake specific fuel consumption (g/kW h) for the blends was significantly lower than that for neat gasoline.
Computational fluid dynamics applied to a cement precalciner
Authors: Giddings D , Eastwick C N , Pickering S J , Simmons K 
Published: October 2002

This paper describes a study of the use of computational fluid dynamics (CFD) to investigate the performance of a precalciner vessel at a cement works, In this vessel, limestone, held in suspension, is calcined to calcium oxide and the endothermic reaction is supported by the combustion of coal. Results are presented from a CFD model that contains all the essential features of the precalciner as operated when burning coal. The model fully represents the reactions and fluid dynamics of the precalciner. Previously unidentified features are illustrated. Certain key features at points in the precalciner, where some limited measurements can be made, are compared with the parameters indicated by the computational model. The measurements are consistent with the results calculated by the model indicating fair validation. The CFD data show the following 1 The gases undergo distinct recirculation. 2 The coal particles entering at one inlet have significantly different trajectories and temperature histories from those entering at the second diametrically opposed inlet. 3 There is 90 per cent completion of coal combustion at the exit. 4 73 per cent limestone in the raw meal is calcined to calcined to calcium oxide at the exit from the precalciner. 5 The highest reaction rate of the raw meal is closer to one side of the vessel due to interaction with the gas flows. Future work is proposed which, firstly, will provide further validation of the results so far attained by selective measurements on the precalciner and, secondly, will model the combustion and aerodynamic behaviour of waste-derived fuels in the precalciner vessel, commencing with shredded car tyre chips.
Off-design performance prediction for diffuser pumps
Authors: Sun J , Tsukamoto H 
Published: October 2002

This paper presents a numerical methodology developed for predicting off-design performance of diffuser pumps. In off-design conditions, the effects of rotor/stator interaction and the pump system characteristics become significant, and both need to be taken into account. The pump computational fluid dynamics (CFD) model and the system characteristic equation were incorporated to allow for flow dynamics in the duct. Flow analysis was applied to an entire circumference to capture the asymmetric flow feature at part-flow caused by rotating stall. An arbitrary sliding interface was exploited to consider the influence of rotor/stator interaction. The methodology was applied to a diffuser pump stage which includes a suction pipe, impeller, diffuser, U-bend, return channel and discharge pipe. Predicted results of the head-flow curve, pressure field and impeller radial forces were validated by the experimental data over the entire flow range. Back flow in the shroud region at small flowrates (from 0 to 40 per cent of design flow) was realistically exhibited. Flow in the region of 81 per cent of design flow displayed unstable features being caused by the occurrence of rotating stall in the impeller, such unsteady phenomena manifest themselves as a drop in the pump head rise, and larger fluctuations in impeller inlet pressure and radial forces. The present study has demonstrated that incorporation of the pump system characteristic equation and the pump CFD model produces a good prediction of pump off-design performance. The developed methodology can provide an alternative to dealing with pump off-design performance.
Advances in solid oxide fuel cells and integrated power plants
Authors: Bevc F 
Published: October 2002

In the last ten years, the solid oxide fuel cell (SOFC) development programme at Westinghouse has evolved from basic material science to the development of fully integrated electric power systems. Since 1986, 11 such systems have accumulated over 45 000 operating hours including 25 kWc atmospheric SOFC systems installed at customer sites in the United States and Japan. A 100 kWe atmospheric SOFC power system is being delivered to a European consortium in 1997. By pressurizing SOFC systems and integrating the fuel cells with a combustion turbine, efficiencies of between 60 and 70 per cent (net LHV, or lower heating value) can be attained. SureCELL™ plant concept designs are being evaluated at 3, 5 and 10 MWe. The plants are characterized by the high efficiencies noted, low emissions, a compact modular design and excellent performance over a wide range of operating conditions. The cost of electricity studies indicates that the integrated plants have a 30–45 per cent economic advantage over similar sized combustion turbine systems. A 3 MWe SureCELL™ SOFC-combustion turbine integrated power system is planned to be operational by the end of this decade.
Thermodynamic processes in solid oxide and other fuel cells
Authors: Gardner F J 
Published: October 2002

Following a review of thermodynamic processes in a generalized fossil-fuelled power system, the theoretical efficiencies of systems based on the isothermal oxidation of methane are discussed. The fuel cell is introduced as a device that converts the change of Gibbs free energy (Δ G) in isothermal oxidation directly to electricity. Ideal efficiencies of fuel cell systems are presented. The Gibbs free energy change in isothermal oxidation of methane is 99 per cent of its lower heating value (LHV). However, direct electrochemical oxidation is not practical yet. Taking this and other factors into account the reversible electrical work from an internally reforming fuel cell could represent ∼79 per cent of the lower heating value at 600°C, falling to ∼67 per cent at 1000°C. With a bottoming heat engine the combined reversible work could be >80 per cent of LHV over this range. Adding such a device as a topping element to a conventional heat engine based system seems a logical next step in the evolution of the efficient fossil-fuelled power plant.
Numerical optimization of a stator vane setting in multistage axial-flow compressors
Authors: Sun J , Elder R L 
Published: October 2002

This paper presents a numerical methodology for optimizing a stator stagger setting in a multistage axial-flow compressor environment. The method involves simultaneous resetting of several blade rows, which influences overall performance in a complex manner. The paper is presented in four parts: modelling the effect of stagger setting on individual stage performance, overall performance including surge point prediction, stagger setting optimization and numerical examples. The stage performance model is a one-dimensional meanline method where correlations are used to introduce real flow effects. The method uses (experimental or predicted) stage characteristics at design (nominal) setting to generate characteristics at other settings. A stage-by-stage model is used to ‘stack’ the stages together with a dynamic surge prediction model. A direct search method incorporating a sequential weight increasing factor technique (SWIFT) was then used to optimize stagger setting. The objective function in this optimization is penalized externally with an updated factor which helped to accelerate convergence. The methodology has been incorporated into a FORTRAN program and validated using data from a seven-stage aircraft compressor with hypothetical variable stagger vanes. Results have demonstrated that variable stagger is a powerful method to rematch stages which can be used to improve desired overall performance. Parametric studies on the optimization algorithm have also been conducted where it showed numerical stability and fast convergence.
Performance analysis of a hydraulic air compressor
Authors: Bidini G , Grimaldi C. N. , Postrioti L 
Published: October 2002

The combined exploitation of different kinds of primary energy source in innovative power plants is a promising way to enhance the energy conversion efficiency. In recent years, a possible utilization of the hydraulic resource for power generation in non-conventional plants has been proposed. The basic concept is to couple a conventional gas turbine combustion chamber and expander with a hydraulic air compressor, a device whose main characteristic is the capability to compress air isothermally using a hydraulic energy source. A hydraulic air compressor-gas turbine power plant, with an extended regeneration at the turbine exhaust, can be characterized by an attractive overall efficiency. The performance of a hydraulic air compressor-gas turbine power plant is strongly influenced by the characteristics of the hydraulic compressor itself. In the present paper, an improved (with respect to the previous literature) model of the hydraulic air compressor and an original loss analysis model are presented. The results of a performance and loss parametric analysis are presented and discussed; maps which relate to the natural site characteristics, the obtainable performance and main plant design parameters are also reported and discussed.
The role of research in the aerodynamic design of an advanced low-pressure turbine
Authors: Harvey N. W. , Cox J. C. , Schulte V , Howell R , Hodson H. P. 
Published: October 2002

The new BR715 engine features an advanced low-pressure turbine aerodynamic design which includes ‘high-lift’ aerofoils. This paper shows how every part of the design methodology has been derived from extensive research instigated by both Rolls-Royce and BMW Rolls-Royce. Of particular importance has been the investigation of unsteady wake-boundary layer interaction on low-Reynolds-number blading and the generation of a database for the validation of the design methods. Preliminary results from cold-flow rig testing have verified the design aims. In particular the aerodynamic efficiency is approximately 1 per cent above the prior technology base.
Reduction of axial piston pump pressure ripple
Authors: Harrison K A , Edge K A 
Published: October 2002

The reduction in source flow ripple in hydraulic systems is the most effective method of reducing pump-generated pressure ripple and system noise. This paper describes reductions in axial-piston pump delivery flow ripple achieved using a novel timing mechanism which is inherently speed, flow and pressure sensing. Fixed-speed tests have shown that the mechanism can significantly reduce axial-piston pump delivery flow ripple over a wide range of delivery pressures and pump displacements. Furthermore, the reduction in pressure ripple achieved with the mechanism has been shown to contribute towards reductions in overall air-borne noise levels of up to 6 dB in a simple system. A simulation model has been produced to predict the behaviour of the prototype mechanism. The model has been compared with the measured delivery flow ripple and achieves good agreement.
Modelling and control of a disk file head-positioning system
Authors: Yamaguchi T 
Published: October 2002

This paper overviews servo control technology in the field of motion control for disk file systems. In the hard disk drive (HDD) system, the head must be positioned on the desired track quickly and precisely, and this performance must be robust. Recent required positioning accuracy is about 50 nm (±3σ). To meet these requirements, many servo control methods have been proposed and applied to the system. Major research subjects for fast movement are a reference trajectory design and a track-seeking servo design. In particular, a two-degree-of-freedom (2 DOF) servo control with a multirate sampling period has been developed for the track-seeking servo. Two design methods of 2 DOF feedforward controller are proposed here. While reading/writing data, very precise positioning on a target data track is required. One of the most effective methods for precise positioning under various disturbances is to increase the servo bandwidth. This paper examines the use of loop shaping, state feedback and a dual-stage actuator servo to increase the servo bandwidth with sufficiently robust stability. Feedforward methods to cancel disturbances are also applied under the condition that the disturbances are either detectable or can be estimated, such as repeatable runout error, which is synchronous to disk rotation.
The long-term monitoring of civil engineering and building structures—developments in techniques for monitoring corrosion in reinforced and post-tensioned concrete
Authors: Hammersley G P , Dill M J 
Published: October 2002

An important step in the progress towards smart structures is the development of reliable systems for the long-term monitoring of performance. Data obtained from monitoring can provide an early warning system to maximize the safe use of structures, contribute towards planned maintenance by giving advanced notice of durability or structural problems and provide information on actual performance, which can be fed back into the design process. This paper sets out to describe some developments in permanent in situ monitoring systems which have achieved practical use on civil engineering and building structures constructed from concrete, concentrating on the key area of corrosion of reinforced and post-tensioned concrete. The techniques are illustrated with case histories.
Smart machine tools
Authors: Corbett J 
Published: October 2002

Improved manufacturing methods have become crucial factors in retaining global competitiveness for a wide range of products. This has led to the development of new automatic supervision techniques for use in smart machine tools. These are necessary because it is not possible to design and manufacture machine tool structures and systems with work zone areas of sufficient accuracy and repeatability to meet the improved performance requirements demanded by many modern manufacturing companies. The principal areas for automatic supervision of the machine tool are the tooling, appropriate machine elements and the overall machine system. Thermal effects have been shown to be the largest source of dimensional errors and apparent non-repeatability of machines. Therefore, for the highest precision machines on-line temperature monitoring and control is of paramount importance. This paper describes the application of automatic supervision techniques applied to the NION diamond turning and grinding machine, developed by Cranfield Precision Engineering Limited, which is the most accurate machine tool, of its size, currently available, as well as an ultra precision five-axis grinding machine, built in Japan by the Toyoda Machine Works Limited. In addition, following a project at Cranfield University, the benefits of on-line measuring techniques are discussed in obtaining new cost effective manufacturing methods for producing aero-engine turbine blades. Further examples are given, including major projects at Liverpool John Moores University and Eindhoven University of Technology, where significant improvements in accuracy capabilities were obtained for a standard cylindrical grinding machine and a five-axis vertical milling machine.