bluuebunny/crossref_metadata_2025_split huggingface dataset:
Press-fit acetabular cup fixation: Principles and testing
Authors: Macdonald W , Carlsson L V , Charnley G J , Jacobsson C M 
Published: October 2002

Pre-clinical testing of the fixation of press-fit acetabular components of total hip prostheses relies on cadaver or synthetic bone, but the properties and geometry of bone models differ from those of physiological bone. Cup designs use varied mechanisms for initial stability in bone; therefore, using different analogues and tests is appropriate. Press-fit cup stability was tested in the following: firstly, polyurethane (PU) foam modelling can-cellous support; secondly, glass-fibre reinforced epoxide (GFRE) tubes modelling acetabular cortical support; thirdly, cadaveric acetabula. Three commercial cups [Harris-Galante II (H-G II), Zimmer; Optifix, Smith & Nephew, Richards; porous coated anatomic (PCA), Howmedica] and an experimental cup with enhanced rim fixation were tested in three modes: direct pull-out, lever-out and axial torque. The fixation stabilities measured in the PU and the GFRE models showed trends consistent with those in cadaver bone, differing in the oversizing and cup geometry. The experimental cup was significantly more secure in most modes than other cups; the H-G II and Optifix cups showed similar stabilities, lower than that of the experimental cup but greater than that of the PCA cup (analysis of variance and Tukey's highly significant difference test; p < 0.001). The stabilities measured in cadaver bone more closely approximated those in GFRE. The use of several bone analogues enables separation of fixation mechanisms, allowing more accurate prediction of in vivo performance.
Proposal for a highly intermittent heating law for discontinuously occupied buildings
Authors: Fraisse G , Virgone J , Menezo C 
Published: October 2002

This article presents an intermittent heating controller which is designed for calculating the supply temperature of hot-water-radiator heating systems. This controller uses a new heating law which has been obtained by inverting a simplified model for calculating the internal temperature of a building in relation to the external temperature, as well as the supply temperature of the distribution circuit and the temperature of the structure. The latter is used to determine the thermal state of the building, which is an important parameter in the evaluation of energy needs when a building is heated in an intermittent mode. During non-occupancy periods, the parameters of the model are automatically modified by a recursive least-squares routine. A second law optimizes the heating restart time during non-occupancy periods; this law also incorporates a learning mechanism. The controller's performance is analysed, and the results are compared with those of a controller using a classical heating law which does not take into account the thermal state of building. Numerical simulations demonstrate that the new heating controller leads to performances comparable with those obtained by classical methods, but for a higher degree of intermittence. This means that the comfort obtained is similar, but that the energy consumption is lower. The new heating law also proves to be advantageous in other ways; it provides faster learning, much better lower temperature control and a reduction in instances of overheating during inter-season periods, when little heating is needed.
Performance prediction of an industrial centrifugal compressor inlet guide vane system
Authors: Coppinger M , Swain E 
Published: October 2002

Variable inlet guide vanes (VIGVs) can significantly extend the stable operating range of industrial centrifugal compressors as a result of imparting swirl to the inlet flow. Typical setting angles range from −20° to +80°; therefore the vanes are normally made from flat plate. An undesirable consequence of the large setting angles required by the vanes is a pressure loss, leading to a decrease in the overall stage efficiency. An ideal inlet guide vane system will therefore induce large swirl angles in the inlet flow with a low associated pressure loss. Efforts have been made to determine the performance characteristics of an existing VIGV design using both an experimental test facility and numerical techniques. The results obtained from these techniques are far more comprehensive than earlier full-scale performance testing. Validation of the performance of the existing design using these techniques has led to the development of a new vane design and potential improvements to the inlet ducting geometry. The test techniques and resulting analyses of the existing design are presented here together with some analyses and predictions of the performance of the improved VIGV system design.
Water spray cooling of gas turbine cycles
Authors: Ritchey I , Fisher E H , Agnew G D 
Published: October 2002

Aerodervative gas turbines intercooled by water spray injection systems have recently entered service. A calculation framework is presented which permits the effect of water spray injection for both intercooling and inlet chilling to be evaluated and compared with conventional cooling techniques for a range of cycles. The calculations are based on representative performance maps for compressors and turbines, focusing upon the actual performance benefits that can be realized from existing turbomachinery. The principal conclusions are that spray intercooling can give a greater power boost than conventional intercooling for a given compressor operating envelope spray inlet chilling can give performance benefits comparable with absorption chilling and intercooling is more attractive at ambient temperatures below 15°C, whereas inlet chilling is preferable at higher temperatures.
Performance of integrated gasification combined cycle power plants integrated with methanol synthesis processes
Authors: Carapellucci R , Cau G , Cocco D 
Published: October 2002

Base-load integrated gasification combined cycle (IGCC) power plants can perform load-following service by integration with a methanol synthesis process. The methanol, produced from a portion of the coal gas and stored in liquid phase, can be used for matching intermediate and peak-load demand. In this paper, the load modulation capabilities of IGCC power plants for the coproduction of electricity and methanol have been investigated. Referring to a conventional duty cycle, the main performance of power plants combining slurry-feed entrained-bed gasification and gas or liquid phase methanol synthesis has been assessed, for two different peaking electric power generation solutions. Moreover, the flexibility of these plants has been evaluated for different operating conditions, some remote from design conditions. The results of the study show that IGCC power plants combining electric power generation and methanol synthesis offer considerable scope for enhancing operating flexibility and load modulation capabilities of coal gasification power plants. The plants designed for advanced liquid phase methanol synthesis process performed best in terms of overall efficiency, plant layout and operating flexibility.
Technological advances in high-efficiency particulate collection
Authors: Parker K R 
Published: October 2002

Particulate control equipment for the larger industrial processes, which can effectively collect particles in the submicrometre range, is limited to the electrostatic precipitator and bag filter as cost effective methods. To meet ever decreasing emission levels, demanded by the Regulatory Agencies, the equipment suppliers and academics are involved in ongoing research and development activities in order to obtain a better understanding of the collection process itself, such as to achieve improved performance and, equally importantly, plant reliability and availability. This paper reviews some of the activities in the electrical, microelectronics, material sciences, fluid flow and finite element analysis fields and indicates how the findings are leading to new designs that are more reliable and also how the improvements are making the equipment more cost effective while operating at a higher performance level. Finally, with the concern over the emission of ‘air toxics’, while both the electrostatic precipitator and bag filter are established technology for effectively removing solid and liquid particulates with sizings well below 1 micrometre there is now an additional requirement for collecting vapour phase materials to meet the latest regulatory emission levels. Some ideas and approaches are examined which can prove effective in collecting the majority of materials classified as ‘air toxics’, such that the equipment will meet the existing and possible future emission standards.
Thermodynamic analysis of hydraulic air compressor-gas turbine power plants
Authors: Bidini G , Grimaldi C N , Postrioti L 
Published: October 2002

Nowadays, the most common way to improve energy conversion efficiency is the integration of different systems, thus achieving a better exploitation of the available exergy potential (e.g. combined cycles, cogeneration, etc.). As a means of producing power in hydroelectric plants hydraulic energy is commonly considered to be almost completely exploited. The aim of this paper is to analyse the possible integration of hydraulic energy sources with conventional, fossil fuel based systems; in particular, power plants based on the combination of an hydraulic air compressor (HAC) and a gas turbine are considered. In an HAC, air is entrained in the water flow in a downcomer pipe and compressed. Once separated from the water in a ‘stilling chamber’ at the bottom of the downpipe, the compressed air is supplied to a combustion chamber and then to a conventional gas turbine expander. An attractive characteristic of HACs is the capability, in principle, to perform an isothermal air compression instead of an adiabatic one, as in conventional compressors. In the present work, a thermodynamic analysis is presented of HAC-gas turbine energy conversion systems, which are compared with conventional hydroelectric and gas turbine power plants. The calculated performance levels of such systems are comparable to those of combined cycle plants, making further technical and economical investigations quite interesting.
A computational and experimental evaluation of the performance of a centrifugal fan volute
Authors: Dilin P , Sakai T , Wilson M , Whitfield A 
Published: October 2002

A detailed experimental study of the performance of two radial-flow fan volutes has been carried out at the Science University of Tokyo. This included a volute with a full tongue, such that no recirculating flow occurred, and the same volute but with the tongue cut back to allow flow recirculation. Detailed velocity and pressure distributions at a wide range of azimuth angles were obtained experimentally and are presented. At the University of Bath a computational model, using the k-e turbulence model, has been used to predict the internal flow of both volutes, with particular attention given to the tongue flow. Predicted flow separation at the volute tongue has been demonstrated experimentally through laser sheet studies at the Science University of Tokyo. The performance of the volutes is discussed and the computational fluid dynamics (CFD) analysis is used to recommend design improvements for the volute.
A new concept for squirrel-cage fan inlet
Authors: Montazerin N , Damangir A , Mirian S 
Published: October 2002

The squirrel-cage fan with a newly introduced outward inlet lip is studied experimentally. Previous research has demonstrated the importance of inlet flow control on the general flow field and vortex generation of such fans. The bell-mouth inlet, which is the common industrial and academic practice, has drawbacks that result in flow separation and turbulence enhancement. The adapted experimental approach is a conceptual study. It is a combination of standard characteristic measurements and detailed laser Doppler anemometry. The measured flow pattern inside the volute demonstrates that the separated flow behind the inlet lip, which for an ordinary inward lip occupies a large part of the rotor blades, disappears. This is promising since removing this separated flow diminishes a major loss-making region in this fan and adds to the effective flow area. It also reduces noise and gives uniform blade loading. The results also show an improvement in performance in comparison with that of a fan with an ordinary inward inlet lip. This modification is industrially feasible with no extra manufacturing cost and therefore can represent a substantial advance over the current practice.
Time-resolved measurements with fast-response probes and laser Doppler velocimetry at the impeller exit of a centrifugal compressor: a comparison of two measurement techniques
Authors: Gizzi W. P. , Roduner C , Stahlecker D , Koppel P , Gyarmathy G 
Published: October 2002

The goal of this work was the investigation of the unsteady flow field existing at the exit of the impeller of a centrifugal compressor and the critical comparison of velocity measurements with two systems based on totally different measurement principles. The paper focuses on the measurement concepts, the accuracy and the error quantification. A one-sensor fast-response probe (FRAP® system) and a commercially available laser Doppler velocimetry (LDV) system were used to perform wall-to-wall traverses and to measure the two main time-resolved velocity components. The test rig was run at the best point of the operating line, at a tip Mach number of 0.75. The mean levels and fluctuations of the velocity vector components were compared. Over the middle, 70 per cent of the channel width, the FRAP® and LDV measurements typically agree within 2–5 per cent of the momentary local flow velocity in terms of both the radial and the circumferential velocity components. The time-mean distributions agree within typically 0–4 per cent. Attention was focused on the near-hub and near-shroud layers where both measurements are affected by wall proximity errors. Largest discrepancies (of 10 per cent) in the time-mean velocity occurred at the shroud where velocity component values could differ by as much as 20 per cent momentarily. These discrepancies should be viewed in relation to the peak-to-peak amplitude of the ensemble-averaged velocity fluctuations which was of the order of 25 per cent in the present compressor.
Tip-clearance-affected flow fields in a turbine blade row
Authors: Sell M , Treiber M , Casciaro C , Gyarmathy G 
Published: October 2002

For effective validation of computational fluid dynamics (CFD) codes for design, numerical simulations must be compared and contrasted with experimental data sets which are well posed and measured. This paper presents, with the emphasis placed primarily upon the description and explanation of the experimental results, a test case designed for CFD validation concerning the flow field generated by the presence of tip clearance in an annular cascade turbine blade row. The test case is based upon a moderately loaded prismatic blade profile, operating with axial inflow and a nominal mid-span exit Mach number of 0.5. In addition to the case with no clearance, three gap heights, representing 1, 3 and 5 per cent of chord length have been selected. These tip clearances were chosen because they represent three conditions where the tip clearance is below, approximately equal to and substantially larger than the inlet boundary layer displacement thickness. At the leading edge this produces different behaviours, with the smallest gap producing a stagnation point, equivalent to the case without tip clearance, while the largest clearance allows throughflow over the leading edge into the tip gap. In the presence of larger tip clearances, the tip leakage flow induces a stagnating flow in the trailing-edge region, which results in a large area of blocked flow in the blade passage downstream of the trailing edge.
An architecture for system-wide fault detection and isolation
Authors: Dassanayake H P B , Roberts R , Goodman C J 
Published: October 2002

A novel approach to distributed fault detection and isolation (FDI) is presented. Consideration is given to an appropriate architecture and communication method for a truly distributed FDI system. As part of the discussion on system architecture, regard is given to the correct level at which fault detection, diagnosis and isolation should be carried out. The case study of an automatic door as part of a building automation system is presented. Recognized faults are induced on the asset and detection methods formulated. It is demonstrated that, by implementing the fault detection algorithms at a lower level, it is possible to carry out FDI over a system consisting of many assets. This allows maintenance staff more precise information regarding the health of the whole system and allows system-wide isolation and in-depth diagnostics to be applied in the event of a fault being detected. The architecture discussed allows the implementation of system-wide FDI at a fraction of the cost of stand-alone systems.
Adaptive fuzzy throttle control for an all-terrain vehicle
Authors: Trebi-Ollennu A , Dolan J M , Khosla P K 
Published: October 2002

This paper describes an adaptive fuzzy throttle control for an all-terrain vehicle (ATV) powered by internal combustion engine. The design objective is to provide smooth throttle movement and zero steady state speed error, and to maintain a selected vehicle speed over varying road slopes for a 2–30 mile/h speed range. Unlike modern production vehicles which have microprocessor-based engine management systems, the ATV's engine is mechanically controlled via a carburettor. A complete mathematical model of the engine is not available, making it very difficult to apply conventional control techniques. Using experience and data collected from extensive experiments conducted on the ATV throttle mechanism, an adaptive fuzzy throttle control algorithm is designed. A candidate Lyapunov function is employed in the adaptive law synthesis to ensure convergence. Experimental results are presented showing the effectiveness of the control algorithm at speeds below 2.74 mile/h (1.2m/s).
A high-level technique for diesel engine combustion system condition monitoring and fault diagnosis
Authors: Twiddle J A , Jones N B 
Published: October 2002

This paper presents a technique for diagnosis of a class of engine faults, which adversely affect the combustion efficiency of a diesel generator set. The diagnosis is made by combining the evidence of two separate estimations of engine load with the outputs from a predictive fuzzy model of engine speed. Certain faults affect the periodicity of the engine speed signal. The variation in periodicity means that the load estimation from power spectral density of the speed signal is not robust. This problem is countered by implementing a reference model to predict speed fluctuations with respect to crank angle. This model has the additional benefit that its output may be used to detect periodic fault symptoms in the speed signal, thereby leading to identification of the individual cylinder affected by the fault. A fuzzy rule based system has been developed to diagnose faults based on the load estimations and the residuals obtained from the reference model. Testing the diagnostic system with data from the normal, and two other separate engine fault conditions, resulted in a classification success rate greater than 90 per cent in each case. A further benefit is reported where the combination of evidence from the three sources effectively validates the load estimation, which may then be used to infer faults in other subsystems.
Diagnostics of a coolant system via neural networks
Authors: Martin K F , Marzi M H 
Published: October 2002

The application of a neural network (NN) to diagnose faults in a machine tool coolant system is described. The measured variable in the system is the pump outlet pressure; the transient response of this as the flow valve is closed is used as a pattern for fault recognition. A two-stage diagnostic system using a back propagation NN at each stage is described and this is trained by using data from the coolant system under healthy (i. e. unfaulty) and faulty conditions. The faults are simulated on the real coolant system. Novel (i. e. previously unmet) faults are defined by maximum values of a ‘deviation’ which is used to allocate faults. The diagnostic system is shown to be capable of first deciding whether the system is healthy or faulty; if faulty, it then decides whether one of the three common faults or a novel fault is occurring. Having made the decision that one of the common faults is occurring, it is then capable of deciding, from four different levels, the approximate severity level of the fault. Of 345 tests on the coolant system the diagnostic system allocated the fault 99 per cent correctly and the severity level 96 per cent correctly.
The behaviour of low-amplitude surface roughness under line contacts: Non-Newtonian fluids
Authors: Hooke C. J. 
Published: October 2002

As a rough surface passes under an elastohydrodynamically lubricated (EHL) contact the surface profile is modified, with long-wavelength components being reduced in amplitude. The behaviour of the shorter wavelengths is complex. Where both surfaces have the same velocity-pure rolling-the roughness passes through the contact unaltered. Where there is relative slip and the fluid is assumed to be piezoviscous and Newtonian, analysis predicts that the roughness will be flattened. It is replaced by a surface profile with a different wavelength travelling through the contact at the entrainment velocity. The amplitude of this complementary wave may be smaller or larger than the roughness it replaces. This behaviour has not been found experimentally and does not occur in soft contacts where piezoviscous effects are absent. This paper extends a previous analysis for Newtonian fluids to include shear rate effects. It shows that while these effects are relatively unimportant for pure rolling they have a major influence where there is relative sliding of the surfaces. The formation of the complementary wave is largely eliminated and, at short wavelengths, instead of being modified the original roughness passes unchanged through the contact.