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Item Open Access Economic and environmental viability assessment of NASA’s turboelectric distribution propulsion(Elsevier, 29-06-29) Alrashed, Mosab; Nikolaidis, Theoklis; Pilidis, Pericles; Alrashed, Wael; Jafari, SoheilThe concept of turboelectric-distributed propulsion (TeDP) has become integral to engineering because of its ability to generate electricity. However, social science compels careful evaluations of TeDP’s environmental and economic impacts—out of caution, such elements must be taken up before TeDP is put into practice. Responding to this call, this research investigates TeDP’s economic and environmental viability with a case study of the National Aeronautics and Space Administration’s (NASA) proposal for a TeDP aircraft, N3-X, using technical aspects and real data integration. The economic assessment measures NASA’s N3-X economic added value for aviation manufacturing, operations, and investors as well as net present value, internal rate of return, and payback period. Meanwhile, the environmental assessment looks at carbon monoxide and dioxide and oxides of nitrogen. The economic and environmental evaluation results establish the viability of TeDP.Item Open Access Performance in sampled data systems(IEEE, 1992-05-01) Whidborne, James F.A performance index for control systems has been defined as the supremum of the absolute error that occurs over all time and all inputs. The input to the system is known only to the extent that it belongs to a known function space. The paper shows how this performance index is determined for certain sampled data systems with an input space characterised only by a bound on the derivative of the input. An example of a design using this performance index is given.Item Open Access Robust controller design using h-infinity loop-shaping and the method of inequalities(IEEE, 1994-12-01) Whidborne, James F.; Postlethwaite, I.; Gu, Da-WeiA new approach to robust controller design is proposed. By using plant-weighting functions as the design parameters, the approach combines the method of inequalities with robust stabilization of normalized coprime factor descriptions of the weighted plant to design explicitly for closed-loop performance and stability robustness. A procedure for the design of robust two degree-of-freedom controllers is presented and is illustrated on a high-purity distillation column exampleItem Open Access Three-dimensional shape measurement using fiber optic low-coherence speckle interferometry(SPIE - International Society for Optics and Photonics, 1998-07-20) Balboa, Itziar; Tatam, Ralph P.A low coherence speckle interferometer implemented using single mode optical fibre and a multimode laser diode as a pseudo-low coherence source is described. The design of the interferometer is presented and demonstrated on simple test objects. Signal processing techniques to improve the performance ofthe system are discussed.Item Open Access Tip timing techniques for turbomachinery HCF condition monitoring(University of Cambridge, 2002) Ivey, P. C.; Grant, K. R.; Lawson, CraigHigh Cycle Fatigue (HCF) has been established as the major common failure mode in the US Air Force large fleet of aero-engines. Corrective measures for this failure mode in themselves deliver additional technical, managerial and cost pressures. Two responses are in place to address this problem; risk mitigation through accelerated engine development fixes and technology transition through targeted and focussed R&D studies. It is the latter that is of interests and is discussed in this paper. Aero-engine blade vibrations of sufficient amplitude cause High Cycle Fatigue, which reduces blade life. In order to observe this vibration a non-intrusive monitoring system is sought. The vibration can be detected by measuring blade tip timing since in the presence of vibration the blade timing will differ slightly from the passing time calculated from rotor speed. Work done to investigate the suitability of a commercially available capacitance probe tip clearance measurement system for application as a non-intrusive turbomachinery blade tip timing measurement device is reported. Capacitance probe results are correlated with simultaneously measure strain gauge results and the performance of the capacitance system in measuring blade vibration is analysed. The growing interest in blade high cycle fatigue within the aerospace industry, and an approach to monitoring their condition are discussed as an extension to the above study. The suggested approach is based upon the tip-timing method, using non-contact optical probes located around the engine’s casing. Two current tip-timing techniques are suggested for the purpose. The techniques are summarised, the experimental validation of both methods outlined, and the approach taken to investigate the potential use as a condition monitoring tool described. The paper is concluded with a discussion of the future use of tiptiming as a condition monitoring tool.Item Open Access Fuel efficient driving training - state of the art and quantification of effects(2002-10-23) af Wåhlberg, Anders E.A new area of traffic education, training in fuel efficient driving, is reviewed. This training is often said to reduce fuel consumption, accidents, emissions, and wear and tear on vehicles. These claims, made mainly by educators and bureaucrats, and said to have scientific backing, are found to be wanting; most of the possible effects are totally unsubstantiated, while the most central, reduction in fuel consumption, is well below the highest figures mentioned. Research problems and general methodology regarding the variable of fuel consumption reduction are discussed. Although it is fairly easy to show the large potential of training under experimental conditions, it is rather complicated in a field setting. However, it is necessary to study the effects in the drivers' natural environment, because of the many possible sources of error in controlled settings which tend to inflate the effect. What is possible during training should therefore rather be seen as a maximum of what can be achieved, while the effect in real life driving is usually far below. Being a new area of research, it is uncertain exactly how effects should be measured, apart from fuel consumption. This problem is discussed and the results from a quantification of effects of training in fuel efficient driving are presented. The changes in driving style are described in terms of acceleration patterns; mean accelerations (over time) increased and mean decelerations decreased, while the time spent on a stable velocity decreased. Also, the mean acceleration and deceleration over distance was fairly well correlated with fuel consumption, and very clear differences could be seen on several acceleration-related variables as a result of training. These results show that acceleration patterns are a workable way of quantifying this type of training.Item Open Access Planar Doppler velocimetry measurements of flows using imaging fibre bundles(SPIE - International Society for Optics and Photonics, 2003-08-03) Nobes, David S.; Ford, Helen D.; Tatam, Ralph P.The development of a planar Doppler velocimetry is described. The technique is capable of measuring the three, instantaneous components of velocity in two dimensions using a single pair of signal and reference cameras. PDV can be used to measure the instantaneous 3-D velocity of a fluid by using an absorption line filter (ALF) to determine the Doppler shifted frequency of a narrow line pulsed laser (Nd:YAG) that has been scattered off particles seeded into the flow. The velocity of the fluid is determined using the Doppler formula and is dependent on the laser direction and the viewing direction. Hence, only one velocity component of the flow is measured. This component can be measured in two spatial dimensions using an array detector such as a CCD camera. To capture the three components, three such measurement heads have been used viewing from different angles. In the technique presented here the three views are ported from the collection optics to a single imaging plane using flexible fibre imaging bundles. These are made up of a coherent array of single fibres and are combined at one end as the input plane to the measurement head. The paper discusses the issues involved in developing a full three-dimensional velocity measurement system.Item Open Access Gas turbine and sensor fault diagnosis with nested artificial neural networks(ASME, 2004) Xiradakis, N; Li, YiguangAccurate gas turbine diagnosis relies on accurate measurements from sensors. Unfortunately, sensors are prone to degradation or failure during gas turbine operations. In this paper a stack of decentralised artificial neural networks are introduced and investigated as an approach to approximate the measurement of a failed sensor once it is detected. Such a system is embedded into a nested neural network system for gas turbine diagnosis. The whole neural network diagnostic system consists of a number of feedforward neural networks for engine component diagnosis, sensor fault detection and isolation; and a stack of decentralised neural networks for sensor fault recovery. The application of the decentralised neural networks for the recovery of any failed sensor has the advantage that the configuration of the nested neural network system for engine component diagnosis is relatively simple as the system does not take into account sensor failure. When a sensor fails, the biased measurement of the failed sensor is replaced with a recovered measurement approximated with the measurements of other healthy sensors. The developed approach has been applied to an engine similar to the industrial 2-shaft engine, GE LM2500+, whose performance and training samples are simulated with an aero-thermodynamic modelling tool — Cranfield University’s TURBOMATCH computer program. Analysis shows that the use of the stack of decentralised neural networks for sensor fault recovery can effectively recover the measurement of a failed sensor. Comparison between the performance of the diagnostic system with and without the decentralised neural networks shows that the sensor recovery can improve the performance of the neural network engine diagnostic system significantly when a sensor fault is present. Copyright © 2004 by ASMEItem Open Access Study of molten aluminium cleaning process using physical modelling and CFD(TMS (The Minerals, Metals & Materials Society), 2004-03-18) Song, Jin L.; Chiti, Fabio; Bujalski, Waldemar; Nienow, Alvin W.; Jolly, Mark R.Furnace treatment is an important step during molten aluminium production by which the dissolved hydrogen and solid impurity particles are removed. Conventionally, a chlorine/inert gas mixture is used for this purpose injected into the molten metal via a simple lance. In order to meet new requirements for furnace emissions and improve efficiency, mechanical agitation through an impeller is becoming more widely used. In this research, the homogenization behaviour of both lance bubbling and mechanical agitation by impeller has been investigated experimentally and numerically. It can be concluded that under the same mean specific energy dissipation rates, the velocity magnitude for mechanical agitation process is about ten times bigger than that for the lance bubbling process, and the mixing time for the mechanical agitation process are much lower than that for the lance bubbling process, so better cleaning or fluxing would be expected.Item Open Access Optical fibre Fizeau-based OCT(SPIE - International Society for Optics and Photonics, 2004-06-09) Casaubieilh, P.; Ford, Helen D.; Tatam, Ralph P.An optical fibre, Fizeau configuration Optical Coherence Tomography (OCT) system is presented in this paper. The interferometer is formed between the distal end of the sample-arm fibre and the sample itself. This ensures 'downlead insensitivity' ; polarisation variation is not a problem, as it is in the standard Michelson configuration. Path-length matching is performed by a secondary, bulk-optic scanning Mach-Zehnder interferometer. In this paper, we demonstrate the use of an optical circulator and balanced detection to permit optimum use of the light and maximise the signal-tonoise ratio.Item Open Access Gas turbine diagnosis using a fault isolation enhanced GPA(ASME, 2004-07) Li, YiguangGas Path Analysis (GPA) and its different derivatives have been developed for more than thirty years and used widely and successfully by many gas turbine manufacturers and operators. In gas turbine gas path component diagnosis, it has been recognized for a long time that GPA would be more successful if degraded components could be located. Unfortunately, only the deviation of measurable parameters is monitored in operation and information about the degraded components is normally not available. In this research, a two-step diagnostic approach is introduced, where a pattern matching method is used first and further developed to isolate degraded components; then Gas Path Analysis is applied to assess the quantity of degradation. A gas turbine performance simulation program, Cranfield University TURBOMATCH, has been modified to simulate the diagnostic process. A model gas turbine engine similar to Rolls-Royce aero AVON is used to test the effectiveness of the approach. It is found that the developed fault isolation method can isolate degraded components accurately and enhance the effectiveness of the quantitative assessment of the degradation with Gas Path Analysis (GPA) in gas turbine diagnostics. Copyright © 2004 by ASMEItem Open Access A review of data fusion models and architectures: Towards engineering guidelines(Springer, 2005-06-21) Esteban, Jaime; Starr, Andrew G.; Willetts, Robert; Hannah, Paul; Bryanston-Cross, PeterThis paper reviews the potential benefits that can be obtained by the implementation of data fusion in a multi-sensor environment. A thorough review of the commonly used data fusion frameworks is presented together with important factors that need to be considered during the development of an effective data fusion problem-solving strategy. A system-based approach is defined for the application of data fusion systems within engineering. Structured guidelines for users are proposed.Item Open Access Work related road safety: Age, length of service and changes on crash risk(Department for Transport: London, 2005-11-30) Dorn, Lisa; Muncie, HelenAge and experience are known to be major factors in road traffic collisions (Maycock et al., 1996) and are commonly used as predictors of crash frequency (Evans and Courtney, 1985). But age and experience are difficult to separate when investigating crash risk (Brown, 1982; Ryan et al., 1998; Mayhew and Simpson, 1990; Bierness, 1996). Experience is closely related to age but independently influences crash risk. For age, mileage-adjusted crash risk declines with age but then rises for drivers over 65 (Maycock et al., 1991). This is thought to be due to physical and cognitive declines in older people and to increased risk-taking in younger drivers (Chipman et al., 1992; Clarke et al., 1998; McGwin and Brown, 1999). For experience, even limited driving experience has a major effect on road safety. For example, there is a disproportionately higher crash rate during the first year of driving, particularly in the first few months after licensure (Sagberg, 1998). For age and experience, Mayhew et al. (2003) found larger decreases in crash risk amongst younger novices compared with older novices during the first few months of driving. This was interpreted as due to greater initial risk-taking amongst younger novices, with on-road driving experience facilitating a more rapid learning rate compared with older novices. They suggest that this was an appropriate point at which to provide training intervention. There is reasonable literature on the effects of age and experience on accident involvement, but little is known about whether these effects can be generalised to professional drivers, especially since professional drivers differ substantially from the general population of drivers.Item Open Access Single camera 3D planar Doppler velocity measurements using imaging fibre bundles(IOP Publishing, 2006) Charrett, Thomas O. H.; Ford, Helen D.; Tatam, Ralph P.Two frequency planar Doppler Velocimetry (2ν-PDV) is a modification of the Planar Doppler Velocimetry (PDV) method that allows velocity measurements to be made, quickly and non intrusively, across a plane defined by a laser light sheet. In 2ν-PDV the flow is illuminated sequentially with two optical frequencies, separated by about 700MHz. A single CCD viewing through an iodine absorption cell is used to capture images under each illumination. The two images are used to find the normalised transmission through the cell, and the velocity information is encoded as a variation in the transmission Use of a single camera ensures registration of the reference and signal images and removes issues associated with the polarization sensitivity of the beam splitter, which are major problems in the conventional approach. A 2ν-PDV system has been constructed using a continuous-wave Argon ion laser combined with multiple imaging fibre bundles, to port multiple views of the measurement plane to a CCD camera, allowing the measurement of three velocity components.Item Open Access Single camera 3D planar Doppler velocity measurements, using two frequency planar Doppler velocimetry (2v-PDV) and imaging fibre bundles(AIAA, 2006) Charrett, Thomas O. H.; Ford, Helen D.; Tatam, Ralph P.A modified Planar Doppler Velocimetry (PDV) technique, two frequency PDV (2v-PDV), is described that allows measurements of the velocity field over a plane defined by a laser light sheet using sequential illumination of the flow with two closely separated (&IGHz) frequencies of laser light. This allows a common-path imaging head to be used containing a single CCD camera instead of the usual camera pair. The problem of image misalignment is now avoided and the polarisation sensitivity of the beam splitter used in two camera imaging heads is also removed. Cost efficiency is improved by the simplification of the system. This paper describes the development of a 2v-PDV system using a continuous wave argon ion laser capable of making time-averaged velocity measurements. Initially a single velocity component system was constructed using acousto-optic modulators to produce the two illumination frequencies required. The system was then expanded to make 3D velocity measurements using a single CCD camera and multiple coherent imaging fibre bundles. Measurements were made on the rotating disc, in order to assess error level in the measurements, and on a seeded axisymmetric air jet. A method of improving the sensitivity of the 2v-PDV system is demonstrated by using both the rising and falling slopes of the iodine absorption line. Reductions in the error levels of velocity measurements of approximately 40% can be achieved using this increased sensitivity method.Item Open Access Effects of initial radius on the propagation of premixed flame kernals in a turbulent environment(AIP, 2006-05-12) Klein, M.; Chakraborty, N.; Jenkins, Karl W.; Cant, R. S.The effects of mean curvature on the propagation of turbulent premixed flames have been investigated using three-dimensional direct numerical simulations (DNS) with single step Arrhenius-type chemistry in the thin reaction zones regime. A number of spherical flame kernels with different initial radius have been studied under identical conditions of turbulence and thermochemistry. A statistically planar turbulent back-to-back flame has been simulated as a special case of a spherical kernel in the limit of infinite kernel radius. Statistical analysis in terms of standard and joint probability density functions (pdfs) clearly indicates that the mean curvature of the flame kernel configuration has a major influence on the propagation behavior of the flame. For the planar flame configuration the density-weighted displacement speed is found to be fairly constant throughout the flame brush, in good agreement with previous DNS results. By contrast, for the flame kernel configuration the density-weighted displacement speed is found to vary strongly through the flame brush, changing from values on the order of the corresponding laminar flame speed near the fresh gas side to considerably smaller values near the burned gas side. The joint pdfs of displacement speed and its components with curvature are extensively studied, allowing for an explanation of the observed phenomena in terms of local flame geometry and its interaction with the turbulent flow fielItem Open Access On mathematical modelling of insect flight dynamics in the context of micro air vehicles(IOP Publishing, 2006-07-10) Zbikowski, Rafal; Ansar, Salman A.; Knowles, KevinThis paper discusses several aspects of mathematical modelling relevant to the flight dynamics of insect flight in the context of insect-like flapping wing micro air vehicles (MAVs). MAVs are defined as flying vehicles ca six inch in size (hand-held) and are developed to reconnoitre in confined spaces (inside buildings, tunnels etc). This requires power-efficient, highly-manoeuvrable, low-speed flight with stable hover. All of these attributes are present in insect flight and hence the focus of reproducing the functionality of insect flight by engineering means. This can only be achieved if qualitative insight is accompanied by appropriate quantitative analysis, especially in the context of flight dynamics, as flight dynamics underpin the desirable manoeuvrability. We consider two aspects of mathematical modelling for insect flight dynamics. The first one is theoretical (computational), as opposed to empirical, generation of the aerodynamic data required for the six-degrees-of-freedom equations of motion. For these purposes we first explain insect wing kinematics and the salient features of the corresponding flow. In this context, we show that aerodynamic modelling is a feasible option for certain flight regimes, focussing on a successful example of modelling hover. Such modelling progresses from first principles of fluid mechanics, but relies on simplifications justified by the known flow phenomenology and/or geometric and kinematic symmetries. In particular, this is relevant to six types of fundamental manoeuvres, which we define as those steady flight conditions for which only one component of both the translational and rotational body velocities is non-zero (and constant). The second aspect of mathematical modelling for insect flight dynamics addressed here deals with the periodic character of the aerodynamic force and moment production. This leads to consideration of the types of solutions of nonlinear equations forced by nonlinear oscillations. In particular, the existence of non-periodic solutions of equations of motion is of practical interest, since this allows steady recitilinear flight. Progress in both aspects of mathematical modelling for insect flight will require further advances in aerodynamics of insect-like flapping. Improved aerodynamic modelling and computational fluid dynamics (CFD) calculations are required. These theoretical advances must be accompanied by further flow visualisation and measurement to validate both the aerodynamic modelling and CFD predictions.Item Open Access Wear debris: basic features and machine health diagnostics(British Institute of Non-destructive Testing, 2006-08-01) Khan, M. A.; Starr, Andrew G.Modern high speed and power machinery components like gears, bearings, pumps, hydraulics and motors normally suffer from wear phenomena during operation. The study of wear debris can help estimate the condition of the surface of a component, so its basic features may be used to diagnose component health prior to failure. In this paper, a review is presented of the current literature related to wear debris and its analysis. The basic features of wear debris are highlighted, and their possible potential to diagnose the health of machine components is discussed. The basic features of wear debris have been classified with respect to the approach of measurement for component health diagnostics. In addition, each feature has been detailed with its possible measurement descriptors, its trend during machine component operation, and its distinct health diagnostics capability. Finally the paper proposes advances in machine component health diagnostics solution, by optimising the diagnostic capabilities of basic wear debris features.Item Open Access A knowledge based expert system for moulded part design(Design Society, 2007) Guenov, Marin D.; Lockett, Helen L.In today's competitive market many consumer products are designed with complex curved shapes to meet customers' demands for styling and ergonomics. These styled products are commonly manufactured using moulding processes because they can produce a wide range of freeform shapes at relatively low cost. However, although injection moulding and metal casting allow a great deal of design freedom they also make significant demands on the designer to ensure that parts are designed with due regard for manufacturability. This paper describes a knowledge based moulding advisor that has been developed to provide design for moulding advice to designers during the design process. The main contributions of the research are the development of a hierarchical knowledge representation to allow moulding advice to be generated at different levels of detail and the integration of the expert system with a geometric part description extracted from a Computer Aided Design (CAD) solid model. A demonstrator for the manufacturing advisor has been implemented using the expert system shell CLIPS and integrated with CAD using feature recognition. The moulding advisor is able to generate tailored design for moulding advice for a range of manufacturing processes and materials and evaluate the manufacturability of a designed part at the feature level. The paper provides a case study for a simple moulded test part.Item Open Access Redesign of an industry test for hot tearing of high performance aluminium casting alloys using casting simulation software(Minerals, Metals & Materials Society, 2007) Smith, A. C. M.; Jolly, Mark R.Hot tearing propensity in aluminium alloys is commonly measured using dog-bone and ring tests. Hot tearing occurs as a result of a number of factors including; level of stress and strain, hot spots and nucleation sites. This paper presents the results of a study to redesign a dog-bone type hot tear test using casting simulation software to ensure that the location of the tearing was always in the same location. In the simulation of the original five fingered die both the stress and strain were sufficiently high for hot tearing but there was no defined hot spot implying that the random hot tear locations would result depending upon suitable nucleation sites. A number of design iterations were carried out to produce more focussed hot spots and to ensure that the die was easy to manufacture and use, and was economically viable.