School of Engineering (SoE)
Permanent URI for this community
Browse
Browsing School of Engineering (SoE) by Title
Now showing 1 - 20 of 2123
Results Per Page
Sort Options
Item Open Access 1966 international toy fair Nuremberg 13 - 18 February(College of Aeronautics, 1966-02) Smith, Charles E.Nuremberg is a magic city. For one week each February this quaint but bustling place becomes an international wonderland. Not only is a fortune in toy business transacted but a very warm and human thing takes place. Visitors renew old associations and make new ones. Germans, Amercians, Britons, Poles, Belgians, French, Italians, Czechs, Swedes, Danes, Russians, Orientals, and others are involved in the largest display of toys in the world; and with each other, Peoples attitudes toward merchandise become stereotyped after a number of years in the toy business. But their attitudes and behavior toward their one time a year friends take on a new vitality each succeeding year. For American toy buyers the Nuremberg Spielwarenmesse (Toy Fair) offers a convenience of shopping not found elsewhere. The slick, high pressure salesmanship of New York is absent here. It is truly a buyers market. For the American toy manufacturer, Nuremberg affords 4 he opportunity to broaden his market and sources of supply as well as the chance to look for hew items, and even more important, new ideas. The exhibitions are held in five connecting buildings and there is an ample sprinkling of restaurants, snack bars, and vendors purveying the popular Nuremberg bratwurst. These are small sausages served with or without sauer- kraut and mustard. The buildings are well lit and well heated. This year these pleasant physical conditions were supplemented by unseasonably warm, clear weather.Item Open Access 2-port as an anlalogue of the Lorentz transformation of special relativity theory(College of Aeronautics, 1961-04) Deards, S. R.If the variables associated with a linear resistance 2-port are identified with the variables of special relativity theory, it is shown that a resistance 2-port transforms its port variables according to the Lorentz equations.Item Open Access A 3D extension to cortex like mechanisms for 3D object class recognition(2012-06-21T00:00:00Z) Flitton, Greg T.; Breckon, Toby P.; Megherbi, NajlaWe introduce a novel 3D extension to the hierarchical visual cortex model used for prior work in 2D object recognition. Prior work on the use of the visual cortex standard model for the explicit task of object class recognition has solely concentrated on 2D imagery. In this paper we discuss the explicit 3D extension of each layer in this visual cortex model hierarchy for use in object recognition in 3D volumetric imagery. We apply this extended methodology to the automatic detection of a class of threat items in Computed Tomography (CT) security baggage imagery. The CT imagery suffers from poor resolution and a large number of artefacts generated through the presence of metallic objects. In our examination of recognition performance we make a comparison to a codebook approach derived from a 3D SIFT descriptor and demonstrate that the visual cortex method out-performs in this imagery. Recognition rates in excess of 95% with minimal false positive rates are demonstrated in the detection of a range of threat itemsItem Open Access 3D planar velocity measurements, using Mach-Zehnder interferometric-filter-based planar Doppler velocimetry (MZI-PDV) and imaging fibre bundles(2008-12-31T00:00:00Z) Lu, Z. H.; Charrett, Thomas O. H.; Ford, Helen D.; Tatam, Ralph P.; David, Sampson; Stephen, Collins; Kyunghwan, Oh; Ryozo, YamauchiThree component planar flow-field measurements are made using imaging fibre bundles to port different views of the measurement plane, defined by a laser light sheet, to a single imaging head. The Doppler frequency shifts of light scattered by particles entrained in the flow are transduced to intensity variations using a Mach-Zehnder interferometric filter. The free spectral range of the filter can be selected by adjusting the optical path difference of the interferometer. This allows the velocity measurement range, sensitivity and resolution to be varied. Any laser wavelength may be used. A phase locking system has been designed to stabilise the interferometric filter.Item Open Access 6U CubeSat design for Earth observation with 6.5m GSD, five spectral bands and 14Mbps downlink(Royal Aeronautical Society, 2010-11-30T00:00:00Z) Tsitas, S. R.; Kingston, JenniferThe design of a 6U Cube Sat including spacecraft systems and imagine payload is described for an Earth observation mission. From a Sun synchronous orbit at an altitude of 600km the design enables imaging with a 6.5m GSD, an optical MTF (on axis) of >59% at half Nyquist and >35% at Nyquist, a 26km swath, 12 bit digitisation and SNR of 120-200:one in five spectral bands; blue, green, red, red edge and near infrared. Data can be downlinked at the rate of 14 Mbps to a 3.7m S band ground station. This design allows an 8kg Cube Sat to perform Earth observation missions equivalent to those of current 50-150kg microsatellites, with a corresponding reduction in cost.Item Open Access Ablation studies of low melting point bodies in a pre-heated supersonic air stream(College of Aeronautics, 1960-02) Cleaver, J. W.This report is an investigation into the melting of axi-symmetric and two-dimensional bogies at a Mach No. of M[infinity] = 1.78 and stagnation temperatures up to 550 [degrees]K. In this temperature range, the most suitable material for the models was found to be an eutectic tin-lead alloy a melting point of 456 [degrees]K. For the cone and hemisphere-cone models two distinct modes of melting were observed. In cases where the estimated equilibrium surface temperature (Tw)o was approximately equal to the material melting temperature Tm, melting occurred only at the stagnation point of the model and was such that a flat surface normal to the gas stream always resulted. If the average rate of heat transfer at the air-liquid interface be defined as qi = LmPm x, where Lm is the latent heat of fusion, Pm is the density of the material and x is the rate of recession of the flat surface, it is found that qi decreases with increase of the radius of the flat nose. A very approximate theory is found to show some agreement with the experimental rates of heat transfer. When (Tw)o was considerably greater than Tm the flat surface was no longer preserved and the resulting steady ablating shape was paraboloidal in nature. When this occurred x was usually constant. This allowed some average steady state heat transfer rates to be evaluated and compared with theory. Preliminary tests were also made with a two-dimensional wedge model.Item Open Access Abradable stator gas turbine labyrinth seals(Cranfield University, 1999-03) Allcock, D. C. J.; Ivey, Paul C.This is a detailed study into the internal aerodynamics of labyrinth seals, with pmic| reference to the effects of abradable honeycomb stators on labyrinth seal leakage.- A extensive experimental programme established tables of friction factor for three different grades of honeycomb used by industry, and examined the effect of both Reynolds number and clearance on these friction factors. The friction factor associated with a aerodynamically smooth surface was also experimentally determined in order to establish the experimental method. The experimental data was used to model the different grades of honeycomb used as stator material in numerical simulations of a number labyrinth seals, and allowed for comparison of the leakage associated with both smooth and abradable stator straight through labyrinth seals. Step-up and step-down seal geometries were also considered, and the effects of pressure ratio, clearance and rotation on labyrinth seal leakage was examined on all modelled seal types. This numerically generated leakage data was comprehensive enough to allow for the creation of a second-generation one-dimensional labyrinth seal leakage predictor tool of the type used by design engineers in network models. This tool accounts for stator material, seal clearance, overall pressure ratio, rotation and seal geometry, and the accuracy associated with this tool allows labyrinth seal leakage to b predicted to within 10%. Functions of discharge coefficient and carry-over factor obtained from the numerical predictions are used by this tool, and as such it is capable of dealing with a large number of different operating conditions for all the seal types modelled.Item Open Access Absence behavior as traffic crash predictor in bus drivers(Elsevier Science B.V., Amsterdam., 2009-12-31T00:00:00Z) af Wåhlberg, Anders E.; Dorn, LisaProblem: Various indicators of health have been shown to be associated with traffic crash involvement. As general health is also related to absence from work, the latter variable may be more strongly related to crashes, especially for professional drivers. Method: Bus driver absence from work was analyzed in association with their crash records. Two British samples and one Swedish sample were used. Results: One of the British samples yielded fair correlation between crash record and absence, while for the other the effect was restricted to the first three months of driving. The Swedish data had effects in the expected direction but these were not significant. Discussion: The use of an indirect, overall measurement of health, may be a viable method for predicting the traffic crash involvement for professional drivers, although replications are needed in larger samples and other populations. Impact on industry: The use of absence records for the identification of at risk drivers would seem to be a simple and useful method for companies with major fleets, and it also shows the importance of promoting employee health and well being at work as a potential method of reducing the cost, not only of absenteeism, but also of crashes in company vehicles.Item Open Access An abstract of a paper by D. Battat 'a new kinetic approach to the shock wave structure'(College of Aeronautics, 1966)Item Open Access Accuracy of high order density based compressible methods in low mach vortical flows(Cranfield University, 2013) Shanmuganathan, Sanjeev; Thornber, BenA new, well posed, two-dimensional two-mode incompressible Kelvin{Helmholtz instability test case has been chosen to explore the ability of a compressible algorithm, Godunov-type scheme with the low Mach number correction, which can be used for simulations involving low Mach numbers, to capture the observed vortex pairing process due to the initial Kelvin{Helmholtz instability growth on low resolution grid. The order of accuracy, 2nd and 5th , of the compressible algorithm is also highlighted. The observed vortex pairing results and the corresponding momentum thickness of the mixing layer against time are compared with results obtained using the same compressible algorithm but without the low Mach number correction and three other methods, a Lagrange remap method where the Lagrange phase is 2nd order accurate in space and time while the remap phase is 3rd order accurate in space and 2nd order accurate in time, a 5th order accurate in space and time nite di erence type method based on the wave propagation algorithm and a 5th order spatial and 3rd order temporal accurate Godunov method utilising the SLAU numerical ux with low Mach capture property. The ability of the compressible ow solver of the commercial software, ANSYS Fluent, in solving low Mach ows is also examined for both implicit and explicit methods provided in the compressible ow solver. In the present two dimensional two mode incompressible Kelvin{Helmholtz instability test case, the ow conditions, stream velocities, length-scales and Reynolds numbers, are taken from an experiment conducted on the observation of vortex pairing process. Three di erent values of low Mach numbers, 0:2, 0:02 and 0:002 have been tested on grid resolutions of 24 24, 32 32, 48 48 and 64 64 on all the di erent numerical approaches. The results obtained show the vortex pairing process can be captured on a low grid resolution with the low Mach number correction applied down to 0:002 with 2nd and 5th order Godunovtype methods. Results also demonstrate clearly that a speci cally designed low Mach correction or ux is required for all algorithms except the Lagrange-remap approach, where dissipation is independent of Mach number. ANSYS Fluent's compressible ow solver with the implicit time stepping method also captures the vortex pairing on low resolutions but excessive dissipation prevents the instability growth when explicit time stepping method is applied.Item Open Access Acoustic emission detection of fatigue crack propagation in a power station steam chest environment(Cranfield University, 1997-02) Cook, J.; Bannister, R. H.This thesis addresses the problem of detecting and positively identifying the approximately known acoustic emission signatures produced through fatigue crack propagation in power station steam chests. This work includes extensive laboratory fatigue testing to produce and record signatures in specimens fabricated from the steam chest steel, on-site recording of the ambience noise levels from a fully operating oil-burning power station and develops and demonstrates the effectiveness of various signal processing techniques at extracting the signatures embedded in the noise. This noise is high amplitude, giving us a low signal to noise ratio, and is broad in the frequency domain, with both regular and irregular high-amplitude metallic noise transients that cover the entire frequency range of interest. It is therefore essential to use sophisticated signal post-processing techniques to detect and to identify the crack signatures. The post-processing techniques developed and employed include time-frequency transformations, matched filters and signal expansion filters implemented in both in the time domain and in various two-dimensional time-frequency domains. From a performance comparison, both on the experimentally recorded data and on data digitally generated for the purpose, we determine the optimum signal processing method for our requirements and provide an assessment of the relative computational efficiencies. Generated for comparison are spurious but similar signatures characteristic of the power station steam chest environment; oxide crushing within an existing dormant crack and stress corrosion cracking signatures produced by the same steel constantly loaded in a corrosive environment. It is demonstrated that there is sufficient distinction between these signatures and those produced by crack propagation.Item Open Access Acoustic emission during run-up and run-down of a power generation turbine.(Elsevier Science B.V., Amsterdam., 2004-05-01T00:00:00Z) Zuluaga-Giraldo, C.; Mba, David; Smart, M.The measurement of acoustic emission (AE) activity at the bearings of power generation turbines is evolving into a viable complementary diagnostic technique especially adept at indicating the early stages of shaft-seal rubbing. This paper reports on an ongoing investigation on the application of acoustic emission for shaft-seal rub detection in power generation turbines. A pre- requisite in developing such a technique requires an understanding of the operational AE background noise. The detection of shaft-seal, and blade-case, rubbing with AE has been reported [Electrical Eng. Japan 110 (2) (1990); Joint ASME/IEEE Power Generation Conference, October 4–8, 1981, St. Louis, MI, USA; International Conference on Condition Monitoring. Oxford, UK, July 2–4, 2003]. In these instances, the observations of AE activity were associated with particular dynamic and process conditions known to cause such defects. However, the effect of variations of turbine loading on AE activity is unknown. This report presents observations of AE activity during the run-up and run-down of a 500 MW steam turbine and is the first known document detailing correlations between AE, vibration and turbine loadItem Open Access Acoustic emission pulse analysis: an integrated system for transducer calibration and signal processing(1982-10) Oliveras, Juan M.; Bannister, R. H.The present thesis covers the pioneering effort of establishing an infrastructure for conducting research into the analysis of Acoustic Emission signatures, with emphasis being placed upon the recovery of the true surface waveform for a given transient input. The topics covered in this work are: The p·rovi s ion of the necessary computer software for the handling and processing of the data. Here, a method is included for the correction of phase errors introduced by the sampling/multiplexing of ·the signals, which provides the basis for the implementation of data convolution.techniques in the frequency domain. J°he development of an experimental rig and source of excitation, later applied to the design of transducers. The development of a new transducer configuration, capable of producing a relatively flat frequency response (±7dB) over the frequency range 300 KHz - 2 MHz. The development of a procedure for the calibration of transducers, based upon a modified reciprocity method. The technique produces the calibration of transducers in relative terms, requiring a comple- . . mentary method to provide the reference level for the calibration. As a means of assessing the proposed techniques, the transducer calibration was applied to the de-convolution of pulses generated with a step forcing function, and the results compared with an equivalent theoretical model previously published.Item Open Access Acoustic Emission Signal Classification in Condition Monitoring Using the Kolmogorov-Smirnov Statistic.(2001-01-01T00:00:00Z) Hall, L. D.; Mba, David; Bannister, R. H.Acoustic emission (AE) measurement at the bearings of rotating machinery has become a useful tool for diagnosing incipient fault conditions. In particular, AE can be used to detect unwanted intermittent or partial rubbing between a rotating central shaft and surrounding stationary components. This is a particular problem encountered in gas turbines used for power generation. For successful fault diagnosis, it is important to adopt AE signal analysis techniques capable of distinguishing between various types of rub mechanisms. It is also useful to develop techniques for inferring information such as the severity of rubbing or the type of seal material making contact on the shaft. It is proposed that modelling the cumulative distribution function of rub-induced AE signals with respect to appropriate theoretical distributions, and quantifying the goodness of fit with the Kolmogorov-Smirnov (KS) statistic, offer a suitable signal feature for diagnosis. This paper demonstrates the successful use of the KS feature for discriminating different classes of shaft- seal rubbing. A hierarchical cluster algorithm was employed for grouping extracted KS values. AE rub signals were simulated with various metallic seals and measured at the journal bearings of a test rig rotating at approximately 1500 rev/min. Also, the KS classification results were directly compared withmore established AE feature vectors.Item Open Access Acoustic Emission Waveform Changes for Varying Seeded Defect Sizes.(2006-01-01T00:00:00Z) Al-Dossary, Saad; Raja, Hamzah R. I.; Mba, DavidThe investigation reported in this paper was centered on the application of the Acoustic Emissions (AE) technology for characterising the defect sizes on a radially loaded bearing. The aim of this investigation was to ascertain the relationship between the duration of AE transient bursts associated with seeded defects to the actual geometric size of the defect. It is concluded that the geometric defect size can be determined from the AE waveform.Item Open Access Acoustic Emissions and monitoring bearing health(Taylor & Francis, 2003-01-01T00:00:00Z) Mba, DavidAcoustic emission (AE) was originally developed for non-destructive testing of static structures. however, over the years its application has been extended to health monitoring of rotating machines and bearings. It offers the advantage of earlier defect detection in comparison to vibration analysis. Current methodologies of applying AE for bearing diagnosis are reviewed. The investigation reported in this paper was centered on the application of standard acoustic emissions IAE) characteristic parameters on a radially loaded bearing. An experimental test-rig was designed to allow seeded defects on the inner and outer race. It is concluded that irrespective of the radial load, rotational speed and high levels of background noise. simple AE parameters such as e.m.s. and AE counts provided an indication of bearing defect. In addition to validating already established AE techniques, this investigation focuses on establishing an appropriate threshold level for AE counts.Item Open Access Acoustic emissions diagnosis of rotor-stator rubs using the KS statistic.(Elsevier Science B.V., Amsterdam, 2004-07-01T00:00:00Z) Hall, L. D.; Mba, DavidAcoustic emission (AE) measurement at the bearings of rotating machinery has become a useful tool for diagnosing incipient fault conditions. In particular, AE can be used to detect unwanted intermittent or partial rubbing between a rotating central shaft and surrounding stationary components. This is a particular problem encountered in turbines used for power generation. For successful fault diagnosis, it is important to adopt AE signal analysis techniques capable of distinguishing between various types of rub mechanisms. It is also useful to develop techniques for inferring information such as the severity of rubbing or the type of seal material making contact on the shaft. It is proposed that modelling the cumulative distribution function of rub-induced AE signals with respect to appropriate theoretical distributions, and quantifying the goodness of fit with the Kolmogorov–Smirnov (KS) statistic, offers a suitable signal feature for diagnosis. This paper demonstrates the successful use of the KS feature for discriminating different classes of shaft-seal rubbing.Item Open Access Acquisition cost estimating methodology for aircraft conceptual design(Cranfield University, 2008) Zhao, Tienan; Fielding, JohnThe research was conducted in the light of a training programme which will train a total of 150 engineers of AVIC I in Cranfield University during a period of 3 years. Cost has become an essential driver to aircraft design, as well as performances due to either the limited defence budget or competitive airline market. Consequently, knowing the possible cost prior to making actual expenditure will help managers to make proper decisions and allocate resources efficiently, and designers to optimize their work. Existing aircraft cost estimating models are outdated and mainly based on a database including both military and civil aircraft with various missions. This research concentrated on commercial jet aircraft and was to develop a suitable acquisition cost estimating methodology for conceptual design from a commercial aircraft manufacturer’s perspective. The literature reviewing took a comprehensive overview of some widely-applied cost estimating methods: Analogy, Parametric, Bottom-up, Feature-based costing, Activitybased costing (ABC), Expert judgement, and etc. Some practical cost models were also reviewed to learn the application of cost estimating in the aerospace industry. Then, analogy and parametric approaches were selected to perform the methodology development considering the limited data available at the conceptual design phase. An investigation was deployed to identify the actual problems in practice. The results helped to recognize the needs of industry. Also, the preparation works for development are presented to understand the environment. With subjective judgement and statistical techniques, a series of cost estimating relationships (CERs) were achieved, in which some historic explanatory parameters remained or were eliminated, and some new ones introduced. Size of aircraft became another variable besides weight. As to engines, all developed explanatory variables have been revealed in prior researches. The validation of CERs proves that they can provide reliable cost estimates with high accuracy and can be applied to conceptual design. In addition, a case study was conducted using a baseline aircraft defined in the group design project (GDP) and presents cost forecasting for the proposed aircraft. At last, discussion and conclusion presents an overview of the research. A framework for cost estimating system can be educed. Also, the future work is proposed for in-depth research.Item Open Access The acquisition of high speed skills. First progress report on D.S.I.R. research project(College of Aeronautics, 1963-04) Whitfield, D.N/AItem Open Access Active Aerodynamic Control of Heavy Goods Vehicles(Cranfield University, 2013-04) Barden, Jason; Garry, Kevin P.; Whidborne, James F.Most heavy goods vehicles in service today are fitted with add-on aerodynamic devices. The most common of which is the cab-mounted roof deflector. Such devices provide appreciable drag savings, however, they are often not optimised for the trailer. When a wind yaw angle is present, their savings also diminish as the yaw angle increases. The work conducted within this thesis investigated the possibility of using an adjustable deflector for active flow control. The optimum deflector height for a given trailer height was initially investigated using wind tunnel testing. The variation of this optimum with yaw angle and container separation was then investigated. From the results a 3D look-up table was generated. A control scheme was proposed that used the 3D look-up table requiring only three measurable inputs. The three inputs required were: the wind yaw angle, the container height and the container separation. A pressure differential located on the deflector was found to linearly relate to the wind yaw angle. This relationship allowed on-road measurement of the wind yaw angle and therefore enabled the development of a prototype controller. Extensive on-road testing and unsteady computational simulation were conducted. The results obtained indicated a mean yaw angle magnitude of around 5 perturbed by four fundamental low frequencies. These frequencies were identified in the runs conducted over the test period and an average frequency established. Higher frequency disturbances were attributed to the wakes of leading heavy goods vehicles and were filtered by a suitably chosen numerical filter. Finally, an estimation of the efficiency of the active device was made using a combination of simulation and full scale testing. From the results obtained, an optimised deflector generated an average drag reduction of 7.4%. An estimated additional drag reduction of 1.9% over the optimised deflector was predicted through use of an active system.