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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.
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.
Open Access
2D low bypass-ratio turbofan modelling
(Cranfield University, 2004-10) Li, Man San; Pilidis, Pericles
Turbofan engines are normally bench-tested with a standard flared bellmouth intake. This is different from the aircraft situation. As a result, an engine installation may experience a degree of inlet flow distortion not normally present during tests. It is, therefore, very desirable to understand the effect of any radial inlet total pressure loss on turbofan engine performance. Steady-state radial inlet distortion may occur, for example, as a result of boundary layers. An early awareness on distortion tolerance is very important to enable the prediction of surge margin. However, synthesis of turbofan performance with distortion is currently not available. This work therefore, investigates in detail the modelling of the fan component of low bypass-ratio turbofan engines within an engine performance simulation program. For example, the air flow in turbofan engines is split after the fan between the core gas generator and the bypass flow. A fan model must be able to simulate the required flow and thermodynamic parameters to the core and bypass flows at fan exit. Conventional fan models, however, are restricted to a fixed bypass ratio versus non-dimensional speed schedule at which the fan has been rig-tested. The fan component also experiences a varying degree of inlet total pressure distortion. Existing engine simulation fan models are unable to quantify this effect on fan performance and on engine performance. The turbofan modelling work conducted here is preceded by an analysis of rig data of Low Bypass Ratio (LBPR) turbo-fan engines to give a firm background basis. The engine modelling uses the component-based iterative solution method for gas turbine performance calculations. Two key outcomes of the work are the following. Firstly, LBPR fans have large circumferential fan exit flow variations as well as radial variations. This includes total temperature profiles which are an order of magnitude higher than those for High Bypass Ratio Fans (HBPR) fans. Secondly, it is inconclusive, at a given non-dimensional speed and flow function, as to whether fan exit profiles are independent of BPR. The fan radial profile modelling starts from an existing modification of a conventional compressor characteristic but also models in 2-D with dependency on the fan exit radial position. The inlet distortion fan model uses a throughflow streamline curvature for radial performance prediction coupled to the 2-D-LBPR fan model. Against this background, a new fan characteristic model has been devised for LBPR fans. In addition, a new inlet distortion performance model has been developed which is able to predict engine performance changes with radial inlet total pressure distortion.
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, Najla
We 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 items
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, Yamauchi
Three 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.
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, Jennifer
The 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.
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.
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.
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, Lisa
Problem: 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.
Open Access
An abstract of a paper by D. Battat 'a new kinetic approach to the shock wave structure'
(College of Aeronautics, 1966)
Open Access
Accuracy of high order density based compressible methods in low mach vortical flows
(Cranfield University, 2013) Shanmuganathan, Sanjeev; Thornber, Ben
A 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.
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.
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 load
Open Access
Acoustic Emission for the detection of shaft-to-seal rubbing in large power generation turbines
(2006-01-01T00:00:00Z) Leahy, M.; Mba, David; Cooper, P.; Montgomery, A.; Owen, D.
An empirical investigation is undertaken in order to assess the potential of the AE technique for the detection of seal-to-rotor rubbing in steam turbines. Rubbing was induced at various axial locations along a 4 ½ tonne test rotor, rotating at 3000 rpm and supported by 7” (178mm) journal bearings. This paper examines the capabilities of bearing mounted AE transducers for the detection of seal-torotor rubbi
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.
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.
Open Access
Acoustic Emission Waveform Changes for Varying Seeded Defect Sizes.
(2006-01-01T00:00:00Z) Al-Dossary, Saad; Raja, Hamzah R. I.; Mba, David
The 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.
Open Access
Acoustic Emissions and monitoring bearing health
(Taylor & Francis, 2003-01-01T00:00:00Z) Mba, David
Acoustic 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.
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, David
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 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.
Open Access
The acoustics of racing engine intake systems
(Elsevier, 2004-04-06) Harrison, M. F.; Dunkley, A.
Naturally aspirated racing engines have tuned intake systems and can now achieve volumetric efficiencies in excess of 125% and peak engine speeds in excess of 18,000 rev/min. Engines designed for single seater racing commonly dispense with the intake manifold and its convoluted and restricting flow path preferring single lengths of pipe feeding each cylinder separately. An investigation into the intake process on a single cylinder racing engine has shown that inertial ram effects make a strong contribution to the intake process at high engine speeds whereas acoustic resonance effects are more important to the rather weak wave action that occurs at low engine speeds. An acoustic model of the resonant wave action has proved useful in distinguishing between these two effects. The attributes of the acoustic model have been compared to those of more traditional time-marching gas-dynamics calculation methods. A decoupled hybrid method has been shown to yield calculations of the wave dynamics in the intake system of a single cylinder racing engine that show fair agreement with measured results up to the 10th harmonic of the engine cycle frequency. In a case study, the intake characteristics of a single cylinder racing engine have been shown to differ only slightly from those expected from the V10 engine on which it is based, although this will only be the case when the dimensions of the intake system are chosen appropriately.

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