1,720,970 research outputs found
'Modelling and validation of a guided acoustic wave temperature monitoring system': Dataset
No full textDataset supports MDPI Sensors Special Issue "Sensors for Severe Environments" article. The article covers the development of a guided wave based temperature monitoring system, which includes a guide on building a COMSOL model and experimental verification. The dataset contains COMSOL models, raw data, and MATLAB code for calculating time of flight.
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Dataset supporting MDPI Sensors article "Temperature hotspot detection on printed circuit boards (PCBs) using ultrasonic guided waves - A machine learning approach"
No full textThis dataset is supporting the publication "Temperature hotspot detection on printed circuit boards (PCBs) using ultrasonic guided waves - A machine learning approach".
Data exported from COMSOL simulations of ultrasonic guided wave propagation across Printed Circuit Boards (PCBs) with temperature hotspots at various component positions. For use in training/testing machine learning classification models. Data contained within MATLAB .mat data ensemble.</span
Investigating how predictions of reverberation time can be affected by incorrect absorption coefficient assumptions
No full textThe methods of predicting reverberation time for any given space rely on the correct choice of absorption coefficients for the room’s surfaces. For many materials the absorption coefficient can be found in literature, taken from measurements carried out using an impedance tube or a reverberation chamber. For other materials finding the absorption coefficient may not be possible, either because the material has not been measured before, or because the construction of the material is different from that found in literature. In this scenario an acoustic consultant will have to choose the closest material they can find, based on what it’s made of, its thickness, its construction, and its positioning. This introduces a degree of error to the acoustic modelling process which may have an impact on the predicted reverberation time, as well as subsequent predictions such as speech intelligibility. This paper examines the variance in reverberation time predictions caused by the use of incorrect absorption coefficients, and compares the results to measurements taken in accordance with ISO 3382-2:2008. This paper also investigates if the use of an acoustic impedance “gun” (by Microflown) is suitable for use in measuring the in-situ absorption coefficients of every surface of a room, to be used in the prediction of reverberation time using acoustic modelling software. If the acoustic impedance of materials can be measured in-situ the calculated absorption coefficient is likely to be more suitable for use in determining the reverberation time of the space, as opposed to using assumed values of absorption taken from literature
Temperature monitoring of nozzle guide vanes using ultrasonic guided waves
No full textThis thesis explores the use of ultrasonic guided waves for the online temperature monitoring of nozzle guide vanes (NGVs). These components are found within the turbine section of jet engines, operated at up to 1800°C. A literature review covering the currently used methods of temperature monitoring for NGVs has identified the potential of a new online sensor. Ultrasonic guided waves can propagate through thin structures such as NGVs, where different modes of propagation exhibit differing properties in respect to their sensitivity to temperature, amplitude, and dispersiveness. The complex geometry of NGVs represents a challenge to the implementation of such a system. Cooling hole arrays and multi-layered thermal barrier coatings are likely to have a considerable impact on wave propagation. In this study the effect of temperature, cooling hole structures, and thermal barrier coatings on wave propagation has been investigated through dispersion curve prediction, experimental measurement, and finite element simulation. An experimental test system has been developed to target modes of interest, and analyse the effect of temperature on wave propagation. The temperature sensitivities of individual modes have been measured successfully. Results are in good agreement with predicted values extracted from dispersion curves, despite the range of errors identified. A finite element model mimicking the experimental setup has been developed and validated against experimental results. The temperature range was extended up to 1000°C for an Inconel 718 plate, which is a Nickel-based super alloy typically used for jet engine components. Results continue to align with predictions at 1000°C. The effect of cooling hole structures on wave propagation are investigated through experimentation and COMSOL simulation. In general, dense hole arrays at the leading edge of a vane limit pulse-echo operation, however pitch-catch operation is still viable with careful mode and wavelength selection. In less dense areas away from the leading edge, temperature hotspot detection is possible in both configurations, although pulse-echo operation is likely to be more applicable. Sensors may need to be operated from both sides of the vane to effectively cover the whole array. Even under the favourable conditions of these models (with limited additional reflections, environmental noise, etc.) identifying changes in temperature at multiple locations is challenging, and the extent to which reflections from cooling holes can be used for this application is highly dependant on the specific geometry of the vane. The effect of thermal barrier coatings on wave propagation has been investigated through the generation of dispersion curves and the use of COMSOL simulations. The range of materials, make up of the layered structure, and the types of application methods typically used have been considered, and the effect of temperature on the system has been evaluated. Dispersion curves generated for the multi-layered composite show how the higher order modes increase in complexity in comparison with the response in a single material. Through-thickness displacement varies across the thickness as material properties vary, with the top coat often exhibiting considerably larger displacement than then other layers. Although the work carried out on a single material (Aluminium or Inconel 718) looked to have promising advantages to working at higher order modes, the application of TBCs complicates signal propagation, causing a greater number of modes to propagate with similar wave velocities, which limits the ability to target a single mode. Operating at a lower frequency where there only the two fundamental modes are present is likely to be the most effective method of targeting/identifying single modes
Development of a ‘bone stethoscope’: A system for aiding early detection of osteoporosis
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Towards in-flight temperature monitoring for nozzle guide vanes using ultrasonic guided waves
Get PDFThe temperature monitoring of nozzle guide vanes is a challenging task due to the extreme temperatures, gas pressures, and cramped conditions of aero-engines. Ultrasonic guided waves are an attractive method of temperature monitoring as the sensors can be placed outside of the gas path without influencing component operation. In this paper the suitability of using ultrasonic guided waves in the form of the S0 Lamb wave mode is investigated by comparing experimentally measured wave velocity change with temperature against theoretical wave velocity extracted from dispersion curves. Waves are transmitted through an aluminium plate using a pitch-catch wedge transducer configuration, and wave velocity is measured using across-correlation function. Temperature is controlled with a hot plate from room temperature to 100°C, and monitored using thermocouples. Results show that this transducer configuration is capable of monitoring a change in temperature based on a change in wave velocity, showing a good agreement with theoretical predictions, within 4.89+/-2.27 m/s on average. The temperature sensitivity of the system is 1.26–1.78 m/s/°C over the range 24°C–94°C. This shows the potential for a guided wave based temperature monitoring system, assuming a suitable transducer configuration can be found that is able to operate at higher temperatures. Further investigation will study the possibility of using Piezoelectric Wafer Active Sensors (PWAS) or waveguides for this application
Surface temperature condition monitoring methods for aerospace turbomachinery: exploring the use of ultrasonic guided waves
No full textTurbine blades and nozzle guide vanes (NGVs) are operated at extreme temperatures in order to maximise thermal efficiency and power output of an engine. In this paper the suitability of existing temperature monitoring systems for turbine blades and nozzle guide vanes are reviewed. Both offline and online methods are presented and their advantages and disadvantages are examined. The use of offline systems is well established but their online equivalents are difficult to implement because of the limited access to components. There is the need for an improved sensor that is capable of measuring temperature in real time with minimum interference to the operating conditions of the engine, allowing operating temperatures to be increased to the limits of the components and maximising efficiency. Acoustic monitoring techniques are already used for a large number of structural health monitoring applications and have the potential to be adapted for use in temperature monitoring for turbine blades and NGVs. High temperatures severely affect the response of ultrasonic transducers. However, waveguides and buffer rods can be used to distance transducers from extreme conditions, while piezoelectric materials such as Yttrium Calcium Oxyborate single crystals and Aluminum Nitride have been developed for use at high temperatures. A new monitoring approach based on ultrasonic guided waves is introduced in this paper. The geometry of turbine blades and NGVs allows Lamb waves to propagate through their structure, and the presence of numerous cooling holes will produce acoustic reflections that can be utilised for monitoring temperature at a number of locations. The dispersive nature of Lamb waves makes their analysis difficult; however, wave velocity in dispersive regions is particularly sensitive to changes in temperature and could be utilised for monitoring purposes. The proposed method has the potential to provide high resolution and accuracy, fast response times, and the ability to place sensors outside of the gas path. Further research is required to develop a monitoring system based on the use of guided waves in extreme environments.</p
Performance change in vocalists with variation in headphone foldback and reverberation level
No full textDataset in support of the Southampton doctoral thesis "Temperature monitoring of nozzle guide vanes using ultrasonic guided waves" dataset
No full textThis dataset contains the raw experimental data, MATLAB scripts, COMSOL models, and material properties used in the production of my thesis. Further information on the use of each file is included in 'readme' file.</span
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