A photographic probe for wet steam

Vernon, Kris (2014) A photographic probe for wet steam. EngD thesis, University of Nottingham.

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The work carried out during this engineering doctorate degree has led to significant advances in the application of photographic measurement techniques to the characterisation of coarse water in wet steam flow, with particular emphasis on the development of a compact measurement probe suitable for application in a low-pressure steam turbine. Through the application of pulsed LED illumination for the first time in a compact probe, photographs at high magnification with excellent resolution are obtainable at significantly shorter exposure times than others reported in the literature. This has the advantage of reducing motion blur enabling reliable quantitative analysis to take place.

Secondary to this, the coupling of high magnification, high resolution photography with pulsed LED illumination has been shown to provide a powerful research tool for flow visualisation across a range of applications, at an order of magnitude lower cost than commercial solutions employing pulsed laser illumination for the same purpose. This builds on the work of others elsewhere in the literature, but again has been proven at shorter exposure times enabling higher magnification with reduced motion blur.

Finally a flexible optical test rig has been designed and manufactured, to act as an experimental test-bed for both photographic and phase-Doppler measurements on two-phase steam and air-water sprays. Phase-Doppler anemometry measurements have been performed on an accelerated jet of two-phase steam in order to perform size and velocity measurement of liquid droplets. This acts as a proof-of-concept for the technique in wet steam given the appropriate optical access. In addition phase-Doppler measurements of an air-atomising water nozzle were used as a validation data set to assess the accuracy and reliability of quantitative data from the photographic probe. In this case quantitative data was extracted from the images through application of a custom-designed image processing algorithm, designed to extract droplet size and velocity information from double-exposure droplet images. In general agreement is good within 10-15% of the PDA measurements. Photographic and PDA measurements have also been taken of an LP spray nozzle, as used in the Alstom model steam turbine test facility. These tests have demonstrated significant differences in the spray characteristics when spraying into air and into vacuum conditions. This provides useful insight for the positioning and application of these spray nozzles in a steamturbine environment

Item Type: Thesis (University of Nottingham only) (EngD)
Supervisors: Azzopardi, B.J.
Hann, D.B.
Keywords: Microphotography, Equipment and supplies, Probes (Electronic instruments), Steam flow
Subjects: T Technology > TJ Mechanical engineering and machinery
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 30933
Depositing User: Airey, Ms Valerie
Date Deposited: 27 Nov 2015 10:46
Last Modified: 14 Oct 2017 08:29
URI: https://eprints.nottingham.ac.uk/id/eprint/30933

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