Browsing by Author "Alhashan, Taihiret"

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    Experimental investigation of bubble activity at an early stage using te acoustic emission technique in two-phase flow systems.
    (2018-01) Alhashan, Taihiret; Addali, Abdulmajid; Teixeira, Joao Amaral
    This thesis presents an experimental investigation and identifies the feasibility of the use of AE technology to detect and monitor both early stage bubble occurrence and throughout the boiling process. The research programme also included monitoring of bubble formation/collapse phenomena in ball and globe valves using AE techniques. It was demonstrated that an AE piezoelectric sensor can detect pressure pulses associated with bubble occurrence during pool boiling and cavitation in flow through valves. For the pool boiling test, a dedicated test-rig was used to diagnose and monitor bubble formation. It was concluded that bubble occurrence is detectable with AE techniques and there is a clear relationship between increasing AE levels and bubble formation during the boiling process. For the valve tests, a purpose-built test-rig was used to monitor and detect cavitation phenomena with various flow rates and different valve opening percentages. It was shown that AE will detect incipient cavitation and that there is a clear correlation between AE signal levels and the flow rate through the ball and globe valves at a constant opening percentage. This investigation successfully demonstrated that AE monitoring is capable of early diagnosis and monitoring of bubble formation phenomena in boiling processes and valves. This research developed a methodology and prototype framework for using the AE technique for detection and diagnosis of early bubble formation and collapse, allowing cavitation development to be tracked, and maintenance activity to be planned to maximise equipment life and minimise downtime.
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    Experimental investigation of the influences of different liquid types on acoustic emission energy levels during the bubble formation process
    (Springer, 2017-09-08) Alhashan, Taihiret; Addali, Abdulmajid; Teixeira, Joao Amaral; Naid, Abdelhamid
    Bubble formation phenomena in a two-phase gas/liquid system occur in many industries that involve boiling; such as desalination stations, nuclear reactors, chemical plants, and fluid piping transportation and processes. Bubble formation phenomena cause problems, such as a decrease in equipment efficiency, vibration, noise, and solid surface erosion. Applications of the acoustic emission (AE) technique for monitoring bubble formation and burst stages in boiling processes are marginal in terms of extension in comparison to other applications of the AE technique. The use of the AE technique in this experimental investigation covers the frequency range between 100 and 1000 kHz, showing that the AE sensor can detect acoustic emissions from an occurrence of bubble formation. Statistically, it was found that the best AE parameter indicator for bubble formation was AE-RMS (root mean square).
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    ItemOpen Access
    Exploration of the possibility of acoustic emission technique in detection and diagnosis of bubble formation and collapse in valves
    (International Organization of Scientific Research, 2016-11-30) Alhashan, Taihiret; Addali, Abdulmajid; Amaral Teixeira, Joao
    The application of acoustic emission (AE) technique in detection and monitoring of bubble formation and collapse in valves are presented in this review. The generation of AE signals and the basic compositions of AE detection system are briefly explained. The applications of AE technique in valves are focused on condition monitoring and detection bubble formation (bubble cavitation), and leakage of water through valves. All results prove that the AE technique works well for detection and diagnosis of failures during valves.
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    Identifying bubble occurance during pool boiling employing acoustic emission technique
    (Elsevier, 2017-12-11) Alhashan, Taihiret; Addali, Abdulmajid; Teixeira, Joao Amaral; Elhashan, Said
    This paper reports the results of a study for the early detection of bubble formation during the boiling process using acoustic emission. The feasibility of using AE technology to detect and monitor early bubble formation during pool boiling is assessed, and the results show that AE technology is an affective tool for this purpose. There is a clear correlation between the AE signal levels and height of the water level above the heated surface during the boiling process. The different types of heated fluid influence AE energy levels during the bubble formation process. Statistically, it was found that the best AE parameters to indicate bubble formation were AE-RMS, AE-Energy and AE-Amplitude.
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    Investigation of the influence of flow rate on bubble formation and collapse in ball values at various opening percentages using an AE technique
    (The British Institute of Non-Destructive Testing, 2018-06-01) Alhashan, Taihiret; Addali, Abdulmajid; Teixeira, Joao Amaral
    Ball valves are popularly used in many different industrial processes and hydraulic systems because of their light weight and simple structure. However, they are susceptible to cavitation phenomena and the growth and collapse of the bubbles formed lead to erosion and pitting of the metal surfaces. This paper presents the monitoring and detection of bubble formation at an early stage in a ball valve using acoustic emission (AE). It is shown that AE will detect incipient cavitation and that there is a clear correlation between AE signal level and the flow rate through the ball valve at a constant opening percentage.