An investigation of the generation of Acoustic Emission from the flow of particulate solids in pipelines
- Authors: Hii, N. , Tan, Chee Keong , Wilcox, Steven , Chong, Zyh
- Date: 2013
- Type: Text , Journal article
- Relation: Powder Technology Vol. 243, no. (2013), p. 120-129
- Full Text: false
- Reviewed:
- Description: This paper is concerned with the generation of the Acoustic Emission (AE) from particulate flow and an investigation of the potential of implementing AE for flow parameters, namely the solid mass flow rate, particle velocity and size, monitoring. A series of experiments has been conducted to gather AE signals from a laboratory scale single flow-loop pneumatic conveying system. Initially, AE sensors were attached to two steel meshes which were placed with a fixed axial distance in the pipeline to study the generation of the AE and subsequently the possibility of using those generated AE to determine particle velocity in the pipeline. Particle velocities measured from this approach were compared with theoretical predictions. The results indicated that this approach could measure the mean particle velocity with reasonable accuracy. The generation of AE on five different sensor mounting locations was also studied. The results showed that sensors mounted on all those locations were able to respond to changes in the flow parameters. However, only two sensor locations (outer bend and Mesh) were chosen for further investigation. The final experimental results indicated that the AE features, namely Root-Mean-Square (RMS) and energy of the AE, are related to the changes in the flow parameters and good correlations were found. Good correlations between the RMS and energy of the AE with the momentum and kinetic energy of the particles, respectively, were also found. Overall, the studies indicated that features of AE have great potential in gas-solid two phase flow parameter monitoring. However, the studies also show that the applicability of the AE techniques to measure solid mass flow rates in practice would require tedious calibration. © 2013 Elsevier B.V.
Damage characterisation of carbon fibre reinforced composite plate using acoustic emission
- Authors: Mohammed, Bizuayehu , Tan, Chee Keong , Wilcox, Steven , Chong, Alex
- Date: 2012
- Type: Text , Conference paper
- Relation: 4th Asia-Pacific Workshop on Structural Health Monitoring p. 184-194
- Full Text: false
- Reviewed:
- Description: Acoustic Emission (AE) is a sensitive technique which can be used to characterise damage in high strength composite plate. This paper describes an extension to an earlier piece of research work carried out by the ERC which resulted in the successful development of a novel source location methodology for the said material. The previous work concentrated on the source location in plate-like composite structures using acoustic emission. The work presented in this paper focuses on establishing the correlation between the different damage types suffered in the material namely de-lamination, matrix cracking, fibre rupture and stringer to skin debonding with key signal features of the AE activities. Controlled bending tests were initially carried out on laterally grooved slender composite specimens to progressively propagate damage in the weakened region of these specimens. The composite laminate plate itself is made from 16 plies of carbon fibre twill weaved in an epoxy matrix with bidirectional fibre alignments in the 0° and 90° directions with 60/40 fibre-matrix volume composition. These prepared samples were fully instrumented with broad band (100 kHz to 1MHz) Physical Acoustic AE sensors linked to the necessary signal conditioning hardware. The AE events were recorded using a high speed DAQ card accessed by customised software written in LabVIEWTM. Gathered raw data were analysed off-line for key signal features including energy and frequency contents and subsequently correlated to actual damage types. It can be concluded from the empirical evidence that feature vectors are distinct to the type of damage. Results gathered from additional test on the progressive skin-stringer debonding of the same material to failure confirmed the uniqueness of the AE feature trends. An integrated system which is capable of both in-situ location of compromised sites and the diagnostic of flaw types in composite plate can potentially find engineering applications including the structural health monitoring of composite aircraft parts.
Detecting burner instabilities using joint-time frequency methods whilst co-firing coal and biomass
- Authors: Valliappan, Palaniappan , Thai, Shee Meng , Wilcox, Steven , Ward, John , Tan, Chee Keong , Jagietto, Krzysztof
- Date: 2011
- Type: Text , Conference paper
- Relation: ASME/JSME 2011 8th Thermal Engineering Joint Conference, AJTEC 2011
- Full Text: false
- Reviewed:
- Description: Conventional coal-fired burners are designed to operate within specific limits that, in part, result from the need to efficiently burn the fuel. These designs have been developed to ensure stable combustion, lower NOx emissions and increase the combustion efficiency through techniques such as air staging and adding swirl to the combustion air. Recent requirements to reduce CO 2 emissions from coal-fired boiler plant has focussed on the co-firing of biomass, primarily wood, either by delivering the pulverised biomass with the coal or through separate burners. To date this approach has typically taken place at substitution levels of around 5% by mass and at these levels the operation of the burners and boiler is not adversely affected. However, as the proportion of biomass increases the fuel characteristics of the blend moves further away from the burner design parameters. This can lead to combustion instabilities and in extreme cases extinction of the flame. In order to co-fire higher concentrations of biomass a system or technique is required that can detect the onset of these instabilities and warn before the combustion conditions become dangerous. In this paper a novel technique based around the Wigner-Ville transform is presented that shows promise at being able to temporarily resolve the conditions that could result in the onset of burner instabilities for three cases; the first will present results from the combustion of 100% bituminous coal, whilst the second and third cases will present the results from experiments where the proportion of biomass was set at 10% and 20% by mass with the same bituminous coal. In each experiment the secondary combustion air was first reduced from a nominal stable condition and then subsequently increased from the same stable condition. It was found that the Wigner transform was able to resolve flicker frequency changes as the airflow rate was reduced. These changes were subsequently used in a neural network to automatically detect drastic changes in the air flow rates to the burner and could provide a means by which utility operators could detect dangerous flame instability conditions in real-time. Copyright © 2011 by ASME.
Development of an intelligent flame monitoring system for steel reheating burners
- Authors: Thai, Shee Meng , Wilcox, Steven , Tan, Chee Keong , Ward, John , Andrews, Graham
- Date: 2012
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy Vol. 226, no. 8 (2012), p. 1014-1031
- Full Text: false
- Reviewed:
- Description: This article describes the development of a system to indirectly monitor the combustion characteristics of individual burners based on measurement and analysis of the signals detected from photodiodes detecting flame radiation signals. A series of experiments were conducted on a 500 kW pilot-scale furnace and on two 4 MW industrial burners located in two steel reheating furnaces. The flame radiation signals were monitored using a lens that transmitted the flame radiation to ultraviolet, visible and infrared photodiodes through a trifurcated optical fibre. The experiments covered a wide range of burner operating conditions including; variations in the burner load and excess air levels and simulations of burner imbalance. The relationships between the dynamic flame radiation signals and the burner operating parameters and conditions were made off-line using neural network models. The present work indicates that the measurement of flame radiation characteristics, coupled with neural networks, provides a promising means of monitoring and adjusting burner performance. © IMechE 2012.