Exploration of the possibility of acoustic emission technique in detection and diagnosis of bubble formation and collapse in valves

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

Investigation of the influence of flow rate on bubble formation and collapse in ball values at various opening percentages using an AE technique

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

Condition Monitoring Philosophy for Tidal Turbines

Renewable energy is currently considered as the main solution to reduce greenhouse gas emission. This has led to great developments in the use of renewable energy for electricity generation. Among many renewable energy resources, tidal energy has the advantage of being predictable, particularly when compared to wind energy. Currently the UK is the world leader in extracting energy from the tide; an estimation shows a potential of 67 TWh per year. In order to ensure safe operation and prolonged life for tidal turbines, condition monitoring is essential. The technology for power generation using tidal turbines is new therefore the condition monitoring concept for these devices is yet to be established. Also, there is a lack of understanding of techniques suitable for health monitoring of the turbine components and support structure given their unique operating environment.In this paper the condition monitoring of a tidal turbine is investigated. The objective is to highlight the need for condition monitoring and establish procedures to decide the condition monitoring techniques required, in addition to highlighting the impact and benefits of applying condition based maintenance. A model for failure analysis is developed to assess the needs for condition monitoring and identify critical components, after which a ‘symptoms analysis’ was performed to decide the appropriate condition monitoring techniques. Finally, the impact of condition monitoring on system reliability is considered

New pH correlations for stainless steel 316L, alumina, and copper(I) oxide nanofluids fabricated at controlled sonication temperatures

This research investigates the pH value of stainless steel (SS) 316L/ deionised water (DIW), alumina (Al2O3)/DIW, and copper (I) oxide (Cu2O)/DIW nanofluids prepared using a two-step controlled sonication temperature approach of 10°C to 60°C. The nanoparticles volumetric concentration of each family of as-prepared nanofluid ranged from 0.1 to 1.0 vol%, using as-received nanopowders, of 18 – 80 nm average particles size. Furthermore, the pH measuring apparatus and the measurement procedure were validated by determining the pH of commercially supplied calibration fluids, of pH 4, 7, and 10. Following the validation, pH correlations were obtained from the experimental measurements of the 0.1, 0.5, and 1.0 vol% nanofluids in terms of varied sonication bath temperatures and volumetric concentrations. Those correlations were then combined into one robust pHnf correlation and validated using the pH data of the 0.3 and 0.7 vol% nanofluids. The new proposed correlation was found to have a 2.18%, 0.92%, and 0.63%, average deviation from the experimental pH measurements of SS 316L, Al2O3, and Cu2O nanofluids, respectively, with an overall prediction accuracy of ~ 92%

Detection of Natural Crack in Wind Turbine Gearbox

This document is the Accepted Manuscript version of the following article: Suliman Shanbr, Faris Elasha, Mohamed Elforjani, and Joao Teixeira, ‘Detection of natural crack in wind turbine gearbox’, Renewable Energy, vol. 118: 172-179, October 2017. Under embargo. Embargo end date: 30 October 2018. The final, published version is available online at doi: https://doi.org/10.1016/j.renene.2017.10.104. © 2017 Elsevier Ltd. This manuscript version is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.One of the most challenging scenarios in bearing diagnosis is the extraction of fault signatures from within other strong components which mask the vibration signal. Usually, the bearing vibration signals are dominated by those of other components such as gears and shafts. A good example of this scenario is the wind turbine gearbox which presents one of the most difficult bearing detection tasks. The non-stationary signal analysis is considered one of the main topics in the field of machinery fault diagnosis. In this paper, a set of signal processing techniques has been studied to investigate their feasibility for bearing fault detection in wind turbine gearbox. These techniques include statistical condition indicators, spectral kurtosis, and envelope analysis. The results of vibration analysis showed the possibility of bearing fault detection in wind turbine high-speed shafts using multiple signal processing techniques. However, among these signal processing techniques, spectral kurtosis followed by envelope analysis provides early fault detection compared to the other techniques employed. In addition, outer race bearing fault indicator provides clear indication of the crack severity and progress.Peer reviewe

Quantifying the economic benefits of using erosion protective coatings in a low-pressure compressor (aero-engine): a case study evaluation

Gas turbine engines (GTEs) frequently operate in desert environments where the main components are exposed to erosive media such as sand and dust. In these circumstances, a crucial problem, particularly with compressor blades, is solid particle erosion (SPE). Positioned in the front of the GTE, the compressors suffer most from SPE in terms of inflicting damage on compressor hardware such as blades, decreasing the GTE’s working life and increasing fuel consumption, energy losses, and efficiency losses. Results obtained from Turbomatch, an in-house performance tool, showed that degraded compressors can experience increased turbine entry temperature (TET) and specific fuel consumption (SFC), which leads to a significant increase in the operating, maintenance and component replacement costs, in addition to fuel costs. Fitting erosion protective coatings (EPCs) is a conventional approach to reduce SPE of the compressor blades of aeroengines. Titanium nitride (TiN), applied via physical vapour deposition (PVD) techniques, is often used to extend the life of compressor blades in erosive conditions. This paper reports the outcomes of a cost benefit analysis (CBA) of whether applying an EPC to the booster blades of an aeroengine is economically beneficial. The case study takes into account the available coatings potential of the market, in addition to all of the available technical data in the public domain regarding the compressor of the research engine. To identify the economic consequences of employing an EPC over the blades of a compressor, a CBA study was carried out by investigating consequent benefits and costs. The results indicate that under certain conditions the application of an EPC can be profitable

The effects of wear on abradable honeycomb labyrinth seals

This thesis reports on work undertaken to understand the effects, due to wear, on the performance of abradable honeycomb labyrinth seals. The phenomena studied are aerodynamic in nature and include compressible flow, turbulent flow, recirculation and separation at a range of pressure ratios from 1.20 up to 3.50. Four primary methods of investigation were used: experimental, numerical using CFD, numerical using theoretical derivations and numerical using established labyrinth seal specific computer codes. Effects of seal clearance, pressure ratio and tooth to groove location have been investigated with overall performance and inter-seal pressure distribution recorded experimentally and numerically for comparison. Worn experimental results, when compared to their unworn equivalent, recorded large increases in mass flow of up to 50% when the labyrinth teeth are located centrally in the groove. Significant performance enhancements were achieved through offsetting the teeth with respect to the groove, particularly in an upstream sense. There was a marked deterioration with the labyrinth teeth located at the groove exit. Inter-seal pressure distributions showed that the first and final teeth did most of the work achieving significantly larger pressure drops which goes against current seal understanding of increasing pressure drop through the seal. Numerical work was undertaken to further investigate these effects. However, due to the complex 3-D geometry of an abradable honeycomb labyrinth seal a 2-D simplification technique was developed to speed up the investigative process. Using this technique CFD was found capable of replicating the experimental data regarding overall seal performance and inter-seal pressure distributions. The pressure on the final tooth proved to be the hardest experimental data to recreate using CFD, particularly at high pressure ratios when shocks are likely to form. Further numerical work was undertaken using computer codes and theoretical derivations. This work proved that the understanding of the seal loss coefficients used by both methods was not adequate for the current study with the experimental data recreated least successfully. Suggestions are given for enhancement of seal design, including axial location and seal computational routines, which will limit the impact of a 1.5% increase in operational cost that is likely to accrue from seal deterioration.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Identifying bubble occurance during pool boiling employing acoustic emission technique

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

Detailed study on stiffness and load characteristics of film-riding groove types using design of experiments

In the application of film-riding sealing technology, there are various groove features that can be used to induce hydrodynamic lift. However, there is little guidance in selecting the relative parameter settings in order to maximize hydrodynamic load and fluid stiffness. In this study, two groove types are investigated—Rayleigh step and inclined groove. The study uses a design of experiments approach and a Reynolds equation solver to explore the design space. Key parameters have been identified that can be used to optimize a seal design. The results indicate that the relationship between parameters is not a simple linear relationship. It was also found that higher pressure drops hinder the hydrodynamic load and stiffness of the seal suggesting an advantage for using hydrostatic load support in such conditions

Fault diagnosis and health management of bearings in rotating equipment based on vibration analysis – a review

There is an ever-increasing need to optimise bearing lifetime and maintenance cost through detecting faults at earlier stages. This can be achieved through improving diagnosis and prognosis of bearing faults to better determine bearing remaining useful life (RUL). Until now there has been limited research into the prognosis of bearing life in rotating machines. Towards the development of improved approaches to prognosis of bearing faults a review of fault diagnosis and health management systems research is presented. Traditional time and frequency domain extraction techniques together with machine learning algorithms, both traditional and deep learning, are considered as novel approaches for the development of new prognosis techniques. Different approaches make use of the advantages of each technique while overcoming the disadvantages towards the development of intelligent systems to determine the RUL of bearings. The review shows that while there are numerous approaches to diagnosis and prognosis, they are suitable for certain cases or are domain specific and cannot be generalised