Detailed state of the art review for the different on-line/in-line oil analysis techniques in context of wind turbine gearboxes

The main driver behind developing advanced condition monitoring (CM) systems for the wind energy industry is the delivery of improved asset management regarding the operation and maintenance of the gearbox and other wind turbine components and systems. Current gearbox CM systems mainly detect faults by identifying ferrous materials, water, and air within oil by changes in certain properties such as electrical fields. In order to detect oil degradation and identify particles, more advanced devices are required to allow a better maintenance regime to be established. Current technologies available specifically for this purpose include Fourier transform infrared (FTIR) spectroscopy and ferrography. There are also several technologies that have not yet been or have been recently applied to CM problems. After reviewing the current state of the art, it is recommended that a combination of sensors would be used that analyze different characteristics of the oil. The information individually would not be highly accurate but combined it is fully expected that greater accuracy can be obtained. The technologies that are suitable in terms of cost, size, accuracy, and development are online ferrography, selective fluorescence spectroscopy, scattering measurements, FTIR, photoacoustic spectroscopy, and solid state viscometers

Erosion and rolling contact wear mechanisms in silicon nitride hybrid bearings.

One remarkable advantage of hybrid bearings over all steel bearings is the elimination of separate oil lubricant system in applications, such as compressors and pumps in refrigeration and air conditioning units. High speed test runs restricted increase in speed due to material wear, which eventually affected the life of bearings. Being low saturation temperature fluids, change of phase is very common in refrigerants and cryogenic liquids, which lead to cavitation. Silicon nitride rolling elements with different sintering additives, properties and microstructure were experimentally studied to understand the nature of cavitation erosion. Advanced surface analysis technique was used study the erosive wear correlation to microstructure of test materials. Cavitation erosion wear initiated by multiple intergranular and transgranular fracture, leading to erosion pit formation. Grain size and grain boundary composition have shown to be the dominant factors for providing resistance to cavitation. Effect of surface defects and lubricant viscosity on cavitation erosion was investigated and is detailed in this thesis. A rotary specimen method was designed to study the effect of cavitation on rolling bodies. Computational modelling of acoustically generated cavitation was attempted and is also reported in this work. A novel test methodology was designed and manufactured by modifying a rotary tribometer to allow controlled experimental testing of two different phenomena rolling contact fatigue and cavitation erosion. This testing made it possible to study rolling and erosive wear mechanisms of rolling elements. Cavitation created far away in this new system is shown to be transported to the rolling contacts. The mechanism of material damage was by surface weakening due to mechanical impact of bubbles, which enhance fluid entrance and hydrodynamic pressure leading to wear initiation. Micro erosion pits formed in the rolling contact, which accelerated the damage by dislodging grains and bunch of grains. This testing method is suitable for a qualitative assessment of cavitation-RCF damage for different fluids with varying viscosities, and operating conditions

Acoustic emission monitoring of propulsion systems : a laboratory study on a small gas turbine

The motivation of the work is to investigate a new, non-intrusive condition monitoring system for gas turbines with capabilities for earlier identification of any changes and the possibility of locating the source of the faults. This thesis documents experimental research conducted on a laboratory-scale gas turbine to assess the monitoring capabilities of Acoustic Emission (AE). In particular it focuses on understanding the AE behaviour of gas turbines under various normal and faulty running conditions. A series of tests was performed with the turbine running normally, either idling or with load. Two abnormal running configurations were also instrumented in which the impeller was either prevented from rotation or removed entirely. With the help of demodulated resonance analysis and an ANN it was possible to identify two types of AE; a background broadband source which is associated with gas flow and flow resistance, and a set of spectral frequency peaks which are associated with reverberation in the exhaust and coupling between the alternator and the turbine. A second series of experiments was carried out with an impeller which had been damaged by removal of the tips of some of the blades (two damaged blades and four damaged blades). The results show the potential capability of AE to identify gas turbine blade faults. The AE records showed two obvious indicators of blade faults, the first being that the energy in the AE signals becomes much higher and is distinctly periodic at higher speeds, and the second being the appearance of particular pulse patterns which can be characterized in the demodulated frequency domain

Aeronautical Engineering: A special bibliography with indexes, supplement 46, July 1974

This special bibliography lists 374 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1974

Advances in Microfluidic Technologies for Energy and Environmental Applications

Microfluidics have aroused a new surge of interest in recent years in environmental and energy areas, and inspired novel applications to tackle the worldwide challenges for sustainable development. This book aims to present readers with a valuable compendium of significant advances in applying the multidisciplinary microfluidic technologies to address energy and environmental problems in a plethora of areas such as environmental monitoring and detection, new nanofluid application in traditional mechanical manufacturing processes, development of novel biosensors, and thermal management. This book will provide a new perspective to the understanding of the ever-growing importance of microfluidics

Index to 1986 NASA Tech Briefs, volume 11, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1986 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Future research directions in the machining of Inconel 718

Inconel 718 is the most popular nickel-based superalloy, extensively used in aerospace, automotive and energy industries owing to its extraordinary thermomechanical properties. It is also notoriously a difficult-to-cut material, due to its short tool life and low productivity in machining operations. Despite significant progress in cutting tool technologies, the machining of Inconel 718 is still considered a grand challenge.This paper provides a comprehensive review of recent advances in machining Inconel 718. The progress in cutting tools’ materials, coatings, geometries and surface texturing for machining Inconel 718 is reviewed. The investigation is focused on the most adopted tool materials for machining of Inconel 718, namely Cubic Boron Nitrides (CBNs), ceramics and coated carbides. The thermal conductivity of cutting tool materials has been identified as a major parameter of interest. Process control, based on sensor data for monitoring the machining of Inconel 718 alloy and detecting surface anomalies and tool wear are reviewed and discussed. This has been identified as the major step towards realising real-time control for machining safety critical Inconel 718 components. Recent advances in various processes, e.g. turning, milling and drilling for machining Inconel 718 are investigated and discussed. Recent studies related to machining additively manufactured Inconel 718 are also discussed and compared with the wrought alloy. Finally, the state of current research is established, and future research directions proposed.<br/

Future research directions in the machining of Inconel 718

Inconel 718 is the most popular nickel-based superalloy, extensively used in aerospace, automotive and energy industries owing to its extraordinary thermomechanical properties. It is also notoriously a difficult-to-cut material, due to its short tool life and low productivity in machining operations. Despite significant progress in cutting tool technologies, the machining of Inconel 718 is still considered a grand challenge.This paper provides a comprehensive review of recent advances in machining Inconel 718. The progress in cutting tools’ materials, coatings, geometries and surface texturing for machining Inconel 718 is reviewed. The investigation is focused on the most adopted tool materials for machining of Inconel 718, namely Cubic Boron Nitrides (CBNs), ceramics and coated carbides. The thermal conductivity of cutting tool materials has been identified as a major parameter of interest. Process control, based on sensor data for monitoring the machining of Inconel 718 alloy and detecting surface anomalies and tool wear are reviewed and discussed. This has been identified as the major step towards realising real-time control for machining safety critical Inconel 718 components. Recent advances in various processes, e.g. turning, milling and drilling for machining Inconel 718 are investigated and discussed. Recent studies related to machining additively manufactured Inconel 718 are also discussed and compared with the wrought alloy. Finally, the state of current research is established, and future research directions proposed.<br/

Acoustic Concepts in Micro-Scale Flow Control and Advances in Modular Microfluidic Construction.

Despite thirty years of research, the full scientific and social impact of microfluidics has not been realized. This dissertation focuses on addressing two key issues to accelerate this realization: micro-scale flow control and microfluidic device construction. We introduce the design of a new acoustic-based mechanism for multiplexed pressure- driven flow control. The device we have developed converts the frequency content of an acoustic signal into four individually addressable pressure outputs, tunable over a range 0-200 Pa with a control resolution of 10 Pa. The pressure generating components of the device consist of a bank of four resonance cavities (404, 484, 532, and 654 Hz), each with an attached rectification structure. We demonstrate how this scheme can be used for programmatic operation of both droplet-based and continuous-flow microfluidic systems using only a single control line. We then explore an alternative acoustic actuation scheme involving frequency dependent attenuation within finite phononic crystals. Specifically, finite element analysis of the band properties of peri- odic two-dimensional microstructures subject to a variety of geometric lattice perturbations is presented. Phononic structures with periodicity over the range of 100-1400 μm were found to exhibit rich band gap effects over 100-300 kHz. We also discuss the utility of one-dimensional transfer matrix method approximations and analysis in the infinite limit as methods for understanding and predicting crystal transmission. Lastly, we describe an advanced modular microfluidic construction scheme using prefabricated polymeric building blocks (MABs) that can be assembled into working devices on-site within minutes. We discuss: (1) development of flexible silicone casting trays for dramatically improved production and extraction of MABs, (2) reliable “off-the-shelf” preparation of 1-3 μm PDMS thin films for facile block assembly with simultaneous block/block and block/substrate bonding, and (3) modification of MAB block design to include self-alignment and sealing structures. Completed MAB assemblies possessed an average channel offset of ±12μm, an average channel angle of ±1 degree, and were found to exhibit the fewest inter-block gaps at a piece convexity of 0 μm. Exemplary MAB devices for performing on-chip gradient synthesis, droplet generation, and total internal reflectance microscopy are also presented.Ph.D.Chemical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/78937/1/langelie_1.pd

Monitoring of the piston ring-pack and cylinder liner interface in diesel engines through acoustic emission measurements

Investigation of novel condition monitoring systems for diesel engines has received much recent attention due to the increasing demands placed upon engine components and the limitations of conventional techniques. This thesis documents experimental research conducted to assess the monitoring capabilities of Acoustic Emission (AE) analysis. In particular it focuses on the possibility of monitoring the piston ring-pack and cylinder liner interface, a critical engine sub-system for which there are currently few practical monitoring options. A series of experiments were performed on large, two-stroke and small, four-stroke diesel engines. Tests under normal operating conditions developed a detailed understanding of typical AE generation in terms of both the source mechanisms and the characteristics of the resulting activity. This was supplemented by specific tests to investigate possible AE generation at the ring-pack/liner interface. For instance, for the small engines measures were taken to remove known AE sources in order to accentuate any activity originating at the interface whilst for the large engines the interfacial conditions were purposely deteriorated through the removal of the lubricating oil supply to one cylinder. Interpretation of the results was based mainly upon comparisons with published work encompassing both the expected ring-pack behaviour and AE generation from tribological processes. This provided a strong indication that the source of the ring-pack/liner AE activity was the boundary frictional losses. The ability to monitor this process may be of significant benefit to engine operators as it enhances the diagnostic information currently available and may be incorporated into predictive maintenance strategies. A further diagnostic technique considered was the possibility of using AE parameters combined with information of crankshaft speed fluctuations to evaluate engine balance and identify underperforming cylinders.EU Competitive and Sustainable Growth Programme, Project no: GRD2-2001-5001