205 results found
McGlashan NR, Childs PRN, Heyes AL, 2011, Chemical looping combustion using the direct combustion of liquid metal in a gas turbine based cycle, Journal of Engineering for Gas Turbines and Power, Vol: Vol 133, Pages: 031701-1-031701-13, ISSN: 0742-4795
Childs PRN, Robb D, 2011, Design, Make, Test, 12th International Conference on Engineering and Product Design Education, Publisher: The Design Society, Pages: 174-179
Aurisicchio M, Eng NL, Nicolas JCO, et al., 2011, ON THE FUNCTIONS OF PRODUCTS, 18th International Conference on Engineering Design (ICED), Publisher: DESIGN SOC, Pages: 443-455, ISSN: 2220-4334
McGlashan NR, Childs PRN, Heyes AL, 2011, Chemical Looping Combustion Using the Direct Combustion of Liquid Metal in a Gas Turbine Based Cycle, Journal of Engineering for Gas Turbines and Power, Vol: 133
A combined cycle gas-turbine generating power and hydrogen is proposed and evaluated.The cycle embodies chemical looping combustion (CLC) and uses a Na based oxygencarrier. In operation, a stoichiometric excess of liquid Na is injected directly into thecombustion chamber of a gas-turbine cycle, where it is burnt in compressed O2 producedin an external air separation unit (ASU). The resulting combustion chamber exit streamconsists of hot Na vapor and this is expanded in a turbine. Liquid Na2O oxide is alsogenerated in the combustion process but this can be separated, readily, from the Na vaporand collects in a pool at the bottom of the reactor. To regenerate liquid Na from Na2O,and hence complete the chemical loop, a reduction reactor (the reducer) is fed with threestreams: the hot Na2O from the oxidizer, the Na vapor (plus some entrained wetness)exiting a Na-turbine, and a stream of solid fuel, which is assumed to be pure carbon forsimplicity. The sensible heat content of the liquid Na2O and latent and sensible heat ofthe Na vapor provide the heat necessary to drive the endothermic reduction reaction andensure the reducer is externally adiabatic. The exit gas from the reducer consists ofalmost pure CO, which can be used to generate byproduct H2 using the water-gas shiftreaction. A mass and energy balance of the system is conducted assuming reactions reachequilibrium. The analysis allows for losses associated with turbomachinery; heat exchangersare assumed to operate with a finite approach temperature. However, pressurelosses in equipment and pipework are assumed negligible—a reasonable assumption forthis type of analysis that will still yield meaningful data. The analysis confirms that thecombustion chamber exit temperature is limited by both first and second law considerationsto a value suitable for a practical gas-turbine. The analysis also shows that theoverall efficiency of the cycle, under optimum conditions and taking into account thework necessary to dr
Howey DA, Childs PRN, Holmes AS, 2010, Air-gap convection in rotating electrical machines, IEEE Transactions on Industrial Electronics, Vol: 58
This paper reviews convective heat transfer within the air-gap of both cylindrical and disc geometry rotating electrical machines, including worked examples relevant to fractional horsepower electrical machines. Thermal analysis of electrical machines is important because torque density is limited by maximum temperature. Knowledge of surface convective heat transfer coefficients is necessary for accurate thermal modelling for example using lumped parameter models. There exists a wide body of relevant literature, but much of it has traditionally been in other application areas, dominated by mechanical engineers, such as gas turbine design. Particular attention is therefore given to the explanation of the relevant non-dimensional parameters, and to the presentation of measured convective heat transfer correlations for a wide variety of situations from laminar to turbulent flow at small and large gap sizes for both radial flux and axial flux electrical machines.
Scott RM, Childs PRN, Hills NJ, et al., 2010, Radial inflow into the downstream cavity of a compressor stator well. 2000-GT-0507, ASME Turbo Expo 2000, Publisher: ASME
The subject of the interaction between the mainstreamannulus flow and seal flows is now receiving increased attentionas a result of concerted attempts to further improve compressorperformance. In an axial compressor the use of a shroud on astator blade row necessitates a trench and results in two suchregions of interaction at the upstream and downstream statorwell cavities with flow limited by a labyrinth seal. Theupstream stator well cavity, with its superposed radial outflow,has received some attention and possess similarities with thecavity downstream of nozzle guide vanes in axial turbines,which have received considerable interest. The downstreamcompressor stator well cavity has, however, been lessextensively studied. Here the flow is dominated by inflow intothe cavity. This inflow is driven by the pressure gradient acrossthe blade row and hence the pressure gradient between theupstream and downstream cavities. This paper presentspreliminary pressure measurements from a high-speed twostageresearch compressor. The experimental results arecompared with two and three-dimensional CFD models. Inorder to gain confidence with CFD for compressor stator wells,the case of inflow into a rotor-stator disc wheelspace has beenrevisited; validating a commercial code, Fluent, for a widerange of flow conditions. This code has then been used topredict the detailed flow structure for the conditions in theexperimental research compressor.
Ozturk HK, Childs PRN, Turner AB, et al., 2010, A three dimensional computational study of windage heating within an axial compressor stator well. ASME Paper 98-GT-119, ASME Turbo Expo 1998, Publisher: ASME
McGlashan NR, Childs PRN, Heyes AL, 2010, Chemical looping combustion using the direct combustion of liquid metal in a gas turbine based cycle. GT2010-23393, ASME Turbo Expo 2010
A combined cycle gas turbine generating power and hydrogen is proposed and evaluated. The cycle embodies chemical looping combustion (CLC) and uses a Na based oxygen carrier. In operation, a stoichiometric excess of liquid Na is injected directly into the combustion chamber of a gas turbine cycle, where it is burnt in compressed O2 produced in an external air separation unit (ASU). The resulting combustion chamber exit stream consists of hot Na vapour, and this is expanded in a turbine. Liquid Na2O oxide is also generated in the combustion process, but this can be separated, readily, from the Na vapour and collects in a pool at the bottom of the reactor.To regenerate liquid Na from Na2O, and hence complete the chemical loop, a reduction reactor (the reducer) is fed with three streams: the hot Na2O from the oxidiser; the Na vapour (plus some entrained wetness) exiting a Na-turbine; and a stream of solid fuel, which is assumed to be pure carbon for simplicity. The sensible heat content of the liquid Na2O and latent and sensible heat of the Na vapour provide the heat necessary to drive the endothermic reduction reaction and ensure the reducer is externally adiabatic. The exit gas from the reducer consists of almost pure CO which can be used to generate by-product H2 using the water-gas shift reaction.A mass and energy balance of the system is conducted assuming reactions reach equilibrium. The analysis allows for losses associated with turbomachinery; heat exchangers are assumed to operate with a finite approach temperature; however, pressure losses in equipment and pipework are assumed negligible - a reasonable assumption for this type of analysis that will still yield meaningful data. The analysis confirms that the combustion chamber exit temperature is limited by both first and second law considerations to a value suitable for a practical gas turbine. The analysis also shows that the overall efficiency of the cycle, under optimum conditions and taking into account t
Childs PRN, 2010, Rotating Flow, Publisher: Butterworth-Heinemann, ISBN: 9780123820983
Swirling, whirling and rotating flow has proved fascinating and challenging throughout the ages with examples including the vortex formed as water exits the bath-tub or the swirling motion seen in a corn field as the wind blows across it the vortices shed from wing tips and the intense vortices and circulations observed in the atmosphere and oceans. The subject provides a talking point and a level of complexity that often defies simple explanation. Rotating flow is critically important across a wide range of scientific, engineering and product applications, providing design and modelling capability for diverse products such as jet engines, pumps and vacuum cleaners as well as geophysical flows. This book introduces and develops the subject of rotating flow with specific subjects including:• an introduction to rotating flow; • fundamental equations,• vorticity and vortices;• rotating disc flow;• flow around rotating cylinders and in a rotating annulus• flow in rotating cavities;• atmospheric and oceanic circulations.
Childs PRN, McGlashan NR, Gosling G, et al., 2010, Linking design, analysis, manufacture and test in the engineering student experience. EPDE2010/216, When Design Education and Design Research Meet. 12th International conference on engineering and product design education., Pages: 210-215
The modern engineer needs to have diverse skills ranging from abilities in re-design, co-design, customisation, management of resources and intellectual property, combined with technical expertise. Design education needs to prepare individuals for these requirements and manage the expectations of the students concerned. A particular challenge is the disconnect between empowered design practice, where the practitioner already has the necessary skills to explore the task, and the novice who is still learning technical and design skills. In order to develop understanding of design processes commonly experienced in industry a combination of projects using fuzzy or constrained briefs are introduced in the first and second years on the MEng in Mechanical Engineering at Imperial College. Constrained briefs defining the limits for the design activity, are sometimes criticised as limiting the creative opportunities for the people involved. Some creative techniques however focus on identifying the constraints and conflicts involved with a view to resolving them. This paper explores a constrained brief project, used for the second year, where students are required to design, manufacture and then test their design for a pump. The project encourages use and exploration of analytical skills, engineering science and form development as well as basic manufacturing skills. Students can use CNC manufacture for their impeller and volute but are required to manually machine the majority of their bearing housing and shaft arrangement. The combination of concept development within constraints, use of analysis and engineering science, development of manufacturing and assembly skills and the student experience derived from testing their designs, are described within this paper.
Childs PRN, Robb DR, 2010, Design, Make, Test., When Design Education and Design Rearch Meet. 12th International conference on engineering and product design education., Publisher: Design Society, Pages: 174-179
In the UK in the 1970s and early 1980s examples of best practice pedagogic experience included the egg-race type of design and make projects embodied in the student projects run by Ken Wallace at the University of Cambridge and Heinz Wolff at Brunel University. These experiences were widely acclaimed in the media and inspired a generation of students. The technically demanding and interdisciplinary nature of such projects has, in some cases, pushed them towards the domain of mechatronics degrees. A further challenge to this form of project is the high resource requirements from staff, to hardware and space. In order to provide a stepping stone between the introductory projects such as bridge or crane building using balsa wood, a group exercise has been introduced that is inspired by the egg-race type leading edge pedagogic practice activities. A project has been developed where students are challenged to build a small hovercraft. Fans and motors are supplied but the students are required to design and build their own hulls. The activity is associated with lectures in sketching, machine elements and fluid mechanics and the fans have been sized requiring careful consideration of the air gap, hull area and mass in order to ensure that the design is compatible with the flow capacity. A further constraint is that the craft must be autonomous and navigate a specified route, with various obstacles. This paper describes the project developed for 160 Year 1 MEng students along with resource requirements and options for scaling and development.
McGlashan NR, Childs PRN, Heyes AL, et al., 2010, Producing Hydrogen and Power Using Chemical Looping Combustion and Water-Gas Shift, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 132, Pages: 031401-1-031401-10, ISSN: 0742-4795
A cycle capable of generating both hydrogen and power with “inherent” carbon capture is proposed and evaluated. The cycle uses chemical looping combustion to perform the primary energy release from a hydrocarbon, producing an exhaust of CO. This CO is mixed with steam and converted to H2 and CO2 using the water-gas shift reaction (WGSR). Chemical looping uses two reactions with a recirculating oxygen carrier to oxidize hydrocarbons. The resulting oxidation and reduction stages are preformed in separate reactors—the oxidizer and reducer, respectively, and this partitioning facilitates CO2 capture. In addition, by careful selection of the oxygen carrier, the equilibrium temperature of both redox reactions can be reduced to values below the current industry standard metallurgical limit for gas turbines. This means that the irreversibility associated with the combustion process can be reduced significantly, leading to a system of enhanced overall efficiency. The choice of oxygen carrier also affects the ratio of CO versus CO2 in the reducer's flue gas, with some metal oxide reduction reactions generating almost pure CO. This last feature is desirable if the maximum H2 production is to be achieved using the WGSR reaction. Process flow diagrams of one possible embodiment using a zinc based oxygen carrier are presented. To generate power, the chemical looping system is operated as part of a gas turbine cycle, combined with a bottoming steam cycle to maximize efficiency. The WGSR supplies heat to the bottoming steam cycle, and also helps to raise the steam necessary to complete the reaction. A mass and energy balance of the chemical looping system, the WGSR reactor, steam bottoming cycle, and balance of plant is presented and discussed. The results of this analysis show that the overall efficiency of the complete cycle is dependent on the operating pressure in the oxidizer, and under optimum conditions exceeds 75%.
Childs PRN, Tsai S-K, 2010, Creativity in the design process in the turbomachinery industry, J. of Design Research, Vol: 8, Pages: 145-164
Creativity is perhaps the most prized human attribute and an essential element of the design process. Some creative ideas are astonishing and brilliant, while others are simple practical ideas previously not thought of. The history of mature markets reveals the importance of innovative approaches to maintain competitive positions. There are many creative methods available which can be used to enhance and provoke our generative activity but professionals tend to restrict their attention to very few methods. This paper explores the creative process and creativity in turbomachinery design. This sector presents particular challenges given the safety critical nature of power generation and flight, and the history of developments can be characterised by evolution without many dramatic breakthroughs. In the light of survey data and practice in other industries, recommendations are made for the application of creative techniques based on pre-disposition, internal and external mapping, idea generation and evaluation for implementation in the turbomachinery industry in order to meet the challenges of competition and reducing environmental impact.
Hall A, Childs PRN, 2010, Innovation design engineering: non-linear progressive education for diverse intakes, 11th Engineering and Product Design Education Conference, Publisher: The Design Society, Pages: 312-317
Coren D, Turner J, Eastwood D, et al., 2010, An Advanced Multi-Configuration Turbine Stator Well Cooling Test Facility. GT2010-23450, ASME Turbo Expo 2009: Power for Land, Sea and Air, 14th - 18th June, 2010,Glasgow
Optimisation of cooling systems within gas turbine engines is of great interest to engine manufacturers seeking gains in performance,efficiency and component life. The effectiveness of coolant delivery is governed by complex flows within the stator wells and the interaction of main annulus and cooling air in the vicinity of the rim seals. This paper reports the developmentof a test facility which allows the interaction of cooling air and main gas paths to be measured at conditions representative of those found in modern gas turbine engines. The test facility features a two stage turbine with an overall pressure ratio of approximately 2.6:1. Hot air is supplied to the main annulus using a Rolls-Royce Dart compressor driven by an aero-derivative engine plant. Cooling air can be delivered to the stator wells at multiple locations and at a range of flow rates which cover bulk ingestion through to bulk egress. The facility has been designed with adaptable geometry to enable rapid changes of cooling airpath configuration. The coolant delivery system allows swift and accurate changes to the flow settings such that thermal transients may be performed. Particular attention has been focused on obtaining high accuracy data, using a radio telemetry system, as well as thorough through-calibration practices. Temperature measurementscan now be made on both rotating and stationary discs with a long term uncertainty in the region of 0.3 K. A gas concentration measurement system has also been developed to obtain directmeasurement of re-ingestion and rim seal exchange flows. High resolution displacement sensors have been installed in orderto measure hot running geometry. This paper documents the commissioning of a test facility which is unique in terms of rapid configuration changes, non-dimensional engine matching and theinstrumentation density and resolution. Example data for each of the measurement systems is presented. This includes the effect ofcoolant flow rate on the metal temp
Yang B, Xu G, Childs P, et al., 2010, Prediction of coolant deflection tendencies in rotating film cooling, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE, Vol: 224, Pages: 2435-2448, ISSN: 0954-4062
Robb DA, Flora H, Childs PRN, 2010, Sketching to solid modelling skills for mechanical engineers, 11th International Conference on Engineering and Product Design Education, Publisher: The Design Society, Pages: 275-280
Childs PRN, McGlashan NR, Heyes AL, 2010, Accessing high thermal efficiency power generation using fluid phase chemical looping. 2010-ISJPPE-0001, 3rd International Symposium on Jet Propulsion and Power Engineering
In order to burn a hydrocarbon fuel efficiently using conventional cycles, very high temperatures are required. Chemical looping combustion offers an alternative cycle for large scale power production. In chemical looping combustion a carrier molecule is used to transport oxygen between two redox reactions, one where the carrier is oxidised and another where it is reduced by reaction with a fuel. Separation of the oxygen carrier from fuel ash can be aided by means of phase difference and this is a key advantage of fluid phase chemical looping combustion where the carrier medium proposed is sodium, potassium or zinc. The principle exploited in fluid phase chemical looping combustion is the recirculation of both energy and entropy. High thermal efficiencies, circa 75% at 35 bar are theoretically achievable taking into account component efficiencies, with separation of nitrogen and carbon dioxide, in combination with the water shift gas reaction, as an inherent part of the cycle if air is used as the oxygen source.
Childs PRN, McGlashan NR, Heyes AL, 2010, Power generation with fluid phase chemical looping combustion ETN 2010-068, 5th International Gas Turbine Conference
A new type of power cycle for large scale generation has been developed based on chemical looping that has theoretically been shown to offer practical thermal efficiencies of between 72% and 82%. Instead of performing hydrocarbon combustion in a single reaction, as in conventional power plant, the hydrocarbon is oxidised using two reactions. An additional species is required, typically a metal, which re-circulates between the two reactions carrying oxygen atoms. The chemical looping technology concerned uses processes comparable to those in the human body for extraction of energy from food but instead of using haemoglobin, metal vapour is used as the carrier for the oxidation and reduction processes. The cycle avoids the large entropy changes associated with Carnot-cycle based engines and high thermal efficiencies are possible with inherent carbon capture for power generation plants. The technology represents a step change in power generation although a series of technical barriers remain for its implementation including equation of state data, detailed chemical kinetics, development of practicable schemes to duct the highly reactive fluid flows and determination of slag melt thermodynamics. This paper explores the cycle development and technology requirements as well as addressing the need to consider cycle variants in power generation.
Regan N, Peng Z, Atkins NR, et al., 2010, An investigation to oil spray characteristics under cross flow environment of internal air system. 2010-ISJPPE-3016, 3rd International Symposium on Jet Propulsion and Power Engineering
For investigating the oil spray characteristics in internal air systems of gas turbine engines, a test rig has been built for simulating the oil leaking jet flow when a fracture takes place on those high flowrate oil supply pipes. With the air flow velocity of cross flow up to 200 m/s, oil sprays with the injection pressure up to 7 bar were provided by an purpose-built injection system. Various injector orifices with different shapes and dimensions were prepared for considering different fracture situation though only one circular nozzle was examined in the current study. While Laser Imaging was used for examining the jet behaviour and flow field with interaction between the oil spray and the cross flow, Phase Doppler Anemometry (PDA) was employed for measuring the size and velocity distributions of oil droplets. Measurements through different planes of the spray were conducted for exploring the droplet break-up and oil-air mixing process. Results showed that the high velocity of cross flow made significant enhancement for both the jet break-up and droplet break-up, in particular those droplets with bigger size, while the momentum flux ratio has very unapparent influence on variation of droplet size distributions. With the penetration of the oil spray, velocity differences between the cross flow and droplets gradually become smaller and this tends to reduce the further droplet break-up at the downstream area. Meanwhile, relevant data also demonstrated that the evaporation of different size droplets was accelerated with high velocity cross flows.
Childs PRN, 2010, Ethics, Assessing creativity in design: emerging themes for engineering, Editors: Ball, ISBN: 978-1-904804-83-3
Childs PRN, 2010, People Metrics, Assessing creativity in design: emerging themes for engineering, Editors: Ball, Publisher: Higher Education Academy Engineering Subject Centre, ISBN: 9781904804833
Hall A, Childs PRN, 2009, Innovation design engineering: non-linear progressive education for diverse intakes, 11th Engineering and Product Design Education International Conference, Pages: 312-317
This paper discusses the non-linear progressive educational techniques developed and adopted by the Innovation Design Engineering (IDE) masters degree at the Royal College of Art and Imperial College, London. In particular a focus is applied to the development of creative processes for diverse intakes without recourse to overt systems presentation. Innovation design engineering is viewed as a cutting-edge product design, experimentation and enterprise discipline with applicants drawn from three areas including engineering, industrial design and other art, design and business disciplines. The co-education of such a diverse intake requires careful balancing of an academic programme to ensure that all parties are stimulated and enabled to expand their knowledge and skills base while also contributing to a communal environment via team-based activities. Designers work at the centre of complex, demanding projects, juggling creatively in teams, to generate great ideas, designs and successful products. In order to achieve such goals it is critical for students to attain high levels of self-reflection, social networking, work-collaboration and interdisciplinarity. This is achieved by surrounding the students with experts and leaders in their fields to support them in their design ventures.Through reflection and theorising, a conceptual base for educating innovative design engineers is explored. One of the techniques described provided evidence to suggest running a design enterprise strand in the programme, a proposal that has now been implemented. Students elect from three learning strands: experimental design; design for manufacture; and design enterprise. The design enterprise strand addresses product, idea and service launching, finance, marketing, commercialisation, designing service support infrastructures and establishing production and supplier relationships. Design for manufacture is the traditional core industrial design activity associated with advanced manufactur
Adams DJ, Beniston LJ, Childs PRN, 2009, Promoting creativity and innovation in biotechnology, TRENDS IN BIOTECHNOLOGY, Vol: 27, Pages: 445-447, ISSN: 0167-7799
Coren D, Childs PRN, Long CA, 2009, Windage sources in smooth-walled rotating disc systems, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE, Vol: 223, Pages: 873-888, ISSN: 0954-4062
Childs PRN, 2009, Labyrinth Seal Flow, Publisher: ESDU, ISBN: 978 1 86246 639 5
Patounas DS, Long CA, Childs PRN, 2009, DISC HEAT TRANSFER IN GAS TURBINE COMPRESSORINTERNAL AIR SYSTEMS, 8th European Conference on Turbomachinery, Pages: 377-386
Experimental disc heat transfer measurements were obtained from the internal air systemin high-pressure compressor cavities of gas turbine engines with axial throughflow using a rigbased on real aero-engine components. Tests were carried out over a range of non-dimensionalparameters representative of real engine conditions (Re up to 10000000 and Rez up to 110000).The heat transfer data were obtained from surface temperature measurements through a2D tapered disc numerical solution. Local values of heat transfer coefficient and Nusseltnumber showed a decreasing distribution with radius close to turbulent natural convection,similar to those found in past research. Study of the average Nusselt number showed that thisincreases with increasing axial Reynolds number and decreases with increasing rotationalReynolds number. These are consistent with increased action of the throughflow inside thecavity and an increase in the Coriolis force attenuating the flow inside the cavity.
Cooke A, Childs P, Sayma N, et al., 2009, A disc to air heat flux error and uncertainty analysis applied to a turbomachinery test rig design, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE, Vol: 223, Pages: 659-674, ISSN: 0954-4062
Farahani A, Childs P, 2009, VALIDATION AND COMPARISON OF STRIP SEAL DESIGNS FOR GAS TURBINE ENGINE NOZZLE GUIDE VANES, ASME International Mechanical Engineering Congress and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1185-1192
Tsai SK, Childs PRN, 2009, TRIZ Incorporating the BRIGHT Process in Design, TRIZ Journal
The theory of inventive problem solving (TRIZ) is widely acclaimed by adoptees and in the academic literature. An apparent disparity exists, however, between the low reported industrial take-up of TRIZ and perceptions in the TRIZ community which indicate more widespread use. A review of TRIZ, design processes and creative problem solving processes are reported, showing differences in the emphasis on creative thinking and the use of iteration. The advantages of a procedure related to the aspects of usability, creative thinking and iteration within the TRIZ environment has been recognised and addressed by the development of a new process named BRIGHT.
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