205 results found
McGlashan NR, PRN C, Heyes AL, et al., 2009, PRODUCING HYDROGEN AND POWER USING CHEMICAL LOOPING COMBUSTION AND WATER-GAS SHIFT. ASME Paper GT2009-59492, 54th ASME Turbo Expo 2009, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 177-188
A cycle capable of generating both hydrogen and power with 'inherent' carbon capture is proposed and evaluated The cycle uses chemical looping combustion (CLC) to perform the primary energy release from a hydrocarbon, producing an exhaust of CO This CO is mixed with steam and converted to H-2 and CO2 using the water-gas shift reaction (WGSR).Chemical looping uses two reactions with a re-circulating oxygen carrier to oxidise hydrocarbons. The resulting oxidation and reduction stages are preformed in separate reactors the oxidiser 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 vs. 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 H-2 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 maximise efficiency. The WGSR supplies heat to the bottoming steam cycle, as well as helping 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 dependant on the operating pressure in the oxidiser, and under optimum conditions, exceeds 75%.
Robb D, Flora H, Childs PRN, 2009, Sketching to solid modelling skills for mechanical engineers, 11th Engineering and Product Design Education International Conference, Pages: 275-280
Hand sketching skills remain an important part of aiding discussions in meetings and are, for example, an essential asset for brainstorming and other ideation activities. The tendency for novice students on entry to engineering and design degree programmes to produce naïve, laboured or ‘glitzy’ sketches and inappropriate CAD representations has previously been identified. This paper describes the strategy implemented at Imperial College London for the MEng in Mechanical Engineering in order to develop key sketching skills across the diverse intake of students and in conjunction with the development of CAD solid modelling and technical drawing capabilities. The approach, based on use of visual diaries, museum and site visits, design, make and test and conceptual exercises has ensured that all students are able to sketch and produce solid models in their first year, although the production of naïve and laboured sketches continues to some extent.
Regan NJ, Atkins NR, Long CA, et al., 2009, AN EXPERIMENTAL STUDY OF SPRAYS IN CROSS FLOW REPRESENTATIVE OF GAS TURBINE ENGINE SECONDARY AIR SYSTEMS GT2009-59709, 54th ASME Turbo Expo 2009, Publisher: AMER SOC MECHANICAL ENGINEERS
The flow in the secondary air system of a gas turbine engine passes over numerous oil supply and scavenge pipes and a fracture in such a pipe will cause a jet of oil to be ejected as a spray. This spray will disperse in the surrounding flow. Accurate and reliable numerical modelling of these sprays presents significant problems due in part to their complexity, but also the lack of experimental data available for model validation. This paper describes the design, manufacture, testing and results from an experimental test rig aimed at spray characterisation. The sprays considered were produced through a round sharp edged nozzle with a 0.57 mm diameter and a length to diameter ratio of 1 61. The spray was introduced normal to the cross flow. Phase Doppler Anemometry was used to determine droplet size and velocity for Weber numbers within the range of 13 < We(g) <580 and Momentum Flux Ratio within the range of 0.8 < q < 136, resulting in 19 different spray fields Each of these spray fields has been characterised at three axial locations. Contours of droplet size, mass flux distribution, axial droplet velocity and transverse droplet velocity are presented. In addition, a pulsed laser sheet and CCD camera were used to analyse the jet behaviour in terms of break up length and jet trajectory.
Energy recovery from IC engines has proved to be of considerable interest across the range of vehicle applications. The motivation is substantial fuel economy gain that can be achieved with a minimal affect on the "host" technology of the vehicle. This paper reviews the initial results of a research project whose objective has been to identify system concepts and control methods for thermal recovery techniques. A vapour power cycle is the means of energy transfer. The architecture of the system is considered along with support of the fuel economy claims with the results of some hybrid vehicle modelling. An overview of the latest experimental equipment and design of the heat exchanger is presented. The choice of control architecture and strategy, whose goal is overall efficiency of the engine system, is presented and discussed. Some initial control results are presented. One important project aim is to identify and implement an optimal control method that allows an explicit balance, between the IC engine output and the recovered work from the vapour power cycle. Initial simulation work shows that there are significant, potential, fuel economy advantages, between 6% and 31%, and that high efficiencies can be achieved at practical operating pressures. Conclusions point to the need to investigate and develop the system control dynamics. Copyright © 2008 SAE International.
Hounsam S, Stobart RK, Cooke AO, et al., 2008, Energy Recovery Systems for Engines. SAE Paper 2008-01-0309, SAE World Congress 2008
Energy recovery from IC engines has proved to be ofconsiderable interest across the range of vehicleapplications. The motivation is substantial fuel economygain that can be achieved with a minimal affect on the“host” technology of the vehicle.This paper reviews the initial results of a research projectwhose objective has been to identify system conceptsand control methods for thermal recovery techniques. Avapour power cycle is the means of energy transfer. Thearchitecture of the system is considered along withsupport of the fuel economy claims with the results ofsome hybrid vehicle modelling. An overview of the latestexperimental equipment and design of the heatexchanger is presented. The choice of controlarchitecture and strategy, whose goal is overall efficiencyof the engine system, is presented and discussed. Someinitial control results are presented. One importantproject aim is to identify and implement an optimalcontrol method that allows an explicit balance, betweenthe IC engine output and the recovered work from thevapour power cycle.Initial simulation work shows that there are significant,potential, fuel economy advantages, between 6% and31%, and that high efficiencies can be achieved atpractical operating pressures. Conclusions point to theneed to investigate and develop the system controldynamics.
Farahani A, Childs PRN, 2008, Validation and comparison of strip seal designs for gas turbine engine nozzle guide vanes, IMECE2008, ASME International Mechanical Engineering Congress and Exposition, Publisher: ASME
Tsai SK, Childs PRN, 2008, TRIZ incorporating the BRIGHT process in design, 8th ETRIA World TRIZ Future Conference
Long CA, Childs PRN, 2007, Shroud heat transfer measurements inside a heated multiple rotating cavity with axial throughflow, 5th Conference on Turbulence, Heat and Mass Transfer, Publisher: ELSEVIER SCIENCE INC, Pages: 1405-1417, ISSN: 0142-727X
Long CA, Miche NDD, Childs PRN, 2007, Flow measurements inside a heated multiple rotating cavity with axial throughflow, 5th Conference on Turbulence, Heat and Mass Transfer, Publisher: ELSEVIER SCIENCE INC, Pages: 1391-1404, ISSN: 0142-727X
Long CA, Childs PRN, 2007, Shroud heat transfer measurements inside a heated multiple rotating cavity with axial throughflow, International Journal of Heat and Fluid Flow, Vol: 28, Pages: 1405-1517
Experimental measurements of heat transfer are made from the inner peripheral surface of a rotating test rig designed to be similar to a gas turbine high pressure compressor internal air system. The test rig comprises a number of annular discs sealed at their periphery by a shroud. An axial throughflow of cooling air enters the test rig and flows through the annular section between the disc bores and a central shaft. Tests were carried out for the following range of rotational speeds and axial throughflow rates: 540 < NR < 10,800 rev/min and (corresponding to the range of rotational and axial Reynolds numbers 4 × 105 < Re < 7.7 × 106 and 3.3 × 104 < Rez < 2.2 × 105). The shroud Nusselt numbers are found to depend on the shroud Grashof number. They are relatively insensitive to changes in axial Reynolds number and two geometrically similar cavities give similar values of Nusselt number. The heat transfer from the shroud is governed by the mechanism of free convection. It is recommended that a modified form of a correlation for Rayleigh–Bénard convection in a gravitational force field be used, with appropriate modification, to predict shroud heat transfer.
Long CA, Miche NDD, Childs PRN, 2007, Flow measurements inside a heated multiple rotating cavity with axial throughflow, International Journal of Heat and Fluid Flow, Vol: 28, Pages: 1391-1404
This paper discusses experimental results from a multiple cavity test rig representative of a high pressure compressor internal air system. Measurements of the axial, tangential and radial velocity components are presented. These were made using a two component, laser doppler anemometry (LDA) system for a range of non-dimensional parameters representative of engine conditions (Re up to 4 × 106 and Rez up to 1.8 × 105). Tests were carried out for two different sizes of annular gap between the (non-rotating) drive shaft and the disc bores. The axial and radial velocities inside the cavities are virtually zero. The size of the annular gap between disc bore and shaft has a significant effect on the radial distribution of tangential velocity. For the narrow annular gap (dh/b = 0.092), there is an increase of non-dimensional tangential velocity V/Ωr with radial location from V/Ωr < 1 at the lower radii to solid body rotation V/Ωr = 1 further into the cavity. For the wider annular gap (dh/b = 0.164), there is a decrease from V/Ωr > 1 at the lower radii to solid body rotation further into the cavity. An analysis of the frequency spectrum obtained from the tangential velocity measurements is consistent with a flow structure in the r– plane consisting of pairs of contra rotating vortices.
Peng Z, New P, Long CA, et al., 2007, Operating characteristics of a high radius pre-swirl cooling system, Hangkong Dongli Xuebao/Journal of Aerospace Power, Vol: 22, Pages: 849-858, ISSN: 1000-8055
An experimental investigation into pre-swirl effectiveness and receiver hole discharge coefficient characteristics for a high radius injection pre-swirl cooling systems was carried out on a physically representative experimental rig with a 450 mm diameter rotor. The receiver holes and pre-swirl nozzle were located at a radius of 181 mm and 180 mm respectively. The experimental work was mainly conducted at 5000-12000 r/min, 4 bar absolute pressure and 1.132 kg/s air supply. The maximum air supply temperature was 190°C. Pressure and temperature distributions in the pre-swirl system were examined with an emphasis on the velocity effectiveness of the pre-swirl system as a whole and on the discharge coefficients of the rotating 'receiver holes' in the rotor. The results showed that the velocity effectiveness increased with increasing swirl ratio resulting in reduced blade cooling flow temperature. Different seal flow configurations caused very different effectiveness at different speeds, but outflow through the inner and outer seals always gave the highest effectiveness compared other configurations. Increasing the seal flow rate reduced the effectiveness. For the coefficient of discharge, except for the low speed range, it increased with increase in swirl ratio for most speeds.
Pett ADW, Coren DD, Childs PRN, 2007, Model validation for a shrouded rotor-stator system with superposed cooling and static protuberances, 52nd ASME Turbo Expo 2007, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1379-1386
Childs PRN, Hamilton T, Morris RD, et al., 2007, Centre For Technology Enabled Creativity, the 8th International Conference on Engineering and Product Design Education, Publisher: The Design Society, Pages: 367-372
Farahani A, Childs P, 2007, Characterisation of static strip seal flow, 52nd ASME Turbo Expo 2007, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1169-1177
Peng Z, New P, Long CA, et al., 2007, An Experimental Investigation of A High Radius Pre-Swirl Cooling System, 8th International Symposium on Experimental and Computational Aerothermodynamics of Internal Flows, Pages: 511-518
An experimental investigation into pre-swirl effectiveness and receiver hole discharge coefficient characteristics for a high radiusinjection pre-swirl cooling systems was carried out on an engine representative experimental rig with a 450 mm diameter rotor. Thereceiver holes and pre-swirl nozzles were located at a radius of 181 mm and 180 mm respectively. The experimental work was conductedat 5000-12000 rpm, 4 bar absolute pressure and 1.132 kg/s air supply. The maximum air supply temperature was 190ºC. Pressureand temperature distributions in the pre-swirl system were examined with an emphasis on the velocity effectiveness of thepre-swirl system as a whole and on the discharge coefficients of the rotating 'receiver holes' in the rotor. The results showed that thevelocity effectiveness increased with increasing swirl ratio resulting in reduced blade cooling flow temperature. Increasing the sealflow rate reduced the effectiveness. For the coefficient of discharge, it increased with increase in swirl ratio for most speeds. Thecoefficient of discharge also decreased with an increase in inner seal flow rate.
Morris RD, Childs PRN, Hamilton T, 2007, Sustainability by design: a reflection on the suitability of pedagogic practice in design and engineering courses in the teaching of sustainable design, European Journal of Engineering Education, Vol: 32, Pages: 135-142
Courses in product design are offered within the United Kingdom at the University of Brighton and the University of Sussex and in both cases are run within engineering departments alongside traditional engineering courses. This paper outlines some of the intrinsic pedagogic practices that are employed by these, and other, design courses. It highlights why creativity is a central tenet within these courses, which has underpinned the successful bid by the universities to jointly become the UK Centre of Excellence in Teaching and Learning in Creativity (CETL in C), and why, in particular, creativity is a key requirement in sustainable design. It supposes why these practices might, and should, offer a suitable role model for more traditional engineering courses.
Childs PRN, 2007, Temperature measurement: resistance thermometry, Publisher: ESDU, ISBN: 978 186 246 595 4
Goergakis C, Whitney C, Woolatt G, et al., 2007, Turbine stator well CFD studies: effect of upstream egress ingestion. GT2007-27406, Publisher: ASME
There is a constant demand in the turbomachineryindustry to improve engine performance, meet stringentenvironmental and safety regulations, and reduce thetime and cost of new product development. Asimprovements in component efficiencies becomeincreasingly difficult to achieve and new materialdevelopment has become more expensive over theyears, more attention is focusing on other areas of gasturbine technology. Internal cooling air systems, inparticular, have been subject to significant research, inorder to reduce the effect of parasitic losses on theoverall engine performance.Often, part of the compressor flow passes directly intoturbine inter-stage cavities primarily for rotor disc cooling.The advantages such a concept offers are (a) betterthermal effectiveness on the rotor disc by having lowerwall temperature (b) preventing, to some degree, theingestion of mainstream hot gases into the cavity. Theseenhancements have to be integrated into the turbinestage without, of course, sacrificing the overallperformance. Detailed knowledge of the flow and heattransfer within these cavities is needed if suchimprovements are to be further pursued.The material presented in this paper investigates theeffect of upstream coolant injection into the mainstreamflow being ingested into a turbine stator well. The coolantinjection comes from an upstream rim seal, and so calledegress. The CFD domain modelled includes both themain gas path and stator well. CFD studies have beenperformed to predict the flow physics in the cavity, andthis has included an investigation of both steady andunsteady effects. This study is extended beyond thecavity flows, and it gives an insight of the mainstream flowparticularly behind the blade rows. The CFD results arecompared with dedicated aerodynamic 3D-blade designcodes. These CFD studies have contributed significantlyin understanding the effect on flow and heat transfer ofupstream turbine coolant injection being subsequentlyingested into a downstream stato
Cooke A, Childs P, Long C, 2007, Investigation into the effect of uncertainty in thermal properties on turbomachinery disc heat transfer using both a Monte Carlo simulation technique and a Taylor series uncertainty propagation method GT2007-27573, 52nd ASME Turbo Expo 2007, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1179-1188
The effect of uncertainties in the thermal properties of components and surrounding fluids is often ignored in the field of experimental turbomachinery heat transfer. The work reported here uses two different methods of uncertainty analysis to help quantify these effects: 1) a stochastic Monte Carlo simulation and 2) a Taylor series uncertainty propagation. These two methods were used on a steady state free disc test case having a turbulent flow regime. The disc modelled was made from IMI 318 titanium and had an inner and outer radius of 0.115 m and 0.22 m respectively, representative of engine and test rig geometry. The disc thickness was 0.016 in. Convective boundary conditions were derived from the relevant equation for local Nusselt number. The applied boundary conditions resulted in local heat transfer coefficients in the range of approximately 120 W/m(2) K to 170 W/m(2) K. Uncertainties for these heat transfer coefficients were a near identical match between the two different uncertainty methods and were found to be 0.66%. Calculated heat flux values fell within the range of approximately 1500 W/m(2) and 5200 W/m(2). The Monte Carlo uncertainty method returned uncertainty values varying from +/- 1.17% to +/- 0.47% from the inner and outer radii respectively. An extended Taylor series of uncertainty propagation returned uncertainties varying from +/- 1.82% to +/- 0.96%, from the inner and outer radius respectively and increased and decreased a number of times in between. These differences are due to assumptions and simplifications which need to be made when using the Taylor series method and shows that a Monte Carlo simulation analysis offers a better way of quantifying the uncertainties associated with disc to air heat transfer as it is more realistic. Studying the magnitudes of uncertainty allows the analyst to understand the impact that uncertainties in thermal properties can have on calculated values of disc to air heat fluxes and heat trans fer coefficient
Childs PRN, 2007, Temperature measurement: thermocouples, ISBN: 9781862465947
ESDU 06018 is one of a series of Data Items concerned with temperature measurement and provides background information and practical guidance on designing temperature measuring systems using thermocouples. The nominal temperature range covered is -272 to 2000 degrees C but the comments will apply, in general terms, to all thermocouple systems. It is aimed at the user who wishes to design and install a practical thermocouple system using improved techniques that will allow temperatures to be measured within known tolerances. ESDU 06018 considers the selection, preparation, and installation of thermocouples, the use of compensating or extension cables, and methods of referencing to a known temperature. The requirements for reliable systems operating to commercial tolerances are also described. Various factors that might impair the accuracy and stability of thermocouples are identified together with methods of reducing their effect. A check list for the design of a thermocouple system is given and a flowchart procedure for selecting appropriate thermocouple materials is provided. The employment of the techniques described will ensure that the temperature of the measuring junction is within known tolerances.
Hamilton T, Morris R, Childs PRN, 2007, 'Learning from Higher Arts Education in Designing Constructivist Learning Spaces: A Case Study of InQbate: The Centre of Excellence in Teaching and Learning in Creativity, Cambridge, 3rd ELIA Teachers' Academy, Publisher: Burlington Press, Pages: 105-108
The aims of ‘InQbate: The Centre of Excellence in Teaching and Learning in Creativity’ aretwofold: to increase the creativity of our teaching, and to improve our teaching of creativity [Childset al, 2006]. This case study outlines how we have addressed these twin goals by drawing on theexperience of the creative disciplines in order to design physical learning spaces that supportcreation-, construction-, performance-, installation- and exhibition-based activities within a socialconstructivist pedagogical model. We hope that this will act as a bridge for increased dialogueand collaboration between Higher Arts Education and non-Arts subjects.
Long CA, Childs PRN, 2007, The effect of inlet conditions on the flow and heat transfer in a multiple rotating cavity with axial throughflow, Journal of Aerospace Power, Vol: 22, Pages: 683-693
Childs PRN, 2007, FLOW IN ROTATING COMPONENTS - DISCS, CYLINDERS AND CAVITIES, Publisher: ESDU, ISBN: 978 1 86246 605 0
ESDU 07004 introduces the subject of flow in applications where rotating machinery components induce flow rotation. There are many examples of rotating and swirling flow in engineering such as the flow between a stationary disc and a rotating disc, in a gas turbine engine or turbocharger, and the flow in an annulus with a rotating inner cylinder, between the armature and stator of an electric motor. In ESDU 07004, the phenomena involved in rotating flows are introduced and guidance on the techniques for modelling specific rotating flow applications involving discs, cylinders and cavities is provided. Emphasis within ESDU 07004 has been placed on presenting correlations based on analytical, experimental and the computational fluid dynamics (CFD) models for parameters such as mass flow, boundary layer thickness, swirl speed, pressure distribution and moment used in parametric design studies and optimisation. ESDU EngineerIssue 17FLOW IN ROTATING COMPONENTS - DISCS, CYLINDERS AND CAVITIESIssue Table of Contents Jane's Information GroupFlow in Rotating Components Aircraft Cabin Noise Interactive Graphs - updateTransverse Rupture of Lugs Temperature Measurement ESDU 07004 introduces the subject of flow in applications where rotating machinery components induce flow rotation. There are many examples of rotating and swirling flow in engineering such as the flow between a stationary disc and a rotating disc, in a gas turbine engine or turbocharger, and the flow in an annulus with a rotating inner cylinder, between the armature and stator of an electric motor. In ESDU 07004, the phenomena involved in rotating flows are introduced and guidance on the techniques for modelling specific rotating flow applications involving discs, cylinders and cavities is provided. Emphasis within ESDU 07004 has been placed on presenting correlations based on analytical, experimental and the computational fluid dynamics (CFD) models for parameters such as mass flow, boundary layer thickness, sw
Childs P, Dullenkopf K, Bohn D, 2006, Internal air systems experimental rig best practice, 51st ASME Turbo Expo, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1333-1343
Cooke A, Childs P, Long C, 2006, An investigation into the uncertainty of turbomachinery disc heat transfer calculations using Monte Carlo simulation methods, 51st ASME Turbo Expo, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1301-1311
Farahani A, Childs P, 2006, Nozzle guide vane static strip seals, 51st ASME Turbo Expo, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1321-1331
Dixon JA, Brunton IL, Scanlon TJ, et al., 2006, Turbine stator well heat transfer and cooling flow optimisation, 51st ASME Turbo Expo, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1375-1383
Childs P, de la Fuente CP, 2006, An investigation of lock plate flow, 51st ASME Turbo Expo, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 1463-1471
Long CA, Childs PRN, 2006, The effect of inlet conditions on the flow and heat transfer in a multiple rotating cavity with axial throughflow, 1st International Symposium on Jet Propulsion and Power Engineering, Pages: 321-328
This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig. Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70 % full scale version of a high pressure compressor stack of an axial gas turbine engine. Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air. Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows (Reφ up to 5 x 106 and Rez up to 2 x 105). Two different builds have been tested. The most significant difference between these two build configurations is the size of the annular gap between the (non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method. The velocity measurements were made using a two component, LDA system. The heat transfer results from the discs show differences between the two builds. This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity. There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig. For the narrow annular gap, there is an increase of non-dimensional tangential velocity Vφ / Ωr with radial location to solid body rotation Vφ / Ωr = 1. For the wider annular gap, the non-dimensional velocities show a decrease with radial location to solid body rotation.
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