205 results found
Jackson RA, Peyton Jones JC, Pan J, et al., 1999, Chemical aspects of the dynamic performance of a three-way catalyst, SAE Technical Papers
The gas components CO, CO2, HC, NOx and the AFR in the exhaust from a SI engine, both upstream and down-stream of a Pd/Rh catalytic converter, have been monitored using fast response analyzers. Regular sequential step changes in the upstream air/fuel ratio (AFR), between two pre-set levels, have been implemented with both long and short periods between the steps. For transitions from rich to lean conditions, and vice-versa, several distinct zones for the output emissions characteristics, corresponding to different states of the catalyst surface, have been identified. These results suggest that, under reducing conditions, hydrogen is stored on the catalyst surface whereas under oxidizing conditions oxygen is stored by two different processes. These chemical insights facilitate the development of realistic models for tailpipe emissions from engines which are perturbed from steady state running. Copyright © 1999 Society of Automotive Engineers, Inc.
Childs PRN, Noronha MB, 1999, 1997 John P. Davis Award - The impact of machining techniques on centrifugal compressor impeller performance, JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME, Vol: 121, Pages: 637-643, ISSN: 0889-504X
Jackson RA, Peyton-Jones JC, Pan J, et al., 1999, Chemical aspects of the dynamic performance of a three-way catalyst. SAE 1999-01-0312, Society of Automotive Engineers International Congress 1999, Publisher: SAE
Childs PRN, Simons RW, 1999, Small priced tools and equipment case study, 21st Annual Conference on Engineering Design Education/6th National Conference on Product Design Education, Publisher: PROFESSIONAL ENGINEERING PUBLISHING LTD, Pages: 275-278
Greenwood JR, Childs PRN, Chaloner P, 1999, Gold leads to PRTs for monitoring high temperatures, GOLD BULLETIN, Vol: 32, Pages: 85-+, ISSN: 0017-1557
Childs PRN, Greenwood JR, Long CA, 1999, Heat flux measurement techniques, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE, Vol: 213, Pages: 655-677, ISSN: 0954-4062
Childs PRN, Nilsson K, 1999, Flow phenomena and functionality of the infant Flow system, 5th Annual Reason Conference
Childs PRN, 1998, Mechanical design, Publisher: Hodder Arnold, ISBN: 9780340692363
Concentrating mainly on rotary machine elements such as bearings, shafts, gears, seals,chains, clutches and brakes, this book provides the methodology for ...
Ozturk HK, Childs PRN, Turner AB, et al., 1998, Three dimensional computational study of windage heating within an axial compressor stator well, ISSN: 0402-1215
Shrouded stator blades are sometimes used to prevent vibration problems, but more often they are used to eliminate blade over-tip leakage flows. A trench or recess referred to as a stator well must be provided in the rotor drum assembly in order to accommodate the stator shroud. This paper presents a computational study of the flow and windage generation within an axial compressor stator well. Windage heating levels for a three dimensional compressible solution of flow through a geometry comprising upstream and downstream stator well cavities, labyrinth seal and the stator blade row are quantified. The potential for hot fluid ejected from the upstream stator well seal into the mainstream annulus, migrating through the blade row and being re-ingested at the downstream stator well seal for further windage heating has been studied using a layered temperature boundary condition at entry to the stator row. The possible reconfiguration of detailed stator well geometry has been explored to identify options for controlling flow rate and reducing windage levels, other than controlling clearances, yielding a 9% reduction in flow rate and a 9% reduction in windage heating.
Childs PRN, Noronha MB, 1997, Impact of machining techniques on centrifugal compressor impeller performance, Pages: 637-643, ISSN: 0402-1215
A large proportion of modern centrifugal impellers are machined from solid forgings rather than made from cast metal. The CNC milling process offers options to manufacturers to minimize manufacturing costs whilst also enhancing performance of the impeller. Efficient manufacturing can result in cutter tool marks and paths and associated roughness remaining on the hub and blade surfaces of impellers as a result of minimizing passes and maximizing the cut. The goal of manufacturers is to allow these marks to be as deep as possible to minimize machining costs but without any negative effects in performance and possibly even enhancing it. There are existing modelling methods that predict the influence of roughness on compressor performance using the definition of an equivalent sand grain roughness. The purpose of this study is to relate the performance directly to the tool mark characteristics that are by-products of machining, namely cusp height, cutter path roughness and orientation of the cutter path relative to the local flow velocity, to review the current modelling techniques for predicting the influence of surface condition on compressor performance and to show the scope for optimization of manufacturing and performance considerations.
Turner AB, Long CA, Childs PRN, et al., 1997, Review of some current problems in gas turbine secondary systems, American Society of Mechanical Engineers (Paper), ISSN: 0402-1215
This paper reviews the current position of five major problem areas in gas turbine secondary air system design. Although the problems are of primary interest to the designer of the coolant flow paths, since they directly affect the temperature, the stresses and thus the life of the major rotating components, three of the problems interact with the main gas path and are thus also the concern of the mainstream aerodynamicist. The five problems reviewed are: prediction of the flow distribution and heat transfer in the high pressure compressor drive cone cavity from the turbine to the rim of the HP compressor running underneath the combustion chamber; the flow penetration and heat transfer in the multiple rotating cavities formed by the multiple discs of the high pressure compressor with a rotating shaft running through the bores; the control of ingestion of hot turbine mainstream gas into the rotor-stator wheelspaces through the rim-seals; the problem of compressor and turbine stator-well heating, particularly compressor stator-wells in which excessive temperatures have been occasionally measured and finally, the pre-swirl coolant system which has to take the blade cooling air across from the stationary casing to the rotating turbine disc in the most advantageous manner.
Bayley FJ, Childs PRN, 1997, Prediction of ingress rates to turbine and compressor wheelspaces, INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW, Vol: 18, Pages: 218-228, ISSN: 0142-727X
Bayley FJ, Childs PRN, 1997, Calculation of hot gas ingress and egress rates in turbomachine wheelspaces, Pages: 521-530, ISSN: 2410-4833
This paper extends methods for modelling ingress and egress rates of flow in the wheelspace formed between a stationary and rotating disc, as in a high pressure turbine, and also in stator wells formed around shrouded stator blade rows. The methods are based on the one dimensional inviscid equation of motion and are developed to model the effects of a circumferentially varying pressure boundary condition, representative of mainstream bladed annulus conditions, as well as rotational and geometrical effects. In particular this paper addresses the selection and influence of coefficients necessary for the applied use of these equations.
Ozturk HK, Turner AB, Childs PRN, 1997, Numerical prediction of axial compressor stator well flows, International Centre for Heat and Mass Transfer, International Symposium on Advances in Computational Heat Transfer
Turner AB, Long CA, Childs PRN, et al., 1997, A review of some current problems in gas turbine internal air systems. ASME Paper 97-GT-325, ASME Aeroengine Congress, Publisher: ASME
Ozturk HK, Childs PRN, Turner AB, 1997, Numerical solution of flow and heat transfer in axial compressor stator wells, IChemE 5th UK National Heat Transfer Conference, Publisher: Institution of Chemical Engineers
Childs PRN, Long CA, 1996, A review of forced convective heat transfer in stationary and rotating annuli, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE, Vol: 210, Pages: 123-134, ISSN: 0954-4062
Childs PRN, Long CA, Turner AB, 1995, A review of convective heat transfer in open and closed rotating annular cavities, 4th UK National Conference on Heat Transfer, Publisher: MECHANICAL ENGINEERING PUBL, Pages: 67-71, ISSN: 1356-1448
Bayley FJ, Childs PRN, 1994, Air temperature rises in compressor and turbine stator wells, American Society of Mechanical Engineers (Paper), Pages: 1-10, ISSN: 0402-1215
This paper considers the fluid dynamic principles determining the consequences of mainstream fluid ingressing to the comparatively shallow space between the rotor disc and the ring used in many designs of axial-flow turbo-machine, especially compressors, to support the stator blades at their inner ends. Windage power due to friction between this fluid and the bounding walls of this annular space, or 'stator well', can lead to substantial temperature rises in this region. The feasible range of flow regimes is first developed, especially as influenced by leakage through the internal seals beneath the stators separating adjacent wells. Using published data, on windage coefficients and the effects of geometry on the flow through the wells, very little of which has been obtained from truly representative flow conditions or geometries, calculations have been made to estimate the likely rises in temperature to be anticipated in realistic well designs. Leakage rates appear, not unexpectedly, to be crucial in determining these temperature rises, but the geometries of the system are little less critical, in particular the ratio of the outer to inner radiuses of the stator well and the outer peripheral clearances between rotor and stator surfaces. Leakage into a well from its adjacent neighbour is shown to lead to higher temperature rises downstream of the labyrinth seal and the possible effects of recirculation through stator wells from the mainstream boundary layer could be significant.
CHILDS PRN, TURNER AB, 1994, HEAT TRANSFER ON THE SURFACE OF A CYLINDER ROTATING IN AN ANNULUS AT HIGH AXIAL AND ROTATIONAL REYNOLDS NUMBERS, 10th International Heat Transfer Conference, Publisher: INST CHEMICAL ENGINEERS, Pages: 13-18
Bayley FJ, Childs PRN, 1994, Air temperature rises in compressor and turbine stator wells. ASME Paper 94-GT-185, ASME Turbo Expo 1994, Publisher: ASME
Rayner D, Vaughan CM, Childs PRN, et al., 1992, Numerical solution of the heat transfer in turbulent, swirling annular flows, Pages: 511-531
A numerical investigation into the heat transfer from a heated inner cylinder, rotating in an annulus with an axial throughflow of air, is presented. The finite difference solution algorithm incorporates the advantages of the SIMPLEC pressure-correction scheme with a Full Approximation Scheme (FAS) multigrid method. The increased efficiency allows a thorough numerical investigation to be undertaken.
Childs PRN, Rayner D, Turner AB, 1992, Heat transfer to a cylindrical drum rotating in an annulus under a single stator blade row, International Centre for Heat and Mass Transfer, International Symposium, Heat Transfer in Turbomachinery
Childs PRN, Turner AB, Vaughan CM, et al., 1992, Heat transfer to a rotating drum in an annulus with a stator blade row and axial throughflow. ASME Paper 92-GT-249, ASME Turbo Expo 1992, Publisher: ASME
Childs PRN, 1991, Heat Transfer at the surface of a cylinder rotating in an annulus with a stator blade row and axial throughflow
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