The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Michael Pfitzner - One of the best experts on this subject based on the ideXlab platform.
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A Comprehensive Investigation of Preswirled Flow Through Rotating Radial Holes
Journal of Engineering for Gas Turbines and Power, 2014Co-Authors: Daniel Riedmüller, Jan Sousek, Michael PfitznerAbstract:This paper reports on the flow (centrifugal = radially outward, centripetal = radially inward) through rotating radial orifices with and without preswirl in the flow approaching the orifice in the Outer Annulus. The aerodynamical behavior of flow through radial rotating holes is different from the one through axial and stationary holes due to the presence of centrifugal and Coriolis forces. To investigate the flow phenomena and the discharge coefficient of these orifices in detail, an existing test rig containing two independently rotating shafts (corotating and counter rotating) was used. To simulate conditions of real gas turbines, where the flow is often influenced by upstream components, various preswirl angles were used in the test rig. Measurements of the flow discharge coefficient in both flow directions through the orifices (centripetal and centrifugal), with and without preswirl generation in the Outer Annulus, are presented at various flow conditions (pressure ratios across orifices, Mach numbers of approaching flow) and for different geometric parameters (length to diameter ratios, sharp/rounded inlet edges). Flow effects that occur with preswirled flow are clarified. A comparison of the experimental data, for both flow directions, shows a similar behavior of the discharge coefficients with increasing shaft speeds. To supplement the experimental data and to better understand the experimental findings, numerical simulations were performed, which show a good agreement with the experimental results. Furthermore, an optimization model with complete automatic grid generation, computational fluid dynamics (CFD) simulation, and postprocessing, was built to enable large parametric studies, e.g., grid independence of the solutions.
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A Comprehensive Investigation of Pre-Swirled Flow Through Rotating Radial Holes
Volume 5C: Heat Transfer, 2014Co-Authors: Daniel Riedmüller, Jan Sousek, Michael PfitznerAbstract:This paper reports on the flow (centrifugal = radially outwards, centripetal = radially inwards) through rotating radial orifices with and without pre-swirl in the flow approaching the orifice in the Outer Annulus. The aerodynamical behavior of flow through radial rotating holes is different from the one through axial and stationary holes due to the presence of centrifugal and Coriolis forces. To investigate the flow phenomena and the discharge coefficient of these orifices in detail, an existing test rig containing two independently rotating shafts (co- and counter rotating) was used. To simulate conditions of real gas turbines, where the flow is often influenced by upstream components, various pre-swirl angles were used in the test rig. Measurements of the flow discharge coefficient in both flow directions through the orifices (centripetal and centrifugal), with and without pre-swirl generation in the Outer Annulus, are presented at various flow conditions (pressure ratios across orifices, Mach numbers of approaching flow) and for different geometric parameters (length to diameter ratios, sharp/rounded inlet edges). Flow effects, that occur with pre-swirled flow are clarified. A comparison of the experimental data, for both flow directions, shows a similar behavior of the discharge coefficients with increasing shaft speeds. To supplement the experimental data and to better understand the experimental findings, numerical simulations were performed, which show a good agreement with the experimental results. Furthermore, an optimization model with complete automatic grid generation, CFD simulation and post-processing, was built to enable large parametric studies e.g. grid independence of the solutions.
D.p. Agrawal - One of the best experts on this subject based on the ideXlab platform.
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Effect of swirl on the flow characteristics in the Outer Annulus of a prototype reverse-flow gas turbine combustor
Experimental Thermal and Fluid Science, 2001Co-Authors: Sanjeev Bharani, S. N. Singh, D.p. AgrawalAbstract:Flow characteristics in the Outer Annulus and its effects on the flow splits through different liner holes have been established by conducting experiments on a full Annulus prototype reverse-flow gas turbine combustor for different intensities of swirl imposed on the inlet flow. Measurements have been taken with a direction-sensitive pressure probe and a standard hot wire probe. It is seen that imposition of swirl improves the uniformity of outlet flow in θ-plane. It is observed that the flow split through the turn-section cooling holes and primary holes remains nearly constant up to S=0.55, while the split through the dilution holes decreases. With increase in the swirl intensity (S=0.84) the flow split through the turn-section and dilution holes increases while flow split through the primary holes reduces. The turbulence intensity level at the outlet is not affected by the imposed inlet swirl.
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Sector model : An approach for experimental studies of gas turbine combustors
Indian Journal of Engineering and Materials Sciences, 1997Co-Authors: Sanjeev Bharani, S. N. Singh, D.p. AgrawalAbstract:An attempt has been made to analyze flow in the Outer Annulus of an annular reverse-flow combustor using a realistic using 120° sector model with realistic design. Velocity distribution has been measured in the Outer Annulus for two inlet conditions and the flow split through dilution, primary and cooling holes have been evaluated. It is observed that the flow split through the turn-section rows of cooling holes as well as swirlers and the inner Annulus does not get affected significantly by the change in the inlet conditions.
Daniel Riedmüller - One of the best experts on this subject based on the ideXlab platform.
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A Comprehensive Investigation of Preswirled Flow Through Rotating Radial Holes
Journal of Engineering for Gas Turbines and Power, 2014Co-Authors: Daniel Riedmüller, Jan Sousek, Michael PfitznerAbstract:This paper reports on the flow (centrifugal = radially outward, centripetal = radially inward) through rotating radial orifices with and without preswirl in the flow approaching the orifice in the Outer Annulus. The aerodynamical behavior of flow through radial rotating holes is different from the one through axial and stationary holes due to the presence of centrifugal and Coriolis forces. To investigate the flow phenomena and the discharge coefficient of these orifices in detail, an existing test rig containing two independently rotating shafts (corotating and counter rotating) was used. To simulate conditions of real gas turbines, where the flow is often influenced by upstream components, various preswirl angles were used in the test rig. Measurements of the flow discharge coefficient in both flow directions through the orifices (centripetal and centrifugal), with and without preswirl generation in the Outer Annulus, are presented at various flow conditions (pressure ratios across orifices, Mach numbers of approaching flow) and for different geometric parameters (length to diameter ratios, sharp/rounded inlet edges). Flow effects that occur with preswirled flow are clarified. A comparison of the experimental data, for both flow directions, shows a similar behavior of the discharge coefficients with increasing shaft speeds. To supplement the experimental data and to better understand the experimental findings, numerical simulations were performed, which show a good agreement with the experimental results. Furthermore, an optimization model with complete automatic grid generation, computational fluid dynamics (CFD) simulation, and postprocessing, was built to enable large parametric studies, e.g., grid independence of the solutions.
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A Comprehensive Investigation of Pre-Swirled Flow Through Rotating Radial Holes
Volume 5C: Heat Transfer, 2014Co-Authors: Daniel Riedmüller, Jan Sousek, Michael PfitznerAbstract:This paper reports on the flow (centrifugal = radially outwards, centripetal = radially inwards) through rotating radial orifices with and without pre-swirl in the flow approaching the orifice in the Outer Annulus. The aerodynamical behavior of flow through radial rotating holes is different from the one through axial and stationary holes due to the presence of centrifugal and Coriolis forces. To investigate the flow phenomena and the discharge coefficient of these orifices in detail, an existing test rig containing two independently rotating shafts (co- and counter rotating) was used. To simulate conditions of real gas turbines, where the flow is often influenced by upstream components, various pre-swirl angles were used in the test rig. Measurements of the flow discharge coefficient in both flow directions through the orifices (centripetal and centrifugal), with and without pre-swirl generation in the Outer Annulus, are presented at various flow conditions (pressure ratios across orifices, Mach numbers of approaching flow) and for different geometric parameters (length to diameter ratios, sharp/rounded inlet edges). Flow effects, that occur with pre-swirled flow are clarified. A comparison of the experimental data, for both flow directions, shows a similar behavior of the discharge coefficients with increasing shaft speeds. To supplement the experimental data and to better understand the experimental findings, numerical simulations were performed, which show a good agreement with the experimental results. Furthermore, an optimization model with complete automatic grid generation, CFD simulation and post-processing, was built to enable large parametric studies e.g. grid independence of the solutions.
Sanjeev Bharani - One of the best experts on this subject based on the ideXlab platform.
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Effect of swirl on the flow characteristics in the Outer Annulus of a prototype reverse-flow gas turbine combustor
Experimental Thermal and Fluid Science, 2001Co-Authors: Sanjeev Bharani, S. N. Singh, D.p. AgrawalAbstract:Flow characteristics in the Outer Annulus and its effects on the flow splits through different liner holes have been established by conducting experiments on a full Annulus prototype reverse-flow gas turbine combustor for different intensities of swirl imposed on the inlet flow. Measurements have been taken with a direction-sensitive pressure probe and a standard hot wire probe. It is seen that imposition of swirl improves the uniformity of outlet flow in θ-plane. It is observed that the flow split through the turn-section cooling holes and primary holes remains nearly constant up to S=0.55, while the split through the dilution holes decreases. With increase in the swirl intensity (S=0.84) the flow split through the turn-section and dilution holes increases while flow split through the primary holes reduces. The turbulence intensity level at the outlet is not affected by the imposed inlet swirl.
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Sector model : An approach for experimental studies of gas turbine combustors
Indian Journal of Engineering and Materials Sciences, 1997Co-Authors: Sanjeev Bharani, S. N. Singh, D.p. AgrawalAbstract:An attempt has been made to analyze flow in the Outer Annulus of an annular reverse-flow combustor using a realistic using 120° sector model with realistic design. Velocity distribution has been measured in the Outer Annulus for two inlet conditions and the flow split through dilution, primary and cooling holes have been evaluated. It is observed that the flow split through the turn-section rows of cooling holes as well as swirlers and the inner Annulus does not get affected significantly by the change in the inlet conditions.
Jill P. G. Urban - One of the best experts on this subject based on the ideXlab platform.
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Identification of cell markers of the nucleus and Annulus of bovine intervertebral discs
International Journal of Experimental Pathology, 2008Co-Authors: Barry K. Derham, Jill P. G. UrbanAbstract:Introduction The intervertebral disc consists of three regions, the nucleus pulpous and the inner and Outer Annulus containing cells with individual phenotypes. However, no molecular markers are known to discriminate between the various cell types. Molecular markers would help identify the cell types through development of the disc, ageing of the disc, cell localization and in pathological states such as degenerative disc disease and scoliosis. Here, we present data revealing major difference between the cell types using SDS-PAGE and mass spectrometry. Such differences will help to develop molecular markers to identify the cell types using immunoblotting and immunohistochemistry. Methods Intervertebral discs were isolated from bovine tails and separated into three distinct regions of the nucleus, inner and Outer Annulus. The isolated regions were separately digested with collagenase and peptidase overnight. The remaining cell suspensions were sieved through a filter to remove large particles and then extensively washed. The cells were then separated into membrane and supernatant fractions by incubation with Triton followed by centrifugation. SDS-PAGE analysis using a variety of acylamide gels of the various fractions revealed bands of interest that where then cut from the gel, digested with trypsin and analysed by mass spectrometry. The peptide mass/charge data were collected and then compared with a databank of known peptide masses to give a composite protein mass. Results Analysis of the membrane and supernatant fractions of the cells from the three distinct regions in the disc by SDS-PAGE revealed unique protein patterns between the regions and fractions. A large broad band from the membrane of nucleus cells was analysed by mass spectrometry that revealed strong matches for myosin and clathrin and a match for basement membrane collagen-IV. A control band from the Outer Annulus also revealed a strong match for myosin and to a lesser extent basement membrane collagen type-IV. A strong SDS-PAGE band from the membrane fraction of the Outer Annulus revealed a mass spectrometry match to actin. Analysis of the corresponding supernatant fraction revealed a strong match to actin, whereas a band of similar molecular weight from the inner Annulus revealed another myosin chain. Conclusion The differences revealed in the protein profile of cells from the three regions of disc and the identification of prominent proteins demonstrate that these differences can be used to identify molecular markers. SDS-PAGE and mass spectrometry analysis of significant bands showed strong matches in the membrane fraction for myosin and clathrin, and also basement membrane collagen-IV. By using immunoblotting and immunohistochemistry, it will be possible to follow the development, ageing and pathology of the three cell types and will hopefully be extended to finding markers that characterize the individual stages of the degenerative changes. This study will also include genechip technology to identify at the RNA level the difference between the three cell types. This work was funded by the EU EURODISC project (QLK6-CT-2002–02582).
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IDENTIFICATION OF CELL MARKERS OF THE NUCLEUS AND Annulus OF BOVINE INTERVERTEBRAL DISCS
2005Co-Authors: Barry K. Derham, Jill P. G. UrbanAbstract:Introduction: The intervertebral disc consists of three regions; the nucleus pulposus and the inner and Outer Annulus contain cells with individual phenotypes. However, no molecular markers are known to discriminate between the various cell types. Molecular markers would help identify the cell types in development, ageing, localisation and pathological states. Here we reveal major differences between the cell types using SDS-PAGE and mass spectrometry, which will help to develop molecular markers. Methods: Intervertebral discs were isolated from bovine tails and separated into three distinct regions; the nucleus, inner and Outer Annulus. Cells were separated by enzyme digestion overnight and then washed extensively. The cells were then separated into membrane and supernatant fractions followed by SDS-PAGE analysis; various fractions revealed bands of interest that were then cut from the gel, digested with trypsin and analysed by mass spectrometry. Results: Analysis of the membrane and supernatant fractions of the cells by SDS-PAGE revealed unique protein patterns between the regions and fractions. A broad band from the membrane of nucleus cells was analysed by mass spectrometry and revealed strong matches for myosin and clathrin. A control band from the Outer Annulus also revealed a strong match for myosin. A strong band from the membrane fraction of the Outer Annulus revealed a mass spectrometry match to actin. Analysis of the corresponding supernatant fraction revealed a strong match to actin, whereas a band of similar molecular weight from the inner Annulus revealed another myosin chain. Conclusion: The differences revealed in the protein profile of cells from the three regions of disc and the identification of prominent proteins demonstrates that such differences can be used to identify molecular markers. Specific molecular markers for cells from different disc regions will aid in both understanding disc pathology and in development of new biological treatments.
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effects of low oxygen concentrations and metabolic inhibitors on proteoglycan and protein synthesis rates in the intervertebral disc
Journal of Orthopaedic Research, 1999Co-Authors: Hirokazu Ishihara, Jill P. G. UrbanAbstract:The intervertebral disc is the largest asvacular structure in the body; consequently, there are steep gradients in O2 concentration, with PO2 falling to as low as 1% O2 in the centre of the disc. We investigated the effect of O2 concentration on the rates of O2 consumption, lactate production, and sulphate and proline incorporation in bovine caudal discs. We also investigated the effects of metabolic inhibitors of energy production pathways on tracer incorporation. Samples from the Outer Annulus and nucleus pulposus were incubated for 24 hours in 1-21% O2. Rates were measured during the last 4 hours of incubation. As O2 concentration was reduced from 10 to 1% O2, O2 consumption rates fell by around 75% and lactate production rates almost doubled; the bovine discs thus showed a positive progressive Pasteur effect. Incorporation rates of [3H]proline and [35S]sulphate were lowest at 1% O2. In the nucleus, but not in the Outer Annulus, the rate of [35S]incorporation peaked at 5% O2, where it was 30% greater than at 21% O2 and 150% greater than at 1% O2. The competitive glycolysis inhibitor 2-deoxyglucose, the oxidative phosphorylation uncoupler 2,4-dinitrophenol, and the oxidative phosphorylation inhibitor sodium azide all markedly reduced sulphate incorporation. These results, together with previous measurements of CO2 production rates, suggest that a functionally significant fraction of the disc's energy is supplied by oxidative phosphorylation. However, low levels of PO2, 2,4-dinitrophenol, and sodium azide have been reported to reduce sulphate incorporation in articular cartilage, a tissue that derives its energy almost entirely from glycolysis.
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Variation with Age in the Pattern of Type X Collagen Expression in Normal and Scoliotic Human Intervertebral Discs
Calcified tissue international, 1998Co-Authors: T. Aigner, K.-r. Greskötter, Jeremy Fairbank, K. Von Der Mark, Jill P. G. UrbanAbstract:The distribution and expression of type X collagen, a calcium-binding collagen, which is a marker of hypertrophic chondrocytes and thought to be involved in cartilage calcification, was examined in situ in nondegenerate (grade I or II) human discs taken at autopsy over a wide age range (fetal–>80 years) and also in scoliotic discs removed at surgery. In the fetal vertebral column, type X collagen was strongly expressed in the hypertrophic chondrocytes of the endplate, but was not seen in other areas. In the cartilaginous endplate of adults, it was found over the whole age range examined, with intensity increasing with age. In the disc matrix itself, type X collagen was demonstrated around individual cells from all individuals older than 50 years, but not in any fetal or autopsy disc from individuals younger than 40 years. In scoliotic discs, however, focal type X collagen expression was seen in 3/8 patients younger than 40 years including one 12-year-old. No type X collagen was found in the Outer Annulus in any autopsy or scoliotic disc, supporting the idea that cells of the Outer Annulus are phenotypically distinct from cells of the inner Annulus and the nucleus. Our results demonstrate for the first time that type X collagen is a possible gene product of the intervertebral disc cells and a potential biochemical component of the disc matrix. They indicate that with age or in scoliosis, some cells from the inner Annulus or nucleus of the disc differentiate to the hypertrophic chondrocyte phenotype. This might be the initiating event for the abnormal calcification described in aged and scoliotic discs in other studies.
