The Experts below are selected from a list of 21768 Experts worldwide ranked by ideXlab platform
Alexander Penn - One of the best experts on this subject based on the ideXlab platform.
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regimes of jetting and bubbling in a fluidized bed studied using real time magnetic resonance imaging
Chemical Engineering Journal, 2020Co-Authors: Alexander Penn, Christopher M Boyce, Klaas P Pruessmann, Christoph R MullerAbstract:Abstract Real-time magnetic resonance imaging was used to study the different flow regimes which occur in a fluidized bed containing a Gas Injection System. The Gas flow rates through the main distributor and a central orifice were varied independently. We identified six different regimes of bubbling and jetting behavior: (1) freely bubbling, (2) permanent jet, (3) spouting, (4) pulsating jet, (5) pulsating jet with bubble collapse and (6) pulsating jet and freely bubbling. While regimes (1–4) have been described previously in the literature, regimes (5) and (6) are described here for the first time. To construct a regime map, the Froude number (Fr) and the ratio of the superficial Gas velocity to the minimum fluidization velocity (U/Umf) were used to describe the System. We observed that bubbles formed predominantly, when U/Umf > 1. Further, we propose an empirical model that predicts the length of jets in the permanent jet regime as a function of Fr and background Gas flow as l jet d or = 0.12 Fr 0.38 1 + U bg U mf 0.81 . The proposed model is in good agreement with tomographic measurements in smaller 3D Systems reported in the literature, indicating that the non-dimensionalized description of jet length using a Fr number is valid throughout a large range of System diameters. Moreover, the bubble breakoff frequency of the pulsating jet regime was assessed by Fourier analysis, demonstrating that the frequency increases with increasing Fr before plateauing.
Christoph R Muller - One of the best experts on this subject based on the ideXlab platform.
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regimes of jetting and bubbling in a fluidized bed studied using real time magnetic resonance imaging
Chemical Engineering Journal, 2020Co-Authors: Alexander Penn, Christopher M Boyce, Klaas P Pruessmann, Christoph R MullerAbstract:Abstract Real-time magnetic resonance imaging was used to study the different flow regimes which occur in a fluidized bed containing a Gas Injection System. The Gas flow rates through the main distributor and a central orifice were varied independently. We identified six different regimes of bubbling and jetting behavior: (1) freely bubbling, (2) permanent jet, (3) spouting, (4) pulsating jet, (5) pulsating jet with bubble collapse and (6) pulsating jet and freely bubbling. While regimes (1–4) have been described previously in the literature, regimes (5) and (6) are described here for the first time. To construct a regime map, the Froude number (Fr) and the ratio of the superficial Gas velocity to the minimum fluidization velocity (U/Umf) were used to describe the System. We observed that bubbles formed predominantly, when U/Umf > 1. Further, we propose an empirical model that predicts the length of jets in the permanent jet regime as a function of Fr and background Gas flow as l jet d or = 0.12 Fr 0.38 1 + U bg U mf 0.81 . The proposed model is in good agreement with tomographic measurements in smaller 3D Systems reported in the literature, indicating that the non-dimensionalized description of jet length using a Fr number is valid throughout a large range of System diameters. Moreover, the bubble breakoff frequency of the pulsating jet regime was assessed by Fourier analysis, demonstrating that the frequency increases with increasing Fr before plateauing.
Dimitrios Hariskos - One of the best experts on this subject based on the ideXlab platform.
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rubidium distribution at atomic scale in high efficient cu in ga se2 thin film solar cells
Applied Physics Letters, 2018Co-Authors: Arantxa Vilaltaclemente, Philip L Jackson, Roland Wuerz, Mohit Raghuwanshi, S Duguay, Celia Castro, E Cadel, P Pareige, Dimitrios HariskosAbstract:The introduction of a rubidium fluoride post deposition treatment (RbF-PDT) for Cu(In,Ga)Se2 (CIGS) absorber layers has led to a record efficiency up to 22.6% for thin-film solar cell technology. In the present work, high efficiency CIGS samples with RbF-PDT have been investigated by atom probe tomography (APT) to reveal the atomic distribution of all alkali elements present in CIGS layers and compared with non-treated samples. A Scanning Electron Microscopy Dual beam station (Focused Ion Beam–Gas Injection System) as well as Transmission Kikuchi diffraction is used for atom probe sample preparation and localization of the grain boundaries (GBs) in the area of interest. The analysis of the 3D atomic scale APT reconstructions of CIGS samples with RbF-PDT shows that inside grains, Rb is under the detection limit, but the Na concentration is enhanced as compared to the reference sample without Rb. At the GBs, a high concentration of Rb reaching 1.5 at. % was found, and Na and K (diffusing from the glass subs...
Mohit Raghuwanshi - One of the best experts on this subject based on the ideXlab platform.
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rubidium distribution at atomic scale in high efficient cu in ga se2 thin film solar cells
Applied Physics Letters, 2018Co-Authors: Arantxa Vilaltaclemente, Philip L Jackson, Roland Wuerz, Mohit Raghuwanshi, S Duguay, Celia Castro, E Cadel, P Pareige, Dimitrios HariskosAbstract:The introduction of a rubidium fluoride post deposition treatment (RbF-PDT) for Cu(In,Ga)Se2 (CIGS) absorber layers has led to a record efficiency up to 22.6% for thin-film solar cell technology. In the present work, high efficiency CIGS samples with RbF-PDT have been investigated by atom probe tomography (APT) to reveal the atomic distribution of all alkali elements present in CIGS layers and compared with non-treated samples. A Scanning Electron Microscopy Dual beam station (Focused Ion Beam–Gas Injection System) as well as Transmission Kikuchi diffraction is used for atom probe sample preparation and localization of the grain boundaries (GBs) in the area of interest. The analysis of the 3D atomic scale APT reconstructions of CIGS samples with RbF-PDT shows that inside grains, Rb is under the detection limit, but the Na concentration is enhanced as compared to the reference sample without Rb. At the GBs, a high concentration of Rb reaching 1.5 at. % was found, and Na and K (diffusing from the glass subs...
Bengt Johansson - One of the best experts on this subject based on the ideXlab platform.
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investigation of performance and emission characteristics of a heavy duty natural Gas engine operated with pre chamber spark plug and dilution with excess air and egr
SAE International journal of engines, 2012Co-Authors: Ashish Shah, Per Tunestal, Bengt JohanssonAbstract:This article deals with application of turbulent jet ignition technique to heavy duty multi-cylinder natural Gas engine for mobile application. Pre-chamber spark plugs are identified as a promising means of achieving turbulent jet ignition as they require minimal engine modification with respect to component packaging in cylinder head and the ignition System. Detailed experiments were performed with a 6 cylinder 9.4 liter turbo-charged engine equipped with multi-point Gas Injection System to compare performance and emissions characteristics of operation with pre-chamber and conventional spark plug. The results indicate that ignition capability is significantly enhanced as flame development angle and combustion duration are reduced by upto 30 % compared to those with conventional spark plugs at certain operating points. Maximum possible dilution (limited by combustion stability index, Coefficient of Variation (COV) of Gross Indicated Mean Effective Pressure (IMEPg)) with excess air and EGR were investigated experimentally at engine speed of 1500 rpm and 5, 12 and 18 bar IMEPg operating load and results indicate that the lean limit is extended by 0.8-1 Lambda unit and 5-8% EGR rate units. It was also observed that pre-chamber spark plugs cause charge pre-ignition at loads exceeding 10-12 bar IMEPg. To avoid this, the minimum amount of dilution, with excess air and then EGR, which is required to operate above 10 bar IMEPg was estimated experimentally. Finally, to compare performance and emission characteristics of operation with these two ignition techniques, the engine was tested on an ESC-like (European Stationary Cycle) 12 mode cycle. Results indicated marginal reduction in cycle averaged NOx emissions with maximum excess air dilution and about 50% reduction with maximum EGR dilution, whereas CO and HC emissions increased. Other operating characteristics like the flame development angle, combustion duration, brake efficiency etc. are also compared for the tested operating range of the test engine. (Less)
