The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Dipal Baruah - One of the best experts on this subject based on the ideXlab platform.
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artificial neural network based modeling of biomass gasification in fixed bed Downdraft gasifiers
Biomass & Bioenergy, 2017Co-Authors: Dipal Baruah, D C Baruah, Manuj Kumar HazarikaAbstract:Abstract The study attempts at developing an artificial neural network (ANN) based model of biomass gasification in fixed bed Downdraft gasifiers. The study is a novel attempt in developing an ANN based model of biomass gasification in fixed bed Downdraft gasifiers as there are very few reported studies of ANN based modeling of biomass gasification in general and even fewer in the field of fixed bed Downdraft gasifiers. In fact, Downdraft gasifiers are one of the most widely used type of gasifiers for small scale operation. The ANN based models were formulated to predict the product gas composition in terms of concentration of four major gas species viz. CH 4 %, CO%, CO 2 % and H 2 %. The input parameters used in the models were C, H, O content, ash content, moisture content, and reduction zone temperature. The architecture of the models consisted of one input, one hidden and one output layer. Reported experimental data were used to train the ANNs. The output of the ANN models were found to be in agreement with experimental data with an absolute fraction of variance (R 2 ) higher than 0.99 in the cases of CH 4 and CO models and higher than 0.98 in the case of CO 2 and H 2 model. The results show the possibility of utilization of the model to predict the percentage composition of four major product gas species (CH 4 , CO, CO 2 and H 2 ). The relative importance of the input variables was also analysed using the Garson's equation.
Natarianto Indrawan - One of the best experts on this subject based on the ideXlab platform.
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co gasification of municipal solid waste and biomass in a commercial scale Downdraft gasifier
Energy, 2018Co-Authors: Prakashbhai R Bhoi, Raymond L Huhnke, Ajay Kumar, Natarianto Indrawan, Sunil ThapaAbstract:Abstract In this study, municipal solid waste was gasified with switchgrass, i.e., co-gasification, using a commercial-scale Downdraft gasifier to produce power. The experiments were performed using a commercial-scale 100 kg/h Downdraft gasifier at co-gasification ratios of 0, 20 and 40%. The hot and cold gas efficiencies, syngas compositions, heating value and yield, gasifier temperatures and tar content were measured and analyzed. The results indicate that co-gasification of up to 40% MSW performed satisfactorily. The heating values of syngas were 6.2, 6.5 and 6.7 MJ/Nm3 for co-gasification ratios of 0, 20 and 40%, respectively. The cold and hot gas efficiencies were 60.1, 51.1 and 60.0% and 65.0, 55.2 and 64.4% for co-gasification ratios of 0, 20 and 40%, respectively.
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scale up of a Downdraft gasifier system for commercial scale mobile power generation
Renewable Energy, 2018Co-Authors: Prakashbhai R Bhoi, Raymond L Huhnke, Ajay Kumar, Sunil Thapa, Natarianto IndrawanAbstract:Abstract The overall goal of this study was to scale-up a patented Downdraft gasifier system for development of a mobile power plant. A 100 kg/h up-scaled Downdraft gasifier system was designed, built and evaluated using switchgrass and eastern redcedar as feedstocks. The effect of equivalence ratio (0.15–0.30) were studied for each of biomass feedstock. Performance parameters, including composition, syngas yield, heating value, tar content, and gasification efficiencies were measured and analyzed. Results showed that biomass type and equivalence ratio have a significant influence on the syngas compositions and calorific value. Maximum gasification efficiencies for switchgrass and redcedar were 64 and 80% at optimal equivalent ratios of 0.22 and 0.24, respectively. Based on syngas quality, the performance of the scaled-up gasifier system was superior to the laboratory-scale reactor.
Scott E Giangrande - One of the best experts on this subject based on the ideXlab platform.
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convective cloud vertical velocity and mass flux characteristics from radar wind profiler observations during goamazon2014 5
Journal of Geophysical Research, 2016Co-Authors: Scott E Giangrande, Tami Toto, Michael Jensen, Mary Jane Bartholomew, Zhe Feng, Christopher R Williams, Courtney Schumacher, Alain Protat, Luiz A T MachadoAbstract:A radar wind profiler (RWP) dataset collected during the two-year DOE ARM Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) campaign is used to estimate convective cloud vertical velocity, area fraction and mass flux profiles. Vertical velocity observations are presented using cumulative frequency histograms and weighted-mean profiles to provide insights in a manner suitable for GCM-model scale comparisons (spatial domains from 20 km to 60 km). Convective profile sensitivity to changes in environmental conditions and seasonal regime controls is also considered. Aggregate and ensemble average vertical velocity, convective area fraction and mass flux profiles, as well as magnitudes and relative profile behaviors, are found consistent with previous studies. Updrafts and Downdrafts increase in magnitude with height to mid-levels (6 to 10 km), with updraft area also increasing with height. Updraft mass flux profiles similarly increase with height, showing a peak in magnitude near 8 km. Downdrafts are observed to be most frequent below the freezing level, with Downdraft area monotonically decreasing with height. Updraft and Downdraft profile behaviors are further stratified according to environmental controls. These results indicate stronger vertical velocity profile behaviors under higher CAPE and lower low-level moisture conditions. Sharp contrasts in convective area fraction and mass flux profiles are most pronounced when retrievals are segregated according to Amazonian wet and dry season conditions. During this deployment, wet season regimes favored higher domain mass flux profiles, attributed to more frequent convection that offsets weaker average convective cell vertical velocities.
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a summary of convective core vertical velocity properties using arm uhf wind profilers in oklahoma
Journal of Applied Meteorology and Climatology, 2013Co-Authors: Scott E Giangrande, Scott Collis, Christopher R Williams, Alain Protat, Jerry M Straka, Steven K KruegerAbstract:This study presents a summary of the properties of deep convective updraft and Downdraft cores over the central plains of the United States, accomplished using a novel and now-standard Atmospheric Radiation Measurement Program (ARM) scanning mode for a commercial wind-profiler system. A unique profilerbased hydrometeor fall-speed correction method modeled for the convective environment was adopted. Accuracyofthevelocity retrievalsfromthis effortis expectedtobe within2ms 21 , with minimalbiasandbase core resolution expected near 1km. Updraft cores are found to behave with height in reasonable agreement with aircraft observations of previous continental convection, including those of the Thunderstorm Project. Intense updraft cores with magnitudes exceeding 15ms 21 are routinely observed. Downdraft cores are less frequently observed, with weaker magnitudes than updrafts. Weak, positive correlations are found between updraft intensity (maximum) and updraft diameter length (coefficient r to 0.5 aloft). Negligible correlations are observed for Downdraft core lengths and intensity.
Richard B Rood - One of the best experts on this subject based on the ideXlab platform.
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using large eddy simulations to reveal the size strength and phase of updraft and Downdraft cores of an arctic mixed phase stratocumulus cloud
Journal of Geophysical Research, 2017Co-Authors: Erika Louise Roesler, Derek J Posselt, Richard B RoodAbstract:Three-dimensional large eddy simulations (LES) are used to analyze a springtime Arctic mixed-phase stratocumulus observed on 26 April 2008 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC). Two subgrid-scale turbulence parameterizations are compared. The first scheme is a 1.5-order turbulent kinetic energy (1.5-TKE) parameterization that has been previously applied to boundary layer cloud simulations. The second scheme, Cloud Layers Unified By Binormals (CLUBB), provides higher-order turbulent closure with scale-awareness. The simulations, in comparisons with observations, show that both schemes produce the liquid profiles within measurement variability, but underpredict ice water mass and overpredict ice number concentration. The simulation using CLUBB underpredicted liquid water path more than the simulation using the 1.5-TKE scheme, so the turbulent length scale and horizontal grid box size were increased to increase liquid water path and reduce dissipative energy. The LES simulations show this stratocumulus cloud to maintain a closed cellular structure, similar to observations. The updraft and Downdraft cores self-organize into a larger meso-γ scale convective pattern with the 1.5-TKE scheme, but the cores remain more isotropic with the CLUBB scheme. Additionally, the cores are often composed of liquid and ice instead of exclusively containing one or the other. These results provide insight into traditionally unresolved and unmeasurable aspects of an Arctic mixed-phase cloud. From analysis, this cloud's updraft and Downdraft cores appear smaller than other closed-cell stratocumulus such as midlatitude stratocumulus and Arctic autumnal mixed-phase stratocumulus due to the weaker Downdrafts and lower precipitation rates.
Roswitha Engelmann - One of the best experts on this subject based on the ideXlab platform.
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Updraft and Downdraft characterization with Doppler lidar: Cloud-free versus cumuli-topped mixed layer
Atmospheric Chemistry and Physics, 2010Co-Authors: Achim Ansmann, J. Fruntke, Roswitha EngelmannAbstract:For the first time, a comprehensive, height-resolved Doppler lidar study of updrafts and Downdrafts in the mixing layer is presented. The Doppler lidar measurements were performed at Leipzig, Germany, in the summer half year of 2006. The conditional sampling method is applied to the measured vertical velocities to identify, count, and analyze significant updraft and Downdraft events. Three cases of atmospheric boundary-layer (ABL) evolution with and without fair-weather cumuli formation are discussed. Updrafts occur with an average frequency of 1-2 per unit length z(i) (boundary-layer depth z(i)), Downdrafts 20-30% more frequently. In the case with cumuli formation, the draft occurrence frequency is enhanced by about 50% at cloud level or near cloud base. The counted updraft events cover 30-34%, Downdrafts 53-57% of the velocity time series in the central part of the ABL (subcloud layer) during the main period of convective activity. By considering all drafts with horizontal extent > 36 m in the analysis, the updraft mean horizontal extent ranges here from 200-420 m and is about 0.16 z(i)-0.18 z(i) in all three cases disregarding the occurrence of cumulus clouds. Downdraft extents are a factor of 1.3-1.5 larger. The average value of the updraft mean vertical velocities is 0.5-0.7 m/s or 0.40 w(*)-0.45 w(*) (convective velocity scale w(*)), and the negative Downdraft mean vertical velocities are weaker by roughly 10-20%. The analysis of the relationship between the size (horizontal extent) of the updrafts and Downdrafts and their mean vertical velocity reveals a pronounced increase of the average vertical velocity in updrafts from 0.4-0.5 m/s for small thermals (100-200 m) to about 1.5 m/s for large updrafts (> 600 m) in the subcloud layer in the case with fair-weather cumuli. At cloudless conditions, the updraft velocities were found to be 20% smaller for the large thermals.
