Factors Affecting Primary Fragmentation During Combustion of Serbian Coals

2005 ◽  
Author(s):  
Milijana J. Paprika ◽  
Mirko M. Komatina ◽  
Franz Winter ◽  
Dragoljub V. Dakic
Keyword(s):  
Coal Particle ◽  
Temperature Response ◽  
Coal Bed ◽  
Two Phase ◽  
Factors Affecting ◽  
Fragmentation Behavior ◽  
Bed Temperature ◽  
Primary Fragmentation ◽  
Dynamic Simulation Model ◽  
Original Size

A two-phase experimental method to establish primary fragmentation behavior of Serbian lignites is presented. The first phase was fragmentation quantification, and second was measuring temperature response of center of coal particle during devolatilization. A dynamic simulation model gave thermal properties of coal used. The influence of various factors such as original size of coal, bed temperature, and coal rank on fragmentation is presented and discussed. A new factor, ratio of coal volatile content and coal thermal diffusivity, as representative of heat and mass transfer processes inside of coal particle, has been introduced and its influence on fragmentation index was analyzed.

The Local Heat Balance in a Stationary Fluidized-Bed Furnace Burning Biomass Fuels

2003 ◽  
Author(s):  
Fredrik Niklasson ◽  
Filip Johnsson
Keyword(s):  
Fluidized Bed ◽  
Combustion Rate ◽  
Heat Balance ◽  
Circulating Fluidized Bed ◽  
Local Heat ◽  
Splash Zone ◽  
Two Phase ◽  
Bed Temperature ◽  
Temperature Constant ◽  
The Vertical Distribution

This work investigates the influence of biomass fuel properties on the local heat balance in a commercial-scale fluidized bed furnace. Experiments with different wood based fuels were performed in the Chalmers 12 MWth circulating fluidized bed boiler, temporarily modified to run under stationary conditions. A two-phase flow model of the bed and splash zone is applied, where the combustion rate in the bed is estimated by global kinetic expressions, limited by gas exchange between oxygen-rich bubbles and a fuel-rich emulsion phase. The outflow of bubbles from the bed is treated as “ghost bubbles” in the splash zone, where the combustion rate is determined from turbulent properties. It is found that a large amount of heat is required for the fuel and air to reach the temperature of the bed, in which the heat from combustion is limited by a low char content of the fuel. This implies that a substantial fraction of the heat from combustion of volatiles in the splash zone has to be transferred back to the bed to keep the bed temperature constant. It is concluded that the moisture content of the fuel does not considerably alter the vertical distribution of heat emitted, as long as the bed temperature is kept constant by means of flue gas recycling.

Implementation of Machine Learning Algorithms for Prediction of Fluidelastic Instability in Tube Arrays

2021 ◽  
Vol 143 (2) ◽  
Author(s):  
Joaquin E. Moran ◽  
Yasser Selima
Keyword(s):  
Machine Learning ◽  
Logistic Regression ◽  
Learning Algorithm ◽  
Machine Learning Algorithms ◽  
Two Phase ◽  
Factors Affecting ◽  
Logistic Regression Models ◽  
Number Of Factors ◽  
Tube Arrays ◽  
Fluidelastic Instability

Abstract Fluidelastic instability (FEI) in tube arrays has been studied extensively experimentally and theoretically for the last 50 years, due to its potential to cause significant damage in short periods. Incidents similar to those observed at San Onofre Nuclear Generating Station indicate that the problem is not yet fully understood, probably due to the large number of factors affecting the phenomenon. In this study, a new approach for the analysis and interpretation of FEI data using machine learning (ML) algorithms is explored. FEI data for both single and two-phase flows have been collected from the literature and utilized for training a machine learning algorithm in order to either provide estimates of the reduced velocity (single and two-phase) or indicate if the bundle is stable or unstable under certain conditions (two-phase). The analysis included the use of logistic regression as a classification algorithm for two-phase flow problems to determine if specific conditions produce a stable or unstable response. The results of this study provide some insight into the capability and potential of logistic regression models to analyze FEI if appropriate quantities of experimental data are available.

Transient Analysis of Nonuniform Heat Input Propagation Through a Heat Sink Base

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Srivathsan Sudhakar ◽  
Justin A. Weibel
Keyword(s):  
Heat Source ◽  
Heat Input ◽  
Heat Sink ◽  
Three Dimensional ◽  
Temperature Response ◽  
Flow Distribution ◽  
Temporal Variations ◽  
Step Response ◽  
Dimensional System ◽  
Two Phase

For thermal management architectures wherein the heat sink is embedded close to a dynamic heat source, nonuniformities may propagate through the heat sink base to the coolant. Available transient models predict the effective heat spreading resistance to calculate chip temperature rise, or simplify to a representative axisymmetric geometry. The coolant-side temperature response is seldom considered, despite the potential influence on flow distribution and stability in two-phase microchannel heat sinks. This study solves three-dimensional transient heat conduction in a Cartesian chip-on-substrate geometry to predict spatial and temporal variations of temperature on the coolant side. The solution for the unit step response of the three-dimensional system is extended to any arbitrary temporal heat input using Duhamel's method. For time-periodic heat inputs, the steady-periodic solution is calculated using the method of complex temperature. As an example case, the solution of the coolant-side temperature response in the presence of different transient heat inputs from multiple heat sources is demonstrated. To represent a case where the thermal spreading from a heat source is localized, the problem is simplified to a single heat source at the center of the domain. Metrics are developed to quantify the degree of spatial and temporal nonuniformity in the coolant-side temperature profiles. These nonuniformities are mapped as a function of nondimensional geometric parameters and boundary conditions. Several case studies are presented to demonstrate the utility of such maps.

Lab Testing and Finite Element Method Simulation of Hole Deflector Performance for Radial Jet Drilling

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Bin Wang ◽  
Gensheng Li ◽  
Zhongwei Huang ◽  
Tianqi Ma ◽  
Dongbo Zheng ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Low Cost ◽  
Geometric Model ◽  
Frictional Resistance ◽  
Finite Element Method Simulation ◽  
Optimization Method ◽  
Structure Design ◽  
Coal Bed ◽  
Factors Affecting ◽  
High Pressure Water Jet

Radial jet drilling (RJD) is an efficient approach for improving the productivity of wells in low permeability, marginal and coal-bed methane (CBM) reservoirs at a very low cost. It uses high-pressure water jet to drill lateral holes from a vertical wellbore. The length of the lateral holes is greatly influenced by the frictional resistance in the hole deflector. However, the hole deflector frictional resistance and structure design have not been well studied. This work fills that gap. Frictional resistances were measured in a full-scale experiment and calculated by numerical simulation. The structure of the hole deflector was parameterized and a geometric model was developed to design the hole deflector track. An empirical model was then established to predict the frictional resistance as a function of the hole deflector structure parameters and an optimization method for designing the hole deflector was proposed. Finally, four types of hole deflectors were optimized using this method. The results show good agreement between the numerical simulation and the experimental data. The model error is within 11.6%. The bend radius R and exit angle β are the key factors affecting the performance of the hole deflector. The validation test was conducted for a case hole deflector (5½ in. casing). The measured frictional resistance was decreased from 31.44 N to 23.16 N by 26.34%. The results from this research could serve as a reference for the design of hole deflectors for radial jet drilling.

Factors affecting the lamellar spacing in two-phase TiAl alloys with fully lamellar microstructures

2001 ◽  
Vol 36 (9) ◽  
pp. 1737-1742 ◽  
Author(s):  
Jiancheng Tang ◽  
Baiyun Huang ◽  
Kechao Zhou ◽  
Wensheng Liu ◽  
Yuehui He ◽  
...  
Keyword(s):  
Lamellar Spacing ◽  
Two Phase ◽  
Tial Alloys ◽  
Factors Affecting ◽  
Fully Lamellar

scholarly journals Numerical Research on Performance of High-Speed Partial Emission Pump

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Qingjiao Shui ◽  
Ting Jiang ◽  
Binghui Pan ◽  
Tianxing Yang ◽  
Wei Pan
Keyword(s):  
Liquid Phase ◽  
High Speed ◽  
Phase Particle ◽  
Characteristic Curve ◽  
Particle Diameter ◽  
Two Phase ◽  
Factors Affecting ◽  
External Characteristic ◽  
Numerical Simulation Methods ◽  
Small Flow

The high-speed partial emission pump is a small flow and high-head pump, which has been widely used. To study the main factors affecting the performance of high-speed partial emission pumps, numerical simulation methods were used to calculate the performance parameters of high-speed partial emission pumps with and without inducers, and the external characteristic parameters were verified through comparison test values. The results show that the head of the high-speed partial emission pump with inducer is nearly 15 m higher than that of the high-speed partial emission pump without inducer. Considering the influence of air in the high-speed partial emission pump on the working performance, the two-phase flow with different flow rates, different particle sizes, and different concentrations was calculated, and the different liquid phase distributions, liquid phase velocity vector diagrams, and external characteristic curve were compared. The results show that under the same flow condition, the gas-phase particle diameter has the most severe influence on the external characteristic.

scholarly journals A review of multiphase flow and deposition effects in film-cooled gas turbines

2018 ◽  
Vol 22 (5) ◽  
pp. 1905-1921 ◽  
Author(s):  
Jin Wang ◽  
Milan Vujanovic ◽  
Bengt Sunden
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Particle Deposition ◽  
Experimental Studies ◽  
Turbulence Models ◽  
Phase Flow ◽  
Two Phase ◽  
Film Cooling Effectiveness ◽  
Factors Affecting ◽  
Multi Phase Flow

This paper presents a review of particle deposition research in film-cooled gas turbines based on the recent open literature. Factors affecting deposition capture efficiency and film cooling effectiveness are analyzed. Experimental studies are summarized into two discussions in actual and virtual deposition environments. For investigation in virtual deposition environments, available and reasonable results are obtained by comparison of the Stokes numbers. Recent advances in particle deposition modeling for computational fluid dynamics are also reviewed. Various turbulence models for numerical simulations are investigated, and solutions for treatment of the particle sticking probability are described. In addition, analysis of injecting mist into the coolant flow is conducted to investigate gas-liquid two-phase flow in gas turbines. The conclusion remains that considerable re-search is yet necessary to fully understand the roles of both deposition and multi-phase flow in gas turbines.

scholarly journals Visual benefit versus visual gain: what is the effect of baseline covariants in the treatment arm relative to the control arm? A pooled analysis of ANCHOR and MARINA

2019 ◽  
Vol 104 (5) ◽  
pp. 672-677 ◽  
Author(s):  
Adnan Tufail ◽  
Philippe Margaron ◽  
Tadhg Guerin ◽  
Michael Larsen
Keyword(s):  
Visual Acuity ◽  
Lesion Size ◽  
Pooled Analysis ◽  
Age Related Macular Degeneration ◽  
Phase Iii ◽  
Two Phase ◽  
Factors Affecting ◽  
Age Related ◽  
The Usa ◽  
Ranibizumab Treatment

BackgroundThis study aimed to elucidate visual benefits of ranibizumab in patients with neovascular age-related macular degeneration (nAMD) compared with control arms and identify factors affecting response.MethodsThis is a post-hoc pooled analysis of two phase III studies, ANCHOR and MARINA, of ranibizumab for the treatment of nAMD. ANCHOR included 83 international sites. MARINA included 96 sites in the USA. Analysis included patients (control, n=323; ranibizumab, n=332) with nAMD and a baseline best-corrected visual acuity (BCVA) of ≥35–<85 letters.ResultsPatients receiving ranibizumab achieved an adjusted mean BCVA superiority of 18.9 and 21.2 letters over 12 and 24 months, respectively, compared with control. Ranibizumab treatment, higher baseline BCVA, lower age and smaller lesion size were positively associated with the ability to achieve BCVA >69 letters. Patients with the highest baseline BCVA had lowest BCVA gains. Ranibizumab treatment, lower baseline BCVA, lower age and smaller lesion size were identified as significant predictors of BCVA gain from baseline at month 24 (all p<0.0001). However, the difference in mean BCVA gains at month 24 between treatment and control groups was similar for all baseline BCVA subgroups (≥35–<55 letters, 21.9 letters; ≥55–<70 letters, 25.2 letters; ≥70–<85 letters, 19.3 letters).ConclusionsHigher baseline BCVA is associated with lower BCVA gains but a greater likelihood of achieving good final BCVA >69 letters due to smaller gains needed to achieve response. Visual benefits, including maintenance of visual acuity (VA), final VA achieved and relative gain compared with natural disease progression, should be considered when assessing treatment response in nAMD.

Prioritizing Risk-level Factors in Comprehensive Automobile Insurance Management: A Hybrid Multi-criteria Decision-making Model

2020 ◽  
pp. 097215092093228
Author(s):  
Zahra Shams Esfandabadi ◽  
Meisam Ranjbari ◽  
Simone Domenico Scagnelli
Keyword(s):  
Insurance Market ◽  
Insurance Companies ◽  
Risk Level ◽  
Automobile Insurance ◽  
Two Phase ◽  
Analytic Hierarchy ◽  
Factors Affecting ◽  
Risk Levels ◽  
Fuzzy Delphi ◽  
The Individual

An efficient risk-level prediction for newly proposed insurance policies plays a significant role in the survival of companies in the highly competitive insurance market. In Iran, risk assessment in comprehensive automobile insurance, which is a part of motor insurance, is only based on the vehicle attributes without proper consideration of personal and behavioural characteristics of driver(s). As a result, pricing is unfair in most of the cases and this can put insurance companies in an unfavourable financial position due to attracting high-risk drivers instead of low-risk ones. In this scenario, to identify and prioritize important factors affecting risk levels and to move towards a fair ratemaking, a two-phase process based on fuzzy Delphi method (FDM) and fuzzy analytic hierarchy process (FAHP) is proposed in this research. Additionally, similarity aggregation method (SAM) is applied to combine the individual fuzzy opinions of the surveyed experts into a group fuzzy consensus opinion. The results of this empirical study contribute to the insurance market of Iran by proposing appropriate weighting of the relevant risk factors to support stakeholders and policymakers for assessing risks more accurately, as well as designing more effective databases and insurance proposal forms.

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