Numerical study of co-firing lignite and agricultural biomass in utility boiler under variable operation conditions

2021 ◽  
Vol 181 ◽  
pp. 121728
Author(s):  
Aleksandar Milićević ◽  
Srdjan Belošević ◽  
Nenad Crnomarković ◽  
Ivan Tomanović ◽  
Andrijana Stojanović ◽  
...  
Keyword(s):  
Numerical Study ◽  
Agricultural Biomass ◽  
Utility Boiler ◽  
Operation Conditions

Estimation of the Occurrence of Micro-Explosion for the Diesel-Biofuel Multi-Components Droplets

2012 ◽  
Author(s):  
Cai Shen ◽  
Chia-fon F. Lee ◽  
Way L. Cheng
Keyword(s):  
Surface Energy ◽  
Minimal Surface ◽  
Weber Number ◽  
Numerical Study ◽  
Engine Operation ◽  
Fuel Droplets ◽  
Fuel Blends ◽  
Operation Conditions ◽  
Simulation Results ◽  
Breakup Model

A numerical study of micro-explosion in multi-component bio-fuel droplets is presented. The onset of micro-explosion is characterized by the normalized onset radius (NOR). Bubble expansion is described by a modified Rayleigh equation. The final breakup is modeled from a surface energy approach by determining the minimal surface energy (MSE). After the breakup, the Sauter mean radius (SMR) for initially small size droplets can be estimated from a look-up table generated from the current breakup model. There exists an optimal droplet size for the onset of micro-explosion. The MSE approach reaches the same conclusion as previous model determining atomization by aerodynamic disturbances. The SMR of secondary droplets can be estimated by the possible void fraction, ε, at breakup and the corresponding surface Weber number, Wes, at the minimal surface energy ratio (MSER). Biodiesel can enhance micro-explosion in the fuel blends of ethanol and diesel (which is represented by a single composition tetradecane). The simulation results show that the secondary atomization of bio-fuel and diesel blends can be achieved by micro-explosion under typical diesel engine operation conditions.

Numerical study of co-firing coal and Cynara cardunculus in a 350 MWe utility boiler

2009 ◽  
Vol 90 (10) ◽  
pp. 1207-1213 ◽  
Author(s):  
Javier Pallarés ◽  
Antonia Gil ◽  
Cristóbal Cortés ◽  
Carlos Herce
Keyword(s):  
Numerical Study ◽  
Cynara Cardunculus ◽  
Utility Boiler

Numerical Study on the Influence of Tip Clearance on Rotating Stall in an Unshrouded Centrifugal Compressor

2017 ◽  
Author(s):  
Wenying Ju ◽  
Shengli Xu ◽  
Xiaofang Wang ◽  
Xudong Chen ◽  
Shuhua Yang ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Leading Edge ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Forming Process ◽  
Impeller Blade ◽  
Tip Clearance Flow ◽  
Rotating Speed ◽  
Operation Conditions

Whole annulus unsteady simulations are performed by CFD with the whole flow passage model from inlet guide vanes to volute of an unshrouded centrifugal compressor. Characteristics and development mechanism of rotating stall are analyzed including the flow field and the impeller blade load in time and frequency domain. Rotating stall with three cells is observed in both two actual operation conditions but the cell rotating speed and the forming process is different. Leading edge tip clearance leakage is a criterion to predict the formation of a spike stall in centrifugal compressors. Tip clearance flow also plays an important role in the moving of rotating instabilities and the propagation of stall cells. It can effectively slow down the stall forming and decrease the pressure load on blade by reduced the tip clearance size at the leading edge.

Numerical study of pulverized coal-fired utility boiler over a wide range of operating conditions for in-furnace SO2/NOx reduction

2016 ◽  
Vol 94 ◽  
pp. 657-669 ◽  
Author(s):  
Srdjan Belošević ◽  
Ivan Tomanović ◽  
Nenad Crnomarković ◽  
Aleksandar Milićević ◽  
Dragan Tucaković
Keyword(s):  
Numerical Study ◽  
Nox Reduction ◽  
Pulverized Coal ◽  
Operating Conditions ◽  
Utility Boiler ◽  
Wide Range

scholarly journals Numerical study on CTF code to predict void fraction in PWR sub channel conditions

2015 ◽  
Vol 5 (4) ◽  
pp. 30-38
Author(s):  
Minh Giang Hoang ◽  
Tan Hung Hoang ◽  
Phu Khanh Nguyen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Void Fraction ◽  
Single Channel ◽  
Numerical Study ◽  
High Quality ◽  
Operation Conditions ◽  
Channel Conditions

CTF is a version of the widely used COBRA-TF code with capability of 3D simulation for core sub channel thermal hydraulics behavior. Recently, CTF is reviewed and the consideration of CTF to predict void fraction in PWR sub channel conditions such as subcooled region still  need more investigation. Due to the fact that the Chen’s correlation of heat transfer coefficient  is developed for relatively low pressure and high quality conditions associated with forced convection vaporization, and is not strictly valid for  PWR operation conditions, so that, in this study,  some runs of single channel in the benchmark based on NUPEC PWR Sub channel and Bundle Tests (PSBT) are used to investigate  void fraction prediction by CTF  in subcooled region and also to verify  some remarkable notice of CTF from other authors. The goal of the study is to evaluate deviation for CTF void fraction prediction in PWR sub channel conditions.

CFD Simulation of the Submerged Cofferdams Effect on the Operation of the Future Tocoma Hydroelectric Power Plant

2009 ◽  
Author(s):  
Milan Stanko ◽  
Andrea Shmueli ◽  
Miguel Asuaje ◽  
Frank Kenyery ◽  
Gonzalo Montilla ◽  
...  
Keyword(s):  
Power Plant ◽  
Velocity Profile ◽  
Cfd Simulation ◽  
Numerical Study ◽  
Computational Cost ◽  
Hydroelectric Power Plant ◽  
Normal Operation ◽  
Hydroelectric Power ◽  
Uniform Velocity ◽  
Operation Conditions

The Tocoma hydroelectric power plant, currently under construction, is located on the lower basin of the Caroni River in Bolivar State in Venezuela. This power plant will have 10 Kaplan turbines in its powerhouse that will generate approximately 2160 MW of hydroelectric power. During its construction, two cofferdams designated “A” and “B” will be built and afterwards will remain submerged. The main purpose of this experimental-numerical study is to analyze the possible future hydrodynamic effects of these structures on the operation of the Kaplan turbines. The presence of the submerged cofferdams could originate tridimensional hydrodynamic behaviors that could produce energy looses and operational and functional problems to the turbines. Two mathematical steady state single phase models using Computational Fluid Dynamics (CFD) Techniques and applying the commercial software ANSYS-CFX were developed. The first model represented the hydroelectric power plant reservoir that was quantitatively and qualitatively calibrated with a Froude Similarity 1:80 Scale Physical Model. Hydrodynamic flow patterns near to the intakes were found in the first model. Those patterns showed a non-uniform velocity profile in the unit’s intakes nearest to cofferdam “B”. The second mathematical model represented the study of the intake, the semi-spiral case and the Kaplan turbine. This model considers the non-uniform velocity profile that was found in the first model as an inlet boundary condition. Two methodologies were used to develop this model: one using two simulations with two overlapping physical domains, and the other one using the whole geometry. It was found that using overlapping domains in order to reduce the computational cost of the total simulation is a good way to obtain physical results with fair accuracy. The general results reported that the velocity profile at the intake of the powerhouse does not produce any stationary non uniform behavior on the velocity and pressure profiles in the unit compared to the uniform velocity profile case. This result could be an indicator that the non uniform condition at the intake of the Kaplan Turbines at Tocoma will not affect the normal operation conditions of the unit.

Numerical Study on Transient Characteristics of a Tubular SOFC Cell

2005 ◽  
Author(s):  
Daisuke Shiomi ◽  
Hiroshi Iwai ◽  
Kenjiro Suzuki ◽  
Hideo Yoshida
Keyword(s):  
Heat Capacity ◽  
Numerical Study ◽  
Sudden Change ◽  
Electric Circuit ◽  
Transient Behavior ◽  
Status Change ◽  
Transient Characteristics ◽  
Operation Conditions ◽  
A Cell ◽  
Steady Simulation

Fundamental performance and the transient characteristics of a small tubular SOFC were numerically investigated. The model simultaneously treats momentum, heat and mass transfer, electrochemical phenomena and an electric circuit. Transient characteristics of a cell upon a sudden change of the cell terminal voltage or the air flow rate were examined. During its process, a steady simulation was first conducted and its result was used as the initial condition for the transient calculation. The transient calculation continued until a steady state under the new boundary condition was obtained. Discussions on the time response of the cell performance and thermal field were made in order to find the key factors mainly affecting the transient characteristics. To confirm what factors affect on the transient behavior, calculations were conducted for two different cell geometries, which have different cell diameters, but have same ratios of cell heat capacity to the heat generating area. As a result, it was found that the transient characteristics of a cell are primarily governed by the balance between the heat capacity of a cell and the heat generation by electrochemical reactions. The large heat capacity of the cell is one of the key problems affecting the transient behavior, limiting its quick response. A numerical demonstration is shown in which a rapid cell status change was achieved by controlling its operation conditions.

Modeling of the Coal-Fired Utility Boiler in a Thermal Power Plant Based on Macro Energy Balance

2013 ◽  
Vol 732-733 ◽  
pp. 29-36 ◽  
Author(s):  
Tong Yu ◽  
Jing Qi Yuan
Keyword(s):  
Energy Balance ◽  
Power Plant ◽  
Thermal Power Plant ◽  
Thermal Power ◽  
Actual Process ◽  
Process Data ◽  
Utility Boiler ◽  
Rolling Parameter ◽  
Operation Conditions ◽  
Main Steam

A modeling method of the coal-fired utility boiler for a 300MW thermal power plant based on energy balance is presented. Key work sections of the power plant are treated as lumped parameter systems and a first-order model with time delay is used to describe the dynamic characteristic of the entire system. As model validation, comparison between model simulations and the actual process data for the energy of the main steam and hot reheated steam is given. Basically, the model is found to be able to track the output power variations of the boiler under different operation conditions. Rolling parameter identification of the model may further improve the model accuracy.

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