scholarly journals CFD Simulation Research on Agglomeration between Coal-fired Ash Fine Particulate and Atomized Droplets

2020 ◽  
Vol 165 ◽  
pp. 01006
Author(s):  
Yiquan Guo ◽  
Junying Zhang
Keyword(s):  
Power Plant ◽  
Flow Field ◽  
Cfd Simulation ◽  
Negative Impact ◽  
Droplet Diameter ◽  
Temperature Drop ◽  
Operating Conditions ◽  
Gas Temperature ◽  
Simulation Research ◽  
Agglomeration Process

In this paper, a collision model between atomized droplets of agglomeration solution and particles is established. On this basis, the effects of flue gas temperature, atomized droplet diameter and other factors on the particle agglomeration process are studied. In addition, the evaporation model of agglomeration solution in the flue of a power plant is established for the coal-fired unit of power plant. Through CFD software, the variation of flow field velocity, temperature and pressure in the flue is simulated to determine whether the chemical agglomeration technology has negative impact on the actual operating conditions of the power plant. The simulation results show that the velocity and pressure of the flow field in the flue have no obvious change after the agglomerating agent is injected. Besides, the temperature drop of about 7°C. The droplets evaporate completely at a distance of 7-8 m after spraying. The evaporation time of droplets is within 1.6 s.

scholarly journals A New Method to Determine the Impact of Individual Field Quantities on Cycle-to-Cycle Variations in a Spark-Ignited Gas Engine

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4136
Author(s):  
Clemens Gößnitzer ◽  
Shawn Givler
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Turbulent Kinetic Energy ◽  
Negative Impact ◽  
Operating Conditions ◽  
Engine Operation ◽  
Gas Engine ◽  
Cycle Simulation ◽  
Simulation Results ◽  
The Impact

Cycle-to-cycle variations (CCV) in spark-ignited (SI) engines impose performance limitations and in the extreme limit can lead to very strong, potentially damaging cycles. Thus, CCV force sub-optimal engine operating conditions. A deeper understanding of CCV is key to enabling control strategies, improving engine design and reducing the negative impact of CCV on engine operation. This paper presents a new simulation strategy which allows investigation of the impact of individual physical quantities (e.g., flow field or turbulence quantities) on CCV separately. As a first step, multi-cycle unsteady Reynolds-averaged Navier–Stokes (uRANS) computational fluid dynamics (CFD) simulations of a spark-ignited natural gas engine are performed. For each cycle, simulation results just prior to each spark timing are taken. Next, simulation results from different cycles are combined: one quantity, e.g., the flow field, is extracted from a snapshot of one given cycle, and all other quantities are taken from a snapshot from a different cycle. Such a combination yields a new snapshot. With the combined snapshot, the simulation is continued until the end of combustion. The results obtained with combined snapshots show that the velocity field seems to have the highest impact on CCV. Turbulence intensity, quantified by the turbulent kinetic energy and turbulent kinetic energy dissipation rate, has a similar value for all snapshots. Thus, their impact on CCV is small compared to the flow field. This novel methodology is very flexible and allows investigation of the sources of CCV which have been difficult to investigate in the past.

Numerical simulation and field test study of desulfurization wastewater evaporation treatment through flue gas

2014 ◽  
Vol 70 (7) ◽  
pp. 1285-1291 ◽  
Author(s):  
Jia-jia Deng ◽  
Liang-ming Pan ◽  
De-qi Chen ◽  
Yu-quan Dong ◽  
Cheng-mu Wang ◽  
...  
Keyword(s):  
Field Test ◽  
Flue Gas ◽  
Cfd Simulation ◽  
Electrostatic Precipitator ◽  
Negative Impact ◽  
Positive Impact ◽  
Field Tests ◽  
Gas Temperature ◽  
Simulation Results ◽  
Desulfurization Wastewater

Aimed at cost saving and pollution reduction, a novel desulfurization wastewater evaporation treatment system (DWETS) for handling wet flue gas desulfurization (WFGD) wastewater of a coal-fired power plant was studied. The system's advantages include simple process, and less investment and space. The feasibility of this system has been proven and the appropriate position and number of nozzles, the spray droplet size and flue gas temperature limitation have been obtained by computational fluid dynamics (CFD) simulation. The simulation results show that a longer duct, smaller diameter and higher flue gas temperature could help to increase the evaporation rate. The optimal DWETS design of Shangdu plant is 100 μm droplet sprayed by two nozzles located at the long duct when the flue gas temperature is 130 °C. Field tests were carried out based on the simulation results. The effects of running DWETS on the downstream devices have been studied. The results show that DWETS has a positive impact on ash removal efficiency and does not have any negative impact on the electrostatic precipitator (ESP), flue gas heat exchanger and WFGD. The pH values of the slurry of WFGD slightly increase when the DWETS is running. The simulation and field test of the DWETS show that it is a feasible future technology for desulfurization wastewater treatment.

CFD Simulation of a Supersonic Steam Ejector for Refrigeration Application

2016 ◽  
Author(s):  
Liju Su ◽  
Ramesh K. Agarwal
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Fluid Pressure ◽  
Turbulence Models ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Working Fluid ◽  
Entrainment Ratio ◽  
Ansys Fluent ◽  
Entrainment Velocity

Supersonic steam ejectors are widely used in many industrial applications, for example for refrigeration and desalination. The experimental evaluation of the flow field inside the ejector is relatively difficult and costly due to the occurrence of shock after the velocity of the steam reaches over the sonic level in the ejector. In this paper, numerical simulations are conducted to investigate the detailed flow field inside a supersonic steam (water vapor being the working fluid) ejector. The commercial computational fluid dynamics (CFD) flow solver ANSYS-Fluent and the mesh generation software ANSYS-ICEM are used to predict the steam performance during the mixing inside the ejector by employing two turbulence models, the k-ω SST and the k-ε realizable models. The computed results are validated against the experimental data. The effects of operating conditions on the efficiency of the ejector such as the primary fluid pressure and condenser pressure are studied to obtain a better understanding of the mixing process and entrainment. Velocity contours, pressure plots and shock region analyses provide a good understanding for optimization of the ejector performance, in particular how to increase the entrainment ratio.

Zero Dimensional Quasi-Predictive Thermodynamic Simulation for Establishing Initial Cylinder Conditions for CFD Simulation of Diesel Combustion

2015 ◽  
Author(s):  
Ryan A. Bandura ◽  
Timothy J. Jacobs
Keyword(s):  
Experimental Data ◽  
Heat Release ◽  
Cfd Simulation ◽  
Fuel Injection ◽  
Initial Conditions ◽  
Thermodynamic Simulation ◽  
Operating Conditions ◽  
Gas Composition ◽  
Gas Temperature ◽  
Rate Of Heat Release

Computational fluid dynamics (CFD) is now a ubiquitous computational tool for engine design and diagnosis. It is often necessary to provide well-known initial cycle conditions to commence the CFD computations. Such initial conditions can be provided by experimental data. To create an opportunity to computationally study engine conditions where experimental data are not available, a zero-dimensional quasi-predictive thermodynamic simulation is developed that uses well-established spray model to predict rate of heat release and calculated burned gas composition and temperature to predict nitric oxide (NO) concentration. This simulation could in turn be used in reverse to solve for initial cylinder conditions for a targeted NO concentration. This paper details the thermodynamic simulation for diesel engine operating conditions. The goal is to produce a code that is capable of predicting NO emissions as well as performance characteristics such as mean effective pressure (MEP) and brake specific fuel consumption (BSFC). The simulation uses general conservation of mass and energy approaches to model intake, compression, and exhaust. Rate of heat release prediction is based on an existing spray model to predict how fuel concentrations within the spray jet change with penetration. Rate of heat release provides predicted cylinder pressure, which is then validated against experimental pressure data under known operating conditions. An equilibrium mechanism is used to determine burned gas composition which, along with burned gas temperature, can be used for prediction of NO in the cylinder. NO is predicted using the extended Zeldovich mechanism. This mechanism is highly sensitive to temperature, and it is therefore important to accurately predict cylinder gas temperature to obtain correct NO values. Additionally, MEP and BSFC are determined. The simulation focuses on single fuel injection events, but insights are provided to expand the simulation to model multiple injection events.

Modification of rotary air preheater toward achieving extended life-span utilizing porous media approach: A case study

2021 ◽  
pp. 095765092110349
Author(s):  
Hamed Hajebzadeh ◽  
Abdulhamid NM Ansari
Keyword(s):  
Porous Media ◽  
Power Plant ◽  
Relative Error ◽  
Mass Flow ◽  
Cfd Simulation ◽  
Maximum Relative Error ◽  
Gas Temperature ◽  
Operational Parameters ◽  
Operating Life ◽  
Porous Media Model

The main goal of this study is to achieve the extended operating life of the rotary regenerative air pre-heater (Ljungström) of Bandar Abbas power plant by modifying operational parameters by decreasing the corrosion. To achieve this goal, a three-dimensional CFD simulation of the Ljungström is carried out, utilizing the thermal non-equilibrium porous media model. Temperatures are validated against measured data from the power plant with a maximum relative error of 5.54% on the Celsius scale, and mass flow rates are validated with a maximum relative error of −5.25%. The effect of the Ljungström key parameters including the rotational speed, cold layer material, inlet air/flue gas temperature, and mass flow rate, are analyzed in presence of leakages and neglecting it, using porous media approach. The leakage effect is investigated considering radial and axial/peripheral clearances. Finally, a simulation is performed by applying feasible improved parameters extracted from the above analyses considering the effect of all parameters together in presence of leakages, which shows a 6.14% improvement in the Ljungström effectiveness, reducing the total leakage to about one-third of the actual model and eliminating any corrosion.

scholarly journals CFD Based Design for Ejector Cooling System Using HFOS (1234ze(E) and 1234yf)

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1408 ◽  
Author(s):  
Anas F A Elbarghthi ◽  
Saleh Mohamed ◽  
Van Vu Nguyen ◽  
Vaclav Dvorak
Keyword(s):  
Cfd Simulation ◽  
Cooling System ◽  
Negative Impact ◽  
Saturation Temperature ◽  
Expansion Ratio ◽  
Operating Conditions ◽  
Primary Flow ◽  
Entrainment Ratio ◽  
Real Gas ◽  
The Impact

The field of computational fluid dynamics has been rekindled by recent researchers to unleash this powerful tool to predict the ejector design, as well as to analyse and improve its performance. In this paper, CFD simulation was conducted to model a 2-D axisymmetric supersonic ejector using NIST real gas model integrated in ANSYS Fluent to probe the physical insight and consistent with accurate solutions. HFOs (1234ze(E) and 1234yf) were used as working fluids for their promising alternatives, low global warming potential (GWP), and adhering to EU Council regulations. The impact of different operating conditions, performance maps, and the Pareto frontier performance approach were investigated. The expansion ratio of both refrigerants has been accomplished in linear relationship using their critical compression ratio within ±0.30% accuracy. The results show that R1234yf achieved reasonably better overall performance than R1234ze(E). Generally, by increasing the primary flow inlet saturation temperature and pressure, the entrainment ratio will be lower, and this allows for a higher critical operating back pressure. Moreover, it was found out that increasing the degree of superheat for inlet primary flow by 25 K improved the entrainment ratio by almost 20.70% for R1234yf. Conversely, increasing the degree of superheat to the inlet secondary flow has a relativity negative impact on the performance. The maximum overall ejector efficiency reached was 0.372 and 0.364 for R1234yf and R1234ze(E) respectively. Comparing the results using ideal gas model, the ejector entrainment ratio was overestimated up to 50.26% for R1234yf and 25.66% for R1234ze(E) higher than using real gas model.

CFD Simulation of a Supersonic Steam Ejector for Refrigeration Application

2015 ◽  
Author(s):  
Liju Su ◽  
Ramesh K. Agarwal ◽  
Subhodeep Banerjee
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Fluid Pressure ◽  
Turbulence Models ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Working Fluid ◽  
Entrainment Ratio ◽  
Ansys Fluent ◽  
Entrainment Velocity

Supersonic steam ejectors are widely used in many industrial applications, for example for refrigeration and desalination. The experimental evaluation of the flow field inside the ejector is relatively difficult and costly due to the occurrence of shock after the velocity of the steam reaches over the sonic level in the ejector. In this paper, numerical simulations are conducted to investigate the detailed flow field inside a supersonic steam (water vapor being the working fluid) ejector. The commercial computational fluid dynamics (CFD) flow solver ANSYS-Fluent and the mesh generation software ANSYS-ICEM are used to predict the steam performance during the mixing inside the ejector by employing two turbulence models, the k-ω SST and the k-ε realizable models. The computed results are validated against the experimental data. The effects of operating conditions on the efficiency of the ejector such as the primary fluid pressure and condenser pressure are studied to obtain a better understanding of the mixing process and entrainment. Velocity contours, pressure plots and shock region analyses provide a good understanding for optimization of the ejector performance, in particular how to increase the entrainment ratio.

Unsteady CFD Simulation of Control Valve in Throttling Conditions and Comparison With Experiments

2013 ◽  
Author(s):  
Giorgio Zanazzi ◽  
Ottmar Schaefer ◽  
Michael Sell ◽  
Colin Ridoutt
Keyword(s):  
Power Plant ◽  
Cfd Simulation ◽  
Renewable Energy Sources ◽  
Control Valve ◽  
Electric Power Industry ◽  
Design Tool ◽  
Operating Conditions ◽  
3D Simulation ◽  
3D Analysis ◽  
Central Research

The operational flexibility of steam power plant is becoming more important as power generation becomes increasingly decentralized, with a growing contribution from renewable energy sources. In a power plant the control valve is a key component to guarantee the control of the plant of which is increasingly demanded to extend the operational capability. At specific operating conditions, the control valve could experience vibrations. In this paper, the physical phenomena of the unsteady aerodynamic excitation force have been investigated by means of CFD techniques. An in-house code was used to simulate the flow-induced vibration. Unsteady transonic 3D simulation generally requires huge computational effort. A novel unsteady quasi-3D approach has been developed and applied as pre-design tool to establish the qualitatively operational map of the valve and to detect the critical operational range, to reduce the number of detailed 3D simulations. The numerical results are compared with experimental test undertaken in the Central Research Institute of Electric Power Industry [4] and full 3D simulation performed with the commercial tool CFX, using the Scale-Adaptive Simulation (SaS) turbulence model. Different pressure drops at certain lift have been selected from the operational map and reproduced numerically. Different modes have been identified, from stochastic behavior with wide width of frequency to periodic flow with one dominant frequency. Results indicate good agreement between the predicted frequency and amplitude and benchmark experiments. The quasi-3D simulation is able to reproduce the principle behavior of the flow field for different drop of pressure and capture the different operational mode. Similar behaviour has been detected also for the selected operating condition in the full 3D analysis. In addition, flutter calculation of the downstream pipe is carried out. It has demonstrated that the implementation of oscillating discharge piping influences the amplitudes and frequency of the upstream flow region.

CFD Simulation Research for Laminar Flow Cooling during Hot Strip Mills

2013 ◽  
Vol 706-708 ◽  
pp. 1237-1240
Author(s):  
Xu Guang Sun ◽  
Chang Hai Wang ◽  
Cheng Long Feng ◽  
Kai Qiao
Keyword(s):  
Fluid Dynamics ◽  
Flow Field ◽  
Cfd Simulation ◽  
Laminar Cooling ◽  
Simulation Research ◽  
Control Precision ◽  
Hot Strip ◽  
Interior Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Hot Strip Mills

This paper presents a computational fluid dynamics (CFD) simulation research for the interior flow field of laminar cooling during hot strip mills. Based on analysis of the flow field, the interior model of cooling is designed precisely, and the result establishes foundation for improving the control precision of cooling control system.

Flow Evolution in a One and a Half Axial Steam Turbine Stage Under Different Operating Conditions

2015 ◽  
Author(s):  
Berardo Paradiso ◽  
Alessandro Mora ◽  
Vincenzo Dossena ◽  
Giacomo Gatti ◽  
Andrea Nesti ◽  
...  
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Mass Flow ◽  
Rotational Speed ◽  
Cfd Simulation ◽  
Guide Vane ◽  
Operating Conditions ◽  
Design Stage ◽  
Inlet Guide Vane ◽  
Turbine Stage

In order to investigate in detail the performance of steam turbine stages the Low Speed Test Rig at Politecnico di Milano has been adapted. The setup consists of a one and an half turbine stage with an inlet guide vane. Two kind of experimental approaches are planned in the project: the first, denominated “performance”, has been carried out by the OGTL department of GE Oil&Gas Florence while, at the same time, Politecnico di Milano performed detailed inter-stage measurements with steady probes and time resolved high response pressure probes. An axial steam turbine stage was tested under several operating conditions in terms of rotational speed, mass flow and inlet angle with the aim to provide the functional curves of the machine together with detailed flow-field measurements. In this paper, a detailed description of the inter-stage flow-field is presented for the most relevant operating condition. Then, a comparison between three different points at the same rotational speed (but different mass flow) is proposed. Finally, the effects of different axial gaps on the overall performance of the stage are discussed. In particular, two different vane-rotor axial gaps have been tested by traversing pressure and temperature probes in three different axial planes. The first measurement plane is located at the first stator exit with the aim to provide details of the inlet swirl angle and 3D flow-field generated by the IGV. In the second plane, located at the rotor exit, the effect of different load conditions on the rotor performance and average flow-field is discussed. Finally, the measurements obtained in the third plane, placed at the second stator exit, are afterwards compared with the one obtained in the first plane, in order to evidence the influence of an unsteady inlet flow-field on the stator behaviour. The aim of the work is to provide very detailed aerodynamic measurements; this large amount of data will be used to validate the results of the CFD simulation carried out in the design stage. In this paper the preliminary findings of the steady flow-field will be presented as the basis for further analysis.

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