scholarly journals Development of mathematical model for co-firing pulverized coal and biomass in experimental furnace

2018 ◽  
Vol 22 (1 Part B) ◽  
pp. 709-719 ◽  
Author(s):  
Aleksandar Milicevic ◽  
Srdjan Belosevic ◽  
Ivan Tomanovic ◽  
Nenad Crnomarkovic ◽  
Dragan Tucakovic
Keyword(s):  
Mathematical Model ◽  
Turbulent Transport ◽  
Combustion Process ◽  
Computer Code ◽  
Transport Processes ◽  
Pulverized Coal ◽  
Combustion Model ◽  
Two Phase ◽  
Processes And Reactions ◽  
Wide Range

A comprehensive mathematical model for prediction of turbulent transport processes and reactions during co-combustion of pulverized fuels in furnace fired by 150 kW swirl stabilized-burner has been developed. Numerical simulations have been carried out by using an in-house developed computer code, with Euler-Lagrangian approach to the two-phase flow modelling and sub-models for individual phases during complex combustion process: evaporation, devolatilization, combustion of volatiles, and char combustion. For sub-model of coal devolatilization the approach of Merrick is adopted, while for biomass devolatilization the combination models of Merrick, and of Xu and Tomita are selected. Products of devolatilization of both the pulverized coal and biomass are considered to contain the primary gaseous volatiles and tar, which further decomposes to secondary gaseous volatiles and residual soot. The residual soot in tar and carbon in coal and biomass char are oxidized directly, with ash remaining. For volatiles combustion the finite rate/eddy break-up model is chosen, while for char oxidation the combined kinetic-diffusion model is used. The comprehensive combustion model is validated against available experimental data from the case-study cylindrical furnace. The agreement of the simulations with the data for the main species in the furnace is quite good, while some discrepancies from experimental values are found in the core zone. The presented model is a good basis for further research of co-combustion processes and is able to provide analysis of wide range of pulverized fuels, i. e. coal and biomass. At the same time, the model is relatively simple numerical tool for effective and practical use.

scholarly journals Numerical simulation of the effect of different NaCl concent on boiler flame combustion process

2021 ◽  
Vol 2108 (1) ◽  
pp. 012097
Author(s):  
Zhihai Cheng ◽  
Jiahao Wang ◽  
Xinhai Han
Keyword(s):  
Alkali Metal ◽  
Radiation Heat Transfer ◽  
Combustion Process ◽  
Pulverized Coal ◽  
Combustion Model ◽  
Two Phase ◽  
Combustion Region ◽  
Zhundong Coal ◽  
High Alkali ◽  
Factsage Software

Abstract Zhundong coal has been widely concerned because of its high alkali metal content, which brings great danger to the combustion of boiler. Therefore, it is extremely necessary to study the laws and characteristics of alkali metal influencing combustion in the burning process of zhundong coal. A gas-solid two-phase flow combustion model of pulverized coal containing NaCl was established by using Fluent software and FactSage software in a hot experimental combustion furnace. The influence of different NaCl content in pulverized coal on pulverized coal combustion process was discussed. The results show that with the increase of NaCl content in pulverized coal from 0 to 1% and 2%, the flame center temperature in the furnace increases about 80°C and 120°C under the same coal content, so it can be concluded that the increase of NaCl content can promote the combustion process of pulverized coal in the furnace. At the same time, it can be calculated that, with the increase of NaCl content, the flame range of the combustion region inside the furnace increases by 1/3. Because NaCl is decomposed by heat during combustion to help combustion, and the radiation heat transfer increases, the flame radiation range inside the furnace will increase.

Experimental Measurements and CFD Evaluation of the Onset Flow Boiling at Low Pressure and High Subcooling Flow of R-11 Within Vertical Annulus

2014 ◽  
Author(s):  
Y. Bouaichaoui ◽  
R. Kibboua ◽  
M. Matkovič
Keyword(s):  
Heat Flux ◽  
Liquid Velocity ◽  
Flow Boiling ◽  
Fluid Model ◽  
Computer Code ◽  
Computational Method ◽  
Subcooled Boiling ◽  
Two Phase ◽  
Local Flow ◽  
Wide Range

The knowledge of the onset of subcooled boiling in forced convective flow at high liquid velocity and subcooling is of importance in thermal hydraulic studies. Measurements were performed under various conditions of mass flux, heat flux, and inlet subcooling, which enabled to study the influence of different boundary conditions on the development of local flow parameters. Also, some measurements have been compared to the predictions by the three-dimensional two-fluid model of subcooled boiling flow carried out with the computer code ANSYS-CFX-13. A computational method based on theoretical studies of steady state two phase forced convection along a test section loop was released. The calculation model covers a wide range of two phase flow conditions. It predicts the heat transfer rates and transitions points such as the Onset of Critical Heat Flux.

Investigation on Reaction Flow Field of Low Emission TAPS Combustors

2014 ◽  
Vol 694 ◽  
pp. 45-48
Author(s):  
Qun Zhang ◽  
Hua Sheng Xu ◽  
Tao Gui ◽  
Shun Li Sun ◽  
Yue Wu ◽  
...  
Keyword(s):  
Combustion Process ◽  
Combustion Efficiency ◽  
Combustion Model ◽  
Outlet Temperature ◽  
Gas Temperature ◽  
Distribution Factor ◽  
Two Phase ◽  
Nox Formation ◽  
Low Emission ◽  
Thermal Nox

A twin annular premixing swirler (TAPS) combustor model of low emissions was developed in this study. And computational studies on combustion process in the combustor model were carried out. Standard k-ε Turbulence Model, PDF non-premixed combustion model, Zeldovich thermal NOx formation model and DPM two-phase model were employed. The distributions of some key performance parameters such as gas temperature, flow velocity, concentrations of NOx and CO emissions were obtained and analyzed. At the same time, combustion mechanics inside the TAPS combustor model were investigated. The computational results indicated that the TAPS combustor employed in this study does a better job of improving key combustion performances such as combustion efficiency, total pressure recovery and outlet temperature distribution factor, and reducing NOx and CO emissions at the same time.

An Appraisal of System Mean Void Fraction and Its Application for the Moving Boundary Simulation of Phase-Change Heat Exchangers

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
S. P. Datta ◽  
R. K. Chandra ◽  
P. K. Das
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Void Fraction ◽  
Heat Exchangers ◽  
Moving Boundary ◽  
Transport Processes ◽  
Closed Form Expression ◽  
Two Phase ◽  
Slip Ratio ◽  
Wide Range

In gas–liquid two-phase flow, void fraction is the most unique parameter which influences all the transport processes. In the most general case, though the void fraction varies nonlinearly with the channel length, many practical simulations make use of the “system mean void fraction.” The present investigation makes a critical assessment of different system mean void fraction models for a wide range of slip velocity and density difference between the phases. To this end, different correlations for slip ratio have been considered and, for all the cases, closed form expression for the system mean void fraction has been presented. The local as well as the system mean void fractions have also been estimated numerically from a heat transfer based model. Predictions from the heat transfer based model and the slip ratio based model have been compared. As an application, the slip ratio based system mean void fraction is used in to build the moving boundary model for phase-change heat exchangers. The prediction of startup transients for both an evaporator and a condenser of an automotive air conditioning system (AACS) agrees well with the experimental results.

Balancing Pulverized Coal Flows in Parallel Piping

1985 ◽  
Vol 107 (3) ◽  
pp. 679-684 ◽  
Author(s):  
A. A. Vetter ◽  
R. S. Vetter
Keyword(s):  
Power Plant ◽  
Entire Range ◽  
Computer Code ◽  
Pulverized Coal ◽  
Two Phase ◽  
Nominal Load ◽  
Load Conditions

The distributions of the two-phase (pulverized coal in air) fuel inputs through the 24 parallel coal transport pipes of a coal-fired power plant are determined with a computer code. The orificing which would provide balanced fuel inputs through these coal transport pipes under nominal load conditions is also calculated with the code. Over the entire range of loading, the orificing determined with the code provides much smaller fuel imbalances than the imbalances which result with the previously installed orificings.

Co-Combustion of Pulverized Coal and Biomass in Fluidized Bed of Furnace

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Mitianiec Wladyslaw
Keyword(s):  
Open Source ◽  
Gas Phase ◽  
Flow Rate ◽  
Combustion Process ◽  
Theoretical Description ◽  
Pulverized Coal ◽  
Numerical Code ◽  
Two Phase ◽  
Inlet Flow Rate ◽  
Combustion Processes

Combustion processes of two fuels, pulverized coal and biomass, in furnaces take place at steady state. Combustion of condensed fuels involves one-way interfacial flux due to phenomena in the condensed phase (evaporation or pyrolysis) and reciprocal ones (heterogeneous combustion and gasification). Many of the species injected in the gas phase are later involved in gas phase combustion. This paper presents results of combustion process of two-phase charge contained coal and wetted biomass, where the carrier was the air with given flow rate. The furnace has three inlets with assumed inlet flow rate of coal, biomass, and air, and combustion process takes place in the furnace fluidized space. The simulation of such combustion process was carried out by numerical code of open source computational fluid dynamics (CFD) program code_saturne. For both fuels, the moist biomass with following mass contents: C = 53%, H = 5.8%, O = 37.62%, ash = 3.6, and mean diameter of molecules equal to 0.0008 m and pulverized coal with following mass contents: C = 76.65%, H = 5.16%, O = 9.9%, ash = 6.21%, and mean molecule diameter 0.000025 m were used. Devolatilization process with kinetic reactions was taken into account. Distribution of the main combustion product in furnace space is presented with disappearance of the molecules of fuels. This paper presents theoretical description of the two-phase charge, specification of the thermodynamic state of the charge in inlet boundaries and furnace space, and thermal parameters of solid fuel molecules obtained from the open source postprocessor paraview.

Modelling the early stage of spark ignition engine combustion using the KIVA-3V code incorporating an ignition model

2003 ◽  
Vol 4 (3) ◽  
pp. 179-192 ◽  
Author(s):  
L Andreassi ◽  
S Cordiner ◽  
V Rocco
Keyword(s):  
Early Stage ◽  
Combustion Process ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Gasoline Direct Injection ◽  
Combustion Model ◽  
Cylinder Wall ◽  
Predictive Capability ◽  
Wide Range

The evolution of early stages of homogeneous mixture combustion in spark ignition (SI) engines represents a critical period that greatly affects the whole combustion process. A proper description of this critical phase represents a major issue, which could strongly influence the overall model predictive capability (i.e. model ability to reproduce the real engine behaviour for a large range of operating conditions without any major tuning). Such requirements become even more important for the simulation of last-generation gasoline direct injection or lean stratified engines, where ignition could determine the functionality of the engine itself. In this paper, after a detailed analysis of the ignition physical process and its modelling issues, the predictive capability of the KIVA-3V code has been improved by substituting the original ignition procedure with a more detailed kernel evolution model based on the one presented by Herweg and Maly in 1992. The ignition model introduced in a KIVA-3V version already modified by the authors (re-zoning algorithm, combustion and turbulence models, cylinder wall heat transfer, etc.) has then been tested in order to assess its level of accuracy in describing this complex phenomenon, by varying the most critical engine operating conditions and keeping combustion tuning parameters unchanged. After comparing ignition model results with the corresponding ones presented by Herweg and Maly, a specific application of the overall model (KIVA-3V + ignition model + turbulent combustion model) has been made to perform an analysis of a compressed natural gas (CNG) fuelled engine for heavy-duty applications. To this aim, the in-cylinder combustion history and the related processes as the temperature distribution and NOx formation have been calculated and verified with reference to the experimental data measured in a wide range of operating conditions of an IVECO turbocharged engine.

Incompressible Turbulent Flow in a Permeable-Walled Duct

1972 ◽  
Vol 94 (2) ◽  
pp. 314-319 ◽  
Author(s):  
E. M. Sparrow ◽  
V. K. Jonsson ◽  
G. S. Beavers ◽  
R. G. Owen
Keyword(s):  
Turbulent Flow ◽  
Turbulent Transport ◽  
Maximum Velocity ◽  
Porous Wall ◽  
Velocity Slip ◽  
Transport Processes ◽  
Porous Surface ◽  
Damping Factor ◽  
Wide Range ◽  
Fully Developed Turbulent Flow

An analysis is made of fully developed turbulent flow in a parallel-plate channel having one porous bounding wall. A velocity slip model is employed to characterize the boundary condition at the porous surface. The turbulent transport processes in the channel are represented via the Prandtl mixing length concept in conjunction with a modified form of the Van Driest damping factor. Numerical results are obtained for Reynolds numbers ranging from 5000 to 200,000 and for a wide range of values of a dimensionless slip grouping. The results show that velocity slip at the porous surface brings about a reduction in the friction factor, the extent of the reduction being accentuated with increasing Reynolds number. The velocity slip also causes a skewing of the velocity profiles, such that the location of the maximum velocity is shifted toward the porous wall.

Developing Effervescent Atomisation for Alternative Fuels

2012 ◽  
Author(s):  
Dancho D. Konstantinov ◽  
Philip J. Bowen ◽  
Richard Marsh ◽  
Peter J. Kay ◽  
Andrew P. Crayford ◽  
...  
Keyword(s):  
Literature Review ◽  
Alternative Fuels ◽  
Combustion Process ◽  
Volume Ratio ◽  
Industrial Applications ◽  
Quality Data ◽  
Operating Parameters ◽  
Extensive Literature ◽  
Two Phase ◽  
Wide Range

A wide range of atomiser types have been developed for industrial applications — such as rotary, pressure, air-assist and air-blast atomisers. Each type works on the principle of applying mechanical or kinetic energy to disintegrate a jet or sheet of liquid fuel, in preparation for combustion. The aim is to sufficiently increase the surface area to volume ratio of the fuel and presents it in a form suitable for a consistent combustion process. Traditional liquid fuels, such as fossil fuels, have been employed for some decades and combustion systems (and atomisers) have been optimised for their use. However, combustion engineers are being increasingly forced to consider the use of alternative, biologically-derived hydrocarbon fuels. Such fuels often have very different viscosities, densities and surface tensions or possess complex, non-linear properties when compared to conventional fuels. Effervescent atomisation is a promising two-phase atomisation technique offering potential improvements in fluid atomisation quality and reductions in fluid operating pressures. It appears particularly well suited to the atomisation of viscous fuels such as biofuels; this applicability to alternative fuels has led to a renewed interest in the method. After an extensive literature review of the current state of this technology [1] an adjustable geometry effervescent atomiser was designed, built and studied at the Cardiff School of Engineering. Water and air were used as the operating fluids. The sprays produced by the atomiser were characterised using a Phase Doppler Anemometry (PDA) system which allowed for simultaneous real-time droplet size and velocity data to be obtained. High quality data was achieved with data rates over 10 kHz and validation rates over 90% in 2-D LDA mode in the high density sprays. A PDA probe designed for dense spray applications was utilised. A number of important operating parameters identified during the literature review phase can be altered on the atomiser, and their effects on fuel spray quality investigated. The operating parameters investigated in this manner included air-to-liquid by mass ratio (ALR), pressure drop as well as a range of geometric parameters. This paper discusses and analyses the influence of ALR on the quality of atomisation and the associated two-phase flow field. Comparisons are made with previous studies and correlations, using earlier versions of the hardware or alternative techniques. Ongoing work will assess and optimise the performance of simulated biofuels mixtures.

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