scholarly journals The effect of surface regression on the downward flame spread over a solid fuel in a quiescent ambient

2007 ◽  
Vol 11 (2) ◽  
pp. 67-86 ◽  
Author(s):  
Mohammad Ayani ◽  
Javad Esfahani ◽  
Antonio Sousa
Keyword(s):  
Solid Fuel ◽  
Flame Spread ◽  
Solid Phase ◽  
Numerical Study ◽  
Control Volume ◽  
Staggered Grid ◽  
Navier Stokes ◽  
Gas Temperature ◽  
Arrhenius Kinetics ◽  
Energy Equations

The present work is addressed to the numerical study of the transient laminar opposed-flow flame spread over a solid fuel in a quiescent ambient. The transient governing equations - full Navier-Stokes, energy, and species (oxygen and volatiles) for the gas phase, and continuity and energy equations for the solid phase (fuel) with primitive variables are discretized in a staggered grid by a control volume approach. The second-order Arrhenius kinetics law is used to determine the rate of consumption of volatiles due to combustion, and the zero-order Arrhenius kinetics law is used to determine the rate of degradation of solid fuel. The equations for the fluid and solid phases are solved simultaneously using a segregated technique. The physical and thermo-physical properties of the fluid (air) such as density, thermal conductivity, and viscosity vary with temperature. The surface regression of the solid fuel is modeled numerically using a discrete formulation, and the effect upon the results is analyzed. The surface regression of the solid fuel as shown affects on the fuel surface and gas temperature, mass flux and velocity of volatiles on the top surface of fuel, total energy transferred to the solid phase, etc. It seems the results to be realistic. .

scholarly journals Numerical study of the coupled natural convection with surface radiation in a cylindrical annular enclosure

2020 ◽  
Vol 330 ◽  
pp. 01029
Author(s):  
Mohamed Amine MEDEBBER ◽  
Abderrahmane AISSA ◽  
Belkacem OULD SAID ◽  
Noureddine RETIEL ◽  
Mohammed EL GANAOUI
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Surface Radiation ◽  
Navier Stokes ◽  
Simpler Algorithm ◽  
Energy Equations ◽  
Volume Method ◽  
Rayleigh Numbers ◽  
Total Average

The interaction of natural convection with thermal radiation of black surfaces in a cylindrical enclosure filled with air has been numerically investigated. The steady-state continuity, Navier-Stokes and energy equations were discretized using the control volume method and solved numerically via the SIMPLER algorithm. Effects of Rayleigh number (Ra), wall emissivity (εp) and height ratio parameter (X) are studied. The result shows that surface radiation significantly altered the temperature distribution and the flow patterns, especially at higher Rayleigh numbers. The total average Nusselt number has also been discussed for valuating heat transfer through the enclosure.

Numerical Performances Study of Curved Photovoltaic Panel Integrated with Phase Change Material

2020 ◽  
Vol 22 (4) ◽  
pp. 1439-1452
Author(s):  
Mohamed L. Benlekkam ◽  
Driss Nehari ◽  
Habib Y. Madani
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Numerical Study ◽  
Numerical Data ◽  
Navier Stokes ◽  
Photovoltaic Panel ◽  
Pv Panel ◽  
Energy Equations ◽  
Solid Liquid ◽  
Change Material

AbstractThe temperature rise of photovoltaic’s cells deteriorates its conversion efficiency. The use of a phase change material (PCM) layer linked to a curved photovoltaic PV panel so-called PV-mirror to control its temperature elevation has been numerically studied. This numerical study was carried out to explore the effect of inner fins length on the thermal and electrical improvement of curved PV panel. So a numerical model of heat transfer with solid-liquid phase change has been developed to solve the Navier–Stokes and energy equations. The predicted results are validated with an available experimental and numerical data. Results shows that the use of fins improve the thermal load distribution presented on the upper front of PV/PCM system and maintained it under 42°C compared with another without fins and enhance the PV cells efficiency by more than 2%.

Numerical Study of the Effect of Inlet Constriction on Bubble Growth During Flow Boiling in Microchannels

2005 ◽  
Author(s):  
Abhijit Mukherjee ◽  
Satish G. Kandlikar
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Boiling ◽  
Navier Stokes ◽  
Channel Cross Section ◽  
Vapor Bubbles ◽  
Reversed Flow ◽  
Cross Sectional ◽  
Parallel Microchannels ◽  
Energy Equations

Flow boiling through microchannels is characterized by nucleation of vapor bubbles on the channel walls and their rapid growth as they fill the entire channel cross-section. In parallel microchannels connected through a common header, formation of vapor bubbles often results in flow maldistribution that leads to reversed flow in certain channels. The reversed flow is detrimental to the heat transfer and leads to early CHF condition. One way of eliminating the reversed flow is to incorporate flow restrictions at the channel inlet. In the present numerical study, a nucleating vapor bubble placed near the restricted end of a microchannel is numerically simulated. The complete Navier-Stokes equations along with continuity and energy equations are solved using the SIMPLER method. The liquid-vapor interface is captured using the level set technique. The results show that with no restriction the bubble moves towards the nearest channel outlet, whereas in the presence of a restriction, the bubble moves towards the distant but unrestricted end. It is proposed that channels with increasing cross-sectional area may be used to promote unidirectional growth of the vapor plugs and prevent reversed flow.

Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls

2000 ◽  
Author(s):  
M. Singh ◽  
P. K. Panigrahi ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Energy Equations

Abstract A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.

scholarly journals Numerical Study on the Solid Fuel Rocket Scramjet Combustor with Cavity

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1235 ◽  
Author(s):  
Chaolong Li ◽  
Zhixun Xia ◽  
Likun Ma ◽  
Xiang Zhao ◽  
Binbin Chen
Keyword(s):  
Solid Fuel ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Combustion Efficiency ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Particle Combustion ◽  
Scramjet Combustor ◽  
Cavity Configuration

Scramjet based on solid propellant is a good supplement for the power device of future hypersonic vehicles. A new scramjet combustor configuration using solid fuel, namely, the solid fuel rocket scramjet (SFRSCRJ) combustor is proposed. The numerical study was conducted to simulate a flight environment of Mach 6 at a 25 km altitude. Three-dimensional Reynolds-averaged Navier–Stokes equations coupled with shear stress transport (SST) k − ω turbulence model are used to analyze the effects of the cavity and its position on the combustor. The feasibility of the SFRSCRJ combustor with cavity is demonstrated based on the validation of the numerical method. Results show that the scramjet combustor configuration with a backward-facing step can resist high pressure generated by the combustion in the supersonic combustor. The total combustion efficiency of the SFRSCRJ combustor mainly depends on the combustion of particles in the fuel-rich gas. A proper combustion organization can promote particle combustion and improve the total combustion efficiency. Among the four configurations considered, the combustion efficiency of the mid-cavity configuration is the highest, up to about 70%. Therefore, the cavity can effectively increase the combustion efficiency of the SFRSCRJ combustor.

scholarly journals Numerical Study of the Internal Flow Field of a Centrifugal Impeller

1994 ◽  
Author(s):  
Mou-jin Zhang ◽  
Chuan-gang Gu ◽  
Yong-miao Miao
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Internal Flow ◽  
Staggered Grid ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
High Reynolds

The complex three-dimensional flow field in a centrifugal impeller with low speed is studied in this paper. Coupled with high–Reynolds–number k–ε turbulence model, the fully three–dimensional Reynolds averaged Navier–Stokes equations are solved. The Semi–Implicit Method for Pressure–Linked Equations (SIMPLE) algorithm is used. And the non–staggered grid arrangement is also used. The computed results are compared with the available experimental data. The comparison shows good agreement.

scholarly journals Numerical and Experimental Investigation of a Supersonic Flow Field around Solid Fuel on an Inclined Flat Plate

2009 ◽  
Vol 2009 ◽  
pp. 1-10 ◽  
Author(s):  
Uzu-Kuei Hsu
Keyword(s):  
Flow Field ◽  
Solid Fuel ◽  
Stokes Equations ◽  
Control Volume ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Short Period ◽  
Volume Method ◽  
Environmental Temperatures ◽  
Gasification Temperature

This research adopts a shock tube 16 meters long and with a 9 cm bore to create a supersonic, high-temperature, and high-pressure flowfield to observe the gasification and ignition of HTPB solid fuel under different environments. Also, full-scale 3D numerical simulation is executed to enhance the comprehension of this complex phenomenon. The CFD (Computational Fluid Dynamics) code is based on the control volume method and the pre-conditioning method for solving the Navier-Stokes equations to simulate the compressible and incompressible coupling problem. In the tests, a HTPB slab is placed in the windowed-test section. Various test conditions generate different supersonic Mach numbers and environmental temperatures. In addition, the incident angles of the HTPB slab were changed relative to the incoming shock wave. Results show that as the Mach number around the slab section exceeded 1.25, the flowfield temperature achieved 1100 K, which is higher than the HTPB gasification temperature (930 K~1090 K). Then, gasification occurred and a short-period ignition could be observed. In particular, when the slab angle was7∘, the phenomenon became more visible. This is due to the flow field temperature increase when the slab angle was at7∘.

scholarly journals Numerical simulation of solidification around a circular cylinder with natural convection

2016 ◽  
Vol 38 (4) ◽  
pp. 295-306
Author(s):  
Vu Van Truong ◽  
Truong Viet Anh ◽  
Hoang Thi Bich Ngoc
Keyword(s):  
Natural Convection ◽  
Solid Phase ◽  
Linear Interpolation ◽  
Navier Stokes ◽  
Immersed Boundary ◽  
Isothermal Temperature ◽  
Temperature Boundary ◽  
Background Grid ◽  
Energy Equations ◽  
Solid Area

An analysis is carried out for solidification around a cold cylinder in a rectangular cavity using numerical simulations. The transient influences of solidification accompanied by natural convection are investigated in detail. The governing equations, in terms of one-fluid formulation, including the Navier-Stokes and energy equations for incompressible Newtonian fluids are written for the whole domain. The no-slip and Dirichlet-type isothermal temperature boundary conditions are both implemented using a linear interpolation technique (immersed boundary method). The solidification interface is represented by connected elements that move on the fixed background grid. Code validations are carried out through various problems. Finally, the temporal dependence of the solid area ratio of the solid phase to the cylinder upon various dimensionless parameters, such as Rayleigh number, Prandtl number, Stefan number, thermal property ratios as well as a parameter indicating the effect of superheat is studied.

A Three-Dimensional Numerical Study of Tin Droplets Landing Sequentially on a Solid Surface

2002 ◽  
Author(s):  
R. Ghafouri-Azar ◽  
J. Mostaghimi ◽  
S. Chandra
Keyword(s):  
Surface Deformation ◽  
Numerical Study ◽  
Control Volume ◽  
Three Dimensional ◽  
Sequential Deposition ◽  
Free Surface Deformation ◽  
Energy Equations ◽  
Simulated Images ◽  
D Model ◽  
Shape And Size

A three-dimensional (3-D) model of spreading and solidification was used to investigate the sequential deposition of two tin droplets for different offset landing. Numerical simulations predicted the shape and size of the landing tin droplet as it spread over a previously landed splat. The model applies a fixed-grid Eulerian control volume to solve the fluid dynamics and energy equations. The Volume of Fluid (VOF) algorithm is used to track the free surface deformation. The comparison of the simulated images and experimental photographs validated the prediction of the model.

Sign in / Sign up

Export Citation Format

Share Document