scholarly journals Numerical modelling of non-premixed biogas and LPG combustion to study carbon nanostructures formation in flame

2021 ◽  
Author(s):  
Manpreet Kaur ◽  
◽  
Jyoti Bharj ◽  
Rabinder S. Bharj ◽  
Rajan Kumar ◽  
...  
Keyword(s):  
Carbon Nanostructures ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Flame Temperature ◽  
Chemical Species ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Burner Exit ◽  
Fuel Flow

This work presents the numerical simulation of biogas and LPG fuelled diffusion flames in an axisymmetric chamber to study in-depth, the formation mechanism of soot and carbon nanostructures in these flames. The simulation is formulated on the set of transport equations that involve the equations for conservation of mass (the continuity equation), momentum (Navier-Stokes equation), energy, and chemical species. The governing equations are solved using ANSYS FLUENT, which is centered on the finite volume method. To predict the soot formation, one step soot model has been incorporated. The solution of these equations permits the estimation of temperature field and species concentrations inside the flame. Simulation is conducted at fixed fuel flow rate and varied oxygen flow rates. The results reveal that the formation of soot and carbon nanostructures is strongly dependent on peak flame temperature and concentration of precursor species formed in the flame. Since two fuels produce an exclusive chemical environment in the flame, the flame temperature and CO concentration that is conducive to the growth of carbon nanostructures is higher for LPG fuel as compared to that for biogas. Hence, the nucleation process of carbon nanostructures is faster for LPG than biogas. Moreover, the reactions taking place inside the flame at different locations can also be predicted from flame temperature and species concentration at that location. Pyrolysis of fuel occur near the burner exit, followed by the nucleation and surface growth of carbon nanostructures in the nearby region and oxidation of formed carbon nanostructures near the flame tip.

Numerical Study on Control of Sunroof Buffeting

2021 ◽  
Vol 13 (2) ◽  
Author(s):  
K. Vijaykumar ◽  
S. Poonkodi ◽  
A.T. Sriram
Keyword(s):  
Numerical Study ◽  
Leading Edge ◽  
Dominant Frequency ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Flow Modification ◽  
Numerical Result ◽  
Modification Technique ◽  
Commercial Solver

Sunroof has become one of the essential features of a luxury car, and it provides natural air circulation and good illumination into the car. But the primary problem associated with it is the buffeting noise which causes discomfort to the passengers. Though adequate studies were carried out on sunroof buffeting, efficient control techniques are needed to be developed from fundamental mechanism. To reduce the buffeting noise, flow modifications at the entrance of the sunroof is considered in this study. The internal portion of the car with sunroof is simplified into a shear driven open cavity, and two-dimensional numerical simulations are carried out using commercial solver, ANSYS Fluent. Reynolds averaged Navier-Stokes equation is used with the realizable k-? turbulence model. The unsteady numerical result obtained in this study is validated with the available experimental results for the dominant frequency. The prediction is good agreement with experiment. Flow modification technique is proposed to control the sunroof buffeting by implementing geometric modifications. A hump has been placed near the leading edge of the cavity which resulted in significant reduction of pressure oscillations. Parametric studies have been performed by varying the height of hump and the distance of hump from the leading edge. There is no prominent difference when the height of the hump is varied. As the distance of the hump from the leading edge is reduced, the sound pressure level decreases.

Conjugate Free Convection Heat Transfer and Thermodynamic Analysis of Infrared Suppression Device with Cylindrical Funnels

2022 ◽  
Author(s):  
Vikrant Chandrakar ◽  
Arnab Mukherjee ◽  
Jnana Ranjan Senapati ◽  
Ashok Kumar Barik
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Convection Heat Transfer ◽  
Navier Stokes ◽  
Bejan Number ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Geometric Ratio ◽  
Flow Rate Increase ◽  
Free Convection Heat

Abstract A convection system can be designed as an energy-efficient one by making a considerable reduction in exergy losses. In this context, entropy generation analysis is performed on the infrared suppression system numerically. In addition, results due to heat transfer are also shown. The numerical solution of the Navier-stokes equation, energy equation, and turbulence equation is executed using ANSYS Fluent 15.0. To perform the numerical analysis, different parameters such as the number of funnels, Rayleigh number (Ra), inner surface temperature, and geometric ratio are varied in the practical range. Results are shown in terms of heat transfer, entropy generation, irreversibility (due to heat transfer and fluid friction), and Bejan number with some relevant parameters. Streamlines and temperature contours are also provided for better visualization of temperature and flow field around the device. Results show that heat transfer and mass flow rate increase with the increase in Ra. Entropy generation and the irreversibility rise with an increase in the number of funnels and geometric ratio. Also, the Bejan number decreases with an increase in Ra and the number of funnels. A cooling time is also obtained using the lumped capacitance method.

PAHs and Soot Emissions in Oxygenated Ethylene Diffusion Flames at Elevated Pressures

2018 ◽  
Author(s):  
Krishna C. Kalvakala ◽  
Suresh K. Aggarwal
Keyword(s):  
Diffusion Flames ◽  
Soot Formation ◽  
Computational Study ◽  
Mixture Fraction ◽  
Flame Temperature ◽  
Primary Objective ◽  
Soot Emission ◽  
Elevated Pressures ◽  
Polycyclic Aromatic ◽  
Soot Emissions

Operating combustion systems at elevated pressures has the advantage of improved thermal efficiency and system compactness. However, it also leads to increased soot emission. We report herein a computational study to characterize the effect of oxygenation on PAHs (Polycyclic Aromatic Hydrocarbons) and soot emissions in ethylene diffusion flames at pressures 1–8atm. Laminar oxygenated flames are established in a counterflow configuration by using N2 diluted fuel stream along with O2 enriched oxidizer stream such that the stoichiometric mixture fraction (ζst) is varied, but the adiabatic flame temperature is not materially changed. Simulations are performed using a validated fuel chemistry model and a detailed soot model. The primary objective of the study was to expand the fundamental understanding of PAH and soot formation in oxygenated flames at elevated pressures. At a given pressure, as the level of oxygenation (ζst) is increased, we observe a significant reduction in PAHs (benzene and pyrene) and consequently in soot formation. Further, at a fixed ζst, as pressure is increased, it leads to increased benzene and pyrene formation, and thus increased soot emission. The reaction path analysis indicates that this can be attributed to the fact that at higher pressures, the C2/C4 path becomes more significant for benzene formation compared to the propargyl recombination path.

The Reynold’s Number Effect in High Swirling Flow in Unconfined Burner

2015 ◽  
Vol 72 (4) ◽  
Author(s):  
Norwazan A. R. ◽  
Mohammad Nazri Mohd. Jaafar
Keyword(s):  
Turbulent Flows ◽  
Gas Turbines ◽  
Swirling Flow ◽  
Numerical Study ◽  
Isothermal Condition ◽  
Navier Stokes ◽  
Reacting Flow ◽  
Ansys Fluent ◽  
Inlet Velocity ◽  
Burner Exit

The numerical simulations of swirling turbulent flows in isothermal condition in combustion chamber of burner were investigated. The aim is to characterize the main flow structures and turbulence in a combustor that is relevant to gas turbines. Isothermal flows with different inlet flow velocities were considered to demonstrate the effect of radial velocity. The inlet velocity, Uo is varied from 30 m/s to 60 m/s represent a high Reynolds number up to 3.00 X 105. The swirler was located at the upstream of combustor with the swirl number of 0.895. A numerical study of non-reacting flow in the burner region was performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) approach method was applied with the standard k-ɛ turbulence equations. The various velocity profiles were different after undergoing the different inlet velocity up to the burner exit. The results of velocity profile showed that the high U0 give better swirling flow patterns.

Aerodynamics of plunging airfoil in wind gust

2018 ◽  
Vol 90 (7) ◽  
pp. 1050-1064 ◽  
Author(s):  
Arpan Das ◽  
Shaligram Tiwari
Keyword(s):  
Navier Stokes ◽  
Wind Gust ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Freestream Velocity ◽  
Content Type ◽  
Naca0012 Airfoil ◽  
Reduced Frequency ◽  
Aerial Vehicle ◽  
Lift And Drag

Purpose Growing application of micro aerial vehicle (MAV) sets in demand for accurate computations of low Reynolds number flows past their wings. The purpose of this study is to investigate the effect of unsteady freestream velocity or wind gust on a harmonically plunging symmetric NACA0012 airfoil at Re = 1,000. The influence of unsteady parameters, such as reduced frequency of plunging motion (0.25 < k < 1.5), non-dimensional plunging amplitude (ho = 0.2) and non-dimensional amplitude of wind gust (0.1 = λ = 0.4) has been studied. Design/methodology/approach Computations have been carried out using commercial software ANSYS Fluent 16.0. To incorporate the plunging motion, the entire reference frame is oscillating, and thereby, a source term is added in the Navier–Stokes equation. Findings The results have been presented in the form of streamlines, vorticity contours, lift and drag signals and their spectra. It is observed that the ratio of plunging frequency to gust frequency (f/fg) has strong influence on periodic characteristics of unsteady wake. It has also been observed that for a fixed plunging amplitude, an increase in value of k results into a change from positive drag to thrust. Practical implications The research has implications in the development of MAV. Originality/value This study is intended to get a better understanding of unsteady parameters associated with gusty flow in flapping wing applications and possible ways to alleviate its adverse effect on it.

Numerical investigation on implication of innovative hydrogen strut injector on performance and combustion characteristics in a scramjet combustor

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sribhashyam Krishna Kireeti ◽  
Gadepalli Ravikiran Sastry ◽  
Santosh Kumar Gugulothu
Keyword(s):  
Transport Model ◽  
Weight Ratio ◽  
Combustion Efficiency ◽  
Navier Stokes ◽  
Mixing Efficiency ◽  
Injection Technique ◽  
Mixing Rate ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Scramjet Combustor

Abstract A detailed numerical analysis on a scramjet combustor is carried out by introducing an innovative shaped strut in place of the conventional strut. The design of newly added strut aids in generating intense vorticity which helps in efficient mixing of fuel and oxidizer. The air from the isolator enters the combustor at Mach 2.0, whereas fuel enters from the trailing edge of the strut sonically. In this study the flow dynamics with finite volume approach on commercial software Ansys-Fluent 20.0 to solve the two-dimensional Reynolds average Navier Stokes equation (RANS) with compressible fluid flow by considering the density-based solver with SST k-ε turbulent model. The species transport model with volumetric reaction and finite rate/eddy dissipation turbulence chemistry interaction is adopted to study the combustion phenomena and validated with the experimental results, and it is found that the interaction of the shear shock layer enhances the mixing rate by intensifying turbulence. The modified strut injector’s mixing efficiency is compared to the base strut and observed that with a 40% reduction in length, the modified strut injection technique exhibited a mixing efficiency of >95%. The combustion efficiency is then estimated streamwise, and the plot follows the same pattern as the mixing efficiency with fuel burns down completely when x = 150 mm for the modified strut whereas x = 200 mm for the base strut. This can compact the combustion chamber and increases the thrust-to-weight ratio. So, the innovative strut adopted can improvise the combustion efficiency.

Influence of innovative hydrogen multi strut injector with different spacing on cavity-based scramjet combustor

2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Sribhashyam K. Kireeti ◽  
Ravikiran Sastry Gadepalli ◽  
Santhosh K. Gugulothu
Keyword(s):  
Recirculation Zone ◽  
Transport Model ◽  
Combustion Efficiency ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Scramjet Combustor ◽  
Separation Layers ◽  
Finite Volume Approach ◽  
And Performance

Abstract In this study, the flow dynamics with finite volume approach on commercial software Ansys-Fluent 20.0 to solve the compressible two-dimensional fluid flow with Reynolds Average Navier Stokes equation (RANS) equation by considering the density-based solver with Shaer stress transport model (SST) k- ω turbulent model. The species transport model with volumetric reaction and finite rate/eddy dissipation turbulence chemistry interaction is adopted to study the combustion phenomena. Additionally, the effect of spacing between the struts on the flow characters and performance of the combustor is studied by increasing the spacing of struts from 1 mm to 4 mm for each increment of 1 mm. It is found that the multi strut improves the mixing and combustion efficiency compared with that of the single strut owing to the formation of a significant separation layer, resulting in multiple shocks, vortices, and a larger recirculation zone. However, when the spacing of struts is increased further, the performance of the combustor is found to be deteriorating owing to the formation of larger separation layers. The recirculation zone is significant when the strut spacing is minimal and shrinks and restricts itself within the cavity when spacing is increased. So, for better performance of combustor, multi strut with minimum spacing is preferable.

scholarly journals Fuel Molecular Structure and Flame Temperature Effects on Soot Formation in Gas Turbine Combustors

1990 ◽  
Vol 112 (1) ◽  
pp. 52-59 ◽  
Author(s):  
O¨. L. Gu¨lder ◽  
B. Glavincˇevski ◽  
M. F. Baksh
Keyword(s):  
Molecular Structure ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Empirical Relationship ◽  
Flame Temperature ◽  
Soot Volume Fraction ◽  
Smoke Point ◽  
Temperature Fields ◽  
Diesel Fuels

A systematic study of soot formation along the centerlines of axisymmetric laminar diffusion flames of a large number of liquid hydrocarbons, hydrocarbon blends, and aviation turbine and diesel fuels was made. Measurements of the attenuation of a laser beam across the flame diameter were used to obtain the soot volume fraction, assuming Rayleigh extinction. Two sets of hydrocarbon blends were designed such that the molecular fuel composition varied considerably but the temperature fields in the flames were kept practically constant. Thus it was possible to separate the effects of molecular structure and the flame temperature on soot formation. It was quantitatively shown that the smoke point height is a lumped measure of fuel molecular constitution. The developed empirical relationship between soot volume fractions and fuel smoke point and hydrogen-to-carbon ratio was applied to five different combustor radiation data, and good agreement was obtained.

scholarly journals Hydrodynamic Performance of Rectangular Heaving Buoys for an Integrated Floating Breakwater

2019 ◽  
Vol 7 (8) ◽  
pp. 239 ◽  
Author(s):  
Xiaoxia Zhang ◽  
Qiang Zeng ◽  
Zhen Liu
Keyword(s):  
Wave Energy ◽  
Numerical Results ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Wave Energy Converters ◽  
Floating Breakwater ◽  
Reaction Forces ◽  
Wave Conditions

Recently, the integrated development of wave energy converters and breakwaters has become popular, moving from traditional passive wave absorption to active energy capture. In this study, rectangular heaving buoys are considered as floating breakwater modules to absorb wave energy. A numerical wave tank is established based on Reynolds Averaged Navier-Stokes equation and User-Define-Function in ANSYS-Fluent commercial software. The numerical results show that incident wave conditions and submerged depth have significant effects on the heaving performance and wave energy absorption of a rectangular buoy. Flow structures around the buoy are shown to exhibit flow separations and vortex shedding, which can provide more information on buoy optimization. Power take-off (PTO) reaction forces are assumed to be a linear function of the translation velocities of the buoy. Numerical results demonstrate that a suitable PTO module can improve the wave power absorption by up to 34.2% for certain buoy and wave conditions, which is valuable for further investigations.

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