Heat Flux Method

Experimental And Numerical Study OfLaminar Burning Velocity Of Methane-Air

Mixture Using Heat Flux Method

Pawan Kumar (SC11B038)

Under the guidance of:Dr. Prathap C.

Asst. Professor, IIST

Indian Institute of Space Science and Technology

Thiruvananthapuram

29 April, 2015

Flat FlameUsing Heat

Flux Method

Introduction

Aim

LaminarBurningVelocity

Heat FluxMethod

ExperimentalResult

NumericalMethod

Results AndDiscussions

ComputationalResult

Conclusions

Scope ofFuture Work

Outline

1 IntroductionAim

2 Laminar Burning Velocity

3 Heat Flux MethodExperimental Result

4 Numerical Method

5 Results And DiscussionsComputational Result

6 Conclusions

7 Scope of Future Work

Flat Flame Using Heat Flux Method 29 April, 2015 2/33


Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Aim

1 To design a new flat flame burner according to VanMaaren (1993) and fabricated it. The burner is validatedaccording to CH4-Air mixture. 1, 2

2 Using Heat Flux MethodExperimentally anchor an adiabatic laminar Flat Flame.Measurement of Laminar Burning Velocity of 1-D adiabaticflame using Flat Flame Burner.

3 2-D and 3-D simulation using ANSYS-FLUENT

4 Comparison of 2-D and 3-D simulation results.

1L. De Goey, A. Van Maaren, and R. Quax, Stabilization of adiabatic premixed laminar flames on a flatflame burner,

2K. J. Bosschaart and d. L. Goey, Extension of the heat flux method to subatmospheric pressures,



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Introduction

Combustion is a rapid oxidation

process of fuel which generates

essentially heat and sometimes light.

• A flame front is a visible part of exothermic reaction.

• Flame is self sustaining zone of localized combustion.



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

On the basis of phases the fuel can be divided in three type :

Fuel

Gas SolidLiquid

Methane(CH4)



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

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Scope ofFuture Work

Types of Flame: On the basis of state of mixedness

• Premixed Flame

• Non-Premixed Flame

The laminar premixed flames can be characterised by thefollowing ways:

• Laminar Burning Velocity

• Quenching Distance: Minimum distance for flame to quench.

• Flammability Limit: The lowest mole fraction of fuel andoxidiser require to anchor a flame.

• Minimum Ignition Energy : Minimum amount of energyrequired to ignite a sustainable flame



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Experimental Methods For Laminar BurningVelocity

Stationary Flames

• Conical Flame Method(Orifice/Nozzle/Slot)

• Counter Flow Method

• Flat Flame Method (Heat FluxMethod)

Propagating Flames

• Cylindrical Tube Method

• Spherical Bomb Method



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Laminar Burning Velocity

is defined as the relative velocity, of unburned reactantspropagating normal to the flame front.

SL = Ug

Flame Front

Unburnt Gas

Burner



Flux Method

Introduction

Aim


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ExperimentalResult

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ComputationalResult

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Scope ofFuture Work

Figure 1: Complete Setup Of Heat Flux Method

11 12

3

7

4

6

1

2

5

8

9

10

A (1). Compressor (5). Methane Cylinder (9). Computer

(2). Air tank with pressure (6). Methane Rotameter (10). Sony Camera

(3). Valve (7). Burner Stand (11). Hotwater Chamber

(4). Air Rotameter (8). Burner with Flame (12). Coldwater Chamber

Experimetal Setup for Flat Flame Burner Using Heat Flux Method



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Heat Flux Method

The heat flux method is based on measuring the net heat lossfrom the flame to the burner.



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Energy Balance

To analyse the heat flux balance in the burner platequantitatively, we will consider the energy equation :

− ∂∂x

[λp,x(r)∂Tp

∂x

]− 1

r∂∂r

[λp,r (r)r ∂Tp

∂r

]= α(x)[Tg − Tp]

λ = Thermal Conductivity (for brass λ = 129Wm−1K−1)α = Volumetric Heat Transfer Coefficient (Wm−3K−1)p= Plateg = gasx and r are axial and radial direction respectively.Tp and Tg = f(x,r)



Flux Method

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Heat FluxMethod

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−1r∂∂r

[λp,r (r)r ∂

∂r

∫ h

oTpdx

]=

∫ h

oα(x)[Tg − Tp]

+λp,x∂Tp

∂x|x=h − λp,x ∂Tp

∂x|x=0 = q(r)

Where as q is net heat transfer . For 1-D flame , q isindependent of r.

Avg .Temperature : Tp(r) = 1h

∫ h

oTpdx

• Temperature gradient along φ is zero because of symmetry.

• Also this is for steady state.



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

−1r∂∂r

[λp,r (r)r ∂Tp(r)

∂r

]= q(r)

h

Assuming that the conduction coefficient λp,r does not dependon temperature, and therefore not on r , equation can be solvedeasily by Integrating over burner plate thickness x=0 to x=h.

Tp(r) = Tcenter − q4λh

r 2

Using the above equation relation between Tp and r isparabolic and axis symmetric.



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


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Scope ofFuture Work

EXPERIMENTAL FACILITY

Figure 2: Burner Head



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


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Scope ofFuture Work

The new burner3 is shown in Figure 1. It consists of a burnerhead, and a plenum chamber.

3Vaan Maaren.



Flux Method

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Aim


Heat FluxMethod

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Scope ofFuture Work

Burner Head

• Perforated Plate

• Heating/Cooling Jacket

Figure 3: Burner Head (Heating/Cooling Jacket)



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

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Scope ofFuture Work

Plate Dia Thickness Hole Dia Pitch Pattern32 2 0.5 0.7 Hexagonal

Table 1: Perforated Plate Specification4

4All dimension are in mm



Flux Method

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Heat FluxMethod

ExperimentalResult

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Scope ofFuture Work

Thermocouple

K-type thermocouples were attached to the brass plate having1.5 mm blind hole at different radial locations, as thetemperature distribution is constant in the tangential direction.

Figure 4: Thermocouple Temperature Variation



Flux Method

Introduction

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Heat FluxMethod

ExperimentalResult

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Scope ofFuture Work

Procedure

1 Supply the air for some time.

2 Supply the hot water in heating jacket and wait till theradial profile temperature of plate become uniform.

3 After that pass the methane and ignite the flame.

4 Wait for certain time for constant temperature.

5 Vary the velocity with keeping the equivalence ratioconstant and change the flow rate of air and CH4 usingrotameter.

6 Also change the equivalence ratio and find thecorresponding velocity.



Flux Method

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Heat FluxMethod

ExperimentalResult

NumericalMethod


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Scope ofFuture Work

Experimental Result:

Figure 5: Laminar Burning Velocity(Sl) vs Equivalence Ratios(φ)



Flux Method

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Heat FluxMethod

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NumericalMethod


ComputationalResult

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Figure 6: Uncertainity in Result of Present Study



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Numerical Method



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

2-D Axis-symmetry Simulation

Quadrilateral 199,064

Total Cells 199,064

Total Points 200,550



Flux Method

Introduction

Aim


Heat FluxMethod

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Pointwise Grid

2-D Computational Grid



Flux Method

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Scope ofFuture Work

ANSYS-FLUENT Problem Setup

There are many options to specify when computational fluiddynamics model needs to be setup.

Table 2: Steps To solve Computational Fluid Dynamics Model

Solver Type Pressure-BasedViscous Model Laminar

Gravitational Effects OFF2D Space Axisymmetric

Pressure Velocity Coupling SIMPLEMomentum Equation Discretization Second-Order Upwind

Species Equation Discretization Second-Order UpwindEnergy Equation Discretization Second-Order Upwind

The viscous model was set to be laminar, since the Reynoldsnumber was kept ( Re< 2000) and the work is at steady state.



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

• Gas : Ideal

• Flow : Laminar

• Inlet pressure : 1 atm

• Inlet Temperature : 300 K

• Fuel : Methane

• Oxidiser : Air

• Chemical Kinetics Scheme : Methane-AirSingle Step Chemistry

• Patching : 2400 K

• Adapation : Gradient Based



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work



Flux Method

Introduction

Aim


Heat FluxMethod

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Results And Discussions

Computational Result:

Figure 7: Mass Fraction (CH4,O2,CO2,H2O) along with AxialCoordinate (m)



Flux Method

Introduction

Aim


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Scope ofFuture Work

3-D Simulation

Figure 8: 3-D Grid

Hexahedral 8,039250

Prism 127,710

Total Cells 8,166960

Total Points 8,398,954



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Comparison between 2-D and 3-D result



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Comparison between 2-D and 3-D result conti..



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Conclusions

In this project work, the methane-air flames has beenanchored on the basis of the experiment , 2D and 3Dnumerical simulation of a perforated-plate burner.

The measured values of laminar burning velocity werecompared with the literature data and the comparison wasgood.

The flame height increase with the increase in the inletvelocity.

Comparision between 2-D and 3-D simulation was alsoreasonably good.



Flux Method

Introduction

Aim


Heat FluxMethod

ExperimentalResult

NumericalMethod


ComputationalResult

Conclusions

Scope ofFuture Work

Scope of Future Work

Future work can be continued through well developedmeasurement technique is as follows:

• Velocity measurement can also be calculated forpropagating flame by using other method like freelypropagating Spherical Flame Method.

• The present design can be modified more importantly withthe application of a microcontroller operated by itsappropriate programming to derive the desired result (as inthe form of velocity) directly on to the display.

• The setup is only suitable for gaseous fuels. So, this setupcan be modified for the measurement of burning velocityof liquid fuels.

• This setup can also be used for see the dilutant effect onlaminar burning velocity.


Thank You!

Heat Flux Method

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