Combustion simulation and the effect of the addition of water content on the formation of Nox and soot

Title: Combustion simulation and the effect of the addition of water content on the formation of Nox and soot.

Objective

1.combustion simulation of diffrent species CO2, H2O, CH4, N2, O2, NOx emissions & Soot formation. 

2.Mass fraction of diffrent species

3. Addtion of water(5 To 30%) in to fuel (methane-air 2step) & to see the effect on NOx, & SOOT. 

Theory

      The basic combustion process where Fuel(hydrocarbon) plus oxidizer (oxygen or air) its called reactant, when this reactant undergo in to reaction there is prduce heat & produces emission like  NOX, SOOT, CO2 & which affect on to the enviorment.

       In this simulation use of Non-Premixed combustion where fuel & air sepratley is enter in to the combustion chamber  & combustion taken place on volumetric based phase. for combustion there is provide the mass fraction for  fuel (CH4)  & oxygen(O2) is 1& 0.23 respectively.

                           

from above reaction calculate the mole fraction of O2= 0.23 & N2=0.77

          For addition of water(H2O) in to the fuel (CH4) there is  use of methane-air 2step

 mixture properties. so, that we can vary the H20 content from 5-30% in to the fuel(CH4).

       

Model for combustion analysis

             Above model is given model for combustion analysis but  for to do the combustion  simuation on  this model is very costly & time consume, so that this 3D model is convert in to the 2D model. for that there is following procedure is implement.

For conversion from 3D To 2D model

Process 1

Process 2

Process 3

From process 2 required surface is copied & past in to new> design sheet 

                         

Process 4

The operation did on process 4 by use of combine tool & finally 2D model is ready form combustion analysis.

Mesh 

Mesh is refined much , so there is taken the element size 1mm, mesh type use triangle & capture the small proximity  Yes with number of cell gap is 3.

Setup for simulation

1. time>steady state

2. 2D Space> Axisymmetric

3. Energy > Turned ON

4. Viscous mode> K-epsilon >standard> standard wall function

5. Species model> Species transport>Volumetric> inlet diffustion> diffusion energy source>                          metane-air-2step>eddy-dissipation interaction

6. Model> NOx> ON>Thermal NOx &Prompt NOx>fuel species>CH4> oxident>oxyegen(O2)

7. Model> Soot Model> one-step

Boundry Condition

1.air_inlet>0.5m/s>300k>species O2>0.23 mole fraction& Other is zero

2. Fuel_inlet>80m/s>300k>species>CH4>1 mole fraction & vary the H20 (5 -30%)

3. Intialiation> Hybrid

Part I:Combustion simulation with zero percent addition of water in to fuel & plot the variation of mass fraction of CO2, H2O, CH4, N2, O2, NOx emissions & Soot.

Residual plot 

simulation run for 1000 iteration but solution is converged at 174 iteration

Temprature contour

following mass fraction is obtain at given four probe line

CO2 contour

CO2 Mass Fraction

from above plot it observed that as proceed the probe line in x-direction there is increase the  CO2 emission & as probe line proceed in Y-direction the CO2 emission is decrease . its because of oxygen available on y-direction is higher which help for reduction CO2.

H2O Contour

H2O Mass fraction

from above plot it observed that as proceed the probe line in x-direction there is increase the  H2O  & as probe line proceed in Y-direction the H2O is decrease . its because of oxygen available on y-direction is higher but less amount of hydogen present.

CH4 Contour

CH4 Mass fraction

from above plot it observed that as proceed the probe line in x-direction there is decrease the CH4 fuel & as probe line proceed in Y-direction the CH4 is much decrease . its because of fuel content near the igniter is higher. 

N2 Contour

 

N2 Mass fraction

from above plot it observed that as proceed the probe line in x-direction there is decrease the N2 & as probe line proceed in Y-direction the N2 is much increase . its because on air inlet side there is higher content N2. 

O2 Contour

O2 Mass fraction

from above plot it observed that as proceed the probe line in x-direction there is decrease the O2 & as probe line proceed in Y-direction the O2 is much increase . its because on air inlet side there is higher content O2 & on fuel inlet side less O2.

Nox Contour

NOx Mass fraction

from above plot it observed that as proceed the probe line in x-direction there is increase the NOx & as probe line proceed in Y-direction the NOx is decrease . Its because on fuel inlet side near the igniter there is higher temprature & which favourable condition for generation of NOx 

SOOT contour

SOOT Mass fraction

from above plot it observed that as proceed the probe line in x-direction there is increase the SOOT & as probe line proceed in Y-direction the SOOT is decrease . Its because on fuel inlet side near the igniter there is higher temprature & which favourable condition for generation of SOOT

Part-II:Combustion simulation with (5-30%)addition of water in to fuel & plot the variation of mass fraction of CO2, H2O, CH4, N2, O2, NOx emissions & Soot.

In this part vary the water(H2O) from 5-30% in to fuel(CH4) & observe the mass fraction of NOx & soot, so for that there is use of Parametric study.

Parametric study

 

1).5% H20 in to fuel (CH4)

Temprature contour

CO2 Contour

CO2 Mass fraction chart

H2O Contour

H2O Mass fraction chart

From above plot we can see that as 5% H20 add in to fuel side in as probe line is move in x-direction there is increase the water content & which help for reduction of emission specially NOx, & SOOT 

CH4 Contour

CH4 Mass fraction chart

N2 Contour

N2 Mass fraction chart

O2 Contour

O2 Mass fraction chart

NOx contour

NOx Mass fraction chart

due to addition of 5% water on fuel side there is slightaly decrease the NOx & its because of the water is help for reduction of temprature near the igniter.

SOOT Contour

SOOT Mass fraction chart

due to addition of 5% water on fuel side there is slightaly decrease the SOOT & its because of the water is help for reduction of temprature near the igniter.

2) 10% H20 in to fuel (CH4)

CO2 Contour

CO2 Mass Fraction Chart

H2O Contour

H2O Mass Fraction Chart

From above plot we can see that as 10% H20 add in to fuel side in as probe line is move in x-direction there is increase the water content & which help for reduction of emission specially NOx, & SOOT. Also we can see the at first probe line there is higher content of water.

CH4 Contour

CH4 Mass Fraction Chart

N2 Contour

N2 Mass Fraction Chart

O2 Contour

O2 Mass Fraction Chart

NOx Contour

NOx Mass Fraction Chart

due to addition of 10% water on fuel side there is decrease the NOx compare with the 5% water addition & its because of the water is help for reduction of temprature near the igniter.

SOOT Contour

SOOT Mass Fraction Chart

due to addition of 10% water on fuel side there is decrease the SOOT compare with the 5% water addition & its because of the water is help for reduction of temprature near the ignite

3) 15% H20 in to fuel (CH4)

CO2 Contour

CO2 Mass Fraction Chart

H2O Contour

H2O Mass Fraction Chart

From above plot we can see the at  first probe line there is higher mass fraction of water content compare to  10 % addition water & which help for reduction of NOx, SOOT near the igniter or flame region.

 

CH4 Contour

CH4 Mass Fraction Chart

N2 Contour

N2 Mass Fraction Chart

O2 Contour

O2 Mass Fraction Chart

NOx Contour

NOx Mass Fraction Chart

due to addtion of 15% water on fuel side there is decrease the NOx compare with the 10% water addition & its because of the water is help for reduction of temprature near the igniter

SOOT Contour

           

SOOT Mass Fraction Chart

due to addtion of 15% water on fuel side there is decrease the SOOT compare with the 10%water addition & its because of the water is help for reduction of temprature near the igniter.

4).25% H20 in to fuel (CH4)

CO2 Contour

CO2 Mass Fraction Chart

H20 Contour

H2O Mass Fraction Chart

From above plot we can see the at  first probe line there is higher mass fraction of water content  compare to  15 % addition water & which help for reduction of NOx, SOOT near the igniter or flame region.

CH4 Contour

CH4 Mass Fraction Chart

N2 Contour

N2 Mass Fraction Chart

O2 Contour

O2 Mass Fraction Chart

NOx Contour

NOx Mass Fraction Chart

Due to addtion of 25% water on fuel side there is decrease the NOx compare with the 15% water addition & its because of the water is help for reduction of temprature near the igniter

SOOT Contour

SOOT Mass Fraction Chart

Due to addtion of 25% water on fuel side there is decrease the SOOT compare with the 15% water addition & its because of the water is help for reduction of temprature near the igniter

Output Result 

NOx Mass fraction VS Vertical Distance Y

 from above plot we can see that as addition of water percentage there is redcution of NOx its because the reduction of temprature  near the core region of flame.

SOOT Mass fraction VS Vertical Distance Y

from above plot we can see that as addition of water percentage there is redcution of SOOT its because the reduction of temprature  near the core region of flame.

Overall Conclusion

1. Its found that after the burning of fuel near the core region of combustion, emission is higher like CO2, NOx, SOOT.

2. As addition of water near the first probe line increase the mass fraction of water , while decreased on fourth probel line.

3. At near the first probe line increase the fuel content CH4 , while decreased on fourth probel line.

4. N2 mass fraction is higher as proceed the probe line in Y-direction, its beacause the on air inlet side there is sending (air+nitrogen(N2)) mass which help the N2 higher on air inlet side.

5. As probe line proceed on Y-direction there is increase the O2 mass fraction, it's because there is sending the air mass on inlet side.

6. As additioon of water content from 5-30% there is reduction of NOx & SOOT. its because of the reduction of temprature which help for reduction of emision.

7. Parametric study help for analyze the NOx, SOOT by addition of H20.