Liquid fuel combustion in fluent

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 October 30, 2012, 00:44 Liquid fuel combustion in fluent #1 Member   Join Date: Apr 2012 Location: Mainz, Germany Posts: 57 Rep Power: 6 Hi everyone, I need help regarding incorporating liquid fuel combustion to my gas turbine geometry. I have completed cold flow analysis. I also achieve combustion using methane. But my goal is to incoporate diesel into combustion. Can anyone help me with this? How do I go about it. Should I use Discrete Phase to incorporate spray and evaporation? I am using Non-premixed combustion. So, for methane I generated the PDF table and ignited the mixture by mentioning mixture fraction in fuel inlet as 1. Do I have to follow the same procedure for liquid fuels as well. PLease help. Regards, Juzer Rangwala I.C Engine and Combustion Laboratory, Indian Institute of Technology, Bombay, rangwala.juzer@gmail.com

 October 30, 2012, 02:57 #2 Senior Member   david Join Date: Oct 2012 Posts: 125 Rep Power: 6 Hi Juzer, There are two types of breakups for the spray modelling viz. the primary breakup and the secondary breakup. The primary breakup is classified into four regimes namely the Rayleigh regime, the first and second wind induced regime and the atomization regime. They are based on the Ohnesorge number. For the modelling of diesel engine, the primary break up falls under the category of atomization. Here, the breakup is at the surface of the nozzle’s hole. The diameter of the droplets are very much smaller than the diameter of the nozzle. You can use the Discrete Phase Model (DPM). It allows the user to model evaporation of the fuel. There are a few disadvantages of using the DPM most notably, its limitation of cell sizes near the nozzle. This is due to the assumption of the Euler-Lagrange approach which states that the particles in a cell would occupy at most 12% of the volume while the rest of the cell will be in the fluid phase(continuum). This has a significant effect in the region around the nozzle area where the primary breakdown falls under the atomization scheme. You can use the Eddy Dissipation model for turbulence-chemistry interaction. As for the Spray model, you can use the Wave Breakup Model of Reitz. I assume that this is a high Webber number you're looking at and hence the choice of this model. You would also need to do something about the ignition delay. I think the Hardenburg Ignition Delay Model would be fine. You would need to inout the activation energy though but this can be found through literature. Hope this helps. Hayder Mohammed, hamdireza and leo_lee like this.

April 16, 2015, 10:17
#3
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sanjeet Limbu
Join Date: Mar 2015
Posts: 91
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Hi

I am also working for partially premixed combustion model to get the ignition time.
But I am getting :1. Low pressure start point, also no combustion happening as pressure is flat not rising
2. Lower fuel mole fraction than what I entered initially of 0.00562, it start from 0.0025

Physic: The compression stroke for the 2D axisymetric mesh containing fluid - 0.00562 n-heptane by mole fraction and remaining air.

If there is some wrong setting i did for not making combustion happening
Attached Images
 combustion model for autoignition.jpg (75.3 KB, 31 views) pressure contour.jpg (67.8 KB, 23 views) molefraction nheptane.jpg (25.9 KB, 17 views) P and T.jpg (25.2 KB, 14 views) CFD post error fot Temp vs time plot.jpg (50.3 KB, 15 views)

April 16, 2015, 10:41
#4
New Member

Hayder Mohammed
Join Date: Apr 2013
Posts: 9
Rep Power: 5
Quote:
 Originally Posted by sanjeetlimbu Hi I am also working for partially premixed combustion model to get the ignition time. But I am getting :1. Low pressure start point, also no combustion happening as pressure is flat not rising 2. Lower fuel mole fraction than what I entered initially of 0.00562, it start from 0.0025 Physic: The compression stroke for the 2D axisymetric mesh containing fluid - 0.00562 n-heptane by mole fraction and remaining air. If there is some wrong setting i did for not making combustion happening
Hi ...I solved liquid fuels and gaseous fuels combustion and got a very good reults...after I made some modification on fluent and cfd post ..

 April 16, 2015, 10:47 #5 Member   sanjeet Limbu Join Date: Mar 2015 Posts: 91 Rep Power: 3 Can u tell what modifications u made As the temperature is not rising as i expected, also the pressureee, but strangely the fuel is vanished - mole fraction reduced to zero

 April 16, 2015, 11:04 #6 New Member   Hayder Mohammed Join Date: Apr 2013 Posts: 9 Rep Power: 5 call me on my skype (theiraqiengineer)

 April 16, 2015, 14:47 #7 Member   sanjeet Limbu Join Date: Mar 2015 Posts: 91 Rep Power: 3 Sorry I donot have skype id , can i use google call , my email- slimbu@mtu.edu

April 16, 2015, 21:07
#8
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sanjeet Limbu
Join Date: Mar 2015
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I am using the ignition delay model for combustion(N2/O2/nC7H16: 89.5/10.307/0.00562) by compression stroke of cylinder... simulation to rapid compression machine. The mixture fuel is inside the cylinder compressed at 30 millisec.
I am able to run the dynamic mesh using the chem kin file for combustion . I got some results...
But I expected the combustion to make temperature rise, but i am getting early rise in temperature, while fuel also dispense early than compression end
If possible can u suggest if I entered any wrong input in initialization or model dialog box

The dynamic mesh used to show compression- for 30 millisec and combustion is expected after 30 millisec

Problem-
Everything related to combustion seem start early before compression stroke end.
Unable to get temperature/pressure rise after compression stroke at 30 ms
The mole fraction for n-heptane start from 0.0025, instead of the 0.00562 I entered in boundary condition for the model.

Please suggest how to set up the model as pressure and very low CFD post results
Attached Images
 mole fraction fuel.jpg (25.1 KB, 7 views) Pressure and Temp early rise.jpg (28.2 KB, 7 views) model_combustion.jpg (52.8 KB, 8 views) combustion model for autoignition.jpg (75.3 KB, 10 views) pressure contour.jpg (67.8 KB, 6 views)

April 16, 2015, 23:51
#9
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sanjeet Limbu
Join Date: Mar 2015
Posts: 91
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I checked by change in initialization mean mixture fraction 0 and 1, so for 298K as initial temp the mean mixture fraction is needed as zero, if I enter mean mixture fraction as 1- the temperature jumps to the PDF calculated 1100K.

Since the fuel mixture become nil if I use the mean mixture fraction as zero

Pl help how to keep both temp also 298 K and fuel mixture as entered in boundary condition PDF calculation
Attached Images
 PDF meam mixture.jpg (13.3 KB, 7 views)

April 18, 2015, 03:46
combustion problem
#10
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haryana
Join Date: Jan 2015
Posts: 2
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Dear friends,

I am working on modeling and simulation of high-velocity oxy-fuel (HVOF) thermal spray process with Kerosene as liquid fuel in workbench Ansys Fluent. I am interested in calculating the velocity and temperature profiles of exhaust combustion products into the atmosphere. The things I have are stated below:

Fuel= Kerosene (C12H22) mass flow rate = 0.00625 kg/s
Oxygen= mass slow rate = 0.02125 kg/s

The combustion process takes place inside the combustion chamber of HVOF spray gun with fuel and oxygen.

C10H20+15O2 - 10CO2+10H2O

The body of Gun is made of copper and liquid cooled to keep it at 50 degrees. The exhaust gases emerged from 8 inch long barrel into open atmosphere.
Please find the attached image of HVOF spray gun
my solution is converging but when i see my temperature contour temperature is found 300k everywhere in the gun. means combustion is not done . then what can i do for calculating my problem.
attached of my whole setting report and temperature contour and residual plot also
Attached Images
 resug5.jpg (64.2 KB, 11 views) Gun geometry,,,,,.jpg (29.5 KB, 13 views)
Attached Files
 report.txt (52.8 KB, 6 views)

April 18, 2015, 04:14
temp. contour
#11
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haryana
Join Date: Jan 2015
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its temperatur contour of my problem
Attached Images
 temp.con.jpg (65.6 KB, 14 views)

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