Week 10 - Simulating Combustion of Natural Gas.

Simulating Combustion of Natural Gas.

Theory:

Computational fluid dynamics modeling of combustion calls upon the proper selection and implementation of models suitable to faithfully represent the complex physical and chemical phenomenon associated with any combustion process. The model should be competent enough to deliver information related to the species concentration, their volumetric generation or destruction rate, and changes in the parameters of the system like enthalpy, temperature, and mixture density. The model should be capable of solving the general transport equations for fluid flow and heat transfer as well as additional equations of combustion chemistry and chemical kinetics incorporated into that as per the simulated environment desired.

Ansys setup:

Meshing

Ansys fluent:

Fill the all attributes according to the problem statement

problem type: pressure based;

time: Steady state ;

model: k - epsilon, species

Boundary conditions: Inlet - inlet velocity(fuel and air);

outlet: pressure outlet

Results:

fuel %and h20%	temp	nox	soot
90%ch4-10%o2	1488.1535	9.62E-05	2.17E-05
80%ch4-20%o2	1386.4531	5.27E-05	1.68E-06
75%ch4-25%o2	1333.1974	3.72E-05	4.56E-07
70%ch4-30%o2	1278.4848	2.52E-05	1.04E-07

Impressions:

As per the above observations, we can say that the addition of water to the fuel helps in decreasing NOx and SOOT Formation.
Water addition leads to increase OH radicals that might have a significant impact in SOOT Oxidation and reduce the SOOT
formed in the Gas Phase.

Added water dilutes calories generated by combustion. That decreases combustion temperature. If temperature reduces sufficiently, NOx cannot form in great concentration.

We can see a small decrease in temperature. Reducing combustion temperature means avoiding stoichiometric ratio. If this ratio is low, it generates a lower concentration of thermal NOx. So, with these or various types of technologies, we can reduce NOx emissions and SOOT formation, which helps us to meet regulatory requirements by the government. And we can reduce its harmful effects on the environment and humans.