Mixture Preparation Effects on Distributed Combustion for Gas Turbine Application - Novel Combustion Concepts for Sustainable Energy Development - page 279

Table 1 Experimental parameters investigated
Case no. Mixing Fuel introduction Air temperature (K)

PR Premixed With air 600

CA Partially premixed Center of air jet 600

NP0 Non-premixed Separate 600

NP1 Non-premixed Separate 600

Dil Mixed mode Mixed mode 600

were observed to stabilize within three minutes for any change in experimental
condition (such as change in equivalence ratio and air preheat temperature for the
same con

guration). During a single experiment, measurements were repeated three
times for each con guration and the uncertainty was estimated to be about

± 10 % for CO emissions. The experiments were repeated at

least three times to ensure the consistency and repeatability of each experiment.
For imaging the OH* chemiluminescent intensity distribution, an ICCD camera
coupled with a narrow band

0.5 PPM for NO and ±

filter centered at 307 nm wavelength for OH* was
used. The gain for all the images obtained was set to 70 with one accumulation per
image and f-stop setting of 4.5. The exposure time was set to 50 ms. The resulting
OH* intensity distributions were then normalized to have the same scale.

2.2 Test Conditions

Detailed investigations were performed on the experimental combustor. The
investigations compared the performance of the combustor under different fuel
injection scenarios. The facility allowed variation of the injection velocity and
nozzle diameter of the fuel and air jets as well as the gas exit diameter. Table 1
summarizes the investigations performed along with the variables manipulated for
each investigation. The case name represents the location of fuel injection. The
dilution case was studied on NP1 con guration.

3 Numerical Simulations

Numerical simulations were performed to help develop an understanding of the
fl field and the mixing process inside the combustor for different air and fuel

stream conditions entering the combustor. For these simulations, commercial
software FLUENT ® code was used. The

ow

fl flow was modeled using finite volume

method. For solving turbulence, standard k- model with standard wall function

was used. For reacting cases, a two-step methane combustion model was adopted to
determine mixing between air,

ε

fuel, and recirculated gases from within the