Abstract: Thermoacoustic instabilities in combustors have
remained a topic of investigation for over a few decades due to the
challenges it posses to the operation of low emission gas turbines.
For combustors burning liquid fuel, understanding the cause-andeffect
relationship between spray combustion dynamics and
thermoacoustic oscillations is imperative for the successful
development of any control methodology for its mitigation. The
paper presents some very unique operating characteristics of a
kerosene-fueled diffusion type combustor undergoing limit-cycle
oscillations. Combustor stability limits were mapped using three
different-sized injectors. The results show that combustor instability
depends on the characteristics of the fuel spray. A simple analytic
analysis is also reported in support of a plausible explanation for the
unique combustor behavior. The study indicates that high amplitude
acoustic pressure in the combustor may cause secondary breakdown
of fuel droplets resulting in premixed pre-vaporized type burning of
the diffusion type combustor.
Abstract: In this paper a numerical technique is used to predict
the metal temperature of a gas turbine vane. The Rising combustor
exit temperatures in gas turbine engines necessitate active cooling for
the downstream turbine section to avoid thermal failure. This study is
performed the solution of external flow, internal convection, and
conduction within the metal vane. Also the trade-off between the
cooling performances in four different hole shapes and configurations
is performed. At first one of the commonly used cooling hole
geometry is investigated; cylindrical holes and then two other
configurations are simulated. The average temperature magnitude in
mid-plan section of each configuration is obtained and finally the
lower temperature value is selected such as best arrangement.
Abstract: Understanding of how and where NOx formation
occurs in industrial burner is very important for efficient and clean
operation of utility burners. Also the importance of this problem is
mainly due to its relation to the pollutants produced by more burners
used widely of gas turbine in thermal power plants and glass and steel
industry.
In this article, a numerical model of an industrial burner operating
in MILD combustion is validated with experimental data.. Then
influence of air flow rate and air temperature on combustor
temperature profiles and NOX product are investigated. In order to
modification this study reports on the effects of fuel and air dilution
(with inert gases H2O, CO2, N2), and also influence of lean-premixed
of fuel, on the temperature profiles and NOX emission.
Conservation equations of mass, momentum and energy, and
transport equations of species concentrations, turbulence, combustion
and radiation modeling in addition to NO modeling equations were
solved together to present temperature and NO distribution inside the
burner.
The results shows that dilution, cause to a reduction in value of
temperature and NOX emission, and suppresses any flame
propagation inside the furnace and made the flame inside the furnace
invisible. Dilution with H2O rather than N2 and CO2 decreases further
the value of the NOX. Also with raise of lean-premix level, local
temperature of burner and the value of NOX product are decreases
because of premixing prevents local “hot spots" within the combustor
volume that can lead to significant NOx formation. Also leanpremixing
of fuel with air cause to amount of air in reaction zone is
reach more than amount that supplied as is actually needed to burn
the fuel and this act lead to limiting NOx formation
Abstract: The objective of this work is to investigate the
turbulent reacting flow in a three dimensional combustor with
emphasis on the effect of inlet swirl flow through a numerical
simulation. Flow field is analyzed using the SIMPLE method which is
known as stable as well as accurate in the combustion modeling, and
the finite volume method is adopted in solving the radiative transfer
equation. In this work, the thermal and flow characteristics in a three
dimensional combustor by changing parameters such as equivalence
ratio and inlet swirl angle have investigated. As the equivalence ratio
increases, which means that more fuel is supplied due to a larger inlet
fuel velocity, the flame temperature increases and the location of
maximum temperature has moved towards downstream. In the mean
while, the existence of inlet swirl velocity makes the fuel and
combustion air more completely mixed and burnt in short distance.
Therefore, the locations of the maximum reaction rate and temperature
were shifted to forward direction compared with the case of no swirl.
Abstract: Results are presented from a combined experimental
and modeling study undertaken to understand the effect of fuel spray
angle on soot production in turbulent liquid spray flames. The
experimental work was conducted in a cylindrical laboratory furnace
at fuel spray cone angle of 30º, 45º and 60º. Soot concentrations
inside the combustor are measured by filter paper technique. The soot
concentration is modeled by using the soot particle number density
and the mass density based acetylene concentrations. Soot oxidation
occurred by both hydroxide radicals and oxygen molecules. The
comparison of calculated results against experimental measurements
shows good agreement. Both the numerical and experimental results
show that the peak value of soot and its location in the furnace
depend on fuel spray cone angle. An increase in spray angle enhances
the evaporating rate and peak temperature near the nozzle. Although
peak soot concentration increase with enhance of fuel spray angle but
soot emission from the furnace decreases.
Abstract: In this paper, a one-dimensional numerical approach is
used to study the effect of applying electrohydrodynamics on the
temperature and species mass fraction profiles along the microcombustor.
Premixed mixture is H2-Air with a multi-step chemistry
(9 species and 19 reactions). In the micro-scale combustion because
of the increasing ratio of area-to-volume, thermal and radical
quenching mechanisms are important. Also, there is a significant heat
loss from the combustor walls. By inserting a number of electrodes
into micro-combustor and applying high voltage to them corona
discharge occurs. This leads in moving of induced ions toward
natural molecules and colliding with them. So this phenomenon
causes the movement of the molecules and reattaches the flow to the
walls. It increases the velocity near the walls that reduces the wall
boundary layer. Consequently, applying electrohydrodynamics
mechanism can enhance the temperature profile in the microcombustor.
Ultimately, it prevents the flame quenching in microcombustor.