On Flame Stabilization by Bluff-Bodies

1980 ◽  
Vol 102 (1) ◽  
pp. 209-214 ◽  
Author(s):  
K. M. Kundu ◽  
D. Banerjee ◽  
D. Bhaduri
Keyword(s):  
Heat Exchange ◽  
Recirculation Zone ◽  
Flame Stabilization ◽  
Flame Stability ◽  
Bluff Bodies

Flame stabilization by bluff-bodies has been investigated to highlight the role of recirculation zone on the phenomenon. It has been observed that close correlations exist between heat exchange from recirculation zone and flame stability as controlled by recirculation strength.

Analysis of Lift off Height and Blow-Off Mechanism of Turbulent Flame by V-Gutter Bluff Body

2015 ◽  
Vol 787 ◽  
pp. 727-731 ◽  
Author(s):  
S. Boopathi ◽  
P. Maran ◽  
V. Caleb Eugene ◽  
S. Prabhu
Keyword(s):  
Bluff Body ◽  
Recirculation Zone ◽  
Turbulent Flame ◽  
Flame Stability ◽  
Bluff Bodies ◽  
Combustion Instabilities ◽  
Test Rig ◽  
Square Duct ◽  
Flame Holder ◽  
Lift Off

The experimental investigation has been carried out to study the stabilization and blowout mechanisms of turbulent flame stabilized by V-gutter bluff body in a square duct at reactive and non-reactive conditions. V-shaped bluff bodies made of stainless steel having 1.6 mm thicknessare used for stabilization of the flame.Experiments have been conducted at selective velocities of commercially available methane and oxygen with 60 degree V-gutter as flame holder. It is observed that at stoichiometric conditions, the V-gutter is dominated by shear layer stabilized flames. The flame stability is influenced by bluff body dimensions and mass flow rate which play a major role in combustion instabilities mixing of air fuel ratio and blow off. The lift off decreases at higher blockage ratios.A strong recirculation zone is found in this test rig immediately downstream of the V-Gutter which gradually subsides and disappears far downstream.The lift off height is not much affected by the velocity of the fuel-air mixture.

scholarly journals Experimental investigation of distance between v-gutters on flame stabilization and NOx emissions

2019 ◽  
Vol 23 (5 Part B) ◽  
pp. 2971-2981 ◽  
Author(s):  
Dias Umyshev ◽  
Abay Dostiyarov ◽  
Andrey Kibarin ◽  
Galya Tyutebayeva ◽  
Gaziza Katranova ◽  
...  
Keyword(s):  
Bluff Body ◽  
Flame Stabilization ◽  
Temperature Fields ◽  
Flame Stability ◽  
Bluff Bodies ◽  
Nox Emissions ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Inlet Velocity ◽  
Exhaust Gas Temperature

Blow-off performance and NOx emissions of the propane and air mixture in a rectangular combustion chamber with bluff bodies were investigated experimentally and numerically. The effects of distance between bluff bodies on NOx emissions, the blow-off limit, and exhaust gas temperature were examined. It was observed that NOx emissions are highly dependent on distance between V-gutters. The re-circulation zone behind the bluff body expands in width based on the decrease of distance between V-gutters, and expands in length with the increase of inlet velocity. The temperature fields behind the bluff body show a similar change, the temperature behind the bluff body reaches its highest when the distance between V-gutters reaches 20 mm, meaning it has better flame stability. The blow-off limit is significantly improved with the decrease of distance between V-gutters. The blow-off limit is greatly improved by reducing the distance between the V-gutters. Maximum blow-off limit of 0.11 is reached in the case of 20 mm, compared with 0.16 at 50 mm at a speed of 10 m/s.

Flame Holding and Combustion Characteristics of a Geometrical Flame Holder

2008 ◽  
Author(s):  
K. A. Ahmed ◽  
D. J. Forliti
Keyword(s):  
Boundary Layer ◽  
High Speed ◽  
Equivalence Ratio ◽  
Recirculation Zone ◽  
Combustion Products ◽  
Flame Stabilization ◽  
Combustion Characteristics ◽  
Bluff Bodies ◽  
Trailing Edge ◽  
Flame Holder

Flame Stabilization in a high-speed premixed environment requires the presence of a mechanism to stabilize the flame. Bluff bodies or geometrical flame holders introduce a recirculation zone that anchor the flame. The current study considers the influence of equivalence ratio and the boundary layer state at the trailing edge of the flame holder on the flowfield and combustion characteristics. It was found that the recirculation zone is shortened as the equivalence ratio increases towards unity. A secondary shear region emerges downstream of the recirculation zone and is caused by the accelerated low-density combustion products. The emergence of the secondary shear region moves upstream with increasing equivalence ratio. Tripping the boundary layer causes a dramatic reduction in the length of the recirculation zone, and the secondary shear region is greatly augmented. Visualizations show that tripping the boundary layer resulted in a greatly disturbed flame near the trailing edge and large flame scales. Flowfield measurements suggest that the heat release is increased by approximately 50% when the boundary layer tripped.

Role of respiratory heat exchange in production of exercise-induced asthma

1979 ◽  
Vol 46 (3) ◽  
pp. 467-475 ◽  
Author(s):  
E. C. Deal ◽  
E. R. McFadden ◽  
R. H. Ingram ◽  
R. H. Strauss ◽  
J. J. Jaeger
Keyword(s):  
Heat Exchange ◽  
Thermal Load ◽  
Tracheobronchial Tree ◽  
Total Heat Flux ◽  
Random Fashion ◽  
Theoretical Predictions ◽  
Per Se ◽  
Exercise Induced ◽  
Respiratory Heat Exchange

We have hypothesized that it is the total heat flux in the tracheobronchial tree during exercise that determines the degree of postexertional obstruction in asthma, and have developed quanititative expressions that relate these two events. We tested this hypothesis by comparing the observed responses to exercise, while our subjects inhaled dry air at various temperatures ranging from subzero to 80 degrees C in a random fashion, to those that we predicted would occur based upon calculations of respiratory heat exchange. We further determined if heat could be transferred from the inspired air to the mucosa so as to offset evaporative losses from the airways. The observed responses fell as air temperature was increased from -11 to +37 degrees C and exactly matched theoretical predictions. Above 37 degrees C, the observed response exceeded predictions, indicating that it was not possible to provide sufficient heat per se in the air to offset the vaporization of water. However, when small amounts of water vapor were added to the inspirate at high temperatures, bronchospasm was virtually abolished and the response again closely matched theoretical expectations. We conclude that the magnitude of exercise-induced asthma is directly proportional to the thermal load placed on the airways and that this reaction is quantifiable in terms of respiratory heat exchange.

Modeling of Confined Flame Stabilization by Bluff Bodies

2001 ◽  
Author(s):  
S Frolov ◽  
V Ya. Basevich ◽  
A Belyaev ◽  
V Posvianskii ◽  
Yu Radvogin
Keyword(s):  
Flame Stabilization ◽  
Bluff Bodies

Combustion Optimization for the ALSTOM GT13E2 Gas Turbine

2006 ◽  
Author(s):  
Ch. Steinbach ◽  
N. Ulibarri ◽  
M. Garay ◽  
H. Lu¨bcke ◽  
Th. Meeuwissen ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Flame Temperature ◽  
Air Entrainment ◽  
Flame Stabilization ◽  
Flame Stability ◽  
Nox Emissions ◽  
Combustion Control ◽  
Control Logic ◽  
The Individual ◽  
Combustion Optimization

The NOx emissions of low NOx premix combustors are not only determined by the burner design, but also by the multi burner interaction and the related distribution of air and fuel flows to the individual burners. Often the factors that have a positive impact on NOx emission have a negative impact on the flame stability, so the main challenge is to find an optimum point with the lowest achievable NOx while maintaining good flame stability. The hottest flame zones are where most of the NOx is formed. Avoiding such zones in the combustor (by homogenization of the flame temperature) reduces NOx emissions significantly. Improving the flame stability and the combustion control allows the combustor to operate at a lower average flame temperature and NOx emissions. ALSTOM developed a combustion optimization package for the GT13E2. The optimization package development focused on three major issues: • Flame stability; • Homogenization of flame temperature distribution in the combustor; • Combustion control logic. The solution introduced consists of: • The reduction of cooling air entrainment in the primary flame zone for improved flame stability; • The optical measurement of the individual burner flame temperatures and their homogenization by burner tuning valves; • Closed loop control logic to control the combustion dependent on the pulsation signal. This paper shows how fundamental combustion research methods were applied to derive effective optimization measures. The flame temperature measurement technique will be presented along with results of the measurement and their application in homogenization of the combustor temperature distribution in an engine equipped with measures to improve flame stabilization. The main results achieved are: • Widening of the main burner group operation range; • Improved use of the low NOx operation range; • NOx reduction at the combustor pulsation limit and hence, large margins to the European emission limit (50 mg/m3 @ 15%O2).

Simulation of Two-Dimensional Turbulent Recirculating Flow Field Behind a V-Shaped Bluff Body

1994 ◽  
Author(s):  
Z. Gu ◽  
M. A. R. Sharif
Keyword(s):  
Flow Field ◽  
Bluff Body ◽  
Flame Stabilization ◽  
Bluff Bodies ◽  
Two Dimensional ◽  
Combustion Chambers ◽  
Recirculating Flow ◽  
Conservative Form ◽  
Curvilinear Grid ◽  
Predictor Corrector

Abstract The two-dimensional turbulent recirculating flow fields behind a V-shaped bluff body have been investigated numerically. Similar bluff bodies are used in combustion chambers for flame stabilization. The governing transport equations in conservative form are solved by a pressure based predictor-corrector method. The standard k-ϵ turbulence closure model and a boundary fitted multi-block curvilinear grid system are used in the computation. The code is validated against turbulent flow over a backward facing step problem. The predicted flow field behind the bluff body is also compared with experiment. It is found that while the qualitative features of the flow are well predicted, there is quantitative disagreement between the measurement and prediction. This disagreement can be partially attributed to the k-ϵ turbulence model which is known to be inadequate for recirculating flows. Parametric investigation of the flow field by varying the shape and size of the bluff body is also performed and the results are reported.

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