LES of premixed and non-premixed combustion in a stagnation point reverse flow combustor

2009 ◽  
Vol 32 (1) ◽  
pp. 1537-1544 ◽  
Author(s):  
Satish Undapalli ◽  
Srikant Srinivasan ◽  
Suresh Menon
Keyword(s):  
Stagnation Point ◽  
Reverse Flow ◽  
Premixed Combustion

Effects of Second-Order Slip and Magnetic Field on Mixed Convection Stagnation-Point Flow of a Maxwellian Fluid: Multiple Solutions

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
M. M. Rahman
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Mixed Convection ◽  
Stagnation Point ◽  
Reverse Flow ◽  
Second Order ◽  
Dual Solutions ◽  
Stagnation Point Flow ◽  
Shrinking Sheet ◽  
Variable Surface

In this paper, we investigate the effects of second-order slip and magnetic field on the nonlinear mixed convection stagnation-point flow toward a vertical permeable stretching/shrinking sheet in an upper convected Maxwell (UCM) fluid with variable surface temperature. Numerical results are obtained using the bvp4c function from matlab for the reduced skin-friction coefficient, the rate of heat transfer, the velocity, and the temperature profiles. The results indicate that multiple (dual) solutions exist for a buoyancy opposing flow for certain values of the parameter space irrespective to the types of surfaces whether it is stretched or shrinked. It is found that an applied magnetic field compensates the suction velocity for the existence of the dual solutions. Depending on the parametric conditions; elastic parameter, magnetic field parameter, first- and second-order slip parameters significantly controls the flow and heat transfer characteristics. The illustrated streamlines show that for upper branch solutions, the effects of stretching and suction are direct and obvious as the flow near the surface is seen to suck through the permeable sheet and drag away from the origin of the sheet. However, aligned but reverse flow occurs for the case of lower branch solutions when the mixed convection effect is less significant.

Product Recirculation and Mixing Studies in a Stagnation Point Reverse Flow Combustor

2007 ◽  
Author(s):  
Mohan Bobba ◽  
Priya Gopalakrishnan ◽  
Karthik Periagaram ◽  
Jerry Seitzman
Keyword(s):  
Stagnation Point ◽  
Reverse Flow

Flame Structure and Stabilization Mechanisms in a Stagnation-Point Reverse-Flow Combustor

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Mohan K. Bobba ◽  
Priya Gopalakrishnan ◽  
Karthik Periagaram ◽  
Jerry M. Seitzman
Keyword(s):  
Stagnation Point ◽  
Reverse Flow ◽  
Turbulent Flame ◽  
Flame Structure ◽  
Reaction Rates ◽  
Diagnostic Techniques ◽  
Flame Stabilization ◽  
Oh Radicals ◽  
Spontaneous Raman Scattering ◽  
High Turbulence

A novel combustor design, referred to as a stagnation-point reverse-flow (SPRF) combustor, was recently developed to overcome the stability issues encountered with most lean premixed combustion systems. The SPRF combustor is able to operate stably at very lean fuel-air mixtures with low NOx emissions. The reverse flow configuration causes the flow to stagnate and hot products to reverse and leave the combustor. The highly turbulent stagnation zone and internal recirculation of hot product gases facilitates robust flame stabilization in the SPRF combustor at very lean conditions over a range of loadings. Various optical diagnostic techniques are employed to investigate the flame characteristics of a SPRF combustor operating with premixed natural gas and air at atmospheric pressure. These include simultaneous planar laser-induced fluorescence imaging of OH radicals and chemiluminescence imaging, and spontaneous Raman scattering. The results indicate that the combustor has two stabilization regions, with the primary region downstream of the injector where there are low average velocities and high turbulence levels where most of the heat release occurs. High turbulence levels in the shear layer lead to increased product recirculation levels, elevating the reaction rates and thereby enhancing the combustor stability. The effect of product entrainment on the chemical time scales and the flame structure is quantified using simple reactor models. Turbulent flame structure analysis indicates that the flame is primarily in the thin reaction zone regime throughout the combustor. The flame tends to become more flameletlike, however, for increasing distance from the injector.

Flame Structure and Stabilization Mechanisms in a Stagnation Point Reverse Flow Combustor

2007 ◽  
Author(s):  
Mohan K. Bobba ◽  
Priya Gopalakrishnan ◽  
Karthik Periagaram ◽  
Jerry M. Seitzman
Keyword(s):  
Stagnation Point ◽  
Reverse Flow ◽  
Turbulent Flame ◽  
Flame Structure ◽  
Reaction Rates ◽  
Diagnostic Techniques ◽  
Flame Stabilization ◽  
Oh Radicals ◽  
Spontaneous Raman Scattering ◽  
High Turbulence

A novel combustor design, referred to as a Stagnation Point Reverse Flow (SPRF) combustor, was recently developed to overcome the stability issues encountered with most lean premixed combustion systems. The SPRF combustor is able to operate stably at very lean fuel-air mixtures with low NOx emissions. The reverse flow configuration causes the flow to stagnate and hot products to reverse and leave the combustor. The highly turbulent stagnation zone and internal recirculation of hot product gases facilitates robust flame stabilization in the SPRF combustor at very lean conditions over a range of loadings. Various optical diagnostic techniques are employed to investigate the flame characteristics of a SPRF combustor operating with premixed natural gas and air at atmospheric pressure. These include simultaneous Planar Laser-Induced Fluorescence (PLIF) imaging of OH radicals, chemiluminescence imaging, Spontaneous Raman Scattering. The results indicate that the combustor has two stabilization regions, with the primary region downstream of the injector where there are low average velocities and high turbulence levels where most of the heat release occurs. High turbulence level in the shear layers lead to increased product recirculation levels, elevating the reaction rates and thereby, the combustor stability. The effect of product entrainment on the chemical timescales and the flame structure is quantified using simple reactor models. Turbulent flame structure analysis indicates that the flame is primarily in the thin reaction zones regime throughout the combustor. The flame tends to become more flamelet like, however, for increasing distance from the injector.

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