Numerical investigations on effects of bluff body in flat plate micro thermo photovoltaic combustor with sudden expansion

Abstract

In order to reveal combustion characteristics of H₂/air mixture in a micro-combustor with and without bluff body, the effects of inlet velocities, equivalence ratios and bluff body’s blockage ratios on the temperature field, pressure of the combustor wall, combustion efficiency and blow-off limit were investigated. The numerical results indicate that the sudden expansion plate micro combustor with bluff body could enhance the turbulent disturbance of the mixed gas in the combustion chamber and the combustion condition is improved. Moreover, a low-speed and high temperature recirculation region was formed between the sudden expansion step and the bluff body so that the high and uniform wall temperature (>1000 K) could be gotten. As a result, it could strengthen the mixing process, prolong the residence time of gas, control the flame position effectively and widen the operation range by the synergistic effect of the bluff body and steps. When the blockage ratio ranged from 0.3 to 0.6, it could be found that the bluff body could play a stabilizing effect and expand combustion blow burning limit, and combustion efficiency firstly was increased with the inlet velocity and equivalence ratio, and then was decreased.

Keywords

micro combustor / bluff body / sudden expansion / numerical investigations

References

[1] KaisareN S, VlachosD G. A review on microcombustion: Fundamentals, devices and applications [J]. Progress in Energy and Combustion Science, 2012, 38(3): 321-359

[2] KhandelwalB, KumarS. Experimental investigations on flame stabilization behavior in a diverging micro channel with premixed methane–air mixtures [J]. Applied Thermal Engineering, 2010, 30(17): 2718-2723

[3] JuY, MarutaK. Microscale combustion: Technology development and fundamental research [J]. Progress in Energy and Combustion Science, 2011, 37(6): 669-715

[4] ChouS K, Yang, WM, ChuaK J, LiJ, Zhang, KL. Development of micro power generators–A review [J]. Applied Energy, 2011, 88(1): 1-16

[5] LiJ, HuangJ, YanM, ZhaoD, ZhaoJ, WeiZ, WangN. Experimental study of n-heptane/air combustion in meso-scale burners with porous media [J]. Experimental Thermal and Fluid Science, 2014, 52: 47-58

[6] Yang, WM, ChouS K, ShuC, Li, ZW, XueH. Development of microthermophotovoltaic system [J]. Applied Physics Letters, 2002, 81(27): 5255-5257

[7] LiJ, HuangJ, ZhaoD, ZhaoJ, YanM, WangN. Diffusion combustion of liquid heptane in a small tube with and without heat recirculating [J]. Combustion Science and Technology, 2012, 184(10/11): 1591-1607

[8] JiC, ZhaoD, LiX, LiS, LiJ. Nonorthogonality analysis of a thermoacoustic system with a premixed V-shaped flame [J]. Energy Conversion and Management, 2014, 85: 102-111

[9] VeeraragavanA, CadouC. Theoretical study of conjugate heat transfer effects on temperature profiles in parallel flow with embedded heat sources [J]. International Journal of Heat and Mass Transfer, 2010, 53(9): 1699-1711

[10] HosseiniS E, BagheriG, WahidM A. Numerical investigation of biogas flameless combustion [J]. Energy Conversion and Management, 2014, 81: 41-50

[11] EJ-q, ZuoW, LiuH-j, PengQ-guo. Field synergy analysis of the micro-cylindrical combustor with a step [J]. Applied Thermal Engineering, 2016, 93: 83-89

[12] TangA, PanJ, YangW, XuY, HouZ. Numerical study of premixed hydrogen/air combustion in a micro planar combustor with parallel separating plates [J]. International Journal of Hydrogen Energy, 2015, 40(5): 2396-2403

[13] SmithA G, MenonS, LovettJ A. Large eddy simulation of a bluff-body–stabilized flame with close-coupled liquid fuel injection [J]. Journal of Engineering for Gas Turbines and Power, 2014, 136(3): 031505

[14] Sánchez-SanzM. Premixed flame extinction in narrow channels with and without heat recirculation [J]. Combustion and Flame, 2012, 159(10): 3158-3167

[15] FanA-w, WanJ-l, MarutaK. Interactions between heat transfer, flow field and flame stabilization in a micro-combustor with a bluff body [J]. International Journal of Heat and Mass Transfer, 2013, 66: 72-79

[16] ZarvandiJ, TabejamaatS, BaigmohammadiM. Numerical study of the effects of heat transfer methods on CH₄/(CH₄+ H₂)-Air pre-mixed flames in a micro-stepped tube [J]. Energy, 2012, 44(1): 396-409

[17] HosseiniS E, WahidM A. Investigation of bluff-body micro-flameless combustion [J]. Energy Conversion and Management, 2014, 88: 120-128

[18] BagheriG, HosseiniS E, WahidM A. Effects of bluff body shape on the flame stability in premixed micro-combustion of hydrogen–air mixture [J]. Applied Thermal Engineering, 2014, 67(1): 266-272

[19] RebolaA, CoelhoP J, CostaM. Assessment of the performance of several turbulence and combustion models in the numerical simulation of a flameless combustor [J]. Combustion Science and Technology, 2013, 185(4): 600-626