Superadiabatic combustion in conducting tubes and heat exchangers of finite length

A review of the combustion and emissions properties of advanced transportation biofuels and their impact on existing and future engines

“…The use of heat-recirculation within a porous reactor allows combustion at extremely low equivalence ratios or with very-low-energy-content fuels, resulting in low NO x exhaust emissions [362,364,365,373]. Similar gains can be achieved with counter-flowing streams of reactive mixtures separated by heatconducting walls [362,366,374], such as the swiss-roll burner [362,363,368,372,374] or the counter-flow heat-exchanging burner [362,374,375]. Recent work has shown that the flames in such burners stabilize through ignition at the locally-high wall temperatures within the excess-enthalpy zone and that flame stretching can significantly increase the flame stabilization over a wider range of firing rates, allowing further fuel-flexibility or variability in the power output, as well as showing that 2-D effects can hinder the flame stabilization for very small channels [370].…”

Analysis of an idealized heat-recirculating microcombustor

“…Two-dimensional calculations were reported before but only for straight channels [9,10], while studies involving aspects of the heat exchange between the cold mixture and hot combustion gases were based on one-dimensional [11,12,18,19] or phenomenological [13][14][15][16][17] models, which in light of the present results are inadequate to properly describe the combustion process. Using time-dependent equations allows not only to determine the possible steady states, but also to discuss their stability and hence whether they are physically realizable.…”

Experimental Investigation of the Effects of Flame Phenomenology on the Wall Temperature Distribution of Mesoscale Nonadiabatic Ducts

“…Heat recirculation in the walls has been shown to promote stabilization of flames in small channels and improve resistance to extinction (Kaisare and Vlachos, 2007;Scarpa et al, 2009). The magnitude of heat losses to the walls affects the reaction zone thickness and the extinction limits (Leach et al, 2006), but upstream heat transfer can also promote stability and improve power density (Leach and Cadou, 2005) and can even allow unusual phenomena such as superadiabatic combustion (Ju and Choi, 2003;Ju and Xu, 2005;Schoegl and Ellzey, 2007).…”

“…Techniques such as heat recirculation, as in Swiss-roll burners Sitzki et al, 2001) and catalytic combustion (Kyritsis et al, 2004;Spadaccini et al, 2003) have shown great promise. Experimental and computational analyses of reactive flow in small-scale ducts have made the importance of hardware-flame interaction apparent (Chao et al, 2007;Ju and Choi, 2003;Ju and Xu, 2005;Kaisare and Vlachos, 2007;Leach and Cadou, 2005;Leach et al, 2006;Pham et al, 2007;Scarpa et al, 2009;Schoegl and Ellzey, 2007). Heat recirculation in the walls has been shown to promote stabilization of flames in small channels and improve resistance to extinction (Kaisare and Vlachos, 2007;Scarpa et al, 2009).…”