Numerical investigation on the performance of bluff body augmented micro cavity-combustor

Bluff body augmented micro-cavity combustors are proposed in this study to enhance the combustion efficiency under high inlet velocities. The original and two types of bluff body supplemented micro cavity combustors, namely CAVITY, TRIANGLE, and FIN combustors are numerically investigated. The results show that the combustion efficiency (eta(c)) of bluff body augmented combustors are higher than that of the CAVITY combustor, and the largest increment of 10.8% is obtained in the FIN combustor. The underlying mechanisms for the improvement in eta(c) of the FIN and TRIANGLE combustors have been analyzed. It is demonstrated that the altered flow field structures and transvers reactant transport induced by the bluff body play dominant roles. Moreover, the local Damkohler number (Da(L)) is introduced, which is defined as the ratio of the local hydrogen reaction rate and the convective mass transport rate. The variation of eta(c), along the streamwise direction in the proposed combustors is determined by the value of Da(L). (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.