Multiple combustion regimes and performance of a counter-flow microcombustor with power extraction

¹ Department y de Fluidos, Universidad Carlos III de Madrid, Leganés 28911, Spain.
² ITAM SB RAS, Novosibirsk, 630090, Russia and Far Eastern Federal University, Vladivostok 690090, Russia.
³ Far Eastern Federal University, Vladivostok 690090, Russia.

^* Corresponding author: eafernan@ing.uc3m.es

Received: 6 April 2018
Accepted: 20 September 2018

Abstract

Power generation usually requires removal of thermal energy from the system. In this paper, we evaluate the impact of the heat removal on the dynamics of a premixed flame in the case of a simple, but representative, counter-current microburner. In this configuration, two opposed streams of fresh gases with the same equivalence ratio ϕ are introduced, at the same velocity U_F, in the burner through narrow, infinitely long channels. The channels are separated by the common wall from which the heat used for power generation is removed. A flame-sheet chemistry model and a realistic, specifically developed, one-step Arrhenius kinetics are used and compared in order to explore the importance of finite-rate chemistry effects. Finite-rate is found to play a significant role especially near the extinction limit (low velocities) and at high temperatures (high velocities) where distributed reaction can lead to autoignition. The changes in the flame stabilization position and operation limits of the burner are analyzed. Significant variations in combustor operation were found when energy is extracted from the system. Power generation efficiency is also studied, to conclude that an optimum level of energy extraction exists for each equivalence ratio and also that an optimum equivalence ratio exists.