Parametric analysis on the combustion and thermal performance of a swirl micro-combustor for micro thermophotovoltaic system

A swirl micro-combustor which has strong capability to stabilize the flame has been developed and is promising to be used in micro thermophotovoltaic power generators in this work. Heat recirculation plays a requisite role in flame stability and thermal performance of micro combustors. Thus, the effects of three parameters (center inlet radius w₁, swirler width w₂, and step height w₃) that determine the size and location of the recirculation zones in a premixed hydrogen/air flame are investigated numerically. The results show that inner recirculation zone and corner recirculation zone generated by a swirler are critical for stabilizing the flame. The parameter w₁ has an insignificant influence on the thermal performance. Enlarging the inner recirculation zone by decreasing w₂ provokes enhanced heat transfer, and increases the temperature level and temperature non-uniformity of combustor walls. The size of corner recirculation zone is increased by increasing w₃, which raises the outer wall temperature uniformity. Based on the parametric analysis, the newly designed micro combustor possesses a high wall temperature level. Additionally, the energy output increment is between 9.1% and 14.2% at hydrogen mass flow rate of 0.0006 g/s when stoichiometric hydrogen/air ratio ranges from 0.6 to 1.4.