Major challenges for micro combustors are high heat losses and inappropriate residence time. In this study, it was aimed to eliminate these challenges via placing bluff bodies into the combustion zone and combusting fuel with oxygen enriched air. To this end, micro combustor models with different geometries were constructed and in these models, premixed H-2/air combustion was simulated by using ANSYS/Fluent CFD code to investigate effects of bluff body shape, location and thickness, and low level O-2 enhancement on performance determining parameters such as rate of conversion of fuel to useable heat, temperature uniformity, pollutant emissions etc. To further analyze effects of micro combustor geometry, a perforated plate was also placed into the combustion zone. Thermal performance of the micro combustor with perforated plate insertion in O-2 enriched conditions was found to be highest in terms of increased reaction kinetics and heat transfer characteristics. The trade-offs of respective design are increased NOx emissions and slightly decreased temperature uniformity. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.