Effects of Central Split Bluff Body on Combustion Characteristics and NOx Emission with Non-Premixed H2/Air Flames

Abstract

ABSTRACT Considering the safety and flashback problems of hydrogen-fueled micro power generation using premixed combustion for thermophotovoltaic applications, we focused on non-premixed hydrogen/air combustion characteristics. However, the fuel/air mixing is significant in the combustion chamber, so we proposed five bluff bodies and investigated the effects of inlet velocity of the fuel on non-premixed hydrogen/air combustion characteristics and flow patterns. A 21-species and 105-reactions hydrogen/air with NOx extended chemical mechanism is experimentally validated. The results show a significant influence of the inlet velocity and bluff body shape on temperature distribution, flame location, and residence time. All five combustors achieved a 99% energy conversion at the exit of the combustion chamber. Combustors B and D characterized by isosceles triangle-like and right triangle-like shapes excel because of improved hydrogen/air mixing behind the bluff body. Combustor D achieves the highest mean outer wall temperature of 992.03 K and lowest pressure loss of 155.56 Pa when the inlet velocity of fuel is 4 m/s. Moreover, the advanced mixing facilitated by the bluff bodies in Combustors B and D resulted in reduced NO emissions, with reductions of 16.8% and 20.3%, respectively, compared to Combustor C. These findings provide insights into combustion dynamics, leveraging bluff body-induced flow structures to enhance the micro combustor thermodynamics.