Experimental investigation on premixed hydrogen/air combustion in varied size combustors inserted with porous medium for thermophotovoltaic system applications

Abstract

Micro combustion stabilization is challenged by the large heat loss ratio, and the operating conditions are narrow because of the small combustor size. In this work, experimental tests combined with numerical simulations are carried out to investigate the premixed H2-air combustion with and without porous medium. The results indicate that the flame stabilization is greatly enhanced in the combustor with porous medium, and the wall temperature with porous medium is 188 K higher than that of the free flame in the tube with a length 22 mm, an outer diameter 7 mm and the wall thickness 0.5 mm. The appropriate porosity of porous medium is selected for each combustor to achieve a better thermal performance and high radiation temperature. With the increase of combustor diameter, the limitations in terms of inlet velocity and flame blowout are expanded and the radiation surface area is also increased for a higher energy output. The radiation temperature and surface area play important roles in the application of micro thermo-photovoltaic system. The combustor with a length 27 mm and an outer diameter 7 mm is able to achieve an optimal balance between the contingent negative variation of radiation surface area and radiation temperature, delivering an electrical power of 1.41 W with an efficiency 1.39% for the micro-TPV system with InGaAsSb PV cells when the H2 flow rate is 3.03 g/h and equivalence ratio Φ = 0.85.