Effects of CO addition and multi-factors optimization on hydrogen/air combustion characteristics and thermal performance based on grey relational analysis

Abstract

Power output and efficiency of the micro-thermophotovoltaic generator are limited by flame instability, tremendous heat loss ratio and short residence time. H2/air premixed combustion with varied CO blending ratios is conducted in a combustor with exit-step, and multi-factors of burner design and operation are discussed for improving the generator thermal performance and broadening its application. Results indicate that CO addition in H2/air premixed combustion contributes to the relocation and stretch of flame, and the comprehensive thermal performance of the burner is significantly augmented. Moreover, combustor structures also effectively alter flame anchoring and heat transmission, and a higher radiation power can be achieved with appropriate exit-step length and height. Particularly, stagger step can further boost radiation power and efficiency of the system. The CO proportion and step height play an important role in radiation power and efficiency based on grey relational analysis. Furthermore, the optimal comprehensive working performance is achieved by combustor St-12-0.4 and the radiation efficiency is 24.8% higher than that of the straight-channel combustor, which provides the highest system efficiency 2.62% and electrical power 2.33 W for the micro-thermophotovoltaic generator under the conditions of CO blended proportion 15% and equivalence ratio 1.0.