Effects of dimethyl ether blending on H2-fueled combustion characteristics and thermal improvement in fuel-lean condition

Abstract

Micro-combustors play a pivotal role in micro powering system due to the potential for high energy density. However, addressing challenges such as incomplete combustion and high heat dissipation losses are essential for optimizing the working performance. So, the blended DME is proposed to micro-combustion, which acts as a promising oxygenated fuel with significant attention due to its higher reactivity, lower pollutant emissions, and carbon–neutral properties. However, the lack of dynamic models applicable to H2/DME fueled combustion in micro condition, so an optimized mechanism for blended H2/DME combustion is developed and validated. The results demonstrate that a reduced mechanism comprising 29 species and 106 reactions (M29-106*) can be commendably employed in micro H2/DME/air combustion simulation, according to the sensitivity analysis and reaction modification. Besides, investigation is conducted to explore micro-combustion characteristics of H2/DME/Air. The result shows that burning process and heat transfer are notably influenced by DME addition, leading to shifts in flame positions and adjustments in combustion reaction rates. So, DME addition enhances energy efficiency and modifies flame location through fluid field optimization and reduced heat loss. The thermal performance of the combustor is significantly improved with DME blending, resulting in higher radiative power and radiation efficiency. However, the choice of DME blending ratio must be carefully considered, as high blending ratios may compromise flame stability and lead to increased exhaust heat losses under fuel-lean conditions. Specifically, burning with 30 % DME addition achieves a radiative power of 20.24 W and a radiative efficiency of 40.57 % at the same chemical energy Ec = 49.9 W, which is 5.57 W and 11.17 % higher than that of pure H2-fueled combustion, respectively. These findings offer valuable insights for the design and optimization of micro-combustors, where compact and efficient power sources are required.