An experimental and kinetic modeling study on the autoignition characteristics of ammonia-based ternary fuels under reflected shock wave conditions

Ammonia has received considerable attention as a renewable and carbon-free fuel in the context of global carbon neutrality. The high-temperature autoignition characteristics of NH3-H2-DME binary and ternary blended fuels were investigated using a shock tube experiment under conditions of T = 1300-2000 K, p = 0.14, 1.0 MPa, and phi = 0.5, 1.0, 2.0. The experiment focused on the effect of the proportion of H2 + DME as the binary active fuel on the ignition delay time reduction rate of pure NH3 blended fuel under various operating conditions. The experimental results showed that the composition of binary active fuels affects the ignition-promoting effect of the active fuel. H2 + DME (1:1) could result in a greater reduction in activation energy for the blended fuels, and the effectiveness of different of active fuels varies considerably depending on the operating conditions. Furthermore, a model for NH3-H2-DME fuels was developed, and the mechanism of action of H2 + DME (1:1) and H2 as active fuels on the ignition characteristics of the blended fuel was thoroughly investigated. Chemical kinetic analysis showed that one of the most important factors for promoting ignition by H2 + DME (1:1) and H2 is the alteration of the pathways for generating reactive H radicals in the initial stage of the reaction, which accelerates the chain reactions to facilitate ignition.