二甲醚与氢气稀混合气在中低温条件下的着火延迟特性

To investigate the ignition delay characteristics of DME/H₂ mixtures at low-to-medium temperature, ignition delay times of lean DME/H₂ mixtures (hydrogen mole fraction in the fuel mixtures of 0%, 50%, 60%, 70%, and 85%) were measured using a rapid compression machine in the compressed temperature range of 628-858 K at compression pressures of 12-22 bars, the equivalence ratios of 0.30-1.00, and the hydrogen blend ratio of 0%-85%. A kinetics model is built to simulate the ignition process using finite element software Chemkin-Pro. The results show that the addition of H₂ to DME mixtures leads to a nonlinear increase in ignition delay time. The inhibition effect of H₂ addition is found to be more pronounced at lower compression pressure with H₂ mole fraction of more than 60%. It is also observed that lean DME/H₂ mixtures show three stage heat release behaviors at lower equivalence ratio of 0.30, i.e., the first stage of low temperature heat release (LTHR) and the second stage of high temperature heat release (HTHR), and the third stage of high temperature heat release. Meanwhile, the three-stage heat release behavior becomes weak as the H₂ mole fraction increases. Further chemical kinetic analysis indicates that DME is mainly consumed during LTHR and the first stage of HTHR whereas H₂ is mainly consumed during the second stage of HTHR.