Coupled chemical effects of carbon dioxide and hydrogen additions on premixed lean dimethyl ether flames

Abstract

Kinetic analysis of coupled effects of CO2 and H2 additions on laminar lean premixed dimethyl ether flames is performed at atmospheric pressure. The coupled effects of H2/CO2 additions on major species, intermediate stable species and radicals are discussed and analyzed in detail. The dilution, thermal and chemical effects of H2 and CO2 are separated and identified. The results show that H2 addition can slightly mitigate the CO2 chemical effects on decreasing the temperatures, H radical concentration, acetylene mole fraction and formaldehyde concentration. After CO2 is added, the H2 chemical effects on increasing the temperatures are enhanced. DME oxidation is promoted by the H2 chemical effects, which is further strengthened by the CO2 addition. Moreover, CO2 addition can reduce the H2 chemical effects on increasing the H radical mole fraction, but strengthen the H2 chemical effects on increasing the production of HO2 and C2H2. CH2O formation can be promoted by the H2 chemical effects, which is enhanced by the CO2 addition. In actually, the H2/CO2 coupled chemical effects almost have no obvious influence on the temperatures and HO2 mole fraction. DME consumption is delayed by the H2/CO2 coupled chemical effects. Furthermore, the H2/CO2 coupled chemical effects can decrease the H radical mole fraction, CH4 concentration, C2H2 mole fraction, CH2O concentration and CH3CHO mole fraction, but increase the CO concentration.