聚甲氧基二甲醚高温高压下喷雾燃烧特性光学诊断研究

The ignition and combustion characteristics of two electric synthetic fuels, polymethoxydimethyl ether PODE3 and PODE3-5, were investigated in a high-temperature high-pressure combustion chamber by means of multiple optical diagnostics. In addition, ndodecane (NC12) and a blend fuel P50 (50% PODE3, 50% NC12, vol) were tested under the same operating conditions as references. During the test, the ignition delay (ID) and spray evolution were quantified using a high-speed Schlieren imaging technique. Meanwhile, the flame lift-off length (LOL) was determined by OH Chemiluminescence. In addition, the transient evolution of formaldehyde and OH were also obtained by means of planar laser induced fluorescence technique. Finally, the liquid length (LL) and the quantification of carbon soot generation were obtained thanks to the diffused back-illumination extinction imaging technique (DBI). The results show that PODE3-5 has significantly longer LL compared to other fuels because of its higher specific heat capacity and latent heat of evaporation requiring higher enthalpy of air coiling; the ID of all fuels are relatively similar under the measured ambient conditions due to similar cetane values; due to the higher oxygen content of PODE fuel, the stoichiometric ratio is close to the spray axis, resulting in the OH* distribution of the two PODE fuels being closer to the spray axis than NC12; formaldehyde is formed in large quantities in PODE fuel under low temperature conditions, and intense heat release occurs in the flame center near the LOL; PODE fuel does not contain C-C bonds and OH distribution in the spray center, so no carbon soot generation is detected under experimental conditions, P50 significantly reduces the amount of carbon soot in the steady-state flame compared to NC12.