Abstract: To investigate the effects of fuel compositions variation on the combustion characteristics of scramjet engines，a series of combustion tests were conducted in a direct-connected test rig fueled with vaporized RP-3 and ethylene under the inflow conditions of Ma=2.92，3.46，stagnation temperature Tt=1430K. The supersonic combustion characteristics of vaporized RP-3 and ethylene were compared and analyzed based on the ignition delay time，static pressure distribution along the combustor wall，thrust increments and fuel specific impulses. The results show that ethylene has a higher combustion performance and fuel utilization efficiency than that of vaporized RP-3 due to its higher activity. For the cases of Ma=2.92，equivalence ratio φ≈0.60 and 1.06，the specific impulses of ethylene are approximately 15% and 7.2% higher than that of vaporized RP-3 respectively. When Ma increases to 3.46，the gaps of specific impulses between ethylene and vaporized RP-3 are slightly enlarged to approximately 18% and 9.6% under approximately equal φ. The test conditions such as the inflow Mach number at the combustor inlet and equivalence ratio have great impacts on the combustion characteristics of scramjet engines. The effects of fuel compositions on combustion characteristics are weakened with the increase of equivalence ratio，and are not sensitive to the inflow Mach number at the combustor inlet.

Key words: Scramjet engine；Combustion characteristic；Vaporized RP-3；Ethylene；Equivalence ratio；Mach number at the combustor inlet

摘要： 为了研究燃料成分变化对超燃冲压发动机燃烧特性的影响，以气化RP-3(中国3#航空煤油)和乙烯为燃料进行了一系列直连式燃烧试验。模型燃烧室入口参数为Ma=2.92，3.46，总温Tt=1430K。基于点火延迟时间、燃烧室壁面静压分布、推力增益和比冲，对比分析了两种燃料的超声速燃烧特性。结果表明，化学活性更高的乙烯比气化煤油具有更高的燃烧性能和燃料利用效率；Ma=2.92，当量比φ≈0.60和1.06时，乙烯的比冲比气化煤油分别约高15%和7.2%；当Ma增加到3.46时，相当的当量比下乙烯和气化煤油之间的比冲差距稍有扩大，约为18%和9.6%。燃烧室入口马赫数和当量比等工况参数对发动机燃烧特性有显著影响。燃料成分对发动机燃烧特性的影响随当量比的提高而弱化，但对燃烧室入口马赫数不敏感。

关键词: 超燃冲压发动机；燃烧特性；气化RP-3；乙烯；当量比；燃烧室入口马赫数