燃烧加热污染空气对超燃冲压发动机性能影响研究

Numerical Investigation of Effects of Vitiated Air on Scramjet Performance

关键词:  超燃冲压发动机  氢燃料  燃烧加热  污染效应  数值计算 

Key words:  Scramjet  Hydrogen fuel  Combustion heating  Vitiation effect  Numerical calculation

摘要:

针对燃烧加热地面试验设备存在的工质污染问题,采用数值模拟方法研究了燃烧加热污染空气对氢燃料超燃冲压发动机性能的影响。以飞行马赫数Ma=6.5,当量油气比ER=0.6为计算基准状态,分别对纯净空气和污染空气来流下氢燃料超燃冲压发动机的整机流场和性能进行了对比计算分析。燃烧化学反应模拟采用了改进的H₂/O₂七组分八方程模型,湍流模型为标准的 k-ε模型,并采用直连式燃烧室试验数据进行了数值方法的验证。研究结果表明:(1)相对于纯净空气来流,污染空气来流下的超燃冲压发动机推力和比冲均有所下降。(2)采用酒精燃烧加热器的前提下,来流参数匹配静温、静压、马赫数时,发动机性能与纯净空气来流下的结果最为接近,而匹配总温、总压、马赫数时相差最大。(3)来流参数匹配总焓、静压、马赫数的前提下,采用氢燃烧加热器时发动机性能与纯净空气来流下的结果最为接近,而采用甲烷燃烧加热器时相差最大。 

Abstract:

Aiming at the problem of test media vitiation by combustion heating associated with ground test facility, the effects of combustion vitiated air on hydrogen-fueled scramjet performance were investigated with numerical approach. At the simulating condition of flight Mach 6.5, fuel equivalence ratio 0.6, the flow-field and performance of the scramjet were numerically calculated within clean free airstream and vitiated airstream respectively. As for the vitiated airstream, several schemes of matched parameter relative to clean air and different combustion heating methods were considered. The modified H₂/O_2reaction mechanism with seven species/eight steps and the standard k-ε turbulence model were employed, which would be firstly validated by the direct-connected combustor test data. The summarized conclusions are:(1) both the thrust and specific impulse of scramjet in the vitiated airflow decrease, compared with those in clean airstream; (2) the overall least discrepancy of scramjet performance within alcohol heating vitiated airstream is found when the static temperature, static pressure and Mach number are matched, while the most discrepancy when the total temperature, total pressure and Mach number are matched; (3) the overall least discrepancy of scramjet performance within hydrogen heating vitiated airstream is found when the total enthalpy, static pressure and Mach number are matched, while the most discrepancy when the methane heater is used. 