超声速状态下正癸烷和RP3的稳焰特性研究

Flame Stabilization Characteristics of n-Decane and RP3

关键词:  超声速燃烧  碳氢燃料  稳焰  理论模型分析

Key words:  Supersonic combustion  Hydrocarbon fuels  Flame stabilization  Theoretical model analysis

摘要:

通过直连蓄热式试验台，研究了正癸烷和RP3航空煤油两种碳氢燃料在超燃燃烧室中的稳焰特性。燃烧室采用双凹腔构型作为稳焰结构，进口总温1000~1150K，进口马赫数2.03，分别采用纯液态喷嘴和气泡雾化喷嘴进行燃料喷射。研究结果表明:在所有试验的总温范围内，正癸烷的稳焰性能比RP3略强，另外，两种燃料在纯液态喷射条件下不易实现稳焰，使用气泡雾化喷嘴能有效提高燃料的稳焰性能。文章建立了一个简单的理论模型，以“驻留时间≥反应延迟时间”作为实现稳焰的判据，计算出各试验工况下的驻留时间与反应延迟时间，发现二者均在1ms量级，计算结果与试验结果吻合较好。最后，根据两种燃料的热物性参数，计算了相同工况下二者的液滴平均直径SMD和蒸发常数，发现SMD在10μm量级，正癸烷的雾化和蒸发特性均略优于RP3，因此从燃料热物性角度说明了正癸烷的超燃稳焰性能略优于RP3的原因。

Abstract:

The supersonic flame stabilization characteristics of n-decane and aviation kerosene (RP3) in a model scramjet combustor were experimentally investigated through the direct-connect supersonic combustion facility with regenerative storage air heater. Two serial cavities were chosen as the flameholders. Total temperature of a Mach 2.03 supersonic inflow ranged from 1000K to 1150K. Pure-liquid injector and aerated-liquid injector were adopted in experiments. The experimental results show that compared to RP3，n-decane provides slightly better characteristics of flame-holding under the conditions of experiments. Furthermore，it is difficult for pure-liquid fuel to achieve flameholding，the aerated-liquid injector can efficiently improve the flame stabilization characteristics. Applying the flameholding criterion residence time≥reaction delay time，a simple theoretical model was established by calculating the residence time and the reaction delay time of each condition. The results show that the order of two characteristic times is 1ms.And the analysis results are agreeable to the experimental ones. SMD and evaporation constant of n-decane and RP3 under the same conditions were calculated based on thermal physical parameters of the two kinds of fuels. The calculation results show that the order of SMD is 10μm，and n-decane provides slightly better atomization and evaporation characteristics which explain the reason why n-decane provides slightly better supersonic flame stabilization characteristics from the point of thermal physical parameters of fuels.