二元低音爆超声速进气道的流动特性研究

Flow Characteristics of a Rectangular Low-Boom Supersonic Inlet

关键词:  低音爆  超声速进气道  发散等熵压缩  零度角唇罩  弯曲激波  局部亚声速区

Key words:  Low-boom  Supersonic inlet  Relaxed isentropic compression  Zero-angle cowl  Curve shock  Partial subsonic region

摘要:

为了揭示低音爆进气道的特殊流动机理，设计了一种新型二元低音爆超声速进气道，其具有零度角唇罩和发散等熵压缩前体这两个典型特征，并通过仿真手段获得了其在典型状态下的流场结构和工作特性。结果表明:由于唇罩内侧倾角过大，在低来流马赫数下([Ma∞]=1.8，2.0)，低音爆进气道在口部产生了唇罩弯曲激波及相应的局部亚声速区，这一流动结构的存在使其在临界状态下的总压恢复系数与外压式进气道相比分别降低了2.3%和5.5%；而在高来流马赫数下([Ma∞]=2.5)，唇罩激波在肩部下游诱导出一个大的分离包，该分离包使得低音爆进气道的性能随下游堵塞度的变化变得敏感。由于本文设计的低音爆进气道外唇罩角为0°，其音爆水平与外压式进气道相比显著降低，其中其音爆在设计马赫数的通流状态下减小了98.6%。此外，进气道的音爆还与其工作状态相关，进气道的溢流程度越大、超声速来流的马赫数越低，音爆水平则越高。

Abstract:

To reveal the particular flow mechanism of low-boom inlet，a rectangular low-boom supersonic inlet is designed，which features a zero-angle cowl and relaxed isentropic compression forebody. A numerical simulation was performed to obtain the flow structure and operating characteristics of the rectangular low-boom inlet working at different operating conditions. The results show that due to the large deflection angle of cowl internal surface，a curve shock and a corresponding subsonic region are formed near the entrance of the low-boom inlet，and the existence of these flow structure reduce the total pressure recovery by 2.3% and 5.5% compared with the external compression inlet in lower incoming Mach number of 1.8 and 2.0 under critical state. While the incoming Mach number becomes higher([Ma∞]=2.5)，a large separation bubble induced by the cowl oblique shock appears in the downstream of the shoulder. The inlet performance is sensitive to the blockage with the influence of this separation bubble. In addition，the boom of the low-boom inlet is decreased significantly because of zero-angle cowl. And the boom of low-boom inlet is reduced by 98.6% compared with the regular supersonic inlet when the inlet operates under fully opened state for the case of Mach 2.0. Moreover，the sonic boom of the supersonic inlet is associated with its operating state with the larger degree of shock spillage and the lower coming flow，Mach number will increase the sonic boom.