Numerical study on pure rocket mode performance characteristics of a RBCC engine
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摘要:
为掌握火箭基组合循环(RBCC)发动机的纯火箭模态性能特性及影响因素,设计构建了中心火箭布局的全轴对称特征RBCC发动机基准流道,以及相同设计膨胀比的半轴对称斜切喷管构型RBCC发动机、连续扩张喷管构型火箭发动机流道,开展了不同推力室室压条件下纯火箭模态三维膨胀流场仿真,获得了不同喷管构型、二次流、火箭推进剂方案下纯火箭模态内流工作特性、推力比冲性能特性。结果表明:纯火箭模态时非理想连续膨胀流动状态导致比冲性能损失,比冲效率在80%以下;大突扩膨胀后产生的强激波总压损失是性能下降的主要机制,全轴对称喷管构型相对于连续扩张喷管时比冲效率下降约8%,半轴对称斜切喷管可以减小膨胀总压损失,提高比冲效率;引入二次流可以调整膨胀-压缩波系结构以减小总压损失,提高二次流总温有利于提升整体性能。
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关键词:
- 火箭基组合循环(RBCC)发动机 /
- 纯火箭模态 /
- 斜切喷管 /
- 比冲效率 /
- 三维流场仿真
Abstract:To gain a comprehensive understanding of the performance characteristics and influencing factors of the pure rocket mode in rocket-based combined cycle (RBCC) engines, a full-axisymmetric characteristic RBCC engine benchmark flow path with a central rocket layout was designed and constructed. Additionally, a half-axisymmetric scarfed nozzle configuration RBCC engine and a continuously expanding nozzle configuration rocket engine flow path with the same designed expansion ratio were developed. Three-dimensional expansion flow field simulations were conducted under different thrust chamber pressures in the pure rocket mode, yielding the internal flow characteristics and thrust specific impulse performance characteristics under various nozzle configurations, secondary flows, and rocket propellant schemes. The results indicated that in the pure rocket mode, the non-ideal continuous expansion flow state led to a loss of specific impulse performance, with the specific impulse efficiency being below 80%. The strong shock wave after the large sudden expansion led to a total pressure loss, which was the main mechanism for performance degradation. The overall axisymmetric nozzle configuration had a specific impulse efficiency decrease of about 8% compared with the continuous expansion nozzle. The semi-axisymmetric scarfed nozzle can reduce the total pressure loss of the expansion and improve the specific impulse efficiency. Introducing a secondary flow can adjust the expansion-compression wave system structure to a certain extent to reduce the total pressure loss. Increasing the total temperature of the secondary flow can be beneficial to enhancing overall performance.
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表 1 不同喷管构型的发动机流道关键尺寸对比
Table 1. Comparison of key dimensions of engine flow channels with different nozzle configurations
流道构型 火箭入口
半径/mm火箭喉部
半径/mm内喷管出口
半径/mm发动机出口
半径/mm收缩比
Ain/At内部膨胀比
Aout/At总膨胀比
Ae/At全轴对称喷管火箭 14 5.207 11.684 63.5 7.229 5.035 148.72 斜切喷管火箭 14 5.207 14.004 63.5 7.229 7.233 148.72 连续扩张喷管火箭 14 5.207 63.5 7.229 148.72 表 2 火箭推力室的模拟工况条件
Table 2. Simulated conditions of rocket thruster
燃料 氧化剂 氧燃比 推力室室压
pc/MPa燃气总温
Tt/K煤油 液氧 2.6 3 3640 6 3640 9 3698 液氢 液氧 7.0 3 3456 6 3546 9 3615 表 3 仿真网格无关性验证
Table 3. Mesh independence study of simulation
网格方案 网格
数量/104燃烧室出口
总压/Pa燃烧室出口
静压/Pa粗网格 120 956472 5588 中等网格 250 961994 5543 细网格 450 962617 5536 表 4 基于APL-10C发动机的典型试验状态工况
Table 4. Typical test conditions for the APL-10C engine
试验工况 氧燃比 火箭室压/MPa 环境压力/MPa 燃气总温/K 工作模态 E02 11.58 3.597 0.1006 3242 纯火箭模态 E04 11.67 3.507 0.1006 3244 E05 11.05 3.362 0.0413 3207 106 11.34 3.514 0.1013 3227 单独推力室 108 10.96 3.369 0.1013 3202 表 5 仿真计算与试验数据的比冲对比
Table 5. Comparison of impulse between the simulation results and experiments data
工况 试验比冲/s CFD比冲/s 相对偏差/% E02 220.9 239.8 8.58 E04 220.0 238.5 8.41 E05 251.5 253.7 0.88 106 264.3 261.7 −0.99 108 265.3 261.3 −1.5 表 6 空气二次流入口参数
Table 6. Parameters of the secondary flow inlet (air)
火箭室压/
MPa流量比/% 二次流
温度/K入口动量/
(kg·m/s)推力
贡献/N3 2 300 0.243 2.349 3 4 300 0.702 2.741 3 8 300 2.024 1.760 6 2 300 0.601 3.637 6 4 300 1.403 5.860 6 8 300 4.039 3.883 9 2 300 0.708 7.862 9 4 300 2.071 9.009 9 8 300 5.979 6.084 表 7 燃气二次流入口参数
Table 7. Parameters of the secondary flow inlet (gas)
火箭室压/
MPa流量比/
%二次流
总温/K入口动量/
(kg·m/s)推力
贡献/N6 2 900 1.432 3.539 6 3 900 2.777 2.855 6 4 900 4.354 2.070 6 2 2 000 2.749 2.930 6 3 2 000 5.446 1.530 6 4 2 000 7.842 0.073 表 8 斜切喷管构型二次流入口参数
Table 8. Parameters of the secondary flow inlet (scarfed nozzle)
火箭室压/
MPa流量比/
%二次流
温度/K入口动量/
(kg·m/s)推力
贡献/N6 2 900 2.739 0.301 6 4 900 6.667 0.603 6 8 900 28.487 6.919 表 9 采用液氢/液氧推进剂时二次流入口参数
Table 9. Parameters of the secondary flow inlet(LH2/LO2 propellant)
火箭室压/
MPa流量比/% 二次流
温度/K入口动量/
(kg·m/s)推力
贡献/N6 2 300 0.291 5.935 6 4 300 0.889 7.011 6 8 300 2.534 7.440 表 10 液氢/液氧与煤油/液氧推力性能推进剂方案的比冲性能特性对比
Table 10. Comparison of specific impulse characteristics between LH2/LO2 and kerosene/LO2 propellants
二次流
流量比/%煤油/液氧 液氢/液氧 比冲/s 比冲效率/% 比冲/s 比冲效率/% 0 286.38 76.32 359.56 76.52 2 285.02 75.99 358.29 76.25 4 283.34 75.52 355.27 75.61 8 277.36 73.92 348.79 74.23 -
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