多凹腔双模态冲压发动机燃料喷注方案试验研究

An Experimental Study on Fuel Injection Strategy of a Multi-Cavity Dual-Mode Scramjet

为了更深入地了解和掌握多凹腔双模态冲压发动机的燃料喷注方案对燃烧室流场结构和工作性能的影响,开展了模拟飞行马赫数4.5-5.0及总温1048-1231K范围内变化的多凹腔双模态冲压发动机地面直连试验。通过试验,得到了不同喷注当量比、喷注位置或喷注级数条件下稳定的壁面压力分布和出口总压数据,并采用一维冲量分析程序对试验数据进行了详细处理和分析。结果表明：提高喷注当量比能有效地提高发动机的推力,但燃烧效率和发动机比冲会降低;将燃料喷注位置提前能使发动机的燃烧效率和推力分别提高5.6%和4.4%;燃料的分配方案对燃烧室的流场结构有明显影响,热力喉道的位置随燃料更集中地在下凹腔喷注而更靠下游,且要形成该热力喉道则需加入更多热量;采用上下游的两级喷注能形成较宽范围的亚声速区,有利于燃料的燃烧释热,可使燃烧室效率和发动机推力分别提高10.4%和10.8%。

A series of direct connected tests of the multi-cavity dual-mode scramjet operated in a simulated flight number range of 4.5 - 5.0 and a total temperature range of 1048 - 1231K were carried out for a further understanding of how the fuel injection strategy affected the flow field structure and the performance of the engine. Steady wall static pressure and outlet total pressure were obtained during the experiments with different fuel injection equivalence ratio, injection position or injection stages. The experimental data was particularly processed and analyzed with the one-dimensional impulse analysis program. According to the results, the thrust of the engine effectively increased as the equivalence ratio is enhanced, but both the combustion efficiency and the specific impulse of the engine are synchronously decreased. The combustion efficiency and the thrust increared 5.6% and 4.4%, respectively, by moving the fuel injection position forward. The flow field structure is obviously influenced by the fuel injection distribution. The more fuel is injected from the downstream cavity, the farther downstream the thermal throat is located. And much more heat is required to form the thermal throat. When the fuel is injected from the upstream cavity and downstream cavity, a wide subsonic region which is to the benefit of the combustion and heat releasing of the fuel is formed. The combustion efficiency and the thrust of the engine increased by 10.4% and 10.8%, respectively, with this strategy.