【作者】 陈健；

【导师】 王振国；

【作者基本信息】 国防科学技术大学 ， 航空宇航推进理论与工程， 2012， 博士

【摘要】 超－超引射器可以减小引射系统的总体尺寸，同时还具有提高系统性能的潜在优势。然而，目前对超－超引射器内的流动特性以及两股超声速射流在引射管道约束下的相互作用及其混合过程鲜有报导。因而，对超－超引射器进行深入研究具有重要的工程应用价值和学术意义。本文综合运用理论分析、实验手段和数值仿真，对超－超引射器的压力匹配和压力恢复等特性进行了深入研究，并对超－超引射器内混合层的发展特点和能量交换规律等机理问题进行了分析。确定引射器中性能损失的来源对于超声速引射器的设计具有重要的指导意义。本文运用热力学中的熵增分析方法，首先对等截面超－超引射器中各种性能损失因素进行了分析，并深入考察了不同工况下各类损失在引射器总体性能损失中所占的比例。随后，结合等截面超－超引射器的一维设计理论，确定了等截面超－超引射器的最优性能点。超声速引射器启动过程中的非定常性和极强的非线性效应使得对该过程的研究存在诸多难点，特别地，有关二次流对超声速引射器启动性能影响的研究目前仍无统一的结论。本文对超声速引射器带不同二次来流时的启动压力进行了测定，深入和系统地研究了不同流量的二次流对超声速引射器启动性能的影响，并采用现代气体动力学理论对二次流影响超声速引射器启动性能的机制进行了深入分析。对等截面超－超引射器内的典型流场结构进行了深入分析，并定义了相应的三类极限压比状态，同时发展了考虑斜激波修正的极限压比理论分析模型，大大提高了对等截面超－超引射器极限压比的预测精度。对不同构型的等截面超－超引射器的压力匹配和压力恢复性能进行了系统的研究，结果表明，等截面超－超引射器在背压影响下形成的扩压和混合同时进行的流动模式使得最大增压比的实验结果远低于理论预测值；二次流马赫数的增加提高了等截面超－超引射器的压力匹配性能，但同时降低了引射器的压力恢复性能；一次流马赫数的增加使等截面超－超引射器的压力匹配性能略有下降，但一次流马赫数改变时引射器的压力恢复性能变化不大；一、二次流总压比的提高降低了引射器的压力恢复性能；一次流冲击角的存在降低了引射器的压力匹配性能，但同时使得引射器的压力恢复性能有所提高。对变截面超－超引射器中超－超引射流场建立的动态过程进行了分析，并对变截面超－超引射器的压力匹配性能和压力恢复性能进行了系统的研究。变截面超－超引射器中型面收缩的混合室所导致的强逆压梯度降低了引射器的压力匹配性能。当混合室收缩角较小时，参数对变截面超－超引射器压力匹配性能的影响与等截面超－超引射器类似，但在较大的混合室收缩角下，变截面超－超引射器的压力匹配规律与等截面超－超引射器存在较大区别。变截面超－超引射器中型面收缩的混合室使得气流在扩压激波前的马赫数大大下降，相应地降低了扩压过程中的总压损失，因而其压力恢复性能明显优于等截面超－超引射器。利用NPLS技术和超声速PIV技术对等截面超－超引射器内引射混合层的时空结构以及速度场结构进行了研究。同时，基于速度场结构对引射混合层的湍流结构和增长速度进行了研究。研究结果表明高速流体压力低于低速流体的压力不匹配状态抑制了引射混合层的增长；而在本文实验范围内，对流马赫数越高混合层的发展越快。建立了基于欧拉处理方法的时均流管分析模型，采用该模型对超－超引射器内动量和能量传递的规律进行了分析。研究结果表明一、二次流之间的压力不匹配和提高一次流温度均可以提高一次流和二次流之间动量和动能的传递速率；温度对引射器内总能量的传递过程具有决定性的作用；提高一、二次流的总温比对引射效率的改进比提高一、二次流总压比更为有效。更多还原

【Abstract】 Supersonic-supersonic ejectors have the advantage of reducing the overall systemlength with a potential increasement in performance. However, researches on the flowcharacteristics of supersonic-supersonic ejectors and the interaction and mixing processof the supersonic primary and secondary flows in the confined mixing chamber havebeen rarely conducted. Therefore, the flow field evolution of supersonic-supersonicejectors should be investigated in details. The present research investigates the pressurematching and recovery characteristics of the supersonic-supersonic ejectorsystematically. The development of the mixing layer and the energy exchange betweenthe primary and secondary flows are also analyzed.It is vital for ejector design to determine the sources of losses in ejectorperformance. In this thesis, the entropy production method was applied to identify andquantify the sources of performace losses of the constant area supersonic-supersonicejector. The composition of the losses and their proportions were examined. Bycombining this thermodynamic method with the one-dimensional aerodynamic theory,the optimum condition of the constant area supersonic-supersonic ejector was obtainedand validated.The starting mechanism of supersonic ejector with a second throat is rathercomplex due to the unsteady and nonlinear effects. Especially, the effect of thesecondary flow on the starting performance of the second-throat supersonic ejector isstill unclear. In the present work, the starting pressure of a second-throat supersonicejector with various secondary flow rate has been measured. Based on the results of thepressure measurements, qualitative analysis has been carried out to clarify the flowbehavior and the physical meaning of the performance diagram.Typical flow fields in the former part of the mixing chamber of the constant areasupersonic-supersonic ejector were analyzed. Three limiting conditions have beendefined. A simplified analytical model has been proposed to predict the limitingpressure ratio which agrees well with the experimental data. The pressure matching andpressure recovery performance of the constant area supersonic-supersonic ejector havebeen investigated systematically. The results show that the experimental maximumcompression ratio was much lower that the theoretical value. This discrepancy may becaused by the different flow pattern between the actual flow field and theoreticalassumption. Besides, when increasing the secondary Mach number, the pressurematching performance increases while the pressure recovery performance decreases.The increasing of the primary Mach number will result in slight desent of the pressurematching performance, but almost no change in the pressure recovery performance. Thepressure recovery performance decreases with the increasing of the stagnation pressure ratio of the primary and secondary flows. The striking angle of the primary flow reducesthe pressure matching performace while improving the pressure recovery performace.The starting process of the supersonic secondary flow in variable areasupersonic-supersonic ejectors was analyzed. The effect of the second-throat on thepressure matching and pressure recovery performance of the ejector was investigatedsystematically. The experimental results indicate that the second-throat lowers thepressure matching performance of the ejector while improving the pressure recoveryperformance. Numerical calculations reveal that the aerodynamic throat opening area ofthe secondary flow which is restricted by the contraction of the mixing chamber, willresult in a lower pressure matching performance. However, the Mach number ahead ofthe shock train is reduced by the converging mixing chamber of the variable areasupersonic-supersonic ejector. The pressure loss caused by the shock train decreases,consequently. And the pressure recovery performance of the variable areasupersonic-supersonic ejector is improved.The development of the mixing layer and velocity fields of the mixing layer werestudied via NPLS and supersonic PIV technique, respectively. Turbulent structures andthe growth rate of the mixing layer were analyzed. Results show that when the staticpressure of the primary flow is lower than that of the secondary flow, the growth rate ofthe mixing layer is smaller than the condition when the static pressures are matched.And in the present work, the growth rate of the mixing layer increases with theincreasing of the convective Mach number.An analytical model based on the Euler methodology was proposed to analyze themomentum and energy exchange between the primary and secondary flows. Resultsshow that the unmatched static pressure of the primary and secondary flows, orincreasing the tempreture of the primary flow, will result in an increasing exchange rateof the momentum and kinetic between the primary and secondary flows. Compared toincrease the stagnation pressure ratio of the primary and secondary flow, increasing thetemperature ratio could improve the efficiency of the ejector more effectively.更多还原