CO2两相引射器混合过程多物理场耦合机制及不可逆损失研究

Using a two-phase ejector to recovery system work has gained great attention. However, due to the lack of the cognition to multi-physical mechanisms in the inner mixing process of a CO2 two-phase ejector, it leads difficult to quantize the irreversible flow losses. This project studies the mutual coupling among the vaporization of metastable state, the expansion of supersonic flow and the boundary effect during the initial mixing of CO2 two-phase ejector, to reveal the coupling mechanism of multi-physical in the mixing process. The CO2 ejector model covering the whole flow region is developed to describe the interior complex flow. Moreover, the PIV technology is used to test the flow field and characteristic in the narrow region of CO2 two-phase ejector under the cycle operation. Then combining the measured pressure along the way of ejector, the established ejector model is modified and completed. And the quantitative methods of irreversible losses of CO2 two-phase ejector are put forward. The change laws of irreversible losses are illustrated under different operating conditions and structural parameters. The internal connections between local loss and whole loss are investigated. The control variables influencing the mixing characteristic and the irreversible loss are found and the regulation measures of ejector irreversible loss are summarized. The project contributes to perfect the two-phase ejector theory and guides the practical application of two-phase ejector, as well as has crucial academic significance and engineering value.

目前应用两相引射器回收系统功量受到广泛的关注。然而由于缺乏对CO2两相引射器内部混合过程多物理场流动机制的足够认知，严重困扰着流动不可逆损失的准确量化。本项目通过研究CO2引射器混合初始涉及的两相流亚稳态汽化、超音速膨胀以及混合流体边界层作用的相互耦合关系，揭示CO2两相引射器混合过程多物理场耦合机制，进而建立反映引射器内部复杂流动的全域模型。而且利用PIV技术在系统循环工况下测试CO2两相引射器狭小区域的流场空间结构和流动特性，并结合引射器内部沿程压力测量修正完善所建数学模型，提出两相引射器不可逆损失量化方法。阐明不同结构和运行工况下不可逆损失的变化规律，分析局部损失和总体损失之间的内在联系，找出影响混合特性和不可逆损失的控制参量，提出引射器不可逆损失的调控措施。本项目有助于完善引射器理论，能够为拓展两相引射器的实际应用提供指导，研究具有重要的学术意义和基础研究价值。

CO2两相引射器主动流在喷嘴内的壅塞流动、在预混合区的超音速膨胀以及与引射流在混合扩压室中的能质传递过程，使得描述其复杂流动和量化不可逆损失尤为困难。本项目从CO2两相引射器多物理机制出发，基于特征线法利用有限差分法建立主动流超音速膨胀模型，描述超音速膨胀波的发展过程；采用双流体模型建立混合室与扩压室分布参数模型，分析主动流和引射流边界冷凝和卷吸特性下的质量传递，以及相间换热的能量传递。进而建立反映引射器复杂流动的全域模型，并获得引射器内部沿程流动参数的分布规律。通过分析不同结构和运行工况下引射器部件效率、传统㶲损、先进㶲损以及热力学熵产的变化规律，阐明局部损失和总体损失的相互作用关系，评估各个部件的优化潜力，归纳出改善不可逆损失的调控措施。.研究表明，喷嘴出口主动流压力呈现典型膨胀-压缩-膨胀的循环过程，形成砖石状激波链结构。主动流的膨胀距随着膨胀角的增大呈现出先增大后减小的趋势，膨胀距离大于喷嘴距时所产生的引射系数较大。在混合扩压室内主动流沿程温度和压力逐渐升高，马赫数逐渐降低，而引射流表现出与之相反的变化趋势。喷嘴的熵产和㶲损随着喷嘴距的增加而增大，且在一定面积比（喷嘴喉部面积与混合室入口截面积之比）情形下会出现最大值。在计算范围内混合室主动流的熵产是扩压室的2.92倍，混合室和扩压室内主动流的比熵增量占引射器总熵增量的68.6%。圆锥混合室结构有利于减少混合过程中的熵产，渐缩混合室结构有助于维持较高的引射器效率，而渐扩结构有助于增压并减少扩压室中的熵产。喷嘴和吸收室的㶲损来源于其本身，混合室的外源㶲损主要来自喷嘴和吸收室，且喷嘴的影响较大。根据优化部件性能和引射器整体性能的目标差异，提出了不同的调控策略。项目的实施有助于发展两相引射器理论，揭示引射器内部复杂的流动规律，指导CO2引射器的实际应用，为后续的深入研究提供理论借鉴。