热力学非平衡对超燃冲压发动机冷态流动影响研究

Effects of Thermal Nonequilibrium on Cold Flow in Scramjets

关键词:  超燃冲压发动机  热力学非平衡  热力学模型  双温度模型  内流  数值模拟

Key words:  Scramjet  Thermal nonequilibrium  Thermodynamic model  Two-temperature model  Internal flow  Numerical simulation

摘要:

随着流动马赫数和温度的变化，热力学非平衡对流动的影响也在变化。为研究热力学非平衡对不同飞行马赫数下的超燃冲压发动机冷态流动的影响，对三个经典的超燃冲压发动机模型，包括JAXA M12-02超燃冲压发动机、DLR超燃冲压发动机以及Hyshot II超燃冲压发动机进行数值模拟。针对每个超燃冲压发动机，分别采用三种热力学模型进行模拟，包括量热完全气体模型（对应冻结流动），单温度模型（对应热力学平衡流动）以及双温度模型（对应热力学非平衡流动）。计算结果表明，热力学模型对超燃冲压发动机内流波系结构的位置有一定影响：从整体上来说，双温度模型计算所得波系位置比量热完全气体模型计算结果靠后，比单温度模型计算结果靠前；不同热力学模型计算所得波系位置在发动机前段相对较为接近，而随着向下游发展，波系位置的差别逐渐增大，这是上游每一道波系位置的差别逐渐累积的结果。在发动机前段，双温度模型计算所得波系位置更接近于量热完全气体模型计算结果。通过分析不同热力学模型计算所得激波角可以对此进行解释。而就本文涉及的三个小尺寸超燃冲压发动机而言，热力学模型对气动力和力矩的影响相对较小。不同热力学模型计算所得气动力和力矩的差别主要来源于计算所得激波串位置的差别。

Abstract:

The effect of thermal nonequilibrium on flows varies with Mach number and temperature. In order to investigate the effect of thermal nonequilibrium on cold flow in scramjets at various flight conditions， three scramjets， namely the JAXA M12-02 scramjet， the DLR strut-based scramjet， and the Hyshot II scramjet， are simulated， which cover a wide range of flight Mach numbers and temperatures. Regarding each scramjet， three thermodynamic models are used for the simulation， including calorically perfect gas model which corresponds to frozen flow， one-temperature model which corresponds to thermal equilibrium flow， and two-temperature model which corresponds to thermal nonequilibrium flow. The simulations show that thermodynamic models have discernible effects on the internal flow of scramjet flows. The location of the shock structures calculated by calorically perfect gas model is more forward than that calculated by one-temperature model， and the result of two-temperature model situates in between. At the forepart of the scramjet， the difference in the locations of shock structures from different thermodynamic models is relatively small， while the difference gradually grows as the flow passes downstream， owing to the accumulation of the difference of upstream shock structures. At the forepart of the scramjet， the result of two-temperature model approximates to that of calorically perfect gas model. These can be explained through analyzing the shock angle calculated by different thermodynamic models. Regarding the aerodynamic forces and moments of the scramjets involved in this paper， only a small quantity of difference is detected between different thermodynamic models. The difference is mainly due to the difference in the locations of the shock structures calculated by different thermodynamic models.