引信新型弹载压电发电机气流控制进气口内流场数值模拟

【作者】 何鹏；

【导师】 陈荷娟；

【作者基本信息】 南京理工大学 ， 机械工程， 2012， 硕士

【摘要】 引信弹载气流压电发电机是配用于现代引信的电源装置,而引信进气口结构是其中气流激励的一个重要机械结构,其进气孔道内的气流速度与湍流度分布情况对发电机正常工作和气流动量传递有着重要的影响。由于应用解析法或实验法分析进气口内流场具有很大的难度,因此,本论文利用计算流体力学(CFD)方法,研究低雷诺数情况下非对称入流对不同特征尺寸的引信进气口结构的流态响应问题。首先,简要叙述了流体动力学数值模拟的计算流体力学方法,讨论了近壁面的切应力输运湍流模型,建立了转捩湍流模型。在此基础上,探讨了本论文所采用二阶迎风空间离散格式与改进的压力耦合方程的半隐式(SIMPLEC)迭代算法和混合网格划分方法。其次,简要叙述了弹丸激波理论与圆管内附面层转捩理论,并对圆管内气流运动控制方程的边界条件进行探讨。根据理论分析,指出引信气流发电机进气口入流可视为非管轴对称的低雷诺数流动。最后,应用改进的湍流转捩模型封闭N-S方程,分别对等截面直孔口、等截面环隙口、变截面喇叭口的三种典型引信进气口进行了内流场数值计算。应用计算流体力学的数值方法,模拟引信等截面直孔口、等截面环隙口、变截面喇叭口三种进气口内流场的流态响应。结果表明,这三种进气口内流场的转捩现象、气流速度和湍流度的气流分布差异系数、壁面摩擦阻力系数、附面层厚度等的响应,将随非对称入流条件的改变而呈现不同规律,其中,等截面环隙柱形口具有气流减速、速度截面分布均匀快、转捩起始位置短特点,且间隙越小其效应越显著,故等截面环隙柱形口是合适的引信弹载气流压电发电机进气口结构。更多还原

【Abstract】 The pneumatic piezoelectric generator of missile-borne fuze is a supply unit for modern fuze, and the air inlet is an important mechanical structure of its air driving system. The distribution of airflow velocity and turbulence intensity in air inlet decides the functioning of generator and the transmission of airflow momentum. Considering that it is very difficult to analyze the flow field in air inlet with analytical method or experimental method, Computational Fluid Dynamics (CFD) is used in the graduation thesis of the research on the response of flow pattern inside the air inlet construction with different characteristic dimensions when the Reynolds number is low and the input flow is asymmetrical.First,the numerical simulation method is described,the shear-stress transport turbulence model of near wall, and buildsthe transition model are discussed. On this basis, this paper studied the Second-order Up-wind discrete format, SIMPLEC and the hybrid-grid partition method which would be applied.Then, the warhead’s shock theory and the transition theory of the boundary layer inside pipe was briefly discussed, and the boundary conditions of governing equation was explored. According to the theoretical analysis, the input flow of the air inlet of the pneumatic piezoelectric generator for fuze can be taken as the asymmetric and low Reynolds number flow.Finally, by applying the improved turbulence-transition model to close N-S equation, numerical calculation of flow field was done in three typical air inlets of fuze, namely, uniform section straight orifice, uniform section annular space and variable section trumpet.The results indicated that numerical simulation method with CFD can be used to simulate the response of flow pattern inside the air inlet of fuze. The responses of transition in three air inlets of fuze, the distribution-difference coefficient of the velocity and turbulence intensity, wall friction resistance coefficient and the thickness of boundary layer appeared different regularity with the changed asymmetric inflow conditions. The uniform section annular space fuze inlet has features of slowed flow, faster uniformly distribution of velocity by section, and shorter initial transition position. These features are more significant when the gap is smaller. Therefore the uniform section annular space fuze inlet is an appropriate air inlet construction for missile-borne pneumatic piezoelectric generator.更多还原