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41.
A theoretical method for solving shock relations coupled with chemical equilibrium and its applications 总被引:2,自引:2,他引:0
In this study, a theoretical method is proposed to solve shock relations coupled with chemical equilibrium. Not only shock waves in dissociated flows but also detonation waves in combustive mixtures can be solved. The global iterative solving process is specially designed to mimic the physical and chemical process in reactive shock waves to ensure good stability and fast convergence in the proposed method. Within each global step, the single-variable equations of normal and oblique shock relatio... 相似文献
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为探究中心锥对旋转爆轰发动机(Rotating Detonation Engine,简称RDE)内外流场结构与推进性能的影响,本文设计了90°、60°、45°、30°、20°、14°锥角与无中心锥7种构型,对燃烧室内径为78mm、外径为88mm、长度为100mm的RDE进行三维数值模拟,推导了适用于带中心锥RDE的推力公式,获得了各构型下详尽的流场参数。结果表明:在本文构型下中心锥对内流场影响很小,各构型的内流场参数与结构基本一致;中心锥对外流场的爆轰产物有轴向加速与径向吸附作用,能够调控尾部区域的流场特性;中心锥对由压差项产生的推力具有显著的提升效果,最佳推力性能出现在20°中心锥构型中,RDE总推力增益达22.8%。研究结果揭示了中心锥对RDE推力影响的作用机理,阐明了锥角对推进性能的影响规律,对带锥形构型的尾喷管设计工作提供了参考。 相似文献
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The problem of aeroelasticity and maneuvering of command surface and gust wing interaction involves a starting flow period which can be seen as the flow of an airfoil attaining suddenly an angle of attack. In the linear or nonlinear case, compressive Mach or shock waves are generated on the windward side and expansive Mach or rarefaction waves are generated on the leeward side. On each side, these waves are composed of an oblique steady state wave, a vertically-moving one-dimensional unsteady wave, and a secondary wave resulting from the interaction between the steady and unsteady ones. An analytical solution in the secondary wave has been obtained by Heaslet and Lomax in the linear case, and this linear solution has been borrowed to give an approximate solution by Bai and Wu for the nonlinear case. The structure of the secondary shock wave and the appearance of various force stages are two issues not yet considered in previous studies and has been studied in the present paper. A self-similar solution is obtained for the secondary shock wave, and the reason to have an initial force plateau as observed numerically is identified. Moreover, six theoretical characteristic time scales for pressure load variation are determined which explain the slope changes of the time-dependent force curve. 相似文献
44.
《中国航空学报》2021,34(1):148-162
In order to apply the air fin successfully and ensure the maneuverability of hypersonic vehicle, a key problem to be studied urgently is the heat flux brought by the fin mounting gap. The appearance of mounting gap and fin shaft can induce many complex flow structures which need more attentions to be investigated. Under Ma 6, Nano-tracer-based Planar Laser Scattering (NPLS) and Temperature Sensitive Paints (TSP) were applied to visualize and measure transient flow structures and heat flux distribution of a swept fin-induced flow field with different height mounting gaps. Complementarily, Reynolds-averaged N-S equations were solved with k-ω SST turbulent model. The heat flux distribution results of numerical simulation and TSP observed the change of high heat flux region with different mounting gap, both in position and magnitude. The streamlines based on Computational Fluid Dynamics (CFD) and flow visualization results obtained by NPLS revealed the cause of high heat flux region. The high heat flux region in this flow field is mainly related to the reattachment of vortex and flow stagnation. The increase of gap height can lead to stronger gap overflow and shaft-induced horseshoe vortex, which are source of the high heat flux around the fin. The case with the highest mounting gap (4 mm) en-counters the most severe aerodynamic heating, both on the surface of fin and plate. Thus, under the premise of ensuring the flexibility of the fin, the gap should be set as small as possible. 相似文献
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Numerical investigation of the impact of asymmetric fuel injection on shock train characteristics 总被引:1,自引:0,他引:1
Numerical simulations are carried out to investigate the impact of asymmetric fuel injection on shock train characteristics using the commercial-code FLUENT. The asymmetry of fuel injection is examined by changing the fuel flow rates of the upper and lower wall fuel injectors. The numerical approach solves the two-dimensional Reynolds-averaged Navier–Stokes (RANS) equations, supplemented with a k-ω model of turbulence. As a result, different ways of fuel injections will always lead to shock train transitions, with the variations of shock train structure, strength and leading edge position. For symmetric fuel injection, the flowfield of the isolator is quite asymmetric with the boundary layer of the upper wall side developing much stronger than that of the lower wall, which is due to the heterogeneity of the incoming flow. Regarding to asymmetric fuel injection with more of lower wall side, though the pressures in the combustor are nearly the same, the first shock of the shock train converts between ‘Distinct symmetric X type shock’ and ‘Obscure and weaker asymmetric shock’ and the shock train leading edge moves upstream with the increase of the asymmetry level. With regard to asymmetric fuel injection with more of upper wall side, ‘incomplete asymmetric X type shock’ occurs and the shock train structures keep nearly the same with low level of fuel injection asymmetry. Unexpected results like unstart will happen when increasing the level of fuel injection asymmetry. And the isolator will come back to normal state by decreasing the differential of upper and lower wall sides fuel injections. 相似文献
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为更简单清晰地对封闭式行星轮系的功率流情况进行判别,利用键合图能量守恒和功率流动的特点,将键合图理论应用于该类轮系的功率流分析中.以功率汇流型、回流型2种形式的封闭式行星轮系为例,根据轮系的传动关系,利用绝对速度法建立轮系的键合图模型,根据提出的功率流向判别依据对轮系进行功率流向判别,得到整个轮系及其转换机构的功率流情况,为轮系的效率计算提供了基础.该方法适用于其它复杂轮系的功率流判别中,比传统方法更具直观性、系统性. 相似文献
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