多组分喷管流中的间接噪声
On indirect noise in multicomponent nozzle flows
摘要：
本文建立了一维非定常喷管流场的模型，用以识别多组分气体中的间接噪声源。首先，从非平衡热力学关系，它表明，在加速流平流成分的不均匀性是由混合物中的不均匀性（i）化学势和（ii）比热容引起的声源。其次，它示出的声学，熵和成分的线性扰动相互独立地发展，它们成为耦合通过平均流梯度和/或在边界处。第三，将方程转换为不变式，并通过具有无限收敛半径的路径序积分的渐近展开找到数学解。最后，计算了有限空间范围内受甲烷-空气组分不均匀扰动的超音速喷管的传递函数。所提出的框架将有助于识别和量化与航空燃气轮机相关的喷嘴中的声源。
英文摘要：
A one-dimensional, unsteady nozzle flow is modelled to identify the sources of indirect noise in multicomponent gases. First, from non-equilibrium thermodynamics relations, it is shown that a compositional inhomogeneity advected in an accelerating flow is a source of sound induced by inhomogeneities in the mixture (i) chemical potentials and (ii) specific heat capacities. Second, it is shown that the acoustic, entropy and compositional linear perturbations evolve independently from each other and they become coupled through mean-flow gradients and/or at the boundaries. Third, the equations are cast in invariant formulation and a mathematical solution is found by asymptotic expansion of path-ordered integrals with an infinite radius of convergence. Finally, the transfer functions are calculated for a supersonic nozzle with finite spatial extent perturbed by a methane-air compositional inhomogeneity. The proposed framework will help identify and quantify the sources of sound in nozzles with relevance, for example, to aeronautical gas turbines.
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