A component-splitting method is proposed to improve convergence characteristics for implicit time integration of compressible multicomponent reactive flows. The characteristic decomposition of flux jacobian of multicomponent Navier-Stokes equations yields a large sparse eigensystem, presenting challenges of slow convergence and high computational costs for implicit methods. To addresses this issue, the component-splitting method segregates the implicit operator into two parts: one for the flow equations (density/momentum/energy) and the other for the component equations. Each part's implicit operator employs flux-vector splitting based on their respective spectral radii to achieve accelerated convergence. This approach improves the computational efficiency of implicit iteration, mitigating the quadratic increase in time cost with the number of species. Two consistence corrections are developed to reduce the introduced component-splitting error and ensure the numerical consistency of mass fraction. Importantly, the impact of component-splitting method on accuracy is minimal as the residual approaches convergence. The accuracy, efficiency, and robustness of component-splitting method are thoroughly investigated and compared with the coupled implicit scheme through several numerical cases involving thermo-chemical nonequilibrium hypersonic flows. The results demonstrate that the component-splitting method decreases the required number of iteration steps for convergence of residual and wall heat flux, decreases the computation time per iteration step, and diminishes the residual to lower magnitude. The acceleration efficiency is enhanced with increases in CFL number and number of species.

翻译：提出了一种分量分裂方法，以改善可压缩多组分反应流隐式时间积分的收敛特性。多组分Navier-Stokes方程通量雅可比矩阵的特征分解会产生大型稀疏特征系统，给隐式方法带来收敛缓慢和计算成本高的挑战。为解决此问题，分量分裂方法将隐式算子分为两部分：一部分用于流动方程组（密度/动量/能量），另一部分用于组分方程组。每部分的隐式算子均采用基于各自谱半径的通量矢量分裂，以实现加速收敛。该方法提高了隐式迭代的计算效率，缓解了时间成本随组分数呈二次增长的问题。发展了两种一致性修正方法，以降低引入的分量分裂误差并确保质量分数的数值一致性。重要的是，当残差趋近收敛时，分量分裂方法对精度的影响极小。通过多个涉及热化学非平衡高超声速流动的数值算例，将分量分裂方法的精度、效率和鲁棒性与耦合隐式格式进行了深入比较。结果表明，分量分裂方法减少了残差和壁面热流收敛所需的迭代步数，降低了每迭代步的计算时间，并将残差降至更小量级。随着CFL数和组分数的增加，加速效率得到进一步提升。