A systematic nonlinear gyrokinetic analysis of microtearing modes (MTMs) in National Spherical Tokamak eXperiment (NSTX) discharges spanning high-, moderate-, and low-collisionality regimes around mid-radius is presented using the fully electromagnetic code CGYRO. The simulations retain the complete set of perturbed fields, impurity species, equilibrium flow shear, and inter-species collisions, yielding electron heat flux predictions in improved agreement with experimental measurements. In the high-collisionality regime, impurity effects are found to play a critical role in reproducing experimentally observed electron heat flux levels. At moderate-collisionality, enhanced zonal flows and fields modify turbulent structures and reduce transport. In the low-collisionality regime, linear analysis reveals coexistence of MTMs and a hybrid ballooning-parity mode; however, nonlinear simulations demonstrate that strong shear suppresses hybrid-mode-driven transport, leaving ion heat fluxes near neoclassical levels, consistent with experimental observations. A collisionality scan of the high-collisionality case is further performed to assess NSTX-U-relevant conditions, revealing a transition at lower collisionality in which enhanced zonal flows and fields significantly suppress MTM-driven turbulence and electron heat transport. Sensitivity studies with respect to equilibrium flow shear, temperature and density gradients, electron , safety factor, and magnetic shear indicate that, at the collisionalities anticipated for NSTX-U, MTMs are expected to contribute to electron heat transport without imposing a dominant confinement constraint. These results provide a nonlinear basis for interpreting collisionality trends in spherical tokamaks and for guiding transport predictions in NSTX-U regimes.
球形托卡马克实验装置（NSTX）在中等半径附近跨越高、中、低碰撞率区域的放电中，微撕裂模（MTMs）的系统性非线性回旋动理学分析，采用全电磁代码CGYRO加以呈现。模拟保留了完整的扰动场集合、杂质种类、平衡流剪切以及种类间碰撞，所得电子热通量预测与实验测量结果的一致性得到改善。在高碰撞率区域，发现杂质效应在再现实验观测到的电子热通量水平方面起着关键作用。在中碰撞率条件下，增强的带状流和带状场改变了湍流结构并降低了输运。在低碰撞率区域，线性分析揭示了MTMs与一种混合气球模宇称模的共存；然而，非线性模拟表明，强流剪切抑制了混合模驱动的输运，使离子热通量保持在近新经典水平，与实验观测一致。进一步对高碰撞率情形进行了碰撞率扫描，以评估与NSTX-U相关的条件，揭示了在较低碰撞率下出现的一种转变，其中增强的带状流和带状场显著抑制了MTM驱动的湍流和电子热输运。针对平衡流剪切、温度和密度梯度、电子β、安全因子和磁剪切的敏感性研究表明，在NSTX-U预期达到的碰撞率下，MTMs预计会对电子热输运有所贡献，而不会施加主导性的约束限制。这些结果为解释球形托卡马克中的碰撞率趋势提供了非线性基础，并为NSTX-U区域中的输运预测提供了指导。