A 3D modeling of the fluid dynamics and heat transfer in an advanced free-piston Stirling engine was conducted. The transient and conjugate fluid dynamics and thermodynamics of the coupling fluid-solid domain over the working cycle were comprehensively investigated. The comparisons among different turbulent CFD models and Sage result of the engine were performed. Results indicate that the k-epsilon turbulence model with improved wall treatment yields reasonable accuracy and stable convergence. The CFD results of the pressure drop in the regenerator are nearly the same as engine Sage design code results, while the pressure drop inside cold heat exchanger has about 10.43% deviation compared to the Sage result. The flow diffuser guide flow more evenly distributed inside the regenerator, but it was found that it causes a vast turbulent dissipation rate. The instantaneous transport variables such as temperature, density and viscosity cannot be treated as uniform distribution due to the complicated interaction and coupling between the fluid-fluid and fluid-solid during the operation. The ejecting and injecting flows result in non-uniformly distributed temperature, pressure and density in the regenerator. The flow friction coefficient in the regenerator over one cycle cannot be simply correlated by typical empirical equations. The linearly distributed temperature profile in the regenerator solid matrix in the Stirling engine is confirmed by this CFD modeling. The optimization results of the diffuser and regenerator are also discussed.

在先进的自由活塞斯特林发动机中进行了流体动力学和传热的3D建模。全面研究了在整个工作循环中流固耦合的瞬态和共轭流体动力学和热力学。进行了不同湍流CFD模型与发动机Sage结果的比较。结果表明，k壁处理得到改进的ε-ε湍流模型产生合理的精度和稳定的收敛。蓄热室中压降的CFD结果与发动机Sage设计规范的结果几乎相同，而冷热交换器内部的压降与Sage结果相比大约有10.43％的偏差。导流器导流在回热器内更均匀地分布，但是发现导流导致巨大的湍流耗散率。由于操作过程中流体-流体与流体-固体之间复杂的相互作用和耦合，因此瞬时输送变量（例如温度，密度和粘度）不能视为均匀分布。喷射流和喷射流导致再生器中温度，压力和密度的分布不均匀。不能通过典型的经验方程简单地将蓄热器中一个周期内的流动摩擦系数关联起来。斯特林发动机中蓄热室固体基质中的线性分布温度曲线已通过此CFD模型确定。还讨论了扩散器和再生器的优化结果。