Full engine physical-field simulation of the dynamic process with variable rotational speed

Compared to system simulations based on low-dimensional mathematical models, physical-field simulations offer broader prospects in the design processes of gas turbine engines. While computational fluid dynamics (CFD) has become a standard practice for evaluating component-level performance, performing three-dimensional (3D) CFD simulations of the full engine, especially for dynamic processes, remains challenging. A key technical issue with existing solvers for these full engine physical-field simulations is that the governing equations, derived using the multi-frame reference method for turbomachinery, do not account for real-time changes in rotational speed. In this paper, the Navier–Stokes (N-S) equation with angular acceleration source term was derived, and the rotor motion equation was introduced to simulate the engine's dynamic process. By comparing the simulation results of the transient state with the steady-state simulation and experimental data, the reliability of the CFD solver based on these improved governing equation was verified. Then, an exploratory simulations were conducted to investigate the transition state of the KJ66 Micro Turbojet Engine, transitioning into a wind-milling state after the fuel was cut off under specific incoming wind speed. The results indicate that dynamic process simulations previously impossible to achieve using traditional unsteady CFD method, such as engine's wind-milling state and fuel cutoff process, can now be successfully conducted based on the improved N-S equations coupled with the rotor motion.