摘要: The rotating disk surface temperature rise due to windage heating effect by numerically modeling the turbulent flow within a rotor-stator cavity which is available with a peripheral shroud and imposed through airflow was dealt with. The windage heating may be defined as viscous friction heating caused by relative velocity differences across the boundary layers between the fluid and the rotating disk surface. The kinetic energy dissipation process could transform the rotating shaft power into thermal heating. Commercial finite volume based solver, ANSYS/CFX was employed to numerically simulate this physical process by using the shear stress transport (SST) turbulence model. CFD results include the rotating disk surface temperature axial distribution and tangential velocity distribution of the fluid domain. The velocity difference between the result obtained by particle image velocimetry (PIV) experiments and CFD simulation are within 5%. The adiabatic disk temperature rise can be calculated by the tangential velocity of disk and fluid in large gap ratio and turbulent parameter. CFD temperature distribution results and those estimated via velocity differences are within 10%.
摘要: An identification-based approach for aircraft engine modeling using the nonlinear Hammerstein-Wiener representation was proposed. Hammerstein-Wiener modeling for both limited flight envelope and extended flight envelope was investigated. Simulation shows that the resulting model can be valid over 10% variation of rotational speed of the engine, compared with those linear models that are only valid over 3%—5% change of rotational speed. It is further demonstrated that the proposed method can be utilized over large envelope up to 20% variation of rotational speed of the engine. The fundamental idea is to use nonlinear models to extend the feasible/valid region rather than those linear models. This may consequently simplify the switching logic in the onboard digital control units. This is often overlooked in aircraft engine control community, but has been emphasized in the research.
