Dr Zixiang Sun

A transient simulation of shutdown cooling for a gas turbine test rig configuration under ventilated natural convection has been successfully demonstrated using a coupled aerothermal approach. Large eddy simulation (LES) and finite element analysis (FEA) were employed for fluid domain computational fluid dynamics (CFD) and solid component thermal conduction simulation, respectively. Coupling between LES and FEA was achieved through a plugin communicator. The buoyancy-induced chimney effect under the axially ventilated natural convection is correctly reproduced. The hotter turbulent flow in the upper part of the annular path and the colder laminar-type air movement in the lower part of the annulus are appropriately captured. The heat transfer features in the annular passage are also faithfully replicated, with heat flux of the inner cylinder reaching its maximum and minimum at the bottom dead center (BDC) and the top dead center (TDC), respectively. Agreement with experimental measurements is good in terms of both temperature and heat flux, and the result of the transient simulation for the shutdown cooling is encouraging too. In addition, radiation is simulated in the FEA model based on the usual gray body assumptions and Lambert's law for the coupled computation. It has been shown that at the high power (HP) condition, the radiation for the inner cylinder is approximately 11% of its convective heat flux counterpart. The importance of radiation is thus clearly revealed even for the present rig test case with a scaled-down temperature setup.

Code_Saturne, an open-source computational fluid dynamics (CFD) code, has been applied to a range of problems related to turbomachinery internal air systems. These include a closed rotor–stator disk cavity, a co-rotating disk cavity with radial outflow and a co-rotating disk cavity with axial throughflow. Unsteady Reynolds-averaged Navier–Stokes (RANS) simulations and large eddy simulations (LES) are compared with experimental data and previous direct numerical simulation and LES results. The results demonstrate Code_Saturne's capabilities for predicting flow and heat transfer inside rotating disk cavities. The Boussinesq approximation was implemented for modeling centrifugally buoyant flow and heat transfer in the rotating cavity with axial throughflow. This is validated using recent experimental data and CFD results. Good agreement is found between LES and RANS modeling in some cases, but for the axial throughflow cases, advantages of LES compared to URANS are significant for a high Reynolds number condition. The wall-modeled large eddy simulation (WMLES) method is recommended for balancing computational accuracy and cost in engineering applications

A transient simulation of shutdown cooling for a gas turbine test rig configuration under ventilated natural convection has been successfully demonstrated using a coupled aero-thermal approach. Large eddy simulation (LES) and finite element analysis (FEA) were employed for fluid domain computational fluid dynamics (CFD) and solid component thermal conduction simulation, respectively. Coupling between LES and FEA was achieved through a plugin communicator. The buoyancy-induced chimney effect under the axially ventilated natural convection is correctly reproduced. The hotter turbulent flow in the upper part of the annular path and the colder laminar-type air movement in the lower part of the annulus are appropriately captured. The heat transfer features in the annular passage are also faithfully replicated, with heat flux of the inner cylinder reaching its maximum and minimum at the bottom dead centre (BDC) and the top dead centre (TDC), respectively. Agreement with experimental measurements is good in terms of both temperature and heat flux, and the result of the transient simulation for the shutdown cooling is encouraging too. In addition, radiation is simulated in the FEA model based on the usual grey body assumptions and Lambert’s law for the coupled computation. It has been shown that at the high power (HP) condition, the radiation for the inner cylinder is approximately 11% of its convective heat flux counterpart. The importance of radiation is thus clearly revealed even for the present rig test case with a scaled-down temperature setup