Publications of Heidmann, James D.
Published in 2003
The NASA Glenn Research Center Multi-Block Navier-Stokes Heat Transfer Code, Glenn-HT, has been developed for and applied to a wide variety of turbine convective heat transfer problems. These problems have included tip clearance flows, internal cooling passage flows, and external turbine blade flows, including film cooling. The code has been validated against experimental data for a wide variety of turbine heat transfer flows. The general multi-block capability of the code makes it useful for computations of complicated three-dimensional flowfields in turbines as well as other propulsion system flowfields where convective heat transfer is important. The code is able to accurately predict wall heat transfer through a combination of detailed boundary layer resolution and advanced modeling capabilities.
Recent code development has concentrated on improving the code’s predictive capability and extending its usefulness to a broader range of flow problems. Conjugate heat transfer capability has been incorporated into the code using the Boundary Element Method to allow simultaneous computation of fluid and solid heat transfer without requiring a solid volume grid. This capability is being extended to layered solids, such as a turbine blade with a thermal barrier coating, as well as to solids with variable thermal conductivity. Reynolds Stress turbulence modeling efforts have been underway to improve predictions through the incorporation of anisotropic effects. Automatic topology generation techniques are being developed to shorten the calculation cycle through automation of the gridding process. This is particularly important for extremely complicated geometries, such as the cooling passages inside turbine blades and vanes, which can require thousands of grid blocks. Efforts are underway to incorporate unsteady flow capability into the code. This may be useful for studying the transient heat transfer phenomena associated with turbine accelerator missions under the Access to Space Program. These and future improvements to the Glenn-HT code are aimed at improved accuracy, speed, and flexibility of the code for future convective heat transfer issues in turbines and other propulsion systems.Download PDF
Published in 2003
We report on the progress in the development and application of a coupled boundary element/finite volume method temperature-forward/flux-back algorithm developed to solve conjugate heat transfer arising in 3D film-cooled turbine blades. We adopt a loosely coupled strategy where each set of field equations is solved to provide boundary conditions for the other. Iteration is carried out until interfacial continuity of temperature and heat flux is enforced. The NASA-Glenn explicit finite volume Navier-Stokes code Glenn-HT is coupled to a 3D BEM steady-state heat conduction solver. Results from a CHT simulation of a 3D film-cooled blade section are compared with those obtained from the standard two temperature model, revealing that a significant difference in the level and distribution of metal temperatures is found between the two. Finally, current developments of an iterative strategy accommodating large numbers of unknowns by a domain decomposition approach is presented. An iterative scheme is developed along with a physically-based initial guess and a coarse grid solution to provide a good starting point for the iteration. Results from a 3D simulation show the process that converges efficiently and offers substantial computational and storage savings.
Keywords: Boundary elements, Coupled phenomena, Finite volume, Heat transfer
Published in 2000
A three-dimensional Navier–Stokes simulation has been performed for a realistic film-cooled turbine vane using the LeRC-HT code. The simulation includes the flow regions inside the coolant plena and film cooling holes in addition to the external flow. The vane is the subject of an upcoming NASA Lewis Research Center experiment and has both circular cross-sectional and shaped film cooling holes. This complex geometry is modeled using a multiblock grid, which accurately discretizes the actual vane geometry including shaped holes. The simulation matches operating conditions for the planned experiment and assumes periodicity in the spanwise direction on the scale of one pitch of the film cooling hole pattern. Two computations were performed for different isothermal wall temperatures, allowing independent determination of heat transfer coefficients and film effectiveness values. The results indicate separate localized regions of high heat flux in the showerhead region due to low film effectiveness and high heat transfer coefficient values, while the shaped holes provide a reduction in heat flux through both parameters. Hole exit data indicate rather simple skewed profiles for the round holes, but complex profiles for the shaped holes with mass fluxes skewed strongly toward their leading edges.Keywords: turbines, cooling, Navier-Stokes equations, film flow, numerical analysis, flow simulation, heat transfer