This study showed that when studying a rotating duct of a given geometry and radial distance from the axis of rotation, the Mach number must be specified in addition to the Reynolds number, the Prandtl number, the rotation number, and the coolant-to-wall temperature ratio because it affects the rotational speed which in turn strongly influences centrifugal buoyancy. This study also showed the nature of the three-dimensional flow induced by Coriolis force, centrifugal buoyancy, and a ISO-degree bend and how that flow affects heat transfer in a U-shaped square duct with smooth walls for three rotation numbers (0, 0.24, and 0.48) and two Reynolds numbers (25,000 and 50,000). The computed heat transfer coefficient on the leading and trailing faces of the rotating duct compares well with available experimental data.This computational study is based on the ensembleaveraged conservation equations of mass, momentum (compressible Navier-Stokes), and energy closed by a low Reynolds number k-co model of turbulence (i.e., wall functions were not used). Solutions were generated by using a cell-centered finite-volume method based on a diagonalized alternating-direction implicit scheme with multigrid. All inviscid terms were approximated by the second-order fluxdifference splitting of Roe. All diffusion terms were approximated conservatively by differencing derivatives at cell faces.
Time-averaged Stanton number and surface-pressure distributions are reported for the first-stage vane row and the first-stage blade row of the Rocketdyne Space Shuttle Main Engine two-stage fuel-side turbine. These measurements were made at 10%, 50%, and 90% span on both the pressure and suction surfaces of the component. Stanton-number distributions are also reported for the second-stage vane at 50% span. A shock tube is used as a short-duration source of heated and pressurized air to which the turbine is subjected. Platinum thin-film pages are used to obtain the heat-flux measurements and miniature silicone-diaphragm pressure transducers are used to obtain the surface pressure measurements. The first-stage vane Stanton number distributions are compared with predictions obtained using a quasi-3D Navier-Stokes solution and a version of STAN5. This same N-S technique was also used to obtain predictions for the first blade and the second vane.
Computations were performed to study the three-dimensional flow and heat transfer in a ribbed U-shaped duct of square cross section under operating conditions that are typical of industrial gas turbines. Basically, all walls were maintained at a temperature of 800 K, and the coolant air at the duct inlet had a temperature of 550 K and a pressure of 10 atm. Both rotating and non-rotating cases were investigated. When rotating, the angular speed was 3,600 rpm. The Reynolds number based on the duct hydraulic diameter was set at 350,000, which represents an upper limit in coolant flow. The results obtained in this study were compared with those from previous numerical studies with a lower Reynolds number, namely 25,000, which represents a lower limit in coolant flow. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy. Turbulence is modelled by two low-Reynolds number k-ω models: an SST version with isotropic eddy diffusivity and a nonlinear version with anisotropic eddy diffusivity from an explicit algebraic Reynolds stress model. Solutions were generated by using a cell-centered finite-volume method, that is based on flux-difference splitting and a diagonalized alternating-direction implicit scheme with local time-stepping and V-cycle multigrid.
Detailed heat transfer measurementa and predictions are given for a turbine rotor with 136° of turning and an axial chord of 12.7 cm. Data were obtained for inlet Reynolds numbers of 0.5 and 1.0 × 106, for isentropic exit Mach numbers of 1.0 and 1.3, and for inlet turbulence intensities of 0.25% and 7.0%. Measurements were made in a linear cascade having a highly three-dimensional flow field resulting from thick inlet boundary layers. The purpose of the work is to provide benchmark quality data for three-dimensional CFD code and model verification. Data were obtained by a steady-state technique using a heated, isothermal blade. Heat fluxes were determined from a calibrated resistance layer in conjunction with a surface temperature measured by calibrated liquid crystals. The results show the effects of strong secondary vortical flows, laminar-to-turbulent transition, shock impingement, and increased inlet turbulence on the surface heat transfer.
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