Secondary flow visualization on stagnation row of a combined impingement and film cooled high-pressure gas turbine nozzle guide vane using PIV technique
In this study, the local jet velocity distribution for a combined impingement and film cooled high-pressure nozzle guide vane system was analyzed, using flow visualization and PIV-assisted measurement. The measurements including flow visualization were performed on the stagnation row of an NGV to understand its complex flow pattern. PIV technique was used to measure the effused coolant jet exit velocity field in two-dimensional vertical planes. The computations were performed by ANSYS FLUENT 14.5 SOLVER using shear stress transport (SST) k-ω turbulence model. Three laboratory test cases that correspond to inlet coolant mass flow rates of 0.0032, 0.0045 and 0.0054 kg/s, at the region of an FIT, were studied. The numerical results for the spanwise coolant velocity at stagnation row of the film holes agreed well with the PIV experimental data on the same vane configuration.Graphical Abstract
An experimental investigation of secondary flow characteristics in a linear turbine cascade with upstream converging slot-holes using TR-PIV
Abstract To study the time-mean and temporal characteristics of secondary flow within a linear GE-E 3 high pressure turbine cascade, a planar Time-Resolved Particle Image Velocimetry (TR-PIV) system is used. In the double-passage cascade, a row of six converging slot-holes is placed upstream of center blade to generate film cooling effect, and different turbulence grids are replaced to create various free-stream turbulence ( Tu in ) levels. In this experiment, the time-mean characteristics of secondary flow, the fast switch process of unsteady leading edge horseshoe vortex (LEHV), and the temporal characteristics of corner vortices (CVs) are completely exhibited by the TR-PIV technique. The influences of the upstream coolant injection and Tu in level on the flow characteristics of LEHV and passage vortex (PV) are discussed. The discussion reveals that: (1) in the case of no coolant injection, a high Tu in level slightly moves the LEHV toward the blade, changes the shape of the PV, increases the fluctuations of the LEHV and PV, and reduces the frequency of the LEHV switch process; (2) at various Tu in levels, the coolant injections suppress the formation of the LEHV, and the LEHV disappears at a high coolant-to-mainstream blowing ratio (BR) of 1.5; (3) a high BR of 1.5 can greatly weaken the PV at various Tu in levels, and relative to the case of low Tu in , the high Tu in level induces a larger reduction; (4) for a low BR, at various Tu in levels, a slight change in the LEHV results in a distinct difference of the PV characteristics; (5) for a high BR, since the LEHV disappears, the Tu in effect on the secondary flow characteristics is slight.
Inverse Design of and Experimental Measurements in a Double-Passage Transonic Turbine Cascade Model
A new transonic turbine cascade model that accurately produces infinite cascade flow conditions with minimal compressor requirements is presented. An inverse design procedure using the Favre-averaged Navier-Stokes equations and k- turbulence model based on the method of steepest descent was applied to a geometry consisting of a single turbine blade in a passage. For a fixed blade geometry, the passage walls were designed such that the surface isentropic Mach number (SIMN) distribution on the blade in the passage matched the SIMN distribution on the blade in an infinite cascade, while maintaining attached flow along both passage walls. An experimental rig was built that produces realistic flow conditions, and also provides the extensive optical access needed to obtain detailed particle image velocimetry measurements around the blade. Excellent agreement was achieved between computational fluid dynamics (CFD) of the infinite cascade SIMN, CFD of the designed double passage SIMN, and the measured SIMN. DOI: 10.1115/1.1929810