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 on fluid flow characteristics in a real coolant channel of LP turbine blade with PIV technique
Abstract Using a planar particle image velocimetry (PIV) system, the fluid flow characteristics including mean velocity and pressure fields in a real coolant channel of a low pressure (LP) turbine blade have been investigated. To understand the flow characteristics within the real LP turbine blade in detail, the studied channel has a real blade-similar cross section, and the entire channel consists of two dividing walls, three passes, a 180° bend, 2 tip exits and 25 trailing edge exits. At first, the flow structures in the channel are captured by the PIV system at an inlet Reynolds number of 44,000, when all the exits are open. The experimental results exhibit different secondary flow features from the previous investigations, which were conducted mostly in simplified two-pass square or rectangular channels. Secondly, through a statistical post-processing of measured instantaneous velocity fields, the Reynolds-averaged Navier–Stokes (RANS) equations are solved to obtain the mean pressure distributions at several typical cross sections. At last, the effects of the inlet Reynolds numbers and coolant ejection from the tip exit above the 1st pass on the flow characteristics are discussed. From the comparisons of the flow characteristics obtained at different flow conditions, it can be concluded that the flow characteristics are sensible to the inlet Reynolds number and coolant ejection from tip exit.
Recalculation of Mass Defects
THE well-known mass defect curve of the old nuclear scheme calculated with regard to α-particles and protons presented a difficulty with its minimum of binding energy for tin and an increasing portion between tin and lead. On the other hand, the mass defect values against protons give a rather smoothly decreasing curve.1 As has already been pointed out,2 the number of α-particles must be considerably reduced from the point of view of the new scheme, which does not admit any electrons in nuclei, but only neutrons and protons (presumably joined as α-particles). The curve of mass defect against protons and neutrons (perhaps with a single ‘central’ α-particle) is very similar to the old curve against protons, but decreases less rapidly. Clearly the new mass defect values relatively to α-particles, neutrons and protons must lie somewhere between the old values computed relative to protons and α-particles respectively (because the number of α-particles is decreased). We may emphasise that this new mass defect curve shows no increasing portion between tin and lead. For illustration we give two typical values: Old: 50Sn124 = 31α + 12&#38;epsiv;; mass defect = 0.158 (in mass units); 82Pb208 = 52α + 22&#38;epsiv;; mass defect = 0.035. New: 50Sn124= 25α + 24ω (ω = neutron); mass defect = 0.304; 82Pb208 = 41α + 44ω; mass defect = 0.366.