Investigation Of Three-dimensional Flow Field Research Articles

Experimental investigation for the effect of rotation on three-dimensional flow field in film-cooled turbine

An experimental investigation of three-dimensional flow field in a film-cooled turbine model is carried out by using particle image velocimeter (PIV) in a low-speed wind tunnel. The effects of different blowing ratios (M=1.5, 2) on the flow field are studied. The experimental results reveal the classical phenomena of the formation of kidney vortex pair and secondary flow in wake region behind the jet hole. And the changes of the kidney vortex pair and the wake at different locations away from the hole on the suction and pressure sides are also studied. Compared with the flow field in stationary cascade, there are centrifugal force and Coriolis force existing in the flow field of rotating turbine, and these forces bring the radial velocity in the jet flow. The effect of rotation on the flow field of the pressure side is more distinct than that on the suction side from the measured flow fields in Y-Z plane and radial velocity contours. The increase of blowing ratio makes the kidney vortex pair and the secondary flow in the wake region stronger and makes the range of the wake region enlarged.

Investigation of three-dimensional flowfield at the exit of a turbine nozzle

The objective of the research reported in this article is to gain a detailed understanding of the flowfield at the exit of turbine nozzles. The flowfield was measured at two axial locations downstream of the nozzle of a single-stage turbine with a miniature five-hole probe. An area traverse was carried out to resolve the flowfield accurately, including the nozzle wake, secondary flow region, horseshoe vortex, and losses. All three components of the velocity, stagnation pressure, static pressure, and pitch and yaw angles have been resolved accurately. A distinct vortex core has been observed near the tip and at the hub. The indications are that the horseshoe vortex and the passage vortex have merged to produce a single-loss core region. Roughly, a third of the blade height passage near the tip and a third of the blade height near the hub is dominated by secondary flow phenomena. Only the middle third of the nozzle behaves according to design. The nozzle wake decay is compared to the wake decay of other blades. The nozzle wake decays much faster than a compressor cascade wake, an annular turbine nozzle cascade wake, or a turbine nozzle wake with a large rotor-stator spacing. This faster decay is attributed to effect of the downstream rotor at very small rotor-stator spacing (20% of nozzle axial chord). These and other data are presented, interpreted, and synthesized to understand the nozzle flowfield.

Hypersonic flows past a yawed circular cone and other pointed bodies

A detailed treatment of inviscid hypersonic flow past a circular cone is given, for small and moderate yaw angles, within the fremework of shock-layer theory. The basic problem of non-uniform validity associated with the singularity of the entropy field is examined and a valid first-order solution is obtained which provides an explicit description of a thin vortical layer at the inner edge of the shock layer. Analytic formulas for pressure and circumferential velocity are given consistent to the second-order approximation including the non-linear yaw effect.The study of the entropy field (which is not restricted to the hypersonic case) also provides corrections to previous work on the yawed cone and confirms the validity of the linear yaw effect on pressure field in the Stone theory.A related investigation of three-dimensional flow fields is presented with special reference to the flow structure near the surface of a pointed, but otherwise arbitrary body. The inviscid streamline pattern on the surface is given by the geodesics originating from the pointed nose as a leading approximation of shock-layer theory. Associated with this streamline pattern is a vortical sublayer which exists generally at small as well as at large angle of attack. At the base of the sublayer, enthalpy and flow speed remain essentially uniform.