Film Cooling Effect of Rotor-Stator Purge Flow on Endwall Heat/Mass Transfer

Abstract

Mass transfer measurements on the endwall and blade suction surfaces are performed in a five-blade linear cascade with a high-performance rotor blade profile. The effects of purge flow from the wheelspace cavity entering the hot gas path are simulated by injecting naphthalene-free and naphthalene-saturated air through a slot upstream of the blade row at 45 deg to the endwall, for a Reynolds number of 6×105 based on blade true chord and cascade exit velocity, and blowing ratios of 0.5, 1, and 1.5. Oil-dot visualization indicates that with injection, a recirculation region is set up upstream of the leading edge, and the growth of the passage vortex is altered. The coolant exiting from the slot is drawn to the suction side of the blade and is pushed up along the suction surface of the blade by the secondary flow. For blowing ratios of 0.5 and 1.0, only a little coolant reaches the pressure side in the aft part of the passage. However, at a blowing ratio of 1.5, there is a dramatic change in the flow structure. Both the oil-dot visualization and the cooling effectiveness maps indicate that at this blowing ratio, the coolant exiting the slot has sufficient momentum to closely follow the blade profile and is not significantly entrained into the passage vortex. As a result, high cooling effectiveness values are obtained at the pressure side of the endwall, well into the midchord and aft portions of the blade passage.

The Aero-Thermal Performance of Purge Flow and Discrete Holes Film Cooling of Rotor Blade Platform in Modern High Pressure Gas Turbines: A Review

“…These observations were considered useful for a preliminary design of cooling holes inside of the passage. In particular, the measured heat transfer coefficient was in agreement with distributions already presented in the literature [48]. Ref.…”

“…In [48], heat transfer measurements and flow visualizations obtained in a rotor cascade with an injection slot upstream of rotor blades were presented at different blowing ratio values. No attempt was made to simulate the impact of rotation.…”

Influence of Combustor Exit Conditions on Cooling Performance of NGV Endwall with Double Row Cooling Holes

“…To validate the prediction performance of the turbulence model, the numerical simulation results have been compared with the experimental data (Papa et al, 2012) of film cooling effectiveness on a blade endwall. The laterally averaged cooling effectiveness with the coolant blowing ratio of 1 is shown in Figure 5.…”

Experimental Investigation on the Effects of DBD Plasma on the Film Cooling Effectiveness of a 30-Degree Slot

“…Many researchers have experimentally studied the effects of slot purge flow on turbine endwall film cooling in a linear turbine cascade. Papa et al [5] investigated the distribution of the Sherwood Appl. Sci.…”