Aerodynamic Effects of High Turbulence Intensity on a Variable-Speed Power-Turbine Blade with Large Incidence and Reynolds Number Variations

Abstract

The effects of high inlet turbulence intensity on the aerodynamic performance of a variable speed power turbine blade are examined over large incidence and Reynolds number ranges. These results are compared to previous measurements made in a low turbulence environment. Both high and low turbulence studies were conducted in the NASA Glenn Research Center Transonic Turbine Blade Cascade Facility. The purpose of the low inlet turbulence study was to examine the transitional flow effects that are anticipated at cruise Reynolds numbers. The current study extends this to LPT-relevant turbulence levels while perhaps sacrificing transitional flow effects. Assessing the effects of turbulence at these large incidence and Reynolds number variations complements the existing database. Downstream total pressure and exit angle data were acquired for ten incidence angles ranging from +15.8° to −51.0°. For each incidence angle, data were obtained at five flow conditions with the exit Reynolds number ranging from 2.12×10 5 to 2.12×10 6 and at a design exit Mach number of 0.72. In order to achieve the lowest Reynolds number, the exit Mach number was reduced to 0.35 due to facility constraints. The inlet turbulence intensity, Tu, was measured using a singlewire hotwire located 0.415 axial-chord upstream of the blade row. The inlet turbulence levels ranged from 8% -15% for the current study. Tu measurements were also made farther upstream so that turbulence decay rates could be calculated as needed for computational inlet boundary conditions. Downstream flow field measurements were obtained using a pneumatic five-hole pitch/yaw probe located in a survey plane 7% axial chord aft of the blade trailing edge and covering three blade passages. Blade and endwall static pressures were acquired for each flow condition as well. The blade loading data show that the suction surface separation that was evident at many of the low Tu conditions has been eliminated. At the extreme positive and negative incidence angles, the data show substantial differences in the exit flow field. These differences are attributable to both the higher inlet Tu directly and to the thinner inlet endwall boundary layer that the turbulence grid imposes. NomenclatureCp s = static pressure coefficient,

Inlet Turbulence and Length Scale Measurements in a Large Scale Transonic Turbine Cascade

“…The incidence angles that are presented apply to the take-off and cruise conditions for the VSPT project. 5 The blades and their nominal inlet flow vectors are shown in Figure 2.…”

Advances in aerodynamics of power turbines for marine and aviation applications

“…In order to cope with the above-mentioned problems, the wide working condition power turbine blades are developing in the direction of highly-loaded, large incidence angle, and low Reynolds number state. The United States has carried out more in-depth research work in this research area, including high-precision calculation methods, 48,55 the influences of incidence angle, 56 inlet turbulence, 57–61 and Reynolds number effects, 62–64 etc. The specific research results can be found in related papers.…”

Simulation of VSPT Experimental Cascade under High and Low Free-Stream Turbulence Conditions

“…The blades were attached to a disk that can be rotated to set inlet flow angles (from axial) in the range −17° ≤ β 1 ≤ +78.8°. During this test, ten incidence angles were examined 10,11 . Detailed three-dimensional flow field data were acquired at incidence angles of +5.8° (β 1 = +40.0°) and −36.7° (β 1 = −2.5°), which represent the cruise and takeoff flight mission points, respectively.…”

“…Nearly laminar flow was obtained by running the tunnel without the turbulence grid. High tunnel free stream turbulence is obtained by utilizing an upstream blowing grid located roughly 5 axial chords upstream of the blade row 11 . Some of the high free stream turbulence conditions are also transitional.…”