Augmentation of Stagnation Region Heat Transfer Due to Turbulence From an Advanced Dual-Annular Combustor

Abstract

Heat transfer measurements have been made in the stagnation region of a flat plate with an elliptical leading edge. The radius of curvature at the stagnation point was similar to that of a first stage turbine vane airfoil used in a large commercial high-bypass turbofan engine. The airfoil was mounted downstream of an arc segment of a dual-annular combustor similar to the type used in an advanced turbine engine. Testing was done in air at atmospheric temperature and at pressures up to 376 kPa to simulate the vane leading edge Reynolds number seen in the engine. Spanwise average stagnation region heat transfer was measured with an electrically heated aluminum strip. Turbulence intensity, length scale and isotropy were measured using standard 2-wire hot wire probes. The combustor contained two annular rows of fuel-air swirlers which were aligned in the radial direction. Both heat transfer and hot wire data were taken at two circumferential positions; one directly downstream of a pair of swirlers and one half way between two pairs of swirlers. Reynolds number based on vane leading edge diameter was varied from 51000 to 160000. The maximum Reynolds number for turbulence measurements was limited to 87000. Turbulence intensity averaged over all test conditions was found to be 31.6%. Average axial, integral length scale was 1.29 cm, which gave a length scale-to-leading edge diameter ratio of 1.08. The turbulence was found to be nearly isotropic with the average ratio of axial to circumferential fluctuating components of 1.15. Heat transfer augmentation above laminar levels was found to vary from 34 to almost 59% depending on the Reynolds number. No effect of circumferential position was found. The heat transfer augmentation was found to be well predicted by a correlation derived from grid generated turbulence.

Experimental Evaluation of an Inlet Profile Generator for High-Pressure Turbine Tests

“…The A summary of the measured turbulence intensities and length scales for three of the isothermal tests is shown in Table 3. The measured turbulence intensities were found to be in an elevated range from 20% < Tu < 30%, which is consistent with real combustor exit flows as reported by Cameron et al [7], Goebel et al [20], and Van Fossen and Bunker [13]. The main difference between these three tests was the position (porosity) of the center shutter at the inlet of the central chamber.…”

“…It was also shown that the effect of temperature non-uniformities at the combustor exit was to reduce the overall cooling effectiveness on the vane by as much as 21%. Van Fossen and Bunker [13] studied heat transfer augmentation in the stagnation region of a flat plate with an elliptical leading edge. The test article was located downstream of an arc segment of a dual-annular combustor.…”

Effects of High Intensity, Large-Scale Freestream Combustor Turbulence on Heat Transfer in Transonic Turbine Blades

“…The steady flowfield matches engine non-dimensional conditions (Mach number and Reynolds number) and the generated turbulence field, intensity and length scale, is consistent with recent reports from modern gas turbine engine combustors (Van Fossen and Bunker, 2002) and reports of turbulence decay through the first stage vane row Thole, 1998, 2000). The turbulence field simulates the core flow turbulence in the turbine, decoupling this turbulence from the turbulence in the wake.…”

“…Van Fossen and Bunker (2002) used a 60° section of a GE 90 dual-annular combustor in a wind tunnel to model the exit flow of a combustor, including inlet swirl vanes, film cooling holes and dilution holes. All three of these combustor components contribute strongly to the combustor exit turbulence conditions.…”

On the Influence of High Turbulence on the Convective Heat Flux on the High-Pressure Turbine Vane LS89

“…In fact, Laser Doppler anemometry measurements by Goldstein et al [3] at the exit of a can-type combustor resulted in turbulence levels in the order of 15-20%. Additionally, Van Fossen and Bunker [4,5] also surveyed the outlet flow of a similar combustor measuring very high levels of turbulence intensity (up to 30%) and integral length scales (~3 cm). These elevated levels of combustor generated freestream turbulence are extremely challenging for research turbine inlet guide vane testing facilities.…”