Effect of Low-NOX Combustor Swirl Clocking on Intermediate Turbine Duct Vane Aerodynamics With an Upstream High Pressure Turbine Stage—An Experimental and Computational Study

Abstract

Flow in an intermediate turbine duct (ITD) is highly complex, influenced by the upstream turbine stage flow structures, which include tip leakage flow and nonuniformities originating from the upstream high pressure turbine (HPT) vane and rotor. The complexity of the flow structures makes predicting them using numerical methods difficult, hence there exists a need for experimental validation. To evaluate the flow through an intermediate turbine duct including a turning vane, experiments were conducted in the Oxford Turbine Research Facility (OTRF). This is a short duration high speed test facility with a 3/4 engine-sized turbine, operating at the correct nondimensional parameters for aerodynamic and heat transfer measurements. The current configuration consists of a high pressure turbine stage and a downstream duct including a turning vane, for use in a counter-rotating turbine configuration. The facility has the ability to simulate low-NOx combustor swirl at the inlet to the turbine stage. This paper presents experimental aerodynamic results taken with three different turbine stage inlet conditions: a uniform inlet flow and two low-NOx swirl profiles (different clocking positions relative to the high pressure turbine vane). To further explain the flow through the 1.5 stage turbine, results from unsteady computational fluid dynamics (CFD) are included. The effect of varying the high pressure turbine vane inlet condition on the total pressure field through the 1.5 stage turbine, the intermediate turbine duct vane loading, and intermediate turbine duct exit condition are discussed and CFD results are compared with experimental data. The different inlet conditions are found to alter the flow exiting the high pressure turbine rotor. This is seen to have local effects on the intermediate turbine duct vane. With the current stator–stator vane count of 32-24, the effect of relative clocking between the two is found to have a larger effect on the aerodynamics in the intermediate turbine duct than the change in the high pressure turbine stage inlet condition. Given the severity of the low-NOx swirl profiles, this is perhaps surprising.

Effect of a Combined Hot-Streak and Swirl Profile on Cooled 1.5-Stage Turbine Aerodynamics: An Experimental and Computational Study

“…The calibration technique and uncertainties are reported in Ref. [21]. The circumferential resolution (determined by the transient response of the probe and the traverse speed) was 0.7 deg or 3.7% of an IP vane pitch.…”

“…Some significant differences between predictions and experiments are therefore unsurprising (see also, for example, Ref. [21]). More accurate prediction of the effects of lean-burn inlet conditions on the IP vane flow would likely require highly accurate BCs (often impossible in practice, where the accuracy extends to unsteady components, for example) or higher fidelity numerical methods (computationally impractical for full-stage analysis).…”

“…More recently, Johansson et al [21] investigated the effects of swirler clocking on the aerodynamics of a low-turning intermediatepressure (IP) vane downstream of the MT1 HP stage in the OTRF. Results showed clear (but complex) changes in IP vane loading distributions and IP vane exit flow structure, which indicated that the effects of swirl persisted through the 1.5-stage turbine.…”

Influence of Swirl Clocking on the Performance of Turbine Stage with Three-Dimensional Nozzle Guide Vane

“…The very early concept of radial airfoil stacking was introduced about sixty years ago. Straight lean and compound lean have been recognized as an effective way to control the reaction, loading and secondary flows [3][4][5][6][7][8][9][10][11]. It has been reported that the straight lean and compound lean can reorganize the vortices and reduce the secondary flow loss.…”

Design, integration and operation of a rotating combustor-turbine-interaction test rig within the scope of EC FP7 project FACTOR

“…by (Andreini et al, 2016) or (Koupper et al, 2016) which were validated against data from a dedicated tri-sector test rig set-up in Florence, Italy (Bacci et al, 2018). Also early in the project, the LPT strut was designed and tested (Johansson et al, 2016).…”