Session: 35-02 Turbine Transition Ducts

Paper Number: 122626

122626 - Impact of Lean on Aerodynamic Performance of a Turbine Rear Structure 

Jet engine components typically have constraints from multiple disciplines that must be considered. One such component is the turbine-rear-structure, situated aft of the low-pressure turbine in a jet engine. The primary aerodynamic function of the turbine-rear-structure is to de-swirl the flow from the low-pressure turbine. However, a turbine-rear-structure design must also take into account constraints related to structural integrity, manufacturing, assembly, and other functions. Due to these additional constraints, some turbine-rear-structures have vanes with large lean angles, sometime up to 30 degrees, with the pressure-side pointing inwards towards the inner end-wall. This is the subject of the present study.

Both experimental and numerical studies were conducted to evaluate the impact of large lean angles on the aerodynamics of a turbine-rear-structure. The experiments used an engine representative turbine-rear-structure with leaned vanes, designed by GKN Aerospace, Sweden. Test were performed in the LPT-OGV rig at Chalmers University of Technology. This test-facility is a large-scale low-speed rotating rig with an LPT stage upstream of the turbine-rear-structure. This provides realistic engine Reynolds numbers and inlet swirl profiles for a turbine-rear-structure. The instrumentation and experimental methods employed in the rig are presented. The experimental results provide valuable data for validating numerical methods used in industry.

The validation efforts revealed that the numerical methods employed in industry today can effectively replicate most of the physical phenomena observed in the measurements with leaned vanes. Simulations were performed using the commercial CFD solver FLUENT, with the kw-SST turbulence model incorporating a gamma-theta transition model. Flow structures observed in experiments were compared and discussed in relation to the numerical results. The adopted numerical method accurately captured the location of the passage vortex and the horseshoe vortex structures near the inner end-wall. The wakes and outlet swirl angles generated by leaned struts were captured with a high level of precision, differing by only 1.5 degrees.

Following a comprehensive validation of the numerical methods, a study was initiated to understand the aerodynamic distinctions between a radial vane design and a leaned vane design operating under the same flow conditions. A radial vane design was created by eliminating the lean angle from a leaned vane design. This modification resulted in a static pressure increase on the pressure side at the hub. Additionally, the results indicated that the horseshoe vortex at the hub shifted tangentially between the two cases analyzed.

The present work primarily discuss results at the design point. Future work will look at the flow behavior at off-design conditions.

Presenting Author: Srikanth Deshpande GKN Aerospace AB

Presenting Author Biography: Presently working as Aerodynamics Engineer at GKN Aerospace , Sweden

Authors:

Srikanth Deshpande GKN Aerospace AB
Mattia Ricchi GKN Aerospace AB
Jonas Larsson GKN Aerospace AB
Valentin Vikhorev Chalmers University of Technology
Valery Chernoray Chalmers University of Technology