Clocking and Potential Effects in Combustor–Turbine Stator Interactions

Tommaso Bacci,Michal Piotrowicz,Pawel Flaszynski

doi:10.3390/aerospace8100285

Tommaso Bacci, Michal Piotrowicz

Open Access

https://doi.org/10.3390/aerospace8100285

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Abstract

Investigations of combustors and turbines separately have been carried out for years by research institutes and aircraft engine companies, but there are still many questions about the interaction effect. In this paper, a prediction of a turbine stator’s potential effect on flow in a combustor and the clocking effect on temperature distribution in a nozzle guide vane are discussed. Numerical simulation results for the combustor simulator and the nozzle guide vane (NGV) of the first turbine stage are presented. The geometry and flow conditions were defined according to measurements carried out on a test section within the framework of the EU FACTOR (full aerothermal combustor–turbine interactions research) project. The numerical model was validated by a comparison of results against experimental data in the plane at a combustor outlet. Two turbulence models were employed: the Spalart–Allmaras and Explicit Algebraic Reynolds Stress models. It was shown that the NGV potential effect on flow distribution at the combustor–turbine interface located at 42.5% of the axial chord is weak. The clocking effect due to the azimuthal position of guide vanes downstream of the swirlers strongly affects the temperature and flow conditions in a stator cascade.

Highlights

The development of autonomous air vehicles with distributed engine control systems is one of the current trends in aviation
It was shown that the nozzle guide vane (NGV) potential effect on flow distribution at the combustor–turbine interface located at 42.5% of the axial chord is weak
The results presented in the paper were obtained for Spalart–Allmaras (SA) and Explicit Algebraic Reynolds Stress Model (EARSM) turbulence models [22,23]

Summary

Introduction

The development of autonomous air vehicles with distributed engine control systems is one of the current trends in aviation. The DLR test rig is a large facility including a combustor simulator and turbine stage, while at the University of Florence a tri-sector rig (three swirlers and six nozzle guide vanes downstream) is available In both cases, measurements were carried out in a combustor simulator representing the typical outlet profiles of modern low NOx combustion chambers, but operating without combustion to enable precise flow field measurements. It was found that the NGV potential effect does not alter temperature patterns, while a significant radial and azimuthal mass flow redistribution was observed up to about 25% of the axial chord length upstream of the vanes The investigations for this configuration reported by [13] show the limitations of the standard method of designing a turbine by using a constant inlet profile rather than combined combustor–turbine models. Due to the convergent (conical) shape of the inner wall and the cobra configuration of the probe, about 6 mm had to be left unexplored (Figure 1, focus on plane 40 area)

Numerical Model Description

Combustor Simulator—Numerical Model Validation

Conclusions

Findings

Further Work