Strut Design for an Extended Operating Range of Industrial Gas Turbine Exhaust Diffusers

Abstract

One of the main requirements for modern gas turbines (GTs) is load-flexible operation at both high efficiencies and low emission rates. Typically, older GT generations are not designed for such operating conditions, which is why their efficiency often drops sharply at off-design condition. Hence, a modernization of the individual GT components is crucial. This work contributes by strut design for an extended operating range of industrial gas turbine exhaust diffusers. Obstacles within the diffuser system, so-called support struts, have been identified as a key factor to the improvement of overall diffuser efficiency. By their interaction with the turbine s load-dependent exit flow profiles, they define the shape of the diffuser performance map and thus the overall efficiency. Geometric variations, such as staggering, sweep, dihedral and discharge boreholes, were investigated with regard to their influence on the diffuser performance characteristics from low partial to high overload condition. Performance maps for 29 different diffuser configurations, incorporating 20 different strut designs, result from this work. The numerical results are supported by experimental validation.