Improvement of a gas turbine exhaust hood and diffuser performance within spatial limitations

Authors

Natalia I Kuklina - Engineering Center “Center of Computer-Aided Engineering” of Peter the Great St. Petersburg Polytechnic University (SPbPU)
Maksim V Smirnov - Peter the Great St. Petersburg Polytechnic University (SPbPU)
Aleksandr A Sebelev - Engineering Center “Center of Computer-Aided Engineering” of Peter the Great St. Petersburg Polytechnic University (SPbPU)
Eugeniy A Volkov - Peter the Great St. Petersburg Polytechnic University (SPbPU)
Nikolay A Zabelin - Peter the Great St. Petersburg Polytechnic University (SPbPU)

Abstract

Gas turbine diffusers and exhaust hoods for power generation units are widely studied nowadays. Numerous designs exist as well as empirically derived ratios for optimal performance. Unfortunately, very few of them are appropriate while facing marine gas turbine exhaust hood design problem. The main restriction in their application is tightly limited space for diffuser and exhaust hood. Classical volute-type hoods, which are satisfactory for land power generation units with almost no space limitations, show poor performance in maritime power systems application. The main challenges are: 1) high pressure loss in hood; 2) high static pressure nonuniformity at the turbine outlet which may cause instability and failures; 3) low pressure recovery coefficient. Bend-type (elbow) hoods within spatial restrictions are prone to generate flow nonuniformity and unsteadiness. On this account, advanced exhaust hood design was proposed to address the abovementioned issues in space limited conditions. RANS CFD simulations were used for the hood enhancement. The first part of the numerical investigation in the current paper is based on isolated exhaust system (diffuser and hood). Then in order to capture the interaction effect between rotor and exhaust system and provide reliable results the two final best exhaust hood models were tested coupled with rotor. The novel exhaust hood design significantly increased pressure recovery coefficient. The paper summarizes recommendations on designing diffusers and exhaust hoods in spatial restrictions on the base of wide related literature overview and deliverables obtained by the authors.