Experimental Aerodynamic Investigations of the 100-MW Two-Shaft Gas Turbine Unit Exhaust Duct

The article describes the results from experimental investigations into the exhaust duct aerodynamics of a stationary two-shaft gas turbine unit (GTU) intended for operation in a combined-cycle plant equipped with a heat-recovery steam generator. The experiments were carried out at the Kirillov Turbine Construction Laboratory of Peter the Great Polytechnic University (SPbPU). The aim of investigations was to experimentally determine the 3D flow structure in the diffuser–exhaust hood flow path and its integral characteristics during operation in combination with the topping turbine stage. The pressure recovery factors and the energy loss coefficients in the diffuser and in the exhaust duct are determined. The circumferential and radial distributions of the 3D flow parameters in the diffuser inlet section are presented. Based on the experimental investigation results obtained for the exhaust duct operating jointly with the topping stage, the main energy loss sources in the duct are determined, and recommendations for improving its aerodynamics are given. A comparative analysis of the exhaust duct’s integral aerodynamic characteristics and of the flow structure parameters obtained during the tests with and without the topping stage is carried out. The results obtained from the comparative analysis of the data obtained in the experiments with the connected topping stage and with the isolated exhaust duct were used for working out recommendations on modeling the stream in the flow paths of two-shaft GTU exhaust ducts.