Benefits of intercooling in power generating gas turbines can be maximized by reducing stagnation pressure loss in the intercooler flow path without adversely affecting the flow pattern in compressors. The intercooler-diffuser isolates the low pressure compressor from the intercooler, recovers the static pressure by decelerating the compressor discharge flow, and uniformly supplies low speed air to the intercooler for effective heat exchange. An experimental investigation was carried out to obtain data in a conceptual design with two sections: an outwardly canted prediffuser and a dump. The test-section was a one-fourth scale model of a typical industrial gas turbine. The diffuser flow is described in terms of the pressure recovery and loss coefficients, velocity vectors, static and stagnation pressure distributions, and the mean velocity and turbulence intensity profiles. The flow resistance by the intercooler was simulated to assess its effects on the upstream diffuser flow. The airflow rate was varied to obtain data at full and part-load operations. The inlet conditions corresponded to naturally developed axisymmetric annulus flow. Results show high stagnation pressure loss and distorted velocity profiles in the dump because of flow recirculation next to the casing. Pressure recovery was confined to the prediffuser and a tail-section downstream of the dump where the flow reattached. Results show that the diffuser flow was practically unaffected by the intercooler and by operation at part-load.

Flow development in an annular contraction is of fundamental and practical importance in various applications including the gas turbine systems. This paper describes an experimental study of flow characteristics in a curved wall annular contraction. The results are presented in terms of the velocity vectors, surface pressure coefficients, static and stagnation pressure distributions, and profiles of mean velocities, turbulence intensity, and Reynolds shear stress. The flow conditions at the entrance were varied to evaluate how they affected the flow development in the passage. Results show that the contraction produced uniform static pressure and axial velocity profiles at the exit plane. Higher inlet turbulence affected the Reynolds shear stress in the contraction although the change in the static and total pressure fields was insignificant. The overall stagnation pressure loss was only 2 to 3 percent of the dynamic head at the contraction exit plane. Results showing only typical data are included in this paper. More extensive data sets to validate computer codes are available from the authors.

Power generating gas turbines employ an inlet duct or contraction to accelerate air to the operating inlet velocity of the compressor. Multiple passages of this kind are necessary in gas turbines with cycle modifications such as intercooling. An experimental investigation was carried out to obtain flow characteristics of a curved wall annular contraction. The results are described in terms of the velocity vectors, surface pressure coefficients, static and stagnation pressure distributions, and profiles of mean velocities, turbulence intensity, and Reynolds shear stress. The upstream flow conditions were changed to evaluate how they affected the flow development in the passage. Results show that the static pressure and axial velocity profiles at the contraction exit were uniform. Higher inlet turbulence increased the Reynolds shear stress although the effect on the static and total pressure fields was negligible. The overall stagnation pressure loss was approximately 2 to 3 percent of the dynamic head at the contraction exit.