In recent years, the energy market undergoes massive changes towards renewable energies. One transition technology to catch up grid fluctuations are gas turbines. One way to cope fast power changes for the gas turbine can be the state-of-the-art application of wet compression. Therefore, water is injected upstream of the compressor inlet, subsequently evaporating throughout the compressor section. This procedure cools the air by evaporative cooling, hence approaching isothermal compression.A further technology is the application of the so called Interstage Injection by injecting in between the stage. One advantage is the avoidance of icing in the first stages as local temperatures are above melting point. Moreover, stage characteristics and load distribution can be adjusted by injecting at several positions of the compressor. Installing the injection at several positions can lead to a more uniform spray distribution, consequently optimizing the evaporation process by the presence of smaller droplets and therefore being less coagulated and deposited on the blades and the casing. In order to investigate previous mentioned effects, an experimental four-stage axial compressor has been enhanced for the injection behind the first stage. Applying twin jet nozzles inside 3D-printed stator blades are found to be a compact and effective injection method for a homogenous spray distribution between the stages.In this paper, the potential of Interstage Injection is assessed by comparing the operating behaviour under “wet” and “dry” conditions. The influence on overall and stage performance, such as pressure ratio, mass flow and torque input are evaluated at different rotational speeds and different water to air ratios.

Evaluation of Performance Gain by Interstage Injection in a Four-Stage Axial Compressor

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

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