Gas turbine commissioning and intake design for utilization of exhaust gas recirculation using computational fluid dynamics

Abstract

As Earth's climate changes at a rapid pace, the power generation industry is exploring ways to reduce carbon emissions without significantly affecting the operation of the existing gas turbine fleet which accounts for a large amount of the industry's output. This research investigates the reduction of carbon emissions from a 3.5 MWe Solar Turbines Centaur 40 power generation gas turbine by implementing exhaust gas recirculation (EGR) in conjunction with carbon capture technologies. This thesis focuses on integrating recirculated exhaust into the gas turbine's air intake system, with emphasis on the design of the exhaust gas recirculation (EGR) mixer and the commissioning of supporting sub-systems for a future experimental setup. This work is split into two sections: EGR mixer design using numerical analysis and commissioning gas turbine experimental test skid. An EGR mixer will ensure minimal flow distortions and even distribution of exhaust gas at the compressor inlet. The EGR mixer design began with research into similar applications but ultimately resulted in the design of a non-intrusive injection method. Three EGR inlet methods were tested to determine how injection geometry impacts mixing and distorts inlet guide van (IGV) flow. An EGR inlet size sweep was conducted to determine the optimal geometry. The models were then tested using Computational Fluid Dynamics (CFD) simulations, where mixing effectiveness was evaluated and quantified using the Coefficient of Variance (COV), along with pressure and mass flow distortion metrics. Results were measured at the package inlet as well as the IGV plane. It was found that method of injection does affect mixing effectiveness, with increased injection pressure resulting in better mixing. A wide injection method, spanning an entire duct length, provides the best tradeoff for minimizing flow distortions while maintaining a well-mixed flow. As regards to the commissioning activities, the intake ducting was designed to meet specifications from Solar Turbines while conforming to lab restrictions within the Colorado State University Energy Campus. Future EGR implementation also had to be considered. Structural integrity assessments and intake duct pressure drop calculations were conducted to verify compliance with manufacturer specifications. A custom filter box and angled duct sections were designed to fit the building structure and accommodate the constraints of the lab space. Enclosure ventilation, purge and drain systems were also designed to meet Solar Turbines specifications, while still conforming to our lab space. Design decisions and hardware specifications of these subsystems are described in this thesis.