Gas turbines are important tools in the global push for efficient use of our energy resources and to minimize the environmental impact. Whether used for aircraft or marine propulsion, oil and gas production, peaking or balancing power generation, or baseload power generation, gas turbines of all sizes rely on the same core technologies to improve efficiency and reliability while reducing emissions.
The Gas Turbine Laboratory (GTL) moved to The Ohio State University in 1995 from Calspan Corporation, where it had been working on these challenges since 1976. Until 1997, the principal emphasis of the effort had been on aerodynamics and heat transfer associated with full-scale turbine stages operating at design corrected conditions. In 1997 the group at GTL initiated design and construction of in-ground spin pit facilities that could be used to obtain aeromechanics research for engine components operating at engine speed and interacting with the stationary shroud.
Detailed measurements for turbine stages operating at properly scaled conditions have provided valuable insights into the relevant flow physics as well as a benchmark for evaluating the accuracy of computational fluid dynamics (CFD) tools. The facility used to perform these measurements is a very large blowdown facility capable of handling multi-stage turbines of diameter up to approximately 36-inches. In addition, several programs have been run using this facility for which the turbine stage is fully cooled and purge flow is provided to the disk cavity. A combustor emulator has been designed and incorporated that allows experimental simulation of the desired high-pressure turbine vane inlet temperature profile.
The lessons of the aeromechanics research performed for engine speed conditions have been successfully incorporated into prediction codes, and significant advancements in the ability of the industry to correctly predict the resulting blade behavior has been demonstrated. The spin pit facilities now include an in-ground compressor facility and an in-ground fan facility. A very large in-ground facility capable of running a bladed disk that is 14-ft. in diameter is currently under construction, representing a $1.2M infrastructure investment at ARC.
The demand for higher fuel efficiency and reduced noise continues to push the trend of increasingly larger bypass ratio turbofan engines with increasingly higher turbine inlet temperature. These trends in aircraft propulsion have levied increasing demands on the turbine (hot) section of modern turbofan engines and on the low-pressure turbine efficiency and work output. Additionally, growth markets for turbofan engines have moved from North America and Europe to the Middle and Far East. Air quality concerns in these new markets are presenting increasing hardship for turbines as airborne deposits collect in cooling passages in gas turbines and reduce performance. To address these issues, two new areas of research have been initiated at the ARC in recent years. The first area focuses on improving low-pressure turbine efficiency using various applications of flow control to reduce both profile and end-wall losses. This work is accomplished in two low-pressure turbine linear cascade facilities at ARC: a large-scale, low-speed facility with simulated unsteady vanes and a smaller-scale, high-speed (transonic) facility. The transonic cascade simulates the flow in higher-work turbines like the Geared Turbofan from Pratt/Whitney. The second area focuses on the issue of harsh operating environments and high temperature. A unique Turbine Reacting Flow Rig (TuRFR) was constructed at ARC in 2008 that simulates the flow exiting a gas turbine combustor as it impacts the first stage turbine nozzle guide vanes. An exciting new development is the design and construction of an upgraded and world class TuRFR facility that will operate at significantly higher temperatures and massflow rates (simulating more modern engine environment), representing a $2M infrastructure investment at ARC.
The faculty currently involved with the aerodynamic, heat transfer, and aeromechanics activity are Professor Michael Dunn and Assistant Professor Randall Mathison. Professor Jeffrey Bons is involved with the low-pressure turbine and high temperature and harsh environment research areas. Dr. Kiran D’Souza has expertise in structural dynamics, damage detection, reduced order modeling, and structural health monitoring.