Project No: FE0007382
Performer: University of Connecticut


Contacts

Richard A. Dennis
Technology Manager, Turbines
National Energy Technology Laboratory
3610 Collins Ferry Road
P.O. Box 880
Morgantown, WV 26507-0880
304-285-4515
richard.dennis@netl.doe.gov

Briggs White
Project Manager
National Energy Technology Laboratory
3610 Collins Ferry Road
P.O. Box 880
Morgantown, WV 26507-0880
304-285-5437
briggs.white@netl.doe.gov

Eric Jordan
Principal Investigator
Department of Mechanical Engineering
University of Connecticut
191 Auditorium Road
Storrs, CT 06269-3139
860-486-2371
jordan@engr.uconnn.edu

Duration
Award Date:  10/01/2011
Project Date:  09/30/2014

Cost
DOE Share: $498,886.00
Performer Share: $158,326.00
Total Award Value: $657,212.00

Performer website: University of Connecticut - http://www.engr.uconn.edu

Advanced Energy Systems - Hydrogen Turbines

Low Thermal Conductivity, High Durability Thermal Barrier Coatings for IGCC Environments

Project Description

The University of Connecticut, in cooperation with Pratt & Whitney and Siemens Energy, will use a novel solution precursor plasma spray (SPPS) process to deposit low thermal conductivity, high durability yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs) and to utilize surface protective layers (SPLs) to provide high temperature contaminant resistance and increased surface temperature capability, while minimizing the use of rare earth elements. The SPPS process provides a unique TBC microstructure that consists of through-thickness vertical cracks for strain tolerance, ultra-fine splats for spallation crack resistance, and the ability to produce very low thermal conductivities. The low thermal conductivities, or low-K (with K representing heat conductivity), will result from planar arrays of fine porosity called inter-pass boundaries (IPBs) and the ability to vary porosity content over wide ranges. The IPBs are generic conductivity lowering features that can be implemented for any TBC. Pratt & Whitney and Siemens Energy will contribute valuable specimens and will test the down-selected low-K TBCs.

The low-K YSZ TBC structure will be created using the SPPS process. Taguchi methods for design of experiments will be used to systematically determine the deposition parameters to minimize the thermal conductivity. Cyclic durability tests of the low-K TBC will be conducted to verify that the excellent durability of the SPPS TBC is preserved. A protective surface layer of gadolinium-zirconium will be added to the low-K YSZ TBC to increase the maximum allowable surface temperature by at least 100 degrees Celsius (°C) and improve its calcium-magnesium-alumina-silicate (CMAS) resistance, while minimizing the heavy use of rare earth elements. This improved contaminant resistance will be verified by testing in CMAS and moisture. Contaminant resistance will be further enhanced by employing two novel approaches, one using aluminum-titanium additions to the YSZ, and the other by deliberately adding calcium sulfate, shown to block CMAS when deposited by natural processes in service engines. The spallation failure mechanisms of the low-K TBC will be defined to provide guidance for subsequent improvements and a sound basis for life prediction methodologies.

Solution Precursor Plasma Spray Process.

Solution Precursor Plasma Spray Process.


Program Background and Project Benefits

Turbines convert heat energy to mechanical energy by expanding a hot, compressed working fluid through a series of airfoils. Combustion turbines compress air, mix and combust it with a fuel (natural gas, coal-derived synthesis gas [syngas], or hydrogen), and then expand the combustion gases through the airfoils. Expansion turbines expand a working fluid like steam or supercritical carbon dioxide (CO2) that has been heated in a heat exchanger by an external heat source. These two types of turbines are used in conjunction to form a combined cycle— with heat from the combustion gases used as the heat source for the working fluid— improving efficiency and reducing emissions. If oxygen is used for combustion in place of air, then the combustion gases consist mostly of carbon dioxide (CO2) and water, and the CO2 can be easily separated and sent to storage or used for Enhanced Oil Recovery (EOR). Alternatively, the CO2/steam combustion gases can be expanded directly in an oxy-fuel turbine. Turbines are the backbone of power generation in the US, and the diverse power cycles containing turbines provide a variety of electricity generation options for fossil derived fuels. The efficiency of combustion turbines has steadily increased as advanced technologies have provided manufacturers with the ability to produce highly advanced turbines that operate at very high temperatures. The Advanced Turbines program is developing technologies in four key areas that will accelerate turbine performance, efficiency, and cost effectiveness beyond current state-of-the-art and provide tangible benefits to the public in the form of lower cost of electricity (COE), reduced emissions of criteria pollutants, and carbon capture options. The Key Technology areas for the Advanced Hydrogen Turbines Program are: (1) Hydrogen Turbines, (2) Supercritical CO2 Power Cycles, (3) Oxy-Fueled Turbines, and (4) Advanced Steam Turbines.

Hydrogen turbine technology research is being conducted with the goal of producing reliable, affordable, and environmentally friendly electric power in response to the Nation's increasing energy challenges. NETL is leading the research, development, and demonstration of technologies to achieve power production from high hydrogen content (HHC) fuels derived from coal that is clean, efficient, and cost-effective; minimize carbon dioxide (CO2) emissions; and help maintain the Nation's leadership in the export of gas turbine equipment. These goals are being met by developing the most advanced technology in the areas of materials, cooling, heat transfer, manufacturing, aerodynamics, and machine design. Success in these areas will allow machines to be designed that have higher efficiencies and power output with lower emissions and lower cost.

The University of Connecticut, in cooperation with Pratt & Whitney and Siemens Energy, will use a novel solution precursor plasma spray (SPPS) process to deposit low thermal conductivity, high durability yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs) and to utilize surface protective layers (SPLs) to provide high temperature contaminant resistance and increased surface temperature capability, while minimizing the use of rare earth elements. Materials research conducted under the Advanced Turbine Program seeks to improve coating materials that will allow for higher temperature operation and increased durability. These improvements will improve turbine efficiency and reduce maintenance, leading to lower capital costs, reduced operating costs, and reduced costs of electricity for consumers.

Accomplishments