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Materials For DE
TECHNOLOGY PRIMER
Materials often limit the ability to achieve
cost effective performance improvements in how we generate
and distribute electric power. Power producing equipment
is pushed to operate at higher pressures, higher
temperatures, and higher speeds. As these
demands increase, materials with improved properties
must be used or developed to achieve our goals.
Improved materials
are critical to the development of compact turbine driven electric
generators, or microturbines. In order to function
more efficiently and with less pollution,
turbines may operate at temperatures approaching
2500°F, and at speeds over 50,000 rpm. Materials with increased strength are needed to withstand these conditions
for long periods of time. Similar challenges
exist for other developing power generation applications
including fuels cells, gas fired reciprocating
engines, industrial turbines, and hybrid and
combined heat and power approaches. Improved
metal alloys, and new ceramic materials are being
considered for these applications. Moreover, as
materials are improved or developed, new manufacturing
methods are often required. The Advanced Materials
Program identifies materials and manufacturing
technologies required for power-generating equipment to meet more stringent efficiency,
life, emissions, and cost goals.
The development of ceramics and ceramic
composites is of particularly high priority. Advanced ceramic materials are being
incorporated into hot-sections (combustion and
hot-gas flow paths) of land-based industrial
gas turbines and microturbines in order to operate at higher temperatures, and subsequently comply with strict emission standards. Monolithic
Si3N4 and Si-based continuous
fiber ceramic composites (CFCCs) are the primary materials under consideration
for several different hot-section components.
Over the past several years, advancements
in the development of more environmentally stable
CFCCs and environmental
barrier coatings (EBCs) have resulted in the
use of these materials as combustor liners in
several microturbine engines. In order
to have lifetimes >25,000 h, however, considerable
materials development work must still be conducted. Research is underway
at Oak Ridge National Laboratory (ORNL) to characterize
the behavior of these materials and to develop
improved EBCs.
Advanced microturbines will
also require improved high-temperature performance
and reliability from their recuperators in order
to achieve higher efficiency. Metallic alloys with more oxidation/corrosion resistance
and tensile/creep strength at higher temperatures
must be developed for microturbine recuperators or, alternatively, a more expensive alloy with
better performance must be selected. ORNL is
working with microturbine manufacturers and materials
suppliers to develop advanced alloys for high
temperature recuperators.
Additional
information accessed in the quarterly progress reports and project descriptions.
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