Project Title:

Fiber Optic Sensors for Long Wavelength Pyrometry andThermometry

  94-1    01.03     9806      

 Fiber Optic Sensors for Long Wavelength Pyrometry and
Thermometry

Abstract:

Radiation pyrometry and thermometry combined with fiber optics
provide powerful sensors for determining surface and gas
temperatures in otherwise unaccessible locations. However,
several applications require that temperature measurements be
made in the long-wavelength infrared (LWIR) where widely-used
silica fibers are non-transmissive. For example, gas turbine
engines components are being fabricated from ceramic materials or
are often coated with ceramic thermal barrier coatings which have
low, variable emissivities at shorter wavelengths. Therefore,
temperature measurements would be more accurate and reproducible
in the LWIR where the emissivities are typically high and stable.
A second example is measurement of gas temperatures where the
dynamic range must be extended to lower temperatures. In this
case, shorter wavelength sensors suffer as the peak of the Planck
function shifts to longer wavelengths. This program will involve
the development and testing of novel fiber optic radiometric
temperature sensors that operate in the LWIR. The key innovation
is the use of hollow sapphire waveguides to carry radiation from
the sensing point to the detector. Hollow sapphire waveguides are
suitable for use at high temperatures and transmit in the LWIR;
no currently available solid-core fibers offer this combination
of features. 

The development of hollow sapphire waveguide-based radiometric
temperature sensor would extend the applicability of LWIR
pyrometry to applications where limited optical access would
otherwise preclude this type of measurement. This will be of
particular benefit to measuring temperatures of turbine engine
components coated with ceramic thermal barrier coatings which
have low and variable emissivities at shorter wavelengths. The
proposed technology will also extend the capabilities of fiber
optic gas thermometers by providing an increased dynamic range
with a single sensor. 

Key Words

Advanced Fuel Research, Inc.
87 Church Street
East Hartford, CT 06108