Fiber optic sensors for gas turbine control

An apparatus for detecting flashback occurrences in a premixed combustor system having at least one fuel nozzle includes at least one photodetector and at least one fiber optic element coupled between the at least one photodetector and a test region of the combustor system wherein a respective flame of the fuel nozzle is not present under normal operating conditions. A signal processor monitors a signal of the photodetector. The fiber optic element can include at least one optical fiber positioned within a protective tube. The fiber optic element can include two fiber optic elements coupled to the test region. The optical fiber and the protective tube can have lengths sufficient to situate the photodetector outside of an engine compartment. A plurality of fuel nozzles and a plurality of fiber optic elements can be used with the fiber optic elements being coupled to respective fuel nozzles and either to the photodetector or, wherein a plurality of photodetectors are used, to respective ones of the plurality of photodetectors. The signal processor can include a digital signal processor

Fiber optic sensors for gas turbine control

An apparatus for detecting flashback occurrences in a premixed combustor system having at least one fuel nozzle includes at least one photodetector and at least one fiber optic element coupled between the at least one photodetector and a test region of the combustor system wherein a respective flame of the fuel nozzle is not present under normal operating conditions. A signal processor monitors a signal of the photodetector. The fiber optic element can include at least one optical fiber positioned within a protective tube. The fiber optic element can include two fiber optic elements coupled to the test region. The optical fiber and the protective tube can have lengths sufficient to situate the photodetector outside of an engine compartment. A plurality of fuel nozzles and a plurality of fiber optic elements can be used with the fiber optic elements being coupled to respective fuel nozzles and either to the photodetector or, wherein a plurality of photodetectors are used, to respective ones of the plurality of photodetectors. The signal processor can include a digital signal processor

Correlation property of length sequences based on global structure of complete genome

This paper considers three kinds of length sequences of the complete genome. Detrended fluctuation analysis, spectral analysis, and the mean distance spanned within time $L$ are used to discuss the correlation property of these sequences. The values of the exponents from these methods of these three kinds of length sequences of bacteria indicate that the long-range correlations exist in most of these sequences. The correlation have a rich variety of behaviours including the presence of anti-correlations. Further more, using the exponent $\gamma$, it is found that these correlations are all linear ($\gamma=1.0\pm 0.03$). It is also found that these sequences exhibit $1/f$ noise in some interval of frequency ($f>1$). The length of this interval of frequency depends on the length of the sequence. The shape of the periodogram in $f>1$ exhibits some periodicity. The period seems to depend on the length and the complexity of the length sequence.Comment: RevTex, 9 pages with 5 figures and 3 tables. Phys. Rev. E Jan. 1,2001 (to appear

Intrinsically Tuning the Electromechanical Properties of Elastomeric Dielectrics:A Chemistry Perspective

Dielectric elastomers have the capability to be used as transducers for actuation and energy harvesting applications due to their excellent combination of large strain capability (100–400%), rapid response (10−3 s), high energy density (10–150 kJ m−3), low noise, and lightweight nature. However, the dielectric properties of non‐polar elastomers such as dielectric permittivity ε r , breakdown strength E b , and dielectric loss ε ″, need to be enhanced for real world applications. The introduction of polar groups or structures into dielectric elastomers through covalently bonding is an attractive approach to ‘intrinsically’ induce a permanent polarity to the elastomers, and can eliminate the poor post‐processing issues and breakdown strength of extrinsically modified materials, which have often been prepared by incorporation of fillers. This review discusses the chemical methods for modification of dielectric elastomers, such as hydrosilylation, thiol‐ene click chemistry, azide click chemistry, and atom transfer radical polymerization. The effects of the type and concentration of polar groups on the dielectric and mechanical properties of the elastomers and their performance in actuation and harvesting systems are discussed. State‐of‐the‐art developments and perspectives of modified dielectric elastomers for deformable energy generators and transducers are provided

Real-Time B-Scan Ultrasonic Imaging Using a Digital Phased Array System for NDE

Phased array systems for electronically steering and focusing ultrasonic fields have been used extensively in medical imaging since the late 1970’s. Despite the advantages of these systems (rapid redirection of beams, dynamic focusing to improve depth-of-field, and reduced mechanical complexity), phased arrays have been used very little for materials characterization. The reason for this lack of phased array technology in materials characterization is simply the wide range of velocity of sound encountered when working with materials and the resulting complexity in the beam former (the electronic system that appropriately delays and sums signals from individual elements of an array to produce a steered, focused beam) of a phased array system that can image in a wide variety of materials. Most medical phased array systems have analog beam formers which are hard-wired assuming the velocity of sound in soft tissue (1.54 mm/μsec), and therefore cannot be easily used to image in metals where the velocity of longitudinal sound waves is 3 or 4 times the velocity in soft tissue. At GE Corporate Research & Development (CRD) we have constructed a phased array system which uses a completely programmable digital beam former. This system provides exceptional flexibility for phased array imaging in a wide variety of materials; allowing focusing and steering using either the longitudinal or transverse wave velocity for any material.</p

Real-Time B-Scan Ultrasonic Imaging Using a Digital Phased Array System for NDE

Phased array systems for electronically steering and focusing ultrasonic fields have been used extensively in medical imaging since the late 1970’s. Despite the advantages of these systems (rapid redirection of beams, dynamic focusing to improve depth-of-field, and reduced mechanical complexity), phased arrays have been used very little for materials characterization. The reason for this lack of phased array technology in materials characterization is simply the wide range of velocity of sound encountered when working with materials and the resulting complexity in the beam former (the electronic system that appropriately delays and sums signals from individual elements of an array to produce a steered, focused beam) of a phased array system that can image in a wide variety of materials. Most medical phased array systems have analog beam formers which are hard-wired assuming the velocity of sound in soft tissue (1.54 mm/μsec), and therefore cannot be easily used to image in metals where the velocity of longitudinal sound waves is 3 or 4 times the velocity in soft tissue. At GE Corporate Research & Development (CRD) we have constructed a phased array system which uses a completely programmable digital beam former. This system provides exceptional flexibility for phased array imaging in a wide variety of materials; allowing focusing and steering using either the longitudinal or transverse wave velocity for any material