Non-intrusive sensor for in-situ measurement of recession rate of ablative and eroding materials
View Patent ↗A non-intrusive sensor for in-situ measurement of recession rate of heat shield ablatives. An ultrasonic wave source is carried in the housing. A microphone is also carried in the housing, for collecting the reflected ultrasonic waves from an interface surface of the ablative material. A time phasing control circuit is also included for time-phasing the ultrasonic wave source so that the waves reflected from the interface surface of the ablative material focus on the microphone, to maximize the acoustic pressure detected by the microphone and to mitigate acoustic velocity variation effects through the material through a de-coupling process that involves a software algorithm. A software circuit for computing the location off of which the ultrasonic waves scattered to focus back at the microphone is also included, so that the recession rate of the heat shield ablative may be monitored in real-time through the scan-focus approach.
1. A non-intrusive sensor for in-situ measurement of recession rate of ablative and eroding materials, comprising:
a housing, which is mounted near an ablative material for which the recession rate is to be monitored;
an ultrasonic wave source carried in the housing;
a microphone, carried in the housing, for collecting the reflected ultrasonic waves from an interface surface of the ablative or eroding material;
a time phasing control circuit for time-phasing the ultrasonic wave source so that the waves reflected from the interface surface of the ablative material focus on the microphone, to maximize the acoustic pressure detected by the microphone, and
a circuit for computing the location off of which the ultrasonic waves scattered to focus back at the microphone,
whereby the recession rate of the heat shield ablative is monitored in real-time.
2. The non-intrusive sensor for in-situ measurement of recession rate of ablatives and eroding materials of claim 1 wherein the ultrasonic wave source is comprised of an annular concentric array of a plurality of piezoelectric ring resonators.
3. The non-intrusive sensor for in-situ measurement of recession rate of ablatives and eroding materials of claim 2 wherein the microphone, having at least one aperture, is arranged at the center of the concentric array of the plurality of piezoelectric ring resonators.
4. The non-intrusive sensor for in-situ measurement of recession rate ablatives and other eroding materials of claim 3 wherein the microphone has a frequency response curve optimized for the resonating frequency of the piezoelectric rings.
5. The non-intrusive sensor for in-situ measurement of recession rate ablatives and eroding materials of claim 2 wherein the plurality of piezoelectric ring resonators is comprised of 6 piezoelectric rings.
6. The non-intrusive sensor for in-situ measurement of recession rate of ablatives and other eroding materials of claim 5 wherein the response curve of each ring is maximized by real-time time-shift tuning, such that the sensor auto-compensates for temperature effects on the ablative material being real-time monitored.
7. The non-intrusive sensor for in-situ measurement of recession rate ablatives and eroding materials of claim 2 wherein the plurality of piezoelectric ring resonators is comprised of 12 piezoelectric rings.
8. The non-intrusive sensor for in-situ measurement of recession rate ablatives and other eroding materials of claim 2 wherein the plurality of piezoelectric ring resonators each have a predetermined width, and wherein the rings are spaced apart from each other.
9. The non-intrusive sensor for in-situ measurement of recession rate of heat shield ablatives of claim 8 wherein the predetermined width is 0.020 inches.
10. The non-intrusive sensor for in-situ measurement of recession rate ablatives and other eroding materials of claim 2 wherein the plurality of piezoelectric ring resonators each have a predetermined width, and wherein the rings are spaced apart from each other, the width of each ring being selected so that the surface area of each ring is the same.
11. The non-intrusive sensor for in-situ measurement of recession rate ablatives and other eroding materials of claim 2 wherein the plurality of piezoelectric ring resonators each have a predetermined width, and wherein the rings are spaced apart from each other so as to minimize cross-talk, to isolate each ring from the other rings.
12. The non-intrusive sensor for in-situ measurement of recession rate of ablatives and other eroding materials of claim 2 wherein the plurality of piezoelectric ring resonators each have the same predetermined width, and wherein the rings are spaced apart from each by the predetermined width.
13. The non-intrusive sensor for in-situ measurement of recession rate of ablatives and other eroding materials of claim 2 wherein the plurality of piezoelectric ring resonators are mounted on a substrate material that can serve as electrical ground if electrically conductive, and including filler material to mitigate against back resonance.
14. The non-intrusive sensor for in-situ measurement of recession rate of ablatives and other eroding materials of claim 13 wherein insulated wires bonded to the opposite end of each ring with respect to the substrate serving as common ground, which were conductively connected to the time-phasing control circuit.
15. The non-intrusive sensor for in-situ measurement of recession rate of ablatives and other eroding materials of claim 14 further including a wear plate connected to the housing on top of the array of rings, to seal the piezoelectric rings from the environment, the wear plate having an opening corresponding to the location of the microphone, and whereas the wear plate can be comprised of single or multi-layer construction, made of a variety of common materials, optimized to coupling the acoustic signal into the ablative material of interest.
16. The non-intrusive sensor for in-situ measurement of recession rate of ablatives and other eroding materials of claim 1 , wherein the sensor may be surface mounted for directing the ultrasonic waves generated by the ultrasonic wave source toward the ablative material for which the recession rate is to be measured.
17. The non-intrusive sensor for in-situ measurement of recession rate of ablatives and other eroding materials of claim 16 wherein the sensor is surface mounted near, but not in direct contact with the ablative material to be monitored, given that acoustic waves can propagate through the added material and into the ablative material of interest with minimum loss.
18. The non-intrusive sensor of claim 1 wherein the microphone has dual apertures, the dual apertures permitting cross-correlation of the dual aperture signals to determine departures from a baseline, which allows for distinguishing if the recession or erosion at the local area of measurement is non-laminate in nature.
19. The non-intrusive sensor of claim 1 further including real-time feedback control, which combines signal processing and dynamic time-shifting to perform scan-focus and track the interface, the algorithm for acoustic velocity compensation is:
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