REG NASA-LLIS-0514-1994 Lessons Learned - Intensity-Modulated Fiber Optic Microphone for Obtaining Measurements of Pressure Fluctuations in Hypersonic Flow Fields.pdf

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1、Lessons Learned Entry: 0514Lesson Info:a71 Lesson Number: 0514a71 Lesson Date: 1994-08-02a71 Submitting Organization: LARCa71 Submitted by: Bernard LewisSubject: Intensity-Modulated Fiber Optic Microphone for Obtaining Measurements of Pressure Fluctuations in Hypersonic Flow Fields Description of Dr

2、iving Event: The measurement of pressure fluctuations in hypersonic flow fields is much more demanding on dynamic pressure sensors than in traditional acoustical applications. Essential sensor specifications for measurement of pressure fluctuations in hypersonic flow are small size (0.02 in.), heigh

3、t temperature (20000F), frequency response (200 kHz), and 0.01-10 PSI dynamic range. The recent availability of high-temperature optical fibers makes the intensity-modulated fiber optic microphone a promising instrument for obtaining these measurements.Small sensor size is desirable to obtain high f

4、requency response and to reduce spatial averaging errors due to the finite size of the sensor. In order to minimize the correction factors needed to account for the latter, it is desirable to have a sensor diameter at least as small as 0.02 in. For measurements in hypersonic flow.One of the predomin

5、ant considerations in hypersonic flow is the high-temperature environment to which the sensors will be exposed. Thus, materials used to fabricate such sensors must be stable in the attendant environment.Sensors whose transduction is based on a material (piezoelectric, piezoresistive, magnetostrictiv

6、e, etc.) Cannot meet the high-temperature requirement with current technology. The condenser microphone has an inherent small-size limitation due to loadings by cable capacitance; further, if a polarization voltage is used, then the necessarily close proximity of the preamplifier to the microphone c

7、artridge will preclude operation at high temperatures. The recent availability of high-temperature optical fibers makes the intensity-modulated fiber optic microphone a promising instrument to fulfill the above requirements.Provided by IHSNot for ResaleNo reproduction or networking permitted without

8、 license from IHS-,-,-Lesson(s) Learned: The recent availability of high-temperature optical fibers makes the intensity- modulated fiber optic microphone a promising instrument for obtaining measurements of pressure fluctuations in hypersonic flow fields.Recommendation(s): For a complete description

9、 of an intensity-modulated fiber optic microphone, see the paper, “Fiber Optic Sensor for Measurements of Pressure Fluctuations at High Temperatures“, by Allan J. Zuckerwar, NASA Langley Research Center. The paper appeared in the ICIASF 89 Record.Evidence of Recurrence Control Effectiveness: N/ADocu

10、ments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Research & DevelopmentAdditional Info: Approval Info: a71 Approval Date: 1997-04-02a71 Approval Name: Elijah C. Kenta71 Approval Organization: 421a71 Approval Phone Number: 757-864-3345Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-