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US 8,896,836 B1Granted
Fluid properties measurements using wavelength modulation spectroscopy with first harmonic detection
AssigneeSouthwest Sciences Incorporated
InventorsShin-Juh Chen, Joel A. Silver
Life of this patent
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Abstract
An apparatus and method for monitoring gas velocity, temperature, and pressure in combustion systems and flow devices, in particular at inlets and isolators of scramjet engines. The invention employs wavelength modulation spectroscopy with first harmonic detection and without the need to scan the full absorption spectra.
Claims20
A method for non-intrusively obtaining the local velocity, pressure, and temperature of a gas, the method comprising the steps of:
- emitting two beams of laser light directed at two different angles across a flow of the gas;
- separately detecting the two beams;
- determining first harmonic line shapes from the detected beams using wavelength modulation spectroscopy and a pair of single point measurements by a computer;
- calculating gas velocity and pressure from wavelength shifts of the line shapes by the computer;
- and
- calculating gas temperature from slopes of the line shapes by the computer;
- wherein wavelength of the two beams is alternated between two fixed wavelengths;
- and having an additional signal channel to provide reference zero-velocity and reference pressure.
5 more elements
An apparatus for non-intrusively obtaining the local velocity, pressure, and temperature of a gas, said apparatus comprising:
- two emitters of beams of laser light directed at two different angles across a flow of the gas;
- detectors for the two beams;
- a computer determining first harmonic line shapes from the detected beams using wavelength modulation spectroscopy and a pair of single point measurements, calculating gas velocity and pressure from wavelength shifts of the line shapes, and calculating gas temperature from slopes of the line shapes;
- a laser controller alternating wavelength of the two beams between two fixed wavelengths;
- and
- a reference cell providing reference zero-velocity and reference pressure.
3 more elements
Dependencies are inferred from the claim text.