Laser sheet tomography apparatus for flow field statistics
AssigneeEn'Urga, Inc.
InventorsYudaya R. Sivathanu, Rony K. Joseph
Life of this patent
Estimating the term…
Abstract
Laser sheet tomography is employed to determine flow field statistics in non-steady and steady flow at high repetition rates. The laser sheet tomography system is divided into two independent optical portions, the laser illuminator and the laser imager. As an absorption instrument, the laser illuminator can be shone directly into the laser imager, or if desired, the two portions can be positioned orthogonally to each other with the laser imager observing the scattered light. The observed light is correlated with known variations in laser intensity of the imager to generate transmittance data from which asymmetry ratios and probability density functions of local absorption coefficients can be computed at time repetition rates of 200 Hz and greater.
Claims22
Apparatus for the non-invasive measurement of characteristics of a gas flowing through a plane within a defined region, the apparatus comprising:
- a laser illuminator for generating laser radiation including a lens system for directing the radiation into said plane and through said defined region as a collimated sheet,
- a second lens system for collecting optical radiation traveling in said plane through said defined region, the second lens system having an optical output,
- an array of n rows of pixels, each row containing K pixels, the array being positioned with respect to the second lens system to receive the optical output of the second lens system and generating a voltage signal indicative thereof, and
- an analyzer coupled to the array of pixels for periodically sampling the voltage signal, the analyzer including computational capacity to compute statistical information relating to the voltage signal output from the array of pixels characteristic of said flowing gas as it passes through said plane, the analyzer including means for computing an asymmetry ratio, As, in accordance with the relation:
- A s = ∑ i = 1 K ( τ i - τ nK + 1 - i ) 2
- where τi is the transmission measured at pixel i in a row of the array.
Apparatus for the non-invasive measurement of characteristics of a gas flowing through a plane within a defined region, the apparatus comprising:
- a laser illuminator for generating laser radiation including a lens system for directing the radiation into said plane and through said defined region as a collimated sheet,
- a second lens system for collecting optical radiation traveling in said plane through said defined region, the second lens system having an optical output,
- an array of n rows of pixels, each row containing K pixels, the array being positioned with respect to the second lens system to receive the optical output of the second lens system and generating a voltage signal indicative thereof,
- an analyzer coupled to the array of pixels for periodically sampling the voltage signal, the analyzer including computational capacity to compute statistical information relating to the voltage signal output from the array of pixels characteristic of said flowing gas as it passes through said plane, the analyzer including means for computing an asymmetry ratio, As, in accordance with the relation:
- A s = ∑ i = 1 K ( τ i - τ nK + 1 - i ) 2
- where τi is the transmission measured at pixel i in a row of the array, and
- a drive circuit coupled to the laser illuminator providing a periodic signal to the laser illuminator causing a periodic variation in intensity of the laser radiation generated thereby, the drive circuit being coupled to the analyzer so that the periodic sampling of the voltage signal output from the array of pixels is synchronized with the periodic variation in intensity of the laser radiation emitted by the laser illuminator.
A method for non-invasively measuring characteristics of a gas flowing through a plane within a defined region, the method comprising the steps of:
- directing laser radiation through a lens system into said plane and through said defined region as a collimated sheet,
- collecting optical radiation traveling in said plane through said defined region with a second lens system having an optical output,
- receiving the optical output of the second lens system with an array of n rows of pixels, each row containing K pixels, and generating a voltage signal indicative thereof,
- periodically sampling the voltage signal output from the array of pixels with an analyzer including computational capacity to compute statistical information relating to the voltage signal output with a characteristic of said flowing gas as it passes through said plane, and
- computing an asymmetry ratio, As, in accordance with the relation:
- A s = ∑ i = 1 K ( τ i - τ nK + 1 - i ) 2
- where τi is the transmission measured at pixel i in a row of the array.
Dependencies are inferred from the claim text.