Feedback mechanism for smart nozzles and nebulizers

• US 20070299561A1
• Filed: 10/12/2005
• Published: 12/27/2007
• Est. Priority Date: 10/14/2004
• Status: Active Grant

• Current Assignee: George Washington University
• Original Assignee: George Washington University
• Inventors: Montaser, Akbar, Kahen, Kaveh, Jorabchi, Kaveh
• Granted Patent: US 7,483,767 B2
• Time in Patent Office: Days
• US Class Current: 700/283
• CPC Class Codes: B05B 12/082 responsive to a condition of the discharged jet or spray, e.g. to jet shape, spray pattern or droplet size
• CPC Class Codes: G01P 5/001 Full-field flow measurement, e.g. determining flow velocity and direction in a whole region at the same time, flow visualisation

Abstract

Nozzles and nebulizers that can be adjusted to produce an aerosol with optimum and reproducible quality based on the feedback information obtained using laser imaging techniques are provides. Two laser-based imaging techniques based on particle image velocimetry (PIV) and optical patternation are provided to map and contrast the size and velocity distributions for indirect and direct pneumatic nebulizations in plasma spectrometry. The flow field of droplets is illuminated by two pulses from a thin laser sheet with a known time difference. The scattering of the laser light from droplets is captured by a charge coupled device (CCD), providing two instantaneous images of the particles. Pointwise cross-correlation of the corresponding images yields a two-dimensional (2-D) velocity map of the aerosol velocity field. For droplet size distribution studies, the solution is doped with a fluorescent dye and both laser induced florescence (LIF) and Mie scattering images are captured simultaneously by two CCDs with the same field of view. The ratio of the LIF/Mie images provides relative droplet size information, which is then scaled by a point calibration method via a phase Doppler particle analyzer (PDPA). Two major outcomes are realized for three nebulization systems: 1) a direct injection high efficiency nebulizer (DIHEN); 2) a large-bore DIHEN (LB-DIHEN); and 3) a PFA microflow nebulizer with a PFA Scott-type spray chamber. First, the central region of the aerosol cone from the direct injection nebulizers and the nebulizer-spray chamber arrangement comprise fast (>13 m/s and >8 m/s, respectively) and fine (<10 μm and <5 μm, respectively) droplets as compared to slow (<4 m/s) and large (>25 μm) droplets in the fringes. Second, the spray chamber acts as a momentum separator, rather than a droplet size selector, as it removes droplets having larger sizes or velocities. Smart-tunable nebulizers may utilize the measured momentum as a feedback control for adjusting certain operation properties of the nebulizer, such as operating conditions and/or critical dimensions.

Claims

1. A feedback mechanism comprising:

an analytical system for performing an evaluation of at least one property of at least one of droplets, particles and aerosol; and

a feedback signal generator for generating a feedback signal based on the evaluation performed by the analytical system, the feedback signal facilitating optimization of at least one operational parameter of a source of the at least one of droplets, particles and aerosol.

2. The feedback mechanism as claimed in claim 1, wherein the at least one property comprises at least one of velocity, size, viscosity, or density.

3. The feedback mechanism as claimed in claim 1, wherein the source comprises at least one of a nebulizer or a nozzle.

4. The feedback mechanism as claimed in claim 3, wherein the nebulizer comprises a direct injection nebulization configuration or a nebulizer-spray chamber.

6. The feedback mechanism as claimed in claim 3, wherein the nozzle comprises a fuel injector or an inhaler.

7. The feedback mechanism as claimed in claim 1, wherein the analytical system comprises at least one of a two laser-based imager, a phase Doppler particle analyzer (PDPA) and a viscometer.

8. The feedback mechanism as claimed in claim 1, wherein the analytical system comprises:

a laser light delivery system for delivering at least two laser pulses to the at least one of droplets, particles and aerosol;

a detector for capturing at least one of a scattering of the laser pulses from the at least one of droplets, particles and aerosol, and a fluorescence from the at least one of droplets, particles and aerosol; and

an image acquisition unit for receiving and processing data from the detector.

9. The feedback mechanism as claimed in claim 8, wherein the laser light delivery system comprises:

a dual cavity frequency-doubled Nd;

YAG pulsed laser;

a mirror; and

a cylindrical lens;

wherein the dual cavity frequency-doubled Nd;

YAG pulsed laser, the mirror and the cylindrical lens are configured to generate a laser sheet

10. The feedback mechanism as claimed in claim 8, wherein the detector comprises a first charge coupled detector (CCD) arranged in a first optical path of the laser pulses scattered from the at least one of droplets, particles and aerosol.

11. The feedback mechanism as claimed in claim 8, wherein the detector further comprises a second charge coupled detector (CCD) arranged in a second optical path of the laser pulses to capture the fluorescence from the at least one of droplets, particles and aerosol, wherein the detector and the laser light delivery system are synchronized, and wherein the first and second CCDs capture an image essentially simultaneously.

12. The feedback mechanism as claimed in claim 11, wherein the detector further comprises:

a narrow band-pass filter configured in the first optical path between the first CCD and the at least one of droplets, particles and aerosol; and

a high-pass filter configured in the second optical path between the second CCD and the at least one of droplets, particles and aerosol.

30. A self-optimizing system comprising:

a feedback mechanism as claimed in claim 1;

a controller configured to receive the feedback signal; and

a source of the at least one of droplets, particles and aerosol;

wherein the controller adjusts the at least one operational parameter of the source based on the feedback signal.

31. The self-optimizing system as claimed in claim 30,wherein the source comprises a nebulizer, the nebulizer comprising a capillary having adjustable dimensions.

32. The self-optimizing system as claimed in claim 31, wherein the capillary comprises a ceramic, whereby the dimensions of the capillary are adjustable by the controller in response to a voltage applied to the capillary.

13. A method for generating feedback comprising:

performing an evaluation of at least one property of at least one of droplets, particles and aerosol; and

generating a feedback signal based on the evaluation, the feedback signal facilitating optimization of at least one operational parameter of a source of the at least one of droplets, particles and aerosol.

14. The method as claimed in claim 13, wherein the at least one property comprises at least one of velocity, size, viscosity or density.

15. The method as claimed in claim 13, wherein the source comprises at least one of a nebulizer or a nozzle.

16. The method as claimed in claim 15, wherein the nebulizer comprises a direct injection nebulization configuration or a nebulizer-spray chamber.

17. The method as claimed in claim 15, wherein the nozzle comprises a fuel injector or an inhaler.

18. The method as claimed in claim 13, wherein the performing of the evaluation comprises utilizing at least one of Particle Image Velocimetry (PIV), phase Doppler particle analyses (PDPA) and viscosity measuring.

19. The method as claimed in claim 13, wherein the performing of the evaluation comprises:

delivering at least two laser pulses to the at least one of droplets, particles and aerosol;

capturing a scattering of the laser pulses from the at least one of droplets, particles and aerosol; and

processing the scattering of the laser pulses from the at least one of droplets, particles and aerosol to evaluate the at least one property of the at least one of droplets, particles and aerosol.

20. The method as claimed in claim 19, wherein the delivering at least two laser pulses to the at least one of droplets, particles and aerosol comprises generating a laser sheet.

21. The method as claimed in claim 19, wherein the capturing of the scattering of the laser pulses comprises arranging a first charge coupled detector (CCD) in a first optical path of the laser pulses scattered from the at least one of droplets, particles and aerosol.

22. The method as claimed in claim 21, wherein the performing of the evaluation further comprises:

capturing a fluorescence from the at least one of droplets, particles and aerosol; and

processing the fluorescence from the at least one of droplets, particles and aerosol to evaluate the at least one property of the at least one of droplets, particles and aerosol.

23. The method as claimed in claim 22, wherein the capturing of the fluorescence comprises arranging a second charge coupled detector (CCD) in a second optical path of the fluorescence from the at least one of droplets, particles and aerosol.

24. The method as claimed in claim 23, wherein the capturing of the scattering of the laser pulses further comprises configuring a narrow band-pass filter in the first optical path between the first CCD and the at least one of droplets, particles and aerosol;

and

wherein the capturing of the fluorescence further comprises configuring a high-pass filter in the second optical path between the second CCD and the at least one of droplets, particles and aerosol.

25. The method as claimed in claim 21, wherein the performing of the evaluation comprises:

recording the scattering of the laser light comprising two consecutive images of the at least one of droplets, particles and aerosol;

dividing the two images into at least two interrogation boxes of m×

n pixels, wherein m and n are positive integers;

calculating a two-dimensional velocity vector;

assessing an average displacement of the at least one of droplets, particles and aerosol via cross-correlation of the at least two interrogation boxes, wherein a cross-correlation function (R_fg) is defined as

$R_{\mathrm{fg}}<br><br>\left(i,j\right)=f<br><br>\left(i,j\right)\otimes <br><br>g<br><br>\left(i,j\right)=\underset{x=0}{\overset{m-1}{\sum <br><br>}}<br><br>\underset{y=0}{\overset{n-1}{\sum <br><br>}}<br><br>f<br><br>\left(x,y\right)<br><br>g<br><br>\left(x-i,y-j\right),$

where f and g are functions corresponding to the at least two interrogation boxes, respectively, in the cross-correlation, g is shifted i and j pixels, i and j being positive integers, in the x and y directions, respectively;

wherein an overlap between the resulting function and f determines a value of the cross-correlation function R_fg(i,j), a position of the maximum in R_fg(i,j) provides a displacement vector during at time period Δ

t, resulting in the velocity vector for a particular one of the at least two interrogation boxes.

26. The method as claimed in claim 25, wherein a velocity profile of flow field is reconstructed from individual velocity vectors for the at least two interrogation boxes across the field.

27. The method as claimed in claim 26, wherein the reconstruction is obtained when the at least two interrogation boxes are defined with a 50% area overlap.

28. The method as claimed in claim 21, wherein two-dimensional velocity fields are measured through Mie scattering.

29. The method as claimed in claim 23, wherein a three-dimensional velocity field is obtained by positioning the first and second CCDs at an angle with respect to each other covering approximately the same field of view, and by reconstructing a z component of the velocity vector, the z component being perpendicular to the laser sheet, two two-dimensional velocity fields observed by the first and second CCDs, respectively, and the x and y components of the two-dimensional velocity fields.

33. A method for optimizing a source of at least one of droplets, particles and aerosol, the method comprising:

performing an evaluation of at least one property of at least one of droplets, particles and aerosol;

generating a feedback signal based on the evaluation; and

optimizing at least one operational parameter of a source of the at least one of droplets, particles and aerosol based on the feedback signal.

34. The method as claimed in claim 33, wherein the performing of the evaluation comprises evaluating a momentum of the at least one of droplets, particles and aerosol, and wherein the feedback signal is generated based on the momentum.