Substance Release Estimation Using Path-Averaged Concentration Measurements

• US 20090055103A1
• Filed: 08/06/2008
• Published: 02/26/2009
• Est. Priority Date: 08/06/2007
• Status: Active Grant

• Current Assignee: Industrial Scientific Corporation (Fortive Corp.)
• Original Assignee: SAFER Systems, LLC (Fortive Corp.)
• Inventors: Gilbert, Ernest, Khajehnajafi, Shahryar
• Granted Patent: US 8,145,439 B2
• Time in Patent Office: Days
• US Class Current: 702/24
• CPC Class Codes: G01N 33/0004 Gaseous mixtures, e.g. polluted air

Abstract

A system and method for using path-averaged concentration measurements for estimating the amount of substance being released from a particular location. One or more open-path sensing systems are set up in appropriate locations around possible substance release sites and tuned to detect a particular substance of interest. Path-averaged concentration measurements of the particular substance are collected over time and communicated to an open-path back calculation algorithm. The algorithm calculates time-averaged measurements for a plurality of time periods. Back calculation is then performed with the time-averaged measurements to estimate the release rate and the total release of the substance.

Claims

1. A computer-implemented substance release estimation method for a substance released into a surrounding medium thereby creating a plume, the method comprising:

calculating a plurality of path-averaged concentration measurements of the substance for a plurality of time instants;

averaging the plurality of path-averaged concentration measurements over the plurality of time instants to obtain a time-averaged measurement of the plurality of path-averaged concentration measurements; and

estimating a release rate of the substance as a function of the time-averaged measurement of the plurality of path-averaged concentration measurements.

2. The method of claim 1 further comprising:

assuming a release rate of the substance;

modeling the plume based on the assumed release rate; and

predicting a width of the plume at each of the plurality of time instants based on the modeling of the plume.

3. The method of claim 2, wherein the modeling adjusts to changes to atmospheric conditions including wind direction, wind speed and stability, over time.

4. The method of claim 2, wherein the calculating the plurality of path-averaged concentration measurements comprises:

collecting a plurality of concentrations of the substance measured at each of the plurality of time instants; and

dividing each of the collected plurality of concentrations by the predicted width of the plume at the corresponding one of the plurality of time instants.

5. The method of claim 4, wherein the collecting the plurality of concentrations comprises:

transmitting a beam of light; and

determining an amount of the light absorbed by the substance along the path of the beam.

6. The method of claim 2, wherein the estimating of the release rate further comprises:

predicting one or more path-averaged concentrations of the substance at each of the plurality of time instants based on the modeling of the plume;

averaging the predicted path-averaged concentrations over the plurality of time instants to generate a time-averaged prediction of the predicted path-averaged concentrations;

comparing the time-averaged prediction of the predicted path-averaged concentrations with the time-averaged measurement of the plurality of path-averaged concentration measurements; and

selecting the assumed release rate as the estimated release rate of the substance based on the comparing.

7. The method of claim 1, wherein the substance is a single gas.

8. The method of claim 1, wherein the substance is a chemical mixture including a plurality of gases.

9. The method of claim 8 further comprising:

receiving concentration measurements of each of the plurality of gases from at least one open-path sensor; and

dynamically identifying chemical properties of the chemical mixture based on the received concentration measurements, wherein the estimated release rate is for the chemical mixture.

10. A substance release estimation system for a substance released into a surrounding medium thereby creating a plume, the system comprising:

at least one sensing system configured to collect a plurality of concentrations of the substance measured at each of a plurality of time instants; and

a computer operably coupled to the at least one sensing system, the computer configured to execute computer program instructions stored in memory, the program instructions including;

calculating a plurality of path-averaged concentration measurements based on the collected plurality of concentrations;

averaging the plurality of path-averaged concentration measurements over the plurality of time instants to obtain a time-averaged measurement of the plurality of path-averaged concentration measurements; and

estimating a release rate of the substance as a function of the time-averaged measurement of the plurality of path-averaged concentration measurements.

11. The system of claim 10, wherein the computer program instructions further include:

assuming a release rate of the substance;

modeling the plume based on the assumed release rate; and

predicting a width of the plume at each of the plurality of time instants based on the modeling of the plume.

12. The system of claim 11, wherein the modeling adjusts to changes to atmospheric conditions including wind direction, wind speed, and stability, over time.

13. The system of claim 11, wherein the computer program instructions for calculating the plurality of path-averaged concentration measurements comprise:

collecting a plurality of concentrations of the substance measured at each of the plurality of time instants; and

dividing each of the collected plurality of concentrations by the predicted width of the plume at the corresponding one of the plurality of time instants.

14. The system of claim 13, wherein the program instructions for collecting the plurality of concentrations comprise:

transmitting a beam of light; and

determining an amount of the light absorbed by the substance along the path of the beam.

15. The system of claim 11, wherein the program instructions for estimating the release rate further comprises:

predicting one or more path-averaged concentrations of the substance at each of the plurality of time instants based on the modeling of the plume;

averaging the predicted path-averaged concentrations over the plurality of time instants to generate a time-averaged prediction of the predicted path-averaged concentrations;

comparing the time-averaged prediction of the predicted path-averaged concentrations with the time-averaged measurement of the plurality of path-averaged concentration measurements; and

selecting the assumed release rate as the estimated release rate of the substance based on the comparing.

16. The system of claim 10, wherein the substance is a single gas.

17. The system of claim 10, wherein the substance is a chemical mixture including a plurality of gases.

18. The system of claim 17, wherein the program instructions further comprise:

receiving concentration measurements of each of the plurality of gases from the at least one sensing system; and

dynamically identifying chemical properties of the chemical mixture based on the received concentration measurements, wherein the estimated release rate is for the chemical mixture.

19. The system of claim 10, wherein the sensing system includes an open-path sensor.

20. The system or claim 10, wherein the sensing system includes both fixed point and open-path sensors.