Leak distance estimation method using correlation measurements at isolated spatial points in a plume
Repeated simultaneous concentration measurements at spatially separated points are used to provide information on the lateral spatial extent of a gas plume. More specifically the spatial correlations in this data provide this information. Fitting a gas plume model directly to this multi-point data can provide good estimates of total plume emission. The distance between the plume source and the measurement points does not need to be known to provide these estimates. It is also not necessary to perform any detailed atmospheric modeling. These estimates of the lateral spatial extent of a gas plume can also be used to provide a distance estimate to the source of the gas plume.
1. A method for estimating a distance to a source of a gas leak from an estimate of a width w of a gas plume from the gas leak, the method comprising:
performing multiple gas concentration measurements at two or more separated measurement points, wherein each data point of the gas concentration measurements is a simultaneous concentration measurement at the measurement points;
providing a time-independent gas plume model having at least plume spatial width w as a fitting parameter, wherein the gas plume model also includes parameters for plume position;
fitting the gas plume model to the data points, wherein the plume position is allowed to be a random variable to enable fitting to observed scatter in the data points, to obtain an estimate w* of the plume spatial width w; and
providing as an output an estimate of a distance X* between the measurement points and a source of the gas plume from the estimate of the plume spatial width w*.
2. The method of claim 1 , wherein the distance X* depends in a monotonically increasing manner on w*.
3. The method of claim 2 , wherein a relationship between X* and w* is derived from an atmospheric plume dispersion model.
4. The method of claim 3 , wherein the atmospheric plume dispersion model is a Gaussian plume model.
5. The method of claim 3 , where the atmospheric plume dispersion model incorporates one or more parameters selected from the group consisting of: wind speed, atmospheric turbulence, solar irradiance, local terrain, surface albedo, surface cover, and nearby wind obstructions.
6. The method of claim 2 , wherein the distance estimate X* is determined from two estimates of w* made at two distinct locations along the path of the propagation of the plume, combined with an assumed functional form for the monotonically increasing function relating w* and X*.
7. The method of claim 6 , wherein the functional form is linear.
8. The method of claim 6 , wherein the functional form is determined from a plume propagation model.
9. The method of claim 6 , wherein the functional form is determined empirically from experimental data.
10. A method for estimating a distance to a source of a gas leak, the method comprising:
performing the method of claim 1 in two orthogonal directions y and z;
wherein all measurement points are in a common measurement plane;
wherein the distance estimate X* depends on both w* y and w* z .
11. The method of claim 10 , wherein the measurement points include three points having y-z coordinates (0,0), (d y ,0), (0, d z ).
12. The method of claim 10 , wherein measurements relating to the two orthogonal directions are performed simultaneously.
13. The method of claim 10 , wherein measurements relating to the two orthogonal directions are performed sequentially and then registered to a common time axis to provide the simultaneous concentration measurements at the measurement points.