Scanned 1-D Gas Plume Profile and Flux Measurements Using Multiple Analysis Instruments
A gas concentration image (i.e., concentration vs. position data) in a cross section through a gas plume is obtained. Such measurements can be obtained by moving a 1D array of gas sample inlets through the gas plume. By combining a gas concentration image with ambient flow information through the surface of the gas concentration image, the leak rate (i.e., gas flux) from the leak source can be estimated. Multiple gas analysis instruments can be employed in connection with sweeping a 1-D array of measurement ports through the gas plume in order to reduce analysis time.
1 . A method for performing gas concentration measurements in an ambient, the method comprising:
simultaneously collecting two or more gas samples from two or more measurement locations, wherein the measurement locations are configured to be on a smooth vertical surface, and wherein the measurement locations are defined by a 1-D array of measurement ports that is moved along the smooth vertical surface;
providing the two or more gas samples to one or more gas analysis instruments to provide gas concentration data points;
relating the gas concentration data points to the two or more measurement locations to provide a gas concentration image of the smooth vertical surface; and
providing the gas concentration image as an output.
2 . The method of claim 1 , wherein the gas concentration data points include measurement time, and further comprising relating measurement time to measurement position to provide the gas concentration image.
3 . The method of claim 1 , further comprising:
obtaining an estimate of ambient flow velocity through the smooth vertical surface; and
computing a gas flux estimate from the gas concentration image and the estimate of ambient flow velocity.
4 . The method of claim 3 , wherein the estimate of ambient flow velocity through the smooth vertical surface is provided as a function of height above ground.
5 . The method of claim 1 , wherein two or more gas analysis instruments are provided for analysis of the gas samples in parallel.
6 . A system for performing gas concentration measurements in an ambient, the system comprising:
a gas flow control manifold configured to simultaneously collect two or more gas samples from two or more measurement locations, wherein the measurement locations are configured to be on a smooth vertical surface, and wherein the measurement locations are defined by a 1-D array of measurement ports that is moved along the smooth vertical surface; and
one or more gas analysis instruments;
wherein the gas flow control manifold is configured to provide the two or more gas samples to the gas analysis instruments to provide gas concentration data points;
wherein the system is configured to relate the gas concentration data points to the two or more measurement locations to provide a gas concentration image of the smooth vertical surface.
7 . The system of claim 6 , further comprising a mast configured to be affixed to a vehicle, wherein the 1 -D array of measurement ports is disposed on the mast.
8 . The system of claim 7 , wherein positions of the measurement ports on the mast can be altered in operation.
9 . The system of claim 6 , further comprising instruments for measuring ambient flow velocity.
10 . The system of claim 7 , further comprising a global positioning system (GPS) receiver to track horizontal position of the vehicle.
11 . The system of claim 7 , further comprising a vehicle speed sensor and a subsystem for converting time and vehicle speed information to position information.
12 . The system of claim 6 , wherein two or more gas analysis instruments are provided for analysis of the gas samples in parallel.
13 . The system of claim 6 , wherein a selected two or more of the measurement ports are connected to a selected one of the gas analysis instruments.
14 . The system of claim 13 , wherein the selected measurement ports are connected to the selected gas analysis instrument such that transit times from each of the selected measurement ports to the selected gas analysis instrument are substantially equal.