The Plume Generators developed for        Program SAFEGUARD

Early in the SAFEGUARD developmental efforts, it became obvious that industrial collections could not provide the flexibility required to comprehensively characterize the performance of the sensor suite.  It's one thing for an industrial entity to allow SAFEGUARD researchers to collect data over their site in the interest of national defense but quite another to tweak their $1,000,000/day process to accommodate our experiment!

So, almost immediately upon our introduction to Program SAFEGUARD, AeroSurvey was asked to design and construct a device capable of producing test plumes that would be under our control.  The first device, completed in early 1997, was capable of emulating real-world stacks in terms of plume diameter (16") and temperature (125 - 300 degrees Celsius).  This device was used in many subsequent SAFEGUARD experiments to produce experimental plumes containing ethanol, methanol, ammonia, sulfur dioxide, and hydrogen chloride. Using this prototype device, hours and hours of spectral data were collected over a range of plume conditions that would have been very difficult to reproduce in industrial collections.

In 1999, we were asked to design and construct three new plume generators that could provide improved airflow and remote operation capabilities.  These second-generation devices, completed and used late in 1999, also offer  increased volatilization capabilities, a larger stack diameter (18"), and automatic data-logging of all operational parameters during use.  The three devices operate individually but can be grouped to produce larger conglomerate plumes or positioned to simulate a more complex matrix of release points.

Below, we offer some photos of the second-generation devices, more detailed explanations where appropriate, and graphic representations of some data logged during a 1999 field experiment.

	The plume generator devices were built as trailers to facilitate transportation.  The stack folds down for transportation.  The trailer deck is 12' long x 6.5' wide.
	The plume generators are operated remotely via PC.  A graphical interface allows the operator to toggle all controls and monitor plume output temperature, exit velocity, propane delivery pressure, and the rate at which analytes are introduced into the plume.
	The PC interface is via a serial port and up to 4000' of 4 wire control cable.  Longer distances are possible with relatively minor modifications.
	The core of the plume generator is a tube axial blower nestled between the two side compartments.  The blower feeds a combustion plenum housing a 2.5 million BTU/hr custom propane burner head. This dragon can really roar. . .
	The rear 18" tailboard is separated from the forward section of the trailer by a firewall and is used to hold the chemicals to be introduced into the plume.  These particular models were built to release either liquids (methanol and ethanol) or gases (ammonia).
	Two liquid feed ports and one gaseous feed port lead into the right side compartment.  The right side compartment contains liquid pumps and flow controllers.  A set of scales on the tailboard is used to produce absolute data concerning analyte introduction rates.

The plot below was created from data logged during a controlled release experiment conducted in December of 1999.  The red line shows the weight of ethanol in the supply carboy declining over time.  The blue line is the output signal from the flow controller.  In this experiment, we stepped through four different release rates as the sensor suite made about 20 passes over the stack, all in the course of about 90 minutes.