General Description of the Model 5 Bubble Generator
With micro-metering valves installed on each output, the SAI™ Model 5 Bubble Generator provides more precise control over the bubble generation process. It is a compact and unique tool for visualizing complex airflow patterns. Helium-filled, neutrally-buoyant bubbles of uniform size, adjustable from 1/32" to 3/16" in diameter, can be generated simultaneously from one or two "Plug-In Heads". These bubbles are capable of tracing intricate air motions without bursting or impacting on objects within the airflow and have a lifespan of 1-2 minutes. It is designed for simplicity of operation in any location where helium and compressed air are available.
In the past, several types of Heads were developed and used for generating bubbles and implanting them in airflows. The Model 5 Bubble Generator is intended primarily for operation with one or two Plug-In Heads, each driving a device that is called a "Mini-Vortex Filter". The Plug-In Head and Mini-Vortex Filter combination represents the most advanced means for high generation rates of "good" bubbles within a compact space. The "heart" of the Head, itself, consists of a concentric arrangement of two stainless steel hypodermic tubes, one inside the other, attached in a cantilever fashion to a cylindrical manifold base or body. Within the Head, helium passes through the inner hypodermic tube and "Bubble Film Solution" (BFS) through the annulus between the inner tube and the outer tube to form the helium-filled bubbles at the tip. A much larger, concentric jet of air, in turn, blows the bubbles continuously off the tip.
Some of the bubbles generated are too heavy and some, too light. The Mini-Vortex Filter removes these "bad" bubbles. Basically, it is a clear, plastic cylinder which utilizes the jet of air from the Head to set up a rotational or cyclonic motion inside. The resulting radial forces then cause the bubbles which are not neutrally-buoyant to separate out.
Layout of Model 5 Console
Within the case, the Console is mounted to the left and the Mini-Vortex Filters with the Heads attached, in the middle. To the right, space is provided for storage of outlet tubes and tubing for the Filters, as well as other miscellaneous items. The Console accurately meters the flow of the helium, air and BFS to the Heads. The helium and air are connected to external supplies. The BFS, though, is stored in an internal PVC cylinder. This solution is driven by pressure tapped from the helium circuit through a check valve. The requirements for external sources of helium and compressed air are quite modest. A cylinder of compressed helium with a 0 to 30 psi pressure regulator is adequate. The helium flow rate is less than 200 ccm for each Head. Air may be from any source which is capable of delivering 1.2 cfm, per Head, at 40 psi. The Console panel is laid out for easy identification of the fittings and valves. From the left, the columns are labeled "HELIUM", "BFS", and "AIR". Starting at the top of the panel, the fittings designated by "IN" are the inlets to the Console. The helium and air supplies are to be connected to their respective inlets in this row. The inlets are 1/4" female quick disconnect fittings. The large fitting in the center of the inlet row is the refill port for the Bubble Film Solution. Below each inlet is a micro-metering valve to regulate the flow of the corresponding constituent to the Head. Micrometer vernier scales are incorporated in the handles of the metering valves to enable the user to reproduce the desired flow rates very precisely. This row of valves is designated by "ADJ". The two rows of toggle valves below the micro-metering valves are designated by "OUT 1" and "OUT 2". These toggle valves allow quick shutdown of any constituent to either Head. The valves are open when the handles are perpendicular to the panel and closed, when they are parallel to the panel. The constituents from the Console are fed to the Heads by means of 2 to 1 paratubing, two 3/32" I.D. and one 1/4" I.D. plastic tubes side by side. There are two holes on the side of the Console panel. The paratubing comes through these holes and lay in front of the filters then loop upward and back down to connect to the Plug-In Heads. The whole unit, including the control "Console", Heads and associated equipment, are packaged within a convenient, durable case.
It is designed for simplicity of operation in any location where helium and compressed air are available. The whole unit may be readily disassembled for maintenance and repair.