Air samplers are finding increased application in a variety of uses. One such application deals with the transportation industry. For example, passengers may be subject to noxious smells or gases or other airborne impurities when traveling in enclosed vehicles such as trains, motor coaches, or airplanes.
When an event occurs during which passengers are subject to odors, smoke, gases, or other undesirable airborne impurities, it is desirable to perform some kind of test or sampling. The testing or sampling of the air supply may be done for several reasons. It may be desired to repeat the incident of impure air flow in order to sample the air and thus trace the source of impurity. Additionally, the testing or sampling may be performed in part to certify that, once corrected, the vehicle in question is again supplying clean air to passengers.
In the example of a modern passenger jetliner, air supply to the interior cabin often begins with the gas turbine engines. In the typical structure of a gas turbine engine, including those used in industrial, marine, vehicle, as well as aerojet applications, air enters the engine inlet and first passes through a series of compressor stages such as a low pressure stage and a high pressure stage. The air then passes through a combustion chamber and, in exiting the engine, crosses turbines such as high pressure and low pressure turbines. However, a significant portion of air that enters the engine inlet passes around the compressors, combustion chamber and turbines, this is called fan air. Additionally air in the compressors may be bled off for deicing and other pneumatic applications through bleed valves. Bleed valves are typically used to select air at a desired pressure within the gas turbine engine during varying power conditions. Alternatively air may be supplied to the air craft cabin through a separate compressor not directly associated with the engine. Environmental control systems used in commercial airliners often draw air from either the bleed valves or ram air. This air may then pass through ductwork, pumps, temperature controls, and other air handling equipment before being vented into the passenger cabin.
Present in these turbine propulsion engines as well as the APU's (auxiliary power units) are fluid sealing systems. Sealing systems typically work to contain materials such as lubricants and hydrocarbons within the engine body. For example sealing systems are employed within a gas turbine engine to prevent trace elements of materials such as fuel or lubricant from leaking from the engine and into the bleed air. However, such sealing systems are not always totally effective, and as a result there may be leakage of fuel or lubricant into the bleed air. Hence hydrocarbons and lubricants within the engine may be the source of semivolatile compounds that result in odors and noxious impurities that may be harmful or unpleasant to the passengers. Hydrocarbons for example can oxidize and produce smoke and particulates in the air flowing into the cabin.
Previous methods used to measure contaminants in engine bleed air have either been inconclusive or have given false readings. One such method incorporates a polyvinylchloride filter to collect a sample of the bleed air followed by looking for the presence of oil by using a black light to make the oil droplets fluoresce. Another method includes the use of a large, stainless steel coil chilled to about −100 degrees F. to condense matter in the bleed air. The condensed matter is then flushed from the coil, evaporated with a solvent (freon) and weighed. In a third method, the bleed air is flowed through absorption tubes in which residue is collected on silica gel, charcoal, or molecular sieves and then evaluated by gas chromatography/mass spectroscopy. The residue can also be analyzed by combusting its organic matter, and measuring the carbon dioxide formed with a flame ionization detector or nitrogen phosphorous detector.
Presently, there is no known equipment available that is designed to sample high volumes of air from a closed system. In particular there is no known equipment designed to take high volume air samples from the interior chamber of a closed aircraft fuselage. Accordingly there is a need for a high volume air sampler that can screen for particulate, volatile, and semivolatile materials present in the air sample.
In a closed environment, such as the fuselage interior of a commercial jet airplane, traditional methods of taking air samples face difficulties. In the typical known method for taking air samples a collector is exposed to the environment where it is desired to take an air sample. One end of the collector is open to the atmosphere and an opposite end of the collector is attached to a pump (typically with an intervening hose). Running the pump pulls a vacuum which serves to pull air through the collector.
The difficulty of such an arrangement in a closed environment is that pulling a vacuum to take the air sample is resisted by the closed nature of where the air sample is in the plane interior. Thus it is difficult to take large volume air samples with this arrangement. However, large volume air samples are sometimes preferred where for example the concentration of the suspected contaminant is relatively low. In such a case it is often necessary to sample a large volume of air in order to capture a sufficient quantity of the contaminant in order to subject the impurity to analysis.
Hence there is a need for a high volume air sampler that addresses one or more of the above-noted objectives. That is there is a need for a high volume air sampler capable of drawing a sufficiently large air sample to detect the presence of certain airborne impurities; and/or that is capable of drawing an air sample in a closed environment of minimal weight and/or that is capable of drawing air samples that pass through the enclosed interior of an airplane fuselage and/or that is compact and portable so as to be used in different airplane shapes and sizes. The high volume air sampler disclosed herein addresses one or more of these needs.