| 摘要 |
A gas sampling device includes a dilution tunnel of particularly effective construction that reduces contamination or soiling of the ducting leading to a filter assembly and improves the accuracy of the results. The gas sampling device has a sampling probe disposable in the gas stream of an engine or the like, and a controlled source of clean and pressurized diluent air. The dilution tunnel includes an air distribution tube defining a plurality of distribution holes therethrough, a collar defining a first annular chamber about the air distribution tube that is connected to the air source, and a porous center tube having a plurality of micron-sized pores connected between the sampling probe and the filter assembly. A second annular chamber is defined between both tubes, and the diluent air supplied thereto is uniformly passed through the porous center tube to effect good mixing of the exhaust gas and diluent air while providing a boundary layer of diluent air that keeps the center tube clean. An alternate embodiment gas sampling device employing master and slave mass flow controllers is also disclosed.
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