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AssigneeAristotle University Thessaloniki Research Committee
InventorsZissis Samaras, Leonidas Ntziachristos
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The present invention relates to a device used for the dilution of exhaust gas (diluter) and in particular for engines or vehicles. More particularly, the invention relates to a device and a method which may maintain a constant dilution ratio regardless of the exhaust gas backpressure in the exhaust line, without using any moving parts. The proposed diluter utilizes a very small fraction of the exhaust gas, sampled through a capillary duct, simply immersed to the exhaust flow, which is otherwise freely exhausting to the atmosphere. The sample flowrate through the capillary is achieved by maintaining a regulated underpressure at the capillary outlet. The diluted exhaust is then collected in a stabilization chamber, where temperature, humidity and residence time may be adjusted to condition the collected aerosol at will. Multiple capillaries and stabilization chambers may be cascaded to increase the dilution ratios. After the final dilution stage, particle samples may be collected on a filter for gravimetric determination or analyzed by number counters, surface monitors or any other technique utilized for the physical or chemical characterization of particles. In a preferred embodiment the capillary duct is realized with a hypodermic needle and two cascaded hypodermic needles/stabilization chambers are combined to provide the desired dilution ratio. In another embodiment, exhaust gas may be led to the diluter's capillary duct by means of two probes, located respectively upstream and downstream of any aftertreatment device, which needs to be characterized. By means of shut-off valves, exhaust gas may be fed to the diluter's capillary by either the upstream or the downstream probe, thus providing an estimate of the filtration efficiency of the device.
A diluter for sampling of exhaust gas, in particular of vehicles or engines, comprising a primary capillary (1) connected to a primary stabilization chamber (2), which said primary stabilization chamber is kept at a pressure below ambient by means of a vacuum pump (9) connected to said primary stabilization chamber by means of a primary outlet duct (4) and where dilution air in said primary stabilization chamber is introduced by means of a primary dilution air duct (3) through a primary mixing tip, wherein there is provided an excess flowrate arrangement for providing an exhaust gas flowrate in excess of the sample flowrate in said capillary (1), which exhaust gas flowrate totally surrounds said capillary inlet tip, wherein said primary capillary (1) is immersed in the exhaust gas flowrate with said arrangement, wherein said diluter draws the exhaust gas via said primary capillary (1).
Method for sampling of exhaust gas in particular of vehicles or engines, notably for working out a diluting device as defined in one of the preceding claims, wherein said stabilization chamber is kept at a pressure below ambient by means of a vacuum pump (9), and where dilution air in the said stabilization chamber is introduced by means of said primary dilution air duct (3) through a primary mixing tip, in that said diluter draws the exhaust gas via the primary capillary (1) which is immersed in the exhaust gas flowrate with said excess flowrate arrangement, which provides an exhaust gas flowrate in excess of the sample flowrate in the said capillary, which exhaust gas flowrate totally surrounds the said capillary inlet tip.
Dependencies are inferred from the claim text.