초록 ▼

A dilution tunnel having a flow chamber structure with an inlet, an outlet, and an internal flow passage for a sample gas, the sample gas being adapted to flow in a flow direction between the inlet and the outlet. The flow chamber structure having a plurality of pores that communicate between an out

A dilution tunnel having a flow chamber structure with an inlet, an outlet, and an internal flow passage for a sample gas, the sample gas being adapted to flow in a flow direction between the inlet and the outlet. The flow chamber structure having a plurality of pores that communicate between an outside region external of the flow chamber structure and the internal flow passage. The pores are adapted to introduce a diluting gas from the outside region into the internal flow passage. The flow chamber structure is adapted to provide a diluting rate of the dilution tunnel that varies in the flow direction of the dilution tunnel.

대표청구항 ▼

The invention claimed is: 1. A dilution tunnel, comprising: a porous tube having an inlet fluidly coupled to an exhaust gas producing source, an outlet, and a flow axis passing through said porous tube, the inlet, and the outlet, said porous tube defining an internal flow passage for exhaust gas be

The invention claimed is: 1. A dilution tunnel, comprising: a porous tube having an inlet fluidly coupled to an exhaust gas producing source, an outlet, and a flow axis passing through said porous tube, the inlet, and the outlet, said porous tube defining an internal flow passage for exhaust gas between the inlet and the outlet, the flow axis defining an axial flow direction of the exhaust gas through said porous tube, and the internal flow passage being substantially symmetrical about the flow axis; said porous tube including a porous section having a plurality of open pores formed in a wall of the porous tube that communicate between an outside region external of said porous tube and the internal flow passage, said pores being adapted to introduce a diluting gas from the outside region into the internal flow passage; and wherein a porosity of said porous section varies in at least one of the axial flow direction and around a periphery of the porous tube. 2. The dilution tunnel according to claim 1, wherein a size of said pores varies in the axial flow direction. 3. The dilution tunnel according to claim 1, wherein a size of said pores varies around the periphery of the porous tube. 4. The dilution tunnel according to claim 1, wherein a density of said pores varies in at least one of the axial flow direction and around the periphery of the porous tube. 5. The dilution tunnel according to claim 1, wherein a cross-sectional area of said porous tube taken in a direction orthogonal to the flow axis varies in the axial flow direction. 6. The dilution tunnel according to claim 2, wherein said porous tube is formed from a plurality of sections of porous tubes, wherein the size of said pores in each section are substantially the same. 7. The dilution tunnel according to claim 3, wherein said porous tube is formed from sintered steel that has been compressed by different amounts in the radial direction so that the size of said pores varies around the periphery of the porous tube. 8. A gas sampling system for analyzing exhaust gas produced by an exhaust gas producing source, comprising: a dilution tunnel fluidly coupled to the exhaust gas producing source; and a gas source that supplies a diluting gas;. wherein said dilution tunnel includes a porous tube having an inlet and an outlet and a flow axis passing through said porous tube, the inlet, and the outlet; said porous tube defining an internal flow passage for exhaust gas between the inlet and the outlet, the flow axis defining an axial flow direction of the exhaust gas through said porous tube; and the internal flow passage being substantially symmetrical about the flow axis; said porous tube including a porous section having a plurality of open pores formed in a wall of the porous tube that communicate between an outside region external of said porous tube and the internal flow passage, said pores being adapted to introduce said diluting gas into the internal flow passage; and wherein a porosity of said porous section varies in at least one of the axial flow direction and around a periphery of the porous tube. 9. The gas sampling system according to claim 8, wherein a size of said pores varies in the axial flow direction. 10. The gas sampling system according to claim 8, wherein a size of said pores varies around the periphery of the porous tube. 11. The gas sampling system according to claim 8, wherein a cross-sectional area of said porous tube taken in a direction orthogonal to the flow axis varies in axial flow direction. 12. The gas sampling system according to claim 8, wherein said dilution tunnel is one of a plurality of interchangeable cartridges for said gas sampling system, wherein each cartridge has a different diluting rate. 13. The gas sampling system according to claim 8, wherein said gas source is a clean air source that supplies clean air to said dilution tunnel; and wherein said gas sampling system further includes a sampling probe upstream of said dilution tunnel and at least one of a gravimetric filter and a particle scanner downstream of the dilution tunnel; a first mass flow controller between said clean air source and said dilution tunnel; and a second mass flow controller downstream of said at least one of said gravimetric filter and said particle scanner. 14. A dilution tunnel, comprising: a porous tube having an inlet fluidly coupled to an exhaust gas sampling probe, an outlet, and a flow axis passing through said porous tube, the inlet, and the outlet, said porous tube defining an internal flow passage for exhaust gas between the inlet and the outlet, the flow axis defining an axial flow direction of exhaust gas through said porous tube, and the internal flow passage being substantially symmetrical about the flow axis; said porous tube having a plurality of pores that communicate between an outside region external of said porous tube and the internal flow passage, said pores being adapted to introduce a diluting gas from the outside region into the internal flow passage; wherein a size of said pores varies in at least one of the axial flow direction and around a periphery of the porous tube. 15. The dilution tunnel according to claim 14, wherein a density of said pores varies in at least one of the axial flow direction and around the periphery of the porous tube. 16. The dilution tunnel according to claim 14, wherein a cross-sectional area of said porous tube taken in a direction orthogonal to the flow axis varies in the axial flow direction. 17. The dilution tunnel according to claim 14, wherein said porous tube is formed from sintered steel that has been compressed by different amounts in the radial direction so that the size of said pores varies around the periphery of the porous tube. 18. A gas sampling system for analyzing a first gas, comprising: a dilution tunnel; and a second gas source that supplies a second gas; wherein said dilution tunnel includes a porous tube having an inlet, an outlet fluidly coupled to a particle analyzing system, and a flow axis passing through said porous tube, the inlet, and the outlet; said porous tube defining an internal flow passage for said first gas between the inlet and the outlet, the flow axis defining an axial flow direction of said first gas through said porous tube, and the internal flow passage being substantially symmetrical about the flow axis; said porous tube having a plurality of pores that communicate between an outside region external of said porous tube and the internal flow passage, said pores being adapted to introduce said second gas into the internal flow passage; and wherein a size of said pores varies in at least one of the axial flow direction and around a periphery of the porous tube. 19. The gas sampling system according to claim 18, wherein a density of said pores varies in at least one of the axial flow direction and around the periphery of the porous tube. 20. The gas sampling system according to claim 18, wherein a cross-sectional area of said porous tube taken in a direction orthogonal to the flow axis varies in the axial flow direction. 21. A dilution tunnel, comprising: a porous tube including an inlet end configured to receive exhaust gas from an exhaust gas producing source, an outlet end in fluid communication with a particle analyzing system, an internal flow passage for the exhaust gas between the inlet and the outlet, and a porous section having a plurality of pores that communicate between a region external of the porous tube and the internal flow passage, the plurality of pores being configured to introduce a diluting gas from the region external of the porous tube into the internal flow passage, wherein a porosity of the porous section varies in at least one of an axial direction and around a periphery of the porous tube, and the pore sizes of the plurality of pores are less than or equal to 5 microns. 22. The dilution tunnel of claim 21, wherein the pore sizes are greater than or equal to 0.5 microns. 23. The dilution tunnel of claim 21, wherein the pore size of at least one pore of the plurality of pores varies along a longitudinal axis of the at least one pore.