Device and process for diluting an aerosol

Abstract

A device dilutes an aerosol without distortion due to loss of particles, especially liquid particles, on wall surfaces. An inlet pipe feeds aerosol as inlet aerosol and an outlet pipe has an inlet opening arranged at a finite distance from an outlet end of the inlet pipe. An annular space surrounds an end area of the inlet pipe. A clean gas line opens, via an outlet opening, into the annular space. A process is provided including feeding the aerosol as inlet aerosol through the inlet pipe, with particle-free clean gas fed to an end area of the inlet pipe and mixed with the fed inlet aerosol into a diluted outlet aerosol. The diluted outlet aerosol is sent to a measuring device. The mass flow of the aerosol sent to the measuring device and that of the added clean gas are maintained at a fixed ratio.

What is claimed is: 
     
         1 . A device for diluting an aerosol, the device comprising:
 an inlet pipe feeding an aerosol as an inlet aerosol;   an outlet pipe with an inlet opening arranged at a finite distance from an outlet end of the inlet pipe;   an annular space surrounding at least an end area of the inlet pipe; and   a clean gas line opening into the annular space via an outlet opening.   
     
     
         2 . A device in accordance with  claim 1 , wherein the distance between the inlet pipe and the outlet pipe is at most equal to the internal diameter of the inlet pipe. 
     
     
         3 . A device in accordance with  claim 2 , wherein the distance between the inlet pipe and the outlet pipe is smaller than an internal diameter of the inlet pipe or the outlet pipe and does not exceed 6 mm. 
     
     
         4 . A device in accordance with  claim 1 , wherein the annular space surrounding the end area of the inlet pipe has a ring width corresponding to 0.4 to 2 times an internal diameter of the inlet pipe. 
     
     
         5 . A device in accordance with  claim 1 , wherein an internal cross section πr 2  of the inlet pipe is at least 8 mm 2 . 
     
     
         6 . A device in accordance with  claim 1 , wherein an internal cross section λr 2  distance between the inlet pipe and the outlet pipe is greater than twice a length L of the inlet pipe, wherein r and L are determined in mm. 
     
     
         7 . A device in accordance with  claim 1 , wherein an internal diameter of the outlet pipe is greater than an external diameter of a facing end of the inlet pipe and is between 1.1 and 1.3 times the external diameter of a facing end of the inlet pipe. 
     
     
         8 . A device in accordance with  claim 1 , wherein:
 the clean gas line has a mass flow controller and a pump; or the clean gas line has a controlled pump and a mass flow meter.   
     
     
         9 . A device in accordance with  claim 1 , wherein the clean gas line has a purification device. 
     
     
         10 . A device in accordance with  claim 1 , wherein an inlet of the clean gas line is in connection with a gas source. 
     
     
         11 . A device in accordance with  claim 1 , wherein:
 an inlet of the clean gas line is arranged downstream of the outlet end of the inlet pipe for the inlet aerosol, and   the clean gas line has a purification device for purifying the outlet aerosol entering the clean gas line via a clean gas line inlet opening.   
     
     
         12 . A device in accordance with  claim 11 , further comprising an optical sensor device arranged between the outlet pipe and an inlet to the clean gas line for measuring the particles of the aerosol. 
     
     
         13 . A device in accordance with  claim 12 , further comprising a branch-off line connected to the clean gas line leading from the outlet opening to an opening of the inlet pipe, the branch-off line having a pump and a mass flow controller, the branch-off line branching off a certain portion of the clean gas as waste air. 
     
     
         14 . A device in accordance with  claim 1 , wherein a lateral outlet opening, in the annular space, is provided for branching off a certain portion of the outlet aerosol downstream of the inlet opening of the outlet pipe and is connected to the clean gas line. 
     
     
         15 . A device in accordance with  claim 1 , further comprising an optical measuring device arranged downstream of the outlet pipe and through which the aerosol flows, wherein the optical measuring device comprises an aerosol spectrometer. 
     
     
         16 . A device in accordance with  claim 15 , wherein the inlet pipe and the outlet pipe leading to a measuring device are aligned with one another. 
     
     
         17 . A system for diluting an aerosol, the system comprising;
 a first device for diluting an aerosol, the first device comprising an inlet pipe feeding an aerosol as an inlet aerosol, an outlet pipe with an inlet opening arranged at a finite distance from an outlet end of the inlet pipe, an annular space surrounding at least an end area of the inlet pipe and a clean gas line opening into the annular space via an outlet opening;   a second device for diluting an aerosol, the second device comprising an inlet pipe feeding an aerosol as an inlet aerosol, an outlet pipe with an inlet opening arranged at a finite distance from an outlet end of the inlet pipe, an annular space surrounding at least an end area of the inlet pipe and a clean gas line opening into the annular space via an outlet opening, wherein the first device and the second device are arranged as a cascade one after another, wherein the outlet pipe of the first device is connected to the inlet pipe of the second device.   
     
     
         18 . A process for diluting an aerosol, the process comprising:
 providing a device for diluting an aerosol, the device comprising an inlet pipe feeding an aerosol as an inlet aerosol, an annular space surrounding at least an end area of the inlet pipe and a clean gas line opening into the annular space via an outlet opening;   feeding the aerosol as an inlet aerosol through the inlet pipe;   feeding particle-free clean gas, via the clean gas line opening, to the annular space and mixing the fed particle-free clean gas with the fed inlet aerosol to form a diluted outlet aerosol;   sending the diluted outlet aerosol to a measuring device; and   maintaining a mass flow of the aerosol sent to the measuring device and that of the added clean gas at a fixed ratio.   
     
     
         19 . A process in accordance with  claim 18 , wherein the clean gas is fed in a controlled manner from an outside gas source as purified clean air, from the surrounding area. 
     
     
         20 . A process in accordance with  claim 18 , wherein outlet aerosol is purified into a particle-free clean gas and this is returned for mixing with the inlet aerosol. 
     
     
         21 . A process in accordance with  claim 18 , wherein inlet aerosol is fed via the inlet pipe having an internal cross section πr 2  that is at least 8 mm 2 . 
     
     
         22 . A process in accordance with  claim 18 , wherein the inlet aerosol is fed via the inlet pipe, whose internal cross section πr 2  is greater than 0.1 times the length L of the inlet pipe, r and L being determined in mm. 
     
     
         23 . A process in accordance with  claim 18 , wherein the clean gas is sent into the annular space, which annular space has a width that is 0.4 to 2 times an internal diameter of the inlet pipe. 
     
     
         24 . A process in accordance with  claim 18 , wherein the clean gas is fed to the inlet aerosol in a gap between an outlet end of the inlet pipe and an inlet opening of an outer pipe, which gap is smaller than an internal diameter of the inlet pipe or the outlet pipe and does not exceed 6 mm. 
     
     
         25 . A process in accordance with  claim 18 , wherein the diluted outlet aerosol generated by mixing inlet aerosol and clean gas enters an outlet pipe with an internal diameter greater than the internal diameter of the inlet pipe, and a difference of the internal diameters is at least 1 mm to 2 mm. 
     
     
         26 . A process in accordance with  claim 18 , wherein the clean gas is fed to the inlet aerosol at a preset fixed volume flow ratio. 
     
     
         27 . A process in accordance with  claim 18 , wherein a ratio of a volume flow of the inlet aerosol to that of the clean gas fed to same is determined by a mass flow controller. 
     
     
         28 . A process in accordance with  claim 18 , wherein the inlet aerosol is fed to the mixing space through a pipe, which has a smaller cross section than the mixing space and that clean gas fed to the mixing space is introduced into the mixing space above an outlet of the feed pipe (as a result of which intensive mixing of inlet aerosol and clean gas is brought about). 
     
     
         29 . A process in accordance with  claim 18 , wherein the outlet aerosol is sent through an optical sensor device before purification. 
     
     
         30 . A process in accordance with  claim 29 , wherein excess clean gas is removed as waste air. 
     
     
         31 . A process in accordance with  claim 18 , wherein only a fixed portion of the outlet aerosol is branched off for purification downstream of the mixing space and is fed again as particle-free clean gas upstream of the mixing space. 
     
     
         32 . A process in accordance with  claim 18 , wherein the outlet aerosol that is not branched off is sent through an optical sensor device, and the optical sensor device comprises an aerosol spectrometer. 
     
     
         33 . A process in accordance with  claim 18 , wherein the aerosol to be measured flows along an axis from an inlet pipe through an outlet to a measuring device, the measuring device comprising an aerosol spectrometer. 
     
     
         34 . A process in accordance with  claim 18 , wherein a portion of the outlet aerosol that is not branched off is fed to another, downstream mixing space and an additional dilution is carried out comprising:
 feeding the aerosol as an inlet aerosol through another inlet pipe;   feeding particle-free clean gas, via another clean gas line opening, to an annular space and mixing the fed particle-free clean gas with the fed inlet aerosol to form a diluted outlet aerosol;   sending the diluted outlet aerosol to a measuring device; and   maintaining a mass flow of the aerosol sent to the measuring device and that of the added clean gas at a fixed ratio.