FIELD OF THE INVENTION
The present invention relates to an adjustable aerodynamic lens system for aerodynamic focusing of aerosols, and more particularly, the adjustable aerodynamic lens system is a hollow tube comprising a plurality of section tubes with varying diameters of focusing orifices that are assembled with a specific order to aerodynamically focus the aerosols passing through the system into a highly collimated aerosol beam with the average focusing size of aerosols ranging between 3 nm and 3 μm.
BACKGROUND OF THE INVENTION
Aerosols generally refer to a dispersed system where either fine solid particles or liquid droplets suspended in a gaseous medium. Commonly seen aerosol includes haze, dust, particulate matters suspended in polluted air, smoke, and salt particles formed from ocean spray. The size of aerosols may span by orders of magnitude ranging from sub nanometer up to hundreds of micrometer.
Aerosols play important roles in numerous important scientific and technical fields, including environmental chemistry, atmospheric chemistry, biological chemistry, biomedical science and interstellar chemistry. While natural aerosols are essential in maintaining the radiative balance for Earth, however, anthropogenic aerosols produced from various human activities have severely disturbed the homeostasis for Earth's environment, which altered the cloud formation/growth microphysics, changed the atmospheric photochemical dynamics, worsened the air quality and caused dramatic adverse health effects for human beings. In 2013, the International Agency for Research on Cancers (IARC) under the World Health Organization (WHO) announced particulate matters (PM) in polluted air as a carcinogenic factor. In an updated report released by WHO in 2014, the mortalities associated with exposures of air pollution were updated to 7 million in 2012, accounting for ⅛ of total global death. Amongst, particulate matters having aerodynamic diameters smaller than 2.5 microns (PM2.5) are particularly harmful to human health as they are capable of penetrating to alveolar or even enter the systemic circulation to cause further adverse health effects.
The physical, chemical, optical and biological properties of aerosols are highly dependent on their chemical compositions, sizes, geometry and internal structures. In light of the development of novel aerosol technology to address various PM2.5 related issues, it is critical to have an in-depth understanding of the physical, chemical, optical and biochemical properties of aerosols.
Aerosols of different chemical compositions and particle sizes have different valence electronic energetic structures which decisively determine their chemical activities upon interacting with other substances. Therefore, it is of essential importance to learn the valence shell electronic energetic structures of aerosols of different chemical compositions and sizes. To achieve this goal and track how the valence electronic structures of aerosols of particular chemical compositions evolve with sizes, it is critical and essential to have the capability to selectively control and modulate the sizes of aerosols to be focused and studied.
In the field of measuring and analyzing aerosols in the environment, one common aerosol measuring technology, termed aerosols mass spectrometry (AMS) includes to use the aerodynamic lens (ADL) system to focus aerosols suspending in the atmosphere to generate a beam of aerosol particles, which is integrated with a mass spectrometer to analyze the chemical compositions of aerosols.
The foregoing ADL system is built based upon the principle of aerodynamics to make the aerosol fluid passing there through having certain sizes of aerosol particles focused into a beam. Such an aerodynamic lens is described in U.S. Pat. No. 8,119,977, entitled “Aerodynamic lens capable of focusing nanoparticles in a wide range”. U.S. Pat. No. 8,119,977 discloses an aerodynamic structure that comprises a cylindrical hollow body having an inlet and an outlet. The hollow body includes a first focusing part and a second focusing part. The first focusing part comprises a plurality of orifice lenses of which inner diameters are gradually decreased in an advancing direction of particle. The second focusing part also comprises a plurality of orifice lens of which inner diameters are gradually increased in the advancing direction of particle.
It is described in U.S. Pat. No. 8,119,977 that with the feature that the orifice lenses in the first focusing part and in the second focusing part are gradually decreased and then gradually increased, the ADL may effectively focus particles with various sizes in the range of 30 to 3,000 nm while the transmission efficiency is 90% or above and the particle beam diameter is less than 1 mm.
As compared to the prior art, U.S. Pat. No. 8,119,977 in virtue of the two focusing parts in the hollow body effectively expands the diameter range of aerosol particles that are allowed to pass through the ADL system to 30 to 3,000 nm. However, in the practical use, the ADL structure is conventionally made to focus aerosol particles covering a wide range of diameters, instead of being made in a customized fashion capable of selectively focusing aerosol particles of a specific size range. As mentioned previously, the size effect is particularly pronounced for ultrafine aerosols, such as PM2.5. Aerosols may show considerably different physico-chemical properties even if they only differ in size. Thus, a critical prerequisite to get further understanding on the inherent characters of aerosols of different sizes is to have the ability to effectively control and focus aerosols of different sizes.
SUMMARY
The primary object of the present invention is to provide an adjustable aerodynamic lens system for aerodynamic focusing of aerosols comprising a plurality of section tubes, wherein the section tubes with varying focusing orifices are able to be assembled in different sequence for different conditions.
An adjustable aerodynamic lens system for aerodynamic focusing of aerosols comprises a hollow tube having an inlet terminal, an outlet terminal and a focusing segment located between the inlet terminal and the outlet terminal, wherein the focusing segment includes a plurality of section tubes assembled in sequence, each of the section tubes has a first connecting end and a second connecting end forming at opposite sides of the section tube respectively and the second connecting end is assembled with the first connecting end of the adjacent section tube, and has a focusing orifice with a orifice diameter forming in the section tube, wherein the orifice diameters of the two adjacent section tubes are different.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram illustrating a multi-function aerosol characterization system according to one embodiment of the present invention for analyzing chemical properties, geometry, internal structure and electronic energetic level structures of aerosols.
FIG. 2 is a perspective view diagram illustrating an aerosol photoelectron spectrometer according to one embodiment of the present invention for analyzing the electronic energetic structures of aerosols.
FIG. 3 is a cross-sectional view diagram illustrating an adjustable aerodynamic lens system for aerodynamic focusing of aerosols according to one embodiment of the present invention.
FIG. 4 is a partial cross-sectional view diagram illustrating the adjustable aerodynamic lens system for aerodynamic focusing of aerosols according to one embodiment of the present invention, showing an inlet terminal of a hollow tube in particular.
FIG. 5 is a partial cross-sectional view diagram illustrating the adjustable aerodynamic lens system for aerodynamic focusing of aerosols according to one embodiment of the present invention, showing an outlet terminal of the hollow tube in particular.
FIG. 6 is a partial cross-sectional view diagram illustrating the adjustable aerodynamic lens system for aerodynamic focusing of aerosols according to one embodiment of the present invention, showing focusing orifices in particular.
FIG. 7A is a photoelectron spectrum obtained using the disclosed technology to measure the valence electronic properties of pure water in the aerosol phase and using synchrotron VUV radiation as the ionization source. The obtained photoelectron spectrum of pure water aerosols comprises the gaseous water evaporated from the aerosol surface and the condensed water in the aerosol.
FIG. 7B is an enlarged view of the above photoelectron spectrum marked by the dashed line showing the condensed water in the aerosol phase obtained using the disclosed technology to measure pure water in the aerosol phase.
FIG. 8 is obtained using the known liquid microjet technology and using He(I) ultraviolet light as the ionization source.
FIG. 9 is obtained using the known liquid microjet technology and using synchrotron VUV radiation as the ionization source.
FIG. 10 is obtained using the known liquid microjet technology, showing that pure water has energy band width ranging between 1.45 and 1.58 electron volts (eV).
DETAILED DESCRIPTION OF THE INVENTION
Together with the technical features as described preciously, the key functions of the adjustable aerodynamic lens system for aerodynamic focusing of aerosols as disclosed in the present invention will be clearly presented through the following embodiments.
It is to be noted that in any of the embodiments shown in the accompanying drawings, the indication of directions (e.g. up, down, left, right, front and rear) for illustrating the structures and movements of the components of the present invention is not absolute but relative. When these components are at the sites as shown, the descriptions are appropriate. Wherever the locations of these components are changed, the indication of directions shall be changed accordingly.
With reference to FIG. 1, a multi-function aerosol characterization system comprises an aerosol infrared spectroscopy apparatus A1, an aerosol photoelectron spectrometer B1 and an adjustable aerodynamic lens system for aerodynamic focusing of aerosols 1. In this embodiment, the aerosol photoelectron spectrometer B1 is an aerosol ultraviolet photoelectron spectrometer.
With reference to FIG. 1, the aerosol infrared spectroscopy apparatus A1 comprise an aerosol generation chamber A11, a valve A12, a Fourier-transform infrared spectrometer A13, a light source A14 and a control module (not shown). The control module precisely controls the temperature and pressure in the aerosol generation chamber A11, so as to make aerosol precursors in the aerosol generation chamber A11 aggregate into clusters which in turn nucleate, including homogeneous and heterogeneous nucleation so as to form an aerosol. The aerosol generation chamber A11 in the aerosol infrared spectroscopy apparatus A1 is configured to generate aerosol particles with well-controlled chemical compositions, and under well-defined ambient conditions, including temperatures, pressures and surrounding species so as to measure the properties of the target aerosol particles such as the vibrational energy levels, structural characteristics and generation mechanism as well as time-evolution using the Fourier-transform infrared spectrometer A13. Therefore, it is capable of generating aerosol particles of different sizes and forms under controlled conditions for detailed analysis on the structural and kinetic properties of aerosols.
With reference to FIGS. 1 and 2, the aerosol photoelectron spectrometer B1 comprises an aerosol source chamber B11, a differential pumping area B12, a photoelectron spectroscopy analysis chamber B13 and an electron energy analyzer B14. The aerosol source chamber B11 serves to make aerosol particles pass through the adjustable aerodynamic lens system for aerodynamic focusing of aerosols 1 and enter into a low-vacuum environment directly after leaving the adjustable aerodynamic lens system for aerodynamic focusing of aerosols 1. The differential pumping area B12 serves to reduce the chamber pressure to the extent such that the focused aerosol particles can enter the photoelectron spectroscopy analysis chamber B13 with a satisfactory vacuum condition necessary for photoelectron spectroscopic measurements. The photoelectron spectroscopy measurements are performed in the photoelectron spectroscopy analysis chamber B13, where the focused aerosol particles are photoionized by photons at specifically controlled photon energies, and the ejected photoelectrons of different kinetic energies are produced in the ionization region where the focused aerosol beam and the photon beam intersects. The ejected photoelectrons are then steered to the electron energy analyzer B14 where the kinetic energies of photoelectrons are analyzed.
With reference to FIG. 3, the adjustable aerodynamic lens system for aerodynamic focusing of aerosols 1 comprises a hollow tube. The aerosol particles generated in the aerosol generation chamber A11 or any other aerosol generation sources, first pass through the valve A12 and then into the hollow tube. In this embodiment, the aerosols passing through the hollow tube are collimated into a focused aerosol beam and steered into the aerosol photoelectron spectrometer B1 for photoelectron spectroscopy measurements and photoelectron kinetic energies analysis. The hollow tube has an inlet terminal 11, an outlet terminal 12 and a focusing segment 13 located between the inlet terminal 11 and the outlet terminal 12. It is to be noted that the hollow tube as shown in FIG. 1 has the inlet terminal 11 connected to the valve A12, and the aerosol particles are guided to the inlet terminal 11 through the valve A12. The hollow tube is partially contained in the aerosol source chamber B11.
With reference to FIGS. 3 and 4, the inlet terminal 11 of the hollow tube has an inlet orifice 111 with diameter 100-500 μm. In this embodiment, the diameter of the inlet orifice 111 is 300 μm. With reference to FIGS. 3 and 5, the outlet terminal 12 of the hollow tube has an outlet orifice 121 with diameter 1-5 mm. In this embodiment, the diameter of the outlet orifice 121 is 3 mm. It is to be noted that the size of the inlet orifice 111 determines the flow rate of the aerosol particles, the aerosol beam width and the pressure of the aerosol photoelectron spectrometer B1 during operation; and the size of the outlet orifice 121 determines the velocity of the aerosol beam and the time it takes to reach the photoionization area.
With reference to FIG. 3, the focusing segment 13 located between the inlet terminal 11 and the outlet terminal 12 includes a plurality of section tubes 131 and a plurality of extension tubes 132 assembled in sequence, wherein the section tubes 131 are close to the outlet terminal 12 and the extension tubes 132 are close to the inlet terminal 11. the inner shape of the section tubes 131 and the extension tubes 132 are limited to cylindrical to achieve aerodynamic focusing, however, the outer shape of the section tubes 131 and the extension tubes 132 can be either cylindrical or non-cylindrical. In the present invention, the section tubes 131 and the extension tubes 132 are characterized in that they are able to be assembled and/or disassembled in a selective manner. The extension tubes 132 jointly form an extended track space that is connected to the inlet orifice 111 and serve to increase the overall length of the focusing segment 13 so as to match the overall length of the aerosol source chamber B11. In this embodiment, the hollow tube has six extension tubes 132 assembled in sequence.
With reference to FIG. 6, each of the section tubes 131 has a first connecting end 1311, a second connecting end 1312 and a focusing orifice 131H, wherein the first connecting end 1311 and the second connecting end 1312 are formed at the two opposite sides of the section tube 131 respectively, and the focusing orifice 131H is formed in the section tube 131. In this embodiment, the focusing orifice 131H is formed on the first connecting end 1311 of the section tube 131.
With reference to FIG. 3, it is to be noted that each of the extension tubes 132 has connecting ends and connecting portions identical to those of the section tubes 131, but is formed as hollow tubes of the same inner diameters as those of the section tubes 131 without any focusing orifice 131H.
With reference to FIG. 6, the second connecting end 1312 is able to assemble with the first connecting end 1311 of the adjacent section tube 131. Preferably, the first connecting end 1311 has a first connecting portion 13111 formed on an outer wall of the first connecting end 1311, and the second connecting end 1312 has a second connecting portion 13121 formed on an inner wall of the second connecting end 1312, wherein the first connecting portion 13111 is inserted into the second connecting portion 13121 of the adjacent section tube 131. In this embodiment, the first connecting portion 13111 is an outer screw thread and the second connecting portion 13121 is an inner screw thread, wherein the outer screw thread of the first connecting portion 13111 and the inner screw thread of the second connecting portion 13121 of the two adjacent section tubes are screwed together.
With reference to FIGS. 5 and 6, the focusing orifice 131H of each section tube 131 has an orifice diameter, wherein the orifice diameters of the two adjacent section tubes are different. The section tubes having their focusing orifices of appropriate diameters are chosen according to the average size of aerosol particles to be focused, and then assembled in sequence, so as to make aerosol fluid passing through to form a beam of aerosol particles with good focusing quality. Preferably, the orifice diameters of the section tubes 131 are varied gradually along a propagation direction of the aerosol beam, wherein the propagation direction of the aerosol is from the inlet terminal 11 toward the outlet terminal 12. In this embodiment, the orifice diameters of the section tubes 131 are decreased gradually along the propagation direction of the aerosol beam.
With reference to FIG. 5, in this embodiment, the plurality of section tubes includes a first section tube 131A, a second section tube 131B, a third section tube 131C, a fourth section tube 131D and a fifth section tube 131E arranged in the propagation direction of the aerosol beam.
With reference to FIG. 5, the section tubes are assembled in sequence, for further explanation, the second section tube 131B locates between the first section tube 131A and the third section tube 131C, the third section tube 131C locates between the second section tube 131B and the fourth section tube 131D, and the fourth section tube 131D locates between the third section tube 131C and the fifth section tube 131E. The focusing orifice 131H in the first section tube 131A has a first orifice diameter, the focusing orifice 131H in the second section tube 131B has a second orifice diameter, the focusing orifice 131H in the third section tube 131C has a third orifice diameter, the focusing orifice 131H in the fourth section tube 131D has a fourth orifice diameter, and the focusing orifice 131H in the fifth section tube 131E has a fifth orifice diameter.
Because the orifice diameters of the section tubes 131 in this embodiment are decreased gradually along a propagation direction of the aerosol beam, the first orifice diameter is larger than the second orifice diameter, the second orifice diameter is larger than the third orifice diameter, the third orifice diameter is larger the fourth orifice diameter, and the fourth orifice diameter is larger the fifth orifice diameter. In this embodiment, the first orifice diameter is 5.0 mm, the second orifice diameter is 4.5 mm, the third orifice diameter is 4.0 mm, the fourth orifice diameter is 3.5 mm and the fifth orifice diameter is 3.0 mm. The fifth orifice diameter is the same as the outlet end 121 described previously. They both have the orifice diameter of 3 mm.
In other embodiments, the orifice diameters of the section tubes 131 are increased gradually along the propagation direction of the aerosol beam. Therefore, the first orifice diameter is smaller than the second orifice diameter, the second orifice diameter is smaller than the third orifice diameter, the third orifice diameter is smaller the fourth orifice diameter, and the fourth orifice diameter is smaller the fifth orifice diameter.
With reference to FIG. 5, the adjacent focusing orifices 131H are separated by a focusing length 133 with influences on the focusing quality and the size of focusable aerosol particles. Preferably, the focusing length 133 ranges between 10 and 100 mm. In this embodiment, the focusing length 133 is 50 mm.
For characterization of the performance of the aerosol photoelectron spectrometer, the present invention further uses the foregoing system to obtain the ultraviolet photoelectron spectrum of a pure water nanodroplet aerosol. The photon energy of the ionization radiation is first set at 25 eV. FIG. 7A is the ultraviolet photoelectron spectrum of pure water in an aerosol state which includes photoelectron signals from two states of pure water, namely the gas phase water molecules evaporated from the surface of pure water aerosols, and the condensed pure water droplets. In FIG. 7A, the numbers marked at some characteristic peaks are the fundamental vibration modes (v1, v2, v3) corresponding to the fine vibrational energetic structures of gas phase water molecules. FIG. 7B is an enlarged view of the same photoelectron spectrum illustrating the condensed pure water in the water droplet state. FIG. 7A and FIG. 7B clearly show the valence shell electronic energetic structure of pure water aerosols and the fine vibrational energetic level structure within its electron energy level structure. FIG. 7A and FIG. 7B demonstrate the superior spectral resolution of the aerosol photoelectron spectrometer of the present invention embodiment. Therein, the photoelectron spectrum of condensed phase water shows the vibrational energetic structure of condensed water for the first time.
Please compare FIG. 7A to FIG. 8, FIG. 9 and FIG. 10. FIG. 8 is obtained by Toennies and coworkers (J. Chem. Phys. 1997, 106, 9013-9031) using the conventional liquid microjet technology and He(I) ultraviolet radiation as the ionization source. In FIG. 8, the upper part is a photoelectron spectrum of gas phase water and the lower part is a photoelectron spectrum of condensed liquid phase water. The ionization energy of condensed phase pure water measured by Toennies and coworkers is 10.92 eV. FIG. 9 is obtained by Winter and coworkers (J. Phys. Chem. A 2004, 108, 2625-2632), also applying the conventional liquid microjet technology, but using synchrotron radiation as the ionization sources. The ionization energy of condensed phase pure water measured by Winter and coworkers is 11.16 eV. FIG. 10 is obtained by Suzuki and coworkers (Phys. Chem. Chem. Phys. 2011, 13, 413-417), also using the liquid microjet technology. The energy band width of pure water ranges between 1.45 and 1.58 eV. By comparing FIG. 7A to FIG. 8, FIG. 9 and FIG. 10, it is obvious that the photoelectron spectrum of condensed water measured by the present invention which utilizes the adjustable aerodynamic focusing system to introduce pure water aerosols into the focused aerosol beam in the aerosol photoelectron spectrometer B1 demonstrates higher spectral resolution than those shown in the related literatures.
The disclosed adjustable aerodynamic lens system for aerodynamic focusing of aerosols 1 has the following advantages:
- 1. The present invention divides the hollow tube into three composite parts so that researchers have improved flexibility to easily and selectively adjust the diameters of the inlet orifice 11, the outlet orifice 12 as well as the diameters of the focusing orifices 131H of the section tubes 131, so as to achieve better control of the size range of target aerosols to be studied. Thereby, the present invention provides a customized set of the section tubes 131 which can be easily assembled/disassembled in a size-selective manner to selectively characterize aerosols of various particle sizes, in contrast to the prior-art aerodynamic focus lens system that usually only has a single, fixed specification, which cannot be changed easily once it is manufactured.
- 2. The aerosol particle beam focused by using the present invention is highly collimated, with a beam width smaller than 1 mm.
- 3. As aerosol particles pass through each of the section tubes 131, the ambient pressure decrease progressively, such that when the aerosol particles arrive at the photoelectron spectroscopy analysis chamber B13 of the aerosol photoelectron spectrometer B1 they are under a high vacuum condition, which is required to carry out the photoelectron spectroscopy or other high vacuum based techniques, including aerosols mass spectrometry.
- 4. The present invention further discloses the control of focusing quality and the beam width of the focused aerosol particles by means of changing the focusing lengths 133 between the focusing orifices 131H.
The present invention has been described with reference to the preferred embodiments and it is understood that the embodiments are not intended to limit the scope of the present invention. Moreover, as the contents disclosed herein should be readily understood and can be implemented by a person skilled in the art, all equivalent changes or modifications which do not depart from the concept of the present invention should be encompassed by the appended claims.
The above-mentioned embodiment provides only an example of a combination between the present invention and photoelectron spectroscopy technology, and does not limit the scope of implementation of the present invention to other aerosol detection technologies. The adjustable aerodynamic focusing lens system as defined in the claims may work with other aerosol detecting technologies, including but not limited to aerosols mass spectrometry (AMS) in order to selectively focus aerosol particles of different sizes of interest.
Patent Application
20170047215
