Simultaneous measurement of the size distribution of aerosol particles and the number of particles of each size in a flowing gaseous medium
阅读：864发布：2023-07-20
专利汇可以提供Simultaneous measurement of the size distribution of aerosol particles and the number of particles of each size in a flowing gaseous medium专利检索，专利查询，专利分析的服务。并且A method and apparatus are described for measuring the size distribution of aerosol particles in a gas stream and the number of particles of each size. Particle-laden gas flows through the apparatus at a controlled velocity. A group of particles located in a first region are rapidly charged by a pulsed corona discharge. The group of charged particles flows downstream into a second region in which an axial electric field is applied. The mobility of the charged particles through the field is a function of their charge, which in turn is a function of their size, so that the larger particles move through the second region faster and thus in less time than slow particles. In this manner, particles having a common size are concentrated in an axial direction as they move downstream. The magnitude of the charge on particles arriving at the downstream end of the second region is related to the elapsed time between the time of the charging pulse and the moment at which the charge is measured to indicate the particle size distribution and number of particles of each size.，下面是Simultaneous measurement of the size distribution of aerosol particles and the number of particles of each size in a flowing gaseous medium专利的具体信息内容。
1. Apparatus for simultaneously measuring the concentration and size distribution of aerosol particles in a flowing gaseoUs medium, comprising: means for causing at least a portion of said gaseous medium to flow through a cylindrical structure in a given direction parallel to the axis thereof; means for generating a timed electrical pulse having a substantially constant voltage throughout its duration, said pulse duration being short in comparison with the time required for said portion of said gaseous medium to flow through said cylindrical structure; means responsive to said pulse for electrically charging a group of said particles in a first region, the axial length of said group in said given direction being short in comparison with the axial length of said cylindrical structure; means for measuring the magnitude of the electric charge on said particles as a function of time elapsed from the charging of said particles; and means effective upstream from said measuring means for subjecting said group of charged particles to an electric field in a second region extending in said given direction for a length that is long in comparison with the axial length of said group of charged particles, said electric field being effective to accelerate said charged particles positively in said given direction, so that said elapsed time for a given charged particle is a function of the magnitude of the charge on said particle.
2. Apparatus according to claim 1, wherein: said means for electrically charging a group of said particles includes means for establishing a high ion density and a strong electric field simultaneously in said first region of said cylindrical structure upstream from said second region.
3. Apparatus according to claim 2, wherein: the quantity of electric charge imparted to any particle of said group depends upon the size of said particle so that the time of arrival of said particle at said measuring means depends upon the size of said particle.
4. Apparatus according to claim 3, wherein: said measuring means includes a device for detecting the total charge on the particles within a particular incremental size range which arrive at said measuring means within an incremental time interval which corresponds with said incremental size range to produce a signal, said measuring means further being responsive to said timed electrical pulse to provide a time reference for said signal for generating a display indicative of the size distribution of the particles in each group and the number of particles of each size.
5. Apparatus for monitoring a flow stream including fluid and particles in said stream to determine the size distribution of said particles and the number of particles of each size, comprising: means for generating an electrical timing pulse, said pulse having a substantially constant voltage throughout its time interval; field charging means responsive to said pulse for electrically charging that portion of said particles located in a first region of said fluid flow stream during said pulse, said first region having a first axial length; means for establishing an axial electric field in a second region extending axially for a second length along said flow stream downstream from said first region, said electric field being effective to accelerate said charged particles positively in the downstream axial direction to separate said charged particles in said axial direction according to the magnitude of the charge thereon so that larger charged particles will traverse said second region in shorter time than smaller charged particles, said second length being long relative to said first length; and means responsive to said timing pulse for detecting the times of traverse of said charged particles of various sizes through said second region and for detecting the total charge on those particles of a given incremental size range which traverse said second region in a given time, said detecting means generating an output signal varying in amplitude and time so that at any given time the signal amplitude depends on the nUmber of particles of a given size and the time of said amplitude depends on the magnitude of said given size.
6. Apparatus according to claim 5, wherein: said establishing means includes an electrode located at each end of said second region and means for applying a selected voltage across said electrodes; and said output signal generating means includes first and second coaxial, electrically conductive cylinders mounted in said flow stream downstream from said second region, said first cylinder surrounding said second cylinder and having an upstream end connected to the electrode located at the downstream end of said second region, said second cylinder having an upstream end spaced down stream from said downstream electrode to form a third region, said axially separated charged particles being effective in said third region to induce in said coaxial cylinders a current varying with respect to time according to the size of the particles and having an amplitude at any particular time according to the total charge density of the charged particles in said third region of said particular time.
7. Apparatus for simultaneously determining the size distribution of aerosol particles and the number of aerosol particles of each size in a gas stream, which comprises: means for defining a flow path for said gas stream and said particles, said flow path having first, second and third regions arranged in seriatim along a longitudinal axis of said flow path, said second region being between said first and third regions and having an axial length substantially exceeding that of each of said first and third regions; means for moving said gas stream and said particles into said first region at a controlled velocity and for moving said gas stream through said second and third regions at said controlled velocity; means for generating a series of electrical timing pulses, each pulse having substantially constant voltage throughout its duration; means responsive to each of said timing pulses for electrically charging only a specific group of particles that are in said first region during a given interval of time commencing with each of said timing pulses, said groups being axially spaced along said flow path; a pair of spaced electrodes, a first of said electrodes being mounted at the upstream end of said second region and a second of said electrodes being mounted at the downstream end of said second region; means connected to said pair of electrodes for establishing an electric field axially across said second region, said axial electric field being effective to increase the axial velocity of the charged particles in each said group relative to said controlled velocity according to the amount of electrical charge on said charged particles so that as said axially spaced groups of charged particles move axially through said second region those of said charged particles of a given group having different sizes become separated axially according to size and particles of the same size become axially concentrated; means responsive to the total charge on said axially concentrated particles of a given group advancing through said third zone for generating an output signal for each said group, said output signal varying with time according to the size distribution of the charged particles in each group and having an amplitude representing the number of particles of each size in said size distribution of said group; and means responsive to said output signal and said timing pulse for indicating the size distribution of the particles in each said group and the number of particles of each size in said size distribution.
8. Apparatus according to claim 5, further comprising: means located upstream and downstream from said field charging means for reducing the turbulence in said fluid flow stream.
9. Apparatus according to claim 6, wherein: said second cylinder is provided with an axial length selected so that all of the particles Charged during said timing pulse enter and remain in said second cylinder until the last of said charged particles enters said second cylinder.
10. Apparatus according to claim 1, which further comprises: means responsive to the temperature of said gas stream for generating a temperature control signal; and means responsive to said temperature control signal for varying the strength of said axial electric field to compensate for changes in the temperature of said gas stream.
11. Apparatus for monitoring the size distribution of particles in a fluid medium and indicating the relative number of particles of each size, comprising: a first tube having an inlet end and an outlet end to permit said fluid medium to flow at a relatively constant velocity through said tube; means for generating a series of timed electrical pulses, each pulse having a substantially constant voltage throughout its duration, said pulse duration being short in comparison with the time required for said fluid medium to flow through said tube; field charging means received in said inlet end of said first tube, said field charging means being responsive to said constant voltage pulses for cyclically electrically charging the particles received in a relatively short axial length of said first tube; a pair of grids mounted across said first tube between said inlet end and said outlet end thereof downstream from said field charging means, said grids being spaced by an axial distance that is substantial as compared to said short axial length; means for applying across said grids an electric potential to produce an electric field extending axially in said tube, said field being effective to axially separate the charged particles according to the magnitude of the charges on the particles; a second tube mounted coaxially in said first tube and having an upstream inlet end secured to said downstream grid for receiving said axially separated charge particles; and a third tube mounted coaxially in said second tube and having an upstream inlet end located downstream from said downstream grid to form an interaction region, said third tube having a screen mounted across said inlet end so that said axially separated charged particles flowing through said interaction region induce a current in said screen and said third tube, said current having an amplitude in proportion to the magnitude of the total charge on the particles in the interaction region at any moment of time and being variable with respect to time according to the size of the particles.
12. Apparatus for simultaneously measuring the concentration and size distribution of aerosol particles in a flowing gaseous medium, comprising: means for moving said gaseous medium at a controlled flow velocity through successive first, second and third separate regions serially arranged along a given direction of movement; means for generating a timed electrical pulse having a substantially constant voltage throughout its duration, said pulse duration being short in comparison with the time required for said medium to flow through said first, second and third regions; means responsive to said pulse for electrically charging those of said particles which are moving through said first region during a given time interval; means for applying an electric field to said charged particles in said given direction within said second region, said electric field being effective to accelerate said charged particles positively in said given direction; and means responsive to the magnitude of the total electric charge on those of said charged particles moving through said third region at successive times elapsed from said given time interval for generating a signal varying with time according to the size distribution of said aerosol particles.
13. A method of measuring the size distribution of aerosol particles in a gas, comprising the steps of: moving said gas and particles in a selected flow paTh and at a controlled velocity through first, second and third regions spaced in seriatim axially along said flow path, said first and third regions being axially short relative to the axial length of said second region; generating a timed electrical pulse having a substantially constant voltage throughout its duration, said pulse duration being short in comparison with the time required for said gas to move through said first, second and third regions; electrically charging those of said particles that are moving through said first region during a time period determined by said pulse to produce a group of charged particles moving axially into said second region; establishing an electric field axially along said flow path to axially separate the charged particles in said group according to size; and measuring the elapsed time between the start of said time period and the time at which the various axially separated charged particles enter said third region to indicate the size distribution of the aerosol particles.
14. A method of measuring the particle size distribution and the number of particles of each size in a gas, comprising the steps of: directing the gas and the particles along a flow path at a controlled velocity; generating a timed electrical pulse having a substantially constant voltage throughout its duration, said pulse duration being short in comparison with the time required for said gas to traverse said flow path; during a short time interval determined by said pulse electrically charging the particles moving through a short axial length of said flow path; subjecting said charged particles to an electric field extending axially along said flow path for a given distance to vary the elapsed time between said time interval and the time at which charged particles having different sizes pass a given location spaced downstream from said electric field, said given distance being substantially longer than said short axial distance; measuring said elapsed times for said charged particles to indicate the size distribution of said particles; and measuring the total charge of said charged particles at said given location for each said elapsed time to indicate the number of particles of each size in said size distribution.
15. Apparatus for measuring the concentration and size distribution of aerosol particles in a gas stream flowing in a given axial direction, comprising: pulsed means effective during a given time interval for electrically charging a group of said particles, said group having a short length in said given direction; means for measuring the magnitude of the electric charge on said particles as a function of time elapsed from said given time interval; means effective upstream from said measuring means for subjecting said group of charged particles to an electric field extending for a relatively long length in said given direction so that said elapsed time for a given charged particle is a function of the magnitude of the charge on said particle; means responsive to the temperature of said gas stream for generating a temperature control signal; and means responsive to said temperature control signal for varying the strength of said axial electric field to compensate for changes in the temperature of said gas stream.
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