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EP-3513162-B1 - RECIRCULATING AEROSOL DILUTER MECHANISM

EP3513162B1EP 3513162 B1EP3513162 B1EP 3513162B1EP-3513162-B1

Inventors

  • JOHNSON, JASON PAUL
  • ANDERSON, ROBERT
  • KOLB, Jeremy Jens
  • AVENIDO, Aaron Serafin
  • PLAUTZ, Robert
  • ISVIK, Steven Keith

Dates

Publication Date
20260513
Application Date
20170914

Claims (8)

  1. A recirculating aerosol dilution system (110) to dilute a sampled aerosol stream and pass a diluted sampled aerosol stream towards a particle measurement portion (140) of a passive aerosol diluter system (100), the recirculation aerosol dilution system (110) comprising: an aerosol sample inlet (101) to receive a sample of an aerosol stream; a primary diluter device (103) having a first inlet coupled pneumatically downstream from the aerosol sample inlet (101) and a second inlet to accept a filtered portion of a portion of the sampled aerosol stream, the primary diluter device (103) to combine the filtered portion with an additional sampled aerosol stream received from the aerosol sample inlet (101); a cyclone separator (105) coupled downstream from the primary diluter device (103); a flow diverter device (127) coupled pneumatically downstream from the cyclone separator (105) to split at least the sampled aerosol stream into a first portion of the sampled aerosol stream and a remaining portion of the sampled aerosol stream to pass the first portion of the sampled aerosol stream towards the particle measurement portion (140), wherein the concentrated aerosol stream divides into two paths, in one path, the majority of the original aerosol stream is cleansed of virtually all particles, in the other path, the remaining small fraction of the aerosol stream retains its original particle concentration, and the two paths re-combine to produce a pre-determined dilution ratio of the aerosol stream; a filter (113) coupled pneumatically downstream of and in fluid communication with the flow diverter device (127) to receive the remaining portion of the sampled aerosol stream from the aerosol sample inlet (101); and a primary dilution-flow orifice portion (120) for metering airflow and coupled pneumatically downstream of and in fluid communication with the filter (113) to provide the filtered aerosol stream to the second inlet of the primary diluter device (103).
  2. The recirculating aerosol dilution system (110) of claim 1, wherein the primary dilution-flow orifice portion (120) includes a critical orifice (119), a differential-pressure gauge (121), a temperature gauge (123), and an absolute pressure gauge (125).
  3. The recirculating aerosol dilution system (110) of claim 1 or claim 2, further comprising a humidity sensor body (107) including temperature gauge (109) and a relative humidity gauge (111) in the flow path between the primary dilution-flow orifice portion (120) and the second inlet of the primary diluter device (103).
  4. The recirculating aerosol dilution system (110) of any preceding claim, wherein the primary diluter device (103) includes a mixing cone.
  5. The recirculating aerosol dilution system (110) of any preceding claim, further comprising a pump (115) and a desiccant dryer (117), wherein the pump (115) is connected to draw dilution airflow from the filter (113) and into the desiccant dryer (117) to pass the dried and filtered airflow towards the primary dilution-flow orifice portion (120).
  6. A method of diluting a sampled aerosol stream in a recirculating aerosol dilution system (110) and passing a diluted sampled aerosol stream towards a particle measurement portion (140) of a passive aerosol diluter system (100), the method comprising: receiving a sample of an aerosol stream at a primary diluter device (103), the primary diluter device (103) having a first inlet coupled pneumatically downstream from an aerosol sample inlet (101) and a second inlet to accept a filtered portion of a portion of the sampled aerosol stream; combining, in the primary diluter device (103), the filtered portion with an additional sampled aerosol stream received from the aerosol sample inlet (101); removing water vapor and large particles from the aerosol stream output from the primary diluter device (103) using a cyclone separator (105); splitting, within a flow diverter device (127), at least the sampled aerosol stream from the cyclone separator (105) into a first portion of the sampled aerosol stream and a remaining portion of the sampled aerosol stream to pass the first portion of the sampled aerosol stream towards the particle measurement portion (140); filtering the remaining portion of the sampled aerosol stream and providing a filtered aerosol stream to the second inlet of the primary diluter device; metering airflow using a dilution-flow primary orifice portion (120) coupled pneumatically downstream of and in fluid communication with the filter (113); and providing the filtered aerosol stream from the dilution-flow primary orifice portion (120) to the second inlet of the primary diluter device (103); wherein the concentrated aerosol stream divides into two paths, in one path, the majority of the original aerosol stream is cleansed of virtually all particles, in the other path, the remaining small fraction of the aerosol stream retains its original particle concentration, and the two paths re-combine to produce a pre-determined dilution ratio of the aerosol stream.
  7. The method of claim 6, further comprising: using a mixing cone in the primary diluter device (103) to recombine the filtered aerosol stream and the sampled aerosol stream received at the sample inlet (101).
  8. The method of claim 6 or claim 7, further comprising: using a pump (115) and a desiccant dryer (117), wherein the pump (115) draws dilution airflow from the filter (113) and into the desiccant dryer (117) to pass the dried and filtered airflow towards the primary dilution-flow orifice portion (120).

Description

PRIORITY APPLICATION This application claims the benefit of priority to U.S. Provisional Application Serial No. 62/394,723, filed on September 14, 2016. BACKGROUND In a number of airborne particle-measurement and particle-concentration studies, a condensation particle counter (CPC, also known as a condensation nucleus counter (CNC)) is used to detect particles in a monitored environment. In a CPC, particles can be detected that are too small to scatter enough light to be detected by conventional detection techniques (e.g., light scattering of a laser beam in an optical particle counter, OPC). The small particles are grown to a larger size by condensation formed on the particle. That is, each particle serves as a nucleation point for the working fluid; a vapor, which is produced by the instrument's working fluid, is condensed onto the particles to make the particles larger. After achieving growth of the particle due to condensation of the working fluid vapor onto the particle, CPCs function similarly to optical particle counters in that the individual droplets then pass through the focal point (or line) of a laser beam, producing a flash of light in the form of scattered light. Each light flash is counted as one particle. However, in certain environments, such as air pollution measurements, engine exhaust research, and regulatory studies involving measurement of size or concentrations of particles in an aerosol stream, the concentration of particles is too high to measure accurately with a CPC. Often, such particle-measurement methods and procedures are defined by a governmental agency, such as the United States Environmental Protection Agency (EPA) or the California Air Resources Board (CARB). Often, a concentration of particles is too high to measure accurately with a CPC. In these environments, particle concentrations can range up to 5 x 109 particles per cubic centimeter or higher. However, many CPCs can only measure particle concentrations accurately at much lower concentration ranges (e.g., perhaps a factor of 104 lower than the stated particle concentration above) before inaccurate monitoring occurs due to coincidence errors (counting two or more particles in an aerosol sample stream simultaneously). Although various capillary-type and orifice dilutors are known in the art, none are capable of accurately providing a known dilution ratio under circumstances of varying temperature and absolute pressure. The problem is often compounded as the actual dilution ratio can vary as a function of time. US 5922976 A describes an aerosol detection system for measuring particle number distribution with respect to particle dimension in an aerosol sample. The system includes an alternating dual-bag sampler, a radially classified differential mobility analyzer, and a condensation nucleus counter. US 2009/044599 A1 concerns a quantitative aerosol dilution system with a first flow path having particle counter connected to an aerosol source of an initial particle concentration via an inlet conduit, and a second flow path connected to the inlet conduit and branching to form a third flow path and a fourth flow path which meet at a junction. An outlet path connects to the junction. A low particle counter, a filter and a flow meter are positioned in the outlet path, facilitating a traceable measurement of the dilution factor of an aerosol particle concentration traceable. SU 808 111 A1 details a system for measuring flow rate ratios in an aerosol sample by diluting the aerosol by mixing the aerosol stream with a stream of pure gas and measuring pressure drops in the flows. An initial aerosol stream is divided into two equal flows, these flows are filtered of aerosol particles; then part of an unfiltered aerosol stream is fed into one of them, both flows are passed through the constriction devices and mixed, the ratio of the pressure drop across one of the narrowing devices to the pressure drop between the narrowing devices is measured, which determines the degree of dilution of the aerosol and, depending on the degree of dilution, controls the flow rate in the unfiltered aerosol stream. US 2007/056395 A1 relates to a particle counter that has a saturator inhaling air in an atmosphere and vaporizing a working liquid therein; and an electrical detection unit electrically shielding an internal space thereof to maintain a temperature of the space to be constant, the air and vaporized working liquid flowing into the electrical detection unit through a side thereof from the saturator, condensing the vaporized working liquid on surfaces of ultrafine particles contained in the air, and charging the particles to measure a current of the charged particles, thereby measuring the number of the particles included in the air. US 5 058 440 A concerns a gas sampling device including a dilution tunnel that reduces contamination or soiling of the ducting leading to a filter assembly. The gas sampling device has a sampling probe disposable in