Patent ID: 12253452

DETAILED DESCRIPTION

The description that follows includes illustrative examples, devices, and apparatuses that embody various aspects of the disclosed subject matter. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide an understanding of various embodiments of the inventive subject matter. It will be evident however, to those of ordinary skill in the art, that various embodiments of the disclosed subject matter may be practiced without these specific details. Further, well-known structures, materials, and techniques have not been shown in detail, so as not to obscure the various illustrated embodiments.

As used herein, the term “or” may be construed in an inclusive or exclusive sense. Additionally, although various exemplary embodiments discussed below focus on counting particles from high-concentration emission sources, the disclosed subject matter is also related to particle counting and removal of volatile and semi-volatile particles from engine emissions without a need of a volatile particle remover (VPR). Upon reading and understanding the disclosure provided herein, a person of ordinary skill in the art will readily understand that various combinations of the techniques and examples may all be applied serially or in various combinations. As an introduction to the subject, a few embodiments will be described briefly and generally in the following paragraphs, and then a more detailed description, with reference to the figures, will ensue.

The various embodiments of the high-temperature condensation particle counter (HT-CPC) disclosed herein show superior performance over contemporaneous reported designs, such as the HT-CPC100of the prior art as shown and described with reference toFIG.1. As disclosed herein, the particle-counting statistics of the disclosed embodiments of the HT-CPC are greatly improved over prior art systems. For example, the sample flows of the disclosed subject matter are about eight times higher than those systems reported previously in the literature. Additionally, the makeup flow and concentric-tube design, discussed in more detail below, keep the optical elements cool, minimize particle losses to the nozzle, and prevent or reduce volatile contents from re-nucleating in the flow path and optics block. The operating temperatures of the disclosed subject matter are also lower than the reported, prior art designs and keep the temperatures well below the working-fluid flash-point of 243° C. (in one exemplary embodiment). Consequently, the lower operating temperatures are advantageous in maintaining better working-fluid stability and a safer instrument by keeping the operating temperatures well below flash points of the various working-fluids. Further, a working fluid that is chemically more stable allows various ones of the disclosed embodiments of the HT-CPC also to use air as the carrier gas without having working fluid oxidation and degradation issues, thereby significantly simplifying instrument design and reducing the operating cost.

In the following detailed description, reference is made to the accompanying drawings that form a part of the high-temperature CPC and in which is shown, by way of illustration, specific embodiments. Other embodiments may be utilized and, for example, various thermodynamic, electrical, or physical changes may be made without departing from the scope of the present disclosure. The following detailed description is, therefore, is to be taken in an illustrative sense rather than in a limiting sense.

In general, a condensation particle counter (also known as a condensation nucleus counter) is used to detect particles in a monitored environment where the particles 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). 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 working fluid of the particle detection instrument, is condensed onto the particles to make them larger. After achieving growth of the particle due to condensation of the working fluid vapor onto the particle, CPCs then function similarly to optical particle counters in that the individual droplets subsequently 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. The science of condensation particle counters, and the complexity of the instrumentation, lies with the technique to condense vapor onto the particles. When the vapor surrounding the particles reaches a specific degree of supersaturation, the vapor begins to condense on the particles. The magnitude of supersaturation determines a minimum-detectable particle size of the CPC. Generally, the supersaturation profile within the instrument is tightly controlled.

With reference now toFIG.2A, a schematic diagram of an exemplary embodiment of an HT-CPC200in accordance with various embodiments disclosed herein is shown. The HT-CPC200is shown to include a saturator block203, a condenser block205, a makeup-flow block215, and an optics block219. In a specific exemplary embodiment, the optics block219comprises an optics block from a TSI® Model 3772 CPC having a slightly modified detector board. The modified detector board is configured to adjust the particle-counting threshold. However, in general, the optics block219incorporates an illumination source (e.g., a laser) and detection optics similar to or the same as other CPCs described above.

The HT-CPC200ofFIG.2Acomprises of two flow streams: a sample flow and a makeup flow. Unlike the prior at HT-CPC100discussed above with reference toFIG.1, which incorporates a TSI® Model 3025 CPC-like capillary flow design, the HT-CPC200includes an inlet to allow a sampled particle-laden gas flow201to be introduced directly into the saturator block203. This design has several advantages over the prior art including a higher sample-flow rate (producing a better statistical sample in less time), a simplified mechanical design, and more accurate and robust flow control and measurement. For example, a sample flow rate of the HT-CPC200flow rate is about eight-times greater, or more, than devices of the prior art. As a result of the higher sample-flow rate, the HT-CPC200counting statistics are significantly better than prior art devices.

Further, during operation of the HT-CPC200, hot gas coming from a flow stream207from the condenser block205(operating substantially above ambient temperature as noted below) is merged with a substantially particle-free output gas214(at approximately ambient room temperature of, for example, about 20° C.) providing a makeup gas-flow prior to entering the makeup-flow block215and subsequently entering the optics block219. The makeup gas-flow serves at least three purposes: (1) keeping the optics block219cool (e.g., to approximately ambient room temperature); (2) diluting any excess working fluid vapors and condensable vapors from the flow stream207to reduce or minimize the vapors from re-nucleating within the flow path and in the optics block219; and (3) supplementing the sampled particle-laden gas flow201to keep the optics flow at about, for example, 1 lpm. The concentric design of the makeup-flow block215keeps particles from the sampled particle-laden gas flow201confined close to a centerline of the flow path as the sampled particle-laden gas flow201is surrounded by gas from the particle-free output gas214. Consequently, particle losses to nozzles are reduces or minimized in the gas flow217entering the optics block219.

The sampled particle-laden gas flow201enters the saturator block203, continues through the condenser block205, and subsequently enters the makeup-flow block215from the flow stream207. The makeup-flow block215in this embodiment is an open-loop design. A makeup-flow apparatus209includes a valve211, to control a volumetric flow or mass flow of gas, and a filter213, to substantially remove any particles from the gas. The filter213may comprise various types of particulate-air filter known in the art, such as a high-efficiency particulate air (HEPA) filter or ultra-low particulate air (ULPA) filter. The valve211may comprise a number of gas-flow control devices known in the art such as a needle valve, a mass-flow controller, a critical orifice, or other type of device. An input to the valve211may comprise clean, dry air (CDA), nitrogen, or any another gas to provide a substantially particle-free output gas214to the makeup-flow block215.

Except for volumetric flowrates, operating temperatures, and working fluids, as described in more detail below, the saturator block203and the condenser block205function similarly to other types of CPCs described above. An example of a prototype of the HT-CPC200was constructed using portions of hardware from a TSI® Model 3777 CPC. To accommodate the high temperatures encountered by the HT-CPC, all O-rings of the Model 3777 were replaced with Kalrez® O-rings (available from E. I. DuPont De Nemours and Co., 1007 Market Street, Wilmington, Delaware 19898, USA) and Delrin® insulators from the Model 3777 CPC (also available from E. I. DuPont De Nemours and Co.) were replaced with Macor® machinable-ceramic pieces (Macor® is available from Corning Glass Works, Houghton Park, Corning, NY 14830, USA) or other high-temperature insulators.

Unlike conventional CPCs, which typically use thermo-electric devices (TEDs) to control condenser temperatures, various ones of the disclosed embodiments of a temperature of the condenser block205of the HT-CPC200are regulated with, for example, two mica heaters. The saturator block203also has two mica heaters (although a person of ordinary skill in the art, upon reading and understanding the disclosure provided herein, will recognize that a larger or smaller number, or other types of heater, may be substituted as well). In this exemplary embodiment, all four heaters are controlled and monitored by standalone proportional-integral-derivative (PID) controllers. Various saturator and condenser temperatures were evaluated and the temperatures of the saturator block203and the condenser block205were eventually set, in this exemplary embodiment of the HT-CPC200, to 235° C. and 160° C., respectively.

Several workings fluids were evaluated for use in the HT-CPC200. In a specific exemplary embodiment, Dow Corning® 705 (DC705), a type of diffusion-pump oil, performed for the example conditions disclosed herein. Dow Corning® 705 is a silicone pump-fluid and includes pentaphenyl trimethyl trisiloxane. For one embodiment of the HT-CPC200, a piece of fiberglass insulation was cut and used as a wick. Approximate exemplary operating parameters of the HT-CPC200and the HT-CPC100of the prior art are summarized in Table I, below. Note that the temperatures for the HT-CPC200are lower and well below the working-fluid flash-point of 243° C. The lower operating temperature may be advantageous to an increased stability of the working fluid as well as a safer instrument. Moreover, a working fluid that is chemically more stable allows various ones of the disclosed embodiments of the HT-CPC to use air as the carrier gas without having oxidation and degradation issues of the working fluid, thereby significantly simplifying instrument design and reducing operating costs.

TABLE IOperating ParametersHT-CPC 100HT-CPC 200(prior art)Sample Flow0.165 lpm0.02 lpmCondenser Flow0.165 lpm0.275 lpmOptics Flow1 lpm1 lpmSaturator235° C.290° C.TemperatureCondenser160° C.250° C.TemperatureOptics~24° C. (not45° C.Temperaturecontrolled)Working FluidDC 705DC 705Carrier GasAirNitrogen

Referring now toFIG.2B, a schematic diagram of an exemplary embodiment using a closed-loop design for flow control of an HT-CPC230and having gas pumps241, in accordance with various embodiments disclosed herein, is shown. The HT-CPC230is shown to include a saturator block233, a condenser block235, a makeup-flow block251, a closed-loop particle-free gas supply239, an optics block253, a downstream filter261, and a downstream critical-orifice263. The saturator block233and the condenser block235may the same as or similar to the saturator block203and the condenser block205ofFIG.2A. However, the saturator block233and the condenser block235ofFIG.2Bmay be configured to operate at temperatures dissimilar to those of the saturator block203and the condenser block205ofFIG.2A. Also, the optics block253may the same as or similar to the optics block219ofFIG.2A. However, the optics block253of the HT-CPC230also incorporates a curtain flow design, using a clean, curtain-flow gas240from the closed-loop particle-free gas supply239. Embodiments of a curtain-flow design are described in more detail with reference toFIGS.2D and2E, below.

In an embodiment, the closed-loop particle-free gas supply239includes three sections: a makeup gas-supply section232, a curtain-flow gas-supply section234, and a recirculation gas-supply section236. As described in more detail below, the gases within these sections use at least a portion of an outlet flow-stream242from the optics block253to provide an input feed gas to the makeup gas-supply section232and the curtain-flow gas-supply section234. The makeup gas-supply section232and the curtain-flow gas-supply section234provide substantially particle-free output gas238and curtain-flow gas240.

The makeup gas-supply section232includes a gas pump241, an orifice243to control a volumetric flow of the gas from the pump, a pressure gauge245to monitor a pressure drop across the orifice243to facilitate flow control, a heat exchanger247, and a filter249. The gas pumps241may comprise one of a variety of gas pumps known in the art such as carbon-vane pumps and other rotary pumps, reciprocating pumps, peristaltic pumps, and a variety of other gas-pump types. As is known in the art, a differential-pressure flow-control device (e.g., a critical orifice) provides a substantially constant flowrate of a gas under varying load conditions. With a more capable gas pump, a constant flowrate can also be achieved with choked flow by using a smaller opening orifice. In this case, the orifice243is referred to as critical orifice and the pressure gauge245is optional. In order for the choked flow to function properly, a minimum pressure drop, ΔP, is maintained across the critical orifice243to provide the substantially constant flowrate. Depending on other conditions, the pressure drop in typically maintained in excess of 350 mm Hg (approximately 14 inches of Hg). The optional pressure gauge245allows for monitoring the pressure drop to maintain the substantially constant flowrate. In this embodiment, the heat exchanger247removes heat from the gas to a desired temperature (e.g., approximately ambient room temperature of approximately 20° C.). In embodiments, the heat exchanger247can also be used to add heat to the gas. The filter249may be the same as or similar to the filter213ofFIG.2A. The makeup gas-supply section232provides clean, filtered gas through the particle-free output gas238that is fed into the makeup-flow block251, where the filtered gas is combined with an outlet flow-stream237from the condenser block235, which includes both the sampled particle-laden gas flow231and vapors from working fluid with the saturator block233, some of which have nucleated onto particles from the sampled particle-laden gas flow231. An outlet flow-stream252includes combined flow-streams from the outlet flow-stream237and the particle-free output gas238.

The curtain-flow gas-supply section234also includes a gas pump241, an orifice243to control a volumetric flow of the gas from the pump, a pressure gauge245to monitor a pressure drop across the orifice243to facilitate flow control, a heat exchanger247, and a filter249. Each of these components within the curtain-flow gas-supply section234may be the same as or similar to the related components of the makeup gas-supply section232. The curtain-flow gas-supply section234provides clean, filtered gas through the curtain-flow gas240that is fed into the optics block253to prevent or reduce an amount of particulate matter and vapor contamination on optical elements within the optics block253. As noted above, embodiments of a curtain-flow design are described in more detail with reference toFIGS.2D and2E, below.

The recirculation gas-supply section236uses at least a portion of the outlet flow-stream242from the optics block253to provide an input feed gas to the makeup gas-supply section232and the curtain-flow gas-supply section234. The recirculation gas-supply section236includes a primary filter255, a secondary filter257, and a gas dryer259. The primary filter255may be the same as or similar to the filter213ofFIG.2A. The secondary filter257may comprise, for example, a charcoal filter. A charcoal filter is known to adsorb certain types of molecules such as hydrocarbons and other molecules that may be present within the sampled particle-laden gas flow231as well as vapors from the working fluid within the saturator block233. The gas dryer259may comprise, for example, a silica dryer to adsorb at least a portion of moisture (e.g., working fluid vapor) from the outlet flow-stream242. The gas dryer259may also comprise one or more other types of chemical or mechanical dryers (e.g., a compressed-gas dryer) as well.

The downstream filter261removes most particles from a remaining portion of an outlet flow-stream from the optics block253that are not sent to the recirculation gas-supply section236. The downstream critical-orifice263limits an amount of the outlet flow-stream from the optics block253that is released as a clean flow-stream265to the environment.

Approximate exemplary operating parameters of the HT-CPC230are summarized in Table II, below. Note that the temperatures for the HT-CPC230are lower and well below the working-fluid flash-point of 243° C. for the Dow Corning® 705 diffusion-pump oil used in this exemplary embodiment. The lower operating temperature may be advantageous to an increased stability of the working fluid as well as a safer instrument. A working fluid that is chemically more stable allows the HT-CPC230to use air as the carrier gas without having oxidation and degradation issues of the working fluid, thereby significantly simplifying instrument design and reducing operating costs.

TABLE IIOperating ParametersHT-CPC 230 OperatingParametersSample Flow0.2 lpmCondenser Flow0.2 lpmOptics Flow2 lpmSaturator Temperature230° C.Condenser Temperature186° C.Optics Temperature~24° C. (not controlled)Working FluidDC 705Carrier GasAir

Referring now toFIG.2C, a schematic diagram of an exemplary embodiment using a closed-loop design for flow control of an HT-CPC270and having a single pump, in accordance with various embodiments disclosed herein is shown. The HT-CPC270is similar to the HT-CPC230ofFIG.2B. However, rather than having separate sections for the makeup gas-supply section232and the curtain-flow gas-supply section234, the HT-CPC270uses a combined makeup and curtain-flow gas-supply section271having the pump273, a combined orifice and pressure gauge combination275, a heat exchanger277, and a filter279. Downstream of the filter279, the gas-supply is split into a particle-free output gas287and a curtain-flow gas289. The curtain-flow gas289is controlled by a valve281and a remaining portion of the gas from the filter279is controlled by a differential-pressure flow-control device that comprises an orifice285and a pressure gauge283.

The particle-free output gas287provides clean, filtered gas through to the makeup-flow block251, where the filtered gas is combined with the outlet flow-stream237from the condenser block235, which includes both the sampled particle-laden gas flow231and vapors from working fluid with the saturator block233, some of which have nucleated onto particles from the sampled particle-laden gas flow231. An outlet flow-stream291from the makeup-flow block251includes combined flow-streams from the outlet flow-stream237and the particle-free output gas287.

The pump273, the combined orifice and pressure gauge combination275, the heat exchanger277, and the filter279may be the same as or similar to related components ofFIG.2B. The valve281may be the same as or similar to the valve211ofFIG.2A.

With reference now toFIG.2D, a cross-sectional view of an optical chamber280of a particle-counting instrument and an aerosol-focusing nozzle287having a curtain-flow device in accordance with various embodiments of the disclosed subject matter are shown. In addition to the optical chamber280and the aerosol-focusing nozzle287,FIG.2Dis shown to include a pair of collection lenses283, a condenser lens297, an aerosol inlet port281, and an aerosol outlet port285. As is known to a person of ordinary skill in the art, the collection lenses283and the condenser lens297can take a variety of forms and shapes.

The aerosol-focusing nozzle287has an upper portion293and an aerosol nozzle outlet295. In an embodiment, the curtain-flow device comprises a plenum chamber289A and a curtain-flow concentrating nozzle289B. During a particle-counting operation, a combination of the plenum chamber289A and the curtain-flow concentrating nozzle289B provides a clean sheath of airflow, through an open area291and over the upper portion293of the aerosol-focusing nozzle287.

The plenum chamber289A and the curtain-flow concentrating nozzle289B are formed substantially to be annular or partially annular around the upper portion293of the aerosol-focusing nozzle287. The plenum chamber289A and the curtain-flow concentrating nozzle289B may therefore be considered to have a toroidal shape.

The plenum chamber289A and the curtain-flow concentrating nozzle289B may be formed from a variety of materials including machined or otherwise formed aluminum, stainless steel, various plastics, and other machinable or formable materials known in the art. In an embodiment, the plenum chamber289A and the curtain-flow concentrating nozzle289B may be machined or formed from a single piece of material. In another embodiment, the plenum chamber289A and the curtain-flow concentrating nozzle289B may be machined or formed from two materials, that are either similar or dissimilar to each other, and that are joined together (e.g., by chemical adhesives, soldering, welding, mechanical fasteners, or other techniques known to a person of ordinary skill in the art).

FIG.2Eshows a cross-sectional view290of the optical chamber280of the particle-counting instrument and the aerosol nozzle having the curtain-flow device at Section A-A ofFIG.2D. A gas-line connector292allows gas-line tubing (not shown) to provide a clean (e.g., filtered), curtain gas to a gas-flow inlet293to the plenum chamber289A. In a specific exemplary embodiment, the gas-line connector292is a barb connector (as shown). However, in other embodiments, the gas-line connector292may be any type of gas-line connector known in the art (e.g., a Swagelok® tube fitting, available from Swagelok Company, Solon, Ohio, USA). The gas-line tubing may comprise various types of tubing including nylon tubing, stainless-steel tubing, brass tubing, or other types of tubing known in the art. The clean gas introduced into the gas-flow inlet293may comprise air (e.g., clean-dry air (CDA)), an inert gas such as argon or hydrogen, or another type of filtered gas that is substantially particle free.

With concurrent reference toFIGS.2D and2E, during operation of the particle-counting instrument, a flow of curtain gas enters the optical chamber280through the gas-line connector292. To ensure the curtain gas enters the optical chamber280substantially uniformly, the curtain gas is directed through the plenum chamber289A and into the optical chamber280through, for example, a narrow opening (e.g., a slit or series of openings) on an uppermost portion of the curtain-flow concentrating nozzle289B. The narrow opening may comprise, for example, a single continuous slit or a series or circular or elongated slits.

One function of the combination of the plenum chamber289A and the curtain-flow concentrating nozzle289B is substantially to equalize flow pressure so that the curtain flow (from the gas-flow inlet293) can be distributed substantially evenly around the upper portion293of the aerosol-focusing nozzle287before passing from the narrow opening in the curtain-flow concentrating nozzle289B into the open area291surrounding the upper portion293, through the narrow opening.

To enhance flow uniformity further, the curtain flow can also be introduced tangentially (e.g., at an angle with reference to a circumferential direction of the plenum chamber289A) into the plenum chamber289A. When the curtain flow is introduced tangentially, a swirling movement of the flow fills up the plenum chamber289A and curtain-flow concentrating nozzle289B quickly. Once inside the optical chamber280, the curtain flow then merges co-axially or nearly co-axially with the aerosol flow that exits from the aerosol nozzle outlet295. Consequently, the aerosol flow is not disrupted and is substantially uniformly surrounded by the curtain flow. Therefore, all or nearly all of the potential contaminants (e.g., particles and vapors) are contained inside the aerosol flow. The combined aerosol flow and curtain flow then passes through the focused light-beam, described above, where particles are illuminated and counted before exiting from the aerosol outlet port285.

A location of the aerosol outlet port285could be anywhere in the optical chamber280as long as it is located downstream of the focused light-beam. However, in one embodiment, the location of the aerosol outlet port285is opposite the aerosol-focusing nozzle287, as shown inFIGS.2D and2E. This location provides the shortest distance between the aerosol-focusing nozzle287and the aerosol outlet port285. When the aerosol outlet port285is opposite from the aerosol-focusing nozzle287, a probability of contaminants traversing the curtain flow to reach the sensitive optical components is reduced or minimized. The straight flow path from the aerosol-focusing nozzle287to the aerosol outlet port285also avoids any change in flow direction, which potentially could introduce flow disturbances resulting in a higher probability of particles and/or working fluid vapors deviating from the flow path and contaminating the optical chamber280, including the optical elements (e.g., one or more surfaces of the collection lenses283and/or the condenser lens297).

In addition to reducing or minimizing contamination within the optical chamber280, the curtain flow also provides an added benefit of reducing particle impaction losses to the walls of the optical chamber280. With the curtain flow, particles are restricted substantially to a middle-portion of the combined aerosol flow and curtain flow. For example, in a CPC instrument, a common issue occurs when warm working-fluid vapors condense on cooler tubing walls resulting in a “foggy” tubing scenario. If excess condensates are formed, CPC flow rates may be affected, thereby resulting in higher measurement uncertainties. The curtain flow design of the disclosed subject matter helps to reduce, minimize, or prevent the foggy tubing issue as the curtain flow allows warm vapors to continue to cool down in the middle-portion of the flow, while separating warm working-fluid vapors from cool tubing walls.

The co-axial or nearly co-axial curtain flow design of the disclosed subject matter has many advantages over an orthogonally filtered air-flow design of the prior art. For example, the co-axial or nearly co-axial curtain flow merges smoothly with the aerosol flow as both flow in the same direction. In comparison, the orthogonally filtered air-flow needs to turn 90 degrees before merging with the aerosol flow. The 90-degree turn in flow direction is likely to generate flow turbulence, which could reduce the effectiveness of the curtain flow. Additionally, to reduce or minimize contamination of the optical chamber280, the particle-laden or vapor-laden aerosol flow can be surrounded substantially fully and uniformly by the curtain flow.

Counting Efficiency, Linearity, and Volatile-Particle Testing of the Various Embodiments of the HT-CPC

For the counting-efficiency test to comply with the EU PMP requirements described above, various embodiments of the HT-CPC units were evaluated with differential-mobility-analyzer (DMA)-classified monodisperse, furnace-generated sodium chloride (NaCl) particles. The calibration reference was a TSI® Model 3068B Aerosol Electrometer. Sample flows from the aerosol electrometer were maintained at 1 lpm. For the linearity testing, DMA-classified 40 nm, atomizer-generated NaCl particles were used. Various concentration levels of the particles were achieved using a dilution bridge. For the volatile-particle test, the various embodiments of the HT-CPC units were challenged with tetracontane. Tetracontane is specified by the PMP and is an isomer of the aliphatic-hydrocarbon family having forty carbon atoms and a chemical formula of C40H82.

FIG.3shows a schematic diagram of a tetracontane particle-generator300used to challenge various embodiments of the disclosed HT-CPC units for the volatile-particle test. The tetracontane particle-generator300is shown to include a heating element301(e.g., an electric Bunsen), a flask303containing an oil305(e.g., corn oil) and a tetracontane block323, a rubber-stopped test tube307, an oil bath thermocouple309, a carrier-gas/tetracontane-vapor thermocouple311, and a carrier-gas inlet tube313. In operation, the heating element301heats the oil305in the flask303, which in turn heats the tetracontane block323. A carrier gas (e.g., nitrogen or air) is introduced into the carrier-gas inlet tube313. Vapors of tetracontane are carried into the rubber-stopped test tube307and are cooled by a cooled quench gas introduced into a quench-gas inlet tube315. Because of the quenching effect, tetracontane particles are formed by homogeneous nucleation. The now-cooled tetracontane-aerosol flow continue to an outlet tube319to produce a tetracontane-aerosol output321. Excess amounts of the tetracontane aerosol flow not needed for the volatile-particle testing may be directed to a vent317.

Referring back now to the use of DMA-classified particles,FIG.4Ashows a counting-efficiency graph400of various embodiments of the HT-CPC disclosed herein; the graph400indicates counting efficiency as a function of particle diameter using sodium-chloride (NaCl) particles to test various embodiments of the HT-CPC. The graph400indicates a D50cut-point of approximately 5 nm for the sample HT-CPC unit tested on different days (as indicated by “SAMPLE 1” and “SAMPLE 2”). As further indicated by the graph400, results from the two different days are in good agreement with each other showing that the performance of the HT-CPC unit is consistent over time. The counting efficiencies for large particles (e.g., greater than about 20 nm) are at about 93%. Additional optimization of the various embodiments of the HT-CPC units has improved counting efficiencies to approximately 100%. At least a portion of the optimization has been occurred by compensating for diffusion losses.

FIG.4Bshows a graph410of particle-counting efficiency as a function of particle diameter using DMA classified sodium chloride particles to challenge various embodiments of the disclosed HT-CPC. The particle-counting efficiency as a function of particle diameter was constructed based on a sampled NaCl gas-flow of 0.2 lpm with a total flow into the optics block at 2 lpm. A temperature of the saturator block was 230° C. and a temperature of the condenser block was 186° C. The counting efficiency at 10 nm is about 69% and consequently readily meets the newly-proposed PMP 10 nm, CPC cut point requirement which stating that the counting efficiency at 10 nm needs to be within a range of 50% to 70%.

FIG.4Cshows a graph430of particle-counting efficiency as a function of particle diameter using DMA classified sodium chloride particles to challenge various embodiments of the disclosed HT-CPC. The particle-counting efficiency as a function of particle diameter was constructed based on a sampled NaCl gas-flow of 0.2 lpm with a total flow into the optics block at 2 lpm. A temperature of the saturator block was about 200° C. and a temperature of the condenser block was about 180° C. The stated operational parameters allow various embodiments of the disclosed HT-CPC to meet PMP current 23 nm, CPC cut point requirement.

In comparison with the counting efficiencies of the various embodiments of the disclosed HT-CPC,FIG.5shows a counting-efficiency graph of the HT-CPC100of the prior art, discussed above with reference toFIG.1, for a variety of different particle types. The particle types include NaCl particles, dispersed particle gel (DPG) particles, ambient particles, tetracontane particles, and theoretical counting-efficiency for the HT-CPC100. As is known to a person of ordinary skill in the art, the DPG is a three-phase foam in which DPG particles comprise polymer particles with viscoelasticity having characteristics of solid particle. Notice the large error bars in the prior art data ofFIG.5. The large error bars are likely due to uncertainties caused by the small sample flow rate of the HT-CPC100of the prior art, which is about ⅛ or less than the flow rate of the disclosed HT-CPC units.

FIG.6Ashows a linearity graph600of various embodiments of the HT-CPC disclosed herein; the graph600indicates normalized counting-efficiency as a function of reference particle concentration. As indicated, the normalized counting-efficiency drops by about 4% at 67K counts/cm3. The decrease in concentration is mainly because some of the pulses in this test dropped below the counting threshold. Therefore, the concentration limit can be adjusted to be higher once the low pulse-height threshold is decreased (as discussed in more detail, below).

FIG.6Bshows another linearity graph610of various embodiments of the HT-CPC disclosed herein; the graph610indicates normalized counting-efficiency as a function of reference particle concentration, the range of concentration being greater (by approximately twice the concentration) than the concentration range ofFIG.6A

Referring now toFIG.7A, a volatile-particle-test graph700for tetracontane particles displayed as an HT-CPC inlet concentration percentage as a function of aerial concentration (in units of particles per cm3) is shown. Since the tetracontane particle-size distributions from the tetracontane particle-generator300ofFIG.3were fairly narrow, the tetracontane particles were used in the volatile-particle test without DMA classification. The number of particles detected by the HT-CPC appeared to be a function of tetracontane p article-concentration at the inlet of the HT-CPC. The HT-CPC particle count increased with increasing inlet concentration. This increase in measured concentration may be due to the volatile contents being re-nucleated when the particle flow was cooled down. The stated PMP volatile-particle protocol of the EU PMP testing described above requires a count of less than 1% of the challenge particles to be measured. Therefore, the various embodiments of the HT-CPC disclosed readily meet the PMP stated requirement.

FIG.7Bshows a volatile-particle-test graph710for tetracontane particles displayed as an HT-CPC inlet concentration percentage as a function of condenser temperature for two different HT-CPC units designed in accordance with the various embodiments disclosed herein. As indicated by the graph710, the measured HT-CPC/inlet concentration decreases with an increasing condenser temperature.

FIG.7Cshows a volatile-particle-test graph730for Emery oil particles displayed as an HT-CPC inlet concentration percentage as a function of condenser temperature for HT-CPC units designed in accordance with the various embodiments disclosed herein. As indicated by the graph710ofFIG.7A, the measured HT-CPC/inlet concentration of the graph730also decreases for with an increasing condenser temperature.

Overall in constructing the various graphs shown above, the false count rate was about 0.01 counts/cm3for about 1 hour of measurement. The test results are summarized in Table III, below.

TABLE IIIResults SummaryTest ResultsD50(NaCl)Tunable, from about 5 nm toabout 23 nmConcentration Limit>67,000cm−3Volatile Particles<0.71% at 64,000cm−3False Count0.01cm−3

CONCLUSIONS

As shown and described herein, various exemplary embodiments of the HT-CPC were developed successfully. The performance of the carious embodiments meets the D50, concentration limit, and volatile-particle requirements of the PMP.

The shapes of pulses from light detection of the particles were good and the pulse heights in even the initial tests were approximately 350 mV. Also, in the initial work using early version of the various embodiments of the HT-CPC, the counting threshold was set to 200 mV. Noise levels were acceptable as the false count rate was 0.01 cm−3. To increase margins on the signal-to-noise ratio for production units, pulse heights larger greater than 500 mV can be used. Results from the various ones of the disclosed embodiments of the HT-CPC units suggested that the pulse heights increase with increasing saturator temperature. However, high saturation temperatures may deplete the working fluid more quickly. An auto-fill function may be used to replenish the working fluid. Also, without the curtain-flow design described herein, a larger amount of working fluid vapors would otherwise condense and deposit on the optics components, thereby requiring more frequent cleaning of the optical elements.

If needed for extremely high particle concentration measurement conditions, an additional dilution step may be used to lower the inlet particle concentration to reduce or eliminate CPC coincidence errors and/or vapor depletion. Also, the dilution flow may be heated to a higher temperature.

Although specific values, ranges of values, and techniques are given for various parameters discussed above, these values and techniques are provided merely to aid the person of ordinary skill in the art in understanding certain characteristics of the designs and embodiments disclosed herein. Those of ordinary skill in the art will realize, upon reading and understanding the disclosure provided herein, that these values and techniques are presented as examples only and numerous other values, ranges of values, techniques, and hardware (including working fluids) may be employed while still benefiting from the novel designs discussed herein that may be employed in various HT-CPC designs. Therefore, the various illustrations of the apparatus are intended to provide a general understanding of the structure and design of various embodiments and are not intended to provide a complete description of all the elements and features of the apparatus that might make use of the structures, features, and designs described herein.

Many modifications and variations can be made, as will be apparent to a person of ordinary skill in the art upon reading and understanding the disclosure provided herein. Functionally equivalent methods and devices within the scope of the disclosure, in addition to those enumerated herein, will be apparent to a person of ordinary skill in the art from the foregoing descriptions. Portions and features of some embodiments may be included in, or substituted for, those of others. Many other embodiments will be apparent to those of ordinary skill in the art upon reading and understanding the description provided herein. Such modifications and variations are intended to fall within a scope of the appended claims. The present disclosure is therefore to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. The abstract is submitted with the understanding that it will not be used to interpret or limit the claims. In addition, in the foregoing Detailed Description, it may be seen that various features may be grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as limiting the claims. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.