Method and apparatus for monitoring the number density of aerosol particles

Abstract

A device (500) for measuring aerosol particles (P0) includes: a charging unit (100) for charging particles (P0) of an aerosol sample flow (FG1) by diffusion charging to form charged particles (P1), and a collecting unit (200) for collecting charges from the charged particles (P1) through diffusion of the charged particles (P1) to provide a current (I1(t)), the current (I1(t)) indicating the number density (n0(t)) of the aerosol particles (P0) of the aerosol sample flow (FG1). The internal pressure (p2) of the collecting unit (200) is maintained at a reduced value (p SET ) to provide a method for detecting p ) of the nanoparticle (P0) with a flat response (R i (d p )).

Description

Technical Field

[0001] Some embodiments relate to measuring aerosol particles. Background Art

[0002] Aerosol emissions from internal combustion engines can be harmful to the environment. Aerosol measurements can be used, for example, to check whether the mass concentration of aerosol particles in the exhaust gases of an internal combustion engine is below a predetermined regulatory limit. The mass concentration of aerosol particles can be measured, for example, by collecting the aerosol particles by a filter and determining the total mass of the collected particles by weighing the filter. After weighing, the average particle mass concentration can be calculated by dividing the total mass of the collected particles by the total volume of gas directed through the filter. Collecting a sufficient amount of aerosol particles by the filter may require a relatively long period of time, for example several hours. Weighing the filter may require manual work or may require the use of expensive automatic weighing equipment.

[0003] The particle deposits collected on the filter can be analyzed, for example, by using microscopy and image analysis. However, determining the original number density of aerosol particles in the exhaust gas by analyzing the collected particle deposits may be difficult or impossible.

[0004] The number density of aerosol particles can be measured, for example, using an aerosol particle counter. Particle counters typically operate based on optical scattering. An aerosol particle counter illuminates an aerosol sample stream, for example with a laser beam, and counts the light pulses caused by the light-scattering aerosol particles. Aerosol particle counters are used, for example, to verify air quality in cleanrooms or to measure the number density of aerosol particles in urban environments. Summary of the Invention

[0005] Some versions relate to an apparatus for measuring the number density of aerosol particles in an aerosol sample flow. Some versions relate to a method for measuring the number density of aerosol particles in an aerosol sample flow. Some versions relate to an apparatus for measuring the number density of aerosol particles emitted from an exhaust pipe. Some versions relate to a method for determining whether the number density of aerosol particles emitted from an exhaust pipe is less than a predetermined limit.

[0006] The exhaust pipe may be, for example, an exhaust pipe of an internal combustion engine. The exhaust pipe may be, for example, an exhaust pipe of a vehicle including an internal combustion engine. The exhaust pipe may be, for example, a pipe of a power station. The exhaust pipe may be, for example, a pipe of a factory.

[0007] According to one aspect, there is provided an apparatus (500), comprising:

[0008] a charging unit (100) for forming charged particles (P1) by charging particles (P0) of the aerosol sample flow (FG1) via diffusion charging,

[0009] a collecting unit (200) for providing a current (I1(t)) by collecting charges from said charged particles (P1) via diffusion of said charged particles (P1), the current (I1(t)) being indicative of the number density (n0(t)) of the aerosol particles (P0) of the aerosol sample flow (FG1),

[0010] - Pressure Reduction Unit (PDU1), and

[0011] - Suction unit (VAC1),

[0012] wherein the pressure reduction unit (PDU1) and the suction unit (VAC1) are arranged to maintain the internal pressure (p2) of the collection unit (200) at a selected value (p SET ).

[0013] According to one aspect, there is provided an apparatus (500), comprising:

[0014] a charging unit (100) for forming charged particles (P1) by charging particles (P0) of the aerosol sample flow (FG1) via diffusion charging,

[0015] a collecting unit (200) for providing a current (I1(t)) by collecting charges from said charged particles (P1) via diffusion of said charged particles (P1), the current (I1(t)) being indicative of the number density (n0(t)) of the aerosol particles (P0) of the aerosol sample flow (FG1),

[0016] - a pressure reduction unit (PDU1) for reducing the pressure of said aerosol sample flow (FG1), and

[0017] - a suction unit (VAC1) for drawing said aerosol sample flow (FG1) via a charging unit (100) to a collecting unit (200),

[0018] Among them, the charging efficiency function ( ) is indicated as the particle size (d p ), the efficiency of the diffusion charge used to charge the particle (P1) as a function of

[0019] Among them, the collection efficiency function ( ) is indicated as the particle size (d p ), the efficiency of collecting charge by diffusion of charged particles (P1) as a function of

[0020] wherein the pressure reduction unit (PDU1) and the suction unit (VAC1) are arranged to maintain the internal pressure (p2) of the collection unit (200) at a selected pressure value (p SET ), so that the collection efficiency function ( ) has a negative slope ( ) at least partially compensates for the charging efficiency function ( ) has a positive slope ( ), select the pressure value (p SET ) is less than or equal to 80 kPa.

[0021] Further aspects are defined in the claims.

[0022] The current provided by the device can be indicative of the instantaneous number density of aerosol particles of the input stream. The current response for detecting particles of different sizes can be adjusted by selecting the internal pressure of the collection cell. The internal pressure of the collection cell can be maintained at a selected reduced value so as to provide a substantially flat current response for detecting the number density of nanoparticles of different sizes. The device can have a substantially flat counting response. The selected value of the internal pressure can be significantly lower than atmospheric pressure. The internal pressure can be selected to provide a substantially flat response, for example, within a particle size range of 40 nm to 200 nm. For example, the response for detecting 40 nm particles can be substantially equal to the response for detecting 100 nm particles, and the response for detecting 200 nm particles can also be substantially equal to the response for detecting 100 nm particles.

[0023] The device can use a combination of diffusive charging and diffusive collection to provide a counting response that can be substantially independent of particle size. For particles in the size range of 40 nm to 200 nm, for example, the current provided by the device can indicate the instantaneous number density of aerosol particles in the input stream. The device can provide a substantially constant response for measuring the number density of particles in the size range of 40 nm to 200 nm. The device can provide a substantially constant response for aerosol samples having a broad size distribution and / or an unknown size distribution.

[0024] The internal pressure of the diffusion collector may have an impact on the efficiency with which the diffusion collector collects the charge of the charged particles. The internal pressure of the charging unit may have different effects on the efficiency with which the particles are charged by diffusion charging. Particle size d P The effect on the charging of particles can be expressed by the charging efficiency function To describe. Particle size d P The effect of the charge on the collected charged particles can be expressed as the collection efficiency function To describe the charging efficiency function The particle size d can be adjusted within the first size range. P increases with the increase of The pressure of the aerosol sample flow in the collection unit may affect the collection efficiency function The pressure of the aerosol sample flow can be maintained at a selected reduced value (p SET ), so that the collection efficiency The negative slope can basically compensate for the charging efficiency The positive slope of the response is preferably such that the overall response is essentially independent of particle size.

[0025] Number density can also be referred to as number concentration. The device can provide an electrical current, which allows for continuous monitoring of aerosol particle number density. The device can be used, for example, to detect rapid changes in aerosol particle number density in exhaust gas. The response time of the monitoring signal can be, for example, less than 1 second, or even less than 0.1 second. The measurement results can optionally be recorded in a memory, such that the recorded results are associated with time information. The recorded measurement results can optionally be timestamped.

[0026] The device can be used, for example, to check whether the number density of aerosol particles in vehicle engine exhaust is below a predetermined limit. The device can be used, for example, to check whether the number density of aerosol particles in vehicle exhaust complies with regulatory limits specified in standards and / or official regulations.

[0027] The reduced internal pressure of the collection cell can also reduce or prevent aggregation of one or more gaseous species of the aerosol sample stream. Aggregation of species can, for example, generate new particles that can interfere with number density measurements. Reduced aggregation can reduce the need to clean the internal surfaces of the device and / or can allow for longer periods of operation without requiring cleaning of the internal surfaces of the device.

[0028] A reduced internal pressure of the device can be provided, for example, by using a critical orifice. The flow rate can be kept substantially constant using a constant reduced internal pressure and a critical orifice. The number density value can be calculated, for example, simply by multiplying the measured current value by a calibration factor.

[0029] Directing the aerosol sample flow through the first critical orifice and directing the dilution gas flow to the sampling line through the second critical orifice can provide a diluted sample aerosol flow at a substantially constant, known dilution ratio.

[0030] The reduced internal pressure can provide a faster aerosol sample flow in the sampling line and the various units of the device. Therefore, the reduced internal pressure can also provide a faster response.

[0031] In embodiments, the method may include measuring a second auxiliary current signal that indicates the charge of aerosol particles exiting the (first) collection cell. The first detector current may indicate the number concentration of particles in the input stream, and the second auxiliary signal may indicate the surface area concentration of aerosol particles in the input stream. The first signal may be substantially independent of particle size, for example, within a size range of 40 nm to 200 nm, while the second signal may be dependent on particle size within a size range of 40 nm to 200 nm. The different characteristics of the first and second signals may, for example, allow for an average particle size to be estimated from these two signals. The method may include determining the average particle size from the first detector current and from the second auxiliary current.

[0032] In an embodiment, the second auxiliary current signal can be used to check the reliability of the measured number density and / or to check whether the measuring device is operating properly. If the particle size distribution of the input stream is known to remain unchanged, a constant second auxiliary current signal can indicate that the measurement result is valid and / or that the measuring device is operating properly. If the particle size distribution of the input stream is known to remain unchanged, a change in the second auxiliary current signal can indicate that the measurement is invalid and / or that the measuring device is not operating properly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In the following examples, several variations will be described in more detail with reference to the accompanying drawings, in which

[0034] FIG1a shows, by way of example, a device for measuring the number density of aerosol particles.

[0035] FIG1b shows, by way of example, a device for measuring the number density of aerosol particles.

[0036] Figure 2a shows by way of example the efficiency of charging particles by diffusion charging.

[0037] FIG2b shows by way of example the efficiency of collecting charge from charged particles by diffusion,

[0038] Figure 2c By way of example, the combined efficiency for detecting particles when charging the particles by diffusion charging and collecting the charge from the charged particles by diffusion is shown,

[0039] Figure 2d shows, by way of example, the normalized response for detecting particles of different sizes.

[0040] FIG2e shows by way of example the penetration efficiency of the size distribution modification unit,

[0041] Figure 2f shows the normalized responses with and without the modified unit by way of example,

[0042] Figure 3 By way of example, an apparatus for measuring the number density of aerosol particles is shown,

[0043] Figure 4a By way of example, a device for measuring the number density of aerosol particles is shown, the device further comprising an auxiliary detector unit for detecting the total charge of the particles,

[0044] FIG4b shows, by way of example, a device for measuring the number density of aerosol particles.

[0045] Figure 5 By way of example, a device for measuring the number density of aerosol particles is shown, the device further comprising a dilution unit for providing a diluted sample flow,

[0046] FIG6a shows by way of example a collecting unit for collecting charges from charged particles by diffusion,

[0047] FIG6 b shows by way of example a collecting unit for collecting charges from charged particles by diffusion,

[0048] FIG. 7 a shows by way of example a charging unit for charging particles by diffusion charging,

[0049] Figure 7b A charging unit for charging particles by diffusion charging is shown by way of example,

[0050] Figure 8a By way of example, a device for measuring aerosol particles is shown, which includes a low-pressure sampling line,

[0051] Figure 8b By way of example, a device for measuring aerosol particles is shown, the device comprising a diluter and a low-pressure sampling line, and

[0052] Figure 8c By way of example, a device for measuring aerosol particles is shown, the device comprising a diluter, a low-pressure sampling line and a modifier unit. DETAILED DESCRIPTION

[0053] refer to Figure 1aThe measurement mechanism 1000 may include an aerosol source SRC1 and an aerosol measurement device 500. The measurement device 500 may be configured to measure aerosol particles P0 of a primary aerosol PG0. The primary aerosol PG0 may be generated by the aerosol source SRC1. The aerosol source SRC1 may be, for example, an internal combustion engine. The primary aerosol PG0 may be guided through or contained in a gas conduit DUC1. The device 500 may obtain an aerosol sample flow FG0 from the primary aerosol PG0. The primary aerosol PG0 may carry aerosol particles P0. The measurement device 500 may continuously monitor the number density of aerosol particles P0 in the primary aerosol PG0.

[0054] The measuring device 500 may be arranged to provide a current I1 ( t ) which is indicative of the number density n0 ( t ) of aerosol particles P0 of the primary aerosol PG0 in the discharge duct DUC1 . The symbol t may represent time.

[0055] The measuring device 500 may include a decompression unit PDU1 , a charging unit 100 , a collecting unit 200 , and a suction unit VAC1 .

[0056] The charging unit 100 may receive an aerosol sample flow (FG0, FG1) from the discharge conduit DUC1, eg, via the sampling line 50. The charging unit 100 may receive an aerosol sample flow (FG1) from the sampling line 50. The aerosol sample flow FG0 may also be referred to as, eg, an input flow FG0.

[0057] The charging unit 100 may include an ion source for generating ions J1. The ions J1 can form charged particles P1 by exchanging charge with neutral particles P0. The ion source may be, for example, a corona discharge DSR1 ( FIG. 3 ). The charging unit 100 may include a corona electrode E1 for generating the corona discharge DSR1. The charging unit 100 may form charged particles P1 from neutral particles P0 through diffusion charging. Ions can migrate near the particles through diffusion, allowing some ions J1 to collide with the particles, transferring charge to them. The charging unit 100 may form charged particles P1 from neutral particles P0 through diffusion of ions J1.

[0058] The apparatus 500 may optionally comprise an ion trap TRAP1 for removing ions J1 from the aerosol sample flow (FG2, FG3). The apparatus 500 may be arranged to provide a substantially ion-free aerosol sample flow (FG3) comprising charged particles P1 formed by diffusion charging.

[0059] In an embodiment, the charging unit 100 may include one or more regions operable as an ion trap TRAP1 , wherein the collection unit 200 may receive the aerosol sample flow ( FG2 , FG3 ) directly from the charging unit 100 .

[0060] The collecting unit 200 may receive an aerosol sample flow (FG3) from the charging unit 100. The collecting unit 200 may include one or more collector elements (E3) for collecting charges from the charged particles (P1). The charged particles (P1) may move by diffusion, wherein some particles (but not all) may contact the collector element (E3). The collector unit 200 may provide a current I1(t) by collecting charges from the charged particles P1. The current I1(t) may be substantially proportional to the net amount of charge transferred from the charged particles to the collector element (E3) per unit time. The current I1(t) may indicate the number density n0(t) of the aerosol particles P0 of the aerosol sample flow FG0 extracted from the discharge conduit DUC1. The current I1(t) may indicate the number density of aerosol particles P0 in the primary aerosol PG0.

[0061] Apparatus 500 may optionally include a dilution system for providing a diluted aerosol stream (FG1) from a sample stream FG0 extracted from a primary aerosol PG0. The sample stream may be optionally diluted according to a dilution ratio. The sample streams (FG1, FG2) may be optionally diluted at a dilution ratio. The number density of aerosol particles in the primary aerosol PG0 may be proportional to the number density of aerosol particles carried by the sample streams (FG1, FG2).

[0062] The suction unit VAC1 may comprise, for example, an ejector or pump PUMP1 for causing the aerosol sample flow to pass through the charging unit 100 to the collecting unit 200. The suction unit VAC1 may draw the aerosol sample flow FG1 into the charging unit 100. The suction unit VAC1 may draw the aerosol sample flow (FG2, FG3) from the charging unit 100 to the collecting unit 200. The suction unit VAC1 may cause the aerosol flow from the charging unit 100 to the collecting unit 200 by drawing the flow FG4 from the collecting unit 200. The suction unit VAC1 may also be arranged to keep the internal pressure p2 of the collecting unit 200 substantially equal to a selected pressure value p SET The suction unit VAC1 may operate together with the decompression unit PDU1 to maintain the internal pressure p2 of the collection unit 200 at a predetermined value p SET . Pressure value p SET It can be significantly less than normal atmospheric pressure (100kPa). SET It may be, for example, less than or equal to 80 kPa. SET It may be, for example, less than or equal to 50 kPa. SETIt may be, for example, less than or equal to 20 kPa.

[0063] The flow rate Q1 of the aerosol flow FG1 can be controlled, for example, by a pump PUMP1 and / or a valve VAL1 ( FIG. 3 , FIG. 8 b ).

[0064] The sample flows (FG0, FG1, FG2, FG3) can be directed through a reduced-pressure critical orifice OR1, where the flow rate Q1 can be determined, for example, from the pressure downstream of the orifice OR1. The pressure downstream of the orifice OR1 can be, for example, substantially equal to the internal pressure p2. The flow rate Q1 can be maintained substantially constant, for example, while the pressure of the primary aerosol PG0 remains substantially constant and the internal pressure (p2) remains substantially constant. In particular, the pressure ratio p2 / p0 can be less than 0.5 to ensure choked (critical) flow through the critical orifice OR1.

[0065] The apparatus 500 may optionally include a flow sensor QSEN1 ( Figure 8b ).

[0066] The suction unit VAC1 may provide an exhaust gas flow EXG1. The exhaust gas flow EXG1 may be discharged, for example, into the ambient air outside the device 500 or into a ventilation duct.

[0067] The collector element E3 of the collecting unit 200 may be arranged to operate at a reduced internal pressure p2. The internal pressure p2 may, for example, be less than or equal to 80 kPa, less than or equal to 50 kPa, or even less than or equal to 20 kPa.

[0068] The lower limit value of the internal pressure p2 of the collection unit 200 may be, for example, 2 kPa (20 mbar). The apparatus 500 may be arranged to operate such that the internal pressure p2 is, for example, greater than or equal to 2 kPa. The internal pressure p2 may, for example, be in the range of 2 kPa to 80 kPa. The internal pressure p2 may, for example, be in the range of 2 kPa to 50 kPa. The internal pressure p2 may, for example, be in the range of 2 kPa to 20 kPa.

[0069] The decompression unit PDU1 may include, for example, one or more orifices OR1 for causing a pressure difference (p0-p2) between the internal pressure p0 of the discharge conduit DUC1 and the internal pressure p2 of the collection unit 200 when the aerosol sample flow (FG0, FG1, FG2, FG3) is directed through the one or more orifices OR1. The decompression orifice OR1 may be located, for example, at the input end (IN0) of the sampling line 50, between the sampling line 50 and the charging unit 100, between the charging unit 100 and the ion trap TRAP1, or between the ion trap TRAP1 and the collection unit 200.

[0070] The collection unit 200 can provide a detector current I1(t) indicating the instantaneous number density of particles. The primary current I1(t) formed by collecting charge from the particles may be very weak. The magnitude of the detector current I1(t) may be, for example, on the order of a few femtoamperes. The apparatus 500 may include a current monitoring unit CMU1 for converting the detector current I1(t) into a detector signal S1(t). The apparatus may include, for example, an electrometer for measuring the magnitude of the primary current I1(t). The current monitoring unit CMU1 may include, for example, an electrometer for measuring the current I1(t) obtained from the collection unit 200. The detector signal S1(t) may indicate the magnitude of the detector current I1(t). The detector signal S1(t) may be substantially proportional to the current I1(t). The detector signal S1(t) may be, for example, a digital signal for facilitating signal processing.

[0071] The apparatus 500 may include a signal processing unit CNT1 for forming a number density value N0(t) from the detector signal S1(t) based on calibration data CAL1. The determined number density value N0(t) may, for example, indicate the number density n0(t) of the aerosol sample flow (FG0, FG1). The determined number density value N0(t) may, for example, indicate the number density of particles of the primary aerosol PG0.

[0072] The calibration data CAL1 may comprise, for example, a proportionality constant for calculating the number density value N0(t) from the detector signal S1(t).The calibration data CAL1 may comprise, for example, a proportionality constant for calculating the number density value N0(t) from the measured detector current I1(t).

[0073] The device 500 may include a voltage source VSU1 for providing an operating voltage V1 to the charging unit 100. A terminal (eg, T1 or T2) of the voltage source VSU1 may be directly or indirectly connected to an electrical ground GND1 of the device 500 to stabilize the potential of the charging unit 100.

[0074] The apparatus 500 may include a voltage source VSU2 for providing an operating voltage V5 to the ion trap TRAP1. Terminals T5 and T6 of the voltage source VSU2 may be directly or indirectly connected to the electrical ground GND1 of the apparatus 500 to stabilize the potential of the ion trap TRAP1. In an embodiment, the charging unit 100 and the ion trap TRAP1 may also receive the operating voltage from the same voltage source (VSU1).

[0075] The aerosol source SRC1 may be, for example, an internal combustion engine. The duct DUC1 may be, for example, an exhaust duct of the engine. The primary aerosol PG0 may be, for example, exhaust gas from the engine. The primary aerosol PG0 may be, for example, exhaust gas from a gas turbine.

[0076] The aerosol source SRC1 may comprise, for example, an internal combustion engine. The aerosol source SRC1 may comprise, for example, a combination of an internal combustion engine and a catalytic converter unit for controlling and / or reducing emissions.

[0077] Internal combustion engines can use, for example, natural gas, synthetic gas, gasoline, diesel, fuel oil, and / or alcohol as fuel during particle emission testing. Sample flow FGO can be taken, for example, before or after the engine's gas cleaning unit. The gas cleaning unit can include, for example, a catalytic converter and / or a gas cleaning filter.

[0078] The current I1(t) obtained from the collection unit 100 of the device 500 can be used, for example, to check whether the particle emissions of the engine are less than a predetermined limit value (LIM1). The limit value can be specified, for example, in a standard and / or official regulation. A number density value can be calculated from the measured current I1(t). The method can include determining a number density value (n0) from the current (I1), comparing the determined number density value (n0) with the limit value (LIM1), and determining whether the number density value (n0) is less than the limit value (LIM1).

[0079] Gas conduit DUC1 can be, for example, the exhaust conduit of an engine SRC1. Conduit DUC1 can be the conduit of a dilution system, wherein the primary aerosol PG0 can be, for example, the diluted exhaust gas of the engine. Conduit DUC1 can be, for example, the channel of a constant volume sampler (CVT channel). Conduit DUC1 can include diluted exhaust gas. Source SRC1 can also be, for example, a furnace, an incinerator, a fluidized bed boiler, an industrial process unit, or a gas turbine. Gas conduit DUC1 can be, for example, the flue gas conduit of a combustion facility. During the particle collection period, apparatus 500 can optionally be maintained in a heated furnace, for example, to stabilize polymerization.

[0080] The source SRC1 may optionally provide a process indicator signal S0(t). The method may include obtaining the process indicator signal S0(t) indicative of an operating parameter of the engine SRC1. The detector current I1(t) may be compared to the process indicator signal S0(t) to determine whether a change in the operating parameter of the particle source SRC1 corresponds to a change in the detector current I1(t).

[0081] Apparatus 500 can be used, for example, to measure particle emissions from an engine SRC1. The engine can be driven according to a first test procedure. The first test procedure can include, for example, adjusting engine control signals (e.g., accelerator pedal position) and / or engine load (i.e., output power) according to a predetermined sequence. Measured detector current I1(t) and / or measured particle number density n0(t) can be compared with process indicator signal S0(t) to determine whether detector current I1(t) correlates with process indicator signal S0(t). Process indicator signal S0(t) can, for example, indicate fuel flow rate, input air flow rate to the engine, engine operating temperature, engine cylinder operating temperature, catalytic converter operating temperature, filter operating temperature, process operating temperature, accelerator pedal setting, engine valve timing, fuel feed pressure, speed of a dynamometer coupled to the engine, engine torque, power transferred from the engine to the dynamometer, or additive flow rate. Aerosol particle source SRC1 can simultaneously provide multiple process indicator signals, each of which can indicate different operating parameters of source SRC1.

[0082] Typically, the various units of the apparatus 500 are arranged such that the collection unit 200 receives charged particles from the charging unit 100 and such that the internal pressure p2 of the collection unit 200 is significantly lower than the ambient pressure p0. The collection unit 200 may be located downstream of the charging unit 100 and downstream of the decompression unit PDU1.

[0083] The device 500 may optionally comprise a modifier unit MOD1 for modifying the size distribution of the aerosol sample flow. The modifier unit MOD1 may, for example, remove particles larger than a predetermined limit (d cut The modifier unit MOD1 may be located upstream of the collecting unit 200. The modifier unit MOD1 may be located, for example, upstream of the charging unit 100 or between the charging unit 100 and the collecting unit 200.

[0084] Referring to Figure 1b, the decompression unit PDU1 can be located, for example, between the charging unit 100 and the collection unit 200. The charging unit 100 can receive an aerosol sample stream FG1. The charging unit 100 can provide an aerosol sample stream FG2, which includes charged particles P1. The ion trap TRAP1 can remove ions from the stream FG2 to provide an aerosol sample stream FG21. The decompression unit PDU1 can reduce the pressure of the stream FG2 to provide an aerosol sample stream FG22. The modifier unit MOD1 can modify the size distribution of the stream FG22 to provide an aerosol sample stream FG3. The collection unit 200 can collect charges from the charged particles in the stream FG3.

[0085] Figures 2a to 2d By way of example, it is illustrated how the response of the apparatus 500 to particles of different sizes P0 can be adjusted by selecting the operating pressure (p2) of the collection unit 200. The apparatus 500 can be arranged to maintain the internal pressure (p2) of the collection unit 200 substantially equal to the selected pressure value p SET .

[0086] Figure 2a shows by way of example the efficiency of charging aerosol particles by diffusion charging. , which is the mobility d of the aerosol particles P0 in the aerosol sample flow P The aerosol particles P0 can be initially neutral or they can carry an initial charge. The formation of charged aerosol particles P1 from the initial aerosol particles P0 by diffusion charging can be based on the charging efficiency Provides aerosol sample flow FG2. Charging efficiency The charging efficiency may indicate the average amount of elementary charge (e) per particle in the aerosol sample flow FG2 provided by the output of the charging unit. A population of particles may be represented in the aerosol sample flow FG2. The charge of each individual particle may exhibit statistical variations.

[0087] Charging efficiency function It can, for example, indicate the average number of elementary charges per particle, which is a function of the mobility of the particle. The elementary charge (e) is equal to 1.602·10 -19 As (As = ampere-seconds).

[0088] Figure 2a The curve shows by way of example the internal pressure p of the charging unit 100. 100 Charging efficiency function at 20kPa .

[0089] FIG. 2b shows by way of example the collection efficiency of the collected charges in the case where the charges from the charged particles P1 are collected by diffusion of the charged particles P1. , which is the mobility size d of aerosol particle P1 P Function of collection efficiency It can be indicated that the collection mobility size is d p The probability of a particle's charge. Depends on the particle size d p , collection efficiency It may be in the range of 0% to 100%.

[0090] For example, collection efficiency It can be substantially equal to 1%, which means that the probability of collecting the charge of the 40 nm particle P1 can be substantially equal to 1%.

[0091] The probability that a particle P1 of size dp passes through the collection unit 200 without transferring charge to the collection unit may be correspondingly equal to 1- For example, the probability that a 40 nm particle passes through the collection cell without transferring charge to the collection cell may be correspondingly equal to 100% - .

[0092] 0% collection efficiency All dimensions can be indicated as d p The particles pass through the collection unit 200 without transferring charge. 50% collection efficiency It can indicate that 50% of the size is d p The particles pass through the collecting unit 200 without transferring charge, and 50% of them have a size of d p The particles transfer the charge to the collection unit 200. 100% collection efficiency It can indicate basically all dimensions d p All particles transfer their charges to the collection unit 200.

[0093] The solid curve in Figure 2b represents the collection efficiency when the internal pressure p2 of the collection unit is equal to 20 kPa. The dotted curve in Figure 2b represents the collection efficiency when the internal pressure p2 is equal to 100 kPa. Collection efficiency The shape of may depend on the internal pressure p2 of the collection unit 200. Collection efficiency function At a given particle size (e.g., d P = 40 nm) ( ) may depend on the internal pressure p2 of the collection unit 200.

[0094] Charged particles P1 move near collecting element E3 by diffusion until some of them contact collecting element E3. Charged particles P1 can transfer charge to collecting element E3 (only) when they contact collecting element E3. The transferred charge, i.e., the charge collected from charged particles P1 to collecting element E3, can contribute to the detector current I1 (t) of collection unit 200.

[0095] The collecting unit can collect the charge of the charged particles, for example by diffusion. The collecting unit need not permanently collect the particles. The collecting unit can also provide a net current if the collected particles are subsequently released back into the airflow as electrically neutral particles.

[0096] The collection unit may be arranged to operate such that the probability of collecting a charged particle is significantly less than 100% at a particle size of 100 nm, thereby increasing the collection efficiency negative slope.

[0097] The reduced internal pressure p2 of the collection unit 200 can enhance diffusion by reducing the aerodynamic drag of the particles to less than 1000 nm. The internal pressure p2 can also affect the collection efficiency curve by reducing the aerodynamic drag. shape.

[0098] FIG2c shows by way of example the combined efficiency of detecting particles in the case where the particle P0 is charged by diffusion charging and where the charge of the charged particle is collected by diffusion collection. , which is the mobility size d of the aerosol particle P0 P Function of combined detection efficiency can be determined as the product of efficiencies, i.e. .Combination efficiency The contribution of charging the particles in the charging unit 100 and the contribution of collecting the charges of the particles in the collecting unit 200 may be included.

[0099] Combined detection efficiency ( ) can indicate the size of d in the aerosol sample flow (FG1) from the charging unit 100 p The average amount of elementary charge (e) transferred per particle (P0) to one or more collecting elements of the collecting unit 200. Combined detection efficiency The contribution of the average amount of elementary charge (e) per particle (P0) of size dp transferred in the charging unit 100 to the aerosol sample flow (FG1) can be taken into account and the detection efficiency is combined The contribution of the probability of collecting the charge of the charged particles in the collection unit 200 may also be taken into account.

[0100] The change of the internal pressure (p2) of the collecting unit (200) ( ) in a predetermined size range RNG1 (e.g., in a size range of 40 nm to 200 nm) may have an effect on the collection efficiency function ( ) of the slope( The combined detection efficiency can be adjusted by selecting the internal pressure (p2) of the collection unit (200) The slope ( ).

[0101] The target value of the internal pressure p2 can be selected by SET ) to select the combined detection efficiency For example, the internal pressure (p2) of the collection unit (200) can be selected so that the collection efficiency function ( ) has a negative slope ( ) at least partially compensates the charging efficiency function ( ) has a positive slope ( ).

[0102] For example, the internal pressure (p2) of the collecting unit (200) may be maintained at a predetermined selected value (p SET ), making the combined detection efficiency The slope ( ) is essentially equal to 0 in the size range of 40nm to 200nm.

[0103] The internal pressure (p 100 ) may be substantially equal to the internal pressure (p2) of the collecting unit 200, or the internal pressure (p 100 ) may be different from the internal pressure (p2) of the collecting unit 200.

[0104] The internal pressure (p 100 ) may be substantially equal to the internal pressure (p2) of the collection unit 200. For example, the charging unit 100 and the collection unit 200 may be located downstream of the decompression unit PDU1 so that the internal pressure (p 100 ) may be substantially equal to the internal pressure (p2) of the collecting unit 200.

[0105] The internal pressure (p2) of the collecting unit 200 can also be significantly lower than the internal pressure (p 100 For example, the decompression unit PDU1 may be located between the charging unit 100 and the collecting unit 200 .

[0106] The internal pressure (p 100 ) may affect the charging efficiency The change of the internal pressure (p2) of the collecting unit 200 may affect the collection efficiency. Internal pressure (p 100 ) for charging efficiency The influence of internal pressure (p2) on the collection efficiency Therefore, the internal pressure (p 100 ) is substantially equal to the internal pressure (p2) of the collection unit 200, the combined detection efficiency can also be adjusted by selecting the internal pressure (p2) of the collection unit 200. The combined detection efficiency can be adjusted at least in the size range RNG1 by selecting the internal pressure (p2) of the collection unit 200 .

[0107] For example, Figure 2c The solid curve can represent the combined detection efficiency when the internal pressure p2 is equal to 20kPa The dotted curve in Figure 2c represents the combined detection efficiency when the internal pressure p2 is equal to 100 kPa. .

[0108] Figure 2d shows the normalized response function R0, which is obtained by combining the detection efficiency Divide by reference value The solid curve shows the normalized response function R0 when the internal pressure p2 is equal to 20 kPa. The dashed curve shows the normalized response function R0 when the internal pressure p2 is equal to 100 kPa. The curve of Figure 2d has been obtained by combining the detection efficiency Divide by reference value Normalized. Reference value It can be equal to the combined detection efficiency at a predetermined particle size (eg, 20 nm or 100 nm).

[0109] For example, in the size range of 40 nm to 200 nm, the combined detection efficiency may be essentially independent of particle size. For example, the detection of a particle with a mobility of 40 nm (d P ) of particles (P0) It can be in the range of, for example, detecting a cell with a mobility size (d P ) of the particles (P0) 0.8 to 1.2 times of that of the 200 nm mobile size (d P ) of the particles (P0) It can be in the range of, for example, detecting a cell with a mobility size (d P ) particle (P0) efficiency 0.8 to 1.2 times of .

[0110] For example, in the size range of 40 nm to 200 nm, the combined detection efficiency may be essentially independent of particle size. For example, the detection of a particle with a mobility of 40 nm (d P ) of particles (P0) ( ) can be detected, for example, in the range of: having a mobility size (d P ) of the particles (P0) 0.9 to 1.1 times that of the 200 nm mobility size (d P ) of particles (P0) ( ) can be detected, for example, in the range of 100 nm with a mobility size (d P ) of the particles (P0) 0.9 to 1.1 times of .

[0111] The internal pressure value (p2) of the collecting unit 200 may be maintained at a predetermined pressure value (p SET ). You can choose the pressure value (p SET ), so that the combined efficiency function It may be substantially flat according to one or more of the criteria listed above.

[0112] Charging efficiency The charge efficiency function may decrease as the particle size increases within a first size range (RNG1). The first size range (RNG1) may be, for example, a range from a particle size of 40 nm to 200 nm. The decreasing charge efficiency function may be approximated by a first exponential function within the first size range (RNG1):

[0113] (1)

[0114] k1 represents the proportional constant. Prepresents the mobility size of the aerosol particles. α represents an exponent. In the case of diffusion charging, the exponent α can be, for example, in the range of 1.05 to 1.50 in the size range RNG1. In the case of diffusion charging using a triode charger ( FIG. 7 b ), the exponent α can be, for example, substantially equal to 1.1 in the size range RNG1.

[0115] Collection efficiency may decrease with increasing particle size in a first size range (RNG1). The increasing charging efficiency function in said size range (RNG1) may be approximated by a second exponential function:

[0116] (2)

[0117] k2 represents a proportionality constant. -β represents an exponent. The value of the exponent -β in the size range (RNG1) can be, for example, in the range of -1.00 to -0.85.

[0118] Combined detection efficiency of the combination of the charging unit 100 and the collection unit 100 Can be formed into charging efficiency and collection efficiency The product of:

[0119] (3)

[0120] Based on equations (1), (2), and (3), the combined detection efficiency It can be approximated as a product of exponential functions:

[0121]

[0122] Low values ​​of the difference α-β may correspond to particle sizes d P Operating conditions that have a small or negligible effect on the counting response of the measuring device 500. The internal pressure p2 of the collecting cell 200 may be chosen such that the difference α-β is, for example, in the range of 0 to 0.65.

[0123] The internal pressure p2 of the collecting unit 200 may have an influence on the exponent β. 100 may have a smaller and / or different effect on the index α. The internal pressure p2 of the collection unit 200 may be selected, for example, such that the index β is substantially equal to the index α. In the case where the pressure has been selected such that the index β is substantially equal to the index α, the combined detection efficiency can be substantially the same as the particle size d in the first size range (RNG1) P The internal pressure of the charging unit 100 (p 100) may, for example, be substantially equal to the internal pressure (p2) of the collecting unit 200 .

[0124] In an embodiment, the apparatus may also be arranged to operate such that the internal pressure p2 of the collecting unit 200 is different from the internal pressure p2 of the charging unit 100. 100 .

[0125] refer to Figure 2e The device 500 may optionally include one or more modifier units MOD1 for modifying the particle size distribution of the aerosol sample flow. The modifier unit MOD1 may be located, for example, upstream of the charging unit 100, or between the charging unit 100 and the collecting unit 200. The modifier unit MOD1 may include, for example, a filter, an impactor, and / or a cyclone separator for modifying the particle size distribution of the aerosol sample flow. The modifier unit MOD1 may include, for example, a filter, an impactor, and / or a cyclone separator for modifying the particle size distribution of the aerosol sample flow according to a predetermined penetration efficiency function. Remove particles from an aerosol sample stream. Penetration efficiency It may have a cutoff size d, for example CUT Used to eliminate particles larger than the cutoff size d from the aerosol sample flow CUT The particles removed make it impossible for the removed particles to transfer the charge from the charging unit 100 to the collecting unit 200. Can indicate size d p The probability that a particle of size RNG1 passes through the modifier unit MOD1. For the size range RNG1 (e.g. from 40 nm to 200 nm), the penetration efficiency can be substantially equal to 100%, wherein substantially all particles can pass through the modifier unit MOD1. CUT Particle penetration efficiency Probably less than 50%. In the size range where modifier unit MOD1 removes essentially all particles, the penetration efficiency It may be substantially equal to 0%.

[0126] The overall detection efficiency of the device 500 Can be formed into penetration efficiency , charging efficiency and collection efficiency The product of:

[0127]

[0128] The modifier unit MOD1 may be arranged to remove particles from the aerosol sample flow, for example by impaction and / or by interception. Selecting the internal pressure (p2) of the collection unit 200 may be used to adjust the overall detection efficiency, for example, in the size range RNG1 from 40 nm to 200 nm. The slope of the RNG1 is obtained by the impaction and / or interception mechanism, which can be used to adjust the overall detection efficiency for larger particles outside the size range RNG1. .

[0129] The detector current I1(t) obtained from the collection unit 200 may be proportional to the particle number density n0(t) of the aerosol sample flow FG1, proportional to the flow rate Q1 of the aerosol sample flow FG1, and proportional to the overall detection efficiency is proportional to the value of the resistor. t represents time. k0 represents the proportionality constant.

[0130] (5)

[0131] The current I1 is proportional to the dimension d P The response R1(d P ) can be defined, for example, as follows:

[0132] (6)

[0133] Combining (5) and (6) allows to calculate the total detection efficiency from Calculate the response R1(d P ), for example:

[0134] (7)

[0135] Therefore, the response R1(d P ) may be related to the overall detection efficiency Proportional. Response function R1(d P ) may have a shape similar to the overall detection efficiency The overall detection efficiency With the particle size d in the size range RNG1 P Basically irrelevant, the response R1(d P ) can be compared with the particle size d in the size range RNG1 P Basically irrelevant.

[0136] For example, the internal pressure (p2) of the collection unit (200) can be selected so that the collection efficiency function ( ) has a negative slope ( ) at least partially compensates the charging efficiency function ( ) has a positive slope ( ).

[0137] For example, the pressure (p2) of the collection unit (200) can be selected so that the pressure (p2) used to detect a particle with a mobility size (d P ) of the particle (P0) current (I1(t)) response (R1(d P )) is in the following range: for detecting a mobility size (d P ) of the particle (P0) (R1(d P )) of 0.9 to 1.1 times, and wherein for detecting a mobility size (d P ) of the particle (P0) current (I1(t)) response (R1(d P )) is in the following range: for detecting a mobility size (d P ) of the particle (P0) (R1(d P )) is 0.9 to 1.1 times.

[0138] For example, the pressure (p2) of the collection unit (200) can be selected so that the pressure (p2) used to detect a particle with a mobility size (d P ) of the particle (P0) current (I1(t)) response (R1(d P )) is in the following range: for detecting a mobility size (d P ) of the particle (P0) (R1(d P )) of 0.9 to 1.1 times, and wherein for detecting a mobility size (d P ) of the particle (P0) current (I1(t)) response (R1(d P )) is in the following range: for detecting a mobility size (d P ) of the particle (P0) (R1(d P )) is 0.9 to 1.1 times.

[0139] For example, the pressure of the collection unit 200 can be selected so as to detect a particle with a mobility size (d P ) of the particle (P0) (R1(d P )) is in the following range: for detecting a mobility size (d P ) of the particle (P0) (R1(dP )) of 0.9 to 1.1 times, and makes it possible to detect a mobile size (d P ) of the particle (P0) (R1(d P )) is in the following range: for detecting a mobility size (d P ) of the particle (P0) (R1(d P )) is 0.9 to 1.2 times.

[0140] The flow rate Q1 can be kept substantially constant. The constant k0, the flow rate Q1 and the total detection efficiency are substantially constant in the detection size range RNG0 of the measuring device 500. The detection size range RNG0 can be, for example, from 40 nm to 400 nm. The detection size range RNG0 can be, for example, from 40 nm to 1000 nm. can be combined and expressed as the calibration constant K CAL .

[0141] (8)

[0142] This can be done, for example, by using the calibration constant k CAL The number density n0 is determined from the measured detector current I1:

[0143] (9)

[0144] Calibration constant K CAL The calibration constant K can be determined, for example, by calibration measurements. CAL The apparatus 500 may be arranged to use a calibration constant K CAL The number density n0(t) is determined from the measured current I1(t). In an embodiment, the measured current I1(t) may be transmitted to an auxiliary computer, and the auxiliary computer may be arranged to calculate the number density n0(t) by using a calibration constant K CAL The number density n0(t) is determined from the measured current I1(t).

[0145] The number density n0 represents the number of aerosol particles per unit volume. The number density n0 can also be called the number concentration.

[0146] refer to Figure 2d , response function R1(d p ) can be obtained by transforming the response function R1(d p ) divided by the reference value R REF To normalize.

[0147] (10)

[0148] Reference value R REF It can be, for example, equal to the response R1 (d p ).

[0149] The internal pressure p2 can be selected to provide a substantially flat response function R1 (d p ) and / or a substantially flat normalized response function R0(d p ). For example, the response function R1(d p )、R0(d p ) can be substantially flat within the ±10% limit at least in the particle size range of 40 nm to 400 nm. For example, the response function R1(d p )、R0(d p ) can be substantially flat within a limit of ±20% at least in the particle size range of 20 nm to 1000 nm.

[0150] The internal pressure (p2) of the collection unit (200) can be selected so that the collection efficiency function ( ) has a negative slope ( ) can compensate the charging efficiency function ( ) has a positive slope ( ) .

[0151] The negative slope can compensate for the positive slope, for example, so that when the internal pressure (p2) of the collection unit is equal to 20 kPa, the normalized response function R0 (d p ) can, for example, be substantially equal to -1% / 100 nm in the size range of 100 nm to 200 nm (RNG2).

[0152] As a comparative example, when the internal pressure of the collection unit is equal to 100 kPa, the normalized response function R0 (d p The slope of ) may, for example, be substantially equal to 17% / 100 nm in the size range of 100 nm to 200 nm (RNG2).

[0153] Referring to Figure 2f, the penetration function of the modified unit MOD1 is Possible impact on overall detection efficiency and the response function R0(d p ) has an impact. For example, you can choose to modify the penetration function of unit MOD1 To provide a substantially flat response near the upper limit of the detection size range RNG0 of the measuring device 500. For example, the penetration function may be selected Cut-off size d cut , so as to provide a substantially flat response near the upper limit of the detection size range RNG0 of the measuring device 500.

[0154] refer to Figure 3 The device 500 may include, for example, a critical orifice OR1 for providing a reduced internal pressure (p2) to the collection unit 200. The decompression unit PDU1 may include the critical orifice OR1. The critical orifice OR1 may be located in, for example, the sampling line 50 of the device 500.

[0155] The charging unit 100 may be arranged to generate ions J1, for example, by a corona discharge DSR1. The charging unit 100 may include a corona electrode E1 for forming the corona discharge DSR1. The corona electrode E1 may be arranged to form the corona discharge DSR1 with a counter electrode E2. In an embodiment, the conductive housing 150 of the charging unit 100 may serve as the counter electrode E2.

[0156] The corona electrode E1 may be, for example, a conductor with a sharp tip. The corona electrode E1 may be, for example, a bare wire with a reduced diameter. The electrode E1 may be connected to the terminal T1 of the voltage source VSU1, for example via the connector CON1. ​​The corona electrode may be mechanically supported, for example, by one or more insulators (ISO1).

[0157] Corona electrode E1 can be arranged to generate ions J1 via a corona discharge DSR1. Corona electrode E1 can operate in conjunction with a counter electrode E2. Electrodes E1 and E2 can be connected to a high-voltage power supply VSU1, such that a voltage difference V1 exists between electrodes E1 and E2. Corona electrode E1 and counter electrode E2 can collectively form an electric field that generates a corona discharge DSR1 near corona electrode E1. The strength of the electric field can locally exceed the dielectric strength of the gas, potentially forming a corona discharge DSR1 near corona electrode E1.

[0158] The generated ions J1 can move relative to the particles P0 by diffusion. Some of the diffused ions J1 may collide with the particles P0, thereby transferring charge to the particles. The charging unit can form charged particles through diffusion charging. The transfer of charge from ions J1 to particles can occur in the charging space (SPC1) of the charging unit 100.

[0159] The output aerosol sample flow FG2 of the charging unit 200 may include electrically neutral particles, charged aerosol particles P1 and ions J1. The particles P0, P1 and ions J1 of the flow FG2 may be suspended in a gas.

[0160] The output aerosol sample flow FG2 of the charging unit 200 may be directed through the ion trap TRAP1 to remove ions J1 .

[0161] The ion trap TRAP1 can be located downstream of the charging unit 100 and upstream of the collection unit 200. The ion trap TRAP1 can remove at least a portion of the ions J1 from the aerosol flows FG2 and FG3 directed to the collection unit 200. Using the ion trap TRAP1 can stabilize the current I1(t). The ion trap TRAP1 can include, for example, two or more deflection electrodes E5 and E6 for providing an electric field that can deflect the ions J1 away from the flow FG3. The electric field can be substantially transverse to the direction of the airflow FG3 passing through the electrodes E5 and E6. The ion trap TRAP1 can include, for example, a pair of substantially parallel electrodes E5 and E6. The electrodes E5 and E6 can be connected to a voltage difference V5 to generate the electric field. The speed of the airflow passing through the space between the electrodes E5 and E6 and / or the magnitude of the electric field can be selected so that a (first) appropriate portion of the charged particles P1 can pass through the ion trap TRAP1 and a (second) appropriate portion of the ions J1 can be deflected away from the flow FG3. Therefore, most of the charged particles P1 can pass through the ion trap TRAP1 to the detector DET1. The lower cutoff size of particles that can pass through the ion trap can be selected by selecting the voltage difference V5. The voltage V5 of the ion trap TRAP1 can optionally be used to adjust the overall detection efficiency curve n tot (d P ) additional parameters for the shape of the .

[0162] The ion trap TRAP1 can form a substantially ion-free aerosol sample flow FG3 by removing ions J1. The aerosol sample flow FG3 can include neutral particles P0 and charged particles P1 suspended in a gas.

[0163] Aerosol sample flow FG3 can be directed to a collection unit 200 for collecting charge from particles P1. Collection unit 200 can include one or more collection elements E3 for collecting charge by diffusion. Charged particles P1 can move near collection element E3 by diffusion. Some charged particles P1 can contact collection element E3, thereby transferring a net amount of charge to collection element E3. Collection element E3 can be galvanically connected to conductor CON3 to direct the collected charge as current I1(t) to current measurement unit CMU1. Collection element E3 can be, for example, a conductive mesh element.

[0164] The collecting unit 200 may be arranged to collect charge by diffusion of the charged particles P1. The collecting unit 200 may be arranged to operate such that the charged particles P1 are not attracted towards the collecting element E3 by the electric field. The electric field near the charge collecting portion of the collecting element E3 may be substantially equal to zero.

[0165] The collecting unit 200 may optionally comprise one or more electrically insulating seals ISO3a, ISO3b for confining the aerosol flow to a region where the electric field is substantially equal to zero.

[0166] The collection unit 200 can be arranged to operate such that the collection efficiency function has a negative slope at least in the particle size range of 100 nm to 200 nm. The collection element E3 can be arranged to collect charge from the particles such that most particles can pass through the collection unit 200. The mesh size of the collection element E3 can be selected such that at least 80% of particles having a mobility size of 200 nm can pass through the collection unit 200.

[0167] The device 500 may include a conductive shield E4. The shield E4 may surround the collecting element E3 to protect the collecting element E3 from electrostatic interference. The shield E4 may surround the collecting element E3, for example, as a Faraday cage.

[0168] Current monitoring unit CMU1 can receive detector current I1(t) from collecting element E3 via conductor CON3. Conductor CON3 can be connected to input terminal (IN3) of current monitoring unit CMU1. Apparatus 500 can optionally include an electrical feedthrough for directing detector current I1(t) from collecting element E3 to current monitoring unit CMU1. The electrical feedthrough can include a portion of conductor CON3 surrounded by electrical insulator ISO3.

[0169] The reference terminal (IN4) of the current monitoring unit CMU1 may be directly or indirectly connected to the electrical ground GND1 of the device 500. The shield E4 may also be directly or indirectly connected to a fixed potential, for example to the electrical ground GND1 of the device 500.

[0170] The suction unit VAC1 may comprise an ejector or pump PUMP1 for drawing the flow FG4 from the collecting unit 200. The suction unit VAC1 may optionally comprise an adjustable valve VAL1 for controlling the flow rate (Q1) via the suction unit VAC1. The suction unit VAC1 may comprise a pressure sensor PSEN1 for monitoring the internal pressure (p2) of the collecting unit 200. The suction unit VAC1 may comprise a control unit CNT2 for adjusting the flow rate of the suction unit VAC1 in order to keep the internal pressure (p2) of the collecting unit 200 substantially equal to a selected pressure value (p SET). The flow rate of the suction unit VAC1 can be adjusted, for example, by adjusting the valve VAL1 and / or by controlling the operation of the pump PUMP1. The control unit CNT2 can provide a control signal for controlling the operation of the valve VAL1 and / or for controlling the operation of the pump based on the signal of the pressure sensor PSEN1. The pump PUMP1 can be, for example, a diaphragm pump, a piston pump, a rotary vane pump or a peristaltic pump. The pump PUMP1 can be located downstream of the collecting unit 200 so that the pump PUMP1 does not remove particles from the flow FG3 before the collecting unit 200 detects the particle P1.

[0171] Apparatus 500 may include a control unit CNT1 for processing measured data and / or for controlling the operation of apparatus 500. Control unit CNT1 may include one or more signal processors for processing data. Control unit CNT1 may, for example, determine a number density value n0(t) based on a detector signal S1(t) obtained from current monitoring unit CMU1. The apparatus may include a memory MEM1 for storing calibration data CAL1. The apparatus may be configured to determine number density value N0(t) from measured detector current I1(t) using a proportionality constant stored as calibration data CAL1 in memory MEM1. The apparatus may include a memory MEM2 for storing computer program code PROG1. The apparatus may be arranged to determine one or more measurement values ​​by executing program code PROG1. Computer program PROG1 may include computer program code that, when executed on at least one data processor, is configured to cause control unit CNT1 to control the operation of apparatus 500. Computer program PROG1 may include computer program code configured to implement processing of measurement data (e.g., signals I1(t), S1(t)) when executed on at least one data processor. The device may include a memory MEM3 for storing the measured detector current value I1(t) and / or for storing the determined number density value n0(t). The device 500 may optionally include a communication unit RXTX1 for receiving and / or transmitting data. The device may optionally include a communication unit RXTX1 for transmitting the measured and / or determined values ​​to an external device, for example, to a server. The communication unit RXTX1 may transmit, for example, the signal S1(t) to, for example, an external portable computer. The communication unit RXTX1 may, for example, transmit the signal S1(t) to, for example, an internet server. The communication unit RXTX1 may receive and / or transmit data, for example, by using wireless transmission, by using an optical cable, and / or by using an electrical cable.

[0172] The apparatus may optionally comprise a user interface UIF1 for receiving user input and / or for providing information to the user. The user interface UIF1 may comprise, for example, a display, a touch screen and / or a keyboard.

[0173] Apparatus 500 may optionally include a user interface UIF1 for providing information to a user and / or receiving user input from the user. User interface UIF1 may include, for example, a display and one or more buttons. User interface UIF1 may include, for example, a touch screen. User interface UIF1 may be configured to display, for example, the magnitude of current I1(t), the measured number density n0(t), and / or the magnitude of auxiliary current I2(t) ( FIG. 4 a ).

[0174] The units 50, PDUs 1, 100, TRAPs 1, 200, 300 can be located, for example, in a cabinet, near the operating engine and / or near the dilution system. The interface UIF1 can also be located remotely from the individual units, so that the interface UIF1 can be located in an ergonomic and / or safe location. A portable computer or mobile device (e.g., a smartphone) can be arranged to communicate with the apparatus 500 via the communication unit RXTX1 and can be arranged to operate as the interface UIF1.

[0175] The data measured by the device 200 can also be processed in a distributed manner. For example, the conversion of the signal S1 into the number density value n0(t) can be performed in a separate data processor. The data may be processed, for example, by a portable computer and / or by using an Internet server.

[0176] The apparatus 500 may optionally include a clock CLK1 for providing time information. For example, the signal S1(t) and / or the measured number density n0(t) may be recorded in the memory MEM3 so that the recorded data is associated with the time information. The recorded data may be timestamped.

[0177] In an embodiment, a dilution gas flow DGO may also be directed to the charging unit 100 to protect the corona electrode E1 of the charging unit 100 from particles of the aerosol sample flow. The protective dilution gas flow DGO may be arranged to keep the corona electrode E1 clean. The sample aerosol flow is directed to the reduced pressure (p) of the charging unit 100 via the first critical orifice OR1. 100，p2), and directing the shielding gas flow DG0 to the charging unit 100 via the second critical orifice OR2 can protect the corona electrode E1 and provide a diluted sample aerosol flow at a substantially constant dilution ratio. The charging unit 100 can be arranged to direct the dilution gas flow DG0 toward the corona electrode E1 to form a substantially particle-free region surrounding the corona electrode E1. The dilution gas flow DG0 can be arranged to flush the corona electrode E1.

[0178] The input aerosol FG0 or the sample flow FG1 may have an initial particle size distribution. The apparatus 500 may comprise a modification unit MOD1 , for example for diluting the sample and / or removing large particles from the aerosol sample flow. The modification unit MOD1 may modify the particle size distribution of the aerosol sample flow.

[0179] The device 500 may include a modification unit MOD1, for example, for diluting the sample and / or removing particles larger than a predetermined cutoff size from the aerosol sample flow. The modification unit MOD1 may include, for example, a dilution unit DIL1 for diluting the aerosol sample flow and / or a particle filter for removing large particles from the aerosol sample flow. The cutoff size may, for example, be in the range of 1 μm to 10 μm. The cutoff size may be selected to provide a substantially linear overall detection efficiency within a size range of 40 nm to 1000 nm. . The cut-off size d can be selected cut To avoid the combined detection efficiency in the size range of 40nm to 200nm The basic linear shape of the cut The sample conditioning unit may be located, for example, before the charging unit 100. The sample conditioning unit may be located after the decompression unit PDU1 so that the sample conditioning unit also has a reduced internal pressure. The sample conditioning unit may include, for example, a filter, a cyclone separator, and / or an impactor. The reduced internal pressure may facilitate the operation of the filter, the cyclone separator, and / or the impactor.

[0180] refer to Figure 4a and 4b The apparatus 500 may optionally include an auxiliary detector unit 300 for detecting the charge of particles P1 leaving the first collecting unit 200. The auxiliary detector unit 300 may detect the total charge carried by the aerosol flow FG4. The auxiliary detector unit 300 may be arranged to detect, for example, at least 50% of the charged particles leaving the collector unit 200. The auxiliary detector unit 300 may provide a current I2(t) that is proportional to the charge of the particles captured by the auxiliary detector unit 300 per unit time.

[0181] The method may include measuring a second auxiliary current I2(t) that is indicative of the charge of the aerosol particles leaving the collection unit 100. The first detector current I1(t) of the collection unit 100 may be indicative of, for example, the particle number concentration of the input stream, and the second auxiliary current I2(t) may be indicative of, for example, the surface area concentration of the aerosol particles. The first current I1(t) may be substantially independent of the particle size, for example, within a size range of 40 nm to 200 nm, while the second current I2(t) may be dependent on the particle size within a size range of 40 nm to 200 nm. The different characteristics of the currents I1(t), I2(t) may allow an average particle size (d) to be estimated from the two signals I1(t), I2(t). P, ave The method may include determining an average particle size (d ) based on the first detector current I1 (t) and the second auxiliary current I2 (t). P, ave ).

[0182] The method may include using the auxiliary detector unit 300 to provide an auxiliary current (I2(t)) that is indicative of the charge of the charged particles (P1) passing through the collection unit 200.

[0183] The method may include determining the average particle size (d ) from the current (I1(t)) of the collection unit 200 and the auxiliary current (I2(t)) from the auxiliary detector unit 300. P, ave ).

[0184] The second auxiliary current I2(t) can be used to check the reliability of the measured number density n0(t) and / or to check whether the measuring device is operating properly. If the particle size distribution of the input flow FG0 is known to remain unchanged, a constant second auxiliary current I2(t) can indicate that the measurement result is valid and / or that the measuring device 500 is operating properly. If the particle size distribution of the input flow FG0 is known to remain unchanged, a change in the second auxiliary current I2(t) can indicate that the measurement is invalid and / or that the measuring device 500 is not operating properly.

[0185] Auxiliary detector unit 300 can collect particles P1 from flow FG4. Auxiliary detector unit 300 can include, for example, a particle filter FIL1 for capturing particles. Filter FIL1 can be referred to as a monitoring filter. Filter FIL1 can be conductive or electrically insulating. Filter FIL1 can be surrounded by a faraday cage FARA1, or the conductive outer layer of filter FIL1 can function as the faraday cage FARA1. Filter FIL1 and / or faraday cage FARA1 can be supported by one or more insulators ISO7. The conductive filter FIL1 can include, for example, sintered conductive particles or conductive fibers. The faraday cage FARA1 and / or the conductive filter FIL1 can be electrically connected to a second current monitoring unit CMU2. Current monitoring unit CMU2 can provide a second current signal S2(t) by measuring a second auxiliary current I2(t). Second current signal S2(t) indicates the magnitude of second auxiliary current I2(t). Signal S2(t) can be, for example, a digital signal. The current monitoring unit CMU2 may include, for example, an electrometer for measuring the second auxiliary current I2 ( t ).

[0186] In the case where the charged particle P1 captured by the filter DFIL inside the Faraday cage FARA1 does not contact the Faraday cage FARA1 , the charge carried by the charged particle P1 can also be detected by using the Faraday cage FARA1 and the current monitoring unit CMU2 .

[0187] The filter FIL1 can be selected so that the filter FIL1 can collect, for example, more than 90% of particles with a size of 200 nm. The filter FIL1 can collect aerosol particles, for example, by interception, inertial impaction, diffusion, gravitational sedimentation and / or electrostatic collection. The filter FIL1 can irreversibly collect particles so that the particles are not released from the detector FIL1 back into the air flow. The detector FIL1 can collect particles during a measurement period so that, for example, less than 10% by mass of the collected particles are released from the detector FIL1 back into the air flow FG5 during the measurement period. The suction unit VAC1 can cause the aerosol flow (F0, FG1, FG, FG3, FG4) by drawing the air flow FG5 from the auxiliary detector unit 300.

[0188] refer to Figure 5Apparatus 500 may include a dilution unit DIL1 for diluting the aerosol sample flow, for example, at a constant dilution ratio. Dilution unit DIL1 may include, for example, a second critical orifice OR2 for directing the dilution gas flow DG0 to sampling line 50. The gas GAS1 used to dilute gas DG0 may be a substantially particle-free gas. The dilution gas GAS1 may be obtained, for example, from a gas cylinder. The dilution gas GAS1 may be, for example, ambient air AIR1. The dilution unit DIL1 may optionally include, for example, a filter FIL2 for removing particles from the dilution gas GAS1.

[0189] The aerosol sample flow (FG0, FG1) can be directed to a reduced pressure p2 via a first critical orifice OR1, and the dilution gas flow DG0 can be directed to the same reduced pressure p2 via a second critical orifice OR2. The aerosol sample flow (FG0, FG1) can be combined with the dilution gas flow DG0, for example, in the sampling line 50 or the charging unit 100, to provide a diluted sample. The pressure ratio p2 / p0 can be, for example, less than 0.5 to ensure choked (critical) flow through the orifices OR1, OR2. This can provide a diluted aerosol sample flow at a constant dilution ratio.

[0190] In an embodiment, the dilution gas flow ( DGO ) may also be directed to the charging unit 100 via the critical orifice ( OR2 ), for example, in order to protect the corona electrode E1 from contamination particles.

[0191] refer to Figure 6a The collecting element E3 of the collecting unit 200 may be, for example, a conductive mesh element. The charge (CHR1) collected by the collecting element E3 may be conducted to the current monitoring unit CMU1 via a conductor CON3. The conductive mesh element may be surrounded by a conductive housing E3a. The element E3 and / or the housing E3a may be supported by one or more insulators ISO3a and ISO3b. The collected charge (CHR1) may be conducted as a current I1(t) via the conductor CON3 to an input terminal T3 of the current monitoring unit CMU1.

[0192] The collection unit 200 can be arranged to operate based on diffusion collection. The collection unit 200 can be arranged to operate so that most aerosol particles can pass through the collection unit 200. The collection unit 200 can be arranged to operate so that less than 20% of particles with a size of 200 nm are captured by the collection element E3. For example, the mesh size of the element E3 can be selected so that less than 20% of particles with a size of 200 nm are captured by the collection element E3.

[0193] The collection unit 200 may include a conductive shield E4. The conductive shield E4 may operate as a Faraday cage to protect the element E3 and / or the housing E3a from electrostatic interference. The shield E4 may be connected to the input terminal IN4 of the current monitoring unit CMU1 and / or the electrical ground GND1 of the device 500.

[0194] The element E3 and / or the housing E3a may be arranged to operate so that the electric field in the vicinity of the element E3 may be small or zero, thereby reducing or avoiding collection of particles by electrostatic forces.

[0195] The size of the elements E3 and / or the gaps between the elements E3 can be selected so that the collection unit 200 can collect the charge (CHR1) primarily by diffusion. The size of the elements E3 and / or the gaps between the elements E3 can be selected to reduce or minimize collection by interception, by inertial impaction, and / or by electrostatic attraction.

[0196] refer to Figure 6b , the collecting element E3 of the collecting unit 200 may also be, for example, a plate element.

[0197] refer to Figure 7a The charging unit 100 may include one or more flow guides BAF1 and BAF2 for increasing the distance between the aerosol flow and the corona discharge DSR1. Increasing the distance can divert the aerosol flow to a region (SPC1) where the electric field EFIELD1 generated by the corona electrode E1 and the counter electrode E2 is weaker. For example, the aerosol sample flow can be directed through the charging space (SPC1) such that the maximum intensity of the electric field EFIELD1 across the aerosol sample flow (FG1) in the charging space (SPC1) is less than 100 V / cm. Reducing the electric field EFIELD1 can increase the relative contribution of diffusion charging. Reducing the electric field EFIELD1 can ensure that particles in the 40 nm to 200 nm size range are charged primarily through diffusion charging. The flow guides BAF1 and BAF2 can guide the aerosol flow away from the corona discharge DSR1. The flow guides BAF1 and BAF2 can direct the aerosol flow to the charging region SPC1 near the counter electrode E2. The charging region SPC1 may be located between the electrodes E1 and E2.

[0198] The apparatus 500 may include a voltage source VSU1 for providing operating power to the charging unit 100. The apparatus 500 may include a high voltage source VSU1 for providing a high voltage V1 to the corona electrode E1 of the charging unit 100.

[0199] High corona voltage V1 and corona current may be conducted from voltage source VSU1 via conductor CON1 to corona electrode E1. Charging unit 100 may include a feedthrough for conducting corona current to corona electrode E1 through housing 150. The feedthrough may include a portion of conductor CON1 and electrical insulator ISO1.

[0200] A charging unit (100) for forming charged particles (P1) from aerosol particles (P0) of a sample flow (FG1) may comprise:

[0201] - an inlet (IN1) for receiving the aerosol sample flow (FG1),

[0202] - a corona electrode (E1) for generating ions (J1) by forming a corona discharge (DSR1) together with a counter electrode (E2),

[0203] - a charging space (SPC1) for forming charged particles (P1) from aerosol particles (P0) of said aerosol sample flow (FG1) by diffusion of generated ions (J1), and

[0204] - one or more flow directors (BAF1) for directing the received aerosol sample flow (FG1) through the charging space (SPC1) such that a maximum intensity of an electric field (EFIELD1) across said aerosol sample flow (FG1) in the charging space (SPC1) is less than 100 V / cm.

[0205] The charging unit 100 may include an outlet OUT1 for providing charged particles (P1) to the aerosol sample flow (FG1). The charging unit 100 may provide a charged aerosol sample flow (FG2), the charged aerosol sample flow (FG2) including the charged particles (P1) and neutral particles (P0).

[0206] The realization of a charging unit (100) with two electrodes (E1, E2) and with a flow director (BAF1) allows a sufficiently accurate and robust structure to be realized at relatively low cost.

[0207] refer to Figure 7b The counter electrode E2 of the charging unit can also be a conductive mesh, which can surround the corona electrode E1. The generated ions J1 can pass through the conductive mesh to reach the charging zone SPC1 outside the grid electrode E2. The ions J1 can charge the particles through diffusion charging in the charging zone SPC1.

[0208] The housing of the charging unit 100 may serve as an auxiliary electrode E2a. The auxiliary electrode E2a may be connected to, for example, a terminal T2a of an auxiliary voltage source VSU1a via a conductor CON2a. The counter electrode E2 may be connected to a terminal T2b of the auxiliary voltage source VSU1a.

[0209] Corona electrode E1 and counter electrode E2 can form an internal electric field EFIELD2. Counter electrode E2 and auxiliary electrode E2a can form an external electric field EFIELD1. The internal electric field EFIELD1 can cause ions J1 to drift from discharge region DSR1 toward counter electrode E2. The intensity of electric field EFIELD1 across charging region SPC1 can be significantly lower than the intensity of internal electric field EFIELD2. The reduced intensity of electric field EFIELD1 across charging region SPC1 can increase the relative contribution of diffusion charging.

[0210] The device may be arranged to provide an auxiliary voltage V1a between the counter electrode E2 and the auxiliary electrode E2a. The auxiliary voltage V1a may have an effect on the charging efficiency curve of the charging unit 100. The auxiliary voltage V1a can optionally be used as an additional operating parameter that can be selected to adjust the overall detection efficiency of the measuring device 500. shape.

[0211] The auxiliary electrode E2a may also be connected (directly) to the counter-electrode E2 to minimize the electric field EFIELD1 across the charging zone SPC1.

[0212] The signals S1(t), S2(t) provided by the current monitoring units CMU1, CMU2 may optionally be compensated, for example, by using a background signal value. The background signal value may be determined experimentally, for example by measuring the current signals I1(t), I2(t) at a flow rate (Q1) of zero or when a substantially particle-free gas is passed through the units 100, 200, 300.

[0213] The sample stream can optionally be diluted. The dilution ratio can be constant, or it can vary, for example, based on the flow rate of the exhaust gas directed to the dilution system. For example, engine exhaust can be directed to a channel of a constant volume sampler, so that the dilution ratio can be varied during a particle emission experiment, for example, based on the engine's power output.

[0214] refer to Figure 8a and 8b , the measurement mechanism 1002 may include an aerosol source SRC1 and an aerosol measurement device 502 .

[0215] The measuring device 502 may include a decompression unit PDU1 , a low-pressure sampling line 50 , an aerosol measuring instrument INSTR1 , and a suction unit VAC1 for drawing an aerosol sample flow FG1 to the aerosol measuring instrument INSTR1 via the low-pressure sampling line 50 .

[0216] Measuring instrument INSTR1 can be, for example, the device 500 described above for measuring particle number density. However, measuring instrument INSTR1 can also be another aerosol measuring device. Measuring instrument INSTR1 can be configured to measure one or more aerosol parameter values ​​of aerosol sample flow FG1. Measuring instrument INSTR1 can be configured to measure one or more aerosol parameter values ​​selected from the following list: particle number density, particle mass concentration, particle size distribution, average particle size, and particle surface area concentration. Measuring instrument INSTR1 can be, for example, an optical particle counter.

[0217] The measuring instrument INSTR1 can optionally provide one or more signals S 11 (t), the one or more signals S 11 (t) indicating one or more measured aerosol parameter values. The measuring instrument INSTR1 may have an inlet IN1 for receiving an aerosol sample flow FG1 and an outlet OUT2 for an outlet flow FG12. The measuring instrument INSTR1 may form an outlet flow FG12 from the aerosol sample flow FG1 by directing the gas phase of the aerosol sample flow FG1 from the inlet IN1 to the outlet OUT2.

[0218] The apparatus (502) may include:

[0219] - Critical orifice (OR1) for reducing the pressure (p 50 ),

[0220] - an aerosol measuring instrument (INSTR1) for measuring one or more aerosol parameter values ​​of an aerosol sample flow (FG1),

[0221] - a sampling line (50) for conducting the aerosol sample flow (FG1) from the critical orifice (OR1) to the aerosol measuring instrument (INSTR1), and

[0222] - a suction unit (VAC1) for drawing the aerosol sample flow (FG1) from the critical orifice (OR1) via the sampling line (50) to the aerosol measuring instrument (INSTR1), wherein the critical orifice (OR1) and the suction unit (VAC1) are arranged to maintain the internal pressure (p 50 ) is less than 50 kPa.

[0223] By being at a reduced pressure (p 50 ) The sampling line 50 guiding the aerosol sample flow FG1 can provide one or more of the following effects:

[0224] - Reduce the risk of polymerization of volatile compounds,

[0225] - Reduce the risk of changes in particle size distribution due to aggregation,

[0226] - Faster response due to higher particle velocity in the sampling line.

[0227] refer to Figure 8b The measuring device 502 may further comprise a dilution unit DIL1 . The dilution unit DIL1 may be arranged to form a diluted sample flow FG1 by combining the input aerosol sample flow FG0 with the dilution gas flow DG0 . The diluted aerosol sample flow FG1 may be directed to the measuring instrument INSTR1 via a low-pressure sampling line 50 .

[0228] Creating a diluted sample stream may also provide one or more of the following effects:

[0229] - Reduce the risk of polymerization of volatile compounds,

[0230] - Reduce the risk of changes in particle size distribution due to aggregation,

[0231] - Faster response due to higher particle velocity in the sampling line.

[0232] The measuring device 502 may comprise a pressure reduction unit PDU1 and an optional dilution unit DIL1. The dilution unit DIL1 may also be arranged to operate as a pressure reduction unit PDU1. The dilution unit DIL1 may comprise one or more orifices OR1 for reducing the pressure (p 50 The dilution unit DIL1 may include one or more first critical orifices OR1 for controlling the flow rate of the input flow FG0. The dilution unit DIL1 may include one or more second critical orifices OR2 for controlling the flow rate of the dilution gas flow DG0. The dilution unit DIL1 may include, for example, the second critical orifice OR2 for directing the dilution gas flow DG0 to the sampling line 50.

[0233] The input flow FG0 can be directed to the pipeline 50 via one or more first critical orifices OR1. The dilution flow DG0 can be directed to the pipeline 50 via one or more second critical orifices OR2. The internal pressure (p 50 ) may be maintained, for example, at less than 50 kPa to ensure critical (choked) flow through the orifices OR1, OR2. The input flow FG0 may have a flow rate QFG0 , and the dilution gas may have a flow rate Q DG0 The internal pressure (p 50 ) is maintained at a predetermined value of less than 50 kPa and directing the flow (FG0, DG0) through the orifices OR1, OR2 can provide a substantially constant dilution ratio (Q FG0 / Q DG0 ).

[0234] The aerosol sample flow (FG0, FG1) can be directed to a reduced pressure p via a first critical orifice OR1. 50 , and the dilution airflow DG0 can be directed to the same reduced pressure p via the second critical orifice OR2 50 The aerosol sample flow (FG0, FG1) can be combined with the dilution gas flow DG0, for example in sampling line 50, to provide a diluted sample. 50 / p0 may for example be less than 0.5 to ensure choked (critical) flow through the orifices OR1 , OR2. This may provide a diluted aerosol sample flow at a constant dilution ratio.

[0235] The dilution unit DIL1 can, for example, dilute the water at a constant dilution ratio (Q FG0 / Q DG0 ) dilutes the aerosol sample flow. The dilution gas GAS1 of the dilution gas DGO can be a substantially particle-free gas. The dilution gas GAS1 can be obtained from, for example, a gas cylinder. The dilution gas GAS1 can be, for example, ambient air AIR1. The dilution unit DIL1 can optionally include, for example, a filter FIL2 for removing particles from the dilution gas GAS1.

[0236] The apparatus (502) may include:

[0237] a dilution unit (DIL1) comprising a first critical orifice (OR1) for reducing the pressure of the input aerosol flow (FG0) and a second critical orifice (OR2) for reducing the pressure of the dilution gas flow (DG0), wherein the dilution unit (DIL1) is arranged to pass the dilution gas flow (DG0) at a reduced pressure (p 50 ) combines the input aerosol sample flow (FG0) with the dilution gas flow (DG0) to form a diluted aerosol sample flow (FG1),

[0238] - an aerosol measuring instrument (INSTR1) for measuring one or more aerosol parameter values ​​of an aerosol sample flow (FG1),

[0239] - a sampling line (50) for conducting the aerosol sample flow (FG1) from the dilution unit (DIL1) to the aerosol measuring instrument (INSTR1), and

[0240] - a suction unit (VAC1) for drawing the aerosol sample flow (FG1) from the dilution unit (DIL1) via the sampling line (50) to the aerosol measuring instrument (INSTR1), wherein the critical orifices (OR1, OR2) and the suction unit (VAC1) are arranged to reduce the internal pressure (p 50 ) maintained at a selected value below 50 kPa SET .

[0241] The suction unit VAC1 may comprise, for example, a pump PUMP1 or an ejector for drawing the aerosol sample flow FG1 to the measuring instrument INSTR1 via the sampling line 50. The suction unit VAC1 may cause the aerosol sample flow FG1 by drawing a flow FG12 from the measuring instrument INSTR1.

[0242] Internal pressure of the sampling line p 50 The lower limit value of may be, for example, 2 kPa (20 mbar). The apparatus 500, 502 may be arranged to operate such that the internal pressure p of the sampling line 50 Greater than or equal to 2kPa. Internal pressure p 50 It may be in the range of 2 kPa to 50 kPa, for example.

[0243] The suction unit VAC1 may optionally include a pressure sensor PSEN1 for directly or indirectly monitoring the internal pressure (p 50 The suction unit VAC1 may optionally comprise a flow rate and / or pressure (p 50 ) valve VAL1.

[0244] The suction unit VAC1 may optionally comprise a control unit CNT2 for controlling the pressure of the pump based on the signal S obtained from the pressure sensor PSEN1. P To control the operation of the pump PUMP1 and / or the valve VAL1. The control unit CNT2 may be arranged to be based on the signal S obtained from the pressure sensor PSEN1. P To control the operation of the pump PUMP1 and / or valve VAL1, thereby reducing the internal pressure (p 50 ) is maintained at a predetermined value (p SET ).

[0245] The pressure sensor PSEN1 can provide a signal S indicating the internal pressure (p2) of the collection unit 200. PThe pressure sensor PSEN1 can provide an indication of the internal pressure (p 50 ) signal S P . It can be achieved by providing a control signal S VAL To control the valve VAL1 and / or by providing a control signal S PUMP to control the pump.

[0246] The apparatus 500, 502 may optionally include a flow sensor QSEN1 for directly or indirectly monitoring the flow rate (Q1) of the aerosol sample flow (FG0, FG1). The flow sensor QSEN1 may provide a signal S indicating the flow rate Q1 of the aerosol sample flow FG1. Q For example, the apparatus 500, 502 may be arranged to Q An alarm is provided if the indicated flow rate Q1 is not within a predetermined range.

[0247] The flow FG12 obtained from the outlet OUT2 of the measuring instrument INSTR1 may include particles and / or volatile compounds, or the flow FG1 may be substantially free of contaminants. The suction unit VAC1 may optionally include a protective filter FIL12 for removing particles and / or volatile gases from the flow FG12. The filter FIL12 may protect the pressure sensor PSEN1, the valve VAL1 and / or the pump PUMP1 from contamination.

[0248] The vacuum unit VAC1 may provide an exhaust gas flow EXG1. After the flow FG12 has been drawn by the suction unit VAC1, the exhaust gas flow EXG1 may be discharged from an outlet, for example into the ambient air outside the device 500, or into a ventilation duct.

[0249] The length L of the low pressure area of ​​the sampling line 50 50 The range may be, for example, 0.5 m to 10 m. The device 502 may be used, for example, to measure aerosols emitted from an internal combustion engine of a vehicle. The inlet (IN0) of the sampling probe (50a) may be inserted into the exhaust pipe (DUC1) of the vehicle to extract the inlet flow FG0.

[0250] An aerosol sample flow (FG0) can also be obtained by positioning the inlet (IN0) of the sampling probe (50a) into the primary aerosol (PG0) emitted from the exhaust pipe (DUC1).

[0251] The sampling line 50 can be used to guide the aerosol sample flow FG1 from the sampling probe (50a) to the measuring instrument INSTR1. The measuring instrument INSTR1 can be located, for example, in a fixed cabinet or on a movable rack. The distance between the inlet of the sampling probe and the measuring instrument INSTR1 can be, for example, in the range of 0.5 m to 10 m.

[0252] refer to Figure 8c The apparatus 502 may further comprise a modifier unit MOD1 for modifying the size distribution of the aerosol sample flow. The modifier unit MOD1 may receive the first aerosol sample flow FG01, for example, from the dilution unit DIL1 or from the sampling probe. The modifier unit MOD1 may form the aerosol sample flow FG1 by removing particles from the first aerosol sample flow FG01. The modifier unit MOD1 may be arranged to provide a flat response for the measuring instrument INSTR1, for example, within a particle size range of 400 nm to 1000 nm. The penetration function of the modifier unit MOD1 may be selected to be: To provide a flat response for the measuring instrument INSTR1, for example, within a particle size range of 400 nm to 1000 nm. The modifier unit MOD1 may comprise, for example, a filter (FIL0), a cyclone separator and / or an impactor for removing large particles from the aerosol sample flow. The filter (FIL0), the cyclone separator and / or the impactor may be arranged to modify the size distribution of the aerosol sample flow by removing less than 100% of the particles within a predetermined size range, thereby providing a substantially flat response (R1(d)) for the measuring instrument INSTR1. P )).

[0253] The modifier unit MOD1 can also be omitted, for example when the aerosol sample flow does not include particles larger than the cut-off size d CUT in the case of particles.

[0254] The pressure reduction unit PDU1 can also be implemented, for example, by one or more orifices OR1. The pressure reduction unit PDU1 can also be implemented, for example, by a filter element, which can introduce flow resistance. For example, the filter (FIL0) can be arranged to reduce the pressure of the aerosol sample flow. For example, the filter (FIL0) can be arranged to operate as a pressure reduction unit PDU1 and / or as a modifier unit MOD1.

[0255] The pressure control unit CNT2 may be arranged to control the valve VAL1 and / or the pump PUMP1 to maintain the internal pressure (p2, p 50 ) is basically equal to the selected value p SETThe pressure control unit CNT2 may be electronic and / or mechanical, for example. The electronic pressure control unit CNT2 may include, for example, a device for storing a predetermined pressure value p SET The mechanical pressure regulator CNT2 may be arranged to control the valve VAL1 based on the pressure measured by the sensor PSEN1 so as to maintain the internal pressure (p2, p 50 ) is basically equal to the selected value p SET .

[0256] It will be apparent to those skilled in the art that modifications and variations of the systems, devices, apparatus, and methods according to the present invention are readily apparent. The figures are schematic. The specific embodiments described above with reference to the accompanying drawings are illustrative only and are not intended to limit the scope of the present invention, which is defined by the appended claims.

Claims

1. A device (500) for measuring aerosol particles (P0), the device (500) comprising: a charging unit (100) for charging particles (P0) of the aerosol sample flow (FG1) by diffusion charging to form charged particles (P1), a collecting unit (200) for providing a current (I1(t)) by collecting charges from the charged particles (P1) via diffusion of the charged particles (P1), the current (I1(t)) being indicative of the number density (n0(t)) of the aerosol particles (P0) of the aerosol sample flow (FG1), - a pressure reduction unit (PDU1) for reducing the pressure of the aerosol sample flow (FG1), and - a suction unit (VAC1) for drawing the aerosol sample flow (FG1) via the charging unit (100) to the collecting unit (200), Among them, the charging efficiency function (η1(d p )) indicates the efficiency of diffusion charging for charging the particles (P1), which is a function of the particle size (d p ), The charging efficiency function (η1(d p )) is approximated by a first exponential function with a first exponent (α), Among them, the collection efficiency function (η2(d p )) indicates the efficiency of collecting charges by diffusion of charged particles (P1), which is a function of particle size (d p ), The collection efficiency function (η2(d p )) is approximated by a second exponential function with a second exponent (-β), wherein the pressure reduction unit (PDU1) and the suction unit (VAC1) are arranged to maintain the internal pressure (p2) of the collection unit (200) at a selected pressure value (p SET ), so that the collection efficiency function (η2(d p ))'s negative slope (Δη2 / Δd p ) at least partially compensates for the charging efficiency function (η1(d p ))'s positive slope (Δη1 / Δd p ), so that the sum of the first exponent (α) and the second exponent (-β) is in the range of 0 to 0.65, the selected pressure value (p SET ) is less than or equal to 80 kPa, wherein the suction unit (VAC1) comprises a pump (PUMP1) for drawing a flow (FG4) from the collection unit (200) and / or a valve (VAL1) for controlling a flow rate (Q1) of the suction unit (VAC1), The suction unit (VAC1) comprises a pressure sensor (PSEN1) and a control unit (CNT2), wherein the pressure sensor (PSEN1) is used to provide a signal indicating the internal pressure (p2) of the collection unit (200), and the control unit (CNT2) is used to adjust the flow rate (Q1) of the suction unit (VAC1) to keep the internal pressure (p2) of the collection unit (200) substantially equal to the selected pressure value (p SET ), Therein, the control unit (CNT2) is arranged to provide a control signal for controlling the operation of the valve (VAL1) and / or for controlling the operation of the pump (PUMP1) based on the signal of the pressure sensor (PSEN1).

2. The device (500) according to claim 1, wherein The collection efficiency function (η2(d p ))'s negative slope (Δη2 / Δd p ) compensates the charging efficiency function (η1(d p ))'s positive slope (Δη1 / Δd p ), so that it can be used to detect the mobility size (d P ) of the particle (P0) current (I1(t)) response (R1(d P )) in the following range: for detecting a mobility size (d P ) of the particle (P0) (R1(d P )).

3. The device (500) according to claim 1 or 2, wherein the device for detecting a mobility size (d P ) of the particle (P0) current (I1(t)) response (R1(d P )) is in the following range: for detecting a mobility size (d P ) of the particle (P0) (R1(d P )) of 0.9 to 1.1 times, and wherein for detecting a mobility size (d P ) of the particle (P0) current (I1(t)) response (R1(d P )) is in the following range: for detecting a mobility size (d P ) of the particle (P0) (R1(d P )).

4. The device (500) according to claim 1 or 2, wherein: The charging unit (100) comprises: a corona electrode (E1) for generating ions (J1) by forming a corona discharge (DSR1) together with a counter electrode (E2), a charging space (SPC1) for forming charged particles (P1) from aerosol particles (P0) of said aerosol sample flow (FG1) by diffusion of generated ions (J1), and - one or more flow guides (BAF1) for guiding the received aerosol sample flow (FG1) through the charging space (SPC1) so that the maximum intensity of the electric field (EFIELD1) across the aerosol sample flow (FG1) in the charging space (SPC1) is less than 100 V / cm.

5. The device (500) according to claim 1 or 2, wherein The pressure reduction unit (PDU1) comprises one or more critical orifices (OR1).

6. The device (500) according to claim 1 or 2, comprising: A dilution unit (DIL1) for forming a diluted aerosol sample flow (FG1) by combining the primary aerosol sample flow (FG1) with a dilution gas flow (DG0).

7. The device (500) according to 1 or 2, comprising: An auxiliary detector unit (300) for providing an auxiliary current (I2(t)) indicating the charge of the charged particles (P1) leaving the collection unit (200).

8. A method for measuring aerosol particles (P0), the method comprising: - forming charged particles (P1) from particles (P0) of the aerosol sample flow (FG1) by diffusion charging using a charging unit (100), - reducing the pressure of the aerosol sample flow (FG1) using a pressure reduction unit (PDU1), - using a suction unit (VAC1) to draw the aerosol sample flow (FG1) via the charging unit (100) to a collecting unit (200), - providing a current (I1(t)) by collecting charge from the charged particles (P1) using the collecting unit (200), wherein the charge is collected from the charged particles (P1) by diffusion of the charged particles (P1), the current (I1(t)) being indicative of the number density (n0(t)) of the aerosol particles (P0) of the aerosol sample flow (FG1), wherein a charging efficiency function (η1(d p )) indicates the efficiency of diffusion charging for charging the particles (P1), which is a function of the particle size (d p ) function, wherein the charging efficiency function (η1(d p )) is approximated by a first exponential function with a first exponent (α), where the collection efficiency function (η2(d p )) indicates the efficiency of collecting charges by diffusion of charged particles (P1), which is a function of particle size (d p ) function, wherein the collection efficiency function (η2(d p )) is approximated by a second exponential function with a second exponent (-β), and - Maintaining the internal pressure (p2) of the collecting unit (200) at a selected pressure value (p SET ), so that the collection efficiency function (η2(d p ))'s negative slope (Δη2 / Δd p ) at least partially compensates for the charging efficiency function (η1(d p ))'s positive slope (Δη1 / Δd p ), so that the sum of the first exponent (α) and the second exponent (-β) is in the range of 0 to 0.65, the selected pressure value (p SET ) is less than or equal to 80 kPa, wherein the suction unit (VAC1) comprises a pump (PUMP1) for drawing a flow (FG4) from the collection unit (200) and / or a valve (VAL1) for controlling a flow rate (Q1) of the suction unit (VAC1), The suction unit (VAC1) comprises a pressure sensor (PSEN1) and a control unit (CNT2), wherein the pressure sensor (PSEN1) is used to provide a signal indicating the internal pressure (p2) of the collection unit (200), and the control unit (CNT2) is used to adjust the flow rate (Q1) of the suction unit (VAC1) to keep the internal pressure (p2) of the collection unit (200) substantially equal to the selected pressure value (p SET ), The control unit (CNT2) provides a control signal for controlling the operation of the valve (VAL1) and / or for controlling the operation of the pump (PUMP1) based on the signal of the pressure sensor (PSEN1).

9. The method according to claim 8, wherein The aerosol sample flow (FG1) is obtained by sampling the exhaust gas (PG0) of an engine (SRC1).

10. The method according to claim 8 or 9, comprising: A number density value (n0) is determined from the current (I1), the determined number density value (n0) is compared with a limit value (LIM1), and it is determined whether the number density value (n0) is less than the limit value (LIM1).

11. The method according to claim 8 or 9, comprising: The aerosol sample flow (FG1) is directed through a first critical orifice (OR1), a dilution gas flow (DG0) is directed through a second critical orifice (OR2), and a diluted aerosol sample flow (FG1) is formed by combining the aerosol sample flow (FG1) with the dilution gas flow (DG0).

Images