Condensation charging-based nanoscale high concentration particle number concentration measuring device and method

Abstract

This invention relates to the field of mobile source exhaust particulate matter monitoring technology, and discloses a device and method for measuring the number concentration of nanoscale high-concentration particles based on condensation charging. The measuring device includes a volatile particle removal device, a two-stage condensation growth device, a unipolar charging device, and a dual-path Faraday cup detection device. Sample gas enters from the inlet of the volatile particle removal device, and the outlet of the volatile particle removal device is connected to the inlet of the two-stage condensation growth device; the outlet of the two-stage condensation growth device is connected to the inlet of the unipolar charging device; and the outlet of the unipolar charging device is connected to the inlet of the dual-path Faraday cup detection device. This invention overcomes the shortcomings of existing technologies, achieving efficient removal of volatile particles, high-concentration measurement, and a 10nm particle size detection limit without dilution for measuring the number concentration of ultrafine particulate matter in motor vehicle exhaust, greatly improving detection sensitivity and measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of mobile source exhaust particulate matter monitoring technology, specifically to a device and method for measuring the number concentration of nanoscale high-concentration particles based on condensation charging. Background Technology

[0002] Mobile sources remain a top priority in air pollution control. Against this backdrop, there is a growing market demand for portable particulate matter number concentration monitoring devices with a detection limit of 10nm.

[0003] In recent years, instruments and equipment for detecting ultrafine particulate matter in motor vehicle emissions have developed in a series. Currently, the monitoring methods for the number concentration of ultrafine particulate matter in motor vehicle emissions are mainly divided into two categories: one is the condensation nucleus particle counting method. Its core principle is to use a condensation nucleus particle counter to cause ultrafine particles to condense and grow to an optically measurable size in a supersaturated steam environment. Subsequently, the particles enter an optical cavity, and the pulse signals generated by the pulses of the scattered light from the particles are counted. Combined with the sampling flow rate parameters, the number concentration of particles in the sample gas can be calculated. Chinese patent document CN116818624A discloses a particulate matter condensation counter based on diethylene glycol and water, which adopts a two-stage condensation scheme of diethylene glycol pre-growth and water main growth, and uses an optical counter to detect the grown micron-sized particles. However, this device relies on optical detection. In high-concentration particulate matter scenarios, it is prone to overlap errors due to the overlapping of the scattered light pulses from the particles, resulting in inaccurate counting and failing to achieve accurate measurement of high-concentration particulate matter.

[0004] Another method is a measurement technique based on the principle of diffusion charging. This method first charges the particulate matter using a specific method, then accurately measures the charge on the particles, and finally uses the detected current value to inversely deduce the number concentration of the particles. Chinese patent document CN218766498U discloses an integrated measuring device for the number concentration of particulate matter in motor vehicle exhaust, which uses the principle of diffusion charging to measure the number concentration of particulate matter. However, due to the limitations of the technical characteristics of diffusion charging, its charging efficiency for small-diameter particles is low, making it impossible to fully charge small-diameter particles. This results in weak measurement signals and large data deviations, making it difficult to meet the accuracy requirements of fine monitoring for the detection of small-diameter particles.

[0005] Existing technology discloses a single-stage condensation diffusion charging scheme (Krasa, H., Fruhmann, VM, Schurl, S., Kupper, M., and Bergmann, A.: Condensation diffusion charging–particle number measurement of high concentrations down to 3 nm[J]. AerosolResearch, 3, 521–534, 2025.), which uses a single working fluid (such as diethylene glycol) to condense and grow particles to the micrometer size in one step before charging and electrical detection. However, this scheme still has several inherent drawbacks when applied to applications such as real-time online monitoring of vehicle exhaust: micrometer-sized droplets have high inertia and low diffusion coefficients, which reduce their transmission efficiency and charging efficiency within the system; growing particles to the micrometer size not only requires a long growth time, limiting the instrument's temporal resolution, but also consumes more saturated vapor, which is prone to signal attenuation due to vapor depletion under high concentration conditions; at the same time, the diethylene glycol used in the article has a certain degree of toxicity and is not suitable for practical monitoring use.

[0006] As can be seen from the above, traditional detection methods and related equipment are no longer sufficient to meet the current demands for refined monitoring of vehicle exhaust emissions. The single-stage condensation-diffusion charging technology, which combines the principles of condensation growth and diffusion charging, still has many shortcomings. Therefore, there is an urgent need to develop a new nanoscale high-concentration particulate matter number concentration measurement device that combines the principles of condensation growth and diffusion charging. This device should be able to accurately measure particulate matter in high-concentration exhaust gases and effectively detect small-diameter ultrafine particles, thus fully meeting the increasingly stringent requirements for mobile source exhaust emission control. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a device and method for measuring the number concentration of nanoscale high-concentration particles based on condensation charging. In the process of measuring the number concentration of ultrafine particulate matter in motor vehicle exhaust, this invention achieves efficient removal of volatile particles, direct measurement in high-concentration scenarios, and achieves a detection limit of 10nm particle size without dilution, while improving the detection sensitivity and accuracy of measurement results for low-concentration particles.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: In a first aspect, the present invention provides a nanoscale high-concentration particle number concentration measurement device based on condensation charging, comprising a volatile particle removal device, a two-stage condensation growth device, a unipolar charging device, and a dual-path Faraday cup detection device connected in sequence. The volatile particle removal device is used to remove volatile particles from the sample gas; The dual-stage condensation and growth device is used to condense and grow particles larger than 10 nm in the sample gas into submicron-sized droplets suitable for electrical detection. The unipolar charging device is used to charge the grown droplets and filter out charged particles and free ions smaller than 10 nm. The dual-path Faraday cup detection device is used to collect charged droplets and invert the number concentration of nanoscale particles in the sample gas by detecting the current value corresponding to the charge.

[0009] In one embodiment, the inlet of the volatile particle removal device is connected to the sample gas via a pipe, and the outlet of the volatile particle removal device is connected to the inlet of the two-stage condensation growth device via a pipe; the outlet of the two-stage condensation growth device is connected to the inlet of the unipolar charging device via a pipe; and the outlet of the unipolar charging device is connected to the inlet of the dual-path Faraday cup detection device via a pipe.

[0010] In one embodiment, the volatile particle removal device includes a metal tank, a heating layer 1 sleeved on the outside of the metal tank, and a heat insulation layer 1 wrapped around the metal tank and the heating layer 1. The interior of the metal tank is divided into a heating zone and a base zone along the airflow direction; the base zone is filled with a cordierite base; the surface of the cordierite base is coated with a catalyst coating. The metal can body includes a metal can body main body and an air inlet and an air outlet disposed at both ends of the metal can body main body; The main body of the metal can is a cylindrical channel, with the air inlet and air outlet located at both ends of the main body of the metal can, and both are conical in shape.

[0011] In one embodiment, the two-stage condensation growth device includes a metal tube, a pre-growth region located at the inlet end of the metal tube, and a secondary growth region located at the outlet end; a heat insulation section is provided between the pre-growth region and the secondary growth region.

[0012] In one embodiment, the pre-growth region includes a heating section one, a condensation section one, and a heat insulation section two between the heating section one and the condensation section one; The heating section includes a second heating layer sleeved on the outside of the metal tube, a second insulation layer wrapped around the second heating layer, a porous medium disposed inside the metal tube, and a storage tank connected to the porous medium. The porous medium is designed as an annular cylinder, which fits tightly against the inner wall of the metal tube after being heated by the second heating layer, and is connected to the storage tank containing the working liquid disposed on the outside of the metal tube through through holes opened in the metal tube wall. The condensation section includes a cooling layer 1 sleeved on the outer wall of the metal pipe and an insulation layer 3 wrapped around the cooling layer 1.

[0013] In one embodiment, the secondary growth region includes a second heating section and a second condensation section arranged along the airflow direction, and an annular cylindrical water-containing porous medium that penetrates the secondary growth region and is tightly attached to the inner wall of the metal tube; a third heat insulation section is provided between the second heating section and the second condensation section. The second heating section includes a third heating layer sleeved on the outside of one end of the metal tube and a fourth insulation layer wrapped around the third heating layer; the second condensation section includes a second cooling layer sleeved on the outer wall of the metal tube and a fifth insulation layer wrapped around the cooling layer.

[0014] In one embodiment, the unipolar charging device includes a housing; the inner cavity of the housing is sequentially divided along the axial direction into a charging region and an ion trapping region; A discharge cavity is provided on one side of the charged region, and an insulating base is installed inside the discharge cavity. A charging needle is installed through the center of the end of the insulating base away from the charged region. The insulating base has a metal ring at one end near the charged region. The metal ring has a through hole in the middle and is coaxial with the charged needle. The metal ring is grounded. A perforated plate is provided at the connection between the discharge cavity and the outer shell; The insulating base has several evenly distributed sheath gas inlets at one end where the charged needle is installed; the outer shell has a sample gas inlet on the side opposite to the discharge cavity. The ion capture area includes a capture electrode and a grounding electrode disposed on the inner wall of the housing; an insulating base two is installed on the inner wall of the housing; the capture electrode is mounted on the insulating base two.

[0015] In one embodiment, the dual-path Faraday cup detection device includes a metal housing, and a first measuring branch, a second measuring branch, a measuring circuit, an insulating base three, an insulating base four encapsulated inside the metal housing, as well as a heating element attached to the outer wall of the metal housing and a heat-insulating shell on the outside of the metal housing. The first measuring branch includes a filter element one, a honeycomb shell one, and an air pump one connected in sequence; the second measuring branch includes a filter element two, a honeycomb shell two, and an air pump two connected in sequence; a filter is also connected in series before the air inlet of the second measuring branch; The filter element one and filter element two are respectively installed inside the honeycomb shell one and honeycomb shell two; the honeycomb shell one and honeycomb shell two are respectively fixedly installed inside the metal shell through insulating base three and insulating base four; The measuring circuit is fixedly installed on the bottom inner side of the metal casing. The measuring circuit surface is provided with spring probe one and spring probe two. Spring probe one is tightly pressed against the bottom of honeycomb casing one, and spring probe two is tightly pressed against the bottom of honeycomb casing two. Air pump one and air pump two are respectively connected to the two air outlets of the metal casing.

[0016] Secondly, the present invention provides a measurement method for a condensation-charged nanoscale high-concentration particle number concentration measuring device as described in any embodiment of the first aspect, comprising the following steps: S1. Pre-treat the sample gas containing nanoscale particles to remove volatile particles from the sample gas; S2. The nanoscale particles in the sample gas after the removal of volatile particles are subjected to two condensation and growth treatments, so that the particles in the sample gas are grown by two working liquid vapors in sequence, and finally grow into submicron-sized droplets suitable for electrical detection. S3. The grown droplets are subjected to unipolar charging treatment, and charged particles and free ions with a particle size smaller than the set value in the sample gas are screened out and removed, while the target size droplets after charging are retained. S4. Collect the charged droplets, detect the electrical signal value corresponding to the charge carried by the charged droplets, and obtain the number concentration of nanoscale particles in the sample gas based on the electrical signal value.

[0017] In one embodiment, step S1 specifically includes: The sample gas containing nanoscale particles is pretreated by passing it through a volatile particle removal device. The metal tank of the volatile particle removal device is heated and the temperature inside the tank is maintained at a preset high temperature. The sample gas flows through the heating zone inside the metal tank and is heated, causing the volatile particles in the sample gas to evaporate into a gaseous state. The gaseous volatile particles flow through the base region inside the metal tank with the sample gas and come into contact with the cordierite substrate with a catalyst coating on its surface. Under the catalytic action of the catalyst, the volatile particles in the sample gas are oxidized and decomposed, thus removing the volatile particles from the sample gas. Step S2 specifically includes: The sample gas, after the removal of volatile particles, is introduced into the pre-growth zone of the two-stage condensation growth device. The working liquid in the storage tank is transported to the porous medium inside the metal tube through capillary action. The metal tube is heated, causing the working liquid in the porous medium, which is in close contact with the inner wall of the metal tube, to evaporate and form saturated vapor. After the sample gas carrying the saturated vapor enters the first condensation section, the metal tube in the first condensation section is cooled and maintained at a preset low temperature, so that the gas flow is cooled to a supersaturated state, activating the nano-sized particles and causing the nano-sized particles to initially condense and grow. Sample gas carrying nanoscale particles that have undergone initial condensation growth is introduced into the secondary growth region of the two-stage condensation growth device. The metal tube of the second heating section is heated to maintain a preset high temperature, causing the liquid water in the water-containing porous medium to evaporate and form a saturated water vapor environment. After the sample gas enters, the water vapor undergoes secondary condensation using the nanoscale particles that have undergone initial condensation growth as condensation nuclei. The sample gas then enters the second condensation section of the metal tube, where the metal tube is cooled and maintained at a preset low temperature. The supersaturation of water vapor in the sample gas begins to decrease, allowing the nanoscale particles that have undergone initial condensation growth to continue condensing and growing into droplets of the target size in the second condensation section. Simultaneously, the remaining water vapor in the gas flow that has not participated in condensation condenses into liquid water on the inner wall of the porous medium in the second condensation section and is transported back to the water-containing porous medium in the second heating section upstream through capillary action for recycling. Step S3 specifically includes: The sample gas carrying droplets is introduced into a unipolar charging device. Dry, clean air is introduced into the discharge chamber of the unipolar charging device, and a preset high-voltage electric field is formed between the charging needle of the unipolar charging device and the grounded metal ring. Under the action of the electric field, part of the dry, clean air is ionized to generate ions. The ions are sprayed into the charging region through the through holes on the metal ring and the through holes in the center of the orifice plate with the clean air flow. Some of the ions collide with the droplets, realizing the charging of the droplets. At the same time, the dry, clean air mixes with the sample gas, reducing the concentration of residual working liquid vapor in the sample gas, thereby inhibiting the further growth of particles. The charged sample gas enters the ion capture region. Using the electric field formed between the capturing electrode and the grounding electrode in this region, charged particles and free ions with a diameter of less than 10 nm in the sample gas are captured and removed, allowing only target-sized droplets carrying charge to pass through. Step S4 specifically includes: Sample gas containing charged droplets is introduced into a dual-path Faraday cup detection device. The sample gas is divided into two equal paths via a three-way valve, entering the first and second measurement branches respectively. The metal casings of both measurement branches provide electrostatic shielding. Heating elements and insulation on the metal casings maintain a constant temperature for both measurement branches. The first measurement branch directly receives the sample gas containing charged droplets. The second measurement branch has a filter connected in series at its inlet to remove charged particles from the sample gas, allowing only gas and residual ions to pass through; this filter serves as a background noise reference branch. Under the negative pressure generated by pumps one and two, the sample gas flows uniformly through filter elements one and two at the same velocity. Filter element one in the first measurement branch traps… All charged droplets in the sample gas are collected. The charge carried by the charged droplets is conducted to the corresponding honeycomb shell 1 through filter element 1. Filter element 2 of the second measurement branch does not capture particles and only reflects the system's background charge and interference. Spring probe 1 and spring probe 2 transmit the charge signals of honeycomb shell 1 and honeycomb shell 2 to the measurement circuit in real time and detect the corresponding current values. The measurement circuit synchronously acquires and differentially calculates the signals of the first and second measurement branches. The background noise signal measured by the second measurement branch is subtracted from the total current signal of the first measurement branch in real time to obtain the net current value contributed only by the charged droplets. Based on the net current value and the pre-established current-particle number concentration calibration relationship, the number concentration of nanoscale particles in the sample gas is obtained by inversion.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are: Compared to traditional condensation growth particle counters (optical CPC) that use optical principles for measurement, this invention innovatively employs the diffusion charging principle for counting particles after condensation growth. This electrical-based detection method fundamentally avoids the particle scattering light pulse overlap problem that easily occurs in optical CPC at high concentrations. Furthermore, since the target size of the condensed particles does not need to reach the micrometer-level size required for optical detection, but only needs to meet the requirements of charging and subsequent screening and detection, this not only shortens the particle growth time and improves the temporal resolution, but more importantly, significantly reduces vapor consumption. This avoids the counting efficiency decay caused by excessive vapor consumption at high concentrations, thus enabling accurate and continuous online measurement of high-concentration particles without the need for a complex dilution system.

[0019] Compared to traditional particulate number concentration detection devices based on the diffusion charge (DC) principle, this invention transforms small-diameter initial nanoparticles into larger droplets during the condensation growth stage, significantly increasing their charge capacity. This completely eliminates the inherent problem of low diffusion charge efficiency of the original small-diameter particles and avoids measurement deviations caused by particle size differences. This invention significantly improves the detection sensitivity for low concentrations and small-diameter particles, achieving a particle size detection limit of 10 nm.

[0020] Compared to the latest single-stage condensation diffusion charging technology, this invention overcomes its inherent limitations through a two-stage condensation growth design and structural optimization of the charging device and Faraday cup device. This invention innovatively employs a two-stage growth chamber design combining ethanol pre-growth and water main growth for rapid growth of small-diameter carbon soot particles from vehicle exhaust. Precise temperature control allows for growth to submicron sizes of 200-500 nm, significantly reducing droplet inertia and ensuring efficient charging of the grown droplets by the diffusion charging method, effectively reducing transmission losses and increasing the measurable concentration range. The charging device design, independent of the sample gas flow channel and incorporating a dry sheath gas for counter-mixing, effectively avoids the impact of droplet adhesion on charging while effectively terminating excessive particle growth by reducing vapor concentration. The dual-path Faraday cup detection device enables continuous and synchronous acquisition of particle signals and system background noise, improving temporal resolution and significantly enhancing the system's signal-to-noise ratio and low-concentration detection sensitivity.

[0021] This invention eliminates the need for complex optical systems and dilution equipment, greatly improving portability and applicability. It also uses safe, low-cost, and readily available ethanol and water as working liquids, making it suitable for various application scenarios such as vehicle-mounted and on-site emission monitoring. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the cascaded nanoscale high-concentration particle number concentration measuring device based on condensation charging in this invention. Figure 2 This is a schematic diagram of the volatile particle removal device in this invention; Figure 3 This is a schematic diagram of the structure of the two-stage condensation growth device in this invention; Figure 4 This is a schematic diagram of the structure of the unipolar charging device in this invention; Figure 5 This is a schematic diagram of the dual-path Faraday cup detection device in this invention.

[0023] in: 100. Volatile particle removal device; 101. Metal tank; 102. Heating layer 1; 103. Insulation layer 1; 104. Heating zone; 105. Cordierite base. 200. Two-stage condensation growth device; 210. Metal pipe; 220. Pre-growth zone; 2210. Heating layer two; 2211. Insulation layer two; 2212. Porous medium; 2213. Storage tank; 2220. Cooling layer one; 2221. Insulation layer three; 223. Insulation section two; 230. Secondary growth zone; 2310. Heating layer three; 2311. Insulation layer four; 2320. Cooling layer two; 2321. Insulation layer five; 233. Aqueous porous medium; 234. Insulation section three; 240. Insulation section one; 300. Unipolar charging device; 301. Outer shell; 302. Discharge chamber; 303. Charging region; 304. Ion capture region; 305. Insulating base one; 306. Charging needle; 307. Metal ring; 308. Orifice plate; 309. Capturing electrode; 310. Grounding electrode; 311. Insulating base two; 312. Sheath gas inlet; 313. Sample gas inlet.

[0024] 400. Dual-channel Faraday cup detection device; 410. Metal casing; 421. Filter element one; 422. Honeycomb casing one; 423. Air pump one; 431. Filter element two; 432. Honeycomb casing two; 433. Air pump two; 440. Measuring circuit; 441. Spring probe one; 442. Spring probe two; 450. Insulating base three; 460. Insulating base four; 470. Heating element; 480. Insulating casing; 490. Filter. Detailed Implementation

[0025] A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0026] like Figure 1 As shown, the present invention discloses a cascaded nanoscale high-concentration particle number concentration measurement device based on condensation charging, comprising: a volatile particle removal device 100, a two-stage condensation growth device 200, a unipolar charging device 300, and a dual-path Faraday cup detection device 400. The above components are connected in series via steel pipes to form a closed-loop detection path. Sample gas enters through the inlet of the volatile particle removal device 100 via the steel pipes; the outlet of the volatile particle removal device 100 is connected to the inlet of the two-stage condensation growth device 200 via a steel pipe; the outlet of the two-stage condensation growth device 200 is connected to the inlet of the unipolar charging device 300 via a steel pipe; and the outlet of the unipolar charging device 300 is connected to the inlet of the dual-path Faraday cup detection device 400 via a steel pipe.

[0027] The volatile particle removal device 100 is used to efficiently remove volatile particles from the sample gas; the two-stage condensation and growth device 200 is used to grow ultrafine particles of 10 nm and above into droplets in the submicron range of 200-500 nm; the unipolar charging device 300 is used to charge the grown droplets and screen out charged particles and free ions smaller than 10 nm; the dual-path Faraday cup detection device 400 is used to collect charged droplets and inversely determine the particle number concentration by detecting the current value corresponding to the charge. Through the cascaded cooperation of the above devices, accurate measurement of high-concentration particle number concentration with a detection limit of 10 nm particle size can be achieved without dilution, fully adapting to the higher standards of refined monitoring of motor vehicle exhaust.

[0028] As a further improvement to the above technical solution, such as Figure 2 As shown, the volatile particle removal device 100 includes a metal tank 101, a heating layer 102 sleeved on the outside of the metal tank 101, and a heat insulation layer 103 wrapped around the metal tank 101 and the heating layer 102; the interior of the metal tank 101 is divided into a heating zone 104 and a base zone along the airflow direction; the base zone is filled with a cordierite base 105.

[0029] Specifically, the metal can 101 includes a main body and an air inlet and an air outlet located at both ends of the main body. The main body is a cylindrical channel, with the air inlet and outlet respectively located at both ends and conical in shape to ensure smooth airflow. In the cylindrical channel, the front half near the air inlet is a heating zone 104, and the rear half near the air outlet is a base region. The base region is filled with a cordierite base 105, which is a ceramic carrier with regular honeycomb pores, made of structurally stable and high-temperature resistant magnesium aluminum silicate. The metal can 101 is made of stainless steel. The heating layer 102 heats the wall temperature of the metal can 101 to 400°C. The cordierite base 105 is filled along the axial direction of the metal can 101 within the base region, with a length of 50 mm. All the inner wall surfaces of the channels of the cordierite substrate 105 are uniformly coated with a catalyst coating, which can significantly enhance the oxidative decomposition effect of volatile particles.

[0030] The function of the heating layer 102 is to stably heat the wall temperature of the metal can 101 to 400°C, causing the volatile particles in the sample gas to evaporate into a gaseous state under high temperature. After the sample gas enters the heating zone 104, the volatile particles in it evaporate into a gaseous state under high temperature. Then, the gaseous volatile particles flow through the substrate region with the gas flow, fully contact the catalyst coating on the inner wall surface of the cordierite substrate 105 pores, and undergo catalytic oxidation and decomposition, ultimately achieving efficient removal of volatile particles from the sample gas and avoiding interference with subsequent particulate matter quantity measurement from the source.

[0031] As a further improvement to the above technical solution, such as Figure 3 As shown, the two-stage condensation growth device 200 includes a metal tube 210, a pre-growth region 220 at the air inlet end of the metal tube 210, and a secondary growth region 230 at the air outlet end; a heat insulation section 240 is provided between the pre-growth region 220 and the secondary growth region 230.

[0032] The pre-growth region 220, the heat insulation section 240, and the secondary growth region 230 are arranged sequentially along the axial direction of the metal tube 210 to form an integrated structure of ethanol vapor pre-growth, water vapor secondary growth, and temperature isolation. This ensures that each functional region works in concert without interfering with each other, providing a continuous and controllable environment for the rapid and stable growth of initial 10nm and above ultrafine particles to the target size.

[0033] Specifically, the pre-growth region 220 is located at the air inlet end of the metal pipe 210, where a working fluid (such as ethanol) is used to achieve initial rapid condensation of particles. This region is further divided into a heating section 1 and a condensation section 1, which are thermally isolated by a heat insulation section 223. In the heating section 1, a heating layer 2210 fitted on the outside of the metal pipe 210 heats the pipe wall, and is covered by a heat insulation layer 2211. The porous medium 2212 inside the metal pipe 210 is tightly attached to the heated inner wall and is connected to the external liquid storage tank 2213 through the pipe wall through-holes, continuously delivering the ethanol working fluid to the heating surface by capillary action, where it evaporates to form stable saturated vapor. Subsequently, the airflow enters the condensation section 1, which is actively cooled by a cooling layer 2220 fitted on the outer wall of the metal pipe 210, and is covered by a heat insulation layer 2221, thus forming a steep cooling zone. Here, the ethanol vapor rapidly becomes supersaturated, prompting the small-diameter particles to undergo their first efficient condensation, achieving initial growth and laying the foundation for subsequent secondary growth.

[0034] As a further improvement to the above technical solution, the secondary growth region 230 is located at the outlet end of the metal tube 210, where water vapor is used to perform secondary condensation on the pre-grown particles, ultimately achieving a submicron range of 200-500 nm. This region consists of a second heating section and a second condensation section, separated by a third insulation section 234. A section of water-containing porous medium 233 is tightly attached to the inner wall of the metal tube 210. The low-temperature airflow, cooled by the pre-growth region 220, first enters the second heating section. Here, the third heating layer 2310 provides heat to continuously evaporate the water in the water-containing porous medium 233. The resulting water vapor mixes with the low-temperature airflow and quickly reaches a supersaturated state, thereby directly driving the water vapor to undergo secondary condensation on the pre-grown particles within the heating section. The fourth insulation layer 2311 wraps around the outside of the third heating layer. The subsequent second condensation section primarily functions to maintain a low temperature through the second cooling layer 2320 and the fifth insulation layer 2321, condensing uncondensed residual water vapor in the airflow into liquid water in the water-containing porous medium 233. This liquid water is then transported via capillary action to the water-containing porous medium 233 of the upstream heating section for recycling, preventing it from entering the downstream and causing interference. By precisely controlling the temperature in this region, the droplet size can be stably limited to the submicron level. Compared to the micron-sized droplets produced by traditional single-stage technology, this design significantly reduces droplet inertia, decreases diffusion losses and wall deposition during transport, and reduces vapor loss, avoiding the problem of excessively high concentrations preventing small-diameter particles from growing sufficiently. This greatly improves the transport efficiency of particulate matter and the upper limit of measurable concentration.

[0035] As a further improvement to the above technical solution, the heat insulation section 1 240, heat insulation section 223, and heat insulation section 3 234 are made of resin material. Their core function is to isolate the temperature between the pre-growth and secondary growth regions 230 and between the regions, to avoid temperature crosstalk, and to ensure that the high and low temperature sections of each region are stable and controllable, providing steep and stable temperature gradient conditions for the two growths of nanoscale particles.

[0036] As a further improvement to the above technical solution, the storage tank 2213 stores a working fluid, which is ethanol. Ethanol has a low boiling point and high volatility, allowing it to evaporate rapidly in the heating section and efficiently form high supersaturation in the condensation section, achieving initial activation and condensation of ultrafine particles of 10 nm and above. In the secondary growth region 230, water vapor is provided through a water-containing porous medium 233. Water has a moderate saturated vapor pressure, and its condensation process is more gradual and controllable, precisely controlling the final droplet size within the submicron range of 200-500 nm, thus avoiding overgrowth.

[0037] As a further improvement to the above technical solution, such as Figure 4As shown, the unipolar charging device 300 includes a housing 301; the inner cavity of the housing 301 is divided into a charging region 303 and an ion capture region 304 along the axial direction, forming a continuous processing channel for particulate charging and small particle / particle screening.

[0038] As a further improvement to the above technical solution, a discharge cavity 302 is provided on one side of the charged region 303. An insulating base 305 is installed in the discharge cavity 302. A charging needle 306 is installed through the center of the end of the insulating base 305 away from the charged region 303. The charging needle 306 is made of tungsten material with high conductivity and high temperature resistance and is connected to an external high voltage source, so that a tip discharge is generated at its top, ionizing the clean air entering the discharge cavity 302 and generating a large number of free ions.

[0039] As a further improvement to the above technical solution, a metal ring 307 is provided at one end of the insulating base 305 near the charged region 303. A through hole is opened in the middle part of the metal ring 307, and it is coaxially arranged with the charged needle 306. The metal ring 307 is grounded, and a stable high-voltage electric field is formed between it and the charged needle 306, thereby improving ionization stability.

[0040] As a further improvement to the above technical solution, a perforated plate 308 is provided at the connection between the discharge chamber 302 and the outer shell 301; a through hole with a diameter of 0.7 mm is provided in the center of the perforated plate 308. The perforated plate 308 can effectively block the sample gas from entering the discharge chamber 302, preventing particulate matter from adhering to the charging needle 306, which would cause distortion of the high-voltage electric field and reduce the charging efficiency; the insulating base 305 has several evenly distributed sheath gas inlets 312 at one end where the charging needle 306 is installed. Clean sheath gas enters the discharge chamber 302 through the inlet, providing a stable airflow environment for the ionization process. At the same time, the sheath gas airflow carries a large number of free ions generated by the discharge, which are carried out through the through hole of the metal ring 307 and the through hole in the center of the perforated plate 308, and injected into the charging region 303, providing a sufficient ion source for the charging region 303.

[0041] As a further improvement to the above technical solution, a sample gas inlet 313 is provided on the side of the outer shell 301 opposite to the discharge cavity 302. The particulate-containing gas flow, after condensation and growth, enters the charged region 303 through the sample gas inlet 313, forming a counter-current mixing with the sheath gas flow entering from the opposite side (discharge cavity direction). This counter-current design allows the test particles to have sufficient contact and collision with free ions, thereby achieving efficient and uniform charging of the particles. At the same time, the dry clean air mixes with the sample gas, reducing the concentration of residual working liquid vapor in the sample gas, thereby inhibiting further growth of the particles. Meanwhile, the charged region 303 provides a reasonably sized space for the counter-current mixing of the gas flow, and effectively avoids the loss of particles caused by the collision of droplets after condensation and growth with the inner wall of the cavity, ensuring the integrity of the number of particles detected subsequently. The ion capture region 304 includes a capturing electrode 309 and a grounding electrode 310 disposed on the inner wall of the outer shell 301; an insulating base 311 is installed on the inner wall of the outer shell 301; the capturing electrode 309 is mounted on the insulating base 311.

[0042] As a further improvement to the above technical solution, the ion trapping region 304 is located downstream of the charged region 303. An insulating base 311 is fixedly installed on the inner wall of the outer shell 301 at a corresponding position. The trapping electrode 309 is fixed on the insulating base 311, and the grounding electrode 310 is installed on the side of the outer shell 301 opposite to the trapping electrode 309. Both are made of highly conductive copper and have a reasonable spacing to form a stable screening electric field. The axial distance between the trapping electrode 309 and the grounding electrode 310 in the ion trapping region 304 has been optimized. The reasonable, relatively long electric field distribution allows a uniform and stable trapping electric field to be formed between the two electrodes. This electric field ensures that excess free ions in the gas flow, as well as unactivated charged nanoparticles (less than 10 nm), are completely trapped and removed.

[0043] The collecting electrode 309 and the grounding electrode 310 are both made of copper; the charging needle 306 is made of tungsten and is connected to a high-voltage source.

[0044] The insulating base 305 is fixedly installed at one end of the outer shell 301, forming a cylindrical discharge cavity 302 inside. The charging needle 306 is made of high-hardness, high-conductivity tungsten material, penetrates the discharge cavity 302 and is fixed at the center of one end of the insulating base 305. The charging needle 306 is connected to an external high-voltage source to generate an ionizing electric field. The metal ring 307 is installed on the insulating base 305 at the other end of the discharge cavity 302. A through hole is opened in the middle of the metal ring 307. The metal ring 307 is grounded and coaxially arranged with the charging needle 306 to ensure uniform electric field distribution. The orifice plate 308 is fixedly installed inside the outer shell 301. A through hole is opened in the center of the orifice plate 308. The space between the orifice plate 308 and the sample gas inlet 313 of the unipolar charging device 300 is the charging region 303, which is used to achieve full collision between particulate matter and ions. The insulating base 311 is installed on the inner side of the other end of the housing 301. The trapping electrode 309 and the grounding electrode 310 are both made of copper with high conductivity. The trapping electrode 309 is fixed inside the insulating base 311, and the grounding electrode 310 is installed inside the housing 301 and located on the other side of the trapping electrode 309. The space between the two is the ion trapping area 304, and particle screening is achieved through the action of an electric field.

[0045] The working principle of the unipolar charging device 300 is as follows: Clean air is introduced into the discharge chamber 302 through the sheath gas inlet 312. A stable high-voltage electric field is formed between the charging needle 306 and the grounded metal ring 307, causing part of the clean air to ionize and generate ions. The ions are sprayed into the charging region 303 through the through hole on the metal ring 307 and the central through hole of the perforated plate 308 with the airflow. They collide fully with the particles that have condensed and grown to the target size in the charging region 303, achieving efficient charging of the particles. Subsequently, the airflow enters the ion capture region 304. The electric field formed by the capturing electrode 309 and the grounded electrode 310 can accurately capture charged particles smaller than 10 nm that have not yet grown and free ions.

[0046] As a further improvement to the above technical solution, such as Figure 5As shown, the dual-path Faraday cup detection device 400 includes a metal housing 410, and a first measuring branch, a second measuring branch, a measuring circuit 440, an insulating base three 450, an insulating base four 460 encapsulated inside the metal housing 410, a heating element 470 attached to the outer wall of the metal housing 410, and a heat-insulating housing 480 on the outside of the metal housing 410. The first measuring branch includes a filter element one 421, a honeycomb housing one 422, and a vacuum pump one 423 connected in sequence; the second measuring branch includes a filter element two 431, a honeycomb housing two 432, and a vacuum pump two 433 connected in sequence; a filter 490 is connected in series before the air inlet of the second measuring branch, and the filter elements one 421 and two 431 are respectively tightly installed inside the honeycomb housing one 422 and the honeycomb housing two 432; the honeycomb housing one 422 and the honeycomb housing two 432 are respectively connected through the insulating base three 450 and the insulating base four 460. The measuring circuit 440 is fixedly installed inside the metal housing 410. The measuring circuit surface is provided with spring probe 441 and spring probe 442. Spring probe 441 is tightly pressed against the bottom of honeycomb housing 422, and spring probe 442 is tightly pressed against the bottom of honeycomb housing 432. Air pump 423 and air pump 433 are respectively connected to the two air outlets of the metal housing 410 to provide stable negative pressure airflow for the entire detection process and ensure that the airflow passes through the filter element at a uniform speed.

[0047] Specifically, filter element 1 421 and filter element 2 431 are made of conductive material with high filtration accuracy and are tightly installed inside honeycomb shell 1 422 and honeycomb shell 2 432 to efficiently capture charged particles in the airflow; insulating base 1 305, insulating base 2 311, insulating base 3 450, and insulating base 4 460 are all made of polyetheretherketone material, which has excellent insulation performance and structural stability, can avoid charge leakage, and ensure detection accuracy.

[0048] Charged particles, after being screened by the monopolar charging device 300, are divided into two paths by the airflow through a three-way valve, entering the first measurement branch and the second measurement branch respectively. The measurement branch is equipped with a metal shell 410, which provides electrostatic shielding, effectively isolates external electromagnetic interference, and ensures the detection accuracy of weak current signals. The shell also integrates a heating element 470 and an insulation shell 480, forming an active temperature control system, which keeps the internal core measuring element at a constant temperature, eliminates measurement drift caused by ambient temperature fluctuations, and ensures the stability of long-term measurements. The first measurement branch directly receives the airflow containing charged droplets; the second measurement branch has a high-efficiency particulate filter 490 connected in series at its inlet end to completely filter out charged particles in the airflow, allowing only gas and any remaining ions to pass through, serving as a background noise reference branch; under the stable negative pressure generated by the pump, the airflow passes through the filter elements at the same uniform velocity in both branches; the filter element of the first measurement branch captures all charged droplets in the airflow, and the charge they carry is conducted to the corresponding honeycomb shell through the filter element; the filter element of the second measurement branch, because it does not capture any particles, only reflects the system's background charge and... Interference; the spring probe is tightly pressed against the bottom of the honeycomb shell, transmitting the charge signal to the measurement circuit 440 in real time and detecting the corresponding current value. The measurement circuit 440 synchronously acquires and differentially calculates the signals from the two branches, subtracting the background noise signal measured by the second measurement branch from the total current signal of the first measurement branch in real time, and obtaining the net current value contributed only by the charged droplets. Finally, the measured current value is inverted and the particulate matter number concentration is calculated through the preset algorithm model, completing the core data output of the entire monitoring process and providing accurate basis for the analysis of particulate matter concentration in motor vehicle exhaust.

[0049] In summary, the cascaded nanoscale high-concentration particle number concentration measurement device based on condensation charging described in this invention eliminates the need for sample gas dilution, simplifies structural design, and improves portability. This invention utilizes the combined effect of condensation growth and unipolar charging to ensure all target particles carry the same charge, facilitating subsequent ion screening and total charge detection, ultimately achieving accurate particle number concentration inversion. For the two-stage condensation growth device 200, this invention adopts a two-stage design combining ethanol pre-growth and water main growth, and with precise temperature control and saturation control of each region, it achieves efficient activation and rapid growth of ultrafine particles down to 10nm, ensuring breakthrough of the detection limit and precise growth of the target size. For the unipolar charging device 300, this invention uses the droplets after secondary condensation growth as the charging object, and makes targeted designs for the charging process and electric field trapping part. By introducing dry and clean air and setting up a charging device independently outside the sample gas channel and a reasonable charging region 303, it achieves the termination of droplet growth and efficient trapping and removal of excess free ions and non-target particles, ensuring the efficiency and accuracy of charging and screening.

[0050] This invention also includes a cascaded method for measuring the number concentration of high-concentration nanoparticles based on condensation charging, the method comprising the following steps: S1. Removal of volatile particles: After being collected through a sampling tube, vehicle exhaust gas enters the volatile particulate removal device 100 for pretreatment. The internal space of the metal tank 101 is maintained at 400°C by heating. The sample gas is heated in the heating zone 104, causing the volatile particles to evaporate into a gaseous state. Subsequently, the gaseous volatile particles flow with the gas flow through the base region of the rear half of the tank, where they come into full contact with the cordierite substrate 105, which is coated with a catalyst. Under the catalytic action of the catalyst, they undergo oxidative decomposition and are converted into CO2 and H2O. This step removes volatile particles from the sample gas, preventing their condensation from interfering with subsequent particulate matter counting.

[0051] S2, condensation and growth of nanoparticles: After removing volatile particles, the sample gas is flowed into the pre-growth zone 220 of the two-stage condensation growth device 200. The working liquid ethanol in the storage tank 2213 is transported to the porous medium 2212 in the metal tube 210 through capillary action. The metal tube 210 is heated and maintained in the range of 35-40°C, so that the ethanol in the porous medium 2212, which is in close contact with the inner wall of the metal tube 210, evaporates and forms saturated vapor. After the sample gas flow carries the saturated ethanol vapor into the condensation section, the metal tube 210 in the condensation section is cooled and maintained in the low temperature range of 10-15°C, so that the gas flow is cooled and supersaturated ethanol vapor is generated. The supersaturation of ethanol vapor at this stage can activate ultrafine particles of 10 nm and above, so that they can initially condense and grow.

[0052] After pre-growth, the gas flow carrying the initial growth particles enters the secondary growth region 230 of the two-stage condensation growth device 200; the inlet section of the metal tube 210 is heated to maintain it at a preset high temperature range of 40-45°C, causing the liquid water in the water-containing porous medium 233 to evaporate and form a saturated water vapor environment; after the lower temperature gas flow enters the high temperature environment, the water vapor will rapidly condense on the surface of the grown droplets. At this stage, the supersaturation of the water vapor can activate droplets of the size after ethanol pre-growth; the gas flow then enters... Downstream of the metal tube 210, the metal tube 210 is cooled and maintained at a preset low temperature of 15-20°C. The supersaturation of water vapor in the airflow begins to decrease slowly, and the secondary growth particles can continue to condense and grow to the submicron range of 200-500 nm in this section. At the same time, the remaining water vapor in the airflow that does not participate in condensation condenses into liquid water on the inner wall of the water-containing porous medium 233 in the condensation section, and is transported to the water-containing porous medium 233 in the upstream heating section through capillary action to complete the recycling.

[0053] S3. Unipolar charging and particle size screening of particulate matter: A gas flow carrying submicron-sized droplets enters the unipolar charging device 300 through the inlet. Dry, clean air is introduced into the discharge chamber 302 through the sheath gas inlet 312, forming a high-voltage electric field between the discharge needle and the grounded metal ring 307. Under the influence of the high-voltage electric field, some of the clean air is ionized, generating ions. These ions are then sprayed into the charging region 303 through the through-holes in the metal ring 307 and the center of the orifice plate 308, where they mix with the sample gas carrying the grown droplets. The dry, clean air further reduces the saturation of residual working liquid vapor in the sample gas. This inhibits further particle growth and ensures that the particle size remains stable within the expected target range. At the same time, some ions diffuse and collide with particles and droplets to obtain charged particles and droplets. Subsequently, the airflow enters the ion capture region 304, and a uniform transverse electric field is formed between the capture electrode 309 and the ground electrode 310. Charged particles and free ions smaller than 10 nm in the airflow are captured by the capture electrode 309 under the action of the electric field. Only charged droplets whose size increases to the submicron level are almost unaffected by the electric field due to their low electromobility and can continue to be transported with the airflow.

[0054] S4. Charge detection and concentration inversion of charged particles: The airflow carrying the screened charged droplets is introduced into the dual-path Faraday cup detection device. The airflow is divided into two equal paths through a three-way valve, which enter the first measurement branch and the second measurement branch respectively. The measurement branch is equipped with a metal shell 410, which provides electrostatic shielding, effectively isolates external electromagnetic interference, and ensures the detection accuracy of weak current signals. The shell also integrates a heating element 470 and an insulation shell 480, forming an active temperature control system to maintain the internal core measuring element at a constant temperature, eliminate measurement drift caused by ambient temperature fluctuations, and ensure the stability of long-term measurements. The first measurement branch directly receives the airflow containing charged droplets; the second measurement branch has a small filter 490 connected in series at its inlet end to efficiently filter out charged particles in the airflow, allowing only gas and any remaining ions to pass through, serving as a background noise reference branch; under the stable negative pressure generated by the pump, the airflow passes through the filter elements at the same constant velocity in both branches; the filter element 421 of the first measurement branch captures all charged droplets in the airflow, and the charge they carry is conducted to the corresponding honeycomb shell 422; the filter element 431 of the second measurement branch, because it does not capture any particles, only reflects the system's background charge. Interference; Spring probe 441 and Spring probe 442 are tightly pressed against the bottom of honeycomb shell 422 and honeycomb shell 432 respectively, transmitting the charge signal to the measurement circuit 440 in real time and detecting the corresponding current value. The measurement circuit 440 synchronously acquires and differentially calculates the signals of the two branches, and subtracts the background noise signal measured by the second measurement branch from the total current signal of the first measurement branch in real time to obtain the net current value contributed only by the charged droplets; Based on the net current value and the pre-established current-particle number concentration calibration relationship, the number concentration of nanoscale particles in the sample gas is obtained by inversion.

[0055] This invention innovatively integrates a volatile particle removal device 100, a two-stage condensation growth device 200, a unipolar charging device 300, and a dual-path Faraday cup detection device 400 in a specific sequence of physical purification, signal amplification, efficient charging, and differential detection, forming a highly synergistic and functionally complementary cascaded measurement system. The devices are directly connected in series via steel and silicone tubes, ensuring short connections and unobstructed flow paths, minimizing particulate matter diffusion losses during transport. Based on the principle of two-stage condensation growth-diffusion charging, this invention innovatively designs the two-stage condensation growth device 200, the unipolar charging device 300, and the dual-path Faraday cup detection device 400. Through structural optimization and precise parameter matching, it ensures that the output of the preceding stage creates optimal conditions for the following stage. This specific sequential cascaded integration is not a simple stacking of modules, but rather a creative design that achieves precise matching of performance parameters and functional synergy between modules.

[0056] The dual-stage condensation growth device 200 used in this invention precisely controls the supersaturation of ethanol and water vapor through temperature control design of the pre-growth region 220 and the secondary growth region, enabling the activation and secondary growth of particles larger than 10 nm. By designing parameters such as gas flow rate and the length of each flow channel, the growth time of particles within the region is precisely controlled, ensuring that particles can rapidly grow to the target size. This transforms smaller particles into submicron-sized droplets suitable for electrical detection, effectively improving the charge efficiency and charge of the droplets. This completely eliminates the limitations of electrical methods for detecting small-diameter particles and avoids measurement deviations caused by particle size differences. Simultaneously, rapid growth reduces vapor consumption, ensuring efficient particle growth at high concentrations and expanding the measurement concentration range.

[0057] The unipolar charging device 300 used in this invention, through its adaptive design for the charging and trapping of grown droplets, lays the foundation for efficient detection of Faraday cup microcurrents. By employing a charging device design independent of the sample gas flow channel, direct contact between the condensed droplets and the charging components is effectively avoided, preventing droplet adhesion from affecting the charging process. Introducing dry, clean sheath gas significantly reduces the vapor concentration of the working liquid in the gas flow, effectively terminating further droplet growth and ensuring precise control over droplet size. The use of a counter-current gas flow mixing design, coupled with a suitably sized charging space, allows for sufficient collision and uniform contact between droplets in the sample gas and free ions carried by the sheath gas, greatly improving charging efficiency and ensuring each droplet acquires sufficient charge. By designing a long-distance trapping electric field distribution and optimizing the electrode spacing and electric field strength, excess free ions and unactivated charged nanoparticles (less than 10 nm) in the gas flow can be efficiently trapped, minimizing background noise interference and significantly improving the signal-to-noise ratio of the detection signal.

[0058] The dual-path Faraday cup detection device 400 used in this invention, through a real-time synchronous differential measurement strategy combined with electrostatic shielding and active temperature control, can deduct background noise from the total signal in real time, achieving stable and accurate capture of weak charge signals, improving detection sensitivity in low-concentration scenarios, and ensuring rapid response capability to transient emissions.

[0059] This invention targets the specific application scenario of precise online measurement of high-concentration, small-diameter particulate matter in vehicle exhaust. First, by employing electrical detection principles and setting submicron-level growth targets, optical overlap errors are fundamentally avoided, and vapor consumption is significantly reduced. This eliminates the need for complex dilution systems, enabling direct, continuous, and in-situ measurement of high-concentration particulate matter. Second, by amplifying the small particle signal through condensation growth and combining it with efficient differential electrical detection, a stable detection limit as low as 10 nm can be achieved without sample dilution, exhibiting extremely high detection sensitivity and accuracy for low-concentration particulate matter. Furthermore, the entire device is compact, uses safe and low-cost working fluids, and is particularly suitable for applications requiring high portability and reliability, such as vehicle-mounted and field-based applications.

[0060] In summary, this invention provides a cascaded nanoscale high-concentration particle number concentration measurement device and method based on condensation charging. This device innovatively integrates a volatile particle removal device 100, utilizing the dual effects of 400℃ high-temperature heating and a cordierite substrate 105 catalyst coating to efficiently remove volatile particles, thereby effectively preventing interference from volatile particles on particle number measurement at the source. The device employs a two-stage condensation growth structure design, using ethanol as the working fluid for pre-growth and water vapor for secondary growth. Through precise temperature control and channel size design of each section, ultrafine nanoscale particles of 10 nm and above are grown into submicron-sized droplets suitable for electrical detection. This overcomes the limitation of traditional diffusion charging methods in charging smaller particles and avoids the reduction in charging efficiency due to excessively large particle sizes, significantly improving the particle charge and enhancing the detection sensitivity and measurement accuracy of small-diameter, low-concentration particles of 10 nm and above. Meanwhile, this device employs a combination of diffusion charging principle and differential dual-path Faraday cup detection device 400 for electrical detection, replacing traditional optical detection schemes. This completely avoids pulse overlap problems in high-concentration scenarios, enabling the measurement of high-concentration particulate matter without dilution. It simplifies the equipment structure, reduces measurement errors, and ensures data accuracy. This invention achieves its core objectives of dilution-free measurement, a 10nm particle size detection limit, and accurate high-concentration measurement through the cascaded synergy of four parts: volatile particle removal, condensation growth, unipolar charging, and electrostatic detection.

[0061] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0062] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0064] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A device for measuring the number concentration of high-concentration nanoparticles based on condensation charging, characterized in that, It includes a volatile particle removal device (100), a two-stage condensation growth device (200), a single-pole charging device (300), and a dual-path Faraday cup detection device (400) connected in sequence. The volatile particle removal device (100) is used to remove volatile particles from the sample gas; The dual-stage condensation and growth device (200) is used to condense and grow particles larger than 10 nm in the sample gas into submicron-sized droplets suitable for electrical detection. The unipolar charging device (300) is used to charge the grown droplets and screen out charged particles and free ions smaller than 10 nm. The dual-path Faraday cup detection device (400) is used to collect charged droplets and invert the number concentration of nanoscale particles in the sample gas by detecting the current value corresponding to the charge.

2. The nanoscale high-concentration particle number concentration measuring device based on condensation charging according to claim 1, characterized in that: The inlet of the volatile particle removal device (100) is connected to the sample gas through a pipe, and the outlet of the volatile particle removal device (100) is connected to the inlet of the two-stage condensation growth device (200) through a pipe; the outlet of the two-stage condensation growth device (200) is connected to the inlet of the unipolar charging device (300) through a pipe; the outlet of the unipolar charging device (300) is connected to the inlet of the dual-path Faraday cup detection device (400) through a pipe.

3. The nanoscale high-concentration particle number concentration measuring device based on condensation charging according to claim 1, characterized in that: The volatile particle removal device (100) includes a metal tank (101), a heating layer (102) sleeved on the outside of the metal tank (101), and a heat insulation layer (103) wrapped around the metal tank (101) and the heating layer (102). The interior of the metal tank (101) is divided into a heating zone (104) and a base zone along the airflow direction; the base zone is filled with a cordierite base (105); the surface of the cordierite base (105) is coated with a catalyst coating. The metal can (101) includes a metal can body and an air inlet and an air outlet disposed at both ends of the metal can body; The main body of the metal can is a cylindrical channel, with the air inlet and air outlet located at both ends of the main body of the metal can, and both are conical in shape.

4. The nanoscale high-concentration particle number concentration measuring device based on condensation charging according to claim 1, characterized in that: The two-stage condensation growth device (200) includes a metal tube (210), a pre-growth region (220) located at the inlet end of the metal tube, and a secondary growth region (230) located at the outlet end; a heat insulation section (240) is provided between the pre-growth region and the secondary growth region.

5. The nanoscale high-concentration particle number concentration measuring device based on condensation charging according to claim 4, characterized in that: The pre-growth region includes heating section one, condensation section one, and heat insulation section two (223) between heating section one and condensation section one. The heating section includes a second heating layer (2210) sleeved on the outside of the metal tube, a second heat insulation layer (2211) wrapped around the outside of the second heating layer, a porous medium (2212) disposed inside the metal tube, and a liquid storage tank (2213) connected to the porous medium; the porous medium is designed as an annular cylindrical shape, which is tightly attached to the inner wall of the metal tube after being heated by the second heating layer, and is connected to the liquid storage tank containing the working liquid disposed on the outside of the metal tube through a through hole opened on the wall of the metal tube; The first condensation section includes a first cooling layer (2220) sleeved on the outer wall of the metal pipe and a third insulation layer (2221) wrapped around the outside of the first cooling layer.

6. The nanoscale high-concentration particle number concentration measuring device based on condensation charging according to claim 5, characterized in that: The secondary growth region includes a second heating section and a second condensation section arranged along the airflow direction, and an annular cylindrical water-containing porous medium (233) that penetrates the secondary growth region and is tightly attached to the inner wall of the metal tube; a third heat insulation section (234) is provided between the second heating section and the second condensation section. The second heating section includes a third heating layer (2310) sleeved on the outside of one end of the metal tube and a fourth insulation layer (2311) wrapped around the third heating layer; the second condensation section includes a second cooling layer (2320) sleeved on the outer wall of the metal tube and a fifth insulation layer (2321) wrapped around the cooling layer.

7. The nanoscale high-concentration particle number concentration measuring device based on condensation charging according to claim 1, characterized in that: The unipolar charging device (300) includes a housing (301); the inner cavity of the housing (301) is divided into a charging region (303) and an ion trapping region (304) along the axial direction. A discharge cavity (302) is provided on one side of the charged region (303), and an insulating base (305) is installed in the discharge cavity (302). A charging needle (306) is installed through the center of the end of the insulating base (305) away from the charged region. The insulating base (305) is provided with a metal ring (307) at one end near the charged area. The metal ring (307) has a through hole in the middle part and is coaxially arranged with the charged needle (306). The metal ring (307) is grounded. A perforated plate (308) is provided at the connection between the discharge cavity (302) and the outer shell (301); The insulating base (305) has a plurality of evenly distributed sheath gas inlets (312) at one end where the charged needle (306) is installed; the outer shell (301) has a sample gas inlet (313) on the side opposite to the discharge chamber (302). The ion capture region (304) includes a capture electrode (309) and a grounding electrode (310) disposed on the inner wall of the housing; an insulating base (311) is installed on the inner wall of the housing (301); the capture electrode (309) is mounted on the insulating base (311).

8. The nanoscale high-concentration particle number concentration measuring device based on condensation charging according to claim 1, characterized in that: The dual-path Faraday cup detection device (400) includes a metal shell (410), a first measurement branch, a second measurement branch, a measurement circuit (440), an insulating base three (450), an insulating base four (460) encapsulated inside the metal shell, a heating element (470) attached to the outer wall of the metal shell, and a heat-insulating shell (480) on the outside of the metal shell. The first measuring branch includes a filter element one (421), a honeycomb shell one (422), and an air pump one (423) connected in sequence; the second measuring branch includes a filter element two (431), a honeycomb shell two (432), and an air pump two (433) connected in sequence; a filter (490) is also connected in series before the air inlet of the second measuring branch. The filter element one and filter element two are respectively installed inside the honeycomb shell one and honeycomb shell two; the honeycomb shell one and honeycomb shell two are respectively fixedly installed inside the metal shell through insulating base three and insulating base four; The measuring circuit is fixedly installed on the bottom inner side of the metal casing. The surface of the measuring circuit is provided with spring probe one (441) and spring probe two (442). Spring probe one is tightly pressed against the bottom of the honeycomb casing one, and spring probe two is tightly pressed against the bottom of the honeycomb casing two. Air pump one and air pump two are respectively connected to the two air outlets of the metal casing.

9. A measurement method for a nanoscale high-concentration particle number concentration measuring device based on condensation charging as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Pre-treat the sample gas containing nanoscale particles to remove volatile particles from the sample gas; S2. The nanoscale particles in the sample gas after the removal of volatile particles are subjected to two condensation and growth treatments, so that the particles in the sample gas are grown by two working liquid vapors in sequence, and finally grow into submicron-sized droplets suitable for electrical detection. S3. The grown droplets are subjected to unipolar charging treatment, and charged particles and free ions with a particle size smaller than the set value in the sample gas are screened out and removed, while the target size droplets after charging are retained. S4. Collect the charged droplets, detect the electrical signal value corresponding to the charge carried by the charged droplets, and obtain the number concentration of nanoscale particles in the sample gas based on the electrical signal value.

10. The measurement method according to claim 9, characterized in that, Step S1 specifically includes: The sample gas containing nanoscale particles is pretreated by passing it through a volatile particle removal device. The metal tank of the volatile particle removal device is heated and the temperature inside the tank is maintained at a preset high temperature. The sample gas flows through the heating zone inside the metal tank and is heated, causing the volatile particles in the sample gas to evaporate into a gaseous state. The gaseous volatile particles flow through the base region inside the metal tank with the sample gas and come into contact with the cordierite base with a catalyst coating on its surface. Under the catalytic action of the catalyst, the volatile particles in the sample gas are oxidized and decomposed, thus removing the volatile particles from the sample gas. Step S2 specifically includes: The sample gas, after the removal of volatile particles, is introduced into the pre-growth zone of the two-stage condensation growth device. The working liquid in the storage tank is transported to the porous medium inside the metal tube through capillary action. The metal tube is heated, causing the working liquid in the porous medium, which is in close contact with the inner wall of the metal tube, to evaporate and form saturated vapor. After the sample gas carrying the saturated vapor enters the first condensation section, the metal tube in the first condensation section is cooled and maintained at a preset low temperature, so that the gas flow is cooled to a supersaturated state, activating the nano-sized particles and causing the nano-sized particles to initially condense and grow. Sample gas carrying nanoscale particles that have undergone initial condensation growth is introduced into the secondary growth region of the two-stage condensation growth device. The metal tube of the second heating section is heated to maintain a preset high temperature, causing the liquid water in the water-containing porous medium to evaporate and form a saturated water vapor environment. After the sample gas enters, the water vapor undergoes secondary condensation using the nanoscale particles that have undergone initial condensation growth as condensation nuclei. The sample gas then enters the second condensation section of the metal tube, where the metal tube is cooled and maintained at a preset low temperature. The supersaturation of water vapor in the sample gas begins to decrease, allowing the nanoscale particles that have undergone initial condensation growth to continue condensing and growing into droplets of the target size in the second condensation section. Simultaneously, the remaining water vapor in the gas flow that has not participated in condensation condenses into liquid water on the inner wall of the porous medium in the second condensation section and is transported back to the water-containing porous medium in the second heating section upstream through capillary action for recycling. Step S3 specifically includes: The sample gas carrying droplets is introduced into a unipolar charging device. Dry, clean air is introduced into the discharge chamber of the unipolar charging device, and a preset high-voltage electric field is formed between the charging needle of the unipolar charging device and the grounded metal ring. Under the action of the electric field, part of the dry, clean air is ionized to generate ions. The ions are sprayed into the charging region through the through holes on the metal ring and the through holes in the center of the orifice plate with the clean air flow. Some of the ions collide with the droplets, realizing the charging of the droplets. At the same time, the dry, clean air mixes with the sample gas, reducing the concentration of residual working liquid vapor in the sample gas, thereby inhibiting the further growth of particles. The charged sample gas enters the ion capture region. Using the electric field formed between the capturing electrode and the grounding electrode in this region, charged particles and free ions with a diameter of less than 10 nm in the sample gas are captured and removed, allowing only target-sized droplets carrying charge to pass through. Step S4 specifically includes: Sample gas containing charged droplets is introduced into a dual-path Faraday cup detection device. The sample gas is divided into two equal paths via a three-way valve, entering the first and second measurement branches respectively. The metal casings of both measurement branches provide electrostatic shielding. Heating elements and insulation on the metal casings maintain a constant temperature for both measurement branches. The first measurement branch directly receives the sample gas containing charged droplets. The second measurement branch has a filter connected in series at its inlet to remove charged particles from the sample gas, allowing only gas and residual ions to pass through; this filter serves as a background noise reference branch. Under the negative pressure generated by pumps one and two, the sample gas flows uniformly through filter elements one and two at the same velocity. Filter element one in the first measurement branch traps… All charged droplets in the sample gas are collected. The charge carried by the charged droplets is conducted to the corresponding honeycomb shell 1 through filter element 1. Filter element 2 of the second measurement branch does not capture particles and only reflects the system's background charge and interference. Spring probe 1 and spring probe 2 transmit the charge signals of honeycomb shell 1 and honeycomb shell 2 to the measurement circuit in real time and detect the corresponding current values. The measurement circuit synchronously acquires and differentially calculates the signals of the first and second measurement branches. The background noise signal measured by the second measurement branch is subtracted from the total current signal of the first measurement branch in real time to obtain the net current value contributed only by the charged droplets. Based on the net current value and the pre-established current-particle number concentration calibration relationship, the number concentration of nanoscale particles in the sample gas is obtained by inversion.

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