In-situ measuring device and method for particulate matter in high-temperature and high-concentration tail gas emissions of symmetric type

Abstract

The present invention relates to a symmetric high-temperature and high-concentration in-situ measuring device and method for particulate matter in tail gas emissions. The device includes a housing, a charging region, a laminar flow trapping module, and a classification region. The charging region includes a charging unit one and a charging unit two symmetrically arranged along the central axis of the housing. Both the charging unit one and the charging unit two include a charging housing installed on the outer side of the housing, an insulating base installed at one end of the charging housing, a discharge needle installed at one end of the insulating base, a metal ring installed at the other end of the insulating base, and an orifice plate installed on the inner side of the housing. The laminar flow trapping module includes a laminar flow device and an electrostatic precipitator. The classification region includes a high-voltage plate, a measurement plate, and a current measurement device. The present invention can solve the deficiencies in the prior art, perform high-temperature, high-concentration, and in-situ measurement of motor vehicle exhaust gas, reduce measurement errors, and improve the accuracy of measurement results.

Description

Technical Field

[0001] The present invention relates to the technical field of tail gas particulate matter monitoring, and particularly to a symmetric high-temperature and high-concentration tail gas emission particulate matter in-situ measurement device and method. Background Art

[0002] With the increasing number of motor vehicles year by year, the problem of motor vehicle tail gas emission pollution has become increasingly serious. China's control over motor vehicle pollutant emission limits has become increasingly strict, and the environmental protection department has an urgent need for portable law enforcement equipment. Existing motor vehicle pollutant measurement equipment is all concentrated in laboratory measurement, with a large volume, which is not convenient for transportation and use in different scenarios. Moreover, currently commonly used measurement methods all need to be measured after dilution and cooling, and affected by the change of the sampling measurement environment temperature, carbon-containing particulate matter of several nanometers in the tail gas is easy to form new particulate matter with carbon as the core during the dilution and cooling sampling process, and the particulate matter emission characteristics (number concentration and median particle size information) have changed greatly after cooling, and non-in-situ online high-temperature measurement is difficult to truly reflect the ultra-fine particulate matter emission characteristics of motor vehicle tail gas. In addition, for nanoscale particulate matter (<100 nm), it is easy to diffuse and lose during the sampling process, resulting in a lower measurement result and underestimating the actual concentration value.

[0003] Chinese Patent CN 201811534753.5 uses the charge method to measure the particulate matter number concentration. This method must dilute and cool the motor vehicle tail gas before sampling, and the necessary modules for providing the equipment operation are more and more complex, which is not conducive to the portable design of the overall equipment, and after the tail gas dilution and cooling treatment, it brings errors to the measurement result. In the charge device structure schemes disclosed in Chinese Patent CN201710262990.X and Chinese Patent CN 201510969843.7, not only will the measurement result deviation be caused by the serious diffusion loss of nanoscale particulate matter, but also when measuring high concentrations, the sampling particulate matter may not be fully charged due to insufficient charged ions, which will also lead to measurement result deviation.

[0004] Therefore, it is necessary to design a high-temperature and high-concentration tail gas emission particulate matter in-situ measurement device that can improve the charging efficiency and does not require cooling of the tail gas. Summary of the Invention

[0005] The purpose of the present invention is to provide a symmetric high-temperature and high-concentration tail gas emission particulate matter in-situ measurement device and method, which can solve the deficiencies in the prior art, perform high-temperature, high-concentration, and in-situ measurement on motor vehicle tail gas, reduce measurement errors, and improve the accuracy of measurement results.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A symmetric high-temperature and high-concentration in-situ measuring device for particulate matter in tail gas emissions, comprising a housing, a charging region provided at one end of the housing, a laminar flow trapping module provided in the middle section of the housing, and a grading region provided at the other end of the housing; a first heating layer and a first heat insulation layer are sequentially provided on the outer side of the housing.

[0008] Furthermore, the charging region includes a first charging unit and a second charging unit symmetrically arranged along the central axis of the housing; the first charging unit and the second charging unit have the same structure, and both include a charging housing installed on one side of the housing, an insulating base installed at one end of the charging housing, a discharge needle installed at one end of the insulating base, a metal ring installed at the other end of the insulating base, and an orifice plate installed on the inner side of the housing; a second heating layer and a second heat insulation layer are sequentially provided on the outer side of the charging housing; the first heating layer and the first heat insulation layer are closely attached to the housing, and the second heating layer and the second heat insulation layer are closely attached to the first charging housing and the second charging housing; the first heating layer, the second heating layer, the first heat insulation layer, and the second heat insulation layer are used for heating and heat preservation.

[0009] Furthermore, the laminar flow trapping module includes a laminar flow device and an electrostatic precipitator arranged coaxially; the laminar flow device is provided with multiple thin plates; the thin plates are used to separate the gas path and keep the gas flow in a laminar state; the electrostatic precipitator is composed of six metal plates installed in parallel, and the gas flow passes through between the plates; the six metal plates are respectively a first plate, a second plate, a third plate, a fourth plate, a fifth plate, and a sixth plate. A first channel is formed between the first plate and the second plate, a second channel is formed between the second plate and the third plate, a third channel is formed between the third plate and the fourth plate, a fourth channel is formed between the fourth plate and the fifth plate, and a fifth channel is formed between the fifth plate and the sixth plate.

[0010] Furthermore, the grading region includes a high-voltage plate, multiple measuring plates, and a current measuring device; the high-voltage plate is connected to a constant high-voltage source; the multiple measuring plates are installed on the same plane and arranged parallel to the high-voltage plate, and are connected to the current measuring device through shielded cables; the current measuring device is located outside the housing; the number of measuring plates is six, which are respectively a first measuring plate, a second measuring plate, a third measuring plate, a fourth measuring plate, a fifth measuring plate, and a sixth measuring plate.

[0011] Furthermore, a sample gas inlet is provided at one end of the housing, and a total flow outlet is provided at the other end. The sample gas inlet is connected to the motor vehicle tail gas pipe; the sample gas inlet and the total flow outlet are coaxially arranged to allow the sample gas to pass through the measuring device quickly and stably.

[0012] Furthermore, a plurality of uniformly distributed sheath gas inlets are provided at the outer end of the insulating base, and the discharge needle is installed through the center of the insulating base.

[0013] Further, a through hole is provided in the middle part of the metal ring; the metal ring is grounded; for uniform discharge, the metal ring is coaxially arranged with the discharge needle; the orifice plate is used to precisely control the ion ejection speed, and a through hole is provided in the center of the orifice plate, and the diameter of the through hole is 0.7 mm.

[0014] The present invention also relates to a measurement method of the above-mentioned symmetric high-temperature and high-concentration tail gas emission particulate matter in-situ measurement device, and the method includes the following steps:

[0015] (1) The high-temperature tail gas discharged from the motor vehicle tail pipe enters the measurement device through the sample gas inlet.

[0016] (2) Clean air is introduced into the charged housing from the sheath gas inlet. A high-voltage electric field is formed between the discharge needle and the grounded metal ring. Under the action of the high-voltage electric field, part of the clean air is ionized to generate ions; the ions are ejected from the through hole in the center of the orifice plate into the charged area along with the clean air; the symmetric charged structure design enables the charged area to be filled with enough ions, and the airflow carrying the ions will not affect the movement trajectory of the particulate matter in the tail gas, allowing it to maintain a straight-line movement; part of the ions collide with the particulate matter to charge the particulate matter, obtaining charged particulate matter.

[0017] (3) The charged particulate matter enters the laminar flow trapping module along with the airflow. First, it passes through a laminator composed of multiple thin plates, enabling the airflow to enter the electrostatic precipitator in a stable laminar flow state; in the electrostatic precipitator, the first electrode plate and the sixth electrode plate are grounded, the second electrode plate and the fifth electrode plate are connected to the high voltage HV1, and the third electrode plate and the fourth electrode plate are connected to the high voltage HV2, where HV2 = 2 * HV1. Therefore, the same high-voltage electric field E1 will be formed in channels one, two, four, and five, and there is no electric field in channel three; when the charged particulate matter passes through the electrostatic precipitator along with the airflow, the charged particulate matter in the airflow passing through channels one, two, four, and five will collide with the electrode plate under the action of the electric field force, while the charged particulate matter in channel three has no electric field force and passes through horizontally at a constant speed.

[0018] (4) The airflow continues to enter the classification area, and a high-voltage electric field will be formed between the high-voltage electrode plate and the housing. The charged particulate matter will deflect downward under the action of the electric field force; due to different electric field forces received, particulate matter in different particle size ranges will collide with different measurement electrode plates; the micro-current signals of each measurement electrode plate are inversed to obtain the particle size spectrum of the particulate matter in the motor vehicle tail gas.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] (1) The charged region in the present invention adopts a symmetric structure, which can provide an environment with sufficient ion concentration. It can not only meet the measurement requirements of high concentration, but also ensure the smoothness of the sample gas passage, making the sample gas always maintain a laminar flow state, greatly reducing the diffusion loss of nanoscale particulate matter, and making the measurement results more accurate.

[0021] (2) The present invention introduces a laminar flow trapping module, which enables charged particulate matter in a turbulent state to enter the classification region after becoming laminar flow, ensuring the accuracy of charged particulate matter classification without introducing additional air flow as a protective air flow.

[0022] (3) The present invention adopts a high-temperature resistant design. The microcurrent measurement circuit that is not resistant to high temperature is connected to the measurement electrode plate with a metal shielded wire to prevent temperature changes from interfering with microcurrent measurement; in addition, the overall device can be heated at a constant temperature, enabling direct measurement of the exhaust gas after it is discharged, avoiding the interference of dilution and cooling sampling on particulate matter emissions from motor vehicle exhaust. Description of the Drawings

[0023] Figure 1 is a schematic structural diagram of the measurement device in the present invention;

[0024] Figure 2 is a schematic structural diagram of the electrostatic precipitator device.

[0025] Wherein:

[0026] 1. Sheath gas inlet, 2. Metal ring, 3. Orifice plate, 4. Sample gas inlet, 5. Outer shell, 6. Insulating base, 7. Discharge needle, 8. Charged region, 9. Laminator, 10. Laminar flow trapping module, 11. Electrostatic precipitator device, 12. Classification region, 13. High-voltage electrode plate, 14. Total flow outlet, 15. Measurement electrode plate, 16. Heating layer two, 17. Heat preservation layer two, 18. Electrode plate one, 19. Electrode plate two, 20. Electrode plate three, 21. Electrode plate four, 22. Electrode plate five, 23. Electrode plate six, 24. Channel one, 25. Channel two, 26. Channel three, 27. Channel four, 28. Channel five, 29. Current measurement device. Detailed Embodiments

[0027] The present invention will be further described below with reference to the drawings:

[0028] As Figure 1 shown, a symmetric high-temperature and high-concentration in-situ measurement device for particulate matter emissions from vehicle exhausts includes an outer shell 5, a charged region 8 provided at one end of the outer shell 5, a laminar flow trapping module 10 provided in the middle section of the outer shell 5, and a classification region 12 provided at the other end of the outer shell 5; a heating layer one and a heat preservation layer one are sequentially provided on the outer side of the outer shell 5.

[0029] Further, the charged region 8 includes a first charged unit and a second charged unit symmetrically arranged along the central axis of the housing; the first charged unit and the second charged unit have the same structure, and both include a charged housing installed on one side of the housing 5, an insulating base 6 installed at one end of the charged housing, a discharge needle 7 installed at one end of the insulating base 6, a metal ring 2 installed at the other end of the insulating base 6, and an orifice plate 3 installed inside the housing 5; a second heating layer 16 and a second heat insulation layer 17 are sequentially arranged outside the charged housing; the first heating layer and the first heat insulation layer are arranged close to the housing 5, and the second heating layer 16 and the second heat insulation layer 17 are arranged close to the first charged housing and the second charged housing; the first heating layer, the second heating layer 16, the first heat insulation layer, and the second heat insulation layer are used for heating and heat preservation.

[0030] Further, the laminar flow trapping module 10 includes a coaxial laminator 9 and an electrostatic precipitator 11; the laminator 9 is provided with multiple thin plates; the thin plates are used to separate the gas path and keep the gas flow in a laminar state.

[0031] As Figure 2 shown, the electrostatic precipitator 11 is composed of six metal plates installed in parallel, and the gas flow passes between the plates; the six metal plates are respectively a first plate 18, a second plate 19, a third plate 20, a fourth plate 21, a fifth plate 22, and a sixth plate 23. A first channel 24 is formed between the first plate 18 and the second plate 19, a second channel 25 is formed between the second plate 19 and the third plate 20, a third channel 26 is formed between the third plate 20 and the fourth plate 21, a fourth channel 27 is formed between the fourth plate 21 and the fifth plate 22, and a fifth channel 28 is formed between the fifth plate 22 and the sixth plate 23.

[0032] Further, the classification region 12 includes a high-voltage plate 13, multiple measurement plates 15, and a current measurement device 29; the high-voltage plate 13 is connected to a constant high-voltage source; the multiple measurement plates 15 are installed on the same plane and arranged parallel to the high-voltage plate 13, and are connected to the current measurement device 29 through shielded cables; the current measurement device 29 is located outside the housing 5; the number of the measurement plates 15 is six, which are respectively a first measurement plate, a second measurement plate, a third measurement plate, a fourth measurement plate, a fifth measurement plate, and a sixth measurement plate.

[0033] Further, a sample gas inlet 4 is provided at one end of the housing 5, and a total flow outlet 14 is provided at the other end. The sample gas inlet 4 is connected to the motor vehicle tail pipe; the sample gas inlet 4 and the total flow outlet 14 are coaxially arranged to allow the sample gas to pass through the measuring device quickly and stably.

[0034] Further, a plurality of uniformly distributed sheath gas inlets are provided at the outer end of the insulating base 6, and the discharge needle 7 is installed through the center of the insulating base 6.

[0035] Further, a through hole is provided in the middle part of the metal ring 2; the metal ring 2 is grounded; for uniform discharge, the metal ring and the discharge needle are coaxially arranged; the orifice plate 3 is used to precisely control the ion ejection speed, and a through hole is provided in the center of the orifice plate 3, and the diameter of the through hole is 0.7 mm.

[0036] The present invention also relates to a measurement method of the above-mentioned symmetric high-temperature and high-concentration tail gas emission particulate matter in-situ measurement device, and the method includes the following steps:

[0037] (1) The high-temperature tail gas discharged from the motor vehicle tail pipe enters the measurement device through the sample gas inlet 4.

[0038] (2) Clean air is introduced into the charged housing from the sheath gas inlet 1. A high-voltage electric field is formed between the discharge needle 7 and the grounded metal ring 2. Under the action of the high-voltage electric field, part of the clean air is ionized to generate ions; the ions are ejected from the through hole in the center of the orifice plate 3 into the charged area 8 along with the clean air; the symmetric charged structure design enables the charged area 8 to be filled with enough ions, and the airflow carrying the ions will not affect the movement trajectory of the particulate matter in the tail gas, allowing it to move in a straight line; part of the ions collide with the particulate matter to charge the particulate matter and obtain charged particulate matter.

[0039] (3) The charged particulate matter enters the laminar flow trapping module 10 along with the airflow. First, it passes through the laminator 9 composed of multiple thin plates to enable the airflow to enter the electrostatic precipitator 11 in a stable laminar flow state; in the electrostatic precipitator 11, the first electrode plate 18 and the sixth electrode plate 23 are grounded, the second electrode plate 19 and the fifth electrode plate 22 are connected to the high voltage HV1, and the third electrode plate 20 and the fourth electrode plate 21 are connected to the high voltage HV2, where HV2 = 2 * HV1. Therefore, the same high-voltage electric field E1 will be formed in the first channel 24, the second channel 25, the fourth channel 27, and the fifth channel 28, and there is no electric field in the third channel 26; when the charged particulate matter passes through the electrostatic precipitator 11 along with the airflow, the charged particulate matter in the airflow passing through the first channel 24, the second channel 25, the fourth channel 27, and the fifth channel 28 will collide with the electrode plate under the action of the electric field force, while the charged particulate matter in the third channel 26 has no electric field force and passes through horizontally at a constant speed.

[0040] (4) The airflow continues to enter the classification area 12, and a high-voltage electric field will be formed between the high-voltage electrode plate 13 and the housing 5. The charged particulate matter will deflect downward under the action of the electric field force; due to different electric field forces received, particulate matter in different particle size ranges will collide with different measurement electrode plates 15; the micro-current signals of each measurement electrode plate 15 are inversely obtained to obtain the particle size spectrum of the particulate matter in the motor vehicle tail gas.

[0041] The above-described embodiments are merely descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the spirit of the present invention's design, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A symmetric high-temperature and high-concentration in-situ measuring device for particulate matter in tail gas emissions, characterized in that: it includes a housing, a charging area arranged at one end of the housing, a laminar flow trapping module arranged in the middle section of the housing, and a grading area arranged at the other end of the housing; a first heating layer and a first heat insulation layer are successively arranged on the outer side of the housing; the charging area includes a first charging unit and a second charging unit symmetrically arranged along the central axis of the housing; the first charging unit and the second charging unit have the same structure, and both include a charging housing installed on one side of the housing, an insulating base installed at one end of the charging housing, a discharge needle installed at one end of the insulating base, a metal ring installed at the other end of the insulating base, and an orifice plate installed on the inner side of the housing; a second heating layer and a second heat insulation layer are successively arranged on the outer side of the charging housing; the first heating layer and the first heat insulation layer are closely attached to the housing, and the second heating layer and the second heat insulation layer are closely attached to the first charging housing and the second charging housing; the laminar flow trapping module includes a laminar flow device and an electrostatic precipitator arranged coaxially; the laminar flow device is provided with multiple thin plates; the electrostatic precipitator is composed of six metal plates installed in parallel, and the air flow passes between the plates; the six metal plates are respectively a first plate, a second plate, a third plate, a fourth plate, a fifth plate, and a sixth plate. A first channel is formed between the first plate and the second plate, a second channel is formed between the second plate and the third plate, a third channel is formed between the third plate and the fourth plate, a fourth channel is formed between the fourth plate and the fifth plate, and a fifth channel is formed between the fifth plate and the sixth plate; the grading area includes a high-voltage plate, multiple measuring plates, and a current measuring device; the high-voltage plate is connected to a constant high-voltage source; the multiple measuring plates are installed on the same plane and arranged parallel to the high-voltage plate, and are connected to the current measuring device through a shielded cable; the current measuring device is located on the outer side of the housing; the number of measuring plates is six, which are respectively a first measuring plate, a second measuring plate, a third measuring plate, a fourth measuring plate, a fifth measuring plate, and a sixth measuring plate.

2. The symmetric high-temperature and high-concentration in-situ measuring device for particulate matter in tail gas emissions according to claim 1, characterized in that: a sample gas inlet is opened at one end of the housing, and a total flow outlet is opened at the other end. The sample gas inlet is connected to a motor vehicle tail gas pipe; the sample gas inlet and the total flow outlet are coaxially arranged.

3. The symmetric high-temperature and high-concentration in-situ measuring device for particulate matter in tail gas emissions according to claim 2, characterized in that: a plurality of uniformly distributed sheath gas inlets are opened at the outer end of the insulating base, and the discharge needle is installed through the center of the insulating base.

4. The symmetric high-temperature and high-concentration in-situ measuring device for particulate matter in tail gas emissions according to claim 3, characterized in that: a through hole is opened in the middle part of the metal ring; the metal ring is grounded; the metal ring and the discharge needle are coaxially arranged; a through hole is opened in the center of the orifice plate, and the diameter of the through hole is 0.7 mm.

5. The measuring method of the symmetric high-temperature and high-concentration in-situ measuring device for particulate matter in tail gas emissions according to claim 4, characterized in that: this method includes the following steps: (1) The high-temperature tail gas discharged from the motor vehicle tail gas pipe enters the measuring device through the sample gas inlet; (2) Clean air is introduced into the charged shell from the sheath gas inlet. A high-voltage electric field is formed between the discharge needle and the grounded metal ring. Under the action of the high-voltage electric field, part of the clean air is ionized to generate electric ions. The electric ions are ejected from the through-hole in the center of the orifice plate into the charged area along with the clean air. Part of the electric ions collide with the particulate matter to charge the particulate matter, and charged particulate matter is obtained. (3) The charged particulate matter enters the laminar flow trapping module with the airflow and enters the electrostatic precipitator through the laminator composed of multiple thin plates. In the electrostatic precipitator, plate one and plate six are grounded, plate two and plate five are connected to high voltage HV1, and plate three and plate four are connected to high voltage HV2, where HV2 = 2 * HV1. Therefore, the same high-voltage electric field E1 will be formed in channels one, two, four, and five, and there is no electric field in channel three. When the charged particulate matter passes through the electrostatic precipitator with the airflow, the charged particulate matter in the airflow passing through channels one, two, four, and five will collide with the plate under the action of the electric field force, while the charged particulate matter in channel three has no electric field force and passes through horizontally at a constant speed. (4) The airflow continues to be introduced into the classification area, and a high-voltage electric field will be formed between the high-voltage plate and the outer shell. The charged particulate matter will deflect downward under the action of the electric field force. Due to different electric field forces received, particulate matter in different particle size ranges will collide with different measurement plates. The micro-current signals of each measurement plate are inversed to obtain the particle size spectrum of particulate matter in vehicle exhaust.

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