CN112065545A - Method for reducing content of monocyclic aromatic hydrocarbon substances in nano-scale particles of diesel engine - Google Patents
Method for reducing content of monocyclic aromatic hydrocarbon substances in nano-scale particles of diesel engine Download PDFInfo
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- CN112065545A CN112065545A CN202010920847.7A CN202010920847A CN112065545A CN 112065545 A CN112065545 A CN 112065545A CN 202010920847 A CN202010920847 A CN 202010920847A CN 112065545 A CN112065545 A CN 112065545A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N9/00—Electrical control of exhaust gas treating apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
- F01N13/0093—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are of the same type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/01—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust by means of electric or electrostatic separators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
- F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
- F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
- F01N3/0222—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0821—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with particulate filters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
- F01N3/0835—Hydrocarbons
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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Abstract
The invention discloses a method for reducing the content of monocyclic aromatic hydrocarbon substances in nano-scale particles of a diesel engine, which comprises the following steps,By the real-time pressure P in the cylinder along with the crank angle
Variation curve of (2) and in-cylinder real-time temperature T along with crank angle
The change curve of the aromatic hydrocarbon judgment system judges the combustion state in the cylinder of the diesel engine, and intervenes in different combustion stages, so as to mainly reduce monocyclic aromatic hydrocarbon formed in the combustion process; secondly, carrying out plasma treatment, OH free radical heating treatment and activated carbon adsorption on the exhaust gas; and step three, judging the concentration of the nano-scale particles with the particle size of less than 100nm in the exhaust process, performing electrostatic adsorption treatment, high-temperature oxidation and particle trap trapping and filtering, and controlling monocyclic aromatic hydrocarbon in the nano-scale particles. The method has obvious effect of reducing the content of monocyclic aromatic hydrocarbon in the nano-scale particles of the engine exhaust.
Description
Technical Field
The invention relates to a method for reducing the emission of vehicle particles, in particular to a method for reducing the content of monocyclic aromatic hydrocarbon substances of nano-scale particles of a diesel engine.
Background
Currently, methods for reducing particulate matter emission, such as Low Temperature Combustion (LTC) and particulate filter (DPF), are proposed for diesel particulate matter from two aspects of combustion control and exhaust gas aftertreatment. The novel combustion mode (such as LTC) can avoid the temperature and equivalence ratio area where a large amount of particulate matters are generated by optimizing the combustion process, and the emission of the particulate matters is greatly reduced. However, on one hand, the novel combustion mode has the problem of narrow working condition range, and on the other hand, the combustion optimization control has a limited effect on reducing the emission of the nano-scale particles. The trapping efficiency of the particulate matter emission of the particulate trap (DPF) can reach about 90%, and the particulate matter emission can be effectively reduced. However, the particulate trap has problems in use, such as an increase in exhaust back pressure when a certain amount of trapped particulates is reached, a decrease in trapping efficiency, and the need for trap regeneration. In addition, the trapping efficiency of the nano-scale particles depends on the trapping principle, structure, material and other factors of the trap, and the efficient trapping of the nano-scale particles cannot be realized.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for reducing the monocyclic aromatic hydrocarbon content of the nano-scale particles of the diesel engine, which reduces the monocyclic aromatic hydrocarbon content in the nano-scale particles which are difficult to control combustion and difficult to trap by an aftertreatment device, thereby reducing the harm of the absorbable nano-scale particles to human bodies.
The technical scheme of the invention is as follows: a method for reducing the content of monocyclic aromatic hydrocarbon substances in nano-scale particles of a diesel engine comprises the following steps:
step one, real-time pressure P in a cylinder is used for measuring the angle of a crankshaft
Variation curve of (2) and in-cylinder real-time temperature T along with crank angle
Judging the combustion state of the diesel engine in the cylinder by the change curve, and increasing the ERG rate when the combustion is in a fast combustion period and the pressure rise rate in the cylinder exceeds a first pressure rise rate threshold value; when the combustion is in a slow combustion period and the oxygen concentration in the cylinder is lower than a first oxygen concentration threshold value, injecting oxygen-containing fuel ethanol, n-butanol or dimethyl carbonate; when the combustion is in a post-combustion period and the temperature in the cylinder is not lower than a first temperature threshold value, spraying oxygen-containing fuel ethanol or n-butanol;
secondly, carrying out plasma treatment, OH free radical heating treatment and activated carbon adsorption on the exhaust gas;
step three, judging the concentration of the nano-scale particles with the particle diameter smaller than 100nm in the exhaust gas obtained in the step two, carrying out electrostatic adsorption treatment on the exhaust gas when the concentration of the nano-scale particles exceeds a first particle concentration threshold value, and otherwise, sequentially trapping and filtering by a first particle trap, a second particle trap and a third particle trap; judging the fractal dimension of the particles of the exhaust gas after electrostatic adsorption treatment, and spraying the atomized methanol and dimethyl ether oxygen-containing mixed fuel into the exhaust gas to perform high-temperature oxidation when the fractal dimension exceeds a first threshold, or directly performing high-temperature oxidation; finally, the particles are collected and filtered by a third particle catcher.
Further, the real-time pressure P in the cylinder is along with the crank angle
The time when the variation curve of the pressure difference is separated from the cylinder pressure curve of the diesel engine under the condition of non-combustion is a fast combustion period, the time when the combustion is in the fast combustion period and the real-time pressure P in the cylinder rises and an inflection point appears is a slow combustion period, and the time when the combustion is in the slow combustion period and the temperature T in the cylinder rises and the inflection point appears is a post-combustion period.
Further, when the oxygen concentration in the cylinder is not higher than a first oxygen concentration threshold value and is higher than a second oxygen concentration threshold value, oxygen-containing fuel ethanol or n-butanol is sprayed, when the oxygen concentration in the cylinder is not higher than the second oxygen concentration threshold value, oxygen-containing fuel dimethyl carbonate is sprayed, and the first oxygen concentration threshold value is larger than the second oxygen concentration threshold value.
Further, the step two comprises performing plasma treatment on the exhaust gas when the concentration of the gaseous aromatic hydrocarbon is greater than a first aromatic hydrocarbon concentration threshold value according to the concentration of the gaseous aromatic hydrocarbon in the exhaust gas of the engine; when the concentration of the gaseous aromatic hydrocarbon is not more than the first aromatic hydrocarbon concentration threshold value but more than the second aromatic hydrocarbon concentration threshold value, carrying out OH free radical heating treatment on the exhaust gas; when the concentration of the gaseous aromatic hydrocarbon is not greater than the second aromatic hydrocarbon concentration threshold value, performing activated carbon adsorption on the exhaust gas; and after the exhaust gas is treated, when the concentration of the gaseous aromatic hydrocarbon is greater than a third aromatic hydrocarbon concentration threshold value, the second step is carried out again, wherein the first aromatic hydrocarbon concentration threshold value is greater than a second aromatic hydrocarbon concentration threshold value, and the second aromatic hydrocarbon concentration threshold value is greater than the third aromatic hydrocarbon concentration threshold value.
Further, after the electrostatic adsorption treatment is carried out on the exhaust gas, whether the voltage drop of the electrostatic adsorption is larger than a voltage drop threshold value is judged, if yes, a reverse voltage is loaded, and then the step of judging the fractal dimension of the particles is carried out, and if not, the step of sequentially carrying out the trapping and filtering through the second particle trap and the third particle trap.
Further, the first particle catcher is made of honeycomb ceramics, and the structural parameters are as follows: the average pore diameter is 22-25 μm, the porosity is 72-76%, the wall thickness is 7-8mil, and the length-to-diameter ratio is 0.5-0.7; the second particle catcher is made of honeycomb ceramics, and the structural parameters are as follows: average pore diameter is 15-18 μm, porosity is 65-68%, wall thickness is 10-12mil, and length-to-diameter ratio is 0.9-1.1; the third particle catcher is made of honeycomb ceramics, and the structural parameters are as follows: the average pore diameter is 10-12 μm, the porosity is 58-62%, the wall thickness is 14-16mil, and the length-to-diameter ratio is 1.3-1.5.
The technical scheme provided by the invention has the advantages that: the method of combined control obviously reduces the content of monocyclic aromatic hydrocarbon substances of the nano-scale particulate matters of the diesel engine by controlling the injection of the oxygen-containing fuel in the combustion process, carrying out plasma treatment, OH free radical heating treatment and activated carbon adsorption on the exhaust gas in the exhaust stage, then carrying out electrostatic adsorption, high-temperature oxidation treatment and finally trapping by a particle trap.
Drawings
FIG. 1 is a flow chart of the method steps of the present invention.
FIG. 2 is a schematic flow chart of the steps of the method of the present invention.
FIG. 3 is a schematic diagram of the exhaust path in step two of the method of the present invention.
FIG. 4 is a schematic flow chart of the method steps of the present invention.
FIG. 5 is a schematic view of the exhaust path in step three of the method of the present invention. .
FIG. 6 is a graph of benzene emission concentration for the present invention and comparative examples.
FIG. 7 is a graph of toluene emission concentration for the present invention and comparative examples.
FIG. 8 is a graph of ethylbenzene effluent concentration for the present invention and comparative examples.
FIG. 9 is a graph of xylene emissions concentration for the present invention and comparative examples.
Detailed Description
The present invention is further described in the following examples, which are intended to be illustrative only and not to be limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalent modifications thereof which would occur to persons skilled in the art upon reading the present specification and which are intended to be within the scope of the present invention as defined in the appended claims.
The specific method for reducing the content of the monocyclic aromatic hydrocarbon substances in the nano-scale particles of the diesel engine mainly comprises the following three steps: step one, real-time pressure P in a cylinder is used for measuring the angle of a crankshaft
Variation curve of (2) and in-cylinder real-time temperature T along with crank angle
The change curve of the aromatic hydrocarbon judgment system judges the combustion state in the cylinder of the diesel engine, and intervenes in different combustion stages, so as to mainly reduce monocyclic aromatic hydrocarbon formed in the combustion process; secondly, carrying out plasma treatment, OH free radical heating treatment and activated carbon adsorption on the exhaust gas; and step three, judging the concentration of the nano-scale particles with the particle size of less than 100nm in the exhaust process to control the monocyclic aromatic hydrocarbon in the nano-scale particles.
Specifically, referring to fig. 1, a cylinder pressure curve (pure compression line) of a diesel engine without combustion is a known parameter, and the first step includes the following steps:
1. detecting whether to spray oil
a) If so, perform "step 2".
b) If not, "no operation".
2. The fuel injection quantity is recorded and then "step 3" is performed.
3. Recording the real-time pressure P in the cylinder along with the crank angle
Is performed (by means of a pressure sensor installed in the cylinder), and then "step 4" is performed.
4. Judging the pressure curve
Whether to break away from the pure compression line
a) If so, step 5 is executed and the in-cylinder pressure P1 at this time is recorded.
b) If not, determining that the combustion is in a stagnation period, and returning to the step 3.
5. It is determined that "combustion is in/in the rapid combustion period", and then "step 6" and "step 7" are performed simultaneously.
6. Step 9 is entered after waiting for the inflection point of the pressure curve (after reaching the maximum value, starting to decrease).
7. Detecting in-cylinder pressure rise rate
And judge
Whether or not greater than 0.25 MPa/. degree.C.A:
a) if so, go to "step 8".
b) If not, "no operation".
8. The EGR rate is set to increase by 5% on the original basis (e.g., the EGR rate is 10% and 15% after the increase) (direct intervention during the fast burn period, EGR is used to reduce the combustion speed), and then the process returns to step 7.
9. It is determined that "combustion is in/in the slow combustion period", and then "step 10" and "step 11" are performed simultaneously.
10. Waiting temperature profile
Step 15 is entered after the inflection point (after reaching the maximum, starting to descend) appears.
11. Detecting the oxygen concentration in the cylinder by using an oxygen sensor, and judging whether the oxygen concentration is higher than 19 percent or not
a) If so, "no operation";
b) if not, go to "step 12".
12. Judging whether the oxygen concentration is higher than 17%
a) If yes, go to step 13;
b) if not, go to "step 14".
13. Ethanol or n-butanol as an oxygenate is injected in an amount of 10% of the initial fuel volume injection amount.
14. The oxygenate dimethyl carbonate was injected in an amount of 5% of the initial fuel volume injection.
15. It is determined that "combustion is in/during the post combustion period", and then "step 16" and "step 17" are performed simultaneously.
16. And (4) waiting for the in-cylinder pressure to be less than P1 to indicate that the combustion process is ended, and ending the step one process.
17. Judging whether the temperature in the cylinder is lower than 2000K:
a) if so, "no operation" (the temperature is too low and the monocyclic aromatic cannot be oxidized).
b) If not, proceed to "step 18".
18. Ethanol or n-butanol as an oxygenate is injected in an amount of 3% of the initial fuel volume injection.
Referring to fig. 2 and 3, the second step of controlling the gaseous monocyclic aromatic hydrocarbon in the exhaust process by plasma treatment, OH radical heating treatment and activated carbon adsorption on the exhaust gas according to the concentration of the gaseous aromatic hydrocarbon in the exhaust gas includes the following steps:
1. detecting the concentration m of the gaseous aromatic hydrocarbon in the exhaust gas by adopting a chromatography-mass spectrometry combined method, and judging whether the concentration m is more than 500 mg/L:
a) if so, go to "step 2".
b) If not, then "judge whether the concentration m is greater than 300 mg/L":
if so, go to "step 3".
If not, go to "step 4".
The "first flow rate control valve 1" introduces the exhaust gas into the "first exhaust passage 2", treats the gaseous monocyclic aromatic hydrocarbon in the exhaust gas by plasma, and then proceeds to "step 5".
The "first flow control valve 1" introduces exhaust gas into the "second exhaust passage 3", and gaseous monocyclic aromatic hydrocarbons in the exhaust gas are treated by OH radical heating treatment, followed by "step 5".
The "first flow rate control valve 1" introduces the exhaust gas into the "third exhaust passage 4", treats the gaseous monocyclic aromatic hydrocarbons in the exhaust gas by activated carbon adsorption, and then proceeds to "step 5".
5. Detecting and judging whether the concentration m of the gaseous aromatic hydrocarbon is more than 150 mg/L:
a) if so, go to "step 6".
b) If not, go to "step 7".
The "second flow control valve 5" directs the exhaust gas into the "return path 6" to return the exhaust gas to the original exhaust port.
7. The exhaust continues to exhaust.
Referring to FIG. 4 and FIG. 5, step three, determining the concentration of the nano-particles with a particle size less than 100nm during the exhaust process, and controlling the monocyclic aromatic hydrocarbon in the nano-particles
1. Detecting the particle size concentration distribution condition of the particles in the exhaust gas by adopting a particle size spectrometer 7 (the particle size detection range is 5 nm-10 mu m), and judging whether the concentration of the nano-scale particles with the particle size of less than 100nm is more than 1.0 multiplied by 106Per cm3”：
a) If so, the exhaust gas is introduced into the "fourth exhaust passage 9" through the third flow control valve 8, and the "step 2" is performed.
b) If not, the exhaust gas is introduced into the "ninth exhaust passage 10" through the third flow control valve 8, and the "step 3" is performed.
2. The particles are charged. The exhaust gas passes through a particulate matter electrostatic loading device (charging device) to load the particulate matter in the exhaust gas with electric charges. (the greater the particle size of the particles, the greater the charge that can be loaded.) then "step 4" is performed.
3. The exhaust gas passes through the first particle catcher 11, the first particle catcher 11 is made of honeycomb ceramics, and the specific structural parameters are as follows: the average pore diameter is 22-25 μm, the porosity is 72-76%, the wall thickness is 7-8mil, and the length-to-diameter ratio is 0.5-0.7. Then "step 9" is performed.
4. And (3) performing electrostatic adsorption on the nano-scale particles in the exhaust gas by adopting electrostatic adsorption (an electric field loading device) with the electrostatic voltage range of 5-100V, and then performing step 5.
5. The actual voltage in the fourth exhaust passage 9 is detected, and whether or not the voltage drop is larger than 15% compared with the electrostatic adsorption (electric field application device) voltage is determined:
a) if so, go to "step 6".
b) If not, go to "step 7".
6. A reverse voltage is applied to the electrostatic adsorption in a voltage range of 5-100V, and at this time, the fourth flow control valve 12 controls the flow of the exhaust gas to the fifth exhaust passage 13, and then "step 8" is performed.
7. The fourth flow control valve 12 controls the flow of exhaust gas to the sixth exhaust passage 14, and then "step 9" is performed.
8. Detecting the scattering intensity of the exhaust particles by adopting an X-ray scattering detection method, calculating the fractal dimension of the particles through the scattering intensity, and judging whether the fractal dimension is greater than 2.5':
a) if so, (indicating that the surface has a high degree of surface irregularities and is likely to adsorb PAH, followed by oxidation) the "step 10" is performed.
b) If not, the process proceeds to "step 11" (capture is performed directly).
9. The exhaust gas passes through the second particle catcher 15, the second particle catcher 15 is made of honeycomb ceramics, and the specific structural parameters are as follows: average pore diameter of 15-18 μm, porosity of 65-68%, wall thickness of 10-12mil, and length-to-diameter ratio of 0.9-1.1. Then "step 14" is performed.
10. The fifth flow control valve 16 controls the flow of exhaust gas to the seventh exhaust passage 17, and then "step 12" is performed.
11. The fifth flow control valve 16 controls the flow of exhaust gas to the eighth exhaust passage 18, and then "step 13" is performed.
12. And spraying the atomized oxygen-containing mixed fuel of methanol and dimethyl ether into the tail gas, and then carrying out step 13.
13. The tail gas is heated to 500 ℃ by adopting an electric heating method, the exhaust particles are subjected to high-temperature oxidation, and then the step 14 is carried out.
14. The exhaust gas passes through the third particle catcher 19, the third particle catcher 19 is made of honeycomb ceramics, and the specific structural parameters are as follows: the average pore diameter is 10-12 μm, the porosity is 58-62%, the wall thickness is 14-16mil, and the length-to-diameter ratio is 1.3-1.5. Then "step 15" is performed.
15. And (4) exhausting the exhaust gas.
Taking a certain diesel engine as an example, the content of monocyclic aromatic hydrocarbons such as benzene, toluene, ethylbenzene, xylene and the like in the nano-scale particulate matters in the exhaust gas is respectively measured without any technical measures, by using low temperature co-combustion (LTC), by using a particle trap (DPF) and by using the method for reducing the content of monocyclic aromatic hydrocarbons in nano-scale particulate matters of the diesel engine designed by the invention, and the results are shown in fig. 6-9. The diesel engine has a certain effect on reducing the content of the single-ring aromatic hydrocarbon substances of the nano-scale particles by adopting low temperature co-fired ceramic (LTC) and a particle trap (DPF), and after the scheme for reducing the content of the single-ring aromatic hydrocarbon substances of the nano-scale particles is adopted, the content of the single-ring aromatic hydrocarbon substances of the nano-scale particles is further reduced compared with the low temperature co-fired ceramic (LTC) and the particle trap (DPF). The scheme of the invention has obvious effect of reducing the content of the monocyclic aromatic hydrocarbon substances of the nano-scale particles of the diesel engine.
Claims (6)
1. A method for reducing the content of monocyclic aromatic hydrocarbon substances in nano-scale particles of a diesel engine is characterized by comprising the following steps:
step one, real-time pressure P in a cylinder is used for measuring the angle of a crankshaft
Variation curve of (2) and in-cylinder real-time temperature T along with crank angle
Judging the combustion state of the diesel engine in the cylinder by the change curve, and increasing the ERG rate when the combustion is in a fast combustion period and the pressure rise rate in the cylinder exceeds a first pressure rise rate threshold value; when the combustion is in a slow combustion period and the oxygen concentration in the cylinder is lower than a first oxygen concentration threshold value, injecting oxygen-containing fuel ethanol, n-butanol or dimethyl carbonate; the combustion is in the afterburning period and the temperature in the cylinderSpraying oxygen-containing fuel ethanol or n-butanol when the temperature is not lower than a first temperature threshold;
secondly, according to the concentration of the gaseous aromatic hydrocarbon in the exhaust gas of the engine, when the concentration of the gaseous aromatic hydrocarbon is greater than a first aromatic hydrocarbon concentration threshold value, carrying out plasma treatment, OH free radical heating treatment and activated carbon adsorption on the exhaust gas;
step three, judging the concentration of the nano-scale particles with the particle diameter smaller than 100nm in the exhaust gas obtained in the step two, carrying out electrostatic adsorption treatment on the exhaust gas when the concentration of the nano-scale particles exceeds a first particle concentration threshold value, and otherwise, sequentially trapping and filtering by a first particle trap, a second particle trap and a third particle trap; and judging the fractal dimension of the particles of the exhaust gas after electrostatic adsorption treatment, spraying the atomized methanol and dimethyl ether oxygen-containing mixed fuel into the exhaust gas when the fractal dimension exceeds a first threshold value, then carrying out high-temperature oxidation, and otherwise, directly carrying out high-temperature oxidation, and then trapping and filtering by a third particle trap.
2. The method for reducing the content of nano-scale particulate matter monocyclic aromatic hydrocarbon substances in diesel engine as claimed in claim 1, wherein said in-cylinder real-time pressure P is dependent on the crank angle
The time when the variation curve of the pressure difference is separated from the cylinder pressure curve of the diesel engine under the condition of non-combustion is a fast combustion period, the time when the combustion is in the fast combustion period and the real-time pressure P in the cylinder rises and an inflection point appears is a slow combustion period, and the time when the combustion is in the slow combustion period and the temperature T in the cylinder rises and the inflection point appears is a post-combustion period.
3. The method for reducing the content of nano-sized particulate monocyclic aromatic hydrocarbon substances in a diesel engine according to claim 1, wherein when the in-cylinder oxygen concentration is not higher than a first oxygen concentration threshold value and is higher than a second oxygen concentration threshold value, an oxyfuel ethanol or n-butanol is injected, and when the in-cylinder oxygen concentration is not higher than the second oxygen concentration threshold value, an oxyfuel dimethyl carbonate is injected, and the first oxygen concentration threshold value is larger than the second oxygen concentration threshold value.
4. The method for reducing the content of the nano-scale particulate matter monocyclic aromatic hydrocarbon substances in the diesel engine as claimed in claim 1, wherein said step two comprises performing plasma treatment on the exhaust gas when the concentration of the gaseous aromatic hydrocarbon is greater than a first aromatic hydrocarbon concentration threshold value according to the concentration of the gaseous aromatic hydrocarbon in the exhaust gas of the engine; when the concentration of the gaseous aromatic hydrocarbon is not more than the first aromatic hydrocarbon concentration threshold value but more than the second aromatic hydrocarbon concentration threshold value, carrying out OH free radical heating treatment on the exhaust gas; when the concentration of the gaseous aromatic hydrocarbon is not greater than the second aromatic hydrocarbon concentration threshold value, performing activated carbon adsorption on the exhaust gas; and after the exhaust gas is treated, when the concentration of the gaseous aromatic hydrocarbon is greater than a third aromatic hydrocarbon concentration threshold value, the second step is carried out again, wherein the first aromatic hydrocarbon concentration threshold value is greater than a second aromatic hydrocarbon concentration threshold value, and the second aromatic hydrocarbon concentration threshold value is greater than the third aromatic hydrocarbon concentration threshold value.
5. The method for reducing the content of monocyclic aromatic hydrocarbon substances in nano-scale particles of a diesel engine as claimed in claim 1, wherein said step of judging whether the electrostatic adsorption voltage drop is larger than the pressure drop threshold value after performing electrostatic adsorption treatment on the exhaust gas, if so, loading a reverse voltage and then entering the step of judging the fractal dimension of the particles, if not, sequentially passing through the second particle trap and the third particle trap for trapping and filtering.
6. The method for reducing the content of monocyclic aromatic hydrocarbon substances in nano-scale particles of a diesel engine as claimed in claim 1, wherein said first particle catcher is made of honeycomb ceramics and has the structural parameters: the average pore diameter is 22-25 μm, the porosity is 72-76%, the wall thickness is 7-8mil, and the length-to-diameter ratio is 0.5-0.7; the second particle catcher is made of honeycomb ceramics, and the structural parameters are as follows: average pore diameter is 15-18 μm, porosity is 65-68%, wall thickness is 10-12mil, and length-to-diameter ratio is 0.9-1.1; the third particle catcher is made of honeycomb ceramics, and the structural parameters are as follows: the average pore diameter is 10-12 μm, the porosity is 58-62%, the wall thickness is 14-16mil, and the length-to-diameter ratio is 1.3-1.5.
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