Soot particle modification method based on in-cylinder combustion regulation and control of automobile engine

Abstract

The invention discloses a soot particle modification method based on in-cylinder combustion regulation of an automobile engine, belongs to the technical field of combustion control of internal combustion engines, and solves the technical problem that the adsorption capacity of soot particles is relatively weak. The method comprises the steps that fossil fuel, oxygen-containing fuel and other fuels with different properties are adopted for engine design of the engine fuel; and then effective control over the combustion process and the combustion path of the engine is achieved by adjusting control parameters such as the air inlet parameter, the oil injection strategy, the operation working condition, the EGR rate and the equivalence ratio of the engine. And finally carrying out carbonaceous test and evaluation on the collected soot particles. The average particle size of the modified soot particles is reduced by 6.3%, the graphitization degree is reduced, and the specific surface area is increased by 39.1%; the pore size distribution range is 2-140nm and belongs to mesopores and macropores, and the total pore volume is increased by 3.5%. This allows the soot particles to have higher oxidation activity and adsorption properties.

Description

Technical Field

[0001] The present invention relates to the technical field of internal combustion engine combustion control, and more specifically, it relates to a method for modifying soot particles based on in-cylinder combustion regulation of an automotive engine. Background Art

[0002] Internal combustion engines are important power sources in fields such as automobiles, ships, construction machinery, agricultural machinery, and military equipment. However, their pollutant emissions pose a great threat to the atmospheric environment and human health. The main component of automotive PM emissions is soot, which is carbon particles with a nanometer to micrometer size and stable chemical properties. Soot enters the after-treatment system with the exhaust gas, is captured by the diesel particulate filter (DPF) and deposited in its carrier. The active sites of the DPF catalyst are covered by low-activity soot, resulting in a significant reduction in catalytic activity. Since the soot emitted by automobiles is composed of graphitic carbon with a stable chemical structure and multiple-layer flake structure, it is more difficult for the soot particles in the DPF to be oxidized. A large amount of soot particles accumulating in the DPF will cause the DPF to become blocked, the back pressure of the engine to increase, and the engine performance to decline. Moreover, the use of precious metals will increase due to the low oxidation reaction activity and high graphitization degree of the soot particles in the DPF, soaring the after-treatment cost.

[0003] In recent years, carbon-based adsorption materials have become a research hotspot in the environmental protection field due to their simple preparation, large adsorption capacity, and low price. Porous carbon can effectively adsorb NOx, and modifying or optimizing its surface properties can greatly improve the adsorption efficiency of NO and NO 2 . Therefore, developing carbon-based adsorption materials for treating automotive NOx emissions is a highly promising automotive exhaust pollution control technology. However, the surface of the soot particles generated by engines fueled with petrochemical diesel has only a small number of microporous structures and weak adsorption ability, so it is difficult to use them for treating mobile source automotive exhaust pollution. Summary of the Invention

[0004] The technical problem to be solved by the present invention is in view of the above-mentioned deficiencies of the prior art. The purpose of the present invention is to provide a method for modifying soot particles based on in-cylinder combustion regulation of an automotive engine.

[0005] The technical solution of the present invention is: A method for modifying soot particles based on in-cylinder combustion regulation of an automotive engine, comprising the following steps:

[0006] Step 1. Design the fuel for the engine relying on fossil fuels and oxygen-containing fuels, and flexibly adjust the blending ratio of various fuels based on the numerical simulation results, so as to achieve the adjustment of the physical and chemical properties of the C / H / O ratio, viscosity, cetane number, and calorific value of the multi-fuel.

[0007] Step 2. Effectively control the engine combustion process and combustion path by adjusting the control parameters of the engine's intake characteristics, injection strategy, operating conditions, EGR rate, and equivalence ratio; that is, based on the method combining physical activation and chemical activation of porous carbon, regulate the characteristic parameters of the particle size distribution, nanoscale structure, porosity, and specific surface area of soot particles in the flame to achieve the purpose of regulating the structure of soot particles;

[0008] Step 3. Install a soot particle collection device at the position after the engine supercharger and before the aftertreatment system to collect the soot particles generated by engine combustion for the evaluation and characterization of carbonaceous materials, and investigate whether the soot particles can adsorb other exhaust pollutants and have the properties and structures that can be rapidly oxidized by DPF.

[0009] As a further improvement, during the process of fuel design and combustion regulation of soot particles, it is necessary to ensure the balance between combustion efficiency and thermal efficiency to ensure that the normal working state of the engine is not affected.

[0010] Furthermore, the oxygen-containing fuel in the fuel design is biodiesel, and the oxygen content of biodiesel is greater than 10%.

[0011] Furthermore, the regulation of intake parameters in the engine combustion process includes the regulation of intake temperature and intake pressure. The intake temperature is 30°C to 50°C after intercooling, and the intake pressure is 0.15 MPa to 0.30 MPa.

[0012] Furthermore, the injection strategy regulation in the engine combustion process adopts a two-stage injection strategy, where the pre-injection accounts for 5% to 15%, and the main injection accounts for 85% to 95%.

[0013] Furthermore, the regulation of operating conditions in the engine combustion process includes the regulation of engine speed and load. The speed is 1000 r / min to 2000 r / min, and the load is 0% to 75%.

[0014] Furthermore, the EGR rate in the regulation of the engine combustion process is 0% to 50%.

[0015] Furthermore, the equivalence ratio in the regulation of the engine combustion process is 1.5 to 3.0.

[0016] Beneficial effects

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] The present invention realizes the modification of soot particles by regulating in-cylinder combustion of an automotive engine. After modification, the average particle size of the soot particles decreases by 6.3%, the graphitization degree decreases, and the specific surface area increases by 39.1%; the pore size distribution ranges from 2 to 140 nm, belonging to mesopores and macropores, and the total pore volume increases by 3.5%. This makes the soot particles have higher oxidation activity and adsorption characteristics. The higher oxidation activity enables the soot to be more easily oxidized, reducing the cost of post-treatment; the stronger adsorption characteristics can effectively adsorb NOx, providing a new idea for treating NOx in automotive emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flow chart of the present invention;

[0020] Figure 2 are the TEM images and corresponding particle size distribution diagrams of pure diesel (D100) soot particles;

[0021] Figure 3 are the TEM images and corresponding particle size distribution diagrams of blended fuel (BD50) soot particles;

[0022] Figure 4 are the TEM images and corresponding particle size distribution diagrams of blended fuel (BD75) soot particles;

[0023] Figure 5 are the TEM images and corresponding particle size distribution diagrams of BD100 biodiesel soot particles;

[0024] Figure 6 is the HRTEM image of pure diesel (D100) soot particles;

[0025] Figure 7 is the HRTEM image of blended fuel (BD50) soot particles;

[0026] Figure 8 is the HRTEM image of blended fuel (BD75) soot particles;

[0027] Figure 9 is the HRTEM image of BD100 biodiesel soot particles;

[0028] Figure 10 is the nitrogen adsorption / desorption isotherm of basic soot particles;

[0029] Figure 11 is the pore size distribution diagram of basic soot particles. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be further described below with reference to specific embodiments in the drawings.

[0031] Refer to Figures 1 to 11, A method for modifying soot particles based on in-cylinder combustion regulation of an automotive engine, comprising the following steps:

[0032] Step 1. Design the fuel for the engine relying on fossil fuels and oxygenated fuels, and flexibly adjust the blending ratio of various fuels based on the numerical simulation results, so as to achieve the adjustment of the physical and chemical properties of the C / H / O ratio, viscosity, cetane number, and calorific value of the multi-fuel;

[0033] Step 2. Achieve effective control of the engine combustion process and combustion path by adjusting the intake characteristics, injection strategy, operating conditions, EGR rate, and control parameters of the equivalence ratio of the engine; that is, based on the method combining physical activation and chemical activation of porous carbon, regulate the characteristic parameters of the particle size distribution, nanoscale structure, porosity, and specific surface area of the soot particles in the flame to achieve the purpose of regulating the structure of the soot particles;

[0034] Step 3. Install a soot particle collection device at the position after the engine supercharger and before the aftertreatment system to collect the soot particles generated by the engine combustion for the evaluation and characterization of the carbonaceous matter, and investigate whether the soot particles can adsorb other exhaust pollutants and the properties and structures that can be rapidly oxidized by the DPF.

[0035] It should be noted that during the process of fuel design and combustion regulation of the soot particles, it is necessary to ensure the balance of combustion efficiency and thermal efficiency to ensure that the normal working state of the engine is not affected.

[0036] Specifically, the oxygenated fuel in the fuel design is biodiesel, and the oxygen content of the biodiesel is greater than 10%. The regulation of the intake parameters in the engine combustion process includes the regulation of the intake temperature and intake pressure. The intake temperature is 30°C to 50°C after being intercooled, and the intake pressure is 0.15 MPa to 0.30 MPa. The injection strategy regulation in the engine combustion process adopts a two-stage injection strategy, where the pre-injection accounts for 5% to 15%, and the main injection accounts for 85% to 95%. The regulation of the operating conditions in the engine combustion process includes the regulation of the engine speed and load. The speed is 1000 r / min to 2000 r / min, and the load is 0% to 75%. The EGR rate in the engine combustion process regulation is 0% to 50%. The equivalence ratio in the engine combustion process regulation is 1.5 to 3.0.

[0037] This invention is tested on a high-pressure common rail diesel engine that meets the national V emission standards.

[0038] As a comparison, first, the soot particles of the engine were collected when pure diesel (D100) was used as the fuel. The engine operating conditions were maintained at medium load and 1200 r / min. Then, TEM and BET tests were carried out on the collected soot particles, and the main particle size distribution of the soot particles was found to be 20 nm ～40 nm, the average soot particle size is 29.29 nm; the specific surface area of soot particles is 113 m 2 / g, the total pore volume is 0.294 m 2 / g, and the average pore diameter is 12.60 nm.

[0039] Next, with reference to the accompanying drawings, through the description of the embodiments, the specific implementation manners of the present invention (such as Figure 1 ) will be further described in detail. It should be noted that this embodiment is narrative and is not used to limit the scope of application of the present invention.

[0040] The following are three embodiments of the present invention, in which biodiesel (oxygenated fuel) partially replaces diesel (fossil fuel) to achieve the fuel design of the present invention.

[0041] First, prepare the commercially purchased diesel and BD100 biodiesel that complies with China's GB25199-2017. The oxygen content of the biodiesel is greater than 10%.

[0042] Table 1 shows the physical and chemical properties of the purchased biodiesel.

[0043]

[0044] Before the test, the engine is preheated and run for about 1 hour to make the cooling water temperature, oil temperature, and cylinder wall temperature close to the actual normal working temperature.

[0045] Example 1

[0046] Prepare a mixed fuel (BD50) with a volume ratio of diesel to biodiesel of 1:1. Shake the prepared fuel on a shaking table for 15 minutes to fully mix the two fuels evenly.

[0047] Connect the mixed fuel BD50, adjust the engine operating conditions to 1500 r / min and 30% load, adopt double injection, that is, the pre-injection accounts for 5% and the main injection accounts for 95%. Set the intake pressure to 0.20 MPa, the intake temperature to 30 °C (after intercooling), the EGR rate to 10%, and the equivalence ratio to 1.5.

[0048] After the engine runs stably, use a particulate collection device to collect the soot particles generated by the engine combustion for 2 hours at the position after the engine supercharger and before the aftertreatment system. And TEM and BET tests are carried out on the collected soot particles. It is obtained that the basic soot particle size is mainly distributed in the range of 15 nm to 35 nm, and the average particle size is 27.44 nm; the soot specific surface area is 158 m 2 / g, the total pore volume is 0.396 m 2 / g, and the average pore diameter is 11.83 nm.

[0049] Example 2

[0050] Prepare a blended fuel (BD75) with a volume ratio of diesel to biodiesel of 1:3. Shake the prepared fuel on a shaking table for 15 minutes to fully mix the two fuels evenly.

[0051] Connect the blended fuel DB75, adjust the engine operating conditions to 1800 r / min and 50% load, adopt double injection, that is, the pre-injection accounts for 10% and the main injection accounts for 90%. Set the intake pressure to 0.25 MPa, the intake temperature to 40 °C (after intercooling), the EGR rate to 15%, and the equivalence ratio to 2.0.

[0052] After the engine runs stably, use a particulate matter collection device to collect the soot particles generated by the engine combustion for 2 hours at the position after the engine supercharger and before the aftertreatment system. And TEM and BET tests were carried out on the collected soot particles, and it was obtained that the basic soot particle size was mainly distributed in the range of 15 nm to 25 nm, and the average particle size was 22.54 nm; the specific surface area of the soot was 120 m 2 / g, the total pore volume was 0.301 m 2 / g, and the average pore diameter was 11.69 nm.

[0053] Example 3

[0054] Connect pure biodiesel (BD100), adjust the engine operating conditions to 2000 r / min and 75% load, adopt double injection, that is, the pre-injection accounts for 15% and the main injection accounts for 85%. Set the intake pressure to 0.30 MPa, the intake temperature to 50 °C (after intercooling), the EGR rate to 20%, and the equivalence ratio to 3.0.

[0055] After the engine runs stably, use a particulate matter collection device to collect the soot particles generated by the engine combustion for 2 hours at the position after the engine supercharger and before the aftertreatment system. And TEM and BET tests were carried out on the collected soot particles, and it was obtained that the basic soot particle size was mainly distributed in the range of 15 nm to 25 nm, and the average particle size was 20.38 nm; the specific surface area of the soot was 125 m 2 / g, the total pore volume was 0.330 m 2 / g, and the average pore diameter was 11.55 nm.

[0056] The TEM, particle size distribution, nitrogen adsorption-desorption curve, and pore size distribution of the soot particles of pure diesel (D100), Example 1 (BD50), Example 2 (BD75), and Example 3 (BD100) are as Figures 2 to 11 shown. Table 2 is a summary of the BET data of the soot particles of pure diesel (D100) and three examples. From Figure 2It can be seen that compared with the soot particles of pure diesel (D100), the average particle size of the soot particles in Example 1 (BD50) decreased by 6.3%, the average particle size of the soot particles in Example 2 (BD50) decreased by 23%, and the average particle size of the soot particles in Example 3 (BD100) decreased by 30%; from Figure 3 It can be seen that compared with the soot particles of pure diesel (D100), the overall microcrystalline length of the modified soot particles decreased, the interlayer spacing increased, and the microcrystalline arrangement became more disordered, indicating that the graphitization degree of the modified soot particles decreased; from Figure 3 、 Figure 4 It is concluded that the modified soot particles have a stronger adsorption rate. In particular, the specific surface area of the soot particles in Example 2 (BD50) increased by 39.1%, the pore size distribution range was 2-140 nm, belonging to mesopores and macropores, and the total pore volume increased by 3.5%. It should be noted that when performing the above examples, the engine can always obtain an indicated thermal efficiency of more than 42%.

[0057] Table 2 summarizes the BET data of the soot particles of pure diesel (D100) and three examples.

[0058] Number <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Total pore volume (m 2 / g)]]> Average pore diameter (nm) D100 113 0.294 12.60 Example 2 (BD50) 158 0.396 11.83 Example 3 (BD75) 120 0.301 11.69 Example 4 (BD100) 125 0.330 11.55

[0059] Through the integration and analysis of a large amount of experimental data, a MAP table of soot particle size and corresponding fuel design ratio and combustion control parameters is made. In specific applications, the corresponding combustion control parameters are selected according to the fuel model (fuel design ratio) to generate soot particles with a required particle size, so that the soot particles have higher oxidation activity and adsorption characteristics. Higher oxidation activity can make soot easier to be oxidized, reducing the cost of post-treatment; stronger adsorption characteristics can effectively adsorb NOx.

[0060] In summary, the modified soot particles obtained by the engine fuel design and combustion path regulation of the present invention have a reduced average particle size, a reduced graphitization degree, and a more open pore structure.

[0061] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for modifying soot particles based on combustion control in a car engine cylinder, characterized in that: The following steps are involved: Step 1. Design the engine fuel based on fossil fuels and oxygenated fuels, and flexibly adjust the blending ratio of various fuels based on numerical simulation results, so as to adjust the physical and chemical properties of the C / H / O ratio, viscosity, cetane number and calorific value of the multi-fuel; Step 2. By adjusting the control parameters of the engine's intake characteristics, injection strategy, operating conditions, EGR rate, and equivalence ratio, effective control of the engine's combustion process and combustion path is achieved; that is, based on a method combining physical activation of porous carbon with chemical activation, the characteristic parameters of the particle size distribution, nanostructure, porosity, and specific surface area of ​​the soot particles in the flame are regulated to achieve the purpose of regulating the structure of the soot particles; Step 3. Install the soot particle collection device after the engine supercharger and before the after-treatment system to collect the soot particles generated by engine combustion for carbon quality evaluation and characterization, to examine whether the soot particles have the properties and structure to adsorb other exhaust pollutants and can be quickly oxidized by DPF.

2. According to the method for modifying soot particles based on combustion regulation in the cylinder of an automobile engine as described in claim 1, in the process of fuel design and combustion regulation of soot particles, it is necessary to ensure the balance between combustion efficiency and thermal efficiency to ensure that the normal working state of the engine is not affected.

3. The method for modifying soot particles based on combustion control in a cylinder of an automobile engine according to claim 1, characterized in that: The oxygen-containing fuel in the fuel design is biodiesel, and the oxygen content of biodiesel is greater than 10%.

4. The method for modifying soot particles based on combustion control in a cylinder of an automobile engine according to claim 1, characterized in that: The intake parameter control of the engine combustion process includes the control of the intake temperature and the intake pressure. The intake temperature is 30°C to 50°C after intercooling, and the intake pressure is 0.15MPa to 0.30MPa.

5. The method for modifying soot particles based on combustion control in a cylinder of an automobile engine according to claim 1, characterized in that: The injection strategy control of the engine combustion process adopts a two-stage injection strategy, in which the pre-injection accounts for 5% to 15% and the main injection accounts for 85% to 95%.

6. The method for modifying soot particles based on combustion control in a cylinder of an automobile engine according to claim 1, characterized in that: The operating condition regulation of the engine combustion process includes regulating the engine speed and load, the speed is 1000r / min to 2000r / min, and the load is 0% to 75%.

7. The method for modifying soot particles based on combustion control in a cylinder of an automobile engine according to claim 1, characterized in that: The EGR rate regulated during the engine combustion process is 0% to 50%.

8. The method for modifying soot particles based on combustion control in a cylinder of an automobile engine according to claim 1, characterized in that: The equivalence ratio of the engine combustion process is regulated to be 1.5 to 3.0.

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