Exhaust aftertreatment system, control method thereof and engine system

Abstract

The invention belongs to the technical field of engine tail gas treatment, and discloses an exhaust aftertreatment system, a control method thereof and an engine system. The exhaust aftertreatment system comprises a first control valve, a supercharger, a second control valve and an aftertreatment assembly, the aftertreatment assembly comprises a DOC, a DPF, an electric heater, a mixer, a first-stage SCR, a second-stage SCR, an ASC and a third control valve, an inlet of the first control valve communicates with an engine body, a first outlet of the first control valve communicates with the supercharger, and a second outlet of the second control valve communicates with the third control valve. A second outlet of the first control valve communicates with the second control valve, an outlet of the supercharger communicates with the second control valve, the electric heater is arranged at an outlet of the DPF, a connecting pipeline is arranged between an outlet of the first-stage SCR and an outlet of the second-stage SCR, the third control valve is arranged on the connecting pipeline, and the opening degree of the third control valve is adjustable. By adjusting the exhaust pressure, the flow, the temperature and the on-off of different paths of the exhaust pipeline, the exhaust temperature can be ensured to increase the conversion efficiency, and the fuel economy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of exhaust gas treatment, and in particular to an exhaust gas after-treatment system and a control method thereof, and an engine system. Background Art

[0002] SCR (selective catalytic reduction) technology is an important technical means to control engine NOx emissions. This technology is to inject standard automotive urea solution (urea concentration is 32.5%) into the SCR mixer, and decompose ammonia (NH3) by heat when it meets the high-temperature exhaust gas. NH3 reacts with NOx on the catalyst surface to achieve NOx reduction, and finally the nitrogen atoms in NOx are converted into N2 that is harmless to the environment, thereby reducing the NOx content in the engine exhaust. The NOx conversion efficiency is mainly related to the urea injection amount, exhaust temperature and airspeed. The urea injection amount is proportional to the bare metal NOx, the exhaust temperature is closely related to the engine operating conditions, and the airspeed is positively correlated with the volume of the SCR catalyst.

[0003] The SCR is far away from the engine exhaust manifold, so the temperature of the exhaust gas is lower when it reaches the SCR. Although the SCR can effectively reduce NOx emissions during normal vehicle operation, the engine temperature is low when the vehicle is cold started or running at low speed and low load. When the exhaust gas reaches the SCR, the SCR cannot be heated to the starting temperature, so the NOx treatment effect is not ideal. This results in the NOx content in the engine exhaust gas still being high when the vehicle is cold started or running at low speed and low load.

[0004] Therefore, an exhaust aftertreatment system is needed to solve the problem of how to quickly heat up the exhaust gas of the engine. Summary of the invention

[0005] The purpose of the present invention is to provide an exhaust after-treatment system and a control method thereof, and an engine system. The exhaust after-treatment system controls the exhaust pressure, exhaust flow and exhaust pipeline to achieve rapid temperature rise under extremely low temperature conditions, so that the SCR catalyst is always in a suitable temperature range, effectively reducing the exhaust back pressure and improving fuel economy.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] An exhaust aftertreatment system, the exhaust aftertreatment system includes a first control valve, a supercharger, a second control valve and an aftertreatment component, the inlet of the first control valve is connected to the exhaust port of the engine body, the first outlet of the first control valve is connected to the inlet of the supercharger, the second outlet of the first control valve is connected to the inlet of the second control valve, and the opening of the second outlet of the first control valve and the opening of the second control valve are both adjustable; the aftertreatment component includes a DOC, a DPF, an electric heater, a mixer, a primary SCR, a secondary SCR, an ASC and a third control valve, the DOC, the DPF, the electric heater, the mixer, the primary SCR, the secondary SCR and the ASC are arranged and connected in sequence, the inlet of the DOC is connected to the outlet of the second control valve, a connecting pipeline is arranged between the outlet of the primary SCR and the outlet of the secondary SCR, the third control valve is arranged on the connecting pipeline, and the opening of the third control valve is adjustable.

[0008] As an optional technical solution, the post-processing component further includes a first temperature sensor, which is disposed at the inlet of the DOC and is used to monitor the intake temperature of the DOC.

[0009] As an optional technical solution, the post-processing component also includes a second temperature sensor, a third temperature sensor and a fourth temperature sensor. The second temperature sensor is arranged between the outlet of the DOC and the inlet of the DPF, and the second temperature sensor is used to monitor the intake temperature of the DPF; the third temperature sensor is arranged at the inlet of the first-stage SCR to monitor the intake temperature of the first-stage SCR, and the fourth temperature sensor is arranged at the outlet of the ASC to monitor the outlet temperature of the ASC.

[0010] As an optional technical solution, the first control valve and / or the third control valve is a bypass control valve.

[0011] As an optional technical solution, the second control valve is a throttle valve.

[0012] The present invention also adopts the following technical solutions:

[0013] A control method for controlling the exhaust gas aftertreatment system as described above, the control method comprising the following steps:

[0014] S10, determining the operating temperature state of the engine body;

[0015] S20, determining the exhaust gas flow load state of the engine body;

[0016] S30, adjusting the working states of the first control valve, the second control valve, the third control valve and the electric heater according to the temperature operating state of the engine body and the exhaust gas flow load state of the engine body.

[0017] As an optional technical solution, S10 includes:

[0018] S11, collecting the gas temperature t1 obtained by the first temperature sensor;

[0019] S12, comparing the gas temperature t1 obtained by the first temperature sensor with the first set threshold value T1 to determine whether t1≤T1, if so, determining that the engine body is in an extremely low temperature operating state; if not, entering S13;

[0020] S13, comparing the gas temperature t1 obtained by the first temperature sensor with the second set threshold value T2 to determine whether t1≤T2, if so, determining that the engine body is in a low-temperature operation state; if not, determining that the engine body is in a medium-high temperature operation state;

[0021] S14. Enter S20.

[0022] As an optional technical solution, S20 includes:

[0023] S21, collecting the real-time speed and real-time torque of the engine body, and comparing the real-time speed and real-time torque with the data in the speed-torque-exhaust flow rate MAP of the engine body to obtain the real-time exhaust flow rate EXHx of the engine body;

[0024] S22, obtaining the exhaust gas flow rate load rate η1x according to the real-time exhaust gas flow rate EXHx of the engine body;

[0025] S23, comparing the exhaust gas flow rate load rate η1x with the first flow rate load rate η1, determining whether η1x < η1, if so, determining that the engine body is in a low load state; if not, entering S24;

[0026] S24, comparing the exhaust gas flow rate load rate η1x with the maximum flow rate load rate η2 to determine whether η1x<η2, if so, determining that the engine body is in a medium load state; if not, determining that the engine body is in a high load state;

[0027] S25. Enter S30.

[0028] As an optional technical solution, S30 includes:

[0029] S301, if the engine body is in an extremely low temperature operating state and the engine body is in a low load state, the second outlet of the first control valve is fully opened, the second control valve is partially closed, the third control valve is fully opened, and the electric heater works at full load;

[0030] S302: If the engine body is in an extremely low temperature operating state and the engine body is in a medium load state, the second outlet of the first control valve is closed, the second control valve is partially closed, the third control valve is partially opened, and the electric heater works at full load;

[0031] S303: If the engine body is in an extremely low temperature operating state and the engine body is in a high load state, the second outlet of the first control valve is closed, the second control valve is partially closed, the third control valve is closed, and the electric heater works at full load;

[0032] S311, if the engine body is in a low-temperature operation state and the engine body is in a low-load state, the second outlet of the first control valve is fully opened, the second control valve is partially closed, the third control valve is fully opened, and the electric heater works at a partial load;

[0033] S312: If the engine body is in a low-temperature operation state and the engine body is in a medium-load state, the second outlet of the first control valve is closed, the second control valve is partially closed, the third control valve is partially opened, and the electric heater works at a partial load;

[0034] S313: If the engine body is in a low-temperature operation state and the engine body is in a high-load state, the second outlet of the first control valve is closed, the second control valve is partially closed, the third control valve is closed, and the electric heater works at a partial load;

[0035] S321: If the engine body is in a medium-high temperature operation state and the engine body is in a light load state, the second outlet of the first control valve is closed, the second control valve is fully opened, the third control valve is fully opened, and the electric heater does not work;

[0036] S322: If the engine body is in a medium-high temperature operation state and the engine body is in a medium load state, the second outlet of the first control valve is closed, the second control valve is fully opened, the third control valve is partially opened, and the electric heater does not work;

[0037] S323. If the engine body is in a medium-high temperature operation state and the engine body is in a high load state, the second outlet of the first control valve is closed, the second control valve is fully opened, the third control valve is closed, and the electric heater does not work.

[0038] The present invention also adopts the following technical solutions:

[0039] An engine system comprises an engine body and the exhaust after-treatment system as described above, wherein the exhaust after-treatment system is arranged downstream of the engine body.

[0040] Beneficial effects of the present invention:

[0041] The invention discloses an exhaust gas aftertreatment system, which comprises a first control valve, a supercharger, a second control valve and an aftertreatment component. The aftertreatment component comprises a DOC, a DPF, an electric heater, a mixer, a first-stage SCR, a second-stage SCR and an ASC and a third control valve which are connected in sequence. The first control valve comprises an inlet, a first outlet and a second outlet. The inlet of the first control valve is communicated with the exhaust port of an engine body, the first outlet of the first control valve is communicated with the inlet of the supercharger, the second outlet of the first control valve is communicated with the inlet of the second control valve, the outlet of the supercharger is communicated with the inlet of the second control valve, the opening of the second outlet of the first control valve is adjustable, the inlet of the DOC is connected to the outlet of the second control valve, the electric heater is arranged at the outlet of the DPF and is used to heat the gas at the outlet of the DPF, a connecting pipeline is arranged between the outlet of the first-stage SCR and the outlet of the second-stage SCR, the third control valve is arranged in the connecting pipeline, and the opening of the third control valve is adjustable. This exhaust after-treatment system adjusts the exhaust pressure, flow and the opening and closing of different routes of the exhaust pipe, so that it can quickly heat up under extremely low temperature conditions, so that the SCR catalyst is always in the appropriate temperature range, effectively reducing exhaust back pressure and improving fuel economy.

[0042] The present invention also discloses a control method for controlling the above-mentioned exhaust after-treatment system, which adjusts the working states of the first control valve, the second control valve, the third control valve and the electric heater according to the temperature state and load state of the engine body, thereby achieving a rapid increase in exhaust temperature and reducing exhaust back pressure, thereby improving fuel economy.

[0043] The present invention also discloses an engine system, including an engine body and the above-mentioned exhaust after-treatment system. The exhaust after-treatment system is arranged downstream of the engine body, which can not only achieve a rapid increase in exhaust temperature so that the SCR catalyst is always in a suitable temperature range, but also fully utilize the performance of the SCR catalyst by controlling the exhaust flow path, effectively reduce exhaust back pressure, and improve fuel economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic structural diagram of an exhaust gas aftertreatment system according to an embodiment of the present invention;

[0045] Figure 2 is a flow chart of a control method according to an embodiment of the present invention;

[0046] Figure 3 It is a control logic diagram of the control method of an embodiment of the present invention.

[0047] In the figure:

[0048] 1. Exhaust after-treatment system; 2. Engine body;

[0049] 10. First control valve; 11. First pipeline; 12. Second pipeline; 13. Third pipeline;

[0050] 20. Supercharger;

[0051] 30. Second control valve;

[0052] 40. Post-treatment component; 41. DOC; 411. First temperature sensor; 42. DPF; 421. Second temperature sensor; 43. Electric heater; 44. Mixer; 441. Urea nozzle; 45. Primary SCR; 451. Third temperature sensor; 46. Secondary SCR; 47. ASC; 471. Fourth temperature sensor; 48. Third control valve; 481. Connecting pipeline. DETAILED DESCRIPTION

[0053] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0054] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0056] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0057] like Figure 1 As shown, in this embodiment, an exhaust aftertreatment system 1 is provided, which includes a first control valve 10, a supercharger 20, a second control valve 30 and an aftertreatment component 40, wherein the inlet of the first control valve 10 is communicated with the exhaust port of the engine body 2, the first outlet of the first control valve 10 is communicated with the inlet of the supercharger 20, the second outlet of the first control valve 10 is communicated with the inlet of the second control valve 30, the outlet of the supercharger 20 is communicated with the inlet of the second control valve 30, and the second outlet of the first control valve 10 and the opening of the second control valve 20 are both adjustable; the aftertreatment component 40 includes DO C41, DPF42, electric heater 43, mixer 44, primary SCR45, secondary SCR46, ASC47 and third control valve 48, DOC41, DPF42, electric heater 43, mixer 44, primary SCR45, secondary SCR46 and ASC47 are arranged in sequence and connected, the inlet of DOC41 is connected to the outlet of the second control valve 30, a connecting pipeline 481 is arranged between the outlet of the primary SCR45 and the outlet of the secondary SCR46, the third control valve 48 is arranged on the connecting pipeline 481, and the opening degree of the third control valve 48 is adjustable.

[0058] Specifically, in this embodiment, the inlet of the first control valve 10 is connected to the exhaust port of the engine body 2 through the first pipeline 11, the first outlet of the first control valve 10 is connected to the inlet of the supercharger 20, the second outlet of the first control valve 10 is connected to the inlet of the second control valve 30 through the second pipeline 12, and the outlet of the supercharger 20 is connected to the second pipeline 12 through the third pipeline 13. When the engine body 2 is operating normally, the exhaust gas energy discharged by the engine body 2 will be used to drive the turbine to rotate. Therefore, the exhaust gas is discharged through the supercharger 20, which will reduce the exhaust gas temperature; when the engine body is in an extremely low temperature operating state and the engine body 2 is under a small load, that is, the exhaust gas flow rate is small, the exhaust gas energy required by the supercharger 20 is small. At this time, a part of the exhaust gas entering the supercharger 20 is bypassed through the second outlet of the first control valve 10, and this part of the higher temperature exhaust gas is sent to the inlet of the second control valve 30 through the second outlet of the first control valve 10, thereby increasing the temperature of the exhaust gas in the third pipeline 13; the outlet of the second control valve 30 is connected to the inlet of DOC41, and the exhaust gas pressure in the third pipeline 13 is adjusted by adjusting the opening of the second control valve 30, thereby increasing the exhaust gas temperature in the third pipeline 13. The exhaust gas in the third pipeline 13 passes through the second control valve 30 and enters the DOC41, DPF42, electric heater 43 in sequence, and then enters the mixer 44. The mixer 44 is provided with a urea nozzle 441, and the mixer 44 is connected to the first-stage SCR45; the electric heater 43 is used to heat the gas at the outlet of the DPF42, which can further increase the temperature of the gas entering the SCR in the low-temperature stage, thereby ensuring that the reaction temperature in the SCR is increased when the engine body 2 is running at low temperature, thereby improving the NOx conversion efficiency and effectively controlling the NOx emissions in the low-temperature operation stage. The outlet of the first-stage SCR45 and the outlet of the second-stage SCR46 are connected via a connecting pipe 481. The third control valve 48 is arranged on the connecting pipe 481. The third control valve 48 can control the on-off of the connecting pipe 481 and adjust the flow rate of the gas in the connecting pipe 481. When the third control valve 48 is opened, the connecting pipe 481 is in a passage state. After the exhaust gas passes through the first-stage SCR45, part of the exhaust gas enters the connecting pipe 481 and directly enters the ASC47. This setting can allow part of the exhaust gas to bypass the second-stage SCR46 and directly enter the ASC47, which can reduce the overall exhaust back pressure. The ASC47 is located at the end of the entire post-treatment system and can process the ammonia escaping from the SCR to convert it into nitrogen to avoid secondary pollution to the environment.

[0059] Specifically, in this embodiment, the mixer 44 is provided with a urea nozzle 441 for spraying urea into the mixer 44, and the electric heater 43 is arranged upstream of the mixer 44, which can prevent urea from forming crystals on the electric heater 43 due to thermal decomposition, thereby affecting the normal operation of the electric heater 43, thereby ensuring the normal operation of the exhaust after-treatment system 1.

[0060] Furthermore, the post-treatment component 40 also includes a first temperature sensor 411, which is disposed at the inlet of the DOC41 and is used to monitor the gas temperature at the inlet of the DOC41. Specifically, in the present embodiment, the first temperature sensor 411 is disposed at the inlet of the DOC41 and is used to monitor the gas temperature at the inlet of the DOC14. The inlet of the DOC41 is connected to the outlet of the second control valve 30. The temperature at the inlet of the DOC41 can basically reflect the operating temperature state of the engine body 2. Then, the opening of the first control valve 10, the second control valve 30 and the third control valve 48 and the working state of the electric heater 43 are controlled by the temperature value obtained by the first temperature sensor 411, so as to adjust the temperature of the gas entering the SCR and effectively control the conversion efficiency of the SCR.

[0061] Furthermore, the exhaust aftertreatment system 1 also includes a second temperature sensor 421, a third temperature sensor 451 and a fourth temperature sensor 471. The second temperature sensor 421 is arranged between the outlet of DOC41 and the inlet of DPF42, and the second temperature sensor 421 is used to monitor the gas temperature at the inlet of DPF42; the third temperature sensor 451 is arranged at the inlet of the first-stage SCR45, and is used to monitor the gas temperature at the inlet of the first-stage SRC45; the fourth temperature sensor 471 is arranged at the outlet of ASC47, and is used to monitor the gas temperature at the outlet of ASC47. Specifically, in this embodiment, the second temperature sensor 421 is arranged between the outlet of DOC41 and the inlet of DPF42, and can monitor the temperature of the gas entering DPF42 in real time, so as to facilitate the control of its temperature when DPF42 is regenerated, thereby ensuring the normal progress of the regeneration process; the third temperature sensor 451 is arranged at the inlet of the first-stage SCR45, and the first-stage SCR45 is located downstream of the electric heater 43. By observing the temperature values ​​of the second temperature sensor 421 and the third temperature sensor 451, it can be determined whether the electric heater 43 is working normally; the fourth temperature sensor 471 is arranged at the outlet of ASC47, and can monitor the outlet temperature of ASC47, and can also reflect the outlet temperature of the second-stage SCR46, while the third temperature sensor 451 is arranged at the inlet of the first-stage SCR45. By comparing the temperature value of the third temperature sensor 451 with the temperature value of the fourth temperature sensor 471, it can be basically determined whether the temperature of the SCR carrier is in a suitable stable range, thereby ensuring the conversion efficiency of the SCR.

[0062] Further, the first control valve 10 and / or the third control valve 48 are bypass control valves. Specifically, in this embodiment, the inlet and the first outlet of the first control valve 10 form a first channel, the first outlet is connected to the inlet of the supercharger 20, the inlet and the second outlet form a second channel, the second outlet is connected to the inlet of the second control valve 30, the first channel is a normally open channel, the opening of the second channel is adjustable, and the exhaust gas flow through the first channel and the second channel can be controlled by controlling the opening of the second channel, thereby controlling the exhaust gas flow entering the supercharger 20, so as to achieve the purpose of controlling the temperature of the exhaust gas in the third pipeline 13; the third control valve 48 is arranged on the connecting pipeline 481, and the third control valve 48 is normally closed, and is used to control part of the exhaust gas to bypass the secondary SCR46 and directly enter the ASC47 to improve the exhaust efficiency when necessary.

[0063] Furthermore, the second control valve 30 is a throttle valve. Specifically, in this embodiment, the second control valve 30 is a throttle valve, and by adjusting the opening of the second control valve 30, the exhaust resistance of the entire engine body 2 can be controlled, thereby facilitating the adjustment of the temperature of the gas.

[0064] Specifically, in the present embodiment, the exhaust aftertreatment system 1 is controlled by a control component ECU of the engine body 2. The ECU is electrically connected to the first control valve 10, the second control valve 30, the third control valve 48, the electric heater 43, the first temperature sensor 411, the second temperature sensor 421, the third temperature sensor 451 and the fourth temperature sensor 471. The ECU can receive data from the first temperature sensor 411, the second temperature sensor 421, the third temperature sensor 451 and the fourth temperature sensor 471, and can control the working states of the first control valve 10, the second control valve 30, the third control valve 48 and the electric heater 43.

[0065] like Figure 2 and Figure 3 As shown, the present invention also provides a control method for controlling the above-mentioned exhaust gas after-treatment system 1, and the control method includes the following steps.

[0066] S10: Determine the operating state of the engine body 2.

[0067] S11 , collecting the gas temperature t1 obtained by the first temperature sensor 411 .

[0068] Specifically, in this embodiment, a first temperature sensor 411 is provided at the inlet of the DOC 41. The first temperature sensor 411 can monitor the temperature at the inlet of the DOC 41 to obtain the gas temperature t1, and then determine the operating state of the engine body 2 according to the gas temperature t1.

[0069] In this embodiment, the ECU collects the real-time temperature of the first temperature sensor 411 while also collecting the real-time temperature values ​​of the second temperature sensor 421, the third temperature sensor 451 and the fourth temperature sensor 471. The real-time temperature of the third temperature sensor 451 can reflect whether the electric heater 43 is working normally, thereby ensuring the normal operation of the exhaust after-treatment system 1.

[0070] S12, comparing the gas temperature t1 obtained by the first temperature sensor 411 with the first set threshold value T1 to determine whether t1≤T1, if so, determining that the engine body 2 is in an extremely low temperature operating state; if not, entering S13.

[0071] Specifically, in this embodiment, a first temperature threshold T1 is set, and the first temperature threshold T1 can be calibrated according to actual conditions. In this embodiment, T1 is taken as 200°C. The gas temperature at the inlet of the DOC41 monitored by the first temperature sensor 411 is t1, and t1 is compared with T1. When t1<T1, the exhaust gas temperature discharged from the engine body 2 at this time is lower than T1, and it is determined that the engine body 2 is in an extremely low temperature operation state.

[0072] S13, compare the gas temperature t1 obtained by the first temperature sensor 411 with the second set threshold value T2 to determine whether t1≤T2, if so, determine that the engine body 2 is in a low-temperature operation state; if not, determine that the engine body 2 is in a medium-high temperature operation state.

[0073] Specifically, in this embodiment, a second temperature threshold T2 is set, and the second temperature threshold T2 can be calibrated according to actual conditions. In this embodiment, T2 is taken as 250°C. Then, the gas temperatures t1 and T2 at the inlet of the DOC41 monitored by the first temperature sensor 411 are compared. When t1≤T2, the exhaust gas temperature discharged from the engine body 2 is lower than T2, and it is determined that the engine body 2 is in a low-temperature operation state; when t1>T2, it indicates that the exhaust gas temperature discharged from the engine body 2 is higher than T2, and it is determined that the engine body 2 is in a medium-high temperature operation state.

[0074] S14. Enter S20.

[0075] S20: Determine the load state of the engine body 2.

[0076] S21, collecting the real-time speed and real-time torque of the engine body 2, and comparing the real-time speed and real-time torque with the data in the speed-torque-exhaust flow MAP of the engine body 2 to obtain the real-time exhaust flow EXHx of the engine body 2.

[0077] Specifically, in this embodiment, a table corresponding to the speed-torque-exhaust flow rate is obtained according to the different speeds, different torques and corresponding exhaust flow rates during the operation of the engine body 2, and it is calibrated to obtain the speed-torque-exhaust flow rate MAP stored in the ECU. When the engine body 2 is working, the real-time speed and real-time torque of the engine body 2 are collected and compared with the speed-torque-exhaust flow rate MAP to obtain the real-time exhaust flow rate EXHx of the engine body 2.

[0078] S22 . Obtain the exhaust gas flow rate load rate η1x based on the real-time exhaust gas flow rate EXHx of the engine body 2 .

[0079] Specifically, in this embodiment, the exhaust gas flow load state of the engine body 2 is determined by the real-time exhaust gas flow load rate η1x, which is the ratio of the real-time exhaust gas flow of the engine body 2 to the maximum exhaust gas flow of the engine body 2.

[0080] The calculation formula of real-time exhaust gas flow load rate η1x is:

[0081] η1x=EXHx / EXHmax*100%

[0082] Among them, EXHx is the real-time exhaust gas flow rate of the engine body 2, and EXHmax is the maximum exhaust gas flow rate of the engine body 2.

[0083] S23, compare the exhaust gas flow load rate η1x with the first flow load rate η1 to determine whether η1x<η1. If so, determine that the engine body 2 is in a low-load state; if not, enter S24.

[0084] Specifically, in this embodiment, the conversion of all NOx in the exhaust gas can be completed by relying only on the first-stage SCR45. At this time, the flow load rate is the first flow load rate η1. When η1x<η1, it means that the exhaust gas flow is small, and the flow load rate of the engine body 2 is low. The conversion can be completed by relying only on the first-stage SCR45. At this time, the third control valve 48 is fully opened to allow the exhaust gas to bypass the second-stage SCR46 through the connecting pipe 481 and enter the ASC47, thereby ensuring the NOx conversion efficiency while reducing the SCR back pressure.

[0085] The calculation formula of the first flow load rate η1 is:

[0086] η1=EXHscr1 / EXHmax*100%

[0087] Among them, EXHscr1 is the maximum exhaust gas flow rate (kg / h) based on the volume of the first-stage SCR45.

[0088] The calculation formula for the maximum exhaust gas flow rate EXHscr1 based on the volume of the first-stage SCR45 is:

[0089] EXHscr1=Tmax*Vscr1 / 1000*1.29

[0090] Wherein, Tmax is the maximum air velocity (- / h), and Vscr1 is the volume of the first-stage SCR45 (L).

[0091] The calculation formula for the maximum airspeed Tmax is:

[0092] Tmax=(EXHmax / 1.29*1000) / Vscr 总

[0093] Among them, Vscr 总 is the volume of all SCR catalysts (L), Vscr 总 =Vscr1+Vscr2.

[0094] S24, compare the exhaust gas flow load rate η1x with the second flow load rate η2 to determine whether η1x<η2, if so, determine that the engine body 2 is in a medium load state; if not, determine that the engine body 2 is in a maximum load state.

[0095] Specifically, in this embodiment, when the real-time exhaust gas flow EXHx of the engine body 2 is large, if η1x<η2 is satisfied, the first-stage SCR45 cannot completely convert the NOx in the exhaust gas, and the first-stage SCR45 and the second-stage SCR46 need to be converted at the same time. By controlling the opening of the third control valve 48, and then adjusting the opening of the connecting pipe 481, a part of the exhaust gas entering the second-stage SCR46 is bypassed, so that both the first-stage SCR45 and the second-stage SCR46 can participate in the conversion, ensuring the conversion efficiency, and reducing the back pressure of part of the second-stage SCR46.

[0096] When η1x is close to η2, it indicates that the exhaust gas flow load of the engine body 2 is very large. At this time, the third control valve 48 is controlled to be completely closed. It is necessary to ensure that all the exhaust gas passes through the first-stage SCR45 and the second-stage SCR46 in sequence to meet the NOx conversion efficiency.

[0097] The calculation formula of the second flow load rate η2 is:

[0098] η2=(EXHmax*γ) / EXHmax*100%

[0099] Wherein, γ is the maximum exhaust gas flow rate ratio, which can be calibrated according to the situation. In this embodiment, γ is taken as 90% as an example.

[0100] S24. Enter S30.

[0101] After the operating temperature state and exhaust gas flow load state of the engine body 2 are determined, it is necessary to adjust the working states of the first control valve 10, the second control valve 30, the third control valve 48 and the electric heater 43 according to the current state of the engine body 2 to improve the conversion efficiency of NOx in the exhaust gas.

[0102] S30 , adjusting the working states of the first control valve 10 , the second control valve 30 , the third control valve 48 and the electric heater 43 according to the operating temperature state of the engine body 2 and the exhaust gas flow load state of the engine body 2 .

[0103] Specifically, the operating temperature state of the engine body 2 can directly reflect the temperature of the exhaust gas discharged by the engine body 2, and the exhaust gas flow load state of the engine body 2 can reflect the flow rate of the exhaust gas discharged by the engine body 2. The working states of the first control valve 10, the second control valve 30, the third control valve 48 and the electric heater 43 are adjusted according to these two parameters, which can effectively adjust the temperature of the exhaust gas, and the heating rate is relatively fast. While improving the NOx conversion efficiency during low-temperature operation, it can also effectively reduce the exhaust back pressure.

[0104] S30 specifically includes the following contents.

[0105] S301. If the engine body 2 is in an extremely low temperature operating state and the engine body 2 is in a low load state, the second outlet of the first control valve 10 is opened, the second control valve 30 is partially closed, the third control valve 48 is fully opened, and the electric heater 43 works at full load.

[0106] Specifically, the engine body 2 is in an extremely low temperature operation state and the engine body 2 is in a low load state. At this time, the exhaust temperature of the engine body 2 is extremely low, and the exhaust volume of the engine body 2 is small; the second outlet of the first control valve 10 is opened, so that part of the exhaust gas enters the third pipeline 13 through the second pipeline 12, which can reduce the energy loss of this part of the exhaust gas, thereby increasing the temperature rise of the exhaust gas in the third pipeline 13; and the second control valve 30 is partially closed, increasing the exhaust gas pressure in the third pipeline 13, which is beneficial to the temperature rise of the exhaust gas in the third pipeline 13; because the first-level SCR45 can fully guarantee the conversion of NOx in the exhaust gas in the low load operation state, the third control valve 48 is fully opened, and most of the exhaust gas passes through the connecting pipeline 481 and bypasses the second-level SCR46 to directly enter the ASC47, reducing the exhaust back pressure caused by the second-level SCR46, and at the same time the electric heater 43 works at full load to heat the exhaust gas entering the first-level SCR45, ensuring the conversion efficiency of the SCR, and at the same time helping to reduce the overall back pressure.

[0107] S302: If the engine body 2 is in an extremely low temperature operating state and the engine body 2 is in a medium load state, the second outlet of the first control valve 10 is closed, the second control valve 30 is partially closed, the third control valve 48 is partially opened, and the electric heater 43 works at full load.

[0108] Specifically, the engine body 2 is in an extremely low temperature operating state and the engine body 2 is in a medium load state. At this time, the exhaust temperature of the engine body 2 is extremely low, and the exhaust volume of the engine body 2 is medium; since the load rate is medium, there are certain requirements for the boost pressure of the supercharger 20. At this time, the second outlet of the first control valve 10 is closed, and the second control valve 30 is partially closed, which can reduce the outflow of exhaust gas in the third pipeline 13, thereby increasing the exhaust gas pressure in the third pipeline 13, and thus facilitating the temperature rise of the exhaust gas in the third pipeline 13; since the primary SCR45 has insufficient capacity to treat NOx in the exhaust gas during the medium load operation state, it is necessary to use the processing capacity of part of the secondary SCR46, and partially open the third control valve 48 to bypass a small part of the exhaust gas and directly enter the ASC47, slightly reducing the exhaust back pressure caused by the secondary SCR46, and at the same time, the electric heater 43 works at full load to heat the exhaust gas entering the primary SCR45, ensuring the conversion efficiency of the SCR while helping to reduce the back pressure.

[0109] S303. If the engine body 2 is in an extremely low temperature operating state and the engine body 2 is in a high load state, the second outlet of the first control valve 10 is closed, the second control valve 30 is partially closed, the third control valve 48 is closed, and the electric heater 43 works at full load.

[0110] Specifically, the engine body 2 is in an extremely low temperature operating state and the engine body 2 is in a high load state. At this time, the exhaust temperature of the engine body 2 is extremely low, and the exhaust volume of the engine body 2 is large; due to the high load rate, the boost pressure of the supercharger 20 needs to be guaranteed, and at this time the second outlet of the first control valve 10 is closed; the second control valve 30 is partially closed, which can increase the pressure of the exhaust gas in the third pipeline 13, and thus is beneficial to the temperature increase of the exhaust gas in the third pipeline 13; because the first-level SCR45 and the second-level SCR46 need to be used in combination in the high load operating state to ensure that the NOx in the exhaust gas is completely treated, at this time, the third control valve 48 is completely closed to ensure that the exhaust gas passes through the first-level SCR45 and the second-level SCR46 in turn to jointly treat NOx, and at the same time the electric heater 43 works at full load to heat the exhaust gas entering the first-level SCR45, thereby improving the conversion efficiency of SCR under low temperature and high load.

[0111] S311. If the engine body 2 is in a low-temperature operation state and the engine body 2 is in a low-load state, the second outlet of the first control valve 10 is opened, the second control valve 30 is partially closed, the third control valve 48 is fully opened, and the electric heater 43 works at partial load.

[0112] Specifically, the engine body 2 is in a low-temperature operation state and the engine body 2 is in a low-load state. At this time, the exhaust temperature of the engine body 2 is slightly low, and the exhaust volume of the engine body 2 is small; the second outlet of the first control valve 10 is opened, so that part of the exhaust gas enters the third pipeline 13 through the second pipeline 12, which can reduce the energy loss of this part of the exhaust gas, and thus is beneficial to the temperature increase of the exhaust gas in the third pipeline 13; the second control valve 30 is partially closed, which can reduce the outflow of exhaust gas in the third pipeline 13, and then increase the exhaust gas pressure in the third pipeline 13, which is beneficial to the temperature increase of the exhaust gas in the third pipeline 13; the third control valve 48 is fully opened, and most of the exhaust gas passes through the connecting pipeline 481 and bypasses the secondary SCR46 to directly enter the ASC47, reducing the exhaust back pressure caused by the secondary SCR46, and at the same time the electric heater 43 works at partial load to heat the exhaust gas entering the primary SCR45, ensuring the conversion efficiency of the SCR while helping to reduce the overall back pressure.

[0113] S312. If the engine body 2 is in a low-temperature operation state and the engine body 2 is in a medium-load state, the second outlet of the first control valve 10 is closed, the second control valve 30 is partially closed, the third control valve 48 is partially opened, and the electric heater 43 works at partial load.

[0114] Specifically, the engine body 2 is in a low-temperature operating state and the engine body 2 is in a medium-load state. At this time, the exhaust temperature of the engine body 2 is slightly low, and the exhaust volume of the engine body 2 is in the middle; since the load rate is in the middle, there are certain requirements for the boost pressure of the supercharger 20, and at this time the second outlet of the first control valve 10 is closed; the second control valve 30 is partially closed, which can reduce the outflow of exhaust gas in the third pipeline 13, thereby increasing the exhaust gas pressure in the third pipeline 13, and thus facilitating the temperature rise of the exhaust gas in the third pipeline 13; since the primary SCR45 has insufficient ability to process NOx in the exhaust gas during the medium-load operating state, it is necessary to use the processing capacity of part of the secondary SCR46, and partially open the third control valve 48, bypass a small part of the exhaust gas to bypass the secondary SCR46 and directly enter the ASC47, slightly reducing the exhaust back pressure caused by the secondary SCR46, and at the same time the electric heater 43 works at partial load to heat the exhaust gas entering the primary SCR45, ensuring the conversion efficiency of the SCR while facilitating reducing the back pressure.

[0115] S313. If the engine body 2 is in a low-temperature operation state and the engine body 2 is in a high-load state, the second outlet of the first control valve 10 is closed, the second control valve 30 is partially closed, the third control valve 48 is closed, and the electric heater 43 works at partial load.

[0116] Specifically, the engine body 2 is in a low-temperature operating state and the engine body 2 is in a high-load state. At this time, the exhaust temperature of the engine body 2 is slightly low, and the exhaust volume of the engine body 2 is the largest. Due to the high load rate, the boost pressure of the supercharger 20 needs to be guaranteed. At this time, the second outlet of the first control valve 10 is closed; the second control valve 30 is partially closed, which can increase the pressure of the exhaust gas in the third pipeline 13, and thus is beneficial to the temperature increase of the exhaust gas in the third pipeline 13; because the first-level SCR45 and the second-level SCR46 need to be used in combination in the high-load operating state to ensure that all NOx in the exhaust gas is treated, at this time, the third control valve 48 is completely closed, and the exhaust gas needs to pass through the first-level SCR45 and the second-level SCR46 in turn to ensure sufficient conversion efficiency of the SCR. At the same time, the electric heater 43 works at partial load to heat the exhaust gas entering the first-level SCR45 to improve the conversion efficiency of the SCR under low temperature and high load.

[0117] S321. If the engine body 2 is in a medium-high temperature operation state and the engine body 2 is in a low load state, the second outlet of the first control valve 10 is closed, the second control valve 30 is fully opened, the third control valve 48 is fully opened, and the electric heater 43 does not work.

[0118] Specifically, the engine body 2 is in a medium-high temperature operating state and the engine body 2 is in a low load state. At this time, the exhaust temperature of the engine body 2 is relatively high and there is no need to increase the exhaust temperature. The second outlet of the first control valve 10 is closed and the second control valve 30 is fully opened. The current engine body 2 has a small load and a high exhaust temperature. The first-stage SCR45 can fully guarantee the conversion efficiency of the SCR. The third control valve 48 is fully opened, so that the exhaust gas passes through the connecting pipe 481 and bypasses the second-stage SCR46 to directly enter the ASC47, thereby reducing the exhaust back pressure caused by the second-stage SCR46. At the same time, the electric heater does not work.

[0119] S322. If the engine body 2 is in a medium-high temperature operation state and the engine body 2 is in a medium load state, the second outlet of the first control valve 10 is closed, the second control valve 30 is fully opened, the third control valve 48 is partially opened, and the electric heater 43 does not work.

[0120] Specifically, the engine body 2 is in a medium-high temperature operating state and the engine body 2 is in a medium load state. At this time, the exhaust temperature of the engine body 2 is relatively high and there is no need to increase the exhaust temperature. The second outlet of the first control valve 10 is closed and the second control valve 30 is fully opened. Since the primary SCR45 has insufficient capacity to process NOx in the exhaust gas during the medium load operation state, it is necessary to use part of the processing capacity of the secondary SCR46. At this time, the third control valve 48 is partially opened, and part of the exhaust gas bypasses the secondary SCR46 and directly enters the ASC47, slightly reducing the exhaust back pressure caused by the secondary SCR46, and the electric heater does not work.

[0121] S323. If the engine body 2 is in a medium-high temperature operation state and the engine body 2 is in a high load state, the second outlet of the first control valve 10 is closed, the second control valve 30 is fully opened, the third control valve 48 is closed, and the electric heater 43 does not work.

[0122] Specifically, the engine body 2 is in a medium-high temperature operating state and the engine body 2 is in a high load state. At this time, the exhaust temperature of the engine body 2 is relatively high and there is no need to increase the exhaust temperature. The second outlet of the first control valve 10 is closed and the second control valve 30 is fully opened. Since the first-stage SCR45 and the second-stage SCR46 need to be used in combination in the high load operating state to ensure that the NOx in the exhaust gas is completely treated, at this time, the third control valve 48 is completely closed to ensure that the exhaust gas passes through the first-stage SCR45 and the second-stage SCR46 in sequence to ensure that the NOx is completely treated. At the same time, the electric heater does not work.

[0123] Preferably, in this embodiment, before the engine body 2 is started, the second outlet of the first control valve 10 is closed, the second control valve 30 is fully opened, the third control valve 48 is closed, and the electric heater 43 does not work.

[0124] The present embodiment also provides an engine system, the vehicle includes an engine body 2, and also includes the above-mentioned exhaust after-treatment system 1, and the exhaust after-treatment system 1 is arranged downstream of the engine body 2. This after-treatment system can quickly increase the exhaust gas temperature by adjusting the exhaust gas pressure, flow rate, temperature in the exhaust gas pipeline and adjusting the direction of the exhaust gas in the pipeline by adjusting the first control valve 10, the second control valve 30, the third control valve 48 and the electric heater 43, ensuring that the SCR is always in a suitable temperature area, and reducing the exhaust gas pressure, thereby improving the fuel economy of the vehicle.

[0125] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An exhaust gas aftertreatment system, characterized in that: The exhaust aftertreatment system (1) comprises a first control valve (10), a supercharger (20), a second control valve (30) and an aftertreatment component (40), wherein the inlet of the first control valve (10) is communicated with the exhaust port of the engine body (2), the first outlet of the first control valve (10) is communicated with the inlet of the supercharger (20), the second outlet of the first control valve (10) is communicated with the inlet of the second control valve (30), the outlet of the supercharger (20) is communicated with the inlet of the second control valve (30), and the opening of the second outlet of the first control valve (10) and the opening of the second control valve (30) are both adjustable; the aftertreatment component (40) comprises a DOC (41), a DPF (42), an electric heater The invention relates to a device (43), a mixer (44), a primary SCR (45), a secondary SCR (46), an ASC (47) and a third control valve (48), wherein the DOC (41), the DPF (42), the electric heater (43), the mixer (44), the primary SCR (45), the secondary SCR (46) and the ASC (47) are arranged in sequence and are connected to each other, wherein the inlet of the DOC (41) is connected to the outlet of the second control valve (30), a connecting pipeline (481) is arranged between the outlet of the primary SCR (45) and the outlet of the secondary SCR (46), and the third control valve (48) is arranged on the connecting pipeline (481), and the opening degree of the third control valve (48) is adjustable.

2. The exhaust gas aftertreatment system according to claim 1, characterized in that: The post-treatment component (40) further comprises a first temperature sensor (411), wherein the first temperature sensor (411) is disposed at the inlet of the DOC (41), and the first temperature sensor (411) is used to monitor the gas temperature at the inlet of the DOC (41).

3. The exhaust gas aftertreatment system according to claim 2, characterized in that: The post-treatment component (40) further comprises a second temperature sensor (421), a third temperature sensor (451) and a fourth temperature sensor (471), wherein the second temperature sensor (421) is arranged between the outlet of the DOC (41) and the inlet of the DPF (42), and the second temperature sensor (421) is used to monitor the gas temperature at the inlet of the DPF (42); the third temperature sensor (451) is arranged at the inlet of the first-stage SCR (45) and is used to monitor the gas temperature at the inlet of the first-stage SCR (45); and the fourth temperature sensor (471) is arranged at the outlet of the ASC (47) and is used to monitor the gas temperature at the outlet of the ASC (47).

4. The exhaust gas aftertreatment system according to claim 1, characterized in that: The first control valve (10) and / or the third control valve (48) are bypass control valves.

5. The exhaust gas aftertreatment system according to claim 1, characterized in that: The second control valve (30) is a throttle valve.

6. A control method for controlling the exhaust gas aftertreatment system according to claim 3, characterized in that: The control method comprises the following steps: S10, determining the operating temperature state of the engine body (2); S20, determining the load state of the engine body (2); S30, adjusting the working states of the first control valve (10), the second control valve (30), the third control valve (48) and the electric heater (43) according to the operating temperature state of the engine body (2) and the exhaust gas flow load state of the engine body (2).

7. The control method according to claim 6, characterized in that: S10 includes: S11, collecting the gas temperature t1 obtained by the first temperature sensor (411); S12, comparing the gas temperature t1 obtained by the first temperature sensor (411) with the first set threshold value T1 to determine whether t1≤T1; if so, determining that the engine body (2) is in an extremely low temperature operating state; if not, proceeding to S13; S13, comparing the gas temperature t1 obtained by the first temperature sensor (411) with the second set threshold value T2 to determine whether t1≤T2, and if so, determining that the engine body (2) is in a low-temperature operation state; if not, determining that the engine body (2) is in a medium-high-temperature operation state; S14. Enter S20.

8. The control method according to claim 7, characterized in that: The S20 includes: S21, collecting the real-time speed and real-time torque of the engine body (2), and comparing the real-time speed and real-time torque with the data in the speed-torque-exhaust gas flow MAP of the engine body (2), to obtain the real-time exhaust gas flow EXHx of the engine body (2); S22, obtaining an exhaust gas flow rate load rate η1x according to the real-time exhaust gas flow rate EXHx of the engine body (2); S23, comparing the exhaust gas flow rate load rate η1x with the first flow rate load rate η1, determining whether η1x < η1, if so, determining that the engine body (2) is in a low load state; if not, entering S24; S24, comparing the exhaust gas flow rate load rate η1x with the maximum flow rate load rate η2, and determining whether η1x < η2; if so, determining that the engine body (2) is in a medium load state; if not, determining that the engine body (2) is in a high load state; S25. Enter S30.

9. The control method according to claim 8, characterized in that: S30 includes: S301. If the engine body (2) is in an extremely low temperature operating state and the engine body (2) is in a low load state, the second outlet of the first control valve (10) is fully opened, the second control valve (30) is partially closed, the third control valve (48) is fully opened, and the electric heater (43) works at full load; S302: If the engine body (2) is in an extremely low temperature operating state and the engine body (2) is in a medium load state, the second outlet of the first control valve (10) is closed, the second control valve (30) is partially closed, the third control valve (48) is partially opened, and the electric heater (43) operates at full load; S303, if the engine body (2) is in an extremely low temperature operating state and the engine body (2) is in a high load state, the second outlet of the first control valve (10) is closed, the second control valve (30) is partially closed, the third control valve (48) is closed, and the electric heater (43) operates at full load; S311. If the engine body (2) is in a low-temperature operating state and the engine body (2) is in a low-load state, the second outlet of the first control valve (10) is fully opened, the second control valve (30) is partially closed, the third control valve (48) is fully opened, and the electric heater (43) operates at a partial load; S312: If the engine body (2) is in a low-temperature operating state and the engine body (2) is in a medium-load state, the second outlet of the first control valve (10) is closed, the second control valve (30) is partially closed, the third control valve (48) is partially opened, and the electric heater (43) operates at a partial load; S313, if the engine body (2) is in a low-temperature operating state and the engine body (2) is in a high-load state, the second outlet of the first control valve (10) is closed, the second control valve (30) is partially closed, the third control valve (48) is closed, and the electric heater (43) operates at a partial load; S321. If the engine body (2) is in a medium-high temperature operation state and the engine body (2) is in a low load state, the second outlet of the first control valve (10) is closed, the second control valve (30) is fully opened, the third control valve (48) is fully opened, and the electric heater (43) is not operated; S322: If the engine body (2) is in a medium-high temperature operation state and the engine body (2) is in a medium load state, the second outlet of the first control valve (10) is closed, the second control valve (30) is fully opened, the third control valve (48) is partially opened, and the electric heater (43) is not operated; S323. If the engine body (2) is in a medium-high temperature operating state and the engine body (2) is in a high load state, the second outlet of the first control valve (10) is closed, the second control valve (30) is fully opened, the third control valve (48) is closed, and the electric heater (43) does not work.

10. An engine system, characterized in that The engine system comprises an engine body (2) and an exhaust gas after-treatment system (1) according to any one of claims 1 to 5, wherein the exhaust gas after-treatment system (1) is arranged downstream of the engine body (2).

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