CN110206621B

CN110206621B - Wide-temperature-window efficient diesel engine post-processing device and control method thereof

Info

Publication number: CN110206621B
Application number: CN201910456099.9A
Authority: CN
Inventors: 朱明健; 胡振奇; 吕俊翔; 王健; 朱正; 张展腾
Original assignee: FAW Jiefang Automotive Co Ltd
Current assignee: FAW Jiefang Automotive Co Ltd
Priority date: 2019-05-29
Filing date: 2019-05-29
Publication date: 2022-01-11
Anticipated expiration: 2039-05-29
Also published as: CN110206621A

Abstract

The invention belongs to the technical field of engine tail gas purification, and particularly relates to a wide-temperature-window efficient diesel engine post-treatment device and a control method thereof. The invention relates to a wide-temperature-window high-efficiency diesel engine post-treatment device and a control method thereof, and mainly solves the technical problem that NO is enabled to be combined and configured on the basis of six traditional post-treatment devices in the country, namely DOC + DPF + SCR_XThe conversion efficiency temperature window is greatly expanded to the low temperature direction, the temperature window for post-treatment is expanded to 150 ℃, the system comprises an (EH) DOC + DPF + SCR tail gas processor combination mode, two-stage reducing agent injection control is timely adopted according to different running working conditions and exhaust conditions of the engine, and quota control of the reducing agent based on the temperature window is respectively carried out before the (EH) DOC and before the SCR, so that the engine is ensured to have efficient NO in a wide temperature window_XThe conversion efficiency.

Description

Wide-temperature-window efficient diesel engine post-processing device and control method thereof

Technical Field

The invention belongs to the technical field of engine tail gas purification, and particularly relates to a wide-temperature-window efficient diesel engine post-treatment device and a control method thereof.

Background

In order to reduce and eliminate harmful emissions of diesel engines and meet the six emission regulations in China at present, technical combination configurations such as oxidation catalysts (DOCs), Selective Catalytic Reduction (SCR) and particulate trapping (DPF) are generally adopted. SCRF technology has been developed in recent years by coating the SCR catalyst directly on the DPF. The advantage of this technique is the ability to treat both NOx and filter PM, and significantly reduce the volume of post-treatment.

Emission regulations will be further strengthened in the future, and the control of emission pollutants is more strict, wherein the most prominent challenge is the problem of insufficient low-temperature conversion efficiency. Because the catalytic reaction temperature window of the catalyst is limited, particularly under the low-temperature condition, such as the temperature below 200 ℃, the conversion efficiency of SCR is very low, and the start-spraying temperature of the urea reducing agent is required to be above 210 ℃, so that the requirement of future ultra-low emission control cannot be met. In recent years, nitrogen oxide adsorption catalysts (PNA) have been developed abroad which adsorb NOx during cold start/low exhaust temperature conditions of vehicles and release NO when the exhaust temperature rises to a certain extent_xTo make NO discharged under low-temperature working condition_xAnd (4) reducing. Although PNA has a certain adsorption capacity, neither sulfur resistance nor storage property of PNA can be maintained for a long time, and NO active treatment of NO is impossible_xAnd the treatment efficiency of the low-temperature discharged pollutants is improved to a limited extent.

Furthermore, in conventional combination aftertreatment devices, reductant injection is very fixed and well defined, with only a single injection prior to SCR or SCRF. Because the injection position is relatively backward, the reduction of the catalytic conversion efficiency caused by the temperature loss of the exhaust pipeline is relatively obvious. Although some patents are based on the combined configuration of DOC + SCRF + SCR, and a double injection mode is formed by respectively arranging one nozzle in front of a SCRF inlet and a SCR, compared with a single injection mode in front of SCRF, the injection precision can be improved, but NO in a low-temperature window interval_xThe improvement in conversion efficiency is still limited.

The traditional DOC + DPF + SCR technical combination mode has the defects that when the catalyst is operated under the low-temperature working conditions of cold start, warm-up and long-time small load, the catalyst does not reach an efficient working area of the catalyst due to low exhaust temperature, particularly below 200 ℃, and a sufficient amount of reducing agent cannot be injected. The requirement of ultralow emission of a future diesel engine cannot be met, and the bottleneck is met in the aspect of improving the conversion efficiency.

Recent research progress adds PNA on the basis of traditional DOC + DPF + SCR combination mode, although NO can be adsorbed during vehicle cold start/low exhaust temperature working condition_xAnd release NO after the exhaust temperature rises to a certain degree_xBut NO NO generation_xCannot fundamentally reduce and eliminate NO in exhaust gas_x. One disadvantage of the use of PNA technology is the poor sulfur tolerance, the susceptibility to sulfur poisoning, and the loss of stored NO at low temperatures after poisoning_xThe ability of (c); and the PNA has a limited capacity to store NOx, and once the cumulative storage amount exceeds the maximum storage limit, storage cannot be continued.

In the traditional reducing agent injection mode, only one reducing agent nozzle is arranged at an SCR inlet for injection control, and the performance of SCR is only exerted; furthermore, an SCR catalyst is added on the DPF, so that the DPF also has a certain SCR function, namely after the SCRF technology is formed, the injection position can be advanced, the exhaust temperature loss is reduced, and the conversion efficiency is improved. A single injection of reductant at the SCRF inlet cannot be performed simultaneously due to the conflict between the injection of reductant and the regeneration of the DPF; large amounts of reducing agent, such as urea solution, increase the likelihood of plugging the DPF carrier. In recent years, a dual injection method in which a reducing agent injection nozzle is arranged at each of the inlet of the SCRF and the inlet of the SCR has been developed, and the reducing agent injection amount before SCRF is reduced, and the main injection is still the injection amount before the SCR. The engine control system can be respectively based on engine working condition data, NOx sensors and ammonia sensors at the upper and lower streams of respective injection positions, and although accurate control can be realized under most working conditions, the cost is higher due to the fact that more high-cost sensors, particularly ammonia and nitrogen oxide sensors, are used; compared with an injection control mode of only arranging one reducing agent nozzle, the conversion efficiency is improved by adopting a double-nozzle injection mode, and the physicochemical mechanisms of the SCRF and the SCR are further exerted.

The solution described in patent document CN201611220481.2 is to arrange a nozzle at the upstream of SCRF, and arrange a nozzle at the downstream of SCRF and at the upstream of SCR, both of which adopt open-loop and closed-loop control methods respectively, based on Map calibrated in advance and NO at the upstream and downstream of each injection position respectively_xSensors and ammonia sensors, while accurate control can be achieved for most operating conditions, the system cost is high due to the use of more expensive sensors, particularly ammonia sensors.

Patent document CN201480080214.2, despite the use of dual closed loop control reductant dosing injection, still uses more sensors, including 5 exhaust temperature sensors, 5 NO_xThe sensor and the 2 ammonia sensors have extremely complex structures, higher cost and reduced reliability. In addition, NO participating in closed-loop control_xAnd the NH3 sensor, are both active during a start-up procedure, and are not effective for closed-loop emissions control during cold-start warm-up.

Patent document CN201711442193.6 discloses that a single urea injection device is provided just before SCRF for injecting the reducing agent, and the amount of the reducing agent cannot be reasonably distributed according to SCRF and the distribution of active sites on the SCR catalyst, wherein the utilization rate of the activity of the SCR catalyst is lower than the utilization rate of the activity on the SCRF, which makes it difficult to fully exert the catalytic function of the SCR catalyst, resulting in a waste of part of the functions.

According to the above patent documents, a dual injection system in which one nozzle is disposed at each of the SCRF inlet and the SCR front can improve the injection accuracy, but NO in the low exhaust temperature window region can be certainly improved as compared with the single injection system before SCRF_xThe improvement of conversion efficiency is still limited, namely when the engine runs under the low-temperature working conditions of cold start, warm-up and long-time small load, the exhaust temperature is low and is generally below 200 ℃ or even lower, at the moment, the efficiency of the SCR catalyst is low, the injection of a reducing agent can not be generally carried out, and NO NO exists_xThe conversion efficiency of (a).

Disclosure of Invention

The invention provides a high-efficiency diesel engine rear part with a wide temperature windowThe technical problem mainly solved by the treatment device and the control method thereof is to make NO be combined and configured on the basis of six traditional post-processors in the country, namely DOC + DPF + SCR_xThe conversion efficiency temperature window is greatly expanded to the low temperature direction, the temperature window for post-treatment is expanded to 150 ℃, the system comprises an (EH) DOC + DPF + SCR tail gas processor combination mode, two-stage reducing agent injection control is timely adopted according to different running working conditions and exhaust conditions of the engine, and quota control of the reducing agent based on the temperature window is respectively carried out before the (EH) DOC and before the SCR, so that the engine is ensured to have efficient NO in a wide temperature window_xThe conversion efficiency.

The technical scheme of the invention is described as follows by combining the attached drawings:

a high-efficiency diesel engine after-treatment device with a wide temperature window comprises an oxidation catalyst 11 with a heating function, a particulate filter 12, a selective catalytic reduction processor 14, a first-stage reducing agent injector J16, a second-stage reducing agent injector J27, a first nitrogen oxide sensor N18, a second nitrogen oxide sensor N29, a first temperature sensor T12, a second temperature sensor T23, a third temperature sensor T34, a fourth temperature sensor T45 and a differential pressure sensor 10; the oxidation catalyst 11 with the heating function, the particulate filter 12 and the selective catalytic reduction processor 14 are connected in series in sequence along the exhaust gas flow direction of the engine 1; the first stage reductant injector J16 is disposed upstream of the heating-enabled oxidation catalyst 11; the second stage reductant injector J27 is disposed downstream of the particulate filter 12 and upstream of the selective catalytic reduction processor 14; the first nitrogen oxide sensor N18 is disposed between downstream of the particulate filter 12 and upstream of the second stage reductant injector J27; the second nitrogen oxide sensor N29 is arranged at an exhaust outlet; the first temperature sensor T12 is disposed upstream of the oxidation catalyst with heating function 11; the second temperature sensor T23 is disposed downstream of the oxidation catalyst with heating function 11; the third temperature sensor T34 is disposed downstream of the particulate filter 12; the fourth temperature sensor T45 is disposed between downstream of the selective catalytic reduction processor 14 and upstream of the second nitrogen oxide sensor N29; the differential pressure sensor is used to measure the exhaust pressure difference between the front and rear ends of the particulate filter 12.

The reducing agents used in the first-stage reducing agent injector J16 and the second-stage reducing agent injector J27 are all pure ammonia gas or all vehicle urea solution or one pure ammonia gas and the other vehicle urea solution.

An auxiliary heating device is arranged at the front part of the oxidation catalyst 11 with the heating function.

A control method of a high-efficiency diesel engine aftertreatment device with a wide temperature window comprises the following steps:

step one, when the average value of the exhaust gas temperatures detected by the first temperature sensor T12 and the second temperature sensor T23 behind the first temperature sensor T12 is between 150 ℃ and 280 ℃, the injection quantity of the first-stage reducing agent injector J16 treats NO according to theoretical equivalence ratio_x40% -50% of the total, second stage reductant injector J27 assumes disposal of the remaining NO_x；

Secondly, with the rise of the temperature detected by the second temperature sensor T23, when the temperature detected by the second temperature sensor T23 is from 200 ℃ to 280 ℃, the equivalent feed ratio of the second-stage reducing agent injector J27 is only increased, so that excessive injection is realized, and the maximum feed ratio of the sum of the first-stage reducing agent injector J16 and the second-stage reducing agent injector J27 is within 120% of the theoretical equivalent;

step three, when the average value of the exhaust gas temperatures detected by the first temperature sensor T12 and the second temperature sensor T23 behind the first temperature sensor T12 is 280-550 ℃, the first-stage reducing agent injector J16 stops injecting the reducing agent for treating NO_xAnd second stage reductant injector J27 is switched into closed-loop mode for injection of reductant;

fourthly, when the average value of the exhaust temperature detected by the first temperature sensor T12 and the exhaust temperature detected by the second temperature sensor T23 behind the first temperature sensor T12 is between the temperature windows of 400 ℃ and 550 ℃, the first-stage reducing agent injection is switched to other purposes, and the second-stage reducing agent injection is still used as main NO_xA feed source of reductant as required for the treatment.

The first stage reductionThe agent injector J16 injection employs an open-loop control method based on pulse spectroscopy, and the first NOx sensor N18 monitors particulate Filter NO in real time for particulate trapping or Selective catalytic reduction functionality_xDischarging of (3); the second stage reductant injector J27 injection employs a closed loop control method based on a feed forward of the first NOx sensor N18 and feedback of the tail second NOx sensor N29.

Control of injection of the first stage reductant injector J16 is controlled based on at least one of the measurements of the first and second temperature sensors T12 and T23; injection control of the second stage reductant injector J27 is jointly controlled based on at least the measurements of the third temperature sensor T34, the first NOx sensor N18, the second NOx sensor N29, and the fourth temperature sensor T45.

The opening and closing of the injection of the first stage reductant injector J16 is controlled by a hysteresis comparison of the average temperatures of the first and second temperature sensors T12 and T23, i.e., when the average T of the temperatures measured by the first and second temperature sensors T12 and T23 is T_averageLess than threshold T_average3When so, injection of first stage reductant injector J16 is stopped; when T is_averageGreater than a threshold value T_average3Yet less than threshold T_average4At time, injection of first stage reductant injector J16 is performed; when T is_averageGreater than a threshold value T_average4When so, injection of first stage reductant injector J16 is stopped; here the threshold value T_average3And a threshold value T_average4Determined by calibration, and a threshold value T_average3Not greater than threshold T_average4(ii) a The opening and closing of the injection of the second stage reductant injector J27 is controlled by a hysteresis comparison of the third temperature sensor T34, i.e., when the third temperature sensor T34 detects a temperature value T₃Not less than threshold T_3AWhen, the injection of the second stage reductant injector J27 is performed, when T₃Less than threshold T_3BWhen injection of the second stage reductant injector J27 is stopped, here threshold T_3AAnd a threshold value T_3BDetermined by calibration, and a threshold value T_3ANot less than threshold T_3B。

The auxiliary heating device on and off control is based on the combined control of the first temperature sensor T12 and the second temperature sensor T23, i.e. when the average value T of the temperature values measured by the first temperature sensor T12 and the second temperature sensor T23 is T_averageLess than threshold T_average1In the meantime, the oxidation catalyst 11 with a heating function is heated; when mean value T_averageAbove another set threshold T_average2I.e. off, where the threshold T is_average1And a threshold value T_average2Determined by calibration, and a threshold value T_average1Not greater than threshold T_average2And a threshold value T_average3，T_average2Not less than threshold T_average3And is not greater than threshold T_average4。

The theoretical equivalent ratio is as follows: the first stage reductant injector J16 injects a fixed feed ratio and the second stage reductant injector J27 injects an adjustable feed ratio; the total amount of the injected feed proportioning of the first-stage reducing agent injector J16 and the second-stage reducing agent injector J27 exceeds the theoretical equivalent proportioning, but the total amount is less than 120%, and the excessive proportioning is beneficial to promoting NO_xThe conversion efficiency.

The invention has the beneficial effects that:

1. when the exhaust temperature is between 150 ℃ and 280 ℃, the injection of a reducing agent is added in front of DOC to ensure that NO is generated_xThe reduction reaction is carried out under the catalytic action of DOC, and NO can be greatly reduced_xDischarging of (3); if the DOC adopts an auxiliary heating technology, such as an Electrically Heated (EH) DOC, the low-temperature window of the DOC is further expanded, and the DOC can tolerate lower exhaust temperature which is as low as about 120 ℃, so that the start-up temperature of the reducing agent is greatly reduced. NO due to SCRF and SCR entering downstream_xThe emission is reduced to a certain degree, which creates conditions for actively improving the charging proportion of the reducing agent, can fully utilize the ammonia storage capacity of the carrier, and further improves NO_xSo that NO in the exhaust gas can be completely eliminated_xThe effect of clean discharge is achieved;

2. by adopting the technical combination of (EH) DOC + DPF + SCR or (EH) DOC + SCRF + SCR, the performances of the DOC and SCR catalysts can be exerted to the maximum extent, and by adopting the quota feeding method, the advantages can be complemented, and the effect is more remarkable than that of the traditional combination;

3. the auxiliary reducing agent J1 is injected in a high-temperature window of 400-550 ℃, and under the action of DOC, strong oxidation reaction is carried out to generate more controllable NO_xThe passive regeneration of the DPF or the SCRF can be assisted, the passive regeneration period is prolonged, and the fuel consumption of the active regeneration is saved.

Drawings

FIG. 1 is a diagram of NO for a wide temperature window high efficiency post processor_xA schematic diagram of the expansion effect of the conversion efficiency temperature window;

FIG. 2 is a schematic diagram of a wide temperature window efficient aftertreatment component arrangement according to an exemplary embodiment;

FIG. 3 is a schematic diagram of a wide temperature window efficient aftertreatment component arrangement according to another exemplary embodiment.

In the figure: 1. an engine; 2. a first temperature sensor T1; 3. a second temperature sensor T2; 4. a third temperature sensor T3; 5. a fourth temperature sensor T4; 6. first stage reductant injector J1; 7. second stage reductant injector J2; 8. a first NOx sensor N1; 9. a second nitride sensor N2; 10. a differential pressure sensor; 11. an oxidation catalyst with a heating function; 12. a particulate filter; 13. a particulate filter with selective catalytic reduction function; 14. a selective catalytic reduction processor.

Detailed Description

Referring to fig. 2, a high efficiency diesel aftertreatment device with a wide temperature window includes an oxidation catalyst 11 with a heating function, a particulate filter 12, a selective catalytic reduction processor 14, a first stage reductant injector J16, a second stage reductant injector J27, a first nox sensor N18, a second nox sensor N29, a first temperature sensor T12, a second temperature sensor T23, a third temperature sensor T34, a fourth temperature sensor T45, and a differential pressure sensor; the oxidation catalyst 11 with the heating function, the particulate filter 12 and the selective catalytic reduction processor 14 are connected in series in sequence along the exhaust gas flow direction of the engine 1; the first stage reductant injector J16 is disposed upstream of the heating-enabled oxidation catalyst 11; the second stage reductant injector J27 is disposed downstream of the particulate filter 12 and upstream of the selective catalytic reduction processor 14; the first nitrogen oxide sensor N18 is disposed between downstream of the particulate filter 12 and upstream of the second stage reductant injector J27; the second nitrogen oxide sensor N29 is arranged at an exhaust outlet; the first temperature sensor T12 is disposed upstream of the oxidation catalyst with an electric heating function 11; the second temperature sensor T23 is disposed downstream of the electrically heated oxidation catalyst 11; the third temperature sensor T34 is disposed downstream of the particulate filter 12; the fourth temperature sensor T45 is disposed between downstream of the selective catalytic reduction processor 14 and upstream of the second nitrogen oxide sensor N29; the differential pressure sensor is used to measure the exhaust pressure difference between the front and rear ends of the particulate filter 12.

An auxiliary heating device is arranged in front of the oxidation catalyst 11 with the heating function, and the auxiliary heating device is preferably electrically heated.

Based on the above arrangement, the reductant injection embodiment of the present invention employs a two-stage reductant injection control scheme, with the first stage reductant injector J16 employing an open-loop control method based on MAP, and the first NOx sensor N18 monitoring the NOx emission concentration in real time after the particulate filter 12, and the second stage reductant injector J27 employing a closed-loop control method based on feedforward and feedback from the second NOx sensor N29. The opening and closing of the first and second stage reductant injectors J16, J27 are configured to be independently actuated; the injection quantity is allocated according to the temperature interval. Specifically, when the average of the exhaust gas temperatures detected by the first temperature sensor T12 and the second temperature sensor T23 thereafter is between 150 ℃ and 280 ℃, the injection amount of the first stage reductant injector J16 is only NO that is processed as needed_x40% -50% of the total, second stage reductant injector J27 assumes disposal of the remaining NO_xAnd the second stage reducing agent spray is increased from 200 ℃ to 280 ℃ along with the increase of the temperature detected by the third temperature sensor T34Injector J27 is proportioned so that over-injection, the combined maximum feed quota of the first and second stages may be within 120% of the theoretical equivalent. When the temperature of exhaust gas is 280-550 ℃, the injection of the first-stage reducing agent injector J16 is stopped, and the normal injection of the second-stage reducing agent injector J27 is carried out according to a closed-loop mode; when the temperature window is 400-550 ℃, the first-stage reducing agent injector J16 is switched to other purposes for assisting DPF to regenerate, and the second-stage reducing agent injector J27 is still used as main NO_xA feed source of reductant as required for the treatment.

Open-loop injection control of the first stage reductant injector J16 is controlled based on at least one of the measurement of the first temperature sensor T12 and the measurement of the second temperature sensor T23. The closed-loop control method of the second stage reductant injector J27 is based on at least the measurements of the first NOx sensor N18, the second temperature sensor T23, the third temperature sensor T34, and the exhaust outlet second NOx sensor N29 and the fourth temperature sensor T45 for combined control.

The on and off control of the electric heater built in front of the oxidation catalyst with heating function 11 is based on the feedback control of the first and second temperature sensors T12 and T23 when the average value T of the temperature values measured by the first and second temperature sensors T12 and T23 is T23_averageLess than threshold T_average1In the meantime, the oxidation catalyst 11 with a heating function is heated by energization; when mean value T_averageAbove another set threshold T_average2I.e. off, where the threshold T is_average1And a threshold value T_average2Determined by calibration, and a threshold value T_average1Not greater than threshold T_average2. A typical example is T_average1Set to 120 ℃ T_average2The temperature was set to 200 ℃.

The opening and closing of the first stage reductant injector J16 is controlled by a combination of a first temperature sensor T12 and a second temperature sensor T23 as measured by a temperature average T of the first temperature sensor T12 and the second temperature sensor T23_averageLess than threshold T_average3When so, injection of first stage reductant injector J16 is stopped; when in useT_averageGreater than a threshold value T_average3Yet less than threshold T_average4At time, injection of first stage reductant injector J16 is performed; when T is_averageGreater than a threshold value T_average4When this is the case, injection of first stage reductant injector J16 is stopped. Here the threshold value T_average3And a threshold value T_average4Determined by calibration, and a threshold value T_average3Less than or equal to threshold T_average4A typical example is T_average3Set to 150 ℃ T_average4Setting the temperature to be 280 ℃;

in a more advantageous manner, the heating-function oxidation catalyst 11 can be arranged closer to the outlet of the exhaust manifold of the engine, while the auxiliary heating function adopted by the heating-function oxidation catalyst 11 is eliminated, so that the system cost is lower, the two-stage injection method still maintains the above manner, and wide-temperature high-efficiency NO treatment can be achieved_xThe efficiency of (c).

The opening and closing of the second stage reductant injector J27 is controlled by a third temperature sensor T34 when a temperature T3 detected by the third temperature sensor T34 is not less than a threshold T3_3AWhen so, injection of the second stage reductant injector J27 is performed; when T3 is less than threshold T_3BWhen injection of the second stage reductant injector J27 is stopped, here threshold T_3AAnd a threshold value T_3BDetermined by calibration, and a threshold value T_3ANot less than threshold T_3BA typical example is T_3A、T_3BAre all set at 200 ℃.

First stage reductant injector J16 and second stage reductant injector J27 with overall theoretical total NO treatment_xThe ratio of the required reducing agent amounts, i.e. the feed quota, is: 40-50% of the dosage of the reducing agent controlled by the first-stage reducing agent injector J16, and the control effect can ensure that the medium-low temperature range is between 150 and 280 DEG C]After passing through the oxidation catalyst 11 with the electric heating function, about 40-50% of NOx in the exhaust gas is reduced, the feeding quota of the reducing agent controlled by the J2 in the second stage is 60-70%, and the control effect can enable the medium-low temperature range to be 200-280 DEG C]After passing through the SCR processor 14, the remainder of the exhaust gasLower NO_xIs reduced. The injection feeding quota of the first-stage reducing agent injector J16 and the second-stage reducing agent injector J27 is controlled within 120% of the theoretically completely-processed required reducing agent quota, and NO is guaranteed_xThe conversion efficiency is exerted to the maximum extent, and meanwhile, the consumption of the reducing agent is saved, and leakage is prevented;

in the medium-high temperature range (280-550℃)]Inner, second stage reductant injector J27 individually controlled reductant dosing quota set to 100% -120% for NO in exhaust_xIs reduced in the selective catalytic reduction processor 14 with high efficiency.

When the temperature window is between 400 ℃ and 550 ℃, the first-stage reductant injector J16 is switched to other uses, such as the regeneration of DPF can be assisted.

In this exemplary scenario, the reductant injected by first stage reductant injector J16 may be configured to be all pure ammonia or all vehicle urea solution; or one of the ammonia gas and the other urea solution is prepared into the vehicle urea solution. If configured as pure ammonia gas, the auxiliary heating function of the oxidation catalyst 11 (with electric heating function) can be simplified to reduce the cost.

Referring to fig. 3, a second exemplary embodiment of the present invention is based on the configuration in the first exemplary embodiment described above, in which the particulate filter DPF 12 is replaced with a particulate filter 13 having a selective catalytic reduction function. The control method of the first stage reductant injector J16 and the second stage reductant injector J27 still maintains the manner described above for reducing NO on the electrically heated oxidation catalyst 11_xThe unspent reducing agent can continue to reduce NO on the particulate filter 13 with the selective catalytic reduction function_xThis way, a wider temperature range and more efficient NO treatment can be achieved_xEfficiency.

Referring to fig. 1, for different exhaust temperature conditions of the engine, the working process of the efficient post-processor with wide temperature window for removing NOx according to the present invention is as follows:

the first stage reductant injector J16 is operated when the average of the exhaust gas temperatures detected by the first temperature sensor T1 and the second temperature sensor T2 thereafter is between 150 deg.C and 280 deg.CIn order to do so, injection of the reducing agent is carried out according to the open-loop MAP control method, the reducing agent being reacted with NO in the DOC_xReacting to reduce NO by 40-50% in the temperature range_xDischarging; at temperatures of 280 ℃ and above, the first stage reductant injector J16 was deactivated. If the oxidation catalyst 11 with the electric heating function further expands the low temperature window of the oxidation catalyst with the electric heating function to about 120 ℃, then the start-spray temperature of the first-stage reducing agent injector J16 expands downward, and NO is reduced on the oxidation catalyst 11 with the electric heating function_xThe efficiency window of (a) is extended to between 120 ℃ and 280 ℃.

When the second temperature sensor T23 detects that the exhaust temperature is 200 deg.C or above, the second stage reductant injector J27 begins to operate, assuming the first stage reductant injector J16 is treating the remaining NO_xAnd (5) discharging. When the exhaust temperature is 280-550 ℃, the second-stage reducing agent injector J27 injects according to a closed-loop control method, and the reducing agent and NO react on the SCR catalyst_xReact to reduce total NO in engine exhaust_xAnd (5) discharging.

By implementing the measures, the engine is ensured to have very high NO under a wide temperature window of 120-550 DEG C_xThe conversion efficiency specifically includes an oxidation catalyst 11 synergistic zone with a heating function and an oxidation catalyst 11 quota synergistic zone with a heating function in a temperature range of 120-170 ℃, a DOC synergistic zone, a DOC and SCR quota synergistic zone in a temperature range of 170-280 ℃, and a traditional SCR efficiency zone at 280-550 ℃ in fig. 1. By combining these efficiency intervals, NO is finally produced_xThe conversion efficiency under the high-temperature and low-temperature working conditions can be fully exerted, and the conversion efficiency under the final cycle working condition can exceed the limit of a single catalyst performance index.

Claims

1. A high-efficiency diesel engine aftertreatment device with a wide temperature window is characterized by comprising an oxidation catalyst (11) with a heating function, a particulate filter (12), a selective catalytic reduction processor (14), a first-stage reducing agent injector J1(6), a second-stage reducing agent injector J2(7), a first nitrogen oxide sensor N1(8), a second nitrogen oxide sensor N2(9), a first temperature sensor T1(2), a second temperature sensor T2(3), a third temperature sensor T3(4), a fourth temperature sensor T4(5) and a differential pressure sensor (10); the oxidation catalyst (11) with the heating function, the particle filter (12) and the selective catalytic reduction processor (14) are sequentially connected in series along the exhaust flowing direction of the engine (1); the first stage reductant injector J1(6) is disposed upstream of a heated oxidation catalyst (11); the second stage reductant injector J2(7) is disposed downstream of a particulate filter (12) and upstream of a selective catalytic reduction processor (14); the first nitrogen oxide sensor N1(8) is disposed between downstream of a particulate filter (12) and upstream of a second stage reductant injector J2 (7); the second nitrogen oxide sensor N2(9) is arranged at an exhaust outlet; the first temperature sensor T1(2) is disposed upstream of the oxidation catalyst with heating function (11); the second temperature sensor T2(3) is disposed downstream of the oxidation catalyst with heating function (11); the third temperature sensor T3(4) is arranged downstream of the particulate filter (12); the fourth temperature sensor T4(5) is disposed between downstream of the selective catalytic reduction processor (14) and upstream of the second nitrogen oxide sensor N2 (9); the differential pressure sensor is used for measuring the exhaust pressure difference between the front end and the rear end of the particle filter (12); the reducing agents used in the first-stage reducing agent injector J1(6) and the second-stage reducing agent injector J2(7) are all pure ammonia gas or all vehicle urea solution or one of the pure ammonia gas and the other vehicle urea solution; an auxiliary heating device is arranged at the front part of the oxidation catalyst (11) with the heating function.

2. A method of controlling a wide temperature window high efficiency diesel engine aftertreatment device according to claim 1, comprising the steps of:

step one, when the average value of the exhaust gas temperatures detected by a first temperature sensor T1(2) and a second temperature sensor T2(3) behind the first temperature sensor is between 150 ℃ and 280 ℃, the injection quantity of a first-stage reducing agent injector J1(6) is used for processing NO according to the theoretical equivalence ratio_X40% -50% of the total amount, second stage reductant injectionDevice J2(7) undertakes to process the remaining NO_X；

Secondly, with the rise of the temperature detected by the second temperature sensor T2(3), when the temperature detected by the second temperature sensor T2(3) is from 200 ℃ to 280 ℃, the equivalent feed ratio of the second-stage reducing agent injector J2(7) is only increased, so that excessive injection is realized, and the maximum feed ratio of the sum of the first-stage reducing agent injector J1(6) and the second-stage reducing agent injector J2(7) is within 120% of the theoretical equivalent;

step three, when the average value of the exhaust gas temperatures detected by the first temperature sensor T1(2) and the second temperature sensor T2(3) behind the first temperature sensor T1(2) is 280-550 ℃, the first-stage reducing agent injector J1(6) stops injecting the reducing agent for treating NO_XAnd second stage reductant injector J2(7) is switched to injection of reductant in a closed-loop manner;

the first stage reductant injector J1(6) injection employs a pulse-spectrum based open loop control method, and a first NOx sensor N1(8) monitors NO in real time after the particulate filter (12)_XDischarging of (3); the second stage reductant injector J2(7) injection employs a closed loop control method based on feed forward of a first NOx sensor N1(8) and feedback of a second NOx sensor N2 (9); control of injection of the first stage reductant injector J1(6) is controlled based on at least one of measurements of a first temperature sensor T1(2) and a second temperature sensor T2 (3); the injection control of the second stage reductant injector J2(7) is jointly controlled based on at least the measurements of the third temperature sensor T3(4), the first NOx sensor N1(8), the second NOx sensor N2(9), and the fourth temperature sensor T4 (5); the opening and closing of the injection of the first stage reductant injector J1(6) is controlled by a hysteresis comparison of the average temperatures of the first and second temperature sensors T1(2) and T2(3), i.e., when the average T of the temperatures measured by the first and second temperature sensors T1(2) and T2(3) is greater than the average T_averageLess than threshold T_average3When so, injection of first stage reductant injector J1(6) is stopped; when T is_averageGreater than a threshold value T_average3Yet less than threshold T_average4While, first stage reductant injector J1(6) is performedSpraying; when T is_averageGreater than a threshold value T_average4When so, injection of first stage reductant injector J1(6) is stopped; here the threshold value T_average3And a threshold value T_average4Determined by calibration, and a threshold value T_average3Not greater than threshold T_average4(ii) a The opening and closing of the injection of the second stage reductant injector J2(7) is controlled by a hysteresis comparison of the third temperature sensor T3(4), i.e., when the third temperature sensor T3(4) detects a temperature value T₃Not less than threshold T_3ASecond stage reductant injector J2(7) injection is performed when T₃Less than threshold T_3BWhen injection of second stage reductant injector J2(7) is stopped, where threshold T is_3AAnd a threshold value T_3BDetermined by calibration, and a threshold value T_3ANot less than threshold T_3B(ii) a The auxiliary heating device on and off control is based on the combined control of the first temperature sensor T1(2) and the second temperature sensor T2(3), i.e., when the average value T of the temperature values measured by the first temperature sensor T1(2) and the second temperature sensor T2(3) is T2(3)_averageLess than threshold T_average1When the catalyst is used, the oxidation catalyst (11) with the heating function is heated; when mean value T_averageAbove another set threshold T_average2I.e. off, where the threshold T is_average1And a threshold value T_average2Determined by calibration, and a threshold value T_average1Not greater than threshold T_average2And a threshold value T_average3，T_average2Not less than threshold T_average3And is not greater than threshold T_average4(ii) a The theoretical equivalent ratio is as follows: the first stage reductant injector J1(6) injected a fixed dosing schedule, while the second stage reductant injector J2(7) injected a variable dosing schedule; the total injection ratio of the first-stage reducing agent injector J1(6) and the second-stage reducing agent injector J2(7) exceeds the theoretical equivalent ratio, but the total amount is less than 120%, and the excessive ratio is helpful for improving NO_XThe conversion efficiency.