EGR type ammonia-diesel fuel engine system, aftertreatment system and method

Abstract

The invention discloses an EGR (Exhaust Gas Recirculation) type ammonia-diesel fuel engine system, an aftertreatment system and an aftertreatment method, and relates to the technical field of engine aftertreatment, and the EGR type ammonia-diesel fuel engine aftertreatment system comprises a backflow pipeline, an EGR valve, a first-stage SCR (Selective Catalytic Reduction), a second-stage SCR, an ammonia sensor, a nitrogen-oxygen sensor and a control module. The EGR type ammonia-diesel fuel engine is combined with the double-SCR system, N2O generated by original emission enters a cylinder through the EGR system to be combusted and decomposed again, and generation of N2O in the original emission of the ammonia-diesel fuel engine is reduced. The original discharged ammonia nitrogen ratio is reasonably controlled through the EGR valve and the original machine, so that unburned ammonia of the original machine can be completely converted through the preceding-stage SCR system and the preceding-stage ASC system, the ammonia is prevented from leaking and entering subsequent DOC and DPF, the problem that N2O emission is too high is avoided, and therefore the limiting value requirement of the next-generation emission regulation is met.

Description

Technical Field

[0001] The present invention relates to the technical field of engine aftertreatment, and particularly to an EGR type ammonia-diesel fuel engine system, an aftertreatment system and a method. Background Art

[0002] Under the background of carbon peaking and carbon neutrality, the research and development of new low-carbon and zero-carbon alternative fuels and their engine technologies are extremely urgent. The development of ammonia-diesel fuel engines is a relatively ideal route at present. Currently, whether for vehicle or marine engines, emission regulations are becoming increasingly strict, and the emission limits for NOx and NH 3 are tightened. Euro 7 increases the N 2 O limit. However, ammonia-diesel fuel engines have high NOx emissions and produce a large amount of unburned ammonia, and there is also a problem that a large amount of N 3 is produced after the reaction of NH x and NO 2 through aftertreatment. Existing aftertreatment is difficult to be directly applied to ammonia-diesel fuel engines, and the development of aftertreatment for ammonia-diesel fuel engines is relatively difficult. Summary of the Invention

[0003] The purpose of the present invention is to provide an EGR type ammonia-diesel fuel engine system, an aftertreatment system and a method to solve the problems existing in the above-mentioned prior art, and reduce the amounts of NO x , N 2 O and unburned ammonia in the exhaust of ammonia-diesel fuel engines.

[0004] To achieve the above purpose, the present invention provides the following solutions:

[0005] The present invention provides an EGR type ammonia-diesel fuel engine aftertreatment system, including: a reflux pipeline, an EGR valve, a first-stage SCR, a second-stage SCR, an ammonia sensor, a nitrogen oxide sensor and a control module.

[0006] Both ends of the reflux pipeline are respectively communicated with an exhaust pipeline and an intake pipeline; the EGR valve is arranged on the reflux pipeline; the first-stage SCR is used to be arranged on the exhaust pipeline downstream of the connection between the reflux pipeline and the exhaust pipeline, and the first-stage SCR only relies on unburned ammonia in the original exhaust to convert NO x ; the second-stage SCR is used to be arranged on the exhaust pipeline downstream of the first-stage SCR; an ammonia reducing agent nozzle is configured on the exhaust pipeline upstream of the second-stage SCR; the ammonia sensor is arranged on the exhaust pipeline upstream and downstream of the first-stage SCR; the nitrogen oxide sensor is arranged on the exhaust pipeline upstream and downstream of the first-stage SCR; the control module is communicatively connected with the ammonia sensor, the nitrogen oxide sensor, the EGR valve and the ammonia reducing agent nozzle; the control module calculates the original exhaust ANR; and judges whether the original exhaust ANR is not greater than the ANR threshold.

[0007] If so, determine whether the ammonia in the tail gas after the first-stage SCR treatment is greater than the ammonia threshold. If not, maintain the normal operation of the engine system and the aftertreatment system. If so, report a fault of low conversion efficiency of the first-stage SCR;

[0008] If not, adjust the opening of the EGR valve until the original exhaust ANR is not greater than the ANR threshold. If the original exhaust ANR is still greater than the ANR threshold after the opening of the EGR valve reaches the maximum opening threshold, determine whether the ammonia in the tail gas after the first-stage SCR treatment is greater than the ammonia threshold;

[0009] If not, maintain the normal operation of the engine system and the aftertreatment system;

[0010] If so, reduce the ammonia substitution rate, adjust the opening of the throttle valve actuator on the intake pipe, or adjust the engine combustion strategy until the ammonia in the tail gas after the first-stage SCR treatment is less than the ammonia threshold.

[0011] Preferably, an EGR cooler and a check valve are further provided on the reflux pipe.

[0012] Preferably, a temperature sensor is provided on the exhaust pipe between the first-stage SCR and the second-stage SCR. The control module uses the measurement data of the nitrogen oxide sensor, ammonia sensor, and temperature sensor on the exhaust pipe between the first-stage SCR and the second-stage SCR as input parameters, and judges and controls the ammonia reductant nozzle to perform open-loop or closed-loop control injection of the ammonia reductant through a preset aftertreatment logic to convert the excess NO x 。

[0013] Preferably, an ASC system is further configured on the exhaust pipe downstream of the first-stage SCR and on the exhaust pipe downstream of the second-stage SCR.

[0014] Preferably, a DOC and a DPF are configured on the exhaust pipe between the first-stage SCR and the second-stage SCR.

[0015] Preferably, a mixer is configured on the exhaust pipe upstream of the second-stage SCR, and the ammonia reductant nozzle is configured on the mixer.

[0016] The present invention also provides an EGR type ammonia-diesel fuel engine system, comprising: an engine, an intake pipe, an exhaust pipe, an ammonia cylinder, an ammonia fuel nozzle, and the EGR type ammonia-diesel fuel engine aftertreatment system as described above; one end of the intake pipe is used for introducing air, and the other end is connected to the engine; one end of the exhaust pipe is used for exhausting gas, and the other end is connected to the engine; the ammonia cylinder stores ammonia fuel; the ammonia fuel nozzle is connected to the ammonia cylinder and is used for injecting the ammonia fuel into the engine.

[0017] Preferably, an air filter, a compressor, an intercooler, and a throttle valve are sequentially arranged on the intake pipe along the intake direction.

[0018] The present invention also provides an EGR type ammonia-diesel fuel engine aftertreatment method, comprising:

[0019] Obtaining the ammonia and NO x concentrations in the original exhaust gas;

[0020] Calculating the original exhaust ANR;

[0021] Judging whether the original exhaust ANR is not greater than the ANR threshold;

[0022] If so, judging whether the ammonia in the tail gas after the first-stage SCR treatment is greater than the ammonia threshold. If not, maintaining the normal operation of the engine system and the aftertreatment system. If so, reporting a fault of low conversion efficiency of the first-stage SCR;

[0023] If not, adjusting the opening degree of the EGR valve until the original exhaust ANR is not greater than the ANR threshold. If the original exhaust ANR is still greater than the ANR threshold after the opening degree of the EGR valve reaches the maximum opening degree threshold, judging whether the ammonia in the tail gas after the first-stage SCR treatment is greater than the ammonia threshold;

[0024] If not, maintaining the normal operation of the engine system and the aftertreatment system;

[0025] If so, reducing the ammonia substitution rate, adjusting the opening degree of the throttle valve actuator on the intake pipe, or adjusting the engine combustion strategy to make the ammonia in the tail gas after the first-stage SCR treatment less than the ammonia threshold.

[0026] Preferably, if it is judged that the ammonia in the tail gas after the first-stage SCR treatment is greater than the ammonia threshold;

[0027] Calculating the theoretical efficiency η1 of converting NO x and the actual efficiency η2 of converting NO x ;

[0028] Judging whether η1 >> η2;

[0029] If so, report an OBD fault indicating low conversion efficiency of the first-stage SCR;

[0030] If not, recalculate the actual efficiency η2 of NO conversion; and determine whether η1 >> η2 until η1 >> η2, then stop and report an OBD fault indicating low conversion efficiency of the first-stage SCR. x

[0031] The present invention has achieved the following technical effects compared with the prior art:

[0032] In the present invention, the EGR valve is used to reintroduce the NO in the original exhaust into the cylinder to participate in combustion, and it is thermally decomposed into N 2 and O 2 to reduce the generation of NO from the original exhaust. 2 2

[0033] In the present invention, by controlling the ammonia-nitrogen ratio in front of the first-stage SCR / ASC system within a reasonable range, the unburned ammonia in the original exhaust is completely reacted through the first-stage SCR / ASC system, thereby avoiding the leakage of ammonia after the first-stage SCR / ASC system into the DOC and DPF for oxidation to generate NO. 2

[0034] When the ANR of the original exhaust is not within the reasonable range, the present invention adjusts the opening of the EGR valve to increase the concentration of NO in the original exhaust, so that the unburned ammonia is completely converted at the current SCR temperature. If the opening of the EGR valve reaches the threshold and there is still ammonia leakage after the first-stage SCR / ASC, then by reducing the ammonia substitution rate, or the throttle valve actuator on the intake pipe or the combustion parameters (adjusting the injection advance angle, pre-injection fuel quantity, rail pressure), the unburned ammonia in the original exhaust is reduced, so that ANR ≤ ANR threshold and the concentration of NH x ≤ NH 3 threshold. 3

[0035] When the ANR of the original exhaust ≤ ANR threshold and the concentration of NH detected by the second ammonia sensor 3 > NH 3 concentration threshold, through the efficiency logic diagnosis of the first-stage SCR / ASC system, report an OBD fault indicating low conversion efficiency of the first-stage SCR / ASC system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0037] Figure 1 ​​​​​Schematic diagram of the EGR type ammonia-diesel fuel engine system provided by the embodiment of the present invention;

[0038] Figure 2 Flow chart of the post-treatment method for the EGR type ammonia-diesel fuel engine provided by the embodiment of the present invention;

[0039] In the figure: 1 - engine; 2 - EGR valve; 3 - return pipeline; 4 - intake pipeline; 5 - exhaust pipeline; 6 - turbine; 7 - first-stage SCR / ASC system; 8 - second-stage SCR / ASC system; 9 - mixer; 10 - ammonia fuel nozzle; 11 - air filter; 12 - compressor; 13 - intercooler; 14 - throttle valve; 15 - EGR cooler; 16 - check valve; 17 - nitrogen cylinder; 18 - voltage stabilizer; 19 - ammonia reducing agent nozzle; 20 - temperature sensor; 21 - nitrogen oxide sensor; 22 - ammonia sensor. Specific embodiments

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0042] Term explanation:

[0043] NH 3 : Represents ammonia gas.

[0044] NO x : Represents nitrogen oxides.

[0045] SCR: Selective catalytic reduction catalyst, which converts NO 3 in the exhaust gas when spraying NH x .

[0046] ASC: NH 3 leakage catalytic converter, used to adsorb and convert NH 3 leakage in the exhaust gas, but the adsorption capacity is limited.

[0047] N 2 O: Nitrous oxide, also known as laughing gas, has a greenhouse effect 298 times that of carbon dioxide.

[0048] ANR: Ammonia-nitrogen ratio, that is, the mass flow ratio of NH 3 and NO x .

[0049] DOC: Diesel Oxidation Catalyst.

[0050] DPF: Diesel Particulate Filter.

[0051] SCR system: Selective Catalytic Reduction system.

[0052] OBD: On-Board Diagnostic system.

[0053] EGR: Abbreviation of Exhaust Gas Recirculation in English.

[0054] In the related art, a dual-SCR route is adopted to convert unburned ammonia and NO x However, there is a problem that the original emission NH 3 in the ammonia-diesel fuel engine is too high. Currently, in the test research, there is about 10,000 ppm of unburned ammonia under high substitution rate conditions, while the concentration of the original emission NO 3 is not high. There is a risk of a large amount of ammonia leakage after the front-stage SCR. Even if there is an ASC after the front-stage SCR, the ammonia leakage capture capacity of the ASC is limited. A large amount of NH x leakage is oxidized to N 3 O after passing through the DOC and DPF. Currently, the existing catalysts cannot directly treat N 2 O. N 2 O is a greenhouse gas, and its greenhouse effect is 298 times that of carbon dioxide. The Euro 7 regulations have been introduced to add N 2 O limits. It is expected that the non-Euro 5 and Euro 7 regulations will also limit N 2 O. In the present invention, by combining an EGR-type ammonia-diesel fuel engine with a dual-SCR system, the N 2 O generated in the original emission enters the cylinder through the EGR system and is burned and decomposed again, reducing the generation of N 2 O in the original emission of the ammonia-diesel fuel engine. By reasonably controlling the original emission ammonia-nitrogen ratio through the EGR valve and the original engine, the unburned ammonia in the original engine can be completely converted through the front-stage SCR and the front-stage ASC system, preventing ammonia leakage from entering the subsequent DOC and DPF, and avoiding the problem of excessive N 2 O emissions, thus meeting the requirements of the next-generation emission regulation limits. 2 O emission is too high, thus meeting the requirements of the next-generation emission regulation limits.

[0055] The following describes the embodiments of the present invention in conjunction with Figures 1 to 2 , describing the embodiments of the present invention.

[0056] The present invention provides a post-treatment system for an EGR type ammonia-diesel fuel engine, comprising: a reflux pipeline 3, an EGR valve 2, a first-stage SCR, a second-stage SCR, an ammonia sensor, a nitrogen oxide sensor and a control module. Both ends of the reflux pipeline 3 are respectively communicated with an exhaust pipeline 5 and an intake pipeline 4; the EGR valve 2 is arranged on the reflux pipeline 3; the first-stage SCR is used to be arranged on the exhaust pipeline 5 downstream of the connection between the reflux pipeline 3 and the exhaust pipeline 5, and the first-stage SCR only relies on unburned ammonia in the original exhaust gas to convert NO x ; the second-stage SCR is used to be arranged on the exhaust pipeline 5 downstream of the first-stage SCR; an ammonia reducing agent nozzle 19 is arranged on the exhaust pipeline 5 upstream of the second-stage SCR; the ammonia sensor is arranged on the exhaust pipeline 5 upstream and downstream of the first-stage SCR; the nitrogen oxide sensor is arranged on the exhaust pipeline 5 upstream and downstream of the first-stage SCR; the control module is communicatively connected to the ammonia sensor, the nitrogen oxide sensor, the EGR valve 2 and the ammonia reducing agent nozzle 19; the control module calculates the original exhaust ANR; and judges whether the original exhaust ANR is not greater than the ANR threshold value;

[0057] If so, then judge whether the ammonia in the tail gas after being treated by the first-stage SCR is greater than the ammonia threshold value. If not, then maintain the normal operation of the engine system and the post-treatment system. If so, then report a fault of low conversion efficiency of the first-stage SCR;

[0058] If not, then adjust the opening degree of the EGR valve 2 until the original exhaust ANR is not greater than the ANR threshold value. If the original exhaust ANR is still greater than the ANR threshold value after the opening degree of the EGR valve 2 reaches the maximum opening degree threshold value, then judge whether the ammonia in the tail gas after being treated by the first-stage SCR is greater than the ammonia threshold value;

[0059] If not, then maintain the normal operation of the engine system and the post-treatment system;

[0060] If so, then reduce the ammonia substitution rate, adjust the throttle actuator on the intake pipeline or adjust the engine combustion strategy until the ammonia in the tail gas after being treated by the first-stage SCR is less than the ammonia threshold value.

[0061] A temperature sensor is arranged on the exhaust pipeline 5 between the first-stage SCR and the second-stage SCR. The control module uses the measurement data of the nitrogen oxide sensor, the ammonia sensor and the temperature sensor on the exhaust pipeline 5 between the first-stage SCR and the second-stage SCR as input parameters, and judges and controls the ammonia reducing agent nozzle 19 to perform open-loop or closed-loop control injection of the ammonia reducing agent through a preset post-treatment logic to convert the excess NO x .

[0062] In the embodiment of the present invention, by combining the EGR type ammonia-diesel fuel engine with a dual SCR system, the NO generated by the original exhaust gas enters the cylinder through the EGR system and is burned and decomposed again, reducing the NO in the original exhaust gas of the ammonia-diesel fuel engine 2 O2 O generation. By reasonably controlling the original ammonia-nitrogen ratio through the EGR valve 2 and the original engine, the unburned ammonia in the original engine can be completely converted through the pre-stage SCR and pre-stage ASC systems, preventing ammonia leakage from entering the subsequent DOC and DPF, and avoiding the problem of excessive N 2 O emissions, thus meeting the requirements of the next-generation emission regulation limits.

[0063] In some embodiments, an EGR cooler 15 and a check valve 16 are further provided on the return pipeline 3.

[0064] In some embodiments, an ASC system is further configured on the exhaust pipeline 5 downstream of the first-stage SCR and the exhaust pipeline 5 downstream of the second-stage SCR.

[0065] The pre-stage ASC system and the first-stage SCR together form the first-stage SCR / ASC system 7; the post-stage ASC system and the second-stage SCR together form the second-stage SCR / ASC system 8.

[0066] In some embodiments, a DOC and a DPF are configured on the exhaust pipeline 5 between the first-stage SCR and the second-stage SCR.

[0067] In some embodiments, a mixer 9 is configured on the exhaust pipeline 5 upstream of the second-stage SCR, and an ammonia reductant nozzle 19 is configured on the mixer 9.

[0068] The embodiments of the present invention have the following effects:

[0069] In the present invention, the NO in the original exhaust is re-introduced into the cylinder through the EGR valve 2 to participate in combustion and is thermally decomposed into N 2 and O 2 and O 2 , reducing the generation of NO from the original exhaust. 2 O generation.

[0070] In the present invention, by controlling the ammonia-nitrogen ratio before the first-stage SCR / ASC system 7 within a reasonable range, the unburned ammonia in the original exhaust completely reacts through the first-stage SCR / ASC system 7, thereby preventing ammonia leakage after the first-stage SCR / ASC system 7 from entering the DOC and DPF and oxidizing to generate N 2 O.

[0071] When the original exhaust ANR is not within a reasonable range, the present invention adjusts the opening of the EGR valve 2 to increase the concentration of NO in the original exhaust, enabling the complete conversion of unburned ammonia at the current SCR temperature. If the opening of the EGR valve 2 reaches the threshold and there is still ammonia leakage after the first-stage SCR / ASC, the unburned ammonia in the original exhaust is reduced by reducing the ammonia substitution rate, or the throttle valve actuator on the intake pipeline, or the combustion parameters (adjusting the injection advance angle, pre-injection fuel quantity, rail pressure), so that ANR ≤ ANR threshold and the concentration of NH x ≤ NH 3 concentration ≤ NH3 Threshold value.

[0072] When the original exhaust ANR ≤ ANR threshold value, and the NH concentration detected by the second ammonia sensor > NH 3 concentration 3 concentration threshold value, through the efficiency logic diagnosis of the first-stage SCR / ASC system 7, report the OBD fault of low conversion efficiency of the first-stage SCR / ASC system 7.

[0073] The present invention also provides an EGR type ammonia-diesel fuel engine system, including: an engine 1, an intake pipe 4, an exhaust pipe 5, an ammonia gas cylinder, an ammonia fuel nozzle 10, and the EGR type ammonia-diesel fuel engine after-treatment system as described above; one end of the intake pipe 4 is used for introducing air, and the other end is connected to the engine 1; one end of the exhaust pipe 5 is used for exhausting exhaust gas, and the other end is connected to the engine 1; the ammonia gas cylinder stores ammonia fuel; the ammonia fuel nozzle 10 is connected to the ammonia gas cylinder and is used for injecting ammonia fuel into the engine 1.

[0074] In some embodiments, an air filter 11, a compressor 12, an intercooler 13, and a throttle valve 14 are sequentially arranged on the intake pipe 4 along the intake direction.

[0075] Specifically, as Figure 1 shown, Figure 1 The symbols of each sensor are schematically shown in the upper left corner. A first nitrogen oxide sensor, a first ammonia sensor, and a first temperature sensor are installed in front of the first-stage SCR / ASC system 7, a second nitrogen oxide sensor, a second ammonia sensor, and a second temperature sensor are installed in front of the DOC, a third temperature sensor is installed in front of the DPF, a fourth temperature sensor is installed in front of the second-stage SCR / ASC, and a third nitrogen oxide sensor, a third ammonia sensor, and a fifth temperature sensor are arranged behind the second-stage SCR / ASC for OBD and OBM emission supervision.

[0076] The whole working process is as follows: Fresh air is mixed with ammonia gas injected from the ammonia fuel nozzle 10 at the intake manifold, and then enters the cylinder to participate in combustion. The in-cylinder direct injection of the combustion improver can be and is not limited to diesel, hydrogen, and dimethyl ether. The exhaust gas after cylinder combustion is discharged after doing work through the turbine 6. The exhaust gas in front of the turbine 6 passes through the EGR cooler 15 and the EGR valve 2 and then is mixed with fresh air. By increasing the inert gas in the fresh mixture (CO 2 、H 2 O, etc.) to inhibit the generation of NO x , a part of N 2 O in the original exhaust participates in in-cylinder combustion again through the EGR system. N 2 O decomposes into N 2 and O 2Discharge. The remaining exhaust gas passes through the first-stage SCR / ASC system 7. No reductant injection device is provided in front of the first-stage SCR / ASC system 7, and only relies on the unburned ammonia in the exhaust gas to convert NO x , behind the first-stage SCR / ASC system 7, a DOC and a DPF are connected. An ammonia reductant nozzle 19 is installed behind the DPF. The injected ammonia reductant is mixed with the exhaust gas through a mixer 9 and reacts in the second-stage SCR / ASC system 8. Based on the measurements of the nitrogen oxide sensor, ammonia sensor, and temperature sensor behind the first-stage SCR / ASC system 7 as input parameters, open-loop or closed-loop control injection of the ammonia reductant is performed through the existing National VI aftertreatment logic judgment to convert the excess NO x .

[0077] The present invention also provides a post-treatment method for an EGR type ammonia-diesel fuel engine, such as Figure 2 , including:

[0078] Obtain the ammonia and NO x concentrations in the original exhaust gas;

[0079] Calculate the original exhaust ANR;

[0080] Judge whether the original exhaust ANR is not greater than the ANR threshold;

[0081] If so, then judge whether the ammonia in the exhaust gas after the first-stage SCR treatment is greater than the ammonia threshold. If not, maintain the normal operation of the engine system and the aftertreatment system. If so, report a fault of low conversion efficiency of the first-stage SCR;

[0082] If not, adjust the opening of the EGR valve 2 until the original exhaust ANR is not greater than the ANR threshold. If the original exhaust ANR is still greater than the ANR threshold after the opening of the EGR valve 2 reaches the maximum opening threshold, then judge whether the ammonia in the exhaust gas after the first-stage SCR treatment is greater than the ammonia threshold;

[0083] If not, maintain the normal operation of the engine system and the aftertreatment system;

[0084] If so, reduce the ammonia substitution rate, adjust the throttle actuator on the intake pipe ( Figure 2 the TVA in is the throttle actuator) or adjust the engine combustion strategy until the ammonia in the exhaust gas after the first-stage SCR treatment is less than the ammonia threshold.

[0085] In some embodiments, if it is judged that the ammonia in the exhaust gas after the first-stage SCR treatment is greater than the ammonia threshold;

[0086] Calculate the theoretical efficiency η1 of the first-stage SCR to convert NO x and the actual efficiency η2 of converting NO x ;

[0087] Judge whether η1 >> η2;

[0088] If so, report the OBD fault of low conversion efficiency of the first-stage SCR;

[0089] If not, recalculate the actual efficiency η2 of converting NO x ; and judge whether η1 >> η2 until η1 >> η2, then stop and report the OBD fault of low conversion efficiency of the first-stage SCR.

[0090] The specific control logic is as follows:

[0091] In the following instruction manual, T1 is the temperature detected by the first temperature sensor; T2 is the temperature detected by the second temperature sensor.

[0092] The ammonia-nitrogen ratio (ANR) of NO x and NH 3 in the original exhaust is set in the range (0.8 - 1), which is the ANR threshold, but not limited to (0.8 - 1). The temperature Tsub of the first-stage SCR / ASC system 7 = (T1 + T2) / 2. Look up the MAP according to the space velocity and Tsub. Tsub is the meaning of the temperature of the after-treatment carrier, and MAP is the three-dimensional data matrix for calibration, mainly reflecting the control parameters (such as fuel injection quantity, intake air pressure, thermal efficiency, etc.) of the diesel engine under specific rotational speed and load conditions, and obtain the accurate ANR value corresponding to the full conversion of NH 3 at the temperature of the first-stage SCR / ASC system 7, ensuring that the NH 3 in the original exhaust fully reacts through the first-stage SCR / ASC system 7. The ammonia-nitrogen ratio calculation formula is as follows:

[0093] NH 3 mass flow rate (mg / s) = NH 3 concentration × exhaust gas flow rate × 277.78 × 17 / 10^3 / 29

[0094] NO x mass flow rate (mg / s) = NO x concentration × exhaust gas flow rate × 277.78 × 46 / 10^3 / 29

[0095] ANR = NH 3 mass flow rate / NO x mass flow rate

[0096] If ANR ≤ ANR threshold, it means that the NO x concentration in the original exhaust is too high, and the NH 3 in the original exhaust can fully react through the first-stage SCR / ASC system 7. Detect the ammonia concentration measured by the second ammonia sensor. If the NH 3 concentration ≤ NH 3Threshold, the unburned ammonia in the original exhaust has completely reacted, and there is no risk of ammonia leakage into the DOC and DPF for oxidation to generate N 2 O. If the NH 3 concentration > NH 3 threshold, it is suspected that the catalyst of the first-stage SCR / ASC system 7 is deteriorated or poisoned. According to the NO x value detected by the nitrogen oxide sensor upstream of the first-stage SCR / ASC system 7 and the NO x value calculated by the model of the first-stage SCR / ASC system 7 downstream, calculate the theoretical NO x conversion efficiency η1 of the first-stage SCR / ASC system 7, and the actual NOx conversion efficiency η2 calculated according to the nitrogen oxide sensors upstream and downstream of the first-stage SCR / ASC system 7. Judge the relationship between η1 and η2. If η1 >> η2, report an OBD fault with low conversion efficiency of the first-stage SCR / ASC system 7. At this time, there is a risk of NH 3 leakage and N 2 O over-limit value.

[0097] Formulas for calculating the efficiency of the first-stage SCR / ASC system 7 model and the efficiency calculated by the sensor:

[0098] η1 = (Value of the first nitrogen oxide sensor - NOx value calculated by the model of the first-stage SCR / ASC system 7 downstream) / Value of the first nitrogen oxide sensor.

[0099] η2 = [Value of the first nitrogen oxide sensor - (Value of the second nitrogen oxide sensor - Value of the second ammonia sensor)] / Value of the first nitrogen oxide sensor.

[0100] If the original exhaust ANR > ANR threshold, it means that the concentration of unburned ammonia in the original exhaust is too high. At this time, it is necessary to control the opening of the EGR valve 2 to increase the NO x concentration in the original exhaust to make the original exhaust ANR within a reasonable range. If the EGR valve 2 is adjusted to the maximum threshold opening, that is, the threshold of the EGR valve 2, detect the reading of the second ammonia sensor. If the NH 3 concentration > NH 3 concentration threshold, then at this time, it is necessary to reduce the ammonia substitution rate, adjust the throttle actuator on the intake pipe, or adjust the original engine combustion strategy (adjust combustion parameters such as injection advance angle, pre-injection fuel quantity, and rail pressure) to reduce the NH 3 concentration in the original exhaust, so as to control ANR ≤ ANR threshold and NH 3 concentration ≤ NH 3 concentration threshold.

[0101] In the present invention, specific examples are used to illustrate the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An EGR type ammonia-diesel fuel engine aftertreatment system, characterized in that: include: A return pipe, the two ends of which are respectively connected to the exhaust pipe and the intake pipe; An EGR valve is disposed on the return pipe; The first stage SCR is used to be arranged on the exhaust pipe downstream of the connection between the return pipe and the exhaust pipe. The first stage SCR only relies on the unburned ammonia in the original exhaust gas to convert NO x ; A second-stage SCR is used to be arranged on the exhaust pipe downstream of the first-stage SCR; an ammonia reducing agent nozzle is arranged on the exhaust pipe upstream of the second-stage SCR; an ammonia sensor, disposed on the exhaust pipe upstream and downstream of the first-stage SCR; a nitrogen oxide sensor, disposed on the exhaust pipe upstream and downstream of the first stage SCR; A control module, wherein the control module is in communication with the ammonia sensor, the nitrogen oxide sensor, the EGR valve and the ammonia reductant nozzle; the control module calculates the original exhaust ANR; And determine whether the original row ANR is not greater than the ANR threshold; If yes, determine whether the ammonia in the exhaust gas after the first-stage SCR treatment is greater than the ammonia threshold. If no, maintain the normal operation of the engine system and the post-treatment system. If yes, report a fault of low conversion efficiency of the first-stage SCR. If not, the opening of the EGR valve is adjusted until the original exhaust ANR is not greater than the ANR threshold. If the original exhaust ANR is still greater than the ANR threshold after the opening of the EGR valve reaches the maximum opening threshold, it is determined whether the ammonia in the exhaust gas after the first-stage SCR treatment is greater than the ammonia threshold. If not, maintain the normal operation of the engine system and the aftertreatment system; If so, the ammonia replacement rate of the engine is reduced, the throttle valve actuator on the intake pipe is adjusted, or the engine combustion strategy is adjusted so that the ammonia in the exhaust gas after the first-stage SCR treatment is less than the ammonia threshold.

2. The EGR type ammonia-diesel fuel engine aftertreatment system according to claim 1, characterized in that: The return pipe is also provided with an EGR cooler and a one-way valve.

3. The EGR type ammonia-diesel fuel engine aftertreatment system according to claim 1, characterized in that: A temperature sensor is provided on the exhaust pipe between the first-stage SCR and the second-stage SCR. The control module uses the measurement data of the nitrogen oxide sensor, the ammonia sensor and the temperature sensor on the exhaust pipe between the first-stage SCR and the second-stage SCR as input parameters, and controls the ammonia reducing agent nozzle to perform open-loop or closed-loop control injection of the ammonia reducing agent through a preset post-processing logic to convert excess NO x .

4. The EGR type ammonia-diesel fuel engine aftertreatment system according to claim 1, characterized in that: An ASC system is also configured on the exhaust pipe downstream of the first-stage SCR and the exhaust pipe downstream of the second-stage SCR.

5. The EGR type ammonia-diesel fuel engine aftertreatment system according to claim 1, characterized in that: The exhaust pipe between the first-stage SCR and the second-stage SCR is provided with a DOC and a DPF.

6. The EGR type ammonia-diesel fuel engine aftertreatment system according to claim 1, characterized in that: A mixer is arranged on the exhaust pipe upstream of the second-stage SCR, and the ammonia reducing agent nozzle is arranged on the mixer.

7. An EGR type ammonia-diesel fuel engine system, characterized in that: include: engine; An air intake duct, one end of which is used to take in air and the other end of which is connected to the engine; An exhaust pipe, one end of which is used for exhaust and the other end of which is connected to the engine; An ammonia cylinder, wherein ammonia fuel is stored in the ammonia cylinder; an ammonia fuel nozzle, connected to the ammonia cylinder and used to inject ammonia fuel into the engine; as well as An EGR type ammonia-diesel fuel engine aftertreatment system as claimed in any one of claims 1 to 6.

8. The EGR type ammonia-diesel fuel engine system according to claim 7, characterized in that: The air intake pipeline is provided with an air filter, a compressor, an intercooler and a throttle valve in sequence along the air intake direction.

9. An EGR type ammonia-diesel fuel engine post-treatment method, characterized in that: include: Obtain ammonia and NO in the original exhaust gas x concentration; Calculate the original row ANR; Determine whether the original row ANR is not greater than the ANR threshold; If yes, determine whether the ammonia in the exhaust gas after the first-stage SCR treatment is greater than the ammonia threshold. If no, maintain the normal operation of the engine system and the post-treatment system. If yes, report the fault of low conversion efficiency of the first-stage SCR. If not, the opening of the EGR valve is adjusted until the original exhaust ANR is not greater than the ANR threshold. If the original exhaust ANR is still greater than the ANR threshold after the opening of the EGR valve reaches the maximum opening threshold, it is determined whether the ammonia in the exhaust gas after the first-stage SCR treatment is greater than the ammonia threshold. If not, maintain the normal operation of the engine system and the aftertreatment system; If so, the ammonia replacement rate is reduced, the throttle valve actuator opening on the intake pipe is adjusted, or the engine combustion strategy is adjusted so that the ammonia in the exhaust gas after the first-stage SCR treatment is less than the ammonia threshold.

10. The post-treatment method of an EGR type ammonia-diesel fuel engine according to claim 9, characterized in that: If it is determined that the ammonia in the exhaust gas after the first-stage SCR treatment is greater than the ammonia threshold; Calculate the first stage SCR conversion of NO x The theoretical efficiency η1 and the conversion of NO x The actual efficiency η2; Determine whether η1>>η2; If so, an OBD fault of low conversion efficiency of the first-stage SCR is reported; If not, repeat the calculation of conversion NO x The actual efficiency η2; and determine whether η1>>η2 until η1>>η2 stops and reports the OBD fault of low conversion efficiency of the first-stage SCR.

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