CN108915826B - SCR electric control system feedforward correction method based on zirconia type NOx sensor - Google Patents

SCR electric control system feedforward correction method based on zirconia type NOx sensor Download PDF

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CN108915826B
CN108915826B CN201810715569.4A CN201810715569A CN108915826B CN 108915826 B CN108915826 B CN 108915826B CN 201810715569 A CN201810715569 A CN 201810715569A CN 108915826 B CN108915826 B CN 108915826B
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CN108915826A (en
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尹自斌
欧顺华
曾步辉
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Jimei University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/14—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/04—Methods of control or diagnosing
    • F01N2900/0404—Methods of control or diagnosing using a data filter
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/04—Methods of control or diagnosing
    • F01N2900/0411—Methods of control or diagnosing using a feed-forward control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/04—Methods of control or diagnosing
    • F01N2900/0412—Methods of control or diagnosing using pre-calibrated maps, tables or charts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/04—Methods of control or diagnosing
    • F01N2900/0416—Methods of control or diagnosing using the state of a sensor, e.g. of an exhaust gas sensor
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

The invention relates to a feed-forward correction method of SCR (Selective catalytic reduction) electric control systems based on zirconia NOx sensors, which comprises the steps of firstly collecting and processing the rotating speed and the torque of a diesel engine by the SCR electric control systemAnd NOx sensor signal information before the SCR reactor; wherein the signal information of the NOx sensor includes O2The concentration of (d) and the concentration of NOx; then, establishing an excess air coefficient calculation model: then executing a MAP (MAP) MAP query program stored in the SCR electronic control system, and querying a MAP MAP of the basic urea injection quantity, the excess air coefficient and the original engine NOx concentration corresponding to the current working condition of the diesel engine; calculating the urea O in turn2-Urea NOx-Urea correction and Urea NOx correction; and finally correcting the urea injection quantity. The invention corrects the basic urea injection quantity, and avoids the over standard of NOx emission and NH3 escape after the SCR reactor caused by the change of the exhaust characteristics of the diesel engine.

Description

SCR electric control system feedforward correction method based on zirconia type NOx sensor
Technical Field
The invention relates to the field of SCR (selective catalytic reduction) of marine diesel engines, in particular to a feedforward correction method for SCR electronic control systems based on zirconia NOx sensors.
Background
According to the provisions of the MARPOL convention VI issued by the International Maritime Organization (IMO), if a ship built after 1/2016 sails in an emission control area, the NOx emission of an engine implements a more strict Tier III standard, the SCR technology has the advantages of good economy, small change on a diesel engine, high NOx conversion rate, insensitivity to sulfur, application range and the like, and is of the technology with great application prospects in the control of the NOx emission of the marine diesel engine.
After the SCR system is additionally arranged on the marine diesel engine, the exhaust back pressure of the marine diesel engine is increased, and the efficiency of the turbocharger is reduced due to the increase of the exhaust back pressure, so that the intake pressure is reduced, the intake air quantity is reduced, and the economical efficiency, the dynamic property, the emission property and other properties of the diesel engine are different from those of the original diesel engine. And with the use of the SCR reactor, urea is crystallized on the bed body of the reactor, and particles are gathered on the bed body, which can cause the pressure drop of the reactor to be gradually increased. The technical state of the marine diesel engine changes along with the use time, and the operating environmental conditions and the quality of used fuel oil change, which result in the change of the exhaust characteristics of the diesel engine. Therefore, the exhaust characteristics (parameters such as the exhaust mass flow rate and the NOx concentration) of the diesel engine during actual operation may deviate from the data at the time of calibration thereof.
The basic urea injection quantity is mainly influenced by the exhaust mass flow and NOx concentration emission of the diesel engine, and the proper urea injection quantity under each working condition of the diesel engine directly influences the NOx concentration and ammonia escape quantity behind the SCR reactor, so that whether the performance of the SCR system meets the emission regulation requirements is influenced.
At present, the urea injection control strategy of the SCR electronic control system mostly adopts an open-loop control strategy based on a urea injection quantity MAP graph or adopts a mode of combining the MAP graph based on exhaust characteristics and NOx concentration values collected by a sensor to establish an original machine emission characteristic prediction model.
The open-loop control strategy based on the urea injection quantity MAP does not consider the influence of exhaust characteristic change on the denitration performance of the SCR system when the diesel engine actually runs, and the influence of exhaust mass flow change of the diesel engine on the denitration performance of the SCR system is ignored based on the feed-forward correction of NOx concentration. Both of which may cause the post-SCR NOx emissions to fail emission legislation requirements and cause NH3The escape exceeds the standard.
Disclosure of Invention
In view of the above, the present invention aims to provide feedforward correction methods for SCR electronic control systems based on zirconia NOx sensors, which are used for correcting the basic urea injection amount and avoiding the NOx emission and NH after SCR reactors caused by the change of the exhaust characteristics of diesel engines3The escape exceeds the standard.
The invention adopts the following scheme that SCR electric control system feedforward correction methods based on zirconia type NOx sensors specifically comprise the following steps:
step S1: the SCR electric control system collects and processes the rotating speed and torque of the diesel engine and the signal information of a NOx sensor in front of the SCR reactor; wherein the signal information of the NOx sensor includes O2The concentration of (d) and the concentration of NOx;
step S2: establishing an excess air coefficient lambda calculation model:
Figure BDA0001717333390000021
in the formula (I), the compound is shown in the specification,
Figure BDA0001717333390000022
to O in exhaust gas2The concentration of (c);
step S3: executing a MAP (MAP) MAP query program stored in the SCR electronic control system, and querying a MAP MAP of the basic urea injection quantity, the excess air coefficient and the original engine NOx concentration corresponding to the current diesel engine working condition;
step S4: calculating urea O according to the excess air coefficient lambda calculated in the step S2 and the MAP of the excess air coefficient MAP obtained by inquiring in the step S3 and the basic urea injection quantity2-Urea correction;
step S5: calculating the Urea NOx-Urea correction quantity according to the NOx concentration collected by the NOx sensor and the original NOx concentration MAP obtained by inquiring in the step S3 and the Urea basic injection quantity;
step S6: the basic injection amount of urea described in step S3 and the urea O described in step S42-Urea injection quantity is determined as the sum of Urea NOx-Urea correction quantity described in S5 and Urea NOx correction quantity.
, the step S4 includes:
step S41: inquiring an excess air coefficient MAP graph under a steady state according to the current operating condition of the diesel engine to obtain an excess air coefficient MAP value under the steady state operating condition;
step S42: the excess air ratio MAP value lambda queried in step S41MAPThe excess air ratio deviation m is obtained in comparison with the excess air ratio λ calculated in step S2:
m＝λ-λMAP；
step S43: judging whether the absolute value of m is greater than 0.1, if not, enabling urea O2-Urea correction Z1 is 0; if yes, go to step S44;
step S44: making urea O2Urea correction Z1 is:
Z1＝n*Urea；
wherein Urea is the basic Urea injection quantity, and n is m/lambdaMAPIs the rate of deviation of the air excess factor.
, the step S5 includes the following steps:
step S51: inquiring a nitrogen oxide NOx concentration MAP under a steady state according to the working conditions of the diesel engine to obtain a NOx concentration value NOx under the steady state working conditionsMAP；
Step S52: the actual concentration value NOx of NOx acquired by the NOx sensor in the step S1Actual valueNOx obtained by the inquiry of step S51MAPBy comparison, the NOx concentration deviation x is obtained:
x＝NOxactual value-NOxMAP；
Step S53: judging whether the absolute value of the NOx concentration deviation x is larger than 50, and if not, making the Urea NOx-Urea correction quantity Z2 be 0; if yes, the flow proceeds to step S54:
step S54: let the Urea NOx-Urea correction Z2 be:
Z2＝y*Urea；
where Urea is a basic Urea injection amount, and y is x/NOxMAPIs the deviation ratio of the NOx concentration.
, the NOx concentration collected by the NOx sensor in the step S1 is filtered by a filter function.
, step of step S2 shows that the exhaust mass flow Q and the excess air ratio lambda of each operating point of the diesel engine are in a linear relationship:
Q＝(1+λ·L)·q；
in the formula, L is the theoretical air demand, and q is the fuel consumption.
By the formulaThe exhaust gas mass flow can be calculated indirectly from Q ═ 1+ λ · L · Q.
Compared with the prior art, the invention has the following beneficial effects: the invention adopts the SCR electronic control system urea injection feedforward correction based on the data of the NOx sensor in front of the SCR reactor, can reduce the workload of the urea injection calibration test of the SCR system, improve the precision and the response speed of the urea injection control, and can improve the transportability and the adaptability of the electronic control system.
Drawings
Fig. 1 is a schematic diagram of the principle of the embodiment of the present invention.
FIG. 2 is O of an embodiment of the present invention2A schematic diagram of urea correction calculation.
FIG. 3 is a diagram illustrating NOx urea correction amount calculation according to an embodiment of the present invention.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
It is noted that the following detailed description is exemplary and is intended to provide further explanation of the invention at unless otherwise indicated.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
As shown in fig. 1, the present embodiment provides feed-forward correction methods for an SCR electronic control system based on a zirconia NOx sensor, which specifically include the following steps:
step S1: the SCR electric control system collects and processes the rotating speed and torque of the diesel engine and the signal information of a NOx sensor in front of the SCR reactor; wherein the signal information of the NOx sensor includes O2The concentration of (d) and the concentration of NOx;
step S2: establishing an excess air coefficient lambda calculation model:
Figure BDA0001717333390000051
in the formula (I), the compound is shown in the specification,to O in exhaust gas2Concentration of (d)%;
step S3: executing a MAP (MAP) MAP query program stored in the SCR electronic control system, and querying a MAP MAP of the basic urea injection quantity, the excess air coefficient and the original engine NOx concentration corresponding to the current diesel engine working condition;
step S4: calculating urea O according to the excess air coefficient lambda calculated in the step S2 and the MAP of the excess air coefficient MAP obtained by inquiring in the step S3 and the basic urea injection quantity2-Urea correction;
step S5: calculating the Urea NOx-Urea correction quantity according to the NOx concentration collected by the NOx sensor and the original NOx concentration MAP obtained by inquiring in the step S3 and the Urea basic injection quantity;
step S6: the basic injection amount of urea described in step S3 and the urea O described in step S42-Urea injection quantity is determined as the sum of Urea NOx-Urea correction quantity described in S5 and Urea NOx correction quantity.
As shown in fig. 2, in the present embodiment, step S4 includes:
step S41: inquiring an excess air coefficient MAP graph under a steady state according to the current operating condition of the diesel engine to obtain an excess air coefficient MAP value under the steady state operating condition;
step S42: the excess air ratio MAP value lambda queried in step S41MAPThe excess air ratio deviation m is obtained in comparison with the excess air ratio λ calculated in step S2:
m＝λ-λMAP；
step S43: judging whether the absolute value of m is greater than 0.1, if not, enabling urea O2-Urea correction Z1 is 0; if yes, go to step S44;
step S44: making urea O2Urea correction Z1 is:
Z1＝n*Urea；
wherein Urea is the basic Urea injection quantity, and n is m/lambdaMAPIs the rate of deviation of the air excess factor.
As shown in fig. 3, in the present embodiment, step S5 includes the following steps:
step S51: inquiring a nitrogen oxide NOx concentration MAP under a steady state according to the working conditions of the diesel engine to obtain a NOx concentration value NOx under the steady state working conditionsMAP；
Step S52: the actual concentration value NOx of NOx acquired by the NOx sensor in the step S1Actual valueNOx obtained by the inquiry of step S51MAPBy comparison, the NOx concentration deviation x is obtained:
x＝NOxactual value-NOxMAP；
Step S53: judging whether the absolute value of the NOx concentration deviation x is larger than 50, and if not, making the Urea NOx-Urea correction quantity Z2 be 0; if yes, the flow proceeds to step S54:
step S54: let the Urea NOx-Urea correction Z2 be:
Z2＝y*Urea；
where Urea is a basic Urea injection amount, and y is x/NOxMAPIs the deviation ratio of the NOx concentration.
In this embodiment, the NOx concentration collected by the NOx sensor in step S1 is filtered by using a filter function.
In the present embodiment, step in step S2 shows that the exhaust mass flow Q and the excess air ratio λ of the diesel engine at each operating point are in a linear relationship:
Q＝(1+λ·L)·q；
where L is the theoretical air demand, 14.5 (humid air) (kg/kg fuel); q is the fuel consumption, kg/h; q is exhaust mass flow, kg/h.
By the formula
Figure BDA0001717333390000071
The exhaust gas mass flow can be calculated indirectly from Q ═ 1+ λ · L · Q.
Table 1 shows the results of a test rig test on a marine diesel engine and the results of a verification of the feed forward correction of the urea injection amount based on a NOx sensor. In table 1, "basic injection amount 1" is a urea injection amount calculated from original engine emission data (without considering the influence of the SCR reactor on the diesel engine exhaust characteristic), "basic injection amount 2" is an injection amount calculated from diesel engine emission data after the SCR reactor is installed (actual urea demand after the SCR reactor is installed), "urea injection amount" is a urea injection amount calculated based on the NOx sensor feedforward correction model on the basis of "basic injection amount 1" (urea injection amount after the SCR reactor is corrected on the original engine exhaust characteristic in consideration of the influence of the SCR reactor on the diesel engine exhaust characteristic), and the deviation rate is a percentage of the deviation of "urea injection amount" from "basic injection amount 2" with respect to the urea injection amount. As can be seen from Table 1, after the SCR reactor is added, the actual demand of urea at each operating point is reduced to different degrees, and the maximum deviation rate of the urea injection quantity calculated by the feedforward correction model in the steps S4 and S5 is maximally close to 9% compared with the actual demand.
Figure BDA0001717333390000072
According to the embodiment, the urea injection feedforward correction of the SCR electric control system based on the data of the NOx sensor in front of the SCR reactor is adopted, so that the workload of the urea injection calibration test of the SCR system can be reduced, the precision and the response speed of urea injection control are improved, and the transportability and the adaptability of the electric control system can be improved.
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.

Claims (5)

1, SCR electric control system feedforward correction method based on zirconia type NOx sensor, characterized by comprising the following steps:
step S1: the SCR electric control system collects and processes the rotating speed and torque of the diesel engine and the signal information of a NOx sensor in front of the SCR reactor; wherein the signal information of the NOx sensor includes O2The concentration of (d) and the concentration of NOx;
step S2: establishing an excess air coefficient lambda calculation model:
Figure FDA0002136778030000011
in the formula (I), the compound is shown in the specification,
Figure FDA0002136778030000012
to O in exhaust gas2Concentration of (d)%;
step S3: executing a MAP (MAP) MAP query program stored in the SCR electronic control system, and querying a MAP MAP of the basic urea injection quantity, the excess air coefficient and the original engine NOx concentration corresponding to the current diesel engine working condition;
step S4: calculating urea O according to the excess air coefficient lambda calculated in the step S2 and the MAP of the excess air coefficient MAP obtained by inquiring in the step S3 and the basic urea injection quantity2-Urea correction;
step S5: calculating the Urea NOx-Urea correction quantity according to the NOx concentration collected by the NOx sensor and the original NOx concentration MAP obtained by inquiring in the step S3 and the Urea basic injection quantity;
step S6: the basic injection amount of urea described in step S3 and the urea O described in step S42-Urea injection quantity is determined as the sum of Urea NOx-Urea correction quantity described in S5 and Urea NOx correction quantity.
2. The method of claim 1 wherein step S4 includes:
step S41: inquiring an excess air coefficient MAP graph under a steady state according to the current operating condition of the diesel engine to obtain an excess air coefficient MAP value under the steady state operating condition;
step S42: the excess air ratio MAP value lambda queried in step S41MAPThe excess air ratio deviation m is obtained in comparison with the excess air ratio λ calculated in step S2:
m＝λ-λMAP；
step S43: judging whether the absolute value of m is greater than 0.1, if not, enabling urea O2-Urea correction Z1 is 0; if yes, go to step S44;
step S44: making urea O2Urea correction Z1 is:
Z1＝n*Urea；
wherein Urea is the basic Urea injection quantity, and n is m/lambdaMAPIs the rate of deviation of the air excess factor.
3. The method of claim 1 wherein step S5 includes the steps of:
step S51: inquiring a nitrogen oxide NOx concentration MAP under a steady state according to the working conditions of the diesel engine to obtain a NOx concentration value NOx under the steady state working conditionsMAP；
Step S52: the actual concentration value NOx of NOx acquired by the NOx sensor in the step S1Actual valueNOx obtained by the inquiry of step S51MAPBy comparison, the NOx concentration deviation x is obtained:
x＝NOxactual value-NOxMAP；
Step S53: judging whether the absolute value of the NOx concentration deviation x is larger than 50, and if not, making the Urea NOx-Urea correction quantity Z2 be 0; if yes, the flow proceeds to step S54:
step S54: let the Urea NOx-Urea correction Z2 be:
Z2＝y*Urea；
where Urea is a basic Urea injection amount, and y is x/NOxMAPIs the deviation ratio of the NOx concentration.
4. The feedforward correction method of SCR electric control system based on zirconia type NOx sensor of claim 1, wherein the NOx concentration collected by the NOx sensor in step S1 is filtered by a filter function.
5. The feed-forward correction method for the SCR electric control system based on the zirconia type NOx sensor as recited in claim 1, wherein the step of in the step S2 is that the exhaust mass flow Q and the excess air coefficient lambda of each operating point of the diesel engine are in a linear relationship:
Q＝(1+λ·L)·q；
in the formula, L is the theoretical air demand, and q is the fuel consumption.
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