Method for controlling exhaust after-treatment system based on NO.SUB.2 medium adjustment

Abstract

A method for controlling an exhaust after-treatment system based on NO.sub.2 medium adjustment includes the following steps: creating a diesel oxidation catalyst (DOC) reaction map, a diesel particulate filter (DPF) reaction map, and a selective catalytic reduction (SCR) reaction map; obtaining an SCR reaction temperature, desired SCR reaction efficiency, and obtaining NO.sub.2 demand according to the SCR reaction map; obtaining a DPF reaction temperature and differential pressure, and obtaining NO.sub.2 consumption from the DPF reaction map; obtaining NO.sub.2 production, and calculating NO.sub.2 input for SCR; if the NO.sub.2 input is not equal to the NO.sub.2 demand, calculating target NO.sub.2 production, obtaining a target DOC reaction temperature corresponding to the target NO.sub.2 production from the DOC reaction map, and adjusting a fuel injection rate so that the DOC reaction temperature is equal to the target DOC reaction temperature.

Claims

1. A method for controlling an exhaust after-treatment system based on NO.sub.2 medium adjustment, comprising the following steps: S1: creating a diesel oxidation catalyst (DOC) reaction map to obtain a relationship between a DOC reaction temperature and NO.sub.2 production, creating a diesel particulate filter (DPF) reaction map to obtain a relationship between a DPF operation temperature and a DPF differential pressure, and NO.sub.2 consumption, and creating a selective catalytic reduction (SCR) reaction map to obtain a relationship between an SCR reaction temperature and an SCR reaction efficiency, and NO.sub.2 demand; S2: detecting an SCR reaction temperature of an SCR via a temperature sensor unit and obtaining a NO.sub.2 demand according to the SCR reaction map based on the detected SCR reaction temperature in order to achieve a desired SCR reaction efficiency; S3: detecting a DPF operation temperature of a DPF via the temperature sensor unit and detecting a DPF differential pressure of the DPF via a pressure sensor unit, and obtaining a NO.sub.2 consumption of the DPF according to the DPF reaction map based on the detected DPF operation temperature and the detected DPF differential pressure; S4: detecting a NO.sub.2 production by a DOC via a concentration sensor unit, and calculating a NO.sub.2 input to the SCR based on the NO.sub.2 production of the DOC and the NO.sub.2 consumption of the DPF; S5: if the NO.sub.2 input is equal to the NO.sub.2 demand, performing step S2 to step S4; otherwise, performing step S6; and S6: calculating a target NO.sub.2 production based on the NO.sub.2 demand and the NO.sub.2 consumption, obtaining a target DOC reaction temperature corresponding to the target NO.sub.2 production based on the DOC reaction map, and adjusting a fuel injection rate so that the DOC reaction temperature is equal to the target DOC reaction temperature, wherein the DOC reaction temperature is controlled by regulating the fuel injection rate and the NO.sub.2 production by the DOC is controlled through regulating the fuel injection rate to control the target DOC reaction temperature such that the NO.sub.2 production by the DOC is equal to the target NO.sub.2 production.

2. The method according to claim 1, wherein the temperature sensor unit comprises one or more DOC reaction temperature sensor(s), one or more DPF operation temperature sensor(s), and one or more SCR reaction temperature sensor(s).

3. The method according to claim 1, wherein the concentration sensor unit comprises one or more NO.sub.2 concentration sensor(s) disposed at a DOC outlet.

4. The method according to claim 1, wherein the concentration sensor unit comprises one or more NO.sub.2 concentration sensor(s) disposed at a DPF inlet.

5. The method according to claim 1, wherein the pressure sensor unit comprises one or more pressure sensor(s) disposed at a DPF inlet and one or more pressure sensor(s) disposed at a DPF outlet.

6. The method according to claim 1, wherein in step S1, the creating the DOC reaction map comprises the following steps: a1: obtaining the DOC reaction temperature; a2: obtaining the NO.sub.2 production with the DOC; a3: recording the relationship between the DOC reaction temperature and the NO.sub.2 production; and a4: repeating the previous steps until the DOC reaction temperature map is obtained.

7. The method according to claim 1, wherein in step S1, the creating the DPF reaction map comprises the following steps: b1: obtaining the DPF operation temperature; b2: obtaining the DPF differential pressure and determining regeneration efficiency of the DPF; b3: obtaining the NO.sub.2 consumption at the DPF; b4: recording the relationship between the DPF operation temperature and the DPF differential pressure, and the NO.sub.2 consumption at the DPF; and b5: repeating the previous steps until the DPF reaction temperature map is obtained.

8. The method according to claim 1, wherein in step S1, the creating the SCR reaction map comprises the following steps: c1: obtaining the NO.sub.2 input; c2: obtaining the SCR reaction temperature; c3: determining the SCR reaction efficiency; c4: recording the relationship between the SCR reaction temperature and the SCR reaction efficiency, and the NO.sub.2 input; and c5: repeating the previous steps until the SCR reaction temperature map is obtained.

9. The method according to claim 1, wherein in step S4, the NO.sub.2 input is equal to a difference between the NO.sub.2 production and the NO.sub.2 consumption; and in step S6, the target NO.sub.2 production is equal to a sum of the NO.sub.2 demand and the NO.sub.2 consumption.

10. The method according to claim 1, wherein in step S6, if a current DOC reaction temperature T1 is equal to the target DOC reaction temperature, the fuel injection rate is kept unchanged; if the current DOC reaction temperature T1 is above the target DOC reaction temperature, the fuel injection rate is reduced; and if the current DOC reaction temperature T1 is below the target DOC reaction temperature, the fuel injection rate is increased.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flowchart according to an example of present disclosure.

(2) FIG. 2 is a schematic diagram of DOC temperature control according to an example of present disclosure.

DETAILED DESCRIPTION

(3) The present disclosure is now described in detail in conjunction with the accompanying drawings and a specific example. The example is implemented on the premise of the technical solutions of the present disclosure. The following presents the detailed implementation and specific operation process. The protection scope of the present disclosure, however, is not limited to the following example.

Example 1

(4) A method for controlling an exhaust after-treatment system based on NO.sub.2 medium adjustment, as shown in FIG. 1, includes the following steps:

(5) S1: a DOC reaction map is created to obtain a relationship between a DOC reaction temperature and NO.sub.2 production. The specific steps are as follows:

(6) a1: obtain the DOC reaction temperature;

(7) a2: obtain the NO.sub.2 production with the DOC;

(8) a3: record a relationship between the DOC reaction temperature and the NO.sub.2 production; and

(9) a4: repeat the previous steps until the DOC reaction temperature map is obtained.

(10) The DPF reaction map is created to obtain a relationship between a DPF reaction temperature and a DPF differential pressure, and NO.sub.2 consumption. The specific steps are as follows:

(11) b1: obtain the DPF reaction temperature;

(12) b2: obtain a DPF differential pressure and determining regeneration efficiency of the DPF;

(13) b3: obtain the NO.sub.2 consumption at the DPF;

(14) b4: record a relationship between the DPF reaction temperature and the DPF differential pressure, and the NO.sub.2 consumption at the DPF; and

(15) b5: repeat the previous steps until the DPF reaction temperature map is obtained.

(16) An SCR reaction map is created to obtain a relationship between an SCR reaction temperature and SCR reaction efficiency, and NO.sub.2 demand. The specific steps are as follows:

(17) c1: obtain the NO.sub.2 input;

(18) c2: obtain the SCR reaction temperature;

(19) c3: determine the SCR reaction efficiency;

(20) c4: record a relationship between the SCR reaction temperature and the SCR reaction efficiency, and the NO.sub.2 input; and

(21) c5: repeat the previous steps until the SCR reaction temperature map is obtained.

(22) S2: the SCR reaction temperature is obtained via a temperature sensor unit and the NO.sub.2 demand is obtained according to the SCR reaction map based on desired SCR reaction efficiency. The temperature sensor unit includes one or more DOC reaction temperature sensor(s), one or more DPF reaction temperature sensor(s), and one or more SCR reaction temperature sensor(s).

(23) In this example, two DOC reaction temperature sensors, two DPF reaction temperature sensors and two SCR reaction temperature sensors are used. In other embodiments, the number of the sensors can be adjusted based on cost and accuracy.

(24) To convert exhaust with high efficiency, the desired SCR reaction efficiency is 90% in this example. After the SCR reaction temperature, NO.sub.2 input that may lead to 90% reaction efficiency of SCR at the current temperature is obtained according to the SCR reaction map. This NO.sub.2 input is the NO.sub.2 demand.

(25) S3: a DPF reaction temperature is obtained via the temperature sensor unit, and a DPF differential pressure is obtained via a pressure sensor unit, and then NO.sub.2 consumption is obtained based on the DPF reaction map. The pressure sensor unit includes one or more pressure sensor (s) disposed at a DPF inlet and one or more pressure sensor (s) disposed at a DPF outlet.

(26) In this example, two pressure sensors are disposed at the DPF inlet while two pressure sensors are disposed at the DPF outlet.

(27) S4: the NO.sub.2 production with the DOC is obtained via a concentration sensor unit, and the NO.sub.2 input for SCR is calculated based on the NO.sub.2 production and the NO.sub.2 consumption. The NO.sub.2 input is equal to a difference between the NO.sub.2 production and the NO.sub.2 consumption. The concentration sensor unit includes one or more NO.sub.2 concentration sensor (s) disposed at the DOC outlet. Since the DOC outlet is connected to the DPF inlet, the concentration sensor unit may also include one or more NO.sub.2 concentration sensor (s) disposed at the DPF inlet.

(28) In this example, two NO.sub.2 concentration sensors are disposed at the DOC outlet.

(29) S5: if the NO.sub.2 input is equal to the NO.sub.2 demand, indicating no need to adjust a working state of each component, step S2 is performed; otherwise, step S6 is performed and the working state is adjusted.

(30) If the NO.sub.2 input is greater than the NO.sub.2 demand, it indicates that the NO.sub.2 input exceeds the NO.sub.2 demand for keeping 90% reaction efficiency of SCR at this reaction temperature. In this case, the NO.sub.x conversion efficiency of SCR will be suppressed. Therefore, the NO.sub.2 input and the DOC reaction temperature both need to be reduced so that the NO.sub.2 production decreases.

(31) If the NO.sub.2 input is less than the NO.sub.2 demand, it indicates that the NO.sub.2 input does not reach the NO.sub.2 demand for keeping 90% reaction efficiency of SCR at this reaction temperature. Therefore, the NO.sub.2 input and the DOC reaction temperature both need to be increased so that the NO.sub.2 production increases.

(32) S6: target NO.sub.2 production is calculated based on the NO.sub.2 demand and the NO.sub.2 consumption, where the target NO.sub.2 production is equal to a sum of the NO.sub.2 demand and the NO.sub.2 consumption. A target DOC reaction temperature corresponding to the target NO.sub.2 production is then obtained based on the DOC reaction map, and the current DOC reaction temperature is adjusted to the target DOC reaction temperature to control the NO.sub.2 production with the DOC to be same as the target NO.sub.2 production.

(33) As shown in FIG. 2, if the current DOC reaction temperature T1 is equal to the target DOC reaction temperature, a fuel injection rate of a tail pipe is kept unchanged. If the current DOC reaction temperature T1 is above the target DOC reaction temperature, the fuel injection rate of the tail pipe is reduced so as to reduce the reaction temperature and increase an oxidation rate of NO. If the current DOC reaction temperature T1 is below the target DOC reaction temperature, the fuel injection rate of the tail pipe is increased so as to increase the reaction temperature and reduce the oxidation rate of NO.

(34) S7: step S2 is repeated until the exhaust after-treatment system stops working.

(35) The foregoing is detailed description of the preferred specific example of the present disclose. It should be understood that a person of ordinary skill in the art can make various modifications and variations according to the concept of the present invention without creative efforts. Therefore, all technical solutions that a person skilled in the art can arrive at based on the prior art through logical analysis, reasoning, or finite experiments according to the concept of the present invention shall fall within the protection scope defined by the appended claims.