Device and method for controlling high-efficiency performance of catalytic converter by using national 7 diesel engine

Abstract

The invention discloses a device for controlling the efficient performance of a catalytic converter of a national 7 diesel engine, which is arranged at the exhaust end of the diesel engine and comprises an EHC, a first-stage SCR, a first-stage ASC, a DOC, a DPF, a second-stage SCR and a second-stage ASC which are sequentially arranged, the device further comprises a first-stage urea spraying device and a second-stage urea spraying device. The first-stage urea spraying device is arranged at the first-stage SCR; and the second-stage urea injection device is arranged at the second-stage SCR. According to the device for controlling the efficient performance of the catalytic converter of the national 7 diesel engine, the EHC (electric heater) is additionally arranged at the first-stage SCR, poisoning of the first-stage SCR is avoided, and meanwhile the effective conversion rate of the first-stage SCR is guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of engine design and manufacturing, and in particular to a device and method for controlling the high efficiency performance of a catalyst in a National VII diesel engine. Background Art

[0002] Europe has released the next stage of vehicle emission regulations, the Euro VII standard, which puts forward stricter requirements on emission pollutants such as NOx, PN, and N2O compared to the current Euro VI standard. my country is currently formulating the National VII emission standard. Based on the reference to the Euro VII standard, the emission limits of relevant pollutants will be more stringent. Therefore, the emission control technology route of the National VII diesel engine will be quite different from that of the National VI. There is now a general consensus in the industry that the diesel engine equipped with a two-stage urea injection after-treatment system can meet the requirements of the National VII regulations. The two-stage urea injection will be the main technical route for the National VII diesel engine. The two-stage urea injection after-treatment system is as follows: Figure 1 As shown, the dual-injection urea injection system can reduce low-temperature NOx emissions, as well as N2O and PN emissions. However, because the first-stage SCR directly contacts diesel engine exhaust, large amounts of pollutants such as hydrocarbons and sulfates accumulate over time. The copper-based molecular sieve structure of the SCR unit is highly sensitive to HC and S, leading to SCR poisoning and reduced conversion efficiency. Preventing first-stage SCR poisoning is a pressing challenge for the industry.

[0003] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0004] The purpose of the present invention is to provide a device for controlling the high efficiency performance of the catalyst of a National VII diesel engine, which can avoid poisoning of the first-stage SCR by adding an EHC (electric heater) at the first-stage SCR while ensuring the effective conversion rate of the first-stage SCR.

[0005] Another object of the present invention is to provide a method for controlling the high efficiency performance of a catalyst in a National VII diesel engine.

[0006] To achieve the above-mentioned objectives, the present invention provides a device for controlling the high efficiency performance of a catalytic converter of a National VII diesel engine, which is arranged at the exhaust end of the diesel engine. The device includes an EHC, a first-stage SCR and a first-stage ASC, as well as a DOC, a DPF, a second-stage SCR and a second-stage ASC, which are arranged in sequence; the device also includes a first-stage urea injection device and a second-stage urea injection device; the first-stage urea injection device is arranged at the first-stage SCR; the second-stage urea injection device is arranged at the second-stage SCR.

[0007] In a preferred embodiment, the device for controlling the high efficiency performance of the catalyst of the National VII diesel engine also includes an SCR upstream NOx sensor and an ASC downstream NOx sensor; the SCR upstream NOx sensor is arranged upstream of the first-stage SCR; the ASC downstream NOx sensor is arranged downstream of the first-stage ASC.

[0008] In a preferred embodiment, the device for controlling the high efficiency performance of the catalyst of the National VII diesel engine further includes an SCR upstream temperature sensor, which is arranged upstream of the first-stage SCR and the second-stage SCR.

[0009] In a preferred embodiment, the device for controlling the high efficiency performance of the catalyst of a National VII diesel engine further includes an engine speed and torque sensor, and the engine speed and torque sensor are arranged on the diesel engine.

[0010] To achieve the above-mentioned another object, the present invention further provides a method for controlling the high efficiency performance of a catalyst in a National VII diesel engine, which is operated by the aforementioned device for controlling the high efficiency performance of a catalyst in a National VII diesel engine, and the method comprises:

[0011] S1: The SCR upstream NOx sensor arranged upstream of the first-stage SCR and the ASC downstream NOx sensor arranged downstream of the first-stage ASC measure the NOx emissions Q1 upstream of the first-stage SCR and Q2 downstream of the first-stage ASC in real time, which serve as input conditions for S2;

[0012] S2: SCR conversion efficiency λ1 = 1-Q2 / Q1. Based on the exhaust temperature, the minimum SCR conversion efficiency λ2 under this operating condition is interpolated from the theoretical SCR conversion efficiency model;

[0013] S3: If λ1 < λ2, it means that the SCR conversion efficiency is very low and high temperature is required to remove HC and sulfate impurities on the surface of the SCR coating. At this time, the engine enters the SCR performance improvement mode;

[0014] S4: If the SCR upstream temperature indicated by the SCR upstream temperature sensor is less than the limit value T1, the DOC coating applied by the electric heater cannot be effectively oxidized, and the engine releases the far post injection, thus entering the electric heating stage. The electric heater starts working and quickly increases the exhaust temperature.

[0015] If the temperature upstream of the SCR is ≥ the limit value T1, the oxidation efficiency of the DOC coating applied by the electric heater is very high and the engine enters the post-injection heating stage;

[0016] S5: The engine is in the post-injection heating stage of SCR performance improvement mode. The post-injection amount is calculated based on the current engine speed and torque. The injector releases the long post-injection, and the diesel is vigorously oxidized and releases heat in the electric heater.

[0017] S6: The exhaust temperature is very high during the post-injection heating stage, impurities on the surface of the first-stage SCR unit are quickly decomposed, and the SCR conversion efficiency is restored.

[0018] In a preferred embodiment, the method for controlling the high efficiency performance of a catalyst in a National VII diesel engine further includes:

[0019] If λ1≥λ2, it means that the SCR conversion efficiency is normal and the engine still operates in the original normal mode without any changes.

[0020] In a preferred embodiment, the method for controlling the high efficiency performance of a catalyst in a National VII diesel engine further includes:

[0021] When the SCR upstream temperature ≥ limit T2, the electric heater stops working.

[0022] In a preferred embodiment, the method for controlling the high efficiency performance of a catalyst in a National VII diesel engine further includes:

[0023] When the accumulated time of high exhaust temperature reaches the set value, the engine exits the SCR performance improvement mode and returns to normal mode.

[0024] Compared with the prior art, the device and method for controlling the high-efficiency performance of the catalyst of the National VII diesel engine of the present invention have the following beneficial effects: this solution adds an electric heater in front of the first-stage SCR, and the unit of the electric heater is coated with a diesel oxidation catalyst (DOC) coating; at the same time, based on the first-stage SCR conversion efficiency, a new SCR performance improvement mode is added to increase the exhaust temperature, clean the impurities in the SCR unit, and restore the SCR performance; the SCR performance improvement mode is divided into an electric heating stage and a post-injection heating stage, the electric heating stage is used for low temperature, and the post-injection heating stage is used for high temperature; by timely starting the electric heating stage and the post-injection heating stage, it can effectively reduce the accumulation of a large amount of hydrocarbons, sulfates and other pollutants in the first-stage SCR that is in direct contact with the exhaust gas discharged by the diesel engine for a long time, and at the same time avoid the occurrence of SCR poisoning and reduced conversion efficiency failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the component configuration structure of a diesel engine aftertreatment device according to one embodiment of the prior art;

[0026] Figure 2 1 is a schematic diagram of the component configuration structure of a diesel engine aftertreatment device according to one embodiment of the present invention;

[0027] Figure 3 The figure is a logic flow diagram of a method for controlling high efficiency performance of a catalyst in a diesel engine according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0029] Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations such as "include" or "comprising", etc., will be understood to include the stated elements or components but not to exclude other elements or other components.

[0030] like Figure 2 As shown, according to a preferred embodiment of the present invention, a device for controlling the high efficiency of a catalyst in a China VII diesel engine is installed at the exhaust end of the diesel engine. The device includes an EHC, a first-stage SCR and a first-stage ASC, a DOC, a DPF, a second-stage SCR, and a second-stage ASC, arranged in sequence. The device also includes a first-stage urea injection device and a second-stage urea injection device. The first-stage urea injection device is installed at the first-stage SCR, and the second-stage urea injection device is installed at the second-stage SCR. The EHC is a newly added electric heater of the present invention, and the ceramic carrier unit inside the electric heater is coated with a diesel oxidation catalyst (DOC) coating.

[0031] In some embodiments, the device for controlling the high efficiency of the catalytic converter in a China VII diesel engine further includes an SCR upstream NOx sensor and an ASC downstream NOx sensor. The SCR upstream NOx sensor is positioned upstream of the first-stage SCR, and the ASC downstream NOx sensor is positioned downstream of the first-stage ASC. The upstream NOx sensor and the ASC downstream NOx sensor are used to monitor NOx levels upstream of the SCR and downstream of the ASC at all times.

[0032] In some embodiments, the device for controlling the high efficiency performance of the catalyst in a National VII diesel engine further includes an SCR upstream temperature sensor, which is disposed upstream of the first-stage SCR and the second-stage SCR. The SCR upstream temperature sensor is used to monitor the temperature upstream of the SCR at any time.

[0033] In some embodiments, the apparatus for controlling the high efficiency performance of a catalyst in a National VII diesel engine further includes an engine speed and torque sensor disposed on the diesel engine. The engine speed and torque sensor is configured to provide engine speed and torque values at any time.

[0034] like Figure 3 As shown, according to a preferred embodiment of the present invention, a method for controlling the high efficiency performance of a catalyst in a National VII diesel engine is operated by the aforementioned device for controlling the high efficiency performance of a catalyst in a National VII diesel engine. The method comprises:

[0035] S1: The SCR upstream NOx sensor arranged upstream of the first-stage SCR and the ASC downstream NOx sensor arranged downstream of the first-stage ASC measure the NOx emissions Q1 upstream of the first-stage SCR and Q2 downstream of the first-stage ASC in real time, which serve as input conditions for S2;

[0036] S2: SCR conversion efficiency λ1 = 1-Q2 / Q1. Based on the exhaust temperature, the minimum SCR conversion efficiency λ2 under this operating condition is interpolated from the theoretical SCR conversion efficiency model;

[0037] The so-called theoretical SCR conversion efficiency model is shown in Table 1:

[0038] Table 1

[0039] exhaust temperature SCR conversion efficiency 300℃ 95％ 250℃ 90％ 200℃ 85％

[0040] If the exhaust temperature of this operating condition is 225° C., based on the model in Table 1, it can be inferred that the SCR conversion efficiency λ2 of this operating condition is 87.5%.

[0041] S3: If λ1 < λ2, it means that the SCR conversion efficiency is very low and high temperature is required to remove HC and sulfate impurities on the surface of the SCR coating. At this time, the engine enters the SCR performance improvement mode;

[0042] S4: If the SCR upstream temperature indicated by the SCR upstream temperature sensor is less than the limit value T1, the DOC coating applied by the electric heater cannot be effectively oxidized, and the engine releases the far post injection, thus entering the electric heating stage. The electric heater starts working and quickly increases the exhaust temperature.

[0043] If the temperature upstream of the SCR is ≥ the limit value T1, the oxidation efficiency of the DOC coating applied by the electric heater is very high and the engine enters the post-injection heating stage;

[0044] Note: Limit T1 is the lowest limit of DOC coating operation, for example, at 220℃, only electric heating is working. Limit T2 is the upper limit of DOC coating operation, for example, at 300℃, no electric heating is required, and the DOC coating can work by itself to meet the conversion rate requirements by releasing the remote post-spray.

[0045] S5: The engine is in the post-injection heating stage of SCR performance improvement mode. The post-injection amount is calculated based on the current engine speed and torque. The injector releases the long post-injection, and the diesel is vigorously oxidized and releases heat in the electric heater.

[0046] Note: The post-injection volume is the post-injection volume data summarized by technicians during the research and development process based on the experimental data on the bench. Please refer to Table 2:

[0047] Table 2

[0048]

[0049] The so-called "injector release far after spraying" means that the diesel injected by the injector is not burned in the cylinder, but is discharged into the EHC for oxidation reaction.

[0050] S6: The exhaust temperature is very high during the post-injection heating stage, impurities on the surface of the first-stage SCR unit are quickly decomposed, and the SCR conversion efficiency is restored.

[0051] In some embodiments, the method for controlling the high efficiency performance of a catalyst in a National VII diesel engine further includes:

[0052] If λ1≥λ2, it means that the SCR conversion efficiency is normal and the engine still operates in the original normal mode without any changes.

[0053] In some embodiments, the method for controlling the high efficiency performance of a catalyst in a National VII diesel engine further includes:

[0054] When the temperature upstream of the SCR exceeds the limit T2, the electric heater stops working. This eliminates the need for high-power electric heaters and upgrades to the vehicle's motor, battery, and wiring specifications, resulting in low manufacturing costs and suitable for widespread adoption.

[0055] In some embodiments, the method for controlling the high efficiency performance of a catalyst in a National VII diesel engine further includes:

[0056] When the accumulated time of high exhaust temperature reaches the set value, the engine exits the SCR performance improvement mode and returns to normal mode.

[0057] In summary, the device and method for controlling the high-efficiency performance of the catalyst of the National VII diesel engine of the present invention have the following beneficial effects: this solution adds an electric heater in front of the first-stage SCR, and the unit of the electric heater is coated with a diesel oxidation catalyst (DOC) coating; at the same time, based on the first-stage SCR conversion efficiency, a new SCR performance improvement mode is added to increase the exhaust temperature, clean the impurities in the SCR unit, and restore the SCR performance; the SCR performance improvement mode is divided into an electric heating stage and a post-injection heating stage, the electric heating stage is used for low temperature, and the post-injection heating stage is used for high temperature; by timely starting the electric heating stage and the post-injection heating stage, it can effectively reduce the first-stage SCR from directly contacting the exhaust gas discharged by the diesel engine for a long time and accumulating a large amount of hydrocarbons, sulfates and other pollutants, while avoiding the occurrence of SCR poisoning and reduced conversion efficiency.

[0058] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A device for controlling the high efficiency performance of a catalytic converter in a National VII diesel engine, which is arranged at the exhaust end of the diesel engine, characterized in that: The device includes an EHC, a first-stage SCR and a first-stage ASC, a DOC, a DPF, a second-stage SCR and a second-stage ASC arranged in sequence; The device further comprises: A first-stage urea injection device is provided at the first-stage SCR; and The second-stage urea injection device is arranged at the second-stage SCR.

2. The device for controlling the high efficiency performance of the catalytic converter of a National VII diesel engine according to claim 1, characterized in that: Also includes: An SCR upstream NOx sensor is disposed upstream of the first-stage SCR and the second-stage SCR; as well as The ASC downstream NOx sensor is disposed downstream of the first-stage ASC and the second-stage ASC.

3. The device for controlling the high efficiency performance of the catalytic converter of a National VII diesel engine according to claim 1, characterized in that: Also included is an SCR upstream temperature sensor disposed upstream of the first stage SCR and the second stage SCR.

4. The device for controlling the high efficiency performance of the catalytic converter of a National VII diesel engine according to claim 1, characterized in that: The invention also includes an engine speed and torque sensor, which is arranged on the diesel engine.

5. A method for controlling the high efficiency performance of a catalyst in a China VII diesel engine, which is operated by the device for controlling the high efficiency performance of a catalyst in a China VII diesel engine according to any one of claims 1 to 4, characterized in that: The method comprises: S1: The SCR upstream NOx sensor arranged upstream of the first-stage SCR and the ASC downstream NOx sensor arranged downstream of the first-stage ASC measure NOx emissions Q1 upstream of the first-stage SCR and Q2 downstream of the first-stage ASC in real time, which serve as input conditions for S2; S2: SCR conversion efficiency λ1 = 1-Q2 / Q1. Based on the exhaust temperature, the minimum SCR conversion efficiency λ2 under this operating condition is interpolated from the theoretical SCR conversion efficiency model; S3: If λ1 < λ2, it means that the SCR conversion efficiency is very low and high temperature is required to remove HC and sulfate impurities on the surface of the SCR coating. At this time, the engine enters the SCR performance improvement mode; S4: If the SCR upstream temperature indicated by the SCR upstream temperature sensor is less than the limit value T1, the DOC coating applied by the electric heater cannot be effectively oxidized, and the engine releases the remote post injection, thus entering the electric heating stage, and the electric heater starts to work, quickly increasing the exhaust temperature; If the temperature upstream of the SCR is ≥ the limit value T1, the oxidation efficiency of the DOC coating applied by the electric heater is very high and the engine enters the post-injection heating stage; S5: The engine is in the post-injection heating stage of SCR performance improvement mode. The post-injection amount is calculated based on the current engine speed and torque. The injector releases the long post-injection, and the diesel is vigorously oxidized and releases heat in the electric heater. S6: The exhaust temperature is very high during the post-injection heating stage, impurities on the surface of the first-stage SCR unit are quickly decomposed, and the SCR conversion efficiency is restored.

6. The method for controlling the high efficiency performance of a catalyst in a National VII diesel engine according to claim 5, characterized in that: Also includes: If λ1≥λ2, it means that the SCR conversion efficiency is normal and the engine still operates in the original normal mode without any changes.

7. The method for controlling the high efficiency performance of a catalyst in a National VII diesel engine according to claim 5, characterized in that: Also includes: When the SCR upstream temperature ≥ limit T2, the electric heater stops working.

8. The method for controlling the high efficiency performance of a catalyst in a National VII diesel engine according to claim 5, characterized in that: Also includes: When the accumulated time of high exhaust temperature reaches the set value, the engine exits the SCR performance improvement mode and returns to normal mode.

Images