A control strategy for determining catalyst sulfur poisoning through SCR conversion efficiency diagnosis

Abstract

The present invention provides a control strategy for determining sulfur poisoning of a catalyst by diagnosing SCR conversion efficiency, comprising the following steps: diagnosing the SCR conversion efficiency to obtain a first SCR conversion efficiency, and if the first SCR conversion efficiency is lower than a first threshold; triggering a DPF regeneration mode; after the DPF regeneration is completed, diagnosing the SCR conversion efficiency to obtain a second SCR conversion efficiency; comparing the second SCR conversion efficiency with a second threshold, and if the second SCR conversion efficiency is higher than the second threshold, determining that the SCR catalyst is sulfur poisoned, and issuing a reminder to the driver to fill with qualified diesel; if the second SCR conversion efficiency is lower than the second threshold, lighting a fault lamp, and inspecting a urea injection system of the entire vehicle; determining whether sulfur poisoning occurs in the catalyst by monitoring the change in SCR efficiency before and after regeneration, and if so, promptly reminding the driver through the vehicle dashboard to go to a regular gas station to fill with diesel that meets the National VI requirements, so as to avoid failure of the post-treatment system due to long-term filling with unqualified diesel.

Description

Technical Field

[0001] The present invention belongs to the technical field of diesel engine aftertreatment, and in particular is a control strategy for determining catalyst sulfur poisoning through SCR conversion efficiency diagnosis. Background Art

[0002] Diesel fuel contains a high sulfur content, and combustion in the engine produces a large amount of SO. Under low-temperature conditions, SO reacts with NH to form ammonium sulfate, which deposits on the catalyst surface, hindering contact between the reactant gas and the active centers, leading to catalyst deactivation. SO also reacts with the active metals in the SCR catalyst to form stable sulfate, which also deactivates the catalyst. Ammonium sulfate and sulfates require temperatures of 450°C or even higher to decompose in order to restore SCR performance.

[0003] When the SCR catalyst becomes inefficient due to sulfur poisoning, the vehicle's aftertreatment system automatically enters regeneration mode, proactively raising the system temperature and promptly removing sulfur deposits from the SCR catalyst surface to restore SCR performance. If the sulfur content of diesel is too high, the vehicle will frequently enter regeneration mode, accelerating the aging of the aftertreatment system. Summary of the Invention

[0004] The present invention provides a control strategy for determining sulfur poisoning of a catalyst through SCR conversion efficiency diagnosis. By monitoring the change in SCR efficiency before and after regeneration, it is determined whether sulfur poisoning has occurred in the catalyst. If so, the vehicle dashboard can promptly remind the driver to go to a regular gas station to refuel with diesel that meets the National VI requirements, thereby avoiding failure of the after-treatment system due to long-term refueling with substandard diesel.

[0005] A control strategy for determining catalyst sulfur poisoning through SCR conversion efficiency diagnosis includes the following steps:

[0006] S1: diagnose the SCR conversion efficiency and obtain a first SCR conversion efficiency. If the first SCR conversion efficiency is lower than a first threshold, proceed to the next step;

[0007] S2: triggering the DPF regeneration mode; in the present invention, diesel is injected into the post-processing system, and the diesel releases heat after combustion to heat the SCR catalyst, thereby achieving regeneration.

[0008] S3: After DPF regeneration is completed, the SCR conversion efficiency is diagnosed to obtain a second SCR conversion efficiency;

[0009] S4: Compare the second SCR conversion efficiency with a second threshold value. If the second SCR conversion efficiency is higher than the second threshold value, proceed to step S5; if the second SCR conversion efficiency is lower than the second threshold value, proceed to step S6;

[0010] S5: The SCR catalyst is judged to be sulfur poisoned, and a reminder is issued to the driver to fill with qualified diesel;

[0011] S6: Turn on the fault light and check the urea injection system of the entire vehicle.

[0012] This control strategy is mainly judged by the recovery of SCR efficiency before and after regeneration. After regeneration, the SCR efficiency is restored. If the second SCR conversion efficiency is higher than the second threshold, it means that the conversion efficiency is significantly improved, proving that the ammonium sulfate and sulfate compounds deposited on the catalyst surface under high temperature conditions have been decomposed and the catalyst has recovered its activity. It can be judged that the sulfur content in the diesel is relatively high and the engine combustion produces a large amount of SO2.

[0013] If the second SCR conversion efficiency is lower than the second threshold, indicating that the efficiency recovery is not significant and the ammonium sulfate and sulfate content is low, then the low SCR efficiency is caused by a urea injection system failure, and the vehicle will proactively perform a urea injection system inspection.

[0014] In step S6: the fault light is turned on, a warning signal is issued on the instrument panel, and then the urea injection system is inspected on the entire vehicle.

[0015] Preferably, in step S3, the duration of diagnosing the SCR conversion efficiency is 0.8 to 1.2 hours.

[0016] Preferably, the first threshold and the second threshold have the same numerical value, the numerical range of the first threshold is 75%~80%, and the numerical range of the second threshold is 75%~80%.

[0017] Preferably, in step 5, the driver is reminded by notifying through the vehicle dashboard. The reminder method is simple and can remind the driver intuitively.

[0018] Preferably, in step S2, the vehicle after-treatment system executes a driving regeneration mode to increase the temperature of the vehicle after-treatment system to above 450 degrees Celsius to remove deposited sulfides on the surface of the SCR catalyst.

[0019] The present invention utilizes the chemical properties of the catalyst matched with the National VI diesel engine and determines whether the catalyst has sulfur poisoning by monitoring the change in SCR efficiency before and after regeneration. If so, the driver can be reminded in time through the vehicle dashboard to go to a regular gas station to refuel with diesel that meets the National VI requirements, avoiding failure of the after-treatment system due to long-term refueling of unqualified diesel.

[0020] Avoid catalytic converter failure caused by filling with substandard diesel; reduce vehicle failures, lower vehicle maintenance costs, improve vehicle utilization, increase drivers' overall income, and at the same time enhance the market reputation of the supporting engine and improve product competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of a control strategy for determining catalyst sulfur poisoning through SCR conversion efficiency diagnosis according to the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Example 1: A control strategy for determining catalyst sulfur poisoning through SCR conversion efficiency diagnosis, comprising the following steps:

[0024] S1: diagnose the SCR conversion efficiency and obtain a first SCR conversion efficiency. If the first SCR conversion efficiency is lower than a first threshold, proceed to the next step;

[0025] S2: trigger DPF regeneration mode;

[0026] S3: After DPF regeneration is completed, the SCR conversion efficiency is diagnosed to obtain a second SCR conversion efficiency;

[0027] S4: Compare the second SCR conversion efficiency with a second threshold value. If the second SCR conversion efficiency is higher than the second threshold value, proceed to step S5; if the second SCR conversion efficiency is lower than the second threshold value, proceed to step S6;

[0028] S5: The SCR catalyst is judged to be sulfur poisoned, and a reminder is issued to the driver to fill with qualified diesel;

[0029] S6: Turn on the fault light and check the urea injection system of the entire vehicle.

[0030] Example 2: A control strategy for determining catalyst sulfur poisoning through SCR conversion efficiency diagnosis, comprising the following steps:

[0031] S1: diagnose the SCR conversion efficiency and obtain a first SCR conversion efficiency. If the first SCR conversion efficiency is lower than a first threshold, proceed to the next step;

[0032] S2: trigger DPF regeneration mode;

[0033] S3: After DPF regeneration is completed, the SCR conversion efficiency is diagnosed to obtain a second SCR conversion efficiency;

[0034] S4: Compare the second SCR conversion efficiency with a second threshold value. If the second SCR conversion efficiency is higher than the second threshold value, proceed to step S5; if the second SCR conversion efficiency is lower than the second threshold value, proceed to step S6;

[0035] S5: The SCR catalyst is judged to be sulfur poisoned, and a reminder is issued to the driver to fill with qualified diesel;

[0036] S6: Turn on the fault light and check the urea injection system of the entire vehicle.

[0037] This control strategy is mainly judged by the recovery of SCR efficiency before and after regeneration. After regeneration, the SCR efficiency is restored. If the second SCR conversion efficiency is higher than the second threshold, it means that the conversion efficiency is significantly improved, proving that the ammonium sulfate and sulfate compounds deposited on the catalyst surface under high temperature conditions have been decomposed and the catalyst has recovered its activity. It can be judged that the sulfur content in the diesel is relatively high and the engine combustion produces a large amount of SO2.

[0038] If the second SCR conversion efficiency is lower than the second threshold, indicating that the efficiency recovery is not significant and the ammonium sulfate and sulfate content is low, then the low SCR efficiency is caused by a urea injection system failure, and the vehicle will proactively perform a urea injection system inspection.

[0039] In this embodiment, in step S3, the duration of diagnosing the SCR conversion efficiency is 0.8 hours. The SCR conversion efficiency after regeneration is detected for a long time to improve the accuracy of the measurement.

[0040] The first threshold and the second threshold have the same value, which is 75%.

[0041] In this embodiment, in step 5, the driver is reminded by notifying through the vehicle dashboard. The reminder method is simple and can remind the driver intuitively.

[0042] In this embodiment, in step S2, the vehicle after-treatment system executes the driving regeneration mode, which increases the temperature of the vehicle after-treatment system to above 450 degrees Celsius, thereby removing the deposited sulfides on the surface of the SCR catalyst.

[0043] In this embodiment, the numerical range of the first SCR conversion efficiency is , and the numerical range of the second SCR conversion efficiency is .

[0044] Example 3:

[0045] The difference between this embodiment and the above-mentioned embodiment 2 is that, in step S3, the duration of diagnosing the SCR conversion efficiency is 1.2 hours, and the first threshold and the second threshold are the same, both of which are 80%.

Claims

1. A control strategy for determining catalyst sulfur poisoning through SCR conversion efficiency diagnosis, characterized in that The steps include: S1: diagnose the SCR conversion efficiency and obtain a first SCR conversion efficiency. If the first SCR conversion efficiency is lower than a first threshold, proceed to the next step; S2: trigger DPF regeneration mode; S3: After DPF regeneration is completed, the SCR conversion efficiency is diagnosed to obtain a second SCR conversion efficiency; S4: Compare the second SCR conversion efficiency with a second threshold value. If the second SCR conversion efficiency is higher than the second threshold value, proceed to step S5; if the second SCR conversion efficiency is lower than the second threshold value, proceed to step S6; S5: The SCR catalyst is judged to be sulfur poisoned, and a reminder is issued to the driver to fill with qualified diesel; S6: Turn on the fault light and check the urea injection system of the vehicle; In step S3, the duration of diagnosing the SCR conversion efficiency is 0.8 to 1.2 hours; the first threshold and the second threshold are the same; the value range of the first threshold is 75% to 80%; in step S2, the vehicle after-treatment system executes the driving regeneration mode to increase the temperature of the vehicle after-treatment system and remove the deposited sulfides on the surface of the SCR catalyst.

2. The control strategy for determining catalyst sulfur poisoning through SCR conversion efficiency diagnosis according to claim 1, characterized in that: In step 5, the driver is reminded by notifying via the vehicle dashboard.

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