A method of identifying sdpf breakage

Abstract

The application discloses a method for identifying SDPF damage, and relates to the technical field of engine aftertreatment systems, and solves the technical problem that the existing installation of differential pressure sensors before and after the SDPF is prone to false positives or false negatives. The method comprises the following steps: acquiring a theoretical NOx conversion efficiency value, a measured NOx conversion efficiency value and a urea / NOx equivalent ratio value, and calculating an efficiency deviation value of the theoretical NOx conversion efficiency value and the measured NOx conversion efficiency value; comparing the urea / NOx equivalent ratio value with a set equivalent ratio limit value, and comparing the efficiency deviation value with a preset efficiency limit value; and when the urea / NOx equivalent ratio value is greater than or equal to the equivalent ratio limit value and the efficiency deviation value is greater than or equal to the efficiency limit value, an SDPF damage fault alarm is performed. The application reduces the influence of the damage position and shape of the SDPF on a single sensor, and reduces the risk of sensor identification errors through comparison of multiple related parameters.

Description

Technical Field

[0001] This invention relates to the field of engine aftertreatment system technology, and more specifically, to a method for identifying SDPF damage. Background Technology

[0002] The China VI emission standard sets clear emission requirements for NOx (nitrogen oxides) and PN (intake and exhaust) in vehicles. Diesel engines use SCR (Selective Catalytic Reduction) to reduce NOx emissions and DPF (Diesel Particulate Filter) to reduce PN emissions. However, in actual vehicle matching, some vehicles have limited space and cannot accommodate conventional catalytic converters. To save space and reduce costs, the SCR and DPF are combined into one, resulting in the SDPF (Selective Catalytic Reduction Filter). The SCR coating is applied to the DPF, allowing a single catalytic converter to reduce both NOx and PN emissions. SDPFs are widely used in diesel pickup trucks, accounting for over 50% of their applications. While SDPFs save space and reduce costs, the NO2 consumed by urea leads to weak passive regeneration capabilities, a faster carbon accumulation rate, a short regeneration cycle, and a higher regeneration frequency.

[0003] Frequent active regeneration can easily lead to SDPF burn-out. Once the SDPF burns out, its PN (particulate air) capture efficiency decreases, causing PN emissions to exceed regulatory requirements. Therefore, it is essential to monitor the SDPF's damage status and report faults promptly. Currently, the primary method is to install differential pressure sensors before and after the SDPF to measure the pressure difference and determine if the SDPF is damaged. However, the differential pressure sensor readings are greatly affected by the gas intake location, the location and shape of the SDPF damage, and therefore may not accurately reflect the true extent of the damage. Thus, current solutions using differential pressure sensors to identify SDPF damage are prone to false alarms or missed detections. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for identifying SDPF damage, which addresses the shortcomings of the existing technology and solves the technical problem that the existing detection method of installing differential pressure sensors before and after the SDPF is prone to false alarms or missed alarms.

[0005] The present invention discloses a method for identifying SDPF damage, the method comprising:

[0006] Obtain the theoretical NOx conversion efficiency value, the measured NOx conversion efficiency value, and the urea / NOx equivalent ratio, and calculate the efficiency deviation value between the theoretical NOx conversion efficiency value and the measured NOx conversion efficiency value;

[0007] The urea / NOx equivalent ratio is compared with the set equivalent ratio limit, and the efficiency deviation value is compared with the preset efficiency limit. When the urea / NOx equivalent ratio is greater than or equal to the equivalent ratio limit and the efficiency deviation value is greater than or equal to the efficiency limit, an SDPF damage fault alarm is triggered.

[0008] To further improve the method, the method for obtaining the theoretical NOx conversion efficiency value, the measured NOx conversion efficiency value, and the urea / NOx equivalent ratio is as follows:

[0009] Step 1: Obtain the upstream temperature, downstream temperature, upstream NOx concentration, downstream NOx concentration, engine speed, engine torque, engine urea injection rate, and exhaust flow rate of the SDPF within a preset time period.

[0010] Step 2: Calculate the temperature value of SDPF using the upstream and downstream temperature values;

[0011] The urea / NOx equivalent ratio is calculated using the engine's urea injection rate, upstream NOx concentration, and exhaust flow rate.

[0012] The upstream specific NOx emission value is calculated using the upstream NOx concentration value, exhaust flow rate, engine speed, and engine torque.

[0013] The downstream specific NOx emission value is calculated using the downstream NOx concentration value, exhaust flow rate, engine speed, and engine torque.

[0014] Step 3: Calculate the theoretical NOx conversion efficiency value using the urea / NOx equivalent ratio and the set temperature correction factor;

[0015] Step 4: Calculate the measured NOx conversion efficiency value using the upstream and downstream NOx emission values.

[0016] Furthermore, in step two, the expression for calculating the temperature value of the SDPF is:

[0017] T SDFP = a×T1+(1-a)×T2;

[0018] Among them, T SDFP T1 represents the temperature value of SDPF, T2 represents the upstream temperature value, T2 represents the downstream temperature value, and a represents the temperature weighting coefficient.

[0019] Furthermore, in step two, the expression for calculating the urea / NOx equivalent ratio is:

[0020] K=v×3600*0.325 / 60.06*2 / C1*28.89 / Q;

[0021] Where K is the urea / NOx equivalent ratio, v is the engine urea injection rate, C1 is the upstream NOx concentration, and Q is the exhaust flow rate.

[0022] Furthermore, in step two, the expression for calculating the upstream NOx emission ratio is:

[0023] M1=∑(0.001586*C1*Q) / ∑(n*T / 9550);

[0024] Where M1 is the upstream NOx emission value, C1 is the upstream NOx concentration value, Q is the exhaust flow rate, n is the engine speed, and T is the engine torque.

[0025] Furthermore, in step two, the expression for calculating the downstream NOx emission value is as follows:

[0026] M2=∑(0.001586*C2*Q) / ∑(n*T / 9550);

[0027] Where M2 is the downstream NOx emission value, C2 is the downstream NOx concentration value, Q is the exhaust flow rate, n is the engine speed, and T is the engine torque.

[0028] Furthermore, in step three, the expression for calculating the theoretical NOx conversion efficiency value is:

[0029] η1=K*β;

[0030] Where η1 is the theoretical NOx conversion efficiency, K is the urea / NOx equivalent ratio, and β is the temperature-based correction factor.

[0031] Furthermore, in step four, the expression for calculating the measured NOx conversion efficiency value is as follows:

[0032] η2=(M1-M2) / M1;

[0033] Where η2 is the measured NOx conversion efficiency value, M1 is the upstream specific NOx emission value, and M2 is the downstream specific NOx emission value.

[0034] Furthermore, the expression for calculating the efficiency deviation value is as follows:

[0035] Δn = η1 - η2;

[0036] Where △η is the efficiency deviation value, η1 is the theoretical NOx conversion efficiency value, and η2 is the measured NOx conversion efficiency value.

[0037] Beneficial effects

[0038] The advantages of this invention are:

[0039] This invention acquires engine parameters and temperature and NOx concentration values ​​upstream and downstream of the SDPF. Using these parameters, the urea / NOx equivalent ratio and efficiency deviation value are obtained. The urea / NOx equivalent ratio is compared with a set limit, and the efficiency deviation value is compared with a preset efficiency limit. An alarm is triggered for SDPF damage, prompting the user to repair it. This reduces the impact of the SDPF's damage location and shape on a single sensor. By comparing multiple relevant parameters, the risk of sensor misidentification is reduced. Attached Figure Description

[0040] Figure 1 This is a flowchart of the method for identifying SDPF damage according to the present invention. Detailed Implementation

[0041] The present invention will be further described below with reference to embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0042] See Figure 1 The present invention provides a method for identifying SDPF damage, the method comprising:

[0043] Step 1: Set a time interval. In this embodiment, the time interval is 10 seconds. Obtain the upstream temperature value, downstream temperature value, upstream NOx concentration value, downstream NOx concentration value, engine speed, engine torque, engine urea injection rate and exhaust flow rate of SDPF within 10 seconds.

[0044] An upstream temperature sensor and an upstream NOx sensor are installed upstream of the SDPF, and a downstream temperature sensor and a downstream NOx sensor are installed downstream of the SDPF. The upstream temperature sensor obtains the upstream temperature value of the SDPF, the downstream temperature sensor obtains the downstream temperature value of the SDPF, and the upstream NOx concentration value of the SDPF is obtained through the upstream NOx sensor.

[0045] Step 2: Calculate the temperature value of SDPF using the upstream and downstream temperature values.

[0046] The expression for calculating the temperature value of the SDPF is:

[0047] T SDFP = a×T1+(1-a)×T2;

[0048] Among them, T SDFPT1 is the upstream temperature value of SDPF, T2 is the downstream temperature value, and a is the temperature weighting coefficient, which is 0.4.

[0049] The urea / NOx equivalent ratio is calculated using the engine's urea injection rate, upstream NOx concentration, and exhaust flow rate.

[0050] The expression for calculating the urea / NOx equivalent ratio is:

[0051] K=v×3600*0.325 / 60.06*2 / C1*28.89 / Q;

[0052] Where K is the urea / NOx equivalent ratio, v is the engine urea injection rate, C1 is the upstream NOx concentration, and Q is the exhaust flow rate.

[0053] The upstream NOx emission value is calculated by taking into account the upstream NOx concentration, exhaust flow rate, engine speed, and engine torque.

[0054] The expression for calculating upstream NOx emissions is:

[0055] M1=∑(0.001586*C1*Q) / ∑(n*T / 9550);

[0056] Where M1 is the upstream NOx emission value, C1 is the upstream NOx concentration value, Q is the exhaust flow rate, n is the engine speed, and T is the engine torque.

[0057] The downstream specific NOx emission value is calculated by taking the downstream NOx concentration, exhaust flow rate, engine speed, and engine torque.

[0058] The expression for calculating downstream NOx emissions is:

[0059] M2=∑(0.001586*C2*Q) / ∑(n*T / 9550);

[0060] Where M2 is the downstream NOx emission value, C2 is the downstream NOx concentration value, Q is the exhaust flow rate, n is the engine speed, and T is the engine torque.

[0061] Step 3: Calculate the theoretical NOx conversion efficiency value using the urea / NOx equivalent ratio and the set temperature correction factor.

[0062] The expression for calculating the theoretical NOx conversion efficiency is:

[0063] η1=K*β;

[0064] Where η1 is the theoretical NOx conversion efficiency, K is the urea / NOx equivalent ratio, and β is the temperature-based correction factor.

[0065] Step 4: Calculate the measured NOx conversion efficiency value using the upstream and downstream NOx emission values.

[0066] The expression for calculating the measured NOx conversion efficiency is:

[0067] η2=(M1-M2) / M1;

[0068] Where η2 is the measured NOx conversion efficiency value, M1 is the upstream specific NOx emission value, and M2 is the downstream specific NOx emission value.

[0069] Step 5: Calculate the efficiency deviation value by combining the theoretical NOx conversion efficiency value and the measured NOx conversion efficiency value.

[0070] The expression for calculating the efficiency deviation value is:

[0071] Δη=η1-η2;

[0072] Where △η is the efficiency deviation value, η1 is the theoretical NOx conversion efficiency value, and η2 is the measured NOx conversion efficiency value.

[0073] Step 6: Compare the urea / NOx equivalent ratio with the set equivalent ratio limit, and compare the efficiency deviation value with the preset efficiency limit. When the urea / NOx equivalent ratio is greater than or equal to the equivalent ratio limit and the efficiency deviation value is greater than or equal to the efficiency limit, it indicates that the SDPF is severely damaged and there is a risk that PN emissions will exceed regulatory requirements.

[0074] Step 7: When the urea / NOx equivalent ratio is greater than or equal to the equivalent ratio limit and the efficiency deviation value is greater than or equal to the efficiency limit, an SDPF damage fault alarm is triggered to prompt the user to shut down and repair it.

[0075] If the SDPF is damaged, and the urea / NOx equivalence ratio is greater than or equal to the equivalence ratio limit, the ammonia stored in the carrier will be distributed to the rear end of the damaged orifice. When the ammonia storage distribution differs from the pre-designed distribution, it leads to a decrease in SCR (Selective Catalytic Reduction) efficiency, resulting in less urea reacting with NOx and causing significant ammonia leakage. This leakage passes through the downstream NOx sensor, which misinterprets the ammonia as NOx, thus lowering the calculated measured NOx conversion efficiency and increasing the efficiency deviation Δη. If the efficiency deviation Δη is greater than or equal to the efficiency limit, it indicates significant SDPF damage, posing a risk of exceeding regulatory requirements for PN emissions. An SDPF damage fault alarm will then prompt the user to shut down and repair the system.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for identifying SDPF damage, characterized in that, The method includes: Obtain the theoretical NOx conversion efficiency value, the measured NOx conversion efficiency value, and the urea / NOx equivalent ratio, and calculate the efficiency deviation value between the theoretical NOx conversion efficiency value and the measured NOx conversion efficiency value; The urea / NOx equivalent ratio is compared with the set equivalent ratio limit, and the efficiency deviation value is compared with the preset efficiency limit. When the urea / NOx equivalent ratio is greater than or equal to the equivalent ratio limit and the efficiency deviation value is greater than or equal to the efficiency limit, an SDPF damage fault alarm is triggered. The method for obtaining the theoretical NOx conversion efficiency value, the measured NOx conversion efficiency value, and the urea / NOx equivalent ratio is as follows: Step 1: Obtain the upstream temperature, downstream temperature, upstream NOx concentration, downstream NOx concentration, engine speed, engine torque, engine urea injection rate, and exhaust flow rate of the SDPF within a preset time period. Step 2: Calculate the temperature value of SDPF using the upstream and downstream temperature values; The urea / NOx equivalent ratio is calculated using the engine's urea injection rate, upstream NOx concentration, and exhaust flow rate. The upstream specific NOx emission value is calculated using the upstream NOx concentration value, exhaust flow rate, engine speed, and engine torque. The downstream specific NOx emission value is calculated using the downstream NOx concentration value, exhaust flow rate, engine speed, and engine torque. Step 3: Calculate the theoretical NOx conversion efficiency value using the urea / NOx equivalent ratio and the set temperature correction factor; Step 4: Calculate the measured NOx conversion efficiency value using the upstream and downstream NOx emission ratios; In step two, the expression for calculating the urea / NOx equivalent ratio is: Where K is the urea / NOx equivalent ratio, v is the engine urea injection rate, C1 is the upstream NOx concentration, and Q is the exhaust flow rate.

2. The method for identifying SDPF damage according to claim 1, characterized in that, In step two, the expression for calculating the temperature value of the SDPF is: Among them, T SDFP T1 represents the temperature value of SDPF, T2 represents the upstream temperature value, T2 represents the downstream temperature value, and a represents the temperature weighting coefficient.

3. The method for identifying SDPF damage according to claim 1, characterized in that, In step two, the expression for calculating the upstream NOx emission ratio is as follows: Where M1 is the upstream NOx emission value, C1 is the upstream NOx concentration value, Q is the exhaust flow rate, n is the engine speed, and T is the engine torque.

4. The method for identifying SDPF damage according to claim 3, characterized in that, In step two, the expression for calculating the downstream NOx emission value is as follows: Where M2 is the downstream NOx emission value, C2 is the downstream NOx concentration value, Q is the exhaust flow rate, n is the engine speed, and T is the engine torque.

5. The method for identifying SDPF damage according to claim 4, characterized in that, In step three, the expression for calculating the theoretical NOx conversion efficiency value is: Where η1 is the theoretical NOx conversion efficiency, K is the urea / NOx equivalent ratio, and β is the temperature-based correction factor.

6. The method for identifying SDPF damage according to claim 5, characterized in that, In step four, the expression for calculating the measured NOx conversion efficiency value is as follows: Where η2 is the measured NOx conversion efficiency value, M1 is the upstream specific NOx emission value, and M2 is the downstream specific NOx emission value.

7. The method for identifying SDPF damage according to claim 6, characterized in that, The expression for calculating the efficiency deviation value is: Where ∆η is the efficiency deviation value, η1 is the theoretical NOx conversion efficiency value, and η2 is the measured NOx conversion efficiency value.

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