Method for identifying SDPF damage

Abstract

The invention discloses a method for identifying damage of an SDPF, relates to the technical field of engine post-processing systems, and solves the technical problem that false alarm or missing alarm is easy to occur in an existing detection mode that differential pressure sensors are mounted in front of and behind the SDPF. The method comprises the following steps: acquiring a theoretical NOx conversion efficiency value, an actually measured NOx conversion efficiency value and a urea / NOx equivalent ratio, and calculating an efficiency deviation value between the theoretical NOx conversion efficiency value and the actually measured NOx conversion efficiency value; the urea / NOx equivalent ratio is compared with a set equivalent ratio limit value, meanwhile, the efficiency deviation value is compared with a preset efficiency limit value, and when the urea / NOx equivalent ratio is larger than or equal to the equivalent ratio limit value and the efficiency deviation value is larger than or equal to the efficiency limit value, SDPF damage fault alarming is conducted. According to the method, the influence of the damage position and shape of the SDPF on a single sensor is reduced, and the risk of sensor identification errors is reduced through comparison of various related parameters.

Description

Technical Field

[0001] The present invention relates to the technical field of engine after-treatment systems, and more particularly to a method for identifying SDPF damage. Background Art

[0002] The National VI regulations have clear emission requirements for NOx (nitrogen oxides) and PN (intake and exhaust) of vehicles. Diesel engines use SCR (selective catalytic reduction system) to reduce NOx emissions and DPF (particulate filter) to reduce PN emissions. In actual vehicle matching, some vehicles have limited space and cannot install conventional catalysts. In order to save space and reduce costs, SCR and DPF are combined into one, resulting in SDPF (selective catalytic reduction filter). The SCR coating is applied to the DPF, so that one catalyst can reduce both NOx and PN emissions. SDPF has been widely used in diesel pickup trucks, accounting for more than 50% of diesel pickup truck applications. Although SDPF saves space and reduces costs, urea consumes NO2, resulting in weak passive regeneration ability of SDPF, fast carbon accumulation rate, short regeneration cycle, and high regeneration frequency.

[0003] Frequent active regeneration can easily cause the SDPF to burn through. After the SDPF burns through, the PN capture efficiency decreases and the PN emissions will exceed regulatory requirements. Therefore, the damage status of the SDPF must be monitored to report the fault in a timely manner. Currently, the main method is to install a differential pressure sensor before and after the SDPF to measure the pressure difference to determine whether the SDPF is damaged. The measurement value of the differential pressure sensor is greatly affected by the gas intake position, the damaged position and shape of the SDPF, and therefore may not truly reflect the damage of the SDPF. Therefore, the current technical solution of using a differential pressure sensor to identify SDPF damage is prone to the risk of false alarms or omissions of the fault. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for identifying SDPF damage in view of the shortcomings of the prior art, so as to solve the technical problem that the existing detection method of installing a pressure difference sensor before and after the SDPF is prone to false alarms or missed alarms.

[0005] A method for identifying SDPF damage according to the present invention comprises:

[0006] Obtaining the theoretical NOx conversion efficiency value, the measured NOx conversion efficiency value and the urea / NOx equivalent ratio, and calculating 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 equivalence 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 equivalence ratio limit and the efficiency deviation value is greater than or equal to the efficiency limit, an SDPF damage fault alarm is issued.

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

[0009] Step 1: 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 the SDPF within a preset time;

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

[0011] The urea / NOx equivalent ratio is calculated by the urea injection rate, the upstream NOx concentration value and the exhaust flow rate of the engine;

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

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

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

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

[0016] Furthermore, in the step 2, the expression for calculating the temperature value of the SDPF is:

[0017] T SDFP =a×T 1 +(1-a)×T 2 ;

[0018] Among them, T SDFP is the temperature value of SDPF, T 1 is the upstream temperature, T 2 is the downstream temperature value, and a is the temperature weighting coefficient.

[0019] Furthermore, in the step 2, the expression for calculating the urea / NOx equivalent ratio is:

[0020] K=v×3600*0.325 / 60.06*2 / C 1 *28.89 / Q;

[0021] Where K is the urea / NOx equivalent ratio, v is the urea injection rate of the engine, C 1 is the upstream NOx concentration value, and Q is the exhaust flow rate.

[0022] Furthermore, in the step 2, the expression for calculating the upstream specific NOx emission value is:

[0023] M 1 =∑(0.001586*C 1 *Q) / ∑(n*T / 9550);

[0024] Among them, M 1 is the upstream specific NOx emission value, C 1 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 the step 2, the expression for calculating the downstream specific NOx emission value is:

[0026] M 2 =∑(0.001586*C 2 *Q) / ∑(n*T / 9550);

[0027] Among them, M 2 is the downstream specific NOx emission value, C 2 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 3, the expression for calculating the theoretical NOx conversion efficiency value is:

[0029] η 1 =K*β;

[0030] Among them, η 1 is the theoretical NOx conversion efficiency, K is the urea / NOx equivalent ratio, and β is the correction factor based on temperature.

[0031] Furthermore, in the step 4, the expression for calculating the measured NOx conversion efficiency value is:

[0032] η 2 =(M 1 -M 2 ) / M 1 ;

[0033] Among them, η2 is the measured NOx conversion efficiency value, M 1 is the upstream specific NOx emission value, M 2 is the downstream specific NOx emission value.

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

[0035] Δn=η 1 -η 2 ;

[0036] Among them, △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 the present invention are:

[0039] The present invention obtains engine parameters and temperature values ​​and NOx concentration values ​​of upstream and downstream of the SDPF, obtains a urea / NOx equivalent ratio and an efficiency deviation value through the engine parameters and temperature values ​​and NOx concentration values ​​of upstream and downstream of the SDPF, compares the urea / NOx equivalent ratio with a set equivalence ratio limit value, and compares the efficiency deviation value with a preset efficiency limit value, and issues an SDPF damage fault alarm to prompt a user to repair it, thereby reducing the influence of the damaged position and shape of the SDPF on a single sensor, and reducing the risk of sensor recognition errors by comparing multiple related parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a flow chart of the method for identifying SDPF damage of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the embodiments, but it does not constitute any limitation to the present invention. Any limited number of modifications made by anyone within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0042] See also Figure 1 A method for identifying SDPF damage of the present invention comprises:

[0043] Step 1: Set a time interval. In this embodiment, the time interval is 10S. 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 the SDPF within 10S.

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

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

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

[0047] T SDFP =a×T 1 +(1-a)×T 2 ;

[0048] Among them, T SDFP is the temperature value of SDPF, T 1 is the upstream temperature, T 2 is the downstream temperature value, a is the temperature weighting coefficient, and a is 0.4.

[0049] The urea / NOx equivalent ratio is calculated based on the urea injection rate of the engine, the upstream NOx concentration value and the exhaust flow rate.

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

[0051] K=v×3600*0.325 / 60.06*2 / C 1 *28.89 / Q;

[0052] Where K is the urea / NOx equivalent ratio, v is the urea injection rate of the engine, C 1 is the upstream NOx concentration value, and Q is the exhaust flow rate.

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

[0054] The expression for calculating the upstream specific NOx emission value is:

[0055] M 1 =∑(0.001586*C 1 *Q) / ∑(n*T / 9550);

[0056] Among them, M 1 is the upstream specific NOx emission value, C 1is 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 the downstream NOx concentration value, exhaust flow, engine speed and engine torque.

[0058] The expression for calculating downstream specific NOx emission value is:

[0059] M 2 =∑(0.001586*C 2 *Q) / ∑(n*T / 9550);

[0060] Among them, M 2 is the downstream specific NOx emission value, C 2 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 coefficient.

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

[0063] η 1 =K*β;

[0064] Among them, η 1 is the theoretical NOx conversion efficiency, K is the urea / NOx equivalent ratio, and β is the correction factor based on temperature.

[0065] Step 4: Calculate the actual NOx conversion efficiency value through the upstream specific NOx emission value and the downstream specific NOx emission value.

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

[0067] η 2 =(M 1 -M 2 ) / M 1 ;

[0068] Among them, η 2 is the measured NOx conversion efficiency value, M 1 is the upstream specific NOx emission value, M 2 is the downstream specific NOx emission value.

[0069] Step 5: Calculate the efficiency deviation value by using 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=η 1 -η 2 ;

[0072] Among them, △η is the efficiency deviation value, η 1 is the theoretical NOx conversion efficiency value, η 2 It is the measured NOx conversion efficiency value.

[0073] Step 6: Compare the urea / NOx equivalent ratio with the set equivalence 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 equivalence ratio limit and the efficiency deviation value is greater than or equal to the efficiency limit, it means that the SDPF is severely damaged and there is a risk of PN emissions exceeding 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 is greater than or equal to the efficiency limit, an SDPF damage fault alarm is issued to prompt the user to shut down the machine for repair.

[0075] If the SDPF is damaged and the urea / NOx equivalent ratio is greater than or equal to the equivalent ratio limit, the ammonia storage injected into the carrier will be distributed to the rear end of the damaged hole. If the distribution of ammonia storage is different from the preset distribution during design, the efficiency of the SCR (selective catalytic reduction system) will decrease, resulting in a decrease in urea that reacts with NOx, thereby generating a large amount of ammonia leakage. The ammonia leakage passes through the downstream NOx sensor, and the downstream NOx sensor will misjudge ammonia as NOx, so the calculated measured NOx conversion efficiency value becomes lower and the efficiency deviation value Δη becomes larger. If the efficiency deviation value Δη is greater than or equal to the efficiency limit, it means that the SDPF is severely damaged and there is a risk that PN emissions will exceed regulatory requirements. The SDPF damage fault alarm will be used to prompt the user to shut down the system for repair.

[0076] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for identifying SDPF damage, characterized in that: The method includes: Obtaining the theoretical NOx conversion efficiency value, the measured NOx conversion efficiency value and the urea / NOx equivalent ratio, and calculating 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 equivalence 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 equivalence ratio limit and the efficiency deviation value is greater than or equal to the efficiency limit, an SDPF damage fault alarm is issued.

2. A method for identifying SDPF damage according to claim 1, characterized in that: The method for obtaining the theoretical NOx conversion efficiency value, the measured NOx conversion efficiency value and the urea / NOx equivalent ratio value is as follows: Step 1: 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 the SDPF within a preset time; Step 2: Calculate the temperature value of SDPF by using the upstream temperature value and the downstream temperature value; The urea / NOx equivalent ratio is calculated by the urea injection rate, the upstream NOx concentration value and the exhaust flow rate of the engine; The upstream specific NOx emission value is calculated by using the upstream NOx concentration value, the exhaust flow rate, the engine speed and the engine torque; The downstream specific NOx emission value is calculated by using the downstream NOx concentration value, the exhaust flow rate, the engine speed and the engine torque; Step 3: Calculate the theoretical NOx conversion efficiency value by using the urea / NOx equivalent ratio and the set temperature correction coefficient; Step 4: Calculate the measured NOx conversion efficiency value through the upstream specific NOx emission value and the downstream specific NOx emission value.

3. A method for identifying SDPF damage according to claim 2, characterized in that: In the step 2, the expression for calculating the temperature value of the SDPF is: T SDFP =a×T1+(1-a)×T2; Among them, T SDFP is the temperature value of SDPF, T1 is the upstream temperature value, T2 is the downstream temperature value, and a is the temperature weighting coefficient.

4. A method for identifying SDPF damage according to claim 3, characterized in that: In the step 2, the expression for calculating the urea / NOx equivalent ratio is: K=v×3600*0.325 / 60.06*2 / C1*28.89 / Q; Among them, K is the urea / NOx equivalent ratio, v is the urea injection rate of the engine, C1 is the upstream NOx concentration value, and Q is the exhaust flow rate.

5. A method for identifying SDPF damage according to claim 4, characterized in that: In the step 2, the expression for calculating the upstream specific NOx emission value is: M1=∑(0.001586*C1*Q) / ∑(n*T / 9550); Among them, M1 is the upstream specific 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.

6. A method for identifying SDPF damage according to claim 5, characterized in that: In the step 2, the expression for calculating the downstream specific NOx emission value is: M2=∑(0.001586*C2*Q) / ∑(n*T / 9550); Among them, M2 is the downstream specific 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.

7. A method for identifying SDPF damage according to claim 6, characterized in that: In the step 3, the expression for calculating the theoretical NOx conversion efficiency value is: η1=K*β; wherein η1 is the theoretical NOx conversion efficiency value, K is the urea / NOx equivalent ratio, and β is the correction coefficient based on temperature.

8. A method for identifying SDPF damage according to claim 7, characterized in that: In the step 4, the expression for calculating the measured NOx conversion efficiency value is: η2=(M1-M2) / M1; Among them, 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.

9. A method for identifying SDPF damage according to claim 8, characterized in that: The expression for calculating the efficiency deviation value is: Δη=η1-η2; Among them, △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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