Remote online determination method of the operating status of the SCR system of a diesel vehicle based on vehicle specific power

Abstract

The present invention discloses a method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power, comprising the following steps: obtaining the time proportion of the operating condition in the low, medium and high speed intervals based on vehicle speed data, selecting a suitable operating condition based on the vehicle operating time and the low, medium and high speed interval proportion requirements; selecting corresponding OBD remote monitoring data for cleaning based on the selected operating condition; calculating the vehicle specific power (VSP); calculating the NOx average emission mass rate in each VSP-bin interval based on the vehicle exhaust NOx mass emission rate calculation formula and the transient operating condition bin division method; calculating the NOx average emission mass rate under each transient operating condition based on the NOx average emission mass rate calculation of each VSP-bin interval, obtaining the VSP-bin NOx peak emission mass rate in the low, medium and high speed intervals, and determining the vehicle SCR operating status based on the magnitude of each peak emission mass rate in different speed intervals. The present invention can effectively diagnose whether the SCR system operating status is normal and avoid continuous ultra-high NOx emissions under abnormal SCR system conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile emission testing and monitoring, and in particular to a method for remote online determination of the operating state of an SCR system of a diesel vehicle based on vehicle specific power. Background Art

[0002] Motor vehicle emissions are increasingly becoming a significant factor affecting urban air quality, negatively impacting human health. According to the 2022 China Mobile Source Environmental Management Annual Report, heavy-duty diesel vehicles, which accounted for only 7% of my country's total vehicle fleet in 2021, accounted for approximately 70.3% of total NOx emissions. As a major precursor to ozone and particulate matter, controlling NOx emissions from heavy-duty diesel vehicles is crucial to the fight against severe air pollution, ozone pollution, and diesel truck pollution.

[0003] With the rapid development of on-board diagnostics (OBD) and the internet, OBD remote monitoring technology has become a crucial tool for monitoring a vehicle's actual road operation, emissions, faults, and system degradation. To address the shortcomings of current regulatory certification tests such as laboratory drive cycles and on-board PEMS, as well as traditional in-use vehicle monitoring methods like annual inspections, exhaust remote sensing, and roadside inspections, OBD remote monitoring technology has been incorporated into standards and policy documents such as GB17691-2018, "Emission Limits and Measurement Methods for Pollutants from Heavy-Duty Diesel Vehicles (China Phase VI)" and the "Action Plan for the Tough Battle Against Diesel Cargo Pollution Control" (Environmental and Atmospheric Administration

[2018] No. 179).

[0004] Exhaust emissions from heavy-duty diesel vehicles are primarily controlled by the proper functioning of their after-treatment systems. Therefore, monitoring the operating status of diesel vehicle after-treatment systems, such as SCR, using OBD remote monitoring technology can effectively prevent excessively high emissions caused by after-treatment system malfunctions.

[0005] Currently, OBD remote monitoring technology primarily relies on OBD fault code analysis to monitor the severity and severity of emissions faults that occur during after-treatment system operation. However, this approach cannot effectively monitor abnormal operating conditions of vehicle after-treatment systems that do not meet the alarm threshold. Summary of the Invention

[0006] The purpose of the present invention is to effectively realize the timely supervision of abnormal operating conditions of diesel vehicle SCR systems, provide a remote online determination method of the operating status of diesel vehicle SCR systems based on vehicle specific power, and provide technical support and basis for environmental protection departments and enterprises to supervise the working conditions of diesel vehicle SCR systems.

[0007] The technical solution adopted to achieve the purpose of the present invention is:

[0008] A method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power comprises the following steps:

[0009] Obtain the vehicle's OBD remote monitoring data and, based on the vehicle speed data, calculate the time proportion of the operating condition in the low-speed, medium-speed, and high-speed ranges. Select the operating condition that meets the requirements based on the vehicle's operating time and the proportion of low, medium, and high speed ranges.

[0010] Based on the selected working conditions that meet the requirements, the corresponding OBD remote monitoring data is selected for data cleaning;

[0011] Calculation of the vehicle's motor vehicle specific power (VSP);

[0012] Based on the vehicle exhaust NOx mass emission rate calculation formula and the transient operating condition bin division method, the vehicle exhaust NOx emission mass rate within the transient operating condition bin interval is obtained. Based on the vehicle exhaust NOx emission mass rate, the average NOx emission mass rate of each VSP-bin interval is calculated;

[0013] Based on the NOx average emission mass rate of each VSP-bin interval, the NOx average emission rate under each transient condition is calculated to obtain the VSP-bin NOx peak emission mass rate P in the low, medium and high speed intervals. (0,40] , P (40,80] and P (80,+∞) , according to the size of each peak emission mass rate in different speed ranges, the vehicle SCR working status is determined.

[0014] The OBD remote monitoring data includes vehicle speed, instantaneous NOx concentration downstream of the SCR, intake volume and engine fuel flow, and the data frequency is 1HZ.

[0015] Among them, the vehicle SCR system operating status diagnostic working condition selection should be carried out within the vehicle driving cycle from the diagnostic point to 2 hours before the diagnostic point, and the working condition with a vehicle speed greater than 0 should last at least 1 hour.

[0016] Among them, the low speed is 0-40km / h, the medium speed is 40-80km / h, and the high speed is greater than 80km / h.

[0017] Among them, when the vehicle speed does not exceed 80km / h, the low-speed and medium-speed operating conditions account for 50%±5%; when the vehicle speed exceeds 80km / h, the low-speed, medium-speed and high-speed operating conditions account for more than 30%.

[0018] During data cleaning, data with SCR downstream NOx instantaneous concentrations greater than 3012.75 and less than -200 ppm were removed, and SCR downstream NOx instantaneous concentrations less than 0 were assigned to 0; and data with engine coolant temperatures not exceeding 70°C were removed.

[0019] For heavy-duty diesel vehicles, the calculation formula for VSP is as follows:

[0020]

[0021] Where: M - gross vehicle weight; v - vehicle speed; a - vehicle acceleration; g - acceleration due to gravity; θ - road slope, dimensionless; A - tire rolling resistance coefficient; B - mechanical rotational friction resistance coefficient 2 ; C - air resistance coefficient; vehicle acceleration a at sampling time i i The calculation formula is as follows:

[0022] a i =(v i+1 -v i ) / 3.6.

[0023] The calculation formula for the vehicle exhaust NOx emission mass rate is as follows:

[0024] ER NOx =0.001587×C NOx ×(Q intake +0.83×Q fuel ) / 3600

[0025] Where ER NOx -- vehicle exhaust NOx emission mass rate; C NOx --Instantaneous NOx concentration downstream of SCR; Q intake --Intake volume, Q fuel --Engine fuel flow;

[0026] The calculation formula for the average NOx emission mass rate in each VSP-bin interval is as follows:

[0027]

[0028] Where, j is the transient operating bin number; k is the transient operating bin number for the vehicle exhaust NOx emission mass rate in the j interval; n is the number of vehicle exhaust NOx emission mass rates in the j interval; ER NOx,j,k --The transient operating condition bin number is the kth vehicle exhaust NOx emission mass rate in the jth interval, --The transient operating condition bin number is the average vehicle exhaust NOx emission mass rate in the j interval.

[0029] Among them, when the maximum speed is greater than 80km / h, P (0,40] <P (40,80] <P (80,+∞) Or when the maximum speed is greater than 80km / h, P (0,40] <P (40,80] ,, determine that the SCR working state is abnormal;

[0030] When the maximum speed is greater than 80 km / h, P (0,40] >P (40,80] >P (80,+∞) , or when the maximum speed is not greater than 80km / h, P (0,40] >P (40,80] ,, determine that the SCR working status is normal.

[0031] The method of the present invention can effectively diagnose whether the operating status of the SCR system is normal, and avoid continuous ultra-high NOx emissions under abnormal SCR system conditions; at the same time, the method of the present invention can support government management departments such as environmental protection in controlling ultra-high emissions caused by abnormal diesel vehicle after-treatment systems, and also provide a method for enterprises to supervise the actual operating performance of their products. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of a method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power according to the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] The remote online determination method of the operating status of the SCR system of a diesel vehicle based on vehicle specific power of the present invention can effectively identify abnormal operating status of the SCR system of a heavy-duty diesel vehicle during actual road driving.

[0035] The present invention provides a method support for supervising the operating status of the SCR system of a diesel vehicle using OBD remote monitoring technology, effectively avoiding high NOx emissions under abnormal conditions of the SCR system.

[0036] like Figure 1 As shown, the method for remote online determination of the operating status of the SCR system of a diesel vehicle based on vehicle specific power according to an embodiment of the present invention is implemented in the following steps:

[0037] 1. Working condition selection

[0038] OBD remote monitoring data parameters include vehicle speed, instantaneous NOx concentration downstream of the SCR, intake air volume, and engine fuel flow rate, with a data frequency of 1 Hz. The vehicle SCR system operating status diagnosis operating condition should be conducted within the vehicle's driving cycle from the diagnostic point to 2 hours before the diagnostic point, and the operating period with a vehicle speed greater than 0 should be at least 1 hour.

[0039] Based on the vehicle speed data of the selected working condition, the time proportion of the working condition in the low speed (0-40km / h), medium speed (40-80km / h) and high speed (>80km / h) ranges is calculated.

[0040] Requirements for the proportion of low, medium and high speed operating conditions: When the vehicle speed does not exceed 80km / h, the proportion of low and medium speed operating conditions is about 50%, with a deviation of ±5% allowed; when the vehicle speed exceeds 80km / h, the proportion of low, medium and high speed operating conditions is more than 30%.

[0041] Based on the vehicle's operating time and the proportion of low, medium, and high speed ranges, the selected operating condition is judged to see if it meets the requirements. If not, the system will scroll forward in 30-minute increments, selecting a 2-hour sample and performing operating condition feature analysis until suitable data is selected.

[0042] 2. Data Cleaning

[0043] Based on the selected qualifying operating conditions, the corresponding OBD remote monitoring data was selected for data cleaning. According to the OBD remote monitoring data format definition requirements in the GB17691-2018 "Heavy-Duty Diesel Vehicle Pollutant Emission Limits and Measurement Methods (China Phase VI)" standard, data with SCR downstream NOx instantaneous concentrations greater than 3012.75 and less than -200 ppm were eliminated. Then, data with SCR downstream NOx instantaneous concentrations less than 0 were assigned to zero. Furthermore, to avoid interference from invalid NOx data when the engine was not fully started, data with engine coolant temperatures below 70°C were eliminated.

[0044] 3. Calculation of the vehicle's specific power (VSP)

[0045] VSP can be used to characterize the power output of the engine required to overcome acceleration resistance, slope resistance, wheel friction resistance, air resistance, and increase vehicle kinetic energy and potential energy during vehicle driving. That is, the power output of the engine to move unit vehicle weight, and its unit is kW / t or m 2 / s 3 .

[0046] Typically, VSP is used to describe the impact of transient operating conditions changes of motor vehicles on emission levels.

[0047] For heavy-duty diesel vehicles, the VSP is calculated as follows:

[0048]

[0049] Where: M - gross vehicle weight, ton; v - vehicle speed, m / s; a - vehicle acceleration, m / s 2 ; g--acceleration due to gravity, 9.81m / s 2 ; θ--road slope, dimensionless; A--tire rolling resistance coefficient, kW s / m; B--mechanical rotational friction resistance coefficient, kW s 2 / m 2 ; C--air resistance coefficient, kW s 3 / m 3 .

[0050] The calculation formula of vehicle acceleration a is as follows:

[0051] a i =(v i+1 -v i ) / 3.6 (2)

[0052] Where: i is the sampling time, s; v is the vehicle speed, km / h.

[0053] According to the vehicle type and weight, the calculation formulas of A, B, and C are shown in Table 1:

[0054]

[0055] Table 1

[0056] 4. Calculation of NOx mass emission rate for transient and VSP-bin vehicle exhaust

[0057] ER NOx =0.001587×C NOx ×(Q intake +0.83×Q fuel ) / 3600 (3)

[0058] Where ER NOx -- Vehicle exhaust NOx emission mass rate, g / s; C NOx --Instantaneous NOx concentration downstream of SCR, ppm; Q intake --Intake volume, kg / h; Q fuel --Engine fuel flow, L / h.

[0059] Based on the transient bin division method (Table 2), the mean of the vehicle exhaust NOx emission mass rate within each VSP-bin interval is calculated, as shown in Equation 4. As shown in Table 2, each speed interval corresponds to multiple VSP interval values. Based on the VSP size, the VSP within the low, medium, and high speed intervals is divided into multiple transient bins. Each transient bin is sequentially numbered and corresponds to a VSP-bin interval, thus including multiple VSP-bin intervals.

[0060] Serial number speed VSP Serial number speed VSP Serial number speed VSP 1 (0,40] (-∞,0) 7 (40,80] (-∞,0) 13 (80,+∞) (-∞,6) 2 (0,40] [0,3) 8 (40,80] [0,3) 14 (80,+∞) [6,12) 3 (0,40] [3,6) 9 (40,80] [3,6) 15 (80,+∞) [12,+∞) 4 (0,40] [6,9) 10 (40,80] [6,9) 5 (0,40] [9,12) 11 (40,80] [9,12) 6 (0,40] [12,+∞) 12 (40,80] [12,+∞)

[0061] Table 2

[0062] The calculation formula for the average NOx emission mass rate of vehicle exhaust in each VSP-bin interval is as follows:

[0063]

[0064] Where, j is the transient operating bin number; k is the transient operating bin number for the vehicle exhaust NOx emission mass rate in the j interval; n is the number of vehicle exhaust NOx emission mass rates in the j interval; ER NOx,j,k --Transient operating condition bin number is the kth vehicle exhaust NOx emission mass rate in interval j, g / s; --The average NOx emission mass rate of vehicle exhaust within the transient operating condition bin number j, g / s.

[0065] 5. Method for determining abnormal SCR working status of heavy-duty vehicles

[0066] Based on the calculation formula of the average NOx emission mass rate of vehicle exhaust in each VSP-bin interval, the average NOx emission mass rate under each transient working condition is calculated, and the VSP-bin NOx peak emission mass rate P in the low, medium and high speed interval is obtained. (0,40] , P (40,80] and P (80,+∞) , according to the size of each peak emission mass rate in different speed ranges, the vehicle SCR working status is determined.

[0067] The specific method for determining the operating status of the vehicle SCR system is as follows:

[0068] When P (0,40] <P (40,80] <P (80,+∞) (maximum speed greater than 80km / h) or P (0,40] <P (40,80] (maximum vehicle speed is not greater than 80km / h), it can be determined that the SCR working state is abnormal;

[0069] When P (0,40]>P (40,80] >P (80,+∞) (maximum speed greater than 80km / h) or P (0,40] >P (40,80] (maximum vehicle speed is not greater than 80km / h), it can be determined that the SCR working status is normal.

[0070] The present invention's method for determining the normal operating status of a heavy-duty vehicle's SCR system can determine the operating status of a heavy-duty diesel vehicle's SCR system during actual road driving using OBD remote monitoring. This method can provide a reference for government and enterprise OBD remote monitoring platforms to identify vehicle SCR system faults, enabling dynamic monitoring of the operating status of diesel vehicle SCR systems and effectively reducing high NOx emissions when the SCR system is operating abnormally.

[0071] The basic principles, main features and advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0072] The embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and all changes that come within the meaning and range of equivalents of the claims are therefore intended to be embraced therein.

[0073] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A remote online determination method for the operating status of a diesel vehicle SCR system based on vehicle specific power, characterized in that: The following steps are involved: Obtain the vehicle's OBD remote monitoring data and, based on the vehicle speed data, calculate the time proportion of the operating condition in the low-speed, medium-speed, and high-speed ranges. Select the operating condition that meets the requirements based on the vehicle's operating time and the proportion of low, medium, and high speed ranges. Based on the selected working conditions that meet the requirements, the corresponding OBD remote monitoring data is selected for data cleaning; Calculation of the vehicle's motor vehicle specific power (VSP); Based on the vehicle exhaust NOx mass emission rate calculation formula and the transient operating condition bin division method, the vehicle exhaust NOx emission mass rate within the transient operating condition bin interval is obtained. Based on the vehicle exhaust NOx emission mass rate, the average NOx emission mass rate of each VSP-bin interval is calculated; Based on the NOx average emission mass rate of each VSP-bin interval, the NOx average emission rate under each transient condition is calculated to obtain the VSP-bin NOx peak emission mass rate P in the low, medium and high speed intervals. (0,40] , P (40,80] and P (80,+∞) , according to the size of each peak emission mass rate in different speed ranges, the vehicle SCR working status is determined.

2. The method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power according to claim 1, characterized in that: The OBD remote monitoring data includes vehicle speed, instantaneous NOx concentration downstream of the SCR, intake air volume and engine fuel flow, and the data frequency is 1HZ.

3. The method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power according to claim 1, characterized in that: The diagnostic working condition for the vehicle's SCR system operating status should be selected within the vehicle's driving cycle from the diagnostic point to 2 hours before the diagnostic point, and the working condition with a vehicle speed greater than 0 should last at least 1 hour.

4. The method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power according to claim 1, characterized in that: The low speed is 0-40 km / h, the medium speed is 40-80 km / h, and the high speed is greater than 80 km / h.

5. The method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power according to claim 1, characterized in that: When the vehicle speed does not exceed 80km / h, the proportion of low-speed and medium-speed operating conditions is 50%±5%; when the vehicle speed exceeds 80km / h, the proportion of low-speed, medium-speed and high-speed operating conditions is more than 30%.

6. The method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power according to claim 1, characterized in that: During data cleaning, data with SCR downstream NOx instantaneous concentrations greater than 3012.75 and less than -200 ppm were eliminated, and SCR downstream NOx instantaneous concentrations less than 0 were assigned to 0; and data with engine coolant temperatures not exceeding 70°C were eliminated.

7. The method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power according to claim 1, characterized in that: For heavy-duty diesel vehicles, the VSP calculation formula is as follows: Where: M - gross vehicle weight; v - vehicle speed; a - vehicle acceleration; g - acceleration due to gravity; θ - road slope, dimensionless; A - tire rolling resistance coefficient; B - mechanical rotational friction resistance coefficient 2 ; C - air resistance coefficient; vehicle acceleration a at sampling time i i The calculation formula is as follows: and i =(in i+1 -v i ) / 3.

6.

8. The method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power according to claim 1, characterized in that: The calculation formula for the vehicle exhaust NOx emission mass rate is as follows: IS NOx =0.001587×C NOx ×(Q intake +0.83×Q fuel ) / 3600 Where ER NOx -- vehicle exhaust NOx emission mass rate; C NOx --Instantaneous NOx concentration downstream of SCR; Q intake --Intake volume, Q fuel --Engine fuel flow; The calculation formula for the average NOx emission mass rate in each VSP-bin interval is as follows: Where, j is the transient operating bin number; k is the transient operating bin number for the vehicle exhaust NOx emission mass rate in the j interval; n is the number of vehicle exhaust NOx emission mass rates in the j interval; ER NOx,j,k --The transient operating condition bin number is the kth vehicle exhaust NOx emission mass rate in the jth interval, --The transient operating condition bin number is the average vehicle exhaust NOx emission mass rate in the j interval.

9. The method for remote online determination of the operating status of a diesel vehicle SCR system based on vehicle specific power according to claim 1, characterized in that: When the maximum speed is greater than 80 km / h, P (0,40] <P (40,80] <P (80,+∞) Or when the maximum speed is not more than 80km / h, P (0,40] <P (40,80] , determine that the SCR working state is abnormal; When the maximum speed is greater than 80 km / h, P (0,40] >P (40,80] >P (80,+∞) , or when the maximum speed is not greater than 80km / h, P (0,40] >P (40,80] , it is determined that the SCR working status is normal.

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