A method for road screening of diesel vehicles with excessive NOx emissions

Abstract

The present application relates to a kind of NO x The method of screening diesel vehicle on road with excessive emission, can screen out NO x Excessive diesel vehicle under the condition of in situ. This method designs new experimental procedure and judgment criteria, contains three combined working conditions of accelerating by pressing accelerator, high speed maintaining and cutting off fuel. Acceleration stage ensures the maximum NO x Emission point, changing working condition makes SCR inlet NO x Concentration curve has the characteristics of rising, falling, maintaining and falling again. According to the fitting curve change rate of SCR outlet NO x , positive and negative judge the working condition of SCR, according to the maximum NO x Concentration value judges whether the original engine emission of diesel vehicle is too high. Accelerate by changing the position of accelerator pedal; according to the position change of accelerator pedal, fit NO x Emission concentration curve in stages, and calculate NOx change rate, use NO x Change rate to reflect the characteristics of NO x Emission concentration curve. First, judge whether SCR is working, if not working and in situ NO x Emission concentration is too high, then NO x Emission is excessive.

Description

Technical Field

[0001] This invention relates to the field of automotive exhaust aftertreatment technology, and more specifically, to a high NO₂... x Methods for road screening of diesel vehicles that exceed emission standards. Background Technology

[0002] Currently, there is a need for effective detection technologies to screen diesel vehicles that exceed emission standards.

[0003] Diesel engine NO x The main reasons for exceeding emission standards are excessive engine combustion and malfunctioning after-treatment systems. Excessive combustion in diesel vehicles is generally due to design flaws in the manufacturing process, and these are relatively rare. However, because the addition of urea in the after-treatment system increases operating costs, more and more consumers and even vehicle manufacturers are falsifying emissions data to save money. Many drivers deliberately artificially inflate exhaust temperatures and NOx levels. x The sensor's deviation aims to reduce or even eliminate urea injection. Therefore, diesel NO x The method for detecting excessive emissions requires simultaneously testing the SCR operation and the original emissions of the diesel vehicle.

[0004] Currently, NO for diesel vehicles x Emissions testing primarily involves wheel rotation tests at testing facilities or real-road testing using complex PEMS (Power Emission Monitoring System) equipment. Both methods require specialized, large-scale testing equipment and are time-consuming, making them unsuitable for real-road testing. Therefore, there is currently a lack of clearly defined and effective screening technologies for diesel vehicles in actual road operation. Summary of the Invention

[0005] To address the problem of the inability to effectively identify diesel vehicles with excessive NOx emissions on actual roads, this invention proposes a method for road screening of diesel vehicles with excessive NOx emissions.

[0006] A high NO x The method for road testing of diesel vehicles is characterized by comprising the following steps:

[0007] A sampling device is installed on the exhaust pipe of the diesel vehicle, on the outlet side of the SCR reactor, to measure the NO at the outlet. x Emission concentration.

[0008] A stationary engine speed variation test in neutral was conducted. This test was performed by changing the accelerator pedal position, and the test must include at least three positional changes: fully depressing the accelerator, maintaining the accelerator position, and releasing the accelerator. To ensure NO... x The emission concentration changes are distinct, and it is best to press the accelerator pedal to the floor within 3 seconds and keep it in that position for at least 10 seconds.

[0009] NO was measured during the above process using a sampling device.x The change in emission concentration over time is denoted as E;

[0010] Piecewise linear fitting is performed on E, segmenting it into three parts: the first maximum, the first minimum, and the second maximum. For example, the segments could be: fully depressed on the accelerator, holding the accelerator, and releasing the accelerator. A single-step linear fitting is used for the segments of fully depressed and releasing the accelerator, while a two-step linear fitting is used for the segment of holding the accelerator. The fitted line segments are differentiated to obtain the rate of change M at different stages.

[0011] Determine whether the fitted line segment possesses at least three significant characteristic segments, i.e., whether the fitted line segment exhibits an upward, stable, or downward trend. For example, the rate of change M1 during the acceleration phase must be greater than 0 ppm / s. 2 The rate of change of the second fitted curve remains zero, with the absolute value of the rate of change of the fitted curve set at 5 ppm / s. 2 The value within the range is considered zero, and the M4 of the fitted curve during the throttle release phase is less than 0 ppm / s. 2 If the fitted line segment does not match the changing trend, it can be determined that the SCR is not working properly;

[0012] According to E, NO is obtained. x The peak emission level E1 is used to determine if the emission level exceeds the threshold, such as 500 ppm. If E1 exceeds the threshold, the original emissions of the diesel vehicle are too high.

[0013] If the NOx peak value exceeds the threshold when the SCR is not operating, it indicates that the NOx level in the diesel vehicle is high. x Emissions exceeded standards.

[0014] In the description of this instruction, reference is made to the terms "3s", "10s", "5 minutes", and "0ppm / s". 2 Descriptions such as "500ppm" indicate that a specific feature or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can modify, change, substitute, and vary the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

[0015] The principle upon which this invention is based is:

[0016] like Figure 1 The dynamic test loop shown will definitely result in NO at the SCR entry point. x The emission concentration changes over time, and the course of this change is predictable. This is because the dynamic test cycle controls the engine speed by varying the accelerator pedal position, thus affecting the NO emissions from the engine. x Gas concentration, NO at SCR inletx The emission concentration curve characteristics are closely linked to engine speed variation characteristics. Therefore, the dynamic test cycle of the engine corresponds to a determined NO... x Characteristics of emission concentration curve changes.

[0017] A diesel vehicle will always get NO when accelerating from a standstill in neutral. x The maximum emission of NO is due to the fact that acceleration leads to a richer fuel-air mixture, resulting in incomplete combustion and increased NO emissions. x The gas concentration is higher. Engines producing more pollutants at varying speeds (likely referring to a constant speed) generate more pollutants than at constant speeds; therefore, NO will only be present during acceleration. x Maximum emissions of gas.

[0018] like Figure 2 The SCR shown will disrupt the NO before and after. x The emission concentration curve over time shows that diesel engines emit NO after combustion. x Enter SCR, NO x NO is discharged after undergoing a catalytic reduction reaction in SCR. x The characteristics of the emission concentration curve were severely disrupted.

[0019] The innovation of this invention: This invention innovatively proposes a practical and simple method for screening NO. x The testing procedure for diesel vehicles exceeding emission standards includes at least three combined dynamic conditions: acceleration from a standstill, maintaining high speed after acceleration, and fuel cut-off. The acceleration condition ensures that the maximum NO emission occurs during the test cycle. x At the emission point, the combined operating conditions ensured that the NO concentration at the SCR inlet was controlled. x Characteristics of concentration curve changes. Based on the specific NO corresponding to changes in operating conditions. x Concentration curve trend of SCR outlet NO x The characteristics of concentration curve changes indicate the SCR's operating status, and then based on NO... x The maximum concentration is used to determine whether the original emissions of a diesel vehicle are too high; a comprehensive screening of NO... x Diesel vehicles exceeding emission standards.

[0020] The beneficial effects of this invention: It proposes a NO x The method for road testing of diesel vehicles exceeding emission standards has been verified to be easy to implement, simple and reliable to operate, and can be used even when upstream NO3-containing samples cannot be obtained. x Assess SCR performance based on emissions data. By combining SCR performance with the engine's original emissions levels, the risk of diesel vehicle emissions exceeding standards can be effectively assessed, solving the problem of ineffective identification of excessive vehicle emissions during actual road testing. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the test cycle principle of the present invention.

[0022] Figure 2 The SCR inlet and outlet NO of the present invention x Concentration change over time graph

[0023] Figure 3 This is a measurement structure diagram provided for an embodiment of the present invention.

[0024] Figure 4 The method application logic diagram provided for the example of the present invention.

[0025] Figure 5 This is a flowchart of the present invention. Detailed Implementation

[0026] according to Figure 1 As shown, by controlling the accelerator pedal position, a variable operating condition test cycle is formed. Changes in the accelerator pedal position affect the accelerator opening, which in turn controls the engine speed, corresponding to a specific NO. x The emission concentration curve variation characteristics. Therefore, the dynamic test cycle of the engine corresponds to a determined NO. x Emission concentration curve characteristics. [From the characteristics of the concentration change curve, it can be seen that the NO emission concentration of diesel vehicle engines...] x The maximum emission point occurs briefly when accelerating to the maximum speed.

[0027] according to Figure 1 and Figure 2 As shown, NO is adjusted according to specific variable operating conditions. x Staged fitting curves for emission concentrations. Specific method: For the collected NO... x The emission concentration curve is marked with points in chronological order to find NO. x The emission concentration initial value, the first maximum value, the first minimum value, the last maximum value, the end value, and the corresponding specific time are divided into different stages according to points. Then, the curve is fitted to obtain the characteristic value of each fitted curve, that is, the trend of change.

[0028] When the SCR is not operating, most of the NO generated by diesel engine combustion... x The gas was discharged directly from the exhaust pipe without being reduced, NO x The gas emission curves exhibit distinct characteristic trends. When the SCR is operating normally, urea acts as a catalyst, increasing catalytic conversion efficiency and reducing NO emissions. x The gas is reduced to N2, H2O, and NO by urea. x The gas does not exhibit a significant trend of change.

[0029] like Figure 3The illustrated embodiment of the invention provides a structural diagram of a measuring device. It includes an SCR outlet and a nitrogen oxide sensor for measuring NO. x Concentration, plot NO x Concentration change curve over time. Determine NO concentration based on the concentration change curve. x The maximum concentration; the data curves are fitted under different operating conditions, and the rate of change of the fitted line segment is calculated. The operating status of SCR is judged based on the rate of change; based on NO... x The maximum emission value is used to determine the original emissions of a diesel vehicle.

[0030] according to Figure 4 The example shown is a logic diagram of the method application.

[0031] After the diesel vehicle has been driving normally, stop it, shift to neutral, and immediately accelerate, recording the NO. x Emission concentration E.

[0032] Based on the changes in accelerator pedal position, the emission concentration curve E is fitted in stages, and NO is calculated. x Emission concentration change rate; NO is obtained from curve E. x Maximum emission concentration.

[0033] Based on the original experimental data, the NO at different stages of the fitted curve was analyzed. x The positive or negative value of the emission concentration change rate should conform to the sequence of throttle position combination changes. The specific calibration range can be adjusted according to the severity of the combined dynamic conditions.

[0034] If the rate of change is within the calibration range throughout the entire process, the diesel vehicle's SCR system is determined to be malfunctioning; under the condition that the SCR is malfunctioning, if NO x If the peak emission exceeds the threshold, the diesel vehicle is considered to have excessive original emissions. By meeting these two criteria, it can be determined that the diesel vehicle contains NO. x The risk of exceeding emission standards.

Claims

1. A type of NO x The method for road screening of diesel vehicles with excessive emissions is characterized by, Includes the following steps: (1) Install a sampling device on the exhaust pipe of the diesel vehicle at the outlet of the SCR reactor to measure the NO at the outlet. x Emission concentration; (2) Conduct a stationary neutral engine speed change test. The test method is achieved by changing the position of the accelerator pedal, and must include at least three position changes: pressing the accelerator pedal to the bottom, holding the accelerator pedal position, and releasing the accelerator pedal. Pressing the accelerator pedal to the bottom causes a sudden increase in the engine fuel supply, making the fuel mixture richer and resulting in the maximum emission value under the stationary neutral test conditions. (3) Measure the NO in the above process using a sampling device. x The change in emission concentration over time is denoted as E; (4) Perform piecewise linear fitting on E, with three segments: pressing the accelerator to the floor, holding the accelerator, and releasing the accelerator. The segments of pressing the accelerator to the floor and releasing the accelerator are fitted with a single linear fit, while the segment of holding the accelerator is fitted with a two-segment linear fit. Differentiate the fitted line segments to obtain the rate of change M at different stages. (5) Determine whether the fitted line segment has more than three significant feature segments, that is, whether the fitted line segment has an upward, stable and downward trend; if the curve change rate of the whole stage meets the value range corresponding to the combined working condition, then it is determined that the SCR is not working properly. (6) Obtain NO from E x The peak emission level E1 is used to determine if the diesel vehicle's original engine emissions are too high. The SCR operation status and the original engine emissions are linked by a gate and have a sequential order: first, the SCR operation status is assessed, then the original engine emissions are checked. If the SCR is malfunctioning and the original engine emissions are too high, then the diesel vehicle's NOx emissions can be determined to be excessive. x Emissions exceeded standards.

2. The NO according to claim 1 x The method for road screening of diesel vehicles with excessive emissions is characterized by: In step (2), the diesel vehicle is kept in neutral, the accelerator is fully depressed within 3 seconds, the maximum speed is reached and maintained for more than 10 seconds, then the accelerator is released, so that NO x The concentration curve shows a characteristic of rising and then falling back to zero.

3. The NO according to claim 1 x The method for road screening of diesel vehicles with excessive emissions is characterized by: In step (5), different throttle positions will change the engine speed, thereby causing the SCR inlet NO to change. x Emission concentration change characteristics, accelerating by pressing the accelerator will lead to NO x The rate of change in emission concentration is positive; when maintaining the throttle position, the rate of change in the first segment of the fitted curve is negative, and the rate of change in the second segment of the fitted curve remains zero, wherein the absolute value of the rate of change of the fitted curve is within 5 ppm / s. 2 The value within is considered zero; the moment of releasing the throttle is NO. x The rate of change in emission concentration was negative.

4. The NO according to claim 1 x The method for road screening of diesel vehicles with excessive emissions is characterized by: In step (5), the SCR inlet NO of the diesel vehicle x The emission concentration curve is affected by the throttle position; SCR operation will disrupt the NO concentration before and after the emission concentration curve. x The rate of change of the emission concentration fitting curve, if the NO at the SCR outlet x If the rate of change of the emission concentration fitting curve does not meet the positive and negative values ​​corresponding to the change of throttle position, it is determined that the SCR is working normally.

5. The NO according to claim 1 x The method for road screening of diesel vehicles with excessive emissions is characterized by: Step (6) involves detecting the NO at the SCR outlet of vehicles exceeding emission standards using the free acceleration method. x The maximum emission concentration is used as a threshold; the free acceleration method measures the emission concentration by accelerating the vehicle three times consecutively while it is in neutral.

6. The NO according to claim 1 x The method for road screening of diesel vehicles with excessive emissions is characterized by: In step (6), the threshold value is determined based on the results of multiple free acceleration tests on different vehicle models. If NO x If the peak emissions exceed the threshold, the original engine's emissions are too high.

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