An engine NOx emission monitoring system and method

Abstract

The present invention discloses an engine NO X emission monitoring system and method. It includes a NOx raw emission monitoring module for calculating the moving average NOx raw ratio emission of the engine; a NOx tail emission monitoring module for calculating the moving average NOx tail ratio emission of the engine; a NOx emission control factor calculation module for calculating the NOx emission control factor according to the moving average NOx raw ratio emission of the engine and the moving average NOx tail ratio emission of the engine; a NOx emission control factor correction module for correcting the NOx emission control factor to obtain the corrected NOx emission control factor; and a NOx raw emission control module for adjusting the engine operating parameters according to the corrected NOx emission control factor. The present invention does not need to collect a large amount of data for big data analysis on the cloud platform, has a simple algorithm, can directly monitor the NOx emission level of the engine in the on-vehicle EECU, and then is used to control the NOx emission of the engine, reducing the risk of NOx emission exceeding the standard and saving fuel at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of engine aftertreatment control, and particularly relates to an engine NO X emission monitoring system and method. Background Art

[0002] NOx emissions are one of the main components of engine exhaust pollutants, and relevant emission regulations have been continuously tightening the limits on NOx emission levels. According to statistics, currently, the NOx emissions of motor vehicles account for about 1 / 3 of the national statistics, and the NOx emissions of medium and heavy-duty diesel vehicles account for more than 80% of all vehicle NOx emissions. In the field of medium and heavy-duty diesel engines, the latest National VI regulations, compared with previous emission regulations, not only put forward more stringent requirements for the NOx emissions of the bench cycle, but also added the NOx limit for the vehicle PEMS test. It is expected that the future National VII emission regulations will continue to tighten the NOx emission limits to reduce environmental pollution.

[0003] Major OEMs mainly use SCR (Selective Catalytic Reducer) to treat NOx emissions. However, the conversion efficiency of SCR for NOx varies greatly under different working conditions. Generally, when the exhaust gas temperature flowing through the SCR is between 240 and 350 °C, the treatment efficiency of SCR for NOx can reach 99.5% or higher, while the efficiency will drop significantly at lower or higher temperatures. Due to the uncertainty of working conditions and the differences in driver driving habits, even though major OEMs generally adopt different methods of exhaust gas temperature control functions, it is difficult to avoid the problem that the SCR operates in the low-efficiency range. In addition, due to the manufacturing consistency problem and control robustness problem of the engine, there will also be certain differences in the original NOx emission level of the engine. In order to ensure the achievement of NOx emission limits and OBD limits, OEMs usually adopt the method of leaving a certain margin during emission calibration to cope with it. However, for some vehicles, it is still easy to have the problem of exceeding the emission limit under certain working conditions. For example, when the vehicle is driving in the city during the cold season, the exhaust gas temperature is relatively low at this time, and the working conditions fluctuate violently, the original NOx emission of the engine is relatively high, and the tailpipe NOx emission is extremely easy to exceed the limit. At this time, in addition to trying to increase the exhaust gas temperature to improve the NOx conversion efficiency, trying to reduce the original NOx emission of the engine is also an extremely important means to ensure NOx emission compliance.

[0004] Patent 1, "A Real-time Warning Method for Excessive NOx Emissions of Vehicles" (CN114991922A), discloses a real-time warning method for excessive NOx emissions of vehicles, including the following steps: Step 1: Collect vehicle data as the vehicle driving data set; Step 2: Divide the vehicle driving data set to obtain vehicle driving segments; Step 3: Process the vehicle driving segments to obtain effective vehicle driving segments; Step 4: Divide the effective vehicle driving segments according to segment division conditions to obtain a driving segment group; Step 5: According to the standard working condition formation strategy, select effective vehicle driving segments from the driving segment group and form the vehicle actual emission test working condition; Step 6: Calculate the vehicle NOx emission level according to the vehicle actual emission test working condition; Step 7: When the vehicle NOx emission level does not meet the requirements, conduct real-time warning according to the warning strategy.

[0005] Patent 2, "NOx Emission Monitoring Method and Device for EGR System of Electronic Control Diesel Engine" (CN103016184A), discloses a NOx emission monitoring method and device for EGR system of electronic control diesel engine, which includes: 1) Set each sensor, EGR valve, and processor; 2) The intake air volume calculation module of the processor calculates the real-time intake air volume and the EGR fully closed reference intake air volume; 3) The EGR rate calculation module calculates the measured EGR rate and the target EGR rate; 4) The EGR valve position monitoring module calculates the measured opening and the target opening of the EGR valve; 5) The EGR valve abnormal state identification module determines the stuck and hysteresis states of the EGR valve according to the measured opening and the target opening of the EGR valve; According to the measured EGR rate and the target EGR rate, the blocked state of the EGR valve can be determined; 6) The NOx emission monitoring module calculates the real-time NOx emission according to the measured EGR rate, the target EGR rate, torque, speed, and the abnormal state of the EGR valve. This invention directly uses the existing sensors of the electronic control diesel engine and the EGR valve position sensor as the NOx emission signal source, which can reduce the application cost and maintenance cost and accurately calculate the real-time NOx emission in real time.

[0006] Patent 3, "NOx Control Method under EGR Fault Mode" (CN114183260A), discloses a NOx control method under EGR fault mode, including the following steps: When the EGR valve fails, issue an EGR valve closing strategy; When the EGR valve is fully closed, enter the next step, otherwise, maintain the current combustion control mode; In the state of closing the EGR valve, adopt different target control requirements in different regions for exhaust temperature management control and economic emission control; When it is detected that the fault related to the EGR valve has self-healed, execute the Nox control strategy exit mechanism and restore to the EGR emission control route. The NOx control method under EGR fault mode of this invention effectively controls the NOx generation within an effective range, thereby achieving the goals of reducing Nox emissions, improving the economy under fault mode, reducing urea consumption, and improving the subjective driving experience.

[0007] Disadvantages of the prior art:

[0008] Patent 1 is only suitable for use in server cloud platforms, with large amounts of data collection and large computing volumes, and is not applicable to on-vehicle EECU real-time NOx monitoring and warning; moreover, on the one hand, the NOx alarm result is not directly given to the moving vehicle, and on the other hand, its real-time performance is poor and does not meet the vehicle control requirements, and it cannot be used for the vehicle to reduce NOx emissions in real time to avoid excessive exhaust emissions. This method is mainly used by vehicle manufacturers or regulatory agencies to monitor the vehicle status using the cloud platform.

[0009] The method described in Patent 2 is used to calculate the instantaneous value of NOx emissions at the engine outlet. On the one hand, due to production consistency issues, fuel quality differences, and control precision issues of different engines, there will be certain differences in NOx emissions itself; on the other hand, the instantaneous value is greatly affected by instantaneous operating conditions and cannot intuitively reflect the level of engine emissions at this time, and the final NOx tailpipe emissions of the vehicle are not completely positively correlated with the original NOx emissions of the engine. In some operating conditions, there may be a situation where the original NOx emissions of the engine are relatively high while the tailpipe emissions are extremely low. Therefore, this real-time NOx emission amount cannot be used for vehicle NOx emission control either. Its more important role is to provide an alternative value for the original NOx emissions of the engine when the current NOx sensor is not working properly, providing the necessary input for calculating the urea injection amount of the SCR system.

[0010] The method described in Patent 3 is only applicable to NOx control in the EGR fault mode and does not have universality and cannot be applied to NOx control during normal vehicle driving. Summary of the Invention

[0011] The purpose of the present invention is to solve the deficiencies existing in the above-mentioned background technology and provide an engine NO X emission monitoring system and method to monitor and control the engine NOx emission level in real time and reduce the risk of excessive engine NOx emissions.

[0012] The technical solution adopted by the present invention is: an engine NO X emission monitoring system, including:

[0013] A NOx original emission monitoring module for calculating the moving average NOx original specific emission of the engine;

[0014] A NOx tailpipe emission monitoring module for calculating the moving average NOx tailpipe specific emission of the engine;

[0015] A NOx emission control factor calculation module for calculating the NOx emission control factor based on the moving average NOx original specific emission of the engine and the moving average NOx tailpipe specific emission of the engine;

[0016] NOx Emission Control Factor Correction Module, which is used to correct the NOx emission control factor to obtain the corrected NOx emission control factor

[0017] NOx Original Emission Control Module, which is used to adjust the engine operating parameters according to the corrected NOx emission control factor.

[0018] Further, the engine moving average NOx original emission ratio is calculated by the following formula:

[0019]

[0020] where bs_nox1 is the engine moving average NOx original emission ratio; n is the time window size; i is the i-th time point in the time window; nox1 i represents the engine original emission NOx concentration at the i-th time point; m_exh i is the engine exhaust gas flow at the i-th time point;

[0021] eng_spd i is the engine speed at the i-th time point; eng_torq i is the engine effective output torque at the i-th time point.

[0022] Further, the engine moving average NOx tail emission ratio is calculated by the following formula:

[0023]

[0024] where bs_nox2 is the engine moving average NOx tail emission ratio; n is the time window size; i is the i-th time point in the time window; nox2 i represents the engine tail emission NOx concentration at the i-th time point; m_exh i is the engine exhaust gas flow at the i-th time point; eng_spd i is the engine speed at the i-th time point; eng_torq i is the engine effective output torque at the i-th time point.

[0025] Further, the NOx emission control factor is calculated by the following formula:

[0026] α = k * α1 + (1 - k) * α2,

[0027] where α is the NOx emission control factor; k is the weight coefficient; α1 is the NOx original emission ratio control factor; α2 is the NOx tail emission ratio control factor.

[0028] Even further, the corrected NOx emission control factor is determined by the following formula:

[0029] α′ = min(max(α + β1 + β2 + β3 + β4, 0), 1)

[0030] Wherein, α′ is the corrected NOx emission control factor; α is the NOx emission control factor; β1 is the rotational speed stability correction coefficient; β2 is the torque stability correction coefficient; β3 is the SCR inlet temperature correction coefficient; β4 is the tailpipe NH3 correction coefficient.

[0031] An engine NO X emission monitoring method, comprising the following steps:

[0032] Calculate the moving average NOx raw ratio emission of the engine;

[0033] Calculate the moving average NOx tailpipe ratio emission of the engine;

[0034] Calculate the NOx emission control factor based on the moving average NOx raw ratio emission and the moving average NOx tailpipe ratio emission of the engine;

[0035] Correct the NOx emission control factor to obtain the corrected NOx emission control factor

[0036] Adjust the engine operating parameters based on the corrected NOx emission control factor.

[0037] Further, calculate the moving average NOx raw ratio emission of the engine through the following formula:

[0038]

[0039] Wherein, bs_nox1 is the moving average NOx raw ratio emission of the engine; n is the time window size; i is the i-th time point in the time window; nox1 i represents the engine raw NOx concentration at the i-th time point; m_exh i is the engine exhaust gas flow rate at the i-th time point;

[0040] eng_spd i is the engine speed at the i-th time point; eng_torq i is the engine effective output torque at the i-th time point.

[0041] Further, calculate the moving average NOx tailpipe ratio emission of the engine through the following formula:

[0042]

[0043] Among them, bs_nox2 is the moving average NOx tailpipe emission ratio of the engine; n is the size of the time window; i is the i-th time point in the time window; nox2 i represents the engine tailpipe NOx concentration at the i-th time point; m_exh i is the engine exhaust gas flow rate at the i-th time point; eng_spd i is the engine speed at the i-th time point; eng_torq i is the effective output torque of the engine at the i-th time point.

[0044] Furthermore, the NOx emission control factor is obtained through the following formula:

[0045] α = k * α1 + (1 - k) * α2,

[0046] where α is the NOx emission control factor; k is the weight coefficient; α1 is the raw emission ratio control factor of NOx; α2 is the tailpipe emission ratio control factor of NOx.

[0047] Even further, the corrected NOx emission control factor is determined through the following formula:

[0048] α′ = min(max(α + β1 + β2 + β3 + β4, 0), 1)

[0049] where α ′ is the corrected NOx emission control factor; α is the NOx emission control factor; β1 is the rotational speed stability correction coefficient; β2 is the torque stability correction coefficient; β3 is the SCR inlet temperature correction coefficient; β4 is the tailpipe NH3 correction coefficient.

[0050] The beneficial effects of the present invention are:

[0051] The present invention needs to collect a large amount of data for big data analysis on the cloud platform. The algorithm is simple, and it can directly monitor the NOx emission level of the engine in the vehicle-mounted EECU, and then be used to control the NOx emission of the engine, reducing the risk of NOx emission exceeding the standard while saving fuel.

[0052] The present invention mainly calculates using the NOx sensor values before and after. The model value is only temporarily substituted when the sensor has not started to work properly yet, which can solve the interference problem of the NOx emission difference caused by vehicle consistency problems and other factors on the NOx monitoring results. Moreover, the moving average NOx emission ratio can better represent the level of the engine emission at this time than the instantaneous value, and the monitoring reliability is higher.

[0053] The present invention has better universality and can be applied throughout the operation of the engine, rather than being limited to the NOx control and economic optimization under the EGR fault mode. Description of the Drawings

[0054] Figure 1 This is the control flow chart of the present invention.

[0055] Figure 2 This is the schematic diagram for calculating the NOx emission control factor of the present invention. Specific embodiments

[0056] The following further describes the specific embodiments of the present invention with reference to the accompanying drawings. It should be noted here that the description of these embodiments is for helping to understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0057] The present invention provides an engine NO X emission monitoring system, including:

[0058] A NOx raw emission monitoring module, configured to calculate the engine moving average NOx raw specific emission according to the front NOx sensor reading / model calculated value and the engine exhaust gas flow rate;

[0059] A NOx tail emission monitoring module, configured to calculate the engine moving average NOx tail specific emission according to the rear NOx sensor reading / model calculated value and the engine exhaust gas flow rate;

[0060] A NOx emission control factor calculation module, configured to calculate the NOx emission control factor according to the engine moving average NOx raw specific emission and the engine moving average NOx tail specific emission;

[0061] A NOx emission control factor correction module, configured to correct the NOx emission control factor according to the operating condition stability, the SCR inlet temperature, and the tail emission NH3 emission amount to obtain the corrected NOx emission control factor

[0062] A NOx raw emission control module, configured to adjust the engine operating parameters according to the corrected NOx emission control factor.

[0063] Based on the above monitoring system, the present invention also provides an engine NO X emission monitoring method, as Figure 1 shown, the process is as follows:

[0064] 1. Engine NOx raw emission monitoring

[0065] The NOx raw emission monitoring module calculates the engine moving average NOx raw specific emission according to the front NOx sensor reading / model calculated value and the engine exhaust gas flow rate by using the moving average window method to reduce the NOx raw emission or improve the engine economy.

[0066] The implementation of the moving average window method is as follows. Four groups of 1*n data are preset within a certain time window, respectively representing four characteristic quantities continuously recorded within a period of time -

[0067] nox1 represents the original NOx concentration of the engine, in ppm. When the current NOx sensor reading is valid, the previous NOx sensor reading is taken; otherwise, the model substitution value is taken, and this substitution value is calculated by the EECU based on engine operating parameters such as engine intake air volume, fuel injection volume, fuel injection timing, intake pressure, and EGR valve opening.

[0068] m_exh represents the engine exhaust gas flow, in kg / h, and is calculated by the EECU based on the intake air flow plus the fuel injection volume per unit time.

[0069] eng_spd represents the engine speed, in rpm, and is calculated by the EECU based on the crankshaft or camshaft tooth signal.

[0070] eng_torq represents the effective output torque of the engine, in N.m. The EECU calculates the indicated output torque based on control parameters such as fuel injection volume, intake air volume, and fuel injection timing, and subtracts the engine friction torque and accessory torque, etc. to obtain the effective output torque.

[0071] A flag bit m is preset to represent the index of the 1*n array, indicating the mth number in the array. Each time, the four values of the newly calculated original NOx concentration of the engine, engine exhaust gas flow, engine speed, and engine effective output torque by the EECU are respectively written into nox1(m), m_exh(m), eng_spd(m), and eng_torq(m), and the moving average NOx original ratio emission of the engine is calculated once; at the next calculation moment, m = m + 1, and this process is repeated until when m = n, after completing the calculation of the moving average NOx original ratio emission of the engine this time, m returns to 1 next time and starts to gradually accumulate again.

[0072] The time window is preferably 1 min to 2 min. If there is one point per 1 s, then n can be selected between 60 and 120. If the time is too short, it is easily affected by instantaneous working conditions and the calculation results fluctuate greatly; if the time is too long, the control real-time performance is poor and the risk of NOx emission exceeding the standard increases.

[0073] The calculation formula for the moving average NOx original ratio emission of the engine is as follows:

[0074]

[0075] Among them, bs_nox1 is the moving average NOx original ratio emission of the engine; n is the time window size; i is the ith time point in the time window; nox1 i represents the original NOx concentration of the engine at the ith time point; m_exhi is the engine exhaust gas flow rate at the i-th time point;

[0076] eng_spd i is the engine speed at the i-th time point; eng_torq i is the effective output torque of the engine at the i-th time point.

[0077] 2. Engine NOx tailpipe emission monitoring

[0078] Similar to the above-mentioned original emission monitoring process, the only difference is that nox1 is replaced by nox2, and the relevant calculation formula is replaced by:

[0079]

[0080] where bs_nox2 is the moving average NOx tailpipe specific emission of the engine; nox2 i represents the NOx concentration in the engine tailpipe at the i-th time point, with the unit of ppm. When the reading of the post NOx sensor is valid, the EECU calculates the NOx concentration value in the tailpipe according to the cross-sensitivity of the post NOx sensor. Otherwise, the model substitution value is taken, and this substitution value is calculated by the EECU according to the SCR catalytic converter model;

[0081] 3. NOx emission control factor calculation

[0082] According to the NOx original emission and tailpipe specific emission of the aforementioned engine, the NOx emission control factor α is obtained by looking up the table and weighted calculation. The value range of this NOx emission control factor α is between 0 and 1, and its magnitude characterizes the level of NOx emission that the engine needs to control. 0 represents the low emission mode of the engine, and 1 represents the high emission economic mode. When the engine emission is relatively low at this time, the engine's original NOx emission can be controlled to move towards the high emission economic mode, and vice versa, the engine's original NOx emission needs to be controlled to move towards the low emission mode. The specific control principle of this NOx emission control factor is as Figure 2 shown.

[0083] where the NOx original specific emission control factor α1 is calibrated by looking up the table according to the NOx original specific emission of the engine, and its value range is between 0 and 1. The value of this factor is negatively correlated with the NOx original specific emission. When the NOx original specific emission is lower, this factor approaches 1, and vice versa, it approaches 0;

[0084] The NOx tailpipe specific emission control factor α2 is calibrated by looking up the table according to the NOx tailpipe specific emission of the engine, and its value range is between 0 and 1. The value of this factor is negatively correlated with the NOx tailpipe specific emission. When the NOx tailpipe specific emission is lower, this factor approaches 1, and vice versa, it approaches 0;

[0085] The weight coefficient k is a coefficient between 0 and 1, representing the proportion of the NOx raw emission control factor α1. It can be calibrated according to the vehicle models of different uses by the vehicle manufacturer. For example, for a logistics vehicle mainly operating in high-speed conditions, its tailpipe NOx may remain at a very low level for a long time. At this time, it is necessary to appropriately increase the proportion of α1. On the contrary, for vehicles mainly operating on urban roads, it is more necessary to control the engine operating mode according to the tailpipe level. At this time, it is necessary to appropriately reduce the proportion of α1. The recommended value range of the k value is 0.3 - 0.6.

[0086] 4. Engine NOx Emission Control Factor Correction

[0087] According to the operating condition stability, SCR inlet temperature, and tailpipe NH3 emission, the NOx emission control factor is corrected.

[0088] When the engine operating condition is stable enough, it is beneficial to control the tailpipe NOx. At this time, even if the engine raw NOx is relatively high, it is possible to control the tailpipe NOx at a very low ideal level. Therefore, according to whether the operating condition is stable, the NOx emission control factor α can be corrected. When the operating condition is stable, α is appropriately increased; on the contrary, α is appropriately decreased. The SCR inlet temperature correction is mainly used when the SCR inlet temperature is about to enter or has entered the SCR low-efficiency area, and the NOx emission control factor α is appropriately decreased to reduce the raw NOx and relieve the emission pressure. The tailpipe NH3 correction is mainly used when it is detected that NH3 begins to appear in the tailpipe, and the NOx emission control factor α is appropriately increased to increase the engine raw NOx to consume the NH3 in the SCR that exceeds the NH3 storage capacity as soon as possible and reduce the NH3 emission.

[0089] The calculation method of the correction coefficient for the engine operating condition stability is as follows: According to the engine speed and torque, the moving average window method is used for both of them to calculate the maximum deviation between any point data within the time window and its average value. The recommended stability determination time window is 20s. If the time window is too small, the determined stability result fluctuates greatly, and finally it is transmitted to the engine mode control with large fluctuations, affecting the control quality; if the time window is too large, the determination of the engine operating condition stability is too slow, and the control real-time performance is not good. The maximum deviation of the engine speed is denoted as Δspd, and the maximum deviation of the engine torque is denoted as Δtorq. The speed stability correction coefficient β1 and the torque stability correction coefficient β2 are obtained by one-dimensional look-up tables for Δspd and Δtorq respectively. The recommended value range of both correction coefficients is -0.3 - 0.3. β1 is negatively correlated with Δspd, and β2 is negatively correlated with Δtorq.

[0090] The calculation method of the correction coefficient for the SCR inlet temperature is as follows: The EECU obtains the SCR inlet temperature T6 through the SCR inlet temperature sensor or calculates it based on the standard heat transfer principle. The SCR inlet temperature correction coefficient β3 is obtained by looking up the table according to the SCR inlet temperature. The recommended value range is -0.3 to 0, and its relationship with the SCR inlet temperature T6 can be referred to the following table:

[0091] T6 / ℃ 180 240 380 450 β3 -0.3 0 0 -0.3

[0092] Generally speaking, the SCR can reach the most efficient state in the temperature range of 240 - 350 °C for the inlet exhaust gas temperature. If the temperature is too low or too high, the conversion efficiency will gradually decrease. Generally, when the temperature is below 180 °C, the urea injection will stop. At this time, the SCR conversion efficiency is extremely low and the risk of urea crystallization is high. Therefore, after the SCR inlet temperature is lower than 240 °C, the NOx emission control factor is gradually reduced, and when it is lower than 180 °C, the correction coefficient β3 is uniformly taken as -0.3. The situation is similar when the temperature exceeds 350 °C. However, considering that the ammonia storage capacity of the SCR also drops sharply when the temperature surges and NH3 leakage is likely to occur at this time, it is necessary to preferentially consume the excess NH3 in the SCR. Therefore, the corresponding temperature for starting to lower the NOx emission control factor is appropriately increased to 380 °C. When the temperature exceeds 450 °C, the correction coefficient β3 is uniformly taken as -0.3.

[0093] The calculation method of the correction coefficient for the tailpipe NH3 is as follows: When the reading of the post-NOx sensor is valid, the EECU calculates the tailpipe NH3 concentration value C_NH3 according to the cross-sensitivity of the post-NOx sensor. The tailpipe NH3 correction coefficient β4 is obtained by looking up the table according to this concentration value. The recommended value range is 0 - 0.3, and its relationship with the tailpipe NH3 concentration can be referred to the following table:

[0094] C_NH3 / ppm 0 10 20 30 β4 0 0 0.1 0.3

[0095] Due to considering the accuracy problem of the tailpipe NH3 calculated by cross-sensitivity, the part less than 10 ppm is considered as calculation error, and at this time, the NOx emission control factor is not corrected. When the tailpipe NH3 is greater than 10 ppm, the tailpipe NH3 correction coefficient β4 is gradually increased, and the part exceeding 30 ppm is uniformly taken as 0.3.

[0096] Engine NOx emission control factor correction: After adding the NOx emission control factor and the four correction coefficients and limiting it to the range of 0 - 1, the corrected NOx emission control factor α ′ is obtained. The specific calculation formula is:

[0097] α′ = min(max(α + β1 + β2 + β3 + β4, 0), 1)

[0098] 5. Engine NOx raw emission control

[0099] The value range of the corrected NOx emission control factor is 0 to 1. Through the magnitude of this control factor, the high or low level of NOx emission that the engine needs to control is characterized. 0 represents the low-emission mode of the engine, and 1 represents the high-emission economic mode. The engine can operate between the two modes according to the magnitude of the emission control factor, thereby adjusting the engine operating parameters in real time.

[0100] Specific implementation examples are as follows. The NOx raw-to-exhaust ratio in the low-emission mode of the engine can be achieved at 4 - 5 g / kWh through good calibration in the WHTC cycle, while the economic mode can be calibrated at 10 - 11 g / kWh. The differences in engine operating parameters between the two modes mainly include the following or their combined applications: the former has a larger EGR rate, higher rail pressure, and larger injection timing compared to the latter. In the medium and small load regions, the opening of the intake throttle valve or exhaust throttle valve is appropriately reduced. For example, if at the current moment α ′ = 0, the engine operates in the low-emission mode, and at the next moment α ′ = 0.1, the changes in engine operating parameters are as follows: the EGR rate decreases, the rail pressure decreases, the injection timing decreases, and if operating in the medium and small load regions, the intake throttle valve or exhaust throttle valve increases moderately.

[0101] Controlling the engine operating parameters according to the corrected NOx emission control factor α ′ can achieve the on-demand reduction of the engine's NOx emissions and reduce the risk of NOx emission exceeding the standard. For regions with better NOx tailpipe emission control, the goal of optimizing the engine economy as much as possible while ensuring that the emissions do not exceed the standard is achieved, which helps to save energy, reduce emissions, and improve customer satisfaction.

[0102] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. The content not detailedly described in this specification belongs to the prior art well-known to those skilled in the art.

Claims

1. An engine NO X emission monitoring system, characterized in that: including a NOx raw emission monitoring module for calculating the moving average NOx raw emission ratio of the engine; a NOx tail emission monitoring module for calculating the moving average NOx tail emission ratio of the engine; a NOx emission control factor calculation module for calculating the NOx emission control factor based on the moving average NOx raw emission ratio and the moving average NOx tail emission ratio of the engine; a NOx emission control factor correction module for correcting the NOx emission control factor to obtain the corrected NOx emission control factor a NOx raw emission control module for adjusting the engine operating parameters according to the corrected NOx emission control factor; The moving average NOx raw emission ratio of the engine is calculated by the following formula: Among them, bs_nox1 is the original specific NOx emission of the engine's moving average; n is the size of the time window; i is the i-th time point in the time window; nox1 i represents the original NOx concentration of the engine at the i-th time point; m_exh i is the exhaust gas flow rate of the engine at the i-th time point; eng_spd i is the engine speed at the i-th time point; eng_torq i is the effective output torque of the engine at the i-th time point; The moving average NOx tail emission ratio of the engine is calculated by the following formula: Among them, bs_nox2 is the engine moving average NOx tailpipe emission ratio; nox2 i represents the engine tailpipe NOx concentration at the i-th time point.

2. The engine NO according to claim 1 X emission monitoring system, characterized in that The NOx emission control factor is calculated by the following formula: α = k * α1+(1 - k) * α2, where α is the NOx emission control factor; k is the weight coefficient; α1 is the NOx raw emission ratio control factor; α2 is the NOx tail emission ratio control factor.

3. The engine NO according to claim 1 X emission monitoring system, characterized in that The corrected NOx emission control factor is determined by the following formula: α′ = min(max(α + β1 + β2 + β3 + β4, 0), 1) Among them, α ′ is the corrected NOx emission control factor; α is the NOx emission control factor; β1 is the rotational speed stability correction coefficient; β2 is the torque stability correction coefficient; β3 is the SCR inlet temperature correction coefficient; β4 is the tailpipe NH3 correction coefficient.

4. An engine NO X emission monitoring method, characterized in that: including the following steps: Calculating the moving average NOx raw emission ratio of the engine; Calculating the moving average NOx tail emission ratio of the engine; Calculating the NOx emission control factor based on the moving average NOx raw emission ratio and the moving average NOx tail emission ratio of the engine; Correcting the NOx emission control factor to obtain the corrected NOx emission control factor; Adjusting the engine operating parameters based on the corrected NOx emission control factor; The moving average NOx raw emission ratio of the engine is calculated by the following formula: Among them, bs_nox1 is the original specific NOx emission of the engine's moving average; n is the size of the time window; i is the i-th time point in the time window; nox1 i represents the original NOx concentration of the engine at the i-th time point; m_exh i is the exhaust gas flow rate of the engine at the i-th time point; eng_spd i is the engine speed at the i-th time point; eng_torq i is the effective output torque of the engine at the i-th time point; The moving average NOx tail emission ratio of the engine is calculated by the following formula: Among them, bs_nox2 is the moving average NOx tailpipe emission ratio of the engine; nox2 i represents the engine tailpipe NOx concentration at the i-th time point.

5. The engine NO according to claim 4 X emission monitoring method, characterized in that The NOx emission control factor is calculated by the following formula: α = k * α1+(1 - k) * α2, where α is the NOx emission control factor; k is the weight coefficient; α1 is the NOx raw emission ratio control factor; α2 is the NOx tail emission ratio control factor.

6. The engine NO according to claim 4 X emission monitoring method, characterized in that The corrected NOx emission control factor is determined by the following formula: α′ = min(max(α + β1 + β2 + β3 + β4, 0), 1) Among them, α ′ is the corrected NOx emission control factor; α is the NOx emission control factor; β1 is the rotational speed stability correction coefficient; β2 is the torque stability correction coefficient; β3 is the SCR inlet temperature correction coefficient; β4 is the tailpipe NH3 correction coefficient.

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