Method for controlling exhaust gas recirculation of engine, control device and working machine

Abstract

The present invention relates to a method for controlling exhaust gas recirculation of an engine, comprising: a detection step in which an oxygen concentration value is detected with a sensor; a comparison step in which the measured oxygen concentration value is compared with a first threshold value; a display step in which information indicating a comparison result of the comparison step is displayed on an operation interface, and under the condition that it is determined that the oxygen concentration value is lower than a first threshold value in the comparison step, the displayed information comprises a prompt about low environment oxygen concentration and a prompt that an operator needs to confirm or deny; a switching step of switching the engine from the normal operation mode to the exhaust gas recirculation correction mode when input information indicating that the operator has confirmed is received; and a correction step in which the flow rate of the exhaust gas recirculation gas is adjusted to ensure the flow rate of oxygen into the engine. The invention further relates to a control device for executing the method and a working machine comprising the control device.

Description

Technical Field

[0001] This invention relates to the field of engine exhaust aftertreatment technology. Specifically, this invention relates to a method for controlling exhaust gas recirculation (EGR) of an engine, such as a diesel engine, in special application conditions such as tunnels, and also to a control device for implementing this method and a working machine including the control device. Background Technology

[0002] With the development of the engineering construction market, construction methods are becoming more and more advanced, tending to use more mechanical equipment to replace inefficient operations such as manual labor.

[0003] Construction machinery such as excavators has engines (e.g., internal combustion engines that burn gasoline, diesel, or biofuels) that output various substances. In some cases, it may be necessary to treat one or more of these substances. This treatment can help meet current and future emissions regulations. The most common substances include hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). x The exhaust system contains particulate matter, such as carbon (C) and soot. While some of these substances can be reduced by carefully controlling engine operating conditions, it is often necessary to provide downstream equipment, such as an emissions cleaning module, to treat at least some of these substances carried in the exhaust fluid.

[0004] Various devices for reducing and / or eliminating substances in exhaust fluids are known. For example, oxidation devices, such as diesel engine oxidation catalysts (DOCs), are known to reduce or eliminate hydrocarbons (HC) and / or carbon monoxide (CO). Specifically, a DOC may have a circular cross-section to eliminate uneven thermal gradients. Exhaust gases from the engine undergo a chemical reaction upon passing through the DOC, oxidizing carbon monoxide (CO), hydrocarbons (HC), and the soluble organic fraction (SOF) of particulate matter to convert those substances into carbon dioxide and water. Additionally, emission cleaning modules may include particulate filters, such as diesel particulate filters (DPFs), to limit the release of particles present in the exhaust into the atmosphere.

[0005] By using an emissions cleaning module, engine emissions can be purified, which means that some of the harmful substances that would otherwise be released into the atmosphere are converted into carbon dioxide (CO2), nitrogen (N2), and water (H2O).

[0006] For diesel engines meeting either the China VI emission standard for road use or the China IV emission standard for non-road use, the government has issued relevant regulations that include on-board testing. This includes using a portable emissions testing system (PEMS) to test mechanical exhaust emissions. The system requires compliance with emission regulations within an ambient temperature range of 10–38°C and an altitude range of 1700m or below.

[0007] With the development of engineering construction, many projects require excavators to work inside tunnels or narrow, enclosed spaces. Due to the low oxygen concentration inside tunnels, engines may be unable to detect the environment, leading to poor combustion and emissions, creating non-compliance risks, and also harming the health of personnel inside the tunnel.

[0008] To address the aforementioned problems, the present invention aims to provide a method and control device capable of confirming tunnel conditions and adjusting and correcting engine EGR after confirmation. Summary of the Invention

[0009] One object of the present invention is to provide a method for controlling exhaust gas recirculation in an engine and a control device for implementing the method, which can effectively solve at least one problem or disadvantage in the prior art.

[0010] According to one aspect of the present invention, a method for controlling exhaust gas recirculation in an engine is provided, the method comprising the following steps:

[0011] The detection step involves using a sensor to detect the oxygen concentration value.

[0012] The comparison step involves comparing the measured oxygen concentration value with a first threshold.

[0013] The display step involves displaying information indicating the comparison result of the comparison step on the operation interface. In the case where the oxygen concentration value is determined to be lower than the first threshold in the comparison step, the displayed information includes a prompt about the low ambient oxygen concentration and a prompt requiring the operator to confirm or deny the comparison.

[0014] The switching step involves, upon receiving input indicating that the operator has confirmed the switch, switching the engine from normal operating mode to exhaust gas recirculation correction mode; and

[0015] The correction step involves adjusting the exhaust gas recirculation flow rate to ensure sufficient oxygen flow into the engine.

[0016] Optionally, the method further includes a determination step, wherein, upon receiving input information that has been confirmed by an operator, a reasonableness determination is performed in the determination step to verify whether the input information is reasonable.

[0017] Optionally, the sensor includes a nitrogen-oxygen sensor disposed in the exhaust system and / or an oxygen sensor disposed in the intake system, wherein the oxygen sensor is located downstream of the intake air filter.

[0018] Optionally, the rationality determination includes: comparing the deviation between the oxygen concentration values ​​detected by the nitrogen-oxygen sensor and the oxygen sensor respectively with a second threshold; and performing verification based on the comparison result.

[0019] Optionally, the reasonableness determination includes: within a first time period, using the sensor to detect the oxygen concentration value in the exhaust gas and comparing it with a normal environment exhaust gas oxygen concentration model, or with an exhaust gas oxygen concentration value predicted based on a combustion model, to obtain the exhaust gas oxygen concentration value deviation within the first time period; and comparing the exhaust gas oxygen concentration value deviation with a third threshold.

[0020] Optionally, the reasonableness determination includes: obtaining the carbon load value of the particulate filter in the exhaust aftertreatment device for the engine, and monitoring whether the carbon load value reaches a fourth threshold; and if the carbon load value reaches the fourth threshold, obtaining the growth rate of the carbon load value and comparing the growth rate with a fifth threshold.

[0021] Optionally, the rationality determination includes: detecting the nitrogen oxide concentration value in the exhaust gas during the second time period, comparing the nitrogen oxide concentration value with the nitrogen oxide concentration model of the normal environment to obtain the nitrogen oxide content deviation during the second time period; and comparing the nitrogen oxide content deviation with a sixth threshold.

[0022] Optionally, the rationality determination includes: obtaining an initial oxygen concentration value using an oxygen sensor (4) at the start of engine operation, and obtaining a current oxygen concentration value using an oxygen sensor (4) after the engine has been operating for a third time period, thereby obtaining the difference between the initial oxygen concentration value and the current oxygen concentration value; and comparing the difference with a seventh threshold.

[0023] Optionally, the rationality determination includes: detecting oxygen concentration values ​​under high-load and low-load conditions respectively, to obtain the change value and rate of change of oxygen concentration values ​​within at least one time period.

[0024] Optionally, the change values ​​and rates of change of oxygen concentration over multiple time periods can be obtained separately.

[0025] Optionally, the method further includes a preset eighth threshold, which is used to specify one or more of the judgment items to determine whether the input information is reasonable. The input information is deemed reasonable if all of the verification results of the one or more items are true. Reasonable input information can indicate that it conforms to tunnel working conditions.

[0026] Optionally, the correction step further includes: determining the fresh air intake flow rate and the exhaust gas flow rate in the current operating condition based on the oxygen concentration in the normal environment, the fresh air intake flow rate in the normal environment, the oxygen concentration of the exhaust gas recirculated by the engine in the normal environment, the exhaust gas flow rate in the engine in the normal environment, the oxygen concentration in the current operating condition, and the oxygen concentration of the exhaust gas recirculated by the engine in the current operating condition, wherein the exhaust gas flow rate in the current operating condition is adjusted by an exhaust gas recirculation valve.

[0027] Optionally, if the exhaust gas recirculation flow rate of the determined engine is less than 0 in the current operating environment, a safety warning for low oxygen concentration is issued to the operator of the working machinery.

[0028] Optionally, the correction step further includes: limiting engine power by reducing fuel quantity, wherein the expected upper limit of fuel quantity is determined based on the oxygen concentration in the current operating environment and the oxygen concentration in the normal environment, as well as the original upper limit of fuel quantity.

[0029] Optionally, the correction step further includes: predicting the remaining operating time of the engine based on changes in engine exhaust flow rate and ambient oxygen concentration over a period of time.

[0030] According to another aspect of the present invention, a control device for controlling exhaust gas recirculation of an engine is also provided, characterized in that the control device comprises:

[0031] The detection module includes a sensor and is used to detect oxygen concentration values;

[0032] A comparison module is used to compare the measured oxygen concentration value with a first threshold.

[0033] The display module is used to display information indicating the comparison result of the comparison module on the operation interface. When the comparison module has determined that the oxygen concentration value is lower than the first threshold, the displayed information includes a prompt about the low ambient oxygen concentration and a prompt that the operator needs to confirm or deny.

[0034] A switching module, configured to switch the engine from normal operating mode to exhaust gas recirculation correction mode upon receiving input information indicating confirmation from the operator; and

[0035] The correction module is used to adjust the gas flow rate of exhaust gas recirculation to ensure the oxygen flow rate entering the engine.

[0036] Optionally, the control module further includes a determination module, which is used to perform a reasonableness determination upon receiving input information that has been confirmed by the operator, in order to verify whether the input information is reasonable.

[0037] Optionally, the sensor includes a nitrogen-oxygen sensor disposed in the exhaust system and / or an oxygen sensor disposed in the intake system, wherein the oxygen sensor is located downstream of the intake air filter.

[0038] Optionally, the control device is further configured to perform the aforementioned method for controlling the exhaust gas recirculation of the engine.

[0039] The present invention also provides a working machine, the working machine including an engine, an intake system for providing fresh air to the engine, and an exhaust system having an exhaust aftertreatment device and an exhaust recirculation device. The working machine also includes the aforementioned control device for controlling the exhaust recirculation of the engine. The control device is capable of switching the engine from a normal operating mode to an exhaust recirculation correction mode, and adjusting the gas flow rate of exhaust recirculation to ensure the oxygen flow rate entering the engine.

[0040] This invention proposes an EGR control method and control device including an EGR correction mode. In this mode, corresponding EGR correction measures can be adopted to ensure that even in specific operating conditions such as tunnels or pits, the intake oxygen mass flow rate is basically equal to that in normal environments (such as well-ventilated areas), thereby ensuring engine power, economy, emission compliance and personnel safety. Attached Figure Description

[0041] The invention will now be described in detail with reference to the accompanying drawings and non-limiting embodiments, in which:

[0042] Figure 1 The arrangement of an engine system of a working machine according to an embodiment of the present invention is schematically shown, including an engine, an intake system and an exhaust system having an exhaust gas recirculation (EGR) device, wherein an oxygen sensor is provided in the intake system;

[0043] Figure 2 A flowchart illustrating a method for controlling engine EGR according to an embodiment of the present invention is shown schematically. Detailed Implementation

[0044] The following description, with reference to the accompanying drawings, illustrates a method for controlling exhaust gas recirculation in equipment operating under special conditions such as tunnels / tunnels, and a control apparatus for implementing the method. In the following description, numerous specific details are set forth to enable those skilled in the art to gain a more complete understanding of the invention. However, it will be apparent to those skilled in the art that implementations of the invention may not include some of these specific details. Furthermore, it should be understood that the invention is not limited to the specific embodiments described. Rather, the invention can be conceived to be implemented with any combination of the following features and elements, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments, and advantages are illustrative only and should not be considered as elements or limitations of the claims unless expressly set forth in the claims.

[0045] Figure 1 The arrangement of the engine system of a working machine according to an embodiment of the present invention is schematically shown. Figure 1 In the illustrated embodiment, the working machinery includes an engine 1, an intake system for supplying fresh air to the engine 1, and an exhaust system with an exhaust gas recirculation device (hereinafter referred to as "EGR device"). The EGR device may include an exhaust gas recirculation valve (hereinafter referred to as "EGR valve") 2, the exhaust gas flow rate through the EGR device can be adjusted by adjusting the opening degree of the exhaust gas recirculation valve 2. In addition, a nitrogen oxide sensor 3 may be installed in the exhaust duct of the exhaust system, which can be used to measure the oxygen concentration in the exhaust gas.

[0046] In addition, an oxygen sensor 4 can be installed, for example, downstream of the intake air filter in the intake system. This oxygen sensor 4 can be used to measure the oxygen concentration in the intake air. The intake system can have a pre-installed connector for the oxygen sensor, allowing it to be installed at any time.

[0047] Without oxygen sensor 4 installed, the engine electronic control module (hereinafter referred to as "engine ECM") detects the absence of the sensor and configures it to "without intake oxygen sensor" mode. In this state, the engine can operate in normal mode. Users can optionally install oxygen sensor 4 before operating in tunnel environments. With an oxygen sensor installed in the intake system, the engine ECM can detect the installation status of oxygen sensor 4 and configure it to "with intake oxygen sensor" mode, and can read the oxygen concentration value.

[0048] When the oxygen concentration measured by nitrogen-oxygen sensor 3 or oxygen sensor 4 is lower than the first threshold Threshold1, which is, for example, 20% (volume percentage; in the following text, unless otherwise explicitly stated, all concentrations or contents referred to are volume ratios), the tunnel working mode is triggered. In this mode, the operating interface can prompt "Oxygen concentration in the working environment is low" and the driver can confirm it a second time, for example by displaying a question on the operating interface: "Are we currently in a tunnel?".

[0049] If the driver confirms (e.g., clicks "Yes" on the interface), the engine can enter EGR correction mode. Simultaneously, to prevent tampering and / or false alarms, a determination is made as to whether the vehicle is inside a tunnel.

[0050] If the driver denies the error (e.g., clicks "No" on the interface), the sensor is deemed to be malfunctioning and an alarm is triggered because the driver determines they are not in a tunnel, but the measured value is too low. In this case, the engine continues to operate in normal mode.

[0051] The following is for reference Figure 2 The method for determining reasonableness should be explained in detail. It should be noted that... Figure 2 This example only illustrates a variety of possible (not exhaustive) determination methods. It is conceivable that only one or a few (not all) of these determination methods could be used; furthermore, it can be done according to... Figure 2 Other orders that differ from the one shown will be judged.

[0052] (1) With oxygen sensor 4 installed, power on the engine but do not start it, so that nitrogen-oxygen sensor 3 in the exhaust system and oxygen sensor 4 in the intake system can work. Read the oxygen concentration values ​​measured by nitrogen-oxygen sensor 3 and oxygen sensor 4 respectively and calculate the deviation between the two to verify the rationality of the driver's input information. If the deviation is less than the second threshold Threshold2 (e.g., Threshold2 = 0.5%), it is determined that the driver is truly in tunnel conditions or meets tunnel conditions, thus confirming that the driver's input information is reasonable.

[0053] (2) If it is actually in a tunnel, the oxygen concentration will be lower and the combustion in the engine cylinder will be worse, and the exhaust oxygen concentration will also be lower.

[0054] Based on this principle, the oxygen concentration in the exhaust gas can be detected by the nitrogen-oxygen sensor 3 over a period of time. The actual measured oxygen concentration is then compared with an exhaust oxygen concentration model measured under normal conditions, or with an exhaust oxygen concentration predicted based on a combustion model (such as an existing combustion model). This comparison yields the deviation between the actual oxygen concentration and the model value or the predicted value, thereby verifying the rationality of the driver's input information. For example, if the deviation exceeds a third threshold (Threshold3) within a predetermined time period, it is determined that the vehicle is indeed in a tunnel, thus confirming the rationality of the driver's input information.

[0055] In one embodiment, Threshold3 is set as a map, where the X-axis represents rotational speed and the Y-axis represents load. A table can be used to output the Z-value (percentage), which is the deviation threshold. For example, a maximum deviation of 3% is set at idle speed. If this deviation remains above 3% at idle speed for a period of time, it is determined that the vehicle is inside a tunnel.

[0056] (3) In the absence of a NOx sensor in the engine system of the operating machinery, since the exhaust aftertreatment program of the existing engine system that meets the China IV emission standard will definitely measure the carbon load of the particulate filter (e.g., diesel particulate filter DPF), the carbon load measured by the carbon particulate sensor (not shown) can be monitored to verify the rationality of the driver's input information. In one embodiment, if the carbon load reaches the carbon load threshold, i.e., the fourth threshold Threshold4 (e.g., Threshold4 = 50%), and the rate of increase thereafter is greater than the rate of increase threshold, i.e., the fifth threshold Threshold5 (e.g., Threshold5 = 50 g / h), then it is determined that the machine is indeed in tunnel conditions, thereby confirming that the driver's input information is reasonable.

[0057] (4) Since the main reason for the deterioration of combustion in the tunnel is the lack of oxygen, while the conditions for NOx generation are high temperature and rich oxygen, the NOx content will be very low under tunnel conditions.

[0058] Based on this principle, the NOx concentration in the exhaust can be detected by the nitrogen oxide sensor 3 over a period of time. The actual measured NOx concentration is then compared with the NOx concentration model measured under normal conditions to obtain the deviation between the actual NOx concentration and the model value. The rationality of the driver's input information is verified by judging whether the deviation is abnormally high during this period (e.g., continuously higher than the sixth threshold Threshold6 during this period).

[0059] In one embodiment, Threshold6 is set as a map, where the X-axis represents rotational speed and the Y-axis represents load. A table can be used to output the Z-value (percentage), which is the deviation threshold. For example, a maximum deviation of 20% is set at idle speed. If the deviation at idle speed remains higher than the Threshold6 value for a predetermined period of time, it is determined that the vehicle is indeed in a tunnel, thus confirming that the driver's input information is reasonable.

[0060] (5) Due to poor ventilation in the tunnel, the oxygen concentration in the environment will decrease after the engine has been running for a long time.

[0061] Based on this principle, the readings of the oxygen sensor 4 in the intake system can be detected before and after a relatively long working time (e.g., 1 hour, 1.5 hours, or 2 hours, etc.) to obtain the initial oxygen concentration value and the current oxygen concentration value, respectively, so as to obtain the decrease value of the oxygen concentration value, and verify the rationality of the driver's input information by comparing the decrease rate with a threshold (e.g., the seventh threshold Threshold7).

[0062] In one embodiment, the working period is set to 2 hours, and Threshold7 = 1% per hour (1% / h). Under normal circumstances, the oxygen content in the air is approximately 21%. After the machinery has been operating continuously for 2 hours, the following conditions are assumed: average load factor > 20% during the working period, and average exhaust flow rate of 500 cubic meters per hour (m³ / h). 3 The average exhaust oxygen concentration is 8%; the fresh air supply volume (i.e., the air supply volume inside the tunnel) is 500 m³ / h. 3 / h, the oxygen concentration of fresh air is 21%; the tunnel is a two-way four-lane tunnel with a standard semi-circular cross-section, the length of the working space is approximately 23 meters (m), the width is 15 meters, and the cross-sectional area is 88m². 2 Two hours later, the oxygen concentration in the ambient air was 14.5%. The calculated oxygen descent rate is (21% - 14.5%) / 2h = 3.25% / h, which is greater than Threshold7. Therefore, it can be determined that the operating machinery is inside the tunnel, confirming the validity of the driver's input information.

[0063] (6) If the ventilation is poor when the machine starts working, or if multiple machines are working at the same time, and the ventilation is improved or other machines are turned off in the later stage of the work, the oxygen concentration will rise; while if it is in a well-ventilated outdoor environment, the oxygen concentration in the intake air is hardly affected by the exhaust.

[0064] Based on this principle, the changes and rate of change of the oxygen concentration value of the oxygen sensor 4 in the intake system can be monitored under both low-load conditions (e.g., the lowest gear) with very low exhaust flow and high-load conditions (e.g., the highest gear) with very high exhaust flow. Furthermore, judgments are made over multiple time periods to repeatedly detect the decrease in oxygen and its rate of decrease, thereby preventing interference from special environmental conditions.

[0065] In one embodiment, under full load condition at 7th gear, the exhaust flow rate is 1200m³ / h. 3 / h, the oxygen concentration (volume percentage) in the exhaust is 7%; the exhaust flow rate at idle is 300m³ / h. 3 / h, oxygen volume concentration in exhaust gas is 4%; assuming the machinery operates within a 20-meter-long space inside the tunnel, the tunnel has a standard semi-circular cross-section with a cross-sectional area of ​​88m². 2 The original oxygen concentration in the space was 21%. Ignoring the changes in oxygen concentration caused by fresh air supply and engine intake, and only considering the change in oxygen concentration caused by exhaust gas displacing the original air, the oxygen concentration in the gas mixture after the machinery operates at speed 7 for 1 hour is:

[0066] [1200m 3 ×7%+((88m) 2 ×20m)-1200m 3 )×21%)] / (88m 2 (×20m)=11%, that is, the rate of descent is (11%-21%) / 1h=-10% / h.

[0067] After the operating machinery has been idling for 1 hour, the oxygen concentration in the gas mixture is:

[0068] [300m 3 ×4%+((88m) 2 ×20m)-300m 3 )×21%)] / (88m 2 (×20m)=18%, that is, the descent rate is -3% / h.

[0069] Suppose that exactly at a certain moment, the ventilation equipment in the tunnel is turned on, or the engine of other working machinery is turned off, resulting in a slowdown in the downward trend of the ambient oxygen concentration, or even a turn to an increase, with an increase rate of +2% / h. However, under the working conditions of gear 7 and gear 1, the oxygen concentration decrease rate of the mixed gas still remains the same as the oxygen change rate at gear 7. Therefore, considering both the increase rate and the decrease rate, the oxygen change rate under the working conditions of gear 7 and gear 1 is -8% / h, while the comprehensive oxygen change rate at idle speed is -1% / h. Then, the oxygen decrease rate under the working conditions of gear 7 and gear 1 is faster than the oxygen decrease rate at idle speed, so it can be preliminarily determined that the engine is actually in the tunnel. In addition, the judgment can be carried out periodically, for example, once every hour. Since the probability of ventilation improvement or other engine shutdown occurring within each hour in the tunnel is very low, if the oxygen concentration decrease is detected several times continuously (for example, 3 times), or the decrease rate in gear 7 is faster than the decrease rate at idle speed, it is determined that the engine of the working machinery is actually in the tunnel. Thus, it is confirmed that the driver's input information is reasonable.

[0070] When programming, judgment flag bits can be set for the aforementioned six rationality judgments, such as bit0 to bit5. Some judgment items or all judgment items can be enabled according to actual needs for comprehensive judgment, that is, to determine whether one or more predetermined conditions are met. For example, the flag bits can be combined into a binary number MergeNum, and an "AND (&&)" operation is performed with the eighth threshold Threshold8, that is: MergeNum must satisfy all the status bits that are 1 after Threshold8 is converted into binary, and these status bits are enabled as the judgment conditions for the tunnel working conditions. [[ID=*]]

[0071] In one embodiment, the binary MergeNum = 0011 1011 (i.e., the decimal number 59), where only bit3 fails the judgment among bit0 to bit5 and is set to 0, and the other bits (bit0, bit1, bit2, bit4, bit5) pass the judgment and are set to 1. The calibration value, that is, the eighth threshold Threshold8 = 0010 1011 (i.e., the decimal number 43). The operation MergeNum && Threshold8 = 0010 1011, which meets the condition of = Threshold8, and it is determined to conform to the tunnel working condition characteristics.

[0072] In another example, the binary MergeNum = 0011 1010, Threshold8 = 0010 1011, and the result obtained after the combined operation is 0010 1010 < Threshold8, so it is determined that it does not conform to the tunnel working condition characteristics.

[0073] If the rationality assessment result is "the driver's input information is confirmed to be reasonable" (i.e., it conforms to the characteristics of tunnel operating conditions), after the engine enters the EGR correction mode, the control objective is to ensure the quality of oxygen entering the engine for combustion. The value of this oxygen quality can be obtained through the following equation:

[0074] C = M1 × O1 + M2 × O2 = M1' × O1' + M2' × O2', (a) where:

[0075] O1 is the oxygen concentration in a normal environment (for example, at standard atmospheric pressure, the oxygen concentration in the air is 21% by volume and 23.3% by mass).

[0076] M1 is the fresh air intake flow rate in a normal environment (e.g., 600 kg / h);

[0077] O2 is the oxygen concentration of the EGR gas in the engine under normal conditions (e.g., 8% by mass).

[0078] M2 is the EGR gas flow rate of the engine under normal conditions (120 kg / h);

[0079] O1' is the oxygen concentration in the current working environment (e.g., tunnel environment) (e.g., the legally mandated lower limit oxygen concentration is 19.5% by volume and 21.7% by mass).

[0080] M1' is the fresh air intake flow rate in the current working environment (e.g., tunnel environment);

[0081] O2' is the oxygen concentration (e.g., 3% by mass) of the EGR gas in the engine under current operating conditions (e.g., tunnel environment);

[0082] M2' is the EGR gas flow rate of the engine in the current operating environment (e.g., tunnel environment);

[0083] Assuming the engine's charging efficiency is constant, that is, the total amount of air (the sum of fresh air and EGR gas) drawn in by the piston is constant, it conforms to the following equation (b):

[0084] M1 + M2 = M1' + M2', (b)

[0085] Given the numerical conditions set above, and combining equations (a) and (b), we can obtain:

[0086] 600×23.3%+120×8%=((600+120)-M2')×21.7%+M2'×3%, then M2'=36.6kg / h.

[0087] Thus, the required tunnel environment EGR gas flow rate (M2') is obtained. Based on this tunnel environment EGR gas flow rate (M2'), the EGR valve opening is adjusted, and the EGR rate (the proportion of gas participating in exhaust gas recirculation in the exhaust) is adjusted accordingly to match the required tunnel environment fresh air flow rate (M1'), thereby ensuring that the intake oxygen mass flow rate is basically equal to that in the normal environment.

[0088] In one embodiment, the original EGR rate can be calculated as: 120kg / h / (600kg / h+120kg / h) = 16.6%, and the new EGR rate after entering the tunnel is: 36.6(kg / h) / 720(kg / h) = 5.1%, indicating that the EGR valve still has adjustment margin for the worst environmental conditions (lower limit conditions) that meet regulatory requirements.

[0089] In specific situations, such as when the oxygen concentration in a tunnel is very low, the EGR gas flow rate of the engine in the current operating environment must be less than 0. This means that even if the EGR valve is completely closed, the intake oxygen mass flow rate cannot be basically equal to that in the normal environment. In this case, the engine ECM can issue a safety warning to the driver and reduce the engine power to reduce the intake flow rate, thereby ensuring good engine combustion and personnel safety.

[0090] For example, engine power can be limited by reducing the amount of fuel, where the upper limit of fuel quantity is calculated using the following equation (c):

[0091] Fuel' = k × O2' / O2 × Fuel, (c) where: k is the correlation coefficient, which is affected by speed and altitude. Generally, under high load and high altitude conditions, the air-fuel ratio (the ratio of air mass to fuel mass) margin is small, while under low load and plain conditions, the air-fuel ratio margin is large; Fuel' is the expected upper limit of fuel quantity; Fuel is the original upper limit of fuel quantity; O2' is the oxygen concentration in the current operating environment; O2 is the oxygen concentration in the normal environment.

[0092] In one embodiment, still based on the relevant numerical settings mentioned above, we can obtain the following from equation (a):

[0093] 600 × 23.3% + 120 × 8% = ((600 + 120) - M2') × O1' + M2' × 3%, where M2' = 0, indicating the EGR valve is completely closed. Therefore, O1' = approximately 21% (mass percentage), which translates to a volume ratio of 18.1%, lower than the legally mandated 19.5% volume ratio requirement. This indicates the current tunnel environment is unsuitable for operator work. Assuming a coefficient k of 0.9, the expected upper limit of fuel quantity relative to the original upper limit is: 0.9 × 18.1% / 21% = 77.6%, resulting in a significant decrease in power. Although the intake oxygen concentration remains unchanged, the power reduction improves combustion efficiency and reduces exhaust pollutant emissions.

[0094] Furthermore, after the engine enters EGR correction mode, the remaining operating time of the machinery can be predicted based on the exhaust flow rate. Based on the accumulated exhaust flow rate, oxygen concentration decrease, and operating time, the remaining time before the oxygen concentration alarm limit is reached in the environment can be roughly predicted, thus reminding the driver to schedule work hours appropriately or take measures to improve ventilation.

[0095] In one embodiment, the average exhaust flow rate of the operating machinery engine over the past 2 hours is 500 m³ / h. 3 / h, the ambient oxygen concentration decreased from 21% to 20%, and then the workload was increased, with the exhaust flow rate increased to 1000m³ / h. 3 / h. Since the rate of decrease in oxygen concentration is proportional to the exhaust flow rate, in order to predict the remaining time t (i.e., the remaining operating time of the engine) for the ambient oxygen concentration to continue decreasing from 20% to 19.5% (the legal lower limit), the relevant values ​​can be substituted into the following equation (d) for calculation:

[0096] 500 m 3 / h × 2h / (1000 m 3 / h × t) = (21% - 20%) / (20% - 19.5%), (d) yields t=0.5 hours (h), that is, reminding the driver that the oxygen concentration in the environment will be unsuitable for operation after 0.5 hours. Similarly, in the case of limiting power by reducing fuel quantity, based on the minimum oxygen volume ratio limit of 18.1% that can be achieved by reducing engine power, the driver can be reminded of the remaining working time of the machine's distance torque limit according to the above equation (d). At the same time, based on the exhaust flow rate Q2 calculated by ECM and the oxygen concentration O2 in the exhaust, Exh (Measured by sensors or obtained based on calibrated model values), the minimum ventilation flow rate Q1 required to ensure the safety of operators (oxygen concentration of 19.5% by volume) can be calculated as follows: Q1 = (19.5% - O2) ExhThe formula is 21% - 19.5%, which indicates the minimum ventilation requirements to ensure operator safety.

[0097] Industrial applicability

[0098] This invention proposes a method for controlling exhaust gas recirculation in equipment operating under special conditions such as tunnels / tunnels, and a control device for implementing the method.

[0099] In existing technologies, some diesel engines install oxygen sensors on the exhaust manifold to monitor the exhaust oxygen content and correct the air-fuel ratio. However, due to the complexity of combustion, the oxygen concentration in the exhaust gas is affected by a variety of factors, making it impossible to accurately identify whether the decrease in exhaust oxygen concentration is caused by a decrease in intake oxygen concentration.

[0100] The oxygen sensor on the exhaust manifold detects a decrease in oxygen content and reduces the amount of fuel to achieve fuel-air balance, but the fundamental problem of low intake oxygen content is not solved.

[0101] If the oxygen sensor is installed in the intake manifold (after the mixing point of fresh air and EGR gas), the gas mixing will be uneven, resulting in large fluctuations in the measured value.

[0102] This invention proposes that the oxygen sensor can be installed after the intake air filter, thus enabling accurate measurement of the fresh intake air oxygen concentration without interference from EGR gas.

[0103] Furthermore, since the oxygen sensor is installed after the intake air filter, it facilitates a reasonableness assessment because there is no residual gas interference when the machine is stopped, and it can detect changes in the ambient oxygen concentration during operation. This reasonableness assessment allows for the determination of whether the driver's input regarding "whether we are working inside a tunnel" is true or false.

[0104] By using an oxygen sensor installed after the intake air filter, the oxygen content in the environment can be monitored to provide safety information to the driver. It can accurately identify changes in oxygen concentration in the tunnel, and when certain conditions are met, appropriate EGR correction measures can be adopted, such as reducing the EGR rate to match the required fresh air intake flow in the tunnel environment, ensuring that the oxygen mass flow rate in the engine intake in the tunnel is basically equal to that in the normal environment, thereby ensuring engine power, economy, emission compliance, and personnel safety.

[0105] Oxygen sensors can be offered as an optional package, only when the machinery needs to enter special operating environments, thus enabling differentiated cost reduction and meeting specific user needs.

[0106] Those skilled in the art will understand that the embodiments described above are exemplary and can be improved upon. The structures described in the various embodiments can be freely combined without causing any conflict in structure or principle.

[0107] After a detailed description of the preferred embodiments of the present invention, those skilled in the art will clearly understand that various changes and modifications can be made without departing from the scope and spirit of the appended claims, and that the present invention is not limited to the embodiments described in the specification.

Claims

1. A method for controlling exhaust gas recirculation in an engine, characterized in that, The method includes the following steps: The detection step involves using a sensor to detect the oxygen concentration value. The comparison step involves comparing the measured oxygen concentration value with a first threshold. The display step involves displaying information indicating the comparison result of the comparison step on the operation interface. In the case where the oxygen concentration value is determined to be lower than the first threshold in the comparison step, the displayed information includes a prompt about the low ambient oxygen concentration and a prompt requiring the operator to confirm or deny the comparison. The switching step involves, upon receiving input indicating that the operator has confirmed the switch, switching the engine (1) from normal operating mode to exhaust gas recirculation correction mode; and The correction step involves adjusting the exhaust gas recirculation flow rate to ensure the oxygen flow rate entering the engine (1).

2. The method for controlling exhaust gas recirculation of an engine according to claim 1, further comprising: In the determination step, if the input information has been confirmed by the operator, a reasonableness determination is performed to verify whether the input information is reasonable.

3. The method for controlling exhaust gas recirculation in an engine according to claim 2, wherein, The sensor includes: The nitrogen oxide sensor (3) installed in the exhaust system, and / or An oxygen sensor (4) is provided in the intake system, wherein the oxygen sensor (4) is located downstream of the intake air filter.

4. The method for controlling exhaust gas recirculation in an engine according to claim 3, wherein, The reasonableness determination includes at least one of the following criteria: a) Compare the deviation between the oxygen concentration values ​​detected by the nitrogen oxygen sensor (3) and the oxygen sensor (4) with the second threshold, and perform verification based on the comparison results; b) During the first time period, the oxygen concentration value in the exhaust gas is detected using the sensor and compared with the normal ambient exhaust gas oxygen concentration model, or with the exhaust gas oxygen concentration value predicted based on the combustion model, to obtain the deviation of the exhaust gas oxygen concentration value during the first time period, and The deviation of the exhaust oxygen concentration value is compared with a third threshold. c) Obtain the carbon load value of the particulate filter (DPF) in the exhaust aftertreatment device for the engine, monitor whether the carbon load value reaches a fourth threshold, and if the carbon load value reaches the fourth threshold, obtain the growth rate of the carbon load value and compare the growth rate with a fifth threshold. d) Detect the nitrogen oxide concentration value in the exhaust gas during the second time period, and compare the nitrogen oxide concentration value with the nitrogen oxide concentration model of the normal environment to obtain the nitrogen oxide content deviation during the second time period, and compare the nitrogen oxide content deviation with the sixth threshold. e) At the start of engine operation, the initial oxygen concentration value is obtained using the oxygen sensor (4), and after the engine has been running for three time periods, the current oxygen concentration value is obtained using the oxygen sensor (4). This yields the difference between the initial oxygen concentration and the current oxygen concentration, and the difference is compared with a seventh threshold. and f) Detect the oxygen concentration values ​​under high load and low load conditions respectively to obtain the change value and rate of change of oxygen concentration value within at least one time period.

5. The method for controlling exhaust gas recirculation in an engine according to claim 4, wherein, In the decision item f), obtain the changes and rates of change of oxygen concentration over multiple time periods.

6. The method for controlling exhaust gas recirculation of an engine according to claim 4 or 5, further comprising a preset eighth threshold, wherein the eighth threshold is used to specify the use of one or more of the determination items to determine whether the input information is reasonable, wherein, If all one or more of the verification results are true, the input information is deemed reasonable.

7. The method for controlling exhaust gas recirculation of an engine according to claims 2 to 5, wherein, The input information reasonably represents the tunnel working conditions.

8. The method for controlling exhaust gas recirculation of an engine according to any one of claims 1 to 5, wherein, The correction step further includes: determining the fresh air intake flow rate and the exhaust gas flow rate in the current operating condition based on the oxygen concentration in the normal environment, the fresh air intake flow rate in the normal environment, the oxygen concentration of the exhaust gas recirculated by the engine in the normal environment, the exhaust gas flow rate in the engine in the normal environment, the oxygen concentration in the current operating condition, and the oxygen concentration of the exhaust gas recirculated by the engine in the current operating condition, wherein the exhaust gas flow rate in the current operating condition is adjusted by an exhaust gas recirculation valve.

9. The method for controlling exhaust gas recirculation of an engine according to claim 8, wherein, If the exhaust gas recirculation flow rate of the engine is less than 0 under the current operating conditions, a safety warning for low oxygen concentration will be issued to the operator of the working machinery.

10. The method for controlling exhaust gas recirculation of an engine according to claim 9, wherein, The correction step further includes: limiting engine power by reducing fuel quantity, wherein the expected upper limit of fuel quantity is determined based on the oxygen concentration in the current operating environment and the oxygen concentration in the normal environment, as well as the original upper limit of fuel quantity.

11. The method for controlling exhaust gas recirculation of an engine according to any one of claims 1 to 5, wherein, The correction step also includes: predicting the remaining operating time of the engine based on changes in engine exhaust flow and ambient oxygen concentration over a period of time.

12. A control device for controlling exhaust gas recirculation in an engine, characterized in that, The control device includes: The detection module includes a sensor and is used to detect oxygen concentration values; A comparison module is used to compare the measured oxygen concentration value with a first threshold. The display module is used to display information indicating the comparison result of the comparison module on the operation interface. When the comparison module has determined that the oxygen concentration value is lower than the first threshold, the displayed information includes a prompt about the low ambient oxygen concentration and a prompt that the operator needs to confirm or deny. The switching module is configured to switch the engine (1) from normal operating mode to exhaust gas recirculation correction mode upon receiving input information indicating that the operator has confirmed the input; and The correction module is used to adjust the gas flow rate of exhaust gas recirculation to ensure the oxygen flow rate entering the engine (1).

13. The control device according to claim 12 further includes a determination module, the determination module being used to perform a reasonableness determination upon receiving input information indicating that the operator has confirmed the input information, so as to verify whether the input information is reasonable.

14. The control device according to claim 13, wherein, The sensor includes: The nitrogen oxide sensor (3) installed in the exhaust system, and / or An oxygen sensor (4) is provided in the intake system, wherein the oxygen sensor (4) is located downstream of the intake air filter.

15. The control device according to claim 14, wherein, The control device is also configured to perform the method for controlling exhaust gas recirculation of the engine as described in any one of claims 4 to 11.

16. A working machine, the working machine comprising an engine (1), an intake system for supplying fresh air to the engine, and an exhaust system having an exhaust aftertreatment device and an exhaust recirculation device, characterized in that, The working machinery further includes a control device for controlling the exhaust gas recirculation of the engine according to any one of claims 12 to 15, the control device being able to switch the engine (1) from normal operating mode to exhaust gas recirculation correction mode, and to adjust the gas flow rate of exhaust gas recirculation to ensure the oxygen flow rate entering the engine (1).

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