Method and device for measuring egr flow, and egr system

Abstract

The application discloses a kind of EGR flow measurement method, device and EGR system, EGR system includes EGR valve and orifice plate sequentially arranged on gas flow path, and orifice plate includes flow-through hole, comprising: when the aperture of flow-through hole is initial aperture, the actual throttle pressure ratio of EGR valve under different speeds of engine is not more than the each test EGR flow of preset throttle pressure ratio;According to each test EGR flow, determine the reference EGR flow;Based on the preset relationship between EGR flow and aperture, determine the preset aperture of flow-through hole according to reference EGR flow;When the aperture of flow-through hole is preset aperture, the first flow of EGR valve and the second flow of orifice plate are obtained;According to first flow and second flow, determine EGR flow, when the aperture of flow-through hole is preset aperture, the orifice plate can reduce the pressure loss generated by fluid in EGR pipeline when high flow, while it can improve the measurement accuracy of EGR flow when low flow.

Description

Technical Field

[0001] This invention relates to the technical field of exhaust gas recirculation (EGR) systems, and more particularly to a method, apparatus, and EGR system for measuring EGR flow rate. Background Technology

[0002] Exhaust gas recirculation (EGR) technology is widely used to reduce nitrogen oxide (NOx) emissions. The EGR system recirculates a portion of the exhaust gas back into the engine, lowering the combustion temperature and thus reducing NOx formation. For the EGR system to operate effectively, accurate measurement and control of the EGR flow rate are necessary.

[0003] Measuring EGR flow solely with a flow meter requires a smaller orifice diameter to meet EGR measurement needs at low flow rates. Conversely, minimizing pressure loss on the EGR fluid (exhaust gas) at high flow rates necessitates a larger orifice diameter. A balance cannot be achieved simultaneously. Summary of the Invention

[0004] This invention provides an EGR and a method and apparatus for measuring its flow rate, so as to balance the accuracy of EGR flow rate measurement at low flow rates and the requirement for low pressure loss of EGR fluid at high flow rates.

[0005] According to one aspect of the present invention, a method for measuring EGR flow rate is provided. The EGR system includes an EGR valve and an orifice plate sequentially disposed in a gas flow path, the orifice plate including a flow hole, comprising:

[0006] When the orifice diameter is the initial orifice diameter, the test EGR flow rate is obtained when the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio at different engine speeds.

[0007] Determine the baseline EGR flow rate based on the test EGR flow rates described above;

[0008] Based on the preset relationship between the EGR flow rate and the orifice diameter, the preset orifice diameter of the flow orifice is determined according to the reference EGR flow rate;

[0009] When the orifice diameter is a preset orifice diameter, the first flow rate of the EGR valve and the second flow rate of the orifice plate are obtained;

[0010] The EGR flow is determined based on the first flow and the second flow.

[0011] Optionally, when the orifice diameter is the initial orifice diameter, the test EGR flow rate is obtained when the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio at different engine speeds, including:

[0012] When the diameter of the flow hole is the initial diameter, the engine is controlled to rotate;

[0013] Obtain the actual throttling pressure ratio of the EGR valve at the current engine speed;

[0014] Determine whether the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio;

[0015] If so, obtain the test EGR flow rate of the engine at the current speed;

[0016] The engine speed is increased by a preset step size;

[0017] Determine whether the current speed of the engine exceeds the preset speed;

[0018] If so, then proceed with the step of determining the baseline EGR flow based on the test EGR flow described above;

[0019] If the current engine speed does not exceed the preset speed, then return to the step of obtaining the actual throttling pressure ratio of the EGR valve at the current engine speed.

[0020] Optionally, if the actual throttling pressure ratio of the EGR valve exceeds the preset throttling pressure ratio, the EGR valve is controlled to reduce the preset opening degree;

[0021] Obtain the actual throttling pressure ratio of the EGR valve after reducing the preset opening degree, and return to the step of determining whether the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio.

[0022] Optionally, a baseline EGR flow is determined based on the test EGR flow, including:

[0023] Among the various test EGR flows, the test EGR flow with the minimum flow value is determined as the baseline EGR flow.

[0024] Optionally, based on the preset relationship between the EGR flow rate and the orifice diameter, the preset orifice diameter of the flow-through orifice is determined according to the reference EGR flow rate, including:

[0025] When the EGR flow rate is obtained as the reference EGR flow rate, the first pressure and the first temperature at the downstream position of the EGR valve are obtained;

[0026] Based on the gas law, the first gas density at the downstream position of the EGR valve is determined according to the first pressure and the first temperature; the gas law is: ρ0=P1*M / (R*T1);

[0027] Based on the first formula, the preset aperture of the flow orifice is determined according to the reference EGR flow rate and the first gas density;

[0028] The first formula is:

[0029] Where ρ0 is the density of the first gas, P1 is the first pressure, M is the molar mass of air, R is the gas constant, T1 is the first temperature, and q m0 The reference EGR flow rate, d0 is the preset orifice diameter of the flow orifice, D0 is the EGR pipeline diameter at the downstream position of the EGR valve, C0 is the first outflow coefficient, ε0 is the first compressibility coefficient of the gas, and ΔP is the preset pressure difference.

[0030] Optionally, when the orifice diameter is a preset orifice diameter, obtaining the first flow rate of the EGR valve and the second flow rate of the orifice plate includes:

[0031] When the orifice diameter is a preset orifice diameter, the effective flow diameter of the EGR valve, the second pressure at the upstream position of the EGR valve, the third pressure between the EGR valve and the orifice plate, and the fourth pressure at the downstream position of the orifice plate are obtained.

[0032] Based on the second formula, the first flow rate of the EGR valve is determined according to the effective flow diameter, the second pressure, and the third pressure;

[0033] The second formula is: Where, q m1 C1 is the first flow rate of the EGR valve, d1 is the second outflow coefficient, D1 is the effective flow diameter of the EGR valve, D1 is the diameter of the EGR pipeline at the upstream position of the EGR valve, ε1 is the second compressibility coefficient of the gas, ρ1 is the second gas density at the upstream position of the EGR valve, P2 is the second pressure, and P3 is the third pressure.

[0034] Based on the third formula, the second flow rate of the orifice plate is determined according to the preset orifice diameter, the third pressure, and the fourth pressure;

[0035] The third formula is: q m2 C2 is the second flow rate of the orifice plate, d2 is the third discharge coefficient, d2 is the preset orifice diameter, D2 is the diameter of the EGR pipeline between the EGR valve and the orifice plate, ε2 is the third compressibility coefficient of the gas, ρ2 is the third gas density between the EGR valve and the orifice plate, and P4 is the fourth pressure.

[0036] Optionally, determining the EGR traffic based on the first traffic and the second traffic includes:

[0037] Obtain the first weight of the first traffic and the second weight of the second traffic;

[0038] The weighted average of the first flow rate and the second flow rate is determined based on the first flow rate, the second flow rate, the first weight, and the second weight.

[0039] The weighted average value is determined as the EGR flow.

[0040] According to another aspect of the present invention, an EGR flow measurement device is provided, wherein the system EGR includes an EGR valve and an orifice plate sequentially disposed in the gas flow path, the orifice plate including a flow hole, comprising:

[0041] The test EGR flow acquisition module is used to acquire the test EGR flow rate when the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio at different engine speeds, with the orifice diameter of the flow orifice being the initial orifice diameter.

[0042] A baseline EGR flow determination module is used to determine a baseline EGR flow based on the test EGR flow.

[0043] The preset orifice diameter determination module determines the preset orifice diameter of the flow orifice based on the preset relationship between the EGR flow rate and the orifice diameter, according to the reference EGR flow rate.

[0044] The flow acquisition module is used to acquire the first flow rate of the EGR valve and the second flow rate of the orifice plate when the orifice diameter of the flow hole is a preset orifice diameter;

[0045] The EGR flow determination module is used to determine the EGR flow based on the first flow and the second flow.

[0046] According to another aspect of the present invention, an EGR system is provided, comprising an EGR valve and an orifice plate sequentially disposed in a gas flow path, the orifice plate comprising a flow hole;

[0047] It also includes a controller for performing the above-described method for measuring EGR flow.

[0048] Optionally, the EGR system further includes a first pressure sensor, a second pressure sensor, a third pressure sensor, a first temperature sensor, a second temperature sensor, and a third temperature sensor;

[0049] The first pressure sensor and the first temperature sensor are disposed between the EGR valve and the orifice plate, the second pressure sensor and the second temperature sensor are disposed upstream of the EGR valve, and the third pressure sensor and the third temperature sensor are disposed downstream of the orifice plate.

[0050] Each of the pressure sensors and each of the temperature sensors is electrically and / or communicatively connected to the controller.

[0051] The EGR flow measurement method provided in this embodiment of the invention first acquires the test EGR flow rates when the actual throttling pressure ratio of the EGR valve does not exceed a preset throttling pressure ratio at different engine speeds, with the orifice diameter of the orifice plate being the initial orifice diameter. Then, a reference EGR flow rate is determined based on the test EGR flow rates. Thus, based on the preset relationship between EGR flow rate and orifice diameter, the preset orifice diameter of the orifice can be determined according to the reference EGR flow rate. In practical applications, by placing an orifice plate with a preset orifice diameter in the EGR pipeline, a more accurate measurement of the EGR flow rate can be achieved by acquiring the first flow rate of the EGR valve and the second flow rate of the orifice plate. This allows the orifice plate with a preset orifice diameter to reduce the pressure loss of the EGR fluid at high flow rates and improve the measurement accuracy of the EGR flow rate at low flow rates.

[0052] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 This is a cross-sectional view of an EGR system provided in an embodiment of the present invention;

[0055] Figure 2 This is a flowchart of a method for measuring EGR flow provided in an embodiment of the present invention;

[0056] Figure 3 This is a flowchart of another method for measuring EGR flow provided in an embodiment of the present invention;

[0057] Figure 4 This is a flowchart of another EGR flow measurement method provided in an embodiment of the present invention;

[0058] Figure 5 This is a schematic diagram of the structure of an EGR flow measurement device provided in an embodiment of the present invention;

[0059] Figure 6 This is a structural block diagram of an EGR system provided in an embodiment of the invention. Detailed Implementation

[0060] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0061] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0062] This invention provides a method for measuring EGR flow rate, which can balance the fluid pressure loss requirements at high flow rates and the flow measurement accuracy at low flow rates. The method can be executed by the EGR flow rate measuring device provided in this invention, which can be implemented in software and / or hardware, and can be configured in the controller of the EGR system.

[0063] Figure 1 This is a cross-sectional view of an EGR system provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the EGR system includes an EGR valve 1 and an orifice plate 2 arranged sequentially in the gas flow path, and the orifice plate 2 includes a flow hole 21.

[0064] Specifically, when exhaust gas passes through the EGR cooler and enters the EGR pipeline, it sequentially passes through EGR valve 1 and orifice plate 2 before entering the engine mixer, thereby reducing combustion temperature and NOx emissions. The diameter (height) of the EGR pipeline where EGR valve 1 is located is H1, and the diameter (height) of the EGR pipeline where orifice plate 2 is located is H2. The diameter D of EGR valve 1 can be equal to the diameter H1 of the EGR pipeline at its location. Thus, when the opening degree θ of EGR valve 1 is 0°, EGR valve 1 blocks the EGR pipeline passage; when the opening degree of EGR valve 1 is at its maximum (opening degree θ is 90°), the gas flow rate of EGR valve 1 is at its maximum.

[0065] Figure 2 This is a flowchart of an EGR flow measurement method provided in an embodiment of the present invention, in conjunction with reference to [reference needed]. Figure 1 and Figure 2 The method includes:

[0066] S110. When the orifice diameter is the initial orifice diameter, obtain the test EGR flow rate when the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio at different engine speeds.

[0067] Specifically, the orifice 21 is the diameter of the flow hole 21. The initial orifice diameter of the flow hole 21 is preferably the diameter H2 at its location in the EGR pipeline. This is equivalent to not having an orifice plate 2, meaning that without an orifice plate 2 in the EGR pipeline, the test EGR flow rate is obtained at different engine speeds. EGR flow rate refers to the amount of gas flowing through the EGR valve 1 and orifice plate 2 per unit time, considering the EGR valve 1 and orifice plate 2 as a whole. The higher the engine speed, the more exhaust gas is produced, resulting in a larger opening of the EGR valve 1 and a larger gas flow rate through the EGR valve 1 per unit time (i.e., a larger EGR valve 1 flow rate). Within a certain range, the EGR valve 1 flow rate increases with increasing engine speed. When no orifice plate 2 is installed in the EGR pipeline, the obtained EGR valve 1 flow rate is the test EGR flow rate. In this case, the flow rate value of the EGR valve 1 can be determined based on the exhaust gas concentration in the EGR pipeline, thus determining the test EGR flow rate.

[0068] The throttling pressure ratio is the ratio of the pressure downstream of the EGR valve to the pressure upstream of the EGR valve. The pressure downstream of the EGR valve is the pressure at the point downstream of the EGR valve, and the pressure upstream of the EGR valve is the pressure at the point upstream of the EGR valve. In other words, when exhaust gas enters the EGR pipeline, the flow path of the exhaust gas is upstream of the EGR valve, then upstream of the EGR valve, and finally downstream of the EGR valve. A higher throttling pressure ratio results in a higher flow rate at the EGR valve, but also a greater pressure loss on the EGR fluid (i.e., the flowing exhaust gas in the EGR pipeline). The test EGR flow rate obtained when the actual throttling pressure ratio does not exceed the preset throttling pressure ratio ensures that the pressure loss on the EGR fluid is within acceptable limits, thus reducing the pressure loss on the EGR fluid at high flow rates (referring to gas flow).

[0069] S120. Determine the baseline EGR flow rate based on the EGR flow rate of each test.

[0070] Specifically, a baseline EGR flow rate for calculating the preset orifice diameter can be determined first. Since each tested EGR flow rate represents the EGR flow rate obtained when the engine is operating at different speeds and the actual throttling pressure ratio does not exceed the preset throttling pressure ratio, the preset orifice diameter determined based on each tested EGR flow rate can at least meet the pressure loss requirements of the EGR fluid under high flow conditions. Based on this, a baseline EGR flow rate is selected from each tested EGR flow rate so that the preset orifice diameter determined based on this baseline EGR flow rate can meet the EGR flow rate measurement accuracy under low flow conditions.

[0071] For example, among the various test EGR flows, the test EGR flow with the minimum flow value is determined as the baseline EGR flow.

[0072] Specifically, the test EGR flow rate with the lowest flow rate value is selected as the reference EGR flow rate. In this way, the preset orifice diameter obtained based on the reference EGR flow rate can meet the measurement accuracy of low flow rates as much as possible.

[0073] S130. Based on the preset relationship between EGR flow rate and orifice diameter, determine the preset orifice diameter of the flow orifice according to the reference EGR flow rate.

[0074] Specifically, the preset relationship can be a point-to-point preset table of EGR flow rate and orifice diameter, or a formula relating EGR flow rate and orifice diameter. In this way, when the EGR flow rate is a known baseline EGR flow rate, the preset orifice diameter of the flow orifice can be obtained by looking up the table or by calculating the formula.

[0075] S140. When the orifice diameter is a preset orifice diameter, obtain the first flow rate of the EGR valve and the second flow rate of the orifice plate.

[0076] S150. Determine the EGR flow rate based on the first flow rate and the second flow rate.

[0077] Specifically, an orifice plate with a preset orifice diameter can be placed in the EGR pipeline, preferably downstream of the EGR valve. In practical applications, when the engine is running, the gas flow rate through the EGR valve (i.e., the first flow rate) and the gas flow rate through the orifice plate (i.e., the second flow rate) can be obtained separately. The combined first and second flow rates determine the EGR flow rate of the EGR system in actual application. In practical applications, the engine speed is related to the actual operating conditions. The higher the engine speed, the larger the opening of the EGR valve, so that the large amount of exhaust gas generated by the engine's rapid rotation can be circulated through the EGR system to the engine mixer. At this time, due to the orifice plate, the pressure on both sides of the EGR valve is also relatively high. The preset orifice diameter ensures that the pressure loss of the EGR fluid is within acceptable limits, reducing the pressure loss requirement of the EGR fluid. When the engine speed is low, less exhaust gas is produced, the opening of the EGR valve is small, meaning that the gas flow through the EGR valve is small, and thus the overall EGR flow of the EGR system is small. At this time, since the flow orifice with the preset diameter can meet the measurement accuracy of low flow, it is more accurate to determine the overall EGR flow of the EGR system by combining the first flow and the second flow.

[0078] The EGR flow measurement method provided in this embodiment of the invention first acquires the test EGR flow rates when the actual throttling pressure ratio of the EGR valve does not exceed a preset throttling pressure ratio at different engine speeds, with the orifice diameter of the orifice plate being the initial orifice diameter. Then, a reference EGR flow rate is determined based on the test EGR flow rates. Thus, based on the preset relationship between EGR flow rate and orifice diameter, the preset orifice diameter of the orifice can be determined according to the reference EGR flow rate. In practical applications, by placing an orifice plate with a preset orifice diameter in the EGR pipeline, a more accurate measurement of the EGR flow rate can be achieved by acquiring the first flow rate of the EGR valve and the second flow rate of the orifice plate. This allows the orifice plate with a preset orifice diameter to reduce the pressure loss of the EGR fluid at high flow rates and improve the measurement accuracy of the EGR flow rate at low flow rates.

[0079] Optional, Figure 3 This is a flowchart of another EGR flow measurement method provided in an embodiment of the present invention, as shown below. Figure 3 As shown, the flowchart of this EGR flow measurement method includes:

[0080] S211. When the diameter of the flow hole is the initial diameter, control the engine to rotate.

[0081] S212. Obtain the actual throttling pressure ratio of the EGR valve at the current engine speed.

[0082] Specifically, refer to the following: Figure 1When the initial orifice diameter is H2, i.e., no orifice plate 2 is installed in the EGR pipeline, the engine rotation can be controlled and the engine stabilized at a certain speed. The pressure at the upstream position of EGR valve 1 and the pressure at the downstream position of EGR valve 1 when the engine is at the current speed can be obtained. The ratio of the pressure at the downstream position of EGR valve 1 to the pressure at the upstream position of EGR valve 1 is determined as the actual throttling pressure ratio of EGR valve.

[0083] S213. Determine whether the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio; if yes, proceed to step S214; if no, proceed to step S221.

[0084] S214. Obtain the test EGR flow rate of the engine at the current speed.

[0085] Specifically, after obtaining the actual throttling pressure ratio of the EGR valve at the current engine speed, the actual throttling pressure ratio of the EGR valve is compared with the preset throttling pressure ratio. The preset throttling pressure ratio can be set according to the pressure loss requirements of the EGR fluid, for example, it can be 0.9. If the actual throttling pressure ratio of the EGR valve is less than or equal to the preset throttling pressure ratio, it means that the pressure loss of the EGR fluid due to the current gas flow is within the allowable range, and the EGR flow rate at this time (i.e., the test EGR flow rate) can be determined.

[0086] S215, Increase the engine speed by a preset step size.

[0087] S216. Determine whether the current engine speed exceeds the preset speed; if yes, proceed to step S217; if no, return to step S212.

[0088] S217. Determine the baseline EGR flow rate based on the EGR flow rate of each test.

[0089] Specifically, after obtaining the test EGR flow rate at a certain engine speed, the engine speed is increased by a preset step size, i.e., the engine speed is controlled to increase by a preset value. After the engine speed increases, it is determined whether the increased speed exceeds the preset speed. If it exceeds the preset speed, the acquisition of the test EGR flow rate is stopped. If it does not exceed the preset speed, the actual throttling pressure ratio of the EGR valve at the current engine speed is obtained, and the test EGR flow rate is acquired again if the actual throttling pressure ratio does not exceed the preset throttling pressure ratio. The preset speed can be a speed less than and close to the engine's maximum speed, and can be set according to design requirements. In a feasible embodiment, the engine speed can also be decreased by a preset step size. In this case, the preset speed can be a speed greater than 0, and can be set according to design requirements.

[0090] For example, in other feasible embodiments of the present invention, after increasing (or decreasing) the engine speed with a preset compensation, the number of times the speed increases (or decreases) can be determined, and it can be determined whether the number of times is equal to the preset number. If the preset number is not reached, the actual throttling pressure ratio of the EGR valve at the current engine speed can be obtained, so that the test EGR flow rate can be obtained again when the actual throttling pressure ratio does not exceed the preset throttling pressure ratio. When the number of times the speed increases (or decreases) is equal to the preset number, the acquisition of the actual throttling pressure ratio is stopped.

[0091] S218. Based on the preset relationship between EGR flow rate and orifice diameter, determine the preset orifice diameter of the flow orifice according to the reference EGR flow rate.

[0092] S219. When the orifice diameter is a preset orifice diameter, obtain the first flow rate of the EGR valve and the second flow rate of the orifice plate.

[0093] S220. Determine the EGR flow rate based on the first flow rate and the second flow rate.

[0094] S221, Control the EGR valve to reduce the preset opening degree.

[0095] S222. Obtain the actual throttling pressure ratio of the EGR valve after reducing the preset opening degree, and return to step S213.

[0096] Specifically, in step S213, when it is determined whether the actual throttling pressure ratio of the EGR valve exceeds the preset throttling pressure ratio, it indicates that the flow rate of the EGR valve is too large, that is, the opening of the EGR valve is too large. At this opening, the gas flow rate causes a large pressure loss on the EGR fluid. At this time, the EGR valve can be controlled to reduce the preset opening to reduce the flow rate of the EGR valve. After reducing the opening of the EGR valve, the actual throttling pressure ratio of the EGR valve is obtained again, and it is determined whether the actual throttling pressure ratio still exceeds the preset throttling pressure ratio. If it still exceeds the preset throttling pressure ratio, the EGR valve is controlled to reduce the preset opening again. This cycle is repeated until the actual throttling pressure ratio does not exceed the preset throttling pressure ratio. Then, the step of obtaining the test EGR flow rate at the current engine speed is executed.

[0097] Optional, Figure 4 This is a flowchart of another EGR flow measurement method provided in an embodiment of the present invention, as shown below. Figure 4 As shown, the flowchart of this EGR flow measurement method includes:

[0098] S311. When the orifice diameter is the initial orifice diameter, obtain the test EGR flow rate when the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio at different engine speeds.

[0099] S312. Determine the baseline EGR flow rate based on the EGR flow rate of each test.

[0100] S313. When the EGR flow rate is obtained as the reference EGR flow rate, the first pressure and the first temperature at the downstream position of the EGR valve are obtained.

[0101] For details, please refer to Figure 1 A first pressure sensor 3 and a first temperature sensor 4 can be installed downstream of the EGR valve. In this way, the first pressure at the downstream position of the EGR valve can be obtained through the first pressure sensor 3, and the first temperature at the downstream position of the EGR valve can be obtained through the first temperature sensor 4.

[0102] For example, the first pressure and first temperature corresponding to each test EGR flow can be obtained at the same time as the test EGR flow. Alternatively, after determining the reference EGR flow, the engine speed can be readjusted to reach the speed corresponding to the reference EGR flow, and the opening of the EGR valve can be adjusted at this speed to make the EGR valve flow equal to the reference EGR flow, and the first pressure and first temperature at this time can be obtained.

[0103] S314. Based on the gas state equation, determine the first gas density at the downstream position of the EGR valve according to the first pressure and the first temperature.

[0104] The gas state equation is: ρ0=P1*M / (R*T1), where ρ0 is the first gas density, P1 is the first pressure, M is the molar mass of air, R is the gas constant, and T1 is the first temperature.

[0105] Specifically, the molar mass M of air and the gas constant R are constants. After obtaining the first pressure P1 and the first temperature T1, the first pressure P1 and the first temperature T1 can be substituted into the gas state equation to determine the first gas density at the downstream position of the EGR valve when the EGR flow rate is the reference EGR flow rate.

[0106] S315. Based on the first formula, determine the preset orifice diameter of the flow orifice according to the reference EGR flow rate and the first gas density.

[0107] The first formula is: q m0 The reference EGR flow rate, d0 is the preset orifice diameter of the flow orifice, D0 is the EGR pipeline diameter at the downstream position of the EGR valve, C0 is the first discharge coefficient, ε0 is the first compressibility coefficient of the gas, ρ0 is the first gas density, P0 is the first pressure, and P1 is the second pressure.

[0108] Specifically, the first formula is the formula for calculating flow rate using the Venturi algorithm. The first discharge coefficient C0 can be set to 1 to avoid the influence of the discharge coefficient on the calculation of the preset orifice size. The first compressibility coefficient ε0 of the gas can be set to 1, or it can be calculated according to the definition of the compressibility coefficient, which is: Where P0 is the pressure upstream of the EGR valve when the EGR flow rate is the baseline EGR flow rate, and k is a thermodynamic constant, which can be 1.4. The preset pressure difference ΔP is the minimum difference between the pressure upstream and downstream of the EGR valve measured under steady-state conditions, which can be 10 kPa. The baseline EGR flow rate q can be used as a reference. m0 The first gas density ρ0 is substituted into the first formula to calculate the preset orifice diameter d0 of the flow orifice. Since the formula is relatively complex, a suitable orifice diameter value can also be selected and substituted into the first formula to calculate the EGR flow rate, choosing a value similar to the baseline EGR flow rate q. m0 The orifice value corresponding to the closest EGR flow rate is used as the preset orifice value, and the orifice value can be selected in the range of 0 to H2.

[0109] S316. When the orifice diameter is a preset orifice diameter, obtain the effective flow diameter of the EGR valve, the second pressure at the upstream position of the EGR valve, the third pressure between the EGR valve and the orifice plate, and the fourth pressure at the downstream position of the orifice plate.

[0110] For details, please refer to Figure 1 When the diameter of the flow hole 21 is a preset diameter, that is, when an orifice plate 2 with a preset diameter is set at the downstream position of the EGR valve, a second pressure sensor 5 can be set at the upstream position of the EGR valve 1, a first pressure sensor 3 can be set between the EGR valve 1 and the orifice plate 2, and a third pressure sensor 7 can be set at the downstream position of the orifice plate 2. In this way, the second pressure at the upstream position of the EGR valve 1 can be obtained through the second pressure sensor 5, the third pressure between the EGR valve 1 and the orifice plate 2 can be obtained through the first pressure sensor 3, and the fourth pressure at the downstream position of the orifice plate 2 can be obtained through the third pressure sensor 7.

[0111] S317. Based on the second formula, determine the first flow rate of the EGR valve according to the effective flow diameter, the second pressure, and the third pressure.

[0112] The second formula is: Where, q m1 ε1 is the first flow rate of the EGR valve, C1 is the second discharge coefficient, d1 is the effective flow diameter of the EGR valve, D1 is the diameter of the EGR pipeline upstream of the EGR valve, ε1 is the second compressibility coefficient of the gas, ρ1 is the second gas density upstream of the EGR valve, P2 is the second pressure, and P3 is the third pressure.

[0113] Specifically, the second discharge coefficient C1 is a constant and can be obtained through bench testing. The effective flow diameter d1 of the EGR valve can be DD*cosθ, where, as a reference... Figure 1θ is the opening angle of EGR valve 1. The EGR pipe diameter D1 upstream of the EGR valve can specifically be the EGR pipe diameter at the location of the second pressure sensor 5. The second compressibility coefficient ε1 of the gas can be obtained through a definition or by looking up a table. When obtained through the definition,

[0114] The second gas density ρ1 at the upstream position of the EGR valve can be the gas density at the EGR valve inlet, which can be obtained through the gas state equation, i.e., ρ1=P2*M / (R*T2), where T2 is the temperature at the EGR valve inlet.

[0115] S318. Based on the third formula, determine the second flow rate of the orifice plate according to the preset orifice diameter, the third pressure, and the fourth pressure.

[0116] The third formula is: q m2 C2 is the second flow rate of the orifice plate, d2 is the third discharge coefficient, d2 is the preset orifice diameter, D2 is the diameter of the EGR pipeline between the EGR valve and the orifice plate, ε2 is the third compressibility coefficient of the gas, ρ2 is the third gas density between the EGR valve and the orifice plate, and P4 is the fourth pressure.

[0117] Specifically, the third discharge coefficient C2 is a constant and can be obtained through bench testing. The EGR pipe diameter D2 between the EGR valve and the orifice plate can be specifically the EGR pipe diameter at the location of the first pressure sensor 3. The third compressibility coefficient ε2 of the gas can be obtained through a definition or by looking up a table. When obtained through the definition... The third gas density ρ2 between the EGR valve and the orifice plate can be the exhaust gas density at the location of the first pressure sensor 3, which can be obtained through the gas state equation, i.e., ρ2=P3*M / (R*T3), where T3 is the temperature at the location of the first temperature sensor 4.

[0118] S319, Obtain the first weight of the first traffic and the second weight of the second traffic.

[0119] S320. Determine the weighted average of the first flow rate and the second flow rate based on the first flow rate, the second flow rate, the first weight, and the second weight.

[0120] S321. Determine the weighted average value as the EGR flow rate.

[0121] Specifically, after obtaining the first flow rate q through the EGR valve m1 and the second flow rate q through the orifice plate m2 Then, obtain the first weight w1 of the first flow and the second weight w1 of the second flow. The first weight w1 and the second weight w2 can be obtained based on experiments or experience. Then, the first flow q can be calculated. m1 and the second flow rate q through the orifice platem2 weighted average The weighted average value is then used to determine the final EGR flow of the EGR system.

[0122] The EGR flow measurement method provided in this invention, when using the orifice diameter of the orifice plate as a preset orifice diameter, acquires pressure and temperature data upstream of the EGE valve, between the EGR valve and the orifice plate, and downstream of the orifice plate. Combining the gas state equation, the definition of the compressibility coefficient, and the flow calculation formula of the Venturi algorithm, the first flow rate of the EGR valve and the second flow rate of the orifice plate are calculated respectively. The weighted average of the first and second flow rates is determined as the final actual EGR flow rate. This improves the accuracy of EGR flow detection at low flow rates and ensures that there is no significant pressure loss on the EGR fluid at high flow rates. It balances the accuracy of flow measurement at low flow rates with the pressure loss problem at high flow rates, making it suitable for wide application.

[0123] Based on the same inventive concept, embodiments of the present invention provide an EGR flow measurement device. This EGR flow measurement device is used to execute the EGR flow measurement method provided in any embodiment of the present invention. The EGR flow measurement device can be implemented by software and / or hardware. Therefore, the EGR flow measurement device provided in the embodiments of the present invention includes the technical features of the EGR flow measurement method provided in any embodiment of the present invention, and can achieve the beneficial effects of the EGR flow measurement method provided in any embodiment of the present invention. Similarities can be referred to the above description of the EGR flow measurement method provided in the embodiments of the present invention, and will not be repeated here.

[0124] refer to Figure 1 The EGR system includes an EGR valve 1 and an orifice plate 2 arranged sequentially in the gas flow path. The orifice plate 1 includes a flow hole 21. Figure 5 This is a schematic diagram of the structure of an EGR flow measurement device provided in an embodiment of the present invention, as shown below. Figure 5 As shown, the EGR flow measurement device includes a test EGR flow acquisition module 100, used to acquire test EGR flows when the actual throttling pressure ratio of the EGR valve at different engine speeds does not exceed a preset throttling pressure ratio, with the orifice diameter of the flow orifice being an initial orifice diameter; a reference EGR flow determination module 200, used to determine a reference EGR flow based on each test EGR flow; a preset orifice diameter determination module 300, used to determine a preset orifice diameter of the flow orifice based on a preset relationship between EGR flow and orifice diameter, according to the reference EGR flow; a flow acquisition module 400, used to acquire a first flow of the EGR valve and a second flow of the orifice plate when the orifice diameter of the flow orifice is a preset orifice diameter; and an EGR flow determination module 500, used to determine the EGR flow based on the first and second flow rates.

[0125] The EGR flow measurement device provided in this embodiment of the invention first acquires the test EGR flow rate when the orifice diameter of the orifice plate is at the initial orifice diameter using the test EGR flow acquisition module, and the actual throttling pressure ratio of the EGR valve at different engine speeds does not exceed the preset throttling pressure ratio. Then, the reference EGR flow rate determination module determines the reference EGR flow rate based on the test EGR flow rates. Thus, the preset orifice diameter determination module determines the preset orifice diameter of the orifice based on the preset relationship between EGR flow rate and orifice diameter and the reference EGR flow rate. In practical applications, by placing an orifice plate with a preset orifice diameter in the EGR pipeline, the flow acquisition module and the EGR flow rate determination module can achieve a relatively accurate measurement of the EGR flow rate by acquiring the first flow rate of the EGR valve and the second flow rate of the orifice plate. This allows the orifice plate with a preset orifice diameter to reduce the pressure loss of the EGR fluid at high flow rates and improve the measurement accuracy of the EGR flow rate at low flow rates.

[0126] Optionally, the test EGR flow acquisition module includes an engine control unit for controlling engine rotation when the orifice diameter is the initial orifice diameter; a first actual throttle pressure ratio acquisition unit for acquiring the actual throttle pressure ratio of the EGR valve at the current engine speed; a throttle pressure ratio judgment unit for determining whether the actual throttle pressure ratio of the EGR valve does not exceed a preset throttle pressure ratio; a test EGR flow acquisition unit for acquiring the test EGR flow at the current engine speed when the throttle pressure ratio judgment unit determines that the actual throttle pressure ratio of the EGR valve does not exceed the preset throttle pressure ratio; a speed adjustment module for increasing the engine speed by a preset step size; a speed judgment unit for determining whether the current engine speed exceeds a preset speed; a reference EGR flow determination module for determining a reference EGR flow based on each test EGR flow when the speed judgment unit determines that the current engine speed exceeds the preset speed; and a first circulation unit for returning to the actual throttle pressure ratio acquisition unit when the speed judgment unit determines that the current engine speed does not exceed the preset speed.

[0127] Optionally, the test EGR flow acquisition module further includes: an opening adjustment unit, used to control the EGR valve to reduce the preset opening when the throttling pressure ratio judgment unit determines that the actual throttling pressure ratio of the EGR valve exceeds the preset throttling pressure ratio; a second actual throttling pressure ratio acquisition unit, used to acquire the actual throttling pressure ratio of the EGR valve after reducing the preset opening; and a second circulation unit, used to return to the throttling pressure ratio judgment unit after the second actual throttling pressure ratio acquisition unit acquires the actual throttling pressure ratio of the EGR valve after reducing the preset opening.

[0128] Optionally, the baseline EGR flow determination module includes a baseline EGR flow unit, used to determine the test EGR flow with the minimum flow value among all test EGR flows as the baseline EGR flow.

[0129] Optionally, the preset orifice diameter determination module includes a first information acquisition unit, used to acquire the first pressure and the first temperature at the downstream position of the EGR valve when the EGR flow rate is the reference EGR flow rate; a first gas density determination unit, used to determine the first gas density at the downstream position of the EGR valve based on the gas state equation, according to the first pressure and the first temperature; the gas state equation is: ρ0=P1*M / (R*T1); and a preset orifice diameter determination unit, used to determine the preset orifice diameter of the flow orifice based on the reference EGR flow rate and the first gas density according to a first formula; the first formula is: Where ρ0 is the first gas density, P1 is the first pressure, M is the molar mass of air, R is the gas constant, T1 is the first temperature, and q m0 The reference EGR flow rate, d0 is the preset orifice diameter of the flow orifice, D0 is the EGR pipeline diameter at the downstream position of the EGR valve, C0 is the first discharge coefficient, ε0 is the first compressibility coefficient of the gas, and ΔP is the preset differential pressure.

[0130] Optionally, the flow acquisition module includes a second information acquisition unit, used to acquire the effective flow diameter of the EGR valve, the second pressure upstream of the EGR valve, the third pressure between the EGR valve and the orifice plate, and the fourth pressure downstream of the orifice plate when the orifice diameter is a preset orifice diameter; and a first flow determination unit, used to determine the first flow rate of the EGR valve based on a second formula, according to the effective flow diameter, the second pressure, and the third pressure; the second formula is: Where, q m1 Here, C1 is the first flow rate of the EGR valve, d1 is the effective flow diameter of the EGR valve, D1 is the diameter of the EGR pipeline upstream of the EGR valve, ε1 is the second compressibility coefficient of the gas, ρ1 is the second gas density upstream of the EGR valve, P2 is the second pressure, and P3 is the third pressure. The second flow rate determination unit is used to determine the second flow rate of the orifice plate based on the third formula, according to the preset orifice diameter, the third pressure, and the fourth pressure. The third formula is: q m2 C2 is the second flow rate of the orifice plate, d2 is the third discharge coefficient, d2 is the preset orifice diameter, D2 is the diameter of the EGR pipeline between the EGR valve and the orifice plate, ε2 is the third compressibility coefficient of the gas, ρ2 is the third gas density between the EGR valve and the orifice plate, and P4 is the fourth pressure.

[0131] Optionally, the EGR flow determination module includes a weight acquisition unit for acquiring a first weight of the first flow and a second weight of the second flow; a weighted average determination unit for determining a weighted average of the first flow and the second flow based on the first flow, the second flow, the first weight, and the second weight; and an EGR flow determination unit for determining the weighted average as the EGR flow.

[0132] Based on the same inventive concept, embodiments of the present invention also provide an EGR system, including an EGR valve and an orifice plate sequentially disposed on a gas flow path. The orifice plate includes a flow hole and a controller. The controller is used for measuring the EGR flow rate in any embodiment of the present invention. Therefore, the EGR provided by the embodiments of the present invention includes the technical features of the EGR flow rate measurement method provided by any embodiment of the present invention, and can achieve the beneficial effects of the EGR flow rate measurement method provided by any embodiment of the present invention. The similarities can be referred to the above description of the EGR flow rate measurement method provided by the embodiments of the present invention, and will not be repeated here.

[0133] Figure 6 This is a structural block diagram of an EGR system provided in an embodiment of the invention, in conjunction with reference to the reference. Figure 1 and Figure 6 The EGR system also includes a first pressure sensor 3, a second pressure sensor 5, a third pressure sensor 7, a first temperature sensor 4, a second temperature sensor 6, and a third temperature sensor 8; the first pressure sensor 3 and the first temperature sensor 4 are disposed between the EGR valve 1 and the orifice plate 2, the second pressure sensor 5 and the second temperature sensor 6 are disposed upstream of the EGR valve, and the third pressure sensor 7 and the third temperature sensor 8 are disposed downstream of the orifice plate; each pressure sensor and each temperature sensor is electrically connected and / or communicatively connected to the controller 9.

[0134] Specifically, the first pressure sensor 3 can acquire the first pressure downstream of the EGR valve 1 when the orifice diameter of the flow hole 21 in the orifice plate 2 is H2, and can also acquire the third pressure between the EGR valve 1 and the orifice plate 2 when the orifice diameter of the flow hole 21 is a preset diameter. Similarly, the second pressure sensor 5 is used to acquire the pressure upstream of the EGR valve 1 (e.g., the second pressure), and the third pressure sensor 7 is used to acquire the pressure downstream of the orifice plate 2 (e.g., the fourth pressure). Each pressure sensor can send the acquired pressure information to the controller 9. Each temperature sensor can acquire the temperature information at its location and send the temperature information to the controller 9.

[0135] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0136] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for measuring EGR flow rate, the EGR system comprising an EGR valve and an orifice plate sequentially arranged in a gas flow path, the orifice plate comprising a flow hole, characterized in that, include: When the orifice diameter is the initial orifice diameter, the test EGR flow rate is obtained when the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio at different engine speeds. Determine the baseline EGR flow rate based on the test EGR flow rates described above; Based on the preset relationship between the EGR flow rate and the orifice diameter, the preset orifice diameter of the flow orifice is determined according to the reference EGR flow rate; When the orifice diameter is a preset orifice diameter, the first flow rate of the EGR valve and the second flow rate of the orifice plate are obtained; The EGR flow is determined based on the first flow and the second flow; The determination of the baseline EGR flow based on each of the test EGR flows includes: among the test EGR flows, determining the test EGR flow with the minimum flow value as the baseline EGR flow; Determining the EGR traffic based on the first traffic and the second traffic includes: obtaining a first weight of the first traffic and a second weight of the second traffic; determining a weighted average of the first traffic and the second traffic based on the first traffic, the second traffic, the first weight, and the second weight; and determining the weighted average as the EGR traffic.

2. The method for measuring EGR flow rate according to claim 1, characterized in that, When the orifice diameter is the initial orifice diameter, the test EGR flow rates are obtained when the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio at different engine speeds, including: When the diameter of the flow hole is the initial diameter, the engine is controlled to rotate; Obtain the actual throttling pressure ratio of the EGR valve at the current engine speed; Determine whether the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio; If so, obtain the test EGR flow rate of the engine at the current speed; The engine speed is increased by a preset step size; Determine whether the current speed of the engine exceeds the preset speed; If so, then proceed with the step of determining the baseline EGR flow based on the test EGR flow described above; If the current engine speed does not exceed the preset speed, then return to the step of obtaining the actual throttling pressure ratio of the EGR valve at the current engine speed.

3. The method for measuring EGR flow rate according to claim 2, characterized in that, If the actual throttling pressure ratio of the EGR valve exceeds the preset throttling pressure ratio, then the EGR valve is controlled to reduce the preset opening degree; Obtain the actual throttling pressure ratio of the EGR valve after reducing the preset opening degree, and return to the step of determining whether the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio.

4. The method for measuring EGR flow rate according to claim 1, characterized in that, Based on the preset relationship between the EGR flow rate and the orifice diameter, the preset orifice diameter of the flow-through orifice is determined according to the reference EGR flow rate, including: When the EGR flow rate is obtained as the reference EGR flow rate, the first pressure and the first temperature at the downstream position of the EGR valve are obtained; Based on the gas law, the first gas density at the downstream position of the EGR valve is determined according to the first pressure and the first temperature; the gas law is: ρ0=P1*M / (R*T1); Based on the first formula, the preset aperture of the flow orifice is determined according to the reference EGR flow rate and the first gas density; The first formula is: Where ρ0 is the density of the first gas, P1 is the first pressure, M is the molar mass of air, R is the gas constant, T1 is the first temperature, and q m0 The reference EGR flow rate, d0 is the preset orifice diameter of the flow orifice, D0 is the EGR pipeline diameter at the downstream position of the EGR valve, C0 is the first outflow coefficient, ε0 is the first compressibility coefficient of the gas, and ΔP is the preset pressure difference.

5. The method for measuring EGR flow rate according to claim 1, characterized in that, When the orifice diameter is a preset orifice diameter, obtaining the first flow rate of the EGR valve and the second flow rate of the orifice plate includes: When the orifice diameter is a preset orifice diameter, the effective flow diameter of the EGR valve, the second pressure at the upstream position of the EGR valve, the third pressure between the EGR valve and the orifice plate, and the fourth pressure at the downstream position of the orifice plate are obtained. Based on the second formula, the first flow rate of the EGR valve is determined according to the effective flow diameter, the second pressure, and the third pressure; The second formula is: In the middle, q m1 C1 is the first flow rate of the EGR valve, d1 is the second outflow coefficient, D1 is the effective flow diameter of the EGR valve, D1 is the diameter of the EGR pipeline at the upstream position of the EGR valve, ε1 is the second compressibility coefficient of the gas, ρ1 is the second gas density at the upstream position of the EGR valve, P2 is the second pressure, and P3 is the third pressure. Based on the third formula, the second flow rate of the orifice plate is determined according to the preset orifice diameter, the third pressure, and the fourth pressure; The third formula is: C2 is the second flow rate of the orifice plate, d2 is the third discharge coefficient, d2 is the preset orifice diameter, D2 is the diameter of the EGR pipeline between the EGR valve and the orifice plate, ε2 is the third compressibility coefficient of the gas, ρ2 is the third gas density between the EGR valve and the orifice plate, and P4 is the fourth pressure.

6. An EGR flow measurement device, wherein the EGR includes an EGR valve and an orifice plate sequentially disposed in a gas flow path, the orifice plate including a flow hole, characterized in that, include: The test EGR flow acquisition module is used to acquire the test EGR flow rate when the actual throttling pressure ratio of the EGR valve does not exceed the preset throttling pressure ratio at different engine speeds, with the orifice diameter of the flow orifice being the initial orifice diameter. A baseline EGR flow determination module is used to determine a baseline EGR flow based on the test EGR flow. The preset orifice diameter determination module determines the preset orifice diameter of the flow orifice based on the preset relationship between the EGR flow rate and the orifice diameter, according to the reference EGR flow rate. The flow acquisition module is used to acquire the first flow rate of the EGR valve and the second flow rate of the orifice plate when the orifice diameter of the flow hole is a preset orifice diameter; EGR flow determination module, used to determine the EGR flow based on the first flow and the second flow; The reference EGR flow determination module includes a reference EGR flow unit, which is used to determine the test EGR flow with the minimum flow value among the test EGR flows as the reference EGR flow. The EGR traffic determination module includes a weight acquisition unit for acquiring a first weight of the first traffic and a second weight of the second traffic; a weighted average determination unit for determining a weighted average of the first traffic and the second traffic based on the first traffic, the second traffic, the first weight, and the second weight; and an EGR traffic determination unit for determining the weighted average as the EGR traffic.

7. An EGR system, characterized in that, It includes an EGR valve and an orifice plate sequentially arranged in the gas flow path, the orifice plate including a flow hole; It also includes a controller for performing the EGR flow measurement method according to any one of claims 1 to 5.

8. The EGR system according to claim 7, characterized in that, It also includes a first pressure sensor, a second pressure sensor, a third pressure sensor, a first temperature sensor, a second temperature sensor, and a third temperature sensor; The first pressure sensor and the first temperature sensor are disposed between the EGR valve and the orifice plate, the second pressure sensor and the second temperature sensor are disposed upstream of the EGR valve, and the third pressure sensor and the third temperature sensor are disposed downstream of the orifice plate. Each of the pressure sensors and each of the temperature sensors is electrically and / or communicatively connected to the controller.

Images