Method for correcting engine exhaust flow measurement

Abstract

The present application relates to a kind of correction methods of engine exhaust flow measurement, the method is by collecting venturi inlet pressure signal P and intake manifold pressure signal P22, obtain differential pressure signal ΔP, wherein positive differential pressure can be characterized as positive flow, negative differential pressure can be characterized as reverse flow;Further by the differential pressure signal ΔP of venturi inlet and intake manifold, differential pressure integral proportion ΔP prop Then according to the corresponding relationship of differential pressure integral proportion ΔP prop And engine speed n and correction coefficient, find out the correction coefficient corresponding to current ΔP prop And n, finally the measured flow is multiplied by correction coefficient, obtain the actual measurement value of the final recirculated exhaust gas amount.The method of the present application compensates the influence of reverse airflow on exhaust flow measurement, improves the accuracy of exhaust flow measurement.Venturi cannot identify reverse flow, and reverse flow will be calculated as positive flow in measured flow, so the influence of reverse flow is eliminated by using the correction coefficient of the present application.

Description

Technical Field

[0001] This invention relates to an engine exhaust measurement, and more specifically to a correction method for engine exhaust flow measurement. Background Technology

[0002] Exhaust Gas Recirculation (EGR) is a technology that returns a small portion of the exhaust gas produced by the engine to the cylinder for re-combustion through an EGR valve. It is an effective means of improving engine emissions. With increasingly stringent diesel engine emission standards, higher requirements are placed on the measurement accuracy of the recirculated exhaust gas volume. Currently, the measurement scheme based on the Venturi tube can no longer meet the accuracy requirements, and therefore cannot provide accurate adjustment control signals for the EGR valve opening control.

[0003] In existing engine exhaust gas recirculation systems, the amount of recirculated exhaust gas is measured using Bernoulli's equation (Equation (1)) based on a Venturi tube:

[0004]

[0005] Where: m is the flow rate, in G / s; A eff The effective cross-sectional area of ​​the Venturi tube is expressed in meters (m²). 2 ;P Dif P represents the pressure difference between the inlet and throat of the venturi tube, in Pa. Abslt R is the inlet pressure of the Venturi tube, in Pa; R is the gas constant (286.9), in J / (kg·K); T is the inlet temperature of the Venturi tube, in K.

[0006] Under certain engine operating conditions, the intake pressure may approach or even exceed the exhaust pressure (inside the EGR valve). When the EGR valve opens, a reverse airflow is generated. When measured using a venturi tube, because the venturi tube cannot detect reverse flow, the reverse flow will be calculated as forward flow, leading to inaccurate exhaust gas flow measurement and thus affecting engine emissions. Summary of the Invention

[0007] To address the above problems, this invention provides a correction method for measuring engine exhaust gas flow rate, which compensates for the influence of reverse airflow on exhaust gas flow rate measurement and improves the accuracy of exhaust gas flow rate measurement.

[0008] The technical solution adopted in this invention is: a correction method for measuring engine exhaust gas flow rate, characterized by comprising the following steps:

[0009] 1) Calculate the pressure difference signal ΔP between the venturi inlet and the intake manifold;

[0010] 2) Calculate the single exhaust pulse cycle T segThe sum of internal pressure difference signals ΔP And the cumulative number of differential pressure signals ΔP, cnt, and record the largest differential pressure signal ΔP. MAX =MAX(ΔP) MAX ,ΔP);

[0011] 3) Record ΔP when the pulse period ends. SUM ,cnt,ΔP MAX ;

[0012] 4) Calculate the integral percentage of pressure difference ΔP prop Then reset timer T and repeat steps 1), 2), and 3);

[0013] 5) Based on the integral ratio of pressure difference ΔP prop By referring to the table of correspondence between engine speed n and correction factor, the correction factor for the actual measured exhaust gas volume is obtained; the measured flow rate is multiplied by the correction factor to obtain the final actual measured value of the recirculated exhaust gas volume.

[0014] As a preferred option, step 1) specifically involves: acquiring the venturi inlet pressure signal P and the intake manifold pressure signal P22, and calculating the pressure difference signal ΔP between the venturi inlet and the intake manifold according to formula (2), where a positive pressure difference can characterize the forward flow and a negative pressure difference can characterize the reverse flow.

[0015] ΔP=P-P22..........(2).

[0016] As a preferred option, in step 4),

[0017]

[0018] As a preferred option, in step 2),

[0019]

[0020] Wherein: T seg Exhaust pulse cycle, unit: s; τ: number of strokes; N: number of engine cylinders; n: engine speed, unit: r / min.

[0021] As a preferred option, T seg It takes 20ms.

[0022] As a preferred option, N=6.

[0023] As a preferred option, n = 1000 rpm / min.

[0024] As a preferred option, τ = 4.

[0025] As a preferred option, the specific steps of step 5) are as follows: First, from the pre-generated differential pressure integral ratio ΔPprop From the correspondence between engine speed n and correction coefficient, find the current ΔP. prop The correction coefficient corresponding to n is then multiplied by the actual measured exhaust gas volume to correct the actual measured exhaust gas volume.

[0026] As a preferred option, the differential pressure integral ratio ΔP prop The relationship between engine speed n and correction coefficient is obtained based on the ratio of theoretical exhaust gas volume to actual measured exhaust gas volume for each stable operating condition.

[0027] The beneficial effects achieved by this invention are as follows: By acquiring the venturi inlet pressure signal P and the intake manifold pressure signal P22, a pressure difference signal ΔP is obtained. A positive pressure difference can characterize the forward flow, and a negative pressure difference can characterize the reverse flow. However, when using a venturi tube for measurement, only the pressure difference between the venturi inlet and the throat is acquired, which cannot reflect the reverse airflow (even if it could, the result would be inaccurate). Furthermore, the pressure difference integral percentage ΔP is obtained from the pressure difference signal ΔP between the venturi inlet and the intake manifold. prop Then, based on the integral proportion of the pressure difference ΔP prop Based on the relationship between engine speed n and correction coefficient, find the current ΔP. prop The correction factor corresponding to n is used, and finally the measured flow rate is multiplied by the correction factor to obtain the final actual measured value of the recirculated exhaust gas volume.

[0028] The method of this invention compensates for the influence of reverse airflow on exhaust gas flow measurement, thereby improving the accuracy of exhaust gas flow measurement. Venturi tubes cannot detect reverse flow, and the reverse flow is often treated as forward flow in the flow measurement. Therefore, the correction coefficient of this invention eliminates the influence of reverse flow. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the engine recirculation system;

[0030] Figure 2 This is a schematic diagram illustrating the calculation of the integral percentage of differential pressure.

[0031] Figure 3 This is a flowchart of the present invention;

[0032] Figure 4 A graph comparing the actual EGR flow rate with the corrected side beam flow rate;

[0033] Figure 5 This is a graph comparing the actual EGR flow rate with the uncorrected side beam flow rate. Detailed Implementation

[0034] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] like Figure 1-3 As shown, a correction method for measuring engine exhaust gas flow includes the following steps:

[0038] 1) Calculate the pressure difference signal ΔP between the venturi inlet and the intake manifold;

[0039] 2) Calculate the single exhaust pulse cycle T seg The sum of internal pressure difference signals ΔP And the cumulative number of differential pressure signals ΔP, cnt, and record the largest differential pressure signal ΔP. MAX =MAX(ΔP) MAX ,ΔP);

[0040] 3) Record ΔP when the pulse period ends. SUM ,cnt,ΔP MAX ;

[0041] 4) Calculate the percentage of differential pressure integral. Then reset timer T and repeat steps 1), 2), and 3);

[0042] 5) Based on the integral ratio of pressure difference ΔP propBy referring to the table of correspondence between engine speed n and correction factor, the correction factor for the actual measured exhaust gas volume is obtained; the measured flow rate is multiplied by the correction factor to obtain the final actual measured value of the recirculated exhaust gas volume.

[0043] By acquiring the venturi inlet pressure signal P and the intake manifold pressure signal P22, the pressure difference signal ΔP is obtained. A positive pressure difference characterizes the forward flow, while a negative pressure difference characterizes the reverse flow. However, using a venturi tube only acquires the pressure difference between the venturi inlet and the throat, which cannot reflect the reverse airflow (and even if it could, the result would be inaccurate). Further, the pressure difference integral percentage ΔP is obtained from the pressure difference signal ΔP between the venturi inlet and the intake manifold. prop Then, based on the integral proportion of the pressure difference ΔP prop Based on the relationship between engine speed n and correction coefficient, find the current ΔP. prop The method of this invention compensates for the influence of reverse airflow on exhaust gas flow measurement, thereby improving the accuracy of exhaust gas flow measurement. Since venturi tubes cannot recognize reverse flow, they will treat reverse flow as forward flow in the flow measurement. Therefore, the correction coefficient of this invention eliminates the influence of reverse flow.

[0044] Example 1: A correction method for measuring engine exhaust gas flow rate, comprising the following steps:

[0045] 1) Collect the venturi inlet pressure signal P and the intake manifold pressure signal P22, and calculate the pressure difference signal ΔP between the venturi inlet and the intake manifold according to formula (2). The positive pressure difference can represent the forward flow, and the negative pressure difference can represent the reverse flow.

[0046] ΔP=P-P22..........(2);

[0047] 2) Calculate the single exhaust pulse cycle T seg The sum of internal pressure difference signals ΔP And the cumulative number of differential pressure signals ΔP, cnt, and record the largest differential pressure signal ΔP. MAX =MAX(ΔP) MAX ,ΔP);

[0048] 3) Record ΔP when the pulse period ends. SUM ,cnt,ΔP MAX ;

[0049] 4) Calculate the percentage of differential pressure integral. Then reset timer T and repeat steps 1), 2), and 3);

[0050] 5) Based on the integral ratio of pressure difference ΔPprop By referring to the table of correspondence between engine speed n and correction factor, the correction factor for the actual measured exhaust gas volume is obtained; the measured flow rate is multiplied by the correction factor to obtain the final actual measured value of the recirculated exhaust gas volume.

[0051] Example 2: A correction method for measuring engine exhaust gas flow rate, comprising the following steps:

[0052] 1) Collect the venturi inlet pressure signal P and the intake manifold pressure signal P22, and calculate the pressure difference signal ΔP between the venturi inlet and the intake manifold according to formula (2). The positive pressure difference can represent the forward flow, and the negative pressure difference can represent the reverse flow.

[0053] ΔP=P-P22..........(2);

[0054] 2) Calculate the single exhaust pulse cycle T seg The sum of internal pressure difference signals ΔP And the cumulative number of differential pressure signals ΔP, cnt, and record the largest differential pressure signal ΔP. MAX =MAX(ΔP) MAX ,ΔP);

[0055] 3) Record ΔP when the pulse period ends. SUM ,cnt,ΔP MAX ;

[0056] 4) Calculate the percentage of differential pressure integral. Then reset timer T and repeat steps 1), 2), and 3);

[0057] 5) Based on the integral ratio of pressure difference ΔP prop By referring to the table of correspondence between engine speed n and correction factor, the correction factor for the actual measured exhaust gas volume is obtained; the measured flow rate is multiplied by the correction factor to obtain the final actual measured value of the recirculated exhaust gas volume.

[0058] Example 3: A correction method for measuring engine exhaust gas flow rate, comprising the following steps:

[0059] 1) Collect the venturi inlet pressure signal P and the intake manifold pressure signal P22, and calculate the pressure difference signal ΔP between the venturi inlet and the intake manifold according to formula (2). The positive pressure difference can represent the forward flow, and the negative pressure difference can represent the reverse flow.

[0060] ΔP=P-P22..........(2);

[0061] 2) Calculate the single exhaust pulse cycle T seg The sum of internal pressure difference signals ΔP And the cumulative number of differential pressure signals ΔP, cnt, and record the largest differential pressure signal ΔP. MAX =MAX(ΔP) MAX ,ΔP);

[0062]

[0063] Where: T seg Exhaust pulse cycle, unit: s; τ: number of strokes; N: number of engine cylinders; n: engine speed, unit: r / min

[0064] 3) Record ΔP when the pulse period ends. SUM ,cnt,ΔP MAX ;

[0065] 4) Calculate the percentage of differential pressure integral. Then reset timer T and repeat steps 1), 2), and 3);

[0066] 5) Based on the integral ratio of pressure difference ΔP prop By referring to the table of correspondence between engine speed n and correction factor, the correction factor for the actual measured exhaust gas volume is obtained; the measured flow rate is multiplied by the correction factor to obtain the final actual measured value of the recirculated exhaust gas volume.

[0067] Example 4: A correction method for measuring engine exhaust gas flow rate, comprising the following steps:

[0068] 1) Collect the venturi inlet pressure signal P and the intake manifold pressure signal P22, and calculate the pressure difference signal ΔP between the venturi inlet and the intake manifold according to formula (2). The positive pressure difference can represent the forward flow, and the negative pressure difference can represent the reverse flow.

[0069] ΔP=P-P22..........(2);

[0070] 2) Calculate the single exhaust pulse cycle T seg The sum of internal pressure difference signals ΔP And the cumulative number of differential pressure signals ΔP, cnt, and record the largest differential pressure signal ΔP. MAX =MAX(ΔP) MAX ,ΔP);

[0071]

[0072] Where: T seg Exhaust pulse cycle, unit: s; τ: number of strokes; N: number of engine cylinders; n: engine speed, unit: r / min

[0073] 3) Record ΔP when the pulse period ends. SUM,cnt,ΔP MAX ;

[0074] 4) Calculate the percentage of differential pressure integral. Then reset timer T and repeat steps 1), 2), and 3);

[0075] 5) First, start with the pre-generated differential pressure integral ratio ΔP prop From the correspondence between engine speed n and correction coefficient, find the current ΔP. prop The correction coefficient corresponding to n is then multiplied by the actual measured exhaust gas volume to correct the actual measured exhaust gas volume.

[0076] Example 5: A correction method for measuring engine exhaust gas flow rate, comprising the following steps:

[0077] 1) Collect the venturi inlet pressure signal P and the intake manifold pressure signal P22, and calculate the pressure difference signal ΔP between the venturi inlet and the intake manifold according to formula (2). The positive pressure difference can represent the forward flow, and the negative pressure difference can represent the reverse flow.

[0078] ΔP=P-P22..........(2);

[0079] 2) Calculate the single exhaust pulse cycle T seg The sum of internal pressure difference signals ΔP And the cumulative number of differential pressure signals ΔP, cnt, and record the largest differential pressure signal ΔP. MAX =MAX(ΔP) MAX ,ΔP);

[0080]

[0081] Where: T seg Exhaust pulse cycle, unit: s; τ: number of strokes; N: number of engine cylinders; n: engine speed, unit: r / min

[0082] 3) Record ΔP when the pulse period ends. SUM ,cnt,ΔP MAX ;

[0083] 4) Calculate the percentage of differential pressure integral. Then reset timer T and repeat steps 1), 2), and 3);

[0084] 5) First, start with the pre-generated differential pressure integral ratio ΔP prop From the correspondence between engine speed n and correction coefficient, find the current ΔP. propThe correction coefficient corresponding to n is then multiplied by the actual measured exhaust gas volume to correct for the actual measured exhaust gas volume; the differential pressure integral percentage ΔP prop The relationship between engine speed n and correction coefficient is obtained based on the ratio of theoretical exhaust gas volume to actual measured exhaust gas volume for each stable operating condition.

[0085] Example 6: Taking a four-stroke six-cylinder engine as an example, exhaust pulse cycle When the engine speed is 1000 rpm / min, the pulse period T seg =20ms, when timer T is greater than or equal to T seg At that time, the pulse cycle ends. A correction method for measuring engine exhaust gas flow according to the present invention includes the following steps:

[0086] 1) Calculate the pressure difference signal ΔP between the venturi inlet and the intake manifold;

[0087] 2) Calculate the sum of the pressure difference signals within the pulse period, i.e., within 20ms. The number of these signals, cnt, is used as the basis for determining the maximum value ΔP among these signals. MAX =MAX(ΔP) MAX ,ΔP);

[0088] 3) Record ΔP when the pulse period ends. SUM ,cnt,ΔP MAX ;

[0089] 4) Calculate the percentage of differential pressure integral. Then reset timer T and repeat steps 1), 2), and 3);

[0090] 5) Based on the integral ratio of pressure difference ΔP prop By referring to the table of correspondence between engine speed n and correction coefficient, the correction coefficient for the actual measured exhaust gas volume can be obtained;

[0091] 6) Multiply the measured flow rate by the correction factor in step 5) to obtain the final actual measured value of the recirculated exhaust gas volume.

[0092] like Figure 4 The graph shows a comparison between the actual EGR flow rate and the corrected measured flow rate. The dashed line “…” in the graph represents the EGR flow rate measured by the independent flow meter, and the solid line “—” represents the corrected measured EGR flow rate. Figure 5The graph compares the actual EGR flow rate with the uncorrected measured flow rate. The dashed line "..." represents the EGR flow rate measured by an independent flow meter, and the solid line "—" represents the uncorrected measured EGR flow rate. With an engine speed of 800 rpm, torque of 1300 Nm, and EGR valve opening of 40%, the EGR flow rate measured by the independent flow meter was 18.6 kg / h, the uncorrected flow rate was 9 kg / h, and the corrected flow rate was 17.5 kg / h. The correction effect is significant.

[0093] The foregoing has shown and described the basic principles and main structural features of the present invention. The present invention is not limited to the above examples; various changes and modifications can be made without departing from the spirit and scope of the invention, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

[0094] It should be noted that the above description of the technical solutions is exemplary, and this specification may be embodied in different forms and should not be construed as limiting it to the technical solutions set forth herein. Rather, providing these descriptions will ensure that the disclosure of this invention is thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Furthermore, the technical solutions of this invention are defined only by the scope of the claims.

[0095] The shapes, dimensions, ratios, angles, and figures disclosed in the description of various aspects of this specification and claims are merely examples, and therefore, this specification and claims are not limited to the details shown. In the following description, detailed descriptions of relevant known functions or configurations will be omitted where it would be determined that they unnecessarily obscure the focus of this specification and claims.

[0096] When using the terms “comprising,” “having,” and “including” as described in this specification, there may be another part or other part unless used, and the terms used are generally singular but may also be plural.

[0097] It should be noted that although various components may appear and be described in this specification using terms such as "first," "second," "top," "bottom," "one side," "the other side," "one end," "the other end," etc., these components and parts should not be limited by these terms. These terms are only used to distinguish one component and part from another. For example, without departing from the scope of this specification, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component; top and bottom components may, under certain circumstances, be interchanged or converted; and components at one end and the other end may have the same or different performance characteristics.

[0098] When describing positional relationships, for example, when the positional order is described as "on," "above," "below," and "next," situations where they are not in contact or are in contact may be included, unless words or terms such as "exactly" or "directly" are used. If it is mentioned that the first element is "on" the second element, it does not mean that the first element must be above the second element in the drawing. The upper and lower parts of the components will change depending on the viewing angle and orientation. Therefore, in the drawings or in actual construction, situations where the first element is "on" the second element can include situations where the first element is "below" the second element and situations where the first element is "above" the second element. When describing temporal relationships, situations where the steps are not consecutive may be included when describing "after," "following," "subsequently," and "before," unless "exactly" or "directly" is used. Features of various embodiments of the invention may be combined or spliced ​​together in part or in whole, and may be implemented in various different configurations as will be fully understood by those skilled in the art. Embodiments of the invention may be implemented independently of each other or may be implemented together in an interdependent relationship.

[0099] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention should be considered within the protection scope of the present invention.

Claims

1. A correction method for measuring engine exhaust gas flow rate, characterized in that: Includes the following steps: 1) Calculate the pressure difference signal ΔP between the venturi inlet and the intake manifold; 2) Calculate the single exhaust pulse cycle T seg The sum of internal pressure difference signals ΔP And the cumulative number of differential pressure signals ΔP, cnt, and record the largest differential pressure signal ΔP. MAX =MAX(ΔP) MAX ,ΔP); 3) Record ΔP when the pulse period ends. SUM ,cnt,ΔP MAX ; 4) Calculate the integral percentage of pressure difference ΔP prop Then reset timer T and repeat steps 1), 2), and 3); where: 5) Based on the integral ratio of pressure difference ΔP prop By referring to the table of correspondence between engine speed n and correction factor, the correction factor for the actual measured exhaust gas volume is obtained; the measured flow rate is multiplied by the correction factor to obtain the final actual measured value of the recirculated exhaust gas volume.

2. The correction method for measuring engine exhaust gas flow rate according to claim 1, characterized in that: Step 1) The specific steps are as follows: Collect the venturi inlet pressure signal P and the intake manifold pressure signal P22, and calculate the pressure difference signal ΔP between the venturi inlet and the intake manifold according to formula (2). ΔP=P-P22.......... (2).

3. The correction method for measuring engine exhaust gas flow rate according to claim 1, characterized in that: In step 2), Wherein: T seg Exhaust pulse cycle, unit: s; τ: number of strokes; N: number of engine cylinders; n: engine speed, unit: r / min.

4. The correction method for measuring engine exhaust gas flow rate according to claim 3, characterized in that: T seg It takes 20ms.

5. The correction method for measuring engine exhaust gas flow rate according to claim 3, characterized in that: N＝6。 6. The correction method for measuring engine exhaust gas flow rate according to claim 3, characterized in that: n = 1000 rpm / min.

7. The correction method for measuring engine exhaust gas flow rate according to claim 3, characterized in that: τ = 4.

8. The correction method for measuring engine exhaust gas flow rate according to claim 1, characterized in that: Step 5) involves the following steps: First, the pre-generated differential pressure integral ratio ΔP prop From the correspondence between engine speed n and correction coefficient, find the current ΔP. prop The correction coefficient corresponding to n is then multiplied by the actual measured exhaust gas volume to correct the actual measured exhaust gas volume.

9. The correction method for measuring engine exhaust gas flow rate according to claim 8, characterized in that: The relationship between the differential pressure integral percentage ΔPprop and the engine speed n and the correction coefficient is obtained based on the ratio of the theoretical exhaust gas volume to the actual measured exhaust gas volume for each stable operating condition.

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