CN115288865B - EGR flow obtaining method and device - Google Patents
EGR flow obtaining method and device Download PDFInfo
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- CN115288865B CN115288865B CN202210959123.2A CN202210959123A CN115288865B CN 115288865 B CN115288865 B CN 115288865B CN 202210959123 A CN202210959123 A CN 202210959123A CN 115288865 B CN115288865 B CN 115288865B
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- 238000000034 method Methods 0.000 title claims abstract description 34
- 230000035485 pulse pressure Effects 0.000 claims abstract description 192
- 239000007789 gas Substances 0.000 claims abstract description 109
- 238000002347 injection Methods 0.000 claims abstract description 19
- 239000007924 injection Substances 0.000 claims abstract description 19
- 239000002912 waste gas Substances 0.000 claims abstract description 19
- 239000000446 fuel Substances 0.000 claims description 11
- 238000010586 diagram Methods 0.000 description 11
- 239000000243 solution Substances 0.000 description 6
- 238000013461 design Methods 0.000 description 2
- 230000010349 pulsation Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0047—Controlling exhaust gas recirculation [EGR]
- F02D41/0065—Specific aspects of external EGR control
- F02D41/0072—Estimating, calculating or determining the EGR rate, amount or flow
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/45—Sensors specially adapted for EGR systems
- F02M26/46—Sensors specially adapted for EGR systems for determining the characteristics of gases, e.g. composition
- F02M26/47—Sensors specially adapted for EGR systems for determining the characteristics of gases, e.g. composition the characteristics being temperatures, pressures or flow rates
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Analytical Chemistry (AREA)
- Exhaust-Gas Circulating Devices (AREA)
Abstract
The application discloses a method and a device for acquiring EGR flow, wherein the method comprises the following steps: exhaust pipe pressure obtained by an exhaust gas pressure sensor of the EGR system; the exhaust pulse pressure is obtained by utilizing the exhaust pipe pressure, the oil injection quantity and the engine rotating speed; obtaining inlet pulse pressure of the venturi meter by using the exhaust pulse pressure, the inlet temperature of the EGR cooler and the inlet temperature of the EGR valve; the exhaust gas flow is obtained from the inlet pulse pressure of the venturi meter. The technical scheme that this application provided has saved venturi differential pressure sensor, has saved the cost. And this application is through calculating exhaust pulse pressure, can fully consider the flow direction of waste gas, deduct the reverse flow of waste gas, and then can obtain forward flowing waste gas flow more accurately to according to waste gas flow come accurate control exhaust emission, and then avoid the exhaust emission to exceed the standard.
Description
Technical Field
The application relates to the technical field of engine emission, in particular to an EGR flow obtaining method and device.
Background
Engines for exhaust gas recirculation (EGR, exhaust Gas Recirculation) use venturi meters to test data, and currently use differential pressure sensors for the pressure at the inlet and outlet of the venturi meter. However, in some cases, irregular sensor drift of the differential pressure sensor may occur, which may cause inaccuracy in the calculated exhaust gas flow, and when the exhaust gas flow is calculated inaccurately, inaccuracy in NOx control of the exhaust gas emission system may be caused, thereby deteriorating fuel consumption rate.
Disclosure of Invention
In order to solve the technical problems, the application provides an EGR flow obtaining method and device, which can accurately obtain the exhaust gas flow and further safely discharge the tail gas.
In order to achieve the above object, the technical solution provided in the embodiments of the present application is as follows:
the application provides a method for acquiring EGR flow, which comprises the following steps:
exhaust pipe pressure obtained by an exhaust gas pressure sensor of the EGR system;
obtaining exhaust pulse pressure by using the exhaust pipe pressure, the fuel injection quantity and the engine rotating speed;
obtaining an inlet pulse pressure of the venturi meter by using the exhaust pulse pressure, the EGR cooler inlet temperature and the EGR valve inlet temperature;
and obtaining the flow of the exhaust gas according to the inlet pulse pressure of the venturi flowmeter.
Preferably, the exhaust pulse pressure is obtained by using the exhaust pipe pressure, the fuel injection amount and the engine speed, and specifically includes:
taking the engine speed and the oil injection quantity as an X axis and a Y axis of Map respectively;
acquiring a pulse pressure crest value and a pulse pressure trough value based on the Map and the exhaust pipe pressure;
and obtaining the exhaust pulse pressure by using the pulse pressure crest value and the pulse pressure trough value.
Preferably, the obtaining the inlet pulse pressure of the venturi meter by using the exhaust pulse pressure, the inlet temperature of the EGR cooler and the inlet temperature of the EGR valve specifically includes:
calibrating an EGR cooler differential pressure Map by taking the exhaust gas flow and the EGR cooler inlet temperature as a horizontal axis and a vertical axis respectively; the exhaust gas flow and the EGR valve inlet temperature are respectively used as a horizontal axis and a vertical axis to calibrate an EGR valve pressure difference Map;
and obtaining the inlet pulse pressure of the venturi flowmeter according to the EGR cooler pressure difference Map, the EGR valve pressure difference Map and the exhaust pulse pressure.
Preferably, the obtaining the inlet pulse pressure of the venturi flowmeter according to the EGR cooler differential pressure Map, the EGR valve differential pressure Map and the exhaust pulse pressure specifically includes:
obtaining a Venturi inlet pressure trough value according to the pulse pressure trough value in the exhaust pulse pressure, the EGR cooler pressure difference Map and the EGR valve pressure difference Map; obtaining a venturi inlet pressure peak value according to a pulse pressure peak value in the exhaust pulse pressure, the EGR cooler differential pressure Map and the EGR valve differential pressure Map;
and obtaining the inlet pulse pressure of the venturi flowmeter according to the venturi inlet pressure trough value and the venturi inlet pressure crest value.
Preferably, the method for obtaining the exhaust gas flow according to the inlet pulse pressure of the venturi flowmeter specifically comprises the following steps:
and obtaining the exhaust gas flow according to the inlet pulse pressure, the inlet pipe pressure, the exhaust gas density, the Reynolds number and the Venturi flow coefficient of the Venturi flowmeter.
The application provides an EGR flow's acquisition device includes:
an exhaust pipe pressure obtaining unit for obtaining an exhaust pipe pressure using an exhaust gas pressure sensor of the EGR system;
an exhaust pulse pressure obtaining unit for obtaining an exhaust pulse pressure using the exhaust pipe pressure, the fuel injection amount, and the engine speed;
an inlet pulse pressure obtaining unit for obtaining an inlet pulse pressure of the venturi meter using the exhaust pulse pressure, the EGR cooler inlet temperature, and the EGR valve inlet temperature;
and the exhaust gas flow obtaining unit is used for obtaining the exhaust gas flow according to the inlet pulse pressure of the venturi flowmeter.
Preferably, the exhaust pulse pressure obtaining unit is specifically configured to take the engine speed and the fuel injection amount as an X axis and a Y axis of Map, respectively; acquiring a pulse pressure crest value and a pulse pressure trough value based on the Map and the exhaust pipe pressure; and obtaining the exhaust pulse pressure by using the pulse pressure crest value and the pulse pressure trough value.
Preferably, the inlet pulse pressure obtaining unit is specifically configured to calibrate an EGR cooler differential pressure Map with an exhaust gas flow and an EGR cooler inlet temperature as a horizontal axis and a vertical axis, respectively; the exhaust gas flow and the EGR valve inlet temperature are respectively used as a horizontal axis and a vertical axis to calibrate an EGR valve pressure difference Map; and obtaining the inlet pulse pressure of the venturi flowmeter according to the EGR cooler pressure difference Map, the EGR valve pressure difference Map and the exhaust pulse pressure.
Preferably, the inlet pulse pressure obtaining unit obtains an inlet pulse pressure of a venturi meter according to the EGR cooler differential pressure Map, the EGR valve differential pressure Map, and the exhaust pulse pressure, and specifically includes: obtaining a Venturi inlet pressure trough value according to the pulse pressure trough value in the exhaust pulse pressure, the EGR cooler pressure difference Map and the EGR valve pressure difference Map; obtaining a venturi inlet pressure peak value according to a pulse pressure peak value in the exhaust pulse pressure, the EGR cooler differential pressure Map and the EGR valve differential pressure Map;
and obtaining the inlet pulse pressure of the venturi flowmeter according to the venturi inlet pressure trough value and the venturi inlet pressure crest value.
Preferably, the exhaust gas flow obtaining unit is specifically configured to obtain the exhaust gas flow according to the inlet pulse pressure, the inlet pipe pressure, the exhaust gas density, the reynolds number and the venturi flow coefficient of the venturi flowmeter.
According to the technical scheme, the application has the following beneficial effects:
according to the EGR flow obtaining method, a venturi differential pressure sensor is omitted, and cost is saved. And this application is through calculating exhaust pulse pressure, can fully consider the flow direction of waste gas, deduct the reverse flow of waste gas, and then can obtain forward flowing waste gas flow more accurately to according to waste gas flow come accurate control exhaust emission, and then avoid the exhaust emission to exceed the standard.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an EGR system provided herein;
FIG. 2 is a flow chart of a method for obtaining EGR flow provided herein;
FIG. 3 is a schematic illustration of one exhaust pulse pressure and venturi inlet pulse pressure provided herein;
FIG. 4 is a schematic diagram of the exhaust pulse pressure acquisition provided herein;
FIG. 5 is a schematic diagram of a trough architecture for achieving venturi inlet pulse pressure provided herein;
FIG. 6 is a graph of a peak architecture for obtaining venturi inlet pulse pressure provided herein;
FIG. 7 is a schematic diagram of the exhaust flow obtained in accordance with the present application;
fig. 8 is a schematic diagram of an EGR flow obtaining apparatus according to an embodiment of the present application.
Detailed Description
In order to better understand the solution provided by the embodiments of the present application, before describing the method provided by the embodiments of the present application, a scenario of application of the solution of the embodiments of the present application is described.
Referring to FIG. 1, a schematic diagram of an EGR system is provided herein.
As can be seen from fig. 1, an exhaust pipe is provided with an exhaust gas pressure sensor 10 (abbreviated as exhaust pipe pressure P), and an EGR cooler 20 (which may be provided with a check valve (or may be provided with a check valve depending on the system)) and an EGR cooler post-temperature sensor 30, an EGR valve 40, a venturi flow meter 50, an intake pressure on an intake manifold (abbreviated as intake pressure p_in) and a temperature sensor 60 are connected in this order along the flow direction of exhaust gas.
Wherein, cyl1-Cyl6 are six cylinders of the engine.
Because there is a possibility that the exhaust gas flows back, that is, flows back, from top to bottom, and from bottom to top in the exhaust gas discharge process, in order to accurately obtain the flow rate of the exhaust gas, the flow direction of the exhaust gas needs to be identified, and the difference between the two directions can be used to obtain the accurate flow rate of the exhaust gas. The technical solutions provided in the present application are described in detail below with reference to the accompanying drawings. In addition, in order to save the cost, the pressure difference sensor of venturi has been saved in this application, but obtains venturi exit pressure difference through calculation, because pressure difference sensor's cost is higher, consequently, the technical scheme that this application provided still can reduce cost.
In order to make the above objects, features and advantages of the present application more comprehensible, embodiments accompanied with figures and detailed description are described in further detail below.
Referring to fig. 2, a flowchart of an EGR flow rate obtaining method is provided in the present application.
The method for acquiring the EGR flow comprises the following steps:
s201: exhaust pipe pressure obtained by an exhaust gas pressure sensor of the EGR system;
since the EGR system is equipped with an exhaust gas pressure sensor, the exhaust pipe pressure can be obtained directly by the exhaust gas pressure sensor.
S202: obtaining exhaust pulse pressure by using the exhaust pipe pressure, the fuel injection quantity and the engine rotating speed;
for a multi-cylinder diesel engine, the pressure on the exhaust side repeatedly appears with regular pressure pulsation (exhaust pulse pressure for short) as the exhaust valve opens and closes. I.e. the actual exhaust pulse pressure is in the form of pulses, e.g. the waveform of the exhaust pressure resembles a sine wave.
Since the exhaust pulse pressure is in the form of pulses, there are peaks and valleys, and it is necessary to obtain the peaks and valleys of the exhaust pulse pressure according to the injection amount and the engine speed.
Because the exhaust gas has backflow, the flow direction of the exhaust gas can be represented by the exhaust gas pulse pressure in a pulse fluctuation mode, wherein when the exhaust gas pulse pressure is larger than the intake pressure, the flow direction of the exhaust gas is positive, namely the exhaust gas flows from top to bottom; conversely, when the exhaust pulse pressure is less than the intake pressure, it is indicated that the exhaust gas flow direction is reversed, i.e., the exhaust gas flows from bottom to top. If the positive flow of exhaust gas is positive and the negative flow is negative, the total flow should be the sum of positive and negative. Obviously, after the flow direction of the exhaust gas is considered, the flow of the exhaust gas can be obtained more accurately, and then the exhaust emission control is performed, so that the exceeding of the exhaust emission is avoided.
S203: obtaining an inlet pulse pressure of the venturi meter by using the exhaust pulse pressure, the EGR cooler inlet temperature and the EGR valve inlet temperature;
since there are also an EGR cooler, an EGR cooled temperature sensor and an EGR valve between the exhaust pipe and the inlet of the venturi meter, the inlet pulse pressure of the venturi meter needs to be obtained from the exhaust pulse pressure, the EGR cooler inlet temperature and the EGR valve inlet temperature.
Since the exhaust pulse pressure is sinusoidal, the inlet pressure of the venturi meter is also pulsed, which becomes the inlet pulse pressure of the venturi meter.
S204: and obtaining the flow of the exhaust gas according to the inlet pulse pressure of the venturi flowmeter.
Since the intake pipe pressure becomes the outlet pressure of the venturi meter, the exhaust gas flow rate can be obtained from the intake pipe pressure and the inlet pulse pressure of the venturi meter, as well as the preset coefficient, the exhaust gas density.
According to the EGR flow obtaining method, a venturi differential pressure sensor is omitted, and cost is saved. And this application is through calculating exhaust pulse pressure, can fully consider the flow direction of waste gas, deduct the reverse flow of waste gas, and then can obtain forward flowing waste gas flow more accurately to according to waste gas flow come accurate control exhaust emission, and then avoid the exhaust emission to exceed the standard.
The specific procedures for obtaining the exhaust pulse pressure and the venturi inlet pulse pressure of the present application are described below with reference to the accompanying drawings.
Referring to FIG. 3, a schematic diagram of exhaust pulse pressure and venturi inlet pulse pressure is provided herein.
It can be seen that the two sine waves included are the exhaust pulse pressure and the modified venturi inlet pulse pressure, respectively, it being understood that these two sine waves are calculated for the present application and are not directly measurable by the sensor. In addition, the pulse pressure peak value and the pulse pressure trough value corresponding to the exhaust pulse pressure are also calibrated in the figure. The intake pressure p_in and the exhaust pipe pressure P can be directly measured by a sensor.
The exhaust pulse pressure is obtained by utilizing the exhaust pipe pressure, the oil injection quantity and the engine rotating speed, and the method specifically comprises the following steps of:
taking the engine speed and the oil injection quantity as an X axis and a Y axis of Map respectively;
acquiring a pulse pressure crest value and a pulse pressure trough value based on Map and the exhaust pipe pressure;
and obtaining the exhaust pulse pressure by using the pulse pressure crest value and the pulse pressure trough value.
Referring to fig. 4, a schematic diagram for obtaining exhaust pulse pressure is provided herein.
Since the exhaust pressure exists in a pulsating form, the exhaust pressure will have a great influence on the accuracy of the entire exhaust gas flow, and thus the time average pressure P (exhaust pipe pressure) needs to be corrected to capture the influence of the pulse on the exhaust gas flow, the exhaust pulse pressure has a peak value p_peak and a Trough value p_gauge, and thus the following two parameters are defined, the pulse peak coefficient c_pulse and the pulse Trough coefficient c_trough:
C_pulse＝(P_peak-P)/P；
C_Trough＝(P-P_tough)/P；
the pulse Peak coefficient c_pulse and the pulse Trough coefficient c_truugh are respectively calibrated into two maps (peak_map and tough_map), and the X and Y axes of the maps are respectively the engine speed and the fuel injection quantity. The exhaust pipe pressure P based on calibration Map and exhaust pressure sensor test can acquire the pulse pressure peak value P_peak and the pulse pressure trough value P_tool in real time, and meanwhile, calibration variables are the exhaust Valve opening duration valve_timing_C (which is a design constant) and the number of engine cylinders Cyl_num (the repetition number of pulse waves is determined), so that the Firing interval Angel_FIG is 720/Cyl_num degrees, and the function of the exhaust pulse pressure sine wave can be acquired according to the parameters.
And respectively calibrating an EGR cooler pressure difference Map (the horizontal axis is the exhaust gas flow, the vertical axis is the temperature after the EGR cooler) and an EGR valve pressure difference Map (the horizontal axis is the exhaust gas flow, the vertical axis is the EGR valve inlet temperature) in the engine along the flow direction of exhaust gas, and rapidly solving the pressure difference of key parts based on the Map, so that the peak value of the Venturi inlet pressure and the trough value of the inlet pressure are solved, and the Venturi inlet pulse pressure can be obtained by combining the opening duration, the ignition interval and the like.
Referring to fig. 5, a trough architecture diagram for achieving venturi inlet pulse pressure is provided herein.
Obtaining the inlet pulse pressure of the venturi flowmeter by using the exhaust pulse pressure, the inlet temperature of the EGR cooler and the inlet temperature of the EGR valve, wherein the method specifically comprises the following steps:
calibrating an EGR cooler differential pressure Map by taking the exhaust gas flow and the EGR cooler inlet temperature as a horizontal axis and a vertical axis respectively; the exhaust gas flow and the EGR valve inlet temperature are respectively used as a horizontal axis and a vertical axis to calibrate an EGR valve pressure difference Map;
and obtaining the inlet pulse pressure of the venturi flowmeter according to the EGR cooler pressure difference Map, the EGR valve pressure difference Map and the exhaust pulse pressure.
Similarly, the inlet pulse pressure of the venturi meter needs to be obtained from the exhaust pipe pressure, the intake pressure, and the exhaust pulse pressure, similarly to the exhaust pulse pressure.
First, fig. 5 illustrates the process of venturi inlet pressure trough value p_low_venturi, obtaining EGR cooler pressure differential Map from exhaust gas flow and EGR cooler inlet temperature, and obtaining EGR valve pressure differential Map from exhaust gas flow and EGR valve inlet temperature. The coefficient p_diff_egr is obtained from the EGR cooler differential pressure Map, and the EGR valve differential pressure Map is obtained from the coefficient p_diff_value. And obtaining a Venturi inlet pressure trough value P_low_venturi according to the pulse pressure trough value P_tool of the exhaust pressure, the coefficient P_diff_egr and the coefficient P_diff_value.
Referring to fig. 6, a graph of peak architecture for obtaining venturi inlet pulse pressure is provided herein.
Fig. 5 illustrates the acquisition of the venturi inlet pressure trough value p_low_venturi, and fig. 6 illustrates the acquisition of the venturi inlet pressure peak value p_high_ven.
The difference between fig. 6 and fig. 5 is that the peak value p_peak, the coefficient p_diff_egr, and the coefficient p_diff_value of the exhaust pressure are used to obtain the peak value p_high_ven of the venturi inlet pressure in fig. 6, and otherwise are the same as in fig. 5, and are not described herein.
Referring to fig. 7, a schematic diagram of obtaining exhaust gas flow is provided herein.
Based on the obtained Venturi inlet pulse pressure and the obtained air inlet pipe pressure, the real-time front-back pressure difference value of the Venturi flowmeter can be obtained, if the system is provided with a one-way valve, only the area with the pressure difference value larger than 0 is integrated in the logic for calculating the exhaust gas flow, and if the system is not provided with the one-way valve, the integration is needed in the whole circulation. According to the average value P1 of the inlet and inlet pipe pressure of the Venturi flowmeter, the temperature T behind the EGR cooler and the gas constant R, the density rho=P1/(R x T) of the exhaust gas can be obtained, according to the assumed exhaust gas flow m and the geometric parameter d (constant value) of the Venturi design throat, the Reynolds number Re of the air flow in the Venturi can be obtained according to the exhaust gas density rho, the relation between the Reynolds number and the Venturi flow coefficient can be used for obtaining the flow coefficient Cd of the Venturi flowmeter under the working condition, the exhaust gas flow in the whole working cycle can be obtained by integrating the exhaust gas density, the pressure difference between the front and the rear of the Venturi, the flow coefficient and the incompressible correction coefficient of the exhaust gas in real time, the exhaust gas flow is compared with the assumed exhaust gas flow in real time, and finally the error rate of the exhaust gas flow is required to be less than 0.05%, namely the calculated convergence is considered to be the accurate value.
Because the technical scheme that this application provided can accurately obtain the waste gas flow, consequently, can carry out tail gas emission's control according to accurate waste gas flow, and then improve tail gas emission quality, avoid tail gas emission to exceed standard.
Based on the method for acquiring the EGR flow provided in the foregoing embodiment, the present application further provides an apparatus for acquiring the EGR flow, which is described in detail below with reference to the accompanying drawings.
Referring to fig. 8, a schematic diagram of an EGR flow obtaining apparatus according to an embodiment of the present application is shown.
The EGR flow obtaining device provided in this embodiment includes:
an exhaust pipe pressure obtaining unit 801 for obtaining an exhaust pipe pressure using an exhaust gas pressure sensor of the EGR system;
since the EGR system is equipped with an exhaust gas pressure sensor, the exhaust pipe pressure can be obtained directly by the exhaust gas pressure sensor.
An exhaust pulse pressure obtaining unit 802 for obtaining an exhaust pulse pressure using the exhaust pipe pressure, the fuel injection amount, and the engine speed;
for a multi-cylinder diesel engine, the pressure on the exhaust side repeatedly appears with regular pressure pulsation (exhaust pulse pressure for short) as the exhaust valve opens and closes. I.e. the actual exhaust pulse pressure is in the form of pulses, e.g. the waveform of the exhaust pressure resembles a sine wave.
Since the exhaust pulse pressure is in the form of pulses, there are peaks and valleys, and it is necessary to obtain the peaks and valleys of the exhaust pulse pressure according to the injection amount and the engine speed.
Because the exhaust gas has backflow, the flow direction of the exhaust gas can be represented by the exhaust gas pulse pressure in a pulse fluctuation mode, wherein when the exhaust gas pulse pressure is larger than the intake pressure, the flow direction of the exhaust gas is positive, namely the exhaust gas flows from top to bottom; conversely, when the exhaust pulse pressure is less than the intake pressure, it is indicated that the exhaust gas flow direction is reversed, i.e., the exhaust gas flows from bottom to top. If the positive flow of exhaust gas is positive and the negative flow is negative, the total flow should be the sum of positive and negative. Obviously, after the flow direction of the exhaust gas is considered, the flow of the exhaust gas can be obtained more accurately, and then the exhaust emission control is performed, so that the exceeding of the exhaust emission is avoided.
An inlet pulse pressure obtaining unit 803 for obtaining an inlet pulse pressure of the venturi meter using the exhaust pulse pressure, the EGR cooler inlet temperature, and the EGR valve inlet temperature;
since there are also an EGR cooler, an EGR cooled temperature sensor and an EGR valve between the exhaust pipe and the inlet of the venturi meter, the inlet pulse pressure of the venturi meter needs to be obtained from the exhaust pulse pressure, the EGR cooler inlet temperature and the EGR valve inlet temperature.
Since the exhaust pulse pressure is sinusoidal, the inlet pressure of the venturi meter is also pulsed, which becomes the inlet pulse pressure of the venturi meter.
An exhaust gas flow obtaining unit 804 for obtaining an exhaust gas flow from the inlet pulse pressure of the venturi meter.
Since the intake pipe pressure becomes the outlet pressure of the venturi meter, the exhaust gas flow rate can be obtained from the intake pipe pressure and the inlet pulse pressure of the venturi meter, as well as the preset coefficient, the exhaust gas density.
The EGR flow obtaining device provided by the application omits a venturi differential pressure sensor and saves cost. And this application is through calculating exhaust pulse pressure, can fully consider the flow direction of waste gas, deduct the reverse flow of waste gas, and then can obtain forward flowing waste gas flow more accurately to according to waste gas flow come accurate control exhaust emission, and then avoid the exhaust emission to exceed the standard.
The exhaust pulse pressure obtaining unit is specifically used for taking the engine speed and the oil injection quantity as an X axis and a Y axis of Map respectively; acquiring a pulse pressure crest value and a pulse pressure trough value based on the Map and the exhaust pipe pressure; and obtaining the exhaust pulse pressure by using the pulse pressure crest value and the pulse pressure trough value.
The inlet pulse pressure obtaining unit is specifically used for calibrating an EGR cooler differential pressure Map by taking the exhaust gas flow and the EGR cooler inlet temperature as a horizontal axis and a vertical axis respectively; the exhaust gas flow and the EGR valve inlet temperature are respectively used as a horizontal axis and a vertical axis to calibrate an EGR valve pressure difference Map; and obtaining the inlet pulse pressure of the venturi flowmeter according to the EGR cooler pressure difference Map, the EGR valve pressure difference Map and the exhaust pulse pressure.
An inlet pulse pressure obtaining unit for obtaining inlet pulse pressure of the venturi flowmeter according to the EGR cooler pressure difference Map, the EGR valve pressure difference Map and the exhaust pulse pressure, wherein the inlet pulse pressure obtaining unit specifically comprises: obtaining a Venturi inlet pressure trough value according to the pulse pressure trough value in the exhaust pulse pressure, the EGR cooler pressure difference Map and the EGR valve pressure difference Map; obtaining a venturi inlet pressure peak value according to a pulse pressure peak value in the exhaust pulse pressure, the EGR cooler differential pressure Map and the EGR valve differential pressure Map;
and obtaining the inlet pulse pressure of the venturi flowmeter according to the venturi inlet pressure trough value and the venturi inlet pressure crest value.
And the exhaust gas flow obtaining unit is specifically used for obtaining the exhaust gas flow according to the inlet pulse pressure, the inlet pipe pressure, the exhaust gas density, the Reynolds number and the Venturi flow coefficient of the Venturi flowmeter.
From the above description of embodiments, it will be apparent to those skilled in the art that all or part of the steps of the above described example methods may be implemented in software plus necessary general purpose hardware platforms. Based on such understanding, the technical solutions of the present application may be embodied essentially or in a part contributing to the prior art in the form of a software product, which may be stored in a storage medium, such as a ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, a server, or a network communication device such as a media gateway, etc.) to perform the methods described in the embodiments or some parts of the embodiments of the present application.
It should be noted that, in the present description, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different manner from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the method disclosed in the embodiment, since it corresponds to the system disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the system part.
It should also be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The foregoing description of the disclosed embodiments, as well as many modifications to those embodiments to enable any person skilled in the art to make or use the disclosure, will be readily apparent to those of ordinary skill in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (6)
1. An EGR flow rate obtaining method is characterized by comprising the following steps:
exhaust pipe pressure obtained by an exhaust gas pressure sensor of the EGR system;
obtaining exhaust pulse pressure by using the exhaust pipe pressure, the fuel injection quantity and the engine rotating speed;
obtaining an inlet pulse pressure of the venturi meter by using the exhaust pulse pressure, the EGR cooler inlet temperature and the EGR valve inlet temperature;
obtaining exhaust gas flow according to inlet pulse pressure of the venturi flowmeter;
the method for obtaining the inlet pulse pressure of the venturi flowmeter by using the exhaust pulse pressure, the inlet temperature of the EGR cooler and the inlet temperature of the EGR valve specifically comprises the following steps:
calibrating an EGR cooler differential pressure Map by taking the exhaust gas flow and the EGR cooler inlet temperature as a horizontal axis and a vertical axis respectively; the exhaust gas flow and the EGR valve inlet temperature are respectively used as a horizontal axis and a vertical axis to calibrate an EGR valve pressure difference Map;
obtaining inlet pulse pressure of a venturi flowmeter according to the EGR cooler pressure difference Map, the EGR valve pressure difference Map and the exhaust pulse pressure;
the method for obtaining the flow of the waste gas according to the inlet pulse pressure of the venturi flowmeter specifically comprises the following steps:
and obtaining the exhaust gas flow according to the inlet pulse pressure, the inlet pipe pressure, the exhaust gas density, the Reynolds number and the Venturi flow coefficient of the Venturi flowmeter.
2. The method according to claim 1, wherein said using said exhaust pipe pressure, fuel injection amount and engine speed to obtain exhaust pulse pressure comprises:
taking the engine speed and the oil injection quantity as an X axis and a Y axis of Map respectively;
acquiring a pulse pressure crest value and a pulse pressure trough value based on the Map and the exhaust pipe pressure;
and obtaining the exhaust pulse pressure by using the pulse pressure crest value and the pulse pressure trough value.
3. The method according to claim 1, wherein said deriving an inlet pulse pressure of a venturi meter from said EGR cooler differential pressure Map, said EGR valve differential pressure Map and said exhaust pulse pressure, comprises in particular:
obtaining a Venturi inlet pressure trough value according to the pulse pressure trough value in the exhaust pulse pressure, the EGR cooler pressure difference Map and the EGR valve pressure difference Map; obtaining a venturi inlet pressure peak value according to a pulse pressure peak value in the exhaust pulse pressure, the EGR cooler differential pressure Map and the EGR valve differential pressure Map;
and obtaining the inlet pulse pressure of the venturi flowmeter according to the venturi inlet pressure trough value and the venturi inlet pressure crest value.
4. An EGR flow rate acquisition device, characterized by comprising:
an exhaust pipe pressure obtaining unit for obtaining an exhaust pipe pressure using an exhaust gas pressure sensor of the EGR system;
an exhaust pulse pressure obtaining unit for obtaining an exhaust pulse pressure using the exhaust pipe pressure, the fuel injection amount, and the engine speed;
an inlet pulse pressure obtaining unit for obtaining an inlet pulse pressure of the venturi meter using the exhaust pulse pressure, the EGR cooler inlet temperature, and the EGR valve inlet temperature;
an exhaust gas flow obtaining unit for obtaining an exhaust gas flow from an inlet pulse pressure of the venturi meter;
the inlet pulse pressure obtaining unit is specifically used for:
calibrating an EGR cooler differential pressure Map by taking the exhaust gas flow and the EGR cooler inlet temperature as a horizontal axis and a vertical axis respectively; the exhaust gas flow and the EGR valve inlet temperature are respectively used as a horizontal axis and a vertical axis to calibrate an EGR valve pressure difference Map; obtaining inlet pulse pressure of a venturi flowmeter according to the EGR cooler pressure difference Map, the EGR valve pressure difference Map and the exhaust pulse pressure;
the exhaust gas flow obtaining unit is specifically configured to: and obtaining the exhaust gas flow according to the inlet pulse pressure, the inlet pipe pressure, the exhaust gas density, the Reynolds number and the Venturi flow coefficient of the Venturi flowmeter.
5. The apparatus according to claim 4, wherein the exhaust pulse pressure obtaining unit is specifically configured to use an engine speed and an injection amount as an X-axis and a Y-axis of Map, respectively; acquiring a pulse pressure crest value and a pulse pressure trough value based on the Map and the exhaust pipe pressure; and obtaining the exhaust pulse pressure by using the pulse pressure crest value and the pulse pressure trough value.
6. The apparatus according to claim 4, wherein the inlet pulse pressure obtaining unit obtains an inlet pulse pressure of a venturi flow meter from the EGR cooler differential pressure Map, the EGR valve differential pressure Map, and the exhaust pulse pressure, specifically comprising: obtaining a Venturi inlet pressure trough value according to the pulse pressure trough value in the exhaust pulse pressure, the EGR cooler pressure difference Map and the EGR valve pressure difference Map; obtaining a venturi inlet pressure peak value according to a pulse pressure peak value in the exhaust pulse pressure, the EGR cooler differential pressure Map and the EGR valve differential pressure Map;
and obtaining the inlet pulse pressure of the venturi flowmeter according to the venturi inlet pressure trough value and the venturi inlet pressure crest value.
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