A METHOD FOR DETERMINING AIR MASS FLOW IN AN ENGINE
FIELD
[0001] The present disclosure relates to the field automobiles. In particular, the present disclosure relates to method for determining the air mass flow in an engine.
BACKGROUND
[0002] Measurement of intake airflow is an important operation in vehicles. Conventionally, the intake airflow measurement is performed by the ECU (Electronic Control Unit) of the vehicle via an HFM (Heated Flow Meter) sensor, also known as MAF (Manifold Air Flow) sensor. However, in the conventional methods for measuring the intake airflow, the ECU does not take into account the changes in the volumetric efficiency due to restriction or changes in airflow path. The intake airflow measurement is determined based on a lookup table, which is pre-fed to the ECU. In accordance with the recent norms, an engine is required to operate in multiple modes, which frequently changes the amount of airflow into engine based on exhaust gas recirculated and intake throttle valve actuation. As such, the intake airflow calculation based on one lookup table becomes unreliable.
[0003] There is, therefore, felt a need for a method to determine the intake airflow, which can accurately gauge the intake airflow for different modes of operation of the engine.
SUMMARY
[0004] The present disclosure envisages a method for determining an air mass flow in an engine based on change in the volumetric efficiency. The method comprises the following steps:

- determining a raw volumetric efficiency of the engine based on a first set of predetermined parameters;
- determining a volumetric efficiency corrected for EGR position based on raw volumetric efficiency and a second set of predetermined parameters;
- determining a raw air mass flow into the engine based on the raw volumetric efficiency and a third set of predetermined parameters;
- determining an EGR air mass flow into the engine based on the volumetric efficiency corrected for the EGR position and the third set of predetermined parameters;
- calculating a difference between the raw air mass flow into the engine and the EGR air mass flow into the engine; and
- determining a corrected air mass flow into the engine based on the difference between the raw air mass flow into the engine and the EGR mass flow into the engine.
[0005] In one embodiment, the first set of predetermined parameters includes speed of the engine and fuel injection quantity.
[0006] In one embodiment, the second set of parameters include EGR valve position, speed of the engine and fuel injection quantity.
[0007] In one embodiment, the third set of parameters include boost pressure, boost temperature and speed of the engine.
[0008] In another embodiment, the boost pressure is measured using sensor placed on the intake manifold, and the corrected air mass flow is calculated using ideal gas equation.
[0009] The present disclosure further envisages a method for determining an air mass flow in the engine based on change in the volumetric efficiency. The method comprises the following steps:

- determining the raw volumetric efficiency of the engine based on first set of predetermined parameters;
- determining a volumetric efficiency corrected for EGR position based on the raw volumetric efficiency and a second set of predetermined parameters;
- determining a volumetric efficiency corrected for ITV position based on the volumetric efficiency corrected for EGR position and a third set of predetermined parameters;
- determining a corrected volumetric efficiency based on the volumetric efficiency corrected for ITV position and a fourth set of predetermined parameters;
- determining a corrected mass air mass flow into the engine based on the corrected volumetric efficiency and a fifth set of predetermined parameters.
BRIEF DESCRIPTION OF DRAWING
[0010] The aspects and other features of the subject matter will be better understood with regard to the following description, appended claims, and accompanying figures. The use of the same reference number in different figures indicates similar or identical items.
[0011] Fig. 1 illustrates a schematic view of a first determination unit, in accordance with one implementation of the present invention.
[0012] Fig. 2 illustrates a schematic view of a second determination unit, in accordance with one implementation of the present invention.
[0013] Fig. 3 illustrates a schematic view of a second determination unit, in accordance with another implementation of the present invention.
[0014] Fig. 4 illustrates a schematic view of a first determination unit, in accordance with another implementation of the present invention.

[0015] Fig. 5 illustrates a schematic view of a first determination unit, in accordance with yet another implementation of the present invention.
[0016] Fig. 6 illustrates a schematic view of the entire process of determining the corrected intake airflow after taking into account the EGR valve position, the ITV valve position, the ambient temperature, and the ambient pressure.
[0017] Figure 7 illustrates a block diagram depicting the steps involved in a method for determining the air mass flow in an engine based on change in the volumetric efficiency, in accordance with one implementation of the present invention.
[0018] Figure 8 illustrates a block diagram depicting the steps involved in a method for determining the air mass flow in an engine based on change in the volumetric efficiency, in accordance with another implementation of the present invention.
DETAILED DESCRIPTION
[0019] The intake airflow is required to be measured for determining the exhaust flow which is the primary input for after treatment controller. As emission norms are getting stringent by the day, the requirement for precise estimation of airflow is quintessential for precise control in emissions.
[0020] The intake airflow, in accordance with the present invention, is estimated based on the following parameters:

[0021] Typically, the intake airflow is estimated as function of volumetric efficiency, measured boost pressure and temperature. The above mentioned parameters change due to operation of Exhaust Gas Recirculation (EGR) and Intake Throttle Valve (ITV) on an engine; hence, the ideal gas equation is used to estimate the fresh airflow and airflow with EGR.
[0022] The ideal gas equation for determination of fresh air mass flow is as follows:
M2i = 0.3484 x (P2i x Vbase)/T2i
[0023] The ideal gas equation for determination of airflow with EGR is as follows:
M22 = 0.3484 x (P22 x VCOrr)/T22 Wherein,

P21 = p22 = Boost Pressure value from Manifold Air Pressure (MAP) sensor T2i = Intake air Temperature (Modelled value) T22 = Intake air Temperature from MAP sensor
[0024] The EGR Flow is then determined by using the following formula:
M21 - M22 = EGR Flow
[0025] Reference is hereinafter directed to Fig. 1, where Fig. 1 illustrates a schematic view of a first determination unit 10. The first determination unit 10 is configured to determine the volumetric efficiency of the engine. Typically, the volumetric efficiency of an engine is determined by taking into account the speed of the engine and the fuel injection quantity. The typical determination unit is pre-fed with a lookup table having volumetric efficiency value against engine spend and fuel injection quantity. This conventional method for determining the volumetric efficiency, however, does not take into account the ITV position or the EGR valve position, which is changing depending upon the mode of operation of engine. As such, the conventional method of determining the volumetric efficiency of the engine is inefficient to determine the volumetric efficiency of the engine having different operational modes, which is now a requirement in the recent norms, e.g., Bharat Stage VI norms.
[0026] This drawback of the conventional method of determining the volumetric efficiency is overcome by the first determination unit 10, as envisaged in the present invention. As seen in Fig. 1, the first determination unit 10 takes into account the effect of the ITV position as well as the EGR valve position apart from the engine speed and the fuel injection quantity. The first determination unit 10 first determines raw volumetric efficiency based on the engine speed, fuel injection quantity, and the pre-fed lookup table. Subsequent to that, the determination unit 10 determines the volumetric efficiency of the multiple mode engine operation by considering the EGR valve position and ITV position by correcting the

raw volumetric efficiency to obtain the corrected volumetric efficiency. The accuracy of airflow calculation is further improved by considering the environmental pressure and temperature condition.
[0027] Reference is hereinafter directed to Fig. 2, wherein Fig. 2 illustrates a schematic view of a second determination unit 12 for determining the intake airflow based on the volumetric efficiency and the ideal gas equation, as previously stated in the present disclosure. The second determination unit 12 is coupled to the first determination unit 10 from where the second determination unit 12 receives the raw volumetric efficiency value and the corrected volumetric efficiency values. The second determination unit 12 determines the intake airflow using the volumetric efficiency values (raw and corrected), the engine speed, the boost pressure value, and the boost temperature value to determine the intake airflow (raw and corrected) using the ideal gas equation.
[0028] Another implementation of the second determination unit 12 is illustrated in Fig. 3. Referring to Fig. 3, the second determination unit 12 determines the intake airflow as follows:
M2i = 0.3484 x (P22 x Vbase)/T2i
[0029] Where VbaSe is the raw volumetric efficiency and M21 is raw intake airflow value. The VbaSe is determined based on the engine speed, fuel injection quantity, and the pre-fed lookup table of the volumetric efficiency value based on the engine speed and the fuel injection quantity. The pressure and temperature values are obtained via the MAP sensor. The raw intake airflow is the airflow without the correction factor of the ITV position and the EGR valve position.
[0030] To accommodate of the effect of the EGR valve position, the volumetric efficiency of the engine needs to be determined with reference to the EGR valve position. This is done by the first determination unit 10.

An exemplary implementation of the first determination unit 10 is illustrated in Fig. 4. Referring to Fig. 4, the change in volumetric efficiency due to the activation of exhaust gas recirculation valve is extracted from a lookup table and curve based on valve position and engine operating speed and fuel injection quantity, which is stored in the first determination unit 10. The product of correction factor provided in the curve based on the valve position and the change in volumetric efficiency value fed in look up table provides the EGR valve position based Volumetric efficiency correction.
[0031] The volumetric efficiency thus obtained is subtracted from the raw volumetric efficiency (VbaSe)- This EGR corrected volumetric efficiency (VEGRCorr) is used to calculate the intake airflow with consideration to EGR using the ideal gas equation, where Intake air pressure (P22) and temperature(T22) required for calculation are measured from TMAP sensor. The equation is as follows:
M22 = 0.3484 X (P22 X VEGRcorr)/T22
[0032] Now, M22 is the intake airflow that takes into account the EGR valve position but not the ITV position. To determine the change in volumetric efficiency owing to the ITV position, another exemplary implementation of the first determination unit 10 is illustrated in Fig. 5. Referring to Fig. 5, the change in the volumetric efficiency due to the activation of Intake throttle is extracted from a lookup table and curve based on valve position, engine operating speed and fuel injection quantity, which is stored in the first determination unit 10. The product of correction factor provided in curve based on the valve position and the change in volumetric efficiency value fed in look up table provides the Intake throttle valve position based Volumetric efficiency correction.
[0033] The volumetric efficiency thus obtained is subtracted from the raw volumetric efficiency. In case of both valve operation (EGR valve and ITV), both the correction values will be subtracted from the raw volumetric

efficiency. The effect of environmental pressure and temperature on volumetric efficiency is also accounted by providing correction values using pre-fed curves for both pressure and temperature. The volumetric efficiency obtained after the above-mentioned correction is termed as Corrected Volumetric efficiency (VCorr) and using this value along with TMAP sensor values (P22, T22) corrected intake airflow is calculated using the following equation:
M22 = 0.3484 X (P22 X VCorr)/T22
[0034] It is to be noted that the difference between the raw intake airflow M21 and EGR corrected intake airflow provides the EGR Flow in to the engine.
[0035] Fig. 6 illustrates the entire process of determining the corrected intake airflow after taking into account the EGR valve position, the ITV valve position, the ambient temperature, and the ambient pressure using the first determination unit 10 and the second determination unit 12, as discussed in the previous sections with reference to Fig. 1 through Fig. 5.
[0036] In accordance with the present invention, the Figure 7 illustrates a block diagram depicting the steps involved in a method 100 for determining the air mass flow in an engine based on change in the volumetric efficiency. The order in which the method 100 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method or any alternative methods. Additionally, individual blocks may be deleted from the method without departing from the spirit and scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.

[0037] At block 102, the method 100 includes determining a raw volumetric efficiency of the engine based on a first set of predetermined parameters. In an embodiment, first set of predetermined parameters includes speed of the engine and fuel injection quantity. In an embodiment, the determination of the raw volumetric efficiency is performed by the first determination unit 10.
[0038] At block 104, the method 100 includes determining a volumetric efficiency corrected for EGR position based on raw volumetric efficiency and a second set of predetermined parameters. In an embodiment, the second set of parameters include EGR valve position, speed of the engine and fuel injection quantity. In an embodiment, the determination of the volumetric efficiency corrected for EGR position is performed by the first determination unit 10.
[0039] At block 106, the method 100 includes determining a raw air mass flow into the engine based on the raw volumetric efficiency and a third set of predetermined parameters. In an embodiment, the third set of parameters include boost pressure, boost temperature and speed of the engine. In an embodiment, the determination of the raw air mass flow into the engine is determined by the second determination unit 12.
[0040] At block 108, the method 100 includes calculating a difference between the raw air mass flow into the engine and the EGR air mass flow into the engine. In an embodiment, the calculation of the difference between the raw air mass flow and the EGR air mass flow is performed by the second determination unit 12.
[0041] At block 110, the method 100 includes determining a corrected air mass flow into the engine based on the difference between the raw air mass flow into the engine and the EGR mass flow into the engine. In an embodiment, the determination of a corrected air mass flow into the engine based on the difference between the raw air mass flow into the

engine and the EGR mass flow is performed by the second determination unit 12.
[0042] In accordance with another implementation of the present invention, the Figure 8 illustrates a block diagram depicting the steps involved in a method 200 for determining the air mass flow in an engine based on change in the volumetric efficiency. The order in which the method 200 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method or any alternative methods. Additionally, individual blocks may be deleted from the method without departing from the spirit and scope of the subject matter described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof.
[0043] At step 202, the method 200 includes determining the raw volumetric efficiency of the engine based on first set of predetermined parameters. In an embodiment, first set of predetermined parameters includes speed of the engine and fuel injection quantity. In an embodiment, the determination of the raw volumetric efficiency is performed by the first determination unit 10.
[0044] At block 204, the method 200 includes determining a volumetric efficiency corrected for EGR position based on the raw volumetric efficiency and a second set of predetermined parameters. In an embodiment, the second set of parameters include EGR valve position, speed of the engine and fuel injection quantity. In an embodiment, the determination of the volumetric efficiency corrected for EGR position is performed by the first determination unit 10.
[0045] At block 206, the method 200 includes determining a volumetric efficiency corrected for ITV position based on the volumetric efficiency corrected for EGR position and a third set of predetermined parameters. In

an embodiment, the third set of predetermined parameters includes intake throttle valve position, speed of the engine and fuel injection quantity. In an embodiment, determination of the volumetric efficiency corrected for ITV position is performed by the first determination unit 10.
[0046] At block 208, the method 200 includes determining a corrected volumetric efficiency based on the volumetric efficiency corrected for ITV position and a fourth set of predetermined parameters. In an embodiment, the fourth set of predetermined parameters includes environmental pressure and environmental temperature. In an embodiment, the determination of the corrected volumetric efficiency is performed by the first determination unit 10.
[0047] At block 210, the method 200 includes determining a corrected mass air mass flow into the engine based on the corrected volumetric efficiency and a fifth set of predetermined parameters. In an embodiment, the fifth set of predetermined parameters include boost temperature, boost pressure and speed of the engine. In an embodiment, the determination of the corrected mass air mass flow is performed by the second determination unit 12.
[0048] Although embodiments for method for determining air mass flow in an engine have been described in language specific to structural features and/or methods, it is to be understood that the invention is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as exemplary embodiments of the system and the method described herein.

WE CLAIM:
1. A method for determining an air mass flow in an engine based on
change in the volumetric efficiency, said method comprising:
o determining a raw volumetric efficiency of the engine based
on a first set of predetermined parameters; o determining a volumetric efficiency corrected for EGR
position based on raw volumetric efficiency and a second
set of predetermined parameters; o determining a raw air mass flow into the engine based on
the raw volumetric efficiency and a third set of
predetermined parameters; o determining an EGR air mass flow into the engine based
on the volumetric efficiency corrected for the EGR position
and the third set of predetermined parameters o calculating a difference between the raw air mass flow into
the engine and the EGR air mass flow into the engine; and o determining a corrected air mass flow into the engine
based on the difference between the raw air mass flow into
the engine and the EGR mass flow into the engine.
2. The method as claimed in claim 1, wherein the first set of predetermined parameters includes speed of the engine and fuel injection quantity.
3. The method as claimed in claim 1, wherein the second set of parameters include EGR valve position, speed of the engine and fuel injection quantity.

4. The method as claimed in claim 1, wherein the third set of parameters include boost pressure, boost temperature and speed of the engine.
5. The method as claimed in claim 1, wherein the boost pressure is measured using sensor placed on the intake manifold.
6. The method as claimed in claim 1 wherein the corrected air mass flow is calculated using ideal gas equation.
7. A method for determining an air mass flow in the engine based on change in the volumetric efficiency, said method comprising:
o determining the raw volumetric efficiency of the engine
based on first set of predetermined parameters; o determining a volumetric efficiency corrected for EGR
position based on the raw volumetric efficiency and a
second set of predetermined parameters; o determining a volumetric efficiency corrected for ITV
position based on the volumetric efficiency corrected for
EGR position and a third set of predetermined parameters; o determining a corrected volumetric efficiency based on the
volumetric efficiency corrected for ITV position and a fourth
set of predetermined parameters; o determining a corrected mass air mass flow into the engine
based on the corrected volumetric efficiency and a fifth set
of predetermined parameters.

8. The method as claimed in claim 8, wherein the first set of predetermined parameters includes speed of the engine and fuel injection quantity.
9. The method as claimed in claim 8, wherein the second set of predetermined parameters includes EGR valve position, speed of the engine and fuel injection quantity.

10. The method as claimed in claim 8, wherein the third set of predetermined parameters includes intake throttle valve position, speed of the engine and fuel injection quantity.
11. The method as claimed in claim 8, wherein the fourth set of predetermined parameters includes environmental pressure and environmental temperature.
12. The method as claimed in claim 8, wherein the fifth set of predetermined parameters include boost temperature, boost pressure and speed of the engine.
13. The method as claimed in claim 8, wherein the corrected air mass flow is calculated using ideal gas equation.