RU2552879C2 - Method of diesel control and control device to this end - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention may be used in supercharge diesels. Proposed method is intended for diesel (1) including pipe (2) to feed air into diesel (1), diesel exit gas exhaust pipe (3), diesel soot filter (31) arranged in exhaust pipe (3) and exit gas circulation system (50, 60) to return exhaust gas into diesel (1). Exhaust gas circulation system comprises off-gas circulation line (60) to receive exhaust gas from exhaust pipe (3) downstream of soot filter (31). Method of diesel control consists in setting the threshold (Sth) for amount of soot getting into off gas circulation system. Besides, actual amount (Saa) of said sooth is defined. Now, the procedure of off-gas circulation line protection is actuated if actual amount (Saa) is higher than said threshold (Sth). Besides it discloses the device to this end.

EFFECT: reduced sooting.

12 cl, 2 dwg

Description

Field and level of technology

The present invention relates generally to a method of operating a diesel engine system, in particular to a turbocharged diesel engine system.

A turbocharged diesel engine system typically comprises a diesel engine having an intake manifold and an exhaust manifold, an intake manifold for supplying clean air from the environment to the intake manifold, an exhaust manifold for discharging exhaust gas from the exhaust manifold into the environment, and a turbocharger that comprises a compressor located in the inlet pipe to compress the air flow passing through it and a turbine located in the exhaust pipe to drive the lump pressor.

The inlet pipe contains an intercooler, denoted as the charge air cooler (ONV), which is located after the compressor of the turbocompressor, to cool the air flow before it reaches the intake manifold.

The exhaust pipe contains a diesel oxidizing catalyst (DON), which is located after the turbine of the turbocharger, to reduce the content of residual hydrocarbons and carbon oxides contained in the exhaust gas, and a diesel particulate filter (DSP), which is located after the DON, to trap solid particles of a diesel engine ( soot) and removing them from the exhaust gas.

In order to reduce pollutant emissions, most turbocharged diesel engine systems currently include an exhaust gas recirculation (EGR) system that is installed to return an appropriate amount of exhaust gas and mix it with clean fresh air entering the diesel engine.

This amount of exhaust gas reduces the amount of nitrogen oxides (NO _x ) generated in the diesel engine during the combustion process.

Existing ROG systems comprise an ROG pipeline for fluidly connecting the exhaust manifold to the intake manifold, an ROG cooler located in the ROG pipeline, and a valve device for controlling exhaust gas flow through the ROG pipeline.

Since the EGR valve connects the exhaust manifold directly to the intake manifold, it determines the EGR by the short-path system (RCP), which returns the high-temperature exhaust gas.

Improved Horn systems, in addition, contain an additional HOG pipe for fluid connection of the exhaust pipe after the DSF with the inlet pipe in front of the turbocharger compressor, an additional HOG cooler located in the additional Horn pipe, and an additional valve device for regulating the exhaust gas flow through the additional Horn pipe .

In fact, in these advanced HOR systems, a long-path HOG (RHL) is provided which includes the aforementioned additional HOG pipe and a portion of the inlet pipe between the additional HOG pipe and the diesel engine.

The purpose of the RPD is to return the exhaust gas having a lower temperature than the temperature of the exhaust gas returned by the RCP.

In accordance with this design, advanced EGR systems are configured to return exhaust gas partly through the RCP and partly through the RDP to thereby maintain the temperature of the intake air in the intake manifold at an optimal intermediate level in any engine operation mode.

The total amount of exhaust gas and the flow rate of exhaust gas coming from the RPD are determined by the electronic control unit (ECU) according to empirically determined data sets or tables in which the total amount of EGR and the flow rate of the RPD are compared with a variety of engine operating parameters, such as, for example, engine speed, engine load and engine coolant temperature.

The efficiency of the air-conditioning system is usually related to the efficiency of its individual components, including an additional cooler, an additional valve device, a turbocharger compressor, and a charge air cooler.

It was found that the effectiveness of each component of the RPD, as a rule, more or less rapidly increases depending on several conditions, such as, for example, the aging of a given component, the heat load to which this component is exposed, and the composition of the exhaust gas passing through this component.

These conditions are taken into account when designing the components of the RPD with the aim of implementing the RPD, the overall effectiveness of which, as you can expect, will remain at a level above the minimum acceptable value for the entire period of the RPD.

Since the RPD is configured to receive exhaust gas after the DSF, its components are usually designed taking into account the conditions under which the exhaust gas entering it contains only a minimal amount of soot.

However, in the case of a decrease in the filtering characteristics of the DSF due to, for example, possible cracks during the life of the real engine, accidental damage or breakdowns, it may turn out that after the DSF and, therefore, in the RPD, an unexpectedly large amount of soot is contained.

The soot contained in the exhaust gas is usually hot and humid, as a result of which it exhibits a tendency to adhere to the internal walls of the RPD pipelines and to the mechanical organs of the RPD components, thereby reducing their effectiveness below the minimum acceptable value until the end of the expected service life.

For example, soot deposits in a heat exchanger, such as an RPD or ONV cooler, cause premature loss of cooling efficiency and throughput, increasing pollutant emissions and degrading diesel engine performance.

In relation to this problem, in fact, only diagnostic methods were proposed based on monitoring the effectiveness of the components of the RPD, which can detect soot deposits in the components of the RPD from the very beginning, but are not able to prevent them.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a strategy for protecting components of an RPD from excessive soot deposition to prevent or at least noticeably reduce the aforementioned problem.

The objective of one embodiment of the present invention is achieved by the features of the present invention set forth in the independent claims. The dependent claims list useful and / or advantageous features of the present invention.

According to the present invention, a method for operating a diesel engine system comprising a diesel engine, an inlet pipe for supplying clean intake air to a diesel engine, an exhaust pipe for discharging exhaust gas from a diesel engine, a diesel particulate filter located in the exhaust pipe, and an exhaust gas recirculation system for returning exhaust gas to a diesel engine, the exhaust gas recirculation system including exhaust gas recirculation along a long path (RDP), which receives exhaust gas from the exhaust pipe after a diesel particulate filter.

The method according to the invention includes the steps of

set the soot threshold (Sth) for the amount of soot entering the RPD (60),

determine the actual amount of soot (Saa) entering the RPD (60), and

start the protection procedure of the RPD if the actual amount of soot (Saa) exceeds the soot threshold (Sth).

The aforementioned protection procedure, as a rule, involves reducing the amount of soot entering the RPD, thereby reducing the risk of premature loss of effectiveness of the RPD.

In accordance with an embodiment of the present invention, determining the actual amount of soot entering the RPD includes:

determination of the amount of soot entering the DSF,

determination of the filtration efficiency of DSF and

the calculation of the amount of soot entering the RPD, as a function of the aforementioned specific amount of soot entering the DSF, and the filtering efficiency of the DSF.

The amount of soot entering the DSF can be estimated using the model of soot in a failed engine.

The DSF filtration efficiency can be defined as a function of the amount of soot entering the DSF.

According to an embodiment of the present invention, determining a DSF filtration efficiency includes:

determination of the amount of soot that is delayed by the DSF, and

calculating the filtering efficiency of the DSF as a function of said delayed amount of soot and the amount of soot entering the DSF.

In this case, the amount of soot that is delayed by the DSP can be estimated using the soot filter clogging model.

In accordance with another embodiment of the present invention, determining a DSF filtration efficiency includes:

determination of the amount of soot leaving the DSF, and

calculating the efficiency of the DSF filtration as a function of the amount of soot leaving the DSF and the amount of soot entering the DSF.

In this case, the amount of soot exiting the DSF can be measured using a soot sensor located in the exhaust pipe after the DSF itself.

According to another embodiment of the present invention, an RPD protection procedure typically involves adjusting at least one combustion control parameter that affects soot formation in a diesel engine in order to reduce soot formation itself.

Such a combustion control parameter may be, for example, the total amount of exhaust gas returned by the EGR system, including the RCP and the RPD, or the amount of exhaust gas returned by the RPG relative to the total amount.

In fact, while the diesel engine system is operating normally, these combustion control parameters are usually adjusted according to the corresponding setting, which is determined by the ECU as a function of one or more operating parameters of the engine, such as, for example, engine speed, engine load, mass intake air flow and engine coolant temperature.

In this regard, the protection procedure of the RDP in the preferred embodiment provides for the determination of a correction factor applied to the set point in order to reduce soot formation.

This correction factor can be defined as a function of the difference between the calculated amount of soot and the soot threshold and ultimately as a function of one or more engine operating parameters, such as, for example, engine speed, engine load, intake air mass and coolant temperature engine.

The method in accordance with the present invention can be implemented in the form of a computer program containing the source code of the program for performing all the steps of this method of the present invention, and in the form of a software product containing means for executing a computer program.

According to a preferred embodiment, the software product comprises a microprocessor control device for an internal combustion engine, for example an engine ECU, in which the program is stored in such a way that the control device defines the present invention in the same way as the method. In this case, when the control device executes the computer program, all the steps of this method are carried out in accordance with the present invention.

The method in accordance with the present invention can also be implemented in the form of an electromagnetic signal, the signal being modulated to transmit a sequence of information bits corresponding to the computer program performing all the steps of this method of the present invention.

Brief Description of the Drawings

The present invention is described below by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a turbocharged diesel engine system; and

FIG. 2 is a flowchart illustrating an operation method in accordance with the present invention.

Description of a preferred embodiment of the invention

The present invention is described below with reference to a car turbocharged diesel engine system.

The turbocharged diesel engine system comprises a diesel engine 1 having an intake manifold 10 and an exhaust manifold 11, an intake manifold 2 for supplying clean air from the environment to the intake manifold 10, an exhaust manifold 3 for discharging exhaust gas from the exhaust manifold 11 into the environment, and a turbocharger 4, which comprises a compressor 40 located in the inlet pipe 2 for compressing the air flow passing through it and a turbine 41 for driving the compressor located in the exhaust pipe 3 compressor 40.

The turbocharged diesel engine system further comprises an intercooler 20, also shown as a charge air cooler (ONV), which is located in the intake pipe 2 after the compressor 40 of the turbocharger 4, for cooling the air flow before it reaches the intake manifold 10, and a valve 21 located in the inlet pipe between the ONV 20 and the intake manifold 10.

The turbocharged diesel engine system further comprises a diesel oxidizing converter (DON) 30, which is located in the exhaust pipe 3 after the turbine 41 of the turbocharger 4, to reduce the content of residual hydrocarbons and carbon oxides contained in the exhaust gas, and a diesel particulate filter (DSF ) 31, which is located in the exhaust pipe 3 after DON 30, to retain solid particles of the diesel engine (soot) and remove them from the exhaust gas.

In order to reduce pollutant emissions, a turbocharged diesel engine system comprises an exhaust gas recirculation (EGR) system for returning exhaust gas and supplying it to diesel engine 1.

The EGR system includes a first EGR pipe 50 for fluidly connecting the exhaust manifold 11 to the intake manifold 10, a first EGR cooler 51 for cooling the exhaust gas, and a first electronically controlled valve device 52 for determining the exhaust gas flow rate through the first EGR pipe 50.

Since the first EGR pipe 50 connects the exhaust manifold 11 directly to the intake manifold 10, it determines the EGR by the short path (RCP), which returns the high temperature exhaust gas.

The Horn system, in addition, contains a second Horn pipe 60, which fluidly connects the branch point 32 of the exhaust pipe 3 with the input point 2 of the intake pipe 2, and a second Horn cooler 61 located in the second Horn pipe 60.

The branching point 32 is located after the DSF 31, while the input point 22 is located after the air filter 23 and in front of the compressor 40 of the turbocharger 4.

The exhaust gas flow rate through the second EGR pipe 60 is determined by a second electronically controlled three-way valve 62, which is located at the inlet point 22.

In fact, a long-path EGR (RPG) is provided in the HOG system, which includes a second HOG pipe 60, including a second HOG cooler 61, and a section of the intake pipe 2 between the inlet point 22 and the diesel engine 1, including the second valve 62, compressor 40 turbocharger 4, ONV 20 and valve 21.

Passing along the HOG along a long path, the exhaust gas becomes much colder than the exhaust gas that passes through the first HOG pipe 50, thereby reaching the intake manifold 10 at a lower temperature.

The turbocharged diesel engine system is controlled by a microprocessor controller (ECU), which is installed to generate control signals and feed them to the valves 52 and 62 to return the exhaust gas partially through the RCP and partially through the RDP, thereby maintaining the temperature of the input air in the intake manifold 10 for optimal intermediate level in any engine operation mode.

In fact, the ECB is designed to determine the setpoint for the total amount of EGR that is supplied to the exhaust manifold 10, to determine the setpoint for the flow of the RDP and to control the valves 52 and 62 in accordance with this.

These settings are determined using the ECU according to empirically determined data sets or tables in which the total number of EGR and RPM flow rate are respectively compared with a variety of engine operating parameters, such as, for example, engine speed, engine load, intake air mass flow rate and coolant temperature engine.

In accordance with the present invention, the ECB is also installed to protect the circuit of the RDP and its components (mainly the second cooler 61, compressor 40 and ONV 20) from excessive soot deposition in case of loss of filtering efficiency of the DSF 31.

The security strategy implemented by the ECB is schematically illustrated in FIG. 2.

This strategy involves setting a soot threshold Sth corresponding to the maximum allowable amount of soot that can enter the RPD.

By the amount of carbon black is meant the mass consumption of carbon black, which can be expressed, for example, in units of milligrams of carbon black per second, per minute, per hour or per kilometer of the distance traveled by the vehicle in which the diesel engine system is installed.

The soot threshold Sth can be determined using an empirical calibration operation that is performed on a diesel engine test system that has the same characteristics as the real one.

Said calibration operation involves setting the minimum allowable duration of the RDP.

The minimum permissible duration of the RPD in the preferred embodiment coincides with the full life of the vehicle, which is usually set at least 160,000 km, taking into account polluting emissions.

In addition, the calibration operation provides the minimum acceptable value of the parameter of the effectiveness of the RDP.

Since the effectiveness of the RPD, as a rule, is limited by the efficiency of each component of the RPD, the effectiveness of the component of the RPD that is most sensitive to soot pollution can be selected as a parameter of the effectiveness of the RPD.

For example, the RDP efficiency parameter may be the cooling efficiency of the second CROW cooler 61, the mechanical efficiency of the compressor 40, or the cooling efficiency of the NVG 20, depending on which the components show a more rapid deterioration in performance due to soot clogging.

In fact, it has been found that the most sensitive component is probably the RPD cooler 61, which results in the cooling efficiency of the latter. essentially can be used as a parameter of the effectiveness of the RDP.

Finally, the calibration operation provides an empirical determination of the maximum amount of soot entering the RPD, for which the selected parameter of the effectiveness of the RPD remains at a level above the specified minimum allowable value until the end of the specified period of the RPD.

Then, the resulting soot amount is taken as the soot threshold Sth and is stored in the memory module of the diesel engine system.

In addition, the protection strategy provides for controlling the amount of soot Saa, which actually enters the RPD during the actual operation of the diesel engine system.

To determine the amount of soot Saa, this strategy involves determining the amount of soot DPFin entering the DSF 31 and the filtering efficiency of the DPF DPFeff.

The DPFeff value can be estimated using the well-known model of soot in a failed engine.

According to the present example, the DPFeff value can be determined in two different ways.

The first method involves determining the amount of soot DPFtrap, which is delayed by the DPF 31, and calculating the filtering efficiency of the DPF DPFeff as the ratio of the delayed amount of DPFtrap soot to the total amount of DPFin soot entering the DPF 31, in accordance with the equation:

$$DPFeff=\frac{DPFtrap}{DPFin}$$

(one)

in which the amount of soot DPFtrap can be estimated using the well-known model of clogging of DSF soot using a pressure drop on the DSF 31.

The second method involves determining the amount of soot DPFout that exits the DSF 31 and calculating the filtering efficiency of the DPF DPFeff as the difference between the unit efficiency and the ratio of the output amount of DPFout soot to the total amount of DPFin soot entering the DSF 31 in accordance with the equation:

$$DPFeff=\mathrm{one}-\frac{DPFout}{DPFin}$$

(2)

in which the amount of soot DPFout exiting the DSF 31 can be estimated using the known soot sensor 33 located in the exhaust pipe 3 after the DSF 31.

The DPFeff filtering efficiency and the amount of soot DPFin entering the DSF 31 are then transferred to the CM computing module, which calculates the amount of soot Saa entering the DPS as a function of the amount of DPFin soot entering the DSP and the DPFeff filtering efficiency.

In fact, the amount of soot Saa can be calculated using the equation:

$$Saa=DPFin\cdot (\mathrm{one}-DPFeff)\cdot \frac{M_{LRE}}{M_{LRE}+M_{out}}$$

(3)

in which M _LRE is the mass flow rate of exhaust gas directed to the second EGR pipe 60, and M _out is the mass flow rate of exhaust gas emitted by exhaust pipe 3 into the environment.

M _LRE and M _out can be measured using mass flow sensors (not shown), which are respectively located in the second EGR pipe 60 and in the exhaust pipe 3 after the branch point 32.

The amount of soot Saa is supplied to the adder A1, which calculates the difference E between the stored soot threshold Sth and the amount of soot Saa.

Then the difference E is supplied to the control device G, which is set to selectively start the protection procedure of the RDP in response to the mentioned difference E.

In particular, if the actual amount of soot Saa does not exceed the soot threshold Sth, this means that the RPD is not at risk of premature loss of efficiency.

In this case, the difference E is not negative, and the control device G remains inactive, as a result of which the diesel engine system continues to function normally.

If, on the contrary, the actual amount of carbon black Saa exceeds the carbon black threshold Sth, this means that the RPD is at risk of more rapid premature loss of efficiency than expected.

In this case, the difference E is negative, and the control device G starts the protection procedure of the RDP.

The RPD protection procedure, as a rule, provides for the regulation of at least one combustion control parameter that affects the formation of soot in the diesel engine 1, in order to reduce the formation of soot itself.

In the present example, the control device G is configured to reduce the total amount of exhaust gas returned by the EGR system, including the RPD and RCP, and / or to reduce the consumption of exhaust gas returned by the EGR.

In fact, it is known that a decrease in the total amount of HOR and / or a decrease in the flow rate of the RPD causes a limitation of the formation of soot in the diesel engine 1, which therefore leads to a decrease in the input of soot into the RPD.

As described above, the total amount of EGR and the RPM flow rate are usually controlled according to the corresponding EGRsp and LREsp settings, which are determined by the ECU as a function of one or more engine operating parameters, such as engine speed, engine load, intake air mass flow rate and cooling temperature engine fluid.

In this regard, the control device G provides a correction factor Cegr and / or a correction factor Clre, which are applied respectively to the mentioned settings EGRsp and LREsp in order to reduce soot formation.

The correction factor Cegr and / or Clre is determined proportionally to the modulus of the difference E and can ultimately be adjusted as a function of one or more engine operating parameters, such as, for example, engine speed, engine load, mass intake air flow rate and engine coolant temperature.

Indeed, the correction coefficients Cegr and Clre are determined by empirically determined data sets or tables M1 and M2, in which the correction coefficients Cegr and Clre are compared with the difference modulus E and one or more of the engine operating parameters.

In more detail, the correction coefficient Cegr of the total amount of EGR is fed to the adder A2, which calculates the difference between the normal EGRsp setting and the Cegr correction coefficient in order to provide a lower EGRsp * setting used for operating the diesel engine system.

Similarly, the RDP flow correction coefficient Clre is applied to an adder A3, which calculates the difference between the normal LREsp setting and the Clre correction coefficient to provide a lower LREsp * setting used to operate the diesel engine system.

If the control device G provides regulation of the flow rate of the air flow control only, the ECU must regulate the flow of the air flow control unit in order to obtain a constant EGRsp setting of the total number of EGR.

If subsequently the soot estimate at the output of the DSF Saa does not exceed the soot threshold Sth, adder A1 will give a non-negative difference E, and the control device G will deactivate the protection procedure by setting the correction factors Cegr and Clre to zero, so that the ECB will normally control the diesel engine system.

Although the present invention has been described with reference to some preferred embodiments and specific applications, it should be understood that the above description should be considered as an example and not as a limitation. Those skilled in the art will recognize that various modifications of the individual embodiments are within the scope of the appended claims. Therefore, the present invention is not limited to the described embodiments, but has the scope defined only by the claims.

Claims (12)

1. A method of operating a diesel engine system comprising a diesel engine (1), an inlet pipe (2) for supplying clean inlet air to a diesel engine (1), an exhaust pipe (3) for discharging exhaust gas from a diesel engine (1), diesel soot a filter (31) located in the exhaust pipe (3), and an exhaust gas recirculation system (50, 60) for returning exhaust gas to a diesel engine (1), wherein the exhaust gas recirculation system includes an exhaust gas recirculation path (60), which the receives exhaust gas from the exhaust pipe (3) after the diesel particulate filter (31), characterized in that:
set the soot threshold (Sth) for the amount of soot entering the exhaust gas recirculation path (60),
determine the actual amount of soot (Saa) entering the exhaust gas recirculation path (60), and
start the procedure for protecting the exhaust gas recirculation path if the actual amount of soot (Saa) exceeds the soot threshold (Sth). 2. The method according to p. 1, characterized in that when determining the actual amount of soot (Saa) entering the exhaust gas recirculation path (60):
determine the amount of soot (DPFin) entering the diesel particulate filter (31),
determine the efficiency (DPFeff) of a diesel particulate filter and
calculate the amount of soot (Saa) entering the exhaust gas recirculation path (60) as a function of the determined amount of soot (DPFin) entering the diesel particulate filter (31) and the filtering efficiency (DPFeff) of the diesel particulate filter. 3. The method according to claim 2, characterized in that the amount of soot (DPFin) entering the diesel particulate filter (31) is evaluated using a model of soot in a failed engine. 4. The method according to p. 2, characterized in that the filtering efficiency (DPFeff) of the diesel particulate filter is determined as a function of the amount of soot entering the diesel particulate filter (31). 5. The method according to p. 4, characterized in that when determining the efficiency (DPFeff) of filtering a diesel particulate filter:
determine the amount of soot that is retained by the diesel particulate filter (31), and
calculate the filtering efficiency (DPFeff) of the diesel particulate filter as a function of the trapped amount of soot and the amount of soot (DPFin) entering the diesel particulate filter (31). 6. The method according to p. 5, characterized in that the amount of soot that is delayed by the diesel particulate filter (31) is evaluated using the model of clogging of the diesel particulate filter with soot. 7. The method according to p. 4, characterized in that when determining the efficiency (DPFeff) of filtering a diesel particulate filter:
determine the amount of soot leaving the diesel particulate filter (31),
calculate the filtering efficiency (DPFeff) of the diesel particulate filter as a function of the amount of soot exiting the diesel particulate filter (31) and the amount of soot (DPFin) entering the diesel particulate filter (31). 8. The method according to p. 7, characterized in that the amount of soot leaving the diesel particulate filter (31) is measured using a soot sensor (33). 9. The method according to p. 1, characterized in that the procedure for protecting the exhaust gas recirculation path involves the regulation of at least one combustion control parameter that affects the formation of soot in a diesel engine (1), thereby reducing soot formation. 10. The method according to p. 9, characterized in that the procedure for protecting the exhaust gas recirculation path determines the correction factor (Cegr, Clre) applied to the setpoint (EGRsp, LREsp) of the combustion control parameter. 11. The method according to claim 9, characterized in that the combustion control parameter is the total amount of exhaust gas returned by the exhaust gas recirculation system (50, 60) and / or the amount of exhaust gas returned by the exhaust gas recirculation path (60). 12. A control device, characterized in that it contains a computer program that includes computer code for implementing the method according to any one of the preceding paragraphs.

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