GB2540758A

GB2540758A - A long route EGR system for a turbocharged automotive system

Info

Publication number: GB2540758A
Application number: GB1513005.7A
Authority: GB
Inventors: Racca Alberto
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2015-07-23
Filing date: 2015-07-23
Publication date: 2017-02-01
Also published as: GB201513005D0

Abstract

A long route Exhaust Gas Recirculation (EGR) system 690 for an internal combustion engine 110 equipped with a turbocharger compressor 240 and with an electric compressor 600 being configured to direct air into an intake line 205 of the internal combustion engine 110, the long route EGR system 690 being provided with an EGR conduit 695 which fluidly connects an exhaust pipe (275, Fig. 1) of the internal combustion engine 110 with the intake line 205, EGR conduit 695 being provided with a first branch 650 stemming from a branching point 655 of the long route EGR conduit 695 for directing recirculated gas through the electric compressor 600 towards a mixing point 665 with the intake line 205 downstream of the turbocharger compressor 240. A second branch 670 may connect the first branch 650 to a point downstream of the primary compressor 240. A method of operating the EGR system 690 dependent on engine load conditions by regulating power supply to the electric compressor is also disclosed.

Description

A LONG ROUTE EGR SYSTEM FOR A TURBOCHARGED AUTOMOTIVE SYSTEM TECHNICAL FIELD

The technical field relates to a long route Exhaust Gas Recirculation (EGR) system for a turbocharged automotive system with an electric compressor.

BACKGROUND

Internal combustion engines may be provided with a forced air system such as a turbocharger in order to increase an engine’s efficiency and power by forcing extra air into the combustion chambers of the cylinders.

The turbocharger comprises a compressor rotationally coupled to a turbine.

In some automotive systems, the compressor may be assisted by an electric compressor. In these systems, a check-valve is positioned in a bypass branch of the electric machine in order to avoid any counterflow towards the turbocharger compressor during the operations of the electric compressor.

In order to reduce NOx polluting emissions, most turbocharged automotive systems comprise an exhaust gas recirculation (EGR) system, which is provided for routing back and mixing an appropriate amount of exhaust gas with the fresh induction air aspired into the engine.

Advanced EGR systems comprise a first EGR conduit which connects the exhaust manifold with the intake manifold, and a second EGR conduit which connects the exhaust line downstream of the aftertreatment systems to the intake line upstream the intake manifold and is connected therein by the interposition of three-way valve or by other means. The second EGR conduit defines a long route which comprises also a relevant portion of the exhaust line and a relevant portion of the intake line.

In this way, the long route EGR is effective for routing back to the intake manifold exhaust gas increasing the enthalpy to the turbine.

In the prior art, in steady state either at Full Load or in Part Load conditions of the engine, all the flow is directed to a charge air cooler upstream of the engine, bypassing the electric compressor.

In transient conditions, the electric compressor is activated and all the flow passes through it. The check-valve prevents any backflow from the outlet of the electric compressor towards the turbocharger compressor.

Nevertheless, some inefficiencies in Brake Specific Fuel Consumption (BSFC) may occur because of the throttling of the air plate in the three-way valve upstream of the turbocharger compressor, especially at low engine speeds and loads, where the engine backpressure is generally low and large amounts of EGR are required to contain the emissions.

An object of an embodiment disclosed is to improve the layout of the long route EGR system for an engine provided with an electric compressor with a view on achieving a valuable BSFC improvement.

This and other objects are achieved by the embodiments of the invention as defined in the independent claims. The dependent claims include preferred and/or advantageous aspects of said embodiments.

SUMMARY

An embodiment of the disclosure provides a long route Exhaust Gas Recirculation (EGR) system for an internal combustion engine equipped with a turbocharger compressor and with an electric compressor, the turbocharger compressor and the electric compressor being configured to direct air into an intake line of the internal combustion engine, the long route EGR system being provided with a long route EGR conduit which fluidly connects an exhaust pipe of the internal combustion engine with the intake line, the long route EGR conduit being provided with a first branch stemming from a branching point of the long route EGR conduit for directing recirculated gas through the electric compressor towards a mixing point with the intake line downstream of the turbocharger compressor.

An advantage of this embodiment is that the above layout of the long route EGR system allows to operate both the turbocharger compressor and the electric compressor in such a way that, during the actuation of the electric compressor, the recirculated exhaust gas is introduced into the main flow at a location downstream of the turbocharger compressor.

This allows a robust condensation protection, avoiding any issues in operations at low ambient temperatures.

According to another embodiment, the long route EGR system comprises a one-way valve located in a portion of the intake duct downstream of the turbocharger compressor.

An advantage of this embodiment is that it allows to direct an air flow towards the electric compressor in transient engine conditions.

According to another embodiment, a recirculating gas valve is provided in the first branch of the long route EGR system upstream of the electric compressor.

An advantage of this embodiment is that it allows to direct a recirculated gas flow towards the electric compressor in partial load engine conditions.

According to still another embodiment, the long route EGR circuit comprises a second branch connecting the one-way valve with a connecting point of the first branch, the connecting point being downstream of the recirculating gas valve.

An advantage of this embodiment is that the second branch allows to selectively direct a main air flow towards the electric compressor.

According to a further embodiment, the recirculating gas valve is an ON-OFF valve.

An effect of this embodiment is that it allows to regulate the mixing of the recirculated gas flow with the main air flow by regulating the power supplied to the electric compressor. This embodiment is also advantageous because power consumption required in the various operations of the system is very different for different engine operating points. Therefore, properly regulating the power supplied to the electric compressor allows for significant energy savings.

According to a further embodiment, the branching point of the long route EGR conduit is located downstream of a long route EGR cooler.

An effect of this embodiment is that the recirculated gas is directed towards the electric compressor at a suitable temperature.

Another aspect of the invention provides for a method of operating a long route EGR system for an internal combustion engine, the method comprising the steps of: - detecting an internal combustion engine partial load steady state; - actuating a one way valve in the intake duct to allow a main air flow in the intake duct downstream of the one way valve; - actuating a recirculating gas valve to allow a recirculated exhaust gas flow in the first branch of the long route EGR conduit; and - regulating a mixing of the recirculated exhaust gas with the main air flow downstream of the one way valve in the intake duct.

An advantage of this aspect is that it allows to operate both the turbocharger compressor and the electric compressor in such a way that, during the actuation of the electric compressor, the recirculated exhaust gas is introduced into the main flow at a location downstream of the turbocharger compressor.

This allows for a robust condensation protection, avoiding any issues in operations at low ambient temperatures.

Another advantage of this aspect is the possibility of decreasing the BSFC by a reduction of pumping losses, as no air throttling is required in front of the turbocharger compressor to recirculate the EGR gases at low loads.

According to another aspect of the invention, the step of regulating the mixing of the recirculated exhaust gas with the main air flow is performed by regulating the electrical power supplied to the electric compressor.

An advantage of this aspect is that, since the power consumption required in the various operations of the system is very different for different engine operating points, by properly regulating the power supplied to the electric compressor it is possible to obtain significant energy savings.

Another aspect of the invention provides for an apparatus for operating a long route EGR system for an internal combustion engine equipped with a turbocharger compressor and with an electric compressor, the turbocharger compressor and the electric compressor being configured to direct air into an intake line of the internal combustion engine, the apparatus comprising: - means for detecting an internal combustion engine partial load steady state; - means for actuating a one way valve in the intake duct to allow a main air flow in an intake duct downstream of the one way valve; - means for actuating the recirculating gas valve to allow a recirculated exhaust gas flow In a first branch of a long route EGR conduit; and - means for regulating a mixing of the recirculated exhaust gas with the main air flow downstream of the one way valve in the intake duct.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, wherein like numerals denote like elements, and in which:

Figure 1 shows an automotive system;

Figure 2 is a cross-section of an internal combustion engine belonging to the automotive system of figure 1;

Figures 3-5 show a portion of the automotive system of Figurel in three different operating conditions; and

Figure 6 is a flowchart representing an embodiment of the invention.

DETAILED DESCRIPTION

Exemplary embodiments will now be described with reference to the enclosed drawings without intent to limit application and uses.

Some embodiments may include an automotive system 100, as shown in Figures 1 and 2, that includes an internal combustion engine (ICE) 110 having an engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crankshaft 145. A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement of the piston 140. The fuel is provided by at least one fuel injector 160 and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pressure fuel pump 180 that increases the pressure of the fuel received from a fuel source 190. Each of the cylinders 125 has at least two valves 215, actuated by a camshaft 135 rotating in time with the crankshaft 145. The valves 215 selectively allow air into the combustion chamber 150 from the port 210 and alternately allow exhaust gases to exit through a port 220. In some examples, a cam phaser 155 may selectively vary the timing between the camshaft 135 and the crankshaft 145.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200. An air intake duct 205 may provide air from the ambient environment to the intake manifold 200.

In other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200.

In still other embodiments, a forced air system such as a turbocharger 230, having a compressor 240 rotationally coupled to a turbine 250, may be provided. Rotation of the compressor 240 increases the pressure and temperature of the air in the duct 205 and manifold 200. A charge air cooler 260 disposed in the duct 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. The exhaust gases exit the turbine 250 and are directed into an exhaust system 270. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move a rack of vanes 295 in different positions, namely from a fully closed position to a fully open position, to alter the flow of the exhaust gases through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

According to the various embodiments of the automotive systems, the turbocharger compressor 240 is complemented by an electric compressor 600 (Figures 3-5).

The exhaust gases of the engine are directed into an exhaust system 270.

The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices 280. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment devices 280 include, but are not limited to, catalytic converters (two and three way), oxidation catalysts, lean NOx traps, hydrocarbon adsorbers, selective catalytic reduction (SCR) systems, and particulate filters.

Other embodiments may include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

While the first EGR conduit defines a short route for the exhaust gas recirculation, in accordance with the present invention, a second EGR system 690 provided with a second EGR conduit 695 which fluidly connects the exhaust line downstream of the aftertreatment systems to the intake line upstream the intake manifold and is connected therein by the interposition of a three-way valve 630 may be provided. The second EGR conduit 695 defines a long route which comprises also a relevant portion of the exhaust line and a relevant portion of the intake line and is better explained with reference to Figure 3-5.

The automotive system 100 may further include an electronic control unit (ECU) 450 in communication with one or more sensors and/or devices associated with the ICE 110 and with a memory system, or data carrier 460, and an interface bus. The ECU 450 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters associated with the ICE 110. The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, a combustion pressure sensor that may be integral within the glow plugs 360, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a cam position sensor 410, a crank position sensor 420, exhaust pressure and temperature sensors 430, an EGR temperature sensor 440, and an accelerator pedal 447 position sensor 445. Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to control the operation of the ICE 110, including, but not limited to, the fuel injectors 160, the throttle body 330, the EGR Valve 320, a Variable Geometry Turbine (VGT) actuator 290, and the cam phaser 155. Note, dashed lines are used to indicate communication between the ECU 450 and the various sensors and devices, but some are omitted for clarity.

Figure 3 shows a portion of the automotive system 100 of Figure 1 in a first operating condition.

In Figure 3, the turbocharger compressor 240 is represented and is located in an air intake duct 205 of the automotive system 100 downstream of a three-way valve 630 and may be assisted by an electric compressor 600.

The three-way valve 630 intercepts air intake duct 205 and is provided with an inlet connected to an outlet of an air filter (not represented for simplicity) in order to receive filtered air coming from the environment and is provided with an outlet that is connected to the inlet of the compressor 240. A further inlet of the three-way valve 630 receives exhaust gas from a long route EGR conduit 695 of the long route EGR system 690 in such a way that the junction between the long route line and the air path is represented by the three-way valve 630.

As an alternative to the three-way valve 630, two separate throttle bodies may be used.

The long route EGR conduit 695 is also provided with a first branch 650 connecting an outlet of a long route EGR cooler 640 with an inlet of the electric compressor 600.

The first branch 650 of the long route EGR conduit 695 stems from a branching point 655 of the long route EGR conduit 695 and is used for directing recirculated gas through the electric compressor 600 towards a mixing point 665 with the intake line 205 downstream of the turbocharger compressor 240.

More specifically, downstream of the electric compressor 600, a third branch 680 of the long route EGR circuit 695 is provided, the third branch 680 terminating in a mixing point 665 that connects the third branch 680 to the intake duct 205.

Also, a one-way valve 610 is provided in a portion of an air intake duct 205 connecting an outlet of the turbocharger compressor 240 with an inlet of a charge air cooler 260, the one-way valve 610 being located in a portion of the intake duct 205 downstream of the turbocharger compressor 240.

Furthermore, a recirculating gas valve 620 is provided in the first branch 650 of the long route EGR system 690, upstream of the electric compressor 600.

More specifically, the recirculating gas valve 620 is provided in the first branch 650 of the long route EGR system 690 connecting an outlet of the long route EGR cooler 640 with an inlet of the electric compressor 600. A second branch 670 of the long route EGR circuit 695 connecting the one-way valve 610 with a branching point 660 of the first branch 650 is also provided, the branching point 660 being downstream of the of the recirculating gas valve 620.

In an embodiment of the invention, the recirculating gas valve 620 may be an ON-OFF valve.

Furthermore, the branching point 655 of the long route EGR conduit 695 is located downstream of a long route EGR cooler 640.

The operative conditions depicted in Figure 3 refer to a first mode of operation of the automotive system 100, namely in steady state full load conditions of the engine 110.

In such condition all the gas and air mass flow passes through the one-way valve 610, which is open, and is fully directed to the charge air cooler 260. The electric compressor 600 is not active and doesn’t participate to the boost build-up.

During a transient manoeuver, the one-way valve 610 is closed and directs all the flow coming from the turbocharger compressor 240 to the electric compressor 600 which is controlled in order to enable a fast torque response (following the path drawn with arrows in Figure 4).

In steady state partial load conditions, the one-way valve 610 is open and directs all the flow from the turbocharger compressor 240, namely the main air flow, to the charge air cooler 260, blocking the flow thorough the second branch 670 towards the electric compressor 600.

Nevertheless, the ON-OFF valve 620 provided in the first branch 650 is open and, through a proper modulation of the electrical power supplied to the electric compressor 600, the required amount of EGR is entrained and delivered to the engine 110.

In other words, when an internal combustion engine 110 partial load steady state is detected, the one way valve 610 in the intake duct 205 is actuated to allow a main air flow in the intake duct 205 downstream of the one way valve 610 and, at the same time, the recirculating gas valve 620 is actuated to allow a recirculated exhaust gas flow in the first branch 650 of the long route EGR conduit 695.

The recirculated exhaust gas and the main air flow are mixed downstream of the one way valve 610 in the intake duct 205, downstream of the mixing point 665.

In case the recirculating gas valve 620 is an ON-OFF valve, the step of regulating the mixing of the recirculated exhaust gas with the main air flow is performed by regulating the electrical power supplied to the electric compressor 600.

Therefore, as expressed in the flowchart of Figure 6, a check is made to verify if the engine 110 is in full load conditions (block 700).

If the answer is positive, the ECU 450 operates the one-way valve 610 to direct the air flow towards the charge air cooler 260 and then to the engine 100, while the electric compressor 600 is kept inactive (block 710).

If the answer is negative, a check is made to verify if the engine 110 is in a transient condition (block 720).

If the answer is positive, the ECU 450 operates the one-way valve 610 to direct directs all the flow coming from the turbocharger compressor 240 to the electric compressor 600. The electric compressor 600 is operated for example by receiving electrical power from a battery (not represented for simplicity - block 730).

If the answer is negative, a check is made to verify if the engine 110 is in a partial load condition (block 740).

If the engine 110 is in such partial load condition, the ECU 450 operates the oneway valve 610 in the intake duct 205 to allow a main air flow in the intake duct 205 downstream of the one way valve 610 and the recirculating gas valve 620 to allow a recirculated exhaust gas flow in the first branch 650 of the long route EGR conduit 695.

The ECU 450 also regulates a mixing of the recirculated exhaust gas with the main air flow downstream of the one way valve 610 in the intake duct 205 by regulating the electrical power supplied to the electrical compressor 600 (mixing phase of block 750).

In the various embodiments of the invention, the calculation steps needed are carried out by the ECU 450 according to computer programs stored in the data earner 460.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERENCE NUMBERS 100 automotive system 110 internal combustion engine (ICE) 120 engine block 125 cylinder 130 cylinder head 135 camshaft 140 piston 145 crankshaft 150 combustion chamber 155 cam phaser 160 fuel injector 170 fuel rail 180 fuel pump 190 fuel source 200 intake manifold 205 air intake duct 210 intake air port 215 valves of the cylinder 220 exhaust gas port 225 exhaust manifold 230 high pressure turbocharger 240 high pressure compressor 250 high pressure turbine 260 charge air cooler 270 exhaust system 275 exhaust pipe 280 exhaust aftertreatment device 290 VGT actuator 295 rack of vanes of the turbine 300 EGR system 310 EGR cooler 320 EGR valve 330 throttle body 340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 400 fuel rail pressure sensor 410 cam position sensor 420 crank position sensor 430 exhaust pressure and temperature sensor 445 accelerator pedal position sensor 447 accelerator pedal 450 electronic control unit (ECU) 460 data carrier 600 electric compressor 610 one way valve 620 ON-OFF valve 630 three-way valve 640 EGR cooler 650 first branch 665 branching point 660 connecting point 665 mixing point 670 second branch 680 third branch 690 long route EGR system 695 long route EGR conduit 700 block 710 block 720 block 730 block 740 block 750 block

Claims

1. A long route Exhaust Gas Recirculation (EGR) system (690) for an internal combustion engine (110) equipped with a turbocharger compressor (240) and with an electric compressor (600), the turbocharger compressor (240) and the electric compressor (600) being configured to direct air into an intake line (205) of the internal combustion engine (110), the long route EGR system (690) being provided with a long route EGR conduit (695) which fluidly connects an exhaust pipe (275) of the internal combustion engine (110) with the intake line (205), the long route EGR conduit (695) being provided with a first branch (650) stemming from a branching point (655) of the long route EGR conduit (695) for directing recirculated gas through the electric compressor (600) towards a mixing point (665) with the intake line (205) downstream of the turbocharger compressor (240).

2. The long route EGR system (690) according to claim 1, wherein a one-way valve (610) is provided in a portion of the intake duct (205) downstream of the turbocharger compressor (240).

3. The long route EGR system (690) according to claim 1, wherein a recirculating gas valve (620) is provided in the first branch (650) of the long route EGR system (690) upstream of the electric compressor (600).

4. The long route EGR system (690) according to claim 3, comprising a second branch (670) connecting the one-way valve (610) with a connecting point (660) of the first branch (650), the connecting point (660) being downstream of the recirculating gas valve (620).

5. The long route EGR system (690) according to claims 3 or 4, wherein the recirculating gas valve (620) is an ON-OFF valve.

6. The long route EGR system (690) according to claim 1, wherein the branching point (655) of the long route EGR conduit (695) is located downstream of a long route EGR cooler (640).

7. A method of operating the long route EGR system (690) of the preceding claims, the method comprising the steps of: - detecting an internal combustion engine (110) partial load steady state; - actuating the one way valve (610) in the intake duct (205) to allow a main air flow in the intake duct (205) downstream of the one way valve (610); - actuating the recirculating gas valve (620) to allow a recirculated exhaust gas flow in the first branch (650) of the long route EGR conduit (695); and - regulating a mixing of the recirculated exhaust gas with the main air flow downstream of the one way valve (610) in the intake duct (205).

8. The method according to claim 7, wherein the step of regulating the mixing of the recirculated exhaust gas with the main air flow is performed by regulating the electrical power supplied to the electric compressor (600).

9. An automotive system (100) comprising a long route EGR system (690) for an internal combustion engine (110) according to claims 1-6 and an Electronic Control Unit (450) configured for carrying out the method according to any of the claims 7-8.

10. A computer program comprising a computer-code suitable for performing the method according to any of the claims 7-8.

11. A computer program product on which the computer program according to claim 10 is stored.

12. A control apparatus for an internal combustion engine (110), comprising an Electronic Control Unit (450), a data carrier (460) associated to the Electronic Control Unit (450) and a computer program according to claim 10 stored in the data carrier (460).