GB2564690B

GB2564690B - A turbocharger having a second compressor for an EGR system

Info

Publication number: GB2564690B
Application number: GB1711653.4A
Authority: GB
Inventors: Edward Caine Jonathan; Penzato Sam; Johnson Steve; Nigel Turner Paul
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2017-07-20
Filing date: 2017-07-20
Publication date: 2019-08-14
Anticipated expiration: 2037-07-20
Also published as: GB201711653D0; GB2564690A

Description

A turbocharger having a second compressor for an EGR system

Technical Field

The present disclosure relates to an Exhaust Gas Recirculation (EGR) system with improved performance, and particularly, although not exclusively, relates to an exhaust gas recirculation system for a motor vehicle.

Background

With reference to Figure 1, an engine assembly 2 for a motor vehicle comprises an intake system 10, a turbocharger 20, an engine 30, and an exhaust system 40.

The intake system 10 comprises an air inlet 12. Air enters the intake system 10 via the inlet 12 and passes through an air filter 14 into a cold inlet duct 16. The inlet air is carried by the cold inlet duct 16 to a compressor 22 of the turbocharger 20. The turbocharger compressor 22 is configured to increase the pressure of inlet gases in order to provide enhanced induction to the engine 30. A hot inlet duct 18 is arranged to carry the compressed inlet gases from the turbocharger compressor 22 to an inlet manifold 32 of the engine 30.

When the inlet gases are compressed by the turbocharger compressor 22, the temperature of the inlet gases also increases. It is desirable for the inlet gases within the engine manifold 32 to be cold and dense, to allow a greater quantity, e.g. mass, of inlet gases to be drawn into the engine 30. The intake system 10 therefore comprises a charge air cooler 19 provided on the hot inlet duct 18 and configured to cool the compressed inlet gases before they are delivered to the inlet manifold 32.

The inlet gases are drawn from the inlet manifold into cylinders (not shown) of the engine 30. The inlet gases are mixed with fuel within cylinders and the mixture of inlet gases and fuel is combusted. The gases produced through the combustion are exhausted from the engine 30 via an exhaust manifold 34 to the exhaust system 40.

The exhaust system 40 comprises a hot exhaust duct 42 configured to carry the exhaust gases from the exhaust manifold 34 to a turbine 24 of the turbocharger 20.

The exhaust gases pass through the turbocharger turbine 24 and are expanded and cooled by the turbocharger turbine 24, which extracts energy from the exhaust gases to drive the turbocharger compressor 22.

The expanded and cooled exhaust gases are carried from the turbocharger turbine 24 to an exhaust outlet 44 of the exhaust system via a cold exhaust duct 46.

Engine assemblies often comprise an Exhaust Gas Recirculation (EGR) system, such as a Low Pressure (LP) EGR system and/or a High Pressure (HP) EGR system, configured to recirculate a portion of the exhaust gases back to the intake system of the engine assembly. By replacing a portion of the oxygen rich inlet air with burnt exhaust gases, the peak temperature of combustion within the engine cylinders is reduced limiting the formation of NOx within the engine 30. Furthermore, by controlling the amount of exhaust gases that are recirculated, the power produced by the engine 30 may be controlled without a throttle being provided within the inlet system, allowing the efficiency of the engine assembly 2 to be increased, particularly at low power levels.

The engine assembly 2 depicted in Figure 1 comprises an LP-EGR system 50 including an LP-EGR duct 52 configured to recirculate a portion of the exhaust gases from a position on the cold exhaust duct 46, e.g. between the turbocharger turbine 24 and the exhaust outlet 44, to a position upstream of the turbocharger compressor 22.

The LP-EGR system 50 comprises an LP-EGR valve 54 configured to control the flow of recirculated exhaust gases within the LP-EGR Duct 52.

Exhaust gases that flow from the cold exhaust duct into the LP-EGR Duct 52 may be at a higher temperature than the inlet air within the cold intake duct 16 upstream of the compressor. It may therefore be desirable for the recirculated exhaust gases to be cooled prior to being introduced into the cold inlet duct 16. The LP-EGR system therefore comprises an EGR cooler 56 provided on the EGR duct 52 and configured to cool the exhaust gases passing through the LP-EGR duct. Cooling the recirculated exhaust gases reduces the temperature of the mixture of EGR gases and inlet air within the turbocharger compressor 22, which improves the efficiency of the compressor.

With reference to Figure 2, the engine assembly 2 may comprise a HP-EGR system 60. The ΗΡ-EGR system 60 may be provided in addition or as an alternative to the LP-EGR system 50 shown in Figure 1. The ΗΡ-EGR system 60 comprises an HP-EGR duct 62 configured recirculate a portion of the exhaust gases leaving the engine back to the inlet of the engine 30. As depicted in Figure 2, the HP-EGR duct may recirculate exhaust gases from the hot exhaust duct 42, e.g. from a position between the exhaust manifold 34 and the turbo charger turbine 24 to the inlet manifold 32. Alternatively, the HP-EGR duct may recirculate the exhaust gases back to a position on the hot inlet duct 18, e.g. between the turbocharger compressor 22 and the inlet manifold 32.

The HP-EGR system 60 comprises an HP-EGR valve 64 configured to control the flow of recirculated exhaust gases through the HP-EGR duct 62.

The exhaust gases within the hot exhaust duct 42 may be at a higher temperature than the exhaust gases within the hot inlet duct 18 and the inlet manifold 32. Hence, it may be desirable for the recirculated exhaust gases to be cooled before they are mixed with the inlet gases within the hot inlet duct 18 or the inlet manifold 32, in order to increase the density of the mixture of inlet air and recirculated exhaust gases within the inlet manifold 32. The HP-EGR system 60 therefore comprises an HP-EGR cooler 66 provided on the HP-EGR duct 62 and configured to cool the recirculated exhaust gases.

In some engine operating conditions, e.g. at high engine power when the turbocharger is operating to increase the pressure of inlet gases within the inlet manifold, the pressure of inlet gases within the inlet manifold 32 and hot inlet duct 18 may be greater than the pressure of exhaust gases within the hot exhaust duct 42. In such engine operating conditions, recirculation of exhaust gases using the HP-EGR system 60 may not be possible.

In contrast to this, since the LP-EGR system recirculates exhausts gases to a position upstream of the turbocharger compressor, the LP-EGR system may be capable of recirculating exhaust gases at substantially all operating conditions of the engine assembly 2.

Recirculating exhaust gases using the LP-EGR system may however lead to deterioration of the turbocharger compressor 22 due to condensing water droplets within the recirculated exhaust gases impacting the blades of the compressor as the recirculated exhaust gases pass though the compressor.

Furthermore, ΗΡ-EGR systems can be easier to control, as the recirculated exhaust gases can be introduced directly into the inlet manifold 32 of the engine, providing an immediate engine response.

It is desirable to provide an EGR system that overcomes the disadvantages of both LP-EGR and ΗΡ-EGR systems.

Statements of Invention

According to an arrangement of the present invention, there is provided a turbocharger assembly for an engine, wherein the engine comprises an Exhaust Gas Recirculation (EGR) system having an EGR duct configured to recirculate engine exhaust gases to an intake of the engine assembly, and wherein the turbocharger assembly comprises: a primary compressor for compressing air into the intake; and a rotor comprising a first turbine section configured to expand engine exhaust gases, and a second auxiliary compressor section configured to compress engine exhaust gases and direct them into the EGR duct, the first and second sections of the rotor being integrally formed with, merged into and/or directly coupled to one another.

The turbocharger assembly may further comprise an exhaust gas outlet and an EGR outlet. A portion of the exhaust gas expanded by the first section of the rotor may flow through the exhaust gas outlet, and a remaining portion of the gas may be compressed by the second section of the rotor and may flow to the EGR duct through the EGR outlet.

The second section of the rotor may be configured to compress the exhaust gases expanded by the first section of the rotor. For example, the second section of the rotor may comprise compressor blades.

The rotor may be configured such that a portion of the exhaust gases bypass the first section of the rotor and impinge on the second section of the rotor unexpanded.

The rotor may comprise turbine blades in the first section which merge into auxiliary compressor blades in the second section.

The turbocharger assembly may further comprise a shaft. The rotor may be provided on the shaft.

The first and second sections of the rotor may be provided one after the other along the shaft.

The second section of the rotor may be provided on the opposite side of the first section relative to the exhaust gas outlet. Alternatively, the first section of the rotor may be provided on the opposite side of the second section relative to the exhaust gas outlet.

The rotor may define a bypass channel. This may be configured to permit exhaust gases to flow past the second section of the rotor without being compressed by the second section of the rotor.

The bypass channel may be defined radially inside of an inner radius of the second section of the rotor.

The rotor may be configured such that a portion of the exhaust gases flows around an outside of the second section of the rotor to bypass the second section.

The turbocharger may comprise a common housing configured to house the first and second sections of the rotor.

The recirculated engine exhaust gas may be introduced downstream of the primary compressor.

To avoid unnecessary duplication of effort and repetition of text in the specification, certain features are described in relation to only one or several aspects or arrangements of the invention. However, it is to be understood that, where it is technically possible, features described in relation to any aspect or arrangement of the invention may also be used with any other aspect or arrangement of the invention.

Brief Description of the Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:

Figure 1 is a schematic view of a conventional engine assembly comprising a low pressure exhaust gas recirculation system;

Figure 2 is a schematic view of a conventional engine assembly comprising a high pressure exhaust gas recirculation system;

Figure 3 is a schematic view of an engine assembly comprising a turbine pumped high pressure exhaust gas recirculation system, according to arrangements of the present disclosure;

Figure 4 is a schematic view of a turbocharger assembly of an engine assembly comprising a high pressure exhaust gas recirculation system, according to arrangements of the present disclosure;

Figure 5 is another schematic view of a turbocharger assembly of an engine assembly, according to arrangements of the present disclosure.

Figure 6 is another schematic view of a turbocharger assembly of an engine assembly, according to arrangements of the present disclosure.

Detailed Description

With reference to Figure 3, an engine assembly 102, according to arrangements of the present disclosure, comprises an intake system 110, a turbocharger assembly 120, an engine 130, an exhaust system 140 and an exhaust gas recirculation (EGR) system 160.

In this arrangement, like reference numbers, increased by 100, identify generally the same components, so that the feature with reference number 102 of this arrangement corresponds to the feature 2 of the arrangement of Figures 1 and 2, and so on. This has been done to avoid unnecessary repetition of similar subject matter.

The engine assembly 102 is different from the engine assembly 2 in that the engine assembly 102 comprises a turbine pumped EGR system 160 according to arrangements of the present disclosure.

With reference to Figure 3, the turbine pumped EGR system 160 according to arrangements of the present disclosure comprises a turbocharger assembly 120, an EGR duct 162, an EGR cooler 166 for cooling EGR gas, and an EGR valve 164 configured to control the flow of gas in the EGR duct.

As shown in Figure 3, the intake manifold 132 of the engine assembly 130 is in fluid communication with the turbocharger assembly 120 by means of the EGR duct 162. The EGR valve 164 is configured to control the flow of recirculated exhaust gases in the EGR duct 162, between the EGR cooler 166 and the intake manifold 132. The EGR cooler 166 is provided to cool the recirculated exhaust gas before it is reintroduced into the intake system in order to increase the density of the intake gases within the inlet manifold.

It may be desirable for the recirculated exhaust gases to be reintroduced upstream of the charge air cooler 119, such that the recirculated exhaust gases are cooled by the charge aircooler 119 together with the inlet air. Therefore, alternatively, the EGR valve 164 may be provided in the EGR duct 162 between the EGR cooler 166 and the charge aircooler 119.

With reference to Figure 4, the turbocharger assembly 120 of the EGR system 160 comprises an inlet air compressor 122 on a compressor side of the turbocharger which compresses the inlet air to the engine, and an exhaust turbine 124 on a turbine side of the turbocharger which is provided with a rotor 123 having a first section 125 configured as a turbine and second section 127 configured as an auxiliary compressor. A shaft 129 connects the compressor 122 to the rotor 123 and enables the rotor 123 to drive the inlet air compressor 122 to rotate.

The first and second sections 125, 127 of the rotor 123 are provided one after the other on the shaft 129. At least parts of the first and second sections may be axially aligned.

The exhaust gas side of the turbocharger comprises an exhaust gas inlet 131, an EGR outlet 133, which is in communication with the EGR duct 162, and a main exhaust gas outlet 135 for expanded exhaust gas. The rotor 123 is housed in and supported by a rotor casing (not shown), in a conventional manner.

When the engine assembly 130 is operating, engine exhaust gas from the exhaust manifold 134 enters the exhaust gas inlet 131 of the turbocharger assembly. The exhaust gas entering the exhaust gas inlet 131 under pressure drives the first section 125 of the rotor to rotate, as the engine exhaust gas expands. The first section 125 is also configured to direct the exhaust gas towards the exhaust gas outlet 135 of the turbocharger assembly 120. The first section 125 of the rotor is provided with turbine blades which are configured to expand the gas. These blades may also be configured to alter the direction of the exhaust gas. For example, the direction of flow of the exhaust gas may change from a radial direction to an axial direction relative to the shaft.

As mentioned above, the rotor 123 is also provided with a second section 127. The two sections 125, 127 of the rotor 123 are integrally formed, merge into and/or are directly coupled to one another. This second section 127 is configured as an auxiliary compressor which compresses engine exhaust gases. The first section 125 drives the second section 127 to rotate, i.e. the first section 125 drives the second section 127 as well as the turbocharger primary compressor 122. The second section 127 of the rotor 123 is configured to direct a portion the exhaust gases to the EGR duct 162 of the turbocharger assembly. The second section 127 may be provided with blades which are configured to compress and direct the exhaust gases which impinge on the blades. The second section 127 may comprise an axial flow compressor or a radial outflow compressor.

In the illustrated arrangement, the second section 127 comprises a radial compressor configured to receive exhaust gases flowing in a substantially axial direction and turn the exhaust gases to flow in a substantially radial direction at the EGR outlet 133. Alternatively, the second section may be an axial compressor portion configured to both receive and output exhaust gases in a substantially axial direction.

Figure 4 is a first arrangement of the invention. In this first arrangement, the exhaust gases entering the turbocharger assembly 120 initially impinge on the first section 125 of the rotor 123. The gases are expanded and directed towards the exhaust gas outlet 135 by the first section 125 of the rotor 123.

The second section 127 of the rotor 123 is provided between the first section 125 of the rotor and the exhaust gas outlet 135. The first section 125 of the rotor 123 is configured, for example with turbine blades, to direct a proportion of the exhaust gas onto the compressor blades of the second section 127. The proportion of exhaust gas which impinges on the second section 127 of the rotor 123 is then re-compressed and directed towards the EGR duct 162. This exhaust gas passes through the EGR outlet 133 into the EGR duct 162.

The blades of the first section 125 may be integrally formed with, merge into and/or be directly coupled to the blades of the second section 127. Alternatively, the blades of the first section 125 may be separate from the blades of the second section 127. For example, the blades of the second section 127 may be positioned between the blades of the first section 127.

To allow most of the exhaust gas entering the turbocharger assembly 120 via the exhaust gas inlet 131 to flow to the exhaust gas outlet 135, the second section 127 may be provided with a bypass channel. Thus, a portion of the exhaust gas bypasses the second section 127 without impinging on the compressor blades of the second section 127. The bypass channel is defined radially inside of an inner radius of the second section 127 of the rotor 123. The exhaust gas which does not impinge on the second section 127 of the rotor flows through the bypass channel and passes into the exhaust gas outlet 135.

The second section 127 of the rotor may also comprise a turbine portion which is configured to expand exhaust gas. For example, the second section 127 may be provided with turbine blades inside an inner radius of the compressor portion of the second section 127 of the rotor 123, which direct gases towards the exhaust outlet 135, and/or expands the gases. These blades may be configured to direct some of the exhaust gas towards the part of the second section 127 configured to compress exhaust gas.

In a second arrangement as shown in Figure 5, the two sections of the rotor 223 are configured in a manner similar to that of the first arrangement (of Figures 3 and 4).

These two sections are integrally formed or directly coupled to one another. The second section 227 is again provided between the first section 225 and the exhaust gas outlet 235.

The exhaust gas entering the turbocharger assembly 220 initially impinges on the first section 225 of the rotor 223. The first section 225 expands and directs the exhaust gas towards the exhaust gas outlet 235. The first section 225 is also configured to direct a proportion of the gas towards the second section 227. The second section 227 is configured to compress exhaust gas which has passed the first section 225. These gases may have been expanded by the first section 227.

The second arrangement differs from the first arrangement in that the second section 227 of the rotor 223 is configured such that a portion of the exhaust gas flows around an outside of the second section 225 of the rotor 223 and bypasses the second section 225. The first section 225 of the rotor 223 is configured to direct some of the gas to the EGR outlet 233 and the rest of the gas to the exhaust gas outlet 235. Thus, a portion of the gas expanded by the first section 225 of the rotor is compressed by the second section 227 of the rotor and passes to the EGR duct 262, and a remaining portion of the gas expanded by the first section 225 passes to the exhaust gas outlet 235.

The first section 225 of the rotor may comprise turbine blades. These blades may be configured to alter the direction of flow of the exhaust gas entering the exhaust inlet 231 to the exhaust outlet 235 and the EGR outlet 233.

The second section 227 is configured to compress exhaust gas in the same way as the first arrangement. The second section 227 is in communication with the EGR duct 262, such that gases passing through this second section 227 pass through the EGR outlet 233 to the EGR duct 262. The second section 227 is provided with compressor blades which are configured to compress gas which has been expanded by the first section and to direct it to the EGR duct 262.

In a third arrangement as shown in figure 6, the turbocharger assembly 320 again comprises a rotor 323 having a first and second section 325, 327. The engine exhaust gas entering the exhaust inlet 331 first impinges on the first section 325 of the rotor 323. The first section 325 expands the exhaust gas and directs it towards the exhaust outlet 335.

In this arrangement, the second section 327 is provided on the opposite side of the first section 325 relative to the exhaust outlet 335. The first section 325 is provided with at least one through channel, such that a portion of the exhaust gas entering the exhaust inlet 331 passes through the first section 325 of the rotor 323 to the second section 327. The exhaust gas which flows to the second section 327 is then compressed by the second section 327 and directed to the EGR duct 362 through the EGR outlet 333.

The exhaust gas which flows to the EGR duct 362 therefore travels through the turbocharger turbine substantially in an opposite direction to the gas flowing to the exhaust outlet 335. This is different from the arrangements previously described, in which the direction of flow of exhaust gas towards the EGR duct 362 and exhaust outlet 335 is similar for at least part of the travel through the first section 325.

The through channel between the first section 325 and the second section 327 may be configured such that the exhaust gas entering the first section 325 is not expanded before passing through the through channel to the second section 327. In this way, a portion of the exhaust gas may bypass the part of the first section 325 configured to expand exhaust gas. Alternatively, the first section 325 may be provided to at least partially expand the exhaust gas before it flows to the second section 327. Turbine blades of the first section 325 may be shaped in order to achieve either of these alternative flow regimes. For example, the blades may be configured to expand a portion of the exhaust gas and to direct it to the through channels.

In all of the above arrangements, the number of components required for the compression of gas into an EGR system is minimized, and the length of the turbocharger assembly is also minimised.

It will be appreciated by those skilled in the art that although the invention has been described by way of example, with reference to one or more exemplary arrangements, it is not limited to the disclosed arrangements and that alternative arrangements could be constructed without departing from the scope of the invention as defined by the appended claims.

Claims

1. A turbocharger assembly for an engine, wherein the engine comprises an Exhaust Gas Recirculation (EGR) system having an EGR duct configured to recirculate engine exhaust gases to an intake of the engine assembly, and wherein the turbocharger assembly comprises: a primary compressor for compressing air into the intake; and a rotor comprising a first turbine section configured to expand engine exhaust gases, and a second auxiliary compressor section configured to compress engine exhaust gases and direct them into the EGR duct, the first and second sections of the rotor being integrally formed with and/or directly coupled to one another.

2. The turbocharger assembly as claimed in claim 1, further comprising an exhaust gas outlet and an EGR outlet, wherein a portion of the exhaust gas expanded by the first section of the rotor flows through the exhaust gas outlet, and a remaining portion of the gas is compressed by the second section of the rotor and flows to the EGR outlet.

3. The turbocharger assembly as claimed in claim 1 or 2, wherein the second section of the rotor is configured to compress the exhaust gases expanded by the first section of the rotor.

4. The turbocharger assembly as claimed in any preceding claim, wherein the rotor is configured such that a portion of the exhaust gases bypass the first section of the rotor unexpanded, and impinge on the second section of the rotor.

5. The turbocharger as claimed in any preceding claim, wherein the rotor comprises turbine blades in the first section which merge into auxiliary compressor blades in the second section.

6. The turbocharger assembly as claimed in any preceding claim, wherein the turbocharger assembly further comprises a shaft, and wherein the rotor is mounted on the shaft.

7. The turbocharger assembly as claimed in claim 6, wherein the first and second sections of the rotor are provided consecutively on the shaft.

8. The turbocharger assembly as claimed in any preceding claim when appendant to claim 2, wherein the second section of the rotor is provided on the opposite side of the first section relative to the exhaust gas outlet.

9. The turbocharger assembly as claimed in any of claims 1 to 7 when appendant to claim 2, wherein the first section of the rotor is provided on the opposite side of the second section relative to the exhaust gas outlet.

10. The turbocharger assembly as claimed in any preceding claim, further comprising a bypass channel configured to permit exhaust gases to flow past the second section of the rotor without being compressed by the second section of the rotor.

11. The turbocharger assembly as claimed in claim 10, wherein the bypass channel is defined radially inside of an inner radius of the second section of the rotor.

12. The turbocharger assembly as claimed in any preceding claim, wherein the rotor is configured such that a portion of the exhaust gases flows around the outside of the second section of the turbine to bypass the second section.

13. The turbocharger assembly as claimed in any preceding claim, further comprising a common housing configured to house the first and second sections of the rotor.

14. The turbocharger assembly as claimed in any preceding claim, wherein the recirculated engine exhaust gas is introduced downstream of the primary compressor.

15. An engine having a turbocharger assembly as claimed in any preceding claim.

16. A vehicle having a turbocharger assembly as claimed in any preceding claim.