GB2488321A

GB2488321A - Exhaust Manifold for a Two-Stage Turbocharged Engine

Info

Publication number: GB2488321A
Application number: GB1103018.6A
Authority: GB
Inventors: Fredrik Westin; Fabio Sciuto
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2011-02-22
Filing date: 2011-02-22
Publication date: 2012-08-29
Anticipated expiration: 2031-02-22
Also published as: GB2488321B; GB201103018D0

Abstract

An exhaust manifold (11, fig.1) for connection of a two-stage turbocharger comprising a high-pressure turbocharger 106 to an internal combustion engine 40, wherein the exhaust manifold (11) comprises a shaped pipe 20 divided in two portions (12,14 fig 1), each portion being connected to a bridge pipe (18) that leads the exhaust gas into the high-pressure turbocharger (106) and allows enough space to house a portion of a high-pressure turbine outlet between the two portions (12,14) of the manifold. The two portions (12,14) may also be connected to the engine via a common flange (16, fig.2). The configuration of the various components allows improvements in the packaging of the two stage turbocharged engine in order to make assembly easier by providing straight bolt access to attach the manifold to the cylinder head.

Description

TWO-STAGE T[JRBCCHARGED ENGINE SYSTEM TECHNICAL FlEW The present disclosure relates to a two-stage turbocharged engine system.

BACXDUZ) Two-stage turbocharged engine systems comprise two sequential turbochargers which are selectively operated in accordance with engine speed and engine load.

As a matter of fact, a known two-stage turbocharged engine systems comprise a high-pressure turbocharger and a low-pressure turbocharger, both having a compressor and a turbine.

The compressor of high-pressure turbocharger is located in the intake line downstream the compressor of low-pressure turbocharger, relative to the flow direction.

The intake line comprises a low-pressure intake line for fluidly connecting the outlet of low-pressure compressor to the inlet of high-pressure compressor, and a high-pressure intake line for fluidly connecting the outlet of high-pressure compressor to the inlet of the cooler device.

The high-pressure turbocharger and the low-pressure turbocharger are arranged such that at low engine speeds both turbochargers are used for charging air into the engine, while as engine speed increases the high-pressure turbocharger is gradually disabled.

The intake line comprises a bypass device arranged for allowing the airflow to bypass the high-pressure compressor when the high-pressure turbocharger is disabled.

The bypass device generally comprises a bypass line for fluidly connecting low-pressure intake line directly to high-pressure intake line, and a valve which is located in said bypass line for opening or closing the passageway.

Systems such as the one described above, while having good performance, may give rise to some technical problems.

In fact, two-stage turbocharged engines, especially in case of small engines give rise to severe space constraints.

At the same time, it must be ensured straight-line access to the bolts for attaching a exhaust manifold to a cylinder head during manufacturing, a fact that creates big constraints on the design of two-stage turbocharger systems.

An aim of an embodiment of the present invention is to improve the packaging of the two-stage turbocharged engine, in order to make possible the attachment of the exhaust manifold to the cylinder head with straight bolt access as generally required by the engine plants.

Another aim of the present invention is to configure an engine exhaust manifold specially arranged for a two-stage turbocharger that allows its easy connection to the engine.

SUFRY

An embodiment of the disclosure provides an exhaust manifold for connection of a two-stage turbocharger comprising a high-pressure turbocharger to an internal combustion engine, wherein the exhaust manifold comprises a shaped pipe divided in two portions, each portion being connected to a bridge pipe that leads the exhaust gas into the high-pressure turbocharger.

An advantage of this embodiment is that it optimizes packaging of both turbochargers, while leaving open space for action onto the exhaust manifold attachment bolts to the engine during manufacturing operations.

According to another embodiment of the invention, a portion of an high-pressure turbine outlet is housed in a space between the two portions of the shaped pipe.

Advantageously, according to this embodiment of the invention, the portions of the shaped pipe are separated in such a way to create an useful additional space inside the engine compartment volume to reduce packaging issues.

According to another embodiment of the invention, the portions of the shaped pipe define separate gas path exiting from different groups of engine cylinders.

An advantage of this embodiment is that, while it creates additional space inside the engine compartment volume, it still allows proper exhaust gas flow.

According to a further embodiment of the invention, a common flange is provided for connection of the shaped pipe to the engine.

An advantage of this embodiment is that it allows an easy mounting of the shaped pipe onto the engine.

According to another embodiment of the invention, the bridge pipe is connected to the high-pressure turbocharger for leading exhaust gas of the engine directly into it.

An advantage of this embodiment is that it allows the two gas path to be reunited and directed into the high-pressure turbocharger.

According to still another embodiment of the invention, the bridge pipe comprises an exit duct for gas exiting from the high-pressure turbocharger, the exit duct leading directly into a low-pressure turbocharger.

An advantage of this embodiment is that it makes possible to pack the low-pressure turbocharger above the exhaust manifold and the high-pressure turbocharger below the exhaust manifold with an improved use of space.

According to still another embodiment of the invention, a short-cut line valve for by-passing the high-pressure turbocharger of the two- stage turbocharger is integral with the bridge pipe or with a low-pressure turbocharger.

An advantage of this embodiment is that it improves compactness of layout.

A still further aspect of the disclosure provides an internal combustion engine equipped with an engine exhaust manifold specially arranged for a two-stage turbocharger, in which one of the turbochargers is above the exhaust manifold and the other turbocharger is below the exhaust manifold.

BRIEF DESCRIPTICV OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of a two-stage turbocharged engine suitable for employing an embodiment of the invention; Figure 2 is a lateral view of an engine equipped with an embodiment of the invention; Figure 3 is a perspective view of an engine equipped with a two-stage turbocharger according to an embodiment of the invention; Figure 4 is a perspective view of a portion of an exhaust manifold according to an embodiment of the invention; Figures 5-6 are a perspective views of a group comprising an high pressure equipped with a bridge pipe according to embodiment of the invention; Figure 7 is a perspective view two-stage turbocharged engine according to an embodiment of the invention; and Figure 8 is a further perspective view two-stage turbocharged engine according to an embodiment of the invention.

DEThILED DESCRIPTICV OF THE DRAWINGS Preferred embodiments will now be described with reference to the enclosed drawings.

In figure 1, a two-stage turbocharger 10 applied to an internal combustion engine 40, equipped with a plurality of cylinders 1-4, is schematically illustrated according to an exemplary actual implementation useful for understanding the various embodiments of the invention and their advantages.

The engine 40 has an intake manifold 42 that comprise a plurality of runners corresponding in number to the number of individual cylinders of the engine 40. The intake manifold 42 communicates with an air inlet 130 via an intake line 80.

As explained in detail in the following description, the engine 40 has an exhaust manifold 11 for connection of the two-stage turbocharger 10 to the internal combustion engine 40.

The exhaust manifold 11 is equipped with a shaped pipe 20 (fig.4) divided in two portions 12,14, each portion 12,14 being connected to a bridge pipe 18 that leads the exhaust gas into a high-pressure turbocharger 106.

The two-stage turbccharger 10 comprises a low-pressure turbocharger 105, having a low-pressure turbine 50 and a low-pressure compressor 51, which is rotated by the turbine 50 by means of a connecting shaft 52.

The two-stage turbocharger further comprises a high-pressure turbocharger 106, having a high-pressure turbine 60 and an high-pressure compressor 61, which is rotated by the turbine 60 by means of a connecting shaft 62.

The inlet of the high-pressure turbine 60 corrmunicates with the exhaust manifold 11 via a high-pressure exhaust line 70.

The outlet of the high-pressure turbine 60 corrrnunicates with the inlet of low-pressure turbine 50 via a low-pressure exhaust line 71.

The inlet of the low-pressure turbine 50 directly corrmunicates with the exhaust manifold 11 via a short-cut line 72 leading into the low-pressure exhaust line 71.

The short-cut line 72 comprises a valve 73 for opening arid closing the passageway.

The outlet of low-pressure turbine 50 corrmunicates with the exhaust outlet 140 via a muffler line 74.

The low-pressure exhaust line 71 directly communicates with a muffler line 74 via a bypass line 75 which comprises a waste gate valve 76 for opening and closing such passageway.

The inlet of low-pressure compressor 51 communicates with the air inlet 130 via connecting intake line 80.

The outlet of low-pressure compressor 51 communicates with the inlet of the high-pressure compressor 61 via a low-pressure intake line 81 and, via a first portion 91 and a second portion 83, corrntunicates with an air cooler 107 from which, via a line 84, exhaust gas is recirculated into the intake manifold 42 of the engine 40.

The two-stage turbocharger 10 also comprises a by-pass arranged for allowing the airflow to bypass the high-pressure compressor 61 when the high-pressure turbocharger 106 is disabled by means of a by-pass line 91 for directly fluidly connecting the low-pressure intake line 81 to an high-pressure intake line 82. A valve 94 located in said by-pass line 91 is provided for selectively opening or closing such passageway.

In operation, at low engine speed, the valves 73, 94 and the waste gate valve 76 are closed, and the intake air is charged in series by both low-pressure compressor 51 and high-pressure compressor 61, making the system work according a two-stage operating mode.

With increasing engine speed, the flow capacity of the high-pressure turbocharger 106 becomes limited, thereby limiting further performance to be obtained. The valve 73 opens the short-cut line 72, allowing part of the exhaust gas to flow from exhaust manifold 11 directly into low-pressure exhaust line 71. At the same time, the flow and pressure within high-pressure exhaust line 70 continue to energize the high-pressure turbocharger 106 to thereby cause charging pressure to be produced. The flow and pressure within low-pressure exhaust line 71 increases due to the flow and pressure from the short-cut line 72 and from the outlet of high-pressure turbine 60 to energize low-pressure turbocharger 105. Therefore, the pressure within high-pressure intake line 81 can be adjusted such that it does not exceed the allowed limit.

When the engine performs at higher speed the opening area of valve 73 reaches a maximum, thus almost all of the exhaust gas flows through the short-cut line 72 into low-pressure exhaust pipe 71 to thereby lose the function of high-pressure turbocharger 106, while energizing low-pressure turbocharger 105 to thereby produce a predetermined charging pressure, making the system work according a single-stage operating mode.

At higher engine speed the high-pressure turbocharger 106 is disabled and the valve 94 opens the bypass line 91, then the air discharged from low-pressure compressor 51 flows directly in the second portion 83 of the high-pressure intake line, thereby bypassing the major portion of the low-pressure intake line 81, the high-pressure compressor 61 and the high-pressure intake line 82.

Finally, when the low pressure turbocharger reaches its limit an actuator 151 opens waste gate valve 76 protecting the turbocharger from overpressure.

In fig. 2 a portion of the exhaust manifold 11 according to an embodiment of the invention is represented.

As mentioned above, the exhaust manifold 11 is equipped with a shaped pipe 20 (better visible in fig. 4), the shaped pipe 20 being divided in two separate portions 12,14 and being ccnfigured in such a way that the exhaust gas exiting from a first group of cylinders 1,2 flows into the first portion 12 of the shaped pipe 20 and the exhaust gas exiting from a second group of cylinders 3,4 flows into the second portion 14.

Preferably a corrmon flange 16 is provided for connection of the shaped pipe 20 to the engine 40.

Moreover, a *bridge pipe 18 is connected to the first and second portion 12,14 of the shaped pipe 20 (fig. 3).

To achieve this connection the shaped pipe 20 may be provided with first and second connection flanges 13,15 for connection to respective first and second connection flanges 23,25 of the bridge pipe 18.

With this arrangement the exhaust gas of the engine 40 flows first into the respective portion of the shaped pipe 20 and then directly, through an inlet duct 21 of the bridge pipe 18, into the high-pressure turbocharger 106.

The bridge pipe 18 may comprise an exit duct 22 exiting from the high-pressure turbocharger 106 and leading directly into a low-pressure turbocharger 105 through low-pressure exhaust line 71.

According to an embodiment of the invention the short-cut line valve 73 for by-passing the high-pressure turbocharger 106 of the two-stage turbocharger 10 is at least partially housed inside the bridge pipe 16.

In alternative, valve 73 can be an integral part of the bridge pipe 18 or be an integral part of the low-pressure turbine housing, or, finally, may have its parts divided between these two elements.

According to another embodiment of the invention the bridge pipe 18 may be integral with one of the turbochargers 105,106.

As can be seen for example in fig. 2, the shape of the exhaust manifold leaves open space for action onto the exhaust manifold attachment bolts 29 to the engine 40 during manufacturing operations.

Furthermore, a portion of an high-pressure turbine outlet 109 is housed in a space between the two portions of the shaped pipe.

The embodiments described allow a simple mounting of one of the two turbochargers 105,106 followed by the second turbocharger where all components are fitted with bolted flanges with straight, or near straight, bolt access.

While at least one exemplary embodiment has been presented in the foregoing surrinary 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.

PEEEREN NUVSERS

1-4 cylinders two-stage turbocharger 11 exhaust manifold 12 first portion of shaped pipe 13 first flange of shaped pipe 14 second portion of shaped pipe second flange of shaped pipe 16 corimon flange of shaped pipe 18 bridge pipe shaped pipe 21 inlet duct (from bridge pipe to HP turbo) 22 exit duct (from the HP turbo to LP turbo) 23 first flange of bridge pipe 25 second flange of bridge pipe 29 bolts for attaching shaped pipe to engine engine 42 intake manifold low-pressure turbine 51 low-pressure compressor 52 connecting shaft (low-pressure turbocharger) 61 high-pressure compressor 62 connecting shaft (high-pressure turbocharger) high-pressure intake line 71 low-pressure exhaust line 72 short-cut line 73 short-cut line valve 74 muffler line low-pressure turbocharger by-pass line 76 waste gate valve intake line 81 low-pressure intake line 82 portion of high-pressure intake line 83 final portion of high-pressure intake line 84 line from air cooler to intake manifold 94 valve (on high-pressure turbocharger by-pass line) low-pressure turbocharger 106 high-pressure turbocharger 107 air cooler 109 high pressure outlet air inlet exhaust outlet

Claims

AIMS1. An exhaust manifold (11) for connection of a two-stage turbocharger (10) comprising a high-pressure turbocharger (106) with an internal combustion engine (40), wherein the exhaust manifold (11) comprises a shaped pipe (20) divided in two portions (12,14), each portion (12,14) being connected to a bridge pipe (18) that leads the exhaust gas into the high-pressure turbocharger (106).
2. An exhaust manifold (11) according to claim 1, in which a portion of an high-pressure turbine outlet (109) is housed in a space between the two portions (12,14) of the shaped pipe (20).
3. An exhaust manifold (11) according to claim 1, in which the portions (12,14) of the shaped pipe (20) define separate gas path exiting from different groups of engine cylinders (1-4).
4. An exhaust manifold (11) according to claim 1, in which a corrrrion flange (16) is provided for connection of the shaped pipe (20) to the engine (40).
5. An exhaust manifold (11) according to claim 1, in which the bridge pipe (18) is connected to the high-pressure turbocharger (106) for leading exhaust gas of the engine directly into it.
6. An exhaust manifold (11) according to claim 1, in which the bridge pipe (18) is integral with one of the turbochargers (105, 106)
7. An exhaust manifold (11) according to claim 6, in which the bridge pipe (18) comprises an exit duct (22) for gas exiting from the high-pressure turbocharger (106), the exit duct (22) leading directly into a low-pressure turbocharger (105).8. 11⁄2n exhaust manifold (11) according to claim 6, in which a short-cut line valve (73) for by-passing the high-pressure turbocharger (106) of the two-stage turbocharger is integral with the bridge pipe (16) or with a low-pressure turbocharger (105).9. An internal ccrribustion engine (40) having associated a two-stage turbocharger (10) and an engine exhaust manifold (24) according to any of the preceding claims, in which one of the turbochargers (105) is above the exhaust manifold (24) and the other turbocharger (106) is below the exhaust manifold (24).