GB2534900A

GB2534900A - Internal combustion engine having a charge cooling system for a two stage turbocharger

Info

Publication number: GB2534900A
Application number: GB1501855.9A
Authority: GB
Inventors: Maria Meano Cesare; Petronzi Vincenzo
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2015-02-04
Filing date: 2015-02-04
Publication date: 2016-08-10
Also published as: GB201501855D0

Abstract

An internal combustion engine 110 having a two stage turbocharger 900 and a charge cooling system 260 for the two stage turbocharger 900, the two stage turbocharger 900 comprising a high pressure compressor 240 and a low pressure compressor 540 for compressing intake air in a compressed air circuit 950, the charge cooling system 260 being equipped with an interstage cooler 267 fluidically connected to an outlet (544, Fig. 5) of the low pressure compressor 540 and to an inlet (242, Fig. 4) of the high pressure compressor 240, with a high pressure cooler 265 fluidically connected to an outlet (244, Fig. 4) of the high pressure compressor 240 and with a high pressure compressor bypass valve 600 being located downstream of the Interstage cooler 267 in a high pressure bypass duct 920 of the compressed air circuit 950 fluidically connecting an outlet (472) of the interstage cooler (267, Fig. 4), upstream of the high pressure compressor 240, with an inlet (474, Fig. 5) of the high pressure cooler 265, downstream of the high pressure compressor 240. The configuration exhibits an optimised layout allowing for easier routing and packaging of the connecting ducts.

Description

INTERNAL COMBUSTION ENGINE HAVING A CHARGE COOLING SYSTEM FOR A

TWO STAGE TURBOCHARGER

* ** 10 TECHNICAL FIELD

* * * *** * The technical field relates to an internal combustion engine having a two stage turbocharger. More in detail, the technical field relates to an internal combustion engine * having a two stage turbocharger and a charge cooling system for the two stage * * turbocharger. ** * * * *

* ** 15 BACKGROUND * ***

* Two stage turbochargers for internal combustion engines are known in the art.

**** Two stage turbocharger systems may comprise a High Pressure (HP) turbocharger * ***** ** * * * * and a Low Pressure (LP) turbocharger, each turbocharger in turn comprising a * ** compressor rotationally coupled to a turbine.

These turbocharger systems may be configured to operate both turbochargers at low/medium speeds and to operate the low pressure turbocharger only at high speed, in other words, in single stage operation. In this second case, the high pressure turbocharger is bypassed.

To increase the maximum boost delivery of a two stage serial turbocharger system, an interstage cooler may be needed, the interstage cooler being positioned between the low pressure compressor and the high pressure compressor.

The effect of the interstage cooler is to cool down the output of LP compressor with two beneficial effects: -increase the HP compressor operating efficiency as it elaborates colder fluid (thus less viscous) -increase the HP compressor boost range as the maximum outlet fluid temperature is limited.

Serial sequential turbocharger systems require a HP compressor bypass valve to switch from two stage to single stage operation, and optionally a LP compressor bypass valve as well. If two separate Charge Air Coolers are used, i.e. interstage cooler between LP and HP compressors and main charge air cooler between LP compressor and intake * ** manifold, a rather complex layout is generated, with consequent high costs, packaging * * * * * * * * space problems, and relevant intake volume and pressure loss, leading to potentially * * poor overall performances. ** * * * *

* ** 15 Actually, the dimensioning of the two coolers, in this particular case, has different * * * targets: * ** * -the interstage one is dimensioned for the air massflow of two stage operation ^ **** * * * * * conditions (low/mid engine speed range) **** -the main charge air cooler is dimensioned for the air massflow of single stage operation (up to maximum power), but it is also kept active in two stage mode, where the massflow is significantly lower. Hence it turns out to be over-dimensioned in this condition, if the target is an optimal trade-off between cooling capacity and volume/pressure loss Moreover, since separate charge air coolers are used, the interstage cooler remains unused in single stage operation.

In a known embodiment, for example, the air exiting from the low pressure compressor flows towards a "T" joint from where it may go towards the interstage charge air cooler when the serial sequential turbocharger is operated in two stage mode or directly towards the main charge air cooler and then to the intake manifold when operated in single stage mode In the same knowns embodiment, the high pressure compressor bypass valve is placed upstream of the interstage cooler and, if open, makes the compressed air flow directly towards the main charge air cooler, bypassing the high pressure compressor, and then to the intake manifold. The interstage cooler remains unused.

In case the serial sequential turbocharger is operated in two stage mode, the compressed air passes through the interstage charge air cooler, then through the high * * * pressure compressor after which a pipe drives the compressed air towards the main * * * ** * * * charge air cooler and the intake manifold. * *

An object of an embodiment disclosed is to provide an internal combustion engine ** * * * * * ** 15 having a two stage turbocharger and a cooling system for the two stage turbocharger * * * that exhibits an optimized layout and, at the same time, allows for an easier routing of the **** connecting ducts and for an easier packaging. **** ** *

* * * This and other objects are achieved by an internal combustion engine having a * ** cooling system for a two stage turbocharger having the features recited in the independent claim.

The dependent claims delineate preferred and/or especially advantageous aspects. SUMMARY An embodiment of the disclosure provides an internal combustion engine having a two stage turbocharger and a charge cooling system for the two stage turbocharger, the two stage turbocharger comprising a high pressure compressor and a low pressure compressor for compressing intake air in a compressed air circuit, the charge cooling system being equipped with an interstage cooler fluidically connected to an outlet of the low pressure compressor and to an inlet of the high pressure compressor, with a high pressure cooler fluidically connected to an outlet of the high pressure compressor and with a high pressure compressor bypass valve, the high pressure compressor bypass valve being located downstream of the interstage cooler in a high pressure bypass duct of the compressed air circuit fluidically connecting an outlet of the interstage cooler, upstream of the high pressure compressor, with an inlet of the high pressure cooler, downstream of the high pressure compressor.

An advantage of this embodiment is that the cooling system for the two stage turbocharger of the internal combustion engine has a very compact layout, in which the * .. interstage charge air cooler is always used. In this way, in single stage mode, the * * * ... * * interstage cooler and the high pressure cooler are operated in series or sequentially for * * the low pressure compressor. ** . * * *

* ** 15 Furthermore, maximum available enthalpy is given to the low pressure stage in full power operation and to the high pressure stage in maximum torque operation.

000% According to an aspect of the invention, in the open position of the high pressure *.**' *"* * * * compressor bypass valve located downstream of the interstage cooler, i.e. when the high * ** pressure compressor bypass valve is open, the high pressure compressor is bypassed, and the interstage cooler and the high pressure cooler receive air compressed only by the low pressure compressor. Advantageously, when the high pressure compressor bypass valve is open it is possible to bypass the high pressure compressor in single stage mode and, at the same time, to utilize both coolers sequentially for the low pressure compressor.

According to another embodiment of the invention, the high pressure bypass duct * * of the compressed air circuit fluidically connects a duct upstream of the high pressure compressor with a duct downstream of the high pressure compressor.

* ** * An advantage of this embodiment is that it allows to bypass the high pressure compressor in single stage mode and, at the same time, to utilize both coolers * * * * 5 sequentially for the low pressure compressor.

According to another embodiment of the invention, both the interstage cooler and the high pressure cooler are mounted side by side on the top of the engine.

An advantage of this embodiment is that it allows for a more integrated overall design also allowing for a lower pressure drop, improving low end torque performance.

According to another embodiment of the invention, one or both the coolers and the high pressure compressor bypass valve are integrated in a single body.

An advantage of this embodiment is that it allows for a more compact overall design. According to another embodiment of the invention, the interstage cooler and the high pressure cooler are be mounted in a staggered configuration in order to leave a space for the high pressure compressor bypass valve integrated therein.

An advantage of this embodiment is that it allows to optimize packaging space.

According to another embodiment of the invention, the interstage cooler and the high pressure cooler are disposed in such a way that the compressed air flows through the interstage cooler in one direction and through the high pressure cooler in an opposite 2 0 direction.

An advantage of this embodiment is that a high pressure bypass duct between the outlet of the interstage cooler and the inlet of the high pressure cooler can be kept short leading to a compact design.

According to still another embodiment of the invention, the interstage cooler and the high pressure cooler are separated by a common wall. ** * * * * * * * * *

* ** * * * ** * * * * . . . * * ** * * * An advantage of this embodiment is that it allows to have a single body cooler, separated by the common wall in two halves.

* * * ** * * According to a further embodiment of the invention, the charge cooling system comprises an interstage cooler bypass duct.

An advantage of this embodiment is that it allows to avoid unnecessary warming of the air by the interstage cooling when the low pressure compressor is bypassed to minimize the pressure drop and the air temperature increase upstream the high pressure compressor, thus maximizing the transient response.

According to a further embodiment of the invention, the cooling system for the two stage turbocharger of the internal combustion engine comprises a low pressure compressor valve in a low pressure bypass duct of the compressed air circuit. The low pressure compressor valve directs air to (i.e. allows passage of the air in) the interstage cooler bypass duct, bypassing the low pressure compressor, when in an open position.

An advantage of this embodiment is that it allows to control the air flow, avoiding interstage cooling when not necessary.

According to still another embodiment of the invention, the low pressure bypass duct of the compressed air circuit fluidically connects an air intake duct of the engine, upstream of the low pressure compressor, with the interstage cooler bypass duct.

An advantage of this embodiment is that it allows to direct air into the interstage cooler bypass duct, bypassing the low pressure compressor.

According to a further embodiment of the invention, the interstage cooler bypass duct is integral with the single body.

An advantage of this embodiment is that it allows for a more compact layout.

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 * 5 automotive system of Figure 1; Figure 3 shows a schematic representation of an internal combustion engine having a two stage turbocharger engine equipped with a charge cooling system according to an embodiment of the invention; and Figures 4-5 show different operating modes of a charge cooling system, according to an embodiment of the invention; Figure 6 shows another embodiment of the invention; and Figure 7 shows a further operating mode of a charge cooling system, according to 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 may be provided, the forced air * * * system comprising a two stage turbocharger 900, the two stage turbocharger may be * * * * ** * * equipped with a charge cooling system 260, both the two stage turbocharger 900 and the * * charge cooling system 260 being described in greater detail hereinafter in connection ** * * . * * * * 15 with Figure 3. * * * *

**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 * e0 EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

* * * 000 * 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 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 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 (Figure 3), 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.

Referring now to Figure 3, the forced air system for the engine 110, comprising the two stage turbocharger 900, is described in more detail.

Such system comprises a two stage turbocharger 900 for the internal combustion engine 110, the two stage turbocharger 900 comprising a high pressure turbocharger 230, equipped with a high pressure compressor 240 rotationally coupled to a high pressure turbine 250, the high pressure turbine 250 being connected upstream to a high pressure turbine inlet duct 255 stemming from the exhaust manifold 225 and downstream to a low pressure turbocharger 530. According to a possible embodiment, * * * SO * * . * * 00 * * * * * O000 * * *00O * * * * * * ** * ** * * * ** * . * ** * * * * * * * * ** * *Ave * * * ** ** * * * . * * * ** the two stage turbocharger 900 is a serial sequential turbocharger.

The low pressure turbocharger 530 is equipped with a low pressure compressor 540 rotationally coupled to a low pressure turbine 550, the low pressure turbine 550 receiving exhaust gas from the high pressure turbine 250 through a low pressure turbine inlet 555.

The turbine 250 rotates by receiving exhaust gases from the 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 the low pressure turbocharger 530.

In Figure 3 a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes to alter the flow of the exhaust gases through the turbine 250 is shown.

In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate. In still other embodiments, the LP turbine 550 may also be a variable geometry turbine (VGT) with a respective VGT actuator (not represented for simplicity).

Furthermore, the exhaust gases exit the low pressure turbine 550 and are directed into the exhaust system 270 through the exhaust pipe 275.

The two stage turbocharger 900 further comprises a high pressure turbine bypass valve 710 and, in some embodiments, may also comprise a wastegate 620.

Moreover, in the two stage turbocharger 900, an air circuit 950 generically indicated with a dashed ellipse in Figure 3, is provided.

In the air circuit 950, a low pressure bypass duct 910 and a high pressure bypass duct 920 are provided, the low pressure bypass dud 910 being intercepted by a low pressure compressor bypass valve 590 and the high pressure bypass duct 920 being intercepted by a high pressure compressor bypass valve 600; the high pressure bypass duct 920 of the air circuit 950 fluidically connects the outlet 472 of the interstage cooler 267 with the inlet 474 of the high pressure cooler 265, as for example represented also in Figures 4-5.

Moreover, the high pressure bypass duct 920 of the compressed air circuit 950 fluidically connects a duct 482 upstream of the high pressure compressor 240 with a duct 484 downstream of the high pressure compressor 240. According to a possible embodiment, as for example shown in figures 4 -5, the duct 482 upstream of the high pressure compressor 240 fluidically connects the outlet 472 of the interstage cooler 267 with the inlet 242 of the high pressure compressor 240. The duct 484 downstream of the high pressure compressor 240 fluidically connects the outlet 244 of the high pressure compressor 240 with the high pressure cooler 265, and preferably with the inlet 474 of the high pressure cooler 265.

Also, the low pressure bypass duct 910 of the compressed air circuit 950 fluidically * .. connects an air intake duct 205 of the engine 110 with the interstage cooler bypass duct * * * ... * * 268.

* * According to an embodiment of the invention, the two stage turbocharger 900 of the ** * 15 internal combustion engine 110 is provided with a charge cooling system 260 in the air * * * circuit 950.

* ** The cooling system 260 is equipped with an interstage cooler 267 fluidically connected to an outlet of the low pressure compressor 540 and to an inlet 242 of the high pressure compressor 240 and with a high pressure cooler 265, fluidically connected * 20 to an outlet 244 of the high pressure compressor 240.

* * * Both the interstage cooler 267 and the high pressure cooler 265 may be Water-cooled Charge Air Coolers (WCACs), namely charge air coolers where the charge air is cooled by a cooling agent such as water or engine coolant liquid.

* According to an embodiment of the invention, the interstage cooler 267 and the high 04.641 25 pressure cooler 265 are integrated in a single body 262, the single body 262 being * * * * * * SID * * * IP * Se * * * * * * *** . * * ** * * * * * * * * ** * ** * * * **** * * * . * * * SS indicated, for example, with a dashed ellipse in Figure 4.

In particular, the interstage cooler 267 and the high pressure cooler 265 may be separated by a common wall 269.

Furthermore, the compressed air circuit 950 of the two stage turbocharger comprises an interstage cooler bypass duct 268. In one embodiment of the invention, the interstage cooler bypass duct 268 may be provided within the single body 262.

As explained in greater detail below, since the high pressure compressor bypass valve 600 is located downstream of the interstage cooler 267 in the high pressure bypass duct 920 of the compressed air circuit 950 fluidically connecting the outlet 472 of the interstage cooler 267 with the inlet 474 of the high pressure cooler 265, when the high pressure compressor bypass valve 600 is open, the interstage cooler 267 and the high pressure cooler 265 receive air compressed by the low pressure compressor 540.

In an embodiment of the invention, the high pressure compressor bypass valve 600 may be integrated in the single body 262, as shown in Figure 6.

In an embodiment of the invention, the high pressure bypass duct 920 of the air circuit 950 conducts compressed air from the outlet 472 of the interstage cooler 267 to the inlet 474 of the high pressure cooler 265.

The high pressure compressor bypass valve 600 directs the compressed air through the compressed air circuit 950 to the high pressure compressor 240, when in a closed position.

When in an open position, the high pressure compressor bypass valve 600 directs the compressed air through the high pressure bypass dud 920, bypassing the high pressure compressor 240, towards the high pressure cooler 265 (Figure 5).

Moreover, in the cooling system 260, the low pressure compressor valve 590 is configured to direct air to the interstage cooler bypass duct 268, bypassing the low * ** * * * *** 0 * . DO * * * * * ** * *** * * *** * **** ** * * * * * *11 pressure compressor 540, when in an open position.

In a possible embodiment of the invention, both the interstage cooler 267 and the high pressure cooler 265 are mounted side by side on the top of the engine 110. The interstage cooler 267 and the high pressure cooler 265 can be mounted in a staggered configuration, such as the one represented in Figure 6, in order to leave a space for the high pressure compressor bypass valve 600 integrated therein.

The operations of the charge cooling system 260 when the two stage turbocharger 900 is of serial sequential are now described with particular reference to Figures 4-7.

When the engine 110 is operating at low or medium speeds or, for example, when engine speed Eapiate and engine load Eioad have suitable values to allow two stage operation of the turbocharger 900 (Figure 4), the low pressure compressor bypass valve 590 in the low pressure bypass duct 910 is closed and, therefore, the air first flows through the low pressure compressor 540 and then through the interstage cooler 267 and then, since also the high pressure compressor bypass valve 600 is closed, through the high pressure compressor 240 and finally through the high pressure cooler 265.

In an embodiment of the invention, the low pressure compressor bypass valve 590 and the high pressure compressor bypass valve 600 can be automatic and be operated as a function of the differential pressure upstream and downstream of the valves 590, 600 which is generated by the activation of the compressors through the control devices of the respective turbines.

In general, therefore, the cooling system 260 is swept by the charge air in one direction from LP compressor outlet 544 to HP compressor inlet 242 and again in the opposite direction from HP compressor outlet 244 to the intake manifold 200. * * * * *

* * * . * * * * * * * * * * * * * * * * * * ** When the engine 110 is operating at high speed, or for example when the engine speed Esp..' and engine load Eload have suitable values to allow single stage operation of the turbocharger 900, the low pressure compressor bypass valve 590 in the low pressure bypass dud 910 is still kept closed and, therefore, the low pressure compressor 540 is operated and the air first flows through the interstage cooler 267.

However, in this case, the high pressure compressor bypass valve 600 in the high pressure bypass duct 920 is opened, and the air flows directly through the high pressure cooler 265, bypassing the high pressure compressor 240 (Figure 5).

In other words, during single stage operation, the interstage cooler 267 and the high pressure cooler 265 work in series or sequentially as a single charge air cooler for the low pressure compressor 540 only.

If the engine 110 reverts back to operating at low or medium speeds, or to conditions that require a two stage operation of the turbocharger, the high pressure compressor 240 is operated again and the low pressure compressor 540 is operated as before described.

Finally, in some particular engine conditions, for example in case of transients from very low engine speed Eves, the interstage cooler bypass dud 268 may be used to bypass the low pressure compressor 540. In this case, the low pressure compressor bypass valve 590 in the low pressure bypass duct 910 is opened (Figure 7).

Bypassing the interstage cooler 267 allows the air to enter the system right upstream of the high pressure compressor 240, avoiding unnecessary pressure drops and undesired air temperature rises, because the coolant temperature is generally higher than the temperature of uncompressed air.

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. * **

* * . *60. * *

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REFERENCE NUMBERS

100 automotive system internal combustion engine (ICE) 120 engine block cylinder cylinder head 135 camshaft piston crankshaft combustion chamber cam phaser 160 fuel injector fuel rail 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 * * * * * ** * * * ** * * * * * * * * Se * * * * * * * * * * * * * * * * * * ** * * * * . . * * * . * a * * * * * * * * * * * * * * * * * * * * * * * * * * * * * . . * ** 240 high pressure compressor 242 inlet of high pressure compressor 244 outlet of high pressure compressor 250 high pressure turbine 255 high pressure turbine inlet duct 260 charge cooling system 262 single body 265 high pressure cooler 267 interstage cooler 268 interstage cooler bypass duct 269 common wall 270 exhaust system 275 exhaust pipe 280 exhaust aftertreatment device 290 VGT actuator 300 EGR system 310 EGR cooler 320 EGR valve 330 throttle body 340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 360 combustion pressure sensor 380 coolant and oil temperature and level sensors 400 fuel rail pressure sensor 410 cam position sensor 420 crank position sensor 430 exhaust pressure and temperature sensor 445 accelerator pedal position sensor 450 electronic control unit (ECU) 460 data carrier 472 outlet of interstage cooler 474 inlet of high pressure cooler 482 duct upstream of the high pressure compressor 484 duct downstream of the high pressure compressor 530 low pressure turbocharger 540 low pressure compressor 542 inlet of low pressure compressor 544 outlet of low pressure compressor 550 low pressure turbine 555 low pressure turbine inlet 590 low pressure compressor bypass valve 600 high pressure compressor bypass valve 620 low pressure turbine bypass valve 710 high pressure turbine bypass valve 900 two stage turbocharger 910 low pressure bypass duct 920 high pressure bypass duct 950 compressed air circuit * * * *** * * . O41 * * * * * .. * * * * O600 * 0 0 0 * * * * O.

Claims

CLAIMS1. An internal combustion engine (110) having a two stage turbocharger (900) and a charge cooling system (260) for the two stage turbocharger (900), the two stage turbocharger (900) comprising a high pressure compressor (240) and a low pressure compressor (540) for compressing intake air in a compressed air circuit (950), the charge cooling system (260) being equipped with an interstage cooler (267) fluidically connected to an outlet (544) of the low pressure compressor (540) and to an inlet (242) of the high pressure compressor (240), with a high pressure cooler (265) fluidically connected to an *.. outlet (244) of the high pressure compressor (240) and with a high pressure compressor * * * * * bypass valve (600), the high pressure compressor bypass valve (600) being located * * * * * 15 compressed air circuit (950) fluidically connecting an outlet (472) of the interstage cooler (267), upstream of the high pressure compressor (240), with an inlet (474) of the high * * pressure cooler (265), downstream of the high pressure compressor (240). **** * **

* * *
2. The internal combustion engine of claim 1, wherein the high pressure bypass * ** dud (920) of the compressed air circuit (950) fluidically connects a dud (482) upstream of the high pressure compressor (240) with a dud (484) downstream of the high pressure compressor (240).
3. The internal combustion engine of claim 1, wherein both the interstage cooler (267) and the high pressure cooler (265) are mounted side by side on the top of the engine (110).
4. The internal combustion engine of claim 3, wherein the interstage cooler (267) * * downstream of the interstage cooler (267) in a high pressure bypass dud (920) of the and the high pressure cooler (265) are integrated in a single body (262).
5. The internal combustion engine of claim 4, wherein the high pressure compressor bypass valve (600) is integrated in the single body (262).
6. The internal combustion engine of claim 5, wherein the interstage cooler (267) and the high pressure cooler (265) are mounted in a staggered configuration in order to leave a space for the high pressure compressor bypass valve (600) integrated therein.
7. The internal combustion engine of claim 1, wherein the interstage cooler (267) and the high pressure cooler (265) are disposed in such a way that the compressed air flows through the interstage cooler (267) in one direction and through the high pressure cooler (265) in an opposite direction.
8. The internal combustion engine of claim 4, wherein the interstage cooler (267) and the high pressure cooler (265) are separated by a common wall (269).
9. The internal combustion engine of claim 1, wherein the cooling system (260) comprises an interstage cooler bypass duct (268).
10. The internal combustion engine of claim 9, wherein the cooling system (260) comprises a low pressure compressor valve (590) in a low pressure bypass duct (910) of the compressed air circuit (950).
11. The internal combustion engine of claim 10, wherein the low pressure bypass 2 0 duct (910) of the compressed air circuit (950) fluidically connects an air intake duct (205) of the engine (110), upstream of the low pressure compressor (540), with the interstage cooler bypass duct (268).11. The internal combustion engine of claim 9, wherein the interstage cooler bypass duct (268) is integral with the single body (262). * GO* * * 000 * * * 00 * * * SO * *^ * . * * 0000 * * * * * 00