GB2504713A

GB2504713A - Turbocharger by-pass system from the compressor outlet to the turbine inlet

Info

Publication number: GB2504713A
Application number: GB1214089.3A
Authority: GB
Inventors: Roberto Cavallo; Vincenzo Petronzi
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2012-08-07
Filing date: 2012-08-07
Publication date: 2014-02-12
Anticipated expiration: 2032-08-07
Also published as: GB201214089D0; GB2504713B

Abstract

The invention provides a turbocharging system of an internal combustion engine (110, fig.1) comprising a turbocharger (230, fig.1) and a by-pass circuit 245, wherein the by-pass circuit comprises a first by-pass valve 242 for hydraulically connecting a compressor outlet 241 and a turbine inlet 251 of the turbocharger; and wherein the by-pass 245 is opened if the compressor outlet pressure is higher than the turbine inlet pressure. The bypass circuit may also have a second by-pass valve (243, fig.3) and a plenum (244, fig.3) located between the by-pass valves. The system improves the operating conditions of the compressor by avoiding surge conditions and additional noise generation.

Description

TURBOCHARGER BY-PASS SYSTEM

TECHNICAL FIELD

The present disclosure relates to a turbocharger by-pass system for improving the compressor operating conditions in an internal combustion engine.

BACKGROUND

As known, the majority of internal combustion engines are turbocharged. A turbocharger is a forced induction device used to allow more power to be produced for an engine of a given size. The benefit of a turbo is that it compresses a greater mass of intake air into the combustion chamber, thereby resulting in increased power and/or efficiency.

Turbochargers are commonly used on truck, car, train and construction equipment engines. They are popularly used with Otto cycle and Diesel cycle internal combustion engines and have also been found useful in automotive fuel cells.

Furthermore, modern internal combustion engines, particularly high speed Diesel engines, are more and more requiring the so called "low end torqu&, which can be achieved by improving the engine boost capability. For turbocharged engines, this requires the capability of fast boost pressure build up, which in turn can beachieved by fast spin up of turbocharger.

Several technologies for turbocharger fast spin up are already known in the technique.

For example, the turbocharger can be realized with a low mass moment of inertia, in other words, lightweight turbine and compressor rotors and shaft. Other solution, and especially for diesel engines, is the Variable Geometry Turbine, in order to get a bigger range with high torque.

As known, on turbacharged engines (especially Diesel engines), in low end torque operating conditions, some issues related to compressor noise may arise. In fact, if the engine is running in steady state full and part load conditions or in transient conditions, as tip-in maneuvers, centrifugal turbochargers may run into surge or marginal surge, leading to noise: root cause of this inconvenience is due to the small amount of air that flows through the compressor. This typically occurs in low-mid engine rotating speed, limiting the capacity of turbocharger to generate boost and consequently torque.

Therefore a need exists for a new layout of a turbocharger system able to overcome the above drawback.

An object of this invention is to provide a turbocharger by-pass system for improving the compressor operating conditions in an internal combustion engine, particularly such operating conditions with risk of surge.

Another object is to provide a diagnostic method to detect possible failure of such new by-pass system.

Still another object of the invention is an apparatus which allows to perform the above diagnostic method.

These objects are achieved by a turbocharger system, by a diagnostic method, by an apparatus, by an engine, by a computer program and computer program product, and by an electromagnetic signal having the features recited in the independent claims.

The dependent claims delineate preferred and/or especially advantageous aspects.

SUMMARY

An embodiment of the disclosure provides a turbocharging system of an internal combustion engine comprising a turbocharger and a by-pass circuit, wherein the by-pass circuit comprises a first by-pass valve for connecting a compressor outlet and a turbine inlet of the turbocharger An advantage of this embodiment is that whenever the air flows through this by-pass circuit, it becomes possible to let the compressor operate in better conditions1 since its operating points spontaneously shift far from the surge line and, consequently, far from the noisy condition.

According to an aspect of the invention, said first by-pass valve is an unidirectional valve adapted for an automatically opening, whenever a pressure at the compressor outlet is higher than a pressure at the turbine inlet.

An advantage of this aspect is that the by-pass valve, however realized, does not require any control being automatically opened by the positive pressure difference between compressor outlet and turbine inlet.

According to another embodiment, said by-pass circuit further comprises a second by-pass valve and a plenum, wherein the plenum is located between said first by-pass valve and said second by-pass valve.

An advantage of this embodiment is that the introduction of a properly dimensioned plenum may allow the system to be less sensitive to mutual phasing of pressure pulsations in compressor outlet and turbine inlet ducts since the plenum behaves as a damper of pressure pulsations.

According to a further embodiment, the invention provides a turbocharger of an internal combustion engine, comprising a compressor and a turbine mechanically connected, and further comprising a by-pass circuit having a first by-pass valve and hydraulically connecting a compressor outlet with a turbine inlet.

An advantage of this embodiment is that the turbocharger has an integrated by-pass circuit, and consequently the invention can be implemented without major packaging issues.

According to an aspect of this embodiment, said first by-pass valve is an unidirectional valve adapted for an automatically opening, whenever a pressure at the compressor outlet is higher than a pressure at the turbine inlet.

According to a still further embodiment, said by-pass circuit further comprises a second by-pass valve and a plenum, wherein the plenum is located between said first by-pass valve and said second by-pass valve.

An advantage of this embodiment is that the introduction of a properly dimensioned plenum may allow the system to be less, sensitive to mutual phasing of pressure pulsations in compressor outlet and turbine inlet ducts, since the plenum behaves as a damper of pressure pulsations.

According to a further embodiment the invention provides a method of operating a turbocharging system of an internal combustion engine, comprising a turbocharger and a by-pass circuit, wherein the by-pass circuit comprises at least a first by-pass valve for connecting a compressor outlet and a turbine inlet of the turbocharger. The by-pass is being activated if a pressure at the compressor outlet is higher than a pressure atthe turbine inlet. An activation of the by-pass means that the compressor outlet and a turbine inlet of the turbocharger are hydraulically connected through by opening at least the first by-pass valve of the by-pass circuit.

The first by-pass valve can be a unidirectional valve adapted for an automatically opening and/or an electronic controlled valve adapted to be opened, whenever a pressure at the compressor outlet is higher than a pressure at the turbine inlet.

An advantage of this embodiment is that the method provides the activation of the by-pass (i.e., the opening of the first by-pass valve or the two by-pass valves), allowing the compressor to operate in better conditions, since its operating points spontaneously shift far from the surge line and, consequently, far from the noisy condition.

According to another embodiment, the invention provides a method of diagnosis of a turbocharger by-pass circuit comprising the following steps: -detecting a malfunction in the air and charging system -deactivating the by-pass circuit, by external line break means.

Consequently, an apparatus is disclosed for performing a method of diagnosis of a turbocharger by-pass circuit, the apparatus comprising: -means for detecting a failure or a malfunction in the air and charging system -means for deactivating the by-pass circuit, by external line break means.

An advantage of this embodiment is that it provides a method for the diagnosis of any * failure of the by-pass circuit, for example a broken pipe or a blocked valve, and for the deactivation of said by-pass circuit, by a controlled external line break means.

According to a still further embodiment an internal combustion engine of an automotive system is provided, the engine comprising a turbocharger, with a turbine, a compressor and a by-pass circuit.

The diagnostic method according to one of its aspects can be carried out with the help of a computer program comprising a program-code for carrying out all the steps of the method described above, and in the form of computer program product comprising the computer program.

The computer program product can be embodied as a control apparatus for an internal combustion engine, comprising an Electronic Control Unit (ECU), a data carrier associated to the ECU, and the computer program stored in a data carrier, so that the control apparatus defines the embodiments described in the same way as the method. In this case, when the control apparatus executes the computer program all the steps of the method described above are carried out.

The method according to a further aspect can be also embodied as an electromagnetic signal1 said signal being modulated to carry a sequence of data bits which represents a computer program to carry out all steps of the method.

A still further aspect of the disclosure provides an internal combustion engine specially arranged for carrying out the method claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows an automotive system.

Figure 2 is a section of an intemal combustion engine belonging to the automotive system of figure 1.

Figure 3 is a simplified scheme of a turbocharger by-pass according to a first embodiment of the invention.

Figure 4 is a simplified scheme of a turbocharger by-pass according to a second embodiment of the invention.

Figure 5 is a graph depicting the pressure behavior at the compressor outlet and at the turbine inlet.

Figure 6 is a graph depicting the air flowrate through the by-pass circuit.

Figure 7 is a compressor collinear graph, pressure ratio vs. flowrate, showing the original and modified operating points of the compressor.

Figure 8 is a flowchart of a diagnostic method of the turbocharger by-pass circuit.

DETAILED DESCRIPTION OF THE DRAWINGS

Some embodiments may include an automotive system 100, as shown in Figures land 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 ignited1 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 increase the pressure of the fuel received 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. An intercooler 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 NOT) 250 with a VGT actuator 290 arranged to move the vanes 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.

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, particulate filters (DPF) or a combination of the last two devices, i.e. selective catalytic reduction system comprising a particulate filter (SCRF). Some embodiments may include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGS 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.

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 equipped with a data carrier 40. 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 4101 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, the 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.

Turning now to the ECU 450, this apparatus may include a digital central processing unit (CPU) in communication with a memory system and an interface bus. The CPU is configured to execute instructions stored as a program in the memory system, and send and receive signals to/from the interface bus. The memory system may include various storage types including optical storage, magnetic storage, solid state storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals toffrom the various sensors and control devices.

The program may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the ICE 110.

The turbocharger by-pass system according to the present invention aims to provide the opportunity to solve different issues related to the low end torque conditions.

Before illustrating the invention, some background considerations must be provided. As known, on turbocharged engines (especially Diesel engines) in low end torque operating conditions some issues related to compressor noise and low oxygen availability may arise. In fact, if the engine is running in steady state full and part load conditions or in transient conditions, as tip-in maneuvers, centrifugal turbochargers may run into surge or marginal surge, leading to noise: root cause of this inconvenience is due to the small amount of air that flows through the compressor. This typically occurs in low-mid engine rotating speed, limiting the capacy of turbocharger to generate boost and consequently torque. Given a certain engine rotating speed, and displacement, countermeasures to this inconvenience could be: a) Reducing the boost level. This measure effectively reduces the risk to have compressor noise, but it has a severe drawback since it reduces maximum fuel injected quantity, thus reducing engine torque output; b) reducing the centrifugal compressor "size', typically its inlet cross section is sensitive to this phenomenon. As drawback, this measure leads to lower flaw capacity during high end engine speed operations, in other words it implies the engine rated power reduction; c) increasing the volumetric efficiency. An increase in volumetric efficiency leads the compressor to operate in better conditions: with higher mass flow, the compressor operating points shifts into higher efficiency region of the compressor map. On the other hand, an engine with strong volumetric efficiency optimization for low end engine speed shows poor volumetric efficiency at rated power (the tradeoff is similar to the previous one, reducing the compressor size).

Moreover, it is well known that compressor noise could also arise in different transient conditions, as tip-out and gear shift maneuvers: in fact, during tip-out transients, the compressor can run into surge or noisy conditions, especially when the engine speed quickly drops down while the compressor still spools at its speed. A typical countermeasure against this phenomenon is the opening of the EGR valve, in order to let the compressor discharge its air through the exhaust line, preventing surge related noises. As drawback, this measure requires proper EGR valve actuation in such conditions and consequently requires dedicated controls implementation to monitor the compressor state.

Finally, a further issue in low end torque conditions is a low oxygen availability to promote soot oxidation. In fact, in this conditions if the combustion system is well optimized, the air usage might be so effective, that a very small amount of oxygen might be available into the exhaust flow, to bum the soot into the DPE. A possible countermeasure would be to increase the air/fuel ratio, but if the boost is already limited by the above mentioned noise problems, it would also lead to torque reduction. Not effective is also the increasing volumetric efficiency, which would lead to the same drawbacks, as shown before for compressor noise prevention. Of course, additional oxygen might be provided by an altemative source (for example, an additional pump), but this would increase the costs of the engine.

Therefore, in order to overcome in a different way the issues, as above described, the proposed system is a by-pass circuit 245, hydraulically connecting a compressor outlet 241 to a turbine inlet 251, in order to spontaneously let a certain amount of compressed air flows into the turbine. This by-pass circuit can be included in a turbocharging system, that is to say, such turbocharging system would include a turbocharge 230 and the by-pass circuit. According to a different solution, the by-pass circuit can be directly integrated into a turbocharger 230. In Figure 3, a first embodiment of the invention is shown. The schematic drawing represents the air circuit from the fresh air inlet, through the compressor 240, the intercooler 260, the intake manifold 200 up to the cylinder head 120. It also shows the exhaust gas route from the cylinder head 120 through the exhaust manifold 225, the turbine 250 up to the exit towards the aftertreatment system (not shown). The compressor outlet 241 is hydraulically connected with the turbine inlet 251 through a by-pass circuit 245 provided with a first by-pass valve 242. Being said valve is an unidirectional automatic valve, whenever the pressure at the compressor outlet 241 is higher than the pressure at the turbine inlet 251, a certain amount of the charged air directly flows to the turbine without passing through the engine.

According to a second embodiment (see Fig. 4), the by-pass circuit is also provided with a second by-pass valve 243 and a plenum 244 in between. The first unidirectional automatic valve 242 will let the charged air flows from the compressor outlet 241 to the plenum 244, whenever the pressure of the compressor outlet will overcome the plenum pressure, while the second unidirectional automatic valve 243 will let the charged air flows from the plenum 244 to the turbine inlet 251, whenever the plenum pressure will be higher than the turbine inlet pressure. An advantage of this embodiment is that the introduction of a properly dimensioned plenum may allow the system to be less sensitive to mutual phasing of pressure pulsations in compressor outlet and turbine inlet ducts, since the plenum behaves as a damper of pressure pulsations.

The way of working of such by-pass circuit is understandable from Fig. 5, which shows a graph depicting the instantaneous pressure 500 in the compressor outlet 241 and 510 in the turbine inlet 251 over a whole engine cycle. The charged air can flow through this by-pass circuit thanks to the instantaneous positive pressure difference (one example of this is marked as 520 in Fig. 5) that takes place between compressor outlet 241 pressure 500 and turbine inlet 251 pressure 510: in fact, over the complete engine cycle (2 revolutions), at mid-low engine speed, the pressure difference is either positive and negative. Arranging properly a connecting pipe with one or two unidirectional automatic valves, it is possible to have air flowing in the desired direction. The air flowrate passing through the by-pass is shown in Fig. 6, a graph depicting the instantaneous air flowrate 530 over a whole engine cycle. As easily understandable, there is a correspondence between periods of available flowrate 530 through the by-pass and periods during which the pressure 500 in the compressor outlet 241 overcomes the pressure 510 in the turbine inlet 251.

Therefore, thanks to this by-pass circuit, the engine is being by-passed: the air flow through the compressor is no longer limited by the engine operating conditions, but a given excess might be spontaneously discharged, requiring this system no additional governors. Consequently, if the air can flow through this by-pass circuit, it becomes possible to let the compressor operate in belier conditions, since its operating points spontaneously shift far from the surge line and consequently noisy condition: in fact due to such additional flow path, the compressor will elaborate a higher flowrate, under the same engine operating condition. In a typical diagram pressure ratio vs. flowrate with iso-efficiency lines and the surge line limiting the operating conditions of the compressor (see Fig. 7), the original operating point 540 of the compressor will shift towards right, as modified operating point 550, that is far from the noisy conditions represented by the surge line. Further advantage is that the energy put by the compressor into the air is partly recovered inside the turbine.

This new by-pass system should not have any negative impact on other systems/operating conditions. For example, in part load conditions, as the EGR has to be driven against the intake pressure, the by-pass route will not have any negative interference, as its arrangement will let it stay constantly closed if the pressure drop is against its opening direction.

Concerning mass air flow measurement accuracy, three different conditions have to be analyzed: in part load condition air measurement shall not be influenced since the by-pass will be spontaneously closed. All the air through the air flow meter will go only into the engine and therefore the air control routine in the ECU software shall not be impaired by wrong measurements; at low end torque and full load, the air flow meter might measure a higher value than the effective engine air consumption, as the by-pass circuit is supposed to work. This might have some impact, in the smoke limitation for example, but proper rearrangement of the smoke limitation strategy shall prevent this effect; at rated power, with midlhigh engine speeds, where the compressor usually runs far away.

from the surge line, pressure drop across the engine by-pass will be always negative (in fact, negative engine pumping is a typical condition) that it will be perfectly sealed, preventing any flow to by-pass the engine. So the air flow measurements will be correct.

Moreover, the invention will not have impact on turbocharger overspeed protection, since this risk is typical for rated power conditions, and is governed by proper control strategies. As stated above, in such conditions this by-pass circuit will be perfectly sealed.

Finally, the boost control strategies should work properly, regardless of the state of such device: both the observer and its actuator, pressure sensor and VGT actuator, shall not be influenced.

Concerning the safety, the by-pass circuit according to the invention is composed only by a pipe, an eventual plenum and one or two unidirectional automatic valves, therefore is intrinsically very reliable. Anyway if a failure or a malfunction would arise, for example a broken pipe or a blocked valve, a very simple method of diagnosis (Fig. 8) of such turbocharger by-pass circuit can be implemented. At first, the method should detect 20 a failure or a malfunction of the air and charging system, by using already existing diagnosis. As known, the Electric Management System (ECU and implemented software) of an internal combustion engine comprises several diagnoses about engine subsystems. One of them is a diagnosis of the air and charging system, which detects any failure or malfunction of the whole air and charging system including failure or malfunction of the related sensors and actuators. Then, the method should actuate the deactivation 21 of the by-pass circuit 245, by external line break means 246, for example a mechanically or electrically controlled valve, which could be a very simple valve like an ON-OFF valve.

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 block

21 block data carrier 100 automotive system internal combustion engine engine block cylinder cylinder head 135 camshaft piston crankshaft combustion chamber cam phaser 160 fuel injector fuel rail fuel pump fuel source intake manilold 205 air intake pipe 210 intake port 215 valves 220 port 225 exhaust manifold 230 turbocharger 240 compressor 241 compressor outlet 242 first by-pass valve 243 second by-pass valve 244 plenum 245 by-pass circuit 246 On-Off Valve 250 turbine 251 turbine inlet 260 intercooler 270 exhaust system 275 exhaust pipe 280 aftertreatment devices 290 VGT actuator 300 exhaust gas recirculation 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 temperature and level sensors 385 lubricating oil temperature and level sensor 390 metal temperature sensor 400 fuel rail pressure sensor 410 cam position sensor 420 crank position sensor 430 exhaust pressure and temperature sensors 440 EGR temperature sensor 445 accelerator position sensor 446 accelerator pedal 450 ECU 500 compressor outlet pressure 510 turbine inlet pressure 520 positive pressure difference between compressor outlet and turbine inlet 530 charged airflow rate through the by-pass 540 compressor original operating point 550 compressor modified operating point C.A. charged air

Claims

CLAIMS1. Turbocharging system of an internal combustion engine (110) comprising a turbocharger (230) and a by-pass circuit (245), wherein the by-pass circuit comprises a first bypass valve (242) for connecting a compressor outlet (241) and a turbine inlet (251) of the turbocharger.
2. Turbocharging system according to claim 1, wherein said first by-pass valve (242) is an unidirectional valve adapted for an automatically opening, whenever a pressure (500) at the compressor outlet (241) is higher than a pressure (520) at the turbine inlet (251).
3. Turbocharging system according to claim 1 or 2, wherein said by-pass circuit (245) further comprises a second by-pass valve (243) and a plenum (244), wherein the plenum is located between said first by-pass valve (242) and said second by-pass valve (243).
4. Turbocharger (230) of an internal combustion engine (110) comprising a compressor (240) and a turbine (250) mechanically connected, and further comprising a by-pass circuit (245) having a first by-pass valve (242) and hydraulically connecting a compressor outlet (241) with a turbine inlet (251).
5. Turbocharger according to claim 4, wherein said first by-pass valve (242) is an unidirectional valve adapted for an automatically opening, whenever a pressure (500) at the compressor outlet (241) is higher than a pressure (520) at the turbine inlet (251).
6. Turbocharger according to claim 4 or 5, wherein said by-pass circuit (245) further comprises a second by-pass valve (243) and a plenum (244), wherein the plenum is located between said first by-pass valve (242) and said second by-pass valve (243).
7. Method of operating a turbocharging system of an internal combustion engine, comprising a turbocharger (230) and a by-pass circuit (245), wherein the by-pass circuit comprises a first by-pass valve (242) for connecting a compressor outlet (241) and a turbine inlet (251) of the turbocharger and wherein the by-pass is being activated if the pressure a pressure (500) at the compressor outlet (241) is higher than a pressure (520) at the turbine inlet (251).
8. Method of diagnosis of a turbocharger by-pass circuit (245) comprising the following steps: -detecting (20) a failure or a malfunction in the air and charging system -deactivating (21) the by-pass circuit (245), by external line break means (246).
9. Internal combustion engine (110) of an automotive system (100), the engine comprising a turbocharging system, with a turbocharger (230) and a by-pass circui (245) according to one of the claims from ito 3.
10. Internal combustion engine (110) of an automotive system (100), the engine comprising a turbocharger (230), with a turbine (250), a compressor (240) and a by-pass circuit (245) according to one of the claims from 4 to 6.
11. A computer program comprising a computer-code suitable for performing the method according to claim 7 or 8.
12. Computer program product on which the computer program according to claim 11 is stored.
13. Control apparatus for an internal combustion engine, comprising an Electronic Control Unit (450), a data carrier (40) associated to the Electronic Control Unit (450) and a computer program according to claim 11 stored in the data carrier (40).
14. An electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim 11.