A vehicle engine system provided with a turbocharger and a control method for controlling such an engine system

Abstract

An engine system (1), the engine system (1) having: an internal combustion engine (ICE); a turbocharger (TC), the turbocharger (TC) being provided with a compressor (C) and a turbine (T); and a supply line (L), the supply line (L) supplying air to the engine (ICE) through the compressor (C); the supply line (L) having a supplementary compression stage, the supplementary compression stage being different from the compressor (C) and being controlled in a manner combined with the regulation of the turbine to limit the back pressure of the exhaust gas flowing out of the engine (ICE); in particular, the compression stage is defined by an injector (E).

Description

[0001] Cross - reference to related applications

[0002] This patent application claims the priority of Italian Patent Application no. 102020000000991, filed on January 20, 2020, the entire disclosure of which is incorporated herein by reference. Technical field

[0003] The present invention relates to a vehicle engine system provided with an internal combustion engine and a turbocharger. Background art

[0004] As is known, in dealing with internal combustion engines supercharged by means of a turbocharger, there is a strong need to reduce the so - called "turbo lag", which is basically a delay in the response time of the supercharger compressor in the case of acceleration starting from a relatively low number of revolutions per minute and / or in the case of acceleration after a driving phase in which the engine braking function is enabled (which usually means blocking the outlet through which the exhaust gases are discharged from the engine).

[0005] To meet this need, some known solutions are configured to increase the boost (commonly called "boost") of the compressed air based on the acceleration command set by the driver and, if necessary, also based on his / her driving style.

[0006] For example, document US7665302 discloses the use of a secondary supply line for another stream of compressed air and a throttle valve arranged downstream of the supercharger compressor on the main supply line. The secondary supply line is connected to the main supply line downstream of the throttle valve. The device is controlled to, for example, close or reduce the air passage flowing through the supercharger compressor when the accelerator pedal of the vehicle is released (i.e., in the case of engine braking), and at the same time supply compressed air to the engine from the secondary line.

[0007] There is a need to improve the known solutions related to "boost" in the compressed air supply to optimize the overall operation of the engine, increase the efficiency of the engine and recover energy in the best way from other operating states of the engine. In particular, it is necessary to reduce the specific fuel consumption of the engine during the cruise phase of the vehicle, for example, defined by a travel section with a constant speed.

[0008] Secondly, the specific solution of document US7665302 needs to be improved because, in this solution, when the compressor speed tends to increase due to the exhaust gases flowing through the turbine during the acceleration phase and the throttle valve remains closed, the restriction or closure caused by the throttle valve in the main line may lead to a phenomenon of unstable operation of the supercharger compressor. These phenomena are generally called "surge", and over time, they may cause deterioration of the compressor blades or destructive events.

[0009] Accordingly, an object of the present invention is to meet the above needs in a simple and economical manner. SUMMARY OF THE INVENTION

[0010] The above object is achieved by a vehicle engine system as defined in claim 1 and a control method for controlling such an engine system as defined in claim 8.

[0011] Furthermore, the dependent claims define specific embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Preferred embodiments of the present invention will be described hereinafter by way of non-limiting example only with reference to the accompanying drawings, in which:

[0013] - Figure 1 shows a schematic view of a preferred embodiment of an engine system provided with a turbocharger according to the present invention; and

[0014] - Figure 2 shows in cross-section a part of the schematic view of Figure 1 the schematic view. DETAILED DESCRIPTION OF THE INVENTION

[0015] Referring to Figure 1 , reference numeral 1 as a whole indicates an engine system (the engine system is shown in part and schematically).

[0016] More specifically, the engine system 1 includes:

[0017] - an internal combustion engine ICE, which includes one or more cylinders CY;

[0018] - a turbocharger TC, which includes a compressor C and a turbine T, and the turbine T operates the compressor C;

[0019] - a supply line L, which supplies air to the cylinders CY of the engine ICE through the compressor C;

[0020] - an air filter AF, which is connected to the inlet of the compressor C such that the compressor C sucks in ambient air through the air filter AF.

[0021] Preferably, a heat exchanger CAC (which is defined, for example, by a so-called "intercooler") is arranged along the pipeline L to cool the compressed air delivered to the engine ICE. The pipeline L also includes an intake manifold IM of the engine, and the intake manifold IM receives the compressed air cooled by the heat exchanger CAC and delivers the air to the intake valve of the cylinder CY. Therefore, the pipeline L includes a branch PTC that pneumatically connects the outlet U of the compressor C to the inlet of the heat exchanger CAC and a branch PTI that connects the outlet of the heat exchanger CAC to the intake manifold IM.

[0022] The engine ICE is supplied with fuel, and the fuel is mixed with the air from the pipeline L in the cylinder. The engine ICE is preferably a compression ignition engine, so that the injected fuel can be diesel fuel.

[0023] The engine ICE generates exhaust gases, and the exhaust gases flow into an exhaust pipeline LTC, in which a turbine T is arranged, so the turbine T is rotated by the gas flow. The startup of the compressor C by the turbine T is preferably mechanical, for example, by means of a direct startup defined by a transmission shaft. However, according to a variant not shown herein, the startup of the compressor C by the turbine T can be electric (i.e., the compressor C is started by an electric motor driven by an electric current, and the electric current is supplied by a battery pack and by at least one generator, and at least one generator is in turn operated by the turbine T).

[0024] In a conventional application, the pressure of the air compressed by the compressor C basically depends on the work of the turbine T, and thus depends on the enthalpy of the exhaust gases upstream of the turbine T, and the enthalpy of the exhaust gases in turn depends on the operating state of the engine ICE. Generally, based on the rotational speed of the turbine T, the compressor C can provide compressed air at a pressure in the range of 1.1 bar to 3.5 bar.

[0025] According to a preferred aspect of the present invention, the engine system 1 further includes an energy source, which is defined by a pressurized air source S in the example shown herein. The source S includes a tank ACC and a supply pipeline L1 connected to the tank ACC, so that the tank ACC can store / accumulate air under pressure. In particular, the pipeline L1 can connect the tank ACC to the compressor by means of a valve (the valve is not shown). For example, the compressor can be operated by the engine ICE and can be defined by a compressor that supplies a vehicle's braking system (the braking system is not shown). However, the compressed air can be supplied to the tank ACC in different ways (for example, by air compression in the cylinder CY during an engine braking operation phase).

[0026] In any case, the air reaching the tank ACC has been filtered in a known manner, which is not shown herein.

[0027] The source S includes a connection pipeline L2 that connects the tank ACC and / or the pipeline L1 to the outlet valve V1. The valve V1 is in turn connected to the pipeline L by means of a connection pipeline L3, such that the tank ACC can deliver air to the intake manifold IN, as described in more detail below. In other words, the valve V1 regulates the air flow from the tank ACC to the pipeline L3. Preferably, the valve V1 is a on-off valve, such that the valve V1 is selectively controlled to allow air to flow through or prevent air from flowing through. If required, the valve V1 can be controlled not only to prevent air from flowing to the pipeline L3 but also to restrict the outlet of the valve V1 and regulate the air flow rate reaching the pipeline L3.

[0028] Conveniently, the pipeline L2 includes a pressure reducer PR that has the function of regulating or restricting the pressure value available downstream of the pressure reducer PR. In particular, the pressure reducer PR is calibrated or controlled in an active manner to adapt the pressure level to the design requirements or the required values at the pipeline L and / or the pipeline L3 (and the needs of possible other compressed air users, where possible other compressed air users are connected to the source S by means of at least one other valve V2). According to a variant not shown herein, the functions performed by the pressure reducer PR and by the valve V1 can be integrated in a single valve.

[0029] According to a preferred aspect of the present invention, the pipeline L3 is connected to the pipeline L by means of an ejector E that is configured such that the air coming from the source S along the pipeline L3 causes a flow compression downstream of the ejector E and a reduction in the air pressure for sucking air from the outlet U of the compressor C, as Figure 2 schematically shown.

[0030] Basically, the ejector E defines a supplementary compression stage that is arranged in series with the compressor C along the pipeline L and is controlled by operating the valve V1 in order to generate a further pressure difference in the air supplied to the engine ICE in addition to the pressure difference already provided by the compressor C.

[0031] The ejector E is arranged downstream of the compressor C and, in particular, is arranged downstream of the compressor C along a branch PTC of the pipeline L. However, according to a variant, the ejector E can be replaced by a different compression device (as described in more detail below) that is arranged upstream or downstream of the compressor C indifferently.

[0032] The configuration of the ejector E includes: an inlet I1 that is connected via a pipeline L3 to a source S; an inlet I2 that is connected to the outlet U of a compressor C; an outlet U1 that is connected to an intake manifold IM, in particular via a heat exchanger CAC to the intake manifold IM; a nozzle E1 that receives air from the inlet I1; a suction chamber E2 in which the aforementioned pressure drop is formed and in which the air flowing out from the nozzle E1 is mixed with the air sucked in through the inlet I2; and a diffuser E3 that has a diverging end section that terminates at the outlet U1 and converts part of the kinetic energy of the air flow into a pressure increase.

[0033] According to a variant not shown herein, the ejector E is of the type with variable geometry, for example of the type including a nozzle that receives air from the pipeline L3 and is adjusted by a tapered pin controlled by a control unit ECU to change the flow cross-section; and / or the ejector E incorporates the function of a suitable flap integrated valve V1 controlled by a control unit ECU.

[0034] Due to the supplementary compression stage defined by the ejector E, the air flow at the outlet U1 has a higher pressure than that obtained by operating the compressor C alone without air from the source S. In this way, the ejector E provides a so-called "boost", i.e., an increase in supercharging. If the source S does not supply air, the pressure downstream of the ejector E is the same as the pressure available at the outlet U, except for the normal load losses present in the pipeline and in the ejector E.

[0035] The ejector E can be advantageously used in specific operating states of an internal combustion engine ICE to obtain supercharging of the turbocharger TC without the "turbo lag" phenomenon (or with a lower "turbo lag" compared to a solution without "boost"). For example, the source S and the ejector E are used in the acceleration phase of the engine ICE when the engine speed in revolutions per minute is relatively low and / or when the rotational speed of the compressor C is relatively low and / or immediately after an engine braking phase. In these cases, when the engine ICE accelerates in response to a command from the driver acting on the accelerator pedal, the work provided by the turbine T tends to increase due to the exhaust gas flow, and at the same time the suction caused by the ejector E affects the compressor C by reducing the resistance at the outlet U, so that the response time of the turbocharger TC is reduced.

[0036] This also results in an advantage in terms of the instantaneous acceleration state with respect to reducing the smoke generated at the exhaust outlet.

[0037] An electronic control unit is provided (which is preferably defined by the control unit ECU that controls the engine ICE) to control the valve V1 to open / close the air supply from the source S and, if necessary, adjust the flow rate and / or the pressure of the air flow according to the operating parameters of the engine ICE and / or the turbocharger TC and / or the pipeline L and / or the source S (the values of these parameters are determined by suitable sensors not shown herein). In particular, the valve V1 is opened and controlled based on the acceleration command given by the driver and based on the instantaneous operating state of the engine to achieve the supply pressure value required by the control unit ECU. For example, as already mentioned above, the control unit ECU is configured to open the valve V1 when the engine ICE accelerates, particularly after the engine braking operation phase that decelerates the vehicle and / or when the compressor C has a rotational speed lower than a given threshold and / or when the torque required by the driver (at the same air / fuel lambda ratio) will require an air quantity larger than the air quantity that can be delivered by the compressor C alone.

[0038] The use of the injector E not only facilitates the acceleration transition, but the use of the injector E also causes an increase in the efficiency of the engine during constant-speed driving, because it can utilize the air that is compressed and supplied to the tank ACC during the braking action started by the engine brake.

[0039] According to a preferred aspect of the present invention, the pipeline L3 passes through the heat exchanger HE to heat the air flowing from the source S to the injector E, so as to reduce the air quantity required to allow the injector E to operate according to the requirements of the control unit ECU. In fact, heating tends to cause an increase in the volume flow rate, which reduces the air flow rate from the tank ACC to obtain the required pressure downstream of the injector E.

[0040] Preferably, the heat exchanger HE uses the heat of the exhaust gas generated by the engine ICE to heat the air delivered to the inlet I1. For example, the heat exchanger HE is connected to the exhaust manifold EM that connects the engine ICE to the exhaust pipeline LTC, or is connected to a known EGR pipeline.

[0041] According to an aspect of the present invention, the turbine T of the turbocharger TC can be adjusted such that the turbine T can change its rotational speed and the work generated.

[0042] In particular, the turbine T is of the variable geometry type, i.e., the turbine T has a stator or distributor with blades that can be adjusted by means of a rotating or axially movable wall, thereby changing the flow cross-section and the angle of incidence of the gas on the blades. As mentioned above, this adjustment changes the rotational speed of the turbine T. As is well known, the change in the geometry of the stator and thus the change in the flow cross-section result in a change in the backpressure of the exhaust gas present between the cylinder CY and the turbine T: for the same operating state of the given engine ICE, when the opening between the blades is larger, the backpressure of the gas and thus the rotational speed of the turbine are lower; conversely, when the opening between the blades is smaller, the backpressure and the speed of the turbine T are higher.

[0043] Therefore, the strategy of controlling the flow by the injector E, i.e., the strategy of controlling the supplementary compression stage, is integrated and coordinated with the strategy of controlling the distributor of the turbine T. In particular, since the rotational speed of the turbine T corresponds to the rotational speed of the compressor C (in the case where the compressor is mechanically operated by the turbine T), the injector E is used to reduce the boost pressure provided by the compressor C alone and thus achieve the required set pressure value, as mentioned above; at the same time, since the work required from the compressor C is reduced, the opening of the variable geometry of the turbine T can be increased. Thus, a boost level can be obtained that is the same as the boost level that could be provided by the compressor C alone without using the injector E, but with the turbocharger TC operating at a lower rotational speed and with a lower backpressure relative to the engine.

[0044] In this way, in the case of a load representative of the cruise speed - which is approximately one-third of the maximum load - the turbine T operates within the range of rotational speed and flow cross-section of the distributor nozzles at which it has a higher efficiency. In particular, compared to the prior art where there is no injector E, the boost provided by the injector E allows the distributor to be closed to a lesser extent, thus keeping the turbine in a region of higher efficiency. Generally speaking, in fact, when the distributor is closed by approximately 60% - 70%, the highest efficiency point of a turbine with variable geometry (e.g., a turbine of the type called "pivoting impeller") is reached. In the case of a low load representative of the cruise speed, in order to maintain the necessary boost pressure in known solutions without an additional compressor, conversely, the turbine is closed by less than 40%.

[0045] Similar considerations also apply to the compressor C, where a lower compression ratio at the same flow rate enables the compressor C to operate in a region of its characteristic map that characterizes higher efficiency.

[0046] These two effects act on each other: since the overall efficiency of the turbocharger TC is the product of the efficiency of the turbine T, the efficiency of the compressor C, and the mechanical efficiency (although this mechanical efficiency is always very high and not affected by the load), the overall efficiency is significantly increased. This improvement affects the engine: to establish a rule of thumb, we can say that a 5 percentage point increase in turbocharger efficiency corresponds to a 1 percentage point increase in the overall engine.

[0047] In addition, this combination or integration between the two controls makes it easier for the engine to accelerate, because this allows the turbocharger to reach a steady state in a short time.

[0048] In addition, at the end of the transition due to acceleration, and after reaching the steady state, i.e., after reaching the cruising state of the vehicle, due to the contribution of the injector E, the distributor of the turbine T can reach a closing degree smaller than that of the known solution without the injector E.

[0049] This allows the vehicle to reach as close as possible to the maximum efficiency opening of the turbine T and achieve the technical goal of minimizing the exhaust back pressure of the engine. Due to this result of minimizing the exhaust back pressure, it is well known that the specific fuel consumption of the vehicle will always be reduced, and even when the intake pressure is higher than the exhaust back pressure, i.e., when there is a positive difference between the boost pressure in the intake manifold IM and the back pressure or pressure in the exhaust manifold EM, the possibility of generating positive power is achieved.

[0050] This is what is defined in the automotive industry as a "positive pumping cycle", which in known solutions can be achieved in a very small area of the engine map, at low speed operation and high load conditions (these terms are opposite to the so-called "negative pumping cycle", which absorbs useful power and is typical of internal combustion engines). In this way, the engine acts like an expander of a virtual pneumatic system, thus generating positive power during the so-called pumping cycle, i.e., during the passive phase of the four-stroke cycle.

[0051] This advantage, i.e., the increase in mechanical energy at the drive shaft, is basically not affected by the energy consumed in storing compressed air in the tank ACC, because when the internal combustion engine ICE operates in the engine braking state, i.e., when the drive wheels do not need to be powered, the compressed energy required for this can be advantageously obtained from the engine system 1.

[0052] As described above, the control performed by the control unit ECU requires adding a further pressure difference to the pressure difference provided by the compressor C in order to obtain a given setpoint for the pressure (or flow rate) of the air supplied to the engine. For example, a closed-loop control based on a first pressure sensor (not shown) is provided, which is designed to detect the pressure of the air supplied to the engine ICE (e.g., the pressure of the air in the intake manifold). In addition, a second pressure sensor (not shown) is arranged between the compression stage defined by the compressor C and the supplementary compression stage defined by the injector E to determine the contributions provided by the two stages in order to establish the total pressure difference of the air flow supplied to the engine.

[0053] At the same time, the variable geometry of the turbine T is adjusted according to a parameter indicating the pressure at the intake of the engine ICE and a parameter indicating the work of the turbine T, such that the parameter under control is maintained within an established range, e.g., maintained at its setpoint. In this regard, it should be noted that the backpressure of the exhaust gas when it flows out of the engine ICE determines the pressure difference across the turbine T, which in turn determines the work generated by the turbine T itself. Therefore, the work and the backpressure are related to each other.

[0054] The range or threshold for establishing when an action is applied to the turbine T can be represented by a fixed value or a value that varies in response to the operating state of the engine ICE and / or the turbine T.

[0055] The rotational speed of the turbine T can advantageously be used as a parameter indicating the work of the turbine T (and thus, indicating the backpressure of the exhaust gas). Preferably, a closed-loop control is provided to perform the adjustment of the variable geometry and to check whether the controlled parameter is below the established threshold. For example, in the case where the parameter is the rotational speed of the turbine T, this quantity can be directly detected by a speed sensor (not shown) or estimated by the control unit ECU based on other data related to the operation of the engine system.

[0056] Therefore, if the said speed tends to exceed the above threshold or setpoint, the control of the control unit ECU substantially opens the distributor to limit the rotational speed of the turbine T (and thus reduce the backpressure), while the supplementary compression stage (defined by the injector E in this particular case) is controlled to provide its contribution to the pressure difference and obtain the setpoint for the limited desired air pressure / flow rate.

[0057] In this way, the supplementary compression stage not only compensates for the inherent faults that may occur in the turbocharger TC during the acceleration transition, but also, in other operating states, if there is no limit to the speed of the turbine T (and thus, no reduction in the backpressure of the engine exhaust), the supplementary compression stage also replaces a part of the work done by the compressor C.

[0058] According to a variant, the limitation of the rotational speed can also be obtained by means of a turbine provided with an exhaust gas flap having a fixed geometry, the exhaust gas flap having an intervention threshold and / or an intervention moment controlled by the control unit ECU. In other words, according to the invention, the turbine can be adjusted by acting on the exhaust gas flap so that a part of the exhaust gas bypasses the impeller of the turbine (instead of acting on a distributor with variable geometry) to limit the rotational speed of the turbine shaft and thus the back pressure of the gas flowing out of the engine.

[0059] Furthermore, as described above, the supplementary compression stage can be different from the injector E. For example, according to a variant not shown herein, the supplementary compression stage can be defined by a supplementary compressor device operated by means of:

[0060] - an electric motor, which in turn is powered by an electrical energy source preferably generated by recovering energy during a braking action of the vehicle; in this case, the source S and the tank ACC are substantially replaced by an energy source having a battery storing electrical energy; or

[0061] - another turbine, such as a steam turbine, which is part of a waste heat recovery system and also absorbs waste heat from the exhaust gas and / or the motor during normal operation of the vehicle in order to convert said heat into mechanical energy (and then, if necessary, into electrical energy); this variant also allows a reduction in the number of gears and / or couplings, since the steam turbine can be directly coupled to the supplementary compressor device; the supplementary compressor device can be defined by a known rotary compressor, such as a centrifugal compressor like compressor C, but provided with an aerodynamic map optimized based on a lower design compressor ratio.

[0062] These variants do not change the possibility of recovering the energy (from braking actions, from waste heat, etc.) that would otherwise be lost and making said energy available on the line L in the supplementary compression stage, while the supplementary compression stage is controlled in combination with the regulation of the turbine T to limit the back pressure of the gas flowing out of the engine ICE.

[0063] For the reasons described above, the advantages of the engine system 1 according to the invention are evident. In fact, the combined control of the geometry of the supplementary compression stage and the turbine allows the engine ICE to be supplied with the energy previously stored during braking actions and / or by using waste heat. Furthermore, a reduction in the exhaust back pressure, even a relatively small one, can generate a relatively large energy difference for the drive shaft, since the work done or saved can be expressed as ΔP x ΔV: even in the case of a low ΔP, if the displacement of the engine (which defines the volume change ΔV) is large, the work can be large, as is the case for industrial engines.

[0064] In fact, the control of the turbine T allows the exhaust backpressure to be reduced until a positive pressure difference is achieved across the cylinder CY (between the pressure in the intake manifold IM and the backpressure in the exhaust manifold EM) to increase the mechanical energy generated at the drive shaft. Additionally, as described above, the turbocharger TC operates in its more efficient operating range.

[0065] Moreover, the engine is more efficient when the injector E is supplied by the source S because the engine can utilize the air compressed during the engine braking phase, and / or the turbocharger TC has a shorter response time compared to known solutions, where the supercharging is provided by a single compressor C.

[0066] In particular, a saturated "boost" can be provided during the acceleration phase without endangering the operating stability of the compressor C, and more generally, without compromising the operating and structural state of the turbocharger TC.

[0067] Furthermore, boost can also be provided only in the cruise state to reduce the power absorbed by the compressor C and optimize the efficiency of the internal combustion engine ICE.

[0068] Moreover, the design, manufacture, and installation of the specific solution with the injector E proposed herein are very simple because the solution has a very small number of components, is very compact, and the number of valves or movable elements to be controlled is also limited.

[0069] As described above, the heat exchanger HE allows the air required by the injector E to be reduced in a very simple and compact manner, especially when the exhaust gases from the exhaust manifold EM are used as the heat source.

[0070] Finally, compared to what has been described above and shown herein only by way of example, the engine system 1 can evidently undergo changes and variations without thereby exceeding the scope of protection described in the appended claims.

[0071] In particular, as described above, the pressurization method of the source S or the tank ACC can be different from the pressurization method of the source S or the tank ACC illustrated above by way of example, but in any case, it is necessary to take into account that the supplementary compression stage is preferably supplied with the energy recovered during the engine braking operation phase and / or from waste heat.

[0072] Moreover, the heat for heating the air in the pipeline L3 can be provided by an electric heater instead of by the heat exchanger HE.

Claims

1. An engine system (1), comprising: An internal combustion engine (ICE); A turbocharger (TC), said turbocharger (TC) including a compressor (C) and a turbine (T); A supply line (L), said supply line (L) supplying air to said engine (ICE) through said compressor (C); Said supply line (L) includes: a supplementary compression stage, said supplementary compression stage being different from said compressor (C); a control device, said control device being arranged to control said supplementary compression stage and to adjust said turbine (T) so as to limit the back pressure of the exhaust gas leaving said engine in a manner combined with the control of said supplementary compression stage, Wherein, said supplementary compression stage includes an injector (E), said injector (E) being connected to a pressurized air source (S) and arranged downstream of said compressor (C) so as to receive air from said source (S) and cause a reduction in air pressure in use that sucks air out of said compressor (C), and Wherein, said engine system further includes a heater for heating the air flowing from said source (S) to said injector (E) in use.

2. The engine system according to claim 1, characterized in that, Said heater is defined by a heat exchanger (HE), said heat exchanger (HE) being arranged to utilize the heat of the exhaust gas generated by said engine (ICE) in use.

3. The engine system according to claim 1, wherein, Said injector (E) has a variable geometry.

4. The engine system according to any one of claims 1 to 3, characterized in that, Said control device is configured to supply air from said source (S) to said injector (E) when the engine is accelerating and at least one of the following occurs: Acceleration is immediately controlled after an engine braking phase; Said compressor (C) has a rotational speed below a given threshold; The torque required for acceleration requires a supply air volume and / or supply air pressure higher than the supply air volume and / or supply air pressure that can be delivered by said compressor (C) alone.

5. The engine system according to claim 1, characterized in that, Said supplementary compression stage includes a supplementary compressor device driven by an electric motor or another turbine, said supplementary compressor device being adapted to be powered by the energy generated during an engine braking phase or by the energy generated through waste heat recovery.

6. A control method for controlling the engine system according to claim 1, said method comprising the following steps: Providing a pressure difference in said supply line by means of said compressor (C); Controlling said supplementary compression stage to provide a further pressure difference for achieving a given set point of the air pressure / air flow rate to be supplied to said engine (ICE); Adjusting said turbine (T) to limit the back pressure of the exhaust gas leaving said engine.

7. The method according to claim 6, characterized in that, Said turbine is adjusted according to a parameter indicating the work generated by said turbine.

8. The method according to claim 7, wherein Said turbine is adjusted to keep said parameter below a given threshold and / or at a given set point.

9. The method according to claim 6, wherein The back pressure of the exhaust gas at the outlet of said engine is reduced relative to the following reference state: said reference state corresponds to using said compressor (C) without adding said further pressure difference.

10. The method according to claim 6, wherein Said further pressure difference is provided by using the energy generated during an engine braking phase or by the energy generated through waste heat recovery.

11. The method according to claim 10, wherein The energy is defined by electrical energy or pressurized air.

12. The method according to any one of claims 6 to 11, characterized in that, The further pressure difference is provided by supplying air from the source (S) to the ejector (E).

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