AN ENGINE UNIT WITH DEDICATED COMPRESSOR, HEATING DEVICE

AND TURBINE ON THE INTAKE AIR CIRCUIT AND AUTOMOTIVE

VEHICLE INCORPORATING SUCH ENGINE UNIT

TECHNICAL FIELD

The present invention generally relates to engine units comprising an internal combustion engine and more particularly a piston engine either of the compression ignition type or the spark ignition type.

BACKGROUND ART

It is well known to use a turbocharger with internal combustion engines in order to raise the available power. The use of a turbocharger, by providing intake air at higher pressure allows introducing more intake gases in the cylinders. The use of a turbocharger increases also the efficiency of the engine unit by converting the otherwise wasted mechanical energy of the exhaust gas for compressing the intake air and raise the intake pressure. To further increase the intake gas pressure, it is also known to combine two turbochargers in series, with a low pressure and a high pressure compressor. Nevertheless, a turbocharger can only benefit from the mechanical energy of the exhaust gases to provide additional intake gas pressure, which has of course its limits, especially at low revolution speeds of the engine. It is also known to increase the air intake pressure by using a compressor mechanically driven by the engine itself, but, in such a case, the energy needed to further compress the intake gas is taken from the engine output, so that the balance of benefits is not positive in all operating conditions.

. Therefore, a need exists to further increase intake gas pressure, for an internal combustion engine, without compromising on the engine's overall efficiency.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide an engine unit having the capacity to deliver increased intake gas pressure and/or density without compromising on the engine's overall efficiency.

An engine unit generally comprises an internal combustion engine, an gas intake circuit and an exhaust gas circuit. The internal combustion engine is a piston two or four stroke engine, either of the spark ignition type, for example a gasoline engine, or of the compression ignition type, for example a diesel engine.

According to the invention the gas intake circuit comprises a dedicated compressor, a dedicated heating device for heating intake gas and a dedicated turbine driving the dedicated compressor, said items being arranged in this order in the direction of the intake gas flow. The group of the dedicated compressor, the dedicated heating device for heating intake gas and the dedicated turbine driving the dedicated compressor, works substantially as a means to increase the intake gas pressure independently of the revolution speed of the engine and therefore increases the available power of the engine, especially at low revolution speed.

The heating of the intake gas may be performed in various ways. According to one aspect of the invention the dedicated heating device comprises a heat exchanger. The use of such exchanger allows recovering of heat otherwise lost. According to one embodiment of the invention the heat exchanger derives heat from the exhaust gas circuit, this recovering of the thermal energy of the exhaust gas increasing the whole efficiency of the engine unit.

According to another aspect of the invention, the dedicated heating device comprises a burner. Not only does the burner give more enthalpy to the intake gas, but also, by burning a part of the oxygen within the intake gas, this burner will allow a tuning of the oxygen ratio of the intake gas and therefore allow a more precise control of the emission of pollutants such as Nitrogen Oxide (NOx) in the exhaust gas.

According to an embodiment of the invention, the dedicated heating device comprises a dedicated heat exchanger and a burner downstream of the heat exchanger. This combination will allow both an increase of the efficiency

of the engine unit and a reduction of pollutant emissions; therefore this combination increases the whole environmental balance of the engine unit.

According to one aspect of the invention, the gas intake circuit further comprises a dedicated cooling device for cooling the intake gas downstream of the dedicated turbine. By reducing the temperature of the intake gas it is possible to reduce pollution. Furthermore the reduction of temperature combined with the augmentation of pressure, increases the ratio pressure to temperature, consequently the density of the intake gases, and therefore increases dramatically the efficiency of the engine. According to another aspect of the invention, the gas intake circuit further comprises dedicated mixing means adapted to collect a part of the intake gas upstream of the dedicated compressor and to mix this collected part of the intake gas with the intake gas downstream of the dedicated turbine or the dedicated cooling device. Such dedicated mixing means allow tuning the air intake temperature and/or the air intake pressure.

In order to further increase its power and efficiency, the engine unit may further comprise a turbocharger having a primary compressor, fluidly connected to the gas intake circuit upstream of the dedicated compressor and driven by a primary turbine fluidly connected to the exhaust gas circuit. The use of such turbocharger allows a recovering of the mechanical energy of the exhaust gas and when associated with the heat exchanger of the dedicated heating means, recovery of both mechanical and thermal energy of the exhaust gas is achieved.

In order to reduce the raise of temperature of the intake gas due to its compression by the turbocharger, the gas intake circuit may comprise, between the primary compressor and the dedicated compressor, a primary cooling device for cooling the intake gas.

According to another aspect of the invention allowing further controlling the pollutants level within the exhaust gas, the engine unit may further comprise an exhaust gas recirculation (EGR) circuit adapted to collect a part of the exhaust gas and to input the collected part of the exhaust gas within the

gas intake circuit. The EGR circuit may be adapted to recirculate high pressure and/or low pressure exhaust gas.

According to one embodiment of the invention, the EGR circuit is adapted to collect high pressure exhaust gas and to input the collected part of the exhaust gas within the gas intake circuit downstream of the dedicated turbine.

According to one aspect of this embodiment and if the gas intake circuit comprises a dedicated cooling device the EGR circuit may input the collected part of the exhaust gas either upstream or downstream of the dedicated cooling device.

According to another aspect of this embodiment the dedicated heating device of the gas intake circuit comprises a heat exchanger which derives heat from the EGR circuit.

According to another embodiment of the invention, the EGR circuit is adapted to collect low pressure exhaust gas and to input the collected part of the exhaust gas in the gas intake circuit upstream of the dedicated compressor.

According to one aspect of this embodiment and when the engine unit comprises a turbocharger the EGR circuit is adapted to input the collected part of the exhaust gas in the gas intake circuit upstream of the primary compressor.

According to an aspect of the invention, EGR circuit comprises an EGR cooling device for cooling the collected part of the exhaust gas.

The various above aspects or embodiments of the invention may be combined in various ways with each others provided the combined aspects or embodiments are not incompatible or mutually exclusive.

Another object of the invention is an automotive vehicle comprising an engine unit according to the invention.

DESCRIPTION OF FIGURES

Other aspects and advantages of the present invention will be apparent from the following detailed description made in conjunction with the

accompanying drawings illustrating schematically some non-limitative embodiments of the invention.

- Fig. 1 is a schematic block diagram of a first engine unit of the invention. - Fig. 2 is a schematic block diagram of a second embodiment of an engine unit of the invention.

- Fig. 3 is a schematic block diagram of a third embodiment of an engine of the invention.

- Fig. 4 is a schematic block diagram of a fourth embodiment of an engine unit of the invention.

- Fig. 5 is a schematic block diagram of a fifth embodiment of an engine unit of the invention.

Corresponding reference numbers indicate corresponding components in the various embodiments illustrated in the drawings.

DESCRIPTION OF THE INVENTION

Referring now to the drawings in greater details there is, schematically illustrated in figure 1 , an engine unit designated as a whole by reference number 1. The engine unit 1 comprises an internal combustion engine 2 provided with an gas intake circuit or system 3 and with an exhaust gas circuit or system 4. The fluids flow directions are shown on the figures by arrows within the gas intake circuit 3 and the exhaust gas circuit 4.

The internal combustion engine is for example a multicylinder four stroke diesel engine. Engine unit 1 comprises, on the gas intake circuit 3, a dedicated compressor dC followed, according to the intake gas flow direction, by a dedicated heating device 5. Downstream of the dedicated heating device 5 there is a dedicated turbine dT driving dedicated compressor dC. Dedicated compressor dC, dedicated heating device 5 and dedicated turbine dT are arranged in this order along the path of the intake gas flow, that is in the intake gas flow direction.

The dedicated turbine dT is operatively connected to the dedicated compressor of dC by a shaft 6. The gas intake circuit 3 comprises, downstream the dedicated turbine dT, a dedicated cooling device dCD for cooling the intake gas before entry in the engine 2. The dedicated cooling device dCD may be of various types such as an air-to-air heat exchanger or an air-to-water heat exchanger connected to a water cooling circuit (not shown) of the engine 2.

When the engine 2 is running, intake gas goes first in the dedicated compressor dC and is then heated by heating device 5. On the embodiment shown on figure 1 , heating device 5 comprises a dedicated heat exchanger dHE which is fluidly connected to the exhaust gas circuit 4 and therefore derives heat from the exhaust gas for raising the temperature of the intake gas. After leaving the dedicated heat exchanger dHE, the intake gas goes through the dedicated turbine dT and then through the dedicated cooling device dCD. The assembly formed by the dedicated compressor dC, the dedicated heat exchanger dHE and the dedicated turbine dT converts the heat energy of the exhaust gas in mechanical energy to raise the pressure of the intake gas.

Heating of the intake gas, between the dedicated compressor dC and the dedicated turbine dT, may be also performed by a burner B, either alone or in combination with another heat source such as the dedicated heat exchanger mentioned above. Here, the assembly formed by the dedicated compressor dC, the burner and the dedicated turbine dT converts the heat energy derived by the burnt fuel into mechanical energy to raise the pressure of the intake gases. When combined with the dedicated heat exchanger dHE, the burner B is situated downstream of the dedicated heat exchanger dHE. In addition to providing heat to the intake gas flow, the burner can be used to consume part of the oxygen contained in the intake gas flow, and therefore , the burner may be used for tuning the oxygen level of the intake gas as, while entering in the intake circuit 3, the intake gas consist of the ambient air. By tuning the oxygen level it is possible to control the pollutant emission of the engine 2. The burner B burns within the intake gas the same fuel as the one used by the engine. It

can also be provided that the burner burns another fuel, and/or that the burner is supplied at least in part with an oxygen containing gas not coming from the gas intake circuit.

It must be understood that, even if, on the shown embodiment, the dedicated heating device 5 comprises both a burner B and a dedicated heat exchanger dHE, the dedicated heating device may, according to the invention, comprise either a burner or a heat exchanger.

The embodiment of the invention shown on figure 1 can be considered as a basic embodiment but some more sophisticated embodiments of the invention can be implemented.

For example, according to the embodiment shown on figure 2, the engine unit 1 further comprises a turbo charger 7 associated with an intercooler or primary heat exchanger pHE. The turbo charger 7 comprises a primary compressor pC located on the intake gas circuit 3, upstream of the dedicated compressor dC. The turbo charger 7 further comprises a primary turbine pT situated on the exhaust gas circuit 4, upstream of the dedicated heat exchanger dHE. The primary turbine pT is operatively connected to the primary compressor dC by a shaft 8 and recovers the mechanical energy of the exhaust gas to drive the primary compressor pC. The primary heat exchanger pHE is situated on the gas intake circuit 3, between the primary compressor pC and the dedicated compressor dC. The primary heat exchanger pHE may be of various types, for example an air-to-water heat exchanger connected to a water cooling circuit (not shown) of the engine 2.

In order to allow a fine tuning of the intake gas pressure and/or temperature, the gas intake circuit further comprises dedicated mixing means 10 adapted to collect a part of the intake gas between the primary heat exchanger pHE and the dedicated compressor dC and to mix this collected part of the intake gas with the intake gas downstream of the dedicated cooling device dCD. Therefore, the dedicated mixing device 10 comprises a three- way control valve 11 whose inlet is fluidly connected to the primary heat exchanger pHE, whereas its first outlet is fluidly connected to the dedicated compressor dC and second outlet is fluidly connected to a first inlet of a three-

way manifold 12. A second inlet of the three-way manifold 12 is fluidly connected to the outlet of dedicated cooling device dCD. The outlet of the manifold 12 is fluidly connected to the downstream part of the intake gas circuit 3 leading to the engine 2. The three-way control valve 11 is controlled by an electronic engine control unit ECU also controlling the burner B. The combination of the turbo charger 7 and the turbine gas like assembly formed by the dedicated compressor dC, dedicated heating device 5 and dedicated turbine dT allows the engine unit 1 to be more efficient than an engine unit having only a turbocharger, as a part of both the mechanical energy and the thermal energy of the exhaust gas is recovered. Further, the use of the burner B, in addition to further increasing the intake gas enthalpy, allows a fine tuning of the oxygen level of the intake gas and therefore enables a control of the emission level NOx within the exhaust gas. In order to increase the global environmental efficiency of the engine unit 1 and as shown on figure 3, the engine unit 1 can further include an exhaust gas recirculation (EGR) circuit 15 adapted to collect a part of the exhaust gas and to input this collected part gas within the gas intake circuit 3. The flow direction of the exhaust gas is shown on the drawings by arrows with the EGR circuit 15. According to the example shown figure 3, the EGR circuit 15 collects high pressure exhaust gas, i.e. gas upstream of the primary turbine pT, and inputs this collected part of exhaust gas within the gas intake circuit 3 downstream of the dedicated turbine dT and upstream of the dedicated cooling device dCD. In order to achieve this, the EGR circuit 15 comprises an EGR control valve 16 controlled by the engine ECU. The control valve 16 is followed by a heat exchanger 17 which perform heat transfer from the EGR gas flowing in the EGR circuit to the gas flowing through the dedicated heating device 5. The heat exchanger 17 may be located between the dedicated heat exchanger dHE and the burner B. The EGR circuit 15 ends in an EGR mixing manifold 18 set on the intake gas circuit 3 between the dedicated turbine dT and the dedicated cooling device CD.

According to another embodiment of the invention shown figure 4, the EGR circuit 15 inputs the collected part of the exhaust gas downstream the dedicated cooling device dCD. Therefore, the mixing manifold 12 further comprises a third inlet fluidly connected to the EGR circuit 15. In order to further minimize the EGR gas temperature, the EGR circuit 15 further comprises an EGR cooling device 19 between the heat exchanger 17 and the mixing manifold 12.

According to the embodiments of the invention shown figures 3 and 4, the EGR circuit 15 works with high pressure exhaust gas but the EGR circuit 15 can also work with a low pressure exhaust gas, i.e; with exhaust gas collected downstream of the primary turbine pT as shown by the embodiment of the invention illustrated figure 5. According to this embodiment, the EGR circuit 15 is connected to the exhaust gas circuit 4 also downstream of the dedicated heat exchanger dHE. The EGR circuit 15 further comprises the EGR control valve 16 followed by the EGR cooling device 19. The EGR circuit ends in a mixing manifold 20 fluidly connected to the gas intake circuit 3 upstream of the primary compressor pC.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it would be understood by those skilled in the art that changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the amended claims.