WO2010035055A1

WO2010035055A1 - Energy recovering system for an internal combustion engine

Info

Publication number: WO2010035055A1
Application number: PCT/IB2008/003191
Authority: WO
Inventors: Lyad Balloul; Michel Vanvolsem; Marc Lejeune
Original assignee: Renault Trucks
Priority date: 2008-09-26
Filing date: 2008-09-26
Publication date: 2010-04-01
Also published as: CN102165173A; EP2337939A1; US20110167809A1

Abstract

The system (10) comprises: - an exhaust line (6) collecting exhaust gas from the engine; - a filter (11) having an active portion inserted between two successive parts of the exhaust line, in order to hold the particles contained in the exhaust gas, and filter rotating means designed to rotate said filter so as to shift the active portion of said filter; - a secondary line (17) carrying intake air towards an area of said filter distinct from said active portion, according to a direction opposite from an exhaust gas flowing direction inside said filter, so as to sweep the particles away from the filter and release them downstream, inside said secondary line. Said secondary line (17) comprises first means (20, 21), located downstream from said filter (11), for burning the particles and thereby heating air flowing in said secondary line, and second means (18, 22) capable of recovering said heat into work.

Description

ENERGY RECOVERING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE

Field of the invention

The present invention relates to an engine arrangement, for example for an automotive vehicle, especially an industrial vehicle. More specifically, the invention relates to an energy recovering system for such an engine arrangement.

Technological background

For many years, attempts have been made to improve vehicle efficiency, and more particularly the engine arrangement efficiency, which has a direct impact on fuel consumption.

A significant amount of energy is included in the exhaust gases which have a high speed, a high temperature, and which, especially in the case of diesel engines, contain particles resulting from an incomplete combustion process in the engine. Several systems have been designed to recover at least part of this energy. However, generally, these systems are capable to use only one of the aforesaid energy sources. Moreover, they can generate undesirable side- effects, such as increased backpressure in the exhaust line, which are prejudicial to the global engine efficiency. Besides, most of the time, a filter is provided to retain and/or oxidize the particles. In order to regenerate the filter, a conventional solution is to use an additional heat or energy source to oxidize these particles. As a result, known engines dissipate uselessly the energy content of the particles. Moreover, the additional heat or energy source is not recovered, which makes the global energy balance even worse.

It therefore appears that, from several standpoints, there is room for improvement in engine arrangements. Summary of the invention

It is an object of the present invention to provide an improved engine arrangement, which can overcome the drawbacks encountered in conventional engine arrangements.

Another object of the present invention is to provide an energy recovering system for an engine arrangement comprising an internal combustion engine which better uses the energy contained in the exhaust gas. According to the invention, such an energy recovering system comprises:

- a main line having an exhaust line capable of collecting exhaust gas from an exhaust manifold of the engine;

- a main filter having an active portion inserted between two successive parts of the exhaust line, in order to hold the particles contained in the exhaust gas, and filter displacing means designed to displace said main filter so as to shift the active portion of said main filter;

- a secondary line capable of carrying intake air towards an area of said main filter distinct from said active portion, according to a direction substantially opposite from an exhaust gas flowing direction inside said main filter, so as to blow the particles away from the main filter and release them downstream, inside said secondary line;

Furthermore, said secondary line is distinct from the main line and it comprises first means, located downstream from said main filter, for oxidizing the particles and thereby heating air flowing in said secondary line, and second means capable of recovering said heat into work.

Therefore, the invention takes advantage of the energy contained in the particles of the main line to create energy which can be used for the operation of various elements of the vehicle. Besides, both an energy recovery and a filter cleaning can be achieved with the system according to the invention.

In concrete terms, a secondary line - distinct from the main line and especially distinct from the intake line which carries intake air towards an engine intake manifold - is provided by the invention. Said secondary line carries air, for example ambient air, which undergoes a series of thermodynamic processes of a thermodynamic cycle making it possible to recover energy from the particles filtered in the main line. Because the main filter is regularly cleaned (and for example continuously cleaned), due to its movement, for example a rotating movement, and to the counterflow of the secondary line, it can have a lower thickness or a lower volume. A consequence of these two factors is that the backpressure on the main exhaust line is reduced.

Consequently, the invention improves the vehicle efficiency, and reduces its fuel consumption.

In an implementation of the invention, the first means comprise a secondary filter suitable for retaining the particles, and heating means capable of promoting an oxidation of the particles held in said secondary filter.

Since the flow in the secondary line is lower, the secondary filter can have a reduced size with respect to the main filter, which is advantageous. This filter can be continuously or periodically cleaned through a process known as regeneration and which in most cases involves the heating means. With a high regeneration frequency, the backpressure in said secondary line is kept low. In an advantageous way, the backpressure which exist in the main line in the prior art is at least partly transferred to the secondary line where it does not interfere with the operation of the internal combustion engine, thanks to the system according to the invention. For example, the heating means comprise an electric heater or a fuel injector. Therefore, particles can be stored in the secondary filter and periodically burned by an additional external energy. But this energy can be at least partially recovered by said second means.

According to an embodiment of the invention, the second means comprise a turbine located downstream from the first means, and may also comprise a compressor located upstream from the main filter on the secondary line, said compressor being driven by the turbine.

Therefore, the secondary line works according to a Brayton cycle. However, other suitable thermodynamic cycles can be used. Preferably, the turbine can be protected by the secondary filter, when present.

In an advantageous way, the system further comprises a fuel burning heater arranged to further heat the air flowing in said secondary line, upstream from the turbine, in order to bring additional energy. This fuel burning heater can be identical to the heating means or can be a separate device. The system may also comprise a control unit designed to control the operation of the fuel burning heater to turn it on or off and/or to control the amount of heat generated by the fuel burning heater.

The purpose of the fuel burning heater is to further heat the gas flow in the Brayton cycle system (i.e. in the secondary line), when needed, to be able to retrieve more energy from the system (thanks to the gas expansion in the turbine) that it would be possible when only the heat recovered through the exhaust heat exchanger and a possible EGR heat exchanger would be used. This additional heat is provided by combustion of fuel, so that the Brayton cycle system then operates as a gas turbine engine.

Therefore, a vehicle can be equipped with a downsized internal combustion engine, which enables a reduction in fuel consumption and exhaust emissions, that can rely on an additional power capacity provided by the fuel burning heater, to face peak operational conditions such as an acceleration phase or a steep road.

The additional mechanical energy generated by the turbine thanks to said fuel burning heater can be used to produce electricity . Alternatively, a transmission device can connect the turbine to the vehicle driveline to transfer the work extracted by the turbine to the internal combustion engine. The fuel burning heater can comprise a combustion chamber where fuel is added to the pressurized and heated air and is burnt. As an alternative,, it could be a simple burner arranged in the secondary line. It is also possible to have a fuel burning heater where the combustion process is external to the secondary line and where the combustion generated heat is transferred to the gas flowing in the secondary line by a heat exchanger. In all cases, the fuel can suitably be provided by the vehicle fuel circuit.

The system may further comprise an alternator designed to produce electricity from the mechanical energy generated by the turbine. Electricity can be used in a hybrid vehicle (i.e. a vehicle powered by an internal combustion engine and an electric motor) or in a conventional vehicle to charge a battery, to power auxiliaries, etc.

Preferably, the system also comprises a heat exchanger between the exhaust line and the secondary line. With this arrangement, air flowing in the secondary line has a higher temperature (because of hot exhaust gas), and therefore it is possible to recover more energy with the second means. Of course, in case of the above-mentioned Brayton cycle, said heat exchanger has to be located, on the secondary line, upstream from the turbine. For example, it can be located upstream from the main filter, on the secondary line.

In an advantageous way, the heat exchanger is located, on the exhaust line, downstream from the main filter, so that the heat exchanger is protected against clogging by the filter.

It is envisaged that the filter displacing means comprise filtering channels which are arranged inside the main filter in a tilted direction with respect to the exhaust gas flow and/or the intake air counterflow in the secondary line. Such a passive arrangement entails the rotation of the main filter when the gas flow in said lines. Alternatively, the filter can be rotated by an electric motor, preferably powered by the electricity generated by the second means.

The system can further comprise means for the treatment of exhaust gas from the exhaust line and / or exhaust air from the secondary line. Such means can implement a selective catalyst reduction, for the treatment of nitrogen oxides (NOx).

The invention also concerns an internal combustion engine equipped with a system as previously described.

These and other advantages will become apparent upon reading the following description in view of the drawing attached hereto representing, as non-limiting examples, embodiments of a vehicle according to the invention.

Brief description of the drawing

The following detailed description of an embodiment of the invention is better understood when read in conjunction with the appended drawing being understood, however, that the invention is not limited to the specific embodiment disclosed. In the drawing,

Figure 1 is a schematic drawing of an internal combustion engine comprising an energy recovering system according to the invention;

Figure 2 is a schematic front view of a main filter for the system according to the invention;

Figure 3 is a schematic cross section of the main filter of Figure 2. Detailed description of the invention

As depicted in Figure 1 , an internal combustion engine typically comprises an engine block 1 defining a plurality of cylinders 2, namely six cylinders in the illustrated embodiment. The engine is for example a diesel engine. However the invention may concern any type of internal combustion engine needing a particle filter to meet ongoing or future legislation limits.

Intake air is carried towards an intake manifold feeding the cylinders 2 through an air intake line 3. Air intake line 3 can include a compressor 4 and an air intake cooler 5 located downstream from said compressor 4.

Exhaust gas formed in each cylinder 2 is collected by an exhaust manifold and then carried through an exhaust line 6 towards the atmosphere.

The exhaust line 6 can suitably comprise a turbine 7 driven by the exhaust gas, said turbine 7 being mechanically connected to compressor 4 by means of a shaft 8.

Intake line 3 and exhaust line 6 define a main line 9 of an energy recovering system 10 according to the invention.

Exhaust line 6 is further equipped with a main filter 11 which is more particularly illustrated on Figures 2 and 3. It has to be noted that said filter performs a mechanical filtering of particles.

According to the invention, the main filter is of the type wherein only a part of the filter is active at a given moment. At a subsequent moment, it is another part of the filter which become active. The previously active portion is, at a further step, cleaned by being discharged of the particles which it has collected when that portion has been active. Of course, at a still further step, that portion, once discharged of its particles, can become active. Various embodiments of such a . filter are for example depicted in documents FR 2 688 266 or FR 2 589 194 In the embodiment represented on the figures, the main filter 11 is very similar to the one depicted in document FR 2 688 266. It is substantially disc-shaped and comprises:

- a peripheral portion 12 and a central portion 13 which form the supporting structure of said main filter 11. These portions 12, 13 can be made of metal or ceramic, which has the advantage of a low heat conductivity; - an intermediate filtering portion 14, having the shape of a ring, located between said peripheral portion 12 and said central portion 13 and embedded in said supporting structure. The filtering material can be ceramic, a fibre-based material or a heat resistant metal. In a refined embodiment of the invention, the filtering portion 14 comprise filter channels 15 (see figure 3) that are arranged in a tilted direction with respect to the direction FD which is orthogonal to the median plane of said filter 11.

Main filter 11 is arranged substantially perpendicularly to exhaust line 6, i.e. perpendicularly to the flow direction FD of exhaust gases. Exhaust line 6 is facing filtering portion 14 and has a cross section which is preferably at most equal to half the surface area of said filtering portion 14. In the embodiment illustrated in Figure 2, exhaust line 6 is a cylinder whose diameter is about four times smaller than the main filter diameter. Alternatively, exhaust line 6 can be shaped substantially as a half moon covering a half of the ring- shaped filtering portion 14, on one side of a diameter thereof.

Finally, exhaust line 6 includes a heat exchanger 16 which is located downstream from main filter 11.

Energy recovering system 10 also comprises a secondary line 17, distinct from main line 9, in which air flows and undergoes a series of thermodynamic processes. In the depicted embodiment, these thermodynamic processes form a Brayton thermodynamic cycle.

Ambient air is first compressed in a compressor 18, then passes through heat exchanger 16 where it is heated by hot exhaust gas, and through main filter 11 , substantially in a direction parallel but opposed to the flow direction FD of exhaust gases.

Secondary line 17 is facing filtering portion 14 of main filter 11. Preferably, in the vicinity of main filter 11 , secondary line 17 has the same shape as exhaust line 6 and a position which is symmetrical to the position of exhaust line 6 with respect to main filter axis 19. In the embodiment illustrated in Figure 2, secondary line 17 is a cylinder whose diameter is about four times smaller than the main filter diameter. Alternatively, secondary line 17 can be shaped substantially as a half moon covering a half of the ring-shaped filtering portion 14, on one side of a diameter thereof. In such a case, exhaust line 6 and secondary line 17 are adapted to the circular geometry of main filter 11 and substantially cover the whole surface area of filtering portion 14. In the refined embodiment of the invention, because of the tilted orientation of filter channels 15 with respect to the flow direction FD of exhaust gas and to the flow direction of air inside secondary line 17, main filter 11 is made to rotate about its axis 19. As a consequence, the particles contained in exhaust gas which are held in main filter 11 are blown away and released in secondary line 17 by the air counterflow. Thus, main filter 11 is substantially continuously cleaned.

In order to monitor the good operation of main filter 11 , an angular speed sensor and/or a differential pressure sensor can be added to system 10. Basically, the main filter is not of the type where the particles are both filtered (i.e. retained mechanically) and then oxidised. It is of the type where the particles are collected at one location and discharged at another location. Here the discharging process is carried out by a reverse flow of air through the filter. In the embodiment described, the filter is of the rotating type and it moves continuously. Nevertheless, it is possible to provide an equivalent filter where the movement is not continuous but sequential and/or where the filtering portion is moved from an active filtering location to a discharging location in another way, such as described in document FR 2 589 194. Also, it could be provided that the mere reverse flow of air through the filter may not be sufficient to remove enough of the particles. Therefore this could be assisted by additional removal means, such as scraper means, to release as much of the particles as possible in the secondary line.

Downstream from main filter 11 , air containing particles flows in secondary line 17 towards a secondary filter 20 suitable for retaining said particles. System 10 further comprise heating means 21 capable of promoting the oxidation of the particles held in said secondary filter 20, in order to clean said filter. For example, heating means 21 can consist of an electric heater or a fuel injector which is periodically in operation when it is needed to clean secondary filter 20. Heating means 21 also perform the function of heating more air flowing in secondary line 17 before it reaches a turbine 22 where it is expanded, thereby transforming the energy conveyed by the gas into mechanical energy.

Turbine 22 is mechanically connected to compressor 18 by means of a shaft 23. The energy produced by the warm air expansion is recovered into mechanical energy on said shaft 23. Said energy is partially used to operate compressor 18. In a further refined embodiment of the invention, said energy can also be used to produce electricity by means of an alternator 24. This electricity can be used in various elements of the vehicle.

System 10 may also comprise means (not shown) for the further treatment of exhaust gas from exhaust line 6 and / or from secondary line 17. In the case of a diesel engine, this could for example be an SCR catalyst for reducing the nitrogen oxides contents of the exhaust gases.

Gaseous leakage from exhaust line 6 towards secondary line 17 must preferably be avoided as much as possible but must not necessarily be excluded as said secondary line 17 comprises a secondary filter 20. In an advantageous way, main filter 11 is contained in a housing avoiding any leakage to the environment.

Among the significant advantages of the invention are the following:

- at least part of the lost energy of the exhaust gas is recovered to generate energy by means of a secondary line arranged as a Brayton cycle or a similar thermodynamic cycle. This is achieved by recovering some of the heat of the engine exhaust gases through the heat exchanger, and by recovering part of the energy contained in the un-burnt particles and which is potentially released by the oxidation of said particles; - the additional energy required to clean the secondary filter, which is used by the heating means, is at least partially recovered with the turbine provided in the secondary line;

- the Brayton cycle efficiency is increased by means of the heat exchanger and the oxidation of particles retained in the secondary filter - the system creates little backpressure in the main line because the main filter does not need to be thick or voluminous as it is continuously cleaned; the backpressure is transferred to the secondary line;

- with the above mentioned arrangement, no energy is required to rotate the main filter; - the engine efficiency can be increased by 1 to 4%; thus the fuel consumption can be reduced

Of course, the invention is not restricted to the embodiment described above by way of non-limiting example, but on the contrary it encompasses all embodiments thereof.

Claims

1. An energy recovering system for an internal combustion engine, said system comprising: - a main line (9) having an exhaust line (6) capable of collecting exhaust gas from an exhaust manifold of the engine; a main filter (11) having an active portion inserted between two successive parts of the exhaust line (6), in order to hold the particles contained in the exhaust gas, and filter displacing means designed to displace said main filter (11 ) so as to shift the active portion of said main filter (11 ); a secondary line (17) capable of carrying intake air towards an area of said main filter (11) distinct from said active portion, according to a direction substantially opposite from an exhaust gas flowing direction (FD) inside said main filter (11), so as to blow the particles away from the main filter (11) and release them downstream, inside said secondary line (17); characterized in that said secondary line (17) is distinct from the main line (9) and in that it comprises first means (20, 21), located downstream from said main filter (11), for oxidizing the particles and thereby heating air flowing in said secondary line (17), and second means (18, 22) capable of recovering said heat into work.

2. The system according to claim 1 , characterized in that the first means comprise a secondary filter (20) suitable for retaining the particles, and heating means (21) capable of promoting an oxidation of the particles held in said secondary filter (20).

3. The system according to claim 2, characterized in that the heating means (21) comprise an electric heater or a fuel injector.

4. The system according to any one of claims 1 to 3, characterized in that the second means comprise a turbine (22) located downstream from the first means (20, 21).

5. The system according to claim 4, characterized in that the second means comprise a compressor (18) located upstream from the main filter (11) on the secondary line (17), said compressor being driven by the turbine (22).

6. The system according to claim 4 or 5, characterized in that it further comprises a fuel burning heater (21) arranged to further heat the air flowing in said secondary line (17), upstream from the turbine (22), in order to bring additional energy.

7. The system according to claim 6, characterized in that it comprises a control unit designed to control the operation of the fuel burning heater (21) to turn it on or off and/or to control the amount of heat generated by the fuel burning heater (21).

8. The system according to any one of claims 4 to 7, characterized in that it further comprises an alternator (24) designed to produce electricity from the mechanical energy generated by the turbine (22).

9. The system according to any one of claims 1 to 8, characterized in that it also comprises a heat exchanger (16) between the exhaust line (6) and the secondary line (17).

10. The system according to claim 9, characterized in that said heat exchanger (16) is located, on the exhaust line (6), downstream from the main filter (11).

11. The system according to any one of claims 1 to 10, characterized in that the filter displacing means comprise filtering channels (15) which are arranged inside the main filter (11) in a tilted direction with respect to the exhaust gas flow (FD) and/or the intake air counterflow in the secondary line (17).

12. The system according to any one of claims 1 to 11 , characterized in that it further comprises means for the treatment of exhaust gas from the exhaust line (6) and / or exhaust air from the secondary line (17).

13. An internal combustion engine, characterized in that it comprises a system (10) according to any one of claims 1 to 12.