Patent Grant
8646262
This application is the U.S. national phase of International Application No. PCT/IB2010/055445 filed 26 Nov. 2010 which designated the U.S. and claims priority to EP 10425133.5 filed 22 Apr. 2010, the entire contents of each of which are hereby incorporated by reference.
The present invention refers to a unit for recovering and converting thermal energy from the exhaust gases of an internal combustion engine of a vehicle, of the type comprising:
Units of this type are disclosed in EP 0 913 561 A2, US 2008/115487 A1 and EP 1 475 532 A2.
Over the last years, the automotive industry has been more and more oriented, in the design of engines, onboard systems and the vehicle itself, towards the reduction of fuel consumptions, pollutant emissions, recyclability of materials and, last but not least, the recovery and the conversion of the energy that would be normally dissipated.
The present invention lies within the latter context, in particular the recovery of thermal energy of the exhaust gases of an internal combustion engine of a vehicle.
The exhaust gases that exit from an internal combustion engine have, after being treated by a catalyst or in a more complex unit for the treatment of pollutant emissions, an amount of thermal energy still useable for producing a useful effect. Such energy is usually dissipated along the exhaust line downstream of the catalyst and in the atmosphere when discharging the gases.
However, the energy of the exhaust gases may be exploited for heating a fluid inside a heat exchanger. Solutions of this type, which envisage the insertion of a heat exchanger arranged in series on the exhaust line downstream of the catalyst, are already known and employ, for example, a layout of the three-way type or of the concentric pipes type which transfer part of the thermal energy contained in the exhaust gases to the cooling water of the engine, thus contributing to reducing the times required to attain the steady thermal condition of the engine itself. This aspect is particularly important due to the fact that, during a cold start, an engine does not operate under optimal lubrication conditions due to the high viscosity of the oil. This, lastly, is susceptible of increasing frictions between the mobile parts of the engine and hence increase fuel consumption.
The systems of known type have a series of drawbacks. First, the layout of the system is typically quite cumbersome with respect to the space generally available inside an engine compartment of a vehicle, hence setting considerable restrictions related to the arrangement of the components. The currently available solution is that of arranging the system beneath the floor of the vehicle (the so-called “underfloor”) beyond the flame damper wall of the vehicle, hence at a position quite distant from the catalyst.
However, advantages of such systems in terms of energy are quite few given that due to this arrangement, the exhaust gases that reach the exchanger have a temperature that is insufficient to guarantee a transfer of energy to the cooling water of the engine such to have a considerable impact on the fuel consumptions of the engine.
In addition, the abovementioned overall dimensions are generally not compatible with the installation of such systems on small vehicles, especially if provided with a central muffler, such as category A or B vehicles, which represent the majority of vehicles circulating in the big cities and urban centres.
Additionally, such vehicles are generally designed in such a manner to have low running costs and low fuel consumption to attract a wide range of customers: using this kind of system, alongside the undeniable advantages it may provide, may make the product more attractive for the customers. Thus, there clearly arises the need to find an alternative solution capable of allowing to overcome the problems listed above.
The object of the present invention is that of overcoming the problems described above. In particular, the object of the present invention is that of providing a unit for recovering the thermal energy contained in the exhaust gases such unit not revealing the drawbacks related to the overall dimensions described previously and which may be installed with least impact on the production costs of the vehicle.
The object of the present invention is achieved by a unit having all the features indicated at the beginning of this description and further characterised in that:
said heat exchanger is arranged so that said U-shaped path is oriented transversely to the direction of the exhaust gas main line, in such a manner that the exhaust gases traversing the heat exchanger flow firstly in the transverse direction away from the exhaust gas main line and then back in the transverse direction towards the exhaust gas main line,
As a result of this specific structure and arrangement, the unit according to the invention is extremely compact, and in particular has a very reduced dimension in the longitudinal direction of the exhaust gas main line. This enables the unit of the invention to be placed in a position very close to the catalytic converter of the vehicle, with the result of a higher thermal power recovery as compared to the heat recovery systems of the prior art, which cannot be installed in that position because of their larger dimension in the longitudinal direction of the exhaust gas main line.
The invention will now be described with reference to the attached drawings, purely provided by way of non limiting example, wherein:
A unit for recovering and converting the thermal energy contained in the exhaust gases of an internal combustion engine according to the present invention is indicated with 1 in
The unit 1 comprises a heat exchanger 2 connected, by means of an interface conduit portion 3, along an exhaust gas main line 4. The interface 3 is in form of an interface conduit portion interposed in the exhaust gas main line 4.
The exchanger 2 is of the so-called U-type, defining therein a substantially U-shaped path 5 for the exhaust gases, starting from an inlet section 6 of the heat exchanger and ending at an outlet section 7 of the heat exchanger. The inlet and outlet sections 6, 7 of the heat exchanger are located on the same side of the heat exchanger and both open on said interface conduit portion 3. As a result of this arrangement, the path 5 within the heat exchanger defines entirely in itself the by-pass path branching out from the exhaust gas main line 4.
The heat exchanger 2 is arranged so that said U-shaped path is oriented transversely to the direction of the exhaust gas main line 4, in such a manner that the exhaust gases traversing the heat exchanger flow firstly in the transverse direction away from the exhaust gas main line 4 and then back in the transverse direction towards the exhaust gas main line 4.
The above mentioned U-shaped path 5 within the heat exchanger 2 is defined by the elements constituting the structure of the heat exchanger, according to a technique know per se in the field of U-type heat exchangers. Typically, this path is constituted by a number of parallel passages defined between a plurality of stacked plates, but any alternative arrangement of pipes or tubes or the like, as known to those skilled in the art, may be adopted. The tubular elements may have any type of cross-section, e.g. circular, or quadrangular or flattened.
These details of construction of the heat exchanger are not disclosed herein, since they can be made in any known way and also because the elimination of these details from the drawings render the latter simpler and easier to understand.
Inside the interface 3, which is essentially configured as a tubular portion interposed in the exhaust gas main line 4, there is arranged a valve 12 for controlling the flow of exhaust gases through the heat exchanger. The valve 12 is located at a position axially intermediate between the merging points of the inlet and outlet portions 6, 7 of the heat exchanger 2 with the conduit portion 3. In the illustrated example the valve 12 is in form of a flap 12, articulated to the portion 3 around an axis 11. An actuator device 12A is arranged for driving the rotation of the flap 12.
The heat exchanger 2 further comprises a heat exchange unit 8 comprising an inlet orifice 9 and an outlet orifice 10. In the present description, by the term “heat exchange unit” it is meant to generally indicate any type of unit for a fluid which must recover heat from the exhaust gases flowing through the path 5.
Referring to
The exhaust manifold 15 is fixed onto the engine 14 and it is fluid dynamically connected therewith for the collection of the exhaust gases coming therefrom. The exhaust manifold 15 is also connected to and fluid dynamically communicating with the unit for treating the exhaust gases 16, in turn connected to and fluid dynamically communicating with the exhaust gas main line 4.
The radiator 17 is fluid dynamically connected to the engine 14 by means of a conduit 23, schematically represented herein and installed on which is the thermostatic valve 22. The radiator 17 is also fluid dynamically connected to the nourice 18 and to the water pump 20 by means of a conduit 24. The water pump is in turn connected mechanically and fluid dynamically (in particular to a cooling circuit) to the engine 14.
The oil cooler 19 is fluid dynamically connected to the engine 14 by means of a conduit 25 and it is connected by means of a conduit 26 to an oil pump (not illustrated) in turn mechanically and fluid dynamically connected to the engine 14.
The heat exchanger for EGR 21 is fluid dynamically connected to the cooling circuit of the engine 14 by means of a conduit 27 and it is fluid dynamically connected to the inlet orifice 9 of the exchanger 2 by means of a conduit 28.
A cabin heater 29 is fluid dynamically connected to the orifice 10 of the exchanger 2 by means of a conduit 30 and it is fluid dynamically connected to the water pump 20 and cooling circuit of the engine 14 by means of a conduit 31.
The exchanger 2 is, as described, connected to the exhaust gas main line 4 by means of the interface 3. A muffler 32 is positioned at the end of the exhaust gas main line 4 before the outlet thereof to the atmosphere.
The unit 1 operates as follows.
Referring to
From here, the water passes through the heat exchange unit 8 and exits therefrom through the outlet orifice 10 moving towards the cabin heater 29 by means of the conduit 30. The water thus leaves the cabin heater 29 through the conduit 31 which is connected to a suction opening of the pump 20. The remaining amount of the cooling water of the engine 14 usually passes through the conduit 23 and flows into the radiator 17, from which it flows out, after being cooled by the air flow which impacts the radiator 17 itself, through the conduit 24 which is also connected to the suction opening on the pump 20.
In case the oil cooler 19 is of the water/oil type, as illustrated in
The actuator device 12A monitors—by means of per se known sensors—the temperature of the cooling water at the exit from the engine 14 to command the movement of the flap 12 of the unit 1.
In particular, referring to
To the rest position of the flap 12, there is associated a normal operating condition, in which the temperature of the cooling water flowing out from the engine 14 is at an optimal value, generally comprised in the range between 80° C.-90° C. approximately. In such condition, the cooling water usually circulates through the radiator 17 and through the heat exchanger of the EGR 21, and it also passes through the heat exchange unit 8 without the occurrence of any heat exchange except for the normal losses of thermal energy within the exchanger 2.
Vice versa, if the temperature of the cooling water flowing out from the engine 14 is lower than the optimal value (for example following a cold start or under particularly cold climatic conditions) it controls the switching of the position of the flap 12 to the operating condition of
As a matter of fact, the flap 12 (
It should be observed that the motion of the exhaust gases in the transverse direction with respect to direction X is determined by the transverse orientation of the heat exchanger 2 with respect to the exhaust gas main line 4, hence the diversion imparted by the flap 12 is strictly related to the geometry and to the arrangement of the exchanger 2 with respect to the exhaust gas main line 4.
The exhaust gases pass through the path 5 transferring heat to the cooling water of the engine 14 which flows in the heat exchange unit 8. Then, the exhaust gases, diverted in the path 5, gain an approaching motion in the transverse direction towards the exhaust gas main line 4, passing through the outlet section 7 before being subjected to a further diversion which returns the motion thereof along direction X.
The heat exchange between the exhaust gases that pass through the path 5 and the cooling water which passes through the heat exchange unit 8 considerably reduces the times required to reach the steady thermal conditions of the engine 14, in particular it reduces the times required to reach the optimal temperature of the cooling water.
It should also be observed that, referring to
The reduction of the times required to reach the steady thermal condition of the engine creates advantages in terms of fuel consumption in that, by attaining the ideal operating temperature within a shorter time, the frictions caused by the high viscosity of oil and the formation of some pollutant species, higher when operating under cold conditions, are considerably reduced.
Furthermore, it should be observed that, by routing the exhaust gases onto a transverse path with respect to the normal flow direction inside the exhaust gas main line 4, it is possible to overcome the encumbrance drawbacks of the prior art solutions described previously.
In fact, the heat exchanger 2 is essentially developed in the transverse direction with respect to the exhaust gas main line 4, hence allowing arranging the unit 1, inside an engine bonnet, at a very close position with respect to the catalyst, in particular it allows positioning thereof before the flame damper wall, hence at a zone in which the temperatures of the exhaust gases are still at a considerable value.
Furthermore, it should be observed that the unit 1 according to the invention is particularly advantageous if compared to the arrangement of the components of the engine compartment of a modern car, in which, due to requirements related to the reduction of pollutant emissions, the unit for treating the exhaust gases 16 has acquired a position as close as possible to the cylinder head of the engine 14 (the so-called “close coupled” position).
Given that the arrangement of a recovery unit immediately on the exhaust manifold 15 and upstream of the treatment unit 16 is not advisable for reasons related to the operating temperature of the unit 16 (taking away part of the heat from the exhaust gases inside the unit 1, the latter would flow into the unit 16 at a temperature too low to obtain high efficiency), and it is clear that the only solution for arranging the unit 1 is by positioning it downstream of the unit 16.
Considering the little space available for example on category A or B vehicles, the unit 1 according to the present invention represents the only viable solution due to its small longitudinal overall dimensions.
Advantageously, referring to
Referring to
A conduit 38 fluid dynamically connects the outlet of the expander 36 to a condenser 39, which is fluid dynamically connected, by means of a conduit 40, to the inlet of the pump 33.
The system illustrated in
A man skilled in the art will observe that the connection between the pump 33, the unit 1, the expander 36 and the condenser 39 is functionally identical to the connection between—respectively—pump, recovery steam generator, expander and condenser in a steam plant operating according to a Rankine thermodynamic cycle.
The pump 33, the heat exchange unit 8, the expander 36 and the condenser 39 fluid dynamically connected to each other by means of the conduits 34, 35, 38, 40 as previously described define a circuit closed and isolated with respect to the internal combustion engine 14, particularly with respect to the cooling circuit thereof.
Such closed circuit is passed through by a working fluid different from the cooling water of the engine 14.
The pump 33 conveys a flow of working fluid in the conduit 34 towards the heat exchange unit 8. Inside the exchanger 2, the working fluid which passes inside the heat exchange unit 8 receives a heat flow from the exhaust gases which possibly pass inside the path 5 and flow out through the outlet orifice 10 in vapour phase.
From here, it is conveyed to the inlet of the expander 36 by means of the conduit 35, in such a manner that the expander 36 generates mechanical work by putting the generator 37 in rotation. The fluid discharged by the expander 36 is collected in the conduit 38 and it is conveyed to a condenser 39, which lowers the temperature thereof and causes a double change of phase thereof from heated vapour to moist vapour and from moist vapour to liquid. Then, the working fluid flows into the conduit 40 and returns to the inlet of the pump 33, then it once again passes through the cycle described previously.
The position of the flap 12 is controlled by the actuator 12A whose operation is regulated by an electronic control unit (not illustrated) and it is modulated depending on the operating conditions of the engine, the power required from the generator 37 and the temperature and pressure of the working fluid at the inlet of the expander 36 and at the outlet of the condenser 39 (i.e. in conduit 35 and in conduit 40).
The position of the flap 12 is modulated between the positions illustrated in
Referring to
In this way it is possible to regulate the flow rate of the exhaust gases which pass through the path 5, allowing for example to reduce possible unwanted back pressures on the engine corresponding to high loads of the engine itself and regulating the thermal power transferred to the working fluid which goes through the Rankine cycle, regulating the fluid dynamic conditions at the inlet of the expander. It should also be observed that, in a manner similar to what usually occurs in the Rankine cycle plant, it is important to monitor the temperature and the pressure of the working fluid at the inlet of the expander in order to prevent exceeding the limits of the component.
It is thus possible to exploit the mechanical power generated by the expander, or, in case it is coupled to an electric generator 37 the electric power, in order to increase the overall energy efficiency of the vehicle. A further advantageous embodiment of a recovery unit according to the present invention is illustrated in
Illustrated in
The system described above and illustrated in
The position of the flap 12 is controlled by the actuator 12A, whose operation is regulated by an electronic control unit (not illustrated), between any of the positions illustrated in
In particular, the position of the flap is controlled according to the temperature indication—provided by a per se known sensor—of the oil in the sump 41.
This allows regulating the heat flow that passes from the exhaust gases to the oil contained in the sump, hence allowing, in case of cold start, to reduce the time required to achieve the ideal temperature of the oil within the sump 41 and circulating in the engine 14.
The quick heating of the engine oil 14 allows, as already described, to considerably reduce fuel consumptions during the cold start step, given that the viscosity thereof is reduced as the temperature increases. Note in such case the particular advantage offered by the use of the unit 1′ according to the present invention. In fact, the essentially transverse development thereof—with respect to the geometry of the exhaust gas main line 4 and to the flow direction of the exhaust gases passing through the gas main line 4 itself—allows submerging the sole exchanger 2′ into the oil sump 41, without the need of passing the exhaust gas main line 4 through the oil sump. The latter condition, as it is evident, would be substantially unavoidable in the case of a prior art solution with the exchanger arranged in series to the exhaust gas main line 4 and aligned to the flow direction of the exhaust gases flowing thereinto.
Such solution, alongside entailing safety problems regarding the occupants of the vehicle, would be entirely useless and harmful for the engine 14. As a matter of fact, having an exhaust pipe submerged in a sump 41 implies the impossibility of eliminating the heat exchange between the exhaust gases of the oil contained in the sump with the ensuing danger of overheating the oil and boiling of the same.
By submerging the sole exchanger 2′, as in the case of the unit 1′, it is possible to modulate the amount of the heat exchange between the exhaust gases and the oil contained in the sump 41 by simply operating on the position of the flap, and interrupting the abovementioned heat exchange by simply rotating the flap 12 towards the resting position illustrated in
Further advantageous applications of the units 1, 1′ are illustrated in
Referring to
A two-position valve 44 is arranged in series on the channel 43, while a second channel 45 arranged on which is a unidirectional valve 46 is positioned branching with respect to the channel 43. The unidirectional valve 46 is arranged to allow a flow solely towards the direction of the bed 42.
The bed 42 is capable of storing and releasing hydrogen depending on the operating conditions of the thermo-fluid dynamic system with which it interacts. In particular, under conditions of cold start the engine 14, the bed 42 and the exchanger 2 may be exploited sequentially for heating the cooling water.
Referring to
Such hydrogen flow enters into the unit 8A and heats, due to the release of formation heat of the metal hydrides, the cooling water that flows in the heat exchange unit 8.
Referring to
This allows heat exchange between the gas inside the path 5 and the cooling water of the engine 14 through methods similar to those previously described. Furthermore, an amount of heat is exchanged between the gases inside the path 5 and the unit 8A, thus causing a hydrogen release towards the bed 42, possible solely due to the unidirectional valve 46 through the channel 45. This allows restoring the hydrogen reserve of the bed 42 making it available for the subsequent cold start of the engine 14.
An identical operating principle is exploited in the application illustrated in
The methods of operation of the system are identical to those of the application of
Referring to
The layers of thermoelectric material are used for producing electrical power to be made available to the vehicle and for such purpose, the temperature difference established therein due to the positioning between the conduit 5 (hotter) and the unit 8 (colder), is exploited to generate an electric voltage and an electric current towards the converter 47 along the electric line 48. The converter 47 processes the current that reaches it through the line 48 and makes it available to the vehicle by means of the line 49.
Analogous is the operation of the system illustrated in
Obviously, the manufacturing details and the embodiments may widely vary with respect to what has been described and illustrated strictly for exemplifying purposes, without departing from the scope of protection of the present invention, as defined by the claims.
For example, provided for may be a flap 12 rotating around an axis arranged not at a position substantially central with respect to the exhaust gas main line 4, but a at a position substantially close to the exchanger 2, as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10425133 | Apr 2010 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2010/055445 | 11/26/2010 | WO | 00 | 11/18/2011 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/132035 | 10/27/2011 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3282046 | Walker et al. | Nov 1966 | A |
| 6155042 | Perset et al. | Dec 2000 | A |
| 6702190 | Nohl et al. | Mar 2004 | B1 |
| 7077776 | Sorab et al. | Jul 2006 | B2 |
| 8011175 | Husges et al. | Sep 2011 | B2 |
| 8146344 | Harada et al. | Apr 2012 | B2 |
| 8261814 | Lempa et al. | Sep 2012 | B2 |
| 8327634 | Orihashi et al. | Dec 2012 | B2 |
| 20080115487 | Harada et al. | May 2008 | A1 |
| Number | Date | Country |
|---|---|---|
| 0 913 561 | May 1999 | EP |
| 1 475 532 | Nov 2004 | EP |
| 1 739 298 | Jan 2007 | EP |
| 2 859 239 | Mar 2005 | FR |
| Entry |
|---|
| International Search Report for PCT/IB2010/055445 mailed Sep. 9, 2011. |
| Written Opinion of the International Searching Authority mailed Sep. 9, 2011. |
| Number | Date | Country | |
|---|---|---|---|
| 20120102934 A1 | May 2012 | US |
