Internal combustion engine system and an exhaust treatment unit for such a system

Abstract

An internal combustion engine system includes a compressor arranged to compress air, at least one combustor, at least one of the at least one combustor being arranged to receive the compressed air, and an exhaust treatment device arranged to process exhaust gases produced by at least one of the at least one combustor, a heat exchanger arranged to receive the compressed air from the compressor before it reaches the at least one of the at least one combustor, and wherein the heat exchanger is arranged to transfer heat from the compressed air to the exhaust treatment device.

Claims

1. An internal combustion engine system comprising a compressor arranged to compress air, and at least one combustor, at least one of the at least one combustor being arranged to receive the compressed air, a heat exchanger arranged to receive the compressed air from the compressor before the compressed air reaches the at least one of the at least one combustor, an exhaust treatment device arranged to process exhaust gases produced by at least one of the at least one combustor, and wherein the system comprises an expander arranged to receive the exhaust gases from the at least one of the at least one combustor, and to expand and extract energy from the exhaust gases, the exhaust treatment device being arranged to receive the exhaust gases from the expander, the heat exchanger is arranged to receive the exhaust gases from the expander, the heat exchanger is arranged to transfer heat from the compressed air to the exhaust treatment device, whereby the temperature of the exhaust treatment device is increased to improve the process therein.

2. The system according to claim 1, wherein the expander comprises a piston.

3. The system according to claim 1, wherein the system comprises a crankshaft, and that the expander is arranged to drive the crankshaft.

4. The system according to claim 1, wherein the system comprises an oil separator arranged to receive exhaust gases from the expander, and to separate oil from the exhaust gases before the exhaust gases reach the exhaust treatment device.

5. The system according to claim 1, wherein the heat exchanger is arranged to transfer the heat to the exhaust treatment device via the exhaust gases.

6. The system according to claim 1, wherein the heat exchanger and the exhaust treatment device are integrated.

7. The system according to claim 6, wherein the heat exchanger comprises a wall separating the air and the exhaust gases, and that the exhaust treatment device comprises an exhaust treatment layer on an exhaust gas side of the wall.

8. The system according to claim 7, wherein the wall of the heat exchanger presents a plurality of protruding flanges on an air side of the wall.

9. The system according to claim 1, wherein the exhaust treatment device comprises a first portion which is integrated with the heat exchanger and a second portion which is arranged to receive heat from the compressed air via exhaust gases received from the heat exchanger.

10. The system according to claim 1, wherein the exhaust treatment device comprises an oxidation catalyst.

11. The system according to claim 1, wherein the exhaust treatment device comprises a selective catalytic reduction (SCR) catalyst.

12. The system according to claim 11, wherein the system comprises an injector arranged to inject reductant for the SCR catalyst, upstream of the heat exchanger.

13. The system according to claim 11, wherein the system comprises the expander arranged to receive the exhaust gases from the at least one of the at least one combustor, and to expand and extract energy from the exhaust gases, the exhaust treatment device being arranged to receive the exhaust gases from the expander, and that the system comprises an injector arranged to inject the reductant for the SCR catalyst, upstream of the expander or into the expander.

14. The system according to claim 1, wherein the heat exchanger is a first heat exchanger, the system further comprising a second heat exchanger arranged to receive the air from the first heat exchanger before the air reaches the at least one of the at least one combustor, and to receive the processed exhaust gases from the exhaust treatment device, the second heat exchanger being arranged to allow heat to be exchanged between the air and the exhaust gases.

15. The system according to claim 1, wherein the heat exchanger forms a buffer volume for the air.

16. The system according to claim 1, wherein the system comprises the expander arranged to receive the exhaust gases from the at least one of the at least one combustor, and to expand and extract energy from the exhaust gases, and that the system comprises in addition to the exhaust treatment device a pre-expander exhaust treatment device arranged to receive exhaust gases from the at least one of the at least one combustor, to provide an exhaust treatment process to the exhaust gases, and to deliver processed exhaust gases to the expander.

17. The system according to claim 16, wherein the pre-expander exhaust treatment device comprises an oxidation catalyst.

18. The system according to claim 16, wherein the pre-expander exhaust treatment device comprises a particulate filter.

19. The system according to claims 17, wherein the pre-expander exhaust treatment device comprises a particulate filter and the particulate filter is located downstream of the oxidation catalyst.

20. The system according to claim 1, wherein the system comprises a crankshaft, and that the combustor comprises a piston arranged to reciprocate in a cylinder, and to drive the crankshaft.

21. The system according to claim 1, wherein the compressor comprises a piston.

22. The system according to claim 1, wherein the system comprises a crankshaft, and that the compressor is arranged to be driven by the crankshaft.

23. The system according to claim 1, wherein the combustor comprises a fuel injector and is arranged to combust fuel and at least a portion of the compressed air in a Diesel cycle.

24. The vehicle provided with an internal combustion engine system according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples. In the drawings:

(2) FIG. 1 is a partially sectioned side view of a vehicle in the form of a truck.

(3) FIG. 2 is a schematic perspective view of an engine system in the vehicle in FIG. 1.

(4) FIG. 3 is a schematic cross-sectional view of the engine system in FIG. 2.

(5) FIG. 4 is a schematic cross-sectional view of an engine system according to an alternative embodiment of the invention.

(6) FIG. 5 shows a cross-section of a part of an engine system according to a further alternative embodiment of the invention.

DETAILED DESCRIPTION

(7) FIG. 1 shows a vehicle in the form of a truck, or a tractor for a semitrailer. It should be noted however that the invention is applicable to a variety of alternative types of vehicles, such as a car, a bus, or a working machine such as a wheel loader. The vehicle comprises an internal combustion engine system 1.

(8) FIG. 2 is schematic and does not show, for simplicity of this presentation, certain parts such as devices for the actuation of inlet and outlet valves in cylinders of the engine system. The engine system 1 comprises a multi-stage compression and expansion internal combustion engine. The engine comprises three combustors 4, in the form of cylinders with pistons, and three piston compressors 3.

(9) The system further comprises an air guide 34 arranged to guide compressed air from the compressors 3 to the combustors 4. The air guide 34 is arranged such that the air therein passes through a heat exchanger 6, described closer below.

(10) The system further comprises three piston expanders 5 arranged to expand exhaust gases from the combustors 4 and to extract energy from the expanded exhaust gases. An exhaust guide 9 is arranged to guide exhaust gases from the combustors 4 to the expanders 5. The exhaust guide 9 comprises a pre-expander exhaust treatment device 91 described closer below. The exhaust guide 9 is further arranged to guide exhaust gases from the expanders 5 to the heat exchanger 6. The exhaust guide 9 is also arranged to guide exhaust gases from the heat exchanger 6 to a post-expander exhaust treatment device 8, described closer below.

(11) It is understood that the engine system may comprise any number of combustors 4, compressors 3, and expanders 5. In this example, the combustors 4, compressors 3, and expanders 5 share a single heat exchanger 6, a single pre-expander exhaust treatment device 91, and a single post-expander exhaust treatment device 8. However, the number of air guides 34, heat exchangers 6, exhaust guides 9, pre-expander exhaust treatment devices 91, and post-expander exhaust treatment devices 8 may vary as well. For example, it is conceivable that a plurality of pairs of air guides 34 and exhaust guides 9 with respective heat exchangers 6 to and from subgroups of the cylinders.

(12) Reference is made to FIG. 3 in which only one of the combustors 4, only one of compressors 3, and only one of the expanders 5 are shown. The piston 401 of each combustor 4 is arranged to reciprocate in the respective cylinder 402, whereby the pistons are all arranged to drive a crankshaft 2 of the engine. For simplicity, the combustor 4, the compressor 3, and the expander 5 are shown as all being located in the same cross-sectional plane; in a real implementation of the embodiment, the combustor 4, the compressor 3, and the expander 5 are preferably offset in relation to each other along the crankshaft 2.

(13) The combustors 4 are provided with respective sets of inlet and outlet valves 403, 404, arranged to be actuated in a manner which may be known per se, e.g. with cams mounted on camshafts, (not shown). The timing and the maximum movements of the valves 403, 404 may also be variable, as is also known per se.

(14) In addition, the combustors 4 are provided with respective fuel injectors 405 for injecting a fuel into the cylinders 402. In this example, the combustors 4 are arranged to provide a Diesel cycle to extract work from the air and fuel provided. However, the invention is equally applicable to engines in which the combustors are arranged to provide an Otto cycle, wherein the engine system may be provided with means for air mass flow control, such as variable inlet and outlet valves 303, 304 of the compressors 3, described further below, for controlling the air supply to the combustors 4. Alternatively, or in addition, the means for air mass flow control may comprise one or more throttles for controlling the air supply to the combustors 4. The engine system may be provided with spark plugs in the combustors.

(15) The pistons 501 of the expanders 5 are arranged to drive the crankshaft 2 with the energy extracted from the exhaust gases from the combustors 4. The expanders 5 are provided with respective sets of inlet and outlet valves 503, 504, arranged to be actuated with cams mounted on camshafts, (not shown). The timing and the maximum movements of the valves 503, 504 may also be variable, as is known per se.

(16) Further, the pistons 301 of the compressors 3 are all arranged to be driven by the crankshaft 2. The compressors 3 are provided with respective sets of said inlet and outlet valves 303, 304, arranged to be actuated with cams mounted on camshafts, (not shown). The timing and the maximum movements of the valves 303, 304 may also be variable, as is known per se.

(17) The pre-expander exhaust treatment device 91 is arranged to provide an exhaust treatment process to the exhaust gases from the combustors 4. The pre-expander exhaust treatment device 91 comprises an oxidation catalyst 11, and a particulate filter 12 located downstream of the oxidation catalyst 11. The pre-expander exhaust treatment device 91 presents in this example a circular cross-section.

(18) The post-expander exhaust treatment device 8 is in this example provided in the form of a selective catalytic reduction (SCR) catalyst. The SCR catalyst 8 is arranged to receive exhaust gases from the expanders 5 and to provide an exhaust treatment process to the received exhaust gases, which process reduces nitrogen oxides (NOx) as is known per se.

(19) Alternatively, the post-expander exhaust treatment device 8 comprises an oxidation catalyst.

(20) The system also comprises three injectors 10 arranged to inject reductant for the SCR catalyst 8. Each injector 10 is arranged to inject the reductant directly into a respective of the expanders 5. The injectors 10 are controllable by a control unit (not shown), to control the timing, the flow and the duration of the redundant injections. Specifically, the timing and duration of the reductant injections are coordinated with the actuations of the expander inlet valves 503, in order to enable good mixing of the reductant with the exhaust gases in the expander. In alternative embodiments, as exemplified below, the injectors 10 are arranged to inject the reductant into the exhaust guide 9, upstream of the expanders 5 and downstream of the pre-expander exhaust treatment device 91.

(21) In alternative embodiments, a single reductant injector may be provided, e.g. where the engine system is provided with a single expander 5 arranged to receive exhaust gases from a plurality of combustors 4. The single reductant injector may be thereby be arranged to inject the reductant upstream of, or into the single expander.

(22) It is understood that the multi-stage compression and expansion internal combustion engine of the system in FIG. 2 and FIG. 3 provides a compression of the air by the compressors 3, and a further compression by the combustors 4. An expansion is provided by the combustors 4, and a further expansion is provided by the expanders 5. The multistage expansion provides a high utilization of the energy in the combustions of the engine. As a result, the exhaust gas temperature downstream of the expanders 5 will be relatively low, e.g. within the range of 50-250 C. This means that the temperature might be too low for the NOx reducing process in the SCR catalyst 8 to be efficient. Such a process may not be possible at all in temperatures below 150 C., and for the process to be fully efficient, the temperature usually have to reach 250 C.

(23) The heat exchanger 6 provides a solution to this problem. The heat exchanger 6 is arranged to receive exhaust gases produced by the combustors 4 and delivered by the expanders 5. The heat exchanger 6 is further arranged to receive compressed air from the compressor 3 before it reaches the combustors 4. The compressed air reaching the heat exchanger 6 may present a temperature of 200-450 C., preferably 260-350 C.

(24) The heat exchanger 6 is arranged for a heat exchange between the compressed air and the exhaust gases. Thereby, the heat exchanger 6 is arranged to transfer heat to the post-expander exhaust treatment device 8 via the exhaust gases. Thus the temperature of the exhaust gases may be increased before reaching the post-expander exhaust treatment device 8 to improve the process therein. The combination of the heat exchanger 6 and the post-expander exhaust treatment device 8 is herein also referred to as an exhaust treatment unit.

(25) In addition to increasing the temperature for said exhaust treatment process, the heat exchanger 6 also forms a buffer volume for the air. The air buffer volume reduces or eliminates any requirements of correlation of the actuation timing of the compressor outlet valves 304 and the combustor inlet valves 403 to avoid losses with pulsating flows. Thanks to the air buffer volume, such valve actuation timing correlation requirements may be relaxed without increasing the risk of pulsating flows. Thereby simpler and cheaper valve control systems may be employed.

(26) It is understood that the air buffer volume of the heat exchanger 6 suitably presents a cross-section which is larger than any lateral cross-section, perpendicular to a local intended air flow direction, of portions of the air guide 34 upstream and downstream of the heat exchanger 6.

(27) The system comprises an oil separator 14 arranged to receive exhaust gases from the expander 5, and to separate oil from the exhaust gases before the exhaust gases reach the heat exchanger 6 and the post-expander exhaust treatment device 8. Thereby, oil introduced to the exhaust gases, e.g. by the expanders 5, will be removed therefrom, avoiding or reducing detrimental effects it may have on the post-expander exhaust treatment device 8.

(28) The expanders 5 in FIG. 3 are herein also referred to as first expanders 5. In addition, the system may comprise one or more second expanders 15 arranged to receive and expand exhaust gases from the post-expander exhaust treatment device 8 and to extract energy from the expanded exhaust gases. The second expander 15, schematically represented in FIG. 3, may be mechanically connected, as indicated in FIG. 3 with a broken line 153, to an additional compressor 31. The additional compressor 31 may be arranged to compress intake air before it reaches the piston compressor 3.

(29) Reference is made to FIG. 4, showing an engine system according to an alternative embodiment of the invention. This embodiment shares features with the embodiment described with reference to FIG. 2-FIG. 3. However, some further advantageous features are also provided.

(30) The engine system in FIG. 4 comprises a first heat exchanger 6, arranged similarly to the heat exchanger in the engine system in FIG. 3. In addition, the system in FIG. 4 comprises a second heat exchanger 7. The second heat exchanger 7 is provided in the path of the air guide 34, between the first heat exchanger 6 and the combustors 4. Thus, the second heat exchanger 7 is arranged to receive the air from the first heat exchanger 6 before it reaches the combustors 4.

(31) Further, the second heat exchanger 7 is provided in the path of the exhaust guide 9, downstream of the post-expander exhaust treatment device 8, and is thereby arranged to receive the processed exhaust gases from the exhaust treatment device 8. Thus, the second heat exchanger 7 is arranged to allow heat to be exchanged between the air and the exhaust gases. In particular, heat may be transferred in the second heat exchanger 7 from the exhaust gases to the air. Thereby, energy in the exhaust gases can be recovered by heating the intake air after the air has delivered heat, by means of the first heat exchanger 6, to the exhaust gases for the post-expander exhaust treatment device 8.

(32) The system in FIG. 4 also comprises three injectors 10 arranged to inject reductant for the SCR catalyst 8 into the exhaust guide 9, upstream of the expanders 5 and downstream of the pre-expander exhaust treatment device 91. More specifically, each injector 10 is arranged to inject reductant into a respective branch 901 of the exhaust guide 9; see FIG. 2. Each branch 901 is arranged to guide exhaust gases from a non-branched portion of the exhaust guide to a respective of the expanders 5. The injectors 10 are controllable by a control unit (not shown), to control the timing, the flow and the duration of the redundant injections. Specifically, the timing and duration of the reductant injections of each injector 10 are coordinated with the actuations of the respective expander inlet valve 503, in order to enable good mixing of the reductant with the exhaust gases in the respective expander 5.

(33) Reference is made to FIG. 5 presenting a detail of a further embodiment of the invention. In the embodiments in FIG. 3 and FIG. 5, the (first) heat exchanger 6 is arranged to transfer the heat to the post-expander exhaust treatment device 8 via the exhaust gases. As an alternative, the heat may be transferred in a more direct manner. In the example in FIG. 5, the heat exchanger 6 and the post-expander exhaust treatment device 8 are integrated.

(34) The heat exchanger 6 comprises a wall 601 separating the air and the exhaust gases. It is understood that the heat exchanger preferably comprises a plurality of such walls, e.g. arranged in parallel with each other. Such a plurality of walls may define alternating cavities for the air and cavities for the exhaust gases.

(35) The post-expander exhaust treatment device 8 comprises an exhaust treatment layer 801 on an exhaust gas side of the wall 601, i.e. on a side of the wall facing a cavity arranged to house the exhaust gases. The exhaust treatment layer 801 is preferably a catalyst. Thus, an exhaust gas part of the heat exchanger 6 is in this example coated with a catalyst. This integration which reduces the total volume of the combination of the heat exchanger 6 and the post-expander exhaust treatment device 8. Also, the integration enhances the heat transfer, and therefore serves to reduce the time to a working catalyst during a cold start procedure of the engine system.

(36) It should be noted that in addition to the integrated catalyst 801, the post-expander exhaust treatment device 8 may also present a portion which is arranged to receive the heat from the heat exchanger 6 via the exhaust gases, e.g. by being located downstream of the heat exchanger as in FIG. 3.

(37) As can be seen in FIG. 5, said wall 601 of the heat exchanger 6 presents a plurality of protruding flanges 602 on an air side of the wall 601, i.e. on a side of the wall facing a cavity arranged to house the air. Such flanges 602 will enhance the absorption of the wall 601 of heat from the compressed air, for transfer of the heat to the exhaust treatment layer 801.

(38) In the embodiments described with reference to FIG. 2-FIG. 4, the pistons of the compressors 3 and the expanders 5 are directly connected to the crankshaft 2 via respective connecting rods. In alternative embodiments, the pistons of the compressors 3 and the expanders 5 may be indirectly connected to the crankshaft 2, e.g. via an additional crankshaft and a chain, belt or gear connection between the crankshafts.

(39) It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.