Internal combustion engine arrangement

Abstract

The present invention relates to an internal combustion engine arrangement for a vehicle, said internal combustion engine arrangement comprising a combustion cylinder housing a reciprocating combustion piston, and an expansion cylinder housing a reciprocating expansion piston, said expansion cylinder being arranged in downstream fluid communication with the combustion cylinder for receiving combustion gases exhausted from the combustion cylinder, wherein the internal combustion engine arrangement further comprises a pressure tank arranged in fluid communication with the expansion cylinder, wherein the internal combustion engine arrangement is further arranged to be operated in a first operating mode in which compressed gas generated in the expansion cylinder is delivered to the pressure tank, and a second operating mode in which compressed gas contained in the pressure tank is delivered from the pressure tank to the expansion cylinder.

Claims

1. An internal combustion engine arrangement for a vehicle, the internal combustion engine arrangement comprising a combustion cylinder housing a reciprocating combustion piston, and an expansion cylinder housing a reciprocating expansion piston, the expansion cylinder being arranged in downstream fluid communication with the combustion cylinder for receiving combustion gases exhausted from the combustion cylinder, wherein the internal combustion engine arrangement further comprises a pressure tank arranged in fluid communication with the expansion cylinder, wherein the internal combustion engine arrangement is further arranged to be operated in a first operating mode in which compressed gas generated in the expansion cylinder is delivered to the pressure tank, and a second operating mode in which compressed gas contained in the pressure tank is delivered from the pressure tank to the expansion cylinder, wherein the internal combustion engine arrangement further comprises a heat regenerator arranged in fluid communication between the expansion cylinder and the pressure tank, the heat regenerator being arranged to absorb heat from the compressed gas generated by the expansion cylinder delivered to the pressure tank, and to release the heat when the compressed gas is transported from the pressure tank to the expansion cylinder.

2. The internal combustion engine arrangement according to claim 1, wherein the expansion cylinder is arranged to compress ambient air and to pump compressed ambient air to the pressure tank when the internal combustion engine arrangement is operated in the first operating mode.

3. The internal combustion engine arrangement according to claim 1, wherein combustion gas from the combustion cylinder is prevented from being directed to the expansion cylinder when the internal combustion engine arrangement is operated in the second operating mode.

4. The internal combustion engine arrangement according to claim 1, further comprising a control unit for selectively controlling the internal combustion engine to be operated in either one of the first and second operating modes.

5. The internal combustion engine arrangement according to claim 4, wherein the control unit is configured to: receive a signal indicative of a braking operation for the vehicle; and control the internal combustion engine arrangement to be operated in the first operating mode when the vehicle is exposed to the braking operation.

6. The internal combustion engine arrangement according to claim 4, wherein the control unit is further configured to: receive a signal indicative of a power level required for the vehicle, compare the required power level with a predetermined threshold limit; and control the internal combustion engine arrangement to be operated in the second operating mode when the required power level exceeds the predetermined threshold limit.

7. The internal combustion engine arrangement according to claim 1, further comprising a valve arrangement positioned in fluid communication with the combustion cylinder, the expansion cylinder and the pressure tank.

8. The internal combustion engine arrangement according to claim 7, further comprising an intermediate tank positioned in fluid communication between the combustion cylinder and the expansion cylinder, the intermediate tank being arranged to contain compressed gas exhausted from the combustion cylinder.

9. The internal combustion engine arrangement according to claim 8, wherein the valve arrangement is arranged downstream the intermediate tank.

10. The internal combustion engine arrangement according to claim 1, wherein the expansion cylinder comprises a geometric compression ratio of at least 40, the compression ratio being a ratio between a maximum and a minimum volume formed by the reciprocating motion of the expansion piston within the expansion cylinder.

11. The internal combustion engine arrangement according to claim 1, further comprising a compression cylinder housing a reciprocating piston, the compression cylinder being arranged in upstream fluid communication with the combustion cylinder for delivery of compressed air to the combustion cylinder.

12. A method for controlling an internal combustion engine arrangement, the internal combustion engine arrangement comprising a combustion cylinder housing a reciprocating combustion piston, an expansion cylinder housing a reciprocating expansion piston, the expansion cylinder being arranged in downstream fluid communication with the combustion cylinder for receiving combustion gases exhausted from the combustion cylinder, a pressure tank arranged in fluid communication with the expansion cylinder, and a heat regenerator arranged in fluid communication between the expansion cylinder and the pressure tank, wherein the method comprises the steps of: determining an operating state of the vehicle; when the vehicle is operated in a first operating state: controlling compressed gas generated in the expansion cylinder to be directed to the pressure tank via the heat regenerator, wherein the heat regenerator absorbs heat from the compressed gas generated by the expansion cylinder delivered to the pressure tank; and when the vehicle is operated in a second operating state: controlling compressed gas contained in the pressure tank to be delivered to the expansion cylinder via the heat regenerator, wherein the heat regenerator releases the heat to the compressed gas when the compressed gas is transported from the pressure tank to the expansion cylinder.

13. A computer program comprising program code means for performing the steps of claim 12 when the program is run on a computer.

14. A computer readable medium carrying a computer program comprising program means for performing the steps of claim 12 when the program means is run on a computer.

15. A vehicle comprising an internal combustion engine arrangement, the internal combustion engine arrangement comprising a combustion cylinder housing a reciprocating combustion piston, and an expansion cylinder housing a reciprocating expansion piston, the expansion cylinder being arranged in downstream fluid communication with the combustion cylinder for receiving combustion gases exhausted from the combustion cylinder, wherein the internal combustion engine arrangement further comprises a pressure tank arranged in fluid communication with the expansion cylinder, wherein the internal combustion engine arrangement is further arranged to be operated in a first operating mode in which compressed gas generated in the expansion cylinder is delivered to the pressure tank, and a second operating mode in which compressed gas contained in the pressure tank is delivered from the pressure tank to the expansion cylinder, wherein the vehicle further comprises a second prime mover different from the internal combustion engine arrangement, wherein the vehicle is configured to be operated in: a first vehicle state in which the vehicle is propelled by providing compressed gas from the pressure tank to the expansion cylinder; and a second vehicle state in which the vehicle is propelled by using the second prime mover.

16. The vehicle according to claim 15, wherein the vehicle is operated in the first vehicle state when a power requirement for the vehicle is higher in comparison to operation in the second vehicle state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments of the present invention, wherein:

(2) FIG. 1 is a lateral side view illustrating an example embodiment of a vehicle in the form of a truck;

(3) FIG. 2 is a schematic illustration of an internal combustion engine arrangement according to an example embodiment;

(4) FIGS. 3a-3c schematically illustrate gas flow of the internal combustion arrangement for operating modes thereof according to an example embodiment;

(5) FIG. 4 is a schematic illustration of an internal combustion engine arrangement according to another example embodiment; and

(6) FIG. 5 is a flow chart illustrating a method for controlling an internal combustion engine arrangement according to an example embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

(7) The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness. Like reference character refer to like elements throughout the description.

(8) With particular reference to FIG. 1, there is provided a vehicle 1 in the form of a truck. The vehicle 1 comprises an engine 100 in the form of an internal combustion engine arrangement 100 as will be described further below in relation to the description of e.g. FIGS. 2 and 3. The internal combustion engine arrangement 100 is preferably propelled by e.g. a conventional fuel such as diesel.

(9) With reference to FIG. 2, a schematic illustration of the internal combustion engine arrangement 100 according to an example embodiment is depicted. According to the example embodiment depicted in FIG. 2, the internal combustion engine arrangement 100 comprises a compression cylinder 102. The compression cylinder 102 comprises a reciprocating compression piston (not shown), i.e. the reciprocating compression piston is housed within the compression cylinder 102 to operate in a reciprocating motion between an upper end, also commonly referred to as top dead center (TDC) and a lower end, also commonly referred to as bottom dead center (BDC). The compression cylinder 102 further comprises an inlet valve 402 at which gas, preferably in the form of air at ambient gas pressure is controllably provided into the compression cylinder 402. The compression cylinder 102 also comprises an outlet valve 404 through which compressed gas is controllably exhausted from the compression cylinder 102. The compression cylinder 102 is preferably operated in a two stroke fashion.

(10) Furthermore, the internal combustion engine arrangement 100 comprises a combustion cylinder 106 arranged in downstream fluid communication with the compression cylinder 102, via a conduit 302. The combustion cylinder 106 comprises a reciprocating piston (not shown), i.e. the reciprocating combustion piston is housed within the combustion cylinder 106 to operate in a reciprocating motion between the TDC and the BDC of the combustion cylinder. The combustion cylinder 106 further comprises an inlet valve 406, at which compressed gas from the compression cylinder 102 is controllably provided into the combustion cylinder 106. The combustion cylinder 106 further comprises an outlet valve 408 through which compressed combustion gas is exhausted from the combustion cylinder 106. The combustion cylinder 106 is preferably operated in a four stroke fashion. Also, the combustion cylinder 106 comprises a fuel injection system (not shown) for providing fuel into the combustion cylinder 106 for combustion therein.

(11) Moreover, the internal combustion engine arrangement 100 comprises an expansion cylinder 110 arranged in downstream fluid communication with the combustion cylinder 106 via a conduit 304. The expansion cylinder 110 comprises a reciprocating expansion piston (not shown), i.e. the reciprocating expansion piston is housed within the expansion cylinder 110 to operate in a reciprocating motion between the TDC and the BDC of the expansion cylinder. The expansion cylinder 110 further comprises an inlet valve 410, at which compressed combustion gas from the combustion cylinder 106 is controllably provided into the expansion cylinder 110. The expansion cylinder 110 further comprises an outlet valve 412 through which expanded combustion gas is exhausted from the expansion cylinder 110 to an aftertreatment system (not shown) or the like.

(12) As further depicted in FIG. 2, the internal combustion engine arrangement 100 comprises a pressure tank 112. The pressure tank 112 is arranged in fluid communication with the expansion cylinder 112 via a pressure tank conduit 111. As will be described further below, the pressure tank 112 is arranged to controllably receive compressed gas from the expansion cylinder 110, and to controllably deliver compressed gas to the expansion cylinder 110, in dependence of a current operating mode of the internal combustion engine arrangement 100. Accordingly, the pressure tank 112 should be designed to withstand gas pressure levels corresponding to at least the gas pressure level of the compressed gas generated in the expansion cylinder 110.

(13) Moreover, in order to control delivery of compressed gas from the expansion cylinder 110 to the pressure tank 112, or from the pressure tank 112 to the expansion cylinder 110, the internal combustion arrangement 100 comprises a valve arrangement 114. The valve arrangement 114 is preferably a three-way valve arrangement connected in fluid communication with the combustion cylinder 106, the expansion cylinder 110 and the pressure tank 112. The valve arrangement 114 is also connected to a control unit 116 for controlling the valve arrangement 114. The valve arrangement 114, and its positions controlled by the control unit 116 will be described in further detail below in relation to the description of FIGS. 3a-3c.

(14) As is further depicted in the example embodiment of FIG. 2, the internal combustion engine arrangement 100 comprises a first 120 and a second 122 intermediate tank. The first intermediate tank 120 is positioned in the conduit 302 and thus arranged in fluid communication between the compression cylinder 102 and the combustion cylinder 106. The first intermediate tank 120 may also be referred to as an intermediate low pressure gas tank. The second intermediate tank 122 is positioned in the conduit 304 and thus arranged in fluid communication between the combustion cylinder 106 and the expansion cylinder 110, or more precisely in fluid communication between the combustion cylinder 106 and the valve arrangement 114. The second intermediate tank 122 may also be referred to as an intermediate high pressure gas tank as the pressure level of the gas contained therein is higher than the pressure level of the gas contained in the first intermediate tank 120. It should however be readily understood that the first 120 and/or second 122 intermediate tanks are additional components that may be incorporated if desired. Hence, it may not be necessary to include the first 120 and/or second 122 intermediate tanks to the internal combustion engine arrangement for the functioning of controlling the internal combustion engine in the various modes described below.

(15) By means of the internal combustion arrangement 100 depicted in FIG. 2, operation thereof is normally executed according to the following. Air is provided into the compression cylinder 102 via the inlet valve 402 of the compression cylinder 102. By means of the reciprocating motion of the compression piston, the air is compressed in a two stroke fashion before being exhausted to the conduit 302 via the outlet valve 404. The compressed air is directed into the first intermediate tank 120 and thereafter directed into the combustion cylinder 106 via the inlet valve 406 of the combustion cylinder 106. During the four stroke operation of the combustion piston in the combustion cylinder 106, the compressed air is even further compressed and combustible fuel is injected into the combustion chamber of the combustion cylinder 106. The compressed combustion gas is, after combustion, directed into the conduit 304 via the outlet valve 408 of the combustion cylinder and further directed into the second intermediate tank 122. The compressed combustion gas is thereafter directed into the expansion cylinder 110 via the inlet valve 410 of the expansion cylinder 110. The compressed combustion gas is, during the reciprocating two stroke motion of the expansion cylinder expanded and directed out from the expansion cylinder 110 via the outlet valve 412. The compression piston, the combustion piston and the expansion piston are connected to the crankshaft (not shown) of the internal combustion engine arrangement 100. The compression piston, the combustion piston and the expansion piston may be directly connected to one and the same crankshaft or connected to the crank shaft via an intermediate crankshaft or the like, which in turn is/are connected to the crankshaft via e.g. gear wheels in meshed connection with each other.

(16) Reference is now made to FIGS. 3a-3c which illustrate three different operating modes for the internal combustion engine arrangement 100 according to example embodiments thereof. In detail, FIGS. 3a-3c schematically illustrate how the valve arrangement 114 is arranged to direct flow of gas for the various operating modes. In FIGS. 3a-3b, the compression cylinder 102, the first 120 and second 122 intermediate tanks, as well as the control unit 116 have been omitted for simplifying the illustration and understanding of the gas flow. Also, the valve arrangement 114 has been schematically depicted in each of FIGS. 3a-3b by focusing on the flow direction. The valve arrangement 114 may thus be designed in different forms as long as being controllable according to the below description.

(17) Firstly, reference is made to FIG. 3a which illustrate the above described normal operation of the internal combustion arrangement 100. As can be seen in FIG. 3a, the valve arrangement 114 is arranged in a normal operating position where compressed gas is delivered from the outlet valve 408 of the combustion cylinder 106 and directed into the expansion cylinder 110 via the conduit 304 and the inlet valve 410 of the expansion cylinder 110. As can also be seen in FIG. 3a, the valve arrangement 114 is preventing compressed gas to be delivered to the pressure tank 112.

(18) The internal combustion engine arrangement 100 is however also arranged to assume a first operating mode and a second operating mode. Reference is therefore made to FIG. 3b which illustrates the flow of compressed gas in the first operating mode. The internal combustion engine arrangement 100 is preferably arranged to be operated in the first operating mode when the vehicle is exposed to engine braking. The main target of the first operating mode is to provide compressed gas generated in the expansion cylinder 110 into the pressure tank 112. As can be seen in FIG. 3b, this is accomplished by positioning the valve arrangement in a first operating position allowing compressed gas to be delivered from the expansion cylinder 110 into the pressure tank 112. The expansion cylinder 110 receives gas in the form of ambient air, preferably through the outlet valve 412. The air/gas is compressed in the expansion cylinder 110 by means of the reciprocating motion of the expansion cylinder. The expansion cylinder 110 then acts as an air/gas pump for pumping the compressed gas from the expansion cylinder 110 into the pressure tank 112 via the pressure tank conduit 111. Hence, the valve arrangement 114 prevents flow of gas from the combustion cylinder 106 to the expansion cylinder 110, while allowing flow of compressed gas to be delivered from the expansion cylinder 110 and into the pressure tank 112.

(19) When the pressure tank 112 comprises a sufficient amount of compressed gas, the internal combustion engine arrangement 100 can be arranged to assume the second operating mode. The second operating mode may also be referred to as an air hybrid mode. This is due to the fact that the internal combustion engine arrangement 100 will be operated by means of compressed gas from the pressure tank 112. The internal combustion engine arrangement 100 is preferably operated in the second operating mode when there is a desire to add additional power to the vehicle, such as for assisting an electric motor, etc. FIG. 3c illustrates the flow of compressed gas when the internal combustion engine arrangement 100 assumes the second operating mode. As can be seen, the valve arrangement 114 is positioned in the first operating position allowing compressed gas to be delivered from the pressure tank 112 to the expansion cylinder 110. Hereby, the compressed gas from the pressure tank 112 propels the internal combustion engine arrangement 100 by forcing the expansion piston to reciprocate within the expansion cylinder 110. As the expansion piston is connected to the crankshaft, propulsion of the internal combustion engine is achieved by forcing the expansion piston to reciprocate within the expansion cylinder 110. As is also depicted in FIG. 3c, the second operating position of the valve arrangement 114 prevents compressed gas from the combustion cylinder 106 to be delivered to the expansion cylinder 110. In the second operating mode, opening and closing timing of the inlet valve 410 of the expansion cylinder can be adjusted to allow more/less compressed gas therein. The first operating position of the valve arrangement 114 thus allows the flow of gas both to and from the pressure tank.

(20) Reference is now made to FIG. 4 which illustrates another example embodiment of the internal combustion engine arrangement 100. The difference between the embodiment depicted in FIG. 2 and the embodiment depicted in FIG. 4 is that the embodiment in FIG. 4 comprises a heat regenerator 140. In more detail, the heat regenerator 140 is arranged in the pressure tank conduit 111 in fluid communication between the valve arrangement 114 and the pressure tank 112. The valve arrangement 114 is in FIG. 4 arranged to assume the different positions as described above in relation to the description of FIGS. 3a-3c. The flow direction in FIG. 4 is therefore illustrated by means of double sided arrows. Thus, flow is directed from the valve arrangement 114 to the pressure tank 112, via the heat regenerator 140, as depicted in FIG. 3b when the internal combustion engine arrangement 100 assumes the first operating mode, and the flow is directed from the pressure tank 112, via the heat regenerator 140, to the valve arrangement 114 when the internal combustion engine arrangement 100 assumes the second operating mode as depicted in FIG. 3c.

(21) The heat regenerator 140 comprises a warm side 142 illustrated by a flame, and a cold side 144 illustrated by a snow flake. During operation, and when the internal combustion engine arrangement 100 assumes the first operating mode, relatively warm compressed gas is directed from the combustion cylinder 106 to the pressure tank 112 via the heat regenerator 140. The heat regenerator 140 absorbs the heat in the compressed combustion gas such that the compressed gas delivered to the pressure tank 112 is substantially at ambient temperature. The heat regenerator 140 thus absorbs the heat and “keeps” the heat until the internal combustion engine 100 assumes the second operating mode. In the second operating mode, the compressed gas in the pressure tank 112 is directed towards the valve unit 114 as depicted in FIG. 3c. When the compressed gas passes the heat regenerator 140, i.e. the gas travels along the heat regenerator 140, the thermal energy is released and transported with the compressed gas flow towards the expansion cylinder 110. By means of the heat regenerator 140, a substantially reversible process is achieved. The compressed gas leaving the heat regenerator 140 in the second operating mode will have substantially the same temperature as the temperature of the compressed gas that entered the heat regenerator in the first operating mode.

(22) When the warm compressed gas from the combustion cylinder 106 is delivered towards the pressure tank 112, a majority of the heat will be absorbed at the warm side 142 of the heat regenerator 140. The heat in the heat regenerator 140 will be progressively reduced on its travel towards the cold side. Hereby, substantially all heat is removed when the compressed gas leaves the heat regenerator 140 and enters the pressure tank 112. As depicted in connection with the heat regenerator 140, a heat wave 150 is generated in the heat regenerator 140. When compressed gas is delivered from the expansion cylinder 110 to the pressure tank 112, the heat wave is moved towards the pressure tank 112 as indicated by the dotted wave with numeral 152. When compressed gas is delivered from the pressure tank 112 to the expansion cylinder 110, the heat wave is moved away from the pressure tank 112 as indicated by the dotted wave with numeral 154. There is thus a heat gradient in the heat regenerator 140, whereby a heat wave is formed when directing compressed gas to and from the pressure tank 112, which is caused by the relatively high energy utilization of the internal combustion engine arrangement 100. Preferably, the heat regenerator should have a relatively steep heat wave, i.e. a relatively steep heat gradient, whereby the temperature of the compressed gas is reduced relatively quickly when entering the heat regenerator 140. This will prevent the heat from leaking from the heat regenerator 140. Also, the thermal conductivity of the heat regenerator 140 should preferably be relatively low in the flow direction of the compressed gas. Also, the heat regenerator 140 should preferably be provided with suitable heat insulation (not shown).

(23) In order to sum up and to describe a method for controlling the above described internal combustion engine arrangement 100 according to an example embodiment, reference is made to FIG. 5 in combination with FIGS. 2-4. When operating the internal combustion engine arrangement 100, such as e.g. in the above described normal operating mode which is depicted in FIG. 3a, an operating state of the vehicle 1 is determined S1. It is thereafter determined if the vehicle is operated in the first operating state or the second operating state. The first operating state preferably corresponds to an engine braking operation of the vehicle, while the second operating state preferably corresponds to a driving state where the vehicle is in need of an increased engine power for a shorter period of time. If it is determined that the vehicle is operated in the first operating state, compressed gas generated in the expansion cylinder 110 is controlled S2 to be directed to the pressure tank 112. Preferably, the compressed gas is directed to the pressure tank 112 via the above described heat regenerator 140 such that heat in the compressed gas is absorbed in the heat regenerator 140 before delivery to the pressure tank 112.

(24) On the other hand, if it is determined that the vehicle is operated in the second operating state, the compressed gas contained in the pressure tank 112 is controlled S3 to be delivered from the pressure tank 112 to the expansion cylinder 110. Preferably, the compressed gas is directed to the expansion cylinder 110 via the heat regenerator 140 for heating the compressed gas before delivery to the expansion cylinder 110.

(25) However, if it is determined that the vehicle is also not operated in the second operating state, and instead operated in a normal operating state, the internal combustion engine arrangement 100 may be controlled S4 to direct compressed gas from the combustion cylinder to the expansion cylinder as depicted and described above in relation to FIG. 3a.

(26) Although the above has described the internal combustion engine arrangement 100 comprising a single compression cylinder 102, a single combustion cylinder 106 and a single expansion cylinder 110, it should be readily understood that other compression-combustion-expansion arrangements are conceivable. For example, two compression cylinders, two combustion cylinders and two expansion cylinders may also equally as well be used. Another alternative is to use a single compression cylinder, a single expansion cylinder and two combustion cylinders. A still further alternative is to use dual compression cylinders, dual combustion cylinders, dual expansion cylinders, wherein an additional compression cylinder is arranged in fluid communication between the dual compression cylinders and the dual combustion cylinders. Furthermore, instead of using a valve as depicted in e.g. FIGS. 3a-3b, the flow of gas to/from the pressure tank can be controlled by controlling the outlet valves of the combustion cylinders. Hereby, the outlet valves of the combustion cylinders can be kept close while delivering compressed gas to/from the pressure tank.

(27) 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.