AIR INTAKE PORT FOR A LEAN-BURN GASOLINE ENGINE

Abstract

An air intake port (10) for a lean-burn gasoline engine (110) comprises an air inlet (14), at least one air outlet (15a, 15b), and an air channel connecting the air inlet (14) to the at least one air outlet (15a, 15b). The air channel comprises an air channel floor (42) and an air channel ceiling (41). The air channel floor (42) is at least substantially flat in a direction of air flow in a region adjacent to the air outlet (15a, 15b).

Claims

1-16. (canceled)

17. An air intake port for a lean-burn gasoline engine, the air intake port comprising: an air inlet, at least one air outlet, and an air channel connecting the air inlet to the at least one air outlet, the air channel comprising an air channel floor and an air channel ceiling, wherein the air channel floor is at least substantially flat in a direction of air flow in a region adjacent to the air outlet.

18. An air intake port according to claim 17, comprising two air outlets, the air channel connecting the air inlet to the two air outlets and comprising an upstream common duct and two downstream port legs, the two downstream port legs branching off from the common duct at a bifurcation point, wherein the air channel floor is at least substantially flat in a direction of flow in at least a downstream half of each of the port legs.

19. An air intake port according to claim 18, wherein the air channel floor is at least substantially flat in a direction of flow along a full length of each of the port legs.

20. An air intake port according to claim 19, wherein the air channel floor is at least substantially flat in a direction of flow in at least a downstream half of the common duct.

21. An air intake port according to claim 20, wherein the air channel floor is at least substantially flat in a direction of flow along a full length of the air intake port.

22. An air intake port according to claim 17, wherein substantially flat is defined as having a difference between a minimum inclination and a maximum inclination that is less than 5 degrees.

23. An air intake port according to claim 17, wherein substantially flat is defined as having a difference between a minimum inclination and a maximum inclination that is less than 2 degrees.

24. An air intake port according to claim 17, wherein substantially flat is defined as having a difference between a minimum inclination and a maximum inclination that is less than 1 degree.

25. A lean-burn gasoline engine comprising; at least one air intake port, the at least one air intake port comprising an air inlet, at least one air outlet, and an air channel connecting the air inlet to the at least one air outlet, the air channel comprising an air channel floor and an air channel ceiling, wherein the air channel floor is at least substantially flat in a direction of air flow in a region adjacent to the air outlet; a combustion chamber with at least one air inlet being connected to the at least one air outlet of the air intake port, the air inlet of the combustion chamber comprising a throat where the air outlet of the air intake port meets the air inlet of the combustion chamber; and a movable valve being arranged to move between a closed state for closing off the air inlet of the combustion chamber and an opened state wherein intake air can flow from the air intake port into the combustion chamber.

26. A lean-burn gasoline engine according to claim 25, wherein the valve comprises a bottom surface that faces the combustion chamber and a top surface that faces the air intake port, and wherein the air intake port and the valve are arranged such that when the valve is in its opened position, the complete bottom surface of the valve is positioned below the air intake port.

27. A lean-burn gasoline engine according to claim 26, wherein the air intake port and the valve are arranged such that when the valve is half-way between its closed position and its opened position, the complete bottom surface of the valve is positioned below the air intake port.

28. A lean-burn gasoline engine according to claim 26, wherein the air intake port and the valve are arranged such that when the valve is in its opened position, the complete top surface of the valve is positioned below the air intake port.

29. A lean-burn gasoline engine according to claim 25, wherein the throat provides a sharp edge with the channel floor, such as to promote a separation of an incoming air flow from a combustion chamber wall.

30. A lean-burn gasoline engine according to claim 29, wherein an angle between the channel floor and an adjacent portion of the throat is at least 225 degrees.

31. A lean-burn gasoline engine according to claim 25, wherein the throat provides a smooth edge with the channel ceiling, such as to adhere an incoming air flow to a combustion chamber ceiling.

32. A lean-burn gasoline engine according to claim 25, wherein the valve comprises a bottom surface that faces the combustion chamber and a top surface that faces the air intake port, and wherein the air intake port and the valve are arranged such that when the valve is in its opened position, the complete bottom surface of the valve is positioned below the air intake port, and wherein the throat provides a sharp edge with the channel floor, such as to promote a separation of an incoming air flow from a combustion chamber wall.

33. A lean-burn gasoline engine according to claim 32, wherein the throat provides a smooth edge with the channel ceiling, such as to adhere an incoming air flow to a combustion chamber ceiling.

34. A lean-burn gasoline engine according to claim 25, wherein the throat provides a sharp edge with the channel floor, such as to promote a separation of an incoming air flow from a combustion chamber wall, and wherein the throat provides a smooth edge with the channel ceiling, such as to adhere an incoming air flow to a combustion chamber ceiling.

35. A lean-burn gasoline engine according to claim 34, wherein an angle between the channel floor and an adjacent portion of the throat is at least 225 degrees.

36. A vehicle comprising a lean-burn gasoline engine according to claim 25.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0027] FIG. 1 shows a vehicle in which the invention may be used;

[0028] FIG. 2 shows an air intake port according to an embodiment of the invention;

[0029] FIG. 3 schematically shows a bottom view of the air intake port of FIG. 2;

[0030] FIGS. 4a and 4b schematically show side views from the plane IV-IV as shown in FIG. 3, into the inside of the air intake port of FIGS. 2 and 3;

[0031] FIG. 5 shows a cross section of a combustion chamber with a retracted piston and a closed inlet valve;

[0032] FIG. 6 shows a close-up of the inlet valve of FIG. 5;

[0033] FIG. 7a shows the inlet valve of FIG. 6 in a partially opened position; and

[0034] FIG. 7b shows the inlet valve of FIGS. 6 and 7a, in a more open position.

DETAILED DESCRIPTION

[0035] FIG. 1 shows a vehicle 100 in which the invention may be used. In this example, the vehicle 100 is a car, but the invention is equally applicable to other vehicles driven by a lean-burn gasoline engine 110. As mentioned above, it is to be noted that air intake port according to the invention and as described herein can be advantageously used in engines burning other fuels or fuel mixtures than gasoline. For example, the air intake port would be useful in a hydrogen burning internal combustion engine. In this vehicle 100, the lean-burn gasoline engine 110 is positioned in the front and coupled to a drivetrain to drive the front and/or rear wheels of the vehicle 100. The energy needed for driving the vehicle 100 is provided by burning fuel in the engine's cylinders causing the cylinder pistons to drive a crankshaft that is mechanically connected to the vehicle's drivetrain.

[0036] Compared to classic internal combustion engines, the lean-burn engine 110 of this vehicle 100 burns the fuel with an excess of air in the air-fuel mixture. Lean-burn engines may mix air and fuel in proportions of, for example, 20:1 (lambda>1.3) or even 30:1 (lambda>2). Advantages of lean-burn engines include more efficient fuel use and lower exhaust hydrocarbon emissions than conventional gasoline engines.

[0037] In order to enable the lean burning of fuel over a large portion of the engine map, i.e. in a large range of different engine speeds as well as engine output power or torque, the engine 110 is designed in such a way to enable a large air flow into the combustion chamber and a good mixing with the relatively small amount of fuel that is to be burnt to ensure a reliable combustion process that will effectively burn all fuel, despite the oxygen rich conditions.

[0038] FIG. 2 shows an air intake port 10 according to an embodiment of the invention. The air intake port 10 has an air inlet 14 and two air outlets 15a, 15b. An air channel connects the air inlet 14 to the two air outlets 15a, 15b. The first, upstream portion of the air channel, starting at the air inlet 14 forms a common duct 11. Ata bifurcation point 13, at a downstream end of the common duct 11, the common duct 11 branches off in two port legs 12a, 12b that provide the two respective air outlets 15a, 15b. The terms upstream and downstream are used to refer to parts of the air intake port 10 relative to flow of air through the air intake port 10 in its normal use with a lean-burn gasoline engine 110. The predominant air flow direction is from an upstream position to a downstream position. It follows that in normal use the engine 110 is downstream of the air intake port 10. The air outlets 15a, 15b are configured to connect to two respective inlets of the combustion chamber. Near the downstream ends of the port legs 12a, 12b, two valve guides 16a, 16 are provided, each being configured to receive a valve stem that is used for controlling the valve that selectively opens and closes the combustion chamber inlets.

[0039] FIG. 3 schematically shows a bottom view of the air intake port 10 of FIG. 2. In addition to what has already been shown in and described with reference to FIG. 2, FIG. 3 shows the air outlets 15a, 15b, and a sloped portion 132 in the common duct floor which leads to the bifurcation point 13. FIG. 3 further shows a plane IV-IV through the air intake port 10, from which the views on the inside of the air intake port 10 as shown in FIGS. 4a and 4b are. In addition thereto, FIG. 3 indicates, with three arrows 33, the direction from which the cross section is viewed in the view of FIGS. 4a and 4b.

[0040] The side views shown in FIGS. 4a and 4b thus show the inside of the air intake port 10 as seen from the plane IV-IV indicated in FIG. 3. As will be explained below, FIGS. 4a and 4b show two slightly different embodiments of the sharp bifurcation angle 133 according to the invention. From this viewpoint inside the common duct 11, we look directly upon a side wall 43 of the common duct 11 and a side wall 44 of one of the leg ports 12a. In addition to a side walls 43, 44, the common duct 11 and the port legs 12a, 12b may have a ceiling 41, a floor 42, and another side wall (not shown). It is noted that the common duct 11 and the port legs 12a are preferably not rectangularly shaped. Depending on the exact shape of the air intake port 10, the boundaries of its floor 42, side walls 43, 44, and ceiling 41 may not be easy to define. The common duct 11 and the port legs 12a, 12b may, e.g., be tubular, oval, rectangular with rounded corners, or have flat floors 42 and/or ceilings 41 with curved side walls. Combinations and variations of such shapes are possible too. In preferred embodiments, however, at least the floor 42 of the common duct 11 is substantially flat.

[0041] In prior art air intake ports with one air intake and two air outlets, the bifurcation point is typically formed as a straight and substantially vertical wall or pillar that connects the air intake floor 42 to the air intake ceiling 41. This vertical wall is situated centrally in the air intake port 10, at the end of the common duct 11. From there, the two port legs 12a, 12b and there opposing inner walls diverge.

[0042] In this case, as can be seen in the side views of FIGS. 4a and 4b, the bifurcation is a gradual transition and not, as in the prior art, a straight wall perpendicular to the air flow 34 through the common duct 11. In a transition zone 134 at the downstream end of the common duct 11, and in or around the centreline of the common duct 11, the ceiling 41 and the floor 42 of the common duct 11 start approaching each other, until the sloped portions 131, 132 of the ceiling 41 and the floor 42 meet each other in the bifurcation point 13. If these sloped portions 131, 132 are sufficiently long, they make a sharp bifurcation angle 133 at this bifurcation point 13. The inventors have found that with such a sharp bifurcation angle, the air flow 34 is allowed to split in two, with far less disturbance than if the bifurcation is formed by a simple vertical wall (or an approximation thereof). In order to achieve this advantageous effect, a bifurcation angle 133 of less than 90? is preferred, however even better results may be obtained with even sharper bifurcation angles of, e.g., less than 75? 55?, or 45?.

[0043] In this example, the bifurcation point 13 is located centrally in the common duct 11, i.e. midway between the two side walls and at equal distances from the floor 42 and the ceiling 41. However, other, less symmetric configurations may be provided without departing from the scope of the invention. For example, the bifurcation point 13 may be positioned somewhat closer to the floor 42, the sloped portion 131 at the ceiling 41 being steeper and/or longer than the sloped portion 132 near the floor 42. In other embodiments the bifurcation point 13 may be somewhat rounded to further reduce air flow disturbances and/or because manufacturing constraints. It is noted that in the event of a slightly rounded bifurcation point 13, the bifurcation angle 133 may be defined as the angle between the duct floor 42 and the duct ceiling 41 measured at a point beyond the rounded edge, e.g. at a position of 5 mm in front of the bifurcation point.

[0044] The sloped portions 131, 132 in the floor and ceiling of the common duct 11 may be substantially straight or curved. In addition to a slope in the longitudinal direction, i.e. in the direction of the air flow, the sloped portions 131, 132 are preferably sloped in the transverse direction too, thereby forming an aerodynamically shaped wedge-like structure.

[0045] According to the invention, the air channel floor 42 of the air intake port 10 of FIGS. 4a and 4b is at least substantially flat in a direction of flow in a region adjacent to the air outlet 15a, 15b, but preferably along the whole port leg 15a, 15b and part or the whole common duct 11 too. The purpose of this flat and even air channel floor 42 is to achieve a stable and undisturbed high-volume air flow that detaches from the underlying surface 42 and is launched into the combustion chamber when reaching the end of the air intake port 10. The term substantially flat may herein, e.g., be defined as having a difference between a minimum inclination and a maximum inclination that is less than 5 degrees.

[0046] Preferably, the flat portion of the air channel floor is designed such that the difference between the minimum and maximum inclination is less than 2, or even 1, degrees. In the example shown, the flat air channel floor 42 is a completely straight floor 42 with a constant inclination. In the event of a non-rectangular air channel, it may be difficult to distinguish the exact transition between the floor 42, walls 43, 44, and ceiling 41 of the air channel. To obtain the described benefits of the described flat floor 42, at least the central and lowest portion of the air channel is designed to be flat. Preferably, however, the floor 42 has a similar flatness in the direction of flow over at least half or even the full width of the air intake port 10. With an air channel floor 42 that is at least substantially flat in a direction of flow in a region adjacent to the air outlet 15a, 15b, flow separation at the combustion chamber inlet significantly improved, thereby allowing the incoming air to first flow across the chamber before descending into the chamber. As a result, the desired tumble is achieved. This tumble is shown and discussed in more detail with reference to FIG. 5.

[0047] It is noted that while the embodiments shown in FIGS. 4a and 4b, have this sloped or curved portion 132 that provides for a smooth transition towards the bifurcation point 13, this will still allow for the floor 42 of the common duct 11 to be at least substantially flat in a direction of air flow. The portions 132 that are sloped or curved part of the side wall 44 separating the two port legs 12a, 12b. The air flow at either side of that side wall 44 can still follow a substantially flat floor 42 in the air flow direction. It is further to be noted that the now presented design of the bifurcation 13 and the substantially flat duct floor 42 both help to provide a stable and undisturbed high-volume air flow that detaches from the underlying surface 42 and is launched into the combustion chamber 50 when reaching the end of the air intake port 10. Both measures add to the same technical effect that is already obtained by the use of a substantially flat floor 42 in at least a downstream portion of the port legs 12a, 12b. However, the advantageous effects of a substantially flat floor 42 in the common duct can also be obtained with a vertical wall type bifurcation.

[0048] FIG. 5 shows a cross section of a combustion chamber 50 with a retracted piston 54 and a closed inlet valve 51. A dotted line 59 provides a simplified 2D representation of the preferred air flow into and through the combustion chamber 50. It is noted that the air flow into the combustion chamber 50 is not possible with a closed inlet valve 51 but is shown for the purpose of illustration only. shows a cross section of a combustion chamber 50 with a retracted piston 54 and a closed inlet valve 51.

[0049] With the valve 51 and air inlet design of this embodiment, it is possible to create a tumble motion of the incoming air, first along the roof of the combustion chamber 50 towards the opposite wall, under the outlet valve 55 that closes off the exhaust outlet 56, and then down along that opposing wall, back over the top surface of the piston 54 and up along the combustion chamber wall in the direction of the inlet valve 51 again. This tumble is preferably kept in motion during the full intake stroke and at least a portion of the compression stroke of the piston 54 moving through the combustion chamber 50. The thus produced tumble helps to obtain an optimal distribution of air and fuel inside the combustion chamber 50 that can then break down into turbulence to facilitate the subsequent combustion process.

[0050] In order to create the desired tumble, the valve 51 and the air inlet of the combustion chamber 50 are designed such that the air flow entering the combustion chamber 50 is promoted to detach from the floor of the port leg 12a, 12b of the air intake port 10 and to flow along the ceiling of the combustion chamber 50. Some of the specific design features that can help to promote the desired tumble are discussed below with reference to FIGS. 6, 7a, and 7b.

[0051] FIGS. 6, 7a, and 7b shows a close-up of the inlet valve 51 of FIG. 5. As can be seen in all these Figures, the air channel floor 42 of the port leg 12a, 12b is flat in the full region up to the air outlet 15a, 15b of the air intake port 10. The flat air channel floor 42 promotes the detachment of the air flow as soon as it leaves the air intake port 10 and enters the combustion chamber 50, which contributes to the desired tumble.

[0052] The movable valve 51 comprises a bottom surface 61 that faces the combustion chamber 50 and a tapered top surface 62 that faces the air intake port 10. The inlet valve 51 is provided at the end of a valve stem 63. This inlet valve 51 is arranged to move by controlling the position of the valve stem 63. The movable valve 51 may be moved between a closed state (FIG. 6) for closing off the combustion chamber inlet and an opened state (FIGS. 7a and 7b) wherein intake air can flow from the air intake port 10 into the combustion chamber 50. The throat comprises a tapered surface 71 that is complementary with the tapered top surface 62 of the movable valve 51, such that when the movable valve 51 is in its closed position, the movable valve 51 at least partially sinks into the throat.

[0053] This tumble is preferably kept in motion during the full intake stroke and at least a portion of the compression stroke of the piston 54 moving through the combustion chamber 50. The complementary tapered surfaces 62, 71 of the intake valve 51 and the throat together ensure that during the compression stroke, when the intake valve 51 is closed, no or little air can get trapped behind the valve 51 or between the valve 51 and an inner surface of the combustion chamber 50 while tumbling through the combustion chamber 50. The further the valve 51 is allowed to sink into the throat, the less disturbance it can cause to the desired tumble. In an embodiment of the invention, the bottom surface 61 of the movable valve 51 may even be substantially flush with an inner surface of the combustion chamber 50 when the movable valve 51 is in its closed position.

[0054] Due to the tapered surface of the throat, and because the valve 51 needs to be able to close off the air inlet, the diameter of the combustion chamber inlet is smaller than the valve diameter. The valve diameter is determined by the bottom surface 61 of the valve 51. In an embodiment of the invention, the diameter of the combustion chamber inlet is less than, e.g., 95% or 90% of a diameter of the bottom surface 61 of the movable valve 51. Not only does this allow for the desired taper 71 in the throat surface, the protruding upstream portion of the throat also helps to shield of the valve edge, thereby directing the air flow over the top surface 62 of the valve 51 (see FIG. 7a) and along the roof of the combustion chamber 50 instead of around the valve edge and down along the wall closest to the combustion chamber inlet.

[0055] This effect can further be enhanced by the protruding upstream portion ending with a sharp edge 73 that promotes detachment of the air flow. In this example, the sharp edge 73 coincides with the outer end of the air channel floor 42 at the air outlet 15a, 15b of the air intake port 10.

[0056] While this is the preferred embodiment, the channel floor 42 may alternatively end at a position in front of or behind the sharp edge 73. In preferred embodiments, the angle between the channel floor 42 and an adjacent portion of the throat is at least 225 degrees. However, angles closer to, or even beyond, 270 degrees are even more preferred. The larger the angle, the smaller the chance that the airflow will adhere to the throat surface and finds a way down into the combustion chamber 50 immediately upon entering.

[0057] Additionally, an optional deflector 72 is provided at an inner wall of the combustion chamber 50 and protruding radially therefrom. The deflector 72 is positioned underneath an outer edge of the bottom surface 61 of the movable valve 51. This deflector 72 is arranged such that an air flow moving up along the inner wall of the combustion chamber 50 is deflected radially inward and away from the outer edge of the bottom surface 61 of the movable valve 51. As a result, the risk of any air being trapped behind the valve 51 when in a closed or almost closed position is reduced. This useful deflector 72, on top of that, brings the additional advantage that during the intake stroke, when the valve 51 is at least partially open and air is drawn into the combustion chamber 50, any air unintentionally bouncing of the top surface 62 of the valve 51 will be prevented from flowing down along the nearest inner wall of the combustion chamber 50. Instead, the deflector 72 will block this astray air flow back into the chamber 50, and in the direction of the desired tumble.

[0058] In a preferred embodiment of this lean-burn gasoline engine 110, the air intake port 10 and the valve 51 are arranged such that when the valve 51 is in its opened position, the complete bottom surface of the valve 51 is positioned below the air intake port 10. This allows the separated air flow leaving the air intake port 10 to flow along the roof of the combustion chamber 50 and towards the opposite chamber wall with minimal disturbance by the valve 51 it has to pass. In an even more preferred embodiment, the complete bottom surface 61 of the valve 51 is already positioned below the air intake port 10 when the valve 51 is only half-way between its closed position and its opened position. This further allows reduced flow disturbance by the valve 51 while the valve is still opening, thereby facilitating the creation of the desired tumble as soon as the valve 51 is opened. In alternative embodiments, the complete bottom surface 61 drops below the air intake port 10 when the valve is, e.g., 60% open.

[0059] In a further embodiment, the air intake port 10 and the valve 51 are arranged such that when the valve 51 is in its opened position, also the complete top surface 62 of the valve 51 is positioned below the air intake port 10, with the tapered angle of the top surface 62 at a similar angle as the port floor, which leads to even less disturbance of the air flow, and helps to direct the air flow across the top of the chamber, with a more prominent and stable tumble as a result. The top surface 62 may be inclined slightly upward at the point where the air flow may hit the valve 51 in order to lift the air flow up in the direction of the chamber ceiling and/or the top end of the opposing wall.

[0060] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.