Exhaust Manifold

Abstract

An exhaust manifold for attaching to exhaust ports of an engine, the manifold having a plenum and a plurality of exhaust runners each associated with a respective exhaust port, the plenum having a progressively tapering cross sectional area along its length as defined by the direction along which successive exhaust runners connect to the plenum and a connector at its larger downstream end, for connecting to further components of the exhaust system, characterized in that the lengths of the gas flow paths in all the exhaust runners, as measured from the end of each runner adjacent the exhaust port to an interior wall of the plenum opposite the other end of the runner, are substantially equal to one another.

Claims

1. An exhaust manifold for attaching to exhaust ports of an engine, the manifold comprising: a plurality of exhaust runners each having a respective exhaust port associated therewith; a plenum coupled to the plurality of the exhaust runners, the plenum having a height, a length defined by the direction along which successive exhaust runners are connected to the plenum, and an internal wall, the plenum having a progressively tapering cross sectional area along its length, and a collector disposed at the largest cross section area of the plenum, the collector defining the downstream of the plenum, and runners being progressively upstream with increased distance from the collector; the plenum and the exhaust runners define a plurality of runner respective gas flow paths defined at least from the end of the respective runner adjacent the respective exhaust port to the interior wall of the plenum, the length of all gas flow paths being substantially equal.

2. An exhaust manifold as claimed in claim 1, wherein the height of the plenum, as measured in the plane orthogonal to the runners and a major axis of the plenum, increases in steps as each successive downstream runner opens into the plenum.

3. An exhaust manifold engine as claimed in claim 1, wherein the height of the plenum, as measured in the plane orthogonal to the runners and a major axis of the plenum, increases linearly along the length of the plenum in a direction from an upstream runner towards the collector at the downstream end of the plenum.

4. An exhaust manifold as claimed in any preceding claim wherein the plenum has at least a section of its length having an oval cross section defining a major axis and a minor axis, the length of the major axis increasing monotonically along its length between the furthest runner and the collector.

5. An exhaust manifold as claimed in claim 4, wherein when fitted within an engine compartment of a vehicle, the major axis is substantially vertical and the minor axis substantially horizontal.

6. An exhaust manifold as claimed in claim 1, wherein the plenum increases in cross sectional area as each successive runner joins the plenum from the farther runner at the most upstream end to the collector at the largest area downstream end.

7. An exhaust manifold for attaching to exhaust ports of an engine, the manifold comprising: a plurality of exhaust runners each having a respective exhaust port associated therewith; a plenum coupled to the plurality of the exhaust runners, the plenum having a height, a length defined by the direction along which successive exhaust runners are connected to the plenum, and an internal wall; the plenum having a mid-section having the largest cross section thereof, the mid-section having a collector coupled thereto; at least one of the plurality of exhaust runners being coupled on each side of the mid-section; and, the plenum cross-section tapering away from the mid-section along the plenum length; the plenum and the exhaust runners define a plurality of runner respective gas flow paths defined at least from the end of the respective runner adjacent the respective exhaust port to the interior wall of the plenum, the length of all gas flow paths being substantially equal.

8. An exhaust manifold as claimed in claim 7, wherein the plenum cross section area decreases after each successive runner which joins the plenum farther from the collector.

9. An exhaust manifold as claimed in claim 7, wherein the plenum cross section area decreases linearly away from the mid-section.

10. A vehicle having an internal combustion engine utilizing exhaust manifold as claimed in claim 1.

11. A vehicle having an internal combustion engine utilizing exhaust manifold as claimed in claim 2.

12. A vehicle having an internal combustion engine utilizing exhaust manifold as claimed in claim 3.

13. A vehicle having an internal combustion engine utilizing exhaust manifold as claimed in claim 4.

14. A vehicle having an internal combustion engine utilizing exhaust manifold as claimed in claim 5.

15. A vehicle having an internal combustion engine utilizing exhaust manifold as claimed in claim 6.

16. A vehicle having an internal combustion engine utilizing exhaust manifold as claimed in claim 7.

17. A vehicle having an internal combustion engine utilizing exhaust manifold as claimed in claim 8.

18. A vehicle having an internal combustion engine utilizing exhaust manifold as claimed in claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention will now be described further by way of example with reference to the accompanying drawings in which:

[0028] FIG. 1 is a block diagram representation of a front end view of an engine bay showing a V-opposed engine;

[0029] FIG. 2 is a side view of the engine of FIG. 1 including a prior art manifold, attached to one of the cylinder head banks of the V-opposed engine;

[0030] FIG. 3 is a front end view similar to that of FIG. 1, showing the engine and prior art manifold of FIG. 2 attached to one of the cylinder head banks, installed within the engine bay;

[0031] FIG. 4 is a block diagram representation of a front end view of an engine bay showing an inline engine;

[0032] FIG. 5 is a top view of the engine of FIG. 4 connected to a manifold according to the present invention; and

[0033] FIG. 6 is a side view of the engine and manifold of FIG. 5 as seen looking through a wall of the engine compartment.

[0034] The various figures described below relate to different embodiments of the invention relating to different engine configurations. Common reference numerals are used for common components throughout.

DETAILED DESCRIPTION

[0035] FIG. 1, shows an engine 10 located within an engine compartment 12. The engine compartment here is represented by four bounding walls forming the outer square of the diagram. In practice, there will most likely be no lower wall on which the engine sits, more likely a sub-frame allowing access to the engine 10 from underneath, but for the purposes of describing this invention, such detail is not necessary. The side walls of the engine compartment 12, are more representative of what is actually provided within a vehicle engine bay. These are typically in the form of wheel arches or bulkhead walls, and form a large flat typically metal surface bounding the engine between typically 3 vertical wallsthe front space being open to receive airflow to heat exchangers which are typically mounted there.

[0036] The view shown in FIG. 1 is a front end view and would therefore be looking through the engine's radiator at the engine 10. The engine is formed from a crank case 14 and due to the V-configuration of this example, two cylinder heads 16 arranged to form a V with the crank shaft axis (not shown).

[0037] Conventional V-configuration engines include an inlet manifold arranged between the cylinder heads above the engine block 14 to allow air into the intake ports (not shown). After combustion has occurred the exhaust gases exit the cylinder heads 16 through the exhaust ports.

[0038] The multiple exhaust ports, corresponding to each cylinder are joined together by a manifold 20 (not shown in FIG. 1, see FIGS. 2 and 3) that provides a single flow path through connector 22 to the exhaust system.

[0039] The figures utilize arrows to indicate the dimension of the manifold which tapers with respect to the orientation of the engine. Arrows labelled 1 show the dimension of the manifold which is approximately constant, whereas arrows labelled 2 show the dimension of the manifold that tapers.

[0040] As seen in the prior art reference of FIG. 2 which shows the right most cylinder head 16 of FIG. 1 viewed from the side, as if looking through the boundary wall of the engine compartment 12, the manifold 20 is formed from a plenum chamber connected to three branch, exhaust runner or header pipes 18. Each of these is connected to a respective exhaust port opening in the side face of the cylinder head 16. In terms of the exhaust gas flow of the manifold, the left most branch pipe 18 in FIG. 2 joins the plenum chamber of the manifold first. The gases flow along the plenum of the manifold (to the right in the diagram) until the next runner 18 from the middle exhaust port of the cylinder head 16 connects to the plenum chamber. The exhaust gas from both these exhaust runners 18 then continues to flow through the plenum until the right most branch pipe 18 connects to the gas stream inside the plenum. All three combined exhaust gas streams then flow out of the connector 22 (sometimes called a collector).

[0041] The tapering manifold clearly shown in FIGS. 2 and 3, reflect the designs of the manifolds disclosed in the prior art references cited in the introduction to this patent application. This is particularly visible in FIG. 2, which shows the shortest path length of the exhaust flow from the left most exhaust runner 18 before hitting the opposing wall of the manifold 20 at an oblique angle. The path length of the middle runner 18 is longer, and the right most runner, adjacent the collector 22, longer still. The disadvantages of this flow path geometry have already been described in detail above.

[0042] FIG. 3 is intended to show this by viewing the engine block and manifold 20 from the front of the engine or left most end of the manifold 20 shown in FIG. 2. In this diagram, the front most face of the manifold 20 is circular and obscures some of the cross sectional shape of the manifold 20 as it becomes progressively more oval as the further two (in FIG. 2, corresponding to the middle and right most) branch pipes 18 connect into the plenum chamber.

[0043] The gases then travel along a combined exhaust path to a further exhaust system component. This may be a catalytic converter, a turbine wheel of a turbocharger or directly to a silencer of the exhaust system. In engine configurations having two or more cylinder heads 16, the exhaust streams from multiple manifolds (each one corresponding with a cylinder head) may be joined together and then exit the exhaust or collectively drive a single turbocharger.

[0044] Typical log manifolds have a plenum of constant cross sectional flow area. This is due to ease of design and manufacture and historical lack of requirement to optimize the flow therethrough. CFD or computational fluid dynamics teaches us that as additional exhaust gas is fed into a common or log manifold due to the successive additional volume of gases, it is preferable to provide a plenum capable of accommodating an increasing volume of gas. For this reason, tapered manifolds exist which grow in internal cross sectional flow area as successive branch pipes join into the plenum chamber of the manifold 20.

[0045] The internal flow path may smoothly increase in cross sectional area or may step up at the junction of each successive exhaust runner 18.

[0046] The present invention recognizes that while it is known to taper the design of the manifold to produce this flow efficiency benefit, there are particular advantages which may be empirically demonstrated which result from the choice of which dimension of the manifold is tapered. The resulting invention is shown in FIGS. 4 to 7.

[0047] For reasons of flow efficiency, the shape of the internal flow path of a manifold is typically round. In the preferred embodiment, the internal flow path would start off substantially round but become progressively more oval with the major axis of the oval increasing in length as the minor axis, or diameter of the original circle remained constant. This is the same as the above mentioned prior art references but for the orientation of the increasing axis relative to the gas stream through the exhaust runners 18.

[0048] FIG. 4 shows a similar view to FIG. 1 but utilizing an engine having an inline configuration, in this case with six cylinders and therefore six exhaust ports attached to one cylinder head 16.

[0049] The available space for the manifold 20 is constrained by the distance from the cylinder head 16 to the side wall of the engine compartment 12 (right hand side of the square shown in FIG. 4). The constant dimension of the manifold is again labelled by an arrow 1 but note in the invention shown in FIG. 4, the arrow 1 points directly towards the exhaust ports rather than normal to as shown in the prior art depiction for FIGS. 1 to 3.

[0050] FIG. 5 shows the manifold 20 of the present invention when viewed from above. The line at the bottom of the diagram represents a dimension restricting side wall of the engine compartment. In this view it is clear that the path lengths of the exhaust gases along all the runners 18 to the opposing wall of the plenum, is constant in the direction of arrow 1.

[0051] FIG. 6, which is a side view similar to FIG. 2, shows that in this depiction of the invention, the collector for allowing the exit of exhaust gases is located in the center of the manifold 20 and so the manifold tapers in two directions from its axial ends corresponding to the first and sixth cylinders towards its widest point in the middle of the manifold between cylinders 3 and 4. In the side view of FIG. 6, the manifold 20 obscures the runners 18 (depicted in dotted lines). This aids in showing that tapering dimension of the manifold is orthogonal to the flow of exhaust gas through the runners 18. The constant dimension of arrow 1 cannot easily be depicted here as it points normal to the plane of the page.

[0052] In the example of the present invention the central collector 22 exits from underneath the center of manifold again directing the flow of exhaust gases toward either a turbo, or the remainder of the exhaust system. Here along the axis of the manifold, in simplified terms, the internal cross sectional shape would start as a circle, around cylinder 1, then stretch into an oval increasing is length until a largest area point between cylinders 3 and 4, then contract again towards a circle in line with cylinder 6, at all times the minor axis of the oval (corresponding to the diameter of the initial circle) being substantially constant. The example of a central collector is not essential to the invention. It is equally possible for the overall design to be similar to that of the prior art example except for the dimensions in which the manifold tapers, as defined by the present invention.