GB2546821A

GB2546821A - An exhaust manifold

Info

Publication number: GB2546821A
Application number: GB1601800.4A
Authority: GB
Inventors: Charles Spray Paul; Ward Chris
Original assignee: JC Bamford Excavators Ltd
Current assignee: JC Bamford Excavators Ltd
Priority date: 2016-02-01
Filing date: 2016-02-01
Publication date: 2017-08-02
Also published as: GB201601800D0

Abstract

An exhaust manifold 16 comprises first and second chambers 36, 38 with inlets 42. Chambers 36, 38 have outlets 28, 26 to be located upstream of first and second entry points of a twin-entry turbocharger (18, Fig. 1). A flow restrictor 40 is located between first and second chambers 36, 38 to restrict gas flow between the chambers. The flow restrictor 40 may be a wall with an aperture (148, Fig. 3) and the aperture may be a semi-circular recessed region 44. The flow restrictor 40 may be integrally formed with the manifold 15 or it may be a separate component (158, Fig. 3) releasably secured to the manifold 16. An engine system (10, Fig. 1) and a method of casting an exhaust manifold comprising a wall with a machined aperture are also claimed.

Description

An Exhaust Manifold

FIELD OF THE INVENTION

The present invention relates to an exhaust manifold and to an engine system comprising an exhaust manifold.

BACKGROUND OF THE INVENTION

Internal combustion (IC) engines are typically provided with turbochargers for compressing air prior to entering the combustion chambers, so as to increase the power output and fuel efficiency of the engine. This air compression process is powered by a turbine in the turbocharger that is driven by the exhaust gases produced by the engine. The exhaust gases flow from the combustion chambers into an exhaust manifold and then into the turbocharger from the exhaust manifold via an outlet. A split outlet exhaust manifold is often used in combination with a twin entry turbocharger so as to impart pulsed energy to said turbocharger, which may further optimise emissions, transient response and/or fuel efficiency.

Often diesel IC engines are also provided with an exhaust gas recirculation (EGR) system. The EGR recirculates a portion of the exhaust gases from the exhaust manifold back into the engine combustion chambers so as to dilute the amount of O2 in the IC engine to reduce the NOx emissions of the engine. However, providing the EGR valve in a split outlet exhaust manifold results in an imbalance in pressure between the two outlets and can result in insufficient pressure in the exhaust manifold to drive a desired amount of the exhaust gases through the EGR system. This problem is increased when a bypass valve is provided in the same section of the exhaust manifold as the EGR valve. In order to address this issue, a variable geometry turbocharger is sometimes provided, but this is an expensive solution due to complexity of the turbocharger design.

The present invention seeks to overcome or at least mitigate one or more problems associated with the prior art.

SUMMARY OF THE INVENTION A first aspect of the invention provides an exhaust manifold for connecting an internal combustion engine to a twin entry turbocharger, the exhaust manifold comprising: a first chamber comprising a first chamber inlet and a first chamber outlet to be located upstream of a first turbocharger entry; a second chamber comprising a second chamber inlet and a second chamber outlet to be located upstream of a second turbocharger entry; and a flow restrictor positioned between the first chamber and the second chamber for restricting gas flow therebetween.

By restricting flow we mean that some gas may pass from the first chamber to the second chamber, but not that there is unrestricted flow.

Advantageously, creating a restricted flow path between the two chambers allows for a proportion of the exhaust gases to flow therebetween which works to partially equalise the pressure in the two chambers and enables one or more of emissions, transient response and fuel economy to be better tuned for a given system.

The flow restrictor may be a wall having an aperture therethrough.

Advantageously, the size of the aperture can be selected to suit the application to enable sufficient gas to flow between the chambers to equalize the pressure to an acceptable level.

The flow restrictor may be a wall having a recessed region. Such a recessed region may be substantially semi-circular.

Advantageously, a recess in a wall is simple to manufacture, more specifically a semicircular recess is a very easily machined shape.

The first and second chambers may be substantially tubular and may be substantially aligned so as to define an internal volume of the exhaust manifold.

The first chamber and second chamber may comprise an equal number of chamber inlets.

The exhaust manifold may be a cast component, and may be cast in a single casting or from multiple castings that are subsequently secured together, either releasably or non-releasably.

The flow restrictor may be integrally formed with the exhaust manifold, e.g. by being integrally cast therewith.

Advantageously, providing the flow restrictor as an integral component provides for a very robust arrangement of exhaust manifold and flow restrictor and may simplify manufacture.

The flow restrictor may be secured, preferably releasably, to the first and second chamber.

Advantageously, providing the flow restrictor as a separate component makes it simpler to provide differing flow restrictions for different engine installations without having to change the entire exhaust manifold. A second aspect of the invention provides an engine system comprising: an internal combustion engine comprising a plurality of combustion chambers; a twin entry turbocharger; an exhaust gas recirculation system; and an exhaust manifold according to any preceding claim, wherein a first entry of the turbocharger is located to be upstream of the first chamber outlet and a second entry of the turbocharger is located to be upstream of the second chamber outlet. A further aspect of the invention provides a method of manufacturing an exhaust manifold, the method comprising the steps of: a) casting an exhaust manifold defining a first chamber and a second chamber separated by a wall; and b) machining an aperture into the wall for enabling exhaust gases to flow therethrough.

The aperture may be a recess in the wall. Such a recess may be semi-circular, i.e. having a semi-circular cross section.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of an engine system comprising an exhaust manifold according to an embodiment of the present invention;

Figure 2 is an isometric view of the exhaust manifold of Figure 1; and

Figure 3 is an isometric view of a flow restrictor according to an embodiment of the present invention. DETAILED DESCRIPTION OF EMBODIMENT(S)

Referring firstly to Figure 1, an engine system according to an embodiment of the present invention is indicated generally at 10. The engine system 10 in the illustrated embodiment is a diesel engine, but it will be appreciated that the benefits discussed hereinafter may also be applicable to a petrol engine. The engine system 10 includes in simplified form an inlet manifold 12 located upstream of a cylinder block 14 containing the combustion chambers 15 of the engine 10 and a cylinder head (not shown). The cylinder block 14 is located upstream of an exhaust manifold 16, which in turn, is located upstream of a twin entry turbocharger 18. The twin entry turbocharger is also known as a twin scroll turbocharger. The engine system 10 also includes an exhaust gas recirculation (EGR) system including an EGR valve 30 located adjacent to the exhaust manifold 16, an EGR tube 32 and an EGR cooler 34, where the EGR cooler 34 is located upstream of the inlet manifold 12.

In a diesel engine, the inlet manifold 12 is configured to receive air, e.g. compressed air from the turbocharger 18. The air is then supplied to the combustion chambers 15, and the fuel is injected directly into the combustion chambers 15 to mix with the air. In alternative embodiments, a fuel-air mixture may be received in the inlet manifold and transported to the combustion chambers 15. In the illustrated embodiment, the cylinder block 14 includes six cylinders, but it will appreciated that other numbers of cylinders may be used. The fuel-air mixture is then combusted to the release the energy contained within. This process provides the kinetic energy, and in doing so releases waste exhaust gases.

The exhaust manifold 16 includes a series of inlets 42 downstream of the cylinder outlets. The exhaust gas then flows from the cylinder block 14 via the cylinder head (not shown) into the exhaust manifold 16, via each of the inlets 42. The exhaust manifold 16 further includes two outlets 26, 28 configured to align with the two entry points of the twin entry turbocharger 18. The first outlet 26 is located upstream and in fluid communication with a first entry (not shown) of the turbocharger 18 and the second outlet 28 is located upstream of and in fluid communication with a second entry (not shown) of the turbocharger 18.

The exhaust manifold 16 is further provided with an EGR valve 30 proximate a longitudinal end of the exhaust manifold 16.When the EGR valve is opened, a portion of the exhaust gases flow through an EGR tube 32 and to an EGR cooler 34 prior to entering the inlet manifold 12. Recycling of exhaust gases into the cylinder block 14 via the inlet manifold 12 reduces the amount of air, and hence increases the amount of exhaust gas, in the fuel-air mixture in the cylinder block. The exhaust gases are inert to the combustion process but have a higher specific heat capacity than air and so reduce in-cylinder gas temperatures. This results in reduced NOx formation. Although not illustrated, it will be appreciated that the turbocharger 18 also includes in this embodiment a bypass valve to enable a portion of the exhaust gases to flow out of the engine system 10 without flowing through the turbine. Again, this may be selectively utilised to enhance fuel economy and reduce emission in certain engine conditions.

Referring to Figure 2, the exhaust manifold 16 is illustrated in more detail. The internal volume of the exhaust manifold 16 is separated into a first chamber 36 and a second chamber 38 by a flow restrictor 40 located therebetween. The flow restrictor 40 is configured to restrict the flow of exhaust gases between the first chamber 36 to the second chamber 38. The first and second chambers 36, 38 are substantially tubular each having a longitudinal axis, where the first and second chambers 36, 38 are aligned, e.g. positioned end-to-end, so as to define a longitudinal axis of the exhaust manifold 16. The flow restrictor 40 is positioned so that an equal number of cylinders is provided in both the first and second chambers 36, 38. In the illustrated embodiment, the flow restrictor 40 is located approximately halfway between the two longitudinal ends of the exhaust manifold 16 so as to divide the internal volume into two approximately equal volume chambers 16, 38. However, it will be appreciated the relative volumes of the first chamber 36 and second chamber 38 may be varied to suit application.

The exhaust manifold 16 includes six inlets 42, which are equally spaced along the longitudinal axis of the exhaust manifold. In the illustrated embodiment, six inlets 42 (corresponding to six combustion chambers of the internal combustion engine) are provided on the exhaust manifold 16. However, it will be appreciated that different numbers of inlets may be provided, for example four inlets may be provided. Three of the inlets 42 are provided on the first chamber 36 with the further three inlets 42 being provided on the second chamber 38.

The first chamber 36 is further provided with a first chamber outlet 26 located upstream of a first turbocharger entry (not shown) and the second chamber 38 is provided with a second chamber outlet 28 to be located upstream of a second turbocharger entry. The first chamber outlet 26 and second chamber outlet 28 are provided on opposing sides of, and adjacent to, the flow restrictor 40.

In the illustrated embodiment, the exhaust manifold 16 is an assembly of multiple cast components (two in this embodiment). However, in alternative embodiments, the exhaust manifold 16 may be cast as a single piece. The exhaust manifold is provided with a substantially planar surface 46 for mounting the twin entry turbocharger 18 thereto via fasteners (not shown) secured to threaded bores 19. In the illustrated embodiment, the flow restrictor 40 is provided in the form of a separating wall with an aperture therethrough. The aperture is provided in the form of a recessed region 44 of the flow restrictor 40. An external surface of the flow restrictor 40 forms part of the planar surface 46, and the recessed region 44 is machined into the flow restrictor 40. In the illustrated embodiment, the machined recess is semi-circular due to ease of manufacturing, but any suitable shape recess may be machined into the flow restrictor 40 to enable exhaust gas to flow therethrough. The size of the machined aperture or recess 44 determines the flow between said first and second chambers 36, 38. In addition, this approach has the flexibility for the aperture size and shape to be adjusted to optimise the characteristics of the engine for different applications by machining away different amounts of material from a standard cast exhaust manifold. In alternative embodiments, the aperture may, for example, be simply drilled through the flow restrictor 40, or the recess may be cast into the exhaust manifold.

In a further alternative embodiment, as is illustrated in Figure 3, the flow restriction may be provided as a separate component 158 and is provided with four bores 119 so as to be connected to the planar surface 46 via fasteners (not shown), such as the fasteners that also secure the turbocharger to the exhaust manifold, to form a part of the exhaust manifold 16. Such a flow restrictor may be substantially cuboid in shape so as to conform to the periphery of the planar surface 46, and may be provided with an aperture 148 therethrough in a direction substantially perpendicular to the planar surface 46 to enable a desired flow of exhaust gases between the first chamber 36 to the second chamber 38.

The aperture 148 comprises a first opening 150 and a second opening 152 configured to enable air to flow out of the first 136 and second 138 chambers, respectively. The first and second openings 150, 152 are separated by a flow restrictor 140, in the form of two opposing protrusions 154, 156 which extend into the aperture 148. In this embodiment, the amount of flow restriction provided can be adjusted by either adjusting the separation x between the protrusions 154, 156 or by adjusting the thickness y of the component 158. In this embodiment, it will be appreciated that the separating wall of the exhaust manifold may not be provided with a recess. It will be further appreciated that the shape of such a flow restrictor may vary to suit the application.

The twin entry twin scroll arrangement, coupled with the two outlets 26, 28 enables the turbine of the turbocharger to be pulsed effectively in response to the airflow from the first and second chambers.

The following table provides an example of the benefits offered to a DieselmaxR™ six cylinder engine manufactured by the present applicant combined with a BorgWamerR™ S200 turbocharger and shows the changes in the relative pressures present in the first chamber 36 and the second chamber 38 in an exhaust manifold 16 having a flow restrictor having a semi-circular recess having a 12.5mm radius.

This reduction in the imbalance between the relative pressures results in a higher pressure in the second chamber 38. The second chamber 38 includes the EGR valve 30 and so this increase in pressure results in an increase in the amount of exhaust gases that flow into the EGR system. This, in turn, results in lower NOx emissions of the internal combustion engine for both of the engine speeds listed above with little or no detriment to specific fuel consumption. Alternatively, the system may instead be tuned to produce an improved specific fuel consumption for a given level of emissions, or a lesser improvement in both emissions and fuel consumption.

Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. An exhaust manifold for connecting an internal combustion engine to a twin entry turbocharger, the exhaust manifold comprising: a first chamber comprising a first chamber inlet and a first chamber outlet to be located upstream of a first turbocharger entry; a second chamber comprising a second chamber inlet and a second chamber outlet to be located upstream of a second turbocharger entry; and a flow restrictor positioned between the first chamber and the second chamber for restricting gas flow therebetween.

2. An exhaust manifold according to claim 1, wherein the flow restrictor is a wall having an aperture therethrough.

3. An exhaust manifold according claim 1, wherein the flow restrictor is a wall having a recessed region.

4. An exhaust manifold according to claim 3, wherein the recess is substantially semi-circular.

5. An exhaust manifold according to any preceding claim, wherein the first and second chambers are substantially tubular and are substantially aligned so as to define an internal volume of the exhaust manifold.

6. An exhaust manifold according to any preceding claim, wherein the first chamber and second chamber comprise an equal number of chamber inlets.

7. An exhaust manifold according to any preceding claim, wherein the exhaust manifold is a cast component.

8. An exhaust manifold according to any preceding claim, wherein the flow restrictor is integrally formed with the exhaust manifold.

9. An exhaust manifold according to any one of claims 1 to 7, wherein the flow restrictor is releasably secured to the first and second chamber.

10. An engine system comprising: an internal combustion engine comprising a plurality of combustion chambers; a twin entry turbocharger; an exhaust gas recirculation system; and an exhaust manifold according to any preceding claim, wherein a first entry of the turbocharger is located to be upstream of the first chamber outlet and a second entry of the turbocharger is located to be upstream of the second chamber outlet.

11. A method of manufacturing an exhaust manifold, the method comprising the steps of: a) casting an exhaust manifold defining a first chamber and a second chamber separated by a wall; and b) machining an aperture into the wall for enabling exhaust gases to flow therethrough.

12. A method according to claim 11, wherein the aperture is a recess in the wall.

13. A method according to claim 12, wherein the recess is semi-circular.

14. An exhaust manifold substantially as hereinbefore described and/or with reference to Figures 1 and 2 of the drawings.

15. An engine system substantially as hereinbefore described and/or with reference to Figures 1 and 2 of the drawings.

16. A method of manufacturing an exhaust manifold substantially as hereinbefore described and/or with reference to Figures 1 and 2 of the drawings.