GB2544809A

GB2544809A - Internal combustion with asymmetric twin scroll turbine and increased efficiency

Info

Publication number: GB2544809A
Application number: GB1521084.2A
Authority: GB
Inventors: Rutledge John
Original assignee: Perkins Engines Co Ltd
Current assignee: Perkins Engines Co Ltd
Priority date: 2015-11-30
Filing date: 2015-11-30
Publication date: 2017-05-31
Anticipated expiration: 2035-11-30
Also published as: GB201521084D0; GB2544809B

Abstract

An internal combustion engine 10 comprising combustion cylinders (11 to 16) configured to output exhaust gas to first and second exhaust manifolds 21, 22, and a transfer conduit 70 between the manifolds comprising a balance valve 74 for controlling flow in the transfer conduit. The engine further comprises a valve controller to control the balance valve element position and an asymmetric twin scroll turbine 30 comprising first and second scrolls 31, 32 fluidly connected to respective exhaust manifolds to direct exhaust gas towards the turbine blades 33. The scrolls have different size cross-sectional areas in a plane through an axis of rotation of the turbine shaft 35. The engine further comprises an electrical machine 50, such as a combined motor and generator, which is coupled to the turbine shaft and wherein the electrical machine supplies rotational energy to the turbine shaft, or converts rotational energy of the turbine shaft into electrical energy. The balance valve may also open or close to vary how much electrical power generation occurs.

Description

Internal combustion with asymmetric twin scroll turbine and increased efficiency Technical Field

The disclosure relates to the field of internal combustion engines and, in particular, to internal combustion engines having an asymmetric twin scroll turbine.

Background

Increasing engine efficiency and performance characteristics is a desire of engine manufacturers and users alike. A conventional turbocharger may be used to increase efficiency and performance characteristics of an internal combustion engine. A turbocharger may comprise a turbine for recovering energy from exhaust gases that are released from a combustion chamber of the engine. A turbocharger may further comprise a compressor for pressurising oxidant that is yet to enter the combustion chamber. The turbine and the compressor may be connected via a common shaft.

The geometry of the turbine within a turbocharger may influence the efficiency with which pressure can be effectively recovered at different engine conditions. Use of a variable geometry turbine or an asymmetric twin scroll turbine may increase the effectiveness of a turbocharger across a wider range of engine conditions.

It is known to use an electrical machine in conjunction with a turbocharger in order either (a) to provide electrical assistance to the turbocharger or (b) to recover energy in the form of electrical energy, depending on the engine conditions.

Summary of the disclosure

Against this background, there is provided an internal combustion engine comprising: a first combustion cylinder or cylinders configured to output exhaust gas to a first exhaust manifold; a second combustion cylinder or cylinders configured to output exhaust gas to a second exhaust manifold; a transfer conduit between the first exhaust manifold and the second exhaust manifold and comprising a balance valve for controlling flow of fluid in the transfer conduit, the balance valve having a balance valve element that is movable between an open position and a closed position; a valve controller configured to control a position of the balance valve element; an asymmetric twin scroll turbine comprising: a turbine shaft; turbine blades surrounding the turbine shaft; a first scroll fluidly connected to the first exhaust manifold and configured to direct exhaust gas towards the turbine blades; and a second scroll fluidly connected to the second exhaust manifold and configured to direct exhaust gas towards the turbine blades, wherein the first scroll has a first cross-sectional area in a plane through an axis of rotation of the turbine shaft and the second scroll has a second cross-sectional area in the plane, the first cross-sectional area being larger than the second cross-sectional area; and an electrical machine coupled to the turbine shaft and having a first mode of operation in which the electrical machine supplies rotational energy to the turbine shaft and a second mode of operation in which the electrical machine converts rotational energy of the turbine shaft into electrical energy.

Brief description of the drawing

Figure 1 shows a schematic representation of an asymmetric twin scroll turbocharger in conjunction with an internal combustion engine exhaust assembly 80.

Detailed description

There is shown in Figure 1 a turbocharger 60 in conjunction with an internal combustion engine exhaust assembly 80 arranged in accordance with an embodiment of the disclosure.

The internal combustion engine 10 may comprise a plurality of combustion cylinders 11, 12, 13, 14, 15, 16 in each of which combustion of fuel in the presence of an oxidant may occur. Each cylinder 11, 12,13, 14,15, 16 may comprise a fuel injector (not shown in Figure 1) for injecting fuel into the cylinder 11, 12,13, 14, 15, 16, an oxidant inlet (not shown in Figure 1) for input of oxidant into the cylinder 11, 12,13, 14, 15,16 and an exhaust outlet for enabling exhaust gas to exit the cylinder 11, 12, 13, 14,15, 16.

The internal combustion engine exhaust assembly 80 may comprise a split exhaust manifold 21,22 having a first side manifold 21 and a second side manifold 22. The split exhaust manifold may be configured to receive exhaust gas from a plurality of cylinders 11, 12, 13, 14, 15, 16 of an internal combustion engine 10. The first side manifold 21 may be fluidly connected to an exhaust outlet of each of a first set of three of the six cylinders 11, 12, 13. The second side manifold 22 may be fluidly connected to an exhaust outlet of a second set of three of the six cylinders 14,15, 16. While the illustration shows a schematic of a V-engine arrangement having two parallel rows of cylinders, as the skilled person would recognise, the cylinders may be in any geometrical arrangement. For example, the cylinders may be arranged in a single row (an inline engine) and the split manifold may be a single component having a divided interior as between the first and second side manifolds.

In this way, approximately half of the exhaust gas from the internal combustion engine 10 may flow into the first side manifold 21 and approximately half of the exhaust gas may flow into the second side manifold 22. It may be that the combustion cylinders 11, 12, 13, 14, 15, 16 are controlled to combust in an order such that exhaust gas flowing into the split exhaust manifold alternates as to which of the first and second side manifolds 21,22 receives the exhaust gas.

The turbocharger 60 may comprise an asymmetric twin scroll turbine assembly 30 and a compressor assembly 40. The asymmetric twin scroll turbine assembly 30 may comprise a first scroll 31 and a second scroll 32, an outlet conduit 36, and turbine blades 33 mounted on a turbine bore 34 that is mounted on a turbine shaft 35. In this way, the turbine blades 33, the turbine bore 34 and the turbine shaft 35 are rotatable about an axis of rotation that is coincident with an elongate axis of the turbine shaft 35. The compressor assembly 40 may comprise air inlet 41, an outlet conduit 46, compressor blades 43 mounted on a compressor bore 44 that is mounted on the turbine shaft 35.

The turbocharger 60 may further comprise an electrical machine 50 coupled to the turbine shaft 35. The electrical machine 50 may comprise a first mode of operation in which the electrical machine 50 may supply rotational energy to the turbine shaft 35 and a second mode of operation in which the electrical machine 50 may convert rotational energy of the turbine shaft 35 into electrical energy. The electrical machine 50 may further comprise a third mode of operation in which it is neither supplying rotational energy to the turbine shaft 35 nor converting rotational energy from the turbine shaft 35. This third mode of operation may be achieved by electrically or mechanically disconnecting one or more features of the electrical machine 50 from the turbine shaft 35.

The inlet conduit 41 of the compressor assembly 40 of the turbocharger 60 may be configured to receive air (oxidant) from atmosphere which may pass through an air filter (not shown in Figure 1) upstream of the inlet conduit 41. The outlet conduit 46 of the compressor assembly 40 may be configured to supply the oxidant inlets (not shown in Figure 1) of each of combustion cylinders 11, 12,13, 14, 15, 16 of the internal combustion engine 10. In this way, air that is received via the inlet conduit 41 of the compressor assembly 40 at or slightly below atmospheric pressure and temperature may be pressurised within the compressor assembly 40 before being passed to the combustion cylinders 11, 12, 13, 14, 15, 16. Downstream of the compressor 50 but upstream of the combustion cylinders 11, 12, 13,14, 15,16 there may be a heat exchanger (not shown in Figure 1), such as an intercooler, configured to extract thermal energy from the compressed air prior to it reaching the combustion cylinders 11, 12, 13,14, 15, 16.

The first side manifold 21 may be in fluid communication with the first scroll 31 of the turbocharger 60 and the second side manifold 22 may be in fluid communication with the second scroll 32 of the turbocharger 60.

The internal combustion engine exhaust assembly 80 may further comprise an exhaust transfer conduit 70 having a first end 71 in fluid communication with the first side manifold 21 and a second end 72 in fluid communication with the second side manifold 22. Between the first end 71 and the second end 72 there may be provided a balance valve 74 for controlling flow of fluid in the transfer conduit 70.

The balance valve 71 may have a fully open position, a fully closed position and a plurality of intermediate positions. In every position other than the fully closed position, flow of fluid may be possible between the first side manifold 21 and the second side manifold 22.

The first scroll 31 of the asymmetric twin scroll turbine assembly 30 may have a first cross-sectional area in a plane through the axis of rotation of the turbine shaft 35. The second scroll 32 of the asymmetric twin scroll turbine assembly 30 may have a second cross-sectional area in the plane through the axis of rotation of the turbine shaft 35. The first cross-sectional area may be larger than the second cross-sectional area. In this way, it may be expected that, where a quantity of exhaust gas entering the first scroll 31 is the same as a quantity of exhaust gas entering the second scroll 32, the pressure in the first scroll 31 is lower than the pressure in the second scroll 32. The energy extracted from the exhaust gas passing through the second scroll 32 may be therefore be greater than the energy extracted from the exhaust gas passing through the first scroll 31 on account of the higher expansion ratio in the second scroll 32. Accordingly, when maximum turbine power is desirable (e.g. to maximise compressor power and engine boost), it may be appropriate to position the balance valve 71 in the fully closed position in order that the high pressure in the second scroll 32 (having the smaller cross-sectional area) is maintained.

Alternatively, where less turbine power is required (due to a lower boost requirement) and/or a reduction in exhaust manifold pressure (to reduce fuel consumption) is desirable, it may be appropriate to position the balance valve 71 in a partially or fully open position in order that the high pressure in the second scroll 32 is reduced by virtue of some exhaust gas flowing from the second side exhaust manifold 22 through the transfer conduit 70 and into the first side exhaust manifold 21 and into the first scroll 31. In this way, reduction in pressure in the second side exhaust manifold 22 may result in reduced turbine power but also in reduced fuel consumption.

Furthermore, it may be appropriate to control the position of the balance valve 71 in view also of the mode of operation of the electrical machine 50. In particular, in the first mode of operation of the electrical machine 50, in which the electrical machine 50 may supply rotational energy to the turbine shaft 35, it may be appropriate to reduce turbine power and pressure in the second side exhaust manifold 22 by positioning the balance valve 74 in or towards the fully open position. This may act to maximise any fuel consumption benefit from electrical machine assistance.

In the second mode of operation of the electrical machine 50 in which the electrical machine 50 may convert rotational energy of the turbine shaft 35 into electrical energy, it may be appropriate to maximise turbine power by increasing pressure in the second side exhaust manifold 22and the second scroll 32 by positioning the balance valve 74 in or towards the fully closed position. This may act to increase the amount of energy extracted by the electrical machine 50 without affecting performance of the engine 50 through a deficit in compressor power.

In the third mode of operation of the electrical machine 50 in which the electrical machine is neither providing additional rotational energy nor generating electrical energy, it may be that a preferred position of the balance valve 74 is dependent upon the extent to which boost is required versus the extent to which reduced fuel consumption is desired.

Accordingly, control of the balance valve may be dependent upon a combination of multiple factors. Where the electrical machine 50 is operating in the first mode of operation or the second mode of operation, whether it is operating in the first mode or the second mode may have greatest influence on the position of the balance valve 74. Where the electrical machine 50 is operating in the third mode of operation, other factors may have a greater influence on the desired position of the balance valve 74 than the mode of operation of the electrical machine. For example, the balance valve 74 might be moved towards or into the fully open position to reduce turbocharger speed, reduce boost or improve fuel consumption. The balance valve 74 may be moved towards or into the fully closed position in order to increase boost, increase exhaust manifold pressure to assist with driving recirculation of exhaust gas in the event that an exhaust gas recirculation system is present or increase the rate of turbocharger speed during an engine transient event such as an acceleration.

While embodiment illustrated in Figure 1 shows the asymmetric twin scroll turbine 30 being a part of a turbocharger 60 having a compressor assembly 40, in some embodiments and applications of the disclosure, the asymmetric twin scroll turbine 30 may not be a constituent of a turbocharger 60 and there may be no compressor. This may particularly be the case when the object of an embodiment is specifically to target electrical power output from the electrical machine 50.

Industrial applicability

The present disclosure may provide an internal combustion engine 10 in combination with an asymmetric twin scroll turbine 30 and an electrical machine 50 coupled to the turbine shaft 35 and a balance valve that can enable or prevent balancing of pressure as between the two scrolls 31,32 of the asymmetric twin scroll turbine 30.

In a first mode of operation, where the electrical machine 50 is configured to supply rotational energy to the turbine shaft 35, the balance valve 74 may be partly or fully open. This may enable gas pressure within the twin scroll turbine 30 to be partly or fully balanced between the two scrolls 31,32 of the twin scroll turbine 30. In this way, a reduction in fuel consumption of the internal combustion engine 10 in light of the electrical energy supplied by the electrical machine 50 may be increased or maximised.

In a second mode of operation, where the electrical machine 50 is configured to convert rotational energy of the turbine shaft 35 into electrical energy, the balance valve 74 may be partly or fully closed. This may result in maximum turbine power by virtue of retaining high pressure in the smaller of the two scrolls 31,32. In this way, a penalty in terms of additional fuel consumption may be reduced or minimised.

In an alternative arrangement, perhaps where a particular level of electricity generation is to be targeted, the position of the balance valve 74 may be regulated specifically in order to achieve a targeted electrical power output. The targeted electrical power output may change with time and hence the position of the balance valve 74 may be regulated in real time, perhaps in combination with other parameters such as those relating to the combustion cycle of the internal combustion engine 10.

Claims

CLAIMS:

1. An internal combustion engine comprising: a first combustion cylinder or cylinders configured to output exhaust gas to a first exhaust manifold; a second combustion cylinder or cylinders configured to output exhaust gas to a second exhaust manifold; a transfer conduit between the first exhaust manifold and the second exhaust manifold and comprising a balance valve for controlling flow of fluid in the transfer conduit, the balance valve having a balance valve element that is movable between an open position and a closed position; a valve controller configured to control a position of the balance valve element; an asymmetric twin scroll turbine comprising: a turbine shaft; turbine blades surrounding the turbine shaft; a first scroll fluidly connected to the first exhaust manifold and configured to direct exhaust gas towards the turbine blades; and a second scroll fluidly connected to the second exhaust manifold and configured to direct exhaust gas towards the turbine blades, wherein the first scroll has a first cross-sectional area in a plane through an axis of rotation of the turbine shaft and the second scroll has a second cross-sectional area in the plane, the first cross-sectional area being larger than the second cross-sectional area; and an electrical machine coupled to the turbine shaft and having a first mode of operation in which the electrical machine supplies rotational energy to the turbine shaft and a second mode of operation in which the electrical machine converts rotational energy of the turbine shaft into electrical energy.

2. The internal combustion engine of claim 1 further comprising a turbocharger comprising the asymmetric twin scroll turbine and a compressor coupled to the turbine shaft, wherein an outlet of the compressor is in fluid communication with an inlet of the first combustion cylinder or cylinders and an inlet of the second combustion cylinder or cylinders.

3. The internal combustion engine of claim 1 or claim 2 wherein the balance valve element is movable between the open position and the closed position via one or more intermediate positions.

4. The internal combustion engine of claim 3 wherein, in the first mode of operation of the electrical machine, the controller controls the balance valve to be substantially or fully open.

5. The internal combustion engine of claim 4 wherein, in the second mode of operation of the electrical machine, the controller controls the balance valve to be substantially or fully closed.

6. The internal combustion engine of any preceding claim in which the electrical machine has a third mode of operation in which the electrical machine neither supplies rotational energy to the turbine shaft nor converts rotational energy of the turbine shaft into electrical energy and in which the controller controls the balance valve to influence one or more of: required fuel consumption; required boost; turbine shaft speed; exhaust gas recirculation capability; or other engine performance characteristic.

7. The internal combustion engine of any preceding claim wherein the electrical machine is mounted directly on the turbine shaft.

8. The internal combustion engine of claim 7 wherein the electrical machine is mounted within a bearing housing of the turbine shaft.

9. The internal combustion engine of claim 7 when dependent upon claim 2 or any claim dependent upon claim 2 wherein the turbine shaft comprises a portion within the turbine, a portion within the compressor, a portion between the turbine and the compressor and an distal portion, wherein the electrical machine is mounted on the distal portion.

10. An internal combustion engine comprising: a first combustion cylinder or cylinders configured to output exhaust gas to a first exhaust manifold; a second combustion cylinder or cylinders configured to output exhaust gas to a second exhaust manifold; a transfer conduit between the first exhaust manifold and the second exhaust manifold and comprising a balance valve for controlling flow of fluid in the transfer conduit, the balance valve having a valve element that is movable between an open position and a closed position; a valve controller configured to control a position of the balance valve element; an asymmetric twin scroll turbine comprising: a turbine shaft; turbine blades surrounding the turbine shaft; a first scroll fluidly connected to the first exhaust manifold and configured to direct exhaust gas towards the turbine blades; and a second scroll fluidly connected to the second exhaust manifold and configured to direct exhaust gas towards the turbine blades, wherein the first scroll has a first cross-sectional area in a plane through an axis of rotation of the turbine shaft and the second scroll has a second cross-sectional area in the plane, the first cross-sectional area being larger than the second cross-sectional area; and an electrical machine coupled to the turbine shaft and configured to convert rotational energy of the turbine shaft into electrical energy; wherein, in response to a signal to increase electrical power generation by the electrical machine, the valve controller controls the valve element to move towards or into the closed position and/or in response to a signal to decrease electrical power generation by the electrical machine, the valve controller controls the valve element to move towards or into the open position.