GB2591999A - Common rail housing for a fuel delivery system - Google Patents

Abstract

A common rail for an i.c. engine emulsion fuel injection system comprises a housing 20 having an elongate cavity 22 fed by a pair of pressurised inlets 30(a), 30(b) which are arranged to be equidistant between a respective pair of outlets 34(a,b), 34(c,d) so that an equal volume of the cavity 22 extends between the inlet 30(a,b) and each outlet of the respective pair of outlets 34(a,b),(c,d). The cavity 22 may be divided into equal volumes by an elongate volume splitter 22 having a set of grooves 66(a-d), 68 (a-d) on respective sides of a central region, eg a shoulder 56, to provide an equal flow rate in parallel to the injectors to improve the homogeneity of the emulsion. Alternatively, the cavity 22 may be replaced by a pair of coaxial cavities (222 (a),(b), fig.8) separated by a wall (225) of the housing, each cavity having a single inlet equidistant from a pair of outlets. The rail may have a single inlet port (196, figs.7,11) feeding a distribution channel (190) between a pair of inlets to the or each cavity 22, (222 (a),(b)).

Description

COMMON RAIL HOUSING

FOR A FUEL DELIVERY SYSTEM

Field of the Invention

This invention relates to a common rail of a fuel delivery system, and in particular to a common rail housing of an emulsion injection system for an internal combustion engine.

Background to the Invention

It is known to provide fluid delivery systems for conveying fuel, such as gasoline, to an internal combustion engine (ICE) of a vehicle. In a popular arrangement, the fluid delivery system is a fuel injection system that delivers fuel to the engine via an array of fuel injectors supplied with fuel from a pressurised accumulator, known as a common rail. Typically, the common rail is controlled to regulate the amount of fuel delivered to the fuel injectors and the fuel injectors are selectively controlled to inject the supply of fuel into the engine.

Modern fluid injection systems also include water injection systems that deliver water into the combustion chambers of the engine to reduce an engine knock tendency. Injecting water in this manner also provides other benefits such as increased fuel economy and engine performance, as well as a decrease in engine emissions.

In known systems, the water may be introduced by port injection (to the air intake manifold), by direct injection (to the engine cylinders) or by emulsion injection, in which water is mixed with the fuel for direct injection into the engine cylinders as a water-gasoline emulsion.

An emulsion injection system typically consumes less water, and requires fewer components, than the other fluid delivery systems that require duplicate parts for separate injection of the water and the fuel. For example, in an emulsion injection system, a single common rail may be used to regulate the delivery of the water and fuel emulsion to the injectors, whereas separate common rails are required in the other fluid delivery systems.

However, it is known that emulsion injection systems can be susceptible to various problems. For example, the homogeneity of the water-fuel emulsion breaks down if the emulsion is not evacuated quickly enough from the common rail or if the emulsion is evacuated unevenly between the respective fuel injectors.

It is common to supply the water-fuel emulsion at high pressure to mitigate these problems and evacuate the water-fuel emulsion from the common rail at high speeds. However, adding the high pressure fluid to the common rail creates large pressure pulsations that disrupt the homogeneity of the water-fuel emulsion, cause noise and damage the components of the emulsion injection system.

It is against this background that the present invention has been devised.

Summary of the Invention

According to an aspect of the invention, there is provided a common rail housing of an emulsion injection common rail for a fuel injection system of a spark ignition engine. The common rail housing comprises: at least one cavity in the common rail housing for accumulating a pressurised fluid comprising a water and fuel emulsion; a plurality of outlets from each cavity, each outlet of the plurality of outlets being connectable to a respective fuel injector for delivering pressurised fluid from said cavity into a respective cylinder of the spark ignition engine; and at least one inlet to each cavity for adding the pressurised fluid to said cavity. For each cavity, the plurality of outlets are spaced apart from one another inside said cavity and each inlet to said cavity is arranged equidistantly between a respective pair of the plurality of outlets from said cavity so that an equal volume of said cavity extends between said inlet and each outlet of said respective pair of outlets.

Advantageously, when the common rail housing is used in an emulsion injection system, this arrangement maximises the homogeneity of the water-fuel emulsion delivered from each cavity outlet to a respective fuel injector.

Optionally, for each cavity, each inlet to said cavity is arranged equidistantly along the length of the cavity between the respective pair of outlets from said cavity. Optionally, each cavity is elongate. Each cavity may also have a uniform cross-section along its length. For example, each cavity may be substantially cylindrical and elongate. In this manner, fluid can flow in substantially the same manner from each cavity inlet to each cavity outlet.

In an example, for each cavity: the plurality of outlets from said cavity comprises a first pair of cavity outlets and a second pair of cavity outlets spaced apart from one another inside said cavity; and the at least one inlet to said cavity comprises a first cavity inlet and a second cavity inlet, the first cavity inlet being arranged equidistantly between the first pair of cavity outlets and the second cavity inlet being arranged equidistantly between the second pair of cavity outlets. In this manner, the common rail housing can be used to provide an equal flow of fluid from each cavity inlet to each outlet of the respective pair of cavity outlets.

Optionally, the at least one cavity in the common rail housing includes a first cavity and a second cavity. The at least one inlet to the first cavity may comprise a first cavity inlet and the plurality of outlets from the first cavity may comprise a first pair of cavity outlets. The at least one inlet to the second cavity may comprise a second cavity inlet and the plurality of outlets from the second cavity may comprise a second pair of cavity outlets. Advantageously, the first and second cavities are fluidly separated so that, in use, an equal volume of fluid flows from the first cavity inlet to each outlet of the first pair of cavity outlets and an equal volume of fluid flows from the second cavity inlet to each outlet of the second pair of cavity outlets In an example, the volume of each cavity that extends between the first cavity inlet and each outlet of the first pair of cavity outlets is equal to the volume of each cavity that extends between the second cavity inlet and each outlet of the second pair of cavity outlets. In this manner, the common rail housing is suitable for providing parallel injection of fluid from the common rail. Optionally, for each cavity, the volume of said cavity that extends between the first cavity inlet and each outlet of the first pair of cavity outlets is equal to the volume of said cavity that extends between the second cavity inlet and each outlet of the second pair of cavity outlets.

Optionally, the volume of the first cavity that extends between the first cavity inlet and each outlet of the first pair of cavity outlets is equal to the volume of the second cavity that extends between the second cavity inlet and each outlet of the second pair of cavity outlets.

Optionally, the common rail housing further comprises an elongate distribution channel, comprising: an inlet port for connection to a high pressure pump; a first outlet port connected to the first cavity inlet; and a second outlet port connected to the second cavity inlet; wherein the inlet port is arranged equidistantly between the first and second outlet ports so that an equal volume of said distribution channel extends between said inlet port and each outlet port of the first and second outlet ports. In this manner, in use, the elongate distribution channel is configured to provide equal portions of fluid to each of the first and second cavity inlets.

Additionally, the first outlet port of the distribution channel may be spaced from the second outlet port of the distribution channel along the length of the distribution channel. A cross-section of the distribution channel may be substantially uniform along the length of the distribution channel, between the first and second outlet ports. The inlet port to the distribution channel may be arranged equidistantly along the length of the distribution channel between the first and second outlet ports. Hence, in use, the flow of fluid from the inlet port to the first outlet port may substantially match the flow of fluid from the inlet port to the second outlet port.

Optionally, each of the first and second cavity inlets is suitable for connection to a high pressure pump.

According to another aspect of the invention there is provided an emulsion injection common rail for a fuel injection system of a spark ignition engine comprising a common rail housing according to an aspect described above and at least one volume splitter. Each cavity of the common rail housing includes a volume splitter arranged inside said cavity. Each volume splitter defines a plurality of fluid delivery channels inside said cavity, each fluid delivery channel connecting one inlet of said cavity to one of the plurality of outlets of said cavity.

Each fluid delivery channel defines an equal volume through which pressurised fluid flows, in use, along said fluid delivery channel, from said inlet to the respective outlet. Advantageously, in use, this arrangement maximises the homogeneity of the water-fuel emulsion delivered from each cavity outlet to a respective fuel injector. Furthermore, the fluid delivery channels define high speed flow paths for delivering fluid to each of the cavity outlets. Advantageously, the high speed flow paths can maximise the speed of fluid delivery from the common rail, which can be used to maintain the homogeneity of a water and fuel emulsion.

Optionally, for each cavity: the respective volume splitter arranged inside said cavity comprises: a dividing member that extends across said cavity; a first portion that extends from a first side of the dividing member; and a second portion that extends from an opposing second side of the dividing member; the dividing member of the volume splitter may extend across said cavity to define a first accumulator volume and a second accumulator volume inside said cavity; the first accumulator volume may comprise a respective portion of said cavity that includes: the first cavity inlet; and the corresponding pair of cavity outlets; and the second accumulator volume may comprise a respective portion of said cavity that includes: the second cavity inlet; and the corresponding pair of cavity outlets; the dividing member of the volume splitter may substantially inhibit the flow of pressurized fluid from the first accumulator volume to the second accumulator volume in said cavity; and the first portion of the volume splitter may form a first volume splitter arranged inside the first accumulator volume and the second portion of the volume splitter may form a second volume splitter arranged inside the second accumulator volume. Advantageously, this arrangement is configured to deliver equal flow rates of fluid to each of the cavity outlets, in use.

In an example, the at least one volume splitter includes a first volume splitter and a second volume splitter. The first cavity may define a first accumulator volume in a respective portion of said cavity that includes: the first cavity inlet; and the corresponding pair of cavity outlets. The second cavity may define a second accumulator volume in a respective portion of said cavity that includes: the second cavity inlet; and the corresponding pair of cavity outlets. Optionally, the first volume splitter is arranged inside the first accumulator volume and the second volume splitter is arranged inside the second accumulator volume.

Advantageously, this arrangement is also configured to deliver equal flow rates of fluid to each of the cavity outlets, in use.

In an example, each of the first and second volume splitters is hollow and comprises an inner surface and an outer surface. The outer surface of each volume splitter may include a respective set of grooves. For each of the first and second accumulator volumes: the inner surface of the respective volume splitter may define, at least in part, a chamber inside said accumulator volume for a damping volume of the pressurised fluid; the outer surface of the respective volume splitter may be complementary to an interior surface of said accumulator volume; and the set of grooves on the outer surface of the respective volume splitter may define a plurality of the fluid delivery channels inside said accumulator volume, each fluid delivery channel connecting the cavity inlet of said accumulator volume to one outlet of the respective pair of cavity outlets of said accumulator volume. Each fluid delivery channel of said accumulator volume may define an equal volume through which pressurised fluid flows, in use, along said fluid delivery channel, from said cavity inlet to the respective cavity outlet. In this manner, equal flows of fluid are provided to each cavity outlet in use.

Optionally, each of the plurality of fluid delivery channels is of equal length between the respective cavity inlet of said accumulator volume and the respective cavity outlet of said accumulator volume.

In an example, the volume through which the pressurised fluid flows along each of the fluid delivery channels, in use, is sufficiently small to substantially maintain homogeneity of the water and fuel emulsion in the pressurised fluid (between the inlet and the respective outlet).

Optionally, the set of grooves on the outer surface of the first volume splitter substantially match the set of grooves on the outer surface of the second volume splitter.

In an example, the outer surface of each volume splitter may be complementary to an interior surface of the respective accumulator volume to inhibit the flow of pressurised fluid between the interior surface of said accumulator volume and the outer surface of the volume splitter, in use. Consequently, the volumetric flow rate of pressurised fluid between the interior surface of said accumulator volume and the outer surface of the volume splitter may be relatively low compared to the volumetric flow rate of pressurised fluid along each of the fluid delivery channels.

Optionally, each of the first and second accumulator volumes includes a passage between the respective chamber and each of the fluid delivery channels inside said accumulator volume, each passage being configured to allow a restricted flow of the pressurised fluid between said chamber and each of said fluid delivery channels, in use. This may help to maintain a damping volume of fluid in the chamber, for example.

Optionally, in use, the volumetric flow rate of the restricted flow of the pressurised fluid is relatively low compared to the volumetric flow rate of pressurised fluid along each of the fluid delivery channels.

According to another aspect of the invention there is provided a fuel injection system for a spark ignition engine comprising: a common rail housing as described in a previous aspect of the invention or an emulsion injection common rail as described in a previous aspect of the invention.

It will be appreciated that preferred and/or optional features of each aspect of the invention may be incorporated alone or in appropriate combination in the other aspects of the invention also.

Brief Description of the Drawings

In order that the invention may be more readily understood, preferred non-limiting embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which like features are assigned like reference numbers, and in which: Figure 1 schematically illustrates an example of a fuel injection system for an internal combustion engine; Figure 2 schematically illustrates a cross-section of an example common rail for use in the fuel injection system shown in Figure 1; Figure 3 schematically illustrates a cross-section of a common rail housing of the example common rail shown in Figure 2; Figure 4 schematically illustrates a side view of a volume splitter of the example common rail shown in Figure 2; Figure 5 shows a perspective view of the volume splitter shown in Figure 4; Figure 6 schematically illustrates a longitudinal cross-section of the example common rail, shown in Figure 1, at an outlet of said common rail; Figure 7 schematically illustrates a cross-section of another example common rail for use in the fuel injection system shown in Figure 1; Figure 8 schematically illustrates a cross-section of a further example common rail for use in the fuel injection system shown in Figure 1; Figure 9 schematically illustrates a cross-section of a common rail housing of the example common rail shown in Figure 8; Figure 10 schematically illustrates a perspective view of a volume splitter of the example common rail shown in Figure 9; Figure 11 schematically illustrates a cross-section of a further example common rail for use in the fuel injection system shown in Figure 1; and Figure 12 illustrates an example of the water content in each engine cylinder in response to a step-change in demand for fluid from each of the common rails shown in Figures 2, 7,8 and 11.

Detailed Description of Embodiments of the Invention Embodiments of the invention relate to a common rail for an emulsion injection system and, particularly, to common rail configurations featuring one or more cavities, for accumulating a volume of a water-fuel emulsion, and a plurality of fluid delivery channels inside each cavity, for delivering the water-fuel emulsion to an array of fuel injectors. Advantageously, each fluid delivery channel connects a cavity inlet (through which the water-fuel emulsion is added to the cavity) to one of a plurality of cavity outlets (through which the water-fuel emulsion is delivered to a respective fuel injector). Each fluid delivery channel defines an equal volume, inside said cavity, through which pressurised fluid flows, in use, from said cavity inlet to the respective cavity outlet so that each fuel injector receives an equal volume of the fluid. This maximises the homogeneity of the water-fuel emulsion delivered to each fuel injector.

Each of the common rail arrangements described below is intended for use in an emulsion injection system for a Spark Ignition (SI) engine. However, it should be appreciated that the common rail arrangements may be suitable for other uses, including the delivery of fuel, or water, in a fluid delivery system of a Compression Ignition (Cl), or SI, internal combustion engine.

To provide context for the invention, Figure 1 shows, in simplified schematic form, a fuel injection system 1 for a spark ignition engine 2. In this example, the spark ignition engine 2 is a four-cylinder engine, having four engine cylinders 4(a-d).

However, as shall become clear in the following description, examples of the invention are not limited for use with a four-cylinder SI engine and may, for example, be suitable for use with any of a two, four, six, eight, ten or twelve cylinder internal combustion engine.

The fuel injection system 1 is configured to pressurise and deliver a supply of a pressurised fluid, comprising a water-fuel emulsion, to each cylinder 4(a-d) of the spark ignition engine 2. For this purpose, the fuel injection system 1 takes the form of an emulsion injection system and includes a high pressure pump 6, a common rail 10, a pressure sensor 12 and a set of fuel injectors 14(a-d) for injecting the pressurised fluid into each engine cylinder 4(a-d) of the spark ignition engine 2. As shown, the set of fuel injectors 14(a-d) includes a first 14(a), a second 14(b), a third 14(c) and a fourth fuel injector 4(d) and each fuel injector 14(a-d) is configured to inject fluid directly into a respective one of the four engine cylinders 4(a-d).

In use, the high pressure pump 6 receives a supply of water and a supply of fuel, such as gasoline, that are mixed together. The high pressure pump 6 pressurises the mixture to produce a pressurised fluid comprising a water and fuel emulsion, which is delivered to the common rail 10. In this manner, the water-fuel emulsion is prepared by a single high pressure pump 6, prior to addition to the common rail 10. However, it shall be appreciated that, in other examples, the fluid injection system 1 may include a first high pressure pump that pressurises the fuel and a second high pressure pump that pressurises the water. The pressurised water and the pressurised fuel may be delivered to the common rail 10 separately, where the water and fuel emulsion may be formed by mixing the pressurised supply of water and the fuel together.

The common rail 10 is configured to accumulate a volume of the pressurised fluid and, additionally or alternatively, to deliver the pressurised fluid to the set of fuel injectors 14(a-d) for injection into the engine 2.

Although not shown in this example, the high pressure pump 6 and/or the common rail 10 may be operated by a control system (not shown) that controls the delivery of pressurised fluid to the set of fuel injectors 14(a-d). For example, the pressure sensor 12 may monitor the pressure inside the common rail 10 and output signals to the control system that are indicative of the pressure in the common rail 10. The control system may then operate the high pressure pump 6 and/or the common rail 10 to pressurise the fluid and/or deliver the pressurised fluid to the fuel injectors 14(a-d) in dependence on the signals.

Examples of the common rail 10 that may be used in the fluid delivery system 1 are provided in Figures 2 to 11, which shall now be described. It should be noted that counterpart features of each example are assigned similar reference numbers, but incremented by 100 moving from one example to the next.

A first example of the common rail 10 shall be described with reference to Figures 2 to 6. Figure 2 shows a cross-sectional view arranged along a longitudinal axis of the common rail 10. As shown, the common rail 10 is an assembly comprising a housing 20 and a volume splitter 50. The volume splitter 50 is arranged inside a cavity 22 of the housing 20, as best shown in Figure 3.

Figure 3 shows a cross-sectional view arranged along a longitudinal axis of the housing 20. In this example, the cavity 22 is elongate and extends from a first end 24 to a second end 26. In this example, the first end 24 of the cavity 22 is closed by interior surfaces of the housing 20. The second end 26 of the cavity 22 may be closed by a plug 28, as shown in Figure 3 for example. It shall be appreciated that, in other examples, the cavity 22 may be closed by a removable sealant or plug, such as the plug 28, at each of the first and second ends 24, 26, which may otherwise be open. For example, the use of such a plug may provide for easier methods of manufacture.

In this example, the cavity 22 is substantially uniform along its length and the cavity 22 is defined by substantially cylindrical cavity walls 23 formed by interior surfaces of the housing 20. However, it shall be appreciated that, in other examples, the cavity 22 may be defined by cavity walls of any other suitable shape that may define an elongate void, for example, with a circular, quadrangular or elliptical cross-section.

In this example, it shall be appreciated that the cylindrical cavity 22 may, for example, be formed by various means, such as a bore hole in the housing 20.

As shown in Figure 3, the housing 20 includes a first cavity inlet 30(a) and a second cavity inlet 30(b) arranged in the cavity walls 23 for the addition of pressurised fluid to the cavity 22. Each of the first and second cavity inlets 30(a,b) is suitable for connection to a respective supply line, extending from the high pressure pump 6 of the fluid injection system 1,to provide a supply of the pressurised fluid, in use. For example, as shown in Figure 3, each of the first and second cavity inlets 30(a,b) may include a respective spout 32(a,b), extending from the cavity 22, for connection to a respective supply line (not shown in Figure 3).

The housing 20 also includes a plurality of cavity outlets 34(a-d), arranged in the cavity walls 23, for the delivery of pressurised fluid from the cavity 22. The plurality of cavity outlets 34(a-d) includes a first cavity outlet 34(a), a second cavity outlet 34(b), a third cavity outlet 34(c) and a fourth cavity outlet 34(d). Each of the plurality of cavity outlets 34(a-d) is suitable for connection to a respective fuel injector 14(a-d) of the fuel injection system 1 (not shown in Figure 3).

As shown in Figure 3, the first and second cavity inlets 30(a,b) may be spaced circumferentially from the plurality of cavity outlets 34(a-d) around the cylindrical cavity walls 23. For example, the first and second cavity inlets 30(a,b) may be arranged on a diametrically opposite portion of the cavity 22 to the plurality of cavity outlets 34(a-d).

Significantly, the first cavity inlet 30(a) is arranged equidistantly between the first and second cavity outlets 34(a,b) so that an equal volume of the cavity 22 extends between the first cavity inlet 30(a) and each of the first and second cavity outlets 34(a,b). More specifically, along its length, the cavity 22 has a uniform cross-section and the distance from the first cavity inlet 30(a) to the first cavity outlet 34(a) is the same as the distance from the first cavity inlet 30(a) to the second cavity outlet 34(b) so that an equal volume is defined between the first cavity inlet 30(a) and each of the first and second cavity outlets 34(a,b). In a corresponding manner, the second cavity inlet 30(b) is arranged equidistantly between the third and fourth cavity outlets 34(c,d). Accordingly, the first and second cavity outlets 34(a,b) may be considered as a pair of cavity outlets corresponding to the first cavity inlet 30(a) and the third and fourth cavity outlets 34(c,d) may be considered as a pair of cavity outlets corresponding to the second cavity inlet 30(b).

Figures 4 and 5 respectively show a side view and a perspective of the volume splitter 50.

The volume splitter 50 is shaped in a complementary manner to the cavity 22 of the housing 20. Accordingly, in this example, the volume splitter 50 is elongate and extends from a first end 51 to a second end 52, along a longitudinal axis, with a substantially cylindrical outer surface 54.

Along its length, the volume splitter 50 includes a shoulder 56 that protrudes from the outer surface 54 of the volume splitter 50 between the first and second ends 51, 52. The shoulder 56 may be disposed halfway between the first and second ends 51, 52, for example.

The shoulder 56 may be cylindrical and forms a region in which the outer diameter of the volume splitter 50 is larger than the outer diameter of the surrounding portions of the volume splitter 50. In this manner, a first portion 58 of the volume splitter 50 extends from the first end 51 of the volume splitter 50 to a first end 59 of the shoulder 56 and a second portion 60 of the volume splitter 50 extends from an opposing second end 61 of the shoulder 56 to the second end 52 of the volume splitter 50. The first and second portions 58, 60 may be substantially symmetrical about the shoulder 56, as shown.

The volume splitter 50 is also tubular and includes an axial opening 62, or bore, that extends along the length of the volume splitter 50 from the first end 51 to the second end 52. The opening 62 extends through the volume splitter 50 to define a substantially cylindrical inner surface 64, having a smaller radius than the outer surface 54.

In other examples, each of the first and second ends 51, 52 of the volume splitter may include an axial opening or bore that extends at least partially along the length of the volume splitter 50. In such examples, the opening in the first end 52 may substantially match the opening in the second end 51 so that the first and second portions 58, 60 of the volume splitter 50 substantially match one another.

In some examples, the volume splitter 50 may also include an internal wall (not shown) that extends at least partially across the axial opening 62. For example, the internal wall may extend radially inward from the inner surface 64 of the volume splitter 50 to substantially close the axial opening 62. The internal wall may be disposed halfway along the length of the volume splitter 50, between the first and second ends 51, 52. In this manner, the internal wall may similarly define a split between the first and second portions 58, 60 of the volume splitter 50 on the inner surface 64 of the volume splitter 50. The internal wall may not extend fully across the opening 62 so as to leave a through hole (not shown) between the first and second portions 58, 60 of the volume splitter 50.

As shown in Figures 4 and 5, the volume splitter 50 also includes a plurality of grooves on the outer surface 54 that define channels for delivering fluid, in use, from the first and second cavity inlets 30(a,b) of the housing 20 to the plurality of cavity outlets 34(a-d).

In particular, in this example, the volume splitter 50 includes a first set of grooves 66(a-d) and a second set of grooves 68(a-d) recessed into the outer surface 54 of the volume splitter 50. The first set of grooves 66(a-d) is disposed on the first portion 58 of the volume splitter 50, on one side of the shoulder 56, and the second set of grooves 68(a-d) is disposed on the second portion 60 of the volume splitter 50, on the other side of the shoulder 56.

The first and second sets of grooves 66(a-d), 68(a-d) substantially match one another and may be symmetrical about the shoulder 56, as shown in this

example.

Considering the first set of grooves 66(a-e) in more detail, the first set of grooves 66(a-d) includes a first groove 66(a), a second groove 66(b), a third groove 66(c), a fourth groove 66(d) and a fifth groove 66(e). Each of the first, third and fifth grooves 66(a,c,e) extends circumferentially around the outer surface 54 of the volume splitter 50. Each of the second and fourth grooves 66(b,d) mainly extends axially along the length of the volume splitter 50.

The first, third and fifth grooves 66(a,c,e) are spaced along the length of the volume splitter 50, with the third groove 66(c) being arranged equidistantly along the length of the volume splitter 50 between the first and fifth grooves 66(a,e).

The second groove 66(b) extends axially along the outer surface 54 of the volume splitter 50 to connect the first and third grooves 66(a,c) together and the fourth groove 66(d) extends axially along the outer surface 54 of the volume splitter 50 to connect the third and fifth grooves 66(c,e) together.

The first and fifth grooves 66(a,e) substantially match one another, having equal groove widths (along the axial length of the volume splitter 50), equal groove lengths (extending circumferentially around the volume splitter 50) and equal groove depths (extending radially into the outer surface 54 of the volume splitter 50). The second and fourth grooves 66(b,d) also substantially match one another, having equal groove lengths (along the axial length of the volume splitter 50), equal groove widths (extending circumferentially around the volume splitter 50) and equal groove depths (extending radially into the outer surface 54 of the volume splitter 50).

It shall be appreciated that the second set of grooves 68(a-e) correspond to the first set of grooves 66(a-e) and include a first groove 68(a), a second groove 68(b), a third groove 68(c), a fourth groove 68(d) and a fifth groove 68(e) substantially as described above.

In the following description, the assembled common rail 10, shown in Figures 2 and 6, is considered in more detail.

During the assembly, the volume splitter 50 maybe introduced through the second end 26 of the cavity 22 and retained in position by the plug 28, for

example.

As shown in Figure 2, in assembled form, the volume splitter 50 is arranged inside the cavity 22 of the housing 20 so that the shoulder 56 of the volume splitter 50 spans across the cavity 22 to engage the cavity walls 23. In this manner, the shoulder 56 acts as a dividing member, effectively dividing the cavity 22 into a first accumulator volume 72 and a second accumulator volume 74. The first accumulator volume 72 extends from the first end 59 of the shoulder 56 to the first end 24 of the cavity 22 and the second accumulator volume 74 extends from the second end 61 of the shoulder 56 to the second end 26 of the cavity 22. Each of the first and second accumulator volumes 72, 74 is suitable for accumulating a respective volume of the pressurised fluid, in use.

It follows that the first accumulator volume 72 is defined by a respective portion of the cavity 22 that includes the first cavity inlet 30(a) and the first and second cavity outlets 34(a,b). Similarly, the second accumulator volume 74 is defined by a respective portion of the cavity 22 that includes the second cavity inlet 30(b) and the third and fourth cavity outlets 34(c,d). Consequently, each of the first and second accumulator volumes 72, 74 includes a respective cavity inlet spaced equidistantly between a corresponding pair of cavity outlets.

Furthermore, as shown in Figure 2, the first portion 58 of the volume splitter 50 is arranged inside the first accumulator volume 72 and the second portion 60 of the volume splitter 50 is arranged inside the second accumulator volume 74 such that the assembled common rail 10 is substantially symmetrical.

As shall become clear in the following description, the volume splitter 50 defines various cavity formations inside the first and second accumulator volumes 72, 74 that are configured to optimise the delivery of the pressurised fluid to the fuel injectors 14(a-d).

In particular, the volume splitter 50 is arranged inside the cavity 22 of the housing such that the first and second sets of grooves 66(a-e),68(a-e) form a plurality of channels connecting the first and second cavity inlets 30(a,b) to the plurality of cavity outlets 34(a-d). This arrangement is described in more detail with reference to the first set of grooves 66(a-e) inside the first accumulator volume 72.

As shown in Figure 2, the first groove 66(a) is arranged in planar alignment with the first cavity outlet 34(a), the third groove 66(c) is arranged in planar alignment with the first cavity inlet 30(a) and the second groove 66(b) extends between the first and third grooves 66(a,c), to define a first channel 76(a) that connects the first cavity inlet 30(a) to the first cavity outlet 34(a). Similarly, the fifth groove 66(e) is arranged in planar alignment with the second cavity outlet 34(b) and the fourth groove 66(d) extends between the third and fifth grooves 66(c,e), so that, collectively, the third, fourth and fifth grooves 66(c-e) define a second channel 76(b) that connects the first cavity inlet 30(a) to the second cavity outlet 34(b).

The first and second channels 76(a,b) are substantially the same because the first and second grooves 66(a,b) correspond to the fourth and fifth grooves 66(d,e) so that the volume defined by the first channel 76(a) is equal to the volume defined by the second channel 76(b).

In this manner, the first set of grooves 66(a-e) defines a pair of channels 76(a,b) of equal volume in the assembled common rail 10 that connect the first cavity inlet 30(a) to the first and second cavity outlets 34(a,b). It shall be appreciated that the second set of grooves 68(a-e) is arranged inside the second accumulator volume 74, in a corresponding manner to the first set of grooves 66(a-e) to define a third channel 78(a) and a fourth channel 78(b) of equal volume that connect the second cavity inlet 30(b) to the third and fourth cavity outlets 34(c,d) respectively. The specific arrangement is not described in detail to avoid obscuring the invention.

In use, these channels 76(a,b), 78(a, b) provide high speed fluid delivery channels for delivering the pressurised fluid to the cavity outlets 34(a-d), as shall become clear in the method of use of the common rail 10.

Within the cavity 22, the volume splitter 50 also defines at least one chamber defined by the inner surface 64 of the volume splitter 50. In use, such a chamber acts as a damping chamber (in a conventional manner) configured to receive a respective volume of the pressurised fluid and to provide damping of the pressure pulsations resulting from the injection of the pressurised fluid into the engine cylinders 4(a-d). The skilled person shall appreciate that the damping volume required will depend on the specific use of the common rail 10 and that the volume splitter 50 may be adapted accordingly to suit such use.

In this example, the volume splitter 50 defines a first chamber 80 inside the first accumulator volume 72, as best shown in the cross-section through the common rail 10 in Figure 6, and a second chamber (not shown) inside the second accumulator volume 74. The first and second chambers 80 are defined by the inner surface 64 of the volume splitter 50 and extend from opposing surfaces of the internal wall (not shown) into the respective ones of the first and second accumulator volumes 72, 74.

Accordingly, in this example, the first chamber 80 takes the form of a cylindrical receptacle defined inside the first accumulator volume 72 and the second chamber (not shown) takes the form of another cylindrical receptacle defined inside the second accumulator volume 74. Each chamber 80 is configured to receive a respective volume of the pressurised fluid that provides damping of the pressure pulsations, as shall become clear in the following description..

Furthermore, the outer surface 54 (as in Figures 4 and 5) of the volume splitter 50 is shaped in a complementary manner to the cavity 22 so that the clearance between the outer surface 54 of the volume splitter 50 and the cavity walls 23 defines a first narrow passage around the first portion 58 of the volume splitter 50 and a second narrow passage around the second portion 60 of the volume splitter 50. As shall become clear in the following description, the clearance is configured such that, in use, fluid in the first accumulator volume 72 can flow (in a restricted manner) between the first and second channels 76(a,b) and the first chamber 80. Similarly, fluid in the second accumulator volume 74 can flow, in a restricted manner, between the third and fourth channels 78(a,b) and the second chamber 80. By way of example, each of the first and second narrow passages may be defined by a radial clearance of less than 0.05mm between the outer surface 54 of the volume splitter 50 and the cavity walls 23. The shoulder 56 engages the cavity walls 23 to substantially inhibit the flow of fluid between the first and second narrow passages.

In the subsequent description, a method of use of the common rail 10 in the fuel injection system 1 is described with reference to Figures 1, 2 and 6.

Prior to operating the engine 2, the common rail 10 will receive an initial supply of a pressurised fluid to fill the first and second chambers 80 with a damping volume of fluid. For example, the high pressure pump 6 may deliver a supply of a pressurised fluid comprising a water and fuel emulsion to the first and second chambers 80 via the first and second narrow passages. Once the first and second chambers 80 (not shown) contain sufficient volumes of fluid for damping, the fluid delivery system 1 is ready for use.

In response to a demand for a supply of pressurised fluid at the fuel injectors 4(a-d), the high pressure pump 6 of the fuel injection system 1 is configured to deliver a supply of pressurised fluid, comprising a water and fuel emulsion, to each of the first and second cavity inlets 30(a, b).

For example, the first cavity inlet 30(a) may receive a first portion of the pressurised fluid and the second cavity inlet 30(b) may receive a second, equal, portion of the pressurised fluid through the respective supply lines.

The first portion of the pressurised fluid enters the first accumulator volume 72 through the first cavity inlet 30(a) and flows along the first and second channels 76(a,b) to the first and second cavity outlets 34(a,b). Similarly, the second portion of the pressurised fluid enters the second accumulator volume 74 through the second cavity inlet 30(b) and flows along the third and fourth channels 78(a, b) to the third and fourth cavity outlets 34(a,b).

Considering this in more detail, and referring to the flow of the first portion of pressurised fluid from the first cavity inlet 30(a) to the first and second cavity outlets 34(a,b) as an example, the pressurised fluid initially flows into the third groove 66(c) from the first cavity inlet 30(a). The pressurised fluid then splits and flows, in equal proportions: i) along the second groove 66(b), into the first groove 66(a) and out of the first cavity outlet 34(a) (towards the first fuel injector 14(a)); and fi) along the fourth groove 66(d), into the fifth groove 66(e) and out of the second cavity outlet 34(b) (towards the second fuel injector 14(b)).

In this manner, in use, the first and second channels 76(a,b) define first and second fluid delivery channels 76(a,b) inside the first accumulator volume 72 that connect the first cavity inlet 30(a) to the first and second cavity outlets 34(a,b).

It shall be appreciated that the first and second cavity outlets 34(a,b) receive equal volumes of the pressurised fluid because: i) the distance along the length of the cavity 22, from the first cavity inlet 30(a) to the first cavity outlet 34(a) is the same as the distance along the length of the cavity 22 from the first cavity inlet 30(a) to the second cavity outlet 34(b); and ii) the first and second fluid delivery channels 76(a,b) define equal volumes through which pressurised fluid flows from the first cavity inlet 30(a) to the respective one of the first and second cavity outlets 34(a,b).

The second portion of the pressurised fluid flows along the third and fourth fluid delivery channels 78(a,b), from the second cavity inlet 30(b) to the third and fourth cavity outlets 34(c,d), in a corresponding manner. However, this is not described in detail to avoid obscuring the invention.

Accordingly, an equal volumetric flow rate of pressurised fluid is provided to each of the fuel injectors 14(a-d), which produces a parallel, as opposed to a series, injection arrangement. The parallel injection arrangement improves the homogeneity of the water and fuel emulsion injected from the fuel injectors 14(a-d).

Furthermore, the volume through which pressurised fluid flows in each fluid delivery channel 76(a,b), 78(a,b) is minimised, whilst not creating excessive back pressure, so that each fluid delivery channel 76(a,b), 78(a,b) defines a high speed flow path through the cavity 22 that minimises the time it takes to deliver the pressurised fluid to the fuel injectors 14(a,b) (e.g. in response to a demand). This short response time is advantageous for several reasons. For example, the short response time maximises the homogeneity of the water and fuel emulsion in the pressurised fluid, which has a tendency to separate, breaking down the homogeneity of the mixture, if the pressurised fluid takes too long to reach the fuel injectors 14(a-d).

To further reduce the response time, the high pressure pump 6 may be configured to deliver the pressurised fluid to each of the first and second accumulator volumes 72, 74 at high pressure, so that the fluid flows through the fluid delivery channels 76(a,b),78(a,b) at a fast rate. However, this high pressure flow of pressurised fluid creates large pressure pulsation as the fluid enters the first and second accumulator volumes 72, 74. Advantageously, the damping volume of pressurised fluid in each of the first and second chambers 80 dampens the pressure pulse. If the pressure pulse is not damped, the homogeneity of the pressurised fluid may be affected.

After the pressurised fluid is injected into the engine 2, excess pressurised fluid is held in the first and second accumulator volumes 72, 74 and may pass from the fluid delivery channels 76(a,b),78(a,b) into the first and second chambers 80 to maintain the respective damping volumes. For example, the excess pressurised fluid may flow along the first and second narrow passages and around rims at the first and second ends 24, 26 of the volume splitter 50 into the first and second chambers 80.

The shoulder 56 substantially inhibits, or prevents, fluid flowing between the first and second accumulator volumes 72,74 and, in this example, the inner wall of the volume splitter 50 may substantially inhibit, or prevent, fluid flowing between the first and second chambers 80. Nonetheless, the through hole in the internal wall allows a suitably restricted flow of pressurised fluid to flow between the first and second chambers 80 to allow for pressure equalisation.

Figure 7 illustrates another example common rail 110, shown in a cross-sectional view arranged along its longitudinal axis.

The common rail 110 includes a common rail housing 120 and a volume splitter 50. The common rail housing 120 is substantially the same as the common rail housing 20 described in relation to the previous example common rail 10 and includes a cavity 22, having a first cavity inlet 30(a) and a second cavity inlet 30(b), as well as a plurality of cavity outlets 34(a-d).

However, in this example, the common rail housing 120 does not include the spouts 32(a,b) that extend from the first and second cavity inlets 30(a,b). Instead, the common rail housing 120 further includes a distribution channel 190, or distribution gallery, configured to deliver a supply of pressurised fluid to the first and second cavity inlets 30(a,b).

As shown in Figure 7, the distribution channel 190 includes a first outlet port 192(a) connected to the first cavity inlet 30(a) and a second outlet port 192(b) connected to the second cavity inlet 30(b).

The distribution channel 190 also includes an inlet port 196, which is configured for adding pressurised fluid to the distribution channel 190 from the high pressure pump 6. In this example, the common rail housing 120 includes a spout 197, extending from the inlet port 196 of the distribution channel 190, for connection to a supply line that extends from the high pressure pump 6.

The distribution channel 190 is configured to receive a volume of pressurised fluid from the high pressure pump 6 and deliver a portion of the pressurised fluid to the cavity 22 at an equal rate through the first and second outlet ports 192(a,b). For this purpose, the distribution channel 190 has a substantially uniform cross-section between the first and second outlet ports 192(a,b) and the distribution channel 190 extends from a first end 193, at the first outlet port 192(a), to a second end 194, at the second outlet port 192(b). The inlet port 196 is arranged equidistantly along the length of the distribution channel 190 between the first and second outlet ports 192(a,b) so that, in use, an equal volume of pressurised fluid flows from the inlet port 196 to each of the first and second outlet ports 192(a,b).

The distribution channel 190 is further configured to store the remaining portion of the pressurised fluid inside the distribution channel 190 to provide a volume of fluid that is able to further damp the subsequent addition of pressurised fluid from the high pressure pump 6.

Accordingly, the distribution channel 190 forms a receptacle in the common rail housing 120 that is large enough to store a sufficient volume of pressurised fluid for damping the pressure pulsations that arise when the pressurised fluid is added from the high pressure pump 6. In this example, the receptacle is elongate and cylindrical, as shown in Figure 7.

The volume splitter 50 is arranged inside the cavity 22 of the common rail housing 120, substantially as described in the previous example common rail 10, and the volume splitter 50 divides the cavity 22 into a first accumulator volume 72 and a second accumulator volume 74, in the manner described previously. Accordingly, the volume splitter 50 also defines respective fluid delivery channels 76(a,b), 78(a,b) in the first and second accumulator volumes 72, 74, connecting the respective cavity inlets 30(a,b) to the respective cavity outlets 34(a-d).

It shall be appreciated that the only differences in the method of usage, compared to the previous example common rail 10, concern the distribution channel 190. It follows from the above that, upon demand for a supply of pressurised fluid at the fuel injectors 4(a-d), the high pressure pump 6 of the fuel injection system 1 delivers a supply of pressurised fluid comprising a water and fuel emulsion to the inlet port 196 of the distribution channel 190. Equal portions of the pressurised fluid flow from the inlet port 196 and along the length of the distribution channel 190 to the respective first and second outlet ports 192(a,b). In this manner, each cavity inlet 30(a,b) receives an equal supply of pressurised fluid which then passes along the respective fluid delivery channels 76(a,b),78(a,b) to the cavity outlets 34(a-d) in the manner described previously.

Once the demand for the supply of pressurised fluid at the fuel injectors 4(a-d) is satisfied, a portion of the pressurised fluid remains in the distribution channel 190 and fills the receptacle to provide a volume of the pressurised fluid that damps any subsequent addition of the pressurised fluid from the high pressure pump 6.

In other example common rails (not shown), the common rail housing and the volume splitter may be substantially as described in the example common rails 10, 110 described above. However, the volume splitter 50 may not include the shoulder 56. Instead, the outer surface 54 of the volume splitter 50 may be configured to form an interference fit inside the cavity 22. Such an interference fit eliminates any clearance between the outer surface 54 of the volume splitter 50 and the cavity walls 23, such that the pressurised fluid can only flow along the fluid delivery channels 76(a,b),78(a,b) and the flow of pressurised fluid between the outer surface 54 of the volume splitter 50 and the cavity walls 23 is prevented. In such examples, the volume splitter 50 may be force fitted into the cavity 22 (or fitted by any other suitable method to maintain zero clearance).

Another example common rail 210 shall be described with reference to Figures 8 to 10. Figure 8 shows a cross-sectional view arranged along a longitudinal axis of the common rail 210. In general, the common rail 210 of this example differs from the common rail 10 of the first example in that the common rail housing 220 includes a first cavity 222(a) and a second cavity 222(b), each defining a receptacle that forms a respective accumulator volume inside the common rail 210. It shall be appreciated that this arrangement differs from the previous example common rail 10 in that the cavity 22 has been replaced by a pair of cavities, i.e. the first and second cavities 222(a,b).

The first and second cavities 222(a,b) are separated by a dividing wall 225 of the common rail housing 220 that extends across each of the first and second cavities 222(a,b) to define a respective end wall of each cavity 222(a,b). In particular, the first cavity 222(a) extends along a longitudinal axis of the common rail housing 220 from a first end 224 to a first side 227 of the dividing wall 225 and the second cavity 222(b) extends along the same axis from an opposing second side 229 of the dividing wall 225 to a second end 226.

The first end 224 of the first cavity 222(a) and the second end 226 of the second cavity 222(b) are open ends of the common rail housing 220 and may be closed by respective plugs 228(a, b), for example.

In this example, the first and second cavities 222(a,b) are arranged coaxially in the common rail housing 220 and substantially match one another. In fact, the first and second cavities 222(a,b) may be considered symmetrical about the dividing wall 225. Such an arrangement can help to ensure that equal amounts of pressurised fluid are delivered from the common rail 210 to the set of fuel injectors 4(a-d). However, it shall be appreciated that, in other examples, the first and second cavities 222(a,b) may differ from one another and need not be arranged coaxially in the common rail housing 220, whilst still providing equal amounts of pressurised fluid to the fuel injectors 4(a-d).

Furthermore, each of the first and second cavities 222(a,b) is elongate and substantially uniform along its length defining a cylindrical receptacle inside the common rail housing 220. Accordingly, the skilled person will appreciate that the first and second cavities 222(a,b) may, for example, be formed by various means, such as bore holes into opposing ends of the housing 220. However, in other examples, the first and second cavities 222(a,b) may take any other suitable shape, such as a rectangular or cuboidal shape.

As mentioned previously, the first cavity 222(a) defines a first accumulator volume 72 of the common rail 210 that includes a first cavity inlet 30(a), a first cavity outlet 34(a) and a second cavity outlet 34(b) substantially as described in the previous example common rail 10.

In a similar manner, the second cavity 222(b) defines a second accumulator volume 74 of the common rail 210 that includes a second cavity inlet 30(b), a third cavity outlet 34(c) and a fourth cavity outlet 34(d), substantially as described in the previous example common rail 10.

The first and second accumulator volumes 72, 74 are fluidly disconnected from one another in this example. However, in other examples, the dividing wall 225 may include a through hole to allow pressure equalisation between the first and second accumulator volumes 72, 74 in the manner of the internal wall of the volume splitter 50 described in the previous example common rail 10.

It shall be appreciated that, despite the differences described above, the common rail 210 described in this example functions in substantially the same manner as the previous example common rail 10 described above.

For this purpose, in this example, the common rail 210 includes a first volume splitter 250(a) and a second volume splitter 250(b) arranged inside the common rail housing 220. In particular, the first volume splitter 250(a) is arranged inside the first cavity 222(a) of the common rail housing 220 and the second volume splitter 250(b) is arranged inside the second cavity 222(b) of the common rail housing 220.

The first and second volume splitters 250(a,b) are each adapted for suitability to the respective one of the first and second cavities 222(a,b). In particular, the first volume splitter 250(a) substantially corresponds to the first portion 58 of the volume splitter 50 described in the previous example common rail 10. In a similar manner, the second volume splitter 250(b) substantially corresponds to the second portion 60 of the volume splitter 50 described in the previous example common rail 10.

It follows that the first volume splitter 250(a) includes a first set of grooves 66(a-e) that provides first and second fluid delivery channels 76(a,b) arranged to connect the first cavity inlet 30(a) to the first and second cavity outlets 34(a,b) in the manner described in relation to the previous example common rail 10. Similarly, the second volume splitter 250(b) includes a second set of grooves 68(a-e) that provides third and fourth fluid delivery channels 78(a,b) arranged to connect the second cavity inlet 30(b) to the third and fourth cavity outlets 34(c,d) in the manner described in relation to the previous example common rail 10.

Hence, in this example, the first and second volume splitters 250(a,b) substantially match one another so that the common rail 210 is substantially the same as the example common rail 10, described previously. The only notable difference is that, the first common rail 10 of Figure 2 includes a single cavity 22 and a corresponding volume splitter 50 with a shoulder 56 and an internal wall that divides the cavity 22 into first and second accumulator volumes 72, 74, whereas the common rail 210 of Figure 8 includes a first and second cavities 222(a,b) that define the respective first and second accumulator volumes 72, 74 with a respective first or second volume splitter 250(a,b) arranged in each accumulator volume 72, 74 Accordingly, it shall be appreciated that the method of using the example common rail 210 is substantially as described in relation to the previous example common rail 10, mutatis mutandis as necessary to account for these differences.

Another example common rail 310 shall be described with reference to Figure 11. Figure 11 shows a cross-sectional view arranged along a longitudinal axis of the common rail 310.

In general, the common rail 310 of the Figure 11 example differs from the common rail 210 of the previous example of Figure 8 in that the common rail housing 320 further includes a distribution channel 190, substantially as described in the example common rail 110 described above Accordingly, the distribution channel 190 includes an inlet port 196, a first outlet port 192(a) and a second outlet port 192(b) substantially as described previously. However, in this example, the first outlet port 192(a) connects to the first cavity inlet 30(a) of the first cavity 222(a) and the second outlet port 192(b) connects to the second cavity inlet 30(b) of the second cavity 222(b).

Accordingly, it shall be appreciated that the method of using the example common rail 310 is substantially as described in relation to the previous example common rail 110, mutatis mutandis, as necessary to account for the differences.

It shall also be appreciated that, in other example common rails (not shown), the common rail housing and the volume splitter may be substantially as described in the example common rails 210, 310 described above. However, each of the first and second volume splitters 250(a,b) may be configured to form an interference fit inside the respective one of the first and second cavities 222(a,b). Such an interference fit may eliminate any clearance between the outer surface 54 of each volume splitter 250(a,b) and the cavity walls 23 of the respective one of the first and second cavities 222(a,b). In this manner, the pressurised fluid may only be able to flow along the fluid delivery channels 76(a,b),78(a,b) 0.e. the flow of pressurised fluid between the outer surface 54 of each volume splitter 250(a,b) and the cavity walls 23 of the respective one of the first and second cavities 222(a,b) may be prevented). In such examples, each volume splitter 250(a,b) may be force fitted into the respective cavity 222(a,b) (or fitted by any other suitable method to maintain zero clearance).

Figure 12 illustrates, in respective example plots, how each of the example common rails 10, 110, 210, 310 responds, in use, to a step-change in demand for pressurised fluid at the fuel injectors 14(a-d).

The plots illustrate the variation in the percentage of water contained in the pressurised fluid at each of the fuel injectors 14(a-d). In this example, the step-change in demand is for 30% water content within the water and fuel emulsion.

As shown, each of the example common rails 10, 110, 210, 310 provides a quick response, providing the pressurised fluid to each of the fuel injectors 14(a-d) within 2.4 seconds. Hence, the pressurised fluid can be injected into the engine 2 in a parallel injection arrangement.

Furthermore, as shown, the percentage of water contained in the water and fuel emulsion of the pressurised fluid at each fuel injector 14(a-d) is substantially equal. Hence, the pressurised fluid received at each fuel injector 14(a-d) is substantially homogenous. This reduces the tendency for engine knock in the engine 2 and provides for increased fuel economy.

It will be appreciated by a person skilled in the art that the invention could be modified to take many alternative forms to that described herein, without departing from the scope of the appended claims.

References used: 1 -Fluid injection system 2 -Spark ignition engine 4(a-d) -Engine cylinders 6-High pressure pump 10-Common rail 12-Pressure sensor 14(a-d) -Fuel injectors 20-Common rail housing 22 -Cavity 23 -Cavity walls 24 -First end of cavity 26 -Second end of cavity 28-Plug 30(a, b) -First and second cavity inlets 32(a, b) -First and second spouts 34(a-d) -First, second, third and fourth cavity outlets 34(a-d) 50-Volume splitter 51 -First end of volume splitter 52 -Second end of volume splitter 54 -Outer surface of volume splitter 56 -Shoulder 58 -First portion of volume splitter 59 -First end of shoulder -Second portion of volume splitter 61 -Second end of shoulder 62 -Axial opening of volume splitter 64 -Inner surface of volume splitter 66(a-e) -First set of grooves 68(a-e) -Second set of grooves 72 -First accumulator volume 74 -Second accumulator volume 76(a,b) -First and second channels 78(a,b) -third and fourth channels 80 -First chamber 110-Common rail 120 -Common rail housing 190-Distribution channel 192(a,b) -First and second outlet ports 193-First end of distribution channel 194-Second end of distribution channel 196 -Inlet port 197-Spout of distribution channel 210-Common rail 220 -Common rail housing 222 (a,b) -First and second cavities 225 -Dividing wall 224 -First end of first cavity 226 -Second end of second cavity 227 -First side of dividing wall 229 -Second side of dividing wall 250(a,b) -First and second volume splitters 310-Common rail 320 -Common rail housing

Claims (16)

1. Claims: 1. A common rail housing (20;120;220;320) of an emulsion injection common rail (10;110;210;310) for a fuel injection system (1) of a spark ignition engine (2), the common rail housing (20;120;220;320) comprising: at least one cavity (22;222(a,b)) in the common rail housing (20;120;220;320) for accumulating a pressurised fluid comprising a water and fuel emulsion; a plurality of outlets (34(a-d)) from each cavity (22;222(a,b)), each outlet of the plurality of outlets (34(a-d)) being connectable to a respective fuel injector (14(a-d)) for delivering pressurised fluid from said cavity (22;222(a,b)) into a respective cylinder (4(a-d)) of the spark ignition engine (2); and at least one inlet (30(a,b)) to each cavity (22;222(a,b)) for adding the pressurised fluid to said cavity (22;222(a,b)); wherein, for each cavity (22;222(a,b)), the plurality of outlets (34(a-d)) are spaced apart from one another inside said cavity (22;222(a,b)) and each inlet (30(a,b)) to said cavity (22;222(a,b)) is arranged equidistantly between a respective pair of the plurality of outlets (34(a,b),(c,d)) from said cavity (22;222(a,b)) so that an equal volume of said cavity (22;222(a,b)) extends between said inlet (30(a,b)) and each outlet of said respective pair of outlets (34(a,b),(c,d)).
2. 2. A common rail housing (20;120;220;320) according to claim 1, wherein each cavity (22;222(a,b)) is elongate and, for each cavity (22;222(a,b)), each inlet (30(a,b)) to said cavity (22;222(a,b)) is arranged equidistantly along the length of the cavity (22;222(a,b)) between the respective pair of outlets (34(a,b),(c,d)) from said cavity (22;222(a,b)).
3. 3. A common rail housing (20;120) according to claim 1 or claim 2, wherein, for each cavity (22): the plurality of outlets (34(a-d)) from said cavity (22) comprises a first pair of cavity outlets (34(a,b)) and a second pair of cavity outlets (34(c,d)) spaced apart from one another inside said cavity (22); and the at least one inlet 30(a,b) to said cavity (22) comprises a first cavity inlet (30(a)) and a second cavity inlet (30(b)), the first cavity inlet (30(a)) being arranged equidistantly between the first pair of cavity outlets (34(a,b)) and the second cavity inlet (30(b)) being arranged equidistantly between the second pair of cavity outlets (34(c,d)).
4. 4. A common rail housing (220;320) according to claim 1 or claim 2, wherein the at least one cavity (222(a,b)) in the common rail housing (220;320) includes a first cavity (222(a)) and a second cavity (222(b)); wherein the at least one inlet (30(a)) to the first cavity (222(a)) comprises a first cavity inlet (30(a)) and the plurality of outlets (34(a,b)) from the first cavity (222(a)) comprises a first pair of cavity outlets (34(a, b)); and wherein the at least one inlet (30(b)) to the second cavity (222(b)) comprises a second cavity inlet (30(b)) and the plurality of outlets (34(c,d)) from the second cavity (222(b)) comprises a second pair of cavity outlets (34(c,d)).
5. 5. A common rail housing (20;120;220;320) according to claim 3 or claim 4, wherein the volume of each cavity (22;222(a,b)) that extends between the first cavity inlet (30(a)) and each outlet (34(a,b)) of the first pair of cavity outlets (34(a,b)) is equal to the volume of each cavity (22;222(a,b)) that extends between the second cavity inlet (30(b)) and each outlet (34(c,d)) of the second pair of cavity outlets (34(c,d)).
6. 6. A common rail housing (120; 320) according to any of claims 3 to 5, further comprising an elongate distribution channel (190), comprising: an inlet port (196) for connection to a high pressure pump (6); a first outlet port (192(a)) connected to the first cavity inlet (30(a)); and a second outlet port (192(b)) connected to the second cavity inlet (30(b)); wherein the inlet port (196) is arranged equidistantly between the first and second outlet ports (192(a,b)) so that an equal volume of said distribution channel (190) extends between said inlet port (196) and each outlet port of the first and second outlet ports (192(a,b)).
7. 7. A common rail housing (120;320) according to claim 6, wherein the first outlet port (192(a)) of the distribution channel (190) is spaced from the second outlet port (192(b)) of the distribution channel (190) along the length of the distribution channel (190); wherein a cross-section of the distribution channel (190) is substantially uniform along the length of the distribution channel (190), between the first and second outlet ports (192(a,b)); and wherein the inlet port (196) to the distribution channel (190) is arranged equidistantly along the length of the distribution channel (190) between the first and second outlet ports (192(a,b)).
8. 8. A common rail housing (20;220) according to any of claims 3 to 5, wherein each of the first and second cavity inlets (30(a,b)) is suitable for connection to a high pressure pump (6).
9. 9. An emulsion injection common rail (10;110;210;310) for a fuel injection system (1) of a spark ignition engine (2) comprising a common rail housing (20;120;220;320) according to any preceding claim and at least one volume splitter (50;250(a,b)); wherein each cavity (22;222(a,b)) of the common rail housing (20;120;220;320) includes a volume splitter (50;250(a,b)) arranged inside said cavity (22,222(a,b)); wherein each volume splitter (50;250(a,b)) defines a plurality of fluid delivery channels (76(a,b),78(a,b)) inside said cavity (22,222(a,b)), each fluid delivery channel connecting (76(a,b),78(a,b)) one inlet (30(a,b)) of said cavity (22;222(a,b)) to one of the plurality of outlets (34(a-d)) of said cavity (22;222(a,b)); and wherein each fluid delivery channel (76(a,b),78(a,b)) defines an equal volume through which pressurised fluid flows, in use, along said fluid delivery channel (76(a,b),78(a,b)), from said inlet (30(a,b)) to the respective outlet (34(a-d)).
10. 10. An emulsion injection common rail (10;110) according to claim 9, when dependent on claim 3, wherein, for each cavity (22): the respective volume splitter (50) arranged inside said cavity (22) comprises: a dividing member (56) that extends across said cavity (22); a first portion (58) that extends from a first side of the dividing member (56); and a second portion (60) that extends from an opposing second side of the dividing member (56); wherein the dividing member (56) of the volume splitter (50) extends across said cavity (22) to define a first accumulator volume (72) and a second accumulator volume (74) inside said cavity (22); wherein the first accumulator volume (72) comprises a respective portion of said cavity (22) that includes: the first cavity inlet (30(a)); and the corresponding pair of cavity outlets (34(a,b)); and the second accumulator volume (74) comprises a respective portion of said cavity (22) that includes: the second cavity inlet (30(b)); and the corresponding pair of cavity outlets (34(c,d)); wherein the dividing member (56) of the volume splitter (50) substantially inhibits the flow of pressurized fluid from the first accumulator volume (72) to the second accumulator volume (74) in said cavity (22); and wherein the first portion (58) of the volume splitter (50) forms a first volume splitter (58) arranged inside the first accumulator volume (72) and the second portion (60) of the volume splitter (50) forms a second volume splitter (60) arranged inside the second accumulator volume (74).
11. 11. An emulsion injection common rail (210;310) according to claim 9, when dependent on claim 4, wherein the at least one volume splitter (250(a,b)) includes a first volume splitter (250(a)) and a second volume splitter (250(b)); wherein the first cavity (222(a)) defines a first accumulator volume (72) in a respective portion of said cavity (222(a)) that includes: the first cavity inlet (30(a)); and the corresponding pair of cavity outlets (34(a,b)); wherein the second cavity (222(b)) defines a second accumulator volume (74) in a respective portion of said cavity (222(b)) that includes: the second cavity inlet (30(b)); and the corresponding pair of cavity outlets (34(c,d)); and wherein the first volume splitter (250(a)) is arranged inside the first accumulator volume (72) and the second volume splitter (250(b)) is arranged inside the second accumulator volume (74).
12. 12. An emulsion injection common rail (10;110;210;310) according to claim or claim 11, wherein each of the first and second volume splitters (58,60;250(a,b)) is hollow and comprises an inner surface (64) and an outer surface (54); wherein the outer surface (54) of each volume splitter (58,60;250(a,b)) includes a respective set of grooves (66(a-e),68(a-e)); wherein, for each of the first and second accumulator volumes (72,74): the inner surface (64) of the respective volume splitter (58,60;250(a,b)) defines, at least in part, a chamber (80) inside said accumulator volume (72,74) for a damping volume of the pressurised fluid; the outer surface (54) of the respective volume splitter (58,60;250(a,b)) is complementary to an interior surface (23) of said accumulator volume (72,74); and the set of grooves (66(a-e),68(a-e)) on the outer surface of the respective volume splitter (58,60;250(a,b)) defines a plurality of the fluid delivery channels (76(a,b),78(a,b)) inside said accumulator volume (72,74), each fluid delivery channel (76(a,b),78(a,b)) connecting the cavity inlet (30(a,b)) of said accumulator volume (72,74) to one outlet (34(a-d)) of the respective pair of cavity outlets (34(a,b),34(c,d)) of said accumulator volume (72,74); and wherein each fluid delivery channel (76(a,b),78(a,b)) of said accumulator volume (72,74) defines an equal volume through which pressurised fluid flows, in use, along said fluid delivery channel (72,74), from said cavity inlet (30(a,b)) to the respective cavity outlet (34(a-d)).
13. 13 An emulsion injection common rail (10;110;210;310) according to claim 12, wherein each of the plurality of fluid delivery channels (76(a,b),78(a,b)) is of equal length between the respective cavity inlet (30(a,b)) of said accumulator volume (72,74) and the respective cavity outlet (34(a-d)) of said accumulator volume (72,74).
14. 14. An emulsion injection common rail (10;110;210;310) according to claim 12 or claim 13, wherein the outer surface of each volume splitter (58,60;250(a,b)) is complementary to an interior surface (23) of the respective accumulator volume (72,74) to inhibit the flow of pressurised fluid between the interior surface (23) of said accumulator volume (72,74) and the outer surface (54) of the volume splitter (58,60;250(a,b)), in use.
15. 15. An emulsion injection common rail (10;110;210;310) according to any of claims 10 to 14, wherein each of the first and second accumulator volumes (72,74) includes a passage between the respective chamber (80) and each of the fluid delivery channels (76(a,b),78(a,b)) inside said accumulator volume (72,74), each passage being configured to allow a restricted flow of the pressurised fluid between said chamber (80) and each of said fluid delivery channels (76(a,b),78(a,b)), in use.
16. 16. A fuel injection system (1) for a spark ignition engine (2) comprising a common rail housing (20;120;220;320) according to any of claims 1 to 8 or an emulsion injection common rail (10;110;210;310) according to any of claims 9 to 15.