This disclosure relates to flow splitters, that is to say, devices used for splitting or dividing a fluid flow along one flow path, such as a pipe, between a number of flow paths, such as a number of pipes.

Gas for fuel is often stored in high pressure cylinders. For example, a natural gas powered vehicle, such as a truck, will typically have four natural gas storage cylinders. When the cylinders are plumbed in series, the filling speed is reduced in proportion to the number of cylinders. In the case of a truck, filling time for four cylinders plumbed in series becomes significant. It may be, for example, in excess of fifteen minutes, which is material in terms of vehicle utilisation. As an alternative, parallel plumbing is sometimes used, but this tends to be achieved with T- or cross pieces in the cylinder connecting pipework or a custom-built manifold. However, both approaches have 90° turns in the flow path and uneven pressure distribution during filling. As a result, the cylinders are not filled equally or fully. Moreover, the T- or cross-pieces introduce joints, each of which is a potential leak site. It is generally desirable to reduce the number of potential leak sites, but, in a high pressure system, as in the case of a natural gas powered vehicle, the risk of leaks is increased.

According to an aspect, there is provided a flow splitter comprising: a one-piece body; a port in the body; a number of passages extending through the body, wherein each passage has one end which defines an opening in a side of the port and another end which defines an outlet from the body; wherein the body is formed in the region of each outlet into an outlet part for connecting an outlet pipe to that outlet; and, wherein, in use, fluid flows into the body through the port, through the openings, through the passages and out of the body through the outlets.

An embodiment of a flow splitter is suitable for use in, for example, filling a number of high pressure gas cylinders in parallel with minimal leaks. A gas inlet pipe is connected to the inlet and individual outlet pipes, one to each cylinder, are connected to each of the outlets. The inlet flow is divided evenly amongst the outlets so that the cylinders are filled equally and fully. The robust design of the flow splitter, including its one-piece body and each outlet part being formed in the region of each outlet, make it particularly suited for high pressure applications.

Each outlet part may be a male part for mating connection with an outlet pipe or a female fitting on an end of an outlet pipe. For example, each outlet part may be standardised connection, such as an SAE J514 hydraulic (37° flare) connection, an SAE J512 hydraulic (45° flare) connection or an SAE J1453 O-ring face seal connection, or a customised connection. Alternatively, each outlet part may be a female part for mating connection with an outlet pipe or a male fitting on an end of an outlet pipe. The male fitting on the end of the outlet pipe may be a standardised connection, such as an SAE J1453 O-ring face seal connection, an SAE J514 (37° flare) connection, SAE J512 (45° flare) connection or a conical metal to metal connection (such as those manufactured by HiP or Autoclave).

Whether to have the outlet parts of the flow splitter as male or female parts depends on how the flow splitter is being utilised. In some uses, having each outlet as a female part may provide a number of advantages including eliminating one fitting and one leak site per outlet pipe, providing a lower cost fitting involving the use of a special tubing nut, and providing a more robust and abuse tolerant connection. In addition, it can provide greater protection for the sealing area from accidents/abuse. This is because the sealing area is inside the flow splitter. Both the port and passages may be generally cylindrical and the number of outlets may = N, and the port diameter may be > (passage diameter). N ^{0 5} .

A flow axis may extend through a mid-point of fluid flow through the port in a direction generally parallel with a direction of fluid flow through the port, wherein each passage may extend away from the port in a generally diverging relationship to the flow axis.

The thickness of the body material at any part of the body may be determined by the burst protection required at that part. The body may be formed in the region of the port into a port part for connecting an inlet pipe to the port. The port part may be a female part for mating connection with a male fitting on an end of the inlet pipe. The openings may be in a side of the port which is the port bottom, which is the side of the port which is innermost within the body, and wherein the port bottom may be cone-shaped.

The body may be adapted for attachment to a support.

The flow splitter may be used in reverse.

The flow splitter may be made using a passage-making tool which is inserted through the port. The tool may be a drill.

Embodiments of the disclosure will now be described, by way of example, with reference to the following drawings, in which:

Figure 1 is an isometric view of an embodiment of a flow splitter;

Figures 2, 2a and 2b are side, rear and front views respectively of the flow splitter shown in Figure 1 ;

Figure 3 is a cross-sectional view of the flow splitter shown in Figure 1 , taken along the line Ill-Ill (Figure 2b);

Figure 4 is an isometric view of another embodiment of a flow splitter;

Figure 5 is a front view of the flow splitter shown in Figure 4;

Figure 6 is a cross-sectional view of the flow splitter shown in Figure 4, taken along the line VI-VI (Figure 5);

Figure 7 is a partial isometric view of a high pressure gas storage system;

Figure 8 is an isometric view of a further embodiment of a flow splitter;

Figure 9 is an isometric view of the flow splitter shown in Figure 8 with each outlet connected to an outlet pipe; and

Figure 10 is a cross-sectional view of one of the outlet connections of the flow splitter shown in Figure 9. With reference to Figures 1 to 3 (not all items are labelled in all figures), an embodiment of a flow splitter splits fluid flow from one inlet pipe (not shown) into equal fluid flows along four outlet pipes (not shown). The flow splitter, indicated generally at 1 , has a body 2, a port 6 and four passages 7 which extend through the body 2. The port 6 has a port bottom 42 which is the innermost side of the port 6. Each passage 7 has one end 32 which defines an opening 34 in the port 6 and another end 36 which defines an outlet 38 from the body 2. In use, fluid flows from the inlet pipe into the body 2, through the port 6, through the openings 34, through the passages 7 and out of the body 2 into the outlet pipes through the outlets 38.

In the region of the port 6, around the port 6, the body 2 is formed into a port part in the form of a boss 3. The port 6 is cylindrical in end (rear) view and its inner cylindrical surface 15 is threaded to receive a threaded pipe fitting (not shown). The inlet pipe fits onto the pipe fitting. Around the open mouth of the port 6, the cylindrical surface 15 is slightly flared to provide a pipe sealing surface 14. Essentially, the boss 3 provides a female part for mating connection with a male fitting on an end of the inlet pipe.

In the region of each outlet 38, around each outlet 38 and extending outwards from each outlet 38, the body 2 is formed into an outlet part in the form of a pipe connection 4. In the illustrated embodiment, each connection 4 is an SAE J514 hydraulic (37° flare) connection having a threaded section 21 (only indicated on one connection 4 in Figure 3) onto which a fitting (not shown) on an end of an outlet pipe is screwed. Flare 20 (only indicated on one connection 4 in Figure 3), assists fitting. Essentially, each connection 4 provides a male part for mating connection with a female fitting on an end of an outlet pipe.

The body 2 is one piece, being machined from a single block of suitable material, such as aluminium. The body material is continuous. The material of the boss 3 and each connection 4 are continuous with the material of the remainder of the body 2. Machining the body 2 from single block of material minimises the number of joints where inlet and outlet pipes are connected to the body 2. This is particularly preferable where the flow splitter 1 is to be used in a high pressure situation, such as, for example, in a natural gas fuel system for a truck, where joints come under high stress. Also, in some applications, again, such as, for example, a natural gas fuel system, a flow splitter needs to survive a significant number of cycles over a number of years in a hostile environment, and a one-piece body performs robustly under such conditions. The North American Standard NGV 3.1 requires a device like a flow splitter to withstand 50,000 cycles from 10% to 125% to 10% of normal working pressure (NWP). The ISO Standard ISO 15500-19 (2012) requires such devices to withstand 100,000 cycles from 2.5% to 150% to 2.5% of NWP.

At any part of the body 2, the thickness of body material is selected to be sufficient for the burst pressure to which that part might be exposed. In order to meet safety requirements, any part must be able to withstand many times its NWP. The North American Standard NGV 3.1 requires a device to survive 2.5 x NWP. The ISO Standard ISO 15500-19 (3012) requires it to survive 4 x NWP.

The direction of fluid flow through the port 6 is from right to left as viewed in Figure 3. The cylindrical axis C of the port 6 extends through a mid-point of fluid flow through the port 6 and is parallel with the direction of fluid flow. The cylindrical axis C therefore constitutes a flow axis through the port 6.

Each passage 7 is the same shape, that is, straight, in the case of the illustrated embodiment, and dimensions. The passages 7 are cylindrical and each has the same internal diameter. Also, the passages 7 are evenly distributed around the flow axis 7 such that, when viewed from the front, the passages 7 are equiangularly spaced by an angle a (see figure 2b). In addition, each passage 7 extends away from the port 6 to its respective outlet 38 in a generally diverging relationship to the flow axis C. An angle β (see figure 3) of divergence of each passage 7 is the same. Such a balanced geometry helps in splitting the fluid flow through the port 6 equally amongst the passages 7. In addition, it helps in achieving the same fluid pressure in each passage 7. Fluid flow rate through the splitter 1 is determined by the relative diameters of the manifold 30 and the passages 7. In general, the passages 7 are narrower than the port 6. If the number of passages 7 = N, for maximum flow, the port diameter > (passage diameter). N ^{0 5} . Having each passage 7 diverging from the flow axis C means that the outlets 38 are spaced apart thereby facilitating use of whatever tool (not shown), such as, for example, a spanner, is required to screw an outlet pipe fitting onto each connection 4. In high pressure applications, push-fitting an outlet pipe on to an outlet connection, for example, would be inadequate; a more robust screw fitting is required, but a screw fitting can only be manipulated if there is adequate space for the necessary tool.

Any sudden changes of direction of fluid flow through the flow splitter can cause pressure drops, which is why the passages 7 diverge from the flow axis at much less than 90°. Preferably the divergence angle β is around 30°, although a combination divergence angle β, body dimensions and outlet spacing can be selected as required. Also, the port bottom 42 is cone-shaped so that the passages 7 intersect the port bottom 42 in a generally perpendicular fashion. Again, this minimises sudden flow disruption.

Holes 5 in the body 2 enable it to be fastened to a support.

The passages 7 are preferably made in the body 2 by drilling. Having a relatively wide diameter to the manifold 30 facilitates insertion of a drill to make the passages 7.

With reference to Figures 4, 5 and 6, another embodiment of a flow splitter 1 is illustrated, which is the same in all respects as the flow splitter shown in Figures 1 to 3 (like parts have been given the same reference numbers), except that it has six, rather than four, passages 7, and the connections 4 are SAE J1453 O-ring seal connections.

With reference to Figure 7, a high pressure natural gas fuel system has four storage cylinders 50. The system is supplied with natural gas through an inlet pipe 52 which is connected to an inlet of a flow splitter 1A as illustrated in figures 1 to 3. Each of the outlets is connected to an outlet pipe 54, of smaller diameter than the inlet pipe 52, which feeds one of the cylinders 50 via a valve 56. The inlet pipe flow is divided equally between the outlet pipes 54 to fill the cylinders 50 equally and fully in parallel, in a reasonable amount of time. Each valve 56 comprises a thermal pressure relief device which has vent 60. Each vent 60 is connected to a vent pipe 58 which is connected to an "outlet" of a flow splitter 1 as illustrated with reference to Figures 1 to 3, operating in reverse, which combines the flows through the vent pipe 58.

With reference to Figures 8, 9 and 10, a further embodiment of a flow splitter 1 is illustrated, which is the same in all respects as the flow splitter shown in Figures 4 to 6 (like parts have been given the same reference numbers, although not all like parts are labelled), except that in the region of each outlet 38 each pipe connection 104 provides a female part for mating connection with a male fitting on an end of an outlet pipe. In addition, the boss 103 is in the shape of a square with rounded corners. As shown in Figure 8, the connections 104 take the form of circular holes formed in a raised disc 150 provided on the opposite face of body 2 to boss 103. The connections 104 are approximately equally spaced around the edge of raised disc 150. The connections 104 provide fluid communication through the flow splitter 1 through passages 7 (not shown) and port 6 as described in relation to the other embodiments. Blind hole 160 is formed in the centre of raised disc 150. Blind hole 160 has a square cross-section such that it can be engaged by an appropriate tool in order to assist in screwing inner cylindrical surface 15 (not shown in Figures 8-10) of port 6 onto a threaded pipe fitting (not shown). Figures 9 and 10 show the flow splitter 1 of Figure 8 with each connection 104 connected to an outlet pipe 200 using a tubing nut 210. It will be appreciated that only a short initial section of each outlet pipe 200 is depicted in Figures 9 and 10. As shown in more detail in the cross-sectional view of Figure 10, each outlet pipe 200 mates with each connection 104 using the SAE J 1453 O-ring Face-Seal format. Each outlet pipe 200 comprises outwardly extending flange 201 at a first end 202. Each flange 201 seats against a step 203 formed in each connection 104 where the fluid path through the flow splitter 1 widens from each passage 7 to each outlet 38. An annular depression 204 is provided in step 203, and an O-ring 205 is provided in the depression 204. In this way, the O-ring 205 seals against flange 201 . A male gland 206 is fitted around each outlet pipe 200 such that it seats against flange 201. A tubing nut 210 is fitted around each outlet pipe 200 at the opposite end of male gland 206 to flange 201. The end of tubing nut 210 which, in use, is closest to flange 201 is provided with annular gap 207 on its internal surface. Annular gap 207 is shaped to mate with the external surface of male gland 206. As the tubing nut 210 extends distally from male gland 206, it then comprises narrow section 208 which is a close fit around outlet pipe 210. Tubing nut 210 is provided with a screw thread 208a on its external surface which is shaped to mate with a corresponding screw thread 21 1 provided on the internal surface of each connection 104. At the end of the tubing nut 210 which is furthest from flange 201 , there is provided a hex 209, ie a section of hexagonal cross-section, for engagement by a suitable tool (not shown) in order to assist in screwing the tubing nut 210 into outlet 138. As is known in the art, other cross-sectional shapes could provide similar functionality. It is generally preferred for the type of connection shown in Figures 8-10 (ie a female part on the flow splitter) that the thread sizes for the threads 208a and 211 should be at least one thread size larger (typically 1/16") than the standard SAE threads. This allows the use of a thicker tubing nut 210.