GB2259329A

GB2259329A - Fluidic entrainment device

Info

Publication number: GB2259329A
Application number: GB9215436A
Authority: GB
Inventors: Geoffrey Hugh Priestman
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1991-09-06
Filing date: 1992-07-21
Publication date: 1993-03-10
Also published as: GB9215436D0

Abstract

A fluidic entrainment device 10 has two cylindrical vortex chambers 11, 12 with communicating axial ports 18 in adjacent end walls 14 of the vortex chambers. Each vortex chamber also has an entraining fluid inlet or outlet port 10 in its peripheral wall 15 and at least one of the chambers an axial inlet port 17 for a fluid to be entrained in its other end wall 13. The entraining fluid enters one of the chambers 12a via one of the peripheral wall ports and creates a vortex flow. A lower pressure region is generated towards the centre of the flow which entrains or draws in fluid from its axial port 17. The fluid mixture passes through a communicating line 21 to the other chamber and exits via its peripheral wall port possibly drawing in further fluid through the other port 17, if provided. The invention aims to overcome problems of cavitation evident in similar devices. <IMAGE>

Description

Fluidic Entrainment Devices This invention relates to fluidic entrainment devices.

Fluidic components for entraining fluids normally rely on a driving jet entraining fluid into a mixing tube and/or diffuser. Examples of such components are the jet pump or ejector and the reverse flow diverter (RFD), an example of which is shown in British patent (1,480,484).

A fundamental limit to the performance of such devices operating with liquids is set by cavitation.

According to this invention a fluidic entrainment device comprises two vortex chambers each having end walls and a peripheral wall, a port in each peripheral wall, an axial port in at least one of the end walls of each vortex chamber and an axial port in one chamber in communication with an axial port in the other chamber.

The ports in the peripheral walls may be tangential and provided with diffusers.

The non-communicating axial ports may each have a converging inlet tube.

The invention may be performed in various ways and one specific embodiment with possible modifications will now be described by way of example with reference to the accompanying drawing which is an exploded view of a vortex entrainer.

In the vortex entrainer the driving force for entraining fluid is provided not by a jet of fluid but by low pressure at the centre of a fluid vortex. The expectation is that because of this fundamentally different entrainment mechanism, the performance should not be limited by cavitation in the normal way.

As with jet pumps and ejectors, the entrainer could be unsymmetrical, i.e. designed to give high performance in one flow direction, or symmetrical like an RFD, in which performance is the same for two directions of flow.

Figure 1 shows an exploded view of a basic symmetrical vortex entrainer 10. The entrainer comprises two hollow vortex devices 11, 12. The device 11 has parallel flat generally circular axially spaced end walls 13, 14 connected by an axial peripheral wall 15 to provide a vortex chamber gila. A conical input tube 16 leads to a central circular port 17 in the wall 13 of the vortex chamber lla, the tube 16 decreasing in crosssection area as it extends towards the port 17. The wall 14 has a central circular port 18 of greater diameter than the port 17.

A tangential port 19 is formed in the wall 15 communicating with a tube 20, the tube 20 diverging as it extends away from the port 19.

The device 12 is similar to the device 11 and the ports 18 of devices 11, 12 are connected by a tube 21.

The tube 21 can be omitted and the walls 14 made to abut, or a single wall 14 can be common to the devices 11, 12.

In one direction of operation, liquid flow enters at the tangential port 19 in the device 12 and forms a vortex in the vortex chamber 12a. The flow passes through the central port 18 into the tube 20 and through the other port 18 into the vortex chamber lla from where the flow exits at the other tangential port 19, in the device 11. The low pressure created at the centre of the fluid vortices in chambers lla, 12a entrains flow into the device 10 via inside and outside entrainment ports 17. The basic design in Figure 1 is symmetrical, in that the same geometry is presented to inlet flow entering at either tangential port 19. In a symmetrical device of course inlet and outlet chamber dimensions correspond.

In this basic design the tangential ports 19 have diffusers 20 to give static pressure recovery from the exiting flow stream. This aids entrainment, giving the device better performance characteristics under output load. However the tubes 20 and 16 could be omitted.

In some cases one of the ports 17 can be closed so that entrainment occurs only at the other port 17.

Figure 1 shows the ports 19 as rectangular but they could be circular with the tubes 20 being conical diffusers.

The axial dimension of the wall 15 can be reduced to increase the action of the devices 11, 12 as radial diffusers of outward flow from the centres of chambers lla, 12a.

In an alternative version of the invention which is intended to operate with one direction of flow only, one chamber 12a, is used as an inlet chamber and the other, lia, is used as an outlet chamber. In this arrangement, there is no need for the tube 20 associated with the outlet chamber lla to be tangential to it. Also, the communicating ports 18 need not be the same, they can be arranged to facilitate flow from the inlet vortex chamber 12a to the outlet vortex chamber lla. Furthermore, the port 17 and its associated conical inlet tube 16 can be omitted from the outlet chamber 1lea.

The entrainer can be used for mixing or separating liquids or for effecting or assisting chemical reactions.

The various dimensions of the devices 11, 12 can be changed and the operating characteristics obtained by experiment.

Claims

1. A fluidic entrainment device comprises two vortex chambers each having end walls and a peripheral wall, a port in each peripheral wall, an axial port in at least one of the end walls of each vortex chamber and an axial port in one chamber in communication with an axial port in the other chamber.

2. An entrainment device according to Claim 1 wherein each vortex chamber is matched with the other so that the action of the vortex entrainer is insensitive to the direction of flow of the entraining fluid.

3. A fluidic entrainment device according to Claim 1 and 2 wherein the ports in the peripheral walls of the vortex chambers are adapted to inject fluid into the vortex chambers tangentially.

4. A fluidic entrainment device according to Claims 1, 2 or Claim 3 wherein the ports in the peripheral walls of the vortex chambers are provided with diffusers.

5. A fluidic entrainment device according to any of Claims 1 to 4 wherein the non-communicating axial inlet ports each have associated with them a converging inlet tube.

6. A fluidic entrainment device according to Claim 1 wherein the two vortex chambers are dissimilar so that fluid flow through device occurs preferentially in one direction.

7. A fluidic entrainment device substantially as hereinbefore described and with reference to the accompanying drawings.