GB2231685A - Flow control - Google Patents

Abstract

A fluidic amplifier 2 is located in a fluid flow line to control the fluid flow rate. The amplifier has an inlet 3 leading into a central chamber and an outlet 4 leading from that chamber. There is at least one further inlet 8 for supplying control fluid to the chamber within the amplifier. The (or each) inlet for control fluid is connected to the main fluid flow line so that fluid from the main fluid flow line is used as control fluid for the amplifier. <IMAGE>

Description

DESCRIPTION OF INVENTION A flow control arrangement.

THE PRESENT INVENTION relates to a flow control arrangement and more particularly a flow control arrangement incorporating a fluidic amplifier such as a vortex amplifier to control the flow conditions.

A vortex amplifier is a fluidic control device having no moving parts which operates as a flow control valve when connected in a fluid flow line.

A conventional vortex amplifier is described in U.K.

Patent No. 1585519 and comprises a casing having a supply fluid inlet extending into a vortex chamber and an outlet leading from the chamber into a diffuser. A plurality of control fluid inlets also extend into the vortex chamber in a tangential direction. Control fluid enters the vortex chamber via the control fluid inlets and mixes with the supply fluid and generates a vortex in the vortex chamber.

The quantity of control fluid supplied to the vortex chamber dictates the throttling effect on the supply fluid. An increase in the quantity of control fluid results in a decrease in the total flow out of the vortex chamber.

The control fluid is supplied to the vortex chamber by means of a fan or the like which is separate from the main system in which the amplifier is incorporated.

Alternatively the control fluid may be drawn into the vortex chamber directly from the ambient air outside of the amplifier. The control fluid may be supplied at a positive or negative pressure i.e. a pressure above or below atmospheric pressure and may be supplied in response to pressure fluctuations in the main flow line in which the amplifier is incorporated.

The present invention seeks to provide an improved flow control arrangement incorporating a fluidic amplifier.

According to the present invention there is provided a flow control arrangement in a fluid flow line, the arrangement incorporating a fluidic amplifier located in the fluid flow line, the amplifier having a supply fluid inlet leading into, and an outlet leading from, a chamber within the amplifier, there being at least one further inlet for supplying control fluid to the chamber within the amplifier, the or each control fluid inlet being connected to the main fluid flow line such that fluid from the main fluid flow line is used as control fluid for the amplifier.

The or each control fluid inlet may be connected to the main fluid flow line at a position downstream of the amplifier. A fan may be located in the main fluid flow line at a position downstream of the amplifier, the control fluid inlet being connected to the main fluid flow line at a position downstream of the fan.

Preferably, a control valve located in the line leading to the control fluid inlet is operable to regulate the supply of control fluid in response to a sensing device located in a part of the system in which the'arrangement is incorporated. I The sensing device may be a temperature or pressure sensor.

Preferably the amplifier is a vortex amplifier.

In order that the present invention may be more readily understood and so that further features thereof will be appreciated, the invention will now be described by way of example with reference to the accompanying drawings in which: FIGURE 1 is a schematic illustration of a flow control arrangement in accordance with the present invention; FIGURES 2 and 3 correspond to Figure 1 and illustrate a sensing device located at varying positions in the flow control arrangements.

Referring initially to Figure 1 of the accompanying drawings a flow control arrangement is illustrated as being connected to a chamber 1, which may in practice be a room within a building where the air must be maintained at certain desired conditions, such as at a predetermined temperature or pressure.

The flow control arrangement incorporates a vortex amplifier 2 connected to the chamber 1 via an inlet line 3.

The vortex amplifier 2 is of the conventional type such as is described above and in U.K. Patent No. 1585519. Thus, air enters the vortex chamber of the vortex amplifier 2 from inlet 3 in a substantially radial direction. The amplifier has an outlet line LI through which air leaves the vortex chamber in an axial direction. Flow along a main fluid flow line through the ,vortex amplifier is indicated by arrows 5 shown upon the inlet line 3 and outlet line 4.

The outlet line 4 extends to the suction side of a fan 6, - the discharge side of which may pass directly to atmosphere or into a ducted system via a line 7.

The vortex amplifier 2 has a plurality of control ports 8, only one of which is illustrated in the drawings. The control ports 8 extend into the vortex chamber of the vortex amplifier, as in a conventional vortex amplifier. Control fluid is supplied to the vortex chamber via the control fluid inlet 8 and the quantity of control fluid supplied to the vortex chamber determines the throttling effect on the main flow through the amplifier.

The control fluid inlet ports 8 are connected by a line 9 to the main fluid flow line at a position downstream of the fan 6. A valve 10 is provided in the line 9 to regulate the quantity of control fluid passing into the vortex chamber of the vortex amplifier. The valve 10 may be coupled to a sensing device 11 fitted to the chamber 1. The device 11 may be a pressure or temperature sensing device and would transmit signals to the control valve 10 which would move accordingly to vary the flow of control fluid into the vortex amplifier which in turn increases or decreases the main fluid flow so as to maintain the desired conditions in the chamber 1.

Depending upon the characteristics of the system in which the control arrangement is provided and upon the flow and pressure generated in the line 7 on the discharge side of the fan 6, it may prove necessary to incorporate a restrictive device 12, such as an orifice plate, manual damper or valve downstream of the point at which the line 9 is connected to the line 7.

In use air from the chamber 1 is drawn into the vortex chamber of the vortex amplifier 2 via the inlet line 3, where it mixes with the control fluid entering the vortex chamber via the control fluid inlet 8. The air subsequently leaves the vortex amplifier via the outlet line 4 passing through the fan 6 and down the line 7 on the discharge side of the fan 6. A small proportion of the main flow passing down the line 7 is diverted along the line 9 and enters the vortex amplifier as control fluid. Thus the control fluid for the vortex amplifier is taken from the main fluid flow line in which the amplifier is located. Approximately 5 to 10% of the main flow passing along the line 7 is required as control fluid.

It will be appreciated that a flow control arrangement in accordance with the present invention is a self contained unit. This arrangement results in significant savings in costs since no external power source is required to supply the pressurized control fluid. In addition maintenance is simplified since there is no separate power source for the control fluid requiring any maintenance.

In addition the risk of contamination within a system in which the control arrangement is located is reduced since the system fluid will be substantially homogenous in certain applications, in contrast with previous arrangements in which the control fluid is drawn from a separate source.

This enables filters on the vortex amplifier control fluid inlet ports to be dispensed with, since any contaminants will be collected by the filters within the system in which the arrangement is incorporated.

In systems which have more than one fan, each performing a different duty, but connected to a common duct or chamber, for example a main fan and a recirculating fan in an air handling unit, it would be possible to use the fluid discharged from one fan as control fluid in a control arrangement associated with the other fan.

Figures 2 and 3 correspond to the arrangement shown in Figure 1 of the drawings, but with the sensing device 11 located at different positions in the arrangement. Thus, in Figure 3 the sensing device 11 is located between the chamber 1 and the vortex amplifier 2 in the inlet duct 3, whilst in the arrangement shown in Figure 4 the sensing device 11 is located between the vortex amplifier 2 and the fan 6 in the outlet line 4.

It will be appreciated that other minor modifications to the above-described arrangements may be made within the scope of the present invention. It is also to be appreciated that the arrangement may be used to control the flow of a gas or a liquid.

Claims (8)

1. A flow control arrangement in a fluid flow line, the arrangement incorporating a fluidic amplifier located in the fluid flow line, the amplifier having a supply fluid inlet leading into, and an outlet leading from, a chamber within the amplifier, there being at least one further inlet for supplying control fluid to the chamber within the amplifier, the or each control fluid inlet being connected to the main fluid flow line such that fluid from the main fluid flow line is used as control fluid for the amplifier.

2. An arrangement according to Claim 1 wherein the or each control fluid inlet is connected to the main fluid flow line at a position downstream of the amplifier.

3. An arrangement according to Claim 2 wherein a fan is located in the main fluid flow line at a position downstream of the amplifier, the control fluid inlet being connected to the main fluid flow line at a position downstream of the fan.

LI. An arrangement according to any one of the preceding claims wherein a control valve located in the line leading to the control fluid inlet is operable to regulate the supply of control fluid in response to a sensing device located in a part of the system in which the arrangement is incorporated.

5. An arrangement according to Claim 4 wherein the sensing device is a temperature or pressure sensor.

6. An arrangement according to any one of the preceding claims wherein the amplifier is a vortex amplifier.

7. An arrangement substantially as herein described with reference to and as shown in any one of the accompanying drawings.

8. Any novel feature or combination of features disclosed herein.