GB2359638A

GB2359638A - Fluid flow regulator

Info

Publication number: GB2359638A
Application number: GB0102709A
Authority: GB
Inventors: Timothy Stephen Rice
Original assignee: Alstom Power NV
Current assignee: Alstom NV
Priority date: 2000-02-02
Filing date: 2001-02-02
Publication date: 2001-08-29
Anticipated expiration: 2021-02-02
Also published as: GB0102709D0; GB2359638B; GB2359638A9; GB0002285D0

Abstract

A fluid flow regulator (2) comprises a vortex chamber (6) in a primary fluid flow path (4), with a bypass fluid flow path (28) having bypass inlet means (26) from the primary fluid flow path (4) upstream of the vortex chamber, and bypass outlet means (38) into the primary fluid flow path through the vortex chamber (6). Vorticity (V) in the vortex chamber is a function of the amount of fluid entering the vortex chamber from the by-pass path, the impedance of the vortex chamber (6) to the flow of primary fluid (A) therethrough being a function of the vorticity. The impedance of the vortex chamber is varied by bypass valve means (30) in the bypass fluid flow path (28) which controls bypass fluid flow and thereby the strength of the vortex in the vortex chamber. The vortex chamber is preferably used in conjunction with a primary valve (16) located in the primary fluid flow path between the vortex chamber and the bypass inlet means to vary fluid flow between substantially zero and a maximum. The regulator may be used to control a supply of motive fluid to a turbine.

Description

2359638 1 FLUID FLOW REGULATION 1 This invention concerns regulation of

fluid flow, and in particular, but not exc lusively, a flow regulator for controlling fluid flow to a turbine.

It is known to utilise a vortex chamber to help control fluid flow through a flu id flow regulator. For example, US patent no. 4,131,134 discloses a fluidic regulator used as a replacement for mechanical control valves in internal combustion engine positive crankcase ventilation systems. The regulator controls the amount of fluid flowing through it by using a vortex chamber to provide a variable orifice valve function. The shape of the vortex chamber produces an acceleration in the fluid flowing through it which causes the flow itself to vary the flow impedance of the regulator in relationship to the pressure differential across the regulator.

In the above patent, it is explained that the inherent characteristics of the vortex chamber provide it with a flow impedance which is a square root function of the pressure differential between its inlet and outlet. Hence (apart from initial adjustments during setting up of the regulator), the vortex produced in the vortex chamber is self-regulating and the regulator itself requires no further control inputs during operation. However, such a device would not be suitable for, e.g., regulating steam flow to a steam turbine, or gas flow to a gas turbine, because, for example, control of such turbines requires their fluid flows to be regulated during operation of the turbines in dependence on a desired speed or torque of the turbine.

According to the invention there is provided a fluid flow regulator comprising: a primary fluid flow path, a vortex chamber in the primary fluid flow path, 2 a bypass fluid flow path having bypass inlet means from the primary fluid flow path upstream of the vortex chamber and bypass outlet means into the primary fluid flow path through the vortex chamber, vorticity in the vortex chamber being a function of the amount of fluid entering the vortex chamber from the by-pass path, the impedance of the vortex chamber to the flow of primary fluid therethrough being a function of the vorticity, and bypass valve means in the bypass fluid flow path for controlling fluid flow therethrough and thereby controlling the impedance of the vortex chamber.

Importantly, such a fluid flow control enables regulation of the fluid flow rate such that variation in the flow rate can be accomplished by relatively small changes in the amount of fluid flowing through the bypass means.

The fluid flow rate through the vortex chamber may vary in inverse relationship to the vorticity therein.

The fluid flow regulator is preferably provided with primary valve means in the primary fluid flow path for varying fluid flow therethrough between substantially zero and a maximum, the primary valve means being located between the vortex chamber and the bypass inlet means.

Such a fluid flow control can allow relatively rapid and substantially complete shut-off of the supply fluid by closure of both valve means and particularly the primary valve means.

The fluid flow regulator may be used to control the supply and flow rate of a variety of fluids for many desired purposes. Amongst those, we believe that it will be useful in the control of motive fluid supplied to turbines. For example, we believe that in the field of turbomachinery applications for the

3 fluid flow control exist in connection with steam turbines, gas turbines, and water turbines. Provided the fluid flow regulator includes the primary valve means, it can utilise changes in vorticity not only to control flow rate of the supply or motive fluid but can also accomplish an emergency rapid shut-off of the motive fluid. An instance where this is highly desirable is where a turbine is driving an electrical power generating means and the electrical load demand suddenly disappears.

The primary valve means may comprise a valve seat and a valve member moveable relative to the valve scat, with an upstream part of the vortex chamber comprising the first valve seat. The primary valve means may be a shuttle valve whereby the valve member is moveable upstream and downstream in the primary fluid flow path. This shuttle valve is conveniently adapted to operate in response to pressure differences between the bypass flow path and a lower pressure location.

The vortex chamber may comprise a converging section converging in a downstream direction towards a throat and a diverging section diverging in a downstream direction away from the throat. The converging section may comprise the valve seat.

Preferably, the bypass outlet means comprises a plurality of passages adapted to direct the fluid from the by-pass means into the vortex chamber substantially tangentially to an internal bore of the chamber. The bypass outlet means may open into the vortex chamber at or substantially at the throat.

If desired the flui.d flow regulator may be in combination with a turbine, and the fluid which flows through the regulator may be motive fluid for the 4 turbine. The turbine may drive electrical power generating means and may be, for example, a steam turbine.

The invention will now be further described, by way of example, with 5 reference to the accompanying drawings in which:

Figure 1 is a diagrammatic representation of a fluid flow regulator according to the invention in an initial, or non-operational, state; Figures 2 to 4 are representations of the fluid flow regulator in Figure 1 in different respective operational states, and Figure 5 is a diagrammatic representation of a cross-section of a throat of a venturi passage used in the regulator of Figures 1 to 4.

With reference to Figure 1 a fluid flow regulator 2 controls flow in the direction of arrow A through a primary fluid flow path comprising a pipe or passage 4. The fluid may be liquid or gas or vapour, but the design as shown is intended as a steam flow admission system for a steam turbine, and in this cage the steam would therefore be at a high temperature and pressure. The passage 4 includes a vortex chamber 6, which is a conduit section formed as a diffuser or venturi comprising a narrow section or throat 8, an upstream converging section 10, and a downstream diverging section 12. Production of the vortex flow in the vortex chamber occurs as described later.

The converging section 10 of the venturi provides a valve seat for a reciprocating primary or shut-off valve 16, which varies fluid flow through it between substantially zero and a maximum. This conveniently takes the form of a shuttle valve mounted in the passage 4 upstream of the venturi and comprises a piston rod 18, a pintle valve member 14 mounted on the downstream end of the rod to co-operate with the valve scat 10, and a double acting piston 20 mounted on its upstream end- The double acting piston 20 slides within a cylinder 22, which is supported on circumferentially spaced radial struts 24 extending between the cylinder and the inner wall of 5 the passage 4.

Upstream of shuttle valve 16 is an opening 26 providing an inlet to a bleed or by-pass path 28 which may be closed and opened by a bypass valve 30 comprising a valve member 32 which can be moved into contact with, or away from, a co-operating valve seat 34. Downstream of bypass valve 30, the by-pass 28 opens into an annular manifold 36 running peripherally of the venturi throat 8. From manifold 36 lead an array of equi-angularly spacedapart passages comprising bores 38 (see Figure 5) opening into the venturi throat 8 in an annular disposition therearound. The bores 38 are each directed substantially tangentially to the inner wall of the venturi throat 8 so that bypass flow 28 is injected tangentially into the venturi throat, thereby establishing vortex flow in the vortex chamber 6. Although probably giving a less than optimum.result, it would also be possible to obtain vortex flow by injecting the bypass flow into the vortex chamber somewhat downstream of the throat 8.

To operate the primary or shuttle valve 16, the cylinder 22 has two inlet/outlet ports connected by respective conduits 40 and 42 to respective inlet/outlet ports of a distribution valve 44 which may comprise a solenoid operated spring-biased spool valve. The distribution valve 44 also has two outlet ports connected by respective conduits 46 and 48 to exhaust or drain means (not shown) at differing pressures. In a steam turbine, conduit 46 is conveniently connected to a vacuum, e.g. a condenser, and conduit 48 may be connected to a mid-point in the cycle. A further inlet port 50 is connected 6 by conduit 52 to the higher pressure in the by-pass 28 at a point between the bypass valve 30 and the by-pass inlet 26.

Continuing with Figures 1 to 4 for a description of operational modes, the invention provides fully adjustable control of flow along primary flow path 4 through regulator 2. Working from the no-flow condition up to full flow:

(1) Figure 1 shows primary valve 16 and bypass valve 30 both closed, with no flow through the regulator 2.

(2) In Figure 2, variable opening of the bypass valve 30 allows for fine control of low flow rates, primary valve 16 still being fully closed.

(3) Figure 3 shows the primary valve 16 and bypass valve 30 both in the fully open position, with the tangentially injected bypass flow causing a strong vortex V in vortex chamber 6, so maximising its flow impedance and minimising flow past primary valve 16. However, the flow impedance of the vortex chamber can be selectively varied over a range by varying the position of the bypass valve to increase or decrease the strength of the vortex, whereby the overall flow rate through regulator 2 can readily be varied.

(4) Finally, in Figure 4, complete closing of the bypass valve 30 eliminates the vortex, the vortex chamber 6 now having a minimum impedance so that a maximum flow rate is allowed by regulator 2.

Referring to the operational mode illustrated by Figure 1 in more detail, in a start-up or non-operational state of the flow regulator 2, primary valve 16 and bypass valve 30 are closed and the distributor valve 44 connects conduit to exhaust via conduit 46 whilst conduit 42 is connected to a supply of fluid under pressure via conduit 52 from the by-pass 28. With primary valve 16 closed, any fluid in primary flow path 4 cannot pass the valve, and none at all may get downstream of the primary valve 16 whilst the bypass valve 30 is also closed.

7 : 1 1 Turning to Figure 2, when bypass valve 30 is opened, fluid from passage 4 goes via the by-pass 28 to the vortex chamber/venturi 6, the primary valve 16 being still closed. The disposition of the bores 38 (see Figure 5) encourages by-pass fluid emerging therefrom to swirl in spiral or vortex flow V downstream of the valve 16. The vorticity (the amount or strength of the vortex flow) is a function of the extent to which valve 30 is open- the more valve 30 is open the greater the vorticity.

Now when the distribution valve 44 is operated to adopt the position in Figure 3 so that the conduits 52 and 40 are connected and the conduit 42 is connected to exhaust through conduit 48, the piston 20 moves to the right under pressure of the fluid from the by-pass path 28, thereby opening the primary valve 16. Hence, fluid in primary flow path 4 can flow past valve member 14 and enter the vortex chamber 6, where it encounters the vortex V. It is thereby induced to swirl and join the vortex motion. With the primary valve 16 fully open as shown in Figure 3, the total flow through the system (i.e., the fluid flow rate along passage section 4A downstream of regulator 2) is moderated by the level or amount of induced swirl. The more the bypass valve 30 is open, and in Figure 3 it is about fully open, the stronger the vorticity and the lower the fluid flow rate at section 4A. In a steam turbine, for example, the valve 30 could'be automatically moved in accordance with a schedule to attain desired turbine speeds or torques.

When it is desired to provide a full supply of fluid without modulation of the flow rate (e.g., when a turbine being supplied is operating at full power), the valve 30 is closed as in Figure 4 to stop engendering of the vortex in vortex chamber/venturi 6. Should it be desired to rapidly stop supply of fluid to passage section 4A (e.g., to effect rapid shutdown of a turbine), operation of the distributor valve 44 causing it to go to its position in Figure 1 can 0 8 cause rapid closure of the primary valve 16 due to fluid pressure in conduit 42. If the valve 30 is open, it too can be closed quickly to prevent bypass fluid supply to the vortex at bores 38.

Although utility of the regulator 2 in control of steam flow to a steam turbine has been particularly mentioned, the fluid supplied along passage 4 may alternatively be gaseous products of combustion for driving a gas turbine, or a liquid, for example water to drive a water turbine. Any of these turbines may be used to drive an electrical generator to produce electrical 10 power.

9

Claims

1. A fluid flow regulator comprising: a primary fluid flow path, a vortex chamber in the primary fluid flow path, a bypass fluid flow path having bypass inlet means from the primary fluid flow path upstream of the vortex chamber and bypass outlet means into the primary fluid flow path through the vortex chamber, vorticity in the vortex chamber being a function of the amount of fluid entering the vortex chamber from the by-pass path, the impedance of the vortex chamber to the flow of primary fluid therethrough being a function of the vorticity, and bypass valve means in the bypass fluid flow path for controlling fluid flow therethrough and thereby controlling the impedance of the vortex chamber.

2. A fluid flow regulator according to claim 1, provided with primary valve means in the primary fluid flow path for varying fluid flow therethrough between substantially zero and a maximum, the primary valve means being located between the vortex chamber and the bypass inlet means3. A fluid flow regulator according to claim 2, in which the primary valve means comprises a valve seat and a valve member moveable relative to the valve seat, with an upstream part of the vortex chamber comprising the first valve seat.

4. A fluid flow regulator according to claim 3, in which said primary valve means is a shuttle valve whereby the valve member is moveable upstream and downstream in the primary fluid flow path.

5. A fluid flow regulator according to any preceding claim, in which the vortex chamber comprises a converging section converging in a downstream direction towards a throat and a diverging section diverging in a downstream direction away from the throat.

6. A fluid flow regulator according to claim 5 as dependent on claim 3 or claim 4, in which the converging section of the vortex chamber comprises the valve seat.

7. A fluid flow regulator according to claim 5 or claim 6, in which said bypass outlet means comprises a plurality of passages adapted to direct the fluid from the by-pass means into the vortex chamber substantially tangentially to an internal bore of the chamber.

8. A fluid flow regulator according to claim 7, in which said bypass outlet means opens into the vortex chamber at or substantially at the throat.

9. A fluid flow regulator according to any of claims 2 to 8, in which the p rimary valve means is operable in response to fluid pressure.

10. A fluid flow regulator according to claim 9, in which the primary valve means is a shuttle valve adapted to operate in response to pressure differences between the bypass flow path and a lower pressure location.

11. A fluid flow regulator according to any preceding claim, in which the rate of flow of fluid in the primary fluid flow path varies in an inverse relationship to the vorticity in the vortex chamber.

12. A fluid flow regulator substantially as hereinbefore described with 30 reference to the accompanying drawings.

13. A fluid flow regulator according to any preceding claim in combination with a turbine, the regulator acting to control flow of motive fluid to the turbine.

14. A combination according to claim 13, in which said motive fluid is steam and the turbine is a steam turbine.