GB2064764A - Gas sampling equipment - Google Patents

Abstract

A plurality of probes (11, Fig. 1) mounted on a rotor 13 sample gas from respective zones of a flame tube to assess, for example, the temperature and/or pressure distribution characteristics thereof. The rotor 13 includes a rotatable shaft 18 in face engagement with a surrounding fixed sleeve 19, and gas passes in use from each probe along a pipe 21 to gas analysing equipment (not shown) by way of a respective annular recess 23 in the shaft 18 and an aligned respective part 24 in the sleeve 19, parts 24 and pipes 25 communicating with respective water-cooled pipes leading to the measuring heads. Disposed between each pair of adjacent recesses 23 are a pair of axially spaced seals 30, and a recess 32 opens onto the internal surface of the sleeve 19 between these seals. In the event of gas leaking past either of the seals 30 in each pair, such as would affect the measurement being carried out, the leakage gas will flow into the respective recess 32 where it can be detected. <IMAGE>

Description

SPECIFICATION Gas sampling equipment This invention relates to gas sampling equipment particularly, though not exclusively, for use in analysing the combustion products and measuring the pressure distribution in an annular flame tube.

According to the present invention, there is provided gas sampling equipment comprising a probe arranged to obtain a sample of gas in use, a rotatable structure on which the probe is mounted, the rotatable structure including a member which is in face engagement with a fixed member having a gas passage therein, a recess in the engaging faces of said members, the recess extending in the direction of rotation of the rotatable structure and providing communication between the probe and the gas passage in a plurality of angular positions of the rotatable structure, and means sealing said engaging faces against the flow of gas between said recess and the surrounding atmosphere, the sealing means including passageway means opening onto said engaging surfaces such that any gas leaking through the sealing means flows into the passageway means.

Preferably, said members are in the form of a shaft and a surrounding sleeve, the external surface of the shaft being in face engagement with the internal surface of the sleeve, and the recess extends circumferentially of said surfaces. Conveniently, the recess is annular and the sealing means is composed of two sealing arrangements which are spaced apart in the direction of extent of the rotation axis of the rotatable structure and between which said recess is disposed, each sealing arrangement including a pair of axially spaced annular seals having disposed therebetween an annular recess which forms part of the passageway means.

Also according to the present invention, there is provided gas sampling equipment comprising a plurality of probes each of which is arranged to obtain a sample of gas in use, a rotatable structure on which the probes are mounted, the rotatable structure including a member which is in face engagement with a fixed member having a plurality of gas passages therein a plurality of recesses in the engaging faces of said members, each recess extending in the direction of rotation of the rotatable structure and providing communication between a respective one of the probes and a respective one of the gas passages in a plurality of angular positions of the rotatable structure, and means sealing said engaging faces against the passage of gas from one recess to another, the sealing means including passageway means opening onto said engaging surfaces such that any gas leaking through the sealing means flows into the passageway means.

Desirably, said members are in the form of a shaft and a surrounding sleeve, the external surface of the shaft being in face engagement with the internal surface of the sleeve, and the recess extends circumferentially of said surfaces. Advantageously, the recesses are annular and are spaced apart in the direction of extent of the rotation axis of the rotatable structure, and the sealing means includes a pair of axially spaced annular seals disposed between each pair of adjacent recesses, the annular seals in each pair having disposed therebetween an annular recess which forms part of the passageway means.

Preferably, the passageway means is disposed in the fixed member.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view, partly in section, of gas sampling equipment according to the present invention; and Figure 2 is a sectional side view of part of the equipment shown in Fig. 1.

Referring to the drawings, the gas sampling equipment illustrated therein is intended for use in measuring the performance characteristics of an annular flame tube (not shown), and is arranged to measure the variation of certain parameters of the flame tube in both the radial and circumferential directions thereof.

To this end, the equipment is provided with three measuring heads each of which includes seven probes spaced apart radially of the flame tube, the measuring heads being movable circumferentially of the flame tube in a manner to be described. One of the measuring heads (henceforth referred to as the "pressure measuring head") is arranged to measure the pressure distribution characteristics of the flame tube, and the probes thereof are of the total head pickup or pilot type. The second measuring head (henceforth referred to as the "temperature measuring head") is arranged to measure the temperature distribution characteristics of the flame tube, and its probes each includes a thermocouple. For the sake of clarity, neither of these measuring heads is shown in the drawings.The third measuring head, which is depicted at 10 in Fig. 1, is used to analyse the combustion products of the flame tube, the probes 11 thereof each being arranged to obtain a sample of gas from a respective radial zone of the flame tube.

The measuring heads are mounted by way of respective hollow arms 1 2 on a rotor 1 3 which is rotatably supported in a housing 14 by means of bearings 15, the measuring heads being equi-angularly spaced about the rotation axis of the rotor. A bevel gear form 1 6 is fixed to the rotor 1 3 and is engaged by a bevel gear 17, so that the rotor can be rotated through a full 360 by suitable rota tion of the gear 17, thereby moving the measuring heads circumferentially of the flame tube.

The rotor 1 3 includes a shaft 1 8 which is surrounded by a sleeve 1 9 fixed to the housing 14, the external surface of the shaft 1 8 being in face engagement with the internal surface of the sleeve 1 9. The shaft 1 8 has a plurality of axial drillings 20 which are angularly spaced about the rotation axis of the rotor 13, each drilling 20 being connected by means of a pipe 21 either to a respective one of the probes 11 of the gas analysing head 10 or to a respective one of the probes of the pressure measuring head.The axial drillings 20 terminate at different points along the length of the shaft 1 8 and each communicate by way of a radial drilling 22 with a respective one of a series of axially spaced annular recesses 23 in the external surface of the shaft 1 8. Each of the annular recesses 23 is in axial registration with a respective port 24 in the sleeve 1 9, each port 24 being connected to a respective pipe 25 by means of an elbow joint 26. The pipes 25 are led through a conduit 27 to a connection member 28 having a series of angularly spaced connectors 29 (only one of which is shown) in its side wall, each pipe 25 communicating with a respective one of the connectors 29.By virtue of the registration of the ports 24 in the sleeve 1 9 with the annular recesses 23 in the shaft 18, the connectors 29 remain in communication with the respective probes in all angular positions of the rotor 1 3. In use, those connectors which are associated with the probes 11 of the gas analysing head 10 are connected to gas analysing equipment (not shown), and those connectors which are associated with the probes of the pressure measuring head are connected to pressure measuring equipment (also not shown).

In order that the gas samples obtained by the probes of the gas analysing head and the pressure measuring head are not affected by their passage across the engaging surface of the shaft 18 and the sleeve 19, the annular recesses 23 in the shaft are sealed from each other and from the surrounding atmosphere by respective sealing arrangements, one such sealing arrangement being provided between each pair of adjacent recesses 23 and further sealing arrangements being disposed between the ends of the sleeve 1 9 and the recesses 23 adjacent thereto. Each sealing arrangement includes a pair of axially spaced annular seals 30 accommodated within respective grooves 31 in the external surface of the shaft 18, and an annular recess 32 disposed between the axially spaced seals 30 in the internal surface of the sleeve 19.The recesses 32 communicate with a common axially extending passage 33 in the sleeve 19, the passage 33 in turn being connected to a pipe 34 by way of an elbow joint 35. The pipe 34, like the pipes 25, is led through the conduit 27 to the connection member 28 and communicates with a connection 35 in the latter. In use, the connection 35 is connected to a gas detector (not shown).

In the event of there being any leakage of gas through any of the sealing arrangement, such as would affect the analysis or measurements being carried out in use, the leaking gas in its passage through the sealing arrangement will flow into the passage 33 via the respective annular recess 32, and can therefore be detected by the gas detector.

The conduit 27 serves not only to lead the pipes 25 and 34 to the connection member 28, but also to convey cooling water to the gas sampling equipment, and to this end the conduit 27 is provided with a water inlet 36 at its end adjacent the connection member 28. At its other end, the conduit 27 opens onto a tubular casing 37 which surrounds the sleeve 1 9 with clearance, an annular chamber 38 being defined between the casing 37 and the sleeve 1 9 on which the elbow joints 26 and 35 are accommodated. The annular chamber 38 communicates via a port 39 with an annular space 40 in the interior of the shaft 18, the space 40 being defined between a side wall of a bore which extends axially along the shaft 18 and a tubular member 41 which is mounted in the bore with clearance.

The annular space 40 opens into a chamber 42 in an enlarged end portion of the shaft 18, the chamber 42 in turn communicating with the interior of each arm 1 2. Cooling water is thus supplied to the measuring heads by way of the inlet 36, conduit 27, tubular casing 37, annular chamber 38, port 39, annular space 40, chamber 42 and the arms 1 2.

A return path for the water is provided by a pipe member 43 housed within each arm 12 and communicating with the interior of the tubular member 41 at an enlarged end portion 44 of the latter. The opposite end of the tubular member 41 communicates with a water outlet 45 by way of a port 46. Water thus flows back from the measuring heads via the pipe member 43, the interior of the tubular member 41, the port 46 and the outlet 45.

Connections 47 from the thermocouples in the temperature measuring head pass along the respective arm 1 2 and enter the interior of the tubular member 41 at the enlarged end portion 44 thereof. The connections 47 pass along the interior of the tubular member 41 to emerge from the shaft 18 at an end thereof remote from the measuring heads. Electrical leads 48 from the connections are wrapped around a tubular former 49 secured to said end of the shaft so that they can coil around and uncoil from the former as the rotor is rotated in use, and pass to appropriate measuring equipment (not shown) via a conduit 50.

An air/water vent is provided which is connected to a pipe 51 via an elbow joint 52 mounted on the sleeve 1 9 (see Fig. 1), the pipe 51 being led along the conduit 27 and communicating with a connection (not shown) similar to the connection 35 in the end surface of the connecting member 28.

Claims (8)

1. Gas sampling equipment comprising a probe arranged to obtain a sample of gas in use, a rotatable structure on which the probe is mounted, the rotatable structure including a member which is in face engagement with a fixed member having a gas passage therein, a recess in the engaging faces of said members, the recess extending in the direction of rotation of the rotatable structure and providing communication between the probe and the gas passage in a plurality of angular positions of the rotatable structure, and means sealing said engaging faces against the flow of gas between said recess and the surrounding atmosphere, the sealing means including passageway means opening onto said engaging surfaces such that any gas leaking through the sealing means flows into the passageway means.

2. Gas sampling equipment as claimed in claim 1, wherein said members are in the form of a shaft and a surrounding sleeve, the external surface of the shaft being in face engagement with the internal surface of the sleeve and the recess extends circumferentially of said surfaces.

3. Gas sampling equipment as claimed in claim 2, wherein the recess is annular and the sealing means is composed of two sealing arrangements which are spaced apart in the direction of extent of the rotation axis of the rotatable structure and between which said recess is disposed, each sealing arrangement including a pair of axially spaced annular seals having disposed therebetween an annular recess which forms part of the passageway means.

4. Gas sampling equipment comprising a plurality of probes each of which is arranged to obtain a sample of gas in use, a rotatable structure on which the probes are mounted, the rotatable structure including a member which is in face engagement with a fixed member having a plurality of gas passages therein, a plurality of recesses in the engaging faces of said members, each recess extending in the direction of rotation of the rotatable structure and providing communication between a respective one of the probes and a respective one of the gas passages in a plurality of angular positions of the rotatable structure, and means sealing said engaging faces against the passage of gas from one recess to another, the sealing means including passageway means opening onto said engaging surfaces such that ar.y gas leaking through the sealing means flows into the passageway means.

5. Gas sampling equipment as claimed in claim 4, wherein said members are in the form of a shaft and a surrounding sleeve, the external surface of the shaft being in face engagement with the internal surface of the sleeve, and the recess extends circumferentially of said surfaces.

6. Gas sampling equipment as claimed in claim 5, wherein the recesses are annular and are spaced apart in the direction of extent of the rotation axis of the rotatable structure, and the sealing means includes a pair of axially spaced annular seals disposed between each pair of adjacent recesses, the annular seals in each pair having disposed therebetween an annular recess which forms part of the passageway means.

7. Gas sampling equipment as claimed in any preceding claim, wherein the passageway means is disposed in the fixed member.

8. Gas sampling equipment substantially as hereinbefore described with reference to the accompanying drawings.