GB2541010A

GB2541010A - Detecting leaks in pipes

Info

Publication number: GB2541010A
Application number: GB1513886.0A
Authority: GB
Inventors: Booth Michael; Wright Jenna
Original assignee: Rolls Royce Deutschland Ltd and Co KG; Rolls Royce PLC
Current assignee: Rolls Royce Deutschland Ltd and Co KG; Rolls Royce PLC
Priority date: 2015-08-06
Filing date: 2015-08-06
Publication date: 2017-02-08
Also published as: GB201513886D0

Abstract

A leak detection apparatus for detecting a leak in one of a plurality of fluid-carrying first pipes comprises a plurality of fluid-carrying first pipes 38a,38b and a plurality of second pipes 42a,42b. One end of each second pipe is in fluid communication with a respective one of the plurality of first pipes. The apparatus also comprises a manifold 44 and the second end of each second pipe is in fluid communication with the manifold. A sensor 46 located within the manifold can sense the temperature within the manifold, and a change in this temperature indicates a leak in one of the plurality of first pipes.

Description

DETECTING LEAKS IN PIPES

The present disclosure concerns an apparatus and method for detecting leakage from a pipe, particularly from one of a plurality of pipes.

With reference to Figure 1, a gas turbine engine is generally indicated at 10, having a principal and rotational axis 11. The engine 10 comprises, in axial flow series, an air intake 12, a propulsive fan 13, a high-pressure compressor 14, combustion equipment 15, a high-pressure turbine 16, a low-pressure turbine 17 and an exhaust nozzle 18. A nacelle 20 generally surrounds the engine 10 and defines the intake 12.

The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two airflows: a first airflow into the high-pressure compressor 14 and a second air flow which passes through a bypass duct 21 to provide propulsive thrust. The high-pressure compressor 14 compresses the air flow directed into it before delivering that air to the combustion equipment 15.

In the combustion equipment 15 the air flow is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high and low-pressure turbines 16, 17 before being exhausted through the nozzle 18 to provide additional propulsive thrust. The high 16 and low 17 pressure turbines drive respectively the high pressure compressor 14 and the fan 13, each by a suitable interconnecting shaft.

In operation, components of the turbines 16, 17 become hot and require cooling. A known way to cool a component (such as a turbine disc) is to bleed air from the compressor 14 (which will be at a lower temperature than the turbine disc) and feed it as cooling air to the component requiring cooling. It is known, for example, to bleed air from the fourth stage of the HP compressor 14 (referred to as HP4) to provide cooling air to the low pressure turbine 17. In one known arrangement, four HP4 bleed valves are provided, circumferentially spaced around the engine 10. The bleed air is carried through four cooling pipes (not shown in the drawing) to the low pressure turbine 17, where it flows into a chamber or plenum adjacent to the disc, thereby providing a flow of cooling air.

It is possible for one of the cooling pipes to fracture in service, with consequent leakage of the cooling air into the surrounding region of the engine. The loss of part or all of the cooling air flow to the turbine disc may have very serious consequences, and therefore it is necessary to detect such a failure so that appropriate action may be taken. Depending on the circumstances, the pilot may be notified of the problem, or an automated system may take the necessary actions. A known way to detect such a failure is to provide a temperature sensor in the region of the engine through which the cooling air pipes are routed between the HP4 offtake and the component to be cooled (this region will be referred to as the detection zone). The temperature measured by the sensor is compared with a predetermined model of the environment in the detection zone, and if the measured temperature deviates from the model by more than a certain amount then a failure is indicated. A problem with this failure detection method is that the air from the fractured pipe has only a small effect on the temperature of the air in the zone, whereas the ambient temperature in the detection zone will vary over a wide range during normal operation of the engine; therefore it is difficult to detect reliably whether a failure has occurred. It is not possible to measure the conditions in each pipe individually, because only a single thermocouple input into the EEC is available.

It would be desirable to have an accurate and reliable way to detect pipe failures, using only a single sensor.

In a first aspect, there is provided a leak detection apparatus for detecting a leak in one of a plurality of fluid-carrying first pipes, the apparatus comprising: a plurality of fluid-carrying first pipes; a plurality of second pipes, one end of each second pipe being in fluid communication with a respective one of the plurality of first pipes; a manifold, the second end of each second pipe being in fluid communication with the manifold; a sensor located within the manifold to sense the temperature within the manifold; in which a change in the temperature within the manifold indicates a leak in one of the plurality of first pipes.

In the event of a fracture or leak in one of the first pipes, the drop in pressure within that pipe will cause air to flow through the second pipes. The resulting change in air temperature within the manifold may be detected to indicate the presence of a leak. Because the temperature sensor is located in the manifold, it is more sensitive to temperature change than a sensor in the zone surrounding the first pipes, and less prone to false alarms.

Each second pipe may be of smaller cross-sectional area than its corresponding first pipe.

The first pipes may extend from a high-pressure region to a low-pressure region and the connections between the first pipes and the second pipes may be near the low-pressure region.

In normal operation there may be negligible fluid flow through the second pipes.

The temperature within the manifold in normal operation is therefore principally influenced by the temperature of the zone surrounding it. In the event of a leak, the change in temperature is more marked and therefore easier to detect.

In a second aspect, there is provided a method for detecting a leak in one of a plurality of fluid-carrying first pipes, the method comprising the steps of: providing a plurality of fluid-carrying first pipes; providing a plurality of second pipes, one end of each second pipe being in fluid communication with a respective one of the plurality of first pipes; providing a manifold, the second end of each second pipe being in fluid communication with the manifold; providing a sensor within the manifold to sense the temperature within the manifold; monitoring the temperature within the manifold while fluid flows through the first pipes; detecting a change in the temperature or pressure within the manifold indicative of a leak in one of the first pipes; signalling to an operator that a leak has been detected.

The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied, mutatis mutandis, to any other aspect of the invention.

Embodiments of the invention will now be described by way of example only, with reference to the Figures, in which:

Figure 1 is a sectional side view of a gas turbine engine, as already described;

Figure 2 is a schematic illustration of a bleed air arrangement incorporating a first arrangement of a leak detection apparatus;

Figure 3 is a schematic illustration of the arrangement of Figure 2, following a fracture of one bleed pipe; and

Figure 4 is a schematic illustration of a bleed air arrangement incorporating a second arrangement of a leak detection apparatus.

Referring to Figure 2, a bleed air flow 32 flows from a source region 34 (corresponding to HP4 bleed offtakes) to a sink region 36 of lower pressure (corresponding to the distribution arrangement in the LP turbine). The bleed air flow 32 flows through two equally-sized bleed pipes 38a, 38b.

The bleed pipes 38a, 38b pass through a detection zone 40. The temperature and pressure of the air in the bleed pipes 38a, 38b are higher than the temperature and pressure in the detection zone 40.

Near to the sink region 36, link pipes 42a, 42b are connected to the bleed pipes 38a, 38b and provide a fluid flow path between the respective bleed pipes and a manifold 44. The link pipes 42a, 42b are smaller in diameter than the bleed pipes 38a, 38b and in this arrangement have an internal diameter of about 6mm.The length of the link pipes is generally dictated by the arrangement of the engine; the diameter of the link pipes is generally kept small to minimise the effect on the engine’s operation; because narrow pipes contain less air, any temperature difference between the air in the link pipes and that in the detection zone will easily dissipate.

The manifold 44 provides a chamber or plenum in fluid communication with both link pipes 42a, 42b, and also comprises a temperature sensor 46, which is operable to detect the temperature of the air within the manifold 44. These features are more clearly shown in the magnified section of Figure 2.

Because the bleed pipes 38a, 38b are the same size, and flow between the same source and sink and through the same detection zone, in normal operation they will carry essentially the same flow and will have the same temperature and pressure profiles along their length. Therefore, in normal operation there will be negligible air flow through the link pipes 42a, 42b. The air in the manifold 44 will therefore be essentially static, and its temperature will stabilise to match the ambient temperature of the detection zone 40.

Figure 3 shows the arrangement of Figure 2 following a fracture 52 of the bleed pipe 38a. Common features are identified by the same reference numerals as in Figure 2.

Air 54 flows out of the fracture 52 into the detection zone 40. As noted above, this will have only a small effect on the temperature and pressure of the air in the zone 40. Because of the leakage 54 through the fracture 52, the temperature and pressure in the region 56 of bleed pipe 38a (downstream of the fracture 52) will be lower than in the corresponding region of the intact bleed pipe 38b. Air will therefore flow from pipe 38b and successively through link pipe 42b, manifold 44 and link pipe 42a into the downstream region 56 of bleed pipe 38a, as shown by the arrows F in the magnified section of Figure 3. As a result of this flow of higher temperature air, the temperature detected by the sensor 46 will increase. This increase in the measured temperature, when received by the EEC, indicates that a bleed pipe has fractured.

It will be appreciated that if the fracture occurs in bleed pipe 38b, the same consequences will ensue, but with air flowing in the opposite direction through the two link pipes 42a, 42b and the manifold 44.

The arrangement shown in Figure 3 therefore provides a robust method for detecting a fracture or leak in a bleed pipe, using only a single temperature sensor.

The arrangement may be modified to serve a larger number of bleed pipes, as shown in Figure 4. As in the arrangement shown in Figures 2 and 3, a bleed air flow 32 flows from a source region 34 (corresponding to HP4 bleed offtakes) to a sink region 36 of lower pressure (corresponding to the distribution arrangement in the LP turbine). In this arrangement, the bleed air flow 32 flows through four equally-sized bleed pipes 138a, 138b, 138c, 138d.

Near to the sink region 36, link pipes 142a, 142b, 142c, 142d are connected to the bleed pipes 138a, 138b, 138c, 138d and provide a fluid flow path between the respective bleed pipes and a manifold 144. The link pipes 142a, 142b, 142c, 142d are smaller in diameter than the bleed pipes 138a, 138b, 138c, 138d and in one arrangement have an internal diameter of about 6mm. The manifold 144 comprises a temperature sensor 46. As in the previously-described arrangement, the bleed pipes are of equal size and so the flow through them will be uniform; the flow through the link pipes in normal operation will therefore be negligible.

In the event that bleed pipe 138a fractures, then as in the previously-described arrangement the reduced pressure downstream of the fracture 152 will cause an air flow from the three intact pipes 138b, 138c, 138d, through their respective link pipes 142b, 142c, 142d and the manifold 144, and through the link pipe 142a into the downstream region of the fractured pipe, as shown by the arrows F’ in the magnified section of Figure 4. As in the arrangement of Figure 3, the resulting higher-temperature air flow through the manifold 144 will result in a clear increase in the temperature measured by the sensor 46, indicating to the EEC that a bleed pipe has fractured.

Of course, if another of the bleed pipes 138a, 138b, 138c, 138d were to fracture, the arrangement would work in the same manner but with different air flows through the link pipes 142a, 142b, 142c, 142d, mutatis mutandis.

It will be understood that the invention is not limited to the embodiments described above and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

Claims

1. A leak detection apparatus for detecting a leak in one of a plurality of fluid-carrying first pipes, the apparatus comprising: a plurality of fluid-carrying first pipes; a plurality of second pipes, one end of each second pipe being in fluid communication with a respective one of the plurality of first pipes; a manifold, the second end of each second pipe being in fluid communication with the manifold; a sensor located within the manifold to sense the temperature within the manifold; in which in normal operation there is negligible flow of fluid through the second pipes, and in which a leak in one of the plurality of first pipes causes a flow of fluid through the second pipes, thereby causing the sensor to detect a change in temperature.

2. The leak detection apparatus of claim 1, in which the first pipes are of equal cross-sectional area.

3. The leak detection apparatus of claim 1 or claim 2, in which the first pipes extend from a common source to a common sink.

4. The leak detection apparatus of any one of the preceding claims, in which each second pipe is of smaller cross-sectional area than its corresponding first pipe.

5. The leak detection apparatus of any one of the preceding claims, in which the first pipes extend from a high-pressure region to a low-pressure region and the connections between the first pipes and the second pipes are near the low-pressure region.

6. A method for detecting a leak in one of a plurality of fluid-carrying first pipes, the method comprising the steps of: providing a plurality of fluid-carrying first pipes; providing a plurality of second pipes, one end of each second pipe being in fluid communication with a respective one of the plurality of first pipes; providing a manifold, the second end of each second pipe being in fluid communication with the manifold; providing a sensor within the manifold to sense the temperature within the manifold; monitoring the temperature within the manifold while fluid flows through the first pipes; detecting a change in the temperature within the manifold indicative of a leak in one of the first pipes.

7. A leak detecting apparatus of the kind set forth substantially as described herein with reference to and as illustrated in Figures 2 to 4 of the accompanying drawings.

8. A method for detecting a leak substantially as described herein with reference to and as illustrated in Figures 2 to 4 of the accompanying drawings.