GB2272768A

GB2272768A - Pressure or temperature measuring apparatus and a cartridge of sensors for use in the same

Info

Publication number: GB2272768A
Application number: GB9321845A
Authority: GB
Inventors: Stephen Charles Cook; Peter David Smout
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1992-11-20
Filing date: 1993-10-22
Publication date: 1994-05-25
Anticipated expiration: 2013-10-22
Also published as: GB2272768B; GB9321845D0

Abstract

A pressure or temperature rake comprises an elongate member 12 which has a single recess 30 in its front flow-a-butting, face 14. Within the recess are located a plurality of pitot tubes 18 and/or temperature sensors. The recess defines a single cavity 32 around the sensors, and bleed slots 34 are provided in the side faces 26 of the member 12 which are in fluid communication with the cavity 32. Pressure tubes 19 or conductors connect the sensors to a remote pressure measuring system through an opening in member 12. The rake is supported in a gas flow a proportion of which passes into the cavity 30. The cavity 30 decelerates the gas and removes any swirl so that the sensors measure accurately. In another embodiment (Figs. 1 to 3, not shown) each sensor is surrounded by its own cavity. A replaceable cartridge containing the sensors may be inserted into the member 12 (Fig. 7, not shown). <IMAGE>

Description

PRESSURE OR TEMPERATURE MEASURING APPARATUS AND A CARTRIDGE OF SENSORS FOR USE IN THE SAME The present invention relates to apparatus for measuring pressure or temperature in a gas flow and to a cartridge of sensors for use in the apparatus.

During the testing of gas turbine engines it is often necessary to measure the pressure and temperature of the gas flow through the engine. Suitably positioned sets of pressure and temperature sensors are used to indicate circumferential and radial pressure and temperature profiles respectively at various axial positions throughout the engine. The sensors are mounted either on leading edges of existing engine components or in the absence of suitable hardware on purpose design poles, known as rakes, which slot into the engine.

Generally pressures are measured using pitot tubes and temperatures are measured using thermocouples. In conventional rakes the pitot tubes or thermocouples are mounted forward of the rake body and each is surrounded by a shroud. The shroud defines a cavity around the pitot tube or thermocouple through which a proportion of the gas flow passes. The shroud reduces flow incidence angle sensitivity and provides a measure of environmental protection.

A problem with conventional rakes is that the shrouds are difficult to manufacture and as they protrude forward of the rake body they are vulnerable. Shrouds have been damaged during installation into or removal from a test engine and difficulties have been encountered in repairing the damaged shrouds.

The present invention seeks to provide a pressure or temperature rake which is easier to manufacture and which is more compact and robust than conventional rakes.

According to the present invention apparatus for measuring pressures and/or temperatures in a gas flow comprises an elongate member which is operationally located in the gas flow, the elongate member having a first surface which confronts the gas flow and a second surface downstream of the first surface, the first surface having a single recess therein in which a plurality of pressure and/or temperature sensors are located to measure pressures and/or temperatures in a plane normal to the direction of the gas flow, the single recess defining a single cavity anround all of the sensors through which in operation a proportion of the gas flow passes, an opening being provided in the elongate member through which means for connecting the sensors to a remote pressure and/or temperature measuring system passes, there being further provided on at least one passageway through the elongate member which is in fluid communication with the cavity and through which in operation the gas flow exits from the cavity.

Preferably the single recess is a slot and the pressure and/or temperature sensors are equispaced from one another within the slot.

The opening in the elongate member may be provided in the second surface of the elongate member which is parallel to the first surface having the recess so that the sensors can pass through the opening in the second surface for location in the recess.

Preferably the recess has a chamfered inlet edge so that the angle at which the rakes can operate in a gas flow is increased.

The at least one passageway through the elongate member may be inclined so that the gas flow does not have to turn abruptly and exits smoothly from the cavities.

The elongate member preferably has an aerodynamic profile to minimise the disturbance it has on the gas flow into which it is inserted.

The plurality of pressure and/or temperature sensors may form an integral part of a cartridge which fits into the at least one recess.

Preferably the pressure sensors are pitot tubes and the temperature sensors are thermocouples.

A cartridge for use in pressure or temperature measuring apparatus comprises an elongate member in which a plurality of pressure and/or temperature sensors are mounted so that they protrude therefrom and being provided with means for attaching the sensors to the means connecting the sensors to remote pressure and/or temperature measuring apparatus.

The present invention will now be described with reference to the accompanying drawings in which, Figure 1 is a top elevational view of a pressure rake in accordance with one embodiment of the present invention.

Figure 2 is a view in the directions of arrow A in figure 1.

Figure 3 is a view in the direction of arrow B in figure 2.

Figure 4 is a top elevational view of a pressure rake in accordance with a second embodiment of the present invention.

Figure 5 is a view in the direction of arrow C in figure 4.

Figure 6 is a view in the direction of arrow D in figure 5.

Figure 7 is a pictorial view of a cartridge of sensors for use in a pressure rake in accordance with the embodiment shown in figure 4.

With reference to figure 1 a pressure rake generally indicated at 10 comprises an elongate member 12 the front face 14 of which has a plurality of equispaced circular recesses 16 therein. Centrally located within each of the circular recesses 16 are pitot tubes 18. The pitot tubes 18 are inserted into the recesses 16 through an opening 22, figure 3, in the rear face 20 of the member 12 and are brazed or glued into position. The circular recesses 16 define annular cavities 17 around each of the pitot tubes 18. Circular passageways, shown as bleed holes 24 in the side faces 26 of the member 12 in figure 2, are in fluid communication with the cavities 17. The circular passageways 24 are inclined so that the gas flow does not have to turn abruptly and exits smoothly from the cavities 17.

The pitot tubes 18 are connected to pressure tubes 19 located in the opening 22 in the rear face 20 of the member 12. The pressure tubes 19 connect the pitot tubes 18 to a remote pressure measuring system (not shown). The pressure measuring system is placed outside of the gas flow to minimise disturbance to the gas flow.

In operation the pressure rake 10 is inserted into a gas stream. A bracket 11 is attached to suitable hardware (not shown) and supports the elongate member 12 in position in the gas stream. A proportion of the gas stream flows into each of the annular cavities 17 and flows axially past the end of the pitot tubes 18. The annular cavities 17 decelerate the gas and remove any swirl in the gas.

Pressure measurements from the pitot tube 18 are transmitted via the pressure tube 19 and are recorded on the pressure measuring system. The gas flow then exits from the cavities 17 through the bleed holes 24 in each side face 26 of the member 12. The area of the inlet to each of the recesses 16 is equal to the area of the bleed holes 24 through which the gas passes from each cavity 16 so that the pressure measured at each pitot tube 18 is not altered.

Figure 4 shows a alternative embodiment of the present invention in which the same numerals have been used for integers common to both embodiments.

The elongate member 12 has a single recess 30 in the front face 14. Within the recess 30 are located a plurality of pitot tubes 18. The pitot tubes 18 are inserted into the recess 30 through an opening 22, figure 6, in the rear face 24 of the member 12. The pitot tubes 18 are equispaced within the recess 30 which defines a single cavity 32 around all of the pitot tubes 18. The recess 30 decelerates the gas and removes any swirl.

Bleed slots 34, figure 5, are provided in both side faces 26 of the member 12 through which the gas exits from the cavity 32. The area of the inlet to the recess 30 is equal to the area of the bleed slots 34 so that the pressure measured by the pitot tubes 18 is not affected.

It will be appreciated by one skilled in the art that although the present invention has been described with reference to a pressure rake 10 that the same design could apply to a temperature rake. However thermocouples instead of the pitot tubes 18 would be mounted in the recesses 16 and 30. The cavities 17 and 32 defined around each of the thermocouples decelerate the gas and remove any swirl in the gas. The low velocity gas flow passes over the thermocouple before exiting through the bleed holes 24 or bleed slots 34 in the side faces 26 of the member 12. The ratio of the area of the inlet to the recesses 16 or 30 to the area of the bleed holes 24 or slots 34 is of the order of 3:1. Each thermocouple would be connected to temperature measuring apparatus by thermocouple cables located in the opening 22 in the rear face 20 of the member 12.

Alternatively a rake may be used which has a combination of temperature and pressure sensors 18 mounted in the recesses 16 or 30 so that temperature and pressure measurements can be taken from a particular location in the gas flow.

The recesses 16 and 30 in the front face 14 of the member 12 perform the same function as the shrouds on a conventional pressure or temperature rake. Replacing the shrouds with the recesses 16 and 30 simplifies manufacture of the rakes and the rakes are more compact and robust than existing rake designs. The inlets to the recesses 16 and 30 may be chamfered to increase the angle at which the rakes can operate in a gas flow.

To minimise the disturbance caused by the rakes in the gas flow they may have an aerodynamic profile.

Alternatively the elongate member 12 may be an existing engine component, such as a vane, the sensors being mounted in a recess at the leading edge of the component.

The pitot tubes 18 or thermocouples could be mounted onto a removable cartridge 40, figure 7, which is inserted into the member 12 through the opening 22 in the rear face 20 of the member 12. The cartridge 40 is held in position in the member 12 by bolts (not shown). The bolts pass through bolt holes 42 in the cartridge and bolt holes 28 and 36, figures 2 and 5, provided in the side faces 26 of the member 12.

Mounting the pitot tubes 18 or thermocouples onto a removable cartridge 40 offers the advantage that should one or more of the sensors fail during a test the repair is simply a matter of replacing the cartridge 40 avoiding any time delay which could compromise the test. Also cartridges 40 with a different number of sensors per unit length or having sensors which are not equispaced could be readily interchanged.

Claims

Claims:

1. An apparatus for measuring pressures and/or temperatures in a gas flow comprising an elongate member which is operationally located in the gas flow, the elongate member having a first surface which confronts the gas flow and a second surface downstream of the first surface, the first surface having a single recess therein in which a plurality of pressure and/or temperature sensors are located to measure pressures and/or temperatures in a plane normal to the direction of the gas flow, the single recess defining a single cavity anround all of the sensors through which in operation a proportion of the gas flow passes, an opening being provided in the elongate member through which means for connecting the sensors to a remote pressure and/or temperature measuring system passes, there being further provided on at least one passageway through the elongate member which is in fluid communication with the cavity and through which in operation the gas flow exits from the cavity.

2. An apparatus as claimed in claim 1 in which the single recess is a slot.

3. An apparatus as claimed in any claim 2 in which the sensors are equispaced from one another within the slot.

4. An apparatus as claimed in any preceding claim in which the opening is provided in the second surface of the elongate member which is parallel to the first surface having the recess so that the sensors can pass through the opening in the second surface for location in the recess.

5. An apparatus as claimed in any preceding claim in which the recess has a chamfered inlet edge.

6. An apparatus as claimed in any preceding claim in which the at least one passageway through the elongate member is inclined.

7. An apparatus as claimed in any preceding claim in which the plurality of sensors form an integral part of a cartridge which fits into the recess.

8. An apparatus as claimed in any preceding claim in which the sensors are pitot tubes which measure pressure.

9. An apparatus as claimed in any preceding claim in which the sensors are thermocouples which measure temperature.

10. An apparatus as claimed in any preceding claim in which the elongate member has an aerodynamic profile.

11. A cartridge of sensors for use in pressure or temperature measuring apparatus as claimed in any preceding claim comprising an elongate member in which a plurality of pressure and/or temperature sensors are mounted so that they protrude therefrom and being provided with means for attaching the sensors to the means connecting the sensors to remote pressure and/or temperature measuring apparatus.

12. A cartridge as claimed in claim 11 in which the sensors are equispaced from one another within the cartridge.

13. A cartridge as claimed in claim 11 or claim 12 in which the sensors are pitot tubes which measure pressure.

14. A cartridge as claimed in claim 11 or claim 12 in which the sensors are thermocouples which measure temperature.

15. An apparatus as hereinbefore with reference to and as shown in figures 4, 5 and 6.

16. A cartridge as hereinbefore described with reference to Figure 7.