Drain for a pressure sensing line

Abstract

A drain includes a vortex throttle, to remove water from a pressure sensing line. The vortex throttle resists the flow of air through it. Therefore, for a given diameter of inlet and outlet ports the mass flow rate through the vortex throttle is much smaller than through a plain hole of the same diameter. The inlet and outlet ports may therefore be made larger than in known arrangements (so reducing the risk of blockage), but the operation of the vortex throttle restricts the mass flow of air through the drain pipe (so minimizing the detrimental effects on the engine's operation). Collected water effectively drains from the pressure sensing line, without the disadvantages of known arrangements.

Claims

1. A drain for a pressure sensing line, the drain comprising: a vortex throttle that includes: a first plate including an inlet port having a first diameter; a second plate having an inlet channel and a vortex chamber; the inlet channel comprising: a flare that is in fluid communication with the inlet port; and a throat that leads into the vortex chamber, the throat having a consistent second diameter along an entire length of the throat, the flare being angled relative to the throat; and a third plate including an outlet port that is in fluid communication with the vortex chamber.

2. The drain of claim 1, wherein the inlet port diameter is between 1 mm and 2 mm.

3. The drain of claim 1, wherein the ratio of the outlet port diameter to the vortex chamber diameter is between 1:5 and 1:7.4.

4. The drain of claim 1, wherein the vortex chamber has a diameter of between 5 mm and 6 mm.

5. The drain of claim 1, wherein the inlet and outlet ports each have a diameter of between 1 mm and 2 mm.

6. The drain of claim 1, wherein the outlet port is arranged concentrically with the vortex chamber.

7. The drain of claim 1, wherein the second diameter of the throat is smaller than the first diameter of the inlet port.

8. The drain of claim 1, wherein the inlet port extends in a thickness direction of the first plate.

9. The drain of claim 1, wherein the outlet port extends in a thickness direction of the third plate.

10. A pressure sensing line, comprising the drain of claim 1.

11. A gas turbine engine, comprising the drain of claim 1.

12. A gas turbine engine comprising the pressure sensing line of claim 10.

Description

(1) Embodiments of the invention will now be described in more detail, with reference to the attached drawings, in which

(2) FIG. 1 is a schematic illustration of a known drain, as already described;

(3) FIG. 2 is a schematic, cross-sectional view of a drain;

(4) FIG. 3 is a schematic, cross-sectional view of part of the drain of FIG. 2;

(5) FIG. 4 is a schematic, exploded view of the components of the vortex throttle of FIG. 3; and

(6) FIG. 5 is a schematic plan view of a vortex throttle.

(7) Like parts in the drawings are identified by like reference numbers.

(8) FIG. 2 shows a schematic, cross-sectional view of a drain in accordance with the invention. As in the embodiment of FIG. 1, a pressure sensing line 10 has an orifice 14. In use, the pressurised air providing the pressure signal flows along the pressure sensing line 10 as shown by the arrows P. A proportion of the air flow P flows through the orifice 14 into a drain pipe 122, as shown by the arrow D, carrying with it any collected water. Within the drain pipe 122 is a vortex throttle 126, whose construction and operation will be described in due course. The air flow D and water flow out of the end of the drain pipe 122 as shown by the arrow 130.

(9) FIG. 3 shows in more detail the section of the drain pipe 122 containing the vortex throttle 126. The air flow D and water flow into the vortex throttle 126 through an inlet port 142 and flow out of the vortex throttle 126 through an outlet port 144. The air flow D and water then flow out of the end of the drain pipe 122 as shown by the arrow 130.

(10) FIG. 4 shows an exploded view of the vortex throttle 126. In this arrangement, the vortex throttle is constructed from three plates welded together, but it will be appreciated that in other embodiments different construction methods may be used, and that a vortex throttle suitable for use in the invention may be constructed from fewer or more than three plates, or may embody the essential features in a different manner entirely. FIG. 5 shows a schematic plan view of a vortex throttle, identifying certain elements and dimensions.

(11) Vortex throttles are known in other technical fields, where they are sometimes referred to as vortex diodes or Zobel diodes.

(12) Referring now to FIGS. 4 and 5, a first plate 152 comprises an inlet port 142 which has a diameter d.sub.i. A second plate 154 comprises an inlet channel 156 which, when the vortex throttle is assembled, is in fluid communication with the inlet port 142. The inlet channel 156 leads tangentially into a vortex chamber 158 which has a diameter d.sub.v. A third plate 160 comprises an outlet port 144 which has a diameter d.sub.o. When the vortex throttle is assembled the outlet port 144 is concentric with the vortex chamber 158 and in fluid communication with it.

(13) The inlet channel 156 comprises a flare 162, with a flare angle , and a throat 164 with a diameter d.sub.t and a length I.sub.t. As may be seen from FIG. 4, the inlet port 142 has a length I.sub.i the outlet port 144 has a length I.sub.o, and the vortex chamber 158 has a vertical height h.sub.v. The vertical height h.sub.y of the vortex chamber 158 has been found to affect the performance losses, and accordingly h.sub.y is selected to minimise these losses. The throat 164 diameter d.sub.t has been found to affect the functionality of the vortex throttle, with the functionality increasing with decreasing d.sub.t; this dimension is therefore selected to be as small as practicably possible.

(14) In use, the air flow D flows into the vortex throttle 126 through the inlet port 142. It then flows through the inlet channel 156, as shown by the arrow 172, and into the vortex chamber 158. Within the vortex chamber 158, it is forced by the shape of the chamber and the position of the exit port 144 to form a vortex, following an inwardly spiralling path as shown by the arrow 174 to reach the exit port 144. The air flow then flows out of the vortex throttle 126 through the exit port 144, as shown by the arrow 130. The formation of the vortex causes the vortex throttle 126 to resist the flow of air through it, so that there is a substantial pressure drop across it. Therefore, for a given diameter of inlet and outlet ports d.sub.i, d.sub.o, the mass flow rate through the vortex throttle is much smaller than through a plain hole of the same diameter.

(15) The inlet and outlet ports may therefore be made larger than in known arrangements (so reducing the risk of blockage), but the operation of the vortex throttle restricts the mass flow of air through the drain pipe 122 (so minimising the detrimental effects on the engine's operation). The invention thus provides effective drainage of collected water from the pressure sensing line, without the disadvantages of known arrangements.

(16) The exact dimensions of the vortex throttle may be varied according to the particular needs of the application. In one arrangement, the elements of the vortex throttle 126 have the following dimensions:

(17) Inlet port diameter d.sub.i 1.6 mm, length I.sub.i 4.5 mm; throat diameter d.sub.t 1.1 mm; throat length I.sub.t 5.1 mm; vortex chamber diameter d.sub.v 5.6 mm, height h.sub.v 1.1 mm; outlet port diameter d.sub.o 1.1 mm, length I.sub.o 4.5 mm.

(18) The flare angle has been found to have a relatively small effect on the operation of the vortex throttle. It has been found that both converging and straight inlets are able to meet the flow requirement; therefore, the flare angle is seen as a non-critical feature. The throat length I.sub.t is also seen as a non-critical feature of the vortex throttle. However, testing has shown that the performance of the vortex throttle is optimal when this dimension is minimised.

(19) The inventor has recognised that the advantages of the invention may be achieved with a range of dimensions for the elements of the vortex throttle 126, some of which may be summarised in terms of the ratios between various dimensions.

(20) In particular, the ratio of vortex chamber diameter d.sub.v to exit port diameter d.sub.o affects the performance of the vortex throttle and should be a minimum of 5:1. Ratios of 5:1 to 7.4:1 are thought to be particularly suitable.

(21) The ratio of the vortex chamber diameter d.sub.v to inlet port diameter d.sub.i is not a critical feature of the invention and the design of the vortex throttle is defined by the ratio of vortex chamber diameter to exit port diameter as discussed above. The dimension d.sub.i is not thought to have a major effect on the operation of the drain. In a particular arrangement, the value for the dimension d.sub.i is at least 1.0 mm. Tests have been carried out on inlet ports with dimension d.sub.i between 1.0 mm and 2.0 mm.

(22) In the arrangement shown in FIGS. 3 and 4, the vortex throttle is constructed from three plates which are welded together; before assembly and welding, the top plate is machined with the inlet port, the middle plate with the vortex chamber, and the bottom plate with the exit port. However, alternative methods of manufacture and assembly may be employed. For example, dowel pins may be used to improve confidence that the vortex throttle will be aligned correctly during assembly.

(23) Any component or feature described in this disclosure may be combined with any other compatible component or feature. Furthermore, it will be appreciated that various alternative or complementary arrangements or components not explicitly described herein are in accordance with the disclosure.