Turbine

Abstract

 A turbine expander has a nozzle ring leading to a turbine wheel, the ring having nozzles on only a portion of its periphery and an obturator ring with an obturator portion extending over a portion of its circumference, the obturator ring being turnable relative to the nozzle to cover or expose a greater or lesser number of nozzles.

Description

[0001] This invention is concerned with turbine expanders and particularly those used at gas well heads to extract power from the reduction of the gas pressure. In such turbines the gas is expanded through a turbine to lower its pressure for subsequent processing or distribution. The power extracted from the expansion is applied as useful energy for example to turn a generator.

[0002] The present invention seeks to provide a basic turbine which can be set to extract a desired quantity of energy from a gas flow.

[0003] According to one aspect of this invention there is provided a turbine expander having a guide nozzle ring having nozzle orifices over only a portion of its circumference and an obturator ring in a face to face sealing relationship with the nozzle ring and having a nozzle obturating portion extending about a portion of its periphery, said obturator ring being turnable relative to the nozzle ring selectively to obturate or open a greater or lesser number of nozzle orifices.

[0004] Preferred embodiments are illustrated in the accompanying drawing in which:

Fig 1 is an axial section of a turbine according to this invention;

Fig 2 is a front view of a nozzle ring according to this invention;

Fig 3 is a front view of an obturator ring of this invention; and

Fig 4 is a part side, part sectional view of the assembled nozzle and obturator rings.

[0005] The turbine comprises a housing 10 having a gas inlet 12, a second housing constituting a gas outlet 14 and a turbine wheel 16 mounted upon a shaft 18. The shaft is mounted in bearings 20 and 22 and terminates in a toothed portion 24 which constitutes the sun gear of an epicyclic gear box 26 of which the output shaft is shown at 28, the specter gas at relatively high pressure enters the turbine from inlet 12, is expanded through the turbine wheel 16 and exits for further processing or distribution through outlet 14.

[0006] The turbine wheel is conventional; it has a hub 30 keyed to shaft 18, a solid disc or web 32 and, around its outer periphery, a plurality of equiangularly spaced vanes 34.

[0007] Immediately upstream of the turbine wheel, there is a nozzle ring 36 having, as described in greater detail hereinafter, a plurality of nozzles or apertures to direct gas flow tangentially into the turbine vanes. The nozzle ring is mounted by bolts to a recessed hub 38 of a shaft housing 40 provided with lubricating ducts 42 and lubricant inlet and outlet connections 44 and 46 respectively. An obturator or nozzle blanking ring, again described in greater detail hereinafter is pressed against the upstream side of the nozzle ring by grub or set screws 48 set in threaded passages of the hub 38 of the shaft housing.

[0008] The nozzle ring is illustrated in greater detail in figures 2 and 4. It has an inner hub section 50 chamfered on its downstream side as at 52 and projecting upstream to be received in the recessed hub of the shaft housing. It is secured to the housing by cheese head bolts 54 passed through recessed bolt holes 56. To ensure correct installation of the nozzle ring it is polarized by having bolt hole 56′ set on a different center than the remaining holes. The nozzles or apertures are set at equal pitch centers in this instance at 1.6°, the centers being indicated by the numerals 1 through 31 about the periphery of the ring and being measured from the leading edges of the air foil shaped configurations which define the apertures. In the particular nozzle ring illustrated there are sixteen nozzles in two opposed groups of eight because this wheel has 31 centers with only 16 nozzles actually being formed and the remaining circumferential parts of the ring being blank. The opposed groups of nozzles are displaced from being diametrically opposed to each other by one half nozzle pitch. It will then be recognized that the blank portion of the nozzle at which is, as viewed in figure 2, the bottom of the ring extends, 8 nozzle pitches while that at the top extends over seven pitches .

[0009] Obturator plate 47 is secured between the radial face of the hub of the shaft housing and the upstream face of the nozzle ring by grub screws, 48 to which access is had from the upstream side of the hub of the shaft housing.

[0010] The plate 47 comprises an inner ring portion 60 and radially outer portions 62 and 64 which extend over arcs of eight and seven nozzle pitches respectively. The radially outer portions are circumferentially located so that the obturator plate can be positioned relative to the nozzle ring to blank either no nozzles or a selected odd number of nozzles from 1 to 15. Clearly by selecting the angular extent of the radially outer portions of the obturator ring to be a different number of nozzle pitches or by varying their number, other combinations are possible.

[0011] It is conceivable to have a single obturating part on the obturator ring but this would tend to lead to imbalance on the turbine wheel.

[0012] It will be appreciated that by adjusting the position of the obturator plate one can adjust the turbine to accommodate pressure and temperature variants in the supply gas, to demand variations downstream of the compressor without the expense of plural turbines of different ratings.

Claims

1. A turbine having a guide nozzle ring with nozzles over a portion of its circumference and no nozzles over another portion of its circumference and an obturator ring in face to face sealing engagement with the nozzle ring and having a nozzle obturating portion extending about a portion of its circumference, said obturator ring being turnable relative to the nozzle ring selectively to obturate a greater or lesser number of nozzles.

2. A turbine as claimed in claim 1 having nozzles over plural portions of its circumference and no nozzles between said portions and wherein the obturator plate has obturating portions equal in number to said plural portions.

3 A turbine having a nozzle ring, over a portion of the circumference of which are disposed a plurality of nozzles disposed at regular pitch centers and another portion which is blank and an obturator in a face to face relationship with the nozzle ring and having an arcuate obturator portion of an angular extent equal to an integral number of nozzle pitches, said obturator being adjustable relative to the nozzle ring to obturate a greater or lesser number of nozzles.

4. A turbine as claimed in claim 3 in which said obturator is ring shaped.

5. A turbine as claimed in claim 3 wherein said nozzle ring has two or more spaced portions of its circumference each with a plurality of nozzles said portions being separated by portions which are blank and said obturator has a number of obturator portions equal to the number of spaced portions of said nozzle ring.

Drawing