Low friction inlet nozzle for a turbo expander

Abstract

A low friction inlet nozzle for a turbo expander including a nozzle cover ring, wherein the nozzle cover ring includes a face, a set of nozzle blades, wherein each nozzle blade includes a face, a set of pressure springs, and a set of axial loading bolts is provided. The axial loading bolts may be configured to accept all or at least a portion of the force which the set of pressure springs induces between the nozzle cover ring and the face of the nozzle blades, thereby locating the first face of the nozzle blade at a predetermined distance away from the face of the nozzle cover ring. The predetermined distance may be between 0.02 and 0.04 mm.

Claims

1. A low friction inlet nozzle for a turbo expander, comprising: a nozzle cover ring, wherein the nozzle cover ring comprises a face, and is configured to receive a first end of a pivot pin, a set of inlet nozzle blades, wherein each inlet nozzle blade comprises a face, and the pivot pin, the pivot pin comprising the first end and a second end, a fixed ring configured to receive the second end of the pivot pin, a set of pressure springs, and a set of axial loading bolts wherein the axial loading bolts are configured to accept all or at least a portion of the force which the set of pressure springs induces between the nozzle cover ring and the faces of the inlet nozzle blades, thereby locating the faces of the inlet nozzle blades at a predetermined distance away from the face of the nozzle cover ring, wherein the first end of the pivot pin is rotationally attached to the nozzle cover ring, and the second end of the pivot pin is rotationally attached to the fixed ring, thereby allowing the inlet nozzle blades to pivot relative to the fixed ring and the nozzle cover ring.

2. The low friction inlet nozzle of claim 1, wherein the predetermined distance is between 0.02 and 0.04 mm.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

(2) FIG. 1 schematically illustrates the cross section of a typical turbo expander as known to the prior art.

(3) FIG. 2 schematically illustrates details of the inlet guide vanes (nozzle blades) as known to the prior art.

(4) FIG. 3 schematically illustrates an exploded cross section of a turbo expander in accordance with one embodiment of the present invention.

(5) FIG. 4 schematically illustrates across section of a turbo expander in accordance with one embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

(6) Illustrative embodiments of the invention are described below. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

(7) It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

FIGURE ELEMENTS

(8) 100=turbo expander 101=nozzle cover ring 102=nozzle cover ring face 103=nozzle cover ring first pivot pin orifice 104=nozzle cover ring axial loading bolt orifice 105=inlet nozzles 106=nozzle pivot pins 107=nozzle first face 108=nozzle second face 109=fixed ring 110=fixed ring face 111=fixed ring second pivot pin orifice 112=fixed ring pressure springs 113=fixed ring axial loading bolts 114=annular inlet 115=adjusting ring 116=cam followers 117=nozzle biased slots 118=expander wheel

(9) With respect to the above identified problems, after analysis and testing, it was found that the root cause of many nozzle failures were the high amount of friction between the moving parts of the nozzle. The various embodiments of the proposed invention reduce this friction, possibly to zero.

(10) As the intention of the present invention is to remedy these problems in situ, to existing turbo-expander installations, as much of the original design as possible must be maintained. In some embodiments of the present invention axial loading bolts 113 are utilized to reduce the preload, possibly to zero.

(11) Turning to FIG. 3, an exploded view of a low friction inlet nozzle for a turbo expander 100 in accordance with one embodiment of the present invention is provided. The nozzle includes a nozzle cover ring 101, wherein the nozzle cover ring 101 comprises a face 102, a first pivot pin orifice 103, and an axial loading bolt orifice 104. The nozzle also includes a set of nozzle blades 105, wherein each nozzle blade 105 comprises a pivot pin 106, a first face 107 and a second face 108. Also included is a fixed ring 109, wherein the fixed ring comprises a face 110 and a second pivot pin orifice 111, a set of pressure springs 112, and a set of axial loading bolts 113. The number of axial loading bolts 113 will depend on the size and design of the turbo expander, but in one embodiment of the present invention, there may be 8 axial loading bolts 113.

(12) Turning to FIG. 4, and in the interest of consistency and clarity maintaining the element numbers from the prior figures, the axial loading bolts 113 are configured to accept all or at least a portion of the force which the set of pressure springs 112 induces between the nozzle cover ring 101 and the first face 107 of the nozzle blades 105. And the first face 107 of the nozzle blade 105 is located at a predetermined distance away from the face 102 of the nozzle cover ring 101. As the preloading force generated by the pressure springs 112 has been reduced to zero, the second face 108 of each nozzle blade 105 is no longer being forced into in contact with the face 110 of the fixed ring 109.

(13) The inventors discovered that a major source of friction arises along the contacting surfaces of the nozzle cover ring 101, nozzle blade 105, and fixed ring 109. This results in sliding friction on the nozzle blades 105. The precondition of slide friction is contact surface (pressure) “Fn”, roughness “μ” and sliding. The force of friction for each blade is F=Fn*μ.sub.o It is clear from this equation that to reduce friction “F”, either the preload “Fn” or the surface roughness “μ” must be reduced. In various embodiments of the present invention, the preload “Fn” is reduced.

(14) In one embodiment of the present invention, the preload that pressure springs 112 places on the nozzle blades 105 is F, as indicated in FIG. 4. The axial loading bolts 113 are adjusted to reduce this preload by drawing the cover ring 101 to the left (as indicated in FIG. 4) and thus away from nozzle blades 105. Once the preload has been reduced to zero, further adjustment of the axial loading bolts 113 produces a gap between the nozzle cover ring 101 and the nozzle blades 105. Once this gap reaches predetermined distance, this is set. This predetermined distance may be between 0.02 and 0.04 mm.

(15) Thus, the friction between the nozzle cover ring 101 and the nozzle blades 105 has been reduced to zero. Also, the friction between the nozzle blades 105 and the fixed ring 109 has been reduced to zero.

(16) It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.