US3207473A - Turbine wobble-overspeed safety - Google Patents

Description

Sept. 21, 1965 c. c. MADDEN 3,207,473

TURBINE WOBBLE-OVERSPEED SAFETY Filed June 26, 1963 2 Sheets-Sheet 1 INVENTOR. CHARLES C. MADDEN ATTORNEY Sept. 21, 1965 Filed June 26, 1963 c. c. MADDEN 3,207,473

TURBINE WOBBLE-OVERSPEED SAFETY 2 Sheets-Sheet 2 INVENTOR. CHARLES C. MADDEN mwaa ATTORNEY United States Patent 3,207,473 TURBINE WOBBLE-OVERSPEED SAFETY Charles C. Madden, Hartford, N.Y., assignor to The Bendix Corporation, Utica, N.Y., a corporation of Delaware Filed June 26, 1963, Ser. No. 290,837 3 Claims. (Cl. 253-52) This invention relates to gas turbine control and more particularly concerns a gas turbine having a shut-down valve and pneumatic safety control means for operating the shut-down valve.

An object of the present invention is to provide a gas turbine system wherein control means will close gas supply valve means when the turbine begins to rotate eccentrically orbegins to overspeed whereby damage to the turbine and associated equipment will be prevented.

Another object is to provide such a gas turbine control system having releasible vent means and closable bleed means connected to pneumatic operating means arranged to be actuated by an eccentrically rotating turbine wheel which results at the beginning of a bearing failure or to be actuated by an overspeeding turbine wheel.

An additional object of the present invention is to provide a single pneumatic control device having cooperating flow-through piston means and spool valve means for a turbine safety arrangement to give shut-down of a turbine in the event either eccentric rotation or overspeed occurs.

The realization of the above objects, along with features and advantages of the invention will be apparent from the following detailed description and the accompanying drawing in which:

FIGURE 1 is a diagramatic representation with parts I in cross section of an embodiment of the invention and actuator at the left and spool valve means at the right and a closed butterfly valve as positioned before start or after eccentric turbine wheel rotation and shows the flowthrough piston means and spool valve means both moved to the right.

Referring to FIGURE 1 of the drawing, the turbine 11 which includes a radial-flow turbine wheel 13, an annular manifold 15 (part omitted) for directing air to the peripheral inlet ends of the curved blades 17 of the turbine wheel 13 and a tubular exhaust duct 19 encasing the side of the turbine wheel 13 which has blades 17 and an an axial hub projection 21. Projection 21 has an axial recess 23 which contains a plurality of J-shaped fly weights 25, a spring 27 confined by plunger shoulder 28 and by' cover 29 and biasing the shoulder 28 against inner ends of the fly weights 25 to resist centrifugal action, and a plunger 31 slidably-mounted in axial bore 33. The pointed outer end of plunger 31 is closely-spaced from the open end 35 of vent conduit 37 to provide an outlet flow path.

Two steel tubes of four equi-spaced tubes 41 having frangible glass tips 43 are shown extending through the exhaust duct 19 so that the tips 43 are closely-spaced to the edges of the blades 17. The clearance (not shown to scale) is about 0.015 of an inch at a wheel radius of about two and a quarter inches. A plurality of at least three equi-spaced tubes 41 are required. These tubes 41 connect via short conduits 45 to an annular tube 47 (surrounding the exhaust duct) which connects at the right to an escape conduit 49. A large air supply pipe 51 connects to the manifold 15. The upper or other side of the turbine wheel 13 has a support shaft 53 extending axially and being mounted in ball bearing 55 which is supported in housing support structure 57. The turbine wheel normally has a fixed plane of rotation in the absence of tilting due to bearing failure or other cause. It is to be noted in FIGURE 2 that the glass tip 43 of a tube 41 is shown broken as if the turbine wheel 13 had rotated slightly eccentrically and arrows suggest the escape of air to the exhaust duct 19 from escape conduit 49.

To the right of the turbine 11, a butterfly valve 61 is mounted in supply pipe 51 with its operating arm 62 connected to a piston rod 63 of a piston actuator 65. This actuator has a cylindrical housing 66, a piston 67 connected to rod 63, and a spring 68 above the piston 67 urging it downwardly. It is to be noted that, before air pressure is available and applied to the bottom of piston actuator 67, the spring 68 normally positions the piston so that the butterfly valve 61 is in closed position. This provides an automatic check of actuator operability at start up.

A first pipe 71 connects to the top interior of piston housing 66 above piston actuator 67 and a second pipe 73 similarly connects below the piston actuator 67. Both of these pipes extend to a control spool valve 75 having a cylindrical housing 76 and a spool or sleeve 77 slidably mounted therein. The interior cylindrical side surface of the valve housing 76 has a left annular recess 78, a central annular recess 79, a right annular recess 80. The sleeve 77 has centrally-located transverse piston wall 81 so that pressure at either side will act on the piston sleeve. Spring 82 is confined between piston wall 81 and the right end or wall of the valve housing 76 and urges sleeve 77 to the left with a small force. First pipe 71 connected to the top of the piston actuator 65 extends through the bottom part of the side wall of housing 76 opening between the left recess 78 and the central recess 79, while the second pipe 73 similarly extends through the housing between the central recess 79 and the right recess 80. The piston sleeve 77 has its left annular recess 83 shown, FIGURE 1, overlapping the left housing recess 78 and the opening of pipe 71 but is adapted, when the piston sleeve 77 moves to the right, to overlap this pipe opening and the central housing recess 79 as shown in FIGURE 2. The piston sleeve 77 also has a right annular recess 84 which as shown, FIGURE 1, overlaps the opening of second pipe 73 and central recess 79 but which will overlap recess and pipe 73 upon rightward sleeve movement as shown in FIGURE 2. Left housing recess 78 has an atmospheric vent pipe 87 connected thereto and right housing recess 80 has a vent pipe 88.

A pipe 91 having a restriction 92 connects central housing recess 79 for the purpose of more precisely controlling flow (together with holes 93) to the left space of spool element or sleeve 77. Pipe 91 provides augmented flow to maintain spool valve 77 in the right position after actuation and closure of plunger 31 due to turbine overspeed. Otherwise, closure -of butterfly valve 61 will cause turbine speed to decay and plunger 31 will open, re-establishing a running condition. It is desired instead to cause full shut down due to an overspeed and the augmented supply through pipe 91 is sufficient to maintain spool valve in the right position even though plunger 31 reopens. In order that spool valve 77 is not locked in the right position on start-up, restriction 92 is provided in pipe 91 which delays the augmented supply permitting pressure to build up faster on the right side of spool valve 77 giving it sufiicient initial movement to close olf the connection of pipe 91 with the left space of spool valve 77.

Pressurized air is supplied to the central housing recess 79 via pressurizing pipe opening into air supply pipe eccentric shut-down.

105 to the right.

3 51 upstream of butterfly valve 61. With the sleeve 77 moved to the left as shown in FIGURE 1, it is apparent that piston actuator 65 is operated to open the butterfly valve 61 since, by the overlapping of the recesses and pipe outlets, the appropriate venting and pressurizing flow paths are provided.

diagrammatic FIGURE 1 in the interest of clarity.

Inorder to move the sleeve 77 to the right at overspeed with pressure build-up and when no glass tip 43 has been broken off, a suitable pressure is normally maintained on the right side of the piston sleeve 77. This is accomplished by means of an orifice 97 in the upper side wall of the sleeve 77. This orifice 97 is sized so that the bleed there-through to annular sleeve groove 98 (continually connected to the left vent recess 80) will maintain a lower pressure and also prevent build-up, respectively during normally running or during overspeed or Thus, when the sleeve piston 77 is positioned leftward, orifice 97 bleeds through groove 98 to right vent recess 80. At overspeed when vent line 37 is blocked and the sleeve 77 moves to the right, a pressure build-up at the right via port 95 (since escape line 49 is closed) is also prevented by bleeding through orifice 97.

Housing 76 includes an extension 101 to the left which provides a piston chamber 103. A flow-through piston element 105 is slidably mounted in chamber 103 and includes an axially-extending tubular projection 107 at the right which extends through Wall 109 to adjacent wall 81 of sleeve 77. A left tubular projection 111 inward of spring 113 abuts left end wall 115 and mates with opening 117 which connects with pipe 37. A flow-through passage 118 is thus provided. Spring 113 urges piston Housing 76 has a passage 121 with a restriction 123 connecting pipe 90 with the annular space to the right of piston 105. Pipe 49 also connects to this a right annular space via passage 125 in housing extension.

From the foregoing, it is apparent during normal operation that pressurized gas is provided to wobble tips 43 through the multi-control 75 as well as to the restricted speed control outlet 35 and to the bottom of butterfly valve actuator 65.

In FIGURE 2 wherein the butterfly valve 61 is closed overrides the sleeve spring force. Piston 105 does not block flow to pipe 49 so that pressure build-up is prevented. Flow to speed control pipe 37 is blocked so that with wobble, rapid pressure build-up results. Sleeve 77 provides reverse venting and pressurizing of piston actuator 65 for closing operation.

The dashed-line showing .of piston 105 suggests its positioning to the left when overspeed shuts down the system with sleeve 77 moved to the right as shown.

In start-up for normal operation from the FIGURE 2 positioning and assuming an inlet pressure of 5-225 p.s.i.g. is to be supplied, the butterfly valve 61 will be in closed position due to piston spring 113 and piston actuator spring 67 but will be moved immediately to open position upon pressurized hot air or gas being supplied via conduit 90 to the pneumatic control 75. Piston 105 is pressurized to inlet pressure via passage 121 and immediately moved against light spring 113 to the left, providing through passage 118 flow to vent pipe 37. The pressure on the left side of the sleeve 77 which is positioned to the right thus becomes significantly less than inlet pressure due to the venting through piston 105 to the end 35 of speed control vent conduit 37 and the speed responsive plunger 31. The pressure on the right side of the sleeve 77 becomes somewhat less than the inlet pressure due to bleed off through the right orifice 97 to the annular groove 98 in the sleeve 77 and recess 80 in housing 76 to atmospheric vent line 88.- Spring 82 and the right side pressure exert a suflicient force so that a greater total force is exerted on the right side of the sleeve 77 than the left side and the sleeve 77 moves rapidly to the left limit. Wall 81 does not contact the piston 105 upon full leftward movement. Inlet air is thus provided to the bottom of the actuator piston 67 via the central valve housing recess 79, the right sleeve recess 84 and pipe 73. The top of the actuator piston 67 is'vented via conduit 71, the left sleeve recess 83 which connects tovent line 87. With butterfly valve 61 thus opened, normal operation positioning as shown in FIGURE 1 results and operation proceeds with suitable speed regulation of the turbine by other valve means and controls (not shown).' It is to be noted that the various flow pathsand springs are so dimensioned and selected so that the control will function with a low inlet pressure of about five p.s.i.g.

In the event of a slight eccentric rotation of the turbine wheel 13 due'to the beginning of a bearing failure (resulting from a lubrication malfunction, for example), one (or more usually) of the frangible glass tips 43 will be broken off to provide a large escape flow paththrough conduit 49 into the low-pressure exhaust shroud. Orifice 123 in line 121 allows a pressure drop on piston 105 if only one tip 43 breaks so that the control will be operative. The pressure on the right side of the piston 105 will be reduced to essentially atmospheric pressure whereby the piston 105 will be moved to the right by its spring 113 on the left side of the piston 105. When the right piston tube 107 approaches and abuts wall 81, pressure rapidly builds up on the left of sleeve 77 so that sleeve 77 is moved and it and piston 105 are positioned as shown in FIGURE 2. This action results in venting the lower side of the actuator piston 67 and pressurizing the upper side to close butterfly valve 61. Venting is provided by conduit 73,-the right sleeve recess 84, the right housing recess 80, and vent line 88. Pressurizing for closing the butterfly valve 61 is provided by central housing recess 79, the left sleeve recess 83 and pipe 71. It is apparent that with close spacing of frangible tips 43 and the rapidacting pneumatic control system, the beginning of eccentric rotation will shut down the turbine and thus prevent damage due to turbine fragments or escaping hot air to the aircraft and will minimize damage to the turbine wheel and exhaust duct.

In the event of turbine, overspeed due to speed regulation failure or a disconnected load, the predeterminedspeed-responsive plunger 31 will approach and essentially close the end 35 of vent conduit 37. This will cause the pressure on the life side of the sleeve 77 (piston tube 107 being spaced from wall 81) to rapidly increase to essentially the inlet airpressure since there is now a highly restricted or closed vent path through conduit 37 for the air supplied from the housing recess 79 through the higher flow passage to the left side ofthe sleeve 77. As mentioned, it is to be noted that bleed orifice 97 opens into the right groove 98 of the sleeve 77 which overlaps the right housing recess 80 connected to vent line 88 whereby a lower pressure is maintained on the right side of the sleeve 77. The light spring 82 and pressure at the right are immediately overcome and the sleeve 77 assumes the position shown inFIGURE 2 with piston actuator 65 being vented and pressurized as above described with reference to eccentric rotation so that the butterfly valve 61 is closed as shown. Piston remains positioned to the left as suggested, by the dashed lines. Pressure build-up at the right side of sleeve piston 77 is prevented because of bleed orifice 97 and its vent connections.

When pressurized gas is not supplied, the positioning will be as shown in FIGURE 2 due to spring 113 overcoming spring 82.

From the foregoing, it is apparent that a single pneumatic control provides a safety shut down in the event of either eccentric rotation or overspeed even when the inlet pressure is in the low range since only a few p.s.i.

are required for operation. Further, cleaning upon each start cycle is provided which prevents hang-up due to dust and other causes.

It is to be understood that persons skilled in the art can make changes in the disclosed embodiment without departing from the invention as set forth in the following claims.

What is claimed is:

1. A gas turbine and single pneumatic control therefor adapted to shut down the turbine in event of eccentric turbine rotation as a result of a bearing failure or in the event of overspeed of the turbine comprised of a turbine wheel having blades,

support means including bearings, supporting said turbine wheel for normal rotation in a fived transverse plane,

inlet means constructed and arranged to supply gas to said turbine blades,

a gas supply pipe connected to said inlet means and having an on-off valve mounted therein,

pneumatic control means fluidly connected to said gas supply pipe upstream of said valve and constructed to open said on-off valve when subject to a predetermined-pressurized gas from said gas supply pipe,

escape means operable by eccentric rotation of said turbine wheel connected to said pneumatic means to provide an escape flow path from said pneumatic means,

said pneumatic means being constructed to close said on-oi'f valve when said escape flow path is provided and a predetermined pressure drop results,

said pneumatic means having a vent flow path during normal operation,

a speed-responsive means operable to close said vent flow path when said turbine wheel rotates above a predetermined speed,

said pneumatic means being constructed to close said on-off valve when said vent flow path is closed and a predetermined pressure exists whereby said turbine is prevented from over-speeding,

said pneumatic means including piston actuator connected to said valve for the opening and closing thereof,

said pneumatic means including spool valve means arranged to pass gas to said piston actuator for opening and for closing said on-off valve in the event of eccentric rotation or overspeed, and

said pneumatic means including a flow-through piston adapted to block said vent flow path in cooperation with said spool valve means when said escape means provides an escape flow path so that said spool valve operates by pressure build-up to efiect closing of said on-oif valve.

2. A gas turbine and single pneumatic control therefor adapted to shut down the turbine in event of eccentric turbine rotation as a result of a bearing failure or in the event of overspeed of the turbine comprised of:

a radial-flow turbine wheel having a shaft extending from one side and on the other side blades and an axial projection,

support means including bearings supporting said turbine wheel shaft for normal rotation in a fixed trans verse plane,

a tubular exhaust duct encasing said turbine blades and said turbine axial projection,

an annular manifold constructed and arranged to supply gas to said turbine blades,

a gas supply pipe connected to said manifold and having a butterfly valve mounted therein,

pneumatic means fluidly connected to said gas supply pipe upstream of said butterfly valve and constructed to open said butterfly valve when subject to a predetermined-pressurized gas from said gas supply pipe,

a plurality of tubes projecting from said exhaust duct from at least three equi-spaced locations and terminating in frangible glass tips adjacent the blades of said turbine wheel,

said frangible tips sealing the ends of said tubes and being constructed to break when contacted by said blades upon eccentric rotation of said turbine wheel to provide an outlet for said tubes,

gas escape conduit means connecting said tubes to said pneumatic means to provide an escape flow path from said pneumatic means to said exhaust duct when one of said frangible tips is broken,

said pneumatic means being constructed to close said butterfly valve when said escape flow path is provided upon breaking of one of said frangible tips as a result of eccentric rotation of said turbine wheel,

a vent conduit having an open end axially-aligned with and spaced from said axial projection of said turbine wheel,

said vent conduit being connected to said pneumatic means to provide a vent flow path to said exhaust duct during normal operation,

a speed-responsive plunger having centrifugal flyweights axially mounted in the projection of said turbine wheel,

said plunger being movable to close said vent conduit when said turbine wheel rotates above a predetermined speed,

said pneumatic means being constructed to close said butterfly valve when said plunger closes said vent conduit whereby said turbine is prevented from overspeeding, and

said pneumatic means including a spring-biased piston actuator operably connected to said butterfly valve,

said pneumatic means including a housing defining first and second chambers having a common wall,

said pneumatic means including spring-biased spool valve means mounted in said first chamber arranged to pass ga to said piston actuator for normal opening and for closing in the event of eccentric rotation breaks one of said frangible tips or overspeed closes said vent conduit,

said pneumatic means including a spring-biased flowthrough piston having an axial projection mounted in said second chamber and having axial passage therethrough,

said spool valve means having a transverse wall,

said flow-through piston axial projection being slidably mounted in said common wall and abutting said transverse wall of said spool valve means to block said axial passage,

said gas supply pipe and said gas escape conduit means being connected to second chamber between said common wall and said flow-through piston,

said vent conduit being connected to an axial opening in said second chamber opposite said flow-through piston, and

said piston axial passage being arranged to mate with said axial opening.

3. A gas turbine and single pneumatic control therefor adapted to shut down the turbine in event of eccentric turbine rotation as a result of a bearing failure or in the event of overspeed of the turbine comprise of:

a turbine wheel having blades,

support means including bearings supporting said turbine wheel for normal rotation in a fixed transverse plane,

inlet means constructed and arranged to supply gas to said turbine blades,

a gas supply pipe connected to said inlet means and having on-off valve mounted therein,

' said pneumatic control means including a piston actuator connected to said on-ofi valve,

said pneumatic control'means including a spool valve -1neans arranged to control gas to said'piston actuator for opening and for closing said on-ofi valve,

gas escape means operable by eccentric rotation of said turbine wheel and connected to said pneumatic means to provide an escape flow path from said pneumatic control means,

a vent conduit being connected to said pneumatic means to provide a vent fiow path during normal operation,

a speed-responsive means operable to close said vent conduit when said turbine wheel rotates above a predetermined speed,

said pneumatic means including a flow-through piston adapted to block said vent conduit in cooperation with said spool valve means when-said escape flow path is provided due to eccentric rotation of said turbine,-

said spool valve responsive to flow through said vent conduit or escape means and operative to close said on-ofl .valve on blockage of flow through said vent conduit in response to turbine overspeed or eccentric rotation c onditions.

References Cited by the Examiner UNITED STATES PATENTS 12/19 Doran 25359 1,498,096 6/24 Herr 25369 1,634,897 7/27 Davis 25359 1,771,720 7/30 Miller 137-31 1,921,903 8/33 Bentley 256-56 LAURENCE V. EFNER, Primary Examiner.

Claims (1)

1. A GAS TURBINE AND SINGLE PNEUMATIC CONTROL THEREFOR ADAPTED TO SHUT DOWN THE TURBINE IN EVENT OF ECCENTRIC TURBINE ROTATION AS A RESULT OF A BEARING FAILURE OR IN THE EVEN OF OVERSPEED OF THE TURBINE COMPRISED OF: A TURBINE WHEEL HAVING BLADES, SUPPORT MEANS INCLUDING BEARINGS, SUPPORTING SAID TURBINE WHEEL FOR NORMAL ROTATION IN A FIVED TRANSVERSE PLANE, INLET MEANS CONSTRUCTED AND ARRANGED TO SUPPLY GAS TO SAID TURBINE BLADES, A GAS SUPPLY PIPE CONNECTED TO SIAD INLET MEANS AND HAVING AN ON-OFF VALVE MOUNTED THEREIN, PNEUMATIC CONTROL MEANS FLUIDLY CONNECTED TO SAID GAS SUPPLY PIPE UPSTREAM OF SAID VALVE AND CONSTRUCTED TO OPEN SAID ON-OFF WHEN SUBJECT TO A PREDETERMINED-PRESSURIZED GAS FROM SAID GAS SUPPLY PIPE, ESCAPE MEANS OPERABLE BY ECCENTRIC ROTATION OF SAID TURBINE WHEEL CONNECTED TO SAID PNEUMATIC MEANS TO PROVIDE AN ESCAPE FLOW PATH FROM SAID PNEUMATIC MEANS, SAID PNEUMATIC MEANS BEING CONSTRUCTED TO CLOSE SAID ON-OFF VALVE WHEN SAID ESCAPE FLOW PATH IS PROVIDED AND A PREDETERMINED PRESSURE DROP RESULTS, SAID PNEUMATIC MEANS HAVING A VENT FLOW PATH DURING NORMAL OPERATION, A SPEED-RESPONSIVE MEANS OPERABLE TO CLOSE SAID VENT FLOW PATH WHEN SAID TURBINE WHEEL ROTATES ABOVE A PREDETERMINED SPEED, SAID PNEUMATIC MEANS BEING CONSTRUCTED TO CLOSE SAID ON-OFF VALVE WHEN SAID VENT FLOW PATH IS CLOSED AND A PREDETERMINED PRESSURE EXISTS WHEREBY SAID TURBINE IS PREVENTED FROM OVER-SPEEDING, SAID PNEUMATIC MEANS INCLUDING PISTON ACTUATOR CONNECTED TO SAID VALVE FOR THE OPENING AND CLOSING THEREOF, SAID PNEUMATIC MEANS INCLUDING SPOOL VALVE MEANS ARRANGED TO PASS GAS TO SAID PISTON ACTUATOR FOR OPENING AND FOR CLOSING SAID ON-OFF VALVE IN THE EVENT OF ECCENTRIC ROTATION OR OVERSPEED, AND SAID PNEUMATIC MEANS INCLUDING A FLOW-THROUGH PISTON ADAPTED TO BLOCK SAID VENT FLOW PATH IN COOPERATION WITH SAID SPOOL VALVE MEANS WHEN SAID ESCAPE MEANS PROVIDES AN ESCAPE FLOW PATH SO THAT SAID SPOOL VALVE OPERATES BY PRESSURE BUILD-UP TO EFFECT CLOSING OF SAID ON-OFF VALVE.

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