US2463898A - Turbine sealing construction - Google Patents

Description

March 8, 1949. v, T, MOORE 2,463,898

.TURBINE SEALING CONSTRUCTION Filed Nov. 24, 1944 3 Sheets-Sheet 1 AM'T'TIJHNEY INVENTOR. VINCENT T. MDIJRE Margh 8, 1949. y. T. MOORE TURBINE SEALING CONSTRUCTION Filed Nov. 24, 1944 3 Sheets-Sheet 2 PIIII'IIII s. w @4- INVENTOR Q ATTEIFINEY Patented Mar. 8,1949

2,463,898 TURBINE SEALING CONSTRUCTION Vincent T. Moore, Ridgewood, N. J., asslgnor to Wright Aeronautical Corporation, a corporation of New York Application November 24, 1944, Serial No. 565,021

1 This invention relates to turbines and is particularly directed to the provision Of sealing means for preventing the loss of the turbine motive fluid between the edges of the turbine nozzle and the turbine wheel.

A conventional turbine comprises a wheel or rotor having a plurality of blades about its periphery and the turbine motive or working fluid is discharged against these rotating blades from a fixed annular nozzle disposed adjacent thereto. Particularly in a reaction turbine, 'unless a suitable seal is provided, there is considerable leakage and waste of the turbine motive fluid radially inward through the space between the turbine wheel and the adjacent fixed edge of the turbine nozzle. If this leakage path is not sealed the loss of turbine motive fluid therethrough will result in a considerable reduction in turbine power and efficiency. Accordingly, it is an object of this invention to provide a simple and effective means for sealing this leakage path between the turbine wheel and its nozzle. To this end applicant introduces a sealing fluid under pressure inwardly of this annular leakage path to oppose leakage of turbine motive fluid therethrough.

It is a further object of this invention to use a liquid vaporized by the heat of the turbine exhaust as-a' sealing fluid. Thisvapor is raised It is a further object of this invention to uti-- 5 Claims. (01. 253-39) a rotating annulus of liquid to Provide the seal between the turbine rotor and the turbine nozzle To this end, the turbine rotor is provided with an inwardly opening channel to which a suitable liquid is supplied and the turbine nozzle structure is provided with a fixed annular baffle member extending into the rotating liquid annulus. With this construction, the pressure difierential across the baffle member causes a relative displacement of the liquid levels on the opposite sides of this member until the difference in the centrifugal force acting on these two liquid columns balances the gas pressure differential thereacross.

Other objects of this invention will become apparent upon reading the annexed detailed description in connection with the drawing in which:

Figure 1 is a diagrammatic viewof a turbine provided with the sealing means or this invention;

Figure 2 is a diagrammatic view or a modification of Figure 1 in which the sealing fluidis also used for cooling the turbine;

Figure 3 is a section view taken along the line 3-3 of Figure 2;

Figure 4 is a detailed view of a modification of the structure illustrated in Figure 3;

Figure 5 is a modification of the system of Fi ure 2; and

lize the sealing fluid for cooling the turbine wheel 'ing liquid thereby cooling the turbine. I In addition, it is an object of this invention to 1 provide automatic means to control the sealing pressure so that there is little or no leakageof the sealing fluid and/ or the turbine motive fluid.

Such automatic means are provided both in the case where the sealing fluid is used only for sealing purposes andin the case where the sealing fluid is also used forv cooling the turbine wheel. Also, it is within the scope of this invention to use Figure 6 illustrates a further form oi. seal between the turbine rotor and nozzle.

Referring first to Figure 1, a gas turbine power plant indicated in part comprises a turbine wheel Ill having one or more sets of turbine blades about its periphery. As illustrated, the wheel I0 is provided with two axially spaced sets of blades turbine motive fluid comprises combustion gases from a combustion chamber shown in part at l8. From the combustion chamber 18, the combustion gases flow through an annular nozzle box vIII having suitable guide vanes 2| which properly 1 direct the combustion gases relative to the blades 12 of the turbine wheel l0.

Fromthe turbine blades the combustion gases discharge through an annular exhaust duct 22. The turbine rotor is jour'naled within suitable fixed supporting members 24 and 26 and the member 26 also carries the nozzle box 28.

With this construction, and particularly in a reaction type turbine, the combustion gases have a substantial pressure above atmospheric between the turbine nozzle and the turbine'blades and therefore in the absence of a suitable seal there will be considerable leakage and loss of combustion gases inwardly through the space between the rim of the turbine wheel and the adjacent edge of the fixed turbine nozzle. To seal this leakage path, an annular labyrinth packing or seal 28 carried by the nozzle 20, is disposed between the inner edge of the nozzle and the rim of the turbine wheel. A second annular labyrinth packing or seal 88 is carried by the supporting structure 26 and is disposed between this structure and the turbine wheel I8 radially inwardly of the packing 28 thereby leaving an annular space 32 therebetween. Y

A sealing liquid is stored in a container 34 and a pump 36 supplies this liquid under suitable pressure through passage 38 to coils 48 disposed in the exhaust duct 22 where the liquid is vaporized by the heat of the exhaust gases. From the coils 48, the vapor is supplied under the pump pressure through conduit 4| to the annular space 32 between the labyrinth packings 28 and 30. The pressure of the sealing vapor is controlled by a valve 42 disposed in a vent line 44 communicating with the annular space 32. I

The valve 42 is connected to a piston 46 having one side vented through a passage 48 and having its other side in communication with the pressure of the combustion gases leaving the turbine nozzle 28 through a conduit 58. The valve 42 is a poppet type valve having its inlet side subjected to the pressure in the annular space 32. With this construction, by properly proportioning the effective areas of the valve 42 and piston 46, the valve 42 can be designed to automatically maintain a pressure in the space 32 substantially equal to the turbine nozzle discharge pressure. The vapor escaping through the valve 42 from the space 32 flows from the valve through a conduit 52 and condensing coils 54 and then back into the container 34. The vapor which leaks past the labyrinth packing 30 is returned to the container 34 through a conduit 56 and a condenser 58.

With the valve 42 automatically maintaining a pressure in the annular space 32 substantially equal to the opposing pressure of the combustion gases on the other side of the labyrinth packing 28, there is substantially no leakage or loss of the combustion gases across the labyrinth packing 28. Also, it should be noted that the pump 36 requires very little power because it raises the sealing fluid to the required pressure while the fluid is still in the liquid state.

The sealing fluid may also be used for cooling the turbine wheel as illustrated in Figure 2.v In this modification a turbine wheel 68 is provided with an annular inwardly facing groove or channel 62 on the upstream side of its rim. The turbine wheel 68 is provided with a pair of axially spaced sets of turbine.blades 64 and 66 disposed about its rim and a fixed set of blades 68- are disposed therebetween. A turbine nozzle 18 having suitable guide vanes 12 directs the combustion gases from the combustion chamber illustrated in part at 14 into the turbine blades and .from which the combustion gases discharge through an annular exhaust duct 16. The turbine wheel and turbine nozzle are supported by suitable diaphragms I8 and 88. An annular labyrinth packing 82 carried by the turbine nozzle is disposed between the turbine nozzle 18 and the rim of the turbine wheel 68: A second annular laby-' rinth packing 84 is carried by the support 88 and is disposed inwardly of the labyrinth packing 82 to provide an annular space 83 therebetween into which the annular groove 62 opens. Except for the provision of the annular groove 62, the structure of Figure 2 so far described is similar to that of Figure 1.

The sealing liquid is carried in a container 86 and a pump 88, connected thereto, supplies sealing liquid to the annular groove 62 through conduit 90 and discharge pipe 92. Because of the high speed rotation of the turbine, the liquid supplied to the annular groove 62 distributes-itself substantially uniformly'around the annular groove 62, the liquid being held in position within the groove by the centrifugal force acting thereon.

The high temperature of the turbine wheel 68 serves to evaporate the sealing liquid within the groove 62, thereby providing a vapor pressure in the annular space 83 suficient to balance the pressure of the combustion gases on the other side of the labyrinth packing 82, at the same time the evaporation of the sealing liquid in the groove 62 is effective to cool the turbine wheel. The magnitude of the vapor pressure in the space 83 is controlled by a valve 94 in a vent passage 96 communicating with the space 83. This valve 94 is connected to a piston 98 having one side vented through passage I89 and having its other side in communication wtih the turbine nozzle discharge pressure through conduit I82. The inner side of the valve 94 is subjected to the sealing vapor pressure in the space 83 through conduit 96. With this construction, as in Figure 1, upon proper design of the relative sizes of the valve 94 and piston 98, the valve 94 will automatically operate to maintain a vapor pressure within the space 83 substantially equal to the turbine nozzle discharge pressure. The sealing vapor escaping through the vent line 96 flows through the valve 94 and then through condenser coils I84 back to the container 86. The sealing vapor leaking past the labyrinth packing 84 returns to the container 86 through a conduit I06 and condenser coils I88.

If the pump 88 is a positive displacement type pump, then in order to prevent excessive quantities of liquid being supplied to the annular groove 62, the pump is provided with a by-pass passage H8 having an automatic relief valve I i2 limiting the pump output pressure. With this arrangement, when the groove 62 fills up to the point at which it covers the end of the discharge pipe 92, the pressure of the liquid within this groove resulting from the centrifugal force acting thereon, serves to reduce the quantity of liquid supplied by the pump 88 to the groove 62. If desired, pipe 92 may be provided with a scoop opening facing against the direction of rotation of the liquid in the groove 62 as best seen in Figure 8. In this way, when the liquid within the groove reaches the level of the scoop opening, the impact pressure of the liquid within the groove 62 on the scoop opening reduces the quantity of liquid delivered thereto by thepump.

'In lieu of the scoopopening at the end of the pump discharge pipe, this pipe may be provided with a float or aqua-plane type valve for closing the open end on the discharge pipe when the liquid within the groove 62 reaches a predetermined level. --Thus, as illustrated in Figure 4, the pump discharge pipe II4, corresponding to pipe 02 of Figure 2, provides a valve seat at its open end and a valve H6 carried by a pivotally mounted aqua-plane type member H8 is adapted to control the size of the valve opening. With this construction, when the liquid in the groove 62 exceeds a predetermined level, the valve H6 is moved in a closing direction by the aqua-plane member I I8 until a balance is reached between the quantity of liquid delivered through the pipe II 4 and the quantity of liquid being evaporated. Figure 5 illustrates a further modification in which the inwardly disposed labyrinth packing about the turbine wheel is made adjustable for controlling the pressure within the annular space between the two sets of labyrinth packings instead of by providing a separate vent passage as in Figures 1 and 2. The construction of the turbine wheel, turbine nozzle, combustion chamber and exhaust conduit are similar to that of Figure 2 and have been designated by similar reference numerals. The supporting. diaphragm I20 for the turbine wheel and turbine nozzle is provided with an outer annular labyrinth packing I22 and an inner labyrinth packing I24 thereby providing an annular space I26 between labyrinth packing I22 and I 24. The turbine wheel groove 62 opens into this annular space I20 as in Figure 2. The inner labyrinth packing I24 is carried by an annular piston member I28 slidably received Within an annular cylinder I30, formed in the support I20.

The sealing liquid is supplied to the annular groove 62 by a pump I32 from a container I34. The pressure of the sealing vapor within the annular space I26 is maintained by controlled movements of the labyrinth packing 124. this end, the pressure within the annular space I26 and the turbine nozzle discharge pressure are transmitted to. opposite sides of .a piston.

which controls the admission of a suitable fluid.

under pressure to the annular cylinder I30 besuitable seal between the turbine wheel and turbine nozzle is reduced to a negligible amount by automatically maintaining the pressure of a sealing fluid on the other side of this packing or seal substantially equal to the pressure of the turbine motive fluid. In any of these modifications the control may be adjusted to maintain a sealing presure slightly above, equal to or slightly below the pressure of the turbine motive fluid leaving the nozzle. If a large quantity of the sealing fluid is readily available it may be desirable to maintain a pressure of the sealing vapor slightly higher than that of the opposed turbine motive fluid in which case there will be a slight leakage of the sealing fluid therein. On the other hand, if the supply of the sealing fluid is quite limited then it becomes desirable to maintain a sealing vapor pressure slightly lower in which case with an eflicient condenser there will be no loss of the sealing fluid during turbine operation. In any of the modifications of Figures 1-5, various sealing liquids may be used but in an aircraft installation where weight is of primary importance, the liquid should have a high boiling point so that it will condense readily within a small low weight condenser, e. g., fuel or water would be satisfactory in an aircraft installation. The use of fuel as a sealing fluid hasthe advantage in that with a suitable fuel and.

. with the automatic control adjusted to provide for a leakage of the sealing fuel vapor into the turbine nozzle discharge, the fuel vapor will be ignited by the high temperature of the combustion gases thereby adding to the power output of the turbine. The use of water as a sealing fluid has the advantage in an installation where it is desired to save weight in that it is possible to recover water from the turbine exhaust to make up for loss in the water supply, thereby making it unnecessary to carry a large supply of water.

The modifications of Figures 2 and 5 have the additional advantage that the evaporation of the hind the labyrinth piston I28. As illustrated, the

turbine nozzle, discharge. pressure is controllably admitted by the valve I 42 to the cylinder I30 from which there is a slight leakage around the piston I28. With this construction, if the pressure in the annular space I26 should increase, the piston I36 will move upwardly thereby decreasing. the pressure transmitted to the cylinder I30. Thereupon the pressure on the left side of the labyrinth packing I24 moves the labyrinth packing and its piston to the right to increase the clearance and leakage around the labyrinth packing I24 until the piston I36 is again balanced. In this way, thevalve I42 automat cally effects adiustments on the labyrinth packing I24 to maintain. the desired vapor pressure within the space I26. The sealing vapor escaping past the labyrinth pack n I24 is returned to he container I34 through a conduit I43 and a condenser I44. videdto limit theoutward travel of the piston I28.

At this point it should be noted that the pressure of the sealing vapor in themodificationof Figure 1' could be controlled by adiustments of the lower labyrinth packingjin a manner similar to the automatic control illustrated in Figure 5.

Suitable stop means, I46 are pro- I60 and, thesubstantially atmospheric pressure sealing liquid at the rim of the turbine wheel also operates, to cool the turbine wheel. It is also within the scope of this invention to use the.

fluid within the annular groove about the rim of the turbine jwheel solely for cooling the turbine wheel.

Figure 6 illustrates a further modified form of the invention for providing a seal between the turbine rotor or wheel and the turbine nozzle box. As illustrated, a turbine wheel I50 is provided with a plurality of turbine blades about its periphery. An annular turbine nozzle I52 directs the combustion gases from a combustion chamber (not shown) into the turbine blades I54 from which the turbine motive fluid discharges into an exhaust conduit I56.

The turbine wheel I50 is provided with an inwardly opening annular groove or channel I58 adiar-ent it rim and on its upstream side. An annular ba-file or seal member I60 is secured at one end to the turbine nozzle I52 and at its other end extends into the annular channel I58. A

suitableliquid is supplied to the channel I56 through pi e I!" and passage'l62 within the annular member I50. v

. The pressure differential between the combustion gases on the one side of the baflle member on theother side causes a.relative displacement in the levels'of the liquid in the annular channel I58 on the opposite sides of the baille member I50 such that the difference in the centrifugal forces acting on the two annular columns of liquid on opposite sides of the battle member I60 balances the gas pressure differential thereacross. Because of the high speed rotation of the turbine wheel, the resulting centrifugal forces acting on the annulus of liquid in the channel I58 are quite large and therefore the difference in the levels of the liquid on opposite sides of the baffle member I60 is quite small. I

With this construction of Figure 6, the bailie or seal member I60 and the annulus of liquid within the channel I58 together prevent leakage of the combustion gases between the turbine wheel and nozzle. Various liquidsmay be used in this modification such as for example lubricating oil or-mercury, it being essentialthat the liquid have a high boiling point so that it remains a liquid in the presence of the high temperatures encountered at the turbine wheel.

The friction between the annular baiile member I60 and the liquid within the annular channel I58 may develop considerable heat.- This heat is dissipated by providing for continual circulation of the liquid into and out of the channel I58. To this end the baflie member I60 is provided with a drain pipe I64 and a drain passage I66 opening into the channel I58 on the low pressure or left side of the baffle member I60 (as viewed in the drawing). With this construction, during turbine operation liquid is continually supplied through conduit I6I and passage I62 and its level rises until it covers the open end of drain passage I66. Thereupon the centrifugal force acting on the liquid forces any additional liquid through the drain passage. In this way liquid is continually circulated through the annular channel I58. The open end of the passage I62 is spaced radially inwardly of the open end of passage I62 so that the liquid within the channel I58 does not prevent or restrict the supply of liquid thereto.

In all the modifications illustrated, a seal is provided which effectively prevents loss of the turbine motive fluid. In addition, in each modification, the pressure of the turbine motive fluid against the turbine rotor is limited by the seal to the' turbine blades and to the rim of the turbine rotor. Therefore because of the seal, the axial thrust exerted by the turbine motive fluid on the turbine rotor is greatly reduced.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modiflcations.

I claim as my invention:

1. A turbine installation comprising a turbinethe side of said'rotor adjacent said spaced ananular packings and opening into the annular space between said packings, and means for supplying a liquid to said channel such that during turbine operation said liquid is vaporized by the turbine heat to provide a fluid pressure in said space inhibiting leakage of the turbine motive fluid therein.

2. A turbine installation comprising a turbine rotor structure, a pair of spaced annular pack: ings, each of said packings being disposed between facing surfaces of said rotor structure and adjacent turbine structure and being carried by at least one of said structures, said rotor having an inwardly facing annular channel disposed on the side of said rotor adjacent said spaced annular packings and opening into the annular space between said packings, means for supplying a liquid to said channel such that during turbine operation said liquid is vaporized by the turbine heat to provide a fluid pressure in said space inhibiting leakage of the turbine motive fluid therein, and means for automatically varying the magnitude of the fluid pressure within said space with changes in the pressure of the opposed turbine motive fluid.

3. A turbine installationcomprising a turbine rotor structure, a pair of spaced annular packings, each of said packings being disposed between facing surfaces of said rotor structure and adjacent turbine structure and being carried by at least one of said structures, said rotor having an inwardly facing annular channel disposed on the side of said rotor adjacent said spaced annular packings and opening into the annular space between said packings, means for supplying a liquid to said channel such that during turbine operation said liquid is vaporized by the turbine heat to provide a fluid pressure in said space inhibiting leakage of the turbine motive fluid therein, and means automatically operable to maintain the depth of the liquid within said channel less than that at which said liquid would spill over the edges of said channel.

4. A turbine installation comprising a turbine rotor structure having a plurality of blades about its periphery, an annular turbine nozzle construction for supplying turbine motive fluid to said blades, a pair of spaced annular packings disposed adjacent the outer periphery of said rotor and inwardly of said blades, each of said packings being disposed between facing surfaces of said rotor structure and adjacent turbine structure and being carried by at least one of said structures, said rotor having an inwardly facing annular channel disposed on the side of said rotor adjacent said spaced annular packings and opening into the annular space between said packings, and means for supplying a liquid to said channel such that during turbine operation said liquid is vaporized by the turbine heat to provide a fluid pressure in saidspace inhibiting leakage of said turbine motive fluid therein.

5. A turbine installation comprising a turbine rotor structure having a plurality of blades about its periphery, an annular turbine nozzle construction for supplying turbine motive fluid to said blades, a pair of spaced annular packings disposed adjacent the outer periphery of said rotor and inwardly of said blades, each of said packings being' disposed between facing surfaces of said rotor structure and adjacent turbine structure and being carried by at least one of said structures, said rotor having an inwardly facing annular channel disposed on the side of said rotor adjacent said spaced annular packings and opening into the annular space between said packings, means for supplying a liquid to said channel such that during turbine operation said liquid is vaporized by the turbine heat to provide a fluid pressure. in said space inhibiting leakage of said turbine motive fluid, and means for automatically varying the magnitude of the fluid 9 10 pressure in said space with changes in the pres- Number Name Date sure of the opposed turbine motive fluid therein- 1.352,743 Hall Sept. 14, 1920 VINCENT T. MOORE. 1,482,602 De Conick Feb. 5, 1924 1,759,074 Van Rijswijk May 20, 1930 REFERENCES CITED 5 1,777,495 Kenyon Oct. 7, 1930 The following references are of record in the 1,878,731 Thompson SePt- 1932 me of this patent, 2,133,879 Thearle Oct.18, 1938 2,331,649 Bittner Oct. 12, 1943 UNITED 'I'ES TENT STA PA s FOREIGN PATENTS Number Name Dat 10 8 9 Feb, 14, 1911 Number Country Date 3 313 3 fifig Aug 19, 1913 148,823 Great Britain Feb. 9, 1922

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