US2184661A - Elastic fluid turbine - Google Patents

Description

Dec. 26, 1939. o. D. H. BENTLEY ELASTIC FLUID TURBINE Filed Oct. 50 1936 4 Sheets-Sheet l W M MM Dec. 26, 1939. o. D. H. BENTLEY ELASTIC FLUID TURBINE Filed 001;. 30, 1936 4 Sheets-Sheet 2 I n.- Liv Dec. 26, 1939.

o. D. H. BENTLEY 2,184,661

ELASTIC FLUID TURBINE Filed Oct. 50, 1936 4 Sheets-Sheet 3 Wm henior Dec. 26, 1939. o. D. H. BENTLEY 6 ELASTIC FLUID TURBINE Filed Oct. 30, 1956 4 Sheets-Sheet 4 50 a o o 0 a u a 231 0 55 27.5 76 I 56 o Z 51 a a 0 76 I 234 2 6 a 75 Z a l 0 gm! l 74' r K 0 a 232 100 9.5 73 J l 67 a 9/3 71 v v J; .1 0o

6 a 1: v m o (I O .92 3K 8g Wl'17LeJJ M 5: weak 4; mmwfi Patented Dec. 26, 1939 UNITED STTES PATENT OFFICE to B. F. Sturtevant Company,

Hyde Park,

Mass, a corporation of Massachusetts Application October 30, 1936, Serial No. 108,458

9 Claims.

This invention relates to elastic fluid-turbines and more particularly to variable speed turbines which are required to operate over a wide range of speeds at high efiiciency.

Elastic iiuid turbines as at present constructed operate at high efiiciency upon fairly definite ranges of speed, these ranges varying with the difierent types of turbine. For example, the axial flow Curtis type operates at high efficiency only at relatively high rotational speeds as, for example, from 2000 to 6000 or 8000 R. P. M. Any reduction in speed below this range results in an immediate and marked loss in efiiciency.

In the helical flow type of turbine, such, for example, as the well-known Sturtevant type, the efiicient speed range is relatively low, say from 500 R. P. M. up to 2000. The operation of this type of turbine at speeds above this range results in a marked loss in efiiciency.

In many types of installation the turbine is required to operate throughout a much "greater range of speed than those at which either of these types give high efficiency. Forexample, turbines which drive the forced or induced draft fans in power stations operate from a minimum speed of a few hundred R. P. M. up to a maximum of several thousand, according to the demand or load. High efiiciency throughout this entire range is obviously greatly to be desired.

It is the object of the present invention to provide a turbine which will satisfy these requirements, and which may operate throughout both the lower and the higher speed ranges, but with a uniformly high efiiciency.

To the above end the present invention contemplates the provision of a single unitary turbine structure, comprising a single rotor and a single casing, with turbine elements such as vanes or buckets and nozzles whereby elastic fluid or steam will drive the rotor at both high and low speeds with a uniformly low water rate and high efficiency.

The present invention further contemplates the provision in such a turbine of a plurality of nozzles and automatic mechanism for automatically controllingsuch nozzles whereby the proper nozzles and valves will be rendered operative to give the maximum eficiency at the desired speed.

In the accompanying drawings which illustrate what is now considered to be the preferred form of the invention as applied to a turbine for driving a forced orv induced draft fan in a power plant, there is shown a combination of the vanes and nozzles of the Curtis high speed axial flow turbine with buckets and nozzles of the Sturtevant low speed helical flow turbine so constructed and arranged that a variable speed of operation from 500 to 6000 or 8000 R. P. M. may be secured at substantially maximum efiiciency throughout such range. v

In the drawings Fig. 1 is a transverse, vertical section of the rotor and nozzles, and Fig. 2 is an axial or horizontal section of the same, taken along the line Z--2 of Fig. 1, of one form or embodiment of the invention; Fig. 3 is a transverse vertical section of the rotor and nozzles of an alternative construction, and Fig. 4 is an axial or horizontal section of the same, taken along the line 44 of Fig. 3; Fig. 5 is a fragmentary development of the vanes or blades and of the nozzles of the first construction shown in Figs. 1 and 2, and Fig. 6 is a similar fragmentary development of the blades and nozzles of the alternative construction shown in Figs. 3 and 4; Fig. 7 is a side view partly in section, and Fig. 8 a diagrammatic view of the automatic mechanism for controlling the admission of steam to the various nozzle segments.

The turbine comprises the usual rotor mounted on a shaft and provided with vanes or blades or buckets, as they are variously termed. The rotor is enclosed in a casing in which is mounted not only the nozzles for directing the steam into or onto the rotor blades or buckets, but also the stationary vanes or buckets to receive the steam from the rotor buckets and redirect it onto or into the rotor buckets. The casing is provided with an internal space which forms an exhaust chamber to receive and collect the steam discharged from the vanes or buckets.

The two designs illustrated differ only in that in the first design the buckets or vanes for the low and high speed operations are disposed side by side on the periphery of the rotor, while in the second design the low speed buckets are positioned intermediate two series of high speed buckets.

In the first construction illustrated in. Figs. 1, 2 and 5, the rotor ll is provided with two series of buckets or vanes. The low speed or helical flow buckets l3 are positioned on the periphery of the rotor at the steam supply end, while the high speed or axial flow buckets, of which there are two, series l5 and H, are located on the opposite or exhaust end of the rotor. These high speed buckets are also on a longer radius or a greater distance from the axis than are the low speed buckets, thus securing higher linear speed for the former than for the latter.

The low speed buckets l3 are formed or cut in the metal of the rotor in the manner commonly employed in the Sturtevant turbine and as shown in United States Letters Patent No. 1,081,22, December 9, 1913, while the high speed blades 55 and H are constructed in the usual manner of the Curtis type turbine.

Steam is supplied to the low speed buckets l3 through the expanding nozzles 2! formed in the nozzle segments 23 which are also provided with reversing or redirecting buckets 25, as is customary in this type of turbine.

The steam supply to the series l5 or the high speed vanes is through the nozzles 2i which in accordance with the usual practice are formed in multiple on a nozzle block 26. The fixed redirecting blades 3! carried by the segmental members 33 secured to the inner face of the casing 35 receive the steam as it is discharged fromthe first series of blades l 5 and redirect it into the second series H where further energy is extracted.

In Fig. l of the drawings four nozzle sets or blocks are shown, the rotor buckets being open and uncovered between such sets to provide the free exhaust of steam. In order to permit this exhaust steam from the low speed buckets which is discharged into the space 38 in the front or steam supply end of the casing to pass to the rear or exhaust chamber of the casing, the segments or members 33 are provided with openings 4|.

The stationary reversing vanes 3! of the high speed section do not extend around the entire periphery of the casing, but only substantially the length of the high speed nozzle flow, as shown in Fig. 5, the space between these sections of the fixed nozzles being occupied by the filler blocks 43 to prevent recirculation of the exhaust steam through the rotor buckets at these points, with consequent loss of efficiency.

In operation, the speed and power developed is controlled by means of suitable valves for the high and low speed nozzles which will out such nozzles successively into and out of operation as desired. For example, for the minimum speeds a single low speed nozzle would be in operation and as additional speed and power were required, additional low speed nozzles would be successively opened. When the speed and power requirements exceeded capacity of all four low speed nozzles, the high speed nozzle block or segment would be rendered operative and additional blocks or segments opened as the requirements for speed or power increased.-

Owing to the much greater capacity of the high speed nozzles than the low speed, it would make little dilference in the water rate whether or not the low speed nozzles were cut ofi when the high speed nozzles were thrown into operation, but such low speed nozzles could either be continued in operation to augment slightly the power or be cut off entirely as might be desired.

Conversely, as the requirements for speed or power diminish, the high speed power segments could be progressively closed until finally the operation was through the low speed nozzle segments alone and at last only a single one of these might be in operation for minimum speed. Preferably the nozzle segments for both high and low speed are alternately and symmetrically disposed around the periphery of the rotor.

In the alternative construction, shown in Figs. 3, 4 and 6, the low speed or helical flow rotor buckets H3 are positioned intermediate the two series of high speed vanes or blades H5 and i ll, with the nozzle segments I23 mounted upon the periphery of the casing. Intermediate such segments are located the fixed high speed redirecting buckets l3l. No filler blocks are required in this construction as the low speed nozzle segments occupy the intermediate space between the fixed or stationary blades. The high speed nozzle segments I29 are positioned as in the former construction.

Provision for the escape of steam from the low speed rotor buckets is found'in the space between the fixed high speed redirecting blades and the low speed nozzle segment, the steam as it passes out of the open or uncovered low speed rotor bucket passing through the high speed rotor buckets ll? into the exhaust space at the rear of the casing.

The devices and mechanisms for securing the above described operation and regulation are shown more or less diagrammatically in Figs. '7 and 8, with automatic control of the delivery of steam to the several nozzles in order to vary the speed of the turbine. and its driven fan for the purpose of maintaining substantially constant steam pressure under varying load conditions.

The several nozzle segments 23 for supplying steam to the helical flow buckets are each connected with the steam chest fill through separate and independent steam pipes and inlet valves. Thus the starting or idling speed nozzle segment shown on Fig. 8 as 23! is connected by steam pipe M with steam chest fill through inlet valve 5 l. When the turbine and fan are to be started or operated at their lowest or idling speed, this valve 6! alone will be open as shown in Fig. 8.

The second nozzle to be supplied with steam when a slightly higher speed of rotation is required is in segment 232 with pipe connection 52 and valve 62. When still higher speed is demanded nozzle segment 233 is supplied with steam through pipe 53 and valve 533, followed by nozzle segment 23d through pipe 5% and valve 64.

At this stage all four nozzles 23 are delivering steam and the turbine and fan are rotating at the top of the low speed range, say, at 2000 R. P. M. and one-eighth maximum power.

As the demand on the fan progressively increases, the nozzles 27 for the high speed vanes or buckets are cut in progressively, first nozzle in segment 215 through steam connection 55 and valve 65, and then those in segments 276, 211 and 2'18 in that order.

Preferably, as each high speed nozzle in succession becomes operative, the lowest speed nozzle will be cut out of operation. Thus when the nozzle in segment 2l5 is cut the nozzle in segment 23! will be cut out, and so on until at maximum speed and power requirements, all the high speed nozzles will be in operation while all the low speed nozzles will be shut oil.

The mechanism for operating the valves which control the supply of steam to the several nozzles comprises a rotatable shaft '5!) carrying the cams H to 18 for engaging the stems of valves 6i to 58 respectively. The cams are so shaped that as the shaft is turned the several valves will be opened and closed in the manner above described.

The cam shaft is turned in the proper direction and to the necessary extent by means of hydraulic devices comprising the cylinder 86, piston Bl, piston rod 82, and rack and gear connection 83. These devices in turn are controlled through the valve 90 within the movable valve cylinder 9! carried on the extension 92 of the piston rod 82. Suitable connections 93 and 9G, having provision (not shown) for movement of the valve casing, conduct the oil or other liquid from the valve casing to and from the cylinder 88. The liquid is supplied to the valve casing and conducted therefrom through supply and exhaust pipes 95 and 95 respectively, having provision (not shown) for movement of the casing.

The valve 88 is controlled from the boiler pressure, being actuated, when the pressure drops, to admit oil to the outer end of the cylinder through connection 94 to rotate cam shaft in the direction of the arrow thereby to throw into operation one or more of the higher speed nozzles and thus increase the speed of the fan. Conversely, when the boiler pressure rises above the predetermined pressure, the valve 99 will be moved in the opposite direction to' cause the cam shaft to be reversely rotated and the higher speed nozzles or nozzle to be cut out and the lower speed to be cut in.

Since valve casing 9! is connected to and moves with piston 8!, the extent to which cam shaft 10 is rotated will be proportional to the drop or rise in steam pressure, thereby avoiding to a large degree over compensation and wide fluctuations in pressure.

The control valve 913 is actuated by means of the diaphragm Hill subjected on one side to the boiler pressure through pipe NH and engaging on the other side the spring pressed head 32 on valve rod H13.

While progressive increase in the size of the nozzles may be varied tosuit different conditions and desired ranges in speed, a satisfactory proportioning of nozzle areas has been found to be in the geometrical ratio of 2. Thus the second low speed nozzle will have twice the cross-sectional area of the first; the third twice that of the second, the fourth twice that of the third; and so on.

The cams for the valves are designed with proper inclinations so that the opening and closing of the valves will be gradual and extend over slightly less than one-eighth of a revolution or 45, thus providing for any desired speed from minimum to maximum with even and uniform change from one to another.

From the foregoing description it is evident that an elastic fluid turbine has been provided having a single rotor and a single casing, but with a plurality of sets of vanes and nozzles for supplying fluid thereto, certain of the buckets and nozzles being operated to drive the rotor at relatively low speeds, but with high efiiciency, and another set of vanes or buckets and nozzles operating to drive the rotor at relatively high speed with the characteristic high eiiiciency of that type of construction, and both sets or portions of both sets, operating to drive the rotor at intermediate speeds, still at high efliciency.

While the present invention has been shown and described in connection with two well known types of low and high speed construction, it is to be understood that it is not limited to these specific constructions except where so set forth in the claims, but may be embodied in other types and arrangements and forms within the range of the appended claims.

I claim:

1. An elastic fluid turbine having, in combination, a casing, a rotor mounted in the casing and having a plurality of sets of blades, one set comprising a series of helical flow blades for driving the rotor at low speeds and exhausting at one side of the rotor and the other set comprising two series of axial flow blades for driving the rotor at high speeds and exhausting at the opposite side of the rotor, a series of redirecting blades positioned between the series of rotor axial flow blades, means for securing the redirecting blades to the casing having provision for the passage of exhaust fluid from the helical flow blades from one side of the rotor to the other, and separate nozzles for delivering elastic fluid to the sets of rotor blades.

2. An elastic fluid turbine having, in combination, a casing, a rotor mounted in the casing and having a plurality of sets of blades, one set comprising a series of helical flow blades for driving the rotor at low speeds and the other set comprising two series of axial flow blades for driving the rotor at high speeds, both sets of blades being positioned on the periphery of the rotor with the series of helical flow blades axially disposed between the two series of axial flow blades, and nozzles for delivering elastic fluid to the blades.

3. An elastic fluid turbine having, in combination, a casing, a rotor mounted in the casing and having a plurality of sets of blades, one set comprising a series of helical flow blades for driving the rotor at low speeds and the other set comprising two series of axial flow blades for driving the rotor at high speeds, both sets of blades being positioned on the periphery of the rotor with the series of helical flow blades axially disposed between the two series of axial flow blades, a series of stationary redirecting blades carried by the casing and axially disposed between the two series of axial flow blades and overlying the helical flow blades, and nozzles for delivering elastic fluid to the blades, the nozzle for the helical flow blades being axially disposed between the two series of axial flow blades and overlying the helical flow blades.

4. An elastic fluid turbine having, in combination, a casing, a rotor mounted in the casing and having a plurality of sets of blades, one set comprising a series of helical flow blades for driving the rotor at low speeds and the other set comprising two series of axial flow blades for driving the rotor at high speeds, both sets of blades being positioned on the periphery of the rotor with the series of helical flow blades axially disposed between the two series of axial flow blades. a plurality of stationary redirecting blades carried by the casing and overlying the helical flow blades, and nozzles for supplying elastic fluid to the blades, the nozzles for the helical flow blades being positioned between series of stationary blades.

5. An elastic fluid turbine having, in combination, a casing, a rotor mounted in the casing and having a plurality of sets of blades, one set comprising a series of helical flow blades for driving the rotor at low speeds and the other set comprising two series of axial flow blades for driving the rotor at high speeds, both'sets of blades being positioned on the periphery of the rotor with the series of helical flow blades axially disposed between the two series of axial flow blades, a plurality of peripherally spaced arc-shaped series of stationary redirecting blades carried by the casing and axially disposed between the two sets of axial flow blades, and nozzles for supplying elastic fluid to the blades, the nozzles for the helical flow blades being positioned between series of stationary blades and peripherally spaced therefrom to provide a space for the escape of the elastic fluid from the helical flow blades.

6. An elastic fluid turbine having, in combination, a casing, a rotor mounted in the casing and having a plurality of sets of blades, one set comprising a series of helical flow blades for driving the rotor at low speeds and the other set comprising two series of axial flow blades for driving the rotor at high speeds, a series of redirecting blades positioned between the series of rotor axial flow blades, means for securing the re-directing blades to the casing constructed and arranged to provide a passage positioned radially outward beyond the axial flow blades for the flow therethrough of fluid exhausted from the helical flow blades.

7. An elastic fluid turbine having, in combination, a casing, a rotor mounted in the casing and having a plurality of sets of blades on the periphery thereof, one set comprising a series of helical flow blades for driving the rotor at law speeds and another set comprising a series of axial flow blades for driving the rotor in the same direction at high speeds, and separate nozzles for delivering elastic fluid to the helical flow blades and to the axial flow blades, the casing having an exhaust space communicating with the helical flow blades and axial flow blades to permit the passage through the axial flow blades of the fluid exhausted from the helical flow blades.

8. An elastic fluid turbine having, in combination, a casing having a fluid exhaust, a rotor mounted in the casing and having a plurality of sets of blades on the periphery thereof, one set comprising a series of helical flow blades for driving the rotor at low speeds and another set comprising a series of axial flow blades positioned intermediate the helical flow blades and the casing exhaust for driving the rotorat high speeds, the axial flow blades of the rotor being spaced from the casing to provide for the passage between the rotor and the casing to the casing exhaust of the fluid exhausted from the helical flow blades.

9. An elastic fluid turbine having, in combination, a casing, a rotor mounted in the casing and having a plurality of sets of blades, one set comprising a series of spaced helical flow blades for driving the rotor at low speeds and the other set comprising two series of axial flow blades for driving the rotor in the same direction at high speeds, both sets of blades being positioned on the periphery of the rotor with the series of helical flow blades axially disposed between the two series of axial flow blades, a series of spaced axial flow l e-directing blades carried by the casing and positioned between the series of rotor axial flow blades, a series of spaced helical flow re-directing blades carried by the casing and positioned between the series of axial flow blades and intermediate the spaced axial flow re-direct- :irig blades, and separate nozzles for delivering elastic fluid to the sets of rotor. blades.

OLIVER D. H. BENTLEY.

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