US1798894A - Steam-turbine plant for high pressures and very high superheating - Google Patents

Description

Maui: 31 1931. w G. NOACK ET AL 1,798,394

STEM! TURBINE PLANT FOR HIGH PRESSUHES AND VERY HIGH SUPERHEATING Filed. July 8, 1922. 2 Sheets-Sheet l xix-Wei h Marsh 31, 1931. -w. e. NOACK ET AL 1,798,894

STEAM TURBINE PLANT FOR HIGH PRESSURES AND VERY HIGH SUPERHEATING' Filed July 8, 1922 2 Sheets-Sheet 2 Inxfeifiz WM) 1% M T %MM u waml.

Patented Man-31, 1931 warren e. NQACK, on 3A1) sienons To a igrrrnens'nnnscnarr nnownnovnnr & co.

STEAM-TURBINE PLANT FOR HIGH rnnssunns AND vnlay men sUPnnnEA'r-Ine Application filed July 8, 1922, Serial No. 573,731, and in Switzerland May 13, 1922., I

This invention relates to steam plant installations, and pertains particularly to in stallations in which it may be desired to employ highly superheated steam.

The general object of the invention is the provision of an installation which will possess good eliiciency not only at normal loads but also at abnormal and subnormal loads.

Another. object is theprovision of an in: stallation particularly qualified for the utilization of highly superheated steam. H

A further object is the provision of an installation which permits the use of highly superheated steam or of lower temperature steam selectively, for different load requirements, with efficient performance, and with out subjection of the control gear or of the parts designed for use of the lower tempera: ture steam to the possibly injurious effects of the highly superheated steam. I Other and further objects will be pointed out or indicated hereinafter or will be apparent to one skilled in the art upon an understanding of the invention or its employment in practice.

In the accompanying drawings forming a part of this specification, we show in diagrammatic fashion certain arrangements of apparatus representative of embodiments of the invention, but it is to be understood that these are presented for purpose of illustration only. and are not to be accorded any inter: pretation calculated to limit the claims short of the true and most comprehensive scope. of

the invention in the art.

In the drawings, Fig. 1 s a diagrammatic QlfSCllGIIliltlClllllS- tration of an installation including a turbine designed for operation by highly superheated steam and an associated turbine designed for operation with lower temperature steam, to-

gether with their control gear for governing,

the supply of steam to them e Fig. 2 is a diagrammatic illustration. of regulating gear as applied to the steam regulating valves ahead of the superheater;

Fig. 3 is a diagrammatic illustration of regulating gear tor controlling the steam supply to the low ressure turbine and illusm the e. nsult an at rertvttha new lating gear for limiting pressure in the supply lmeyand e Fig. 4 1s a detail 1n the nature of a cross section through one of the regulating devices,

the section being taken on line ll of Fig. 2.

1t isrecognized that certain improvements 1 in efficiency in some steam turbine instal-1aa A113 D M Y or zva qafswlrz mera Astions may be i ed y u e of h g team,

pressure derived from high superheati-ng. The use of highly superheated steam requires, however, certain special characterise tics in the construction of the turbine which are not required in turbines constructedi or f use of lower temperature steam. Likewise,

the control of the steam supply to the high,

pressure turbine, when highly superheated steam is employed, involves certain conside erations which do. not Wi e in thehandling of lower temperature steam, said consideratlons having to do principally with the safetributes to the safety and the efficiency of the a guarding of the control gear from the pronounced thermal effects of the highlysuper installation. Described generally, one form of installationcontemplated by the present invention includes a high pressure turbine especially qualified for working with highly superheated steam, a low pressure turbine arranged to he WOIkBCl with either or both the exhaust steam from the high pressure turbine and steamirom the supply line, a superheater for superheating steam from the supply line for the high pressure turbine,

I control gear between. the superheater and the supply line forcontrolling the steam supply to the high pressure turbine,together with appropriate regulating. and control gear for governing steam supplyto the low pressure turbineand to the low. high, pressure turbines conjointly.

For amore detailed understanding of the invention, reference is to the" assembly illustrated in the drawings, wherein m the reference character adesignates ahigh preser t aa y,

sure turbine qualified or o highly superheated steam, and low presf ti itbme. I wil beuad rataod r erring to these turbines as the high pressure and low pressure turbines, those terms are employed for the purpose of designation only, because, while the invention contemplates that the high pressure turbine is properly qualified for operation by highly superheated steam, the low pressure turbine" may be of normal design suitable for using normal pressure steam or steam of normal superheatsl The reference character 0 designates a steam supply line which may be supplied with --steam at'boiler pressure or at normal superheats. Between the supply line and the high pressure turbine is-interposed a superheater or superheaters, designated d 0Z (1 and d wherein the steam is highly superheated, and from which it is led to the high pressure turbine through the pipes 6 e 6 and e to supply the nozzle ring or rings f. On itsexhaust side, the high pressure turbine is connected to the steam inlets of the low pressure turbine by a pipe'g, which is controlled by a valve 00, and a" branch pipe it affords a second supply connection for the i low pressure turbine, from the supply line 0.

The steam regulating valves for the high pressure turbine are interposed between the supply line a and the superheaters (Z d (Z and (Z said regulating valves being desig-, nated a, n n andn and a regulating valve 0 is arranged in the branch line it for controlling supply of steam from the line 0 directly to the low pressure turbine. These regulating valves as herein illustrated are of the type operated by a servo-system, as exemplified in British Patent No. 3,893/1914,

being operated by oil supplied under pressure inthe servo lines m, m and p, wherein the eflectlve pressure is'regulated by governors i and 2' operated by'the turbines. The

principle of--operation of such regulating gear may be ascertained more clearly, by reference to Figs. 2 and 3. Referring to Fig.

2, it will be understood that oil under pres-' sure is suppliedfrom a servo pump Z (Fig. 1) to line m which leads it to the regulator cylinders under the pistons 9 wherein it is effective in opposition to the influence of the springs r to determine the'vertical position of the pistons. The pistons are connected to the valves n andof, and in accordance with" their positions, govern the passage ofsteam through the valves from the supply line 0. The effective pressure" of the oil in .line m is determined by the position of the valve sleeve k of the governor 2' which valve sleeve assumes different positions in accordance with the speed of the governor to vary the effective size of itslateral discharge aperture and in that manner vary the leakage of,

oil from the servoline to regulate the pressure effective under the pistons g Thus, the regulating valves 72 min and n are governed from the highpressure turbine, while regulating valve 0 is governed in similar manner from the low pressure turbine through the instrumentality of the governor i, servo pump Z and pressure regulator k. The valve 0 may also be controlled by the governor 2' by way of servo lines we and p, as illustrated in Fig. 1. Valve 0 may be cut off from control by regulator 11 by the closing of valve y in the servo line. The high pressure turbine may be cutout completely by closing the valve 12 in thesupply line and the valve 00 between the low and high pressureturbines. The arrangement of the governing gearis such that, through the regulating instrumentalities' above described, a decrease in the speed of either turbine results in an increase of the oil pressure under the valve regulating pistons, causing the pistons to be lifted and their valves'to be given an opening movement to increase the steam admission to the superheaters, in the case of the valves n n a and n", or to the low pressure turbine, in the case of the valve 0.

ing operation ofvalve n and upon correspending increase in the pressure condition in the oil line, and so on, opening operation of valves 7?, n and 0 following in the order named and upon still further increase in pressure conditions in the oil line by corresponding increments. At maximum load, therefore, whereat the oil pressure is greatest, all of the valves will be open. An increase in speed of the governor results in decrease of the oil pressure and a corresponding reverse operation ofthe valves concerned.

In operation at normal load on the tur-' bines, steam from the supply line 0 is sup plied to the superheaters (Z (Ed and d in accordance wlth the load requlrements, un: V der regulation of valves n m n and n In the superheaters this steam'is highly supers heated, and from them is delivered to the high pressure turbine, in which it is expanded back to anormal pressure suitable for use in a'low pressure turbine, to which it is led through the connection 9'. At overloads, live steam may be admitted from supply line 0 to the low pressure turbine by way of branch pipe h, by the regulating operation of valve 7 0 in response to a speed drop of either or both of the turbines, valve 0 throttling the pressure ofthis directly supplied steam to a pressure equal to that prevailing in the series connection 9, in the event the line pressure exceeds same. At subnormal load, the high pressure turbine may be cut out completely lation of the sort described. Inthe first place,

the: high pressure turbine; being independent of the structural limitations of the low pressure turbine, it may embody the special structural features which enable it to. meet the requirements exacted by the high temperature and pressure of the highly superheated steam, and it may be constructed with small wheel diameters, to admit of rapid revolution without excessive wheel velocities. Accordingly, it may be built as a relatively small but eificientunit and at an economical cost. In the second place, the control gear, such as the valves for controlling the steam supply to the high pressure turbine, may be of normal construction, because they are not subjected to the extreme temperatures of the highly superheated steam. Thus, while, by virtue of the manner in which the installation is organized, the regulating gear is qualified to .uhigh temperature effects and possesses the combined advantages of economy in cost and rehabihty in operation. Another important advantage in the direction of overall efficiency and reliability of the installation resides in the permissible latitude in distribution of load between the two turbines. If it is assumed, for instance, that the highest admissible superheating be 460 to 500 (1, and that the steam be expanded in the high pressure or primary unit to 300 or 350 (1, which temperature can be considered as normal for the present practice and harmless for the materials and type of construction used in the low pressure turbine, the turbines may be designed so that the low pressure unit can take a load of from two to three times that of the high pressure unit. The low pressure unit, therefore, can be qualified to deliver from two-thirds to three-fourths of the whole output of the installation. Consequently, even in event that it may be necessary to cut out the high pressure unit for repair or from other abnormal circumstance,

the installation can be operated with the low pressure unit alone to supply the greater portion of the demand on the plant. Thus, while the plant is qualified to avail of the advantages to be derived from the use of highly superheated steam for normal operation,/it can have a capacity for assuming a substantial overload demand and also for supplying the greater proportion of the normal demand even in the event of disablement oi the high pressure unit. In the event of the last mentioned contingency, the output of the low pressure unit maybe increased; by

anfincrease of the line pressure above its normal, which may be doneeconomlcally due to the fact that-the super-heaters for the high pressure turbine would be cut out at such time, and the heat sources normally devoted tothem may be diverted to increasing the line pressure. For the purpose of preventing such over-regulation of valve 0 as to cause too great a load to be taken over by the low pressure turbine when working on an alternating current system, or such that the turbine is endangered by too high pressure, a

mum for which the regulator t is set, limit valve will be opened and further opening of valve 0 by its regulating gear q? forestalled.

It is contemplated that the output of both turbines is directed to a common end, such a as the generation of electric power for a system, Consequently, the turblnes maybe arranged to drive respective generators WlllCll supply thesystem jointly, or they may be connected to the same generator by suitable gearing arrangement. It will be understood also that the steam "connections betweenthe turbines may be variously arranged to attain the necessary result of utilizing the heat drop of the highly superheated steam in the high pressure turbine to an extent effective to expand the steam to. a temperature suitable for employment in the low pressure turbine without subjecting the latter to conditions of temperature and pressure which require the special structural features that characterize the high pressure turbine; Yet another advantage of the invention resides in the fact that it can be appliedto existing installations by the addition of the high temperature turbine for operation in conjunction with a normal pressure turbine already installed, and the addition of such boiler and superheater equipment as may be necessary. In this way, an uneconomical plant may be converted into an economical one without exchanging the more expensive portions of the installation.

WVhatwe claim is:

1. In a steam plant installation, in combination, a high pressure turbine, a lower pressure turbine, a steam supply, a superheater connected between the steam supply and the high pressure turbine, a connection between said turbines for supplying the lower pressure turbine with Working steam expanded in thehighpressure turbine,a valve connected between the steam supply and superheater One such arrangement is illus for controlling steam supply to the high pressure turbine by way of the latter, and governing gear for said valve responsive to operation of either of the turbines.

2. In a steam plant installation, in combina tion, a high pressure turbine, a lower pressure turbine, a steam supply, asuperheater connected between the steam supply and high pressure turbine, a connection between said turbines for supplying the lower pressure turbine with working steam eqanded in the high pressure turbine, a supply connection between the lower pressure turbine and steam supply for supplying the former with working steam, valves between the steam supply and superheater and in said supply connection for controlling steam supply to the turbines, and governing gear for said valves responsive to operation of either of said turbines.

3. A combination as specified in claim 2, wherein the governing gear operates'to open the valve in said supply connection under conditions of overload on the turbines.

4. In a steam plant installation, in combination, a high pressure turbine, a lower pres sure turbine, a steam supply, a superheater connected between the steam supply and high pressure turbine, a connection between said turbines forv supplying the lower pressure turbine with working steam expanded in the high pressure turbine, a supply connection between the lower pressure turbine and steam supply for supplying the former with working steam, valves in said supply connection and between the steam supply and superheater for controlling supply of steam to said turbines and governing gear responsive to operation of either of said turbines for controllingsaid valves:

5. In a steam plant installation, in combination, a high pressure turbine constructed 1 for operation by highly superheated steam, a lower pressure turbine constructed for operation by normal pressure steam, a steam supply, a superheater connected between the steam supply and high pressure turbine, at

7 connection between said turbines forsupplying the lower pressure turbine with working 7 steam expanded in the high pressure turbine, a valve connected between the steam supply and superheater for controlling supply of steam to the high pressure turbine, and governing gear responsive to operation of either of said turbines for controlling said valve.

6. A combination as specified in claim 5, in which the lower press re turbine is adapted to carry the major proportion ofthe aggregate output load of the two turbines.

'7. A combination as specified in claim 2, together with automatic means for limiting the maximum steam admission through the valve in said supply connection.

7 .8. In a steam plantinstallation, in combination, a high pressureturbinaa lower pres sure turbine, a steam supplyflt super-heater I connected between the steam supply and high pressure turbine, a connection between said turbines for supplylng the lower pressure turbine with working steam expandedin the high pressure turbine, a supply connection between the lowerv pressure turbine and the steam supply for supplying the former with working steam, a valve connected between the steam supply and superheater for controlling supply of steamto the high pressure turbine,

a second valve for controlling steam admission to the lower pressure turbine from saidsupply connection, governing gear responsive to operation of the lower pressureturbine for controlling said second valve, and

we have signed our 85

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