US2058479A - Turbine for hot driving media - Google Patents

Description

0ct.'27, A1936. y A. LYsHoLM TURBINE FOR4 HOT DRIVING MEDIA Filed March 6, 1934 3 Sheets-Sheet 1 a 7mo 7lVNTOR BZ;

' ATTORNEY Oct. 27, 1936.

A. LYsHoLM TURBINE FOR HOT DRIVING MEDIA Filed March e, 1954 s sheets-sheet 2 www.

ATTORNEY Oct. 27, 1936. A. LYsHoLM TURBIN FOR HOT DRIVING MEDIA 5 Sheetsheet 5 Filed March 6,- 1934 VENTOR 'AMK 6%/ ATT'oR NEY Painted oet-.27, 193s TURBINE'FOB HOT DRIVING MEDIA Au L'yshoim, smixiwim,v sweden, assigner u Aktlebolnget Milo, Stockholm, Sweden, a corporation of Sweden Application March 6, In Germany The invention refers to turbines for hotdrlving media, and particularly to gas turbines l One of the greatest diiiculties in the conl struction of such turbines is the control over the high temperatures and the resulting stresses and alterations of the machine parts, particularly 0f.v` r the blade systems, coming into contact with the hot driving medium.

The invention particularlyrelates to such ture`l` :v bines, in which the blade carriers, which may bei' turbine disks or turbine rings, increase with r'e-L snect to the diameter from the inlet to the out let. Such turbines are the radial ilow turbines,v for example, especially the double rotation radial., -0 how turbinesin which the blade rings lincrease g radially outwards Vfrom stage to stage, and. iure, thermen-e, axial ow turbines, the disk diameters oi which increase progressively from the pointof j inlet unto the outlet.

In turbines of this kind, the inlet takes place-,at

'the point of the smallest blade ring diameter'- or disk diameter. Here, the highest temperatures occur, however. By reason of this, the tempera` ture stresses, particularly also the creeping, are here the highest, while these temperature stresses decrease considerably toward the outlet. On the other hand, the stresses referring to the strength ci material which result from the centrifugal force upon rotation of the turbine, are considerably smaller on the inlet side of such turbines than in the stages ci a greater diameter located adjecent to the outlet.

Accordingly, the blade systems will be dierentiy strained by the temperature influences and the amic inuences in the various stages of the blade systems. This, however, brings about dimculties as regards the construction, insofar as it should be aimed at in all stages to keep the clearance losses as small as possible. The varying stresses in the different stages will have an interfering eiect, however.

in order to bring about animprovement here, it is suggested, according to the invention, to

y make the blade carriers of a small diameter operating in thev range of the higher temperature out of a material which is less sensitive toward creeping, preferably austenite material of austenite structure, and the blade carriers of a greater diameter operating within the range of the lower temperatures out of a material of great strength, preferably martensite material.

Fora better understanding oi the nature of the invention, reference .may be had to the ac,

companying drawings forming a part of this 1934, SerlalNo. '114,227 March 10, 1933 f s (o1. 25a-sc) specication and the following description thereof. j In the drawingsz- Fig. 1 represents diagrammaticallythe induence oi the selectionof materials for the turbine 5 construction;

""Fig. 2 shows a rotor of an axial how turbine designed according to the invention: Fig. 3 an axial iiow turbine; and

f Fige a radial flow turbine constructed accord- 10 a ing' to .the invention. 1

` Fig. 1 shows a number of curves calculated for C' acreeping of 10,000 hours. Curve l gives 40% f the limit of thel stretching strain of martens'itic Anriaterial, that is' to say strains .which in the conl5 struction oi turbines generally are permitted as avbasls for construction.v It will be seen from the curve that the permissible stretching strain decreases with a rising temperature up to 430 C. from 3'? to 28 kg./sq. mm. The inuence of the 2G creeping will be seen from curve 2, which shows that for martensitio material the permissible strain on the material decreases very considerably, owing to the creeping which occurs on a temperature rise from 430 to 500 C. Curve 3 25 shows 40% of the limit of the stretching strain of austenitic material, and curve 0 the influence of the creeping of this material.

The illustration thus shows that up to a temperature of 430 C. the creeping is of no conse- 30 quence relatively to the stresses referring to the strength oi the material through the dynamic forces, so that, consequently, martensitlc material may be used altogether to advantage for temperatures below 430 C. The curve further shows, 35 however, that this material becomes exceedingly sensitive on an increase of the temperature and is then no longer sumcient in higher temperature ranges, depending on the decisive iniiuence of the creeping.

Fig. 1 thus shows it to be altogether possible to build turbines for high material temperatures, provided the selection of materials for the different temperature zones of the turbine is properly made with respect to the knowledge gained from the turbine.

For example, at a temperature of 700 C., that is to say 973 C. absolute, the strain must not exceed 5 ieg/sq. mm. It can be shown, however, that Vboth in the double rotation turbines, for instance according to the Ljungstrm system, and also in conical axial ow turbines, the strains may be kept below 3-4 kg/sq. mm., and that, consequently, turbine operation at a temperature of 700 C. is readily possible. 55

Fig. 2 shows diagrammatically the construction of a rotor of a conical axial ow turbine embodying the invention. The hollow rotor shaft l consists of martensitic material, which while being sensitive toward creeping possesses a comparatively great strength. The turbine disks 2, 3, are made integral with said rotor shaft. The sensitivity of the martensitic material, of which this turbine part consists, is of no consequence in the temperature range in which the rotors operate, the creeping being here Without appreciable influence.

Thrust onto this hollow rotor shaft is a rotor part 5 carrying the disks E, '1, 8. This part ls made from austenitic material, which is considerably less sensitive toward creeping than the martensitic material. Thus thedivision of the rotor into two construction zones made from diilerent materials suficiently answers the strains'occurring in the turbine both through the dynamic influences and through the temperature.

Fig. 3 shows the half of a conical axial ow turbine constructed on the principles evolved in the foregoing. The turbine disks 9-I4 operate in a high temperature range, within which the iniluence of the creepingis predominant. By reason of this, these disks are made from a material which is insensitive toward creeping, especially austenitic material. The line :I: shows the temperature limit,. above which the dynamic inuences on the strength predominate, whereas the inuences of the creeping are in the background. The turbine disks I5--I9 situated behind the line .frrc are thus made from a material of greater strength, which .may be more 'sensitive 'toward creeping, such material being preferably a martensitic material.

The double rotation radial ow turbine according to Fig. 4 is built in the same manner, in principle, the line :r-:r again indicating the temperature limit, for instance 500 C., below which the influence of the creeping and above which the dynamic strength influences predominate. Accordingly, the blade carriers 2li-26 are made from a material which is insensitive .toward creeping, especially austenitic material, whereasl the blade carriers 21-35 may be made from a material of greater strength, especially martensitic material, which may be more sensitive toward creeping inasmuch as the lower temperatures and the higher rotational speeds predominate above the limit :v -w.

The strengths and temperatures indicated in Fig. 1 are average values only, which may change according to the material used; these values, however, hold good on an average for the construction materials generally used. From the nature of the values of strength given in Fig. 1,

-it will be evident that the austenitic and martenblade carriers of different materials and to locate the limit, at which the change of construction materials takes place, where the iniluences of the creeping and of the dynamic strength inuences will predominate.

What I claim iszl. In turbine apparatus, a turbine rotor adapted to receive gaseous motive uid at a temperature of at least 700 C. and to expand such motive'iluid in a plurality of stages to a temperature at least as low as 400 C. through a path of ow from an inlet of relatively small diameter in a direction having a substantial component of ow in radially outward direction comprising a plurality of blade carriers of progressively increasing diameter from the inlet to the outlet end ofl said rotor, the blade carriers constituting the inlet portion of the rotor and adapted to carry blades for expansion of the motive fluid from its inlet temperature to a temperature of the order of 430 C. consisting of material of austenitic structure, and the blade carriers constituting the. outlet portion of the rotor and adapted to carry the blades for expansion of the motive fluid from said temperature of the order of 430 C. to the exhaust temperature consisting of material of martensitic structure.

2. In turbine apparatus, a turbine rotor for expanding gaseous motive fluid admitted to the turbine at a temperature .suiliciently high to producecreep, said rotor comprising a plurality of bladel carriers for blades providing multiple stage expansion of motive fluid in the turbine in a path of iiow from an inlet of relatively very small diameter to an outlet of relatively very large diameter as compared with the inlet diameter, the blade carriers of relatively small diameter in the inlet portion of the rotor and within the temperature zone of the turbine where 'the temperature of the motive fluid'during normal operation of the turbine causes creep producing conditions consisting of a suitable turbine steel of austenitic structure and the blade carriers of relatively large diameter in the outlet portion of the rotor consisting of asuitable turbine steel of martensitic structure.

3. In turbine apparatus, a turbine rotor for expanding gaseous motive uid admitted to the turbine at a temperature suiciently high to produce creep, said rotor providing a path of flow for motive uid having a relatively large component of ilow in radially outward direction from an inlet of relatively very small diameter and said rotor including a plurality of blade carriers the diameters of which progressively increase materially from the inlet end to the outlet end of the rotor, whereby the diameter of the carrier at the outlet end of the rotor is several times the diameter of the carrier atl the inlet end of the rotor, the carriers constituting thevinlet portion of thefrotor and located in a temperature zone where creep producing conditions are produced by the motive fluid in the normal operation of -the turbine consisting of a suitable turbine steel of austenitic structure and the blade carriers constituting the outlet portion of the rotor and located in a relatively much lower temperature zone consisting of a suitable turbine steel of martensitic strucy

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