US1529780A - Steam turbine - Google Patents

Description

March 17, 1925. G. FORNER STEAM TURBINE Filed April 19, 1924 tion.

Patented Mar. 17, 1925;

GEoRe'Fo'RNE-R, oF-j'nnnn n; enniv mity hssienogn no ieMENGES BnsOHA-FT BROWN,

BovERI AND(CI'E.','10F 'QBZADEN, SWITZERLAND.

enema-E.

zen of the German "*RepabIi-e, fesiding at Berlin, (lre'i'unaiiy, have invented-certain new and useful Improvements "in Steam Tiirthestaged1"op,*thealte tion 5 does 'not occur bines.

of "which tli'e following "is P a specifica- This invention fiel-a'tes {to steam turbine velocity stages 'ti'ltll sliglit reaemon and more particularly =to-"a -mosey-stag where in a sllgh-t expansion takes 'plaee'avith-in the v bladin'g. v

Suchstages have "already been eonstruted and also "described in-"the literature "of "the art. In theset 'knoivn "stages the reaetio'n is very small and ocenrson lyfin thefirst rings of blades, and is not --l:'oiu.1d=i n the "othler rings of blades. That iman ne'r f Working has very zgiave diiawbaeks. :=Inwtpressu1-'e stages having no reaction 'the relative velocit-y is'considerably (greater in the first ring than in the last :ring of blades. Gonsequently' the 'i'otor -:-blad'es of the ring'of blades are much longer than those 0f the first ring of "blades. This heivev'er, does not help theid'esigner; the lelfgth'O'CE the blades in the first ring presents no d'ilii'cnl'ty to him, and "it llS I the length of' th'e' blades -in the last row or rows of blades which he would be glad to red-nee. I Those d'i 'a-wbaeks "of the known 'eons'tru'otion are obvi'ated -'aecord-ing to the present invention by arranging for 'the expansion to take place only in these rings of blades in which the relative entrance velocity is less than the velooityof sound.

This Will be correct in niostea'sesonly Tor the last rings of blades. Of partictlla'r iadvantage-in thisi'i'nproved'conneotion is the arrangement that the expansion in the blades iso'arried "onlyfto-sue h an extent that the relative =-eXit velocity is less {than the velocity ofso'und. Byth-is means the drawback is avoided that when .the yeloeity' of sound is greatly exceeded, the blade piassages would have to "be eoii'stru'eted "the form of sum-gee nozzles if a 'eons'i'derahle deflection '0" ies-tea'ln'fjet i's'not' desired. many cases it is not aflvant g eens to allow the expansion to exceed, inthe nozzles, the velocity 'ofsoun'd.

This invention allows the last blades to be made much shorter than in the case of no or only a slight reaction according to the known process, with theresult that rotor frition is "diminished, and owin to the is'lhzrller tli vergehcefo fth'e steam jets a "higher eliifcleney is attained. AFt'urther 'a'dvantage {is that the 1"otor"cl1inens1ons "can -b'e "so proo'itioiiedthat When ai teration'o'ce'uiis in 'iinone 'i'ing of blades eloneer in the nozzles alone, we thus avoids large "impact losses.

It is also advisable to"distributethe'atldipansioiwdrep 'overfi the; rings of bla-desthat eom n qa'estien in'isuehianianiler-that th'eirela vefinicrease in the kinetie energy in :th-e inings 0f bla d'es i's' in i x' erse proportion to the rela'ltiveentrance velocity. It is advisable to arrange the f'expansion in the rings "of blades in -'sueh a 'manner that the aeomponent of the relativefiexi t 'Velooity atri g ht -angles to tlle'direetio n of thei'zperipheral a eloei-ty is approximatelyei1ua-l in the Tings of'blads? that come in :q-uestion. The accompanying drawings illustrate one Way ofoaf'itying the invention into "efieet.

1"is"=adiag nan1 of the pressures in "the different sta'ge'sef ltnow'n'tui' bine's.

Figs 2 is a velooity diagram eorrespo-nd to "the same.

Fig. 3- rep'r'esents diagrammatiea ll the improved turbine in section, throu h one nozzle, two pairs of retort-blades "and-one pair of stationary gn'ide blades of the half turbine sho-wn in sectional "elevation in ig.5 is a diagram oftlie' pres sures in the diflerentstages of e-i i n-proved turbine. V

6f'i's a verse y-diagram eriespmiding to'th'e same; h 1

and A 'iiidi 1 e 'the nozzles for'thfe' old and the new arrangement respeetive'ly, B, D and "In s. 1"a nd Sft-he lines ti arers'in h, B, ,3 A, G; rep'i esent by their iglit the mapamrive -p ressiires in theeesp-eetive-stages. i

essu e in the 1105216. A is eom leteivvelocity from B is also greater than the critical velocity so that the channel between the individual blades of B must also be cons 'structed so as to diverge on the outlet side by suitably profiling the blades. Similarly, the steam passes into the guide blades C and from there to the second rim D of the rotor wheel. Since, in this case, the whole'blading works at the same pressure, no energy is supplied, apart from that due team outlet Velocity from the nozzle, so that the velocity decreases not only owing to the outputbut also owing to the friction in the blades. The result of this is that for the purpose of enlarging the channels for the flow between the blades the outletangle from the blades must grow continually larger and the radial I. D increase at the samet1me.

len th of theblades must also substantially In the present invention, the steam energy in the nozzle is not converted into speed wlth the full available pressure drop since, as shown in Figures3 and 4,the nozzle and the blading of the wheel is so dimensioned that in the, nozzle A"a'pproximately critical velocity isattained, so that the relative entrance-velocity into the first rotor blades lies just below the critical velocity. Naturally, then, the relative exit velocity from this first row of moving blades B also lies below the critical velocity. The velocity through the reversing row of blades G" decreases again,but according to the presentinvention apart of the still available pressure drop is to be used in order to bring the veishing of the exit surface ofthe reversing guide blade-C and of the second blade rim D is'made in conjunction with the decrease in the exit velocity from the nozzles A and v the subsequent increase in the velocities in the reversing guide blade C and the second 'row of moving blades D. The radial dimensions of the nozzles A and possibly of the first ring of blades B is therefore greater in the proposed blading than in the usual- I constant pressure blading and, on the other hand, the blading of the reversing guide blade C and of the second rimD is smaller.

In the usual constant pressure turbine stage, knownas a velocity stage, the whole pressure energy of the working steam is cqn Y dividual blades.

locity O-R.

Similarly for the reverse segment or guide blade ring I get the absolute entrance velocity O-S and absolute exit velocity O-T, and lastly for the second rotor rim the relative velocity at the entrance O U' and the relative velocity at the outlet'O.V or the absolute outlet velocity O W."

In view of the fact that during the whole operation no more energy is supplied, the

said velocities continually decrease.

In the blading according to the invention, in addition to the conversionof the major portion of the available pressure energy of the steam into the velocity O"P-, a, moderate conversion also takes place in the in- The velocities O+R, O,S, OT, O'-U", OV and OVV therefore decrease much less andin consequence the blading smaller radial dimensions.

What I claim is 1. A steam turbine velocity stage with slight reaction, in which the reaction eiiect takes place only in the last blades in which the relative entrance velocity is smaller than the so-called critical velocity.

2. A steam turbine velocity stage as. claimed in claim 1, wherein the expansion in the blades is carried only to such adegr'ee that the relative exit velocity is smaller than the velocity of sound.

3. A steam turbine. velocity stage as claimed in claim 1, wherein the nozzles are in the form of non-enlarged guide devices, the expansion in these nozzles being carried alteration has efiiect inmore than one ring of blades. v 6. A steam turbine velocity stage as claimed'in claim 1, wherein the axial component of the exit velocity is approximately the same in all the rings of blades.

" In testimony whereof I have signed my name to this specification. ,2 I GEORG FORNER.

may be made of n only to such a degree that the velocity of

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