The American Society of Mechanical Engineers

P rogress in D esign a n d P e rfo rm a n c e of
M o d e rn L arg e S team T u rb in e s for
G e n e ra to r D riv e
B y G. B. W A R R E N ,1 SC H EN EC TA D Y , N . Y,
T h e first p o r tio n o f t h is p ap er review s b riefly t h e p rogress
o f tu r b in e a n d p o w er-p la n t d e sig n over t h e la s t 20 y e a rs.
T h e second p o r tio n illu s tr a te s w ith n u m e r o u s a ssem b ly
dra w in g s th e p rogress o f r ecen t tu r b in e d e sig n a n d sh o w s
b o th th e sta n d a rd a n d t h e sp ecia l ty p e s o f tu r b in e s b ein g
b u ilt t o m e e t p resen t r e q u ir e m e n ts. In a d d itio n , it s e ts
fo r th t h e gen era l p r in c ip le s g o v ern in g tu r b in e c o n s tr u c ­
tio n a n d illu s tr a te s so m e o f th e n e w tu r b in e c o n str u c tio n s
d esig n ed t o w ith s ta n d e x tr e m e ly h ig h p ressu res a n d t e m ­
p eratu res. T h e tren d o f tu r b in e r e lia b ility a n d tu r b in e
e c o n o m y is sh o w n , a n d a n u m b e r o f t e s t r e s u lts o f la rg e
m o d e m tu r b in e s are m a d e a v a ila b le.
T h e th ir d se c tio n d isc u sse s d e ta ile d c o n sid e r a tio n s o f
tu r b in e d e sig n , a n d illu s tr a te s n u m e r o u s tu r b in e p a r ts
d esig n ed fo r t h e u tiliz a tio n o f h ig h p ressu res a n d h ig h
te m p eratu r e s, b u t w h ic h m a y b e o f in te r e st fo r o th e r field s
o f a p p lic a tio n .
PART I—TRENDS IN POWER-PLANT AND TURBINE
DESIGN
THE progress of turbine design and construction since its
inception has consisted largely in:
1 Building turbines and the attached generators of
higher unit capacities to meet the growing demands for more
power, and so permit reduction of the plant investment per unit
of output.
2 Continuously modifying and refining the design, manufacturing
processes, and materials used in order to increase the
reliability of operation and to reduce the outage time which has
always been one of the chief concerns of operators of such equipment.
3 Utilizing higher initial steam pressure and temperature,
coupled with improved heat cycles, such as regenerative feedwater
heating, resuperheating, air preheating, etc., to decrease
the fuel consumption per unit of output.
4 Designing the turbine to utilize an ever-increasing proportion
of the available energy in the steam cycle being used at the
time.
The decrease of over-all plant investment through greater
reliability of the turbine generator, and the decrease in investment
and operating costs resulting from improved efficiency
have always been of much greater significance to the owners of
such equipment than reduction of first cost of the turbine and
generator alone. The major endeavor, therefore, has been to
improve these two factors through the use of new knowledge,
new materials, and new tools and manufacturing processes.
The principle of diminishing returns must be observed, however,
1 Designing Engineer, Turbine Engineering Department, General
Electric Company. Mem. A.S.M.E.
Contributed by the Power Division and presented at the Semi-
Annual Meeting, Milwaukee, Wis., June 17-20, 1940, o f T h s A m e r i­
c a n S o c ie t y o f M e c h a n ic a l E n g i n e e r s .
Notis: Statements and opinions advanced in papers are to be
understood as individual expressions of their authors, and not those
of the Society.
and increased m aterial and labor cannot be added out of proportion
to the returns obtained, and every effort has been m ade to
reduce costs where not inconsistent w ith th e foregoing prim ary
objectives.
W ith these forces a t work, the turbine designers and builders
have never been perm itted to rest on their oars. E ach year has
seen new problems and new conditions to be met.
H ydrogen cooling2 has m ade possible larger 3600-rpm generators,
and has within the last few years perm itted building m any
turbines for 3600 rpm rather than 1800 rpm.
M uch of the progress mentioned has been summarized in a
paper by W. E. Blowney,3 b u t in order still further to illustrate
this situation, Fig. 1 brings up to date a num ber of curves first
published by E rnest L. Robinson4 before the W orld Power
Conference in Japan in 1929. The new figures show the average
steam conditions for the turbines sold by General Electric each
year, while the original curves showed but the maximum conditions.
A b etter conception is thus gained of the trends.
Several conclusions can be draw n from these curves:
(a) Although th e largest possible unit a t any given speed has
steadily increased, and the large units have been effectively
utilized in reducing operating and fixed costs on the large utility
systems, the average size of unit sold in the U nited S tates (units
above 10,000 kw only considered) has increased but slowly.
(b) Increases in th e maximum pressure and tem perature
have been followed by a steady rise in th e average pressure and
tem perature for which machines have been sold, thus certifying
to the fact th a t the pioneering done by a few power-plant owners
has been followed by a general advance for th e entire industry.
(c) The foregoing is further attested to by th e alm ost continuous
downward trend of the fuel consumption both for the
best plants available and th e somewhat similar trend for the
average. Although it would appear from this latter curve th a t
the continued progress in th e average coal consum ption m ay have
slowed up, a closer examination of all the facts will serve to indicate
th a t this is not th e case.
T he reduction in the coal consumption of th e best plants i«
! "The Hydrogen-Cooled Turbine Generators,” by D. S. Sn«ll,
Trans. A.I.E.E., vol. 69, 1940, pp. 35-50.
“Hydrogen-Cooled Turbine Generators,” by M. D. Ross and C. C.
Sterrett. Trans. A.I.E.E., vol. 59, 1930, pp. 11-17.
“Hydrogen Cooled Generators,” by E. H. Freiburghouae and D . S.
Snell, Power, vol. 82, no. 8, 1938, pp. 38-41.
“Hydrogen as a Cooling Medium for Electrical Machines,” by
Edgar Knowlton, Chester Rice, and E. H. Freiburghouae, Trans.
A.I.E.E., vol. 44, 1925, pp. 922-934.
“The Application of Hydrogen-Cooling to Turbine Generators,”
by M. D. Ross, Trans. A.I.E.E., vol. 50, 1931, pp. 381-380.
“Liquid Film Seal for Hydrogen-Cooled Machines,” by C. W.
Rice, General Electric Review, vol. 30, 1927, pp. 516-530.
“Hydrogen Cooling of Rotating Machines,” by C. M. Lafoon,
Trans. A.I.E.E., vol. 55, 1938, pp. 703-709.
5 “Turbine Trends,” by W. E. Blowney, Power, vol. 83, no. 1,
1939, pp. 74-76.
* “General Trend of Steam Turbine Development by the General
Electric Company,” Trans. Tokio Sectional Meeting, World Power
Conference, Tokio, Japan, 1929, vol. 3, pp. 1066-1078.