Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE - INVENTION
This invention is concerned with a new class
of heat engines where the working fluid, for example
steam, is used in its two-phase region with vapor and
liquid occurring simultaneously for at least part of the
cycle, in particular the nozzle expansion. The fields
of use are primarily those where lower speeds and high
torques are required, for example, as a prime mover
driving an electric generator, an engine for marine and
land propulsion, and generally as units of small power
output. No restrictions are imposed on the heat source,
which may be utilizing fossil fuels burned in air, waste
heat, solar heat, or nuclear reaction heat etc.
The proposed engine is related to existing
lS steam turbine engines; however, as a conse~uence of using
large fractions o liquid in $he expanding part of the
cy~le, a much smaller number of stages may usually be
required, and the turbine may handle liquid only. Also,
the thermodynamic cycle may be altered considerably rom
the usual Rankine cycle, inasmuch as the expansion is
taking place near the liquid line of the temperature-
entropy diapgram, and essentially parallel to that line~
as described below. In contrast to other proposed
two-phase engines with two components (a high-vapor
~5 prèssure component and a low-vapor pressure componentf
see U.S. Patents ~os.3,879,949 and 3,972,195), the presPnt
engine is limited to a single-component fluid, as for
example water, the intent being -to simplify the working
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~luid storage and handling, and to improve engine
reliability by employing well proven working media o~
high chemical stability.
SUMMARY OF T~IE INVENTION
It is a major object of the invention to provide
an economical engine of low capital cost due to sim~le
construction, low fuel consumption, high reliabllity, and
minimum maintenance requirements.
The objective of low fuel consumption is achieved
by "Carnotizi~g"the,leat engine c~cle in a fashion similar
to regenerative feed-water preheating, which consists
in extracting expanding steam from the tur~ine in order
to preheat feed-water by condensation of the extracted
steam. Since the pressure of the heat emitting condensing
vapor and the heat absorbing feed-water can be made the
same, a direct-contact heat exchanger may be used, which
is of high effectiveness and t~pically of very small slæe.
Further, and in contrast to the conventional
regenerative feed-water heating scheme, the expanding steam
is of low quality, typically of 10 to 20~ mass fraction
of vapor in the total wet mixture flow. As a result, the
enthalpy change across the nozzle i5 reduced to such a
degree that a two-stage turbine, for example, is able to
handle the entire expansion head at moderate stress levels.
By way of contrast, a comparable conventional im~ulse
steam turbines would require about fifteen stages. The
turbine itself may consist of a liquid turbine that may
be combined with a rotary separator in the manner to be
described.
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These and other objects and advantagss of the
invention, as well as the details of an illustrative
embodiment, will be more fully unde~stood from the
following description and drawings, in which:
DR~WING DESCRIPTION
Fig. 1 .is an axial vertical elevation, in
section, schematically showing a two-stage liquid turbine,
` with recuperator;
Fig. 2 is a vertical section showing de-tails
of the Fig. 1 apparatus, and taken along the axis;
Fig. 3 is an axial view of the Fig. 2 apparatus;
Fig. 4 is a flow diagram;
Fig. 5 is a temperature-entropy diagrami and
Fig. 6 is a side elevation of a nozzle, taken
lS in ~ection.
DETAILED DESCRIPTION
Referring first to Fig. 1, the.~rime mover
apparatus shown includes fixed, non-rotatiny structure
19 including a casing 20, an output shaft 21 rotatable
about axis 22 to drive and do work upon external device 23;
rotary structure 24 within the casing and directly connected
to sha~t 21; and a free wheeling rotor 25 within the casing.
A bearing 26 mounts the rotor 25 to a casing flange 20a;
a bearing 27 centers shaft 21 in the casing bore 20_;
bearings 23 and 29 mount structure 24 on fixed structure
19; and bearing 30 centers rotor 25 relative to structure 24.
In accordance with the invention, first nozzle
means, as for example nozzle box 32, is associated with
fixed struckure 19, and is supplied with wet steam for
expansion in the box. As also shown in Figs. 2 and 3, the
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nozzle box 32 typically includes a series of nozzle
segments 32a spaced about axis 22 and located between
parallel walls 33 which extend in planes which are normal
to that axis. The nozzles define venturis, including
convergent portion 34 throat 35 and divertent portion 36.
Walls 33 are integral with fixed structure 19. Wet
steam may be supplied from boiler BB along paths I35 and
1`36 to the nozzle box. Figs. 2 and 3 shows ~he provision
of fluid injectors 37 operable to inject fluid such as
wa~er into the wet steam path as defined by annular manifold
39, immediately upstream of the'nozzles 32. Such fluid
may be supplied via a 1uid inlet 38 to a ring-shaped
manifold 39 to which the injectors are connected. Such
~njectors provide good droplet distribution in the wet
steam, for optimum turbine operating efficiency, expansion
of the steam through the nozzles accelerating the water
droplets for maximum impulse delivery to the turbine
vanes 42. A steam inlet is shown at I36a.
Rotary turbine structure 24 provides first vanes,
as for example at 42 spaced about axis 22, to receive and
pass the water droplèts in the steam in the noz21e means
32. In this regard, the steam fracti3n increases when
expanding. Such first vanes may extend in axial radial
p~anes, and are typically spaced about axis 22 in circular
sequence. They extend between annular walls 44 and 45
of structure 24, to which an outer closure wall 46 is
joined. Wall may form one or more nozzles, two being
shown at 47 in Fig. 3. Nozzles 47 are direc-ted generally
counterclockwise in Fig. 3, whereas nozzles 32 are
directed generally clockwise, so that turbine s~ructure 24
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rotates clockwise in Fig. 3. The turbine structure is
basically a drum ~hat contains a ring of liquid (i.e.
water ring indicated at 50 in Fig. 3), which is collected
from the aroplets issuing from nozzles 32. Such water
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issuing as jets from nozzles a7 is under pressurization
generated b~ the rotation of the solid ring of water 50.
In this manner, the static pressure in the region 51
outwardly of the turbine structure need not be lower than
the pressure of the nozzle 32 discharge to assure proper
liquid àcceleration across such nozzles 47. The radial
vanes 42 ensure solid body rota-tion of the rins Of liguid
at the speed of the structure 24. The vanes are also
useful in assuring a rapid acceleration of the turbine
from standstill or idle condition.
Water collecting in region 51 impinges on the
freely rotating rotor 55 extending about turbin2 rotor
structure 24, and tends to rotate that rotor with a
rotating ring of water collecting at 56. A non~rotating
scoop 57 extending into zone 51 collects water at the
inner surface of the ring 56, the scoop communicating
with second nozzle means 58 to be described, as via ducts
or paths lS~-X63.Accordingly, expanded first stage liquid
(captured by free-wheeling drum or rotor 55 and scooped up
~y pitot opening 57) may be supplied in pressurized
state to the inlet of second stage nozzle 58.
Also shown in Fig. 1 is what may be referred
to as rotary means to receive feed water and to centrifugally
pressurize same. Such means may take the foxm of a
centxifugal rotary pump 60 mounted as by bearings 61 to -
fixed structure 19. The pump may include a series of
discs 62 which are normal to axis 22, and which are located
within and rotate with pump casing 63 rotating at the
same speed as the turbine structure 24. For that PurpOse,
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a connection 64 may extend between casing 63 and the
turbine 24. The discs of such a pump ~as for example
a Tesla pump) are closely spaced apar~ so as to allow
the liquid or water discharge from inlet spout 65 to '
distribute generally uniformly among the individual
slots between the plates and to flow radially outwardly,
while gaining pressure.
A recuperative zone 66 is provided i~wardly
of the turbine wall structure 24a,to communicate with
the discharge 60a of rotating pump 60, and with the
nozzle box 32 via a series of steam passing vanes 68.
The latter are connected to the turbine rotor wall 24b
to receive and pass steam discharsing from nozzles 32,
imparting further torque to the turbine rotor. After
passage bet~een vanes 68, the steam is drawn into direct
heat exchange contact with the watQr droplets spun-ofL
from the pump 60, in heat exchange, or xecuperative
zone 66. Both liquid droplets and steam have equal
swirl velocity and are at equal static pressure in
rotating zone 66, as they mix therein.
The mix is continuously withdrawn for further
heating and supply to the ~irst nozzle means 32. For
the puxpose, a scoop 70 may be associated with fixed
structure 19, and extend into zone 66 to withdraw the
fluid mix for supply via fixed ducts 71 and 72 to boiler
or heater BB, from which the fluid mix is returned via
path 1~ to the nozzle means 32.
The second stage nozzle means 58 receives
water from scoop 57, as previously described, and also
steam spill-over from space 66, as via paths 74 and 75
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ad~acent tuxbine wall 24c. Such pressurized steam mixed
with liquid from scoop 57 is expanded in the second
nozzle means 58 producing vapor and water, the vapor
being ducted via paths 78 and 79 to condenser CC. Fourth
vanes 81 attached to rotating turbine wall 24d receive
pressure application from the flowing steam to extract
energy from the steam and to develop additional torque.
The condensate from the condenser is returned via path
83 to the inlet 65 of p~unp 60. The water from nozzle
means 58 collects in a rotating ring in region 84,
imparting torque to vanes 85 in that reyion bounded by
turbine rotor walls 86 and 87, and outer wall 88. For
that purpose, the construction may be the same as that of
the first nozzle means 32, water ring 50, vanes 42 and
walls 44-46. Nozzles 89 discharge wat~r from the rotating
ring in region 84, and correspond to nozzles 47. Free
wheeling rotor 55 extends at 55a about nozzles 47, and
collects water discharging from the latter, forming a ring
in zone 91 due to centrifugal effectA Non-rotary scoop
90 collects water in th~ ring formed by rotor extent 55a,
and ducts it at 92 to path 83 for return to the TESLA
pump 60.
The cylic operation of the engine will now be
described by reference to the temperature-entropy diagram
of Fig. 5, wherein state points are shown in capital
letters. Arabic numerals refer to the compone~ts already
referred to in Figs. l-3.
Wet steam o~ condition ~ is delivered ~ro~ the
boiler to nozæle box 32 (Fig. l). The special two-phase
nozzles use the expanding vapor for the acceleration of
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the liquid drop:lets so that the mix-turç of wet steam
will enter the turbine ring 42 (Fig. 3) at nearly
uniform velocity, at the thermodynamic condition ~ .
The liquid will then separate from the vapor and issue
through the nozzles 47 (Fig. 3) and collect in a rotating
ring in the drum 55 (Fig. 1). The scoop 57 will deliver
collected liquid to th~ nozzle box 58 at condition ~ .
The saturated expanded steam from nozzle 32 at a co~dition
~ (not shown~ in the meantime will drive vanes 68 and
enter the recuperator 66.
In the recuperator the vapor will be partially
condensed by direct contact with feed-water originally
at condition ~ from ~coop 90 in Fig. 1, mixed with
condensate as it is returned from the condensex CC~ Both
streams o~ liquid (at condition ~ ) whether supplied by
scoop 90 or that returning from the condenser CC is pumped
up at 60 to the static pressure of the steam entering.
zone 66 ~Fig. 1). The heat exchange b~ direct contact
occurs across the surfaces of spherical droplets that
are spun-off from the rota-ting discs of the TESLA pump,
and into zone 66.
The heated liguid of condition ~ that is
derived from preheating by the steam and augmented by
condensate formed at condition ~ , is scooped up at 70
and returnea to the boiler B~ by stationery lines 71 and 72.
The steam which was not fully condensed in the
recuperator 66 will pass on at 74 to nozzle box 58 where
it is mixed with the liquid that was returned by scoop 57.
The mixture will be at a conditîon ~ , corresponding
to the total amount o~ preheated liquid of condition ~ and
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saturated vapor of condition ~ .
The subsequen~ nozzle expansion at 58 from
condition ~ to ~ results in similar velocities as produced
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in the expansion ~ to ~ in nozzle 32. The issuing jet can
therefore dri~e the second liquid turbine efficien~ly at
the speed of the first turbine, so that direct coupling
o~ the two stages is possible.
The path of the liquid collected in dr~m 25 (Fig.1) at
the condition E was already described as i~ is passed on
to the inlet 65 of pump 60. The saturated vapor at
condition ~ (not shown) i5 ducted at 78 and 79 to ~he
condenser CC, which is cooled hy a separate coolan~. The
condensate at condition E is then also returned at 83 to
the pump inlet 65.
Alternate ways of condensing the steam of
condition ~ may be envisione~ that are similar to the
method employed herein to condense steam of condition ~
at intermediate pressure in the recuperator. The difference
is that a direct contac-t low pressure condense~ will
require clean water to he used for the coolant, so that
mixing with the internal working medium is possible. Such a
liquid coolan~ will probabl~ bes~ be cooled itself in a
separate conventional li~uid-to-liquid or liquid-to-air
heat exchanger,so that it may be re-circulated continuously
in a closed, clean system.
The turhine engine described in Fig. 1 is a
two-staga unit with only one intermediate recu,arator.
~n analysis of the efficiency of the thermodynamic cycle
shows that the performance is improved among others by
'two factors: -
1) increased vapor quality of the steam
(relative mass fra'c,tionof saturated steam)
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2) An increased number of intermediary
recuperators. Since an increase in vapor quality raises
the magnitude of the nozzle discharge velocity, a compromise
is called for betwee~ number of pressure s~ages, allowed
rotor tip speed, and number of recuperators. Note that
saturated steam may be extracted at equal increments
along the nozzle; at least two recuperators operating at
intermediate pressure levels may be arranged per stage
in order to improve the cycle efficlency without increasing
the nozzle velocity.
Other types of liquid turbines may be used
instead o~ the particular tur~ine shown in Fig. 1 and
Fig. 2. See for example U.S. Patents 3,8?9,949 and 3,972,195.
Also, a more conventional turbine with buckets
around the periphery may be employed and which admi~s a
homogeneous mixture oE saturated steam and satùrated water
droplets.
Good efficiencies for such turbines are obtainable
if the droplet siz,e of the mixture emerging ~rom the nozzle
is kept at a few microns or less. '
, To achieve the latter, the converging-diverging
nozzle may ~e designed with a sharp-edged throat as a
transition ~rom a straight converging cone 200 to a
straight diverging cone 201. See Fig~ 6 showing such a
nozzle 202.
Fig. 1 also shows annular partition 95 integral
with rotor 55, and separating rotary ring o~ water 56 from
rotary ring 91 o~ water.
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