U.S. patent application number 13/474471 was filed with the patent office on 2012-12-13 for expander lubrication in vapour power systems.
This patent application is currently assigned to City University. Invention is credited to Ahmed Kovacevic, Ian Kenneth Smith, Nikola Rudi Stosic.
Application Number | 20120312009 13/474471 |
Document ID | / |
Family ID | 34855353 |
Filed Date | 2012-12-13 |
United States Patent
Application |
20120312009 |
Kind Code |
A1 |
Smith; Ian Kenneth ; et
al. |
December 13, 2012 |
EXPANDER LUBRICATION IN VAPOUR POWER SYSTEMS
Abstract
A vapour power generating system including a closed circuit for
a working fluid, and includes a heat exchanger assembly for heating
the fluid under pressure with heat from the source, a separator for
separating the vapour phase of the heated fluid from the liquid
phase thereof, an expander for expanding the vapour to generate
power, a condenser for condensing the outlet fluid from the
expander, a feed pump for returning condensed fluid from the
condenser to the heater and a return path for returning the liquid
phase from the separator to the heater. The liquid phase of the
working fluid contains a lubricant which lubricant is soluble or
miscible in the liquid phase and a bearing supply path is arranged
to deliver liquid phase pressurised by the feed pump to at least
one bearing for a rotary element of the expander.
Inventors: |
Smith; Ian Kenneth; (London,
GB) ; Stosic; Nikola Rudi; (London, GB) ;
Kovacevic; Ahmed; (London, GB) |
Assignee: |
City University
London
GB
|
Family ID: |
34855353 |
Appl. No.: |
13/474471 |
Filed: |
May 17, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11921836 |
Mar 24, 2009 |
8215114 |
|
|
PCT/GB2006/002148 |
Jun 9, 2006 |
|
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13474471 |
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Current U.S.
Class: |
60/531 |
Current CPC
Class: |
F01D 25/22 20130101;
F05D 2220/31 20130101; F01K 25/06 20130101; F01K 25/04 20130101;
F01C 1/16 20130101; F01C 21/04 20130101 |
Class at
Publication: |
60/531 |
International
Class: |
F01K 13/00 20060101
F01K013/00; F01K 19/00 20060101 F01K019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2005 |
GB |
0511864.1 |
Dec 23, 2005 |
GB |
0526413.0 |
Claims
1. A closed circuit vapor power generator system comprising: A. a
closed circuit; B. a working fluid in the closed circuit, the
working fluid comprising a vapor phase, a liquid phase, and a
lubricant soluble or miscible in the liquid phase; C. a working
fluid heater in the closed circuit; D. a heat source in
communication with the working fluid heater; E. a separator in the
closed circuit in communication with the working fluid heater; F.
an expander in the closed circuit in communication with the
separator; G. a condenser in the closed circuit in communication
with the expander; H. a working fluid feed pump in the closed
circuit in communication with the working fluid heater; I. a
working fluid return path in the closed circuit from the separator
to the working fluid heater; and J. a bearing lubricant supply path
in the closed circuit from the working fluid feed pump to at least
one bearing element for at least one rotary element of the
expander.
2. The closed circuit vapor power generator system of claim 1
wherein: (i) the heat source is in heating communication with the
working fluid heater; (ii) the separator is in working fluid
transfer communication with the working fluid heater; (iii) the
expander is in working fluid transfer communication with the
separator; (iv) the condenser is in working fluid transfer
communication with the expander; and (v) the working fluid feed
pump is in working fluid communication with the working fluid
heater.
3. The closed circuit vapor power generator system of claim 1
wherein the working fluid heater includes an evaporator section and
a heater section, and the working fluid return path leads to a
junction between the working fluid heater and the evaporator
section.
4. The closed circuit vapor power generator system of claim 1
wherein collection spaces are in communication with the at least
one bearing element.
5. The closed circuit vapor power generator system of claim 1
wherein the bearing lubrication supply path includes a working
fluid cooling heat exchanger.
6. The closed circuit vapor power generator system of claim 1
wherein the expander is a rotary expander.
7. The closed circuit vapor power generator system of claim 2
wherein the expander is a rotary expander.
8. The closed circuit vapor power generator system of claim 6
wherein the expander includes two rotary expander screws.
9. The closed circuit vapor power generator system of claim 7
wherein the expander includes two rotary expander screws.
10. The closed circuit vapor power generator system of claim 8
wherein the bearing fluid supply path leads to the at least one
bearing element for a first rotary screw and the at least one
second bearing element for a second rotary screw.
11. The closed circuit vapor power generator system of claim 1
wherein a liquid phase receiver is in communication with the
condenser and the feed pump.
12. The closed circuit vapor power generator system of claim 2
wherein a liquid phase receiver is in working fluid transfer
communication with the condenser and the feed pump.
13. The closed circuit vapor power generator system of claim 1
wherein the heat source comprises a source of moderate or low grade
heat.
14. The closed circuit vapor power generator system of claim 1
wherein the heat source includes an internal combustion engine.
15. The closed circuit vapor power generator system of claim 1
wherein the working fluid includes an organic fluid.
16. The closed circuit vapor power generator system of claim 1
wherein the working fluid includes chlorotetrafluoroethane,
tetrafluroethane, pentafluoropropane, or light hydrocarbons such as
isoButane, n-Butane, isopentane, or n-Pentane.
17. The closed circuit vapor power generator system of claim 1
wherein the at least one bearing element for the at least one
rotary element of the expander is a heat generating bearing,
whereby the at least one rotary element of the expander evaporates
liquid phase of the working fluid.
18. The closed circuit vapor power generator system of claim 1
wherein the working fluid heater includes a single pass boiler.
19. The closed circuit vapor power generator system of claim 1
wherein working fluid heater is in heating communication with an
internal combustion engine and the working fluid includes an
organic working fluid.
20. The closed circuit vapor power generator system of claim 1
wherein a percentage by weight of lubricant is up to 5% of a weight
of the working fluid.
21. The closed circuit vapor power generator system of claim 1
wherein the percentage by weight of lubricant is 0.5 to 2% of the
weight of the working fluid.
22. The closed circuit vapor power generator system of claim 2
wherein a percentage by weight of lubricant is up to 5% of a weight
of the working fluid.
23. The closed circuit vapor power generator system of claim 2
wherein the percentage by weight of lubricant is 0.5 to 2% of the
weight of the working fluid.
24. A closed flow circuit vapor power generating system comprising:
A. a closed flow mixed lubricant-working fluid circuit; B. a mixed
lubricant-working fluid heater in the closed flow mixed
lubricant-working fluid circuit; C. an expander having an expander
support structure and being in the closed flow mixed
lubricant-working fluid circuit in flow communication with the
mixed lubricant-working fluid heater; D. a condenser in the mixed
lubricant-working fluid closed flow circuit in flow communication
with the expander; E. a working fluid feed pump in the closed flow
mixed lubricant-working fluid circuit in flow communication with
the condenser and the mixed lubricant-working fluid heater; and F.
a mixed lubricant-working fluid supply path in the closed flow
mixed lubricant-working fluid circuit in flow communication from
the working fluid working fluid feed pump to the expander support
structure.
25. The closed flow circuit vapor power generating system of claim
24 wherein: (i) the expander includes a first screw and a second
screw, the first screw supported by a first screw support structure
and the second screw supported by a second screw support structure;
and (ii) the mixed lubricant-working fluid supply path is in flow
communication from the working fluid feed pump to the first screw
support structure and second screw support structure.
26. The closed flow circuit vapor power generating system of claim
24 wherein the mixed lubricant-working fluid heater comprises a
source of moderate or low grade heat.
27. The closed flow circuit vapor power generating system of claim
26 wherein the mixed lubricant-working fluid heater includes a
single pass boiler.
28. The closed flow circuit vapor power generating system of claim
24 wherein the expander support structure includes a screw expander
bearing in lubricating communication with the working fluid feed
pump.
29. The closed flow circuit vapor power generating system of claim
24 wherein the source of heat is in heating communication with an
internal combustion engine and the working fluid includes an
organic working fluid.
30. The closed flow circuit vapor power generating system of claim
24 further comprising a mixed lubricant-working fluid including a
liquid phase, a vapor phase, and a lubricant miscible with or
soluble in the liquid phase, and wherein a percentage by weight of
the lubricant in the liquid phase is up to 5% of a weight of the
mixed lubricant-working fluid.
31. The closed flow circuit vapor power generating system of claim
24 wherein the percentage by weight of lubricant is 0.5 to 2% of
the weight of the working fluid.
32. A vapor power generating system comprising: A. a closed circuit
with a lubricating working fluid; B. a pressurized lubricating
working fluid heater in the closed circuit; C. a heat source in
communication with the pressurized lubricating working fluid
heater; D. a separator in the closed circuit in communication with
the pressurized lubricating working fluid heater; E. a power
generating expander in the closed circuit in communication with the
separator; F. a working fluid condenser in the closed circuit in
communication with the power generating expander; G. a working
fluid feed pump in the closed circuit in communication with the
working fluid condenser and the pressurized lubricating working
fluid heater; H. a working fluid return path in the closed circuit
from the separator to the pressurized lubricating working fluid
heater; I. a working fluid bearing supply path in the closed
circuit from the working fluid feed pump to at least one bearing
section for at least one rotary element of the power generating
vapor phase expander; and J. a condenser in the working fluid
bearing supply path.
33. The vapor power generating system of claim 32 further
comprising a working fluid in the closed circuit and having a vapor
phase, a liquid phase, and a lubricant mixed with the liquid
phase.
34. The vapor power generating system of claim 32, wherein the
percentage by weight of the lubricant in the liquid phase of the
lubricating working fluid is less than or equal to 5% of a weight
of the working fluid.
35. The vapor power generating system of claim 32 wherein the
percentage by weight of the lubricant in the liquid phase of the
lubricating working fluid is 0.5 to 2% of the weight of the working
fluid.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 11/921,836, filed Mar. 24, 2009, which is the national stage of
International Application No. PCT/GB2006/002148, filed Jun. 9,
2006, which claims the benefit of GB0526413.0, filed Dec. 23, 2005,
and GB0511864.1, filed Jun. 10, 2005, all of the above referenced
disclosures are hereby incorporated by reference in their
entireties.
[0002] This invention relates to the lubrication of expanders used
in closed-circuit vapour power generating systems in which
lubricant is soluble in, or miscible with, the working fluid. The
invention is particularly, but not exclusively, concerned with
systems for generating power from moderate or low grade heat
sources such as geothermal brines, industrial waste heat sources
and internal combustion engine waste heat streams where the maximum
temperature for the working fluid of the system is rarely in excess
of 150.degree. C. Such systems typically use organic working fluids
such as tetrafluroethane, chlorotetrafluoroethane
1.1.1.3.3-Pentafluoropropane or light hydrocarbons such as
isoButane, n-Butane, isoPentane, and n-Pentane and operate on the
Rankine cycle or some variant of it.
[0003] According to one aspect of the invention there is provided a
vapour power generating system for generating power by using heat
from a source of moderate or low grade heat, comprising a closed
circuit for a working fluid, the system including heating means for
heating the fluid under pressure at a temperature not usually more
than 200.degree. C. with heat from the source, a separator for
separating the vapour phase of the fluid from the liquid phase
thereof, an expander for expanding the vapour to generate power, a
condenser for condensing the outlet fluid from the expander. feed
pump means for returning condensed fluid from the condenser to the
heater and a return path for returning liquid phase from the
separator to the heater, wherein the liquid phase contains a
lubricant for the bearing which lubricant is soluble or miscible in
the liquid phase and a bearing supply path is arranged to deliver
liquid phase pressurised by the feed pump means to at least one
bearing for a rotary element of the expander. The condenser may
also initially desuperheat the vapour from the expander.
[0004] With this system the lubricant is dissolved or emulsified
with the liquid phase of the working fluid and a proportion of the
liquid phase leaving the separator is fed along the bearing supply
path to the bearing where heat generated in the bearing evaporates
the working fluid, leaving sufficiently concentrated lubricant in
the bearing to provide adequate lubrication of the bearing.
Preferably, collection spaces are provided around and below the
bearing. Lubricant leaving the bearing and entering the expander
travels to the condenser with the working fluid exhaust from the
expander. The lubricant again mixes with, or dissolves in, the
liquid phase formed in the condenser and returns, via the feed
pump, to the heater. Build-up or deposit of lubricant in the
evaporator section of the heater, which would reduce its
efficiency, is prevented by its retention in the liquid
recirculating through the evaporator section and partially drawn
off to flow through the expander, condenser and feed pump.
Advantageously, each bearing supporting the rotary element or
elements of the expander is lubricated in this manner. The total
mass of lubricant required is not more than 5% of the mass of
working fluid. Typically 0.5% to 2% is sufficient.
[0005] The expander may be a rotary expander. The expander may for
example be a turbine of the radial-inflow or axial flow type.
Particularly where power outputs up to about 3 MW are required, the
expander may be of the twin-screw type. Where the twin-screw type
expander is of the lubricated rotor type, the lubricant will be an
appropriate oil and some of the mixture of oil and liquid from the
separator will be fed into the expander, typically through the
normal lubrication port provided for lubricated rotor twin-screw
machines or a similar port nearer the high pressure port.
[0006] According to another aspect of the invention there is
provided a vapour power generating system for generating power by
using heat from a source of heat, comprising a closed circuit for a
working fluid, the system including heating means for heating the
fluid under pressure with heat from the source to generate vapour,
a plural screw expander for expanding the vapour to generate power,
a condenser for condensing the outlet fluid from the expander and
feed pump means for returning condensed fluid from the condenser to
the heater wherein a bearing supply path is arranged to deliver
liquid phase pressurised by the feed pump means to at least one
bearing for a rotary element of the expander, and the liquid phase
delivered to the at least one bearing contains a lubricant for the
expander which lubricant is soluble or miscible in the liquid
phase.
[0007] In embodiments of the invention the liquid phase may be
delivered from an intermediate point of the heater.
[0008] The invention will now be further described by way of
example with reference to the drawings in which:
[0009] FIG. 1 is a circuit diagram of a vapour power generating
system according to the invention,
[0010] FIG. 2 is a circuit diagram similar to FIG. 1 but
incorporating a modification,
[0011] FIG. 3 is a sectional view through the rotor axes of a twin
screw expander suitable for use in the circuit of FIG. 1 or 2,
[0012] FIG. 4 is a longitudinal section on the line IV-IV of FIG.
3,
[0013] FIG. 5 is a diagram showing the vertical disposition of
components of a system similar to those shown in FIGS. 1 and 2,
and
[0014] FIG. 6 is a circuit diagram of an alternative embodiment of
the invention using a single pass boiler.
[0015] The Organic Rankine Cycle system shown in FIG. 1 defines a
closed circuit for an organic working fluid having a boiling point
at atmospheric pressure below 100.degree. C. Up to 5% (usually
between 0.5 and 2%) by weight of a compatible natural or synthetic
lubricating oil is added to the fluid.
[0016] The circuit comprises a heat exchanger assembly 1 for
heating the working fluid in counterflow heat exchange with a hot
liquid such as geothermal brine or waste from an industrial source
at a temperature up to about 150.degree. C.
[0017] The heat exchanger assembly 1 defines a path 2 for the hot
fluid from the source, the path 2 extending from an inlet 3 to an
outlet 4. The assembly also defines a path, extending in
counterflow heat exchange with the path 2, through a heater section
5, for heating liquid working fluid, and an evaporator section 6
for evaporating at least some of the working fluid.
[0018] A line 7 leads from the outlet of the evaporator 6 to a
separator 8, at a higher level than the heater section 5, for
separating the vapour component of the evaporator output from the
liquid component. Lines 9 and 10 serve to return the hot liquid
component to the junction 11 between the heater and evaporator
sections 5 and 6.
[0019] A line 12 connects the vapour output of the separator 8 to
the inlet 13 of a twinscrew expander 14 for expanding the vapour to
a lower pressure and thereby generating power to drive an external
load such as an electrical generator G.
[0020] A line 15 leads from the exhaust outlet 16 of the expander
to a condenser 17 for condensing the expanded vapour in heat
exchange with a cooling fluid flowing through a circuit 18.
[0021] A line 19 connects the liquid outlet of the condenser to a
feed pump F for returning the liquid to the heater under pressure
through a line 20. To lubricate and cool the bearings of the
expander 14, a line 21 leads from the junction 22 of the lines 9
and 10 to inlets 27, 28 in bearing housings 23, 24 containing
bearings for the rotating elements of the expander.
[0022] The bearing housings 23, 24 provide sufficient space around
the bearings for the oil content of the liquid working fluid to be
concentrated as the working liquid evaporates into the expander as
a result of heat generated in the bearings. Since much of the
working fluid leaves the separator 8 as vapour, and thus free of
this oil, the oil content in the lines 9, 10 and 21 will already be
increased. As oil leaves the bearings and flows into the expander,
it is constantly replaced by further oil from the line 21. The oil
leaves the expander outlet 16 with the vapour and dissolves into
the liquid condensed in the condenser 17.
[0023] Since the separator 8 is higher than the heater section 5
(and preferably higher than the evaporator 6), and since the column
of liquid in the line 9 is denser than the column of fluid in the
evaporator 6 and line 7, there will be continuous circulation
through the evaporator section.
[0024] Similarly, the feed pump F ensures continuous circulation
through the heater section 5. By tapping off the flow from the
junction 22 to the bearings, a continuous circulation occurs
through the heater section, bearings, condenser and feed pump so
that an accumulation of oil on the surfaces of the heater and
evaporator sections, which would lower their efficiencies, is
prevented.
[0025] Where the expander is of the lubricated-rotor type, the line
21 may also be connected, by a line 25, to the normal oil-supply
port 26 of the expander.
[0026] The circuit shown in FIG. 2 differs from that shown in FIG.
1 in that the lubricant-containing liquid tapped off from the
junction 11 is cooled, for example from 80.degree. C. to 35.degree.
C., in a heat-exchanger 30, in counterflow with the liquid
delivered by the feed pump F to the inlet of the heater section 5.
Thus, the outlet of the feed pump F is connected by a line 31 to
the inlet of a pre-heater section 32 of the heat exchanger 30. The
outlet of the pre-heater section 32 is connected by a line 33 to
the inlet of the main heater section 5.
[0027] Instead of feeding the lubricating flow directly from the
junction 22 to the bearings, this flow is taken by a line 34 to the
inlet of a cooler section 35 of the heat exchanger to flow
therethrough in cooling heat exchange with the liquid in the
pre-heater section 32 before being fed by a line 36 to the expander
bearings 23, 24. Where the expander is a twin-screw expander, the
lubricating flow may also be taken to the rotor surface lubrication
inlet 37.
[0028] By cooling the lubrication flow, for example from 90.degree.
C. to 35.degree. C., the risk of the working liquid flashing into
vapour, and thus interrupting the supply of lubricant, is avoided.
Further, the flow can be controlled by means of restrictors or
control valves, again without vaporisation. By this means also heat
that would otherwise be wasted in the bearings is recovered and
used to increase the power output of the expander. The flow rate
delivered to the inlet 37 depends on the working fluid and the
operating conditions of the cycle but typically is of the order of
two to four times the total flow delivered to the rotor
bearings.
[0029] FIGS. 3 and 4 show a twin-screw expander suitable for use in
the circuits of FIGS. 1 and 2. The expander has a housing 40
containing a helically lobed rotor 41 meshing with a helically
grooved rotor 42. The rotor profiles, as seen in cross section are
of the low friction type having helical involute bands in the
region of their pitch circles, being preferably of the type
disclosed in EP 0,898,655. The rotors 41 and 42 are supported in
rolling bearings 43, 44 in the bearing housings 23, 24. The rotor
41 has an extension 45 projecting through the bearing housing 24,
with a sealing assembly 46, to drive the external load such as the
generator G.
[0030] The housing is formed with the rotor surface lubrication
inlet 37 in a position just downstream of the vapour inlet 13 to
ensure a sufficient pressure drop to provide an adequate
lubrication flow.
[0031] The working liquid portion of this flow forms the major part
of this flow and is free to vaporise and provide work as it flows
through the expander while depositing lubricant on the rotor
surfaces. The resulting surplus lubricant is carried by the flow of
vapour leaving the expander to the condenser and is thus
recirculated.
[0032] It may be found advantageous to provide collecting spaces
(47, 48) adjacent to the rotor bearings.
[0033] Where the source of heat is formed by the exhaust gases and
cooling jacket of an internal combustion engine,
chlorotetrafluoroethane is a particularly suitable working
fluid.
[0034] As shown in FIG. 5, the condenser 17 is positioned at the
highest point in the system and the heater 1 and feed pump are
positioned low down. Since the expander 14 is of the positive
displacement type (e.g. twin screw expander) which can tolerate the
possible presence of liquid droplets in the vapour flow, the
separator 8 and liquid return line 9 can be omitted. Instead, the
vapour from the evaporator section 6 is supplied by a line 51 to
the inlet 13 of the expander 14.
[0035] The expander inlet 13 is at the bottom at one end and the
low pressure vapour outlet 16 is at the top of the expander (in
contrast to the orientation shown in FIG. 4). Although excess oil
will tend to be expelled with the vapour into the line 15, residual
oil may remain in the expander 14. This will ensure adequate
lubrication of the rotor surfaces under all working conditions, and
also improve the sealing of the working fluid by filling up the
leakage gaps formed by the inevitable clearances between the rotors
and between the rotors and the casing with oil.
[0036] As shown, the liquid condensed in the condenser 17 is
conveyed by a line 19A to a liquid receiver 52 which holds a
reservoir of working liquid. Liquid from the receiver 52 is
conveyed by a line 198 to the inlet of the feed pump F. The
hydrostatic head between the condenser 17 and the feed pump reduces
or avoids the risk of cavitation in the inlet to the feed pump.
[0037] If it is found that the build of up oil in the expander is
too great, an oil return line 53, of very small bore, connects an
outlet 54 in the bottom of the casing of the expander to the return
path from the condenser to the feed pump, in this case being
connected to the liquid receiver 52. The outlet 54 is positioned
just up stream of the main outlet 16 of the screw expander in a
position where the pressure is just sufficiently higher than that
in the receiver 52 to enable the excess oil to leave the
expander.
[0038] The heater 1, preferably a plate-type heat exchanger and the
liquid flow to the bearings of the expander may be accumulated in a
storage vessel 55 before or after cooling in the heat exchanger 30
and being supplied to the bearing housings 23 and 24 and if
necessary to the rotor surface lubricating inlet 26.
[0039] As shown in FIG. 6, in an alternative embodiment the working
fluid is heated in a single pass boiler 60 in which cold liquid
enters at the inlet 61 and slightly wet vapour leaves at the exit
62, without internal recirculation through a separator. In this
case, the lubricant e.g. oil contained in the working fluid cannot
accumulate in the boiler but is transported by the vapour to enter
the expander 14. However, the presence of oil in the working fluid
has the effect of raising the saturation temperature of the vapour
for a given pressure and this effect can be used to advantage in
this embodiment.
[0040] At oil concentrations of 5% or less, by mass, this
temperature displacement is, in most cases, negligible and the
working fluid thermodynamic properties are virtually identical with
those of the pure working fluid. In the case of a boiler in which
the working fluid recirculates through the evaporator, the
recirculation flow rate is normally at least 5 times the bulk flow
of fluid through the boiler. Thus, if the oil concentration is
initially, say 2% by mass, the increase in concentration of oil as
a result of evaporation of about 20% of the fluid, has a negligible
effect on the fluid behaviour.
[0041] However, in a single pass boiler, with the same initial
concentration of oil, the presence of oil has an increasing effect
on the fluid behaviour as evaporation proceeds. Thus, initially, as
evaporation proceeds, the working fluid behaves as a pure fluid.
However, when 80-90% of the evaporation is complete, the oil
concentration in the remaining liquid will become significant and
further heat transfer to it, from the external heat source to the
boiler, will result in the remaining liquid becoming superheated
while retaining most of the oil. This means that the working fluid
will enter the expander 14, as a wet vapour, with some 5-10% liquid
containing a high percentage of oil. In a screw or any other type
of positive displacement expander, the presence of liquid can be
beneficial since [0042] i) It may help to seal the gaps and
lubricate the machine. [0043] ii) It evaporates during the
expansion process and thereby decreases the superheat with which
organic working fluids normally leave the expander 14.
[0044] Thus, the superheated liquid effectively carries the oil to
the rotating parts of the expander and leaves an oil deposit there
as expansion proceeds in exactly the same manner as it would, if
drawn from the recirculated liquid of a conventional boiler.
[0045] The oil build up in the expander will eventually drain or be
transported into the condenser 17 where it will be redissolved or
entrained. Thus, the cold working fluid leaving the feed pump will
contain oil. Cold liquid can therefore be drawn from downstream of
the pump and delivered directly to the bearings without preheating
and the consequent need of a regenerative heat exchanger. Thus, the
use of a single pass boiler leads to further simplification to the
lubrication system, as shown.
[0046] Although it is not shown in FIG. 6, the arrangement of that
figure could also include a liquid receiver arrangement of the type
shown in FIG. 5 to collect and hold liquid condensed in the
condenser 17 and/or excess oil from the expander.
* * * * *