The present invention relates to a rotary phase separator
system, useful particularly in two-phase separation.
Because of re-supply constraints in long duration missions,
such as space missions, minimizing mass, volume and power are essential. Closed
Advanced Life Support Systems (ALS), including Air Revitalization Subsystem, Water
Revitalization Subsystem, etc., are desirable. In a typical Advanced Air Revitalization
System, water is electrolyzed into oxygen (02) and hydrogen (H2) in an oxygen generation
subsystem. Water is also consumed in various hygiene needs, physiological loads
and other life support functions. A typical Water Recovery System (WRS) will regenerate
water from various wastewater streams.
One WRS system is a Sabatier System which is designed to
recover water and does so via a reaction that produces water vapor mixed with gases
(primarily methane and CO2). CO2 reacts with H2 and generates water and
methane according to the following Sabatier reaction:
CO2 + 4H2 →
2H2O + CH4
The Sabatier system accomplishes this by utilizing hydrogen,
carbon dioxide, and waste products from the life support system to produce water
and methane.
The catalytic methanation reaction between CO2 and H2 is
exothermic and self-sustainable. Water vapor generated from the Sabatier reactor
can be recovered by passing the product gases through a condenser in which the water
is condensed, yielding a two-phase flow (water in mostly gas stream). The recovered
water is then recycled back into the life support system to provide oxygen; while
the methane can be used for propulsion, or can be broken down further to recover
the hydrogen. This technology is applicable not only to transit phases of exploration,
but surface habitats as well as in-situ propellant production.
Accordingly, it is desirable to provide a compact and lightweight
two-phase separator system which separates water from gas, accumulate the water,
and pumps the water at higher pressure for downstream processing and use while minimizing
power consumption.
According to the invention, there is provided a rotary
phase separator system comprising:
- a housing;
- a hydrodynamic bearing mounted within said housing;
- a rotating assembly mounted to said hydrodynamic bearing for rotation within
said housing, said rotating assembly comprising:
- a hollow shaft defined along an axis of rotation;
- a primary separating impeller mounted within an impeller shaft section of said
hollow shaft for rotation therewith;
- a gas outlet tube mounted within said hollow shaft;
- an accumulator section mounted about said axis of rotation for rotation with
said hollow shaft, said accumulator section defining a first diameter; and
- an impeller pump section mounted about said axis of rotation for rotation with
said hollow shaft, said impeller pump section defining a second diameter greater
than said first diameter;
- a two-phase input port within said housing, said two-phase input port being
in communication with said impeller shaft section; and
- a gas outlet port within said housing along said axis of rotation, said gas
outlet port being in communication with said gas outlet tube.
The invention also provides a rotating assembly for a rotary
phase separator system comprising:
- a hollow shaft defined along an axis of rotation;
- an accumulator section mounted about said axis of rotation for rotation with
said hollow shaft, said accumulator section defining a first diameter; and
- an impeller pump section mounted about said axis of rotation for rotation with
said hollow shaft, said impeller pump section defining a second diameter greater
than said first diameter.
The invention also provides a method of recovering a liquid
from a two phase flow comprising the steps of:
- (1) rotating a hollow shaft about an axis of rotation at a first speed;
- (2) introducing the two-phase flow into the rotating hollow shaft;
- (3) separating the two-phase flow such that a liquid component is centrifugally
separated radially outward relative to the axis of rotation;
- (4) collecting a gas component generally along said axis of rotation;
- (5) accumulating the liquid component within an accumulator section;
- (6) selectively rotating the hollow shaft about the axis of rotation at a second
speed greater than the first speed; and
- (7) pumping out the liquid component in response to said step (6).
The rotary phase separator system according to embodiments
of the present invention generally includes a rotary drum separator (RDS) and a
motor assembly. The motor assembly drives a rotating assembly of the RDS in response
to a controller which drives the RDS at two operation speeds. A low speed is used
for separating and accumulating water from gas. A higher speed is used for pumping
the water once the accumulator is full.
In operation, the two-phase flow (water in mostly gas stream)
is input into an impeller shaft section of a hollow shaft through a two-phase inlet
tap. The two-phase flow is centrifugally flung to the outer diameter of the impeller
shaft section that moves the water radially outward while allowing the gas to communicate
and collect within a central shaft section along an axis of rotation. The primary
separating impeller provides ample flow area for the gas while maintaining small
clearances to the central shaft section and thence to a gas outlet tube. A secondary
separating impeller mounted within the hollow shaft facilitates separation capability
and robustness to further minimize liquid (if present) injection into an inlet of
the gas outlet tube.
The accumulating function is effectuated inside an accumulator
section and an impeller pump section that form an annulus around the center hollow
shaft. The water rotates at essentially shaft speed since it is fully enclosed by
the accumulator section and the impeller pump section and has virtually no exposure
to stationary walls. The "full" level of the accumulators is at the hollow shaft
OD (outside diameter). The "empty" level of the accumulator section is at the accumulator
OD. The smooth outside walls of the drums minimize power losses. A minimized diameter
to length ratio also minimizes power losses. As the accumulator section and the
impeller pump section fill with liquid, the gases therein are forced radially inward
back into the hollow shaft toward the axis of rotation and through the shaft gas
communication apertures and thence into the inlet of the gas outlet tube.
The pumping function is accomplished by the impeller pump
section which is facilitated by the internal vanes between the impeller disks. Once
the accumulation section is "full" the liquid is pumped through the tangential outlet
located at the maximum diameter of the device to maximize both static and dynamic
head.
The RDS operates on a two-speed schedule. At low speed,
about 1000 rpm, the RDS creates enough of an artificial gravity field to effectively
separate the gas and liquid phases. The gas port is always open when the Sabatier
is in process mode generating water; therefore the vent gases flow through the RDS
with very little pressure drop. Once the liquid level of the separator reaches the
high end of the operating range ("full"), the controller increases the speed of
the RDS to about 2000 rpm. At this speed, the pressure generated by the centrifugal
and velocity forces of the liquid in the impeller shaft section of the rotating
assembly is sufficient to overcome the system backpressure and the liquid empties
from the RDS. The high speed condition is maintained for a sufficient length of
time such that the liquid level drops to the low end of the operating range ("empty").
The present invention therefore provides, at least in its
preferred embodiments, a compact and lightweight two-phase separator system which
separates water from gas, accumulates the water, and pumps the water at higher pressure
for downstream processing and use while minimizing power consumption.
Various features and advantages of this invention will
become apparent to those skilled in the art from the following detailed description
of the currently preferred embodiment, given by way of example only. The drawings
that accompany the detailed description can be briefly described as follows:
- Figure 1 is a general schematic view of a Sabatier Reduction system to which
the present invention may be applied;
- Figure 2 is a perspective view of a rotational assembly for a rotary drum separator
in accordance with the present invention;
- Figure 3A is a perspective view of a rotary drum separator in accordance with
the present invention;
- Figure 3B is a sectional view of the rotational assembly taken along line 3B-3B
in Figure 3A;
- Figure 3C is a sectional view of the rotational assembly taken along line 3C-3C
in Figure 3A;
- Figure 3D is a sectional view of the rotational assembly taken along line 3D-3D
in Figure 3A;
- Figure 4 is an expanded cut away perspective view of a shaft of the rotational
assembly for the rotary drum separator;
- Figure 5 is an expanded perspective view of the shaft of the rotational assembly
for the rotary drum separator; and
- Figure 6 is a graphical representation of an operating map for the rotary drum
separator.
Figure 1 illustrates a general perspective view of a Sabatier
Reduction system 10 which receives the hydrogen by-product from electrolytic oxygen
generation and metabolic carbon dioxide that is concentrated by a molecular sieve
bed and reacts them to form methane and water. The reactor products are cooled in
a heat exchanger 12 where the water product condenses to liquid. The liquid water
and methane gas are then separated in a rotary phase separator system 14, with the
water being delivered to the water bus and the methane released out the vacuum vent
duct. Potable water is thereby provided.
The rotary phase separator system 14 generally includes
a rotary drum separator (RDS) 16 and a motor assembly 18. The motor assembly 18
drives the RDS 16 through a rotating assembly 20 (Figure 2) in response to a controller
22 (illustrated schematically).
The RDS preferably operates at two operation speeds. A
low speed is used for separating and accumulating water from gas. A higher speed
is used for pumping the water once the accumulator is full. It should be understood
that other two-phase reduction systems will also benefit from the RDS 16 designed
according to the present invention. The rotary phase separator system 14 provides
for separation of methane gas and liquid water phases at about 10 psia (69 kPa),
and pumping of the liquid to a water bus pressure of up to 18 psia (124 kPa). The
rotary phase separator system 14 achieves this pumping at less than 100 Watts, and
separation at less than 25 Watts.
Referring to Figure 3A, the RDS 16 includes a housing assembly
24 within which the rotating assembly 20 (Figure 2) rotates about an axis of rotation
A. Preferably, the housing assembly 24 includes a first housing portion 26 and a
second housing portion 28 which enclose the rotating assembly 20 and provide passageways
for fluid circulation. A water outlet tangential port tap 30 is tangential to the
housing outer diameter and as such collects the water at maximum velocity head.
A pressure port 32 provides for identification of a fill level. A radial port 34
normal to the rotating assembly 20 rotation serves as a static pressure port. A
gas outlet port 36 is located along the RDS 16 centerline A and two two-phase inlet
ports 38 are located adjacent thereto. It should be understood that although only
particular taps are described, any multiple of taps may be utilized with the present
invention. It should be understood that taps 32T, 34T, 36T may be respectively located
in the housing assembly 24 to provide communication with the respective ports 32,
34, 36. That is, the taps 32T, 34T, 36T provide connections with the housing assembly
24 and porting defined therein. Preferably, the internal volume of the separator
will hold approximately 170 cc of water when full with a working volume of 70 cc
mounted around the rotating assembly 20.
Referring to Figure 3B, the rotating assembly 20 is mounted
on a first and a second hydrodynamic bearing 40, 42 for rotation about the axis
of rotation A. The bearings 40, 42 preferably provide both radial and thrust functions.
The rotating assembly 20 includes a hollow shaft 44 which contains a primary separating
impeller 46 and a secondary separating impeller 48. The motor provides leak free
operation at sub-ambient pressure. The hollow shaft 44 contains a gas outlet tube
56 to the gas outlet port 36 located opposite the motor.
The primary separating impeller 46 includes internal vanes
60 (Figure 4) that facilitate spinning of the two-phase liquid at shaft speed in
order to develop the proper 'g' levels to drive the liquid radially outward while
allowing the gas to remain adjacent the gas outlet tube 56.
The secondary separating impeller 48 inside the hollow
shaft 44 facilitates separation capability and robustness. This secondary separating
impeller 48 includes internal passages 62 (Figure 4) that are drilled at an angle
to the axis of rotation A to drive liquid (if present) away from an inlet 64 to
the gas outlet tube 56 and radially outward. The secondary separating impeller 48
also serves as a way to clear away any liquid from near the inlet 64 that may result
from a shut-down and restart situation.
The hollow shaft 44 supports a stepped drum 50 (also illustrated
in Figures 2 and 3C) for accumulation and pumping. The stepped drum 50 is mounted
on the shaft 44 that is supported by the hydrodynamic bearings 40, 42. The stepped
drum 50 is stepped such that there is a smaller diameter accumulator section 52
and a relatively large diameter impeller pump section 54. The accumulator section
52 is utilized to provide the primary accumulator function. The impeller pump section
54 is utilized for the pumping function.
The aspect ratio of the stepped drum 50 is preferably sized
to minimize power for both the accumulating and pumping functions. The accumulator
section 52 has a relatively small diameter to minimize power losses and uses axial
length to accomplish volume for accumulation. The impeller pump section 54 of the
drum has a larger diameter in order to achieve pumping head but has a small axial
length in order to minimize power losses.
The impeller pump section 54 includes impeller disks 58
each having internal vanes 60 that facilitate the pumping function (also illustrated
in Figure 3D). The stepped drum 50 is preferably manufactured from two identical
"half" drums assembled opposite to each other which readily facilitates manufacture
(Figure 3C). Preferably, the stepped drum 50 includes smooth exterior walls on the
stepped drum 50 to minimize power losses. Smooth rotating walls of the stepped drums
adjacent to smooth stationary walls formed in the housing assembly 24 typically
exhibit less drag than non-smooth geometry thereby minimizing the power required
to rotate the rotational assembly 20.
Preferably, a labyrinth type geometry seal 78 is located
on the outer diameter of the accumulator section 52 of stepped drum 50 to minimize
the flow of a recirculation loop from the high-pressure side of the pump (at the
largest diameter) to the inlet side of the pump. It should be understood that various
seal arrangements may be used with the present invention.
The hollow shaft 44 includes a multitude of shaft gas communication
apertures 68 (also illustrated in Figures 4 and 5) in communication with the accumulator
section 52 and the impeller pump section 54. A multitude of liquid communication
ports 70 (also illustrated in Figure 4) are located adjacent an outer diameter of
an impeller shaft section 72 which contains the primary separating impeller 46.
The liquid communication ports 70 provide communication between the primary separating
impeller 46 and the accumulator section 52. Preferably, the liquid communication
ports 70 are circumferentially located and angled outward relative to axis A about
the hollow shaft 44 adjacent a junction 74 between the impeller shaft section 72
and a central shaft section 76.
In operation, the two-phase flow (water in mostly gas stream)
is input into the impeller shaft section 72 of the hollow shaft through the two-phase
inlet port 38. The two-phase flow is centrifugally flung to the outer diameter of
the impeller shaft section 72 that moves the water radially outward through the
liquid communication ports 70 while allowing the gas to communicate into the central
shaft section 76. The primary separating impeller 46 provides ample flow area for
the gas while maintaining relatively small clearance to the central shaft section
76 and thence to the inlet 64 of the gas outlet tube 56 to avoid liquid carryover.
The secondary separating impeller 48 facilitates separation capability and robustness
to further minimize liquid (if present) entry into the inlet 64 of the gas outlet
tube 56.
The accumulating function is effectuated inside the accumulator
section 52 and the impeller pump section 54 that create a stepped annulus around
the center hollow shaft 44. The water rotates at essentially shaft speed since it
is fully enclosed by the accumulator section 52 and the impeller pump section 54
and has virtually no exposure to stationary housing walls. The "full" level is at
the OD of the hollow shaft 44. The "empty" level of the accumulator will be at the
OD of the accumulator section 52. The smooth outside walls of the stepped drum 50
minimize power losses. A minimized diameter to length ratio also minimizes power
losses. Notably, as the accumulator section 52 and the impeller pump section 54
fill with liquid, gases therein (if present) are forced toward the axis of rotation
A and back into the hollow shaft 44 through the shaft gas communication apertures
68 and thence into the inlet 64 of the gas outlet tube 56.
The pumping function is accomplished by the impeller pump
section 54 which is facilitated by the internal vanes 60 between the impeller disks
58. Once the accumulator section 52 is "full," the liquid is pumped through the
tangential outlet port 34 located at the maximum diameter of the impeller pump section
54 to maximize both static and dynamic head.
Preferably, the RDS 16 operates on a two-speed schedule.
At low speed, about 1000 rpm, the RDS 16 creates enough of an artificial gravity
field to effectively separate the gas and liquid phases. The gas outlet port 36
is open when the Sabatier is in process mode generating water; therefore the vent
gases flow through the RDS 16 with very little pressure drop. Pressure port 32,
the gas outlet port tap 36 and the radial port 34 (Figure 3) at the drum outer diameter
allow monitoring of the liquid level via differential pressure. Applicant has calibrated
the pressure vs. volume in both 1-g and 0-g environments. Once the liquid level
reaches the high end of the operating range ("full"), the controller (Figure 1)
increases the speed of the RDS 16 to about 2000 rpm. At this speed, the pressure
generated by the centrifugal and velocity forces in the impeller shaft section 72
of the rotating assembly 20 is sufficient to overcome the system backpressure and
the liquid empties from the RDS 16. The high speed condition is maintained for a
sufficient length of time such that the liquid level drops to the low end of the
operating range as generally illustrated in the graphical representation of Figure
6.
It should be understood that relative positional terms
such as "forward," "aft," "upper," "lower," "above," "below," and the like are with
reference to the normal operational attitude of the vehicle and should not be considered
otherwise limiting.
It should be understood that although a particular component
arrangement is disclosed in the illustrated embodiment, other arrangements will
benefit from the instant invention.
Although particular step sequences are shown, described,
and claimed, it should be understood that steps may be performed in any order, separated
or combined unless otherwise indicated and will still benefit from the present invention.
The foregoing description is exemplary rather than defined
by the limitations within. Many modifications and variations of the present invention
are possible in light of the above teachings. The preferred embodiments of this
invention have been disclosed, however, one of ordinary skill in the art would recognize
that certain modifications would come within the scope of this invention. It is,
therefore, to be understood that within the scope of the appended claims, the invention
may be practised otherwise than as specifically described. For that reason the following
claims should be studied to determine the true scope and content of this invention.
