1. FIELD OF THE INVENTION
[0001] The invention relates in general to the field of jet pump design. Specifically, the
invention describes a jet pump design that utilizes a variable corrugated ogive to
enhance fluid mixing and, therefore, the operational efficiency of the pump.
2. BACKGROUND OF THE INVENTION
[0002] A conventional use of jet pump technology is in combination (series) with a standard
rotary pump where the available net positive suction head is low. In these situations
a jet pump can be used to increase the pressure of a low pressure fluid to provide
the necessary head for a standard (e.g., rotary) pump. Hence, often times jet pumps
are used as "booster" pumps; they 'boost' the pressure of a low pressure fluid so
that it may be pumped by a standard pump.
[0003] In this role a well known function of traditional jet pump technology is to transfer
kinetic energy from a high-energy (high velocity, high pressure) fluid (HEF) to a
low-energy (low velocity, low pressure) fluid (LEF). Energy transferred into the LEF
is stored in the form of potential energy and results in an increase in the fluid's
pressure. Energy transfer, and therefore jet pump efficiency, is enhanced by a thorough
mixing of the low- and high-energy fluids.
[0004] One key operational problem with conventional jet pumps, which utilize standard de
Laval nozzle jets, is their low efficiency due to poor mixing of the low- and high-energy
fluids.
3. SUMMARY OF THE INVENTION
[0005] An apparatus for increasing the mixing efficiency of low- and high-energy fluids
within a jet pump is described. A jet pump utilizing said enhanced mixing apparatus
is referred to as a corrugated jet pump.
[0006] A corrugated jet pump incorporates a corrugated annular nozzle ogive that, during
pumping operations, creates alternating low and high velocity zones in the ogive of
the nozzle. These different velocity zones propagate shear planes that enhance the
jet pumps downstream mixing. At the same time the core, or central portion, of the
corrugated annular nozzle ring creates alternating vortices in the low- and high-energy
fluids which also enhances mixing. The corrugated annular nozzle incorporates composite
laminates for its fabrication. Advantages of the corrugated jet pump design include:
(1) an overall reduction in boost pump length of as much as 75%, (2) a tremendous
weight savings, and (3) significantly reduced production manufacturing costs.
4. BRIEF DESCRIPTION OF DRAWINGS
[0007] Figure 1 is a cross-sectional view of one embodiment of the invention.
[0008] Figure 2 is an end-view of one embodiment of the invention.
[0009] Figure 3 is a cut-away view of fluid mixing within one embodiment of a corrugated
jet pump.
[0010] Figure 4 is another cross-sectional view of an annular two-corrugation embodiment
of the invention.
5. DETAILED DESCRIPTION OF A SPECIFIC EMBODIMENT
[0011] One illustrative embodiment of the invention is described below as it might be implemented
for a jet pump designed to pump cryogenic fluids, e.g., liquid oxygen (LOX) or liquid
hydrogen (H
2). In the interest of clarity, not all features of an actual implementation are described
in this specification. It will of course be appreciated that in the development of
any such actual implementation (as in any mechanical design) numerous implementation-specific
decisions must be made to achieve the developers' specific goals and subgoals, such
as compliance with system- and business-related constraints, which will vary from
one implementation to another. Moreover, it will be appreciated that such a development
effort might be complex and time-consuming, but would nevertheless be a routine undertaking
of mechanical design engineering for those of ordinary skill having the benefit of
this disclosure.
[0012] In reference to Figures 1 and 2, high-energy fluid 90 is injected into a corrugated
jet pump via a volute, or constant velocity manifold 100. Low-energy fluid 80 can
be provided from a storage tank (not shown) and enters the corrugated jet pump at
the main inlet 105. After the HEF is injected into the LEF's path, via an injection
nozzle 110, the two fluids begin to mix after leaving the corrugated annular nozzle
ogive 115.
[0013] As the low- and high-energy fluids mix within the corrugated annular nozzle ogive
115, the velocity of the fluid in the corrugate's valley regions 120 is less than
the velocity of the fluid in the corrugate's crown regions 125. These regions of differing
velocity set up shear planes within the fluid (comprised of low- and high-energy fluids),
thereby enhancing the jet pump's mixing action. The shear planes also generate vortices;
two vortices per crown region. These vortices, or swirling actions, further enhance
the jet pump's mixing action, as indicated by arrows 150.
[0014] In a conventional jet pump the nozzle ogive has a constant cross-sectional area.
This is analogous to a piece of cardboard, no matter where you cut a flat piece of
cardboard the inner structure is constant. That is, no matter where along a conventional
ogive you look, its cross-sectional area is constant. The corrugated annular nozzle
ogive of the invention, however, exhibits a position dependent cross-sectional area.
For instance, the magnitude of the valley-to-crown distance at cut 130 is less than
the magnitude of the valley-to-crown distance at cut 135. Thus, the area of the nozzle's
throat 140 is less than the area of the nozzle's exit 145. The invention's fluctuating
geometry imparts differing velocities into the low and high energy fluids which creates
shear planes and, thereby, improves the ability of a jet pump to mix the two fluids.
[0015] Many conventional jet pump designs have length-to-diameter ratios of approximately
7:1. These large values (implying long jets, relative to their diameter) are necessary
to ensure that the low- and high-energy fluids have sufficient time to thoroughly
mix. Thus, length-to-diameter ratios are one indication of a jet pump's mixing efficiency.
Using a corrugated annular nozzle ogive, as shown in Figures 1, 2 and 4, a jet pump's
length-to-diameter ratio can be brought down to between 1:1 or 1.5:1 - indicating
a significant improvement in the jet pump's mixing efficiency. A shorter pump also
consumes less material in its manufacture, making a corrugated jet pump less costly
and lighter than a conventional jet pump.
[0016] Figure 3 is a straight embodiment for which numeric designators retain previous definitions.
This embodiment uses two sets of corrugations 115. Efficient mixing is indicated by
arrows 150.
[0017] As shown in cross-section in Figure 4, a jet pump in accordance with the invention
may have two concentric rings of corrugated nozzles 115 that efficiently mix high
90 and low 80 energy fluids. As previously mentioned, this two-ring configuration
can decrease the required length for efficient mixing, indicated by arrows 150 (Fig.
3), thus minimizing the size (length) and weight of the jet pump system.
5.1 Design Considerations
[0018] An exemplary jet pump in accordance with the invention has a discrete mass flow rate,
ẇ, ratio between the HEF (
ẇHEF) and LEF (
ẇLEF) which is dependent on the pressure differential between the two fluids and the required
net positive suction head of the rotary pump for which the jet pump is a booster.
The mass flow rates of the two fluids typically depend upon the required head of the
rotary pump and the location where the HEF source is tapped off, i.e., where the HEF
source is tapped off relative to the jet pump's injection nozzle 110.
[0019] The mass flow rate and the pressure difference between the HEF and LEF define the
fluid velocities of the two streams and dictate the cross-sectional areas of the nozzle
jets 140 and the LEF suction (inlet) port 105. The aforementioned areas can utilize
any variation of geometry's, e.g., circular or rectangular. The area of the nozzle's
throat 140 (
Athroat) is equal to the mass flow rate of the HEF divided by the product of the HEF's velocity
(
vHEF) and its density (ρ
HEF):

The area of the LEF inlet port 105 (
ALEF Inlet) is equal to the mass flow rate of the LEF divided by the product of the LEF's velocity
(
vLEF) and its density (ρ
LEF):

[0020] The operational velocities of the HEF and LEF are, in part, determined by the pressure
difference between the two fluids and can be determined by means of a hydrodynamic
analysis which takes into account head and line loss and acceleration within the nozzle.
The location and configuration of the corrugated nozzle jets is a variable and depends
upon the allowable mixing length (usually between 0.5 and 1.5 inlet flow diameters)
and the required pump performance.
[0021] The circumferential spacing 200 (Fig. 2), the amplitude of the corrugates 205 and
the throat to exit area ratio of the nozzle (ε) is set to maximize mixing effectiveness.
The relative spacing of the two nozzle rings is set to eliminate reverse flow in the
center of the mixing region.
[0022] The thickness of the corrugations is dependent on the pressure difference between
the HEF and LEF, the throat to exit area ratio of the nozzle (ε), the nozzle's attachment
scheme and the material used to form the corrugated nozzle. Material selection depends
on the type of fluids being pumped.
[0023] It has been found that a jet pump in accordance with the invention can be positioned
as close as one-half of the flow diameter to the inlet of the rotary pump. As one
of ordinary skill in the field would understand, the actual position is dependent
upon the specific system requirements.
[0024] In summary, some of the design parameters that affect the construction of the invention's
corrugate apparatus include:
1. Pressure differential between low- and high-energy fluids.
2. Pressure of incoming high-energy fluid.
3. Discharge pressure of mixed fluid.
4. Mass flow rate of the low-and high-energy fluids (the larger the jet pump's total
mass flow rate, the larger the jet pump and, therefore, the larger the corrugated
annular nozzle).
5. Type/temperature of the fluid being pumped (the temperature of the fluids being
pumped determine the materials of choice for the composite laminates of the corrugated
annular nozzle).
5.2 Some Benefits of the Invention
[0025] Some advantages of the composite laminate corrugated jet pump design include:
1. An overall reduction in boost pump length of as much as 75%.
2. The low density of the composite laminate corrugated surface, and the reduction
in length made possible by the increased mixing efficiency of a corrugated jet pump
design, reduce weight.
3. Significantly reduced production manufacturing costs.
[0026] It will be appreciated by those of ordinary skill having the benefit of this disclosure
that numerous variations from the foregoing illustration will be possible without
departing from the inventive concept described herein. Accordingly, it is the claims
set forth below, and not merely the foregoing illustration, which are intended to
define the exclusive rights claimed in this application program.