Information
-
Patent Grant
-
6666192
-
Patent Number
6,666,192
-
Date Filed
Wednesday, November 14, 200122 years ago
-
Date Issued
Tuesday, December 23, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 520
- 123 519
- 123 518
- 123 516
- 123 198 D
- 251 12915
- 137 62525
-
International Classifications
-
Abstract
Disclosed herein is a fluid control valve comprising a valve seat, and a nozzle proximate the valve seat. The nozzle includes a convergent section and a divergent section formed by a semi-circular profile. Also disclosed herein is a system for controlled feeding of volatile fuel components from a free space of a fuel tank to an engine manifold, the system comprising a storage chamber in fluid communication with the free space of the fuel tank, and a valve in fluid communication between the storage chamber and the engine manifold. The valve includes a valve seat and a nozzle proximate the valve seat. The nozzle includes a convergent section and a divergent section formed by a semi-circular profile.
Description
BACKGROUND
The present disclosure generally relates to fluid control valves and systems. Fluid control valves may be used in systems for the controlled feeding of volatile fuel components present in the free space of a fuel tank into an intake manifold of an internal combustion engine. A system of this type is disclosed U.S. Pat. No. 4,901,702. The system includes a vent line connecting the free space to the atmosphere. In the vent line there is disposed a storage chamber containing an absorption element, as well as a line connecting the storage chamber to the intake tube, which can be shut off by an electromagnetic check valve. Between the check valve and the intake tube there is disposed an auxiliary valve with a control chamber. The auxiliary valve can be closed by a vacuum actuator in dependence upon the pressure difference between the control chamber and the atmosphere. During low engine operating speeds in the near idling range, the flow rate of volatile fuel components through the apparatus is reduced so as to prevent the excessive enrichment of the mixture fed to the engine; at high engine operating speeds when the differential pressure between the engine and the tank is reduced, the non-return valve employed is wide open.
Another system of this type is disclosed in U.S. Pat. No. 5,284,121. This system comprises a pneumatically actuated purge control valve for opening or closing a flow line which connects an upper space of the fuel tank with the intake pipe, a controller for controlling the operation of the valve, a throttle section formed in series with the purge control valve, and pressure and temperature sensors which are located on the upstream side of the throttle section for detecting a pressure and a temperature of the evaporated fuel. When a value detected by the pressure sensor exceeds a predetermined value of pressure for providing a critical pressure ratio at which a flow rate of the evaporated fuel at the throttle section substantially equals to a sonic velocity, the controller opens the pneumatically actuated purge control valve to cause a purged flow of the evaporated fuel whose flow rate is constant. Simultaneously, the controller calculates a purged flow rate of the evaporated fuel from the detected values of the pressure and temperature sensors and a time period during which the purge control valve is opened. On the basis of the calculated purged flow rate, a reduction correction is made to an amount of the fuel to be supplied to the engine in order to maintain an air-fuel ratio in the optimum condition.
U.S. Pat. No. 5,460,137 provides another system of this type. This system includes a venting line that connects the free space of the fuel tank to the atmosphere. Along this line is interposed a storage chamber containing an absorption element having at least one line which connects the storage chamber to the intake manifold and which can be sealed by an electromagnetically actuated valve. The valve includes a seat and a Laval-type nozzle arranged downstream of the seat. The Laval-type nozzle allows the valve to employ a valve seat having a relatively small orifice cross section while maintaining generally the same mass throughput as a valve employing a relatively large valve seat with a standard cylindrical nozzle. The relatively small orifice cross section allows the valve to employ relatively small actuating forces to open and close the valve, thereby allowing the valve to be held in the closed position during clocked control for a longer period of time so that the excessive enrichment of the fuel-air mixture can be avoided.
SUMMARY
Disclosed herein is a fluid control valve comprising a valve seat and a nozzle proximate the valve seat. The nozzle includes a convergent section and a divergent section formed by a semi-circular profile.
Also disclosed herein is a system for controlled feeding of volatile fuel components from a free space of a fuel tank to an engine manifold. The system comprises a storage chamber in fluid communication with the free space of the fuel tank, and a valve in fluid communication between the storage chamber and the engine manifold. The valve includes a valve seat and a nozzle proximate the valve seat. The nozzle includes a convergent section and a divergent section formed by a semi-circular profile.
The above described and other features are exemplified by the following figures and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike:
FIG. 1
is a schematic view of an exemplary system for the controlled feeding of volatile fuel components from the free space of a fuel tank to an engine manifold;
FIG. 2
is a perspective view of the fluid control valve of
FIG. 1
;
FIG. 3
is a cross-sectional view of the fluid control valve of
FIG. 2
;
FIG. 4
is a cross-sectional view of the outlet port of
FIG. 3
; and
FIG. 5
is another cross-sectional view of the outlet port of FIG.
3
.
DETAILED DESCRIPTION
Referring to
FIG. 1
, an exemplary embodiment of a system
10
for the controlled feeding of volatile fuel components from a free space
12
of a fuel tank
14
to an intake manifold
16
of an internal combustion engine
18
is shown. The system
10
includes an air filter
20
and a throttle valve
22
, which may be located inside the intake manifold
16
. System
10
also includes a fluid control valve
24
having an outlet port
26
in fluid communication with intake manifold
16
and an inlet port
28
in fluid communication with an outlet
30
of an absorption element
32
. Absorption element
32
is located within a storage chamber
34
, and may be an activated carbon filter or the like. An inlet
36
of absorption element
32
is in fluid communication with the free space
12
of fuel tank
14
and with a diagnostic unit
38
. Diagnostic unit
38
is in electrical communication with fluid control valve
24
and may in communication with the indicating instruments
40
.
During the operation of the internal combustion engine
18
, volatile fuel components from the free space
12
of the fuel tank
14
pass into the storage chamber
34
via the inlet
36
of absorption element
32
and are taken up by the absorption element
32
. Vacuum in the intake manifold
16
of the internal combustion engine
18
draws the volatile fuel components from chamber
34
through the outlet
30
of absorption element
32
and through the fluid control valve
24
. The volatile fuel components are fed from fluid control valve
24
to the manifold
16
in the flow direction
42
towards the throttle valve
22
. The flow of volatile fuel components from chamber
34
to the intake manifold
16
can be sealed by fluid control valve
24
.
Fluid control valve
24
is controlled (i.e., opened and closed) in response to various signals received from diagnostic unit
38
. The Diagnostic unit
38
monitors various environmental and vehicle variables to estimate the amount of fuel vapors stored in the absorption element
32
. The diagnostic unit
38
serves to monitor and control the fluid control valve
24
. The passage of volatile fuel components into the intake manifold
16
is regulated as a function of input variables such as the position of the throttle valve
22
, the speed of rotation of the internal combustion engine
18
, and/or the composition of the exhaust gas.
Referring to
FIG. 2
, a perspective view of an exemplary embodiment of the fluid control valve
24
is shown. Fluid control valve
24
includes a housing
100
that is, preferably, cylindrical in shape and molded from plastic. Inlet port extends along a radial surface
102
of housing
100
, generally parallel to a longitudinal axis
104
of the outlet port
26
. Also extending from radial surface
102
, diametrically opposite inlet port
28
, is a mounting bracket
106
. Extending from an end surface
108
of housing
100
is a terminal housing
110
. An opposite end surface
112
of housing
100
is formed in part by a flange
109
that extends outward from radial surface
102
. Outlet port
26
is received within an aperture formed by flange
109
.
Inlet port
28
includes a first tubular section
114
that extends generally parallel to longitudinal axis
104
, and a second tubular section
116
that extends generally perpendicular to longitudinal axis
104
. Second tubular section
116
is attached to first tubular section
114
at an end
118
of first tubular section
114
proximate end surface
112
of housing
100
. An end
120
of first tubular section
114
proximate end surface
108
of housing is configured to receive tubing from system
10
(e.g., tubing from outlet
30
of absorption element
32
as shown in FIG.
1
). Second tubular section
116
includes a plug
122
disposed in an end thereof. Plug
122
seals the end of second tubular section
116
to prevent the volatile fuel components from escaping as they pass through first tubular section
114
and second tubular section
116
into housing
100
. Preferably, inlet port
28
is integrally molded with housing
100
.
Mounting bracket
106
includes two legs
124
that extend from radial surface
102
. Each leg
124
includes a generally “C” shaped guide
126
formed on an end of leg
124
distal from radial surface
102
. The “C” shaped guides
126
include slots
128
that are arranged in opposition to each other, such that a mounting plate (not shown) may be slidably received within slots
128
to secure fluid control valve
24
to the mounting plate. Preferably, mounting bracket
106
is integrally molded with housing
100
.
Terminal housing
110
is configured to retain an electrical terminal (not shown) for electrically coupling fluid control valve
24
and diagnostic unit
38
(FIG.
1
). Preferably, terminal housing
110
is integrally molded with housing
100
.
Outlet port
26
includes a generally flat, circular end cap
130
and a nozzle portion
132
that extends from end cap
130
along longitudinal axis
104
. A free end
134
of nozzle portion
132
is configured to receive tubing from system
10
(e.g., tubing to inlet manifold
16
as shown in FIG.
1
).
Referring to
FIG. 3
, a cross-sectional view of fluid control valve
24
is shown. Received in housing
100
is a tubular guide
200
around which a coil winding assembly
202
is disposed. The tubular guide
200
slidably supports a valve plunger
204
that is formed of a ferrous material (e.g., steel). Valve plunger
204
and coil winding assembly
202
form an actuator
205
for opening and closing fluid control valve
24
. Also extending within tubular guide
200
is a stop member
206
, which is prevented from axial movement by frictional engagement with housing
100
or by mechanical engagement with an end cap
208
disposed in housing
100
. Tubular guide
200
is retained at one end by a spacer
210
, which abuts housing
100
, and the other end of tubular guide
200
is retained by an annular wall
212
. Valve plunger
204
extends through an aperture in annular wall
212
.
Disposed on one end of valve plunger
204
is a sealing device
214
. Disposed on the opposite end of valve plunger
204
is a spring
216
, which extends between valve plunger
204
and stop member
206
. Spring
216
biases valve plunger
204
towards outlet port
26
. In the embodiment shown, sealing device
214
is a resilient stopper including a lip
218
extending axially from its periphery. In the closed position of fluid control valve
24
, as shown in
FIG. 3
, spring
216
forces sealing device
214
, via valve plunger
204
, into contact with a valve seat
220
formed on outlet port
26
, thus preventing the flow of volatile fuel components through valve
24
. While sealing device
214
is shown here as a resilient stopper including lip
218
, it will be recognized that sealing device
214
may include a resilient stopper having a flat sealing surface (e.g., without lip
218
). Alternatively, sealing device
214
may include a surface formed on valve plunger
204
, or any device that interfaces with valve seat
220
to form a fluid-tight seal.
Outlet port
26
includes a flange
222
extending axially from the periphery of end cap
130
, and nozzle portion
132
, which extends through end cap
130
. Preferably, flange
222
, end cap
130
and nozzle portion
132
are integrally molded. End cap
130
is received within the circular opening formed by flange
109
of housing
100
to form a generally flat, coplanar surface with flange
109
. Valve seat
220
is formed on a generally flat end surface of nozzle portion
132
. The inside surface of nozzle portion
132
is shaped to form a nozzle
224
, as will be described in further detail hereinafter.
Coil winding assembly
202
includes a plurality of wire turns (windings)
226
disposed around a coil bobbin
228
. Coil winding assembly
202
is retained at one end by annular wall
212
and at an opposite end by the inside wall of housing
100
. The windings
226
are electrically coupled to a terminal
232
mounted within terminal housing
110
. The flow of current through windings
226
induces a magnetic force on valve plunger
204
, causing valve plunger
204
to move towards stop member
206
, against the force of spring
216
, thereby separating sealing device
214
from valve seat
220
and placing fluid control valve
24
in an open position.
In the open position, volatile fuel components can flow past sealing device
214
and valve seat
220
. The fluid path through fluid control valve is indicated by arrows
234
, and extends from inlet port
28
through a notch
236
disposed in flange
222
into a chamber formed by flange
222
, end cap
130
, and annular wall
212
. From this chamber, fluid passes between the sealing device
214
and valve seat
220
(when valve
24
is open) into the nozzle portion
132
, where the fluid passes through the nozzle
224
and out of fluid control valve
24
.
During use, the windings
226
are supplied with a pulse-width modulated direct current having a variably duty cycle. This causes the fluid control valve
24
to open and close at the frequency of the pulse-width modulated direct current, and the relative time periods that the valve is open and closed depends on the duty cycle. This is known as “pulse width modulated control”. As the duty cycle increases, the amount or volume of flow per unit time will increase and vice versa.
Referring to FIG.
4
and
FIG. 5
,
FIG. 4
is a longitudinal section of outlet port
26
, as indicated at
4
—
4
in
FIG. 5
, and
FIG. 5
is a transverse section of outlet port
26
, as indicated at
5
—
5
in FIG.
4
. As shown in FIG.
4
and
FIG. 5
, nozzle
224
includes, in the direction of fluid flow, a cylindrical entrance section
300
, a convergent section
302
, a throat
304
, a divergent section
306
, and a cylindrical exit section
308
. Cylindrical entrance section
300
has a diameter d
1
, which extends perpendicular to longitudinal axis
104
, and a length L
1
, which is measured along longitudinal axis
104
. Cylindrical exit section
308
has a diameter d
3
, which extends perpendicular to longitudinal axis
104
, and a length L
4
, which is measured along longitudinal axis
104
. In the present embodiment, diameter d
1
is equal to diameter d
3
, and length L
1
is smaller than or equal to length L
4
. It will be recognized, however, that the diameters d
1
and d
3
and the lengths L
1
and L
2
may be varied as needed for a specific application. Preferably, L
1
is selected to prevent the turbulence created by the flow bending 90 degrees at the valve seat entrance from extending into the convergent section
302
. Preferably, L
1
is selected to have laminar flow in the convergent portion of the semi-circular profile restriction.
Within convergent section
302
, the inside diameter of the nozzle
224
decreases from the diameter d
1
at the cylindrical entrance section
300
to a diameter d
2
at the throat
304
, over a length L
2
, as measured along longitudinal axis
104
. As shown in
FIG. 4
, the profile of the convergent section
302
, from diameter d
1
to diameter d
2
, is formed by a radius r
1
. Within divergent section
306
, the inside diameter of the nozzle
224
increases from the diameter d
2
at the throat
304
to the diameter d
3
at the cylindrical exit section
308
, over a length L
3
, as measured along longitudinal axis
104
. The profile of the divergent section
306
, from diameter d
2
to diameter d
3
, is formed by the radius, r
1
. Thus, the convergent and divergent sections
302
and
304
, are formed by a semi-circular profile having a radius r
1
. The throat
304
is the cross sectional flow area at the apex of this semi-circular profile. Throat
304
has a diameter d
2
, which is less than d
1
and d
3
.
The transition between cylindrical entrance section
300
and convergent section
302
, as indicated at
310
, and the transition between divergent section
306
and cylindrical exit section
308
, as indicated at
312
, may be blended to prevent fluid turbulence in these regions. Similarly, edges at inlet and outlet cross sections
314
and
316
of nozzle
224
may be radiused to prevent fluid turbulence in these regions.
The throat diameter d
2
is selected based on the maximum required flow through the fluid control valve
24
. For example, referring to FIG.
1
and
FIG. 4
, throat diameter d
2
may be selected to set the maximum flow of volatile fuel components through valve
24
required by the application at the relatively high differential pressures existent during idle operation of internal combustion engine
18
.
After the diameter d
2
is selected, the diameter d
1
is then selected to insure that the nozzle will have enough flow to allow for choked flow at the lower differential pressures existent during wide throttle operation of internal combustion engine
18
. Preferably, diameter d
1
can be greater than or equal to about 1.2 times diameter d
2
. More preferably, d
1
can be greater than or equal to about 1.4 times diameter d
2
. The maximum dimension of d
1
may be set to insure that the smallest force available to open valve
24
(e.g., the magnetic force induced by windings
226
on valve plunger
204
) is greater than the maximum vacuum force on the sealing device
214
(FIG.
3
).
The radius r
1
is then selected to insure that the convergent, divergent semi-circular profile will create a choked flow at low vacuum levels. The radius r
1
may also be selected to accommodate d
1
, d
2
, and L
1
in the space available for nozzle
224
. That is, the radius r
1
may be selected to insure that the semi-circular profile creates a convergent section
302
wherein the diameter decreases from d
1
to d
2
, and to insure that the lengths L
1
, L
2
, and L
3
fit within the overall length available for nozzle
224
. For the application described herein, the radius r
1
can be less than or equal to about 100 millimeters, with less than or equal to about 64 millimeters preferred. Also for the application described herein, the radius r
1
can be greater than or equal to about 5 millimeters, with greater than about 9.6 millimeters preferred.
Rather than employing a Laval-type or Venturi-type nozzle, valve
24
employs a relatively simple nozzle design. Nozzle
224
employs a semi-circular profile to form the convergent and divergent sections of the nozzle. Use of the semi-circular profile allows the nozzle to be designed without regard for the angles of the convergent and divergent sections, which must be considered in the design of a Laval-type or a Venturi-type nozzle. In addition, because the angles of the convergent and divergent sections are not important in manufacturing tolerance considerations, manufacturing of a valve
24
including the nozzle
224
is simplified from that possible with valves including nozzles of the Laval-type or Venturi-type.
While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. For example, while nozzle
224
is described herein as being used in a fluid control valve
24
employing an electromagnetic actuator
205
, it will be appreciated that nozzle
224
may be used in a fluid control valve
24
employing a pneumatic actuator such as that described in U.S. Pat. No. 5,284,121. In another example, while inlet port is described herein as extending parallel to longitudinal axis
104
, it will be appreciated that inlet port may extend at an angle to longitudingal axis
104
, such as described in U.S. Pat. No. 4,830,333. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
- 1. A fluid control valve comprising:a valve seat; a nozzle proximate said valve seat, said nozzle including a convergent section and a divergent section being formed by an arcuate profile being defined by a radius, wherein said radius is greater than or equal to about 5 millimeters.
- 2. The fluid control valve of claim 1, wherein said nozzle further includes:a cylindrical entrance section in fluid communication with said convergent section.
- 3. The fluid control valve of claim 1, wherein said nozzle further includes:a cylindrical exit section in fluid communication with said divergent section.
- 4. The fluid control valve of claim 1, wherein said nozzle further includes:a cylindrical entrance section in fluid communication with said convergent section; a cylindrical exit section in fluid communication with said divergent section; and wherein said cylindrical entrance section and said cylindrical exit section have the same diameter.
- 5. The fluid control valve of claim 2, wherein said cylindrical entrance section includes an axial length selected to prevent turbulent fluid flow from entering said convergent section.
- 6. The fluid control valve of claim 1, wherein said radius of said arcuate profile is greater than about 9.6 millimeters.
- 7. A fluid control valve comprising:a valve seat; a nozzle proximate said valve seat, said nozzle including a convergent section and a divergent section being formed by an arcuate profile being defined by a radius, wherein an apex of said arcuate profile forms a throat of said nozzle, said cylindrical entrance section includes a diameter greater than or equal to about 1.2 times a diameter of said throat.
- 8. The fluid control valve of claim 7, wherein said diameter of said cylindrical entrance section is greater than or equal to about 1.4 times said diameter of said throat.
- 9. A fluid control valve comprising:a valve seat; a nozzle proximate said valve seat, said nozzle including a convergent section and a divergent section being formed by an arcuate profile being defined by a radius, wherein said arcuate profile has a radius less than or equal to about 100 millimeters.
- 10. The fluid control valve of claim 9, wherein said radius of said arcuate profile is less than or equal to about 64 millimeters.
- 11. A system for controlled feeding of volatile fuel components from a free space of a fuel tank to an engine manifold, the system comprising:a storage chamber in fluid communication with the free space of the fuel tank; a valve in fluid communication between said storage chamber and the engine manifold, said valve including: an inlet port, an outlet port in fluid communication with said inlet port, said outlet port including: a valve seat, and a nozzle proximate said valve seat, said nozzle including a convergent section and a divergent section formed by an arcuate profile, a valve plunger including a sealing device disposed on an end thereof, and an actuator in operable communication with said valve plunger for opening and closing a fluid path between said valve seat and said sealing device, wherein said arcuate profile has a radius greater than or equal to about 5 millimeters.
- 12. The fluid control valve of claim 11, wherein said nozzle further includes:a cylindrical entrance section in fluid communication with said convergent section.
- 13. The fluid control valve of claim 12, wherein said cylindrical entrance section includes an axial length selected to prevent turbulent fluid flow from entering said convergent section.
- 14. A system for controlled feeding of volatile fuel components from a free space of a fuel tank to an engine manifold, the system comprising:a storage chamber in fluid communication with the free space of the fuel tank; a valve in fluid communication between said storage chamber and the engine manifold, said valve including: an inlet port, an outlet port in fluid communication with said inlet port, said outlet port including: a valve seat, and a nozzle proximate said valve seat, said nozzle including a convergent section and a divergent section formed by an arcuate profile and said nozzle having a cylindrical entrance section in fluid communication with said convergent section, a valve plunger including a sealing device disposed on an end thereof, and an actuator in operable communication with said valve plunger for opening and closing a fluid path between said valve seat and said sealing device, wherein an apex of said arcuate profile forms a throat of said nozzle, said cylindrical entrance section includes a diameter greater than or equal to about 1.2 times a diameter of said throat.
- 15. The fluid control valve of claim 14, wherein said diameter of said cylindrical entrance section is greater than or equal to about 1.4 times said diameter of said throat.
- 16. The fluid control valve of claim 12, wherein an apex of said arcuate profile forms a throat of said nozzle having a first diameter, said cylindrical entrance section includes a second diameter, and wherein said first and second diameters are selected to insure that fluid passing through said nozzle during operation of said internal combustion engine will be choked.
- 17. The fluid control valve of claim 11, wherein said actuator is an electromagnetic actuator.
- 18. The fluid control valve of claim 11, wherein said nozzle further includes:a cylindrical exit section in fluid communication with said divergent section.
- 19. A system for controlled feeding of volatile fuel components from a free space of a fuel tank to an engine manifold, the system comprising:a storage chamber in fluid communication with the free space of the fuel tank; a valve in fluid communication between said storage chamber and the engine manifold, said valve including: an inlet port, an outlet port in fluid communication with said inlet port, said outlet port including: a valve seat, and a nozzle proximate said valve seat, said nozzle including a convergent section and a divergent section formed by an arcuate profile, a valve plunger including a sealing device disposed on an end thereof, and an actuator in operable communication with said valve plunger for opening and closing a fluid path between said valve seat and said sealing device, wherein said arcuate profile has a radius less than or equal to about 100 millimeters.
- 20. The fluid control valve of claim 19, wherein said radius of said arcuate profile is less than or equal to about 64 millimeters.
- 21. The fluid control valve of claim 11, wherein said radius of said arcuate profile is greater than about 9.6 millimeters.
- 22. The fluid control valve of claim 11, wherein said cylindrical entrance section includes a diameter selected to insure that a force provided by said actuator for opening said fluid path between said valve seat and said sealing device is greater than a vacuum force on said sealing device.
- 23. A system for controlled feeding of volatile fuel components from a free space of a fuel tank to an engine manifold, the system comprising:a storage chamber in fluid communication with the free space of the fuel tank; a valve in fluid communication between said storage chamber and the engine manifold, said valve including: an inlet port, an outlet port in fluid communication with said inlet port, said outlet port including: a valve seat, and a nozzle proximate said valve seat, said nozzle including a convergent section and a divergent section formed by an arcuate profile, a valve plunger including a sealing device disposed on an end thereof, and an actuator in operable communication with said valve plunger for opening and closing a fluid path between said valve seat and said sealing device, wherein said nozzle further includes: a cylindrical entrance section in fluid communication with said convergent section; a cylindrical exit section in fluid communication with said divergent section; and wherein said cylindrical entrance section and said cylindrical exit section have the same diameter.
- 24. An outlet port configured for use with a fluid control valve, the outlet port comprising:a valve seat; a nozzle proximate said valve seat, said nozzle including a convergent section and a divergent section each being formed by an arc profile being defined by a radius; a cylindrical entrance section being in fluid communication with said convergent section; a cylindrical exit section being in fluid communication with said divergent section, wherein an apex of said arc profile forms a throat of said nozzle, said cylindrical entrance section having a diameter equal to a diameter of said divergent section.
- 25. The outlet port as in claim 24, wherein the diameter of said cylindrical entrance section is greater than or equal to about 1.2 times a diameter of said throat.
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