GB2174760A - Gas entrainment devices - Google Patents
Gas entrainment devices Download PDFInfo
- Publication number
- GB2174760A GB2174760A GB08609659A GB8609659A GB2174760A GB 2174760 A GB2174760 A GB 2174760A GB 08609659 A GB08609659 A GB 08609659A GB 8609659 A GB8609659 A GB 8609659A GB 2174760 A GB2174760 A GB 2174760A
- Authority
- GB
- United Kingdom
- Prior art keywords
- pressure
- section
- gas
- recovery section
- recovery
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/10—Preparation of respiratory gases or vapours
- A61M16/12—Preparation of respiratory gases or vapours by mixing different gases
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/10—Mixing gases with gases
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/30—Injector mixers
- B01F25/31—Injector mixers in conduits or tubes through which the main component flows
- B01F25/312—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof
- B01F25/3121—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof with additional mixing means other than injector mixers, e.g. screens, baffles or rotating elements
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/30—Injector mixers
- B01F25/31—Injector mixers in conduits or tubes through which the main component flows
- B01F25/312—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof
- B01F25/3124—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof characterised by the place of introduction of the main flow
- B01F25/31242—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof characterised by the place of introduction of the main flow the main flow being injected in the central area of the venturi, creating an aspiration in the circumferential part of the conduit
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/30—Injector mixers
- B01F25/31—Injector mixers in conduits or tubes through which the main component flows
- B01F25/312—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof
- B01F25/3125—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof characteristics of the Venturi parts
- B01F25/31253—Discharge
- B01F25/312532—Profiled, grooved, ribbed discharge conduit, or being provided with baffles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/30—Injector mixers
- B01F25/31—Injector mixers in conduits or tubes through which the main component flows
- B01F25/312—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof
- B01F25/3125—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof characteristics of the Venturi parts
- B01F25/31253—Discharge
- B01F25/312533—Constructional characteristics of the diverging discharge conduit or barrel, e.g. with zones of changing conicity
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/40—Static mixers
- B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions
- B01F25/43—Mixing tubes, e.g. wherein the material is moved in a radial or partly reversed direction
- B01F25/433—Mixing tubes wherein the shape of the tube influences the mixing, e.g. mixing tubes with varying cross-section or provided with inwardly extending profiles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/40—Static mixers
- B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions
- B01F25/43—Mixing tubes, e.g. wherein the material is moved in a radial or partly reversed direction
- B01F25/433—Mixing tubes wherein the shape of the tube influences the mixing, e.g. mixing tubes with varying cross-section or provided with inwardly extending profiles
- B01F25/4331—Mixers with bended, curved, coiled, wounded mixing tubes or comprising elements for bending the flow
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/40—Static mixers
- B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions
- B01F25/43—Mixing tubes, e.g. wherein the material is moved in a radial or partly reversed direction
- B01F25/433—Mixing tubes wherein the shape of the tube influences the mixing, e.g. mixing tubes with varying cross-section or provided with inwardly extending profiles
- B01F25/4336—Mixers with a diverging cross-section
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04F—PUMPING OF FLUID BY DIRECT CONTACT OF ANOTHER FLUID OR BY USING INERTIA OF FLUID TO BE PUMPED; SIPHONS
- F04F5/00—Jet pumps, i.e. devices in which flow is induced by pressure drop caused by velocity of another fluid flow
- F04F5/44—Component parts, details, or accessories not provided for in, or of interest apart from, groups F04F5/02 - F04F5/42
Abstract
A gas entrainment device of compact form having high pressure recovery performance is disclosed. The device comprises a pressure-recovery section having at least one, and preferably a multiplicity of, sharp-edged grooves or steps in its wall, the grooves or steps being transverse to the gas flow direction. The device may be of folded configuration, with the flow path turning sharply at the downstream end of the pressure-recovery section. The device is suitable for mixing air and oxygen to produce a breathable gas mixture at an oronasal mask or intratracheal tube in a medical breathing system such as a ventilator. <IMAGE>
Description
SPECIFICATION
Entrainment devices
This invention concerns gas entrainment devices such as are widely used in medical breathing systems such as ventilators in order to conserve the use of oxygen and to achieve breathable gas mixtures of suitable composition by dilution of oxygen flowing from a source of this primary gas.
Hitherto the space occupied by such entrainment devices, and the shape of that space, has been unimportant because such devices have only been fitted to relatively large-sized equipment assemblies.
However, if it is desired to fit such a device to the so-called patient valve of a ventilator and that is associated with an oronasal mask or intratracheal tube, the size, mass and configuration of the device assumes a much greater importance, as will readily be understood. Moreover in such an application the requirement to maintain selected ventilation performance irrespective of changes in the patient's compliance, makes it important that the entrainment device achieves the maximum pressure recovery for a given entrainment ratio.
Pressure recovery in an entrainment mixer is achieved by exchanging velocity energy for pressure energy in the mixed gas downstream of the point at which the gases are mixed. This energy exchange is accomplished by expanding the flow cross section in a pressure-recovery section, either abruptly, to create standing vortices, or smoothly as in a diffuser.
It is known that, in the face of a rising pressure gradient, detachment of a gas stream from the walls of an expanding passage can easily be provoked. In practice it is found that if the flow path immediately downstream of an entrainment device is sharply deviated in direction, the attainable pressure recovery is severely impaired. It is thought likely that the momentum changes associated with a change in flow direction near the end of a section in which the pressure is rising causes local boundary layer detachment and subsequent breakaway of the main stream.
Thus the ideal configuration for an entrainment device having a pressure-recovery section designed for maximum pressure recovery is one in which the flow path is essentially straight and symmetrical from the point of injection of the primary gas to a point some distance downstream of the pressure-recovery section. Unfortunately this ideal configuration is very space-consuming and inconvenient in the context of a patient valve for ventilator equipment and it would be convenient for the attainment of compactness in such an application if the flow path could be sharply folded.
An objective of the present invention is to provide a gas entrainment device that offers this possibility without significant loss of pressure recovery performance.
In accordance with the invention, a gas entrainment device having a pressure-recovery section is characterised by at least one sharp-edged step or groove in the wall of the pressure-recovery section and extending transversely of the gas flow direction.
The or each step or groove is preferably continuous and perpendicular to the axis of the pressurerecovery section. Thus in embodiments in which the pressure-recovery section is circular in cross section, the or each step or groove is conveniently a continuous annular step or groove perpendicular to the axis of the pressure-recovery section.
There may be several said steps or grooves arranged at various locations distributed in the wall of the pressure-recovery section in the direction of the gas flow path therethrough. Preferably at least one step or groove is positioned immediately adjacent to the upstream end of the pressure-recovery section, but one or more other steps or grooves may also be located nearer the downstream end of the pressure-recovery section, and there may for instance be a continuous series of steps or grooves throughout the length of the pressure-recovery section, the latter thus having a generally expanding flow cross section defined by a series of steps or contiguous grooves.
It is thought that the steps or grooves create standing vortices and thereby controlled turbulence in the edge of the gas stream through the pressure-recovery section, energizing and re-energizing the boundary layer so as to limit the growth and detachment of this and to promote stable attachment of the main stream to the walls of the pressure-recovery section. However we do not intend to be bound by this theory of the manner in which the steps or grooves accomplish the observed significant increase in pressure recovery in entrainment devices having pressure-recovery sections furnished with such steps or grooves and followed by flow path sections sharply deviated in direction, as compared with equivalent arrangements not having such stepped or grooved pressure-recovery sections.
The invention will be further explained with reference to the accompanying drawings in which:
Figure 1 is a schematic illustration of an idealised gas entrainment device having a pressure-recovering diffuser followed by a co-axial rectilinear flow path section of constant cross section;
Figures 2(aJ and (b) illustrate the effects of a sharp deviation of flow path downstream of the diffuser of a device such as shown in Figure 1; and
Figure 3 is a diagrammatic illustration of the pressure-recovery section and following flow path section of a gas entrainment device in accordance with the invention.
Referring to the drawings, Figure 1 illustrates in diagrammatic axial section a gas entrainment device comprising a nozzle section a through which a primary or entraining gas is accelerated to flow through an entrainment chamber having lateral entrainment gas ports b followed by a pressure-recovery section in the form of a diffuser c of smoothly expanding cross section that joins a coaxial flow path d of constant cross section. The flow lines shown in Figure 1 represent the flow paths of gas in the device and it will be seen that entraining gas entering the nozzle section a is ac celerated and enters the entrainment chamber as a jet that by momentum exchange with entrainment gas entering through ports b accelerates this entrainment gas to form a mixed stream that enters the diffuser c at its entry e.Flowing through the diffuser c, the mixed gas stream expands in cross section and is thereby slowed, exchanging kinetic energy for pressure energy so that the mixed gas stream flows in the parallel flow path section d at a higher pressure but a lower velocity relative to the conditions at the diffuser entry e.
Figures 2(a) and 2(b) illustrate the effect of substituting the co-axial flow path d of Figure 1 by a flow path section fthe axis of which is at right angles to that of the diffuser c. In Figure 2(a) the flow lines show how, at the change in direction, adverse pressure and momentum effects provoke detachment of the stream from the flow path wall on the inside of the bend. When once detachment has occurred as a result of these adverse conditions and perhaps provoked by some flow pertubation, the flow pattern settles to that illustrated by the flow lines in Figure 2(b). It will be seen that under these conditions there is substantially less expansion of the mixed gas stream and, consequently, pressure recovery in the diffuser c than if the flow had remained attached to the diffuser walls throughout the length thereof and at all points around its circumference.
Figure 3 illustrates the pressure-recovery section, constituted as in Figures 1 and 2 by a generally smooth expanding diffuser, of an entrainment device embodying the invention. In this Figure the diffuser is represented at c and leads to a parallel flow path section fat right angles to the axis of the diffuser, as in Figure 2. However, in accordance with the invention the diffuser c is provided with three annular, sharp-edged, steps or grooves g in its wall adjacent to the diffuser entry e, and with a further sharp-edged annular step or groove h near the downstream end of the diffuser c. It can be seen that the flow lines follow the walls of the diffuser c and flow path 8 without the detachment as represented in Figure 2.
It has been observed that a diffuser having steps or grooves such as illustrated in Figure 3 provides substantially enhanced pressure recovery, as compared with the ungrooved equivalent diffuser, for substantial deviations of the flow path immediately downstream to the diffuser and that a relatively high percentage of the pressure recovery available with the ideal rectilinear arrangement (Figure 1) can be achieved by the use of the stepped or grooved diffuser.
As explained, the drawings are diagrammatic and are intended only to illustrate the principles of the invention. In practical embodiments the entrainment device will be sized and configured to the appropriate to the gas flow and entrainment ratio requirements of the application, the pressure ratio and the primary gas pressure of the nozzle, the design of the device to suit desired values of these parameters being generally in accordance with conventional practices in the art.
In a typical embodiment, intended to mix oxygen with air to provide an oxygen-enriched breathing gas mixture for a ventilator/resuscitator device, the entrainment device receiving pulses of oxygen as primary gas at a pressure of 2.5 bar and intended to dilute this by entrainment of air to produce a gas having a 45% oxygen content, the nozzle of the entrainment device has a diameter of about 0.65mm, delivering to an entrainment chamber or receiver having a diameter of about 2.68mm leading to a pressure recovery section having, in this instance, a constant clear bore diameter of about 4.0mm and comprising four ramped grooves having a depth of about 4.5mm, at about 2.2mm axial spacing.
Claims (7)
1. A gas entrainment device having a pressurerecovery section characterised by at least one sharp-edged step or groove in the wall of the pressure-recovery section and extending transversely of the gas flow direction.
2. A device according to claim 1, in which the or each said step or groove is continuous and perpendicular to the axis of the pressure-recovery section.
3. A device according to claim 2, in which said pressure-recovery section is circular in cross section and the or each said step or groove is a continuous annular step or groove perpendicular to the axis of the pressure-recovery section.
4. A device according to any one of claims 1 to 3, in which at least one said step or groove is disposed immediately adjacent to the upstream end of the pressure-recovery section.
5. A device according to any one of claims 1 to 4, in which said pressure-recovery section has a generally expanding flow cross section defined by a series of steps or contiguous grooves.
6. A gas entrainment device having a pressurerecovery section substantially as described with reference to Figure 3 of the accompanying drawings.
7. Every novel feature and every novel combination of features disclosed herein.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8609659A GB2174760B (en) | 1985-05-02 | 1986-04-21 | Entrainment devices |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB858511171A GB8511171D0 (en) | 1985-05-02 | 1985-05-02 | Entrainment devices |
| GB8609659A GB2174760B (en) | 1985-05-02 | 1986-04-21 | Entrainment devices |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8609659D0 GB8609659D0 (en) | 1986-05-29 |
| GB2174760A true GB2174760A (en) | 1986-11-12 |
| GB2174760B GB2174760B (en) | 1989-06-28 |
Family
ID=26289204
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8609659A Expired GB2174760B (en) | 1985-05-02 | 1986-04-21 | Entrainment devices |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2174760B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0691137A2 (en) | 1994-07-05 | 1996-01-10 | pneuPAC Limited | Gas mixing devices for resuscitation/lung ventilation apparatus |
| WO1996041685A1 (en) * | 1995-06-09 | 1996-12-27 | Alan Patrick Casey | Nozzle for delivering liquid/gas mixture |
| WO2014162107A1 (en) | 2013-04-04 | 2014-10-09 | Smiths Medical International Limited | Resuscitator arrangements and flow monitoring |
| WO2016097669A1 (en) * | 2014-12-19 | 2016-06-23 | Smiths Medical International Limited | Entrainment devices and respiratory therapy devices |
| WO2020223507A1 (en) * | 2019-05-02 | 2020-11-05 | Respire Llc | Delivery system for therapeutically conditioned air |
-
1986
- 1986-04-21 GB GB8609659A patent/GB2174760B/en not_active Expired
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0691137A2 (en) | 1994-07-05 | 1996-01-10 | pneuPAC Limited | Gas mixing devices for resuscitation/lung ventilation apparatus |
| EP0691137A3 (en) * | 1994-07-05 | 1996-03-06 | Pneupac Ltd | Gas mixing devices for resuscitation/lung ventilation apparatus |
| US5605148A (en) * | 1994-07-05 | 1997-02-25 | Pneupac Limited | Gas mixing devices for resuscitation/lung ventilation apparatus |
| WO1996041685A1 (en) * | 1995-06-09 | 1996-12-27 | Alan Patrick Casey | Nozzle for delivering liquid/gas mixture |
| US6010077A (en) * | 1995-06-09 | 2000-01-04 | Casey; Alan Patrick | Nozzle for delivering liquid/gas mixture |
| WO2014162107A1 (en) | 2013-04-04 | 2014-10-09 | Smiths Medical International Limited | Resuscitator arrangements and flow monitoring |
| WO2016097669A1 (en) * | 2014-12-19 | 2016-06-23 | Smiths Medical International Limited | Entrainment devices and respiratory therapy devices |
| WO2020223507A1 (en) * | 2019-05-02 | 2020-11-05 | Respire Llc | Delivery system for therapeutically conditioned air |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8609659D0 (en) | 1986-05-29 |
| GB2174760B (en) | 1989-06-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PE20 | Patent expired after termination of 20 years |
Effective date: 20060420 |