Patent Publication Number: US-2022213904-A1

Title: Jet pump

Description:
The disclosure relates to a jet pump with a jet nozzle for accelerating a propellant. 
     Jet pumps use a fluid jet comprising a propellant in order to draw in and accelerate a suction medium. The suction action is brought about by the propellant flowing past the suction medium, wherein the suction medium is also carried by the propellant when the flow speed of the propellant is sufficiently high. In order to accelerate a propellant, it is guided under pressure through a nozzle, which accelerates the propellant. If the suction pressure and the propellant pressure have a subcritical pressure relationship, a convergent nozzle is used to accelerate the propellant in the jet pump. In the event of supercritical pressure relationships, a convergent/divergent nozzle, a so-called Laval nozzle, is used in order to further accelerate the propellant which has been accelerated to the speed of sound in the convergent portion of the Laval nozzle. A Laval nozzle, with propellants which flow at subsonic speed, leads to a deceleration of the flow speed since the divergent portion of the Laval Nozzle acts as a diffusor for the propellant. 
     SUMMARY 
     An object of the disclosure, according to an embodiment, is to provide an improved jet pump which enables an operation at sub-critical and supercritical pressure relationships. 
     The disclosure relates to a jet pump comprising a jet nozzle for accelerating a propellant, wherein the jet nozzle has a convergent inlet portion and an outlet portion which is connected to the convergent inlet portion, wherein the outlet portion comprises an inner space which is surrounded by an inner wall and which diverges at an opening angle, wherein there is provision according to an embodiment of the disclosure for the opening angle to be constructed in such a manner that a propellant which flows through the outlet portion at subsonic speed is released from the inner wall and a propellant which flows through the outlet portion at supersonic speed is guided by the inner wall. 
     The disclosure, according to an embodiment, provides for a jet pump having a jet nozzle whose convergent inlet portion accelerates a propellant which flows through the convergent inlet portion, wherein the propellant flows at subsonic speed before flowing through the inlet portion. If the propellant after flowing through the inlet portion and the acceleration then continues to have subsonic speed, it also flows through the outlet portion at subsonic speed. The outlet portion of the jet nozzle has in this instance a divergent inner wall, that is to say, the cross section of the outlet portion increases from the convergent inlet portion. The jet nozzle may in this instance be a specially constructed Laval nozzle. The opening angle of the divergent inner wall is in this instance so large that a propellant flowing at subsonic speed through the outlet portion is released from the inner wall of the outlet portion. The outlet portion of the jet nozzle consequently does not act for the propellant which is flowing at subsonic speed as a diffusor so that no deceleration of the speed of the propellant is brought about when flowing through the outlet portion. Instead, only the convergent inlet portion of the jet nozzle acts on the propellant flowing at subsonic speed. The jet nozzle acts on the propellant which flows at subsonic speed as a convergent nozzle. If the propellant is accelerated by the convergent inlet portion to the speed of sound, it is further accelerated by the divergent inner space of the outlet portion. The propellant is in this instance guided by the divergent inner wall of the outlet portion since it is not released from the inner wall in this instance. In this instance, the outlet portion acts as a nozzle for the propellant which is flowing at supersonic speed and further accelerates the propellant. Consequently, the jet nozzle acts as a Laval nozzle for propellant which is flowing at supersonic speed. 
     The disclosure, according to an embodiment, consequently provides for a jet pump which, both under subcritical pressure conditions, that is to say, when the propellant at subsonic speed brings about the suction action, and under supercritical pressure conditions, that is to say, when the propellant at supersonic speed brings about the suction action, is operated with a single jet nozzle. The action of the outlet portion on the flowing propellant is in this instance automatically adjusted by the opening angle of the inner wall. As a result of the disclosure, according to an embodiment, therefore, an automatic, cost-effective and simple switching of the jet pump to different pressure relationships is provided. 
     The inner wall of the outlet portion may be constructed in such a manner that the propellant flowing through the outlet portion is released from the inner wall during a transition from supersonic speed to subsonic speed. In other words, the inner wall of the outlet portion may be constructed in such a manner that propellant flowing through the outlet portion is released from the inner wall during a transition from a supercritical pressure relationship to a subcritical pressure relationship. 
     Consequently, the pressure during operation of the jet pump can be changed from the supercritical pressure relationship to the subcritical pressure relationship, wherein pressure shocks are prevented during the switching operation. This brings about an additional expansion of the range of application of the jet pump. 
     Furthermore, the inner wall of the outlet portion may be constructed in such a manner that the propellant flowing through the outlet portion during a transition from subsonic speed to supersonic speed is positioned against the inner wall and is guided by the inner wall. In other words, the inner wall of the outlet portion may be constructed in such a manner that the propellant flowing through the outlet portion during a transition from the subcritical pressure relationship to the supercritical pressure relationship is positioned against the inner wall and is guided by the inner wall. 
     Consequently, a frictionless transition from the subcritical pressure relationship to the supercritical pressure relationship may be carried out. This further expands the range of application of the jet pump. 
     Furthermore, a pressure relationship of a propellant pressure of the propellant to a suction pressure at the outlet portion may be between 1.05 und 5, preferably between 1.1 und 2.5. 
     Consequently, the jet pump may be operated in a broad pressure range, wherein the pressure relationships in comparison with a desired suction pressure may be subcritical or supercritical. 
     Consequently, both at a low pressure relationship, in which the propellant flows at subsonic speed, and with a high pressure relationship, in which the propellant flows at supersonic speed, an adequate suction pressure for the operation of the jet pump is provided. 
     The jet pump consequently has a subcritical and a supercritical operating range in which it can be operated. Consequently, the jet pump can be operated in a wide range of applications. 
     Advantageously, per an embodiment, the opening angle is more than 7°. 
     With opening angles of more than 7°, the release of the propellant which is flowing through the outlet portion at subsonic speed from the inner wall is further promoted. Consequently, an adhesion of the propellant flowing through the outlet portion to the inner wall of the outlet portion at subsonic speeds is prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Other features, details and advantages of the disclosure will be appreciated from the wording of the claims and from the following description of embodiments with reference to the drawings, in which: 
         FIG. 1  is a schematic illustration of the jet pump, 
         FIGS. 2 a, b    are schematic illustrations of the jet nozzle, and 
         FIGS. 3 a, b    are schematic illustrations of examples of the outlet portion. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic sectioned illustration of a jet pump, wherein the jet pump is designated  10  in its entirety. The jet pump  10  has a propellant tank  12 , a jet nozzle  14 , a suction medium tank  18 , a mixing chamber  20  and a diffusor  22 . 
     The propellant is provided in the propellant tank  12 . The propellant may be a compressible propellant in this instance. The propellant may be acted on in the propellant tank  12  with a pressure or be stored under pressure in the propellant tank  12 . The pressure relationship may, for example, be between 1.05 and 5, preferably between 1.1 and 2.5. Under this propellant pressure, the propellant flows during operation of the jet pump  10  from the propellant tank  12  to the jet nozzle  14 . This is illustrated by the arrow  30 . 
     The propellant nozzle  14  has in this instance a convergent inlet portion  28  and an outlet portion  26  having a divergent inner space  40 . The outlet portion  26  and the convergent inlet portion  28  are connected to each other. The connection location of the convergent inlet portion  28  with the outlet portion  26  has the smallest cross section of the jet nozzle  14 . 
     The convergent inlet portion  28  has a cross section which tapers. The propellant flows initially into a region of the convergent inlet portion  28  with a large cross section. As a result of the tapering of the cross section of the convergent inlet portion  28 , the propellant flowing through the convergent inlet portion  28  is accelerated. 
     Depending on the propellant pressure, the propellant is accelerated by the convergent inlet portion  28  to a subsonic speed or the speed of sound when the propellant flows through the convergent inlet portion  28 . 
     The outlet portion  26  adjoins the tapered end of the convergent inlet portion  28 . In this instance, the outlet portion  26  comprises an inner wall  38  which laterally surrounds the inner space  40 . In this case, the inner wall  38  may in one embodiment surround the inner space  40  in the form of a conical covering face, as illustrated in  FIG. 3 a   . In another embodiment, the inner wall  38  may surround the inner space  40  in the form of a covering face having a bell-like shape, as illustrated in  FIG. 3   b.    
     The inner space  40  has in this instance an inlet opening which is connected to the outlet opening of the convergent inlet portion  28 . Furthermore, the inner space  40  has an outlet opening which is larger than the inlet opening of the inner space  40 . The inner wall  38  extends between the inlet opening and the outlet opening of the inner space  40 . The inner space  40  is in this instance constructed in a divergent manner and diverges at an opening angle  16 . The inner wall  38  defines the opening angle  16  directly in accordance with the narrowest cross section at the inlet opening of the inner space  40 . The opening angle  16  of the inner wall  38  may in this instance change with increasing spacing from the inlet opening. 
     The opening angle  16  is in this instance selected in such a manner that a propellant flowing through the outlet portion  26  at subsonic speed is released from the inner wall  38  and a propellant flowing through the outlet portion  26  at supersonic speed is guided by the inner wall  38 . That is to say, the inner wall  38  does not influence a propellant flowing through the outlet portion  26  at sub-sonic speed. Instead, the propellant which flows at subsonic speed is released from the inner wall  38  and flows as a jet from the outlet opening of the convergent inlet portion  28  through the outlet portion  26  and out of the jet nozzle  14 . 
     The opening angle  16  is further selected in such a manner that a propellant flowing through the outlet portion  26  at supersonic speed is guided by the inner wall  38 . An expansion, carried out perpendicularly to the flow direction, of the propellant flowing through the outlet portion  26  is in this instance limited by the inner wall  38 . An outer region of the flow of the propellant therefore flows along the inner wall  38 . 
     In this instance, the opening angle  16  may be at least 7°. An upper limit of the opening angle  16  may, for example, be between 8° and 45°. 
     As a result of the expansion which is carried out perpendicularly to the flow direction and which is limited by the inner wall  38 , the propellant is further accelerated and flows at an increased supersonic speed from the outlet portion  26 . 
     After leaving the outlet portion  26 , the propellant flows past an opening of the suction medium tank  18  and brings about a suction pressure. 
     The suction medium is also carried and accelerated by the propellant flowing past the suction medium tank  18 . The propellant and the suction medium thereby reach the mixing chamber  20 . Whilst the propellant and the suction medium flow through the mixing chamber  20 , the propellant and the suction medium are mixed. 
     The mixing chamber  20  is adjoined by a diffusor  22  in which the propellant and the suction medium which is mixed therewith are decelerated. The diffusor  22  comprises an outlet opening  24 . The propellant and the suction medium can flow out of the jet pump through the outlet opening  24 . 
       FIGS. 2 a  and 2 b    are a schematic cross section through the jet nozzle  14 , wherein the flow of the propellant through the jet nozzle  14  is indicated by means of flow lines  32 ,  34 . 
     In this instance, the propellant in  FIG. 2 a    is accelerated to the speed of sound by means of the convergent inlet portion  28 . In the convergent inlet portion  28 , this is indicated by the merging flow lines  32 . From the convergent inlet portion  28 , the propellant which has been accelerated to the speed of sound flows into the outlet portion  26 . In the outlet portion  26 , the flow lines  32  diverge from each other. The outer flow lines  32  extend in this instance along the inner wall  38 , whereby it is indicated that the propellant is guided along the inner wall  38  through the inner space  40 . The propellant is in this instance expanded and the speed is consequently further increased to supersonic speed. 
     In  FIG. 2 b   , the propellant is also accelerated by means of the convergent inlet portion  28  but the speed of the propellant remains below the speed of sound. The propellant therefore flows at subsonic speed out of the convergent inlet portion  28 . The flow lines  34  are compressed in the convergent inlet portion  28 . 
     Since the opening angle  16  of the divergent inner wall  38  is selected in such a manner that a propellant flowing at subsonic speed is released from the divergent inner wall  38 , the propellant is not expanded in the outlet portion  26 , but instead flows as a free jet through the outlet portion  26 . This is illustrated by the flow lines  34  in the outlet portion  26 , which extend substantially parallel with each other. The free jet has in the outlet portion  26  an almost constant width  36 . 
     The width  36  of the subsonic flow of the propellant in the outlet portion  26  is therefore smaller than a clear width of the inner space  40  which is laterally delimited by the inner wall  38 , wherein the clear width increases as a result of the divergent inner wall  38 . 
     Consequently, the inner wall  38  is prevented from acting as a diffusor for the propellant flowing at subsonic speed and the propellant is braked by the outlet portion  26 . 
     The pressure of the propellant in the convergent inlet portion  28  can be increased or decreased during operation. The inner wall  38  of the outlet portion  26  is in this instance constructed in such a manner that the propellant flowing through the outlet portion  26  during a transition from the supercritical pressure relationship to the subcritical pressure relationship is released from the inner wall  38 . Conversely, the propellant flowing through the outlet portion  26  during a transition from a subcritical pressure relationship to a supercritical pressure relationship will be positioned against the inner wall  38  and be guided by the inner wall  38 . 
     This means that the speed of the propellant in the outlet portion  26  can change between supersonic speed and subsonic speed without there being any disruption to the operation of the jet pump  10 . The jet pump  10  can consequently be operated both at a supercritical pressure relationship and at a subcritical pressure relationship. 
     In this instance, at a suction pressure of 0.98 bar and a propellant pressure of 1.1 bar, a subcritical pressure relationship can be adjusted at which the propellant flows through the outlet portion  26  at a subsonic speed, wherein the flowing propellant is released from the inner wall  38 . 
     At a suction pressure of 0.98 bar and a propellant pressure of 2.5 bar, a supercritical pressure relationship at which the propellant flows at supersonic speed through the outlet portion  26  can consequently be adjusted, wherein the flowing propellant is guided by the inner wall  38 . 
     The invention is not limited to one of the embodiments described above but can instead be modified in a variety of ways. 
     All of the features and advantages derived from the claims, the description and the drawings, including structural details, spatial arrangements and method steps, may be inventively significant both individually and in extremely varied combinations. 
     All the features and advantages, including structural details, spatial arrangements and method steps, which follow from the claims, the description and the drawing can be fundamental to the invention both on their own and in different combinations. It is to be understood that the foregoing is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims. 
     As used in this specification and claims, the terms “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation. 
     LIST OF REFERENCE NUMERALS 
     
         
           10  Jet pump 
           12  Propellant tank 
           14  Jet nozzle 
           16  Opening angle 
           18  Suction medium tank 
           20  Mixing chamber 
           22  Diffusor 
           24  Outlet opening 
           26  Outlet portion 
           28  Convergent inlet portion 
           30  Flow direction 
           32  Supersonic flow lines 
           34  Subsonic flow lines 
           36  Width of free jet 
           38  Inner wall 
           40  Inner space