Abstract:
Devices for measuring at least one parameter of a medium flowing in a line, having an inlet conduit an outlet conduit, having the disadvantage in the prior art that liquids flowing into the inlet conduit can reach a measurement element and alter the measurement characteristic curve behavior of the measurement element. A device of the invention has, between the inlet conduit and outlet conduit, a deflection conduit with a separation element, by which the liquids are separated out and therefore do not reach the measurement element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 USC 371 application of PCT/DE 01/01492 filed on Apr. 18, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is based on a device for determining at least one parameter of a flowing medium and on a method for separating a liquid from a medium flowing in a line. 
     2. Description of the Prior Art 
     A device with a measurement conduit is already known (German Patent Disclosure DE 197 35 891 A1) in which a measurement element is accommodated that is bathed there by the inflowing medium. The medium flows from an inlet conduit first into a deflection conduit, which has a larger flow cross section than the inlet conduit and has a right-angled corner, so that there is an abrupt flow transition in the form of a step to the inlet conduit. Next, deflected by the corner of the deflection conduit, the medium flows along the peripheral face of the deflection conduit into an outlet conduit adjoining it transversely and leaves the outlet conduit through an outlet opening and then mixes again with the medium flowing past the device. 
     An inlet conduit longitudinal axis and an outlet conduit longitudinal axis are inclined by a predetermined angle from the longitudinal axis of the line, so that the inlet conduit has a region that is shaded from a main flow direction. The measurement element is disposed in the shaded region of the measurement conduit, to prevent soiling and resultant defects in the measurement element. 
     Water entering the intake line, for instance if the roadway is wet with rain, can sometimes cause contamination of the measurement element. Natural components of dissolved salts contained in this splashing water then cause a drift in the characteristic curve of the measurement element, because of the formation of a salt crust on the diaphragm of the sensor part. Although the inclination of the measurement body does form a partitioned-off region, nevertheless liquid particles reach the measurement conduit. 
     From German Patent Disclosure DE 197 41 031 A1, a measuring device with an inlet conduit is known in which a speeding up of the flow in the inlet conduit can be maintained by the design of two walls of the inlet conduit, but it is known that this leads only to stabilizing the flow of the medium in the inlet conduit, in particular in the measurement conduit. 
     SUMMARY OF THE INVENTION 
     The device and method according to the invention have the advantage over the prior that a measurement element is protected against liquid in a simple way. 
     It is advantageous to embody a liquid separation element in a conduit at least partly in labyrinthine fashion, because in this way liquid can be separated out yet liquid from the outside cannot penetrate into the conduit. 
     It is advantageous to embody the liquid separation element in an inner wall of a deflection conduit of the device, because this improves the separation. 
     Internested annular-arclike elements, which are simple to produce from a technical standpoint, are an advantageous embodiment of the liquid separation element. 
     It is advantageous to increase the flow resistance of the liquid separation element compared to the flow resistance of a measurement conduit, because as a result the great majority of the gaseous component of the flowing medium remains in the measurement conduit. 
     It is also advantageous to provide a deflection conduit in the inlet conduit that deflects the flow from the inner wall, because the deflection of the flow is facilitated thereby. 
     For good separation of liquid, it is advantageous that there is a detachment edge in the deflection conduit, which prevents deposited water from moving in the form of a wall film into the measurement conduit. 
     To stabilize the measurement signal, it is advantageous that the flow cross section of the inlet conduit and/or the outlet conduit narrows in the flow direction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Exemplary embodiments of the invention are explained in further detail in the ensuing description, taken with the drawings, in which: 
     FIG. 1 is a fragmentary elevation view, partly in section, of a device according to the invention; 
     FIG. 2 is a detail of a section through FIG. 1; 
     FIG. 3 is a section taken along the line III—III of FIG. 2; 
     FIG. 4 is a section taken along the line IV—IV of FIG. 2; and 
     FIG. 5 is a further exemplary embodiment of the device of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 schematically shows how a device  1  of the invention is incorporated in a conduit or line  3  within which the medium, which is a gas-liquid mixture, flows. 
     The device  1  comprises a measurement housing  6 , represented by a lower rectangle drawn in dot-dashed lines, and a carrier housing  7 , represented by an upper rectangle drawn in dot-dashed lines, in which latter housing an electronic evaluation unit, for instance, is accommodated. The measurement housing  6  and carrier housing  7  can merge integrally with one another or can be individual parts that are joined together. The measurement housing  6  and the carrier housing  7  have a common longitudinal axis  10 , which can for instance also be a center axis. The carrier housing  7  for instance protrudes partway out of the line  3 . 
     The measurement housing  6  has a side face  8 , which is located in the plane of the drawing. 
     The device  1  is introduced, for instance in plug-in fashion, into a wall  15  of the line  3 . The plastic or metal wall  15  defines a flow cross section, in the center of which a center axis  16  extends in the direction of the flowing medium, parallel to the wall  15 . The direction of the flowing medium, hereinafter called the main flow direction, is indicated by corresponding arrows  20  and extends from left to right in the drawing. 
     FIG. 2 shows the plan view on the measurement housing  6  in a sectional plane parallel to the plane of the drawing in FIG. 1, with a conduit  22  that has an inlet conduit  24  into which the medium flows through an inlet opening  25 . There is an inlet conduit flow direction  29  in the inlet conduit  24 . Disposed at the end of the inlet conduit  24  is a deflector element  33 , which deflects the flow from an inner wall into a deflection conduit  40 , which causes a detachment downstream and improves a phase separation of the individual mixture components. In the deflection conduit  40 , the flowing medium is deflected and flows into an outlet conduit  44 , which at least in part also forms a measurement conduit  47 . An outlet conduit flow direction  50  prevails in the outlet conduit  44 . In the measurement conduit  47 , the medium flows past at least one measurement element  60 , which is disposed on a sensor carrier  56 . At the end of the outlet conduit  44 , the medium strikes an outflow element  51 , as a result of which the medium is deflected and thus flows back into the line  3 . By means of the outflow element  51 , the flow direction of the medium in the outlet conduit  44  is rotated at least partway around the longitudinal axis  10 . The medium emerging through at least one outlet opening  53  (FIG. 4) then flows approximately in the main flow direction  20 . This improves the measurement signal performance in the case of reverse flows. 
     The outlet opening  53  or the outlet conduit  44  can, however, also be designed as in DE 197 41 031 A1, which is hereby incorporated by reference. 
     Disposed in the deflection conduit  40  on its outer periphery is a separation element  70 , which is embodied, for instance on its inner wall  41  facing in the main flow direction  20 , in labyrinthine fashion. The separation element  70  has at least one separation inlet  64  and at least one separation outlet  68 , which connect the deflection conduit  40  with the line  3  and through which a liquid separated out at the wall passes out of the deflection conduit  40  into the line  3 . 
     To prevent too much gas from leaving the inlet conduit  24  through the separation element  70 , the flow resistance of the separation element  70  is increased over that of the inlet conduit  24  and outlet conduit  44 . 
     A sharp outflow edge  73  is disposed in the inlet conduit  24  or in the deflection conduit  40 , for instance on the deflector element  33 ; this edge prevents a liquid, such as water, deposited on a lower side wall  42  of the inlet conduit  24  from participating in the deflection in the measurement conduit  47  in the form of a wall film in the direction of the measurement element  60 . The wall film detaches at the outflow edge  73  from the side wall  42  of the inlet conduit  24  and is entrained by the flow. Because of the greater inertia of the liquid compared to the gas, the liquid strikes the inner surface of the outer wall  41  of the deflection conduit  40 , for instance, where it can form a wall film again. This wall film migrates through the separation inlet  64  into the separation element  70  and leaves it through the separation outlet  68  into a rear chamber  71 . The medium that is deflected in the deflection conduit  40  and forced against the inner wall  41  by centrifugal forces pushes the wall film into the separation inlet  64  in the process. At an upper side wall  43  of the inlet conduit  24 , which is opposite the lower side wall  42 , for instance, the wall film need not detach from the side wall but instead is pushed directly into the separation inlet  64 . 
     Liquids in the conduit  22  that do not form any wall film strike the inner wall  41  and are thereby separated out of the conduit  22 . 
     The labyrinthine separation element  70  for instance comprises three annular-arc elements  76 , which are internested. At least one shunt  79  is disposed in the region of the separation outlets  68  and protects against water or liquid entering from the line  3 . 
     FIG. 3 shows a section taken long the III—III of FIG. 
     The conduit  22  narrows in the inlet conduit  24  in the flow direction  29 , so that a stabilization of the flow takes place. 
     The rear chamber  71 , on the side face  8  along the longitudinal axis  10 , has slits  72  through which the liquid that has been separated out returns to the conduit  3 , in which the liquid no longer causes any negative effects. 
     FIG. 4 shows a section taken along the line IV—IV of FIG.  2 . 
     The outlet conduit  44  also narrows in the outlet conduit flow direction  50 . Once the flowing medium has flowed past the sensor carrier  56  with the measurement element  60 , it strikes the outflow element  51 . The outflow element  51  is embodied in the shape of a W, for instance, and deflects the outlet flow direction  50 , so that the medium, through at least one outlet opening  53 , enters the line  3  again and flows onward in the main flow direction  20  again. In this exemplary embodiment, there are two outlet openings  53 . 
     The outflow element  51  protrudes past a side face  54  of the measurement housing  6 . The primary flow  3  creates a negative-pressure zone (detachment) at the outflow element  51  in the region of the outlet opening  53  and thus exerts suction on the flow in the measurement conduit  44 . Because the outflow element  51  protrudes past the side fact  54 , a reverse flow that is present in some phases is fed into the measurement conduit  44  and measured. 
     FIG. 5 shows a further exemplary embodiment of the device  1  of the invention. The difference from the exemplary embodiment of FIG. 2 is essentially that the outlet conduit  44  is the closest to the carrier housing  7 , and the inlet conduit  24  is disposed on a lower end of the measurement housing  6 . Also, the sensor carrier  56  has two measurement elements  60 , which measure the volumetric flow and the pressure, for instance. 
     The foregoing relates to preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.