DETERMINING AN ACTUAL VALUE AND/OR AN ACTUAL VALUE RANGE OF AT LEAST ONE STATE VARIABLE OF A FLUID IN A FLUID FLOW BY MEANS OF AT LEAST ONE INDICATOR PARTICLE

Abstract

The invention relates to a method for determining an actual value and/or an actual value range of at least one state variable of a fluid in a fluid flow by means of at least one indicator particle (9) introduced into the fluid. In addition it is proposed that the at least one indicator particle (9) is designed and provided for an irreversible property change of an indicator property of the indicator particle (9) in the case of a certain indicator value of the at least one state variable in the fluid flow and/or as a clear function of the actual value when a certain period of time has elapsed after the indicator particle (9) has been introduced into the fluid, wherein the indicator particle (9) is detected at a detection point, the indicator property of the indicator particle (9) is evaluated and the actual value and/or the actual value range of the state variable is inferred from the indicator property upstream of the detection point. The invention also relates to a method for operating a fluid-guiding device (7), an indicator particle (9) and a device (7) for determining the actual value and/or actual value range of the at least one state variable.

Claims

1. Method for determining an actual value and/or an actual value range of at least one state variable of a fluid in a fluid flow by means of at least one indicator particle (9) introduced into the fluid, characterized in that the at least one indicator particle (9) is provided and designed for an irreversible property change of an indicator property of the indicator particle (9) in the presence of a specific indicator value of the at least one state variable in the fluid flow, and/or as a clear function of the actual value at the end of a certain period of time after the indicator particle (9) is introduced into the fluid, wherein the indicator particle (9) is detected at a detection point, the indicator property of the indicator particle (9) is evaluated and the actual value and/or the actual value range of the state variable upstream of the detection point is inferred from the indicator property.

2. Method according to claim 1, characterized in that the at least one indicator particle (9) is part of a large number of indicator particles (9) which are introduced into the fluid, wherein the indicator value of the state variable for a first part of the indicator particles (9) corresponds to a first indicator value and for a second part of the indicator particles (9) corresponds to a second indicator value and/or the period of time corresponds to a first period of time for the first part of the indicator particles and to the second period of time for the second part of the indicator particles.

3. Method according to one of the preceding claims, characterized in that the first part of the indicator particles (9) and the second part of the indicator particles (9) are introduced into the fluid simultaneously or in a time-delayed manner and/or at the same point of introduction (8) or at spaced-apart points of introduction (8), wherein the first part is provided with an unchangeable first identification independent of the respective indicator property and the second part is provided with an unchangeable second identification independent of the respective indicator property.

4. Method according to one of the preceding claims, characterized in that the at least one indicator particle (9) is detected and the indicator property is evaluated without contact in the fluid or after the at least one indicator particle (9) has been removed from the fluid.

5. Method according to one of the preceding claims, characterized in that if the property change does not occur, the indicator value (9) is changed until the property change occurs, or if the property change occurs, the indicator value is changed until the property change does not occur, wherein from a first indicator value of the indicator value, at which the property change did not occur, and from a second indicator value of the indicator value at which the property change occurred, the actual value and/or the actual value range of the state variable is inferred.

6. Method according to one of the preceding claims, characterized in that at least one prediction value for the state variable is calculated using a model of the fluid flow and the movement of a particle in the fluid flow, in particular along the trajectory of the at least one modeled indicator particle, and is verified using the at least one indicator particle (9), wherein the model is adjusted to the actual value and/or the actual value range if the prediction value deviates from the actual value and/or actual value range determined by means of the at least one indicator particle (9).

7. Method for operating a fluid-guiding device (1), wherein an actual value and/or an actual value range of at least one state variable of the fluid in a fluid flow present in the device (1) is determined by means of at least one indicator particle (9) introduced into the fluid, in particular using the method according to one or more of claims 1 to 6, characterized in that the at least one indicator particle (9) is responsible for an irreversible change in the properties of an indicator property of the indicator particle (9) is designed and introduced in the presence of a specific indicator value of the at least one state variable in the fluid flow, and/or as a clear function of the actual value at the end of a certain period of time after the indicator particle (9) into the fluid, wherein the indicator particle (9) is detected at a detection point, the indicator property of the indicator particle (9) is evaluated and the actual value and/or the actual value range of the state variable upstream of the detection point is inferred from the indicator property.

8. Method according to claim 7, characterized in that if the actual value and/or the actual value range deviates from a previously determined actual value and/or actual value range and/or from a predicted value and/or predicted value range determined using a model of the fluid flow, a malfunction of the fluid-guiding device (1) is recognized.

9. Indicator particle (9) for determining an actual value and/or an actual value range of at least one state variable of a fluid in a fluid flow, in particular using the method according to one or more of claims 1 to 6, characterized in that the indicator particle (9) is provided and designed for an irreversible change in properties of an indicator property of the indicator particle (9) is designed and introduced in the presence of a specific indicator value of the at least one state variable in the fluid flow, and/or as a clear function of the actual value at the end of a certain period of time after the indicator particle (9) has been introduced into the fluid.

10. Indicator particle according to claim 9, characterized in that the state variable is a normal stress and/or a shear stress of the fluid and the indicator particle (9) has a base body (13) having a particle shell enclosing a cavity, wherein a reference pressure is present in the cavity and the particle shell is provided and designed to irreversibly change and/or break the indicator property in the form of its shape when the normal stress deviates from the reference pressure by a specific pressure difference, and/or wherein the particle shell is provided and designed to irreversibly change and/or break the indicator property in the form of its shape for this purpose when the shear stress deviates from a reference tension.

11. Indicator particle according to one of the preceding claims, characterized in that on the base body (13) there is a sensor material which provides the indicator property and is state variable-sensitive, wherein the state variable is the fluid pressure, a fluid temperature or a fluid concentration.

12. Indicator particle according to one of the preceding claims, characterized in that the base body (13) is covered by a protective cover (15) so that the base body or the sensor material is only exposed to the fluid after the specific period of time has elapsed after being introduced into the fluid.

13. Indicator particle according to one of the preceding claims, characterized in that a plurality of sensor elements (14) and/or sensor regions are formed on the base body (13), wherein a first part of the sensor elements (14) or sensor regions made of the sensor material and a second part of the sensor elements (14) or sensor regions consists of a sensor material that is different from the sensor material.

14. Indicator particle according to one of the preceding claims, characterized in that the sensor elements (14) and/or sensor regions are covered by the protective cover (15) with different cover thicknesses.

15. Device (7) for determining an actual value and/or an actual value range of at least one state variable of a fluid in a fluid flow by means of at least one indicator particle (9) introduced into the fluid, in particular using the method according to one or more of claims 1 to 6 and/or of the indicator particle according to one or more of claims 9 to 14, characterized in that the at least one indicator particle (9) is responsible for an irreversible change in the properties of an indicator property of the indicator particle (9) is designed and introduced in the presence of a specific indicator value of the at least one state variable in the fluid flow, and/or as a clear function of the actual value at the end of a certain period of time after the indicator particle (9) into the fluid, wherein the device (7) is provided and designed to detect the indicator particle (9) at a detection point, to evaluate the indicator property of the indicator particle (9) and to infer the actual value and/or the actual value range of the state variable upstream of the detection point from the indicator property.

Description

[0057] The invention is explained in more detail below with reference to the embodiments shown in the drawing, without restricting the invention. In the drawings:

[0058] FIG. 1 is a schematic representation of a device for determining an actual value or actual value range of at least one state variable of a fluid, in particular a liquid fluid, in a fluid flow, and a fluid-guiding device,

[0059] FIG. 2 is a schematic representation of a first embodiment of the indicator particle,

[0060] FIG. 3 is a schematic representation of a second embodiment of the indicator particle,

[0061] FIG. 4 is a schematic representation of a third embodiment of the indicator particle, and

[0062] FIG. 5 is an indicator particle and a diagram in which a pressure of the fluid is plotted along trajectories covered by a plurality of indicator particles in the fluid.

[0063] FIG. 1 shows a fluid-guiding device 1, namely a jet pump, which has a suction medium inlet 2, a propellant medium inlet 3 and an outlet 4. The propellant medium inlet 3 is designed in the form of a nozzle and opens into a mixing chamber 5. As an extension of the propellant medium inlet 3, a diffuser 6 is fluidically connected to the mixing chamber 5. The mixing chamber 5 is fluidically connected to the outlet 4 via the diffuser 6. The suction medium inlet 2 is also fluidically connected to the mixing chamber 5.

[0064] The fluid-guiding device 1 is supplied with a first fluid, the so-called propellant medium, at high pressure and—optionally—high temperature via the propellant medium inlet 3. Accelerating this first fluid through the nozzle 3 leads to a lower pressure of the first fluid in the mixing chamber 5 in relation to a pressure at the suction medium inlet 2. As a result, a second fluid, the so-called suction medium, which is present at the suction medium inlet 2—at an optionally low temperature—is conveyed from the suction medium inlet 2 into the mixing chamber 5 with a further reduction in pressure. The first fluid and the second fluid mix in the mixing chamber 5 and in the subsequent diffuser 6 with temperature equalization and renewed pressure increase before a fluid mixture consisting of the two fluids leaves the device through the outlet 4. In this case, the first fluid and the second fluid can be of the same substance.

[0065] The fluid-guiding device 1 is assigned a device 7 which is used to determine an actual value or an actual value range of at least one state variable of a fluid present in the fluid-guiding device 1. To this extent, the device 7 can also be referred to as a measuring device. In order to determine the actual value or the actual value range, one (or more) indicator particles 9 are introduced into the fluid at an introduction point 8 or at a plurality of introduction points 8 (in each case). In the embodiment shown here, the introduction point 8 is at the suction medium inlet 2. In terms of flow, it can also be present between the suction medium inlet 2 and the mixing chamber 5, i.e. in any case upstream of the mixing chamber, the diffuser 6 and the outlet 4. The indicator particles 9 are introduced by means of an introduction device 10, which is only indicated here. After the indicator particles 9 have been introduced into the fluid, they pass through the fluid-guiding device 1 starting from the introduction point 8 along a respective trajectory 11a, 11b or 11c. Downstream of the introduction point 8 there is a detection device 12 which is used to detect the indicator particles 9. The indicator particles 9 are detected, for example, by means of an optical detection device. This is indicated here only extremely schematically.

[0066] The indicator particles 9 are provided and designed in such a way that they are subjected to an irreversible property change of an indicator property of the respective indicator particle 9 when a specific indicator value of the state variable to be determined is present. In the embodiment shown here, the shape of the indicator particles 9 is used as an indicator property. It can be seen that in the region of the detection device 12 one of the indicator particles 9 has a changed shape, whereas the other indicator particles 9 have the same shape as when they were introduced into the fluid at the introduction point 8. From this it can be inferred that the indicator particle 9, which has changed its shape, has reached a region of the fluid flow along the respective trajectory 11a, 11b or 11c in which the state variable has an actual value which corresponds to an indicator value of the indicator particle 9 or exceeds or falls below this. If the actual value corresponds to this or if the actual value exceeds or falls below the indicator value, the irreversible property change occurs, in this case a change in shape. For this purpose, the indicator particles 9 are present in a first embodiment, in which the state variable is the fluid pressure and the indicator value of the indicator particles is selected such that the change in shape that occurs indicates the occurrence of cavitation in the fluid flow. FIG. 2 shows a schematic representation of a second embodiment of the indicator particle 9 or one of the indicator particles 9. In the embodiment shown, the indicator particle 9 has a base body 13 on which at least one sensor element 14 made of a sensor material (in the embodiment shown here several sensor elements 14) is formed. Only a few of the sensor elements 14 are identified as examples. In each case, several structurally identical sensor elements are preferred, distributed evenly over the surface of the indicator particle. The sensor elements 14 are covered by a protective cover 15, wherein the protective cover 15 for the various sensor elements 14 has different cover thicknesses that are constant over the respective sensor element 14. Structurally identical sensor elements preferably have the same protective cover, in particular with the same cover thickness. The protective cover 15 is designed in such a way that it is degraded by the fluid after the indicator particle 9 has been introduced into the latter, so that the sensor elements 14 are only directly exposed to the fluid after a certain period of time. The sensor material from which the sensor elements 14 are made is sensitive to state variables or state variable values. This means that the sensor material is subjected to the irreversible change in its indicator property as soon as it comes into contact with the surrounding fluid, wherein the indicator property changes according to the actual value or actual value range of the state variable immediately after the respective sensor element 14 has been exposed to the fluid. Provision can be made here for the property of the sensor material of the different sensor elements 14 to change irreversibly when the same or different indicator values are present. Provision can also be made for the property of the sensor material of the different sensor elements 14 to change as a clear function of the actual value of the state variable directly after the sensor elements 14 come into contact with the surrounding fluid. The sensor material can additionally or alternatively be designed for different state variables of the fluid.

[0067] The use of a plurality of identical sensor elements distributed over the particle surface enables the indicator property of an indicator particle to be recorded optically in a very simple manner. An unambiguous assignment of the cover thickness and surface of a sensor element allows a very simple assignment between the detected indicator property and the point in time (after the indicator particle has been introduced into the fluid) at which the actual value or actual value range was present.

[0068] FIG. 3 shows a schematic representation of a third embodiment of the indicator particle 9. In principle, reference is made to the above explanations and only the differences are discussed below. These lie in the fact that several sensor element arrangements 16 emanate from the base body 13, of which only a few are identified as examples. Each of these sensor element arrangements 16 has a plurality of sensor elements 14. This is also only indicated as an example. The sensor element arrangements 16 each extend outwards starting from the base body 13 and are spaced apart from one another. The protective cover 15 is present in the intermediate spaces 17 present between the sensor element arrangements 16 (again only identified as an example). After the indicator particle 9 has been introduced into the fluid, the protective covering 15 is removed from the outside inwards. This means that the sensor elements 14 are subjected to the fluid one after the other in terms of time.

[0069] Each of the sensor elements 14 is designed in such a way that the property of the sensor material changes irreversibly if the specific indicator value of the state variable is present when the fluid is applied to it. Alternatively, each of the sensor elements 14 is designed in such a way that the property of the sensor material changes irreversibly as a clear function of the actual value of the state variable directly after the sensor material comes into contact with the surrounding fluid. The sensor elements 14 are particularly preferably designed in such a way that the irreversible property change is only possible immediately at the beginning of the exposure of the respective sensor element 14 to the fluid. Accordingly, when evaluating the indicator property of the indicator particle 9 or the indicator properties of the sensor elements 14, a time sequence of the actual value or actual value range of the state variable along one of the trajectories 11a, 11b and 11c can be evaluated.

[0070] FIG. 4 shows a schematic representation of a fourth embodiment of the indicator particle 9. Reference is again made to the above explanations. Again, there are a number of sensor element arrangements 16 which each have a number of sensor elements 14. The sensor elements 14 are each arranged or formed directly on the base body 13. For example, there is a central sensor element 14 which is encompassed by the other sensor elements 14, for example in a ring shape. Each of the sensor element arrangements 16 is covered by the protective cover 15 which is formed on the base body 13 in the shape of a segment of a sphere, for example. The protective cover 15 is arranged in such a way that it overlaps at least part of the sensor elements 14, preferably all of the sensor elements 14, before the indicator particle 9 is introduced into the fluid. Since the protective cover 15 is dissolved by the fluid over time and the thickness of the cover of the protective cover 15 for the sensor elements 14 is different, the sensor elements 14 are again exposed to the fluid one after the other. This configuration of the indicator particle 9 also enables fine temporal resolution of the course of the actual value or actual value range of the state variable, in particular along the respective trajectory 11a, 11b or 11c of the indicator particle 9 (Langrange's description) or the local actual values of the state variable in the fluid flow (Euler's description), preferably after the trajectories 11a, 11b and 11c of the indicator particles 9 have been determined within the framework of a calibrated model of the fluid flow and the particle movement.

[0071] FIG. 5 shows an indicator particle 9 and a diagram in which a pressure p is plotted over a distance s of the trajectories 11a, 11b and 11c for the fluid-guiding device 1 described with reference to FIG. 1. The indicator particle 9 shown is representative of several identical indicator particles 9. These each have the base body 13, which is hollow and made of a defined material. The base body 13 is defined by an outer diameter D, a cavity 18 with an inner diameter d, a reference pressure in the cavity 18 of the base body 13 and a specific wall thickness w=D−d. A curve 19a shows the course of the pressure along the trajectory 11a, a course 19b along the trajectory 11b and a course 19c along the trajectory 11c. All trajectories start at pressure p.sub.0 at the introduction point 8 and end at pressure p.sub.4 in the outlet 4. For the indicator particle 9 assigned to the trajectory 11a, the local fluid pressure, starting from the pressure p.sub.0, initially falls below the vapor pressure p.sub.D of the fluid, so that cavitation bubbles form, which implode as a result of the pressure increase after the vapor pressure p.sub.D is exceeded and lead to very high pressure peaks in the fluid (above the specified indicator value p.sub.I), which then cause a permanent change in shape of the indicator particle. This is not the case for the indicator particles 9 assigned to the trajectories 11b and 11c, so that these—as indicated—retain their shape.