Flow distribution measurement of a liquid spray stream

Abstract

A measurement device for measuring a flow distribution of a liquid spray stream which has been atomized by a nozzle may comprise: a sensing wire; at least one further sensing wire; an electric power supply; a measurement unit; and a second grid of parallel sensing wires. The sensing wires may be positioned within a spray volume of the liquid spray stream and arranged in parallel with respect to each other to form grids of parallel sensing wires. The electric power supply unit may supply an electric current to the sensing wires. The measurement unit may measure an ohmic resistance change of the sensing wires. The first axis defined by the parallel sensing wires of the first grid and a second axis defined by the parallel additional sensing wires of the second grid may enclose a slanted angle.

Claims

1. A measurement device for measuring a flow distribution of a liquid spray stream which has been atomized by a nozzle, the measurement device comprising: a plurality of first sensing wires positioned within a spray volume of the liquid spray stream and arranged in parallel with respect to each other to form a first array of parallel first sensing wires, the first array defining a plane; an electric power supply unit electrically connected with the plurality of sensing wires and configured to supply an electric current flowing through the plurality of sensing wires, a measurement unit electrically connected to the plurality of sensing wires for measuring an ohmic resistance change of each sensing wire of the plurality of sensing wires resulting from a cooling of the respective sensing wire, and a second array of parallel second sensing wires comprising a plurality of second parallel additional sensing wires parallel to each other in the plane and non-parallel to the first sensing wires, wherein the sensing wires of the second array are electrically connected to the electric power supply unit for an additional electric current to each one of the sensing wires in the second grid, wherein the sensing wires of the second array are electrically connected with the measurement unit for measuring, for each one of the sensing wires of the second array, an ohmic resistance change, and wherein a first axis defined by an extent of the parallel sensing wires of the first array and a second axis defined by an extent of the parallel additional sensing wires of the second array define a first angle, and a third array of parallel third sensing wires, the third array comprising a plurality of parallel third sensing wires electrically connected with the electric power supply unit for supplying an additional electric current to each one of the plurality of third sensing wires, wherein each third sensing wire is parallel to the other third sensing wires in the plane and non-parallel to the first sensing wires and non-parallel to the second sensing wires, and wherein each of the plurality of third sensing wires are electrically connected with the measurement unit for measuring a respective ohmic resistance change.

2. The measurement device as set forth in claim 1, wherein the first axis and the second axis enclose an angle of at least approximately 90.

3. The measurement device as set forth in claim 1, wherein at least some sensing wires comprise an insulating coating.

4. The measurement device as set forth in claim 1, further comprising five further arrays such that altogether eight arrays of parallel sensing wires are provided, wherein the eight arrays are distributed within the plane in such a manner that in between two angularly neighboring arrays an angle of 22.5 is enclosed.

5. The measurement device as set forth in claim 1, further comprising a translation unit configured for spatially translating one or more arrays along a translation axis in such a manner that a distance between the one or more arrays and the nozzle is variable.

6. The measurement device as set forth in claim 1, wherein the first array and the second array and the third array form a first grid system which can be positioned within the spray volume of the liquid spray system at a first distance with respect to the nozzle, wherein the measurement device further comprises at least one second grid system comprising at least three arrays of parallel sensing wires electrically connected with the electric power supply unit for supplying an additional electric current to each one of these sensing wires, and wherein these sensing wires are electrically connected with the measurement unit for measuring, for each one of these sensing wires, an ohmic resistance change.

7. The measurement device as set forth in claim 6, wherein both the first grid system and the at least one second grid system are arranged parallel with respect to each other such that there is a predefined distance between the two grid systems.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a measurement device comprising a single sensing wire according to the teachings of the present disclosure.

(2) FIGS. 2a and 2b illustrate the basic principle of measuring the temporal course of a flow distribution of a liquid spray stream which has been atomized by a nozzle by employing the measurement device shown in FIG. 1.

(3) FIGS. 3a and 3b illustrate the basic principle of measuring the temporal course and along one axis the spatial course of a flow distribution of a liquid spray stream which has been atomized by a nozzle by employing a measurement device comprising a plurality of parallel arranged sensing wires.

(4) FIG. 4a shows a grid system comprising eight different grids each having 25 sensing wires which are arranged within one common grid plane, wherein the eight grids are distributed within the common grid plane in such a manner that in between two angularly neighboring grids an angle of 22.5 is enclosed.

(5) FIG. 4b shows a visualization of a spatial two-dimensional flow distribution.

(6) FIG. 5 shows a grid arrangement comprising five grid systems as shown in FIG. 4a, which grid arrangement can be used for measuring the spatial flow distribution of a liquid spray stream within a three dimensional measurement region.

DETAILED DESCRIPTION

(7) In different figures, similar or identical elements or features are provided with the same reference signs or with reference signs which are different from the corresponding reference signs only within the first digit. In order to avoid unnecessary repetitions elements or features which have already been elucidated with respect to a previously described embodiment are not elucidated again at a later position of the description.

(8) FIG. 1 shows an example measurement device 100 according to teachings of the present disclosure. The measurement device 100 comprises a sensing wire 110, which is connected, via two connection leads 152, with a control unit 130.

(9) The control unit 130 comprises an electric power supply unit 140 and a measurement unit 150. During operation, the electric power supply unit 140 drives an electric current through the sensing wire 110. This electric current heats up the sensing wire until in a thermal condition of equilibrium the sensing wire 110 adopts a certain temperature.

(10) When particles of a liquid spray stream 195, which has been ejected by a nozzle 190, impinge onto the sensing wire 110, the temperature of the sensing wire 110 will decrease. As a consequence, the ohmic resistance of the sensing wire 110 will also decrease. Thereby, the amount of the decrease of the ohmic resistance of the sensing wire 110 will be indicative for the intensity of the liquid flow stream 195.

(11) According to the embodiment described here the electric current is provided by a voltage source of the electric power supply unit 140. As a consequence, when the ohmic resistance of the sensing wire 110 decreases, the current flowing between an input end 110a and an output end 110b of the sensing wire 110 increases. This current increase is measured by the measurement unit.

(12) The single sensing wire 110 is able to measure instantaneously the mass flow of the liquid spray stream 195 impinging onto the sensing wire 110. This is achieved by heating up the sensing wire 110 with an electric current, which is provided by the electric power supply unit 140. The sensing wire 110 is suspended within the liquid spray stream 195 like a toaster wire. The wire's electrical resistance increases as the wire's temperature increases, which limits electrical current flowing through the sensing wire 110. When particles of the liquid spray stream 395 hit the sensing wire 110, the sensing wire 110 cools down and, as a consequence, decreases its resistance, which in turn allows a higher current to flow through the sensing wire 110. As a higher current flows, the temperature of the sensing wire 110 increases until the temperature (and resistance) reach thermal equilibrium again. The amount of current required to maintain the temperature of the sensing wire 110 is proportional to the mass of the flow of the liquid spray stream 195 hitting the sensing wire 110. An integrated electronic circuit being comprised in the measurement unit 150 converts the measurement result of the current into a corresponding voltage signal. This voltage signal is indicative for the amount of the flow of the liquid spray stream 195 hitting the sensing wire 110.

(13) FIGS. 2a and 2b illustrate the basic principle of measuring a flow distribution of a liquid spray stream 195 which has been atomized by a nozzle 190 by employing the measurement device 100 shown in FIG. 1. Since only one single sensing wire 110 is used, only the temporal course of a flow distribution of the part of the liquid spray stream 195 can be measured which part impinges onto the sensing wire 110.

(14) FIG. 2a illustrates the temporal development of the liquid spray stream 195 at time points t1, t2, t3 and t4, which liquid spray stream 195 has been atomized by the nozzle 190 at a time t=0. FIG. 2b shows the dependency of the corresponding flow of the liquid spray stream 195 impinging onto the sensing wire 110 on the time t.

(15) FIGS. 3a and 3b illustrate the basic principle of measuring not only the temporal course of a flow distribution of a liquid spray stream 395 but also the spatial dependency of the flow distribution along one direction, here called the x-direction. In order to achieve this, the corresponding measurement device comprises not only one but a plurality of sensing wires 310 which form a grid 312 of parallel sensing wires 310. Thereby, in accordance with the sensing wire 110 of the measurement device 100 shown in FIG. 1, each one of the parallel sensing wires 310 is connected both to a not shown electric power supply unit and to a not shown measurement unit. This means that in accordance with the signal processing elucidated above for the single sensing wire 110 the current through each sensing wire 310 is measured. Again, for each sensing wire 310 the increase of the current compared to a thermal state of equilibrium is indicative for the amount of liquid flow stream 395 impinging onto the respective sensing wire 310.

(16) FIG. 3a illustrates the temporal development and the spatial development along the x-direction of the liquid spray stream 395 at time points t1, t2, t3 and t4, which liquid spray stream 395 has been atomized by a nozzle 390 at a time t=0. FIG. 3b shows the dependency of the corresponding flow of the liquid spray stream 395 impinging onto the sensing wires 310 on the time t and on the position x along the x-direction.

(17) FIG. 4a shows a grid system 414 comprising eight different grids each having 25 sensing wires which are arranged within one common grid plane. The eight grids are distributed within the common grid plane in such a manner that in between two angularly neighboring grids an angle of 22.5 is enclosed. Again, each sensing wire of each grid is electrically insulated from all other sensing wires. Further, each sensing wire is, in accordance with the sensing wire 110 of FIG. 1, connected both to a non-depicted electric power supply unit and to a non-depicted measurement unit.

(18) FIG. 4b shows a visualization of a spatial two-dimensional flow distribution which has been measured by a measurement device comprising the grid system 414 shown in FIG. 4a.

(19) Various embodiments of the measurement device use a combination of several series of electrical conductible insulated sensing wires and the concept of geometrical tomography (retrieval of information about a geometric object from data concerning its projections on planes). This kind of measurement has a very low response time and then can be used to give an almost continuous measurement.

(20) Using the grid system 414, wherein a number of grids (e.g., eight grids) each comprising parallel sensing wires (e.g., 25 wires) are angled with respect to each other, provides a measurement device being capable of measuring the flow distribution of a liquid spray stream vs. x, y and vs. time. Thereby, an algorithm similar to the one used in tomography imaging can be used.

(21) According to the embodiment described here the grid system 414 is a 50 mm diameter pattern build out of 8 grids of 25 wires each with a 22.5 angular spacing between angularity neighbored grids. Accordingly, the grid system 414 described here includes 200 sensing wires, each of them has a controlled current flowing through it. A not depicted electronic microprocessor is able to measure the current for each sensing wire, and then to calculate the flow impinging onto the respective sensing wire. This allows for calculating a visualization as shown in FIG. 4b which can change with time. This means that one is able to characterize the two dimensional spatial dependency of a liquid spray stream shape in a dynamic mode. For high frequency pulsed sprays, a device like this would allow to measure an event to event deviation.

(22) FIG. 5 shows a grid arrangement 516 comprising five grid systems 514a, 514b, 514c, 514d and 514e. Each one of the five grid systems 514a-e corresponds to the grid system 414 shown in FIG. 4a. Each sensing wire of the whole grid arrangement 516 is electrically insulated from all other sensing wires. Further, each sensing wire is, in accordance with the sensing wire 110 of FIG. 1, connected both to a non-depicted electric power supply unit and to a non-depicted measurement unit.

(23) With the grid arrangement 516 the spatial flow distribution of a liquid spray stream within a three dimensional measuring region can be measured and the flow distribution of a liquid spray stream vs. x, y, z and vs. time can be measured.

(24) Such a three dimensional and time dependent measurement of the flow distribution of a liquid spray stream could also be realized by a single grid system which is moved by means of a translation unit along a translation axis in such a manner that a distance between the grid system and the nozzle is varied. Then, for each distance (e.g. a certain z-position of the grid system) a two dimensional (along x- and y-direction) and time dependent measurement can be accomplished.

(25) The measurement devices according to the teachings of the present disclosure provide the advantage that a liquid spray stream can be dynamically measured and, compared to known measurement systems, can be measured with a higher resolution. Thereby, the sensing wire size or diameter and the displacement between two neighboring sensing wires can be much smaller respectively closer as compared to the cell size of known measurement systems, which are described in the introductory portion of this document.

(26) It should be noted that the term comprising does not exclude other elements or steps and the use of articles a or an does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.