• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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    • 专利摘要:
    Apparatus and method for determining the number of solid particles in a fluid stream, in particular in exhaust gases of internal combustion engines. The device comprises a measuring channel (1) for the fluid flow to be measured, a saturation unit (2) for saturating the fluid with vapors of an operating medium (3), a condensation unit (4) for cooling the fluid flow and a counting unit (5) for counting the flow rate Cooling condensate droplets (6) formed on the particles. The counting unit (5) has a lighting device (7), at least one light sensor (9) and a computing unit (11) connected to the light sensor (9) for determining the number of solid particles. The lighting device (7) generates a carpet of light (8) arranged on a cutting plane through the measuring channel (1), which defines a measuring surface which extends substantially over the entire cross-sectional area of the measuring channel (1). The light sensor (9) has a plurality of sensor elements (10) for scanning the entire extent of the measuring surface.
    公开号:AT516759A4
    申请号:T50394/2015
    申请日:2015-05-12
    公开日:2016-08-15
    发明作者:
    申请人:Avl List Gmbh；
    IPC主号:
    专利说明:

    Apparatus and method for determining the number of solid particles in one
    fluid flow
    The subject invention relates to an apparatus and a method for determining the number of solid particles in a fluid stream, in particular in exhaust gases of internal combustion engines. The apparatus comprises a measurement channel for the fluid flow to be measured, a saturation unit for saturating the fluid with vapors of a resource, a condensation unit for cooling the fluid flow and a counting unit for counting the condensate droplets formed on the particles during cooling, wherein the counting unit comprises a lighting device, at least a light sensor and a computing unit connected to the light sensor for determining the number of particles. According to the method according to the invention, the fluid flow to be measured passes through the measuring channel.
    With the increasing demands on the environmental compatibility of internal combustion engines, the development of reliable devices for the measurement of the number of solid particles in the development and testing of such machines is becoming increasingly important. A distinction is made here between an integral particle measurement, which uses statistical calculations to deduce the total particle density based on a detection result, and a particle count, in which each individual particle is detected in the fluid flow and the total number of particles present in the fluid flow is counted.
    In order to ensure a reliable count of all particles, particle counters of the prior art are designed as a one-dimensional particle counter, in which the particle flow after the condensation unit is passed through a separating nozzle. The particles can therefore be singulated with a sufficiently high probability, i. H. One after the other, exit from the nozzle to allow a count of the individual particles as possible without coincidences. At the exit of the nozzle then the counting unit is arranged. This has a lighting unit, with which the area behind the outlet opening of the nozzle is generally illuminated with laser light, which is scattered by the particles emerging from the nozzle. The scatter is measured by a light sensor and the scattering events are counted. A distinction is made here between a bright field measurement, in which the sensor detects the laser beam and detects the darkening caused by the particle, and a dark field measurement, in which the sensor is protected from directly incident laser light and the scattered light that occurs when a particle passes through the laser beam, measured in the form of a flash of light. Due to the singling nozzle, the particles to be measured generally move at high speeds of, for example, about 10-100 m / s through the detection volume. The high passage velocities and the relatively small size of the condensed droplets (about 5-20pm) require a high sensitivity and a high temporal resolution of the sensors.
    Prior art particle counters are currently capable of handling fluids with a particle density of up to 20,000 particles / cm3. This count limit is determined primarily by the coincidence probability. Coincidence occurs when two particles pass the laser beam so close to each other that only one pulse is detected instead of two individual pulses. It is an object of the subject invention to significantly increase the count limit and at the same time the reliability of the count.
    According to the invention, this and other objects are achieved by a device of the type mentioned above, in which the illumination device can be used to produce a carpet of light arranged on a cutting plane through the measurement channel, which defines a measurement surface which extends substantially over the entire cross-sectional area of the measurement channel, and wherein the light sensor for scanning the entire extension of the measuring surface has a plurality of sensor elements. This makes it possible to carry out the particle counting over a flat area, so that no separating nozzle is required. As a result, the speed of the condensate droplets in the area of the counting unit is reduced at a comparable volume flow, so that the time resolution requirements of the sensor element are reduced. The count limit can be increased by increasing the number of sensor elements provided on the light sensor. The term "scanning" means a measuring process and the recognition of the passage of a condensate droplet through the carpet of light. Under carpet of light is understood here an arrangement whose areal two-dimensional extent the thickness, ie expansion in a third dimension (hereinafter referred to as the thickness d of the carpet of light), clearly outweighs.
    In order to increase the detection accuracy, the illumination device can advantageously have at least one laser light source.
    In a preferred embodiment, the light sensor may have at least one linear arrangement of a plurality of sensor elements, whereby a very simple sensor arrangement is possible. "Linear" arrangement here means preferably immediately adjacent side by side or sequentially (for example line-like) arrangement of the sensor elements.
    To further increase the detection accuracy, for example, two linear arrays of a plurality of sensor elements may also be arranged in an angular configuration, for example at right angles to one another. This can prevent miscounting due to overlapping condensate droplets, thereby increasing the count limit. In a variant of the invention, the two linear arrangements are both in the plane of the carpet of light.
    In the context of the subject invention, the term "count limit" refers to the particle concentration which can be reliably counted with a specific configuration and under certain flow conditions. A reliable counting method can be designated as having reached a predefined reliability value, which can be defined, for example, as a percentage of undetected particles. For certain applications, for example, the tolerable coincidence probability could be 10%. In practice this would mean that of the 20,000 particles / cm3, a maximum of 2,000 particles would not be detected. If two particles can no longer be counted or resolved independently of one another, this situation is referred to as "coincidence". The coincidence probability therefore corresponds to the ratio of the number of undetected particles to the total particle number.
    In an advantageous manner, at least one optical fiber bundle unit can be arranged in front of the light sensor for focusing stray light. As a result, the reliability of the count can be increased, since with the fiber bundle unit certain areas of the measuring surface can be assigned to specific sensor elements.
    Furthermore, the light sensor (or possibly several of the light sensors) may be arranged in the cutting plane in an advantageous manner. As a result, good light detection can be achieved both in bright field measurement and in dark field measurement. As mentioned above, the carpet of light is part of the cutting plane. For a bright field measurement, the light sensor for direct measurement of the light of the carpet of light may be arranged for this purpose, i. that the light sensor is arranged in the sectional plane such that the light of the illumination device strikes the sensor elements directly and without any elements arranged therebetween.
    In an advantageous manner, between the light sensor and the measuring channel, a lens unit, optionally with a diaphragm, can be arranged in order to obtain a sharper sensor signal for each condensate droplet.
    In order to realize a dark field measurement with a light sensor arranged in the sectional plane, the light sensor according to the invention can be shielded by a shield from the beam path of the carpet of light, wherein preferably at least one lens unit for focusing scattered light can be arranged between the shield and the light sensor. As a result of the shielding, the sensor unit can also be arranged in the sectional plane in the case of a dark field measurement, whereby it is possible in conjunction with the lens unit to measure a particularly high proportion of the scattered light with the sensor unit.
    In an advantageous embodiment, the at least one lens unit can have a diaphragm arrangement. This increases the depth of field of the lens unit for particle detection, whereby droplets of condensate can be reliably detected in the entire area of the measuring area.
    In a further advantageous embodiment of the invention, the normal to the sectional plane with the axis of the measuring channel a crest angle α between 30 ° and 60 °, preferably 45 °, include. This allows advantageous use of two-dimensional light detectors, such as CCD and CMOS image sensors. Due to the inclined cutting plane, these sensors can be arranged outside the measuring channel.
    In this case, the light sensor may advantageously have a two-dimensional array of sensor elements and a lens unit, wherein preferably the optical axis of the unit of light sensor and lens unit is aligned substantially normal to the measuring surface. As a result, the sensor element can be focused on the measuring surface in order to accurately detect the condensate droplets passing through the carpet of light over the entire measuring surface. "Substantially normal" in this context means that the optical axis is oriented so that the range of depth of field of the lens array suitable for measuring condensate droplets extends over the entire area of the measurement area.
    In one variant of the invention, the light sensor according to the invention a two-dimensional array of sensor elements and a lens unit, wherein preferably the alignment of the objective main plane of the lens unit, the image plane of the light sensor and the plane of the measuring surface of the Scheimpflug condition corresponds. As a result, an advantageous angle for the focusing plane can be selected, whereby the proportion of the light scattered by a particle can be increased.
    The invention further relates to a method for determining the number of solid particles in a fluid stream, in particular in exhaust gases of internal combustion engines, wherein the fluid flow to be measured passes through a measuring channel, a saturation unit, in which the fluid is saturated with vapors of a resource, a condensation unit, in the fluid stream is cooled, and a counting unit, in which the condensate droplets formed on the particles during cooling, are counted. According to the invention, in the area of the counting unit, a sectional plane through the measuring channel can define a measuring surface on which a carpet of light is produced for illuminating the condensate droplets passing through the measuring surface, the light deflections caused by the condensate droplets passing through the carpet of light being dependent on the passage location through the carpet of light be measured by at least one sensor element of a plurality of sensor elements comprising light sensor and wherein the measurements are evaluated by a computing unit for determining the number of solid particles.
    The method according to the invention makes it possible to simultaneously measure condensate droplets over the entire flat area of the measuring surface, which is spanned by the carpet of light, so that the requirement of a separating nozzle is eliminated. The location-dependent measurement makes it possible to avoid detection errors that can occur when several particles pass through the carpet of light at the same time.
    In an advantageous manner, the carpet of light can be formed with preferably highly-collimated laser light in order to increase the measurement accuracy. In the context of the present application, the term "highly-collimated" is understood in particular to mean a laser light carpet in which the beam divergence in the carpet layer is at most 0.1 mrad.
    In an advantageous embodiment, the light of the carpet of light and / or scattered light can be selectively shielded by means of shield systems. As a result, a desired beam path can be defined or an undesired beam path can be prevented.
    In an advantageous embodiment of the method according to the invention, the measuring surface may extend over the entire part of the cross-sectional area traversed by the particle stream, preferably substantially over the entire cross-sectional area of the measuring channel. This minimizes false counts and thus significantly raises the count limit.
    Preferably, the ratio of the width of the measuring surface to the mean diameter of the condensate droplets can be greater than 100, preferably greater than 500 and particularly preferably greater than 1000. An increase in the measuring area, based on the size of the condensate droplets, allows an increase in the count limit. The numerical values mentioned above mean that the width of the measuring surface corresponds to 100, 500 or 1000 times the mean diameter of the condensate droplets.
    Advantageously, at least two or more of the following parameters can be adapted to each other to optimize the counting accuracy: the thickness d of the carpet of light, the size of the measuring area, the speed of the fluid flow, the particle density in the
    Fluid flow, the particle distribution in the fluid flow, the size of the condensate droplets, the time resolution of the sensor unit. In this case, in particular in a dark field measurement, the count limit is increased when the thickness d of the carpet of light is reduced.
    Advantageously, the light deflection can be measured by light sensors which have at least one linear arrangement of a multiplicity of sensor elements or two linear arrangements of a multiplicity of sensor elements arranged at an angle to one another or a two-dimensional array of sensor elements. As a result, the method can be adapted to a large number of different conditions.
    In a further advantageous embodiment of the invention, the arithmetic unit can detect overlapping measurements of multiple condensate droplets by means of error detection algorithms, whereby on the one hand the counting accuracy and on the other hand also the counting limit can be increased.
    The subject invention will be explained in more detail below with reference to Figures 1 to 15a, which show by way of example, schematically and not limiting advantageous embodiments of the invention. It shows
    1 shows a particle counting device according to the invention;
    FIG. 2 shows a schematic representation of the counting unit of the device according to the invention in accordance with a first embodiment; FIG.
    3 is a schematic representation of the counting unit of the device according to the invention in accordance with a second embodiment;
    4 shows a schematic representation of the counting unit of the device according to the invention in accordance with a third embodiment;
    Fig. 5 is an illustration of the optical path of the embodiment of Fig. 4;
    6 shows a schematic representation of the counting unit of the device according to the invention in accordance with a fourth embodiment;
    Fig. 6a is a diagram of the signal intensities calculated for the detector array of Fig. 6;
    7 shows a schematic representation of the counting unit of the device according to the invention in accordance with a fifth embodiment;
    8 shows a schematic representation of the counting unit of the device according to the invention in accordance with a sixth embodiment;
    9 is a schematic representation of the counting unit of the device according to the invention according to a seventh embodiment;
    10 is a diagrammatic representation of second consecutive counts of a one-dimensional counting unit;
    11 a and 11 b show a comparison of the detection of a measuring surface with a linear sensor unit and with two angularly arranged sensor units;
    12 shows a schematic illustration of a linear sensor unit for explaining the minimum measuring distance between two particles;
    13 shows a diagrammatic representation of the measurement result in the case of two closely successive condensate droplets;
    14 shows a diagram of the temporal resolution of the measurement result of two closely successive condensate droplets;
    FIG. 15 shows an illustration of a condensate droplet modeled for a simulation; FIG. and
    15a is a diagram of the light intensity calculated for the condensate droplets of FIG. 15 as a function of the polar angle φ.
    In the following description of the figures, like elements are provided with the same reference numerals for reasons of clarity, the reference numbers being for the sake of clarity only and not to be construed restrictively.
    1 shows a particle counter according to the invention, which essentially comprises a saturation unit 2 with a storage container 15 for a resource 3, a condensation unit 4 downstream in the flow direction of the saturation unit 2 and a counting unit 5 through which a measurement channel 1 for the measurement fluid passes. The measuring fluid with the particles to be counted passes in the measuring channel 1 through an inlet 22 first into the saturation unit 2, in which by means of the operating means, e.g. Butanol, a saturated atmosphere is generated. The operating medium can be supplied, for example, via a porous wall layer or a Wiek 16, the flow channel in the interior of the saturation unit. For example, in the case of butanol as a resource, the temperature in the saturation block may be 25 ° C, which may optionally be maintained by suitable heating means (not shown).
    After the saturation unit 2, the measuring channel 1 leads the measuring fluid into a subsequent condensation block 4, in which the temperature of the fluid flow is reduced by cooling to, for example, about 8 ° C., condensate forming on the particles. As a result, each particle grows to a condensate droplets 6, which is sufficiently large to be detected by the following counting unit 5 can. For example, in the measurement of exhaust gases, the original particles may be in the order of -100 nm, for example, with the condensate droplets 6 growing to a diameter of about 5-20 pm. Since the particles act only as condensation nuclei, their size has only a minor effect on the size of the condensate droplets 6. of the condensation unit 4, in which the flow path in the measuring channel 1 usually extends from bottom to top, the grown particles enter a counting unit 5, which is shown only schematically in Fig. 1. Subsequent to the counting unit 5, a vacuum pump is provided (not shown), which ensures the flow path.
    In the counting unit 5, a laser light source 7 and a light sensor 8 are arranged so that the change of light incident from the light sensor 8, which occurs when a condensate droplets 6 passes through the beam path of the laser light source 7, registered by a computing unit 11 and evaluated to count the particles becomes.
    As stated above, it has hitherto been necessary in the prior art to constrict the particle beam with a singling nozzle before the measurement in such a way that the condensate droplets could in each case only pass through the nozzle into the counting unit substantially one at a time. At the exit of the nozzle, the laser light could then be focused so that each condensate droplet 6 has caused a sufficiently strong change in the light incidence measured by the light sensor in order to be able to measure the condensate droplet with a sufficiently high counting accuracy.
    In order to avoid the disadvantages and limitations that this singling nozzle entails, the subject invention utilizes an improved counting unit 5, schematically illustrated in FIG. 1, with which it is possible to supply the condensate droplets 6 also over a large cross-sectional area no separation of the condensate droplets 6 takes place, and can pass through the many condensate droplets 6 simultaneously to reliably measure.
    Fig. 2 shows a first embodiment of the counting unit 5 according to the subject invention. In this case, a flat laser beam is generated by a laser light source 7, which is located in
    Form of a substantially two-dimensional carpet of light 8 extends across the cross section of the measuring channel 1 for the particle flow. The carpet of light 8 spans substantially the entire cross-section of the measuring channel 1 and impinges on the laser light source 7 opposite side of the measuring channel 1 on an elongated light sensor 9, which has a plurality of individual sensor elements 10 along its longitudinal extent. Whenever a condensate droplet 6 passes the carpet of light 8, this weakens the laser intensity at this point and therefore causes a signal drop at the corresponding sensor element 10. The measurement performed by this light sensor 9 is therefore referred to as a bright field measurement, and accordingly the light sensor 9 can be used as a bright field Light sensor can be called.
    Each condensate droplet 6 consists of a small, generally opaque particle core, around which the condensate droplet 6 has formed as a generally translucent spherical droplet. When a laser beam strikes this condensate droplet 6, different light diffraction, light scattering and refraction processes occur which lead to a scattering intensity characteristic of the condensate droplet 6 as a function of the polar angle. Due to the scattering intensity, which starts from a condensate droplet 6 as a function of the light exit angle, a signal increase at one or more adjacent sensor elements 10 can occur simultaneously with the signal drop in a first sensor element 10. An evaluation of the respective signal pattern allows a conclusion to the point at which the condensate droplets 6 has traversed the carpet of light.
    FIG. 15 schematically illustrates how the light incident on a condensate droplet 6 (represented by the large arrow) is scattered, the intensity of the scattered light (represented by small arrows) being dependent on a spherical detector 23 from the polar angle φ was calculated using a simulation model. In the model behind the condensate droplets 6 in the illumination direction (ie at a polar angle of 0 °) a shield 12 is arranged, so that only the scattered light impinges on the spherical detector 23.
    FIG. 15 a shows a diagram of the light intensity calculated for the condensate droplet 6 of FIG. 15 as a function of the polar angle φ. It can be seen that the scattered light at a low polar angle φ is the strongest, the maximum in the range of φ <15 ° occurs. The intensity then decreases sharply with increasing polar angle, and reaches minimum values in the range between approximately 80 ° and 140 °. A smaller peak value can be recognized in the range between approximately 150 ° and 180 °, which corresponds to the range of retroreflection.
    In addition to the attenuation of the laser intensity of the carpet of light 8 in the cover of a condensate droplet 6, the scattered light emanating from the condensate droplet 6 can thus also be evaluated in order to detect the condensate droplet 6. Instead of in the plane of the carpet of light 8 (ie the cutting plane) arranged light sensor 9 of FIG. 2, or in addition to this, therefore, a light sensor 9 'may be provided outside the plane of the carpet of light 8, which caused by a condensate droplets 6 stray light as a signal increase. Such a light sensor 9 'is referred to as a dark field light sensor and is indicated in FIG. 2 by the reference numeral 9'.
    Also, the dark field light sensor 9 'has in the illustrated embodiment, a plurality of linearly arranged sensor elements 10', wherein for a dark field light sensor, other arrangements for the sensor elements 10 'in question, since they are not linearly arranged in the plane of the carpet 8 have to be.
    The light sensor 9 'measures with each condensate droplets 6, which passes through the carpet of light 8, with its sensor elements 10', a signal pattern, which may differ depending on the passage of the condensate droplet 6 and can be evaluated for the particle count.
    Accurate matching of the evaluation to the type of particles measured and knowledge of the different patterns of signal rise and fall on different sensor elements 10, 10 'allows detection of whether the signal pattern is from a single condensate droplet 6 or from two or more consecutive ones the view of the light sensor 9, 9 'overlapping condensate droplets 6 has been generated. However, a reliable evaluation of these signal patterns is not always clearly possible, so that, as required, more complex embodiments may be required. In order to determine, for a particular application, the particular patterns and corresponding parameters for the evaluation, accurate tests are required, which are cumbersome but still within the skill of one of ordinary skill in the art having the benefit of the teachings of the subject disclosure.
    Although under particularly favorable conditions a single linear light sensor 9, 9 ', be it a dark field light sensor 9' or a bright field light sensor 9, may be sufficient to perform a count with acceptable accuracy, this may be insufficient for many applications. The accuracy of the counting can therefore be increased by evaluating the signals measured by the two light sensors 9 and 9 'jointly with the embodiment shown in FIG. 2, that is to say combining a bright-field and a dark-field measurement. In particular, in the measurement of condensate droplets 6 overlapping from the perspective of the bright field light sensor 9, the pattern measured by the dark field light sensor 9 'can enable an accurate evaluation of the number of condensate droplets 6 present at the same time in the light carpet 8.
    FIG. 3 shows a further embodiment according to the invention for the dark field measurement. In this case, the carpet of light 8 is limited to the measuring channel 1 by a shield 12. Behind the shield 12 is a lens unit 13, which in the case shown consists of two aspherical lenses. The lens unit 13 serves to focus scattered light, which is deflected by condensate droplets 6 above or below the plane of the carpet of light 8 past the shield 12, so that it falls on a dark field light sensor 9 ', although in the plane of Luminous carpet 8 is arranged, but is shielded by the shield 12 from directly incident laser light. The arrangement of a dark field light sensor 9 'behind the shield 12 in the plane of the carpet of light 8 is advantageous because it optimally utilizes the maximum light intensity of the stray field of the condensate droplet 6. Thus, by the provided behind the shield 12 lens assembly 13, the dark field light sensor 9 'measurable yield of stray light can be maximized. In order to direct the scattered light to the light sensor 9 ', other optical elements and lenses may also be used, such as cylindrical lenses or prisms.
    The embodiment illustrated in FIG. 3 results in a very pronounced signal pattern, in particular in the case of condensate droplets which pass through the carpet of light 8 near the focal point, which is preferably arranged in the middle of the measuring channel, and condensate droplets 6 which are in the vicinity of the focusing line 17, produce clearly distinct signal patterns, and where the respective different signal patterns allow conclusions to be drawn about the passage point. In this context, the "focus line" is the line through the focal point that runs parallel to the light sensor 9 '. In the case of condensate droplets 6, which pass through the carpet of light 8 in front of and behind the focusing line 17, a less pronounced signal is produced due to the different depth of field of the lens arrangement 13, so that it is also possible to draw conclusions about the passage point. Since the signal decreases very sharply with increasing distance to the focusing line 17, however, this embodiment is only suitable for measuring channels 1 with a small diameter or with a shallow depth.
    In order to increase the depth of field of the lens arrangement 13, and thereby facilitate a measurement of the condensate droplets 6 further away from the focusing line 17, a diaphragm 18 may be provided between the two aspherical lenses of the lens arrangement 13, as shown in FIG is shown. With this arrangement, it is possible, regardless of the position of the condensate droplet 6 in the carpet of light 8 to obtain clear signals from the light sensor 9 '. Fig. 5 illustrates the operation of such a panel in a sectional view taken along the plane of the carpet of light 8 of the device shown in Fig. 4.
    FIG. 6 shows a further advantageous embodiment of the counting unit 5 of the device according to the invention, in which case the plane of the light carpet 8 is arranged at an angle of 45 ° to the flow direction of the measuring channel 1. A lens unit 13, whose lens axis is aligned normal to the plane of the carpet of light 8, is arranged outside the measuring channel 1 so that the object plane coincides with the plane of the carpet of light 8. In the image plane, a light sensor 9 'is arranged with a two-dimensional arrangement of sensor elements 10', for example an image sensor, which may be designed as a CCD or CMOS sensor, or may have another known type.
    It would also be possible to carry out the embodiment shown in Fig. 6 with only one linear sensor arrangement by using cylindrical lenses instead of the two plano-convex lenses shown. However, this would worsen the achievable count limit.
    The arrangement of FIG. 6 leads to a sharp image recording of each condensate droplet 6, which traverses the carpet of light 8, regardless of its position in the measuring surface, since the entire measuring range lies in the object plane of the lens unit 13. By providing a two-dimensional light sensor 9 ', an optimum counting limit can thus be achieved without the need for additional lens systems or sensors.
    FIG. 6a shows the signal distribution effected by five condensate droplets 6a-6e on a two-dimensional sensor field, wherein five pronounced peak values can be seen, which each represent a condensate droplet 6a-6e. The measurement diagram shown in FIG. 6a was obtained by a simulation of a test arrangement according to FIG. 6 with the simulation program Zemax from Radiant Zemax, Redmond, WA 98053, USA, using the following parameters: rectangular laser source, x-width: 20 mm, y-width: 5 pm, analysis jets: 4x109, energy: P = 0.1 W, wavelength λ = 632.8 nm; Diameter of condensate droplets: DParticle = 5 pm; Refractive index of condensate droplets: n = 1.411; Position of condensate droplets in the carpet of light [x, y, z] in mm: P1 = [0, 0, 0], P2 = [5, 0, 0], P3 = [-5, 0, 0], P4 = [0.1 , 0, 5], P5 = [-0.1,0, -5], Rectangular detector, size of sensor field: x-width: 5mm, y-width: 5mm, number of pixels: 1000 x 1000; Lenses from Edmund Optics: Assortment number: 48182.
    The simulation was performed on five condensate droplets 6a-6e arranged in the carpet of light. Condensate droplets arranged along the Y-axis were displaced by 0.1 mm in the X-direction in order to avoid overlapping of several consecutive condensate droplets. Fig. 6a shows the intensity distribution as a function of the pixel position of the two-dimensional light sensor 9 '. As can be seen from FIG. 6a, all condensate droplets 6a-6e are clearly imaged by the light sensor, regardless of their position. In the arrangement of FIG. 6, in which the optical axis is oriented at a right angle to the plane of the light carpet 8, a value of 6.75 × 10 -8 W was determined for the detected scattered light energy at the detector. This places high demands on the quality and measurement accuracy of the light sensor 9 '.
    In order to increase the light intensity measurable by the light sensor, the inventors have sought an arrangement in which the optical axis of the lens array is at a lower angle to the plane of the carpet of light so that scattered light having a higher intensity can be received by the light sensor. As shown in Fig. 15a, the scattered light intensity at a polar angle to the laser beam axis of 90 ° is very small, but sharply increases at a smaller polar angle.
    FIG. 7 shows a further embodiment in which the objective axis of the lens unit 13 is oriented at an angle of 45 ° to the plane of the light carpet 8, so that the measurable scattered light intensity is increased at this angle. This arrangement corresponds to the Scheimpflug condition: This geometric principle describes the alignment of the object plane 19 of an optical system when the image plane 21 is not aligned parallel to the lens plane 20. The condition for maximum sharpness is that the object 19, image 21 and lens plane 20 intersect in a common straight line.
    The assembly was simulated under the same conditions set forth above for Fig. 6, and a value of 1.59 x 10 -6 W was determined for the energy received by a single condensate droplet from the light sensor 9 '. This corresponds to an improvement in the luminous efficacy by a factor of about 25, compared to the arrangement according to FIG. 6.
    Fig. 8 shows a further embodiment for the dark field measurement, in which no lens arrangement is required. In this case, the linear light sensor 9 'is preceded by a fiber bundle unit 14. Optical fiber bundles are fields of individual fiber optic cables with a given numerical aperture. By using low numerical aperture beams, only the light from certain areas penetrates through the fiber bundles. As a result, stray light can be directed to the sensor elements 10 'of the light sensor 9' in a targeted manner in order to detect condensate droplets 6 in a specific region of the measuring surface. Each of the sensor elements 10 'can thereby be assigned a specific area of the measuring area.
    FIG. 9 shows a further arrangement in which a bright field light sensor 9 is used, which is arranged in the plane of the light carpet 8. Between the light sensor 9 and the measuring area (i.e., the area of the carpet of light 8 which lies within the cross section of the measuring channel 1), a lens arrangement 13 with a diaphragm 18 is provided. (Instead of the lens unit 13, alternatively, a fiber bundle unit could also be used).
    Experiments carried out by means of an arrangement according to FIG. 9 revealed distinct signal patterns, irrespective of the position of the condensate droplets 6, whereby considerations were made as to how the coincidence probability can be reduced in order to increase the reliability and the counting limit. In Fig. 10 to 14, some approaches are shown, which are to be considered in minimizing the coincidence probability.
    FIG. 10 shows a signal of a single sensor element with two countable pulses h and l2 immediately following each other. The pulse count is performed based on a threshold value S. This results in a minimum time Tm at which the two consecutive pulses li, l2 are detected as two separate signals. The time Tdj corresponds to the pulse length of a pulse h at a predetermined threshold S. For pulses with a shorter time interval, the signal between the pulses does not fall below the threshold S, so instead of two pulses one is counted and thus there is a coincidence case.
    Another possible cause of cases of concurrency is explained in FIGS. 11a and 11b, in which two sensor arrangements are compared. In both representations, three condensate droplets 6a, 6b, 6c pass through the carpet of light at the same time, with a light sensor 9 having a plurality of linearly arranged sensor elements 10 being provided on the left side, as is used, for example, in the embodiment of FIG. 9 for brightfield detection , From the point of view of the light sensor 9, a condensate droplet 6a is covered by the condensate droplet 6b in front of it, so that the sensor detects the two condensate droplets 6a, 6b as a single condensate droplet.
    In order to reduce the coincidence probability considerably, as shown in FIG. 11b, two light sensors 9a, 9b, each with a plurality of linearly arranged sensor elements 10a, 10b, can be arranged at an angle to each other, each light sensor 9a, 9b having its own Lighting device and optionally may be associated with a separate lens unit (lens units and lighting devices are not shown in the schematic representation of FIG. 11 a and 11 b for reasons of clarity).
    In the evaluation of Konizidenzfällen is further required for a correct count lateral minimum distance xmin (relative to the longitudinal axis of the light sensor 9) between two condensate droplets 6a, 6b to be considered, as shown in Fig. 12. Condensate droplets that fall below this lateral distance are detected by the light sensor 9 as a condensate droplets.
    The influencing factors on the counting accuracy set out above can be determined and evaluated experimentally, computationally or by simulation on the basis of a specific parameterization, in particular by a suitable adjustment of the thickness d and the intensity of the carpet of light, the size of the measuring surface Speed of the fluid flow, the particle density and particle distribution in the fluid flow, the size of the condensate droplets, the time resolution and sensitivity of the sensor unit and the selection and arrangement of the measuring device to achieve optimum counting accuracy. For this purpose, in particular also several embodiments set forth herein can be combined with each other. Such modifications as well as the determination of a suitable parameterization are within the ability of one of ordinary skill in the art.
    For detecting the signals of overlapping condensate droplets different error detection algorithms can further be applied. As a basis for such algorithms, for example, the time profile of the measurement signal of one or more sensor elements can be used, as shown schematically in Fig. 13 and 14, for example.
    The right-hand side of FIG. 13 shows a diagram with the voltage profile of a detection of two closely successive condensate droplets measured by a sensor element. These condensate droplets 6a and 6b are shown schematically on the left side of FIG. 13 in front of the carpet of light 8 with the thickness d. The voltage waveform first rises from a base level V0 to a first value V-i indicating that the first condensate droplet 6a is completely in the region of the carpet of light. When the second condensate droplet 6b penetrates into the region of the carpet of light 8, the voltage curve increases to a second value V2, which corresponds to the changed light intensity, when both parts are simultaneously in the region of the carpet of light 8. Thereafter, when the first condensate droplet 6a exits the carpet of light 8, the voltage drops back to the value V-i and, when the second condensate droplet 6b leaves the carpet of light, to the base value V0. This characteristic curve would contribute to a high coincidence probability for a count which is based only on a threshold value S. By an evaluation that takes into account not only the threshold value S, but also the voltage curve, the count limit can be corrected over a wide range using statistical methods such as the evaluation by applying the Lambert-W function assuming a Poisson distribution.
    Error corrections can not only be applied to the signal values of individual sensor elements, but also the measured values of several sensor elements can be used for the error correction, as illustrated in FIG. In this case, a temporal sequence of measuring steps of eight linearly juxtaposed sensor elements 10a-10h is shown, which could arise, for example, when two condensate droplets 6a, 6b traverse the area of the light carpet scanned by these sensor elements 10a-10h, the condensate droplets being from the viewpoint partially overlap the light sensor. This leads to the illustrated time course of the measurements, wherein the condensate droplets 6a and 6b are represented by two spatially and temporally overlapping regions. In the overlapping area A, a particularly intense sensor signal is measured, which indicates that the measurement of the sensor elements 10d and 10e in the overlapping area A during these measuring steps was influenced by both condensate droplets 6a, 6b. Using statistical methods, such as the evaluation by applying the Lambert-W function assuming a Poisson distribution, the signals can be evaluated and the particle density can be determined correctly.
    Bezuaszeichen:
    Measuring channel (1) saturation unit (2)
    Resources (3)
    Condensation unit (4) counting unit (5)
    Condensate droplets (6)
    Lighting device (7)
    Carpet of light (8)
    Light sensor (9)
    Sensor elements (10)
    Computing unit (11)
    Shielding (12)
    Lens unit (13)
    Fiber bundle unit (14)
    Reservoir 15 porous wall layer or Wiek 16
    Focusing line 17
    Aperture 18
    Object level 19
    Lens plane 20
    Image plane 21
    Inlet 22 spherical detector 23
    权利要求:
    Claims (20)
    [1]
    claims
    1. A device for determining the number of solid particles in a fluid stream, in particular in exhaust gases of internal combustion engines, the device having a measuring channel (1) for the fluid flow to be measured, a saturation unit (2) for saturating the fluid with vapors of a resource (3), a condensation unit (4) for cooling the fluid flow and a counting unit (5) for counting the droplets of condensate (6) formed on the particles during cooling, the counting unit (5) comprising a lighting device (7), at least one light sensor (9) and a with the light sensor (9) connected computing unit (11) for determining the number of solid particles, characterized in that with the illumination device (7) on a cutting plane through the measuring channel (1) arranged light carpet (8) can be generated, which is a measuring surface which extends substantially over the entire cross-sectional area of the measurement channel (1), and that the L has a plurality of sensor elements (10) for scanning the entire extent of the measuring surface.
    [2]
    2. Apparatus according to claim 1, characterized in that the illumination device (7) has at least one laser light source.
    [3]
    3. Apparatus according to claim 1 or 2, characterized in that the light sensor (9) has at least one linear arrangement of a plurality of sensor elements (10).
    [4]
    4. Apparatus according to claim 3, characterized in that two linear arrangements of a plurality of sensor elements (10) at an angle, preferably a substantially right angle to each other are arranged.
    [5]
    5. Device according to one of claims 1 to 3, characterized in that the light sensor (9) for focusing scattered light at least one optical fiber bundle unit (14) is upstream.
    [6]
    6. Device according to one of claims 1 to 5, characterized in that the light sensor (9) is arranged in the cutting plane.
    [7]
    7. Device according to one of claims 1 to 6, characterized in that the light sensor (9) for direct measurement of the light of the carpet of light (8) is arranged.
    [8]
    8. Device according to one of claims 1 to 7, characterized in that between the light sensor (9) and the measuring channel (1) a lens unit (13), optionally with a diaphragm (18) is arranged.
    [9]
    9. Device according to one of claims 1 to 6, characterized in that the light sensor (9) by a shield (12) from the beam path of the carpet of light (8) is shielded, preferably between the shield (12) and the light sensor (9) at least one lens unit (13) is arranged for focusing scattered light.
    [10]
    10. The device according to claim 9, characterized in that the at least one lens unit (13) has a diaphragm arrangement.
    [11]
    11. Device according to one of claims 1 to 10, characterized in that the normal to the sectional plane with the axis of the measuring channel an apex angle α between 30 ° and 60 °, preferably 45 °, includes.
    [12]
    12. Device according to one of claims 1 to 11, characterized in that the light sensor (9) has a two-dimensional array of sensor elements (10) and a lens unit (13), wherein preferably the optical axis of the unit of light sensor (9) and lens unit (13) is aligned substantially normal to the measuring surface.
    [13]
    13. Device according to one of claims 1 to 11, characterized in that the light sensor (9) has a two-dimensional array of sensor elements (10) and a lens unit (13), wherein preferably the alignment of a main objective plane of the lens unit (13), the image plane of the light sensor (9) and the plane of the measurement surface corresponds to the blade plow condition.
    [14]
    14. A method for determining the number of solid particles in a fluid stream, in particular in exhaust gases of internal combustion engines, wherein the fluid flow to be measured passes through a measuring channel, a saturation unit in which the fluid is saturated with vapors of a resource, a condensation unit in which the fluid flow is cooled, and a counting unit, in which the condensate droplets formed on cooling the particles are counted, characterized in that defined in the area of the counting unit a sectional plane through the measuring channel a measuring surface, at which for illuminating the passing through the measuring surface condensate droplets Light carpet is generated, wherein the light deflections caused by the condensate droplets when passing through the carpet of light depending on the passage through the carpet of light of at least one sensor element of a plurality of sensor elements comprising light sensor we measured and wherein the measurements are evaluated by a computing unit to determine the number of solid particles.
    [15]
    15. The method according to claim 14, characterized in that the carpet of light is formed with preferably high-collimated laser light.
    [16]
    16. The method according to claim 14 or 15, characterized in that light of the carpet of light and / or scattered light is selectively shielded by aperture and / or shielding.
    [17]
    17. The method according to any one of claims 14 to 16, characterized in that extending the measuring surface over the entire part of the cross-sectional area traversed by the particle flow, preferably substantially over the entire cross-sectional area of the measuring channel.
    [18]
    18. The method according to any one of claims 14 to 17, characterized in that the ratio of the width of the measuring surface to the mean diameter of the condensate droplets is greater than 100, preferably greater than 500 and more preferably greater than 1000.
    [19]
    19. The method according to any one of claims 14 to 18, characterized in that at least two or more of the following parameters to optimize the counting accuracy are coordinated: the thickness (d) of the carpet, the size of the measuring surface, the speed of the fluid flow, the particle density in fluid flow, the particle distribution in the fluid flow, the size of the condensate droplets, the time resolution of the sensor unit.
    [20]
    20. The method according to any one of claims 14 to 19, characterized in that the light deflection of light sensors are measured, which have at least one linear array of a plurality of sensor elements or two at an angle arranged linear arrangements of a plurality of sensor elements or a two-dimensional array of sensor elements ,
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    同族专利:
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    WO2016180906A1|2016-11-17|
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    AT516759B1|2016-08-15|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    ATA50394/2015A|AT516759B1|2015-05-12|2015-05-12|Apparatus and method for determining the number of solid particles in a fluid stream|ATA50394/2015A| AT516759B1|2015-05-12|2015-05-12|Apparatus and method for determining the number of solid particles in a fluid stream|
    DE112016002145.3T| DE112016002145A5|2015-05-12|2016-05-12|Apparatus and method for determining the number of solid particles in a fluid stream|
    PCT/EP2016/060615| WO2016180906A1|2015-05-12|2016-05-12|Apparatus and method for determining the number of solid particles in a fluid flow|
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