Method for determining the particle velocity of an aerosol and aerosol measuring instrument

Abstract

The invention relates to a method for determining the particle velocity of an aerosol by means of an aerosol measuring instrument. An aerosol-particle flow flows through a measuring chamber and is illuminated with an electromagnetic beam. Scattered light is received and detected by a sensor. The signal duration in time of the scattered light signal is determined and the particle velocity of the aerosol is determined from the signal duration. Furthermore, the invention specifies an aerosol measuring instrument for determining the particle velocity of an aerosol, which is configured for carrying out the steps of the method according to the invention. Furthermore, a computer program with program code sections is specified, which is designed for carrying out the steps of the method according to the invention.

Description

Technical Field

[0001] This invention relates to a method for determining the particle velocity of aerosols and an aerosol measuring instrument. Background Technology

[0002] A method known in the prior art involves illuminating aerosol particles flowing through a measuring chamber using an electromagnetic beam, receiving the scattered light, and detecting the scattered light signal from the aerosol particles using a sensor. Particle velocity is a key parameter for characterizing aerosols. However, determining the particle velocity of an aerosol requires an additional, deterministic measuring instrument. Therefore, the known method for determining particle velocity is structurally costly and expensive. The corresponding situation applies to known aerosol measuring instruments. Summary of the Invention

[0003] Therefore, the objective of this invention is to eliminate the drawbacks of the prior art and improve the method by means of which the particle velocity of aerosols can be easily determined. Correspondingly, the equipment is suitable for known aerosol measuring instruments.

[0004] The task is solved by the method claimed in this invention. The method is characterized by determining the temporal duration of the scattered light signal from the aerosol-particle and determining the particle velocity of the aerosol based on the signal duration. In terms of apparatus, the task is solved by the aerosol measuring instrument claimed in this invention. This aerosol measuring instrument is characterized by a processing unit constructed such that the temporal duration of the scattered light signal from the aerosol-particle can be determined and the particle velocity of the aerosol can be determined based on the signal duration. According to this invention, a computer program having program code segments is provided, the computer program being designed to perform the steps of the method according to this invention when executed on a computer or a corresponding computing unit.

[0005] This invention is based on the fundamental idea that the duration of the measured scattered signal corresponds to the residence time of the aerosol particles in the measuring chamber. This concept allows the particle velocity of the aerosol to be determined by determining the signal duration. This eliminates the need for additional measuring instruments, such as flow meters, to determine the particle velocity of the aerosol. Consequently, the particle velocity can be determined more simply, and particularly structurally, more easily.

[0006] Preferably, the determined signal duration of the scattered light signal is corrected in order to achieve a more accurate determination of the particle velocity of the aerosol.

[0007] To correct for the signal duration, at least 10, preferably at least 100, and particularly preferably at least 500 measurements of the scattered light signal can be performed. Preferably, at least one measurement is performed on each individual aerosol particle, particularly all measurements are performed on each individual aerosol particle, wherein the aerosol particles are capable of flowing through the measurement chamber individually. This improves the accuracy of determining the signal duration. For example, correction can be performed through statistical analysis of the measurements. This is particularly equivalent to time-of-flight analysis of the aerosol particles.

[0008] The correction of the signal duration is performed, for example, by means of a frequency distribution of the signal duration. Here, each signal duration is assigned a corresponding frequency. The intervals of signal durations can be grouped, wherein preferably one signal duration is assigned to each group. The groups can be configured for a measurement channel in signal technology. Graphically, the frequency distribution is equivalent to, for example, a histogram in which the signal durations are plotted with respect to their respective frequencies.

[0009] To improve the accuracy of signal duration correction, the frequency distribution of the signal duration can be interpolated, preferably by means of piecewise polynomial interpolation. For example, spline interpolation, especially cubic spline interpolation, can achieve improved correction of signal duration.

[0010] In another advantageous embodiment of the invention, at least one, particularly a local maximum, of the frequency distribution is determined to correct for the signal duration. The maxima of the frequency distribution of the signal duration correspond to aerosol particles that flow through the measurement chamber in a direct path. The dispersion of the measured signal duration is based on collision processes occurring while traversing the measurement chamber or along an inclined path. By determining the maxima of the frequency distribution, more reliable conclusions about the actual particle velocities of the aerosols can be drawn. Depending on the geometry of the measurement chamber, multiple local maxima of the frequency distribution can be formed. Preferably, all local maxima of the frequency distribution are determined. According to the invention, these local maxima correspond to the maximum values ​​of the frequency distribution within, in particular, a user-defined interval.

[0011] The particle size of the aerosol can be determined, for example, by an aerosol measuring instrument, and the correction of the signal duration can be performed based on the particle size of the aerosol. By correcting the signal duration in relation to the particle size, the particle velocity of the aerosol can be determined more accurately. For this purpose, for example, a correction value can be assigned to each particle size, where the correction value corresponds to the particle size-related effect on the determined signal duration. The signal duration determined for this purpose, based on the particle size, can be corrected in relation to the particle size by calculating the correction value. In particular, the frequency distribution of the signal duration can be corrected in relation to the particle size. In another embodiment, the correction of the determined signal duration is performed based on the aerosol-particle material, which further improves the accuracy of the method. Here, a correction value can be assigned to each material of the aerosol-particle.

[0012] Preferably, a statistical variance parameter is determined using the frequency distribution to characterize, for example, the deviation of the frequency distribution. The variance parameter is assigned, for example, to a local maximum of the frequency distribution. For this purpose, the half-width (FWHM) of the at least one local maximum can be determined, the half-width corresponding to the deviation of the frequency distribution about the local maximum.

[0013] In another embodiment of the method according to the invention, the correction of the signal duration is based on the geometry of the measuring chamber. If the aerosol enters the measuring chamber, for example, at a first location, traverses the measuring chamber, and exits the measuring chamber at a second location, the particle velocity of the aerosol can be determined from the determined signal duration over time, knowing the path traversed within the measuring chamber. In another embodiment, the aerosol traverses the measuring chamber along at least two different paths. In this case, the frequency distribution has at least two local maxima. The number of determined signal durations corresponds to the number of possible paths along which the aerosol can flow through the measuring chamber. Because the particle velocity of the aerosol must be the same regardless of the path traversed through the measuring chamber, knowledge of the path traversed through the measuring chamber allows for correction of the determined signal duration for calculating the particle velocity of the aerosol.

[0014] Preferably, the correction for the signal duration includes a constant, which is particularly independent of the aerosol particle size. This constant is, for example, equivalent to an offset value configured for the aerosol measuring instrument and is also, particularly, independent of the aerosol particle velocity and / or the geometry of the measuring chamber. The constant is a time value and is, for example, within the range of 2µs to 10µs, preferably between 4µs and 6µs.

[0015] In an advantageous embodiment of the invention, at least two signal durations are used to determine the constant, each of which corresponds to a local maximum value in the frequency distribution. In particular, the quotient of two preferably calibrated signal durations is used. Especially preferably, to determine the constant, the correlation between the determined signal duration and the particle velocity is determined, particularly by means of measurements using a flow meter.

[0016] To correct signal duration, multiple steps can be implemented, such as using signal technology filtering, such as high-pass filtering and / or low-pass filtering, or filtering for noise suppression.

[0017] The volumetric flow rate of the aerosol is preferably determined by the determined particle velocity, for example, based on its flow behavior within the measuring chamber. In another advantageous embodiment of the invention, the aerosol flows through the measuring chamber as a laminar flow. Preferably, the aerosol flows through the measuring chamber as a uniform flow, wherein, according to the meaning of the invention, no significant acceleration of the aerosol is performed. In this case, the volumetric flow rate of the aerosol corresponds to its particle velocity.

[0018] In terms of equipment, the aerosol measuring instrument particularly has a display device by means of which the particle velocity of the aerosol and / or parameters configured for the particle velocity of the aerosol can be output.

[0019] The processing unit is preferably configured such that it performs the steps of at least one of the methods mentioned above. The electromagnetic beam can be configured as a preferably multi-colored beam and / or as a laser beam.

[0020] The processing unit of the aerosol measuring instrument can be connected to a flow device, which is specifically configured to adjust the flow velocity and / or particle velocity of the aerosol to a user-defined value. Preferably, the determined particle velocity value of the aerosol is transmitted to the flow device. For example, the flow device has at least one pump and / or at least one ventilator. The flow device is configured to generate a particularly variable airflow.

[0021] The invention can specify that the cross-section of the measuring chamber has a basic polygonal, particularly quadrilateral, shape. The measuring chamber can have at least one, preferably at least two, defined paths for aerosol movement through the measuring chamber, in order to simplify the determination and / or correction of signal duration. In an advantageous embodiment of the invention, the measuring chamber is configured as square. Preferably, the cross-section of the measuring chamber can have a basic T-shaped shape. This, for example, creates three paths for the aerosol, wherein the first path is longer than the other two paths, and the other two paths are of equal length.

[0022] The computer program according to the present invention is preferably executed on the control unit of the aerosol measuring instrument. Attached Figure Description

[0023] Other advantages and features of the invention arise from the claims and the following description, wherein various embodiments of the invention are described in detail with reference to the accompanying drawings. (Figures:)

[0024] Figure 1 A schematic diagram of an aerosol measuring instrument according to the present invention is shown.

[0025] Figure 2 A schematic diagram of the aerosol measuring instrument is shown.

[0026] Figure 3 A schematic cross-section of a measuring chamber with a basic rectangular shape is shown.

[0027] Figure 4 A flowchart of the method according to the present invention is shown.

[0028] Figure 5 A schematic cross-section of a measuring chamber with a basic T-shaped form is shown.

[0029] Figure 6 Another embodiment of the method according to the invention is illustrated in flowchart form.

[0030] Figure 7 The frequency distribution of the signal duration is shown.

[0031] Figure 8 The distribution of signal duration in relation to particle size is shown.

[0032] Figure 9 Show Figure 8 The distribution of interpolation,

[0033] Figure 10 Another frequency distribution of the signal duration is shown in histogram, and

[0034] Figure 11 Show Figure 10 Histogram after correction related to particle size. Detailed Implementation

[0035] Figure 1 The diagram illustrates an aerosol 10 containing solid and liquid aerosol particles 11 in a gas 12, such as air. These aerosol particles 11 may be, for example, water droplets, carbon black particles, material debris, pollen, and / or other organic and chemical substances.

[0036] In the region of aerosol 10, the aerosol measuring instrument 13 is set in the form of an aerosol spectrometer, the aerosol spectrometer being used to measure the particle diameter d of the aerosol.p Correspondingly, the particle size distribution c of aerosol 10 and aerosol-particle 11 was measured. n Aerosol particles 11 are thus drawn through by a downstream flow device (in the form of a pump device 32) via the inlet opening 14 of the aerosol meter 13 and through the flow tube 15, wherein the pump device 32 is located downstream. Figure 1 Roughly shown in the middle. The flow tube 15 is in accordance with... Figure 2 The aerosol measuring instrument 13 is roughly configured to be set perpendicular to the plane of the attached drawing.

[0037] Aerosol particles 11 are individually irradiated in the flow tube 15 by a collimated light beam 18 perpendicular to their flight direction. This collimated beam originates from the multicolor light source 16 and lens 17. Based on the resulting divergence, the aerosol particles 11 emit scattered light 19, which strikes a converging lens 20 perpendicular to both the flight direction of the aerosol particles 11 and the irradiation direction from the light source 16. The converging lens 20 focuses the scattered light 19 onto a photoelectric sensor 21, which detects the signal of the scattered light 19 and converts it into an electrical signal. An electronic processing unit 22 then processes the electrical signal and compares it with the particle diameter d of the aerosol particles 11. p Correspondingly determine the particle size distribution c n The spatial overlap of the beam 18, the measured scattered light 19, and the detected portion of the aerosol-particle 11 in the flow tube 15 defines a virtual spatial measurement chamber 23 in which the particle size distribution c is determined. n The flow of aerosol 10 and therefore aerosol-particle 11 in the area of ​​the measuring chamber 23 is laminar and uniform.

[0038] In the measurement, the light intensity of the scattered light 19 and, consequently, the electrical signal intensity, are measures of the particle size of the aerosol-particles 11, to which the particle diameter d is correspondingly configured. p This determines the particle size of aerosol-particle 11.

[0039] Figure 3 The measuring chamber 23 in the square embodiment is shown in cross-section with a basic rectangular shape. Aerosol particles 11 are incident one by one into the measuring chamber 23 in the upper region 24 and exit from the measuring chamber in the lower region 25. The movement of the aerosol particles 11 conforms to a laminar, uniform flow, such that the aerosol particles 11 undergo substantially no acceleration or deceleration within the measuring chamber 23. Therefore, the velocity v of the aerosol particles 11... p The duration of the motion through the measuring chamber 23 is constant.

[0040] Figure 4 The flowchart illustrates the method according to the invention: In order to determine the particle velocity v of aerosol-particle 11 p A time-dependent detection A is performed on the signal of scattered light 19 from aerosol-particle 11. The duration of the scattered light 19 signal is referred to as the signal duration t in this invention. s In the next step of the method, the particle velocity v is... p The signal duration t from aerosol-particle 11 s The following calculation B:

[0041] v p =s m / t s ,

[0042] Among them, s m It is the path traversed through the measuring chamber 23, between the upper region 24 and the lower region 25, and the geometry of the measuring chamber 23 is known. m The value is stored in processing unit 22. It is used to determine the signal duration t. s Each measurement was performed on a single aerosol-particle 11.

[0043] Particle velocity v p The value of C is output via a display device (not shown) on the aerosol measuring instrument 13. Particle velocity v p Since the lamellar, uniform flow of aerosol 10 in measuring chamber 23 is approximately equivalent to its flow velocity v a The flow rate is output via a display device.

[0044] Figure 5 Another embodiment of the measuring chamber 23 is shown, the measuring chamber having a T-shaped bottom surface in cross-section. The measuring chamber 23 has a centrally located first region 26 that is longer in the vertical direction, wherein a second region 27 that is shorter in the vertical direction is provided to the left of the first region 26, and a third region 28 that is shorter in the vertical direction is provided to the right of the first region 26. The path s1 corresponds to the movement of aerosol-particle 11 through the first region 26, and the path s2 corresponds to the flow movement of aerosol-particle 11 through the second region 27 or through the third region 28.

[0045] Figure 6 This illustrates a method for determining particle velocity v according to the invention. p Another embodiment of the method, wherein the method begins with step A as described above, i.e., the detection signal duration t s Begin. To determine the particle velocity v more precisely. p Now, let's continue with the correction signal duration t. s Therefore, in determining the signal duration ts The next step, C, continues with measurements and performs a total of 500 measurements, storing the signal duration t. s Each measurement is also performed on a single aerosol particle 11.

[0046] In the next method step, the signal duration frequency distribution E is created: signal duration t s The corresponding frequencies are plotted in histogram 29, which is exemplarily shown in... Figure 7 As shown in the figure. Due to the technical realities of signal technology, the signal duration t in the illustrated embodiment is... s The measurement channels are summarized as having intervals of 0.54 µs. This results in a histogram 29, which has two local maxima 30 and 31. The right-hand maximum 30 corresponds to the movement of aerosol-particle 11 through the first region 26 of the measurement chamber 23, and the left-hand maximum 31 corresponds to the movement of aerosol-particle 11 through its second region 27 or its third region 28.

[0047] In another method step, the determined signal duration t is determined. s The correction F is related to particle size. Experiments have shown that it is effective for different particle diameters d. p Measuring different signal durations t s This contradicts the fact that, in the lamellar and uniform flow of aerosol 10, all aerosol particles 11 move at the same particle velocity v. p Motion. The subsequent correction F takes into account the effect of particle size on the determined signal duration t. s The impact.

[0048] To compensate for this effect, following the method described above, the configured signal duration t is first determined for different particle sizes of aerosol-particle 11. s Among these, based on signal technology conditions, the range of particle size is summarized as channels, similar to following... Figure 7 Create a histogram as shown in Figure 29. The signal duration t is determined for each channel configuration. s The average value. Figure 8 The signal duration is shown based on the characteristics of the particle size of indoor air (black line), cement (dashed line), standard dust (gray line), and titanium dioxide (TiO2, dotted line). The curves for observing standard dust are shown below. Figure 9 .

[0049] The signal duration t of a channel s Determined as a reference value; in Figure 9 In the embodiment shown, channel 110 is selected as the reference channel, and the signal duration ts The corresponding reference value is approximately 19.65 µs and in Figure 9 Shown as a horizontal line. For the remaining channels, determine the signal duration t. s The difference ∆t between the value and the reference value. The difference ∆t is... Figure 9 The corresponding channel is represented and configured for the particle size. The difference ∆t configured for the particle size is therefore equivalent to the duration t of the correction signal related to the particle. s The significance of the correction value. Interpolation allows for a more accurate determination of the difference ∆t. The determined signal duration t is corrected in relation to particle size. s The duration of the signal is calculated using a correction value ∆t configured for the particle size.

[0050] Figure 10 Histogram 29 shows the determined signal duration t. s Another frequency distribution, in which no correction related to particle size has been performed. Figure 11 Show Figure 10 The histogram after correction is shown in Figure 29. Figure 9 The uncorrected histogram and Figure 11 A comparison between the corrected histograms shows that the maxima are 30 and 31. Figure 11 The corrected histogram is compared to in Figure 9 The middle part is larger and narrower. The determined signal duration t s The particle size-related corrections therefore allow for more accurate determination of the maxima 30, 31 and thus allow for more accurate determination of the particle velocity v. p .

[0051] To determine the quality of the measurement and the correction related to particle size, the full width at half maximum (FWHM) configured to a maximum of 30 on the right is calculated, which corresponds to the statistical variance parameter. Figure 9 In the comparison of uncorrected histograms, Figure 10 The corrected histogram, especially for the right-hand maximum of 30, has a lower half-width.

[0052] In accordance with Figure 6 In another step of the method, the signal duration t is determined. s The correction G is obtained by a constant t0, which is particularly related to the particle size and particle velocity v. p It is irrelevant and, in this respect, specifically equivalent to a zero-order effect. For a given signal duration t... s Applicable to:

[0053] t s =t w +t0,

[0054] Among them, t w This is equivalent to the actual signal duration. The particle velocity v of aerosol 10 is determined using a flow meter (not shown). p The constant t0 can be determined as follows:

[0055] t0=s / v p –tw

[0056] The value of constant t0 is stored in aerosol meter 13, and a flow meter is no longer needed for subsequent measurements.

[0057] After implementing the aforementioned correction, the particle velocity v p In the final step C, the output is displayed via a display device as already described. Based on the flow characteristics of aerosol 10, the flow velocity v of the aerosol... a Equivalent to particle velocity v p .

[0058] The determined particle velocity v of aerosol 10 p The pump device 32, which transmits the aerosol to the aerosol measuring instrument 13, delivers the aerosol particle velocity v. p Adjust to the user-defined value.

[0059] The method according to the present invention is implemented by executing a corresponding computer program on the processing unit 22 of the aerosol measuring instrument 13.

Claims

1. Used to determine the particle velocity (v) of aerosol (10) by means of an aerosol measuring instrument (13). p The method, in which, In a measuring chamber (23), an electromagnetic beam (18) is used to irradiate aerosol particles (11) of an aerosol (10) flowing through the measuring chamber (23). A sensor (21) receives the scattered light (19) and detects the signal of the scattered light (19) from the aerosol particles (11). The method is characterized by determining the duration (t) of the signal of the scattered light (19) from the aerosol particles (11) in time. s And according to the duration of the signal (t) s Determine the particle velocity (v) of aerosol (10). p ), by means of signal duration (t) s The frequency distribution of the scattered light (19) is used to correct the signal duration (t) of the signal. s ).

2. The method according to claim 1, characterized in that, In order to correct the signal duration (t) s Perform at least 10 measurements of the signal of the scattered light (19), and / or at least one of the measurements of a single aerosol-particle (11).

3. The method according to claim 1, characterized in that, The signal duration (t) s The correction is performed by interpolation.

4. The method according to claim 3, characterized in that, In order to correct the signal duration (t) s Determine at least one local maximum (30, 31) of the frequency distribution.

5. The method according to claim 1, characterized in that, The particle size of the aerosol (10) is determined by an aerosol measuring instrument (13), and the signal duration (t) s The correction is performed based on the particle size of the aerosol (10), wherein the signal duration (t) is corrected in relation to the particle size. s ), and assign a correction value (∆t) to each particle size of the aerosol (10).

6. The method according to claim 4, characterized in that, The variance parameter is determined by means of the frequency distribution, which is the local maximum (30, 31) assigned to the frequency distribution.

7. The method according to claim 1, characterized in that, The signal duration (t) s The calibration is performed based on the geometry of the measuring chamber (23).

8. The method according to claim 1, characterized in that, The signal duration (t) s The correction includes a constant (t0) that is independent of the particle size of the aerosol (10), wherein at least two defined signal durations (t0) are used to determine the constant (t0). s The durations of these two signals are respectively assigned to a local maximum (30, 31) of the frequency distribution.

9. The method according to claim 8, characterized in that, To determine the constant (t0), measurements are taken using a flow meter to determine the duration of the signal (t). s ) and particle velocity (v p The correlation between them.

10. The method according to claim 1, characterized in that, From the determined particle velocity (v) p Determine the flow velocity (v) of the aerosol (10). a ).

11. The method according to claim 1, characterized in that, The aerosol (10) flows through the measuring chamber (23) as a laminar flow and / or uniform flow.

12. Used to determine the particle velocity (v) of aerosol (10) p (13) aerosol measuring instrument, of which, Aerosol particles (11) are placed in a measuring chamber (23) such that the aerosol particles (11) can be irradiated by an electromagnetic beam (18), wherein the scattered light (19) of the aerosol particles (11) can be received by a sensor (21) and the signal of the scattered light (19) of the aerosol particles (11) can be detected. The processing unit (22) is configured to determine the signal duration (t) of the scattered light (19) of the aerosol particles (11) over time. s And according to the duration of the signal (t) s It can determine the particle velocity (v) of aerosol (10). p ), by means of signal duration (t) s The frequency distribution of the scattered light (19) is used to correct the signal duration (t) of the signal. s ).

13. The aerosol measuring instrument according to claim 12, characterized in that, The processing unit (22) is configured to perform the steps of the method according to any one of claims 1 to 11.

14. The aerosol measuring instrument according to claim 12, characterized in that, The electromagnetic beam (18) is configured as a multi-colored beam.

15. The aerosol measuring instrument according to claim 12, characterized in that, The processing unit (22) is connected to a flow device (32), which is configured to reduce the particle velocity (v) of the aerosol (10). p Adjust to the user-defined value.

16. The aerosol measuring instrument according to claim 12, characterized in that, The cross-section of the measuring chamber (23) has a basic polygonal shape.

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