WO2016207186A1

WO2016207186A1 - Measuring apparatus and measuring method for monitoring the drift of optical systems

Info

Publication number: WO2016207186A1
Application number: PCT/EP2016/064352
Authority: WO
Inventors: Helmut Pongratz; Walter Lukesch; Alexander Bergmann; Patrick FALK
Original assignee: Avl Ditest Gmbh
Priority date: 2015-06-22
Filing date: 2016-06-22
Publication date: 2016-12-29
Also published as: AT517420B1; AT517420A1

Abstract

Apparatus and method for measuring the turbidity of a particle-laden exhaust gas flow, in particular opacimeter, comprising a measuring chamber (3) which extends along a measurement axis (2) and is filled with and has the exhaust gas flow flowing through it for the turbidity measurement, a radiation detector (4) which is arranged outside the measuring chamber (3), a radiation source (5) which is arranged outside the measuring chamber (3) and the measuring radiation from which enters the measuring chamber (3) along the measurement axis (2) through an inner measuring radiation opening (7), permeates the exhaust gas flow in the measuring chamber (3) at least once, emerges from the measuring chamber (3) again through an inner measuring radiation opening (7) and strikes the radiation detector (4) in a form attenuated by the particle-laden exhaust gas flow, wherein a drift detector (23) which is in the form of a calibration radiation detector, in particular, is provided at a distance from the measurement axis (2).

Description

Measuring device and measuring method for drift monitoring of optical

systems

The invention relates to a device and a method according to the preamble of an independent patent claim.

In particular, the invention relates to a device for indirect particle measurement by measuring the turbidity of an exhaust gas stream, wherein the exhaust gas stream is optionally a diverted partial flow of an exhaust gas stream of an internal combustion engine or a partial exhaust stream taken from the tailpipe of the exhaust gas of a motor vehicle with an exhaust aftertreatment system.

Optionally, the device according to the invention is suitable or adapted to be used in an exhaust emission test in the context of a legal assessment or review of a motor vehicle or its exhaust aftertreatment system. In particular for a motor vehicle with a diesel engine exhaust gas measurements or particle measurements are prescribed in workshop inspections. Due to ever stricter pollutant or particle limit values, there is a fundamental demand for particle or turbidity measuring instruments with high measuring accuracy.

Devices for turbidity measurement of a particle-laden exhaust gas stream,

in particular opacimeters, are known and published in different embodiments.

For example, opacimeters are known which comprise a tubular measuring chamber through which the exhaust gas stream flows and a transilluminating device for scanning the measuring chamber. Due to the particles contained in the exhaust gas, parts of the radiation originating from a light source of the transilluminator are absorbed, scattered or reflected, so that the radiation is attenuated. This attenuated radiation is detected by a light detector. From the difference between the emitted radiation and the detected radiation, the opacity or the turbidity of the exhaust gas flow can be deduced. In order to improve the measurement accuracy and reliability of conventional opacimeters, the light source and the light detector are placed outside the measuring chamber and optionally protected by a scavenging air curtain from direct contact with the exhaust stream. However, conventional ones deteriorate

Barrier air curtains the measuring accuracy of the meter as it passes through the

Blocking air flow to a turbulence of the exhaust gas in the boundary region between sealing air and exhaust gas flow comes, whereby the illuminated measuring length varies in an unpredictable manner. Since the turbidity of the light beam is significantly dependent on the measuring length, this effect leads to measured value fluctuations or to a measurement inaccuracy.

In addition, unwanted attenuation of the measuring beam may also occur due to particles in the sealing air sucked in from the surroundings, whereby the measuring accuracy is in turn worsened.

Another known problem of conventional turbidimeters is the measurement drift, which is caused, for example, by temperature or pressure fluctuations in the region of the turbidity measurement

Detector and / or caused in the light source. According to the prior art, the measurement drift before the measurement and after the

Measurement compensating parameters recorded, which then allow a linear correction or by using calibration curves, a subsequent correction of the measured values obtained.

There is thus a conflict of objectives between different arrangements for

Improve measurement accuracy and reliability of conventional particle or turbidity meters.

The object of the invention is, in particular, to solve this conflict of goals.

The object of the invention is particularly characterized by the features of

independent claims solved.

Optionally, the invention relates to a device for turbidity measurement of a particle-laden exhaust stream, in particular an opacimeter comprising a along a measuring axis extending measuring chamber, which is filled and traversed for measuring turbidity of the exhaust stream, arranged outside the measuring chamber radiation detector disposed outside the measuring chamber radiation source whose measuring radiation enters the measuring chamber along the measuring axis through an inner measuring beam, the exhaust gas flow in the measuring chamber penetrated at least once, exits through an inner Meßstrahlöffnung again from the measuring chamber and attenuated by the particle-laden exhaust gas stream strikes the radiation detector, and at least one barrier air arrangement extending between the radiation source and the measuring chamber and / or between the

Radiation detector and the measuring chamber and / or between an optionally provided mirror and the measuring chamber extends.

Optionally, it is provided that the blocking air arrangement comprises at least two sealing air channels running side by side and transversely to the measuring axis and through which sealing air flows, wherein a first sealing air channel is arranged between a second sealing air channel and the measuring chamber, wherein the inner

Measuring beam opening of the measuring chamber opens into the first sealing air channel, and wherein the sealing air channels along the measuring axis measuring beam openings for the passage of the measuring radiation.

If appropriate, it is provided that the flow velocity of the barrier air of the first barrier air channel deviates in the region of the measurement axis from the flow velocity of the barrier air of the second barrier air channel in the region of the measurement axis.

If appropriate, it is provided that, when the barrier air arrangement is flowed through, the pressure of the blocking air of the first barrier air channel in the region of the measuring axis deviates from the pressure of the blocking air of the second barrier air channel in the region of the measuring axis.

Optionally, it is provided that the first sealing air channel along the

Sperrluftströmung a cross-sectional taper or a continuous

Has cross-sectional tapering, and that the first sealing air channel in the region of the measuring axis has a smaller cross-section than in the region of the junction and in particular is nozzle-shaped. Optionally, it is provided that the first sealing air channel along the sealing air flow has a cross-sectional taper, and that the second

Barrier air duct along the sealing air flow a substantially constant

Or that the second barrier air channel along the blocking air flow has a cross-sectional widening, or that the second barrier air channel along the sealing air flow has a cross-sectional taper, which is smaller than that

Cross-sectional taper of the first barrier air channel.

If appropriate, it is provided that, when the barrier air arrangement is flowed through, the pressure of the blocking air in the region of the measuring axis in the first blocking air channel is smaller than the pressure of the blocking air in the region of the measuring axis in the second blocking air channel.

Optionally, it is provided that the speed of the sealing air in the region of the measuring axis in the first sealing air channel is greater than the speed of the blocking air in the region of the measuring axis in the second sealing air channel.

If appropriate, it is provided that, when the barrier air arrangement is flowed through, the pressure of the blocking air in the region of the measuring axis in the first sealing air channel is equal to or slightly smaller than the pressure of the exhaust gas stream in the measuring chamber in the region of the inner zone arranged between the measuring chamber and the first sealing air channel

Measuring beam opening.

Optionally, it is provided that the sealing air arrangement has a third

Barrier air duct comprises, between the second barrier air duct and the

Radiation source, between the second barrier air channel and the radiation detector and / or between the second barrier air channel and the optionally provided outside the measuring chamber mirror for deflecting the measuring radiation is arranged.

If necessary, it is provided that, when the barrier air arrangement is flowed through, the pressure of the blocking air in the region of the measuring axis in the second barrier air channel is less than or equal to the pressure of the blocking air in the region of the measuring axis in the third barrier air channel.

If necessary, it is provided that the speed of the sealing air in the region of the measuring axis in the second sealing air channel is greater than or equal to the speed of the Blocking air in the range of the measuring axis in the third sealing air channel is.

Optionally, it is provided that the barrier air arrangement comprises at least one fan whose fan output is adjacent to the junction of a barrier air channel or a plurality of barrier air channels.

Optionally, it is provided that the fan is designed as an axial fan, wherein the axis of rotation of the axial fan substantially parallel to the course of Strömungsbzw. Barrier air duct or the flow or sealing air passages runs.

Optionally, it is provided that the fan is designed as a radial fan, wherein the axis of rotation of the radial fan is substantially normal to the course of the barrier air duct or the barrier air ducts.

Optionally, it is provided that a compensation volume for damping pulsations is provided between the fan outlet and the mouth of a sealing air channel or the sealing air channels. The air is thus first led out of the blower into a compensation volume in order to minimize pulsations of the pump and concomitant pressure fluctuations.

Optionally, it is provided that along the measuring axis directly before and immediately after the measuring chamber per a sealing air arrangement is provided, so that the

provided inside opposite ends of the measuring chamber

Measuring jet openings, in each case an adjacent first sealing air channel open.

Optionally, it is provided that both sides of the measuring chamber, along the

Measuring axis, in particular directly in front of and directly after the measuring chamber, one each

Barrier air arrangement is provided that the sealing air arrangements each comprise at least one fan, and that the fans are independently controllable, controlled, controlled or regulated and in particular that the one or a fan of a blocking air arrangement independently of one or the fan of the other blocking air arrangement controlled controllable , controlled or regulated. Optionally, it is provided that the inner measuring beam opening in a the

Measuring chamber limiting measuring chamber wall is provided, wherein the

Measuring chamber wall on its side facing the first sealing air passage in the

Is formed substantially following the course of the first barrier air channel and in particular transversely or normal to the measuring axis.

Optionally, it is provided that the inner measuring beam opening in a the

Measuring chamber limiting measuring chamber wall is provided, wherein the

Measuring chamber wall forms a tear-off edge together with the Meßstrahlöffnung, so that a constant gauge length is provided, which extends from the trailing edge of one side of the measuring chamber to the trailing edge of the other side of the measuring chamber, optionally emerging from the Meßstrahlöffnung exhaust gas through the sealing air or the blocking air flow the tear-off edge sheared off and

is transported or is.

Optionally, it is provided that the barrier air arrangement comprises at least one transverse to the measuring axis extending and traversed by sealing air barrier air channel, and that a drift detector is provided at a distance from the measuring axis. If appropriate, the drift detector is designed as a calibration radiation detector in all embodiments.

Optionally, it is provided that the drift detector and the radiation detector substantially identical radiation detectors, in particular identical

Photodetectors or photodiodes are.

Optionally, it is provided that the drift detector and the radiation detector are arranged side by side on one side of the measuring chamber, and with the exception of that caused by the direct irradiation by the measuring radiation

Energy input substantially the same environmental conditions and

especially exposed to the same ambient temperature.

Optionally, it is provided that the radiation detector and the drift detector are arranged next to or directly next to the radiation source, or that the Radiation source is arranged in a plane substantially normal to the measuring axis between the radiation detector and the drift detector.

Optionally, it is provided that the radiation source, the radiation detector and the drift detector are arranged on one side of the measuring chamber,

and that a mirror reflecting the radiation of the radiation source is provided on the opposite side, outside the measuring chamber, through which the radiation coming from the radiation source and passing through the measuring chamber along the measuring axis is reflected back through the measuring chamber onto the measuring chamber

Radiation detector is steered.

Optionally, it is provided that the mirror is a plane mirror or that the mirror is a curved mirror through which the radiation of the radiation source is focused or focused on the radiation detector.

Optionally, it is provided that a barrier air arrangement is provided, which extends between the mirror and the measuring chamber, and the transverse to the measuring axis of

Blocking air flows through or can be flowed through.

Optionally, it is provided that a reflection surface is provided, is reflected by the outgoing radiation from the radiation source to the drift detector, so that caused by the blocking air attenuation of the emanating from the radiation source radiation is detectable by the drift detector.

Optionally, it is provided that the reflection surface in the region of

Radiation source and the drift detector nearest barrier air arrangement or is arranged in the barrier air duct.

Optionally, it is provided that the reflection surface is a wall of a

Barrier air duct or provided on a sealing air duct surface is or comprises.

Optionally, it is provided that a monitoring device is provided for forming an adjusted output measured variable, wherein the corrected

Output variable a difference of the measured variable of the radiation detector minus is a proportional to the measured variable of the drift detector measured variable. The monitoring device is optionally in all embodiments

Calibration.

Optionally, it is provided that a monitoring device for

continuous or intermittent formation of an adjusted output measured variable is provided during the measurement, wherein the corrected output measured variable a continuously or intermittently formed difference of the measured variable of

Radiation detector minus a proportional to the measured variable of the drift detector measure is.

Optionally, the invention relates to a method for turbidity measurement of a particle-laden exhaust gas stream, in which the exhaust gas flow is conveyed through a measuring chamber extending along a measuring axis, and wherein the measuring radiation along the measuring axis, starting from a radiation source, a blocking air flow passes through a measuring beam opening into the measuring chamber in that the measuring chamber and the exhaust gas stream flowing therein are penetrated and attenuated at least once, exit the measuring chamber through a measuring beam opening, pass through a blocking air flow and strike a radiation detector provided in the region of a drift detector arranged at a distance from the measuring axis, comprising the following steps:

continuous or intermittent generation of a measured variable by the

Radiation detector

continuous or intermittent generation of a measured variable by the

Drift Detector,

- Continuous or intermittent formation of an adjusted output measured variable during the measurement, wherein the corrected measured variable is formed by subtracting a proportional to the measured variable of the drift detector measured variable of the measured variable of the radiation detector.

Optionally, it is provided that the radiation source and the radiation detector are arranged on one side of the measuring chamber and that on the

opposite side, outside the measuring chamber, a the radiation of

Radiation source is provided reflecting mirror through which the of the Radiation source coming, the measuring chamber along the measuring axis penetrating radiation reflected and is directed back through the measuring chamber to the radiation detector.

Optionally, it is provided that the radiation detector is arranged next to or directly next to the radiation source.

If appropriate, it is provided that a partial flow is branched off from a farther outward barrier air duct, and is conducted through the respective measurement jet opening into the adjacent, further inside, blocking air duct. This partial flow of the blocking air flow acts against optionally emerging from the measuring chamber particles, whereby the blocking air effect is improved. This can be effected in particular by the nozzle-shaped configuration of a sealing air channel. However, it is also in accordance with the idea of the invention to increase the pressure instead of reducing the pressure in a barrier air channel in the other barrier air channel. This can be effected for example by fluidic precautions, such as a throttle at the barrier air duct outlet.

Optionally, it is provided that a plurality of blowers are provided in a blocking air arrangement, which each open into a sealing air channel. Thus, two barrier air ducts may be provided, each barrier air duct is provided with its own fan. Optionally, the fans of a barrier air arrangement are separately controllable or controllable. By the choice or variation of the

Blocking air flow rate or the delivery rate of the blower can also

Fluidic conditions are created that increase the efficiency of the

Improve blocking air arrangement.

Optionally, it is provided that the blocking air flow is substantially parallel to the direction along which the exhaust gas enters the measuring chamber.

Optionally, however, the blocking air flow deviates from this direction.

Optionally, the blocking air flow is opposite to the direction of incoming exhaust gas. Optionally, in conventional installation position, the fan is arranged above or below, so that the blocking air flow is directed downward or upward. Optionally, a measuring beam opening or several measuring beam openings act as a diaphragm, as a result of which the radiation emanating from the radiation source is reduced to a measuring beam substantially following the measuring axis. Optionally, that measuring beam opening acts as a diaphragm which is closest to the radiation source. Optionally, the inner measuring beam opening acts as a diaphragm, which in the

Measuring chamber wall is provided, which is closest to the radiation source. The measuring beam and the aperture may have a round, square or rectangular cross-section.

Optionally, the device comprises a sampling probe for introduction into an exhaust tailpipe of a motor vehicle and a supply line connected to the sampling probe, for example designed as a hose line, for feeding the exhaust gas sample or the exhaust gas stream into the measuring chamber.

The device can be used for the calibration of the optical measuring system with a

Transmissionsfilter be set up. The one to use for calibration

Transmission filter can have a defined degree of turbidity, which is between 40% and 60%, based on a measuring chamber length of 430 mm. Optionally, the turbidity level is at or between 30%, 50% and 75% filter based on a gauge length of 215mm. The device can additionally be set up for the continuous measurement of the turbidity of the exhaust gas flow.

The sampling probe may have a means for attachment to the tailpipe, wherein a distance of the probe from the tube wall of at least 5 mm is maintained. The removal system is preferably designed such that no external air influences the measurement result.

The measuring chamber is preferably constructed such that it is uniformly flowed through by the exhaust gas and the measurement result is not falsified by the influence of the sealing air arrangements.

Preferably, a heating device is provided, so that the wall temperature of the measuring chamber in the measurement at all points more than 70 ° C, optionally about 100 ° C. The effective gauge length is preferably about or exactly 430mm. For example, in one-mirror versions, the length of the measuring chamber along the measuring axis is only about 215 mm, but the measuring chamber is interspersed twice, resulting in a measuring length of about 430 mm.

The radiation source used is preferably an incandescent lamp with a color temperature between 2800 K and 3250 K or a green LED with a wavelength between 550 nm and 570 nm. When using an incandescent lamp as a radiation source, the radiation detector may be designed to have a spectral sensitivity equal to the sensitivity curve of the human eye.

As an example, an axial fan with the following data can be used as fan:

Dimensions: about 60x60x25mm

Delivery rate: 10-80m ³ / h, preferably about 50-60 m ³ / h

Power consumption about 2-5W

Speed of the rotor about 1000-10000 min ^"1 , for example 8200min ^{" 1}

By way of example, a photodiode with the following parameters can be used as radiation detector and / or drift detector:

Detector surface: for example, about 7.5mm ²

Reverse voltage: e.g. about 60 v

Maximum dark current: e.g. about 30 nA

Maximum wavelength: e.g. about 900 nm

Angular degrees at half intensity: e.g. about 65 °

Dark current: e.g. about 2 nA

Photocurrent: e.g. about 55 uA

Power loss: e.g. about 215 mW

The term barrier air can also be referred to as purge air in all embodiments.

The invention will be further described with reference to exemplary embodiments and with reference to the figures, in which a schematic

Sectional view of components of a device according to the invention, in Fig. 2 is a schematic sectional view of details of another embodiment of a 3 shows a detail view of a section of an embodiment of a device according to the invention, and FIG. 4 shows a detail of a further embodiment of a device according to the invention.

Unless otherwise indicated, the reference numerals given below correspond to the following components:

Exhaust gas stream 1, measuring axis 2, measuring chamber 3, radiation detector 4, radiation source 5, blocking air flow 6, measuring jet opening 7, blocking air arrangement 8, sealing air 9, first sealing air channel 10, second sealing air channel 11, third sealing air channel 12, small cross section 13 (of the sealing air channel), opening 14 (of the barrier air channel), mirror 15, fan 1 6, fan outlet 17, rotation axis 18 (of the axial fan), end 19 (of the measuring chamber), measuring chamber wall 20, tear-off edge 21, measuring length 22, calibration radiation detector 23, reflection surface 24, monitoring device 25, supply line 26, Outlet opening 27, housing 28.

Fig. 1 shows a schematic sectional view of components of a

Device according to the invention. An exhaust gas stream 1 is conducted via a feed line 26 into a measuring chamber 3. The measuring chamber 3 preferably follows substantially tubular to the measuring axis 2. Furthermore, the measuring chamber 3 comprises at least one, preferably a plurality of outlet openings 27 for the exit of the exhaust gas flow. 1

In all embodiments, at the lateral ends 19 of the measuring chamber 3 or at a lateral end 19 of the measuring chamber 3 may be provided in each case a measuring chamber wall 20 and / or a cup-shaped or pan-shaped deflecting element. In all embodiments, the supply line 26 may open into the measuring chamber 3 approximately in the middle, transversely to the measuring axis. By this arrangement, a uniform distribution of the exhaust gas in the measuring chamber 3 can be effected. Furthermore, in all embodiments in the region of the lateral ends in each case at least one

Outlet opening 27 may be provided, so that the exhaust gas flow in the region of

Feed line 26 enters the measuring chamber 3, is divided there and exits at the lateral outlet openings 27 from the measuring chamber 3. In all

Embodiments, the measuring chamber 3 may have a smooth inner wall, so that the response in the measurement is improved.

For particle measurement are shown in FIG. 1, a radiation detector 4 and a

Radiation source 5 is provided. The radiation source 4 can in all Embodiments as a light source, for example as an LED, in particular as LED with a wavelength that substantially corresponds to a green color spectrum may be formed. The radiation detector 4 can be used in all embodiments

be formed for example as a light detector, photodetector or photodiode.

The radiation emitted by the radiation source 5 passes through an inner

Measuring beam opening 7 in the measuring chamber 3, where it passes through the provided in the measuring chamber 3 exhaust gas to from another or the same inner

Measuring beam opening 7 to emerge again from the measuring chamber 3. According to FIG. 1, the radiation detector 4 and the radiation source 5 are arranged on one side of the measuring chamber. On the other side of the measuring chamber 3, a mirror 15 is provided. This mirror 15 is arranged and formed such that the of the

Radiation source 5 outgoing and the measuring chamber 3 passing through the measuring radiation reflected at the mirror 15 and back through the measuring chamber 3 on the

Radiation detector 4 is directed and in particular focused or bundled. The radiation from the radiation source 5 impinging on the radiation detector 4 follows in FIG

Essentially the measuring axis 2. In the present embodiment, the measuring axis 2 consists essentially of two straight lines, which through the mirror 15 for

Steering on the arranged next to the radiation source 5 radiation detector 4 acute angle to each other.

To prevent contamination of the optical components, in particular of the

Radiation detector 4, the radiation source 5 and / or the mirror 15 to prevent these components outside the measuring chamber and in particular away from the exhaust stream 1 are arranged. In order to protect the optical components radiation detector 4, radiation source 5 and mirror 15, at least one, preferably a plurality of blocking air arrangements 8 may be provided. In the present

Embodiment is provided on both sides of the measuring chamber 3 each have a blocking air arrangement 8. The sealing air arrangements 8 each comprise at least one

Barrier air channel, which flows transversely to the measuring axis 2 of sealing air 9 or

can be flowed through. The blocking air flow 6 essentially follows the course of the sealing air channels. In the present embodiment of FIG. 1 are per

Barrier air arrangement 8 two barrier air ducts provided - in particular a first barrier air duct 10 and a second barrier air duct 1 1. The first barrier air channel 10 is between the second barrier air channel 12 and the measuring chamber 3 is arranged. At the end 19 of the measuring chamber 3, a measuring chamber wall 20 is arranged, in which the inner

Measuring beam opening 7 is provided for the entry of the measuring radiation. The

Blocking air flow 6 of the first sealing air channel 10, but also the sealing air channel 10 itself, essentially follow the course of the measuring chamber wall 20, so that the blocking air flow parallel to the surface extension of the inner measuring beam opening 7 passes it. The second barrier air channel 1 1 extends substantially parallel to the first barrier air channel 10. All barrier air channels are preferably along the

Measuring axis 2 provided with measuring beam openings 7, so that the measuring radiation, coming from the radiation source 5, along the measuring axis 2 for

Radiation detector 4 can be passed. The measuring radiation also passes through the blocking air 9.

Optionally, the embodiment of Fig. 1 comprises a third sealing air channel 12, not shown, which may be provided outside the second sealing air channel 1 1, as shown in particular in Fig. 2.

FIG. 2 shows a further embodiment in a schematic sectional view, the features of which essentially correspond to the features of FIG. 1. In the

Embodiment of FIG. 2, the radiation detector 4 and the radiation source 5 are arranged on opposite sides of the measuring chamber 3. In this embodiment, the mirror of Fig. 1 can be omitted. As a result, the measuring axis 2 is the shortest

Connection between the radiation source 5 and the radiation detector 4 is defined. The measuring radiation which strikes the radiation detector 4 from the radiation source 5 through the measuring chamber essentially follows the measuring axis 2. Furthermore, in the embodiment of FIG. 2, a third sealing air channel 12 is provided. Both

Barrier air arrangements 8 of the present embodiment thus comprise three sealing air channels 10, 11, 12.

However, it also corresponds to the idea of the invention that in any

Embodiment only two barrier air ducts are provided, that on one side two and on the other side three sealing air ducts or optionally that on one or both sides only a sealing air duct is provided. The blocking air arrangement 8 comprises at least one fan 16. The fan 1 6 is formed in the present embodiment as an axial fan. The axis of rotation 18 of the axial fan runs in a preferred manner parallel to the course or along the course of one or more barrier air ducts and in particular parallel to

Main extension direction of the blocking air flow 6. According to a preferred

Embodiment is the fan outlet 17 of the blower 16 directly to the

Junction 14 of the or the barrier air ducts 10, 1 1, 12 attached.

Fig. 3 shows a schematic sectional view of an inventive

Contraption. An optionally sealing trained housing 28 is penetrated by the supply line 26 for supplying the exhaust stream 1. The exhaust gas stream 1 is directed into the measuring chamber 3. The measuring chamber 3 comprises at each of its lateral ends 19 and at its lateral ends 19 a measuring chamber wall 20 which extends

optionally cup or pan-shaped inwards, so that the

Exhaust gas stream 1 is deflected in this area and in particular is deflected inward or is. In the region of the measuring chamber wall 20 or within the measuring chamber walls 20, outlet openings 27 are provided for exiting the exhaust gas flow 1, wherein the exhaust gas flow subsequently preferably collects in the interior of the housing and leaves the device or the housing through an outlet opening (not shown). A radiation source 5 emits radiation which is guided through measuring air openings 7 through the sealing air and into or through the measuring chamber 3. The

Barrier air arrangement 8 comprises a blower 1 6, through the sealing air 9 through the

Barrier air ducts 10, 1 1, 12 is passed. In the present embodiment, the first barrier air channel 10 has a cross-sectional taper. This means in particular that the sealing air duct 10 in the region of the junction 14 a larger

Cross-sectional area than in the region of the measuring axis 2, where the sealing air channel 10 has a smaller cross-sectional area 13. By this arrangement is a

formed nozzle-like shape. As a result of this nozzle-like shape, the sealing air 9 has a lower velocity in the region of the junction 14 than in the region of the measuring axis 2 or in the region of the smaller cross section 13. As a result, the blocking air 9 has a higher pressure in the region of the junction 14 than in the region of the junction Range of the measuring axis 2 or as in the region of the smaller cross-sectional area 13. For this Fluidic assumptions is assumed in all embodiments that the sealing air channel is flowed through.

The second barrier air channel 1 1 has a substantially constant cross-section in the present embodiment. Optionally, in all

Embodiments of the second barrier air channel 1 1 to a widening or tapering, wherein preferably the taper of the second sealing air channel 1 1 is formed smaller than the taper of the first sealing air channel 10. This means in particular that the ratio of inlet cross-section through the smaller

Cross-section of the first barrier air channel 10 is greater than the cross-sectional ratio of the confluence cross-section through the smaller cross-section of the second barrier air channel 1 first

By one of the above-mentioned configurations, the fluidic effect can be achieved that in the region of the measuring axis 2, in the second barrier air channel 12 is a slightly higher pressure p2, as in the adjacent region of the first

Barrier air channel 10. As a result, a partial flow of the blocking air flow 6 of the second barrier air channel 1 1 through a first barrier air channel 10 with the second

Barrier air channel 1 1 connecting measuring beam port 7 from the second barrier air duct 1 1 in the first barrier air duct 10 passed. The effect is known in particular as a venturi effect. This flow from the second barrier air channel 1 1 through the measuring jet opening 7 into the first barrier air channel 10 advantageously takes place counter to the flow of the exhaust gas 1 to be prevented in the direction of the radiation source 5 or the direction of that optical element which is to be protected by the blocking air arrangement 8.

Optionally, a third barrier air channel 12 is provided. According to the present embodiment, the third barrier air channel 12 is the same as the second barrier air channel 1 1. Optionally, more than three, for example 4, 5, 6 or more barrier air channels 12 are provided.

Preferably, the measuring chamber 3 is limited in the region of the first sealing air channel 10 by a measuring chamber wall 20. This measuring chamber wall 20 is penetrated by the inner measuring beam opening 7. The pressure of the exhaust gas stream 1 in the region of the inner measuring jet opening 7 of the measuring chamber wall 20 and in particular in the area The measuring axis 2 in the region of the measuring chamber wall 20 may be slightly greater than or equal to the pressure of the blocking air 9 in the first barrier air channel 10 in the region of the same measuring jet opening 7. This pressure conditions prevents blocking air 9 from entering the measuring chamber 3 and thereby falsifying the measurement results. Rather, a small or negligible part of the

Exhaust gas stream 1 through the measuring beam opening 7 of the measuring chamber wall 20 from. By this configuration, and in particular by the nozzle-like configuration of the first sealing air channel 10, exhaust gas entering the sealing air channel 10 is discharged rapidly and constantly transversely to the measuring axis 2. In particular, a tear-off edge 21 is formed by the measuring chamber wall 20 and the measuring beam opening 7. By means of this tear-off edge 21, by the configuration of the barrier air arrangement 8 and / or by the configuration of the measuring chamber wall 20, the measuring length 22 is advantageously kept constant.

4 shows a further embodiment of a device according to the invention in a schematic sectional illustration. The components correspond to

In the present embodiment, the radiation source 5 and the radiation detector 4 are arranged on one side of the measuring chamber 3. On the other side of the measuring chamber, a mirror 15 is preferably provided, via which the output from the radiation source 5 and through the

Measuring chamber 3 guided radiation back to the radiation detector 4 is reflected and in particular bundled.

In addition to the radiation detector 4, a drift detector 23 is provided. This

Drift detector 23 is arranged outside the measuring axis 2 or spaced from the measuring axis 2. This means that the measuring beam, which is passed through the measuring chamber 3, falls on the radiation detector 4 away from the drift detector 23.

The drift detector 23 is in particular configured to detect disturbances or disturbing influences in order to allow a calibration or a correction of the measurement

enable.

Preferably, the drift detector 23 is arranged on the same side as the

Radiation detector 4. According to the present embodiment, the

Radiation source 5 arranged on the same side of the measuring chamber 3. Especially the radiation detector 4, the radiation source 5 and the drift detector 23 are arranged in close proximity to one another, so that they are basically the same with the exception of the radiation to be detected by the radiation detector

Environmental conditions are exposed. In particular, the temperature generally prevailing in this area, the prevailing pressure and possibly also vibrations in both radiation detectors 4, 23 are almost identical. In particular, it is advantageous if the radiation detector 4 and the drift detector 23 are designed as identically constructed radiation detectors, in particular as identical photodiodes. Since the drift detector 23 is arranged away from the measuring axis and thereby measures only disturbance variables, the measured variable of the drift detector 23, or one to this

Measured value proportional value, for calibration or correction of the

Output values are subtracted from the measured value of the radiation detector 4.

Optionally, a reflection surface 24 is provided. This reflection surface 24 can also be arranged outside the measuring axis 2 or away from the measuring axis 2. Radiation, in particular scattered light, from the radiation source 5 to the drift detector 23 is reflected by the reflection surface 24. The reflection surface 24 is preferably arranged in the region of a sealing air channel and is preferably arranged in a sealing air channel of that blocking air arrangement 8, which lies closer to the drift detector 23. As a result, there is no exhaust gas between the drift detector 23 and the reflection surface 24, but almost exclusively blocking air 9. According to this embodiment, the measured quantity generated by the drift detector 23 is therefore also a measure of the weakening of the measuring radiation by the blocking air.

To form a corrected measured value or to form corrected measured values, a monitoring device 25 can be provided. In this

Monitoring device 25, the measured variable of the radiation detector 4 can be corrected by suitable combination with the measured variable of the drift detector 23. In particular, the measured variable of the drift detector 23 or a measured variable proportional to this measured variable is subtracted from the measured variable of the radiation detector. This calibration or correction can be carried out continuously or intermittently by the present configuration, in particular during the measurement. In general, it is noted that the invention is determined in particular by the features of the claims and is in no way limited to the stated embodiments. Thus, the configuration of the barrier air ducts according to FIGS. 1 or 2 can be combined with a drift detector according to FIG. 4. Also not shown embodiments in which only one barrier air channel per side is provided, may be provided with a drift detector to the measured variable of

Radiation detector to correct. In all embodiments, the supply line for supplying the exhaust gas into the measuring chamber may be arranged on one side of the measuring chamber, and the discharge opening for discharging the exhaust gas from the

Measuring chamber on the other side, whereby the measuring chamber is flowed through by the exhaust stream in one direction.

Claims

claims

1 . Device for measuring the turbidity of a particle-laden exhaust gas stream (1), in particular opacimeter, comprising:

a measuring chamber (3) which extends along a measuring axis (2) and which is filled and flowed through by the exhaust gas flow (1) for measuring the turbidity,

a radiation detector (4) arranged outside the measuring chamber (3),

a radiation source (5) arranged outside the measuring chamber (3) whose measuring radiation enters the measuring chamber (3) along the measuring axis (2) through an inner measuring jet opening (7), the exhaust gas flow (1) in the measuring chamber (3) at least once permeated, exits through an inner measuring beam opening (7) again from the measuring chamber (3) and through the particle-laden exhaust gas stream (1) attenuated meets the radiation detector (4),

- And at least one barrier air arrangement (8) extending between the

Radiation source (5) and the measuring chamber (3) and / or between the

Radiation detector (4) and the measuring chamber (3) and / or between an optionally provided mirror (15) and the measuring chamber (3), wherein the blocking air arrangement (8) at least one transverse to the measuring axis (2) extending and of sealing air (9) flowed through the sealing air duct (10, 1 1, 12), characterized in that spaced from the measuring axis (2) a drift detector (23) is provided which in particular as

Calibration radiation detector is formed.

2. Apparatus according to claim 1, characterized in that the drift detector (23) and the radiation detector (4) are substantially identical

Radiation detectors, in particular identically constructed photodetectors or

Photodiodes are.

3. Apparatus according to claim 1 or 2, characterized in that the

Drift detector (23) and the radiation detector (4) on one side of

Measuring chamber (3) are arranged side by side, and with the exception of those caused by the direct irradiation by the measuring radiation

Energieeintrags, are exposed to substantially the same environmental conditions and in particular the same ambient temperature.

4. Device according to one of claims 1 to 3, characterized in that the radiation detector (4) and the drift detector (23) are arranged next to or directly adjacent to the radiation source (5), or that the radiation source (5) in one to the measuring axis ( 2) is arranged in a substantially normal plane between the radiation detector (4) and the drift detector (23).

5. Device according to one of claims 1 to 4, characterized in that the radiation source (5), the radiation detector (4) and the drift detector (23) are arranged on one side of the measuring chamber (3),

and that on the opposite side, outside the measuring chamber (3), a mirror (15) reflecting the radiation of the radiation source (5)

is provided, through which the radiation from the source (5) coming, the measuring chamber (3) along the measuring axis (2) passing through radiation reflected and back through the measuring chamber (3) to the radiation detector (4) is directed.

6. The device according to claim 5, characterized in that the mirror (15) is a curved mirror through which the radiation of the radiation source to the radiation detector (4) is focused or focused.

7. Device according to one of claims 5 or 6, characterized in that a sealing air arrangement (8) is provided which extends between the mirror (15) and measuring chamber (3), and the transverse to the measuring axis (2) of sealing air (9). flows through or flowed through.

8. Device according to one of claims 1 to 7, characterized in that a reflection surface (24) is provided, through which radiation from the radiation source (5) outgoing radiation to the drift detector (23) is reflected, so that by the drift detector (23) through the blocking air (9) caused attenuation of the radiation from the radiation source (5) outgoing radiation is detectable.

9. Apparatus according to claim 8, characterized in that the

Reflection surface (24) in the region of the radiation source (5) and the Drift detector (23) nearest barrier air arrangement (8) or in the

Barrier air channel (10, 1 1, 12) is arranged.

10. Apparatus according to claim 8 or 9, characterized in that the

Reflection surface (24) is a wall of a sealing air channel (10, 1 1, 12) or on a sealing air duct (10, 1 1, 12) provided surface or comprises.

1 1. Device according to one of claims 1 to 10, characterized in that a monitoring device (25) for forming a rectified

Output measured variable is provided, wherein the corrected Ausgangsmessgröße is a difference of the measured variable of the radiation detector (4) minus a measured variable proportional to the measured variable of the drift detector (23).

12. Device according to one of claims 1 to 1 1, characterized in that a monitoring device (25) for continuous or intermittent formation of a corrected Ausgangsmessgröße is provided during the measurement, wherein the corrected Ausgangsmessgröße a continuously or intermittently formed difference of the measured variable of the radiation detector ( 4) minus a measured variable proportional to the measured variable of the drift detector (23).

13. A method for turbidity measurement of a particle-laden exhaust stream,

in which the exhaust gas flow is conveyed through a measuring chamber running along a measuring axis,

and in the measuring radiation along the measuring axis, starting from a radiation source, a blocking air flow passes through, through a

Measuring beam opening enters the measuring chamber, the measuring chamber and the exhaust gas flowing therein at least once passes through and thereby attenuated, exiting through a Meßstrahlöffnung from the measuring chamber, a

Permeated by a blocking air flow and impinges on a radiation detector which is provided in the region of a drift detector arranged at a distance from the measuring axis,

comprising the following steps:

continuous or intermittent generation of a measured variable by the Radiation detector

continuous or intermittent generation of a measured variable by the drift detector,

- continuous or intermittent formation of a corrected

Output measured variable during the measurement, wherein the corrected measured variable is formed by subtracting a proportional to the measured variable of the drift detector measured variable of the measured variable of the radiation detector.