Pipeline sensor having a pipeline probe for sampling fluid from a pipeline and operating method

Abstract

A pipeline probe (20) for sampling fluid from a main fluid flow (Fm) in a pipeline (10) defines an elongated supply channel (21) and an elongated exhaust channel (22). The supply channel has at least one inflow opening (23) for transferring a partial flow (Fp) from the main fluid flow into the supply channel; the exhaust channel has at least one outflow opening for returning the partial flow from the exhaust channel to the main fluid flow after the partial flow has passed through an environmental sensor (30). The pipeline probe also includes at least one compensating opening (26) connecting the supply channel and the exhaust channel in a region between the closed end and the open end of the supply channel and the exhaust channel. By the presence of the compensating opening (26), a jet flow (Fj) is generated, which serves to reduce the pressure difference between the supply channel and the exhaust channel when the pipeline probe is exposed to the main fluid flow (Fm).

Description

Technical Field

[0001] The present invention relates to a pipeline probe for sampling a fluid from a main fluid flow in a pipeline, to a pipeline sensor equipped with such a pipeline probe, and to a method of operating such a pipeline sensor. Prior art

[0002] From the prior art, the following pipeline detector is known, which is used to transfer a partial flow from the main fluid flow in the pipeline, pass the partial flow to a sensing element arranged outside the pipeline, and return the partial flow to the pipeline after the partial flow has passed the sensing element. The pipeline detector usually has a tubular shape, which defines a longitudinal axis extending perpendicular to the main fluid flow in the pipeline. The pipeline detector defines two channels: a supply channel, which is used to transfer the partial flow from the pipeline to the sensing element outside the pipeline; and a discharge channel, which is used to return the partial flow from the sensing element to the pipeline. Each of the supply channel and the discharge channel is usually closed at the end located inside the pipeline and opened at the other end located outside the pipeline. The open end is in fluid communication with the sensing element. In order to transfer the partial flow from the pipeline to the supply channel, one or more inflow openings are provided in the wall of the supply channel. Usually, but not necessarily, these inflow openings face the fluid flow in the pipeline. Similarly, in order to return the partial flow to the main fluid flow, one or more outflow openings are provided in the wall of the discharge channel.

[0003] Examples of duct detectors of various shapes and structures are disclosed in US 2006 / 0027353 A1, US 2008 / 0257011 A1, US 2013 / 0160571 A1, US 2013 / 0255357 A1, EP 2 835 592 A1, and DE 10 2014 010 719 A1.

[0004] In operation, the pipe detector is arranged in the pipe so that the main fluid flow hits the pipe detector laterally and bypasses the pipe detector. Due to the Bernoulli / Venturi effect, the deflection of the main fluid flow will usually lead to a positive back pressure at the inflow opening and a negative pressure at the outflow opening. As a result, a pressure difference is generated between the supply channel and the discharge channel, the size of which depends on the flow rate of the main fluid flow in the pipe. This pressure difference will in turn drive a partial flow through the pipe detector, the flow rate of the partial flow being strongly dependent on the flow rate of the main fluid flow.

[0005] In some applications, it is desirable to minimize the pressure difference between the supply channel and the exhaust channel or at least minimize the dependence of the pressure difference on the flow rate of the main fluid flow. This is true in particular if the sensing element is a particle counter, since variations in the flow rate of the partial flow inevitably lead to undesirable variations in the number of particles passing the particulate matter sensor per unit time. Therefore, it may be desirable to keep variations in the pressure difference between the inflow opening and the outflow opening to a minimum.

[0006] US 2005 / 0097947 A1 discloses a duct detector, which forms a first passage extending from an air inlet to an air outlet. A second passage extends around a diverter plate to form a bypass of the first passage. An airflow measuring element is arranged in the second passage to measure the flow rate or flow of air passing through the second passage. If the airflow entering the duct detector contains dust or liquid matter, the dust or liquid matter passes through the first passage and is blocked from entering the second passage. Thereby preventing dust or liquid matter from contaminating the airflow measuring device in the second passage. In an embodiment, a step portion is formed at the intersection of the first passage and the second passage, thereby increasing the cross-section of the first passage there. Therefore, the dust or liquid matter contained in the airflow is temporarily blocked at the step portion. In another embodiment, the diverter plate has an inclined portion protruding into the first passage and tilted toward the air outlet. In another embodiment, the diverter plate has an inclined portion protruding into the first passage and tilted toward the air inlet. The inclined portion has a through hole.

[0007] EP 3 258 241 A2 discloses a particulate matter sensor device comprising a flow channel extending between a flow inlet and a flow outlet, a radiation source and a radiation detector. A flow conditioning device is provided for reducing the deposition of particulate matter on the radiation source, the radiation detector or on the channel walls in close proximity thereto. Summary of the invention

[0008] It is an object of the present invention to provide a duct detector which exhibits a reduced pressure difference between the supply channel and the discharge channel in the presence of a main fluid flow and / or a reduced dependence of the pressure difference on the flow rate of the main fluid flow.

[0009] This object is achieved by a pipeline detector according to claim 1. Further embodiments of the invention are given in the dependent claims.

[0010] Therefore, a pipeline detector for sampling fluid from a main fluid flow in a pipeline is provided. The pipeline detector defines an elongated supply channel and an elongated discharge channel, and the supply channel and the discharge channel extend substantially along the longitudinal axis of the pipeline detector. In operation, the longitudinal axis of the pipeline detector will advantageously extend across the main fluid flow, preferably perpendicular to the main fluid flow. Each of the supply channel and the discharge channel has a closed end and an open end, and the open end is configured to be directly or indirectly connected to an environmental sensor. The supply channel has at least one inflow opening, the at least one inflow opening is preferably formed in the lateral peripheral surface of the supply channel (the term "lateral" is used relative to the longitudinal axis of the pipeline detector), and the at least one inflow opening is used to transfer a partial flow from the main fluid flow to the supply channel. Similarly, the discharge channel has at least one outflow opening, the at least one outflow opening is preferably formed in the lateral peripheral surface of the discharge channel, and the at least one outflow opening is used to return the partial flow from the discharge channel to the main fluid flow after the partial flow has passed the environmental sensor. According to the invention, the pipeline detector comprises at least one compensation channel, which connects the supply channel and the discharge channel in a region between their respective closed ends and open ends so as to reduce the pressure difference between the supply channel and the discharge channel when the pipeline detector is exposed to the main fluid flow.

[0011] The inflow opening and the compensation channel are arranged and sized to allow a jet to pass through the inflow opening, and the jet is directed toward the compensation channel. When the pipeline detector is exposed to the main fluid flow, a jet is generated, and the inflow opening faces the main flow or is oriented relative to the main flow in some other way, so that a portion of the main fluid flow will enter the supply channel through the inflow opening. The portion of the main fluid flow that passes through the inflow opening is accelerated to form a jet. When the jet passes through the compensation channel, the jet is decelerated. In other words, the maximum flow velocity of the jet is higher upstream of the compensation channel (i.e., on the supply channel side) than downstream of the compensation channel (i.e., on the discharge channel side). The deceleration causes a negative pressure difference between the upstream and downstream sides of the compensation channel, which offsets the positive pressure difference caused by the back pressure at the inflow opening and the negative pressure caused by the Bernoulli / Venturi effect at the outflow opening. By appropriately selecting the dimensions of the inflow opening and the compensation channel, the jet flow can be tailored so that the negative pressure difference compensates the positive pressure difference to such an extent that both the value of the pressure difference generated between the supply channel and the exhaust channel and its dependence on the flow rate of the main fluid flow are greatly reduced.

[0012] In order to ensure that the jet is directed towards the compensating channel, the inflow opening and the compensating channel are preferably aligned along a common jet axis. The jet axis preferably extends across the longitudinal axis of the pipeline detector, in particular, perpendicular to the longitudinal axis. In use, the jet axis can advantageously be arranged along the direction of the main fluid flow. In some embodiments, the outflow opening is also arranged along the same jet axis. This can simplify the manufacture of the pipeline detector.

[0013] In order to decelerate the jet flow when it passes through the compensation channel, preferably, the free cross-sectional area of ​​the compensation channel is larger than the free cross-sectional area of ​​the inflow opening. In addition, preferably, the outflow opening has a free cross-sectional area greater than or equal to the free cross-sectional area of ​​the compensation channel to avoid excessive flow resistance at the outflow opening.

[0014] In particular, assuming that the inflow opening and the compensation channel have circular cross-sectional shapes, a first geometric diameter D1 can be defined for the inflow opening, and a second geometric diameter D2 can be defined for the compensation opening. Further assuming that the downstream end of the inflow opening and the upstream end of the compensation opening are separated by a distance W, the opening angle α can be defined by the following equation:

[0015]

[0016] The above definition of the opening angle can be easily extended to the case where the inlet opening and the compensating channel do not have a circular cross-sectional shape by replacing the geometric diameters D1 and D2 of the inlet opening and the compensating channel with their corresponding hydraulic diameters. The hydraulic diameter D of the opening or channel is defined as D=4A / P, where A is the cross-sectional area and P is the circumference of the opening / channel. For a circular cross-section, the hydraulic diameter is the same as the geometric diameter. It is advantageous if the opening angle so defined is in the range of 2° to 4°. This finding is independent of the exact cross-sectional shape of the inlet opening and the compensating channel, at least as long as the aspect ratio of each opening or channel is not too large. In the context of the present disclosure, the term "aspect ratio" should be understood as relating to the ratio between the longest diameter dimension and the shortest diameter dimension of the net cross-section of the opening or channel, the term "diameter dimension" relating to the distance between two points on opposite sides of the perimeter of the net cross-section, with the straight line through these points passing through the geometric center (center of mass) of the net cross-section. For example, under this definition of the term "aspect ratio", the aspect ratio of a circle is 1:1; for a square, the aspect ratio is etc. In particular, the above preferred range of opening angles of 2° to 4° is expected to be valid at least as long as the aspect ratio is below about 2.5:1, for example for rectangles whose ratio between long and short sides is below about 2:1, trapezoids whose average length to height ratio is between about 1:2 and about 2:1, ellipses whose ratio between major and minor axes is below 2.5:1, etc. Ideally, the cross-sectional area of ​​the inflow opening and the cross-sectional area of ​​the compensation channel are selected and oriented so that the cross-sectional area of ​​the compensation channel completely covers the cross-sectional area of ​​the inflow opening in a projection along the injection axis. For larger aspect ratios, different opening angles may be optimal.

[0017] In some embodiments, the compensating channel is formed by a compensating opening in a partition wall common to both the supply channel and the exhaust channel. In particular, the duct probe may have a tubular shape, preferably a cylindrical shape, and the duct probe may include a straight, flat partition wall separating the exhaust channel from the supply channel in the duct probe. In other embodiments, the compensating channel may be formed in a different manner, for example, if these channels are formed by separate conduits, the compensating channel may be formed by a short tube between the supply channel and the exhaust channel.

[0018] The duct detector can be supplemented by an environmental sensor to form a complete duct sensor. The environmental sensor can include a measuring channel and a sensing element inside or adjacent to the measuring channel, the measuring channel being directly or indirectly connected to the open ends of the supply channel and the discharge channel of the duct detector. In this way, a portion of the flow entering the supply channel through the inflow opening flows through the supply channel into the measuring channel, passes through the sensing element, and flows from the measuring channel through the discharge channel into the outflow opening. The connection between the duct detector and the environmental sensor can be direct, for example by mounting the sensor housing of the environmental sensor directly on the duct detector, or the connection between the duct detector and the environmental sensor can be indirect, for example via a rigid or flexible tube.

[0019] In particular, the environmental sensor may be a particulate matter sensor.In order to generate the partial flow at a defined flow rate, the environmental sensor may comprise a fan.

[0020] A method of operating such a pipeline sensor may include:

[0021] Arranging a pipeline detector in the pipeline, wherein a longitudinal axis of the pipeline detector extends across a main flow direction of the pipeline;

[0022] generating a main fluid flow through the conduit in a main flow direction so that the jet flows through the inflow opening towards the compensating channel; and

[0023] The partial flow is diverted from the inflow opening into the supply channel, the partial flow is passed through the measuring channel, past the sensing element, and the partial flow is passed through the discharge channel to the outflow opening.

[0024] In particular, the duct sensor is operated under such conditions that the jet flow is decelerated when it passes through the compensation channel, i.e., the jet flow has a higher maximum velocity upstream of the compensation channel than downstream of the compensation channel, so as to effectively reduce the pressure difference between the supply channel and the discharge channel. The jet flow is generated by accelerating the fluid passing through the inflow opening. In particular, advantageously, the jet flow has a maximum velocity in the supply channel downstream of the inflow opening and upstream of the compensation channel, which maximum velocity exceeds the average velocity of the main fluid flow at the same location that would occur without the duct detector.

[0025] Advantageously, the fluid of the main fluid flow is a compressible fluid.Preferably, the fluid is a gas, in particular, the fluid is air or an aerosol, ie a suspension of fine solid particles or liquid droplets in a gas such as air.

[0026] As already discussed, the environmental sensor may be a particulate matter sensor, and the method may include determining the particle concentration and / or size distribution in the partial flow using the particulate matter sensor. However, the environmental sensor may also be any other type of sensor for determining at least one characteristic of the partial flow, such as a gas sensor for determining the composition and / or concentration of one or more analyte gases in the partial flow, a humidity sensor, a temperature sensor, etc.

[0027] The environmental sensor may include a fan, and the method may include maintaining the partial flow using the fan. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, which are intended to illustrate the current preferred embodiments of the present invention, rather than to limit the present invention.

[0029] Figure 1 shows in a highly schematic manner a longitudinal cross-sectional view of a duct sensor comprising a duct detector according to the prior art;

[0030] Figure 2 Shows the description Figure 1 2D plot of simulated pressure distribution inside and outside the pipeline detector;

[0031] Figure 3 Shows the description Figure 1 A diagram showing a change in the pressure difference between the supply channel and the discharge channel of the pipeline detector as the flow rate of the main fluid flow in the pipeline changes;

[0032] Figure 4A longitudinal cross-sectional view of a duct sensor comprising a duct detector according to the invention is shown in a highly schematic manner;

[0033] Figure 5 A diagram illustrating the relative sizes of the inflow opening, the compensating opening, and the outflow opening is shown;

[0034] Figure 6 Shows the description Figure 4 2D plot of simulated pressure distribution inside and outside the pipeline detector;

[0035] Figure 7 Shows the description Figure 4 A diagram showing a change in the pressure difference between the supply channel and the discharge channel of the pipeline detector as the flow rate of the main fluid flow in the pipeline changes;

[0036] Figure 8 A front view of a portion of a duct probe having two inflow openings of different sizes and two associated compensating openings is shown in a highly schematic manner;

[0037] Fig. 9 A front view of a portion of a duct probe having a slit-shaped inflow opening and an associated slit-shaped compensating opening is shown in a highly schematic manner;

[0038] Fig.10 a cross-sectional view of a duct probe having a cylindrical shape and having a dividing wall dividing the interior of the duct probe into a supply channel and a discharge channel is shown in a highly schematic manner; and

[0039] Fig.11 A cross-sectional view of a duct probe having an elliptical outer boundary and two separate ducts inside, which form a supply channel and a drain channel, is shown in a highly schematic manner. DETAILED DESCRIPTION

[0040] Figure 1 A duct sensor comprising a duct detector 20 according to the prior art is shown in a highly schematic manner and not to scale.

[0041] The environment sensor 30 comprises a sensor element 31 accommodated in a sensor housing 32. The sensor housing 32 defines a measuring channel 33 in which or in the vicinity of which the sensor element 31 is arranged.

[0042] The environmental sensor 30 is arranged outside the pipe 10 carrying the main fluid flow Fm. The pipe 10 is defined by a pipe wall 11. An elongated pipe probe 20 extends from a sensor housing 32 through a probe opening of the pipe wall 11 to the inside of the pipe 10. The pipe probe 20 defines a longitudinal axis L extending perpendicular to the main fluid flow Fm. Inside the pipe probe 20, the following two parallel channels extend along the longitudinal axis L: a supply channel 21 and a discharge channel 22. These channels are separated by a partition wall 25. Each channel is closed at its respective end located inside the pipe 10 and is open at its respective end connected to the environmental sensor 30 outside the pipe 10. A lateral inflow opening 23 is present in the circumferential side wall of the supply channel 21, facing the main fluid flow Fm. A lateral outflow opening 24 is present in the circumferential side wall of the discharge channel 22. The outflow opening 24 is arranged downstream of the inflow opening 23 relative to the main fluid flow Fm, away from the main fluid flow Fm.

[0043] At its open end, the supply channel 21 leads to the measuring channel 33. The measuring channel 33 in turn leads to the discharge channel 22. The measuring channel 33 forms the only connection between the supply channel 21 and the discharge channel 22. In particular, the supply channel 21 and the discharge channel 22 are not connected anywhere along the length of the duct detector 20 between their closed and open ends, i.e. the partition wall 25 does not have any openings.

[0044] In operation, the main fluid flow Fm in the pipeline 10 hits the pipeline detector laterally. Due to the Venturi / Bernoulli effect, the main fluid flow Fm generates a positive back pressure at the inflow opening 23 and a negative pressure at the outflow opening 24. The pressure difference generated between the inflow opening 23 and the outflow opening 24 depends on the flow rate of the main fluid flow Fm.

[0045] Due to the pressure difference, a partial flow Fp is generated by the pipeline sensor. The partial flow enters the supply channel 21 through the inflow opening 23. The partial flow Fp flows upward through the supply channel 21 into the measurement channel 33, passes through the sensor element 31, and passes downward through the discharge channel 22, and then leaves the pipeline detector 20 at the outflow opening 24. The sensor element 31 detects one or more characteristics of the partial flow Fp. The flow rate of the partial flow Fp strongly depends on the pressure difference between the supply channel 21 and the discharge channel 22, which in turn strongly depends on the flow rate of the main fluid flow Fm.

[0046] Figure 2The simulated pressure distribution inside and outside the pipeline detector 10 is shown. The data shown in this figure is generated by numerical simulation of fluid dynamics using the software COMSOL Multiphysics version 5.4. The following assumptions are made in the simulation: the pipeline 10 has a square cross-section with a net width of 120 mm and a height of 100 mm. The pipeline detector 20 has a circular cross-section with an outer diameter of 15 mm and a wall thickness of 1.5 mm. Inside the pipeline detector, a straight, flat partition wall 25 with a thickness of 1.5 mm separates the supply channel 21 from the discharge channel 22. The length of the portion of the pipeline detector 20 extending inside the pipeline is 50 mm. The inflow opening 23 has a circular shape with a diameter of 2.0 mm. Its center is located at a distance of 30 mm from the pipe wall. Similarly, the outflow opening 24 has a circular shape with a diameter of 2.0 mm; its center is also located at a distance of 30 mm from the pipe wall. The fluid used for simulation is air under standard conditions (1013 hPa, 20°C). The main fluid flow Fm is assumed to have a uniform velocity distribution at the pipe inlet, with a velocity of 12 m / s. The k-epsilon turbulence model is used. The flow resistance of the environmental sensor is assumed to be essentially infinite, resulting in negligible flow of the partial flow Fp.

[0047] Figure 2 The simulation results in show that there is a considerable pressure difference dp between the supply channel 21 and the exhaust channel 22.

[0048] The simulation is repeated for different flow rates of the main fluid flow Fm, with the flow velocity at the pipe inlet ranging between 0 and 12 m / s. Figure 3 It is shown that the pressure difference dp strongly depends on the flow velocity v of the main fluid flow Fm in the pipeline 10. The pressure difference dp increases continuously and monotonically with the increase of the flow velocity and roughly follows a quadratic function. At a flow velocity of 6m / s, the pressure difference is about 32Pa. At a flow velocity of 12m / s, the pressure difference is about 130Pa.

[0049] Such a strong dependence of the pressure difference on the flow rate of the main fluid flow Fm may be undesirable. This is particularly true in applications where the environmental sensor 30 is a particulate matter sensor for determining the concentration and / or size distribution of particulate matter in the main fluid flow. A particulate matter sensor of a known type is used as a particle counter and includes a radiation source and a radiation detector. The radiation source, typically a laser, generates radiation in a measurement region. The radiation is scattered by particles entering the measurement region. The radiation detector, typically a photodetector, records a single scattering event from a single particle. From the frequency of the scattering events and the flow rate through the measurement region, the number concentration of the particles can be inferred. From the intensity of each scattering event, the size of each particle can be inferred. By combining these two quantities, a measure of the mass concentration of the particles can be obtained. Since the flow rate determines the number density, it is desirable to closely control the flow through the environmental sensor 30. However, the presence of a considerable and strongly varying pressure difference between the supply channel 21 and the exhaust channel 22 makes it difficult to control the flow rate.

[0050] Figure 4 A duct sensor according to an embodiment of the invention is shown in a highly schematic manner and not to scale. The general arrangement of the duct sensor is similar to Figure 1 The prior art duct sensor in the present invention. Furthermore, the duct sensor comprises an environmental sensor 30, which comprises a sensor element 31 and a sensor housing 32 defining a measurement channel 33 for the partial flow Fp. In the present example, the environmental sensor 30 further comprises a fan 34 for actively maintaining the partial flow Fp through the measurement channel 33. However, in other embodiments, the fan may be omitted. Furthermore, in the present example, the sensor element 31 is arranged in the measurement channel 33 in such a way that the partial flow Fp passes through the sensor element 31. However, in other embodiments, the sensor element 31 may be arranged adjacent to the measurement channel 33 so that the partial flow flows over the sensor element 31, such as Figure 1 Implementation method in .

[0051] like Figure 1 In the prior art embodiment, the supply channel 21 and the discharge channel 22 extend inside the pipeline detector 20 along its longitudinal axis L, and these channels are parallel to each other and separated by a straight, flat, elongated partition wall 25. Figure 1 In the prior art embodiment of FIG. 1 , each channel is closed at its respective end located inside the pipe 10 and is open at its respective end connected to the sensor housing 30 outside the pipe 10. Figure 1 In the prior art embodiment of FIG. 2 , lateral inflow openings 23 are present in the circumferential side wall of the supply channel 21 , facing the main fluid flow Fm, and lateral outflow openings 24 are present in the circumferential side wall of the discharge channel 22 , downstream of the inflow openings 23 .

[0052] and Figure 1 Compared to the prior art embodiment in FIG. 1 , a compensation channel 26 is present between the supply channel 21 and the discharge channel 22 in the region between their respective closed and open ends. The compensation channel 26 is formed by a compensation opening in a partition wall 25 that separates the supply channel 21 from the discharge channel 22. The inflow opening 23 and the compensation channel 26 are aligned along a common injection axis. The injection axis extends perpendicularly to the longitudinal axis L of the pipeline detector along the flow direction of the main fluid flow Fm. In this example, the outflow opening 24 is also aligned with the injection axis.

[0053] Due to the presence of the compensation channel 26, a jet flow Fj is generated through the inflow opening 23, and the jet flow is directed toward the compensation channel 26. When the jet flow passes through the compensation channel 26, the jet flow is decelerated, thereby generating a negative pressure difference between the supply channel 21 and the discharge channel 22. This negative pressure difference offsets the positive pressure difference caused by the main fluid flow Fm when the main fluid flow Fm hits the pipeline detector 20 and deflects around the pipeline detector 20. Therefore, the jet flow Fj serves to reduce the pressure difference between the supply channel 21 and the discharge channel 22 that would exist in the absence of the compensation channel 26. At the same time, the jet flow Fj reduces the dependence of this pressure difference on the flow rate of the main fluid flow Fm.

[0054] Simulations were performed to determine if Figure 4 The expected velocity distribution in and around the pipe detector is shown. Figure 2 The same assumptions are made in the simulations described above. The simulations show that the jet flow Fj is significantly accelerated when it passes through the inflow opening 23 and is decelerated again when it passes through the compensation channel 26. The maximum flow velocity of the jet flow Fj is much greater in the supply channel 21 upstream of the compensation channel 26 than in the discharge channel 22 downstream of the compensation channel 26. The maximum flow velocity of the jet flow Fj is also significantly greater than the average flow velocity of the main fluid flow Fm that would occur at the same location and at the same total flow through the pipeline without the pipeline detector.

[0055] In order to ensure that the flow velocity of the jet Fj is greater on the upstream side of the compensation channel 26 than on the downstream side of the compensation channel 26, the cross-sectional area of ​​the compensation channel 26 is advantageously greater than the cross-sectional area of ​​the inlet opening 23. In addition, in order to prevent the outlet opening from forming a bottleneck with excessive flow resistance, the cross-sectional area of ​​the outlet opening 24 is advantageously greater than or equal to the cross-sectional area of ​​the compensation channel 26. Figure 52 is shown by way of example. In this example, it is assumed that the inflow opening 23, the compensation channel 26 and the outflow opening 24 have a circular shape. The inflow opening 23 and the outflow opening 24 are each formed in the circumferential wall 27 of the pipeline detector; the compensation channel 26 is formed in the partition wall 25. The diameter of the inflow opening 23 is designated as D1, the diameter of the compensation channel 26 is designated as D2, and the diameter of the outflow opening 24 is designated as D3. The corresponding cross-sectional areas are designated as A1, A2 and A3, respectively. The width of the supply channel 21 measured between the inflow opening 23 and the compensation channel 26 along the injection axis N is designated as W. In this example, the discharge channel 22 has the same width W between the compensation channel 26 and the outflow opening 24. In order to decelerate the jet when it passes through the compensation channel 26, the cross-sectional area of ​​the compensation channel 26 is slightly larger than the cross-sectional area of ​​the inflow opening 23, that is, D2>D1. In the present example, the cross-sectional area of ​​the outflow opening 24 is identical to the cross-sectional area of ​​the compensation channel 26 , ie D3 = D2 .

[0056] In general, among others, the parameters D1, D2, D3 and W can be adjusted to optimize the dependence of the pressure difference between the supply channel 21 and the discharge channel 22 on the flow rate of the main fluid flow Fm. In order to more easily quantify the difference between the size of the inflow opening 23 and the compensation channel 26 independent of the absolute size, a dimensionless opening angle α can be introduced, which is defined by the following relationship:

[0057]

[0058] Instead of using the geometric diameters D1 and D2 , the corresponding hydraulic diameters may be used.

[0059] In order to evaluate the effect of the jet flow Fj on the pressure difference between the supply channel 21 and the discharge channel 22, the above Figure 2 The simulations shown in the figure assume the same assumptions as described in the Figure 4 The simulation of the pressure distribution inside and around the pipeline detector in FIG. The opening angle α is varied, and the dependence of the pressure difference between the supply channel 21 and the discharge channel 22 on the flow velocity of the main fluid flow Fm upstream from the pipeline detector is evaluated for each opening angle. It has been found that the optimal value of the opening angle α is (2.7±0.3)°, resulting in the smallest change in the pressure difference for flow velocities between 0 and 12 m / s. Although for the above combined Figure 2 This result was obtained for the particular detector size discussed, but it is expected that the result will depend only weakly on the absolute size of the detector, the precise shape of the detector, or the shape of the opening, as long as these variations are within reasonable limits. Of course, for duct detectors of completely different geometries or for openings of completely different shapes (e.g., narrow slots with large aspect ratios), different opening angles may be optimal.

[0060] Figure 6 A two-dimensional graph is shown showing the pressure distribution generated at the optimum opening angle of 2.7° for a flow rate of 12 m / s. Figure 2 Compared with the figure outside the pipeline detector in FIG. 1 , the pressure distribution is almost unchanged. However, due to the jet flow Fj, the pressure in the inflow opening drops sharply (from almost +100Pa to about -10Pa). The pressure in the supply channel 21 drops from about +100Pa to about -6Pa. On the other hand, the pressure in the discharge channel 22 rises again from about -27Pa to about -6Pa, which is also caused by the jet flow Fj. The total pressure difference generated between the supply channel 21 and the discharge channel 22 is almost zero.

[0061] Figure 7 The dependence of the simulated pressure difference dp between the supply channel 21 and the discharge channel 22 on the flow velocity of the main fluid flow Fm upstream from the pipeline detector is shown for an optimized opening angle of 2.7°. For flow velocities between 0 and 12 m / s, the pressure difference never exceeds 1.7 Pa, has a maximum value at a flow velocity of about 6 m / s, and is close to zero at a flow velocity of 12 m / s. This is consistent with Figure 3 In contrast to the simulated pressure difference of the conventional pipeline detector in , the pressure difference rises sharply with the increase of flow velocity and exceeds 120 Pa when the flow velocity is 12 m / s. These simulation results show that the present invention can achieve a significant reduction in pressure difference and a significant reduction in the dependence of pressure difference on the flow rate of the main fluid flow Fm.

[0062] Although simulations have been performed for a compensation channel 26 in the form of a single inflow opening 23, a single outflow opening 24 and a single compensation opening, each of which has a circular shape, a different number and geometry of these openings are conceivable. Figure 8 and Fig. 9 is shown by way of example.

[0063] Figure 8 It is shown that more than one set of inflow openings and compensation channels can be provided. These sets can have different sizes. In this way, the dependence of the pressure difference on the flow rate of the main fluid flow Fm can be further optimized. Figure 8 In the example of FIG. 1 , a first jet is generated by a first inflow opening 23 and a first compensation channel 26. A second jet is generated by a second inflow opening 23 'and a second compensation channel 26 '. Due to the different sizes of the inflow openings and the compensation channels, the negative pressure difference caused by each jet will be different for the two jets. By tailoring the sizes of the inflow openings and the compensation channels, the dependence of the pressure difference between the supply channel and the discharge channel on the flow rate of the main fluid flow Fm can be optimized. Figure 8Instead of providing a separate outflow opening for each group of first and second inflow openings and the compensating channel, it is conceivable to provide a single common outflow opening.

[0064] Fig. 9 It is shown that the inflow opening, the outflow opening and the compensation channel can each have a cross-sectional shape different from a circle. In the present example, the cross-sectional shape of the inflow opening and the cross-sectional shape of the compensation channel are slit-shaped and trapezoidal, the cross-sectional area of ​​the compensation channel completely covering the inflow opening in the projection along the common injection axis. By optimizing the shape and size of the inflow opening and the compensation channel, the dependence of the pressure difference between the supply channel and the discharge channel on the flow rate of the main fluid flow Fm can be optimized again.

[0065] Of course, many other shapes of inflow openings and compensating channels are conceivable.

[0066] Although the simulations in the above examples were performed for cylindrical pipe detectors with straight, flat dividing walls, different detector designs may be used. Fig.10 and Fig.11 In Fig.10 In the embodiment of the duct detector, there is a circular cross section and a straight flat partition wall 25 in which a compensation channel 26 in the form of a simple compensation opening is formed. The partial flow Fp through the supply channel 21 and the discharge channel 22 is indicated by a dot in a small circle and a cross in a small circle, the dot indicating the flow direction out of the plane of the drawing and the cross indicating the flow direction into the plane of the drawing. The jet Fj is indicated by an arrow drawn in dashed lines. In Fig.11 In an embodiment, the duct detector has an elliptical cross section. Two parallel conduits are arranged in the duct detector, forming a supply channel 21 and a discharge channel 22. A compensation channel 26 is formed by a short tube 28 between the conduits. Many other detector designs are conceivable, including designs with more than one supply channel and / or more than one discharge channel.

[0067] Although in Figure 4 In the embodiment of FIG. 1 , the environmental sensor 30 is directly connected to the open ends of the supply channel 21 and the exhaust channel 22 , but it is also conceivable to connect the environmental sensor 30 to the duct detector 20 via a rigid or flexible tube.

[0068] The present invention is particularly advantageous if the environmental sensor 30 is a particulate matter sensor for determining the concentration and / or size distribution of particulate matter in the primary fluid flow. However, the environmental sensor 30 need not be a particulate matter sensor. In other embodiments, the environmental sensor may be a gas sensor for determining the composition and / or concentration of one or more analyte gases in the primary fluid flow, a humidity sensor, a temperature sensor, etc.

[0069] The present invention allows for close control of flow through the environmental sensor 30, for example by using an integrated fan, without the need to compensate for pressure differentials within the duct probe created by the primary fluid flow.

[0070] Reference numerals list

[0071] 10 Pipe 32 Sensor housing

[0072] 11 Pipe wall 33 Measuring channel

[0073] 20 Duct detector 34 Fan

[0074] 21 Supply channel Fm Main fluid flow

[0075] 22 Discharge channel Fp Partial flow

[0076] 23, 23' into the opening Fj jet flow

[0077] 24, 24' Outflow opening L Longitudinal axis

[0078] 25 Partition wall N Injection axis

[0079] 26, 26' compensation channel A1, A2, A3 cross-sectional area

[0080] 27 Circumferential wall D1, D2, D3 diameter

[0081] 28 Tube W Width

[0082] 30 Environmental sensor α Opening angle

[0083] 31. Sensing element

Claims

1. A pipeline probe (20) for sampling a fluid from a main fluid flow (Fm) in a pipeline (10), The duct probe (20) defines an elongated supply channel (21) and an elongated discharge channel (22), wherein the supply channel (21) and the discharge channel (22) extend substantially along a longitudinal axis (L) of the duct probe (20), Each of the supply channel (21) and the exhaust channel (22) has a closed end and an open end, wherein the open end is configured to be directly or indirectly connected to an environmental sensor (30), The supply channel (21) has at least one inflow opening (23) for transferring a partial flow (Fp) from the main fluid flow (Fm) into the supply channel (21), and the discharge channel (22) has at least one outflow opening (24) for returning the partial flow (Fp) from the discharge channel (22) to the main fluid flow (Fm) after the partial flow (Fp) has passed the environmental sensor (30), The pipeline detector (20) comprises at least one compensation channel (26) connecting the supply channel (21) and the discharge channel (22) in a region between the closed end and the open end of each of the supply channel (21) and the discharge channel (22), in, The inflow opening (23) and the compensating channel (26) are arranged and dimensioned so that a jet (Fj) passes through the inflow opening (23), the jet being directed towards the compensating channel (26), and The inflow opening (23) and the compensation channel (26) are arranged and dimensioned so that the jet flow is decelerated when passing through the compensation channel (26) so as to reduce the pressure difference (dp) between the supply channel (21) and the discharge channel (22) when the pipeline probe is exposed to the main fluid flow (Fm).

2. The pipeline detector according to claim 1, wherein: The inflow opening (23) and the compensating channel (26) are arranged and dimensioned in such a way that the jet (Fj) is induced by accelerating a portion of the main fluid flow passing through the inflow opening (23).

3. The pipeline detector (20) according to claim 1 or 2, wherein: The inflow opening (23) and the compensating channel (26) are aligned along a common injection axis (N).

4. The pipeline detector (20) according to claim 1 or 2, wherein: The inflow opening (23) has a first cross-sectional area (A1), and the compensation channel (26) has a second cross-sectional area (A2), which is larger than the first cross-sectional area (A1).

5. The pipeline detector (20) according to claim 4, in, The inflow opening (23) has a first hydraulic diameter D1, wherein the compensation channel (26) has a second hydraulic diameter D2, and wherein the downstream end of the inflow opening (23) and the upstream end of the compensation channel (26) are spaced apart by a distance W, Where the opening angle α is defined by the following equation: And wherein the opening angle α is in the range of 2° to 4°.

6. The pipeline detector (20) according to claim 1 or 2, wherein: The duct detector comprises a partition wall (25) which separates the discharge channel (22) from the supply channel (21), and wherein the compensation channel (26) is formed by a compensation opening in the partition wall (25).

7. A pipeline sensor, comprising: A duct detector (20) according to any one of the preceding claims; as well as Environmental sensor (30), The environmental sensor (30) comprises a measuring channel (33) and a sensing element (31) arranged inside or near the measuring channel (33), and the measuring channel (33) is directly or indirectly connected to the open end of the supply channel (21) and the open end of the discharge channel (22).

8. The pipeline sensor according to claim 7, wherein: The environmental sensor (30) is a particulate matter sensor.

9. The pipeline sensor according to claim 7 or 8, wherein: The environmental sensor (30) includes a fan (34).

10. A method for operating a pipeline sensor according to any one of claims 7 to 9, the method comprising: Arranging a pipeline detector (20) of the pipeline sensor in a pipeline (10), wherein a longitudinal axis (L) of the pipeline detector (20) extends across a main flow direction of the pipeline (10); generating a main fluid flow (Fm) through the pipeline (10) in the main flow direction, thereby causing a jet flow (Fj) to pass through the inlet opening (23), the jet flow being directed towards a compensation channel (26) and being decelerated when passing through the compensation channel (26) so as to reduce the pressure difference (dp) between the supply channel (21) and the discharge channel (22) when the pipeline probe is exposed to the main fluid flow (Fm); and A partial flow (Fp) is transferred from the inflow opening (23) into a supply channel (21), passed through a measuring channel (33), past a sensing element (31), and passed through a discharge channel (22) to an outflow opening (24).

11. The method according to claim 10, wherein: The jet (Fj) is caused by accelerating a portion of the main fluid flow passing through the inflow opening (23).

12. The method according to claim 10 or 11, wherein: The jet flow (Fj) has a maximum velocity that exceeds the average velocity of the main fluid flow (Fm) in the absence of the pipeline detector (20).

13. The method according to claim 10 or 11, wherein: The environmental sensor (30) is a particulate matter sensor, and wherein the method comprises using the particulate matter sensor to determine a particle concentration and / or size distribution in the partial flow.

14. The method according to claim 10 or 11, wherein: The environmental sensor (30) comprises a fan (34), and wherein the partial flow (Fp) is maintained by the fan (34).

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