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DE-102013223372-B4 - DEVICE FOR DETERMINING A FLOW PARAMETER OF A FLUID STREAM

DE102013223372B4DE 102013223372 B4DE102013223372 B4DE 102013223372B4DE-102013223372-B4

Abstract

Device for determining a flow parameter (VD) of a fluid flow (FS), in particular a breathing gas flow, with a flow sensor (10) for generating an electrical signal (ΔTP) corresponding to the flow parameter (VD), which has a sensor chip (5, 5') having a substantially planar surface (2) on which a thermal membrane sensor element (12) is arranged, wherein the thermal membrane sensor element (12) has a first temperature sensor (7) and a second temperature sensor (7') as well as a heating element (3) arranged between the temperature sensors (7, 7'), and with a fluid channel (17) having a wall (4) for guiding the fluid flow in a flow direction (ST1), in which the surface (2) of the sensor chip (5, 5') is arranged, wherein the fluid channel (17) is designed such that the fluid flow (FS) flows along the same straight main flow line (HSL) on both sides of the sensor chip (5) when viewed in the flow direction (ST1), so that the fluid flow (FS) flows towards the sensor chip (5, 5') along a straight line, and that the fluid flow (FS) flows away from the sensor chip (5, 5') along the same straight line, wherein the surface (2) of the sensor chip (5, 5') is arranged parallel to the main flow line (HSL) and wherein a flow deflecting element (6) is associated with the surface (2) of the sensor chip (5, 5') which deflects at least one partial flow (UTS) of the fluid flow (FS) such that the partial flow (UTS) is directed obliquely towards the surface (2), wherein the flow deflection element (6) has a triangular shape in a section parallel to the main flow line (HSL) and perpendicular to the surface (2), wherein a point of the triangular shape faces the surface (2), wherein preferably a side of the triangular shape extending from the point intersects a straight line parallel to the main flow line (HSL) at an angle of at least 20°, preferably at least 30°, particularly preferably at least 40°, and/or at most 70°, preferably at most 60°, particularly preferably at most 50°.

Inventors

  • Frank Hedrich
  • Matthias Storz
  • Gerhard Kattinger
  • Sophie Billat
  • Rolf Bronner

Assignees

  • GS Elektromedizinische Geräte G. Stemple GmbH
  • Hahn-Schickard-Gesellschaft für angewandte Forschung e.V.

Dates

Publication Date
20260513
Application Date
20131115

Claims (18)

  1. Device for determining a flow parameter (VD) of a fluid flow (FS), in particular a respiratory gas flow, comprising a flow sensor (10) for generating an electrical signal (ΔTP) corresponding to the flow parameter (VD), which has a sensor chip (5, 5') having a substantially planar surface (2) on which a thermal membrane sensor element (12) is arranged, wherein the thermal membrane sensor element (12) has a first temperature sensor (7) and a second temperature sensor (7') as well as a heating element (3) arranged between the temperature sensors (7, 7'), and comprising a fluid channel (17) with a wall (4) for guiding the fluid flow in a flow direction (ST1), in which the surface (2) of the sensor chip (5, 5') is arranged, wherein the fluid channel (17) is configured such that the fluid flow (FS), viewed in the flow direction (ST1), flows along the same path on both sides of the sensor chip (5). a straight main flow line (HSL) such that the fluid flow (FS) flows towards the sensor chip (5, 5') along a straight line, and that the fluid flow (FS) flows away from the sensor chip (5, 5') along the same straight line, whereby the surface (2) of the sensor chip (5, 5') is arranged parallel to the main flow line (HSL) and wherein a flow deflecting element (6) is associated with the surface (2) of the sensor chip (5, 5') which deflects at least a partial flow (UTS) of the fluid flow (FS) such that the partial flow (UTS) is directed obliquely towards the surface (2), whereby the flow deflecting element (6) has a triangular shape in a section parallel to the main flow line (HSL) and perpendicular to the surface (2), wherein one apex of the triangular shape faces the surface (2), wherein preferably one side of the triangular shape extending from the apex a straight line running parallel to the main flow line (HSL) intersects at an angle of at least 20°, preferably at least 30°, particularly preferably at least 40°, and/or at most 70°, preferably at most 60°, particularly preferably at most 50°.
  2. Device for determining a flow parameter (VD) of a fluid flow (FS), in particular a respiratory gas flow, comprising a flow sensor (10) for generating an electrical signal (ΔTP) corresponding to the flow parameter (VD), the sensor chip (5, 5') having a substantially planar surface (2) on which a thermal membrane sensor element (12) is arranged, the thermal membrane sensor element (12) comprising a first temperature sensor (7) and a second temperature sensor (7') as well as a heating element (3) arranged between the temperature sensors (7, 7'), and a fluid channel (17) with a wall (4) for guiding the fluid flow in a flow direction (ST1), in which the surface (2) of the sensor chip (5, 5') is arranged, the fluid channel (17) being configured such that the fluid flow (FS) is viewed in the flow direction (ST1). The fluid flows along both sides of the sensor chip (5) along the same straight main flow line (HSL), such that the fluid flow (FS) flows towards the sensor chip (5, 5') along a straight line, and the fluid flow (FS) flows away from the sensor chip (5, 5') along the same straight line, wherein the surface (2) of the sensor chip (5, 5') is arranged parallel to the main flow line (HSL), and wherein a flow deflecting element (6) is associated with the surface (2) of the sensor chip (5, 5'), which deflects at least a partial flow (UTS) of the fluid flow (FS) such that the partial flow (UTS) is directed obliquely towards the surface (2), wherein the flow deflecting element (6) has a trapezoidal shape in a section parallel to the main flow line (HSL) and perpendicular to the surface (2), wherein a shorter base side (29) of the trapezoidal shape faces the surface (2), preferably a side (15) of the trapezoidal shape extending from the shorter base side (29) intersects a straight line parallel to the main flow line (HSL) at an angle (α) of at least 20°, preferably at least 30°, particularly preferably at least 40°, and/or at most 70°, preferably at most 60°, particularly preferably at most 50°.
  3. Device for determining a flow parameter (VD) of a fluid flow (FS), in particular a respiratory gas flow, comprising a flow sensor (10) for generating an electrical signal (ΔTP) corresponding to the flow parameter (VD), which has a sensor chip (5, 5') having a substantially planar surface (2) on which a thermal membrane sensor element (12) is arranged, wherein the thermal membrane sensor element (12) has a first temperature sensor (7) and a second temperature sensor (7') as well as a heating element (3) arranged between the temperature sensors (7, 7'), and comprising a fluid channel (17) with a wall (4) for guiding the fluid flow in a flow direction (ST1), in which the surface (2) of the sensor chip (5, 5') is arranged, wherein the fluid channel (17) is configured such that the fluid flow (FS), viewed in the flow direction (ST1), flows along the same path on both sides of the sensor chip (5). a straight main flow line (HSL) such that the fluid flow (FS) flows towards the sensor chip (5, 5') along a straight line, and the fluid flow (FS) flows away from the sensor chip (5, 5') along the same straight line, whereby the surface (2) of the sensor chip (5, 5') is arranged parallel to the main flow line (HSL) and wherein a flow deflecting element (6) is associated with the surface (2) of the sensor chip (5, 5') which deflects at least a partial flow (UTS) of the fluid flow (FS) such that the partial flow (UTS) is directed obliquely towards the surface (2), whereby the flow deflecting element (6) has a hexagonal shape in a section parallel to the main flow line (HSL) and perpendicular to the surface (2), wherein a first side (28) of the hexagonal shape is formed parallel to the surface (2) and faces the surface (2), wherein preferably a side (27) of the hexagonal shape extending from the first side (28) intersects a straight line parallel to the main flow line (HSL) at an angle (α) of at least 20°, preferably at least 30°, particularly preferably at least 40°, and/or at most 70°, preferably at most 60°, particularly preferably at most 50°.
  4. Device for determining a flow parameter (VD) of a fluid flow (FS), in particular a respiratory gas flow, comprising a flow sensor (10) for generating an electrical signal (ΔTP) corresponding to the flow parameter (VD), the sensor chip (5, 5') having a substantially planar surface (2) on which a thermal membrane sensor element (12) is arranged, the thermal membrane sensor element (12) comprising a first temperature sensor (7) and a second temperature sensor (7') as well as a heating element (3) arranged between the temperature sensors (7, 7'), and a fluid channel (17) with a wall (4) for guiding the fluid flow in a flow direction (ST1), in which the surface (2) of the sensor chip (5, 5') is arranged, the fluid channel (17) being configured such that the fluid flow (FS), viewed in the flow direction (ST1), flows along the same path on both sides of the sensor chip (5). a straight main flow line (HSL) such that the fluid flow (FS) flows towards the sensor chip (5, 5') along a straight line, and that the fluid flow (FS) flows away from the sensor chip (5, 5') along the same straight line, wherein the surface (2) of the sensor chip (5, 5') is arranged parallel to the main flow line (HSL) and wherein a flow deflecting element (6) is associated with the surface (2) of the sensor chip (5, 5') which deflects at least a partial flow (UTS) of the fluid flow (FS) such that the partial flow (UTS) is directed obliquely towards the surface (2), wherein the flow deflecting element (6) has a rhomboid shape in a section parallel to the main flow line (HSL) and perpendicular to the surface (2), wherein a tip of the rhomboid shape faces the surface (2), and preferably a side of the rhomboid shape extending from the tip is parallel to the The main flow line (HSL) intersects at an angle (α) of at least 20°, preferably at least 30°, particularly preferably at least 40°, and/or at most 70°, preferably at most 60°, particularly preferably at most 50°.
  5. Device according to one of the preceding claims, wherein the flow deflection element (6) is designed such that the partial flow (UTS) is directed obliquely towards the surface (2) in the flow direction (ST1) and in an opposite flow direction (ST2).
  6. Device according to one of the preceding claims, wherein a gap (14) between the surface (2) and the flow deflection element (6) is open in at least one direction perpendicular to the main flow line (HSL) and parallel to the surface towards the surface (2).
  7. Device according to one of the preceding claims, wherein the deflecting element (6) is arranged centrally to the thermal membrane sensor element (12) when viewed along the main flow line (HSL).
  8. Device according to one of the preceding claims, wherein the flow deflection element (6) is symmetrical in a section parallel to the main flow line (HSL) and perpendicular to the surface (2) with respect to an axis of symmetry (SA) perpendicular to the main flow line (HSL).
  9. Device according to one of the preceding claims, wherein the flow deflection element (6) is arranged in the fluid channel (17) such that a free cross-section (16) is provided between a side of the flow deflection element (6) facing away from the sensor chip (5, 5') and the wall (4) of the fluid channel (17), and/or wherein a free cross-section (18) is provided between a side of the sensor chip (5, 5') facing away from the flow deflection element (6) and the wall (4) of the fluid channel (17).
  10. Device according to one of the preceding claims, wherein the flow deflection element (6) is arranged in the fluid channel (17) such that it forms part of the wall (4), and/or wherein the sensor chip (5') is arranged in the fluid channel (17) such that it forms part of the wall (4).
  11. Device according to one of the preceding claims, wherein a minimum distance between the surface (2) and the deflecting element (6) is at least 0.5 mm, preferably at least 0.6 mm, particularly preferably at least 0.8 mm, and/or at most 2.0 mm, preferably at most 1.5 mm, particularly preferably at most 1.2 mm.
  12. Device according to one of the preceding claims, wherein the sum of the cross-sectional area (20) of the flow sensor (10) in the fluid channel (17) and the cross-sectional area (21) of the deflecting element (6) in the fluid channel (17) in a plane perpendicular to the main flow line (HSL) is at most 50%, preferably at most 30%, particularly preferably at most 10%, of the cross-sectional area bounded by the wall (4) of the fluid channel (17).
  13. Device according to one of the preceding claims, wherein the deflecting element (6) is designed as a freestanding deflecting finger (6).
  14. Device according to one of the preceding claims, wherein the thermal membrane sensor element (12) is arranged on a freestanding sensor finger (5).
  15. Device according to Claim 14 , wherein an extent (L) of the sensor finger (5) in a direction perpendicular to the main flow line and parallel to the surface is at least three times as large, preferably four times as large, particularly preferably five times as large, as an extent (W) of the sensor finger (5) in a direction parallel to the main flow line.
  16. Device according to Claim 14 or 15 , wherein the membrane sensor element (12) is arranged in a first third of the surface (2) at a free end (5a) of the sensor finger (5), and wherein the free end (5a) of the sensor finger (5) is opposite a fixed (5b) end of the sensor finger (5) to which electrical leads (19) are connected to the sensor finger (5).
  17. Device according to one of the preceding claims, wherein a side (26) of the flow sensor (10) facing the fluid flowing in the first flow direction (ST1) and/or a side (26') of the flow sensor (10) facing the fluid flowing in the second flow direction (ST1) is shaped such that the cross-section of the fluid channel (17) narrows in the respective flow direction (ST1; ST2).
  18. Device according to one of the preceding claims, wherein the flow parameter (VD) is a flow rate, a mass flow rate, a volume flow rate (VD) and/or a flow velocity of the fluid flow.

Description

The present invention relates to a device for determining a flow parameter of a fluid flow. Flow sensors for determining flow parameters, such as flow rate, mass flow rate, volumetric flow rate, or flow velocity of a fluid, are known in various designs and with different measuring principles from the prior art. The fluid can be a gas or a liquid. The gas or liquid can contain several different components or substances. Air, for example, can be such a gas or fluid containing water vapor. Flow meters are used in a wide variety of technical fields, such as aerospace, vehicle and engine control, heating and ventilation technology, and industrial process engineering. If, for example, air is considered a fluid, such a flow sensor is often also referred to as an anemometer, an air mass meter, or an air volume flow sensor or air mass flow sensor. Flow meters are also used in medical technology; for example, in spirometers, they are used to measure respiratory gases, i.e., the time-resolved measurement of the volume flow during inhalation and exhalation. Such a time-resolved measurement of the volume flow during inhalation and exhalation can be performed, for example, with thermal flow sensors, in particular with microelectromechanical membrane sensors (MEMS membrane sensors), in which the essential components such as heaters and temperature sensors are located on a thin membrane. In general, thermal flow sensors have the advantage of high measurement sensitivity at low fluid flow velocities. Breath gas measurement using thermal sensor elements, particularly MEMS membrane sensors, offers the advantages of high measurement sensitivity at low flow velocities for detecting the crucial reversal point between expiration (inhalation) and inspiration (exhalation) for mechanical ventilation, high measurement dynamics across the entire flow measurement range, and precise temporal resolution of highly dynamic respiratory curves. The lower the thermal mass of the sensor, the higher its temporal resolution, which is approximately 1 ms in the case of the MEMS sensor. The technical challenge in measuring respiratory gases or reliable volumetric flow rates with thermal sensors lies in the fact that the exhaled gas is 100% saturated with water. This can lead to condensation and increased aerosol formation under adverse operating conditions, as the temperatures of the hoses and the measuring device can fall below the dew point. MEMS sensors generally require significantly less energy than comparable thin-film sensors and are therefore particularly suitable for battery operation in portable devices. However, unlike thin-film sensors, their operating temperature is typically below 100°C, meaning that water droplets deposited on the sensor can have an uncompensable impact on the measurement signal, leading to inaccurate readings or even a complete signal loss. The heating energy emitted by the heating element during sensor operation is insufficient to heat away a large droplet within a reasonable timeframe. As a result, water accumulation on the sensor usually remains stable and does not evaporate. Evaporation can only occur during inspiration due to the maximum humidity during expiration. Since sensor failure during ventilation is critical, erroneous measurements due to water accumulation must be rare and, if they do occur, only last for a short time (< 10 seconds). For several years now, the so-called chamber head sensor has become established as a MEMS immersion sensor for measuring the flow of dry gases, and it would also be suitable for use in ventilation technology. In this sensor, the sensor chip is located in a small flow channel integrated into the tip of a probe. For measurement, the probe, or rather its tip, is positioned with the chamber opening parallel to the gas flow (e.g., in a pipeline) so that a defined portion of the flow passes through the small flow channel and is measured there. This arrangement can also be described as a tube-in-tube bypass. However, this measuring device is unsuitable in the presence of aerosols, as these can accumulate in the chamber via capillary action and disrupt the sensor signal. Furthermore, the entire measuring chamber, with its relatively high thermal mass, would have to be heated to a temperature above the dew point. This would significantly affect the temperature of the measured gas, potentially even leading to evaporation. A higher fungification temperature would involve a significantly higher energy expenditure. According to the DE 196 36 095 A1 An airflow sensor comprises a sensing device with a centrally mounted heating device located between two temperature-sensitive sensing elements along a flow path, wherein the sensing device is substantially flat between a first and second point along the flow path, and the heating device and the sensing elements are all located between the first and second point; a streamlined body having a convex, curved surface with respect to the sensing