System for measuring shear stress of a fluid with enhanced sensitivity

Patent metadata

Field	Value
Publication number	US-2016109348-A1
Application number	US-201514885433-A
Country	US
Kind code	A1
Filing date	Oct 16, 2015
Priority date	Oct 17, 2014
Publication date	Apr 21, 2016
Grant date	—

Abstract

A measurement system of a tangential force applied by a fluid is provided. The system includes a pipe in which the fluid flows, the pipe includes an inner surface contacting the fluid, and a cavity arranged in the inner surface of the pipe: and a MEMS and/or NEMS device measuring the tangential force including a support, a moving plate suspended from the support by a pivot link, the moving plate including a first face on which the fluid applies a tangential force. The device is fixed to the pipe such that the first face of the moving plate is flush with the inner surface of the pipe. The device includes two piezoresistive strain gauges suspended between the moving plate and the support, the tangential force applying force to the gauges.

First claim

1 - 25 . (canceled)

26 : A measurement system for measuring a tangential force applied by a fluid, said system comprising:
a pipe in which the fluid is intended to flow, the pipe extending over at least a portion along a given direction, referred to as the flow direction, the pipe comprising an inner surface that will be in contact with the fluid, and at least a cavity located in said inner surface of the pipe, at least one MEMS and/or NEMS device for measuring the tangential force comprising a support with a median plane and a moving plate, said moving plate being suspended from the support by at least one pivot link, said pivot link having a centre line perpendicular to the median plane of the support, said moving plate comprising a first face on which the fluid applies a tangential force and a second face opposite the first face, said device being fixed to the pipe and being located in the cavity such that the first face of the moving plate is flush with at least a zone of the inner surface of the pipe surrounding the cavity, said device also comprising at least one piezoresistive strain gauge suspended from and mechanically connected to the moving plate and the support, said gauge being arranged in the cavity such that the tangential force applied to the first surface of the moving plate by the fluid along the flow direction applies a compression or tension force to said piezoresistive strain gauge.

27 : The measurement system according to claim 26 , wherein the distance separating the plane containing the first face of the moving plate and the plane containing at least the zone surrounding the cavity is less than or equal to 200 μm.

28 : The measurement system according to claim 26 , wherein the gauge is located as close to the axis of the pivot link as possible.

29 : The measurement system according to claim 26 , comprising at least two gauges mounted in differential and electrically connected as a half Wheatstone bridge or at least four gauges mounted in differential and electrically connected as a Wheatstone bridge.

30 : The measurement system according to claim 26 , wherein the moving plate is suspended from the support by two pivot links, said device comprising at least two piezoresistive gauges.

31 : The measurement system according to claim 30 , wherein at least one rigid force transmission arm connects the moving plate to each pivot link, at least one piezoresistive strain gauge being suspended between a force transmission arm and the support.

32 : The measurement system according to claim 30 , wherein each force transmission arm is connected to the moving plate by at least elastically deformable member at least along the direction perpendicular to the fluid flow.

33 : The measurement system according to claim 26 , wherein the strain gauge is between 100 nm and 500 nm thick and the moving plate is between 3 μm and 40 μm thick.

34 : Measurement system according to claim 26 , wherein the pivot link comprises two beams with approximately equal lengths anchored onto the support at two separate points and anchored onto the moving plate at a point through which the axis of the pivot link passes.

35 : Measurement system according to claim 26 , comprising a limiter for limiting the fluid flow between the moving plate and the support.

36 : Measurement system according to claim 35 , wherein the limiter comprises structuring of the support and/or of the moving plate so as to form at least one low flow section zone between the support and the moving plate.

37 : Measurement system according to claim 36 , wherein structuring is done on the second face of the moving plate and/or on a zone of the support facing said face.

38 : The measurement system according claim 26 , comprising a device for preventing fluid flow between the moving plate and the support.

39 : The measurement system according to claim 38 , wherein the device for preventing comprises a flexible element at least partially encapsulating the moving plate and preventing fluid from flowing between the moving plate and the support.

40 : The measurement system according to claim 39 , wherein the element is a polymer or a polyimide.

41 : The measurement system according to claim 38 , wherein the device for preventing comprises a film made from a flexible material covering the first face of the moving plate and at least part of the support.

42 : The measurement system according to claim 39 , wherein the moving plate comprises slots, said slots being closed off by the flexible element or by the film.

43 : The measurement system according to claim 26 , comprising a reducer for reducing the sensitivity to parasite accelerations and vibrations.

44 : The measurement system according to claim 43 , wherein said reducer comprises a counterweight fixed to the moving plate and protected from the fluid so that no tangential force is applied to it.

45 : A system to measure the flow rate of a fluid flowing in a pipe comprising at least one measurement system according to claim 26 .

46 : The method of making a measurement system according to claim 26 , this method comprising:
the formation of a cavity in the inner surface of a pipe, manufacturing of a tangential force measurement device from a stack formed from a substrate, a sacrificial layer and at least a first layer of a conducting or semiconducting material, comprising formation of at least one piezoresistive gauge in the first layer, formation of the moving plate and the at least one pivot link in said stack and release of the gauge, the moving plate and the pivot link.

47 : The method of making a measurement system according to claim 46 , wherein after the gauge has been formed, a protection portion is formed on said gauge before the formation of a second layer of a conducting or semiconducting material on the first layer of a conducting or semiconducting material.

48 : The method of making a measurement system according to claim 47 , wherein after the protection portion has been formed, the second layer of a semiconducting, conducting or insulating material is formed on the first layer of a conducting or semiconducting material, and in which the moving plate and the pivot ink are at least partly formed.

49 : The method of making a measurement system according to claim 46 , comprising a step to fill at least the lateral gap between the moving plate and the support to form the device for preventing fluid flow between the moving plate and the support.

50 : The method of making a measurement system according to claim 46 , comprising a step in which a film is formed on the moving plate and on at least part of the support so as to close off the lateral gap between the moving plate and the support, to form the device for preventing the fluid flow between the moving plate and the support.

51 : The measurement system according to claim 26 , wherein the distance separating the plane containing the first face of the moving plate and the plane containing at least the zone surrounding the cavity is less than or equal to 100 μm.

Assignees

• Commissariat Energie Atomique

Inventors

• Robert Philippe
• Coutier Caroline

Classifications

• G01N11/02 Primary

  by measuring flow of the material · CPC title

• G01F1/28 Primary

  by drag-force, e.g. vane type or impact flowmeter · CPC title

• G01L1/04

  by measuring elastic deformation of gauges, e.g. of springs · CPC title

• G01F1/206

  Measuring pressure, force or momentum of a fluid flow which is forced to change its direction · CPC title

• G01L1/18

  using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material · CPC title