EMRP-ENG59: Sensor development and calibration method for inline detection of viscosity and solids content of non-Newtonian liquids

• Forschungsstelle: METAS
• Projektnummer: F-5135.30037
• Projekttitel Englisch: EMRP-ENG59: Sensor development and calibration method for inline detection of viscosity and solids content of non-Newtonian liquids

Schlüsselwörter (Englisch)

Rheology, complex fluids, non-Newtonian fluids, viscosity, density, solid content

Kurzbeschreibung (Englisch)

Various industries, including the oil and gas industry, are in need of sensors and a metrology standard for the measurement of the viscosity of complex, non-Newtonian fluids. Typical non-Newtonian fluids are paint, blood, soup, and drilling fluids and contain a large amount of solids and a viscosity that changes with the velocity gradient or shear rate. As an example, a good fresh paint holds the solids in place and does not flow due to gravity. It should flow to some extent, however, while painting a wall.
It is known that the underlying non-Newtonian physics do influence the measurement of commonly used viscosity meters, but the resulting uncertainty and inaccuracy has never been evaluated systematically. The joint research project (JRP) ENG59 NNL will review the physics impacting the viscosity of non-Newtonian liquids, and map out the fundamental measurement uncertainties of existing viscosity measurement tools as well as potential alternative measurement techniques.
In addition, the typical use of upgraded or new viscosity measurement techniques is outside the laboratory in harsh operational conditions. On drilling platforms, for example, the sensors have to function continuously and reliably. This requires on site calibration methods and continuous, in line or ad line solutions. The ultimate objective of the JRP is to evaluate the preferred measurement methods in actual field conditions and at full scale on the drilling rig test facility of the international research institute for oil and gas (IRIS). As a result of this JRP a new metrology standard will be developed for in-line viscosity measurements of non-Newtonian fluids. Creating such a standard will require intense scientific work. Furthermore, a calibration guide for rheology sensors will be developed.

This project is part of the European Metrology Research Programme (EMRP, http://www.euramet.org/index.php?id=emrp); it is partly funded by the European Union on the basis of Decision No 912/2009/EC.

Projektziele (Englisch)

• Define a standardised calibration method for viscosity measurement devices measuring non-Newtonian fluids at a range of temperatures and rates of shear in their operational environment. This will include the development of a set of non-Newtonian calibration liquid in the form of Standard Reference Materials.
• Investigate the applicability of existing measurement standards on non-Newtonian fluids.
• Develop and improve sensors for inline measurement of viscosity, density, particle size distribution and solids content.

Abstract (Englisch)

Calibration standards
The project was unable to reproducibly produce a set of validated calibration standards in the form of CRMs for complex, non-Newtonian fluids. External to this project, attempts by the National Institute of Science and Technology (NIST) in the USA to formulate a Standard Reference Material (SRM) for concrete have been plagued by similar issues with reproducibility over the course of at least 7 years. Inadequate definition of the formulation and preparation method is believed to be the most significant cause of this.

Physical behaviour of complex fluids using existing viscometer techniques and rheometers
At project partners VSL, PTB, METAS, IPQ, INRIM and CNAM new, advanced, rotational rheometers were purchased and added to their previously available (capillary flow) instrumentation for measuring the viscosity of Newtonian fluids. A rheometer measures the way in which a liquid flows in response to applied stresses, and these new rotational rheometers measure torque and (rotational) speed and can operate in such a way that either of these is maintained at a programmable constant value. For non-Newtonian fluids, where viscosity may change with the applied mechanical shear, knowledge of the duration of the shear, its rate and direction of change (i.e. either increasing or decreasing) is vital. Modern electronically commuted motors under software and firmware control can be used for this. However, traceable calibration to the SI base units of torque, speed and temperature measured using such advanced techniques remains a challenge.

IMBiH developed a Computational Fluid Dynamics (CFD) model for a rotational rheometer using two different arrangements of the rotor and stator and for non-Newtonian fluids with or without added particulate matter. The CFD model helped to evaluate the limits of operation of rotational rheometers. In particular, the onset of instability in fluid motion inside the measurement geometry was studied.

As part of a researcher exchange program between IPQ and PTB (receiving host) the influence of viscosity on density measurement devices using vibrating parts was successfully quantified. In addition, a method for using laser doppler velocimetry to measure the flow of translucent non-Newtonian fluids was developed.

Project partner, INRIM investigated the use of pycnometry for density measurements of non-Newtonian fluids. CNAM and METAS also investigated the effect of particulate material on the viscosity of a (non-) Newtonian carrier fluid.

Umsetzung und Anwendungen (Englisch)

The complexity of quantitatively understanding the behaviour of non-Newtonian fluids was communicated by the project to industrial stakeholders. Awareness of this prompted a number of parties from industry and academia to join the project as collaborators, such as IFPEN (The French Institute of Petroleum), the University of Texas and Aspect Imaging (a world leader in the design and manufacture of imaging systems for medical and industrial applications). It is anticipated that such organisations will continue with the efforts to develop reference fluids that exhibit non-Newtonian characteristics and to develop measurement techniques for rheometry.

Currently and external to this this project, new instrumentation for the inline measurement of viscosity of real world fluids, i.e. opaque fluids laden with particulate material exhibiting non-Newtonian temperature dependent behaviour, are being developed and introduced. A pulsed ultrasound velocity profile meter developed for food industry applications has recently become a candidate for drilling rig applications and magnetic resonance imaging velocimetry is being adapted to fit practical field requirements. In the future, whirling tube type instruments may well also be used for the evaluation of non-Newtonian fluids but currently such instruments suffer from unacceptable temperature sensitivity. In the meantime there are still no dedicated and traceable instruments for the measurement of viscosity for non-Newtonian fluids.

It is now recognised that the technical solutions currently used with commercial rotational rheometers for the evaluation of non-Newtonian fluids, are significantly impacting the effort required to traceably calibrate such instruments. Therefore, a recipe is urgently needed to reproducibly produce non-Newtonian reference materials for the calibration of such instruments. This will require strict controls and adherence to protocols and should build upon the lessons learnt within this project.