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Rapidly changing temperatures and pressures encountered in many production environments make accurate calibrations difficult to perform

Accurate pressure and temperature measurements are a key requirement in the process controls of a range of European industries. For many this is a simple process, but for some – where the temperature or pressure can change rapidly or reach extremeness, such as in engines used in automotive and marine sectors or some manufacturing processes – this is currently extremely difficult or impossible.

Current practices to calibrate pressure and temperature sensors only operate under static conditions, which limits the accuracy of measurements – with errors up to 10% occurring in some systems. Improved measurements in this area could lead to better knowledge of the environments of internal combustion engines for example and open up the possibility of enhancing engine performance in terms of engine power and fuel consumption.

World-first

The EMPIR project Development of measurement and calibration techniques for dynamic pressures and temperatures (17IND07, DynPT) has, for the first time, provided traceability of measurements in the pressure range from 5 MPa to 30 MPa. This is the range required for measurements relevant to industry for internal combustion engine applications.

To do this project partners have developed and implemented a range of calibration techniques and developed new dynamic pressure and measurement standards.

Calibration devices and methods

• LNE-ENSAM (France) improved its primary dynamic calibration standard using fast-opening devices and shock tubes and developed a method using a reference transducer to calibrate secondary transfer standards and working standards. This work was published in the journal Measurement Science and Technology.
• RISE (Sweden) developed a system, based on rapid shutter systems, for calibrating radiance thermometer and high temperature black bodies, and was able to measure up to 2200 °C with temperature uncertainties below 5 °C and response time of 1 ms.
• In another approach NPL (UK) modified an existing blackbody setup modified for calibrating dynamic thermometers to provide traceability to the International Temperature Scale of 1990 (ITS-90). The performance was demonstrated by calibrating an ultra-high-speed combustion pyrometer over the temperature range from 1073 K to 2873 K with residuals < 1 % measurement uncertainty.
• The  KTH (Sweden)  developed a temperature bench based on shock tube method for dynamic calibrations with μs step response up to a temperature of 3000 °C with an uncertainty of 3 % (k = 2).
• PTB (Germany) developed a system for calibrating and testing dynamic pressure sensors used for ammunition safety testing.
• TUBITAK UME (Turkey) developed a dynamic pressure standard up to 400 MPa based on a drop-weight method. Experimental measurements were performed from 50 MPa to 400 MPa with a 2 % measurement uncertainty.
• VTT MIKES (Finland) developed a dynamic pressure calibrator for Testo Industrial Services GmbH, enabling Testo to provide SI traceable calibrations of dynamic pressure sensors to their customers, mainly in the automotive industry.

Dynamic sensor development

• NPL developed a fibre-optic combustion pyrometer capable of measuring  up to 250 kHz for temperatures up to 3300 K. Calibration of the instrument against the ITS-90 traceable blackbody standard was performed followed by field trials at Wärtsilä, Finland, a ship engine manufacturer. This work has featured in an article in the Institute and Measurement Control’s PRECISION magazine (March 2023).
• DTU, the Technical University of Denmark, developed a spectroscopic band shape sensor. As a special feature of this sensor both temperature and pressure data are recorded from the combustion process.
• VTT MIKES developed a novel dynamic pressure sensors that can withstand harsh condition, such as inside a combustion engine were pressures and temperatures can reach up to 300 bar and 2000 K, respectively.

These new instruments were tested under real-world operating conditions – such as inside a maritime combustion engine. The overall target uncertainties of 2 % and 5 % for dynamic pressure and temperature measurements respectively, in combustion engine applications was achieved. Linking these new methods and instruments to the SI system of units has allowed, for the first time, the ability to accurately measure rapidly changing temperatures and pressures including methods of estimating uncertainties.

The work on developing and testing the novel dynamic sensors was  published in a special issue of the industry-oriented PTB-Mitteilungen which also highlights other achievements of the project.

Based on the work of the project VTT MIKES is currently developing a primary standard for dynamic pressure up to 5000 bar for the Central Office of Measures (GUM) in Poland with the aim of launching the first accredited calibration service in Europe in 2024 at the Kielce University of Technology.

Calibration services, guidelines and new measurement technologies are now available to European industries to facilitate a shift from static to much needed dynamic methods.

The coordinator of the project Richard Högström said about the work:

“As an outcome of the project, industry has now the necessary tools for ensuring quality of dynamic measurements in demanding industrial applications. This will boost innovation potential and contribute to better quality products, improved energy, and material efficiency, supporting competitiveness of European industries”.  

This EMPIR project is co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States.

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