This paper presents a high sensitive micro-sensor designed for pressure measurements in a wide range around atmospheric pressure, for application in aerodynamics. The sensor is a temperature-resistance transducer operating with the Pirani effect, which states that below a certain pressure limit, the thermal conductivity of a gas is pressure-dependent. The sensor presents a wide measurement range between 10 kPa and about 800 kPa, in both constant current and constant temperature mode. The last mode enables high-sensitive measurements with a maximum of sensitivity around atmospheric pressure, enabling the use of the sensor for applications in aerodynamics and fluid dynamics, such as active flow control.
Résumé. Cet article présente l'amélioration de la chaîne de mesure du LNE permettant la réalisation de l'ohm à partir du farad. Celle-ci est mise en oeuvre afin de déterminer le quantum de résistance RK issu de l'effet Hall quantique à partir d'un condensateur calculable permettant la réalisation du farad dans le SI. Elle comporte différents ponts d'impédances coaxiaux en deux et quatre paires de bornes dont l'élément central est un transformateur étalon. Nous décrivons dans cet article une nouvelle génération d'autotransformateurs étalons double étage conçus et caractérisés dans le but d'améliorer la chaîne de mesure d'impédance du LNE et réduire l'incertitude globale sur la détermination de RK à une valeur proche de 10 -8 .
This study presents a test campaign carried out at IFPEN aimed at understanding and characterizing the thermal behaviour of electric motors incorporating direct oil cooling. Several cooling systems and oils are evaluated at different operating points and the effect of parameter variations is investigated. Experimentations are defined and performed to understand and quantify the impact of different oils and direct cooling systems on the performances of the electrical machine. The test results make it possible to verify and quantify the gain on the thermal behaviour obtained by adding an oil injection system directly to the active parts of the machine in addition of an indirect water jacket cooling. This gain is observed for a representative set of operating points and oil injection parameters. The impact of physico-chemical properties of oils on direct cooling performance is assessed by comparison of several oils. The viscous friction losses are also identified. The results presented include a repeatability and reproducibility study for speed values up to 14 krpm and continuous powers up to 60 kW.
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