Design and realization of an instantaneous concentration measurement system for wind tunnel applications

The aim of this project work is the design and realization of an instantaneous concentration measurement system to be used with binary gas mixtures. The design is focused on the simplicity of the set up and on its compactness, and it is specifically intended to be used in wind tunnel applications. The outcome of the design process for the specified system is an aspirating hot-wire probe based on a polypropylene 3D printed body and a simple single wire sensor. Specifically, a 3D printing machine based on the Material Jetting (MJ) technology was used for the probe manufacturing. One of the most important design features is the possibility to get access to the wire through the removal of a single probe component, which is a nearly effortless operation. This feature allows to repair the broken wire sensor without the need of substitute the whole probe. From these design specifications it could be understood that due also to its dimensions, the probe must be handled with care, and it cannot operate inside hot flows or uncontrolled flow temperature and pressure conditions. It was not possible to test the probe behaviour in presence of flows with composition variations due to the lack of the necessary instrumentation to perform this kind of experiments. Nonetheless, the design effectiveness could be confirmed by verifying that the hot-wire signal remained constant when the probe was exposed to a variable speed constant composition flow. This proved the probe insensitivity to external flow speed, and it opened the possibility to further testing sessions involving gases.