Development of a schlieren system for a mobile rocket combustion chamber

The optical system has been developed in order to investigate a mobile rocket combustion chamber through schlieren technique. The design process has been presented in a consecutive perspective, despite of the non-sequentiality that characterizes any decision-making route, in order to facilitate the reading. A brief introduction to the combustion chamber test bench, as well as to the rising interest of space industry and agencies in green propellants, is promptly followed by theoretical background about schlieren technique and its application in an optical diagnostic perspective. It is also presented a computational method for numerical evaluation, implemented in a Matlab routine for image-processing. The project design develops from studies on conventional and novel configurations up to detail design and optimization, including in the process also cost-benefits analysis for the selection of components, Matlab routines for sizing and verification purposes, as well as developing of a complete CAD model as a tool for calibration procedures. Indeed, it is offered a step-by-step calibration procedure to the operator, that includes a specific section dedicated to most common practical issues and alternative solutions. The design process ends up by drafting a brief list of possible improvements in order to increase its reliability for future applications. A brief summary of main results, coming from a preliminary test session on a flat flame burner, is offered to the reader, in order to outline a standard setting for a correct calibration of the system. A specific test campaign aims to highlight the optical system sensitivity to changes in temperature and density due to mixture ratio variations.