Design of an Optical Measuring Stand for the Analysis of iSTC-21v Jet Engine Fuel Nozzle Spray

This paper presents the design and verification of a measuring device intended for the experimental determination of the spray cone angle of a pressure swirl fuel nozzle used in small turbojet engines, specifically the iSTC-21v. The primary objective was to develop an objective and cost-effective method to measure this angle without relying on optical components such as high-speed cameras or laser systems. The device is designed as a modular platform, allowing future integration of optical techniques. The proposed test bench evaluates the fuel spray pattern using strain gauge-based measurement of the liquid volume collected in a set of concentric collection rings. This method enabled the experimental determination of the spray cone angle, which was then compared with a mathematical model developed based on the nozzle’s geometric and hydraulic parameters. The difference between modeled and experimental values of the spray angle was within ±4%, confirming the reliability of the chosen approach. Although the current system does not support droplet size or distribution analysis, it provides a solid foundation for further development using optical diagnostics. In future stages, the system is intended to be used for testing alternative fuels and analyzing their effects on the processes of atomization, ignition, and combustion in small jet engines. Additionally, these insights may serve as valuable input for the development of control algorithms that account for fuel spray characteristics, helping to improve engine start-up reliability and operational performance.