Can optical fiber compete with profile analysis tensiometry in critical micelle concentration measurement?

Critical micelle concentration (CMC) is one of the important nominal characteristics of the surfactants which can be measured using various methods. In this study, to detect the CMC of two ionic surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), two methods were utilized: (a) optical fiber and (b) drop profile analysis tensiometry (PAT) techniques. The spectrum width center and surface tension of the solutions at different concentrations of the surfactant were measured. The preliminary outcomes showed a compliance between optical fiber method and PAT technique. However, there were differences in the behavior of two surfactants in optical fiber measurement. In this method, when the solid surface of fiber is put in the system, the interactions between surfactant molecules and the fiber surface must be carefully considered.

An Optical Fiber Measurement System for Blade Tip Clearance of Engine

The benefits of reducing the tip clearance have been receiving many scholars’ attention all the time, which bring turbine efficiency increasing, emissions reduction, payloads increasing, and mission range abilities extension. In order to gain the blade tip clearance dynamically, a prototype optical fiber measurement system was built and tested based on the rotor test rig. The optical fiber tip clearance measurement system consists of the reflective intensity-modulated optical fiber bundle (sensor), main signal processing unit, high-speed data acquisition card, and a computer. The static performance and dynamic performance experiments were conducted to verify the performance of the system we designed. In addition, the results show that the accuracy of the system is 25 μm or better; the stability of the measurement system was evaluated in room temperature. The clearance measurement range is about 5 mm, and sensitivity of the sensor is 0.0733/mm. Furthermore, the typical tip clearance dynamic measurement experiment results show that the system has good dynamic response characteristics as well. The system will provide a new tool for engine health monitoring or fast active tip clearance control.