Experimental validation of small piezoelectric end sensors for unsteady force measurement

Understanding aerodynamic forces on a turbomachinery blade is essential in order to design turbomachines for fatigue and sound radiation. In a previous paper by the authors, shaped piezoelectric end pressure sensors were designed to take advantage of the oscillating nature of the unsteady lift forces generated on a rotor blade particularly at higher harmonics. The pressure sensor shape and distribution were validated theoretically using computational analysis and so it was desired to validate this design experimentally. To investigate the concept experimentally, a setup consisting of a uniform beam instrumented with the designed piezoelectric PVDF pressure sensors under a spinning cylinder with air flowing through a helical slot cut into its surface was designed in order to model a typical rotor blade in a rotating pressure field. The total unsteady force on the beam was calculated using results obtained from the piezoelectric sensors as well as from force gauges beneath the beam. This paper presents the comparison of these results and suggests improvements for future experimentation.