Development of instrumentation to capture unsteady & flutter phenomena in the fan rotors of Gas Turbine Engines

A prototype three stage axial fan was designed for (≈ 3.5:1) pressure ratio with transonic blading. Initial tests had shown the symptoms of flutter at part speed even at ISA-SLS inlet conditions. The intensity of flutter became severe at higher inlet P and T conditions. The fan was modified with casing treatment on the first stage of rotor casing area. The test results have exhibited encouraging results. During the process of testing, in order to validate the mathematical model for flutter, the prototype low pressure compressor module was instrumented with pulsating pressure transducer on the casing in addition to the strain gauging of 1R, 2R rotor blades and 1S, 2S stator blades in the low pressure compressor. The results so obtained were analyzed and compared with strain data captured during the same testing. This pulsation data was in full agreement with strain data and also with the mathematical model developed earlier for detection of flutter and rotating stall. It is evident that the mathematical model results and the results obtained during the LPC test to measure flutter and rotating stall component are comparable and thus validated the model. This paper brings out the test preparation of module, preparation of the test stand, online monitoring of data, express analysis of test results and study of the same to exhibit the match with mathematical model of the Aerodynamic phenomena.