This paper describes the design optimization study of an under platform damper to mitigate high vibration problem of a gas turbine rotor blade under resonance condition. An existing theoretical model explicitly, Casba friction damper model was used to evaluate the dynamic characteristics of the turbine blade with under platform damper. Turbine blade is approximated as two degrees of spring-damper-mass system, which is dynamically equivalent to real turbine blades for its first two eigen values. Blade tip response predictions were carried out for different damper mass, stiffness and coefficient of friction under simulated rotational speed of the rotor, to arrive at an optimum mass to control the blade tip response. As a practical application, along with damper mass optimization, shape and mass distribution of the damper is obtained by design trials to ensure good contact between the blade root and damper upper surface. Contact analysis was carried using the ANSYS software. The asymmetric skewed damper geometry posed complications with respect to modelling and optimisation. In realistic application, with the kind of uncertainties in contact pattern, variation in friction coefficient, geometric tolerances, validation/verification plays a major role in assessing the design. As part of verification of this damper design, a full scale gas turbine engine test program was envisaged and completed. Modified optimum damper was implanted as a design change, engine was instrumented for blade vibration measurement. Non-Intrusive Stress Measurement system was used for measuring blade tip amplitudes from all the blades in the rotor. Test blade tip vibration was analysed and compared against the predications. This optimised damper configuration has showed significant reduction in blade amplitudes during full-scale gas turbine testing, in comparison to original design proving the efficacy of new modified damper.

Here a suitable TMD system (water tank as a lumped mass without sloshing effect) is modeled on top/intermediate storey of building. The Response Spectrum method is considered as per IS 1893-Part1-2002. Seven RCC framed buildings are considered; rectangular buildings with vertical irregularity of 10, 14 and 20 storey with height to depth ratio (H/D) as 0.875, 1.23 and 1.6, respectively; and 14 storey L-shaped building with H/D as 1.23; rectangular buildings with vertical regularity of 10, 14 and 20 storey with H/D as 3.9, 5.44 and 8, respectively. The TMDs are modeled, with 3% total weight of each floor, using eight different cases. In total 63 building models are analyzed with/without TMDs by ETABS software and the results are presented. It is found that for extracting the maximum benefits, the buildings shall be modeled with three TMDs using 3-Gauss points at the intermediate storey as it reduces all the three parameters viz. time period, base shear and storey drift simultaneously to the maximum possible extent; and the reduction in the base shear is significant for buildings with smaller H/D as well as with higher H/D too. The TMD models are found to improve the performance of buildings under earthquake loads.

Here a suitable TMD system (water tank as a lumped mass without sloshing effect) is modeled on top/intermediate storey of building. The Response Spectrum method is considered as per IS 1893-Part1-2002. Seven RCC framed buildings are considered;

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Experimental Modal Analysis (EMA) is a conventional technique for establishing the modal parameters of the components. The modal parameters are the dynamic characteristics viz. frequency, mode shapes and damping that are used for assessing and validating the design predictions through correlation studies. For this task EMA technique is adopted to assess the dynamic characteristics of an additive manufactured (AM) turbine wheel of a turbocharger. Correlation studies are undertaken to validate the theoretical model developed. These Correlation studies ensured that there is no major deviations to proceed for high speed spin testing of this turbine wheel in simulated environment. The possible interference or resonances in the operating range are identified for safe operation of the test rotor.