Search

In this paper, the field uniformity of axial electric field component inside an anisotropic jet engine environment is analyzed by using Ansys HFSS simulation tool. The standard deviation based approach is used for the analysis of uniformity in jet engine. Using full wave simulation analysis, the electric field values are extracted from the jet engine containing one set of 24 blades. Moreover, the effect of position of transmitting antennas on field uniformity is analyzed by using two different transmitting antenna positions. Furthermore, the effect of number of rotating blades on the field uniformity is also analyzed. Finally, distribution of standard deviation of electric field with respect to the dimension of jet engine is performed. 2015 IEEE. Scopus 2-s2.0-84964815091

The present work focuses on the unsteady aerodynamics and aeroelastic properties of a small-medium sized wind-turbine blade operating under ideal conditions. A tapered/twisted blade representative of commercial blades used in an experiment setup at the National Renewable Energy Laboratory is considered. The aerodynamic loads are computed using Computational Fluid Dynamics (CFD) techniques. For this purpose, FLUENT ® , a commercial finite-volume code that solves the Navier-Stokes and the Reynolds-Averaged Navier-Stokes (RANS) equations, is used. Turbulence effects in the 2D simulations are modeled using the Wilcox k-w model for validation of the CFD approach. For the 3D aerodynamic simulations, in a first approximation, and considering that the intent is to present a methodology and workflow philosophy more than highly accurate turbulent simulations, the unsteady laminar Navier-Stokes equations were used to determine the unsteady loads acting on the blades. Five different blade pitch angles were considered and their aerodynamic performance compared. The structural dynamics of the flexible wind-turbine blade undergoing significant elastic displacements has been described by a nonlinear flap-lag-torsion slender-beam differential model. The aerodynamic quasi-steady forcing terms needed for the aeroelastic governing equations have been predicted through a strip-theory based on a simple 2D model, and the pertinent aerodynamic coefficients and the distribution over the blade span of the induced velocity derived using CFD. The resulting unsteady hub loads are achieved by a first space integration of the aeroelastic equations by applying the Galerkin’s approach and by a time integration using a harmonic balance scheme. Comparison among two- and three- dimensional computations for the unsteady aerodynamic load, the flap, lag and torsional deflections, forces and moments are presented in the paper. Results, discussions and pertinent conclusions are outlined.

The operational modal analysis, OMA, allows estimating the dynamic properties of a structure, natural frequencies, damping ratios, and mode shapes, without measuring the input forces. According to the main hypothesis concerning the input excitation, i.e., stochastic with frequency independent spectra (at least in the frequency band of interest), it is not theoretically possible to apply the OMA procedures in structures characterized by the presence of harmonic components in the excitation loading. In this paper, an approach capable to identify the presence of harmonic excitations, acting together with a broad band stochastic loading, and then to remove their effects in the modal parameter estimate is presented. The approach is based on the joint use of the statistical parameter called “entropy” and the already developed output-only procedure based on the application of the Hilbert transform properties to the output response signals. The capability to improve the OMA procedures is investigated numerically and through whirl tower experimental tests of a rotating blade in which both stochastic and harmonic contributions to the dynamic excitations have been provided by the perturbations arising from the operative conditions. A sensitivity analysis has been also performed to evaluate the effects of the filtered responses, in the time domain, on the statistical characterization, required to distinguish the operational frequencies from the natural ones.

To evaluate the accurate performance and characteristics of turbomachinery, it is important to measure the unsteady flow phenomena downstream of the rotating blades. This paper presents the development of a fast-response total pressure probe and the necessary calibration procedure for the measurement of unsteady flow field at the exit of blades. The fast-response total pressure probe is fabricated by installing a sensor in the cylindrical head of the probe. In terms of simplicity of the measurement system and data reduction method, this method is more competitive over established methods that use multiple sensors. A novel scheme of using fast response probe and virtual instrumentation technology has been successfully implemented in the current programme in place of conventional measurement methods like five-hole probe, three-hole probe and hot wire anemometer. The experiment is conducted in an axial flow compressor using virtual instrumentation technology with components like signal conditioning system, A/D card, and TTL triggering circuitry. Further processing was done with the help of LabVIEW software. The objective of measuring the 2-dimensional flow at the exit of the rotor was achieved by a technique developed in the laboratory. The data are compared with steady state data and the match between the fast response data and steady data is quite good.

Offshore wind turbines are complex structural and mechanical systems located in a highly demanding environment. This paper proposes a multi-level system approach for studying the structural behavior of the support structure of an offshore wind turbine. In accordance with this approach, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessment in various sub-problems, which can be solved by means of sub-models at different levels of detail, both for the structural behavior and for the simulation of loads. Consequently, in a first place, the effects on the structural response induced by the uncertainty of the parameters used to describe the environmental actions and the finite element model of the structure are inquired. After that, a meso- level FEM model of the blade is adopted in order to obtain the detailed load stress on the blade/hub connection.

The purpose of this paper is to provide a complete view of methods for the prediction of noise generated by rotating blade devices, based on the solution of the wave equation. Analysis and results from numerous papers are reported to present the historical development and the state of the art in the field of open rotor acoustics.