The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Boris I Mamaev - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic development and investigation of turbine transonic Rotor Blade cascades
Thermal Engineering, 2015Co-Authors: E V Mayorskiy, Boris I MamaevAbstract:An intricate nature of the pattern in which working fluid flows over transonic Blade cascades generates the need for experimentally studying their characteristics in designing them. Three cascades having identical main geometrical parameters and differing from one another only in the suction side curvature in the outlet area between the throat and trailing edge were tested in optimizing the Rotor Blade cascade for the reduced flow outlet velocity λ2 ≈ 1. In initial cascade 1, its curvature decreased monotonically toward the trailing edge. In cascade 2, the suction side curvature near the trailing edge was decreased, but the section near the throat had a larger curvature. In cascade 3, a profile with inverse concavity near the trailing edge was used. The cascades were blown at λ2 = 0.7–1.2 and at different incidence angles. The distribution of pressure over the profiles, profile losses, and the outlet angle were measured. Cascade 1 showed efficient performance in the design mode and under the conditions of noticeable deviations from it with respect to the values of λ2 and incidence angle. In cascade 2, flow separation zones were observed at the trailing edge, as well as an increased level of losses. Cascade 3 was found to be the best one: it had reduced positive pressure gradients as compared with cascade 1, and the relative reduction of losses in the design mode was equal to 24%. The profiles with inverse concavity on the suction side near the trailing edge were recommended for being used in heavily loaded turbine stages.
E V Mayorskiy - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic development and investigation of turbine transonic Rotor Blade cascades
Thermal Engineering, 2015Co-Authors: E V Mayorskiy, Boris I MamaevAbstract:An intricate nature of the pattern in which working fluid flows over transonic Blade cascades generates the need for experimentally studying their characteristics in designing them. Three cascades having identical main geometrical parameters and differing from one another only in the suction side curvature in the outlet area between the throat and trailing edge were tested in optimizing the Rotor Blade cascade for the reduced flow outlet velocity λ2 ≈ 1. In initial cascade 1, its curvature decreased monotonically toward the trailing edge. In cascade 2, the suction side curvature near the trailing edge was decreased, but the section near the throat had a larger curvature. In cascade 3, a profile with inverse concavity near the trailing edge was used. The cascades were blown at λ2 = 0.7–1.2 and at different incidence angles. The distribution of pressure over the profiles, profile losses, and the outlet angle were measured. Cascade 1 showed efficient performance in the design mode and under the conditions of noticeable deviations from it with respect to the values of λ2 and incidence angle. In cascade 2, flow separation zones were observed at the trailing edge, as well as an increased level of losses. Cascade 3 was found to be the best one: it had reduced positive pressure gradients as compared with cascade 1, and the relative reduction of losses in the design mode was equal to 24%. The profiles with inverse concavity on the suction side near the trailing edge were recommended for being used in heavily loaded turbine stages.
R. Szczepanik - One of the best experts on this subject based on the ideXlab platform.
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Tip-Timing Steam Turbine Rotor Blade Simulator
Journal of Vibration Engineering & Technologies, 2018Co-Authors: L. Piechowski, R. Rzadkowsk, P. Troka, P. Piechowski, L. Kubitz, R. SzczepanikAbstract:Background The traditional method of experimentally determining Bladed disc vibration is with the use of strain gauges. The disadvantage of this method is the fact that only a few Rotor stage Blades can be measured, i.e. vibration data are limited to only a few Blades. This problem led to the development of a different approach, one using the non-intrusive Blade tip-timing technique. Methods Presented in this paper is a tip-timing simulator with one sensor in the casing and one in the shaft for a steam turbine Rotor Blade rotating up to 3000 rpm. Results The simulator results were compared with the experimental results of a 380-MW steam turbine. Conclusions The presented simulator gives only the Blade vibration amplitudes instead of Blade displacements. This approach can be applied to many other sensors. Simulators such as the one described above are able to replace costly physical experiments, verify any tip-timing system’s operation and accuracy and serve as a very useful designing tool for the development of prototype tip-timing systems.
Konrad Vogeler - One of the best experts on this subject based on the ideXlab platform.
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periodical unsteady flow within a Rotor Blade row of an axial compressor part ii wake tip clearance vortex interaction
Journal of Turbomachinery-transactions of The Asme, 2008Co-Authors: Ronald Mailach, Ingolf Lehmann, Konrad VogelerAbstract:In this two-part paper, results of the periodical unsteady flow field within the third Rotor Blade row of the four-stage Dresden low-speed research compressor are presented. The main part of the experimental investigations was performed using laser Doppler anemometry. Results of the flow field at several spanwise positions between midspan and Rotor Blade tip will be discussed. In addition, time-resolving pressure sensors at midspan of the Rotor Blades provide information about the unsteady profile pressure distribution. In Part II of the paper, the flow field in the Rotor Blade tip region will be discussed. The experimental results reveal a strong periodical interaction of the incoming stator wakes and the Rotor Blade tip clearance vortices. Consequently, in the Rotor frame of reference, the tip clearance vortices are periodical with the stator Blade passing frequency. Due to the wakes, the tip clearance vortices are separated into different segments. Along the mean vortex trajectory, these parts can be characterized by alternating patches of higher and lower velocities and flow turning or subsequent counter-rotating vortex pairs. These flow patterns move downstream along the tip clearance vortex path in time. As a result of the wake influence, the orientation and extension of the tip clearance vortices as well as the flow blockage periodically vary in time.
Uttam K. Chakravarty - One of the best experts on this subject based on the ideXlab platform.
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A Study of the Aerodynamics of a Helicopter Rotor Blade
Volume 1: Advances in Aerospace Technology, 2019Co-Authors: Mohammad Khairul Habib Pulok, Uttam K. ChakravartyAbstract:Abstract In any congested area, where a fixed-wing aircraft cannot perform, rotary-wing counterparts are the best-suited option for its vertical take-off and landing capacity. The vibration induced by the Rotor Blade is a significant problem in helicopter performances. Rotor aerodynamic loading, Rotor dynamics, and fuselage dynamics are the elements that contribute to the vibration of a helicopter. Among these elements, the key reason for the helicopter vibration is the aerodynamic loading. Determining aerodynamic loading is one of the most important criteria to design a Rotor Blade and to minimize vibration. Rotor harmonic airloads are generated from the rapid variation of flow around the Rotor Blade due to the vortex wake. A rapid drop in the circulation near the Blade tip causes tip vortices which are the reason for the maximum lift at the tip of the Blade. Consequently, tip vortices become the primary source of harmonic airloads. In this study, a specimen of Bo 105 helicopter Rotor Blade is considered to observe the aerodynamic characteristics under the external flow of air. The coefficients of lift and drag of the specimen for different angles of attack and azimuth angles are estimated. The resonance frequencies and the mode shapes are obtained. Computational results are validated by the experimental analyses of a small-scaled model of the Rotor Blade. From the study, the coefficient of lift is found to increase with the angle of attack up to a critical value. Similarly, the coefficient of drag increases with the angle of attack. The resonance frequencies significantly change with scaling the Rotor Blade.
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A Case Study of the Unsteady Response of a Hingeless Helicopter Rotor Blade
Volume 1: Advances in Aerospace Technology, 2019Co-Authors: Pratik Sarker, Uttam K. ChakravartyAbstract:Abstract The helicopter is an essential means of transport for numerous tasks including carrying passengers and equipment, providing air medical services, firefighting, and other military and civil tasks. While in operation, the nature of the unsteady aerodynamic environment surrounding the Rotor Blades gives rise to a significant amount of vibration to the helicopter. In this study, the unsteady forced response of the Bo 105 hingeless helicopter Rotor Blade is investigated at the forward flight in terms of the coupled flapping, lead-lag, and torsional deformations. The mathematical model for the steady-state response of the Rotor Blade is modified to include the unsteady airfoil behavior by using the Theodorsen’s lift deficiency function for three degrees of freedom of motion. The nonlinear mathematical model is solved by the generalized method of lines in terms of the time-varying deflections of the Rotor Blade. The unsteady airloads are found to create larger deformations compared to that of the steady-state condition for a given advance ratio. The azimuth locations of the peak loadings also vary with different degrees of freedom. The first three natural frequencies and mode shapes of the Rotor Blade are presented. The model for the forced response analysis is validated by finite element results.
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Vibration Analysis of a Composite Helicopter Rotor Blade at Hovering Condition
Volume 1: Advances in Aerospace Technology, 2016Co-Authors: Pratik Sarker, Colin R. Theodore, Uttam K. ChakravartyAbstract:The helicopter is an essential and unique means of transport nowadays and needs to hover in space for considerable amount of time. During hovering flight, the Rotor Blades continuously bend and twist causing an increased vibration level that affects the structural integrity of the Rotor Blade leading to ultimate Blade failure. In order to predict the safe allowable vibration level of the helicopter Rotor Blade, it is important to properly estimate and monitor the vibration frequencies. Therefore, the mathematical model of a realistic helicopter Rotor Blade composed of composite material, is developed to estimate the characteristics of free and forced bending-torsion coupled vibration. The cross-sectional properties of the Blade are calculated at first and are then included in the governing equations to solve the mathematical model. The natural frequencies and mode shapes of the composite helicopter Rotor Blade are evaluated for both the nonrotating and rotating cases. The time-varying bending and torsional deflections at the helicopter Rotor Blade tip are estimated with suitable initial conditions. The validation of the model is carried out by comparing the analytical frequencies with those obtained by the finite element model.
