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Blade element rotor theory
\"Blade Element Rotor Theory presents an extension of the blade element rotor theory to describe the dynamic properties of helicopter rotors. It focuses on the more precise mathematical determination of the forces and moments by which a rotor affects its rotorcraft at specified flight conditions and control positions. The book is intended for graduate students and researchers studying rotor dynamics and helicopter flight dynamics. Analyzing the impact of non-uniform blade parameters, the book covers blade twisting, non-rectangular planform shape of a blade, and inhomogeneous airfoil along a blade\"-- Provided by publisher.
Book
Rotorcraft Aeromechanics
A rotorcraft is a class of aircraft that uses large-diameter rotating wings to accomplish efficient vertical take-off and landing. The class encompasses helicopters of numerous configurations (single main rotor and tail rotor, tandem rotors, coaxial rotors), tilting proprotor aircraft, compound helicopters, and many other innovative configuration concepts. Aeromechanics covers much of what the rotorcraft engineer needs: performance, loads, vibration, stability, flight dynamics, and noise. These topics include many of the key performance attributes and the often-encountered problems in rotorcraft designs. This comprehensive book presents, in depth, what engineers need to know about modelling rotorcraft aeromechanics. The focus is on analysis, and calculated results are presented to illustrate analysis characteristics and rotor behaviour. The first third of the book is an introduction to rotorcraft aerodynamics, blade motion, and performance. The remainder of the book covers advanced topics in rotary wing aerodynamics and dynamics.
eBook
Linear and nonlinear rotordynamics
A wide-ranging treatment of fundamental rotordynamics in order to serve engineers with the necessary knowledge to eliminate various vibration problems. New to this edition are three chapters on highly significant topics: Vibration Suppression - The chapter presents various methods and is a helpful guidance for professional engineers. Magnetic Bearings - The chapter provides fundamental knowledge and enables the reader to realize simple magnetic bearings in the laboratory. Some Practical Rotor Systems - The chapter explains various vibration characteristics of steam turbines and wind turbines. The contents of other chapters on Balancing, Vibrations due to Mechanical Elements, and Cracked Rotors are added to and revised extensively. The authors provide a classification of rotating shaft systems and general coverage of key ideas common to all branches of rotordynamics. They offers a unique analysis of dynamical problems, such as nonlinear rotordynamics, self-excited vibration, nonstationary vibration, and flow-induced oscillations. Nonlinear resonances are discussed in detail, as well as methods for shaft stability and various theoretical derivations and computational methods for analyzing rotors to determine and correct vibrations. This edition also includes case studies and problems.
eBook
The numerical modeling of rotor–stator rubbing in rotating machinery: a comprehensive review
The rotor–stator rubbing in rotating machinery generated as a consequence of rotor imbalance, shaft misalignment, and casing deformation is a potential threat to the machinery that seriously affects its performance. Timely prediction and correction of the rubbing are essential for the prolonged life of the machinery and its overall performance. A complete understanding of the system behavior during interaction is a great challenge for researchers working in the field of rotor dynamics. Rubbing phenomena involve complex contact nonlinearities and associated thermal effects, which makes the analysis very difficult. Research works in this field are started with the analysis of simple two degree-of-freedom models and now dealing with extensive three-dimensional finite element models. This paper provides a comprehensive review of different numerical models of rotor–stator rubbing with respect to their ability in simulating the actual response characteristics. A detailed description of contact modeling is also presented with the advantages and disadvantages of each model. Different methods for solving the numerical models are briefly explained. In addition, a commentary on different emerging techniques of rub identification is also reported. Finally, some informed recommendations on future directions are made by stating what lacks in the current research activities.
Journal Article
An intuitive representation and analysis of multi‐rotor wind turbine whirling modes
A multi‐rotor wind turbine (MRWT) is a concept that can reduce the size of the rotor blades compared to a single‐rotor wind turbine (SRWT). Making a cost‐optimized MRWT requires a detailed understanding of its stability properties. This paper aims to establish a physical and intuitive representation of whirling modes for three‐bladed isotropic SRWT and MRWT. An aeroelastic simulation of a nonlinear SRWT model is presented to empathize the importance of whirling. The whirling concept is introduced by simplifying the complexity of the wind turbine rotor into two models. From the models, edgewise and flapwise whirling modes are analyzed. An analytical model of a two‐rotor wind turbine is examined to present the edgewise whirling modes of MRWT. The flapwise whirling modes for MRWT are introduced by using results from edgewise whirling and findings from previous research. The MRWT whirling analysis shows whirling from multiple rotors creates reaction forces to the supporting structure when the rotors have the same speed. This results in whirling coupling modes at the same natural frequency. One is a rotor symmetric whirling mode where the rotors whirling are in phase and a rotor asymmetric mode where whirling of the rotors are out of phase. The whirling coupling effects are minimized in the case that the rotors have different speeds.
Journal Article
Grinding of the grains according to parameters of hummers in double-staged grinder-crusher
Parameters of hummers in double staged grinder-crusher were studied for qualitative grinding of the grains. In order to determine performance indicators, an experimental sample of a grinder-crusher for stepwise grinding of grain was developed. In double stage grinder-crusher when hummers 3-4 mm thick were installed around rotor in 4 rows with 20 mm rotor height the best grinding of the grain was achieved.
Journal Article
Role of artificial intelligence in rotor fault diagnosis: a comprehensive review
Artificial intelligence (AI)-based rotor fault diagnosis (RFD) poses a variety of challenges to the prognostics and health management (PHM) of the Industry 4.0 revolution. Rotor faults have drawn more attention from the AI research community in terms of utilizing fault-specific characteristics in its feature engineering, compared to any other rotating machinery faults. While the rotor faults, specifically structural rotor faults (SRF), have proven to be the root cause of most of the rotating machinery issues, the research in this field largely revolves around bearing and gear faults. Within this scenario, this paper is the first of its kind to attempt to review and define the role of AI in RFD and provides an all-encompassing review of rotor faults for the researchers and academics. In addition, this study is unique in three ways: (i) it emphasizes the use of fault-specific characteristic features with AI, (ii) it is grounded in fault-wise analysis rather than component-wise analysis with appropriate fault categorization, and (iii) it portrays the current research and analysis in accordance with different phases of an AI-based RFD framework. Finally, the section on future research directions is aimed at bridging the gap between a laboratory-based solution and a real-world industrial solution for RFD.
Journal Article
Aerodynamic and Aeroacoustic Interactional Effects for a µUAV
An experimental campaign has been conducted at the Italian Aerospace Research Center to quantify the interactional effects caused by rotor-rotor interaction on a commercially available µ UAV platform. Aerodynamic and aeroacoustic measurements have been carried out for different configurations: data obtained for the isolated rotor, i.e. the baseline configuration, has been compared to the quadcopter configuration. Additionally, the quadcopter with a single operating rotor has been tested to isolate the effects of the quadcopter’s supporting arms. As expected, the aerodynamic performance of the quadcopter configuration is worse than the baseline configuration, although by a small margin, with the quadcopter exhibiting a 5% reduction in the overall thrust coefficient. The presence of the quadcopter’s support arms also degraded the acoustic field, causing the single rotor configuration to be more annoying to listeners across all azimuth angles.
Journal Article
A CFD Study on High‐Thrust Corrections for Blade Element Momentum Models
This paper presents a reanalysis of four axial‐flow rotor simulation datasets to study the relationship between thrust and axial induction factor. We concentrate on high‐thrust conditions and study variations in induction factor and loads across the span of the different rotor blades. The datasets consist of three different axial‐flow rotors operating at different tip‐speed ratios and, for one dataset, also at different blockage ratios. The reanalysis shows differences between the blade‐resolved CFD results and a widespread empirical turbulent wake model (TWM) used within blade element momentum (BEM) turbine models. These differences result in BEM models underestimating thrust and especially power for axial‐flow rotors operating in high‐thrust regimes. The accuracy of BEM model predictions are improved substantially by correcting this empirical TWM, producing better agreement with blade‐resolved CFD simulations for thrust and torque across most of the span of the blades of the three rotors. Additionally, the paper highlights deficiencies in tiploss modelling in common BEM implementations and highlights the impact of blockage on the relationship between thrust and axial induction factors.
Journal Article
Aeroelastic load analysis of a co‐rotating quad‐rotor wind turbine
An aeroelastic analysis is carried out to assess the loads on a selected quad‐rotor wind turbine vis‐à‐vis those on an equivalent rated single‐rotor turbine, with a specific focus on a comparison of support structure loads (e.g., tower root, yaw‐bearing, and boom loads). A quad‐rotor wind turbine with combined rated power of 6 MW and a single‐rotor with equivalent machine rating are modeled in SIMAPCK coupled with AerodynV15 (including turbulent wind input from TurbSim) to calculate the aerodynamic loads. A correction for tower/boom shadow is implemented in Matlab to account for reduction in (axial) incoming wind due to the presence of support structures that carry the rotors. The performance of the quad‐rotor wind turbine, with the single‐rotor as baseline, is carried out for load cases selected from wind turbine certification standard (IEC‐61400‐1) covering the following: nominal loads under normal wind speed profile, fatigue loads under normal turbulence, and ultimate loads under extreme turbulence. Results show that, comparing the quad‐rotor tower root loads to those of the single‐rotor turbine under extreme turbulence, the side‐side force is up to 31% higher, the force‐aft bending moment is up to 15% higher, and the normal force is up to 46% higher due to additional boom/nacelle inertial loads.
Journal Article