An assessment of a dual-rotor wind turbine system and the implications of rotor phasing

Decomposition analysis of renewable energy demand and coupling effect between renewable energy and energy demand: Evidence from China

In the marine industry, it is important to improve the performance of tida turbines to reduce power generation costs. Modification of existing tidal turbine models is necessary to boost performance. The main objective of the present study is to investigate the hydrodynamic performance of a model variable length blade tidal turbine by modifying the baseline rotor to improve the performance using blade element momentum theory (BEMT). The QBlade BEMT simulation results were validated with the available published data and are in good agreement. Furthermore, the key performance parameters (i.e. thrust, moment, and power coefficient) and power output were predicted using the BEMT code for different blade configurations of the model rotor. The simulation results were compared with a standard conventional fixed blade turbine model. Based on the results from the simulations, with the increase in the rotor blade lengths, the performance parameters, particularly peak power coefficients, were observed to be improved up to 10%. The power extraction was also enhanced up to 79% below-rated tidal velocities without any loss in performance at the rated condition. Hence, the model is more efficient compared to the conventional models.

This paper studies a novel dissimilar coaxial rotor concept with significantly reduced rotor–rotor aerodynamic interaction during hovering flight. The proposed concept’s performance is systematically compared with regular coaxial and conventional single rotor configurations using 1) analytical and 2) blade element momentum theory (BEMT)-based analysis for hover flight condition. The hover performance among different rotor configurations is compared using a baseline main rotor combined with various antitorque mechanisms. Through this study it is established that the dissimilar coaxial rotor configuration shows improved performance for torque equilibrium cases when compared to both conventional and regular coaxial configurations for moderate- to high-thrust conditions with power reduction of 16–37% when compared to a conventional single main rotor–tail rotor configuration and 14–17% of power saving when compared to a regular coaxial rotor during hovering flight with rotor thrust in the range of . The analytical method from momentum theory and BEMT results correlate well for the induced and profile torque balanced conditions. The proposed concept appears to be an efficient alternative to the conventional single main rotor with tail rotor and regular coaxial rotor for hovering flight conditions within the scope of the analysis.

Passively adaptive tidal turbine blades: Design tool development and initial verification

Greater penetration of wind energy demands better utilization of available wind. This has led to a formidable increase in the rotor diameter over the past few years. Bigger rotors call for lighter, more flexible blades to reduce loads and improve fatigue life. As a result, future blades will deform substantially more than the relatively stiff blades of the past. More efficient use of wind power also calls for incorporating advanced active and passive control strategies and increasing the range of velocities over which wind energy is captured. Hence an improvement in the quality of numerical simulations capable of capturing the effects of these deformations is key to innovations in windturbine technology. The code on which this research aims to improve upon is called the Dynamic Rotor Deformation - Blade Element Momentum model (DRD-BEM) introduced by Ponta et al. It combines an advanced structural model with an aerodynamic model implemented in a parallel HPC supercomputer platform. The structural part simulates the response of heterogeneous composite blades, based on a variation of the dimensional reduction technique proposed by Hodges and Yu. This approach reduces the 3-Dimensional complexity of the blade section into a stiffness matrix for an equivalent beam, substantially reducing the computational effort required to model the structural dynamics at every time step. The aerodynamic model is based on an advanced implementation of the Blade Element Momentum (BEM) theory, where all velocities and forces are re-projected into the deformed configuration at that instant. This ensures that the effects of all the complex modes of rotor deformation and subsequent rotation of airfoil sections are accounted for while computing the aerodynamic forces. As a result of the out of plane attitudes of the rotor sections introduced by blade deformations and various control strategies the hitherto small radial component of aerodynamic forces in the hub must now be taken into account. In this research we present a way to extend the capabilities of DRD-BEM by taking into consideration the 3-Dimensional effects of these forces on rotor interference. In this method, called the 3-D DRD-BEM, the coordinate system where the momentum balance is performed in BEM theory is moved, from the hub, to the instantaneous position and alignment of the blade section in its deformed configuration. Another aspect that becomes important as blades become more flexible and control strategies become more complex, is the high axial induction factor regime of turbine operation. This becomes more

Dynamic characteristics of an aeroengine dual-rotor system with inter-shaft rub-impact

In order to study the dynamics in a dual-rotor system in the presence of a bearing pedestal early looseness fault, a 12-degree-of-freedom dual-rotor system bearing pedestal looseness fault dynamic model considering gyroscopic moments is developed. The Newmark-β method is used to solve the developed model. The dynamic response characteristics of the dual-rotor system when the bearing pedestal is loosened are analyzed. A dual-rotor fault simulation test bench is built to carry out bearing pedestal looseness fault simulation experiments. The comparative results show that the fault frequency distribution pattern in the simulation analysis envelope spectrum is consistent with the experimental results, which proves the validity of the proposed dynamics model. It is found that there is clippings in the rotor vibration signal when there is a bearing pedestal early looseness fault in the dual-rotor system. In the envelope spectrum there are high and low pressure rotor rotation frequency, the sum of frequencies and 2-fold the characteristic frequency of rotor rotation frequency. With the increase of rotational speed ratio, the amplitude of envelope spectrum characteristic frequency increases. When the bearing pedestal is loose, the loose rotor axis trajectory is elliptical-like, and the rotor axis trajectory has a tendency to be more chaotic. Capturing the vibration signal characteristics of a dual-rotor system at very small loosening angles is necessary for preventing larger looseness, which is crucial for fault prediction.

Insights into the nonlinear behaviors of dual-rotor systems with inter-shaft rub-impact under co-rotation and counter-rotation conditions

This paper evaluates the impact of climate policy uncertainty on renewable and non-renewable energy consumption in the United States over the quarterly data from 2000Q1 to 2021Q3. Economic growth and crude oil prices are added to the energy consumption functions as control variables. The paper considers several approaches to model both renewable and non-renewable energy demand. It is found that crude oil prices promote non-renewable energy demand and climate policy uncertainty reduces it. Surprisingly, the impact of economic growth on non-renewable energy consumption is positive but insignificant. It is also observed that economic growth promotes renewable energy demand, and crude oil prices reduce it. Furthermore, climate policy uncertainty positively affects renewable energy demand in the long run. Some policy implications are provided for reducing non-renewable energy consumption and promoting renewable energy use in the United States through climate policy implementation.

Rotor systems installed in a transportation system or under seismic excitations are considered to have a moving base. Although extensive research has been conducted on the dynamic behavior of the single-rotor system under base motions, few studies have dealt with the dynamics of dual-rotor systems, especially the counter-rotating dual-rotor systems used in airplane engines. Moreover, mass unbalance and gravity are unavoidable excitations for most rotor systems. Therefore, the vibration properties of a counter-rotating dual-rotor system with the coupled effects of base motions, mass unbalance and gravity are investigated in this paper for the first time. Using the Lagrange principle associated with the finite element method, a general model for dual-rotor systems under base motions was established by using Timoshenko beam elements, leading to a detailed analysis of the natural properties and harmonic responses of the system. The results revealed that different whirling modes (backward, forward or both) may be mutually excited. This research can be helpful for the design and vibration analysis of dual-rotor systems concerned with base motion.

Modern wind turbine systems increasingly demand higher torque, improved power extraction, and enhanced efficiency. Computational Fluid Dynamics (CFD)–based simulation has emerged as a robust tool for optimizing rotor configurations before prototyping. This review consolidates the simulation-focused research on single rotor, dual rotor, and ducted dual rotor wind turbines, emphasizing torque, power output, and flow characteristics. Studies consistently show that dual rotor systems outperform single rotor designs, while the integration of convergent–divergent ducts or shrouds further augments mass flow rate and pressure recovery through diffuser action. Simulation-based findings reveal that ducted dual rotor systems may deliver 30–90% higher torque and 140% higher power output than bare single rotor configurations at comparable wind speeds. This review synthesizes advancements in simulation methodologies, rotor–duct aerodynamics, and performance trends, providing a consolidated understanding of CFD-driven optimization in multi-rotor wind turbine systems.

Bangladesh is wellon course to become one of the leading emerging market economies in the world. Hence, it can be expected that the economic growth of Bangladesh would substantially increase over the next decade. This, in turn, is likely to boost the energy consumption levels of the nation whereby meeting the surge in the energy demand would be a crucial agenda of the government. Therefore, it is important to understand the factors that influence the nation's energy demand. Against this backdrop, this paper aims to evaluate the macroeconomic determinants of total, renewable, and non-renewable energy demands in Bangladesh between 1980 and 2014. Besides, the analysis is conducted for both primary energy and electricity consumption levels. The econometric methods used in this study controlled for the structural break issues in the data. The key findings, in a nutshell, show that economic growth and household consumption expenditure positively influence the overallprimary energy and electricity demands in Bangladesh while income inequality exerts opposite effects. Besides, technological innovations are found tobe reducing the total and non-renewable energy demand in Bangladesh while increasing the demand for renewable energy. On the other hand, positive oil price shocks are found to be ineffective in influencing the renewable energy demand but slightly reducing the non-renewable energy demand. Finally,the causality estimates portray the feedback hypothesis in almost all the cases to highlight the inter-relationships between economic growth and energy demand in Bangladesh. Hence, in line with these findingsseveral critically important policy implications are suggested for managing the overall energy demand in Bangladesh.

This paper discusses the interaction of support structures on the dynamics of a dual rotor system. The system considered is a dual rotor, supported on flexible bearings, which are in turn mounted in a flexible casing. ANSYS® is used for modeling and meshing the dual rotors and the casing. The rotors are modeled using solid elements. The bearings are simulated as springs, wherein the direct and cross coupled stiffness and damping coefficients are applied. The casing is also modeled and meshed in ANSYS® using solid elements. Different spin speeds are applied to the dual rotor system. The casing is also rotated at a zero spin speed. The Stress stiffening and spin softening options are also set on for the dual rotor system. The system natural frequencies are obtained for different spin speeds and the Campbell diagram of the system is plotted. The critical speeds due to per revolution excitations are then extracted from the Campbell diagram.

In recent times, the application of small-scale horizontal axis wind turbines (SHAWTs) has drawn interest in certain areas where the energy demand is minimal. These turbines, operating mostly at low Reynolds number (Re) and low tip speed ratio (λ) applications, can be used as stand-alone systems. The present study aims at the design, development, and testing of a series of SHAWT models. On the basis of aerodynamic characteristics, four SHAWT models viz., M1, M2, M3, and M4 composed of E216, SG6043, NACA63415, and NACA0012 airfoils, respectively have been developed. Initially, the rotors are designed through blade element momentum theory (BEMT), and their power coefficient have been evaluated. Thence, the developed rotors are tested in a low-speed wind tunnel to find their rotational frequency, power and power coefficient at design and off-design conditions. From BEMT analysis, M1 shows a maximum power coefficient (Cpmax) of 0.37 at λ = 2.5. The subsequent wind tunnel tests on M1, M2, M3, and M4 at 9 m/s show the Cpmax values to be 0.34, 0.30, 0.28, and 0.156, respectively. Thus, from the experiments, the M1 rotor is found to be favourable than the other three rotors, and its Cpmax value is found to be about 92% of BEMT prediction. Further, the effect of pitch angle (θp) on Cp of the model rotors is also examined, where M1 is found to produce a satisfactory performance within ±5° from the design pitch angle (θp, design).

The advent of electric Vertical Take-Off and Landing (eVTOL) aircraft represents a significant shift in aerospace design, driven by the promise of cleaner, quieter, and more efficient urban air mobility solutions. This research addresses the critical need to understand and optimize eVTOL aircraft design and performance through a comprehensive, multidisciplinary approach. The current body of knowledge on eVTOL aircraft design is expanding, yet significant gaps and limitations persist. Traditional non-electric VTOL aircraft and commercial aviation designs do not adequately address the unique complexities introduced by electric propulsion such as energy efficiency, power-to-weight trade-offs, and integrated aerodynamic and propulsion systems. This research aims to bridge these gaps by conducting a detailed comparative study on the advancements in eVTOL aircraft design and configurations, providing critical insights into design trade-offs and innovations enabled by electric propulsion. The objectives of this research are fourfold: First, to conduct a detailed comparative study on the advancement of eVTOL aircraft design and configurations. This study identifies and compares evolving attributes and configuration types that influence aircraft sizing and performance, highlighting how electric propulsion technology diverges from traditional non-electric VTOL and commercial aviation design paths. Second, the research involves designing and developing a comprehensive multidisciplinary eVTOL aircraft model to assess and evaluate aircraft performance across various flight regimes. This model uses a generalized framework to account for different eVTOL components from initial to detailed design phases, integrating theoretical formulations and empirical data to provide a full performance analysis of all flight segments during an aircraft mission. Third, the study characterizes eVTOL aircraft transition performance during the conversion between vertical and horizontal flight phases. Utilizing a trimming approach and flight trajectory model with Blade-Element Momentum Theory, this research offers improved modeling and characterization of the critical transition phase for different eVTOL configurations. Fourth, the research quantifies the benefits and designs of lifting surfaces for eVTOL aircraft in terms of aerodynamics, stability, and handling qualities. It develops and validates both analytical and experimental models to optimize wing configurations, with subscale flight testing providing empirical validation of the performance and characteristics of different wing designs. Methodologies employed in this research include aircraft parametric design and performance analysis, developing a comprehensive model to analyze and compare the performance of various eVTOL configurations, considering aerodynamics, propulsion, and flight performance. Additionally, flight trajectory-based transition analysis is formulated through detailed transition models based on transitional trajectories to characterize the transition phase for different eVTOL configurations. Wing configuration design and optimization is also conducted through a parametric study and subscale experimental testing to validate wing configurations, focusing on aerodynamics, flight performance, stability, and handling qualities. This research provides a detailed framework for evaluating eVTOL aircraft design and performance, offering specific insights into key design trade-offs such as wing and rotor configurations, energy efficiency, aerodynamic stability, and transition flight dynamics enabled by electric propulsion. The findings introduce methodologies for optimizing aircraft configurations to balance efficiency, stability, and power requirements, directly addressing challenges such as minimizing drag, enhancing lift, and achieving smooth transition phases. These contributions deliver practical tools for aerospace engineers, eVTOL manufacturers, urban air mobility planners, and regulatory bodies, supporting the development of sustainable and efficient urban air mobility solutions. This thesis presents a comprehensive exploration into the design, performance, and optimization of winged eVTOL aircraft such as Lift+Cruise, Tiltrotors and Lift+Tiltrotor configurations. This research achieves its objectives by conducting a detailed comparative study, developing a robust performance model, characterizing critical transition phases, and optimizing wing configurations for eVTOL aircraft. These advancements provide a significant contribution to the field by delivering valuable insights and practical tools for future eVTOL design and development. The study underscores the dynamic and multidisciplinary nature of eVTOL innovation, emphasizing the necessity of rigorous validation through both analytical and experimental methodologies. As eVTOL technology progresses, the findings of this research will play a pivotal role in shaping the next generation of aerial transportation, ensuring improved efficiency, enhanced safety, and suitability for the expanding demands of urban and regional air mobility.