Single Rotor Research Articles

Design of an Active Axis Wind Turbine (AAWT) That Can Balance Centrifugal and Aerodynamic Forces to Reduce Support Infrastructure While Maintaining a Stable Flight Path

This study introduces a novel approach to wind energy by investigating a novel Active Axis Wind Turbine design. The turbine is neither a horizontal nor vertical axis wind turbine but has an axis of operation that can actively change during operation. The design features a rotor with a single blade capable of dynamic pitch and tilt control during a single rotor rotation. This study examines the potential to balance the centrifugal and aerodynamic lift forces acting on the rotor blade assembly, significantly reducing blade, tower, foundation and infrastructure costs in larger-scale devices and decreasing the levelised cost of energy for wind energy. The design of a laboratory prototype rotor assembly is optimised by varying the masses and lengths in a lumped mass model to achieve equilibrium between centrifugal and lift forces acting on the turbine’s rotor assembly. The method involves an investigation of the variation of blade pitch angle to provide a balance between centrifugal and aerodynamic forces, thereby facilitating the cost advantages and opening the opportunity to improve the turbine efficiency across a range of operation conditions. The implication of this study extends to different applications of wind turbines, both onshore and offshore, introducing insight into innovation for sustainable energy and cost-effective solutions.

Method for Determining the Number of Propellers in an Aircraft from a Radar Image Obtained by Inverse Synthesis of the Antenna Aperture

The inverse antenna aperture synthesis technology used to construct a radar image of an aircraft’s propellers has shown high efficiency. The radar image allows to visualize the blades of the rotors included in the functional group (traction rotors of an aircraft, rotors of a twin-rotor helicopter, rotors of a multicopter). In the case of a single rotor in an aircraft (an airplane’s tractor rotor, a single-rotor helicopter’s main rotor), the radar image is simple and clearly perceptible. In the case of several propellers belonging to the same functional group, the ana ysis of the radar image becomes significantly more complicated. This is due to the random relative position of the blades of different propellers at the moment the image begins to be constructed, as well as the possible random coincidence of the spatial position of the blades belonging to different propellers. In this regard, determining the number of propellers in an aircraft is a new urgent task, the solution of which allows us to obtain additional information for recognition. The method under consideration for determining the number of propellers is based on the most common design features – the blades in the propeller follow at the same angular interval, in the propellers of the functional group the number of blades is the same.

Effects of Wake Separation on Aerodynamic Interference Between Rotors in Urban Low-Altitude UAV Formation Flight

In recent years, unmanned aerial vehicle (UAV) formation flight has become an effective strategy for urban air mobility (UAM). However, close rotor separation during formation flight leads to complex aerodynamic interference between rotors, significantly affecting UAV flight performance and operational safety. This study systematically examines the effects of axial and lateral rotor separation on the rotor’s thrust performance through wind tunnel experiments. The tests simulate horizontal, vertical, and hovering states by generating relative airflow in the wind tunnel, focusing primarily on the thrust coefficient changes of the bottom rotor at various separations. The results are compared with a single rotor operating under the same conditions without wake interference. Additionally, computational fluid dynamics (CFD) simulations using the Fluent software were conducted to investigate the effect of wake interactions by analyzing the velocity flow field between the two rotors in different separations. Both the experimental and simulation results demonstrate that rotor aerodynamic performance is notably influenced by wake interactions. Under hovering and vertical states, substantial aerodynamic interference occurs in the region directly beneath the top rotor, within 1D ≤ Z ≤ 3D. This interference gradually diminishes as the rotor separation increases. Additionally, the thrust coefficient of the bottom rotor decreases with increasing flight speed due to the wake, and at higher flight speeds, the wake tends to contract. When the lateral separation is X = 0D, the mid-sectional flow field of the two rotors exhibits symmetry; however, with lateral separation, the symmetry of the bottom rotor’s wake velocity field is disrupted. During the horizontal flight, the rotor wake tilts backward due to the relative airflow, and the extent of this influence is governed by both rotor rotational speed and flight velocity. Therefore, when UAVs operate in formation, it is crucial to account for these factors affecting aerodynamic performance, and rotor separation must be optimized to enhance flight safety and efficiency.

Hopping potential wells and gait switching in a fish-like robot with a bistable tail

Fish outperform current underwater robots in speed, agility, and efficiency of locomotion, in part due to their flexible appendages that are capable of rich combinations of modes of motion. In fish-like robots, actuating many different modes of oscillation of tails or fins can become a challenge. This paper presents a highly underactuated (with a single actuator) fish-like robot with a bistable tail that features a double-well elastic potential. Oscillations of such a tail depend on the frequency and amplitude of excitation, and tuning the frequency–amplitude can produce controllable oscillations in different modes leading to different gaits of the robot. This robot design is inspired by recent work on underactuated flexible swimming robots driven by a single rotor. The oscillations of the rotor can propel and steer the robot, but saturation of the rotor makes performing long turns challenging. This paper demonstrates that by adding geometric bistability to the flexible tail, turns can be performed by controllably exciting single-well oscillations in the tail, while exciting double-well oscillations of the tail produces average straight-line motion. The findings of this paper go beyond the application to a narrow class of fish-like robots. More broadly we have demonstrated the use of periodic excitation to produce bistable response that generate different gaits including a steering gait. The mechanics demonstrated here show the feasibility of applications to other mobile soft robots.

Design and experimental verification of propulsion system for a Mars quadcopter

Due to the Mars rotorcraft can conduct extensive surface exploration of Mars and carry sampler for collecting samples on the Martian surface, it is gradually becoming the mainstream exploration devices for Mars missions. In response to the thin atmosphere on Mars, with the flight duration and sample-carrying capacity of the quadcopter as constraints, we design the propulsion system parameters for the Mars quadcopter with the function of sampling on the Martian surface. A method for evaluating rotor performance indicators, including mass and Mach number at the tip of the blade, is proposed. Based on the evaluation index and the steady RANS method for predicting the lift and drag characteristics of the rotor, an appropriate rotor diameter for the Mars quadrotor is selected. The method combining NSGA-II and two-dimensional steady RANS is employed to optimize the airfoil of the Mars quadcopter blade under the condition of a chord length of 40 mm, a Mach number of 0.43, an angle of attack of 20°, and a Reynolds number based on chord of 6080. Experimental verification for the lift-to-drag characteristics of the single rotor is conducted in an environment simulating the atmospheric density on the Martian surface. The results show that the blade after optimization can generate a thrust of 5.95 N and consume power of 164.9 W, at the rotational speed of 3650 r/min. Based on the test bench with the function of sliding up and down for testing aerodynamic performance of quadcopter, the temperature of the motor and battery discharge characteristics of the Mars quadcopter are conducted. The results of the test show that the quadrotor can provide a thrust-to-weight ratio of 1.66 for the Mars quadcopter while meeting the design requirement of 3 min.

Multirotor drone noise: numerical approach for aeroacoustics and in-flight noise prediction

Nowadays, multirotor drone usage has become widespread for various purposes: amateur or professional videos, building inspection, civil security, military defense, etc. But this usage increase has also seen growing concerns about community noise annoyance in inhabited areas, acoustic detectability for security and military purposes, or remote wildlife monitoring. Predicting the drone noise can now be accurately achieved thanks to computational aeroacoustics (CAA). The present work deals with the aeroacoustic simulation and measurement of a quadcopter drone and in-flight condition prediction. The CAA simulation of a single rotor is first compared with test bench measurements in an anechoic room. Comparison for the full drone is then derived from this single-rotor comparison. Finally, the study is further extended to in-flight comparisons, in order to show that CAA simulation can help design quieter drones in real operating conditions.

Unsteady Loads of a Scaled Rotor on and Near the Landing Deck of the NATO Generic Destroyer with Concurrent Stereo PIV and Surface Pressure Measurements

Rotorcraft shipboard operations are risky and demand high piloting skills. To gain further understanding and familiarize pilots with these complicated scenarios, various methods of computational simulations have been used in the past decades. Yet, some simulation methods may not capture a realistic response of the rotorcraft due to simplified modeling of the interactional aerodynamics in order to achieve real-time capability for pilot training. Thus, improvements to these simulations are required, and experimental data that unveil the interactional aerodynamics and dynamics between the rotor and ship are needed for computational validation efforts. In this study, an extensive experimental investigation of the ship???rotor dynamic interface problem was conducted to gain a general understanding of the interactional aerodynamics between a 1:100 wind-tunnel-scale NATO Generic Destroyer and a representative single main rotor, operating both stationary and dynamically moving in space in the vicinity of the landing deck. Data obtained through simultaneous measurements of rotor hub loads, ship deck surface pressures, and stereoscopic particle image velocimetry flow fields gave valuable insight into the highly coupled aerodynamic phenomena. Results showed that the rotor hub loads exhibited a high dependency on both the wind direction and also the position of the rotor relative to the landing deck. A bifurcation in the regions of high unsteady thrust was observed under certain wind conditions due to the ship airwake, impacting different portions of the rotor disk. The inflow angles across the rotor disk were estimated and assessed through flow field measurement, revealing how the ship airwake altered the rotor inflow and wake structure that contributed to the unique change in rotor loads under various hovering conditions.

Influence of tip air injection on the unsteady blade force under circumferential pressure distortion

In order to further understand the impact of tip air injection on compressor stability under circumferential pressure distortion, a series of experimental studies on tip air injection under uniform and circumferential distortion were conducted on a low-speed single rotor axial flow compressor. The unsteady measurements were carried out by use of microsensors and strain gauges bonded on the rotor blade surfaces, and a collection of dynamic pressure sensors installed on the casing wall. Results indicate that with the increase in the injected momentum ratio, the load at the leading edge near the rotor blade tip obviously decreases, thereby delaying the stall. By comparing the pressure distribution on the rotor blade surface under different injected momentum ratios, tip air injection can effectively suppress flow separation at the blade tip to enhance flow capability. In addition, it can also weaken the fluctuation of tip leakage flow and reduce the dynamic stress similar to natural vibration near the blade root both in stationary and rotating coordinate systems. Under the condition of inlet circumferential distortion, tip air injection can significantly reduce the load at the distorted region and suppress the low-frequency disturbances measured on the rotor blade surface caused by inlet distortion. In addition, the dynamic stress near the blade root can also be effectively reduced by tip air injection. It implies that tip air injection can both extend the stall margin and reduce blade vibration when suffering from circumferential distortion; thus, the compressor can safely operate.

The influence of the rotor spacing distance and rotating speed ratio on the power production of dual rotor wind turbines using a modified two-way interaction blade element momentum method

The present study aims to develop an accurate and fast improved blade element method (BEM) with two-way rotor-rotor interaction model which can account for two-way rotor-rotor interaction and the influence of rotor spacing while most previous BEM models for co-axis dual rotor wind turbines (DRWT) ignore the rear to front rotor interaction effect. A modified BEM model distinct from computationally intensive Computation Fluids Dynamics (CFD) model, is proposed for DRWTs. Validation of the present model is conducted by comparing it with experimental data from referenced literature for both co- and counter-rotating configuration. In our case study, for both co- and counter-rotating configurations, the power coefficient (CP) maps exhibit a double-hump shape instead of a single peak on the power output -λ curve observed in a single rotor wind turbine system. This characteristic may lead the DRWT to a local CPmax condition rather than the global CPmax while pursing the optimum operational condition. Although the counter-rotating DRWT can achieve a higher CPmax for most rotor spacing ratio (S/R) cases, it exhibits inferior power output than the single rotor for the S/R = 0.1 case. The present model can serve as a rapid and accurate model for configuring and control strategy evaluating DRWTs.

An improved wiener filter-based method for identifying stall inception of transonic compressor

The development of the modern aviation industry poses high demands on the design of aircraft engines recently. However, the stability of compressor flow is one of the key factors affecting further improvements in engine performance. The design of next-generation aircraft engines imposes higher requirements on compressor loading, which leads to the emergence of many new stall inceptions. As a result, the onset and evolution of flow instability become more complex. For accurately capturing stall inceptions of transonic compressors, the strong pressure disturbances caused by shock waves at the blade tip and the complex flow within blade passages result in significant challenges. To address this issue, this study draws inspiration from the design methods of Wiener filters in the field of speech recognition. Based on the characteristic signal mutations during rotating stall in compressors, a Wiener filter approach that uses time-delayed signals as noise estimates during filter training is developed. The method can be used for both offline and online analysis. It was applied to analyze the stall signals of a single rotor from a 1.5-stage transonic axial compressor under distorted inlet conditions at transonic rotational speeds and the entire stage under uniform inlet conditions at subsonic rotational speeds. The results indicate that, under inlet distortion, the compressor generates disturbance signals in the distorted sector before stall, and the earliest spike-inception disturbance occurs at the circumferential position of the rotor leaving the distorted sector. Under uniform inlet conditions, random disturbances could be detected throughout the circumference before stall onset, developing into spike waves at a circumferential location that subsequently triggered stall. Compared to conventional low-pass filters, discrete wavelet transforms, and empirical mode decomposition, the Wiener filter yielded more prominent spike wave structures in the filtered signals. Under distorted inlet conditions, the Wiener-filtered signals showed a 1 % decrease in autocorrelation coefficient and a 3.7 % increase in root mean square (RMS) upon the appearance of spike waves, more pronounced than the 0.5 % decrease in autocorrelation coefficient and 1.8 % increase in RMS achieved by conventional methods. Under uniform inlet conditions, the Wiener filter also detected a 9.7 % increase in RMS upon the appearance of spike waves, more pronounced than the 6.3 % increase observed with conventional methods.

Design and analysis of a single-stage supersonic turbine with partial admission

Supersonic impulse turbines are commonly used to harvest waste heat from systems based on organic Rankine cycles, automotive applications, and gas-generator liquid rocket engines. This research aims to design and analyze a single-stage supersonic turbine with a rated power of approximately 440 KW. We present a comprehensive preliminary design roadmap followed by design parameters optimization. The preliminary sizing is carried out using one-dimensional flow analysis, while the blade geometrical design is performed using the two-dimensional method of characteristics. The turbine performance is then analyzed through numerical simulations on three-dimensional models. Comprehensive parametric analyses are conducted to examine the turbine performance sensitivity to changes in partial admission (PA), mean radius, and turbine blade height using three-dimensional sliding mesh techniques (SMT). The current analysis simulates the full turbine to capture PA effects, rather than focusing on a single periodic sector as is common in turbomachinery simulation practices. Different PA scenarios are investigated, emphasizing a single rotor passage over a complete rotor cycle in a partially admitted turbine, and examining its charging and discharging mechanisms. Flow tracking over such a blade shows that the turbine rotor exhibits compressor-like behavior over most of the unadmitted zone, contributing to efficiency drops and severe transients.

Tetrakis(trimethylsilyl)silane as a standard compound for fast spinning Solid-State NMR experiments

The development of magic angle spinning (MAS) at rates ranging from 30 kHz to greater than 100 kHz has substantially advanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy 1H-detection methods. The small rotors required for such MAS rates have a limited sample volume and low 13C-detection sensitivity, rendering the traditional set of standard compounds for SSNMR insufficient or highly inconvenient for shimming and magic-angle calibration. Additionally, the reproducibility of magic angle setting, chemical shift referencing, and probe position can be especially critical for SSNMR experiments at high fields. These conditions suggest the need for a high signal-to-noise ratio (SNR) 1H-detection standard compound, which is preferably multi-purpose, to simplify instrument set up for ultra-fast MAS SSNMR instruments at high magnetic fields. In this study, we present the results for setting magic angle and shimming using tetrakis(trimethylsilyl)silane (TTMSS, or TKS), a tetramethylsilane (TMS) analogue, at near 40 kHz and demonstrate that we can achieve favorable results in less time but with equal or superior precision as traditional KBr and adamantane standards. The high SNR and TMS-like chemical shift of TKS also opens the possibilities for using TKS as an internal standard with biological samples. A single rotor containing a four-component mixture of TKS, adamantane, uniformly 13C, 15N-labeled N-acetyl valine and KBr was used to perform a complete configuration and calibration of a SSNMR probe without sample changes. We anticipate TKS as a standard compound to be especially effective at very high MAS conditions and to greatly simplify the instrument set up for high and ultra-high field SSNMR instruments.

Scanning Lagrangian Particle Tracking To Measure 3D Large Scale Aerodynamics Of Quadcopter Flight

We present large-scale time-resolved and volumetric measurements of the flow surrounding a quadcopter drone. Cases with hovering flight, forward flight - with and without ground-effect - as well as lift-off scenarios have been realized. Five high-speed cameras were used to capture images of hundreds of thousands heliumfilled soap bubbles being illuminated by pulsed LED arrays. The arrays were operated in a dual-scanning mode, where the front and the back part of the volume are illuminated intermittently, each with a frequency of 3 kHz. The cameras were recording at 6 kHz, thereby capturing both sub-time-series in a single measurement run. Compared to a full illumination of the volume, we can either reduce the number of particles imaged on the cameras given a fixed tracer concentration - facilitating the reconstruction - or operate at a higher tracer concentration while keeping the number of imaged particles fixed. The dual time-series were evaluated by Lagrangian Particle Tracking, using the Shake-The-Box method, yielding dense fields of particle tracks. For the current results, the time series for both sub-volumes were evaluated independently. For the final contribution, an integrated evaluation scheme, alternatingly operating on both time-series is foreseen. After the tracking step, flow structures were identified using the data assimilation method FlowFit. The temporally and spatially highly resolved results document the strong interaction of the wakes induced by several rotors, as well as the interaction of wing tip vortices stemming from a single rotor. Brown-out effects are documented in forward flight. Averaged results of hovering flight enable an evaluation of the azimuthal distribution of the downwash- and outwash-velocities resulting from the geometric layout of the four rotors. By having highly resolved data encompassing the whole flight vehicle, the forces conveyed by the drone to the liquid can be determined via surface- or volume-integration.

Hydrodynamic Development and Optimisation of a Retrofittable Dual-Mode Propeller Turbine

Dual-mode propellers, as propulsion and turbine devices, have found widespread application in renewable energy systems for marine vehicles, particularly in sailing boats and yachts. However, the existing dual-mode propellers in these contexts are typically chosen in an off-the-shelf manner, indicating a lack of hydrodynamic optimisation to enhance both the propulsion and energy generation efficiency in the same rotor. To address this limitation and furnish scientific validation of the design of a dual-mode propeller turbine rotor optimised to achieve a balanced performance in both propulsion and energy generation, rigorous experimentation was conducted using specialised software, Rotorysics 2019, and a case study vessel, the Princess Royale. Utilising prior experimental data for this propeller turbine, code validation was undertaken to ensure accurate prediction of the effects of the pitch, blade count and expanded area ratio on the performance in both modes. With the intention of achieving optimal power generation and propulsion efficiencies in conjunction with a single rotor, the findings reveal that the optimised fixed-pitch propeller exhibits dual functionality. They serve as both propulsion and tidal/current turbines with balanced efficiency. They are particularly suitable for low-speed vessels such as yachts anchored in currents or for sailboats utilising a propeller as a towed turbine. Through thorough testing and analysis, the concept of a dual-mode propeller turbine was feasible. Analysing them separately, in terms of the propulsion, the best geometry found through numerous tests of different expanded area ratios, blade number, pitch and speed was the 3-blade, 0.6 pitch ratio, which achieved a propulsive efficiency of 54.33% (0.5433204) and a power coefficient of 0.291843. Conversely, if the focus was on power generation while maintaining excellent propulsive efficiency, the optimal geometry would be the 5-blade, 0.6 pitch ratio, which offers a power coefficient of 0.348402 and a propulsive efficiency of 48.55% (0.48547). However, when using both power generation and propulsion as the criteria, the 5-blade, 0.6 pitch ratio, with an EAR of 0.387142, is superior, with balanced optimisation, offering a propulsive efficiency of 52.53% (0.52527) and a power coefficient of 0.319718. As expected, this encompasses a higher blade number for increased power generation efficiency and a higher pitch ratio for increased propulsive efficiency.

Comprehensive Analysis of Pressure Drop Phenomena in Rotating Packed Bed Distillation: An In-Depth Investigation.

A rotating packed bed (RPB) is an innovative intensification technology that improves its separation capabilities in high-gravity conditions. This process increases efficiency with smaller equipment size and footprint than conventional packed columns. Although significant advancements have been made regarding RPBs, most studies only focused on single or dual rotor configurations in addressing dry pressure drop. Hence, multiple rotor systems in industrial settings can enhance economic efficiency by minimizing the necessity for numerous RPBs. This study investigated the pressure drops and holdup in a three-stage rotor-based RPB under actual process conditions using natural gas as the feed. A novel pressure drop correlation was introduced based on the nitrogen removal process from the natural gas in continuous RPB distillation operations. Consequently, the correlation between centrifugal acceleration, turbulent, and momentum effects demonstrated remarkable accuracy within ±15%. This outcome also highlighted the importance of meticulous design considerations in RPB-based applications due to the complex correlation between centrifugal forces, liquid holdup, and gas flow rates. The reflux feed ratio, liquid holdup, rotating speed, and F-factor effects were examined to comprehend the RPB distillation process. Overall, the correlations between the critical parameters offered crucial insights to prevent process upsets (such as flooding), contributing to advancing RPBs in practical industrial settings.

Assessment of the azimuthal loads variation by a bi-rotor configuration

Multi wind turbine configurations are emerging in the offshore wind energy market. The modelling of the aerodynamics of these systems is challenging, due to the small lateral distance between rotors and the subsequent interaction between wakes. Previous analysis in the literature showed that, due to this interaction, multi wind turbine concepts present the advantage of an increment in power production, if the rotors are laterally aligned. However, the counterpart in the variation of the blade loads throughout the revolution, has yet to be analysed in depth. This study focuses on the differences observed in azimuthal cycles of blade aerodynamic loads in side-by-side bi-rotor configurations, as an initial analysis of their potential impact on fatigue loads. The analysis has been developed using two aerodynamic codes, with different levels of fidelity. These models are: a Free Vortex filament Method (FVM) combined with an unsteady Lifting Line (LL) model, and a URANS-blade resolved approach. The simulations show that the sectional blade loads are affected by the adjacent rotor, changing the shape of the aerodynamic load cycles along the azimuth. The load azimuthal distributions predicted by a FVM and a URANS models have been compared, showing agreement on the shape of the cycle with slight differences on maximum peak values, specially at the inner sections of the blade. The FVM model has predicted increments in the blade load cycles, with respect to a single rotor case, with a maximum amplitude of a 3% for out-of-plane forces, and a 8% for in-plane forces. The difference in the azimuthal position of both rotors (phase shift angle) mainly affects the azimuthal shape and not so much the characteristic amplitude of these cycles. Finally, including geometric angles as tilt or pre-cone, produces imbalances between the blade sectional forces of the different rotors.

Primary investigation on Ram-Rotor Detonation Engine

The study presents a new type of detonation engine called the Ram-Rotor Detonation Engine (RRDE), which overcomes some of the drawbacks of conventional detonation engines such as pulsed detonation engines, oblique detonation engines, and rotating detonation engines. The RRDE organizes the processes of reactant compression, detonation combustion, and burned gas expansion in a single rotor, allowing it to achieve an ideal detonation cycle under a wide range of inlet Mach numbers, thus significantly improving the total pressure gain of the propulsion system. The feasibility and performance of RRDE are discussed through theoretical analysis and numerical simulations. The theoretical analysis indicates that the performance of the RRDE is mainly related to the inlet velocity, the rotor rim velocity, and the equivalence ratio of reactant. Increasing the inlet velocity leads to a decrease in the total pressure gain of the RRDE. Once the inlet velocity exceeds the critical value, the engine cannot achieve positive total pressure gain. Increasing the rim velocity can improve the total pressure gain and the thermodynamic cycle efficiency of RRDE. Increasing the equivalence ratio can also improve the thermodynamic cycle efficiency and enhance the total pressure gain at lower inlet velocities. While at higher inlet velocities, increasing the equivalence ratio may reduce the total pressure gain. Numerical simulations are also performed to analyze the detailed flow field structure in RRDE and its variations with the inlet parameters. The simulation results demonstrate that the detonation wave can stably stand in the RRDE and can adapt to the change of the inlet equivalence ratio within a certain range. This study provides the preliminary theoretical basis and design reference for the RRDE.

Technical, Economical, and Marketing Analyses of Corotating Dual‐Rotor Wind Turbines

In this study, a comprehensive analysis is done on a dual rotor wind turbine (DRWT) in co‐rotating arrangement. First, a co‐rotating dual rotor is designed and its performance is analyzed by blade element momentum theory simulation. Later, the designed co‐rotating DRWT is manufactured and then tested in the field by mounting the wind turbine on a truck. Running the truck steadily at different speeds while logging the performance parameters of the wind turbine, the power curve of the DRWT is obtained. Then, using the power curve of the co‐rotating DRWT and the actual wind measurement data from Çatalca Istanbul, the annual electricity generation of the designed turbine is calculated. The present techno‐economic analysis states that the co‐rotating DRWTs are more efficient compared to single rotor wind turbines (SRWTs), in accordance with the literature. Analyses show that with DRWT, around 22% higher power generation can be achieved. Additionally, the payback period for DRWT was found to be less than 1 year. The marketing strategy for introducing the product emphasizes identifying and targeting early adopters and influencers within the market. The present techno‐economic analysis states that the co‐rotating DRWTs are more efficient compared to SRWTs, in accordance with the literature.

Numerical study on aerodynamic performance improvement and efficiency enhancement of the savonius vertical axis wind turbine with semi-directional airfoil guide vane

The growth of greenhouse gases increased the need for wind energy resource. Savonius vertical axis wind turbines (VAWT) have high potential as a turbomachine. Optimization methods such as flow injection on the rotor suction side to flow control on buckets developed as Savonius VAWTs operating range and efficiency are lower than other VAWTs. In this study, the semi-directional airfoil guide vane (SDAGV) was introduced to improve the aerodynamic performance and increase the efficiency of Savonius VAWT. The results indicate that the vane installation at the lower upstream of the rotor yields a power coefficient (Cp) of 0.12, representing a 140% growth compared to a single Savonius rotor. Furthermore, this installation extended the operating range of the turbine from a tip speed ratio (TSR) of 0.51–0.8. According to the results, it was found that more passages could improve efficiency. Five types of symmetrical airfoil profiles were evaluated for the guide vane. The NACA0010 airfoil profile, which has lower thickness than the others, obtained 7% higher efficiency than the base case consisting of NACA0012. Also, the optimal stagger angle for configurations NACA0021, NACA0018 was found to be 45°, and for NACA0010 and NACA0012 was determined to be 30°, respectively.

Performance Improvement of Winged Compound Helicopter Due to Differential Flap Deflections

A lift-offset system for a single-rotor-type compound helicopter is proposed to improve the aerodynamic performance in high-speed flight. The proposed system utilizes the differential flap deflections on the fixed wings to produce a rolling moment, which is counteracted by the single main rotor, causing the rotor to operate in a lift-offset state. The performance of the proposed system is evaluated through numerical simulations. At first, the effect of lift offset with regard to lift-share ratio on the rotor performance is investigated. Then, the impact of lift offset due to the differential flaps on the overall effective lift-to-drag ratio is studied. The results show that the lift offset significantly improves the rotor performance and the overall effective lift-to-drag ratios, especially at larger rotor lift-share ratios. The overall effective lift-to-drag ratio increases by 10% due to the differential flaps compared to the zero-flap deflections. It is concluded that the lift offset due to the differential flaps achieves more efficient cruising flight for a single-rotor-type compound helicopter.