Rotating detonation engines (RDEs) have received significant attention from industry and academia alike, owing to their numerous advantages, such as pressure gain combustion, high operation ...frequency, and near-constant thrust output. Furthermore, there is considerable interest in combining RDEs with gas-turbine engines to further improve their overall system performance. This study examines the propagation characteristics of continuous rotating detonation waves (CRDWs) with a turbine guide vane (TGV). We develop an experimental model of a hydrogen–air rotating detonation combustor integrated with a TGV section and record the high-frequency pressure oscillations and static pressure upstream and downstream of the TGV section. The experimental results indicate that: the interactions between CRDW and the turbine blade cause the reflected shock propagating backwards to the combustor. Both pressure oscillation amplitude and static pressure decline at downstream of TGV. Notably, the pressure oscillation attenuation by the TGV is influenced by the direction of CRDW propagation. When the CRDW propagation direction and the flow path direction of the guide vane are opposite to each other, the pressure oscillation attenuation increases. The findings obtained herein provide benchmark data that help improve the fundamental understanding of CRDW and TGV interaction, and can be used to develop detonation-based propulsion technology.
•Rotating detonation combustor integrated with a turbine model to improve performance.•Verification of rotating detonation combustor operation characteristics.•Detailed discussion of interactions between the rotating detonation wave and turbine blade.•Quantitative analysis of pressure oscillation across the turbine under various conditions.•Relationship between pressure amplitude attenuation and detonation propagation direction.
There are currently no commercial solar-hybrid gas turbine systems readily available off-the-shelf. Several operation and control challenges still exist, and significant development effort is still ...required to provide technically proven units. To address this gap, this study modeled the performance of a solar-hybrid micro gas turbine (MGT) system, considering both steady-state and transient operation. Based on the component matching, the equilibrium running point shifted on the compressor characteristic, to counter the additional system pressure losses, and ensure a useful work output, albeit with a reduced surge margin. Solar-hybrid operation was only possible for solar share of at least 20%, while the work output and cycle thermal efficiency drop below standard operation levels beyond certain solar share. In contrast to standard operation, a higher nominal work output of 20 kW, at a lower SFC of 0.0004 kg/kWh and a higher cycle thermal efficiency of 8% was predicted, the latter potentially increasing to 20% with recuperation. Solar-hybrid equilibrium running could eliminate the risk of running into compressor surge. The findings from this study should guide operation and control strategies for the proposed, and future solar-hybrid MGT systems, which should in turn contribute to their development and commercialization.
•The MGT system equilibrium running point shifted, reducing the surge margin.•Solar-hybrid operation was only possible for solar share of at least 20%.•Work output and cycle efficiency drop below standard MGT levels at given solar share.•Sudden change in solar irradiation corrected by altering the fuel flow.•Solar-hybrid equilibrium running could eliminate the risk of running into surge.
•Framework for preliminary assessment of urban wind energy potential at large scales.•Extension of the knowledge on small-scale wind power potential assessment.•Focus on the roof-mounted wind ...turbines.•1st and 2nd step: collecting potential building data and respective wind speed characteristics.•3rd step: obtaining turbine characteristics from manufacturer, modeling or experiment.•Last step: estimating the annual urban wind energy production (AEP).
Urban wind energy can provide a decentralized local source of energy for residential areas and reduce the cost of energy by avoiding the losses/costs of long-distance energy transmission. In this perspective, a preliminary assessment of urban wind energy is highly desired by turbine developers, investors and policy makers. However, given the large number of parameters involved, predictions of the wind energy potential in urban areas are very challenging. The present paper, therefore, intends to present a straightforward framework to provide a preliminary and large-scale assessment of the urban wind energy potential, i.e. at city or country scales, for roof-mounted turbines. The framework is based on four main steps: (i) collecting the building data, i.e. the number of potential candidate high-rise buildings and their height and rooftop surface area; (ii) obtaining the annual mean wind speed statistics at the height of these buildings and sorting the building data based on these statistics; (iii) obtaining the turbine characteristics and determining the average number of turbines per building roof; (iv) calculating the annual energy production (AEP). The application of the framework is then illustrated at the country scale for the Netherlands. In this case, the urban wind energy potential is assessed by considering the installation of 18,156 small wind turbines on the roofs of 1513 existing high-rise buildings in 12 major cities in the Netherlands, yielding an annual energy production of 150.1 GWh.
•Used tuned mass-damper-inerter (TMDI) for vibration control of wind turbine blades.•Closed-form expressions for optimal tuning and damping ratios of TMDIs derived.•Numerical simulations show TMDIs ...can impressively control edgewise vibrations.•TMDIs require significantly less (55%) damper stroke than classical TMDs.
This paper proposes the use of a tuned mass-damper-inerter (TMDI) for the mitigation of edgewise blade vibrations in wind turbines. The hollow nature of the wind turbine blades is utilized to install a TMDI at a location close to the tip of each blade. A flexible multi-modal offshore wind turbine model is developed in order to study the dynamics of wind turbine blade vibrations. Uncontrolled, TMD controlled and TMDI controlled models are derived. These models are developed using the Euler–Lagrangian approach and lead to time-varying systems with the possibility of negative damping. Closed-form expressions for the optimal tuning and damping ratios of blade-mounted TMDIs are derived. Numerical simulations are then presented to demonstrate the performance of the TMDI controlled blades. The results show that TMDIs can control edgewise vibrations in wind turbine blades while requiring significantly less damper stroke than classical TMDs. The inclusion of the inerter in the damper had a significant effect on the damper stroke with reductions of up to 55% demonstrated. These impressive reductions in damper stroke come at the cost of very slightly increased blade vibration as compared to the TMD controlled case. This is a trade-off that must be considered in the design of a wind turbine.
The main challenge of establishing a model to predict the flow fields of turbomachinery was insufficient data. This study aimed to establish a generalizable and accurate model on a small-scale ...dataset to cost-effectively predict the surface pressure distribution of a turbine rotor cascade with widely varying geometries and boundary conditions. To meet this purpose, a novel concept of transfer learning was introduced, which was defined as transferring knowledge from a large-scale but low-fidelity dataset to a small-scale but high-fidelity dataset. A Conditional Generative Adversarial Neural Network was designed as the pre-trained network for the transfer learning to regress the surface pressure distributions. Two models transferred from datasets with different fidelity and an independent model were established and compared in detail. The results showed that the proposed method successfully reduced the modeling cost with a low error in predicting the surface pressure distributions. The model transferred from the higher-fidelity dataset had better generalization performance, which reduced the root mean square error and modeling cost by 40.2% and 9 times, respectively. The presented method could serve as a base framework for modeling surface pressure distribution of complex objects using a small-scale dataset.
•Modeling on a small-scale high-fidelity dataset.•The concept of transfer learning is introduced for modeling.•The 3-D distribution of surface pressure can be reconstructed.•The model is of low cost and good generalization performance.
For NREL Phase VI horizontal axis wind turbine, a flow control method to suppress the flow separation by setting micro-cylinder in front of the blade leading edge is proposed, and the corresponding ...numerical simulation analysis for the aerodynamic performance of wind turbine is conducted. Firstly, the results predicted by simulation are confirmed experimentally. Under the same operating condition, the simulation and experimental results of low-speed shaft torque are compared, along with results from other studies. It can be found that the simulation results can accurately reflect the basic physical characteristics of flow field for NREL Phase VI wind turbine. Secondly, the influence of different diameters and positions of micro-cylinders on aerodynamic performance of wind turbine is discussed. Numerical results suggest that under different stall conditions, setting appropriate micro-cylinders in front of the blade leading edge can effectively suppress flow separation on wind turbine blades without increasing the load of wind turbine. Moreover, under different wind speeds, micro-cylinders with different diameters and positions have various impacts on aerodynamic performance of wind turbine. Through numerical calculation, the blade torque can maximally have an increase of 27.3% by setting a micro-cylinder with proper diameter and position in front of the blade leading edge.
•Micro-cylinder is set in front of the blade leading edge to increase blade torque.•Simulation results are compared with experimental results for validation.•Influence of diameters and positions of micro-cylinders are discussed numerically.•Blade torque can be improved obviously with proper setting of micro-cylinders.•Flow separation can be suppressed effectively by setting appropriate micro-cylinders.
•An innovative theory is introduced to predict the performance of Savonius turbine.•A concept of stagnation pressure and Newton’s impulse momentum principle are used.•Theory considers the effect of ...two types of rotors namely with end plate and. without end plate.•Presented theory is validated with the published experimental results.•Model predicts Cpmax within 6.7% in comparison with experimental results.
A theoretical study is introduced to predict the hydrodynamic performance of a vertical axis Savonius turbine with semicircular vanes. This theory is based on the concept of stagnation pressure rise at the turbine vanes and Newton’s second law of impulse momentum principle. The present theory predicts the performance of a Savonius rotor with semicircular vane including overlapping vanes. Although the present model is derived for semicircular vanes, it can also be used for any type of the vanes with minor modifications.
For the validation of an investigated theory, the results obtained by the presented theory is compared with the experimental results available in the published literatures. The comparison of the results are done for two major cases of the Savonius turbine, i. Turbine with an end plate and ii. Turbine without end plates for low aspect ratio. The calculation shows that, the theoretically calculated results predicts the maximum power within 3.6% and maximum coefficient of power within 6.67% variation.
It can be conclude that the present theory will be most useful to decide the best design configurations of Savonius turbine unit for specific available flow conditions and quick performance prediction of a Savonius turbine for different operating conditions.
Currently, the development of floating wind turbines and wave energy converters (WECs) is both facing the challenge of high cost-of-energy (CoE). A promising way to reduce the CoE is to employ ...combined wind and wave energy concepts because they can share the same floating platform, mooring systems, and electrical cables and thus reduce the construction cost. Several combined concepts with floating horizontal axis wind turbines (HAWTs) have been proposed and studied. Compared to floating HAWTs, floating vertical axis wind turbines (VAWTs) have a good potential for CoE reduction. Therefore, this study proposes a novel combined wind and wave energy concept, which consists of a spar-type floating VAWT and a torus-shaped point absorber WEC. This combined concept utilizes the relative heave motion between the torus and the spar buoy to harvest wave energy. Fully coupled simulations under turbulent wind and irregular waves are carried out to evaluate its power performance and to assess the effect of the additional torus on the dynamic behavior of the floating VAWT. The results indicate that introducing the WEC contributes to the total power production while causing limited impacts on the power production and dynamic responses of the floating VAWT. The proposed combined concept is promising.
•A novel combined wind and wave energy concept is proposed.•The relative heave motion between the torus and the spar buoy is utilized.•Fully coupled simulations are carried out to evaluate its power performance.•The effect of the torus on the dynamic behavior of the floating VAWT is assessed.•Introducing the WEC contributes to the total power production with limited impacts.
Resolving the controversy about hydropower is only possible based on reliable data on its ecological effects, particularly fish welfare.
Herein, we propose a comprehensive assessment of conventional ...and innovative hydropower using a dataset of 52,250 fish.
The effects of hydropower on fish were most harmful at sites with Kaplan turbines, showing ≤83% mortality. Innovative hydropower, often termed ‘fish‐friendly’, caused ≤64% mortality.
Our findings suggested that the runner peripheral speed, number of turbine blades and turbulence at turbine outlets were the most important factors.
Synthesis and applications. To reduce the impact of hydropower on fish, site‐specific characteristics such as head drop, bypass options and river‐specific species composition need to be more intensively considered in optimal turbine technologies and operation modes.
To reduce the impact of hydropower on fish, site‐specific characteristics such as head drop, bypass options and river‐specific species composition need to be more intensively considered in optimal turbine technologies and operation modes.
•The paper proposes a robust practice for monitoring of wind turbine.•A DIC system on a drone is used as a sensing technique for dynamic measurements.•The DIC on a UAV enables robust in-situ ...measurements.•A dynamic stitching technique is used to enable high-resolution dynamic monitoring.
With the recent demands for more efficient clean renewable energy sources, wind turbines are designed that have large rotor blade diameters. These large-sized wind turbines need to be periodically monitored to prevent catastrophic failures. This paper aims to develop a practice for obtaining the vibration characteristics of wind turbine blades that can be eventually used for structural health monitoring of these structures. This monitoring technique needs to be robust and non-contact to prevent any interference with the operation of the wind turbine. In this work, a digital image correlation (DIC) system installed on a drone is used as a sensing technique to obtain the dynamic characteristics of rotating wind turbine blades. The DIC uses a stereo-camera system to record the deflections of the blades and provides non-contact measurements. The unmanned aerial vehicle (UAV) enables on-site robust measurements. Furthermore, a dynamic stitching technique is used after DIC measurement to obtain vibration characteristics of the entire blade with high accuracy. The proposed health monitoring technique can be used by engineers for remote structural health monitoring of wind turbines during operation in both offshore and inland wind farms.
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