Turbine Rotor Design Research Articles

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.

Nonlinear vibration characteristics of an aeroengine cantilever flexible rotor considering interference fit and unbalance

Aeroengine power turbine rotor is a typical nonlinear rotor system, in which the interference connection between long shaft and short shaft has a prominent influence on the coupling vibration of the system, especially at high speed, the nonlinear stiffness change of interference contact is more obvious. Therefore, the paper considers the change of the contact characteristics of the long shaft and the short shaft of the turbine rotor, and the nonlinear restoring force of the bearing to analyze the dynamic characteristics of the rotor. Firstly, according to the theory of elasticity, the contact parameters under different speed states are calculated, the contact stiffness model under interference fit is established, and the relationship between contact stiffness and speed is analyzed. Secondly, according to the Hertz contact theory, a bearing nonlinear restoring force model considering time-varying characteristics is established. Finally, the dynamic model of the bearing-flexible rotor coupling considering interference contact is established. The influence of contact parameters and unbalance parameters on the nonlinear vibration characteristics of the rotor is analyzed by amplitude-frequency curve, bifurcation diagram, time-domain waveform, spectrum diagram, trajectory diagram and Poincaré diagram. In addition, the simulation results are compared with the experiment results of the rotor test rig to verify the accuracy of the established dynamic model. By analyzing the influence of different parameters such as interference magnitude, unbalance position, unbalance magnitude and unbalance couple on the nonlinear vibration of the rotor, the basis for the design and vibration control of the cantilever turbine rotor is provided.

Tidal turbine hydrofoil design and optimization based on deep learning

The optimal design of hydrofoils is critical to improve the hydrodynamic performance of the tidal turbine. However, the global optimization of hydrofoils is limited by the high dimensionality of the design space, which requires extensive computational fluid dynamics simulations. This paper proposes an interactive framework for hydrofoil design and optimization based on deep learning. Generative adversarial networks are used to parameterize the hydrofoil design, which automatically learns representations from existing hydrofoils and controls new hydrofoil generation using fewer variables to reduce optimization dimensions. Moreover, the surrogate model based on convolutional neural networks is constructed, which realizes the mapping of hydrofoil design and operating parameters to hydrodynamic performance parameters. The framework can generate a large number of smooth and realistic hydrofoils with three design variables and quickly predict the performance, enabling effective optimization design of hydrofoils. The results show that the optimized hydrofoil shapes have larger lift-to-drag ratios than those of the common hydrofoils. Furthermore, the optimized hydrofoil is applied to the design of 3D horizontal axis tidal turbine blades. The simulation results show that the framework is effective and stable, which can facilitate the design of tidal turbine rotors and provide hydrofoils with higher power coefficients.

Fluid dynamic design of a vertical axis wind turbine rotor under low wind speed

The design of the rotor geometry of a vertical axis wind turbine (VAWT) type H, for power generation at low wind speeds, is presented. The computational simulation allowed us to establish that the NACA 0018 profile offers a better ratio of lift and drag coefficients in contrast to NACA 0021 and NACA 0025, so this geometry was selected as the working profile. Then, to generate a power of 30W, the dimensions of the airfoil chord, the radius, and the rotor's height were found from the blade tip speed ratio (TSR) values and the power coefficient. The results obtained indicate that the appropriate dimensions of the rotor at low-speed conditions are, a diameter of 2 m, a height of 2.16 m, and several blades of 3, for a rotation speed of 9 rad/s. Finally, an agreement was found between the angular velocity calculated theoretically, for the proposed rotor dimensions, and that obtained from the ANSYS-CFD simulation.

Multi-scale contact induced period-doubling vibrations in rotor systems: Numerical and experimental studies

Bolted disk structure has the advantages of easy production and assembly and it is widely adopted in the design of gas turbine rotors. However, the discontinuity of bolted structure and the contact effects between the disks produce complex nonlinear properties to the rotor system, resulting in difficulties in solving the vibration dynamics of the rotors. In this paper, in order to reflect the contact effect between the rotor disks more accurately, a multi-scale contact mechanics model considering the whole deformation process of the material is deduced based on the skewed distribution theory. The contact effect between disks is considered by introducing an equivalent material layer. Newmark-β method is applied to obtain the dynamic response of the rotor system under different preloads. A multi-disk rotor-bearing test bench is designed to conduct dynamic tests to verify the accuracy of the contact modeling method and obtained dynamic results. Numerical and experimental results show that adjusting the preloads has the effect to change the bifurcation state of the rotor system and the increase in the preloads leads to the period-doubling bifurcation phenomenon moving toward low speed, and leads to the early appearance of some combined frequency components (such as 2fn-fr, where fn is the working frequency and fr is the oil film whirl frequency). This research provides a theoretical reference for the modeling, dynamic behavior prediction as well as fault diagnosis of rod-fastened gas turbine rotor systems.

Biradial turbine rotor aerodynamic design and parametric analysis

The paper presents a study on the aerodynamic design of self-rectifying biradial turbine rotors for applications in wave energy conversion. The aim is to improve the biradial turbine efficiency and understand the specific speed range for which the turbine operation is most efficient. A rotor geometry generation method is presented, adding more degrees of freedom to the original method by improving the rotor meridional profile definition and relative flow velocity distribution. The new meridional channel definition allows tuning the rotor specific speed in the design phase. The prescribed relative flow velocity distribution improves the rotor inlet-to-outlet pressure gradient distribution. The research comprises geometry parametrisation, and three-dimensional flow simulations with a Reynolds-averaged Navier–Stokes equations solver to understand the effect of the design parameters on the rotor performance. The increase in total-to-total efficiency of the new rotor design is near 1%, demonstrating the good aerodynamic performance of the original design. It is shown that the turbine’s specific speed can increase by 5.4%, and the specific diameter can decrease by 6.0% compared to the original design without reducing turbine efficiency.

Effect of the Phase-Shift Angle on the vertical axis Savonius wind turbine performance as a renewable-energy harvesting instrument

Wind energy is the third-largest renewable energy source after hydro and solar energy, so it has great potential in increasing renewable energy as a percentage of national energy. However, wind energy installation is only at 0.25% of the existing potential; so, it still needs to be developed. One of the development efforts is to optimize the wind turbine rotor design. Savonius rotors are among the most popular rotors to convert wind energy into electrical energy. The Savonius turbine is a simple structure, easy to modify to upgrade Savonius performance, and can be operated at low velocity. Phase-shift angles of 0°, 30°, 60°, and 90° were utilized in this study on a two-stage Savonius wind turbine. This study was carried out using Solver CFX utilizing the Computational Fluid Dynamic technique on the ANSYS Student version software. An SST (shear stress transport) turbulence model with steady-state turbulence was used. The purpose of this study was to assess the influence of PSA on the performance of the Savonius two-stage turbine. Factorial design analysis was used in conjunction with the CFD approach. The results indicated that PSA influenced the Savonius turbine’s performance, with 30° being the optimal PSA. Simultaneously, the Cpmax may be obtained using 0.29. The factorial design study with two components revealed that the Phase-Shift Angle had a considerable effect on rotor performance, and the two factors (TSR and PSA) had an interaction.

Multidisciplinary Collaborative Design and Optimization of Turbine Rotors Considering Aleatory and Interval Mixed Uncertainty under a SORA Framework

The turbine rotor is the key component of the turbine, which has a great impact on the construction cost and power generation efficiency of an entire hydropower station. Receiving the torque of the runner transmission and completing the specified power generation is its main function. There are many uncertain factors in the design, manufacture, and operation environment of a turbine rotor. Therefore, it is necessary to optimize the mechanism on the premise of ensuring that the mechanical system meets high reliability and high safety levels. This article uses the multidisciplinary reliability analysis and optimization method under random and interval uncertainty to quantitatively analyze the uncertainty factors, and then optimally solves the RBMDO problem of the turbine rotor mechanism. Through the finite element simulation analysis of the optimized design scheme, the rationality and feasibility of the obtained results are further verified.

Analysis and Validation of Glauert Rotor Design

The design of industrial wind turbine rotors is generally based on the blade-element/momentum (BEM) approach introduced by Glauert (1935). Essentially, the theory consists of combining a blade-element approach with axial momentum theory, and then introducing a tip correction to account for the finite number of rotor blades. This is required, as the momentum theory is based on representing the rotor by a disk, corresponding to a rotor with infinitely many blades. The optimum design properties are obtained by optimizing the local power coefficient at each blade element. This is typically accomplished by solving a simple analytical system of equations for the axial and tangential inductions factors, ignoring at first the tip correction. The tip correction is subsequently introduced to correct the design variables. In the present work we analyse the implications of including the tip correction directly in the optimization. As a result of the analysis, we find the somewhat surprising result that the maximum optimal interference factor is not 1/3, as normally encountered for optimum rotor design, but 2/5. In the paper we prove this analytically and use the theory to design optimum rotors, which subsequently are benchmarked by comparison to results from a numerical lifting line model.

Using Small Wind Turbine Technology to Design an AntiFrost Fan

Anti-frost fans (AFFs) are widely used in agriculture to reduce the frost damage to crops. The small wind turbine rotor design code (SWRDC) was adapted to design the blades of an anti-frost fan to maximize the mass flow rate through the rotor while minimizing the blade mass and aerodynamic noise. Using a random sample set of 60 baseline designs, the design is iterated using a genetic algorithm to obtain an optimized design with a mass flow rate of 3.11 kg/s, a blade mass of 6.96 kg, and with a noise level of 72.8 dB.

Towards the development of an advanced wind turbine rotor design tool integrating full CFD and FEM

Large, highly flexible wind turbines of the new generation will make designers face un-precedent challenges, mainly connected to their huge dimensions. To tackle these challenges, it is commonly acknowledged that design tools must evolve in the direction of both improving their accuracy and turning into holistic, multiphysics tools. Furthermore, the wind turbine industry is reaching a high level of maturity, and ever more accurate and reliable design tools are required to further optimise these machines. Within this framework, the study shows the development of an integrated platform for blade design integrating 3D CFD flow simulations and 3D-FEM structural analysis. Artificial intelligence techniques are applied to develop an optimization procedure based on the proposed tool. The potential of the new platform has been tested on the well-known test case of the MEXICO rotor, for which an optimization of the blade design has been carried out. Exploring a design space sampled with 2000 CFD and FEM computations, increases in blade torque have been obtained at each of the three tip-speed ratios (TSR) investigated, ranging from 6% at the nominal TSR to 14% at the lowest one, while stresses on the blade are kept almost unaltered.

A deep learning-based optimization framework of two-dimensional hydrofoils for tidal turbine rotor design

Convolutional Neural Network (CNN) is a commonly used deep learning algorithm due to its excellent capability in identification of structural features and parameter predictions in many domains. In addition, it has incomparable advantages of high analysis efficiency and generalization performance. However, it has been questioned in the research community on whether CNN method can be applied to effectively predict hydrofoil performance for hydraulic machinery design. To this end, this paper demonstrates a novel optimization platform using CNN for hydrofoil performance prediction, which can effectively and accurately obtain the optimized hydrofoils results in aid of the structural design of tidal turbine. The prediction model uses signed distance function (SDF) to graphically represent the shape of the hydrofoil which is subsequently imported into CNN as the network input. Three different hydrofoil performance properties including the lift coefficient, drag coefficient and pressure coefficient of surface are used as output to train the neural network. In order to guarantee the accuracy of the forecasting model, Computational Fluid Dynamics (CFD) method characterized by high precision is applied to generate the dataset for neural network training. The results show that it can accurately predict the hydrodynamic parameters at a lower angle of attack with extremely short period of time. On top of the established hydrofoil performance prediction model, the Pareto curve of the optimized hydrofoils is obtained and applied to the design of 3D horizontal axis tidal turbine (HATT) blades. It proves that the optimization platform is effective and versatile in a manner that achieves both accurate and rapid prediction/optimization of the hydrofoil, which greatly facilitates to apply it for the tidal turbine rotor design.

Editorial: Towards Innovation in Next Generation of Wind Turbine Rotor Design

Editorial: Towards Innovation in Next Generation of Wind Turbine Rotor Design

A numerical structural analysis of ducted, high-solidity, fibre-composite tidal turbine rotor configurations in real flow conditions

Establishing a design and material evaluation of unique tidal turbine rotors in true hydrodynamic conditions by means of a numerical structural analysis has presented inadequacies in implementing spatial and temporal loading along the blade surfaces. This study puts forward a structural performance investigation of true-scale, ducted, high-solidity, fibre-composite tidal turbine rotor configurations in aligned and yawed flows by utilising outputs from unsteady blade-resolved computational fluid dynamic models as boundary condition loads within a finite-element numerical model. In implementation of the partitioned-approach fluid–structure interaction procedure, three distinct internal blade designs were analysed.Investigating criteria related to structural deformation and induced strains, hydrostatic & hydrodynamic analyses are put forward in representation of the rotor within the flow conditions at the installation depth. The resultant axial deflections for the proposed designs describe a maximum deflection-to-bladespan ratio of 0.04, inducing a maximum strain of 0.9%. A fatigue response analysis is undertaken to acknowledge the blade material properties required to prevent temporal failure.

Preliminary design, optimization and CFD analysis of an organic rankine cycle radial turbine rotor

• Optimized design for radial turbine of 220 kW operating with Organic Rankine Cycle. • The objective function has increased the efficiency considering loss models. • 1D optimization based on Controlled Random Search Algorithm (CRSA) • Computational Fluid Dynamics (CFD) applied for preliminary design optimized. • The novelty is the application of optimization methodology in the preliminary design. • The total-total efficiency of the radial turbine increased 2.65% after optimization. The present study describes the development of a preliminary design of a rotor for a radial turbine operating in an organic Rankine cycle. An optimization algorithm is applied to the preliminary design in order to obtain a better configuration of the geometric parameters that provides good quantification of the efficiency in the turbine, a priori, since the application of optimization processes applied to three-dimensional problems consume a lot of computational resources. The strategy makes it possible to obtain an optimized geometry to obtain flow field analyzes by applying computational fluid dynamics techniques. The working fluid R236fa was used for comparison with the literature, as it presents a positive slope of the saturation curve, and thus it is possible to work with lower temperatures. The R245fa working fluid is more suitable to the operating conditions of the proposed cycle, allows an overpressure in the condenser and allows higher levels of system efficiency. The losses at the rotor nozzle were initially modeled using a mean line design approach. The preliminary design was implemented in a commercial code Matlab®, as well as the optimization algorithm, CRSA (Controlled Random Search Algorithm), and the real gas formulations were used based on the NIST REFPROP® database. The present study is presented under three work routes: i) Development of the preliminary design methodology for a radial turbine that operates with ORC producing 50 kW of power, in order to compare with other methodologies presented in the literature. The results were compared with results observed in the literature, and demonstrate agreement between the reference geometry and the thermodynamic parameters. The total-total efficiencies of the reference turbine designs were 76.23% (R236fa) and 79.28% (R245fa); ii) Optimization by CRSA of the preliminary design of a radial turbine developed on the basis of flow coefficient and load coefficient correlations. A three-dimensional analysis of the flow through the blade section using computational fluid dynamics was performed in the final optimized design to confirm the preliminary design and subsequently analyze its characteristics. The optimization focused on the R245fa working fluid. Although several optimized preliminary designs are available in the literature with efficiency levels of up to 90%, the preliminary design choices made will only be valid for machines operating with ideal gases, that is, exhaust gases typical of an air-breathing combustion engine. For machines operating with real gases, such as organic working fluids, the design options need to be rethought and a preliminary design optimization process must be introduced. As an important result observed, an efficiency of 82.4% was obtained in the final design of the radial turbine operating with R245fa after the optimization process.

Experimental and numerical investigations of the blade design effect on Archimedes Spiral Wind Turbine performance

An assessment has been launched on two Archimedes Spiral Wind Turbine (ASWT) rotor designs, fixed and variable-angles, to get the best performance. Such a turbine has the privilege of the low-speed axial flow turbine. This turbine is characterized by its simple design, ease of manufacture, and can be used in the generation of electric power in remote areas and new urban communities. The investigation of the two Archimedes Spiral Wind Turbine rotor designs was conducted numerically and experimentally. Numerical investigations are performed to predict the full performance of the turbine under different conditions and experimental measurements are acquired to validate the numerical results. A detailed comparison of the results for both designs demonstrates the higher performance of the variable-angle design over the fixed-angle one. The results indicate that the power and torque coefficients increase with the increase in wind velocity for both designs. However, the variable-angle design produces a power that represents a 14.7% increase over the fixed-angle design.

Verification of Rotordynamic Design Using 1/5 Scaled Model Rotor of 270 MW-Class Gas Turbine Center-Tied Rotor

Gas turbine power generation is relatively minor in terms of pollutant emissions, such as nitrogen oxides or sulfur oxides, as compared to thermal power generation using coal or petroleum. This is because of the use of liquefied natural gas, known as an eco-friendly power generation solution. Large gas turbines used for power generation are suitable for the power load demanded by modern society, which fluctuates very much with respect to power consumption because it takes only about 10–20 min to reach the entire output from the start-up. A large gas turbine used for power generation is a rotating machine that features a high degree of difficulty in mechanical design due to its fast start-up characteristics, structural complexity, and high operating temperature, while also emphasizing stability. Customers are demanding operational reliability as a prerequisite before evaluating the performance of a gas turbine. It is very important to design and verify the rotor dynamics sufficiently and accurately from the design stage prior to fabrication in light of that it is very difficult to change the rotor dynamics characteristics once the design is completed and finished. Many researchers are trying to improve the design completeness, but the researches that actually design and verify the power generation gas turbine are limited only to a few manufacturers with the original technology, so there is little verification of actual gas turbine. In this paper, rotor dynamics analysis and verification of a 270 MW class DGT-300H gas turbine rotor newly developed by DHI. To verify the center tie-rod type rotor design of a large gas turbine for power generation, which was conceptually designed using in-house design tools, a 1/5 scaled model was designed by applying the dynamic scaling law. In order to verify the suitability of the applied tie-rod design, the characteristics of the variation of the natural frequency with the variation of the pre-tightening force were tested in order to confirm the dynamic proper pre-tightening force. The design of the scaled model rotor was created, the model was designed and fabricated, and the natural frequencies were analyzed and tested to confirm the validity of the design method and the suitability of the analysis results. After the design of the large gas turbine rotor for 270 MW class power generation, the natural frequencies of the rotor before the blade installation were analyzed and the suitability of the design was verified by implementing a vibration test of the rotor before blade installation.

A Deep Learning-Based Optimization Framework of Two-Dimensional Hydrofoils for Tidal Turbine Rotor Design

A Deep Learning-Based Optimization Framework of Two-Dimensional Hydrofoils for Tidal Turbine Rotor Design

Aerodynamic modeling of simplified wind turbine rotors targeting small-scale applications in Sri Lanka

A design and optimization procedure of simplified wind turbine rotors for small-scale applications is presented. The need for this research has arisen from the recent national initiative of the government of Sri Lanka titled ‘Battle for Wind Energy’ in promoting small scale grid connected wind plants for electricity customers under Net Metering scheme. The main objective of this research is to assist local developers to design optimum rotors for given electrical generators (as determined by customer requirements), suitable for wind characteristics at specific locations. Another objective is to enhance local manufacturing capabilities by providing a design option of a simplified rotor blade geometry. A study on the correlation between population density of electricity customers and wind energy potentials was carried out to categorize the demand centres based on wind energy potentials in proposing series of small-scale wind turbine designs. A unique and improved rotor design procedure is presented which attempts to match the point of maximum performance of a rotor (design tip speed ratio) with the design wind speed of a given location by considering generator performance. The new design procedure showed successful convergence on a unique blade diameter for each rotor configuration that allowed the design tip speed ratio to match the design wind speed. The performance evaluation of rotor designs showed that high solidity rotors work better on the low wind potential region while low solidity rotors dominate medium and high wind potential regions. The performance reductions of simplified rotor designs are not significant and therefore would be an effective way to enhance value addition through local manufacture. Problem statement•Lack of a rotor design procedure that considers generator performance.•Lack of a rotor design procedure for blades with an optimum simplified geometry.•Geographical mismatch between high resource sites and location of electricity consumers in Sri Lanka.•Lack of optimized small-scale wind turbine designs for sites with different wind potentials in Sri Lanka.•Limited opportunities for local manufacture in Sri Lanka. Major novel contributions•Identification of geographical locations most suitable for promoting small-scale wind turbines.•Creation of rotor design procedures for optimized and simplified blade geometries considering generator performance.•Creation of optimized and simplified wind turbine rotor designs for different wind potential regions in Sri Lanka.

Initial performance and load analysis of the LowWind turbine in comparison with a conventional turbine

We present the preliminary design of a high capacity LowWind turbine rotor with a specific power of 100 W/m 2, a rated power of 3.4MW and a 208m diameter rotor. The turbine is designed for optimal system integration and thus with a considerably increased power production at low to medium wind speed and stopped at 13 m/s. The AEP of the turbine, due to the large swept rotor area, is 40-45% higher than the AEP of a conventional on-shore turbine, the IEA Task 37 reference wind turbine with a 130 m diameter rotor and the same rated power of 3.4 MW. Initial aeroelastic simulations show that the loads of the LowWind turbine are generally higher than on the IEA turbine although comparable for some components at steady wind. For Design Load Case 1.2 (DLC1.2) for normal operation in turbulence we see a typical increase of around 20-40% of tower and rotor fatigue loads. However, this moderate increase for such big increase of rotor diameter is only obtained due to the highly flexible light weight rotor designed with a combination of peak shaving and blade bend twist coupling and for a low stop wind speed of 13 m/s.