Blade Profile Research Articles

Study on cavitation performance improvement of high-power centrifugal pump impeller

High power centrifugal pump is frequently used in large project for water resources allocation. Cavitation phenomenon causes noise and vibration and affects the centrifugal pump unit stability. The impeller model was used an initial impeller to be developed, and the impeller geometry, the blade profile, blade inlet edge were optimized by design method based on numerical simulation technique to improve cavitation performances. The 3D model with the initial and optimized impeller were simulated to obtain cavitation characteristic. The results of optimization impeller are compared and verified by model test. The numerical simulation results show that the pressure distribution is distributed on the blade surface is uniform and the location of lowest pressure is reasonable. The test results show that the optimized design significantly increases the ratio of plant cavitation coefficient σp to incipient cavitation coefficient σi and critical cavitation coefficient σ1 of the impeller under normal operation conditions, the safety margin of cavitation is increased. It was confirmed from numerical simulation and model test results that the impeller blade optimization is a reasonable and effective method for cavitation performance improvement. The study results provides design reference for the cavitation performance improvement and safe operation of high power centrifugal pump.

Investigations on the performance of a novel hybrid twisted tapered, three-bladed horizontal axis small wind turbine

Small wind turbines could bring a lot of difference in providing power to remote and inaccessible locations. These turbines could be mounted on rooftops as standalone units or hybrid units. One of the factors deciding the magnitude of power generation in wind turbines is the rotational speed of the blades. A proper blade selection and orientation could make a lot of difference in such a scenario. This work is focused on a novel hybrid twisted tapered three-bladed wind turbine made of NACA4412 and E193 blade profiles, for better aerodynamic performance and high structural stability. A simple tapered three-bladed turbine (STBT) was considered for performance comparison using testing parameters like tip speed ratio, coefficient of performance, actual power generated at wind velocities (2 m/s to 8 m/s) and pitch angles (0, ± 2o, and ± 10o). The results indicate that the hybrid twisted-bladed turbine (HTBT) generated 1.52 times more power at −10oAoA, and 1.11 times more power at −2oAoA; the increase in power between 42.5% to 121.5%, the increase in rotor speed from 30.5% to 94.4%, over the simple tapered blade-mounted turbine. However, the simple tapered blade profiled wind turbine performed better without altering the blade pitch angle.

3-D Reconstruction and Measurement of Blade Profiles With Laser-Scanning Sensor via Multiview Registration Based on Dynamic Encoding of Feature-Coordinate Information

Currently, optical-based method provides a feasible means for blade reconstruction and measurement. However, as the key step, multi-view registration is still heavily reliant on the measurement system's motion stability and geometric accuracy. Moreover, the complex and high-reflective freeform surface of blades may result in both insufficient overlaps and less prominent overlap-area features between adjacent views, making accurate multi-view data alignment difficult. Thus, we propose a method to realize accurate 3-D reconstruction and measurement of blade profiles based on a scanning system with a laser-sensor and a coarse-to-fine registration strategy. Firstly, coarse alignment of the multi-view data is achieved by calibrating the system's rotational axis using the blade datum plane feature, which can provide a good initial value for the fine registration and improve the reconstruction efficiency. Then, a fine registration algorithm based on the dynamic encoding of feature-coordinate fusion information is proposed to refine the coarsely aligned data and reduce the effect of system motion error on registration accuracy. Here, the introduction of fusion information can effectively eliminate the redundant correspondences to continuously optimize the matching probability between multi-view data in each iteration, improving registration accuracy and efficiency. Finally, experiments on typical blades and comparison with the other fine registration algorithms demonstrate the accuracy and robustness of the proposed method.

An Aerodynamic Investigation of the Last-Stage Turbine in an Upgraded Gas Turbine

Abstract Due to the lengthy certification process for newly designed turbine blades, product upgrading of industrial gas turbine units is often performed solely on compressor and combustor. Since their inlet conditions are significantly changed, the entire four-stage turbine operates far away from its original design point, leading to decreased efficiency, and increased flutter risk. This investigation first performs numerical simulations to study the flow field change of the last-stage turbine in a gas turbine before and after product upgrading. To reduce the load of the last-stage turbine without reducing the power output of the whole turbine, the enthalpy drops of turbine are reallocated to the front three stages. After modifying the blade profile based on S1 stream surface analysis, a CFD simulation is carried out on the modified three-dimensional blade passage. It is shown that the modified blade design greatly reduces the Mach number at the tip outlet of the last-stage blade, thus possibly reducing flutter risk and improving the aerodynamic efficiency of the turbine. This paper also attempts to redesign the blade geometry by different radial blade stacking of both forward sweep and backward sweep. It is found that the backward-swept blade modification can effectively reduce the endwall flow loss. This work presents the improvements of the aerodynamic efficiency of last-stage through a series of improvement methods and provides a reference for future detailed optimization of this last-stage turbine.

Separation-induced transition on a T106A blade under low and elevated free stream turbulence

The separation-induced transition on the suction surface of a T106A low pressure turbine blade is a complex phenomenon with implications for aerodynamic performance. In this numerical investigation, we explore an adverse pressure gradient-dominated flow subjected to varying levels of free stream excitation, as the underlying separation-induced transition is a critical factor in assessing blade profile loss. By comprehensively analyzing the effects of free stream turbulence (FST) on the transition process, we delve into the various mechanisms which govern the instabilities underlying bypass transition by studying the instantaneous enstrophy field. This involves solving the two-dimensional (2D) compressible Navier–Stokes equation through a series of numerical simulations, comparing a baseline flow to cases where FST with varying turbulent intensity (Tu=4% and 7%) is imposed at the inflow. Consistent with previous studies, the introduction of FST is observed to delay flow separation and trigger early transition. We explore the different stages of bypass transition, from the initial growth of disturbances (described by linear stability theory) to the emergence of unsteady separation bubbles that merge into turbulent spots (due to nonlinear interactions), by examining the vorticity dynamics. Utilizing the compressible enstrophy transport equation for the flow in a T106A blade passage, we highlight the various routes of bypass transition resulting from different levels of FST, emphasizing the relative contributions from baroclinicity, compressibility, and viscous terms.

Impeller optimization using a machine learning-based algorithm with dynamic sampling method and flow analysis for an axial flow pump

Design optimization for widely used axial flow pumps presents a formidable challenge due to the significant impact of numerous parameters associated with impeller geometry on hydraulic performance. The expansive design space raises concerns about the cost and time implications of the optimization process. This paper introduces a machine learning-based algorithm with a dynamic sampling approach to enhance the hydraulic performance of axial flow pumps. The focus is on an axial flow pump designed for China’s South-to-North Water Diversion Project. Optimization involves selecting 15 design variables governing impeller geometry, considering meridional shape and mean blade profiles. The optimization process predicts hydraulic performance using CFD methods, with a primary objective of maximizing efficiency at the axial flow pump’s design point while maintaining pump head around the design value. The results indicate that the proposed machine learning-based algorithm exhibits commendable convergence, delivering a notable improvement in performance. For instance, the optimized axial flow pump displays 2% efficiency increase compared to the initial design. Further analysis employing concepts like entropy generation rate and boundary vorticity flux reveals that the optimized pump has more uniform flow near the pressure side of the impeller blade. Additionally, design optimization effectively suppresses flow separation at the blade trailing edge near the impeller hub. This study offers valuable insights and a practical tool for the design optimization of axial flow pumps.

Vertical Axis Turbine Performance at Different Parameters: Effects of Generated Turbulence

The need to increase the energy efficiency and energy harvesting of vertical axis wind turbines is growing as a consequence of the quick expansion in the energy sector. Therefore, it is crucial to comprehend how a turbine operates. In this study, the more often used VAWT—vertical axis wind turbine—has been experimentally evaluated. Various performance graphs have been produced as a result. At various wind speeds, S1014 and S1020 airfoils are employed. Aspect ratio and angle of attack were noted, and the performance of the turbine was investigated in relation to the impact of the current produced by the turbulence generating plate. The subsonic wind tunnel setup utilized during the testing consisted of a 15 W DC motor and a 0.1 Nm torque meter. The findings demonstrated that the S1014 type blade profile was more efficient and boosted performance of the two types.

Performances and Acoustic Noise of Model Intelligent Wind Power Unit

The authors invented the superior wind power unit which is composed of the tandem wind rotors and the double rotational armature type generator without the traditional stator. The large-sized front wind rotor and the small-sized rear wind rotor drive the inner and the outer rotational armatures respectively, as for the upwind type. The unique rotational conditions of the tandem wind rotors and the fundamental performances were presented at the previous papers. Continuously, this paper discusses experimentally the effect of the blade profiles of tandem wind rotors on the performances and investigated the acoustic noise emitted from tandem wind rotors. The output of the tandem wind rotors with the desirable profiles is higher than the output of the traditional single wind rotor. The acoustic noise is induced mainly from the flow interaction between the front and the rear wind rotors, and is dominant at the blade passing frequency.

Wind tunnel assessment of small direct drive wind turbines with permanent magnets synchronous generators

Most of the small wind turbines for battery charging application are direct drive type with permanent magnets synchronous generators. A major problem in designing small direct drive wind turbines is the matching between the power curves of turbine and generator. The maximum power is extracted out from wind and fed into the load only if it is a match between the power curves of turbine rotor and generator. The assessment of the main components performances which contribute to the conversion process, namely turbine and generator, is made in wind tunnel. The experiments described below were carried out on wind turbines with carefully studied blade profile and permanent magnets synchronous generator, designed using a dedicated procedure. The paper describes the experimental layout and the results of the wind tunnel tests of two wind turbines, 250W and 1kW, designed for battery charging. The work has two objectives: measurement of the power curve of the turbine and the performances of the turbine-generator assembly with the load and the verification of the design method for maximum power delivered to the load.

Optimised design of downhole turbodrills with bending-torsional tilting blade

Deep dry hot rock mining drilling operations confronts several challenges including the high-temperature conditions in the downhole environment, the unreliable performance of surface drives, and the difficult drillability of geothermal reservoir rocks. As a result, the use of downhole motors in drilling operations becomes an imperative selection. The all-metal turbodrill presently stands as the sole downhole motor capable of effectively drilling in deep wells with temperatures exceeding 180°. Although it can withstand high temperature, the output torque is small. In this study, we focus on the optimised design of the turbodrill blades with the objective of enhancing the output torque, addressing the prevailing issue of limited output torque. First, the structural parameters and parametric design are determined based on turbine blade design theory. Utilizing the quintic polynomial method, a two-dimensional blade profile is generated. Subsequently, an output torque model applicable to unsteady flow conditions is derived using the moment of momentum theorem in its integral form; Utilizing the designed blade profile, the Unigraphics NX (UG) software is used to illustrate the combination of spatial twisting, bending and tilting of the blade for the combination of the modelling method, and a three-dimensional bending-torsional tilting blade was achieved. Subsequently, numerical analysis, employing Computational Fluid Dynamics (CFD) simulation software, was conducted to examine the impact of intricate spatial modelling on the blade's flow field parameters. The optimal parameters for blade spatial modelling were ascertained to be a twist lofting radius of 63 mm, a bending angle of 30°, and an inclination angle of 3°. The blade in the hydraulic efficiency is reduced by only 2.7% of the case, the output torque increased by 18.87%, improving the performance of the turbodrill, so that the turbodrill in the geothermal development drilling has a good application prospect.

CFD and Taguchi based optimization of air driven single stage partial admission axial turbine blade profiles

Single-stage axial flow turbines are typically used in underground mining machines and underwater vehicles due to their safety and small size. However, the high-pressure ratio and small mass flow rates force the flow inside the turbine to be supersonic. The blade design of such turbines with high-flow velocity leads to high losses and low turbine efficiencies at conventional design values. In this paper, the 1D design of the turbine is carried out using the meanline design method. The results of the design algorithm are compared with both experimental, CFD (Computational Fluid Dynamics), and a well-known commercial software AxSTREAM. After validating the design, Taguchi method is used to analyze 6 different parameters (Blade Shape, Nozzle Shape, Cord Length, Solidity Ratio, Nozzle Angle and Blade Thickness) affecting the turbine performance and the optimum blade profile is compared with the conventional blade design. The optimum design isentropic efficiency (68.267%) outperformed the conventional design turbine isentropic efficiency (61.759%) by about 11%. This paper provides a different insight into the conventional turbine design method.

Unsteady assessment and alleviation of inter-blade vortex in Francis turbine

Inter-blade vortex refers to a specific type vortex cavitation observed in Francis turbines under partial loads and its adverse impact is widely recognized as a crucial factor that limits the safety and stability of hydraulic turbines. The present study endeavors to examine the spatiotemporal evolution attributes of inter-blade vortex and its contribution to the generation of unstable pressure fluctuations. To achieve this, a comprehensive investigation is conducted using a reduced-scale Francis model turbine with low head, combining numerical investigations and visualization experiments. The study demonstrates that the vapor volume associated with the inter-blade vortex experiences periodic pulsation, with a frequency proximate to the rotational frequency of the runner. Within the turbine runner, cavitation exhibits a dynamic cycle of incipience, growth, expansion, and localized collapse. The most remarkable cavitation disintegration occurs at the convergence point of the trailing edge of the runner blade and the band, wherein the most pronounced amplitude of pressure fluctuation is also discerned. In addition, this research establishes a direct correlation between pressure fluctuations and vapor volume, revealing that the acceleration of the vapor volume is accountable for the occurrence of pressure fluctuations with heightened magnitude. Furthermore, an optimization campaign successfully reduces the cavitation volume by 88.58% and 78.99% at two specific points of interest, resulting in the nearly complete elimination of high-amplitude pressure pulsations. Building upon these findings, data mining techniques are implemented to identify that the blade profile at a spanwise height of 0.75 significantly influences the enhancement of turbine hydraulic performance. Additionally, it has been ascertained that the design parameter governing the geometric placement of the blade trailing edge plays a pivotal role in reducing the intensity of the inter-blade vortex. This study yields invaluable insights into the underlying mechanism of unsteady phenomena induced by inter-blade vortex and formulates a hydraulic optimization approach capable of enhancing the operating stability of the Francis turbine.

Optimization of a High Pressure Turbine Blade and Sector-Based Annular Rig Design for Supercritical CO2 Power Cycle Representative Testing

Abstract As part of the ongoing research into the design of hardware for zero emission cycles, a first-stage high-pressure turbine (HPT) blade is optimized for a 300 MWe supercritical CO2 (sCO2) power cycle using the surrogate-assisted genetic algorithm optimizer in Numeca FINE/Design three-dimensional with objectives of increasing efficiency and decreasing heat load to the blade. Supercritical CO2 property tables are constructed from NIST REFPROP data for the condensable gas simulation in FINE/Turbo. A detailed mesh sensitivity study is performed for a baseline design to identify the proper-grid refinement and efficiently allocate resources for the optimization. Seventy design variables are selected for the initial population generation. Self-organizing maps are then used to focus the design variables on the most important ones affecting the objective functions. The optimization results in approximately 3000 three-dimensional Reynolds Averaged Navier Stokes simulations of different blade shapes with increases in efficiency of up to 0.85% and decreases in heat load of 14%. Families of blade shapes are identified for experimental testing in an annular rig at the Purdue Experimental Turbine Aerothermal Laboratory. A design to adapt the annular cascade for testing optimized geometries is introduced, which features eccentric radius sectors allowing for scaled-up geometries of sCO2 optimized blade profiles to be tested at design cycle representative conditions at high Reynolds numbers in dry air. Analysis into the effects of Reynolds number, working fluid, and geometric relations are presented to prove the efficacy of the test method.

Effect of laser hardening and post hardening shot peening on residual stress evolution in X5CrNiCuNb16-4 steel for steam turbine blade applications

Laser-hardening process produces higher surface hardness and provides deeper hardness profile into the material. This increment in hardness reduces water-droplet erosion on steam turbine blades. In the present study, a steam turbine blade profile was subjected to laser-hardening process primarily on the suction side of the profile. This hardening process transformed tempered martensite structure of the unaffected material to a fine martensite structure at the processed zone with an intermediate transition zone being present in between them. The fine martensite was responsible for spike in hardness profile at the surface. When the laser-hardened blade was subjected to operational stresses, a number of parallel cracks formed on the blade profile in the direction perpendicular to the blade axis. Detailed investigations in the form of residual stress mapping revealed that a narrow interfacial region beside laser-hardened zone over the profile of the processed blade material, indicated presence of tensile residual stresses. This region was responsible for the formation of parallel cracks over the blade profile. A shot peening process was introduced post laser-hardening which resulted in the elimination of the tensile residual stress, thus, mitigating crack formation over the blade profiles upon application of operational stresses.

Optimization of CDA Blade Based on Surrogate Model

Abstract In order to shorten the design cycle of compressor blades and improve the performance evaluation and efficiency of compressor blade profiles, a blade database using CFD based on the key parameters of the arc in the CDA blade profile and the inlet conditions of the blade profile is constructed. Based on this database, a model for the total pressure loss coefficient surrogate that can predict variable operating conditions is proposed. By combining the total pressure coefficient surrogate model with genetic algorithms, efficient optimization of CDA blade profiles can be achieved. By comparing the prediction results of the total pressure loss coefficient surrogate model with the CFD results, it was found that the mean square error of the prediction was between 0.03% and 0.04%, with a correlation coefficient higher than 0.97. The optimization results show that using this method for optimization reduces the total pressure loss coefficient of the original blade profile by 15% while significantly reducing optimization time and greatly improving optimization efficiency.

Use of an optical profilometer to measure the aerodynamic shape and the twist of a wind turbine blade

This study introduces a metrological approach to measure the aerodynamic shape and the twist of a wind turbine blade. The optical profilometer measurement technique used is laser triangulation. A camera records the image of a line projected onto a section of the blade and, by reconstructing the airfoil shape, the twist angular position of the profile with respect to the axial line of the blade is determined. This methodology is applied to test different sections of a Wortmann FX 63-137 airfoil with a length of 1700 mm. The results of the aerodynamic shape and twist angle are quantitatively verified by comparing them with the ideal or design values. The reconstruction process achieved a resolution of 0.06 mm, and measurement errors in the twist angular position were less than 0.1°. The presented method is efficient, accurate, and low cost to evaluate the blade profiles of low-power wind turbines. However, due to its easy implementation, it is expected to be able to measure any full-scale wind blade profile up to several meters in length.

Numerical simulation and experimental data blade investigation of horizontal wind turbine

The article presents the results of numerical simulation of a wind turbine blade. The fundamental formulas of the theory of aerodynamics, on which the calculations are based, are presented. Computer models of air movement near the blade are shown. Data on the distribution of speed have been obtained. The coefficient of wind energy utilization depends on the parameters of both the oncoming flow and the blade profile. This coefficient is different for vertical and horizontal wind turbines. To improve the operation of the wind turbine, it is proposed to use non-network algorithms. The neural network should collect data on the received errors in the system of mechanization and automatic control. Errors in control systems are analyzed, individual parameters are weighted to stabilize the operation of the wind turbine as a whole.

Inspection of thin-walled blade profile considering curvature characteristics and machining deformation

Inspection of thin-walled blade profile considering curvature characteristics and machining deformation

Blade Profile Reconstruction via Multiview Registration Based on Bidirectional Correspondence and Global Distance Weight

Blade Profile Reconstruction via Multiview Registration Based on Bidirectional Correspondence and Global Distance Weight

Optimization of blade profile for governing stage in peak regulating condition

Optimization of blade profile for governing stage in peak regulating condition