Outer Blade Research Articles

Numerical study on the influence of flow direction and fluid type on heat transfer and pressure drop in a two-tube spiral heat exchanger with innovative conical turbulators

In this research, numerical analysis will be conducted on the thermal and hydraulic performance of a spiral two-tube heat exchanger. The study employs an innovative turbulator design with curved outer blades and a semi-conical section with two openings. Numerical simulations were conducted using the commercialized Finite Volume Method (FVM) program, ANSYS FLUENT 18.2. The finite volume method was employed to analyze thermal and fluid equations and parameters. A comparison was made between two distinct flow directions, namely positive and negative currents, utilizing a comprehensive range of three working fluids. The numerical findings indicate that employing counter-current flow with a Water/MOS2−Fe3O4 fluid nanohybrid results in superior endothermic performance. These results indicate that a maximum thermal efficiency improvement of roughly 17.54 % and 8 % can be achieved by using the counterflow configuration with the nanohybrid fluid Water/MOS2−Fe3O4 at a mass flow rate of m˙ = 0.008 kg/s, in comparison to alternative models. Furthermore, the results showed that the Water/MOS2−Fe3O4 fluid nanohybrid performs better than the Ag-HEG/Water nanohybrid fluid when used in counterflow and parallel flow configurations, starting at a Reynolds number of 600. With a counterflow configuration in the two tubes, the Water/MOS2−Fe3O4fluid nanohybrid achieves the highest thermal performance coefficient in the two-tube heat exchanger.

Qualitative Investigation of Wake Composition in Offshore Wind Turbines: A Combined Computational and Statistical Analysis of Inner and Outer Blade Sections

High-fidelity numerical simulations are used to thoroughly analyze the evolution of the wake behind a megawatt-scale offshore wind turbine. The wake features are classified in terms of wake dynamics composition and the associated turbulence characteristics originating from the inner and outer sections of the blades. Understanding the wake is essential for developing compact layouts for future wind farms. We employed a transient Sliding Mesh Interface (SMI) technique to analyze the fully dynamic wake evolution of the offshore NREL 5MW full turbine. Our high-fidelity results have been validated against previously published results in the literature. We thoroughly investigated the dominant structures of the wake using Proper Orthogonal Decomposition (POD) techniques, which we applied to transient simulations of fully developed flows after five wind turbine revolutions over the snapshot data. Our findings show that the inner section of the blades, which is composed of airfoils with larger cross-sections, is responsible for the dominant components of the wake, while the contribution of the wake from the outer section of the blade is significantly lower. Therefore, designing more aerodynamic sections for the blade’s inner section can help reduce the dominant wake components and thus decrease the inter-turbine distance in future wind farms.

Introducing a design procedure for Archimedes Screw Turbine based on optimization algorithm

Archimedes screw turbines have gained popularity in generating power from flowing water. One aspect that hasn't been considered yet is optimizing those parameters that are considered assumptions in the prediction models. In this research, a simple procedure was introduced to design an appropriate Archimedes screw turbine for a given site using a prediction model and an optimization model. First, the mathematical efficiency prediction model of Archimedes screw turbines was developed and validated with experimental and real-world Archimedes screw turbine data. Then, the grey wolves optimization algorithm was developed to be used as an actual engineering application, sensitively analyzed, and coupled with the prediction model. The prediction models were evaluated. The model convergence was investigated, and then, the optimization parameters were found to get maximum efficiency. The results revealed that the optimum number of iterations and grey wolves are 200 and five, respectively. Also, the best values for the inner diameter to the outer diameter ratio, the pitch to the outer diameter ratio, tilt angle, and blade number were found in ranges: 0.43–0.56, 1–1.2, 20–22.5, and 2–4, respectively.

Studies on Performance of Distributed Vertical Axis Wind Turbine under Building Turbulence

As a part of the new energy development trend, distributed power generation may fully utilize a variety of decentralized energy sources. Buildings close to the installation location, besides, may have a considerable impact on the wind turbines’ operation. Using a combined vertical axis wind turbine with an S-shaped lift outer blade and Φ-shaped drag inner blade, this paper investigates how a novel type of upstream wall interacts with the incident wind at various speeds, the influence region of the turbulent vortex, and performance variation. The results demonstrate that the building’s turbulence affects the wind’s horizontal and vertical direction, as well as its speed, in downstream places. The wall’s effect on wind speed changing in the downstream area is thoroughly investigated. It turns out that while choosing an installation location, disturbing flow areas or low disturbing flow zones should be avoided to have the least impact on wind turbine performance.

Evaluation of mechanical cutting for disassembly of fast reactor fuel assemblies

ABSTRACT In the fuel reprocessing of fast reactors, it is necessary to cut and pull out the wrapper tube from the fuel assembly, and then cut and remove the fuel pins. Mechanical cutting has no problems such as causing thermal damage to the fuel pins due to laser cutting, and the cutting position can be accurately set, but the replacement of the cutting-off wheel (CW) due to wear or breakage is a problem. In previous studies, the cutting-off wheel with a cubic boron nitride outer blade (CBN CW) was considered a promising CW. In this study, durability of the CBN CW was evaluated based on the grinding ratio obtained from the cutting test using the material of the fuel assembly, and the grinding ratio was considered from the viewpoint of material physical properties. In addition, the effect of preventing the CBN CW breakage (which is a rapid increase in the grinding resistance) by controlling the feed speed, and the cutting mechanism from the CBN CW contact area were considered from evaluation of the CBN CW rotation motor current.

Performance investigation of a Savonius rotor by varying the blade arc angles

Wind energy is a promising source of renewable energy due to its availability. Savonius turbine is a vertical axis wind turbine that converts kinetic energy from the wind to mechanical energy. The current research investigates the performance of the conventional Savonius turbine by varying the position of the endpoints based on varying the blade arc angle. In addition, the outer blade arc angle of a modified configuration, which generated by varying the gap ratio, is also investigated. The ANSYS-Fluent package is used to perform the numerical simulation of the turbine to solve the equations of the unsteady Reynolds Averaged Navier–Stokes (RANS). The flow characteristics through the turbine are resolved by using the SST k-ω turbulence model. The numerical result of the conventional configuration is validated by using previous numerical and experimental research works. The current investigation proved that varying the outer and inner blade arc angles to 160° and 20° enhanced the maximum power coefficient by 4.5% and 12.9%, respectively. Furthermore, the maximum power coefficient of the modified Savonius rotor at a gap ratio of 0.1333 and an outer blade angle of 180° increased by 13.6% compared to the conventional profile.

Numerical Simulation of Unsteady Cavitation Flow in a Low-Specific-Speed Centrifugal Pump with an Inducer

Cavitation is an undesirable phenomenon in the pumps. In this paper, unsteady cavitation flow in a low-specific-speed centrifugal pump with an inducer is investigated based on the full cavitation model and standard k-ε turbulence model using the commercial software PumpLinx. The numerical results of external performance curve and cavitation performance curve of design condition agree well with that of the experiment. The bubbles in the inducer mainly appear on the outer blade leading edge. The regions of larger vapor volume fraction in the inducer and impeller increase with the decreasing of NPSHa. The regions of larger vapor volume fraction in the inducer expand from the outer edge of the blade inlet to the hub on suction surface. Under very low NPSHa, the impeller may be filled with bubbles in the passage and the pump head drops drastically, and there exist distinct back flows near the suction surface of the blade and impeller outlet. Affected by pre-swirl of inducer outlet and the circle flow of impeller blade inlet, the amplitude of pressure fluctuation near the impeller inlet is obviously larger than that at the inlet in the inducer. The dominant frequency of pressure fluctuation for four monitoring points is shaft frequency. Compared with the non-cavitation flows, the maximum amplitudes of pressure pulsation increase for cavitating flow.

Optimization of a high-temperature recuperator equipped with corrugated helical heat exchanger for improvement of thermal-hydraulic performance

The main aim of present study is to optimize a high-temperature recuperator equipped with corrugated helical heat exchanger numerically. This heat exchanger has inner corrugations and/or outer blades. Different geometrical parameters are analyzed according to thermal-hydraulic performance (THP) of the studied helical heat exchanger. The model with the maximum THP evaluation criteria index is introduced as the optimum model. Moreover, the effects of ash fouling characteristics on THP of recuperator are presented. The ash particles material is chosen K2SO4 with the density of 2665 kg/m3. As it is realized in this paper, in case of simulating the problem in steady-state condition, employing the two-phase model achieves to higher average Nusselt number (Nu) values versus all considered mass flow rates. However, it should be noted that in these two approaches the ash fouling characteristics are not determined. By transient solving, the ash fouling characteristics are applied on the outer wall of helical heat exchanger and therefore the convectional heat transfer coefficient is reduced. Hence, in case of employing two phase approach (with ash fouling characteristics) model, lower average Nu values are achieved and it is clear that these values are more validated than attained values from two other approaches. Usage of inner and/or outer corrugations has a substantial influence on THP of recuperator and increases the PEC index values versus all considered mass flow rates sharply. The recuperator equipped with finned helical heat exchanger with a = 3 mm, b = 7 mm, H = 8 mm, g = 2 mm and f = 3 mm is introduced as the optimum model in present work.

On the electrical breakdown of GFRP wind turbine blades due to direct lightning strokes

Lightning puncture damage on the wind turbine blades can pose a severe threat to the safe operation of large-capacity wind turbines. We investigated its formation by performing long air gap discharge experiments under positive and negative downward leaders. Upward streamers were observed to emit from the sample blade before its electrical breakdown. To explain this phenomenon, a numerical model considering the streamer discharge in air, charge transport in GFRP laminate and surface charge accumulation on air-solid interfaces was established. It is found that streamer discharges can be triggered inside the blade hollow to generate space and surface charges, which strengthen the electric field on the outer blade surface and contribute to the upward streamer initiation. The upward streamer development leads to the accumulation of surface charges with opposite polarities on the two sides of GFRP laminate, which causes the electric field on the GFRP laminate to exceed its electrical breakdown threshold. The electrical breakdown, which occurs before the thermal effect of lightning current appears, is the initial stage of lightning puncture damage of blades. The electrical discharge inside the blade hollow and the surface charge accumulation on the GFRP blade should be suppressed to prevent the puncture damage of blades.

Propeller Turbine Design for Power Generation

The national electrification ratio is only 72.95%. As many as 27.05% of the territory in Indonesia has not been reached by electricity with various obstacles, one of which is because of the remote location so that access is difficult. One of the efforts to overcome the electricity problem is to take advantage of the potential energy sources around people's residences. One potential that might be used is a water energy source with low head and discharge. Ideally, this is done by using a generator system that uses a propeller type turbine. The difficulty of making propeller turbines is especially in the manufacture of housings and turbine blades. In this research, an attempt is made to simplify the turbine housing and turbine blades so that they are easy to manufacture. The design is made for Head (H) : 5 m Water flow (Q) : 0.11 m3/s Viscosity (ρ) : 998 kg/m3 Gravity (g) : 9.81 m/s2 Assumed hydraulic efficiency (ηh) : 0 ,80 Power (P) : 4,37 kW, Angle of attack (180o-β∞) 16o, Glide angle 55o, Thickness of inner blade(λ) 2,16o, Thickness of outer blade(δ) 2o. Simplification of the turbine housing is carried out by making the turbine housing from pipe iron and the simplification of the turbine blade is carried out by making turbine blades by eliminating the aerodynamic cross section of the blades, so that the blades can be made of steel plates without casting as is treated in aerodynamic sections. To see the effect of aerodynamic and non-aerodynamic cross-sectional shapes on efficiency, an efficiency test will be carried out.

Study on the wear of spiral drum cutting coal containing rock

AbstractSignificant load fluctuations are encountered when cutting the coal rock using the shearer spiral drum, causing excessive drum wear. Thus, a coupling discrete element model of coal‐rock was developed, and the discrete element method and multi‐body dynamics were used to build a two‐way coupling simulation model of coal rock drum cutting. The drum wear was analyzed, along with the pick and spiral blade wear positions. The results have shown that the pick wear is primarily concentrated at the pick tip and the shaft shoulder, while the outer spiral blade edge blade is generally worn near the pick root. The maximum wear depth obtained in the simulation was 0.00316 mm. The tangential cumulative energy of the drum and the normal cumulative energy were 1.794e5 and 7.819e4 J, respectively. The friction wear of the drum was more prominent compared to the impact wear. By using a single factor method, the relationship between the drum rotational speed, traction speed, rock firmness coefficient, cutting depth, and spiral blade angle, and drum wear was obtained. Finally, it was concluded that the study at hand provides a quick and straightforward way to study drum wear law.

Modeling for prediction of design parameters for micro-hydro Archimedean screw turbines

The present research aimed to develop a model for predicting the optimal efficiency of Archimedes Screw Turbines (ASTs) under different conditions using Response Surface Methodology (RSM). In RSM, the effect of several independent parameters (inputs) on a response parameter (output) is investigated. Among different geometric and flow parameters of an AST, screw’s outer diameter, blade number, inclination angle, rotation speed, available head, and flow were used to define the efficiency of ASTs. The well-known Buckingham Pi theorem was used to describe non-dimensional relationships between independent and response parameters. A Face-Centered Central Composite Design response surface was used for the investigation. To this end, the desired ranges of dimensionless effective parameters were considered. Computational Fluid Dynamics (CFD) was employed to determine AST’s efficiency in the considered ranges. Finally, a quadratic prediction model was developed, with R2 of 0.9755 and a maximum P-value of 0.0001. The maximum value of the relative error was 4.75%, and the maximum efficiency was obtained as 83.4% while blade number, inclination angle, dimensionless diameter were 4, 27°, and 0.731, respectively. The accuracy of the developed model, which is only valid for small laboratory-scale Archimedes screws due to the utilized laboratory-scale screw data, was reasonable.

Numerical optimization for blades of Intermig impeller in solid–liquid stirred tank

The multiphase flow in the solid–liquid tank stirred with a new structure of Intermig impeller was analyzed by computational fluid dynamics (CFD). The Eulerian multiphase model and standard k–ε turbulence model were adopted to simulate the fluid flow, turbulent kinetic energy distribution, mixing performance and power consumption in a stirred tank. The simulation results were also verified by the water model experiments, and good agreement was achieved. The solid–liquid mixing performances of Intermig impeller with different blade structures were compared in detail. The results show that the improved Intermig impeller not only enhances the solid mixing and suspension, but also saves more than 20% power compared with the standard one. The inner blades have relatively little influence on power and the best angle of inner blades is 45°, while the outer blades affect greatly the power consumption and the optimized value is 45°.

Flow pattern analysis of an outflow radial turbine for twin-turbines-OWC wave energy converters

OutFlow Radial (OFR) Turbines have been recently proposed for Oscillating Water Column (OWC) devices based on a Twin Turbine Configuration (TTC). Previous experimental studies showed that these turbines are a feasible alternative to axial unidirectional turbines without rectifying systems.In this paper, a validated CFD model is employed to achieve a better understanding on how the OFR turbine is working in an OWC energy converter for both direct and reverse modes. The turbine geometry corresponds to a second prototype proposed in a previous publication, with a total-to-static peak efficiency of 54%. The key of the performance in reverse mode is the vortical structure created within the blade-to-blade passage, almost choking the flow rate through the rotor. It is also concluded that increasing the outer blade angle leads to a worse performance in reverse mode, although the global performance is improved due to the rotor efficiency gain in direct mode. Finally, it has been also observed that the kinetic energy at the outlet during direct mode still remains as the major source of loss, penalizing the attainable maximum efficiency. Future work should be focused on the reduction of this residual energy to boost the application of these OFR turbines for TTCs.

A Numerical Investigation of Air/Mist Cooling Through a Conjugate, Rotating 3D Gas Turbine Blade With Internal, External, and Tip Cooling

Abstract This paper describes a numerical investigation to study the effect of injecting mist (tiny water droplets) into the cooling air used to cool down rotating gas turbine blades. In this study, the conjugate heat transfer method is used which consists of the simulation of the air/mist fluid flow inside and outside the blades as well as the heat conduction through the blade body. The complete 3D blade with internal cooling passages and external film cooling holes on the surface and blade tip is simulated in a rotating, periodic sector of the blade. The discrete phase model (DPM) is used to simulate and track the evaporation and movement of the tiny water droplets. The rotation effect of the turbine blade is included in the computational fluid dynamics (CFD) simulation by using the moving reference frame method. The effects of different parameters such as the mist/air ratio (10–20%) and the mist droplets size (20–40 µm) on mist cooling enhancement are investigated. The results show that the mist cooling enhancements are about 10–25% on the outer surface of the blade and reach 50% in some locations inside the blade on the internal cooling passages walls. Most of the liquid droplets completely evaporate inside the internal cooling passages; only a limited amount of mist is able to escape from the film cooling holes to enhance the blade outer surface and blade tip cooling. The effect of 10% mist on enhanced cooling can be converted to an equivalent of a 30% reduction in cooling air flow.

Design and implementation of a crossflow turbine for Pico hydropower electricity generation

This study covered the design, implementation and performance evaluation of a crossflow turbine at various nozzle positions. The chosen blade material was analyzed using ANSYS for stress and deformation degree under the impact of hydraulic jets to ascertain its suitability while in operation. The shaft was analyzed under static and dynamic conditions using ANSYS in order to ensure a non-plastic deformation of the shaft at both conditions. The outcome of this analysis was employed in the harmonic response analysis of the runner shaft. Convergent tests were done for both the blade and runner shaft analysis. An experiment was designed for the evaluation of the crossflow turbine performance using optimal (custom) design tool of response surface methodology and 69 simulations/runs were obtained. The factors considered in the experimental design are: nozzle distance from the shaft, nozzle height and attack angle. The crossflow turbine was constructed using computed design values for all the machine's parts. The runner blades were positioned specifically at 28° outer blade angle and 90° inner blade angle. The turbine was tested under a water head and flow rate of 6.4m and 0.0042m3/s respectively. The shaft power and efficiency were evaluated using their respective formula. The responses were optimized in order to get the optimum position of the nozzle that would give the best performance of the responses using the two factor interaction (2F1) mathematical models in coded factors, developed for each of the response. The results obtained, proved that low carbon steel material was suitable for the turbine blading and the shaft is safe at both static and dynamic conditions since the induced stresses and deformations never exceeded the permissible range. Also, each of these considered nozzle positions had a significant effect on the responses with the nozzle height and attack angle having a combined effect on the performance of the turbine. The best turbine performance was obtained at lower angle of attack, nozzle distance very close to the runner shaft and at a nozzle height that will actualize greater energy impartation to the upper and lower blade profiles. The developed mathematical models for each response has higher correlation value, suggesting that the models are suitable for predicting the responses at the considered factor levels. An optimal nozzle distance, height and attack angle of 102mm, 413mm and 5° respectively, were obtained. At this nozzle position, the alternator gave an output of 35watts and 6V. When two voltage transformers were employed, it gave 200Volts AC. The turbine can be commercialized on large scale for greater output power using the determined optimal nozzle positions.

An immunohistochemical study of the effects of orexin receptor blockade on phospholipase C-β3 level in rat hippocampal dentate gyrus neurons

ABSTRACT Orexin-A (hypocretin-1) is a neuropeptide that is produced in the lateral hypothalamic area (LHA) and promotes widespread cortical activation. We investigated the effect of SB-334867, a selective orexin receptor 1 (OXR1) antagonist, on phospholipase C-β3 (PLCβ3) level using slices of rat hippocampus preparations and immunohistochemistry. We used three Wistar rats in each of three groups. The control group was untreated rats and SB vehicle and SB groups received SB vehicle and 10 mg/kg SB-334867 daily from postnatal day (PND) 12 to PND30, respectively. We found that the orexin receptor antagonist decreased the PLCβ3 level in the inner and outer blades of dentate gyrus (DG) compared to SB vehicle treated rats. Orexin may increase the PLCβ3 level in most regions of the rat hippocampus.

Turbulent coagulation of micron and submicron particles in swirling flow

Coagulation of fine particles in turbulent swirling flow is investigated experimentally and numerically. First, different swirl producers are compared and helical blade is adopted due to its enhanced diffusion and convection in the radial direction. Then, study on structural parameters of helical blade is carried out, the result shows that smaller diameter of inner blades or shorter axial spacing between inner and outer blades can create better performance. Finally, research on the effect of operating parameters is conducted. The result implies that lower velocity or higher particle concentration helps improve coagulation performance, since diffusion and particle interaction are strongly affected by the turbulent two-phase flow field. The patterns of coagulation for micron and submicron particles are slightly different due to varied particle dynamics, specifically, breakup is an important factor for larger particles. Rising temperature has positive effect on coagulation of submicron particles because of enhanced thermal motions. Comparatively, the thermal effect is negligible for the micron particles. The study analyzed the mechanism behind turbulent coagulation in swirling flow, from which directions for optimal design are provided.

Outer Hinged Blades Vertical Shaft Kinetic Turbine Flow Pattern Visualization

The Micro hydro power plant (MHPP) development can be used to supply electricity to people living in remote areas. Because the electricity needed in this area is usually not too big. In remote areas and located far from the electricity transmission network, electricity supplies from small capacity power plants is needed, especially those that utilize renewable local energy potential. The energy utilization as electricity generation is by utilizing available kinetic energy (water potential and water flow speed). The research carried out experimentally and then optimized with Response Surface Methodology. The optimization results are then tested again so as to obtain verification results from the optimization value. Furthermore, based on the value of optimization, visual observations are made to see the flow behavior that occurs on the outside hinged blade and turbine chamber. From the visual observations, it was found that not all the water flow hit the turbine blade surface. On the blade back side, the water flow that hits the turbine blade will increase the turbine rotation. On the blade front side, the water flow that hits the outer blade will open the blade and the water flow will come out immediately from the turbine so that it will reduce the negative torque or back rotation.

Assessment of arthroscopic shavers: a comparison test of resection performance and quality

BackgroundArthroscopic shavers play an indispensable role in arthroscopic debridement. They have exquisite structures and similar designs. The purpose of this study was to establish a reproducible testing protocol to compare the resection performance and the quality (tensile strength, torsional strength, and corrosion resistance) of different arthroscopic shavers with comparable designs. We hypothesized that there could be little difference in resection performance and quality between these shavers.MethodsIncisor Plus Blade (IPB; Smith & Nephew, Andover, MA) and Double Serrated Plus Blade (DSPB; BJKMC, Shanghai, China) were selected for resection performance and quality test. For resection performance testing, the resection torque, which is the minimum torque required to cut off silicone blocks with the same cross-sectional area, was measured to evaluate the resection performance of shaver blades when the other factors remain the same. For quality testing, tensile and torsion tests of the shavers’ joint part were performed, and ultimate failure load and maximum torque were measured and compared. The corrosion resistance of these blades was assessed by the boiling water test based on the ISO13402.ResultsNo significant difference existed in the resection torque between the shaver blades of IPB and DSPB (P = 0.54). To the failure load of shavers’ joint parts, IPB was significantly higher than DSPB, both in the outer and inner blades (P < 0.0001). The maximum torque of the joint part had no significant difference between IPB and DSPB (for inner blades P = 0.60 and outer blades P = 0.94). The failure load (for both IPB and DSPB P < 0.0001) and maximum torque (for IPB P = 0.0475 and DSPB P = 0.015) of the inner blades were higher than those of the outer blades. No blemishes were observed on the surface of the blades after corrosion resistance tests.ConclusionsThis study provided some new methods to evaluate the resection performance and quality of different shavers. The resection performance, the torsional strength of the joint part, and the corrosion resistance of IPB and DSPB may show comparable properties, whereas the tensile strength of the shavers’ joint part showed some level of difference.