Blade Count Research Articles

Effects of blade solidity on the transient start-up characteristics of pipeline-type spherical hydraulic turbine

The pipeline-type spherical hydraulic turbine is an emerging residual pressure recovery device that aligns with the development needs of smart urban water management. However, in practical industrial applications, due to the uncertainty of water flow, hydraulic turbines may experience frequent start-stop cycles. If the start-up performance of the hydraulic turbine is poor, adding auxiliary start-stop equipment will make the generator module more complex. Furthermore, blade solidity is considered a key factor affecting the start-up performance of spherical hydraulic turbines.Therefore, This study employs the Six-Degree-of-Freedom (SDOF) solver to investigate the transient start-up characteristics of Spherical hydraulic turbines with different chord lengths and blade numbers. Experimental validation was conducted to affirm the reliability of numerical simulations using SDOF solver. Through numerical simulations, it was determined that there exists an optimal chord length for pipeline-type Spherical hydraulic turbines under unloaded conditions, ensuring their optimal start-up performance. Subsequently, based on this optimal chord length, the impact of different blade numbers on the start-up performance of pipeline-type Spherical hydraulic turbines was assessed. The study revealed that the best start-up performance is achieved when the chord length is c/d = 0.2 and the blade count is N = 5. This research provides valuable insights for the engineering application of pipeline-type Spherical hydraulic turbines.

Design and Analysis of a Liftfan for eVTOL Aircraft

Abstract Ducted liftfans provide greater hovering efficiency to eVTOL aircraft than open propellers of equal disk area. Liftfans are designed with minimised length to limit propulsor weight added and drag incurred during forward flight. Three challenges posed by the liftfan propulsor configuration are addressed in this paper. First, instead of a single-row propeller, liftfans require the design of a fully integrated stage. To maximise the hovering figure of merit, a non-dimensional measure of power consumption, the preliminary and 3D design variables of the rotor and splittered-diffuser stator rows are optimised simultaneously using 3D CFD. The resulting prototype liftfan design is validated through experimental testing. Second, despite efficiency improvements during hover, liftfans sustain additional inlet distortion and drag during forward flight due to their surrounding nacelles. A low-order model is developed to investigate the maximum range for different fan designs with varying diffuser area ratios and forward flight tilt angles. Design selections are validated using full annulus 3D CFD and experimental wind tunnel tests. Third, as the electric motors of liftfans are mounted within the hub, fan-driven active cooling is necessary to prevent overheating. The stagnation pressure losses incurred by cooling airflow must be minimised without impeding heat transfer. Low-order models are developed to predict motor heat transfer and loss and to guide the design of a mixed-flow cooling fan. Experimental testing and 3D CFD simulations confirm that the addition of forward sweep and adoption of a high blade count can reduce cooling fan losses.

Scale-Resolving Simulations of Turbulent Flow Retaining the Exact Blade Count With the Time-Inclined Method

Abstract Simulations of the T106 low-pressure turbine linear cascade with incoming wakes have been conducted to demonstrate the suitability of the time-inclined method for retaining the exact blade count in scale-resolving simulations. The time-inclined method has been implemented into a high-order unstructured time-marching code based on the flux reconstruction method. The pitch ratio between the upstream incoming wakes and the cascade is not a small integer, and the time-inclined method is used to reduce simulations to a single-passage computational domain. Three-way comparisons have been generated: the solution of the direct periodic full domain, spanning several blade passages, is compared to the single-passage time-inclined solution and to a single-passage solution that approximates the pitch ratio to the nearest integer. Two sets of virtual experiments, which differ in modeling of the incoming perturbations, are reported. First, the immersed boundary approach is used to introduce a cascade of moving bars that act as the trailing edges of the preceding row and generate incoming wakes. The second set of simulations introduces wake-like perturbations at the inlet section of the computational domain. The present work shows that the time-inclined method, retaining the exact blade count, can produce very accurate results for turbulence-resolving simulations. Moreover, the time-inclined method outperforms the standard single-passage methodology in most of the variables of interest and is equivalent in the rest.

Optimizing ventricular assist device rotor design parameters through computational fluid dynamics and design of experiments.

Heart failure is among the most widespread diseases globally. With the rapid rise in the number of affected individuals and the significant disparity between organ demand and supply, the relevance of implantable devices has grown each year. However, these devices face various regulatory restrictions, and obtaining approval requires outstanding performance. This paper focuses on optimizing the design parameters of a rotor for an axial flow ventricular assist device (VAD) currently under development. The parameters investigated include splitters, inlet blade angle, outlet blade angle, blade count, rotational speed, clearance gap, blade thickness, and rotor length. The study aims to maximize pressure rise and hydraulic efficiency while minimizing the torque required to drive the rotor. The D-optimal method was employed to create an experimental design for the simulations. By comparing R², adjusted R², and RMS error across different regression models, the quadratic regression model emerged as the most effective for deriving a suitable mathematical model from the numerical results. The validity of these models was confirmed through the consistency between predicted and observed outcomes.

Effect of wrap angle on performance of Pump As Turbine (PAT) in both pump and turbine modes

Abstract Pump as turbine (PAT) is used in small hydropower plants to generate electricity for remote hill regions and the integration of other renewable resources. Generally, the efficiency of centrifugal pumps operating in turbine mode is low. To improve efficiency, variables such as wrap angle, blade thickness, and blade count can be optimized for turbine mode; however, such changes may lead to a decrease in PAT performance in pump mode. To explore the effect of wrap angle on PAT performance in pump mode, flow simulations were carried out at conditions with wrap angle and discharge variations between 85°-120° and 8-16 kg/s, respectively. With a decrease in wrap angle in pump mode compared to the rated design condition, both efficiency and head rise were improved at the partial load condition. A design with a 120° wrap angle provided a 5.15 % improvement of efficiency in turbine mode compared with the available empirical relation; however, a minor decrease of 0.5% in pump mode was observed. Such zones with high efficiency in turbine mode with less compromise in pump mode should be identified for PAT.

Toward high-lift low-solidity design for incidence tolerant gas turbine blade profile

Gas turbines operating under wide operational conditions require minimizing losses across a wide range of incidences. This study employed a blade profile efficient within a 50° incidence range to assess the effect of solidity on performance across wide incidences. The aim was to evaluate the feasibility of adopting high-lift, low-solidity designs for incidence-tolerant blade profiles. The results showed that solidity has both positive and negative effects on loss across a wide range of incidence angles. Increasing the pitch-to-axis chord ratio (the inverse of solidity) from 0.8 to 1.1 not only reduces the blade count by 37.5 % but also enhances performance at negative incidences, reducing the total pressure loss coefficient by up to 17.5 %. However, at positive incidences, the losses increased significantly as the solidity decreased. To expand the operational range of the low-solidity blade profile at positive incidences, strategic integration of leading-edge refinement and maximum deflection adjustment was applied to precisely control losses. This enabled the low-solidity blade profile to maintain lower loss levels compared to conventional high-solidity profiles up to an incidence of 7°, at which point the losses become comparable. The findings indicate that employing high-lift designs with optimized leading-edge and maximum deflection for incidence-tolerant blade profiles is feasible.

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.

Unsteady Aerodynamic Forcing Due to Distortion in a Boundary Layer Ingesting Fan

Abstract Boundary Layer Ingestion (BLI) is a concept with the potential to reduce energy consumption needed for aircraft propulsion. For the fan this results in a need to work well in an environment of increased continuous distortion. The objective of this study is to increase the understanding of unsteady aerodynamic forces due to total pressure distortion in a BLI fan. This is done by using computational fluid dynamics to analyze a fan design intended for a BLI installation. Results include low subsonic to transonic operating speeds and distortion in a wide range of wave numbers. The forcing exhibits a significant dependency on the aeroacoustic cut-on/cut-off condition. This is in particular true at part speed where the normalized unsteady force rises sharply before dropping suddenly as the corrected speed or engine order increases. Unsteady pressure in the blade passage is observed to exhibit the same increase in level followed by a sudden drop once the cut-on limit is passed and undamped pressure waves propagating out from the blade row appear. The unsteady forces on the first three modes exhibit different sensitivities to the distortion wavelength but all are affected by the acoustic condition. By comparing results for the reference fan to a similar fan design with a higher blade count the cascade properties of the blade row are found to dominate the interaction. A result of this is that a higher blade count fan may be less affected by the distortion, and be less prone to propagate noise due to low engine order distortion.

Novel designs of blade mixer impellers from the discrete element method and topology optimization

Granular mixers are essential for manufacturing products that require bulk materials as precursors. The modeling of mixers is aided by the discrete element method (DEM), which can simulate the flow of bulk material. DEM is applied in mixer design studies by varying a few design parameters and analyzing the predicted performance, but systematic design via optimization methods has yet to be performed. In this work, we utilized a combined DEM and topology optimization approach to design blade mixer impellers for improved mixing and reduced energy consumption. A DEM model was formulated from a blade mixer setup and validated with experimental particle flow data. The computational cost of the model was then reduced by employing larger particle sizes in the simulations. A binary genetic optimization algorithm was used afterwards to find the tilt angle, number, and shape of impeller blades that would improve mixing or reduce the required driving power. The high mixing impellers have four blades that each have cavities at the center and the tip. The increased blade count promotes convective mixing, while the cavities enhance shear mixing. Meanwhile, the low energy impellers have two blades that both have cavities at the center and less material at the blade tips. These minimize particle-impeller collisions, which in turn reduce the power required to drive the impeller. This work demonstrates the use of optimization methods to design the shape of impeller blades – a variable often overlooked in conventional DEM studies. Our approach may be used to systematically design other mixer types as well.

Unsteady Flows and Component Interaction in Turbomachinery

Unsteady component interaction represents a crucial topic in turbomachinery design and analysis. Combustor/turbine interaction is one of the most widely studied topics both using experimental and numerical methods due to the risk of failure of high-pressure turbine blades by unexpected deviation of hot flow trajectory and local heat transfer characteristics. Compressor/combustor interaction is also of interest since it has been demonstrated that, under certain conditions, a non-uniform flow field feeds the primary zone of the combustor where the high-pressure compressor blade passing frequency can be clearly individuated. At the integral scale, the relative motion between vanes and blades in compressor and turbine stages governs the aerothermal performance of the gas turbine, especially in the presence of shocks. At the inertial scale, high turbulence levels generated in the combustion chamber govern wall heat transfer in the high-pressure turbine stage, and wakes generated by low-pressure turbine vanes interact with separation bubbles at low-Reynolds conditions by suppressing them. The necessity to correctly analyze these phenomena obliges the scientific community, the industry, and public funding bodies to cooperate and continuously build new test rigs equipped with highly accurate instrumentation to account for real machine effects. In computational fluid dynamics, researchers developed fast and reliable methods to analyze unsteady blade-row interaction in the case of uneven blade count conditions as well as component interaction by using different closures for turbulence in each domain using high-performance computing. This research effort results in countless publications that contribute to unveiling the actual behavior of turbomachinery flow. However, the great number of publications also results in fragmented information that risks being useless in a practical situation. Therefore, it is useful to collect the most relevant outcomes and derive general conclusions that may help the design of next-gen turbomachines. In fact, the necessity to meet the emission limits defined by the Paris agreement in 2015 obliges the turbomachinery community to consider revolutionary cycles in which component interaction plays a crucial role. In the present paper, the authors try to summarize almost 40 years of experimental and numerical research in the component interaction field, aiming at both providing a comprehensive overview and defining the most relevant conclusions obtained in this demanding research field.

Smart Blade Count Selection to Align Modal Propagation Angle with Stator Stagger Angle for Low-Noise Ducted Fan Designs

The rotor–stator interaction noise is a major source of fan noise. Especially for low-speed fan stages, the tonal component is typically a dominant noise source. A challenge is to reduce this tonal noise, as it is typically perceived as unpleasant. Therefore, in this paper, we analytically, numerically and experimentally investigate an acoustic effect to lower the tonal noise excitation. Our study on an existing low-speed fan indicates a reduction in tonal interaction noise of more than 9 dB at the source if the excited acoustic modes propagate parallel to the stator leading edge angle. Moreover, a design-to-low-noise approach is demonstrated in order to apply this effect to two new fan stages with fewer stator than rotor blades. The acoustic design of both fans is determined by an appropriate choice of the rotor and stator blade numbers in order to align the modal propagation angle with the stator stagger angle. The blade geometries are obtained from aerodynamic optimization. Both fans provide similar aerodynamic but opposing acoustic radiation characteristics compared to the baseline fan and a significant tonal noise reduction resulting from the impact of the modal propagation angle on noise excitation. To ensure that this effect can also be applied to other low-speed fans, a design rule is derived and validated.

Optimization of Blades and Impellers for Electric Vehicle Centrifugal Pumps via Numerical Analysis

Since the 2015 Paris Agreement, efforts for environmental protection have gained prominence worldwide. Accordingly, electric vehicles have become increasingly relevant. Thus, improving the performance of the water pump, a key component of cooling systems in electric vehicles, is crucial. Electric vehicles operate on batteries and motors, making their cooling systems remarkably complex. Efficient operation of the water pump is directly related to the stable performance of electric vehicles and is therefore critical. This study conducted numerical analyses using Ansys Fluent to evaluate water pump performance by varying key parameters, namely, number of blades and outer diameter of the impeller. When the number of blades was changed to 7, 9, 11, and 13, the efficiency, head, and thrust tended to increase. In particular, for blade counts greater than 11, the fluid flow was found to stabilize with negligible effect on pump performance. When the outer diameter of the impeller was 70, 69, 68, and 67 mm, although efficiency decreased, the head and thrust tended to increase. Based on these comprehensive results, a structure was proposed for the shape of the optimized water pump. The development of efficient and stable water pumps is expected to contribute to the performance improvement of electric vehicles.

Impact of impeller blade count on inlet flow pattern and energy characteristics in a mixed-flow pump

Mixed-flow pumps, which amalgamate centrifugal and axial-flow attributes, play a pivotal role in various sectors due to their high efficiency and versatility. This paper, utilizing numerical simulation and experimental validation, addresses the critical role of impeller blade count in mixed-flow pump performance. It investigates the effect of the number of impeller blades on the energy dissipation mechanism and inlet flow pattern of a mixed-flow pump. The results reveal that dynamic and static interference effects, along with the separation vortex due to flow separation, are the main sources of energy dissipation in the pump. Under part-load and part-overload conditions, the increase in the number of blades contributes to the improvement of the flow pattern and performance but may induce more intense rotating stall effects under part-load conditions. In overload conditions, the increase in the number of blades significantly amplifies the volume of the inlet vortex structure, consequently deteriorating the inlet conditions of the impeller. This study provides valuable insights for the design and optimization of mixed-flow pumps.

Optimization of an axial-flow mine ventilation fan based on effects of design parameters

Underground mining safety relies heavily on ventilation, which is energy and maintenance intensive. An optimization method for an axial-flow Chinook ventilation fan, analyzing parameters like angle of attack, tip clearance, rotation speed, hub-to-tip ratio, and rotor blade count using Design of Experiments (DOE) and regression is proposed. The numerical solutions are confirmed with experimental data. Considering a Mach number of 0.4, compressible flow conditions are analyzed using a two-equation turbulence model. During stall, fan efficiency drops to 47 %. High fatigue probability is observed at the blade-root intersection in stall conditions. The optimization pinpoints several operational configurations that meet the required performance while preserving the fan's structure. A particular off-design optimal point indicates that reducing the blade count and decreasing the tip-clearance lead to an average performance improvement of 9 %, with significant benefits in noise, cost, weight, and energy consumption. The numerical forecasts demonstrate precision with an average discrepancy of less than 5 %.

Numerical Studies on Effects of Blade Number Variations on Performance of Sludge Pumps

The sedimentation of sludge in pangasius catfish ponds constitutes a notable challenge for the economic advancement of Vietnamese farmers. Sludge formation is the result of a composite process involving residual food, waste material, and algae, which undergo decomposition, thereby releasing hazardous gases such as hydrogen sulfide (H2S), ammonia (NH3), and nitrogen dioxide (NO2). These emissions subsequently diminish oxygen levels within the ponds, adversely affecting the growth of catfish. Removal of the accumulated sludge is deemed necessary every two months throughout the catfish cultivation cycle. A proficient sludge pump, designed to function effectively within the Vietnamese environmental context, becomes imperative to address this predicament. The primary objective of this research paper is to explore the influence of blade count on the performance metrics of a sludge pump. Given that pangasius ponds typically exhibit depths ranging from 2 to 4 meters, this study is predominantly centered on assessing pump performance within the specified head range of 2 to 4 meters. Employing the computational fluid dynamics (CFD) methodology, the research delves into the fluid dynamics of sludge pumps featuring impeller blades numbering 7, 8, 9, and 10. These pumps are modeled as semi-open impeller centrifugal pumps operating at a speed of 2200 revolutions per minute (rpm), with the k-e turbulence model and the time-averaged Navier-Stokes equation serving as the fundamental analytical framework.

Impact of solidity and speed ratio on the performance of a contra-rotating fan

In this study, the effects of solidity and rotor speed ratio on the performance of a contra-rotating fan are investigated numerically. Simulation results have been validated by experimental tests. The test stand construction and the measurements have been performed according to ISO-5801 standard. In order to investigate the effect of blade solidity, simulations have been conducted with constant blade count of the front rotor and four configurations of the rear rotor (having 6, 8, 12 and 16 blades), and also constant blade count of the rear rotor and three configurations of the front rotor (having 8, 12, and 16 blades). Results suggest that there is an optimum solidity for the rear rotor, which gives maximum pressure rise and efficiency. Furthermore, the effects of the rotor speed ratios have been investigated in this study. It is shown that the speed of the front rotor is more effective on the fan performance, as compared to the rear rotor. Results reveal that the performance drop caused by a 25% reduction in the rear rotor blade count, can be compensated by 5% increase of the front rotor rotational speed. Therefore, a suitable choice of the speed ratio can result in light-weight and high-performance contra-rotating stages.

Analisis Variasi Jumlah Sudu Terhadap Torsi Yang Dihasilkan Pada Turbin Vortex

Water turbines, particularly vortex turbines, represent a promising alternative energy source with significant potential for development. Vortex turbines are a relatively novel type of water turbine, offering ample opportunities for further research. This study aims to assess the efficiency of different blade variations, specifically 3, 4, and 5 blades. Computational Fluid Dynamics (CFD) analysis was conducted using Solidworks 2022 software. The simulation results indicate that the torque values for 3 blades, 4 blades, and 5 blades were 0.26 Nm, 3.02 Nm, and 4.96 Nm, respectively. Efficiency calculations were performed using a formula, yielding efficiencies of 0.9% for 3 blades, 11.91% for 4 blades, and 20.74% for 5 blades. These results suggest that higher blade counts lead to greater efficiency.

Noise Reduction Design Method and Validation of Unequal-Pitch Blade Fan for Traction Motor

The traction motor of trains is an essential component that generates the traction force, but it has a significant influence on the indoor and outdoor acoustic environment during the running condition. To enhance passenger comfort and bolster the environmental performance of trains, regulatory standards and specifications governing train noise have imposed elevated criteria on both tonal noise and the overall A-weighted sound pressure level emanating from traction motors. This paper proposes an aerodynamic noise optimization design method based on aerodynamic interference. The objective function of the optimization is defined as the blade-passing frequency (BPF) noise and the A-weighted overall sound pressure level of the traction motor fan. The simulated annealing algorithm is used to optimize the circumferential distribution of the blades. The optimized unevenly spaced blade configuration of the fan effectively reduces the BPF sound pressure level amplitude by 4.6 dBA and the overall A-weighted sound pressure level by 1.2 dBA. The calculation results agree well with the experimental results. The study reveals that unevenly spaced blades contribute to better noise reduction at lower rotational speeds. However, the effect diminishes at higher speeds. The relationship between noise reduction and blade count is nonlinear, suggesting an optimal count for specific speeds.

Effect of diameter, twist angle, and blade count on the thermal-hydraulic performance of a decaying twisted swirler

Inserting a decaying swirler into a heat exchanger has been shown to improve heat transfer with minimal effect on the friction factor. The study analyses the effect of diameter, twist angle, and blade count on the thermal-hydraulic performance of a Decaying Twisted Swirler (DTS) in a horizontally heated tube. The diameter, twist angle, and DTS's blade count are examined for 13.5 mm–15.5 mm with a 0.5 mm interval, 0°–360° with a 60° gap, and 2 to 6 blades, respectively. The Nusselt number, friction factor, and thermal-hydraulic performance are examined for Reynolds numbers between 4583 and 35000. The relative Nusselt number and friction factor increase as DTS diameter and twist angle increase, reaching a maximum value at Re = 4583. Despite this, the relative Nusselt number dispersed as the blade count increased. The relative friction factor increases as the blade count increases. Maximum relative Nusselt number and friction factor reached 1.64 and 3.25, respectively with DTS's 15.5 mm diameter, 360° angle, and 4 blades. Nonetheless, the thermal-hydraulic performance is greatest when the DTS has a diameter of 15.5 mm, a twist angle of 180°, and 2 blades with 1.17.

Loss-of-Control Prediction of a Quadcopter Using Recurrent Neural Networks

Loss of control (LOC) is a prevalent cause of drone crashes. Onboard prevention systems should be designed requiring low computing power, for which data-driven techniques provide a promising solution. This study proposes the use of recurrent neural networks (RNNs) for LOC prediction. Four architectures were trained in order to identify which RNN configuration is most suitable and if this model can predict LOC for changing aerodynamic characteristics, wind conditions, quadcopter types, and LOC events. One-hundred and seventy-two real-world LOC events were conducted using a 53 g Tiny Whoop, a 73 g URUAV UZ85, and a 265 g GEPRC CineGO quadcopter. For these flights, LOC was initiated by demanding an excessive yaw rate (2000 deg/s), which provokes an unrecoverable upset and subsequent crash. All RNNs were trained using only onboard sensor measurements. It was found that the commanded rotor values provided the clearest early warning signals for LOC because these values showed saturation before LOC. Moreover, all four architectures could correctly and reliably predict the impending LOC event 2 s before it actually occurred. Furthermore, to investigate generality of the methodology, the predictors were successfully applied to flight data in which the quadcopter mass, blade diameter, and blade count were varied.