Blade Rotational Speed Research Articles

Simulation optimization and experimental validation of hydraulic impact in pruning machines

Abstract This study addresses the instability caused by hydraulic shocks in fruit tree pruning machines during operation and proposes an optimization scheme that combines simulation with experimentation. We investigated the mechanisms of load shock in the hydraulic system through mathematical modeling and LS-DYNA simulation analysis. The optimal operating parameters were determined using mechanical and orthogonal analyses: a forward speed of 4 km h−1, a pruning tool angle of 60°, and a saw blade rotation speed of 1200 r min−1. Additionally, we employed AMESim simulation to optimize the hydraulic system of the pruning machine by designing a dual accumulator configuration to effectively suppress hydraulic shocks. We validated the optimized system through simulations and experimental tests, demonstrating significant reductions in pressure fluctuations, with cutting efficiency improved by 30% and pressure fluctuations reduced by 26.7%. This study not only presents an innovative dual accumulator design but also validates its effectiveness in pruning machines through simulations and experiments, thereby enhancing the operational efficiency and stability of agricultural machinery.

Numerical assessment of ice formation processes and its impact on a variable-pitch unmanned aerial vehicles propeller in forward flight

Unmanned aerial vehicles (UAVs) encounter significant challenges in freezing climates, as atmospheric ice accretion adversely impacts both flight safety and aerodynamic performance. This study provides an in-depth numerical investigation into the ice accretion process and its implications on the aerodynamic performance of UAV propeller. The analysis explores at various propeller blade pitching angles and rotational speeds. Detailed flow field analysis around propeller blade surfaces is conducted to address the performance degradations associated with ice accretion. The investigation reveals a noteworthy shift in ice shapes and extents with varying pitching angles and rotational speeds. The iced propeller demonstrates increased aerodynamic losses, marked by large size separation bubbles aft the ice shapes at outer radial locations. Remarkably, at higher pitching angles, the iced propeller outperforms the baseline propeller, followed by a propeller with increased rotating speed. For both baseline and higher pitching angles, the most significant losses in thrust coefficient 57.60% and 25.39%, respectively, occur at −2 °C, accompanied by maximum spikes in power coefficient of 140.08% and 93.92% at −4 °C. Meanwhile, an increase in rotating speed results in a decrease in thrust coefficient by 48.60% and an increase in power coefficient by 150.66% at an icing temperature of −4 °C.

Methodical and algorithmic aspects of mathematical modeling of a screw aircraft power plant

The article describes the solution of a scientific problem that consists in expanding the functionality of the program “Calculation of the traction-economic and mass-specific characteristics of the power plant and aircraft motion parameters” through the introduction of additional algorithms and mathematical models for calculating the altitude-speed characteristics of screw aircraft power installations. At the same time, an internal calculation of the aircraft propeller thrust is used according to experimental aerodynamic coefficients, which makes it possible to increase the efficiency and reliability of complex theoretical studies of power plants of various types as part of aircraft at the stage of external design. A description is given of the developed algorithms: an algorithm for converting power on the output shaft of a gas turbine engine into thrust of an aircraft power plant; a mathematical model of a propeller that provides calculation of its thrust from experimental aerodynamic coefficients; an algorithm for determining the thrust of the power plant, taking into account the compressibility of the air and the interaction of the propeller and the elements of the airframe of the aircraft. Some features of the mathematical modeling of an aircraft propeller are revealed, in particular, the principle of propeller control by influencing the blade angle and rotational speed depending on the aircraft flight speed and a method for constructing the field of aerodynamic characteristics of an aircraft propeller in a wide range of blade angle and speed coefficient. In conclusion, the results of verification of the modified program are presented with an analysis of the obtained altitude-speed characteristics.

Influence of rotation speed and frequency on the decision of Columba livia domestica (homing pigeon) to cross the rotor-swept area of paper blades mimicking a wind turbine

Abstract To reduce bird collisions with wind turbines, automatic detection systems have been developed to slow the blades down when a bird is approaching. We experimentally tested whether blade rotational speed (i.e., number of rotations per min) and frequency (i.e., number of times a blade passes a point per min) affected the decision time (i.e., time to take-off), path choice (i.e., the position in the aviary), and decision to cross the rotor-swept area in Columba livia domestica (rock dove [domestic variety]; aka homing pigeon; hereafter, pigeon). We used a homemade device with paper blades, mimicking the movement of wind turbine blades. We adjusted the paper blade dimensions and achromatic contrast with the background to match the visual capabilities of pigeons, increasing the probability of detection. Pigeons were less likely to cross the rotor-swept area at higher speeds and frequencies, independent of their decision time. When pigeons crossed the rotor-swept area (43 out of 160 trials), 63% collided with the blades, regardless of blade speed or frequency. Pigeons chose to avoid the rotor-swept area after they had travel half the distance to the wind turbine. Pigeons were not better able to avoid the rotor-swept area when blades were rotating at low speed and/or frequency and often collided with the blades. Thus, slowing blades to a low rotational speed may not reduce collisions with some species and a complete turbine shutdown may be necessary. The feasibility and economic costs of regular complete shutdowns after the deceleration triggered by the automatic detection systems need further investigation.

Two-point statistics in non-homogeneous rotating turbulence

Time-resolved two-dimensional two-component particle image velocimetry measurements with high spatial resolution are carried out in a water tank agitated by four blades rotating at constant speed. Different blade geometries and rotation speeds are tested for the purpose of modifying turbulent flow conditions. In all cases where no baffles are used to break the rotation, the Zeman length is an order of magnitude smaller than the Taylor length. Compared with the cases with baffles which break the rotation, in the unbaffled cases turbulence production and/or mean advection are significant and the turbulence nonlinearity is dramatically reduced for the horizontal (i.e. normal to the axis of rotation) two-point turbulence fluctuating velocities. This nonlinearity reduction is manifest not only in the interscale turbulent energy transfer but also in the interspace turbulent energy transfer, which nearly vanishes. However, the nonlinearity is not reduced for the vertical two-point turbulence fluctuating velocities: the corresponding interscale turbulent transfer rate is in fact intensified, and its dependence on the two-point separation distance, as well as that of the corresponding interspace turbulent transfer rate, which does not vanish, is significantly modified. Even though non-homogeneities are very different for different blades and rotation speeds in the unbaffled cases, the horizontal fluctuating velocity's second-order structure function collapses with scalings which resemble predictions for homogeneous turbulence subject to strong rotation. The vertical fluctuating velocity's second-order structure function does not collapse for different blade geometries by neither these nor the Kolmogorov predictions.

Computational Exploration of Variable-Pitch Fans as Thrust Reversers and Their Influence on Noise Abatement in Turbofan Propulsion Systems

Variable pitch propellers, once confined to turboprop engines, are now revolutionizing turbofan applications. Recent breakthroughs in materials and technology, exemplified by Pratt & Whitney’s geared turbofan engine, underscore the practicality of variable pitch systems. Ongoing research promises to extend their adoption across diverse engine types, significantly enhancing safety and performance. This study investigates a novel approach to enhance reverse thrust using dual-row radial fans with adjustable pitch angles. These fan blades exhibit geometry variations, combining features from both turbofan motor fan blades and turbo- propeller motor blades. The results are promising: this configuration nearly triples the thrust force, producing approximately 292.917 kilo-newtons. Moreover, it enables the generation of reverse thrust equivalent to 25.077 kilo- newtons. These enhancements are achieved while reducing blade rotational speed from 5200 revolutions per minute to 3200 revolutions per minute and inlet airspeed from 660 km/h (at maximum power) to 220 km/h. Additionally, a notable 11% reduction in noise level at the blade tips has been observed. This research sheds light on the potential of innovative fan blade designs to revolutionize reverse thrust capabilities in turbofan engines, contributing to safer and more efficient aircraft landings.

A comprehensive comparison of film cooling characteristics of shaped holes on the leading edge of rotating blade

This study numerically investigates the cooling characteristics and flow features of various hole geometries on the rotating blade leading edge. A comprehensive comparison of cooling effectiveness, heat transfer coefficients, net heat flux reduction, and discharge coefficients is conducted among laidback fan-shaped, fan-shaped, laidback, cone holes, and cylindrical holes with two different diameters. Detailed flow and thermal field analysis reveals the impact of geometry on cooling performance. The blade rotational speed is 600 rpm, with a Reynolds number of 12.4 × 104, blowing ratios from 0.5 to 2.0, and fixed injection and spanwise angles at 90° and 30°. Shaped holes share a uniform hole exit-to-inlet area ratio, and cylindrical holes match their inlet or exit areas. The RANS equations were closed using the SST k-ω turbulence model coupled with the Gamma Theta transition model, and an unstructured grid of 13.0 million cells was employed to attain relatively accurate predictive results. Results show that the lateral expansion on the leading edge significantly enhances cooling performance, with fan-shaped holes outperforming others, especially at high blowing ratios. Additionally, cooling effectiveness and discharge coefficient on the leading edge correlate strongly with hole geometric parameters. Shaped holes with equal area ratios show similar discharge coefficients. Cooling effectiveness at high blowing ratios is proportional to the effective exit width, provided that the coolant flows smoothly without severe lift-off.

小麦制粉粒度检测装置供料部件设计与研究

To address the issues of poor timeliness and delayed feedback in traditional wheat milling processes for manual particle size detection, a wheat milling online particle size detection device has been designed. This paper focuses on the design optimization of the key feeding component in the device, which affects the accuracy of particle size detection. The feeding component adopts shaftless screw blades. Through theoretical analysis, the main parameter ranges affecting the throughput capacity of the shaftless screw conveyor are determined. A Box-Behnken experiment is designed to obtain the optimal parameter combination for each factor: outer diameter of screw blades 23.8 mm, inner diameter of screw blades 6.4 mm, pitch 11.2 mm, and blade rotation speed 288.9 r/min. Simulation and test stand experiments are conducted using the above parameter combination. The simulation results show that the average throughput capacity of the feeding component is 2.85 kg/h, while the average throughput capacity of the test stand experiment is 2.84 kg/h, with a coefficient of variation of uniformity of 1.33%. These results indicate that the above parameter combination meets the design requirements for the feeding component in the device.

Effect of blade rotational speeds on the performance of cassava milling machine

Abstract Cassava (Manihot esculenta) is a food source of carbohydrates in Indonesia. Cassava flour is used as raw material for processed food products. A performance evaluation of the cassava milling machine has been carried out by varying the blade rotational speeds. There are three parameters related to machine performance and two parameters related to cassava flour. The machine performance parameters are capacity, electric power, and specific energy, while the cassava flour parameters are temperature and particle size distribution. The performance evaluation showed that the higher the blade rotational speeds, the higher the capacity and electrical power, at 8000 rpm the resulting capacity and electrical power are 465.5 kg/hour and 2418.8 W respectively. At the same blade rotational speeds, the lowest specific energy is also obtained, at 19,540.52 J/kg. In all variations of blade rotational speeds, there is an increase in temperature from cassava chips to cassava flour, an average of 2.7 °C. Meanwhile, the cassava flour particle size showed that in each variation of the blade rotational speed, the dominant flour size is 60-80 mesh. At a blade rotational speed of 8000 rpm, the cassava flour particle size of 60-80 mesh is the largest when compared to other blade rotational speeds at 45% of the cassava flour produced by flouring. Based on statistical analysis, by varying the blade rotational speeds, it is stated that there are no significant differences in the results of the performance parameters except for the flouring capacity parameter at blade rotational speeds of 8000 rpm.

Potential and Limitations of Anomaly Detection via Tower-Radar Monitoring of Wind Turbine Blades in Regular Operation with Convolutional Networks

The authors have already presented a first analysis of a field study on radar- based structural health monitoring of rotor blades on two operational wind turbines. This analysis will now be extended with measurements from a third operational wind turbine used as a case study for structural monitoring of individual rotor blades over different time intervals and blade modifications. More precisely, a sensor box with a 35 GHz FMCW radar and a highspeed camera was positioned at 90m height on the turbine tower, collecting radar data for structural information and videos for automatic ground truth labelling. After two months of collecting data, each individual rotor blade of that turbine was differently modified and measured again. The radar-facing surface of one rotor blade was partially coated with a microwave absorber foil, while an equivalent foil was applied to the backside of the second rotor blade. The third rotor blade was intentionally left unchanged for the sake of comparability. This study investigates potential limitations like general dataset complexity in radar-based anomaly detection for operational wind turbines. Furthermore, the discriminative ability of a convolutional neural network for classifying moving rotor blades is discussed when encountering feature drift through changing environmental and operational conditions, i.e. metadata like nacelle orientation, rotor blade pitch and rotation speed.

Drift potential and coverage ratio analysis of an air induction nozzle under an agricultural drone with various operating condition; an indoor test

Delivering pesticides in the agricultural field has been a venturing advancement in the past decades with the aim of target spraying. Agricultural drones have been introduced as useful assets for target spraying, however, the turbulent downwash flow generated by the drone blades accelerates the atomization process that attributes to the drift potential. In this experimental study, the effect of downwash flow on an air induction nozzle is compared to that of a conventional flat fan XR nozzle under various drone operating conditions to evaluate the best working condition. The test was carried out in an indoor facility in which the effect of environmental parameters can be minimized. The 2D patternation of the droplet deposition known as coverage ratio was evaluated using water-sensitive papers with the change of operating conditions, including nozzle type, drone speed, flying height, and blade rotational speed. As the drone flight speed, height, rotational speed, and nozzle position changed, alterations in droplet size and coverage uniformity were observed along with propagation in the drift effect. In addition, the coverage ratio of the AI nozzle was higher than that of the XR nozzle.

A recursive calculation method of vibration displacements using blade tip timing in angular domain

Blade tip timing (BTT) is a non-contact measurement technique that can be used to monitor blade vibration in turbomachinery. The raw data measured by BTT is the arrival time of all blades at the same stage. However, most blade vibration monitoring methods based on BTT require the use of blade vibration displacements, which are derived from the raw arrival time data, the blade rotation radius and speed. Conventional BTT methods calculate blade tip displacements by comparing the measured arrival time with the ideal arrival time. The ideal arrival time is obtained by assuming that the rotational speed is constant in a revolution, which is inconsistent with the fact, especially when the rotational speed changes rapidly. In this paper, a recursive calculation method called recursive BTT is proposed to reduce the influence of rotational speed fluctuation on the accuracy of blade tip displacement calculation. Recursive BTT calculates the displacements in the angular domain instead of the time domain. A recursive formula is constructed in the angular domain to calculate the blade vibration displacement by using the angle between the vibrating blades. Compared with the conventional BTT method, which relies on the once-per-revolution (OPR) signal, recursive BTT makes full use of the arrival time of all blades at the same stage to calculate the displacements. The advantage of recursive BTT is illustrated through a simulation, a laboratory test and a full-scale aeroengine test. To evaluate the reliability of the calculated displacements, strain signals are resampled to compare with the calculated displacements in the laboratory test. In the full-scale aeroengine test, due to the lack of strain signals, BTT displacements are used to track the blade natural frequency to qualitatively indicate the influence of displacements on blade vibration monitoring. The results of finite element analysis and modal test are used for verification in the full-scale aeroengine test. Simulation and experimental results demonstrate that compared with existing methods, recursive BTT is robust for calculating blade vibration displacements.

The numerical simulation investigates the influence of agitator parameters on particle suspension characteristics

This study investigates the effect of different agitator parameters in a baffleless stirred reactor on solid particle suspension during quaternary ammonium chitosan synthesis. Computational Fluid Dynamics (CFD) simulations investigate different agitator configurations, including blade diameter, rotational speed, and bottom clearance, to optimize chitosan particle distribution. Reducing the bottom clearance reduces particle accumulation, but can create stagnant zones that may disrupt fluid flow. Increasing the rotational speed improves particle distribution until a saturation point is reached. Increasing paddle diameter improves axial fluid circulation. Optimal settings for the vane size of a 180 mm reactor vessel are identified as 0.45 times the diameter, with a speed of 350 rpm, and a bottom clearance of 0.25 times the diameter. These simulations provide critical insight into the suspension of solid particles in baffleless stirred reactors and provide valuable guidance for optimizing stirrer parameters.

Accumulation characteristics of precipitation static on rotating wind turbine blades and its influence on the lightning attachment characteristics

AbstractThe linear velocity at the tip of large wind turbine blades can reach 100 m/s, generating static electricity through friction with airborne particles. However, the accumulation characteristics of precipitation static on the blade surface and its impact on the lightning attachment characteristics are rarely reported. The authors constructed a platform for measuring charges on rotating wind turbine blades and employed the electrostatic probe method to obtain the accumulation characteristics of surface charges under different environmental conditions. The experimental results show that positive charges accumulate on the blade surfaces, peaking at 0.69 μC/m2 under experimental conditions. The charge density is positively correlated with airborne particle concentration and blade rotation speed, while it is negatively correlated with relative air humidity. Additionally, the authors developed a model of the electric field distribution on wind turbine blades considering the effects of precipitation static. Simulation results indicate that the electrostatic field induced by precipitation static weakens the field strength in the vicinity of receptors, reaching a minimum of only 38% of the original strength, thereby increasing the probability of lightning protection failure. The findings provide an effective supplement to the lightning attachment mechanism of rotating wind turbine blades.

Determination Size Distribution of Shredded Vineyard Pruning Residues According to Variety

In this study, it was aimed to determine the particle size distribution of vineyard pruning residues shredded with a shredding machine according to grape variety. Pruning residues of three grape varieties, respectively, Boğazkere, Öküzgözü and Şire were used for the experiments. For shredding experiments, a wood chipper machine powered by a 15 HP thermal engine was used. Trials were conducted at three different engine speeds (1500 rpm, 2000 rpm, 2500 rpm). There are 3 shredding blades on the chopper unit of the machine. The blades are driven by gasoline engine with the a belt and pulley system. The study was carried out at three different blade rotation speed. Particle size distribution was determined for each rotation speed and grape variety. Sieves with diameters of 12.5-50 mm were used to calculate the particle size distribution. According to the results, an inverse relationship was obtained between the blade rotation speed and the size length of the shredded branches for all varieties. The ratio of the size and length of the chopped/chopped residues passing through the sieves varied according to the blade speeds. Also, the significant difference were found between varieties (p

The Impact of Varying Mixing Rates in a Surfactant-Free Fuel Emulsion Mixer on the Efficiency and Emissions of a Diesel Engine

The research focuses on water diesel emulsion (WDE), a topic that has captivated researchers for an extended period. While previous studies predominantly employed surfactants to enhance mixing efficiency, their non-economic feasibility in transportation logistics has prompted a shift in recent investigations. This study presents experiments utilizing a cost-effective WDE comprising 15% water and a mixer devoid of surfactants to investigate the impact of mixer blade rotation on engine performance, fuel consumption, and NOx emissions. NOx emission tests were conducted under a constant engine speed of 2,000 rpm and a 75% load (3,23 kW). The optimal brake-specific fuel consumption (BSFC) for the 15% WDE fuel occurred at a blade rotation speed of 3,000 rpm, resulting in a 1% power reduction (from 4,41 kW to 4,38 kW), a 13.3% decrease in BSFC (from 694,98 gr/kW.h to 602,52 gr/kW.h), and a 30% reduction in NOx emissions (from 54 ppm to 38 ppm). This discovery holds promise for future advancements in green energy applications within the transportation sector.

侧扫式秸秆还田机切割粉碎装置设计与试验

This paper aims to solve the problems of complex structure, poor straw crushing effect and high power consumption of existing straw returning machines. A cutting and crushing device with moving and fixed blades has been developed. The moving blade has collision and automatic retraction functions, which can effectively reduce destructive damage caused by blade obstacles and extend its service life. The double-type single-support cutting method has the advantages of improving the straw crushing effect and reducing the running power consumption. The effects of blade rotational speed, blade offset angle and blade number under the condition of composite single-support cutting were tested according to the uneven ratio of straw throwing and the qualification ratio of straw crushed length. The optimal combination of working parameters of the cutting and crushing device was determined: blade rotational speed of 1968 r/min, blade offset angle of 5°, blade number of 4. The test results show that the uneven ratio of straw throwing is 17.18%, and the qualification ratio of straw crushed length is 92.23%. The operation effect of the side-sweeping straw returning machine was tested on the field. All operating indicators are equipped with cutting and crushing devices, and the results show that all operating indicators meet the technical requirements of straw return.

Design and performance research of cyclonic mechanical gripper

To achieve effective gripping of large planar and flexible targets while reducing the risk of scratching, a novel cyclonic-type mechanical gripper based on rotating blades is studied. Firstly, the working principle of this cyclonic gripper is analyzed in detail, followed by the structural design of the gripper unit. Using Fluent computational fluid dynamics software, the flow characteristics of the airflow within the cyclonic gripper chamber are analyzed, and the influence of gripper structural parameters on suction force is investigated. Finally, a suction force testing platform for the cyclonic gripper is constructed, and experimental validation of the simulated suction force results is conducted. The research indicate that the proposed cyclonic-type mechanical gripper based on rotating blades can effectively grip targets, while the suction force is closely related to parameters such as blade rotation speed, number, and diameter.

Machine Learning for Prediction of Energy Consumption and Broken Force in the Chopping Process of Maize Straw

The main causes of high productional costs and greenhouse gas emissions in the chopping process of maize straws are high energy consumption and breaking force. Addressing these issues, this paper proposes a solution that leverages machine-learning algorithms to select appropriate operational parameters for chopping devices, thereby reducing energy consumption and the cutting force. In this study, the peak breaking force of the stalk (PB), the energy consumption of the stalk chopping (EC) and the slide-cutting momentum of the disc blade (SM) were set as dependent variables, and the rotation speed of the Y-type blade (RSY), transmission ratio (TR) and slide-cutting angle (SA) were set as independent variables. Various techniques, including back-propagation (BP), a radial basis function (RBF), an artificial neural network (ANN), support vector regression and a stepwise polynomial regression model, were applied using a 6-fold cross-validation approach to determine the most effective predictive models. The results indicated that the BP-ANN model performs best in predicting the PB (R2Test = 0.9860) and SM (R2Test = 0.9561), while the RBF-ANN model yields the highest accuracy in predicting the EC (R2Test = 0.9255) under the optimal parameters. Subsequently, a verification test was conducted using randomly selected training and testing data based on the selected predicted functions. The results demonstrated that the R2Train and R2Test data for PB, EC and SM are all above 0.95, indicating that the BP and RBF neural networks are capable of accurately predicting the nonlinear relationship between the dependent variables (EC, SM and PB) and independent variables (RSY, TR and SA) in practical applications.

Membrane clarification of pomegranate and carrot juices using scraped surface membrane unit, a comparative study

The membrane processes are used for clarification of fruit juices, but fouling is a limiting phenomenon. The blade rotation in scraped surface membrane unit can increase flow turbulence and thus reduce fouling phenomenon. This unit was used to clarify the carrot juice (which has a cloudy texture) and pomegranate juice (which has a non-cloudy texture) to compare the effect of juice texture on the efficiency of process. The process was performed at three transmembrane pressures (1, 1.5 and 2 bar), three feed flow rates (5, 10 and 15 ml/s) and three blade rotation speeds (0, 147.5 and 222.5 RPM) and changes in permeate flux and volume concentration factor (VCF) and fouling mechanism were studied. The results showed that the rotation of the blade, especially at 222.5 RPM, increased the permeate flux and VCF during clarification of both juices. Also, reduction of feed flow rate increases the effectiveness of blade rotation during membrane clarification of juices. Comparison between two juices showed that the increase in permeate flux and VCF after blade rotation for pomegranate juice was higher than the increase value for carrot juice, especially in the early stages of the process. But, decreasing the transmembrane pressure makes the effect of blade rotation on carrot juice that has a cloudy texture more than pomegranate juice that has a non-cloudy texture, especially when the blade rotation speed is low. The cake formation is the main fouling mechanism in the most tests and SEM images confirm that blade rotation has a significant effect on reduction of cake layer thickness.