Vertical Rotor Research Articles

Acoustic properties and attenuation of coupled shaft-submarine hull system under various excitation transfer paths

Pump-jet propulsor excitation transfers to submarine hull along rotor-shaft and duct-stator paths simultaneously. The investigations on the effects of excitation transfer paths on structural vibration and acoustic radiation of submarine are limited. The present work aims to investigate vibro-acoustic characteristics of coupled shaft-submarine hull system utilizing a theoretical wavenumber analysis method and conduct acoustic design. The energy functional of the coupled structure-fluid system of the research object is first developed, and the displacement components of the jointed shell and the acoustic pressure are expanded by the Fourier series along circumferential direction. This allows for obtaining vibro-acoustic responses in the circumferential wavenumber-frequency domain, by which the predominant wavenumbers contributing to acoustic radiation are identified. The discussions reveal that the modes n = 0 and n = 1 respectively dominate the acoustic radiation under axial and vertical rotor loads. The acoustic radiations under duct-stator load are mainly contributed by mode n = 0, and the higher order modes n = 1 and n = 2 determine several acoustic peaks. Furthermore, two acoustic design schemes are proposed to suppress the wavenumbers with high radiation efficiency. It is proven that the design of the symmetric inner foundation and the application of new material are two efficient ways to improve acoustic performance of the submarine.

Design of Vertical Rotor Metering Plate for Precision Seeding of Okra: Incorporating Physical and Engineering Properties

Design of Vertical Rotor Metering Plate for Precision Seeding of Okra: Incorporating Physical and Engineering Properties

HYBRID MULTICOPTER DESIGNS

Hybrid unmanned aerial vehicles are such vehicles that employ more than one type of energy delivery system used for the powered flight. Hybrid drones are not restricted to using electrical power. Nevertheless, most such drones employ electric propulsion through the implementation of brushless three phase electrical motors in their rotors due to the inherent high efficiency and ease of control of such devices. Electrical energy for the motors is supplied by various sources such as batteries, hydrogen fuel cells, internal combustion engine electrical generators, etc. The current battery technology offers flight times from 10 minutes to 2 hours depending on the payload and drone design. For longer flight times a hybrid power system is required. The common hybrid drone design involves a combination of batteries and internal combustion engine electrical generator. The current article introduces two novel hybrid unmanned aerial vehicle designs. The first exhibits improved efficiency due to implementation of hybrid power system powering two horizontal tandem counter-rotating direct driven rotors and at least four electrically driven smaller horizontal attitude control rotors. The second presented herein invention offers addition of a horizontal rotor or rotors rendering the design a compound multicopter. The vertical rotor or rotors are also direct driven improving efficiency.

Energy efficiency assessment of alternative power supply system for isothermal wagon for live fish transportation

The research object is the power supply system of isothermal car for live fish transportation. The aim of the work is to assess the reduction of total energy costs when supplying electricity to an isothermal wagon for live fish transport by alternative sources in the form of wind turbines and solar panels. It is proposed to use centrifugal and centripetal wind turbines with vertical rotor as sources of mechanical energy of the aeration system of water tanks with live fish, and flexible solar panels placed on the roof of the isothermal wagon and thermoelectric converters as additional sources of electrical energy. When calculating the total energy costs for supplying electric power to the isothermal wagon for live fish transport, data from the literature sources were used. According to the calculations, by adding alternative sources of electricity to the existing isothermal wagon power supply system for fish transport, the total energy costs can be reduced by more than 30%.

Semi-Analytical Analysis of a Rigid Rotor Mounted on Four-Pad Hydrostatic Squeeze Film Damper with Single-Action Membrane-Type Restrictors

Abstract The current study is a semi-analytical analysis of the vibratory behaviour of a rigid vertical rotor, supported by a new hydrostatic squeeze film damper (HSFD), consisting of four hydrostatic pads fed through four single-action membrane-type variable-flow restrictors. The Reynolds equation based on the Newtonian theory of lubrication is used and then adapted to our work, which is solved semi-analytically. In this paper, we study the effect of different parameters, the eccentricity, membrane geometry coefficient, pressure ratio and rotational speed, on the main characteristics of a four-pad HSFD. From the simulation results, we observed that at the critical speed, the rigid rotor fed by membrane restrictor shows a decrease in transmitted forces, a decrease in vibration response and good system stability as compared with a similar rotor fed by capillary restrictor. From the results reported in this work, we observed good agreement between our study and other works.

Promoting the Maneuverability and Fault-Tolerant Control Capabilities of Dual-System/Hybrid VTOL UAVs

This paper presents an active fault-tolerant flight control system (FCS) design for the dual-system/hybrid VTOL UAV configuration that maximally exploits its inherent over-actuation abilities to provide higher levels of fault-tolerance and reliability compared to that of the other VTOL UAVs configurations up to this point. The significance of this study is to convert the main drawback of having the vertical rotors as dead weights during the cruise to a key advantage where all the UAV's controls are kept active during all the flight phases raising the UAV's fault-tolerance and maneuverability abilities. The FCS proposed elaborates on a new architecture for the hierarchical automatic control loops using the dynamic inversion control to design the trajectory tracking virtual commands and employing optimal dynamic control allocation to optimally resolve the controls redundancy. Regarding fault-tolerance, the presented FCS handles simultaneous failures and jamming of all the control surfaces during flight where the control commands to the healthy controls (vertical rotors) were automatically adapted such that the trimming and trajectory tracking were successfully maintained till the mission end. Additionally, this paper addresses for the first time the employment of the controls redundancy to enhance the VTOL UAV's maneuverability in fault-free cases, where we present a study of reducing the minimum turn radius of the UAV when the vertical rotors are employed with the control surfaces during the maneuver. A reduction of 38% in the coordinated steady-level minimum turn radius turn at 35 m/sec flight speed was achieved.

Simplified transformation matrices of journal bearings in vertical application

Rotodynamic simulation of complex or/and large systems, for instance hydropower machines, may consist of models with many degrees of freedom and require multidisciplinary computations such as fluid-thermal-structure interactions or rotor-stator interactions due to electromagnetic forces. Simulating such systems is often computationally heavy and impractical, especially in the case of optimization or parametric study, where many iterations are required. This has, therefore, created a need for simplified dynamic models to improve computational efficiency without significantly affecting the accuracy of the simulation result. The purpose of this paper is to present simplified coordinate transformation matrices for journal bearings in vertical rotors, which require less computational effort. Matrix multiplications, which appear during coordinate transformation, were eliminated, and the bearing stiffness and damping matrices in the fixed reference frame were represented by local coefficients instead. The dynamic response of a vertical rotor with eight-shoe Tilting pad journal bearings was simulated using the proposed model for two operational conditions, i.e., when the rotor was spinning at constant and variable speeds. The results from the proposed model were compared to those from the original model and validated through experiments. The conclusion was that the presented simulation model is time efficient and can effectively be used in rotordynamic simulations and analyses.

Winter-time Hydraulic Jump over the Pokhara Valley, Nepal

The Pokhara Valley is set to be one of the aviation hubs of Nepal with the opening of an international airport. The complex mid-hill mountainous topography of the Gangi-Himalaya and the characteristic wind system of the valley make safe aviation rather challenging over the valley. This study using the Weather Research and Forecasting modeling system shows that hydraulic jump-like phenomena occur regularly during winter in the western and central part of the Pokhara Valley during late afternoon/early evening when the airport may remain relatively busy. The jump occurs over the western part of the valley when the regional southwesterly plain to mountain wind via the Putalibazar Valley intrudes into the Valley crossing the Deurali-Mattikhan hill. The jump-like flow is accompanied by the formation of a mild reverse roller above the jump region and the head-on convergence with the northeasterly katabatic/drainage wind from Parche-Namarjung along the southeast–northwest oriented valley axis generating an updraft of as much as 0.4 to 0.8 m s-1. The southwesterly overrides northeasterly generating clockwise vertical rotors and high turbulence over the northeastern region of the valley. An early prediction of possible wind hazards at high spatiotemporal resolutions are highly desired to make aviation activities in the region safer for civil aviation.

Effect of Stem Diameter, Cutting Speed and Moisture Content on Cutting Torque for Green Gram Harvesting

The study was conducted during November, 2021 at Department of FMPE, CAET, OUAT, Bhubaneswar, Odisha, India to investigate the torque requirement and ascertain optimum peripheral cutting velocity of rotary cutting disc based on varying stem diameter and moisture content of green gram . The cutting operation was simulated to find the cutting torque in the instrumented soil bin, which comprises of test trolley, processing trolley and vertical rotor assembly with vertical shaft having serrated cutting disc. Sample plant stems of green gram were firmly fixed in the plant stem holder, and buried beneath the soil to simulate the natural standing of the crop as in the actual field condition. The cutting torque required to cut the stem of green gram at different crop moisture content (39.2, 41.4 and 42.9% (wb)), peripheral cutting velocity (20, 25, 30, and 35 ms-1) and plant stem diameter (2.95, 3.97 and 4.96 mm) was measured. It has been observed that peripheral cutting velocity of disc, stem diameter and moisture content of plant affected cutting torque at 1% level of significance. The cutting torque increased with decrease in moisture content and increase in diameter of plant stem of green gram. The cutting torque increased with an increase in peripheral cutting velocity up to the critical velocity of 30 ms-1, but the value decreased after critical peripheral velocity.

Influence of pivot support stiffness on dynamic characteristics of vertical rotor system

The pivot-jewel bearing pair is the only dynamic and static contact component of the flexible vertical rotor system, and its support stiffness directly affects the dynamic response of the rotor system. A non-linear dynamic model of the vertical rotor system is established, and the effect of different elastic pivot stiffnesses on the dynamic behavior of the rotor system is investigated in combination with experiments. The results show that with the increase of rotational speed, the system has the dynamic characteristics of alternating period 1 and quasi period, and when the speed reaches 550 r/s, 1/3 times low frequency whirl occurs and when the speed rises to 675 r/s, the low frequency amplitude is higher than the rotational frequency amplitude. With the increase of the elastic pivot stiffness, the amplitude of the low frequency whirl at the lower end of the rotor decreases continuously but the proportion of the “width” gradually increases. The rotational speed corresponding to the large amplitude quasi periodic motion of the rotor is delayed from 550 r/s to 650 r/s. The research results can provide a theoretical basis for the optimal design of the bearing subsystem of the vertical rotor system.

Study of the dependence of the natural frequencies of a rotor system with a vertically positioned rotor on the preload

The article discusses the possibility of using a method for determining the preload force for trust and radial bearings of spindle assemblies for high-speed milling. Previously, a method was developed and tested for determining the preload force of bearing supports on high-speed grinding electrospindles with a horizontal spindle.
 The object of study is a support with angular contact bearings 7004 ACD_P4A SKF and a vertical rotor. An information-measuring system has been developed, which consists of PCB 352C34 vibration acceleration sensors, a Vishay 614 force sensor, an NI-cRIO-9056 controller, NI 9250, NI 9237 and NI 9481 modules, and software written in the National Instruments Labview language.
 The system of test actions has been improved due to its automation. Test effects began to be carried out using a solenoid with a core, which was controlled by an NI controller and developed software. Due to this, the same time delay was formed between the test action and the start of recording the vibration acceleration signal.
 Vibration acceleration signals are obtained for the entire preload range. To study the controllability of the unit, two vibration acceleration sensors were used: with a parallel and perpendicular arrangement of the axes of the direction of vibration and test action. For the first and second groups of vibration accelerations, spectral transformations were carried out, and the amplitude-frequency characteristics of the assembly were obtained for the entire range of preload values.
 As a result of the work, it was concluded that the presented methodology and criteria are applicable to high-speed milling spindle assemblies with a vertical rotor. It is also shown that this technique can be automated.

Development of a Test Rig for the Measurement of Small Wind Turbines in a Wind Tunnel

Abstract This paper describes the development, design and function of a test rig for the measurement of small wind turbines in a wind tunnel and presents the first exemplary measurements of the performance characteristics of various horizontal and vertical rotors. A central part of this test rig is the developed control system with an electronic load, which enables an automated recording of the measured values for the evaluation of the power coefficients (cp) and tip-speed ratio (λ) values. Another challenge emerges owing to the known differences in the power spectrum, because the power coefficients of drag rotors (<20%) are different from those of buoyancy rotors (<40%). The system was adapted to the different ranges by means of a stepless switching using various resistors. The entire control and regulation unit was compactly implemented using a programmable logic controller (PLC) and dynamically linked to the operating parameters of the wind tunnel. This enables an automated operation of the wind tunnel during the determination of the performance parameters of the investigated wind turbines.

Analysis of the dry whirl and dry whip response in a vertical active magnetic bearing drop test rig

A horizontal rotor is usually the research subject of rotor drop failure in active magnetic bearing (AMB) test rigs. However, research shows, that a vertical rotor drop failure is not sufficiently understood at present. The experiments in other research studies show that the vertical rotor dynamic response is not simple whirl behavior after dropping on the touchdown bearing (TDB), which concludes dry whirl and dry whip processes, where the former is synchronous forward whirl, and the latter is subsynchronous forward whirl. To predict the dynamic response of a vertical rotor drop failure, theoretical research based on a rotor-TDB model system is developed in this paper, and the effectiveness of this model is validated by an AMB-TDB rotor experiment. The conclusion is that the natural whirl speed and the resulting critical speed clearly distinguish two states of forward whirl motion. When the rotation speed is less than the critical speed, the rotor is in a dry whirl state; otherwise, it behaves as in a dry whip. The rotor unbalance is introduced in the model, which explains the change in the whirl speed. Moreover, the influencing factors on the natural whirl speed are analyzed in depth. The result shows that parameters of the TDB, such as the friction coefficient and protective clearance, and the rotor unbalance have significant effects.

Comprehensive analysis of fluid-film instability in journal bearings with mechanically indented textures

This paper theoretically and experimentally investigates the effects of textures produced by a mechanical indentation on the stability of journal bearings. The research primarily aims at lightly loaded journal bearings used, e.g. in vertical rotors and microturbines. The results show that textures located close to the minimum oil film thickness can noticeably improve the stability at low specific loads but have only a negligible effect at a specific load of 0.15 MPa. The texturing also impacts the bearing temperature, which is closely related to the bearing friction. Since the textured journal bearings are prone to the formation of cavities in the oil film, the paper also deals with computational methods. It is demonstrated that an accurate estimate of stability threshold requires very dense computational meshes, which are impractical for mass-conserving treatment of cavitation due to CPU requirements. Interestingly, errors due to non-conservation of mass are up to the same magnitude as uncertainties due to employed numerical algorithms. The results demonstrate that numerical results describing lightly-loaded textured journal bearings are very sensitive to the density of the computational mesh. Hence, the simplified cavitation treatment can be legitimate in applications where the CPU time is a concern, such as the optimisation, iterative algorithms and time-integration of equations of motion.

Suspension of high concentration solids in a pilot scale jet-flow high shear mixer

This work firstly applied a pilot scale jet-flow HSM with high energy efficiency in suspension operation of high concentration solids. The applicability of Zwietering’s criterion for jet-flow HSM was evaluated and improved. The effect of different structural parameters on the critical speed for just-off-bottom suspension and power consumption was investigated. The jet-flow HSM can complete suspension task at high solids concentration exceeding 40 wt%. The Njs and the Pjs of jet-flow HSM would obviously increase with increasing the solids concentration. Besides, the Njs and the Pjs for downforce rotor are the smallest compared with vertical rotor and lifting rotor, and the Njs reduces while the Pjs increases with deceasing the blade angle. The Njs and the Pjs rapidly reduce with increasing the bottom opening of stator. The visualization was carried out to analyze the status of solids dispersion in stagnant regions of tank bottom. Furthermore, the optimum solid loading was determined by evaluating the specific power εjs. Finally, prediction models for Njs, Pjs, and εjs were established, which can provide the effective guidance for the application of jet-flow HSM in practical suspension operation.

Perancangan Pembangkit Listrik Tenaga Gelombang Laut Dan Surya Sebagai Solusi Mengatasi Kelangkaan Energi Listrik Di Daerah Pesisir

Hybrid Power Plants are prototypes of ocean wave and solar power plants based on vertical rotors and solar panels. Hybrid Power Plants are motivated by petroleum production, the lack of equitable distribution of electrical energy on the most underdeveloped area in Indonesia, and the government's latest energy mix targets regarding solar and ocean wave energy. Based on the geographical location, Indonesia has the potential for ocean waves and solar energy. Hybrid Power Plants based on vertical rotors and solar panels aim to overcome the scarcity of electrical energy in coastal areas. The vertical rotors and solar panels in this prototype are influenced by the characteristics of the ocean wave height and the intensity of sunlight. In this program using the methods of literature study, design, manufacture of prototypes, and testing. The prototype has a working principle of converting solar energy into DC voltage, the DC voltage flows into Solar Charge Controller to be maximize battery charging. In addition, the vertical rotor converts the motion of ocean wave into AC voltage, the AC voltage flows into rectifier and filter to be a DC voltage that can be charged into battery. Both of which can then be used by fishermen for their daily electricity needs. The results of the solar panel test at 1 PM get the output with a voltage of 14.21V and a current of 2.46A. Meanwhile, from the vertical rotor simulation results, the output voltage data is 17.19V with a period of 0.03s. With the results of these tests, it is hoped that this prototype can be a solution to overcome the scarcity of electrical energy in the coastal area and in the future it can be done to increase the prototype so that the output can be increased and can be used for many fishermen needs.Keywords : Hybrid Power Plants, solar panels, vertical rotors, testing, rarity.

Speed-Dependent Bearing Models for Dynamic Simulations of Vertical Rotors

Many dynamic simulations of a rotor with a journal bearing employ non-linear fluid-film lubrication models and calculate the bearing coefficients at each time step. However, calculating such a simulation is tedious and computationally expensive. This paper presents a simplified dynamic simulation model of a vertical rotor with tilting pad journal bearings under constant and variable (transient) rotor spin speed. The dynamics of a four-shoes tilting pad journal bearing are predefined using polynomial equations prior to the unbalance response simulations of the rotor-bearing system. The Navier–Stokes lubrication model is solved numerically, with the bearing coefficients calculated for six different rotor speeds and nine different eccentricity amplitudes. Using a MATLAB inbuilt function (poly53), the stiffness and damping coefficients are fitted by a two-dimensional polynomial regression and the model is qualitatively evaluated for goodness-of-fit. The percentage relative error (RMSE%) is less than 10%, and the adjusted R-square (Radj2) is greater than 0.99. Prior to the unbalance response simulations, the bearing parameters are defined as a function of rotor speed and journal location. The simulation models are validated with an experiment based on the displacements of the rotor and the forces acting on the bearings. Similar patterns have been observed for both simulated and measured orbits and forces. The resultant response amplitudes increase with the rotor speed and unbalanced magnitude. Both simulation and experimental results follow a similar trend, and the amplitudes agree with slight deviations. The frequency content of the responses from the simulations is similar to those from the experiments. Amplitude peaks, which are associated with the unbalance force (1 × Ω) and the number of pads (3 × Ω and 5 × Ω), appeared in the responses from both simulations and experiments. Furthermore, the suggested simulation model is found to be at least three times faster than a classical simulation procedure that used FEM to solve the Reynolds equation at each time step.

Experimental analysis of a large range of the load capacity for the axial AMB in the HTR-PM

An axial active magnetic bearing (AMB) is equipped to provide axial support of the vertical rotor of the helium circulator in the High Temperature Gas-cooled Reactor Pebble Bed Module (HTR-PM). The axial AMB is required to support the rotor and the aerodynamic load. High-strength alloy steel is selected as the material of the thrust disk. Maximum load capacity of the axial AMB in the HTR-PM helium circulator is analyzed with the consideration of the rotating velocity and the material strength. Also, experiments are conducted based on a 1:1 prototype to reveal a large range of the load capacity for the axial AMB. The dynamic electromagnetic force corresponding to the allowable stress, the rotational velocity, and other parameters of the axial AMB, such as B-R Curve, resistance and inductance, are revealed. Effect of the heat treatment to the load capacity is also discussed. The results will provide some theoretical and engineering reference to the design and the type selection of the axial AMB in the rotor system of the HTGR (High Temperature Gas-cooled Reactor) energy conversion system.

Dynamic characteristics analysis of a vertical Jeffcott rotor-brush seal system

ABSTRACT Turbomachinery is used widely in the energy and power industries. The configuration of the rotor system is one of the major concerns in rotating machinery. This paper describes the development of a mathematical dynamic model of the vertical Jeffcott rotor–brush seal system considering bristle interference. The effects of the main structural and operating parameters, such as the rotational speed, rotor mass, installation distance of the brush seal, and system damping, on the nonlinear dynamic behavior of the vertical system are analyzed. The bifurcation points, stability, and vibration responses of the system are investigated using axis orbits, time histories, Poincaré maps, spectrum diagrams, bifurcation diagrams, and largest Lyapunov exponents. The results indicate that the amplitude of a vertical rotor system is smaller than that of a horizontal rotor system. The amplitude decreases as the installation distance and damping level increase. Reducing the rotor mass would enhances the stability of a rotor system.

Development and application of a numerical analysis method for investigating hydro static and hydrodynamic responses of pocket bearing rotor systems

A numerical tool is presented for simulating the dynamics of a vertical rotor attached with pocket bearing assembly immersed in a liquid pool. The journal of the bearing has a heterogeneous geometry with the presence of pockets and grooves. The fluid pressure supplied to the pockets is a quadratic function of shaft speed. The radial, circumferential and axial flow paths constitute a complex fluid network in the coupled system. The network has been conceived as an assemblage of straight and curved fluid flow paths for the generic applications. An efficient solution strategy has been employed involving both analytical and numerical techniques.A Case study was performed on a representative pocket bearing assembly that is commonly used in the coolant pumps of sodium cooled fast reactor. The study has brought out some specific dynamic characteristics of such bearings. The flow field exhibits both hydrostatic and hydrodynamic effects, thereby hybrid bearing characteristics. The dynamic characteristics are strong function of spinning velocity, eccentricity and angular orientation of the rotor in fluid annulus. Based on an elaborate parametric study, a rotor dynamic stability chart has been established for the practical applications. Interestingly, the dynamic behavior within a limited operating regime exhibits the characteristics of a large eccentric homogeneous rotor rotating in fluid annulus with moderate gaps, predicted by Antunes et al. (1996). Moreover, it is found that the pocket type bearing has better stability control, mainly due to lower added fluid mass. The numerical tool is experimentally validated by comparing the displacements measured on a shaft coupled with pocket bearing assembly, rotating in a water pool.