Wide Range Of Rotational Speeds Research Articles

PSD estimation and modal parameter identification for random vibrations with blade tip timing measurement

Abstract Blade tip timing (BTT) is a vibration measurement technique for blade health monitoring. Most of the existing BTT analysis methods are suitable for deterministic vibration signals but are ineffective for random vibration signals that often occur in practice. Statistical analysis of BTT data is significant for random vibration analysis and improving blade monitoring efficiency. This study proposes a compressive model for power spectral density (PSD) estimation and modal parameter identification. The efficiencies of three compressive sensing algorithms, including the least absolute shrinkage and selection operator (Lasso), nonnegative least squares (NLS), and nonnegative orthogonal matching pursuit, are compared. The effects of the duration of the signal and the frequency resolution on the quality of the estimated PSD and the identified parameters are discussed. According to the analysis, to obtain accurate damping ratios, it is recommended that the duration of the signal be greater than 3000 revolutions. A Q criterion based on the half-power bandwidth is proposed to determine the set of frequency resolutions. Numerical and field tests were conducted to verify the proposed method. The results indicate that the NLS algorithm is recommended to use. The root-mean-square errors of the identified natural frequencies and damping ratios obtained by the proposed method were 0.065 Hz and 0.023%, respectively. The proposed method was verified at different rotational speeds in a field test, demonstrating the capability of the method over a wide rotational speed range and providing more opportunities to detect blade damage.

The influence of cooling medium and cooling channel on heat transfer of textured seal in presence of viscous dissipation

When operating at high speed, the mechanical seal produces a large amount of frictional heat on the seal face. If the heat is not dissipated in time, it could lead to the thermal failure of the seal face. In the field of tribology research, the technology of textured surface is a method to enhance the heat dissipation rate. Numerical analysis is carried out based on the SST k-ω turbulence model and the energy equation with viscous dissipation term, and the results are validated by the experimental data published in the reference. In a wide range of rotational speeds, cooling medium with varied Pr numbers is employed to confirm the performance of textured side-wall in heat transfer enhancement. The shape of the seal chamber is also changed to provide guidance for the design of the cooling channel. The results show that a larger Pr number increases the heat transfer enhancement of the textures; it is advisable to utilize a cooling channel that gradually decreases in size; and the flushing should not be perpendicular to the stator; additionally, it is important to ensure that the cooling channel is not too narrow. By means of appropriate design, the maximum temperature of seal face can be reduced by over 40 °C (22.2 %) at 20,000 rpm.

Self-powered online practical machine condition monitoring and wireless communication achieved on integrated, efficient, and durable triboelectric nanogenerator

Triboelectric nanogenerator (TENG) can effectively scavenge ambient mechanical energy with cost, weight, and effectiveness advantages despite critical issues of TENG such as integration to complex components, low current output, and durability. In this work, we designed an adaptive TENG on a mechanical shaft for harvesting rotational energy which can easily assemble and disassemble. The proposed TENG presents an excellent performance for a wide range of rotational speeds (0–2000rpm) and delivers a high power of up to about 80mW (a high short circuit current of 3mA) for a size of 216 cm3, which is high enough for many types of machine condition monitoring purposes. The designed TENG has been evaluated under the noncontact mode of operation within a 0–0.5mm gap between TENG films. The TENG demonstrates excellent electrical stability of 99% without surface wear under noncontact mode within the whole test period for continuous operation of 420,000 cycles. The contact mode with a contact pressure of 0.76 Pa results in 90% electrical stability and apparent surface degradation. Moreover, it is demonstrated that the proposed TENG can power a wireless vibration sensor (60 mW) within 10 minutes energy harvesting for 9 seconds to send data via Bluetooth to a smartphone at up to 30 m, and a wireless temperature sensor (1.2 mW) in real-time for machine condition monitoring.

Итоги разработки методики проектирования линейки винто кольцевых движителей с умеренной и большой нагрузкой мощностью на площадь для беспилотных воздушных судов транспортного назначения

For unmanned aircraft for transportation purposes, the key issue is the choice of characteristics of lifting thrusters, which should have sufficient efficiency at limited dimensions. In this paper, the methodology of numerical modeling of propeller ring thrusters, propellers rotating in a ring, is sequentially considered. The characteristics of propellers with propellers differing in the number of blades, geometric twist of blades, degree of coverage of the area swept by the propeller and blade length are studied. Dependences of thrust and power coefficients, as well as propulsion efficiency values for a wide range of rotational speeds and engine power supplied to the propellers are obtained. The issue of propulsor optimization is considered separately. The results are compared with TsAGI reference experimental data.

Влияния кинематических параметров на процесс кавитационной обработки промывочных жидкостей и тампонажных растворов

The paper presents a numerical study of the original design of the rotary pulsating apparatus (RPA). In comparison with the traditional geometry, the simulation of a combined channel consisting of a narrowing section of the rotor and a diverging stator was performed for the first time. The results of numerical simulation of the RPA operation without additional inlet pressure in a wide range of rotor speeds are presented. Distributions of static pstat and total ptot pressure are obtained. The points of extremes and patterns of their changes are revealed. The length of the cavitation cavity in the RPA channel is determined, the equations of dependence. The cavitation characteristics of the RPA were evaluated. The distribution of the volume fraction of the vapor phase and the mathematical dependenceof the maximum value of the vapor phase on the frequency with equal pressures at the inlet and outlet are obtained.

Test bench development and implementation for experimental determination of mechanical losses in single cylinder internal combustion engines

As mechanical efficiency has great relevance in the alternative engine performance, the authors research in the development of testing facilities to characterize the sources of engine mechanical losses. The present paper deals with the realization of a hardware platform to conduct experimental studies in small combustion engines to experimentally characterize the mechanical losses of a single-cylinder internal combustion engine by means of the indicated diagram and motoring methods. The system was completed by means of an electrical motor-generator coupled to a single-cylinder air-cooled spark ignition engine, a self-developed electronic hardware control, and a PC-based instrumentation and data acquisition system. Specifications of load-motoring-starting system, including the description of the proprietary electronic load regulation system, are detailed. Also, the instrumentation system of in-cylinder and intake pressures; Temperatures of intake air, exhaust gases, lubricant oil, and engine block; effective torque and crankshaft position are described, including the signal acquisition system. The methodologies for indicated diagram and motoring method are described, mentioning the required measurements to apply each method and the engine load-temperature considerations when an engine is tested in fired or motored conditions. The platform was used to study the mechanical losses of the engine under motored and fired conditions under a wide range of rotational speeds and throttle openings, allowing to draw conclusions about the operating features of the developed test bench in itself, and also about the mechanical losses of the engine tested. Initially, samples of cylinder pressure, torque, intake pressure as function of crank angle and indicate diagram were obtained, showing similar waveforms present in related literature. Then, variations of the aforementioned temperatures against rotation speed and throttle opening and results for the mechanical losses determined by indicated diagram and motoring methods are shown. Finally, two empirical correlations are proposed to estimate the mechanical losses. In the future the hardware platform will be utilized to investigate in-cylinder engine parameters, detailed thermal and mechanical engine performance

An ultra-compact lightweight electromagnetic generator enhanced with Halbach magnet array and printed triphase windings

Electromagnetic generator (EMG) plays a pivotal role in in-situ power supply for low-power electronics. However, a major challenge associated with EMGs is the limited power density. To address this issue, various strategies have been proposed, including magnetic field augmentation of magnets, magnetic flux variation rate escalation at the coil, and structural miniaturization. In this study, we present an innovative ultra-compact electromagnetic generator (UL-EMG) in light weight that integrates the Halbach magnet arrays and printed circuit board (PCB) technologies. The UL-EMG incorporates a 12-layer printed triphase windings into its PCB stator, thereby upgrading both device compactness and output performance. To assess the performance of the UL-EMG, comprehensive bench tests were conducted. Interestingly, results indicate that at a low rotational speed of 200 rpm, the UL-EMG achieved a peak AC output power and power density of 54.9 mW and 1.25 kW/m3, respectively, representing a 22-fold expansion compared to conventional EMGs. Moreover, the UL-EMG exhibited exceptional output characteristics across a wide range of rotational speeds, significantly bolstering its capacity to drive various low-power electrical appliances. This study paves a novel path for heightening the power density of EMGs and highlights the promising application prospects of compact EMGs in in-situ power supply advancement.

Tribological characteristics of hard-to-hard matching materials of cylinder block/valve plate interface in electro-hydrostatic actuator pumps

Axial piston pumps, serving as the essential power component in electro-hydrostatic actuators (EHA), play a crucial role in achieving advanced actuation by ensuring high efficiency and reliability. The cylinder block/valve plate interface, which is the greatest contact area inside the axial piston pump, significantly affects both leakage and energy dissipation. The interface experiences significant friction loss and severe wear in aerospace applications, primarily due to the rapidly changing mixed and boundary lubrication conditions under a wide range of speed and pressure. Therefore, to improve the efficiency and reliability of electro-hydrostatic actuators, strengthening the cylinder block/valve plate interface is a key problem to overcome. Previous studies have demonstrated that the utilization of soft-to-hard matching materials enhances the friction characteristics of the interface, but it also results in relatively severe wear on the soft material. Therefore, in this study, we propose the concept of employing hard-to-hard matching materials as a strategy to mitigate wear in axial piston pumps. An optimized friction simulation test apparatus is adopted, which contains a simulated piston structure to take the piston stirring effect into consideration. Experimental results show that the implementation of hard-to-hard materials leads to a substantial improvement in the wear resistance of the interface under a wide range of rotational speed (300–6000 rpm). The wear depths of the TiAlN/TiAlN (hard-to-hard) matching material are only 28.6%~34.7% of the tin bronze/TiAlN (soft-to-hard) matching material. Besides, compared with traditional tin bronze/nitrided (soft-to-hard) matching material, the hard-to-hard matching materials improve both friction and wear performance. The hard-to-hard matching materials provide a novel approach to reinforce the cylinder block/valve plate interface, and thus to promote volumetric efficiency and extend the service life of the axial piston pump.

Study of the Friction Stir Welding For A516 Low Carbon Steel

The main objective of present work is to describe the feasibility of friction stir welding (FSW) forjoining of low carbon steel with dimensions (3 mm X 80 mm X 150 mm). A matrix (3×3) of weldingparameters (welding speed and tool rotational speed) was used to see influence of each parameter onproperties of welded joint .Series of (FSW) experiments were conducted using CNC milling machineutilizing the wide range of rotational speed and transverse speed of the machine. Effect of weldingparameters on mechanical properties of weld joints were investigated using different mechanical testsincluding (tensile and microhardness tests ). Micro structural change during (FSW) process wasstudied and different welding zones were investigated using optical microscope. The stir weldingexperiments conducted that show the low carbon steel can be welded using (FSW) process withmaximum welding efficiency (100.02%) in terms of ultimate tensile strength using best result ofwelding parameters (700 RPM, 25 mm/min, tool rotational speed and welding speed respectively and0.2 mm plunging depth of welding tool) ,there is afirst time that we obtain the efficiency reach to100.02 % to weld this type of low carbon steel by FSW. The corrosion resistance was measure whichis the new test on the welding by this way and we obtained different result from the result ontraditional welding processes and the result that obtained show the corrosion resistance for thiswelding plate better than the base metal. Maximum temperature has been calculated numerically byusing the ANSYS program. The obtained peak temperature is 1102°C, A percentage minimum of themelting point .

Sustainable energy development technique of vertical axis wind turbine with variable swept area – An experimental investigation

The vertical axis wind turbine is one of the most attractive propulsion systems for sustainable energy generation around the globe. The performance of a vertical axis wind turbine is greatly dependent on wind speed, blade set angle and more importantly the rotational speed. The effective utilization of wind speed and rotational speed on power generation would be enhanced by the improvement of energy capturing capability. Therefore, an attempt has been made to develop the vertical axis wind turbine with a variable swept area of blades to enhance the torque and power output over a wide range of rotational speeds and set angles. In the first phase, the wind turbine is designed with flexibility in blade set angles through modification on the swept area and the developed wind turbine has been subjected to various wind speeds and rotational speeds in a wind tunnel. The experimental results revealed that the torque and power are increased with an increase in wind speed and rotational speeds under blade set angle of 30° to 120°. The peak torque and power have been attained at the average speed of the turbine and it has been eventually increased for a higher blade set angle. For constant set angle, the performance characteristics are also improved due to the enhancement in energy capturing ability of wind turbine at the variable swept area. Furthermore, torque and power coefficient are evident in a similar pattern at all wind speeds and rotational speeds under different tip speed ratios. The maximum torque coefficient would be around 0.3 for the tip speed ratio of 0.2–0.3 and the attainment of the peak value of power and torque coefficient has been shifted towards higher speed due to the improvement in blade dimensions. Thus, it is revealed that the vertical axis wind turbine with enhanced swept blade area would be an attractive propulsion system for sustainable energy generation.

A comparative study between two lubrication nano-additives (Bi2O3 & TiO2) based on vibration response analysis

The purpose of this paper is to present a vibration monitoring analysis of a hydrodynamic journal bearing working with nano-additives lubricants.The vibration response is generated on bearings at various rotational speeds and dynamic load conditions.These bearings were tested experimentally by adding two types of nano additives; Bismuth (3) oxide (Bi2O3), which is considered a green, nontoxic metal, as well as a new additive, and nano Titanium dioxide (TiO2), which is moderately toxic, with SN150 base oil.The performance of additives was studied on the base oil. The comparisons between the two nano-additives Bi2O3 with (1, 2, and 4 wt. %) and TiO2 with (1 and 1.25 wt. %) were studied experimentally with the SN150 base oil. And the obtained results manifested that at different concentrations of Bi2O3 and TiO2 in the SN150 base oil for each rotational speed and dynamic load, there was a reduction in the vibration system response, where Bi2O3 has a good performance at a wide range of rotational speed and dynamic load. At the same time, TiO2 performs better at higher rotational speed and dynamic load.

Improvement of energy efficiency in the drive system of an electric car with PMSM

Thanks to the advantages, i.e. high overload, high power density factor, wide range of rotational speed, low moment of inertia, as well as high torque-to-inertia ratio, PMSM AC motors are currently widely used in electric cars. The article presents a new method of PMSM control through the modification of the Clarke and Park transforms that enables to improve the efficiency of the mechatronic system due to the energy criterion. The article shows analytical tests confirming the possibility of maintaining the reactive power at zero level in the inverter-PMSM circuit. The analytical tests were supported by simulation tests with the use of the MATLAB-SIMULINK program.

Optoelectronic system for controlling an alternating current motor. Electrical and electronic design

A control system for a three-phase induction motor was designed with the use of optoelectronic components and methods. Motor speed was controlled by changing supply voltage frequency. This solution ensures a wide range of rotational speeds, constant torque and effective start-up of an induction motor. The designed motor is supplied with direct current converted to three-phase alternating current. The adopted solution relies on renewable sources of energy to produce DC power. The designed electric motor is controlled by changing supply voltage frequency. Input voltage with the desired waveform is generated by the motor’s electronic system that relies on two microcontrollers. The presented solution features a user interface.

Friction Stir Spot Welding of Different Thickness Sheets of Aluminum Alloy AA6082-T6.

Friction stir spot welding (FSSW) is one of the important variants of the friction stir welding (FSW) process. FSSW has been developed mainly for automotive applications where the different thickness sheets spot welding is essential. In the present work, different thin thickness sheets (1 mm and 2 mm) of AA6082-T6 were welded using FSSW at a constant dwell time of 3 s and different rotation speeds of 400, 600, 800, and 1000 rpm. The FSSW heat input was calculated, and the temperature cycle experience during the FSSW process was recorded. Both starting materials and produced FSSW joints were investigated by macro- and microstructural investigation, a hardness test, and a tensile shear test, and the fractured surfaces were examined using a scanning electron microscope (SEM). The macro examination showed that defect-free spot joints were produced at a wide range of rotation speeds (400–1000 rpm). The microstructural results in terms of grain refining of the stir zone (SZ) of the joints show good support for the mechanical properties of FSSW joints. It was found that the best welding condition was 600 rpm for achieving different thin sheet thicknesses spot joints with the SZ hardness of 95 ± 2 HV0.5 and a tensile shear load of 4300 ± 30 N.

Effect of guide vane on the performance of a sail wing turbine for wave energy conversion

Abstract In an Oscillating Water Column (OWC) based wave energy plant, the sea wave motion is used to drive an air column in an air chamber and that results in a bi-directional airflow. An air turbine for bi-directional airflow is used to convert the pneumatic energy into mechanical energy. The sail wing turbine can be used as an air turbine for wave energy conversion because it has a special structure in which the shape of the sail changes in reciprocating airflow and always can rotate in the same direction. In addition, the sail wing turbine does not experience the stalling effect and can acquire energy at a wide range of rotational speed and flow rate. In our previous studies, the performance of the sail wing turbine for bi-directional airflow has been investigated by using a wind tunnel test. In the present study, in order to further improve the performance of the sail wing turbine, guide vanes were installed, and the effect of the guide vane on the performance was investigated by a wind tunnel test and a computational fluid dynamics (CFD) analysis under a steady flow condition.

Application of gear hydraulic machines in the composition of hydrostatic transmissions

Hydraulic machines serve either to impart energy to the fluid flowing through them, or to obtain energy from the fluid for its further useful use. The number of hydraulic machines used in the national economy is increasing annually, due to the fact that, in comparison with electric motors, they have smaller overall dimensions and weight, and also have a higher ratio of torque on the output shaft to the moment of inertia of the rotor. In agriculture, hydraulic machines are widely used in crop production. Through the use of hydraulics and automation, the development of complex mechanization of production processes is carried out, which provides for the development of machines of increased power and reliability. Also, the use of hydraulic machines allows you to relieve the structure of rigid mechanical connections and allows a wide range of adjustment of the unit operation. The most widely used today are two types of hydraulic machines - piston and gear. The use of hydraulic piston machines places high demands on the degree of purification and quality of transmission oil, as well as on the qualifications of technical personnel to ensure quality maintenance. Gear hydraulic machines are less demanding on the purity of the working fluid, as well as simplicity in design, are quite reliable, have a low cost price and a wide range of rotational speeds, in addition, they are able to create a relatively high pressure with low weight. The overall efficiency of gear hydraulic machines, which is 90%, is slightly inferior to that of piston hydraulic machines, which reaches 93%, respectively. The given characteristics of gear hydraulic machines allow us to consider them, taking into account modern design features, as a power basis for a hydrostatic transmission, with a limitation in power of application.

Бесконтактный генератор с регулируемым возбуждением

Wind turbines are further developed toward improving their reliability and efficiency, and reducing maintenance costs during long-term operation. For this purpose, synchronous generators with excitation from permanent magnets are used, the parameters of which determine in many respects the efficiency and dimensions of the power plant as a whole. The article proposes a new design of a brushless synchronous generator with excitation longitudinal with respect to the rotor rotation axis. The generator features a simple design of its rotor poles and double frequency of the secondary winding voltage. The possibility of manufacturing the stator housing from cheap plastic or similar non-magnetic materials is noted, due to which a reduction in the generator mass and cost can be achieved; such generator can find use mainly in small and medium capacity power plants. To close the rotor excitation magnetic flux, longitudinal magnetic cores with coils on them are installed in the slots of the non-magnetic stator housing. This makes it possible to improve heat removal from the secondary winding and simplify the assembly. Smooth adjustment of the output voltage in a wide range of rotation speeds is possible. The results of modeling the magnetic field in the air gap between the stator and rotor and the output voltage waveform for the basic magnetic system configuration are presented.

DESIGN AND LAYOUT OF AN ELECTRIC MOBILE VEHICLE FOR FARMING

Currently, there is an active use of electric transport, including farms, in order to perform technological processes in premises for keeping animals and growing plants. In this regard, there is a need to improve its technical characteristics, increase the traction force, which serves as the most important physical quantity in an electric vehicle. (Research purpose) The research purpose is developing a chassis and main components of the vehicle, choose a traction electric motor of a mobile vehicle with an electric drive. (Materials and methods) An analysis of manual transmission switching in electric vehicles was performed. The article presents the layout of the electric tractor chassis. (Results and discussion) The main components of an electric vehicle (mobile vehicle) are: chassis; traction battery; control charger; electric drive, including multi-speed gearboxes. The use of a gearbox allows you to expand the range of applications of the vehicle. The article presents the type and voltage of the battery to increase the service life of the traction battery. (Conclusions) The chassis and main components of the vehicle were designed. A traction electric motor of a mobile vehicle was chosen. With the use of the proposed complex of the main components of an electric mobile vehicle, it becomes possible to use a manual transmission, which allows increasing the torque. Since the electric motor has a wide range of rotation speed, two mechanical gears (working and transport) are sufficient. A sample of a mobile vehicle was used in the experimental studies.

ANSYS CFX STUDY OF AERODYNAMIC CHARACTERISTICS DURING BLADE PROFILE ROTATION

Currently, wind energy is one of the most developing areas, which is primarily due to the absence of emissions of harmful substances into the atmosphere. Wind power allows providing electricity to remote areas, where fuel delivery, as well as the construction of thermal power plants is laborious and expensive. The effective development of wind turbines should solve the following tasks: the creation of the necessary driving force and the possibility of using a high coefficient of wind energy, which does not contradict the maintenance of the ecological balance of the territory. An electric generator for a household wind turbine must provide electricity in a wide range of rotation speeds and be able to work independently without automation and external energy sources. The study of the numerical implementation of the method of aerodynamic analysis of the wind turbine blade in rotational motion in the ANSYS CFD software package is by far the most promising and dynamically developing direction in the field of aerodynamics calculations. The results of approbation of the mixed calculation method using a dynamically variable and stationary finite-volume mesh are presented. The use of a mixed design scheme allows for calculations of wind turbines inside the building, while it becomes possible to minimize the required power for the study.

Numerical measurement of flow fluctuations to quantify cohesion in granular materials.

The flow of cohesive granular materials in a two-dimensional rotating drum is investigated using discrete element method simulations. Contacts between particles are modeled based on the widely used model of the spring-dashpot and Coulomb's friction law. A simplified model of intermediate range attraction between grains (i.e., cohesion) has been used in order to reproduce the flow of electrostatic or wet granular materials. Granular flow is generated by means of a rotating drum and the effect of the rotation speed, the friction between the grains, and the cohesion are studied. Significantly different flow behaviors are observed when cohesion is added. Plug flow appears in the rotating drum for a wide range of rotation speeds when cohesion becomes sufficiently strong. We propose a measurement of surface flow fluctuations to quantify the strength of cohesion, inspired by the previous observation of plug flow. Then, we make use of the results to include the effect of cohesion into a theoretical flow model. A good agreement is obtained between theory and numerical measurements of the granular bed's dynamic angle of repose, which allows us to propose a method for estimating the microscopic cohesion between grains based on the measurement of surface fluctuations.