scholarly journals Pre-Pressure Optimization for Ultrasonic Motors Based on Multi-Sensor Fusion

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2096
Author(s):  
Ning Chen ◽  
Jieji Zheng ◽  
Dapeng Fan
Keyword(s):  
Temperature Rise ◽  
Power Dissipation ◽  
Contact Region ◽  
Experimental Tests ◽  
Optimization Criterion ◽  
Maximum Efficiency ◽  
Axial Pressure ◽  
Ultrasonic Motors ◽  
Electric Cylinder ◽  
Speed Fluctuations

This paper investigates the pre-pressure’s influence on the key performance of a traveling wave ultrasonic motor (TRUM) using simulations and experimental tests. An analytical model accompanied with power dissipation is built, and an electric cylinder is first adopted in regulating the pre-pressure rapidly, flexibly and accurately. Both results provide several new features for exploring the function of pre-pressure. It turns out that the proportion of driving zone within the contact region declines as the pre-pressure increases, while a lower power dissipation and slower temperature rise can be achieved when the driving zones and the braking zones are in balance. Moreover, the shrinking speed fluctuations with the increasing pre-pressures are verified by the periodic-varying axial pressure. Finally, stalling torque, maximum efficiency, temperature rise and speed variance are all integrated to form a novel optimization criterion, which achieves a slower temperature rise and lower stationary error between 260 and 320 N. The practical speed control errors demonstrate that the proportion of residual error declines from 2.88% to 0.75% when the pre-pressure is changed from 150 to 300 N, which serves as one of the pieces of evidence of the criterion’s effectiveness.

scholarly journals Thermal Analysis of AlGaN/GaN HEMTs Considering Anisotropic And Inhomogeneous Thermal Conductivity

2021 ◽  
Author(s):  
Yao Li ◽  
Zixuan Zheng ◽  
Qun Li ◽  
Hongbin Pu
Keyword(s):  
Thermal Conductivity ◽  
Temperature Rise ◽  
Power Dissipation ◽  
Thermal Characteristics ◽  
Maximum Temperature ◽  
Base Temperature ◽  
Initial Growth ◽  
Boltzmann Transport ◽  
Growth Interface ◽  
Anisotropic Thermal Conductivity

Abstract To examine the differences of thermal characteristics introduced by material thermal conductivity, anisotropic polycrystalline diamond (PCD) and GaN are analyzed based on the accurate model of grain sizes in the directions of parallel and vertical to the interface and an approximate solution of the phonon Boltzmann transport equation. Due to the space-variant grain structures of PCD, the inhomogeneous-anisotropic local thermal conductivity, homogeneous-anisotropic thermal conductivity averaged over the whole layer and the typical values of inhomogeneous-isotropic thermal conductivity are compared with/without anisotropic GaN thermal conductivity. The results show that the considerations of inhomogeneous-anisotropic PCD thermal conductivity and anisotropic GaN thermal conductivity are necessary for the accurate prediction of temperature rise in the GaN HEMT devices, and when ignoring both, the maximum temperature rise is undervalued by over 16 K for thermal boundary resistance (TBR) of 6.5 to 60 m2K/GW at power dissipation of 10 W/mm. Then the dependences of channel temperature on several parameters are discussed and the relations of thermal resistance with power dissipation are extracted at different base temperature. Compared with GaN, SiC and Si substrates, PCD is the most effective heat spreading layer though limited by the grain size at initial growth interface.

Ecological Optimization of Generalized Irreversible Chemical Engines

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Lingen Chen ◽  
Dan Xia ◽  
Fengrui Sun
Keyword(s):  
Mass Transfer ◽  
Entropy Production ◽  
Production Rate ◽  
Power Output ◽  
Optimization Criterion ◽  
Ecological Function ◽  
Maximum Efficiency ◽  
Entropy Production Rate ◽  
Output Entropy ◽  
Ecological Optimization

Optimal ecological performance of generalized irreversible chemical engine cycles with both linear and diffusive mass transfer laws are derived by taking an ecological optimization criterion as the objective, which consists of maximizing a function representing the best compromise between the power output and the entropy production rate of the chemical engines. In this paper, the relations between the ecological function, power output, entropy production rate and the efficiency of a chemical engine cycle with irreversibilities of mass transfer, mass leakage and internal dissipation, in which the mass transfer, are derived. This paper also derives the maximum ecological function and the corresponding power output, entropy production rate and efficiency, the maximum power output and the corresponding ecological function, entropy production rate and efficiency, and the maximum efficiency and the corresponding ecological function, power output and entropy production rate. The results can provide some theoretical guidelines for the design of practical chemical engines.

Processing Map for Hot Deformation of Homogenized AZ61 Mg Alloy

2013 ◽  
Vol 716 ◽  
pp. 240-243 ◽  
Author(s):  
Ching Hao Liao ◽  
Horng Yu Wu ◽  
Shyong Lee ◽  
Cheng Tao Wu ◽  
Chui Hung Chiu
Keyword(s):  
Power Dissipation ◽  
Processing Map ◽  
Flow Instability ◽  
Local Maximum ◽  
Mg Alloy ◽  
Deformation Condition ◽  
Maximum Efficiency ◽  
Processing Maps ◽  
Compression Tests ◽  
Az61 Mg Alloy

Based on the experimental results from the hot compression tests of homogenized cast AZ61 Mg alloy, processing maps were constructed by superimposition of the instability maps over the power dissipation maps. The domain with the efficiency of power dissipation reaching a local maximum and flow instability region were identified in the processing maps. The processing map obtained at a strain of 0.6 exhibited only one domain with local maximum efficiency of power dissipation. The microstructure observations showed that variation in microstructure was related to the deformation condition, which was associated with the variation in efficiency of power dissipation.

A Solution for Experimental Modeling the Axial Fans With High Efficiency and Reduced Noise

2020 ◽  
Author(s):  
Victorita Radulescu
Keyword(s):  
High Efficiency ◽  
Experimental Tests ◽  
Rotation Velocity ◽  
Industrial Applications ◽  
Rotor Blades ◽  
Experimental Results ◽  
Computational Method ◽  
Maximum Efficiency ◽  
Axial Fan ◽  
Experimental Stand

Abstract Present paper describes some experimental results obtained for modeling an axial fan with newly designed blade profiles, having high efficiency, low vibrations and noise. The axial fan was firstly designed by computational method, during a research project with our industrial partner SAVEB SA. One of the company objectives is represented by the production of the axial industrial fans, dedicated to different users to eliminate the smoke and the air pollutants from industrial halls, according to their specific needs. In the beginning, are presented some aspects of the theoretical aspects used in the numerical modeling for designing the rotor blades. Some considerations concerning the selection of the incidence angles of 10°, 15°, and 20° are mentioned. The profiles were selected from the recommended schemes, for different industrial applications, as the industrial halls for the air or gas circulation without corrosive, abrasive, or toxic agents, metallic dust, or with crowding/sticking suspensions contents. For this type of axial fan, the content of suspensions should not exceed 50 mg/m3. Further is presented the experimental stand, in conformity with actual standards, STAS 7466-84 and DIN 24163, equipped with a hydrometer with an error less than 3%, barometer with an error less than 1 mm Hg, stroboscope and tachometer with an error less 0,5% from the total rotation velocity, two voltmeters, with an error less 0,5, two wattmeters, etc. For the experimental tests was selected a fan with a diameter of 630 mm, which as standard execution has a maximum efficiency of 56%, in six different constructive variants: a rotor with 12 profiles and directory device with 11 blades, with 6 blades and directory device, etc. As the first variant of the rotor’s profiles has been used two solutions for the realization as two technological options, both of them tested in the laboratory. There are detailed some schemes adopted for the measurements and tests, and finally the adopted solution for measuring different characteristic parameters like efficiency, noise, and vibrations produced by the axial fan. Next are illustrated part of the measurement reports and the corresponding charts. Of the total amount of experimental results were selected for measuring scheme III and IV for their optimum energetic characteristics and high efficiency. All four diagrams are presented for both selected solutions used in the realization of the fan rotor blades. Finally, some conclusions and references are presented.

Experimental Analysis of a Vapor Chamber Applied to Thermal Management of Microelectronics

2015 ◽  
Vol 1120-1121 ◽  
pp. 1368-1372 ◽  
Author(s):  
Daniel Henrique de Souza Obata ◽  
Thiago Antonini Alves ◽  
Márcio Antonio Bazani ◽  
Amarildo Tabone Paschoalini
Keyword(s):  
Thermal Management ◽  
Integrated Circuit ◽  
Heat Sink ◽  
Power Dissipation ◽  
Pure Aluminum ◽  
Experimental Tests ◽  
Working Fluid ◽  
Vapor Chamber ◽  
Airflow Velocity ◽  
Circuit Power

In this research, a vapor chamber embedded in the base of a heat sink was experimentally analyzed for the application in thermal management of microelectronics. The vapor chamber was produced by a copper and molybdenum alloy with length of 240 mm, width of 54 mm, thickness of 3 mm, and capillary structures composed by copper screen meshes. The working fluid used was de-ionized water. The pure aluminum heat sink was cooled by air forced convection and the evaporator vapor chamber was heated using an electrical resistor simulating integrated circuit power dissipation. The experimental tests were done in a suction type wind tunnel with open return for a heat load varying from 20 to 80 W and for an airflow velocity varying from 1 to 4 m/s. The experimental results showed that the considered vapor chamber worked successfully, maintaining low operating temperature.

scholarly journals Analysis of Rolling Force for Extra-Thick Plate with CA Criterion

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Shun Hu Zhang ◽  
Lei Deng ◽  
Peng Li
Keyword(s):  
Temperature Rise ◽  
Power Dissipation ◽  
Thick Plate ◽  
Control Method ◽  
Rolling Force ◽  
Yield Criterion ◽  
Inner Product ◽  
Relative Reduction ◽  
Force Model ◽  
Theoretical Results

In order to solve the nonlinear integral difficulty of the Mises yield criterion, a linear yield criterion, called the collaborative approximation (CA) yield criterion, is proposed by the collaborative control method. According to the approximation method, the mathematical expression of the CA yield criterion is derived as a linear function of the three principal stresses. The theoretical results based on the yield criterion in the form of the Lode parameter are verified with the classical test data, and a good agreement is found. Meanwhile, for the purpose of proving the effectiveness of the yield criterion, its specific plastic power is derived and applied to establish the rolling force model of an extra-thick plate. In the modeling, the internal power of plastic deformation is obtained by using the derived specific plastic power, while the shear power dissipation and the frictional power dissipation are obtained by using the methods of strain vector inner product and average velocity integration. Then, the analytical solution of the rolling force is obtained and then extended to the one accounting for the temperature rise. The maximum errors of the predicted rolling torque and rolling force without considering the temperature rise are 12.72% and 11.78%, respectively, while those considering the temperature rise decrease to 3.54% and 5.23%, respectively. Moreover, the influence of relative reduction, friction factor, surface temperature, and the temperature rise of the workpiece on the theoretical results is discussed.

Rotating Stall Model and Simulation of Two-Stage Centrifugal Compressors

2007 ◽  
Author(s):  
Lorenzo Scano ◽  
Gianmario L. Arnulfi
Keyword(s):  
Fluid Dynamic ◽  
Experimental Tests ◽  
Stationary Flow ◽  
Computer Code ◽  
Rotating Stall ◽  
Single Stage ◽  
Maximum Efficiency ◽  
Centrifugal Compressors ◽  
Two Stage ◽  
Multi Stage

Often turbo-compressors exhibit the maximum efficiency condition very close to the stall limit, so that it would be highly interesting to have a deep comprehension of this phenomenon. Despite the large diffusion of the multi-stage centrifugal compressors in different fields of the technology, such as natural gas pipe-lines or chemical factories, at the best authors’ knowledge, to date no theoretical model exists for rotating stall in these machines. This paper deals with a model for simulating multi-stage centrifugal compressor flow pattern during rotating stall. The model is not able to capture the stall inception, so the velocity and pressure fields are calculated throughout the machine once rotating stall has developed. The model consists of an implementation of that proposed by Moore for single-stage centrifugal compressors, so the simplifying hypotheses are: irrotational upstream fluid flow, inviscid and incompressible flow, stationary flow in the frame rotating at the same frequency of the stall cell; infinite blades are supposed both in rotors and return channel. Even if these fluid-dynamic hypotheses are really strong, it is worth of note that the reference models for rotating stall simulation in turbo-compressors (namely the Moore’s models) are based, at the present time, on them. In a previous step of this research, the authors utilized a semi-empirical approach, with phases changes between first and second diffuser based on experimental data. Now this hypothesis is removed and the model is fully analytical. The mathematical model is solved by numerical way, leaving the original semi-analytical scheme of Moore, so allowing the stall cell propagation frequency to be calculated. The computer code is written in C language for Linux operating system. It was tested in single-stage configuration with results according to Moore’s theory; for two-stage setup, obtained results appear consistent and qualitatively according with experimental tests and, unlike the single stage analysis, only fast rotation waves were found.

Application of a Thermodynamically Based Wear Estimation Methodology

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
A. B. Aghdam ◽  
M. M. Khonsari
Keyword(s):  
Wear Rate ◽  
Temperature Rise ◽  
Experimental Tests ◽  
Sliding Contact ◽  
Dry Sliding ◽  
Loading Conditions

Entropic and energy-based approaches are employed for prediction of wear in dry sliding contact between crossed cylinders. The methodology requires measurement or estimation of the temperature rise in the sliding system. The results of experimental tests reported in literature in conjunction with measured degradation coefficients are used to examine the validity of the proposed methodology. The approach presented is shown to be capable of predicting the wear rate for different tribopairs and under different loading conditions.

Temperature Measurement of Microscopic Areas Within a Simulated Head/Tape Interface Using Infrared Radiometric Technique

1986 ◽  
Vol 108 (1) ◽  
pp. 29-34 ◽  
Author(s):  
R. Gulino ◽  
S. Bair ◽  
W. O. Winer ◽  
B. Bhushan
Keyword(s):  
Friction Force ◽  
Temperature Rise ◽  
Magnetic Tape ◽  
High Speed ◽  
Contact Region ◽  
Infrared Band ◽  
Load Curve ◽  
Recording Head ◽  
Infrared Measurement ◽  
Infrared Microscope

This study concerns the infrared measurement of steady-state and transient temperatures of microscopic areas within the contact region formed by a magnetic tape passing over a simulated recording head. This research demonstrates that the tape surface temperature can be measured within specific limits of response time and sensitivity. Due to its high tranmissivity in the relevant infrared band, sapphire was chosen as the material to be used in the fabrication of a simulated recording head. A Barnes RM2A infrared microscope was the principle radiometer used, while a best effort was made in scanning with an AGA Thermovision 750. The friction force versus load characteristics of the head-magnetic tape interface were also observed. The high speed measurements were divided into two regimes; non-contact hydrodynamic film region, and tape-head contact regime. The temperature measurements displayed a strong correlation with the measured friction force versus load curve. Almost no temperature rise was found in the noncontact hydrodynamic film region while a temperature rise of a few degrees Celsius was found when there was tape-head contact. The results with the AGA Thermovision 750 were consistent with the measurements obtained with the Barnes RM2A.

Technique for Studying Overcurrent Behavior in YBCO Coated Conductors Using a Localized Magnetic Field

2005 ◽  
Vol 868 ◽  
Author(s):  
J. Yates Coulter ◽  
Stephen P. Ashworth ◽  
Paul C. Dowden ◽  
Jeffrey O. Willis
Keyword(s):  
Magnetic Field ◽  
Temperature Rise ◽  
Power Dissipation ◽  
High Temperature Superconductor ◽  
Coated Conductors ◽  
Spatial Gradient ◽  
Current Events ◽  
Ybco Coated Conductors ◽  
Superconductor Tape ◽  
Localized Magnetic Field

AbstractOver current stabilization of YBa2Cu30x (YBCO) coated conductor high temperature superconductor tape is required in most applications. The conductor must carry currents in excess of the critical current, Ic, without damage during over current events. Conductor damage is the result of joule heating and excessive temperature rise in regions with low Ic. We have developed and applied a measurement technique using a locally applied magnetic field with a high spatial gradient to define a small area over which the Ic is depressed. By measuring the voltage and temperature as a function of current, power dissipation and temperature rise were determined. Unstabilized conductors experienced thermal runaway and are easily damaged. Copper stabilizers applied by electroplating decreased dramatically the temperature rise and increased the level of power dissipation compared with the unstabilized conductor.

Sign in / Sign up

Export Citation Format

Share Document