Suitable Rotational Speed Research Articles

On-line Configuration Identification and Control of Modular Reconfigurable Flight Array

With the increasing complexity of the working environment and the diversification of mission requirements of UAVs, traditional UAVs have a fixed structure and single function. It is difficult to be applied in occasions with complex environments and changing load demands. The modular reconfigurable flight array (MRFA) is composed of no less than four isomorphic unit modules that are freely spliced together. By adding or removing flight unit modules and adjusting the arrangement of flight unit modules, the configuration of the MRFA can be changed, so that it can adapt to complex environments and then complete different flight missions. In the process of MRFA research and development, online configuration identification has become one of important problem to be solved. In this paper, a configuration recognition algorithm is designed based on the breadth-first searching method to identify the online structure of MRFA firstly. Then, the dynamic model of the aircraft is carried out according to the obtained configuration information. At the same time, the mathematical model and configuration information of the MRFA are combined to establish an optimization control allocation mechanism to allocate suitable rotational speed for multiple rotors. Finally, several examples are carried out to show that the proposed technology can recognize the configuration with 100% recognition rate and average online recognition time 569.4ms. Then a cascade PID controller is designed to realize the flight control of the irregular MRFA with faster tracking performance of no more than 40 seconds.

Analysis of Efficiency Characteristics of a Deep-Sea Hydraulic Power Source

Deep-sea submersibles carry limited energy sources, so a high efficiency of the equipment is required to improve endurance. In the deep-sea environment, the hydraulic power source is filled with oil, which causes structural deformation of the power source and changes in the physical properties of the medium, leading to unknown changes in the efficiency characteristics of the power source. In order to explore the efficiency characteristics of the deep-sea hydraulic power source composed of a gear pump and a DC (direct current) brushless motor in a variable sea depth environment, we undertook the following. First, considering the effects of seawater pressure and temperature on the physical properties of the medium and the radial clearance deformation of the gear pump, a mathematical model for the total efficiency of the hydraulic power source was established. The results indicate that the deformation of the pump body is mainly determined by the seawater pressure and working pressure. Subsequently, by analyzing the effects of the two factors on the efficiency of the power source, respectively, when the oil temperature range is large enough, the total efficiency of the power source will increase and then decrease under six sea depths; the total efficiency of the power source decreases with the increase in the rotational speed. However, in a land environment, the trend of the efficiency characteristics of the power source is opposite to that of the remaining six deep-sea environments, both in terms of oil temperature and rotational speed. Finally, the efficiency trend of the power source with changes in sea depth under rated conditions was obtained. Under different sea depth ranges, the optimal operating oil temperatures and suitable rotational speed ranges of the power source could be obtained. This paper could provide a certain theoretical basis for the research and development of deep-sea equipment.

Evaluation of quality of thick photoresist film by acoustic resonant imaging technique

In this paper, the effects of coating conditions on the thickness and quality, especially the hardness and density, of a photoresist film are reported. The photoresist film was deposited on a Si wafer by a spin coater under various conditions, including baking temperature, rotation speed, and the number of coats. The thickness of the film was measured by a surface profilometer. The sound velocity, which is closely related to hardness, and the density of the film were obtained by acoustic resonant imaging technique. The thickness and sound velocity of the film increased with increasing the number of coats and decreased with increasing the baking temperature and the rotation speed. Furthermore, the density of the film reached its maximum value for each condition. From multiple regression analysis, it was found that, among the three parameters of coating conditions, the rotation speed affects the quality of the film the most. It was shown that a dense photoresist film is obtained by deciding the baking temperature and number of coats in advance, then choosing a suitable rotation speed.

A comprehensive review of micro-scale expanders for carbon dioxide related power and refrigeration cycles

• Developments of micro-scale expanders in carbon dioxide cycles are summarized. • Comparison between turbines and volumetric expanders are analysed. • Relations between flow rate, pressure ratio and rotational speed are highlighted. • Challenges and future development directions for expanders outlined. In recent decades, the carbon dioxide cycles, including supercritical carbon dioxide cycle, transcritical carbon dioxide Rankine cycle and refrigeration cycle, have been proven effective due to the high efficiency and compact structure, and received increasing interests. The performance of the expander in the power cycles, particularly in micro-scale applications, is one of the essential components that determine the cycle performance and still remains a significant challenge. This paper presents a critical overview of micro-scale (<200 kW) expanders for carbon dioxide cycles. Five types of expanders, including axial and radial turbines (dynamic expanders), scroll, piston and vane expanders (volumetric expanders), are evaluated from experimental and numerical aspects. Expansion mechanisms, rotational speed, isentropic efficiency, pressure ratio and mass flow rate are considered. The review suggests that the volumetric expanders stand certain advantages in the micro-scale carbon dioxide cycles due to the more suitable rotational speed and potentially less leakage. For all expanders, internal and external leakages remain a vital challenge that greatly reduce their performance and efficiency, which urgently needs to be addressed.

Machining and Characterization of Double-Helical Grooves on Cylindrical Copper Parts by Wire Electric Discharge Turning

In the work, the design and development of a novel Wire-EDM setup with double-wire guide discs is presented. It facilitates sparks to be generated between the workpiece and wire at two locations separated by the helical pitch distance. This sparking causes two helical grooves to be generated simultaneously on the surface of the workpiece when it is given suitable rotational speed and table feed. In this work, machining is carried out on rods of 1.5 mm diameter. Helical groves with helix angles ranging from 35 to 500 were generated and characterized. This method of machining the double helical grooves with a single pass reduces the machining time and eliminates the complexities involved in machining one groove at a time. It was observed that the proposed method is suitable for machining double helical grooves with helix angles in the range of 40 - 50°. The parts produced by the mentioned method can be used as EDM tools for generation of high aspect ratio holes in turbine blades and injection nozzles.

Geometry shape selection of NACA airfoils for Mars rotorcraft

Mars rotorcraft, as an aerial auxiliary platform can assist Mars rover to complete exploration missions, is of great significance in the field of planetary exploration. The complex terrain on Mars limits the working range of the Mars rover, whereas a rotorcraft can acquire high detection speed and efficiency, even fixed-point sample using the ability of vertical takeoff and landing. Very little work has been done to analyze the Mars rotorcraft hovering process and there is also limited experimental data exist on the unique Mars flight conditions. A proper understanding of the hovering process is necessary to design a Mars rotorcraft and verify whether it is appropriate or not. In this work, a modified BEMT-CFD model is developed to analyze inflow distribution in the wingspan direction and to predict the aerodynamic performance of the rotor system. Based on the developed model, a suitable airfoil is selected and the operational parameters are investigated to design a suitable rotor configuration for the Mars rotorcraft. Hover experiments demonstrate that the modified model can effectively predict the rotor hover performance. Using the suitable blade pitch angle and rotational speed, the rotor can generate enough thrust to support a 500 g rotorcraft to fly in the simulated Mars environment.

Magnetic stirring assisted hydrothermal synthesis of fibrous-V6O13 cathode material for lithium-ion battery

In this work, magnetic stirring was used to assist hydrothermal, and V6O13 was synthesized by controlling different rotational speeds. The research shows that the appropriate rotational speed can promote the crystallization degree of V6O13. When the rotation speed is 1200 r/min, the structure of the sample becomes fibrous, which facilitates the transportation of lithium ions. As the speed increases, the first discharge capacity of the sample increases, and after 100 cycles, the capacity retention rate is also improved. Compared with the sample without speed, the capacity retention rate of the sample of VO-1200 increases by 18.3%. Applying suitable rotation speed during the synthesis of V6O13 is beneficial to improving the electrochemical performance.

Simulation and Analysis of Flow Field in Sludge Anaerobic Digestion Reactor based on Computational Fluid Dynamics

Abstract Because of the complexity of flow and the opacity of sludge, usually we can’t gain a precise and comprehensive sight of sludge flow type and its associated flow characteristics in the anaerobic digestion (AD) reactor. In the present study, we focused on the sludge rheological properties as well as the flow behavior in the digester. The viscosity decreased with the increase of shear rate, and sludge as a kind of pseudo-plastic fluid was proved. Based on computational fluid dynamics (CFD), taking sludge rheological index and rotational speed into consideration, then the flow field distribution in the digester was obtained. The fluid velocity raised with increase in rotational speed, moreover, fluid near blades had higher velocity while it was almost stagnant in the areas near reactor bottom and top as well as reactor wall and stirring shaft. The effect of rheological index on improving the velocity of fluid farther from impeller exceeded the influence on fluid at the impeller installation height. Regarding dead zone fraction as an indicator of the mixing effect, it was recommended that the suitable rotational speed for AD of 96 % moisture content sludge is 40 r/min. Finally, the reactor performance was optimized respectively from impeller form and reactor configuration, the results showed that both combined impellers and oval reactor can reduce dead zone volumes and produce a better mixing effect.

Repeated Impact Method and Devices to Simulate the Impact Fatigue Property of Drillstring

It is well known that drillstring failures are a pendent problem in drilling engineering, because of the fatigue accumulation caused by the low amplitude-repeated impact. In order to reveal the effect of low amplitude-repeated impact on the failure mechanism of the drillstring, a repeated impact method and instrument have been developed based on the Charpy impact method, by which a series of tests have been performed in the condition of non-corrosive medium and with H2S environment respective. Test results of non-corrosive medium environment indicates that, with the increase of single impact energy, the low amplitude-repeated impact resistance of drillstring decreases significantly; For H2S corrosion environment, the low amplitude-repeated impact resistances with H2S is much lower than that without H2S corrosion, and high strength material such as V-150 drillstring is more sensitive to H2S corrosion media. Furthermore, based on the experiment data, the accumulation fatigue model to predict the service life of the drillstring is developed, which could be used to predict the fatigue life. Research fruits are very vital to select a suitable rotational speed for drilling job and drillstring design.

EIGER detector: application in macromolecular crystallography.

The development of single-photon-counting detectors, such as the PILATUS, has been a major recent breakthrough in macromolecular crystallography, enabling noise-free detection and novel data-acquisition modes. The new EIGER detector features a pixel size of 75 × 75 µm, frame rates of up to 3000 Hz and a dead time as low as 3.8 µs. An EIGER 1M and EIGER 16M were tested on Swiss Light Source beamlines X10SA and X06SA for their application in macromolecular crystallography. The combination of fast frame rates and a very short dead time allows high-quality data acquisition in a shorter time. The ultrafine ϕ-slicing data-collection method is introduced and validated and its application in finding the optimal rotation angle, a suitable rotation speed and a sufficient X-ray dose are presented. An improvement of the data quality up to slicing at one tenth of the mosaicity has been observed, which is much finer than expected based on previous findings. The influence of key data-collection parameters on data quality is discussed.

Facile control of nanosized ZSM-22 crystals using dynamic crystallization technique

Hydrothermal synthesis of ZSM-22 zeolite was investigated under rotating and static crystallization conditions. The effect of crystallization temperature, speed of horizontal rotation, Si/Al ratio and water content were studied on the properties of the produced ZSM-22 zeolites. The static crystallization resulted in microscale ZSM-22 particles combined with the impurities of ZSM-5 and cristobalite, whereas crystallization at suitable rotational speed resulted in smaller and pure ZSM-22 crystals. Depending on the rotational speed, ZSM-22 zeolite with different crystal sizes, morphologies and crystallinities were produced. The crystallinity and morphology of the resulted ZSM-22 zeolite were examined using XRD patterns and FE-SEM images.

Weibull Statistics of Tensile-Shear Strength of 5083 Aluminum Alloy after Friction Stir Spot Welding

Friction stir spot welding has been adopted to replace resistance spot welding for Al alloys. This study investigates the effects of plunge depth, rotation speed, and welding duration on the microstructural characteristics of the weld, bonding strength and reliability of 5083 Al alloy. Bonding strength is evaluated using a tensile-shear test and the reliability is analyzed using a Weibull model. According to the experimental results, the major difference in the microstructure was the range of the stirring zone (SZ). The range of the SZ and the tensile-shear failure loading (TSFL) were enhanced when the welding duration or plunge depth was increased. The optimal rotation speed changed with plunge depth. Two fracture modes (tearing mode and cup pull-out mode) appeared for all parameter combinations. When the range of the SZ was deep and broad, the cup pull-out mode was the main fracture mechanism. The TSFL of the cup pull-out mode was higher than that of the tearing mode. Furthermore, the Weibull parameters of the cup pull-out mode were higher and the distribution curve shapes were better. Higher plunge depth, longer welding duration, and a suitable rotation speed made the fracture mode of the tensile-shear test be the cup pull-out mode and led to high bonding strength and good reliability. [doi:10.2320/matertrans.M2014281]

A Novel Method to Fabricate CNT/Mg–6Zn Composites with High Strengthening Efficiency

A novel method was developed to fabricate carbon nanotubes (CNTs)-reinforced Mg matrix composites. The method consists of two steps: CNTs pre-dispersion by ball-milling and the ultrasonic melt processing. Mechanical ball-milling effectively pre-dispersed CNTs on Zn flakes with suitable rotational speed and ball-milling time. Serious CNT entanglements were dispersed by the ball-milling. However, ball-milling for a long time at high speed would damage the morphology of CNTs. The ultrasonic overcame the poor wettability between Mg melt and CNTs and then dispersed pre-dispersed CNTs in the Mg melt. CNTs were distributed well in the composites and maintained integrated structure. CNTs significantly improved the mechanical properties of the matrix. The strengthening efficiency reached to 37.1, which proves the superiority of this novel method. Besides grain refinement, load transfer may make a great contribution to the improvement of the strength for the composites.

DEVELOPMENT OF EQUIPMENT FOR LOADING POST-HARVEST PRODUCTS ON HIGH MEANS

This research represents some designable and operational factors for development of a product handling machine. A throwing machine was developed to suit the loading of tubers, such as: potatoes – sugar beet – table beet. The important designing and operating factors were studied, including: rotational speed – angle of throwing from the machine to fall a trailer – and initial throwing height. A model was made to simulate the machine by scale 1:2 with some changes in rotational speed, vanes angle, initial height, and throwing angle to suit tubers. The experiment was run on potato tubers. This machine is for use in loading tubers on trailers after harvesting for sorting and storage. Experiment included: range of rotational speeds from 300 to 800 rpm, two vanes rotor driven by motor shaft, three angles of throwing (55, 65, and 75 degrees), and changes in height of throwing and distance to the trailer. Results revealed the following * The most suitable angle of machine to throwing is 75 degree with horizontal direction * The most suitable rotational speed range with less damage in tubers is 500 to 600 rpm * Radial vanes was given best results * The maximum tubers throwing height was 3:4 m * The suitable horizontal distance to trailer with the highest throwing conditions of experiment was 3:5 m. The maximum efficiency of loading by designed machine model was 77% .

A Repeated Impact Method and Instrument to Evaluate the Impact Fatigue Property of Drillpipe

It is well known that drillpipe failures are a pendent problem in drilling engineering. Most of drillpipe failures are low amplitude-repeated impact fatigue failures. The traditional method is using Charpy impact test to describe the fracture property of drillpipe, but it cannot veritably characterize the impact fatigue property of drillpipe under low amplitude-repeated impact. Based on the Charpy impact and other methods, a repeated impact method and instrument have been proposed to simulate the low amplitude-repeated impact of downhole conditions for drillpipe. Then, a series of tests have been performed using this instrument. Test results demonstrate the drillpipe upset transition area nonhomogeneity is more severe than drillpipe body, which is the key factor that leads to washout and fracture frequently of it. As the one time impact energy increases, the repeated impact times decrease exponentially, therefore, the rotational speed has a great effect on the fatigue life of drillpipe, and it is vital to select a suitable rotational speed for drilling jobs. In addition, based on SEM fractographs we found that the fracture surface of repeated impact is similar to the fatigue fracture, and there are many low cycle fatigue characteristic features on fracture surface that reveal very good agreement with the features of drillpipe fatigue failures in the field.

Auto-tuning of a two-degree-of-freedom rotational pendulum absorber

A dynamic vibration absorber is effective in suppressing harmonic excitation by tuning its natural frequency to match the excitation frequency. The rotational pendulum absorber (RPA) has a wide-range of natural frequencies that are continuously tunable by setting a suitable rotational speed. In this paper it is shown how to automatically tune the rotational speed of a two-degree-of-freedom RPA by detecting the phase between the vibration of the primary structure and that of the RPA. For this purpose the speed response of the RPA is introduced in addition to the frequency response. It is seen that if the excitation frequency is above a critical value dependent on the parameters of the RPA, the second vibration mode of the RPA is effective, allowing a relatively low rotational speed for the pendulums. The speed tuning algorithm is tested on a flexible plate that is subject to excitations of around 80Hz, which do not generate visible oscillations but emit audible noise instead. Experimental results confirm the noise-level reduction effect of the RPA.

Viable and Rapid Determination of Organochlorine Pesticides in Water

AbstractVortex‐assisted liquid–liquid microextraction (VALLME) procedure was developed for the determination of different organochlorine pesticides (OCPs) in water samples by GC‐MS. After the determination of the most suitable extraction solvent and rotational speed of the vortex, parameters such as vortex extraction time, solvent volume, ionic strength of the sample were optimized by using a 23 factorial experimental design. The optimized extraction conditions for 5 mL water sample were as follows: extraction solvent, bromoform; solvent volume, 50 µL; vortex extraction time, 2 min at 3000 rpm with no ionic strength adjustment, centrifugation 5 min at 4000 rpm. Limits of detection (LODs) and quantification (LOQs) were in the range of 0.011–0.052 and 0.037–0.173 µg/L, respectively. Mean recoveries of OCPs from fortified water samples are 96% for three different fortification levels between 0.1 and 5 µg/L and relative standard deviations of the recoveries are below 6%. The performance of the developed method was compared with traditional liquid–liquid extraction on real water samples including tap water, well water, surface (lake and stream) water, municipal wastewater, and treated municipal wastewater and comparable extraction efficiencies were obtained. The proposed VALLME procedure requires small volumes of solvent and water sample. It is viable, rapid, and easy to use for the determination of OCPs in water samples by using GC‐MS.

The Influence of Cultivation Conditions on Mycelial Growth and Exopolysaccharide Production of Culinary-Medicinal Mushroom Pleurotus citrinopileatus Singer (Agaricomycetideae)

The effects of submerged culture conditions on the mycelial growth and exopolysaccharide (EPS) production by Pleurotus citrinopileatus in submerged culture were studied. Using the one-factor-at-a-time method, the suitable rotation speed and inoculation density for the mycelial biomass and EPS production were found to be 100 rpm and 10%, respectively. The medium volume, carbon and nitrogen sources were 100 mL fructose and soy peptone for the mycelial growth and 50 mL glucose and peptone for the EPS production. To study the interactions between glucose (1.32−4.68 g/100 mL), peptone (0.32−3.68 g/100 mL), and initial pH (3.32−6.68), the central composite rotatable design and response surface methodologies were used. The trials were performed in 250-mL flasks containing 50 mL of medium under the condition of 25°C and 100 rpm for 14 days. The components were found to be 3.50 g glucose/100 mL, 3.68 g peptone/100 mL, and initial pH 5.0, and the mycelial biomass of 1.34 g dry cell weight/100 mL and EPS of 64.20 mg/100 mL were obtained in submerged cultures, which were higher than those obtained in the basal medium, respectively. In a 5-L stirred-tank bioreactor, maximum mycelial biomass of 1.10 g dry cell weight/100 mL and EPS of 90 mg/100 mL were achieved, and the fermentation time was shortened from 14 days to 10 days under these cultivation conditions.

Using a helical micro-tool in micro-EDM combined with ultrasonic vibration for micro-hole machining

This paper presents a novel process using micro-electro-discharge- machining (micro-EDM) combined with ultrasonic vibration by a helical micro-tool electrode to drill and finish micro-holes. During the machining processes, a micro-tool is directly fabricated by wire electro-discharge grinding (WEDG) using micro-EDM combined with various methods for machining the micro-hole and by ultrasonic vibration to finish the hole wall. In this work, circular micro-holes are machined in a high nickel alloy by cylindrical and helical electrodes. Using a helical micro-tool electrode for micro-EDM combined with ultrasonic vibration (HE-MEDM-UV) can substantially reduce the EDM gap, taper and machining time for deep micro-hole drilling. In addition, using a helical micro-tool with micro ultrasonic vibration finishing (HE-MUVF), good surface quality and less taper of the hole wall can be obtained by applying a suitable electrode step variation, rotational speed and ultrasonic amplitude with a machining time of approximately 25 min. According to scanning electron microscopy (SEM) micrographs and atomic force microscopy (AFM) measurement, HE-MUVF can indeed improve the surface roughness from 1.345 µm Rmax before finishing to 0.58 µm Rmax after HE-MUVF. This result demonstrates that using HE-MEDM-UV combined with MUVF can yield micro-holes of precise shape and smooth surface.

Effects of operating conditions on infiltration of molten aluminum and heat transfer in a centrifugal force field

AbstractThis paper presents the results of an analysis aimed at determining the influence of changing operating conditions in the centrifugal infiltration casting. It considers the effect of centrifugal force on infiltration and heat transfer. The molten aluminum flow with heat transfer though SiC porous media in a centrifugal force field is described using a mathematical and physical model by employing the local thermal nonequilibrium between the solid and fluid phases. The calculation results show that the temperature difference between molten aluminum and SiC porous media in the infiltrated region decreases with the contact time. There are two distinctly noticeable stages of infiltration velocity: the onset stage of infiltration, which drops down sharply, and the following stage of smooth velocity. The operating conditions have important effects on the infiltration velocity and temperature patterns of fluid and solid. A suitable rotational speed and SiC volume fraction should be chosen to ensure the flow of molten metal in the porous preform and diminish the temperature difference between fluid and solid. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(6): 501–510, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10114