Rotational Speed Conditions Research Articles

Improvement of One-Dimensional Analytical Model of Rotating Long Orifice with Chamfered or Radiused Inlet

In this paper, computational fluid dynamics calculations were conducted under various kinds of complex working conditions for rotating long orifice. As one of the most important structures of throttling and pressure limiting, orifice plays a significant role in flow control of the whole system. The existing empirical correlation was improved by correction on characteristics of low Reynolds number and compressibility. Then, improved one-dimensional analytical model of rotating long orifice with chamfered or radiused inlet was developed by programming. The model was verified against the results of commercial computational fluid dynamics codes. It turns out that the model has high precision, excellent convergence, and can predict the flow parameters under working conditions of low Reynolds number, supersonic and high pressure ratio with an acceptable error. And only geometric features, rotational speed and boundary conditions are required for one-dimensional modeling. Thus, it can be applied in the one-dimensional calculation and design of secondary air system widely.

Improvement of One-Dimensional Analytical Model of Rotating Long Orifice with Chamfered or Radiused Inlet

In this paper, computational fluid dynamics calculations were conducted under various kinds of complex working conditions for rotating long orifice. As one of the most important structures of throttling and pressure limiting, orifice plays a significant role in flow control of the whole system. The existing empirical correlation was improved by correction on characteristics of low Reynolds number and compressibility. Then, improved one-dimensional analytical model of rotating long orifice with chamfered or radiused inlet was developed by programming. The model was verified against the results of commercial computational fluid dynamics codes. It turns out that the model has high precision, excellent convergence, and can predict the flow parameters under working conditions of low Reynolds number, supersonic and high pressure ratio with an acceptable error. And only geometric features, rotational speed and boundary conditions are required for one-dimensional modeling. Thus, it can be applied in the one-dimensional calculation and design of secondary air system widely.

Influence Research of Flow Capacity on Temperature Field of Hydrostatic Thrust Bearing

Temperature field of sector cavity multi-pad hydrostatic thrust bearing is significantly affected by flow capacity, and different flow capacity can carry different shearing heat, so temperature field of oil film is obviously changed. For this problem, the lubrication theory and the Computational Fluid Dynamics have been used to simulate influence of flow capacity on temperature of sector cavity multi-pad hydrostatic thrust bearing, to gain relationship between inlet flow capacity and temperature of sector cavity multi-pad hydrostatic thrust bearing, achieve the optimal design of such products. Results are shown that along with the flow capacity increasing, the temperature of hydrostatic thrust bearing also becomes lower under constant rotational speed condition.

실험계획법에 의한 AZ31 마그네슘 합금의 마찰교반용접 특성에 관한 연구

In this paper, the design of experiment with two-way factorial design was adopted and from that, optimum values of welding variables including the welding speed and rotation speed were found to improve the strength of AZ31 magnesium alloy sheets joined by the friction stir technique. Tool with shoulder diameter of 12 mm and pin diameter of 3.5 mm was used. Also the welding direction was aligned with the material rolling direction, and dimensions of the AZ31 magnesium alloy sheets were <TEX>$100{\times}100{\times}2mm$</TEX>. Conditions of rotation speed were 1000, 1100 and 1200 rpm and those of welding speed were 200, 300 and 400 mm/min. As far as this work is concerned, the optimal conditions for friction stir joint were predicted as the rotation speed of 1200 rpm and welding speed of 200 mm/min.

A Study on the Rod Type Ultrasonic Motor

This study is to explore a rod type ultrasonic motor, it can solve the traditional ultrasonic motor with a high speed, but only low torque (or low loading ability) the shortcomings. Or want to improve the traditional ultrasonic motor with high torque (or high loading ability), but speed is too low the drawback. In other words, this study is expected to perform the ultrasonic motor, hope that we can have both higher speed and higher torque of the effect (or higher loading ability), and it can be applied to drive the optical lens (or electro-mechanical systems ) or applied to toggle the slider (or linear rails ). Based on the experimental results, we found that maximum rotational speed is 200rpm under conditions of 180Vp-p, 33.7kHz and 53gw preload. And the maximum loading ability and torque is respectively 4.13kgw and 0.273Nm under conditions of 180Vp-p, 33.7kHz and 15rpm rotational speed. Under similar size and driving conditions, its rotational speed is 3.8 times that of the conventional ultrasonic motor and the loading ability is 7.0 times the conventional ultrasonic motor.

Optimization of Tensile Strength of Friction Welded AISI 1040 and AISI 304L Steels According to Statistics Analysis (ANOVA)

Abstract Materials difficult to weld by fusion welding processes can be successfully welded by friction welding. The strength of the friction welded joints is extremely affected by process parameters (rotation speed, friction time, friction pressure, forging time, and forging pressure). In this study, statistical values of tensile strength were investigated in terms of rotation speed, friction time, and friction pressure on the strength behaviours of friction welded AISI 1040 and AISI 304L alloys. Then, the tensile test results were analyzed by analysis of variance (ANOVA) with a confidence level of 95 % to find out whether a statistically significant difference occurs. As a result of this study, the maximum tensile strength is very close, which that of AISI 1040 parent metal of 637 MPa to could be obtained for the joints fabricated under the welding conditions of rotation speed of 1700 rpm, friction pressure of 50 MPa, forging pressure of 100 MPa, friction time of 4 s, and forging time of 2 s. Rotation speed, friction time, and friction pressure on the friction welding of AISI 1040 and AISI 304L alloys were statistically significant regarding tensile strength test values.

Extraction of oil from jatropha seeds using a twin-screw extruder: Feasibility study

The objective of this study was to evaluate the feasibility of mechanical pressing to extract oil from jatropha seeds using a twin-screw extruder. Experiments were conducted using a co-rotating (Clextral BC 21, France) twin-screw extruder. The influence of operating conditions on oil yield, specific mechanical energy and oil quality was examined. Operating conditions included screw configuration, pressing temperature and screw rotation speed.Generally, it was the screw configuration, or profile, that most affected oil extraction efficiency. The best oil yields, a minimum 57.5%, were obtained with a trituration zone composed of 10 monolobe and 10 bilobe paddles, and a pressing zone composed of 50mm long, reverse pitch screws with a −33mm pitch. In addition, oil extraction yield increased with decreasing temperature and screw rotation speed. Highest oil extraction yield (70.6%) with good press cake quality (residual oil content lower than 8%) was obtained under operating conditions of 153rpm screw rotation speed, 5.16kg/h inlet flow rate of jatropha seeds, and 80°C pressing temperature. The corresponding expressed oil was inexpensive to produce (71Wh/kg seed processed or 314Wh/kg expressed oil for specific mechanical energy) compared with another continuous technique, i.e. the single expeller press, commonly used for mechanical extraction of jatropha oil. Its quality was also satisfactory for biodiesel production. The acid value, the density and the kinematic viscosity were 5.4mg of KOH/g of oil, 915kg/m3 and 36.7×10−6m2/s, respectively.

백색광간섭계를 이용한 금형용 강재 구멍가공면의 조도 측정

In this study, NIMAX material has been processed using the three-dimensional measuring instrument and white light interferometer. they were tested to roundness and surface roughness and results are as follows: As for a cutting characteristic, it indicated that F4 showed a lower result than 2F showed due to the high hardness of the material and showed a good result when spindle rotation speed and tool feed were low. As for the measurement of roundness through 3-Dimensional measuring machine, it indicated that 4F showed a good result like the condition of cutting component and that roundness showed a good result when spindle rotation speed of 1,700 rpm and tool feed speed of 85 mm/min were applied. As for the surface roughness of processing surface, Surface roughness showed better 4F than 2F and conditions of spindle rotation speed 1,700 rpm, tool feed rate 55 mm/min showed good results in the Ra .

Microstructural Evaluation of Friction Stir Processed D2 Tool Steel

Modification of AISI D2 tool steel was conducted by friction stir processing (FSP). Effects of tool rotational speed on microstructural evolution and mechanical properties were investigated. Though coarse primary carbides in the size of 10-50 m were observed before FSP, fine carbides smaller than 20 m and martensitic matrix with fine grains were obtained after FSP. High hardness of over 900 HV, higher than the hardness in conventional D2 tool steel, was achieved under the condition of moderate rotational speed.

Prediction of wind turbine gear micropitting under variable load and speed conditions using ISO/TR 15144-1: 2010

Wind turbine gearbox operates under a wide array of highly fluctuating and dynamic load conditions caused by the stochastic nature of wind and operational wind turbine controls. Micropitting damage is one of failure modes commonly observed in wind turbine gearboxes. This article investigates gear micropitting of high-speed stage gears of a wind turbine gearbox operating under nominal and varying load and speed conditions. Based on the ISO standard of gear micropitting (ISO/TR 15144-1:2010) and considering the operating load and speed conditions, a theoretical study is carried out to assess the risk of gear micropitting by determining the contact stress, sliding parameter, local contact temperature and lubricant film thickness along the line of action of gear tooth contact. The non-uniform distributions of temperature and lubricant film thickness over the tooth flank are observed due to the conditions of torque and rotational speed variations and sliding contact along the gear tooth flanks. The lubricant film thickness varies along the tooth flank and is at the lowest when the tip of the driving gear engages with the root of the driven gear. The lubricant film thickness increases with the increase of rotational speed and decreases as torque and sliding increase. It can be concluded that micropitting is most likely to initiate at the addendum of driving gear and the dedendum of driven gear. The lowest film thickness occurs when the torque is high and the rotational speed is at the lowest which may cause direct tooth surface contact. At the low-torque condition, the varying rotational speed condition may cause a considerable variation of lubricant film thickness thus interrupting the lubrication which may result in micropitting.

Accelerated Immunoassays Based on Magnetic Particle Dynamics in a Rotating Capillary Tube with Stationary Magnetic Field

A rapid and simple magnetic particle-based immunoassay has been demonstrated in a capillary mixing system. Antibody-coated micrometer size superparamagnetic polystyrene (SPP) particles were used in an assay for rabbit IgG in a sandwich (noncompetitive) format. The kinetics of the assay was compared between a plate-based system and a single capillary tube. The interaction between the antigen (R-IgG) and the antibody (anti-R-IgG) that was carried by the SPP particles in a rotating capillary was tested under a stationary magnetic field. Competing magnetic and viscous drag forces helped to enhance the interaction between the analyte and the capture antibodies on the particles. The dimensionless Mason number (Mn) was employed to characterize the magnetic particle dynamics; a previously determined critical Mason number (Mn(c)) was employed as a guide to the appropriate experimental conditions of magnetic field strength and rotational speed of the capillary. The advantage of the rotating capillary system included a short assay time and a reduced reactive volume (20 μL). The results show that the immunoassay kinetics were improved by the formation of chains of the SPP particles for the conditions that corresponded to the critical Mason number.

마찰교반용접에 의한 5456-H116 합금의 용접 형상과 기계적 특성

The use of Al alloys instead of fiber-reinforced plastic(FRP) in ship construction has increased because of the advantages of Al-alloy ships, including high speed, increased load capacity, and ease of recycling. This paper describes the effects of probe diameter on the optimum friction stir welding conditions of 5456-H116 alloy for leisure ship, measured by a tensile test. In friction stir welding using a probe diameter of 5 ㎜ under various travel and rotation speed conditions, the best performance was achieved with a travel speed of 61 ㎜/min. Using a probe diameter of 6 ㎜, rotation speeds of 170-210 rpm, and a travel speed of 15 ㎜/min produced a rough surface and voids because of insufficient heat input produced by the low rotation speed. At 500-800 rpm, chips were observed, although there were no voids, and the weld surface was excellent. However, at 1100-2500rpm, many chips were produced due to excessive heat input. Heat effects were very evident on the bottom. For a travel speed of 15 ㎜/min, heat input caused by friction increased as the rotation speed increased. The mechanical characteristics were degraded by accelerated softening due to increasing heat input.

Antifouling microfiltration strategies to harvest microalgae for biofuel

Microalgae are microorganisms that can fix CO2 by using the energy from the sun and transforming it into organic molecules such as lipids (i.e. feedstock for biodiesel production). Microfiltration is a promising method to be considered in the harvesting step. In this study, two antifouling methods were tested in order to minimize permeability decrease over time, at low trans-membrane pressure filtration.Preliminary experiments were performed to find optimum conditions of transmembrane pressure, rotational speed and membrane pore size. Pilot experiments were carried out in the optimal conditions using microalgae obtained from the culture step and from a previous concentration process based on sedimentation. Fouling was significantly minimized, and the permeability plateau increased up to 600L/h/m2/bar.Three microalgae species were tested: Phaeodactylum tricornutum (Pht), Nannochloropsis gaditana (Nng) and Chaetoceros calcitrans (Chc).An economic assessment was also performed, which demonstrated that dynamic filtration is economically more efficient than tangential cross-flow filtration.

Influence of Pin Profile on Quality of Friction Stir Lap Welds in Carbon Fiber Reinforced Polypropylene Composite

In recent years, interest on friction stir welding has grown more since such a joining technique allows welding of light weight alloys like aluminum and its alloys which are difficult to weld or even unweldable with the traditional fusion welding processes. This process can also be one of the joining processes considered for welding polymer matrix composites such as polypropylene composites which find a number of applications in different industries. This paper presents the effect of tool pin profile on surface appearance and tensile shear strength of friction stir lap welds in carbon fiber reinforced poly- propylene composites with 4 mm thickness. Four high speed steel tools with different pinprofiles of threaded cylindrical, threaded cylindrical-conical, simple cylindrical-conical and threaded conical were employed for this study. Using these tools, lap welds were made under similar conditions of tool rotational speed, welding speed and tilt angle. Specimens were prepared for tensile shear testing. The tensile shear test results showed that the threaded cylindrical-conical tool produced a weld with better surface appearance and higher tensile shear strength.

Sensorless Control of Switched Reluctance Motor Based on Dynamic Thresholds of Phase Inductance

A new sensorless control scheme for switched reluctance motor drives is presented in this article. This scheme is based on the basic characteristics that the phase inductance changes periodically with the rotor position. First, according to the inductance characteristics, the inductance model can be constructed. Based on the inductance model, the phase inductance at the turn-off angle of the active phase and the turn-on angle of the next phase can be calculated as the two dynamic thresholds. The real inductance is estimated using the terminal measurements of the active phases. By comparing the estimated phase inductance of the active phase with the dynamic thresholds, the drive signals of each phase can be obtained for controlling the switched reluctance motor directly without rotor position information. This sensorless method is quite easy for implementation and possesses good speed-regulating performance. Besides, in order to start the switched reluctance motor from standstill or start those with initial rotor speed conditions without any hesitation, a full-cycle phase inductance subregion method is utilized. Simulation and experimental results are presented and compared for verification.

Statistical analysis of accelerometer data in the online monitoring of a power slip ring in a wind turbine

The use of a shock accelerometer for the continuous in-service monitoring of wear of the slip ring on a wind turbine generator is proposed and supporting results are presented. Five wear defects in the form of out-of-round circumference acceleration data with average radial dimensions in the range 5.9–25 µm were studied. A theoretical model of the acceleration at a point on the circumference of a ring as a function of the defect profile is presented. Acceleration data as a continuous function of time have been obtained for ring rotation frequencies that span the range of frequencies arising with the variation of wind speeds experienced under all in-service conditions. As a result, the measured RMS acceleration is proven to follow an overall increasing trend with frequency for all defects at all brush pressures. A statistical analysis of the root mean square of the time acceleration data as a function of the defect profiles, rotation speeds and brush contact pressure has been performed. The detection performance is considered in terms of the achievement of a signal to noise ratio exceeding 3 (99.997% defect detection probability). Under all conditions of rotation speed and pressure, this performance was achieved for average defect sizes as small as 10 µm, which is only 0.004% of the ring diameter. These results form the basis of a very sensitive defect alarm system.

Design and performance characterization of a new shear enhanced module with inbuilt cleaning arrangement

BACKGROUND: Shear enhanced membrane modules are becoming popular as they enable high permeate flux in almost all membrane filtration processes due to the high shear rate they generate at the membrane surface. In this article, the design of a new shear enhanced module with unique hydrodynamic cleaning facility is proposed. The device, presently at laboratory scale was named the Spinning Basket Membrane (SBM) module because of its inherent structural similarity with the well known Spinning Basket Reactor. An aqueous solution of polyethylene glycol was chosen as test fluid for the present study. RESULTS: The module was characterized under different parametric conditions of transmembrane pressure (TMP), feed concentration (C0) and rotational speed of the basket (Ω). It was observed that with its inbuilt cleaning facility the module was able to restrict the flux decline to within 15% of its start up value, even after 21 h of continuous running, with a maximum initial flux as high as 612 L m−2 h−1. CONCLUSION: Based on the performance of the module, it may be concluded that this module could be scaled up for nearly uninterrupted industrial operation with reduced requirement for chemical cleaning, which is rare in the membrane industry to date. Copyright © 2012 Society of Chemical Industry

Tensile Fracture Behavior of Friction Stir Processed Al-7Si-0.3Mg Cast Alloy

Elimination of porosity and refinement of the normally coarse cast microstructure ofaluminium cast alloys by the intensive plastic deformation during friction stir processing (FSP) iswell known. However less is known about the mechanical behavior of the FS processed regionwhich contains zone/pass boundaries and macro/microstructure segregations. In the present study ofFS processed cast Al-7Si-0.3Mg alloy, microstructures featuring the deformed α-Al, fragmented Siparticles and their distribution in the processed region were related to the fracture paths duringtensile testing. It has been found that under the condition of a high rotation speed and minimum pinoverlap there is a strong upward flow of deformed cast material in thermomechanial affected zone.The arrays of Si particles in that flow have provided favorable paths for crack propagation duringtensile testing. As a result, tensile elongation and thus UTS values are low. The mechanism of thatupward flow and FSP conditions for reducing the flow and thus for improving properties of theprocessed region are discussed.

S051042 バタフライ風車と四重多流管理論の提案

In this study, a new type of vertical axis wind turbine (VAWT) named as Butterfly Wind Turbine had been proposed, which has armless blades consisting of a closed curve. Since a part of flow intersects the Butterfly Wind Turbine rotor four times, a new flow-field model used in BEM (Blade-Element Momentum) theory was proposed. The model was named as Quadruple-Multiple Streamtube (QMS) model, which nests the Double-Multiple Streamtube (DMS) model. Power characteristics of three kinds of VAWTs, that is, general single-straight-blade VAWT, double-straight-blade VAWT, and Butterfly VAWT, were simulated based on the BEM theory using the QMS model. The results show that, under the condition of a constant chord length, the Butterfly Wind Turbines improve the starting performance of general VAWT as well as double-straight-blade VAWTs. Furthermore, a Butterfly VAWT equipped with tapered blades shows higher power coefficient at low rotational speed condition, without significant decrease in maximum power coefficient.

The application of order tracking for vibration analysis of a varying speed rotor with a propagating transverse crack

Propagating cracked rotor vibrations may contain substantial information on the rotor crack conditions. Capturing the characteristic vibrations due to the non-stationary response of rotors of which the speed change, is useful for condition monitoring of such systems. From the literature it is clear that vibrations at harmonics of the rotational speed, as well as transient responses, may be considered key indicators of cracks in rotors. Since faults other than cracks, such as misalignment and imbalance also generate harmonic vibrations, the non-order related vibrations therefore become important characteristics in detecting cracked rotor problems. But these signals may present with small amplitude and may easily be missed among the non-stationary harmonic vibrations. Therefore, clear identification of harmonic as well as non-order related (transient) vibrations are both important for detecting cracks in rotor systems. In this paper, a finite element model is used to calculate the response of a rotor with a propagating transverse crack under varying rotational speed conditions. various order tracking techniques, i.e. computed order tracking, Vold-Kalman filter order tracking, Gabor order tracking, are implemented to remove the varying speed harmonic vibrations so that the non-order related vibrations in which information about the cracks are contained, are emphasized. And some other signal processing methods that may achieve similar effects, i.e. double re-sampling method and intrinsic mode function from empirical mode decomposition, are also discussed for comparisons to these order tracking techniques. The paper demonstrates the advantages of order tracking methods in rotor crack detection.