Influence Of Rotational Speed Research Articles

Analysis of temperature field and convection heat transfer of oil-air two-phase flow for ball bearing with under-race lubrication

PurposeUnder-race lubrication can increase the amount of lubricating oil entering a bearing and greatly improve lubrication and cooling effects. The oil-air two-phase flow and heat transfer characteristics inside a ball bearing with under-race lubrication play a key role in lubrication and cooling performance. The purpose of this paper is to study these two characteristics, and then provide guidance for lubrication and heat dissipation of bearing with under-race lubrication.Design/methodology/approachIn this paper, a simplified three-dimension heat transfer model of ball bearing with under-race lubrication is established; the coupled level set volume of fluid method is used to track the oil-air two-phase flow, and the Palmgren method is used to calculate the heat generation. The influence of rotation speed and inlet velocity on oil volume fraction, temperature and convection heat transfer is investigated. A temperature test for under-race lubrication is carried out.FindingsBecause of the centrifugal force, lubricating oil is located more on the outer ring raceway. As the rotation speed decreases and the inlet velocity increases, the oil volume fraction increases and the temperature decreases. Furthermore, the area with high oil volume fraction has a large convection heat transfer coefficient and low temperature. The error between the simulation temperature and the test temperature is within 10%.Originality/valueThe research on the temperature field and convection heat transfer characteristics of under-race lubrication ball bearings at different rotation speeds and inlet velocities is rarely involved.

Influence of rotational speed on torque/force generation and shaping ability during root canal instrumentation of extracted teeth with continuous rotation and optimum torque reverse motion.

To evaluate how different rotational speeds affect the torque/force generation and shaping ability of rotary root canal instrumentation using JIZAI (MANI, Utsunomiya, Japan) nickel-titanium instruments in continuous rotation and optimum torque reverse (OTR) motion. Mesial root canals of extracted mandibular molars were instrumented up to size 25, 0.04 taper using JIZAI instruments, and anatomically matched canals were selected based on geometric features of the canal [canal volume (mm3 ), surface area (mm2 ), length, 15°-20° curvature and radius of curvature (4-8mm)] after micro-computed tomographic scanning. An automated root canal instrumentation and torque/force analysing device was programmed to permit a simulated pecking motion (2s downward and 1s upward at 50mmmin-1 ). The selected canals were prepared with size 25, 0.06 taper JIZAI instruments using continuous rotation or OTR motion and further subdivided according to the rotational speed (300 or 500rpm, n=10 each). Real-time clockwise/counterclockwise torque and downward/upward force were recorded using a custom-made torque/force analysing device. Then, the registered pre- and post-operative micro-computed tomographic datasets were examined to evaluate the canal volume changes and centring ratios at 1, 3, 5 and 7mm from the apical foramen. Data were analysed using two-way analysis of variance or the Kruskal-Wallis test and Mann-Whitney U test with Bonferroni correction (α=5%). Maximum upward force and clockwise torque were significantly smaller in 500rpm groups than in 300rpm groups (P<.05); however, no significant difference was found between continuous rotation and OTR motion (P>.05). OTR motion developed higher maximum counterclockwise torque than continuous rotation (P<.05). Maximum downward force, canal volume changes and centring ratios were not significantly different among all groups (P>.05). There was no file fracture in any of the groups. Under laboratory conditions using JIZAI instruments, a rotational speed of 500rpm generated significantly lower maximum screw-in forces and torque values than rotational speed of 300rpm. Continuous rotation and OTR motion performed similarly in shaping the canals.

Batch reactor scale-up of the mixing-sensitive Bechamp reaction based on the heat pulse method

Knowledge and control of mixing in batch processes can prevent yield losses during scale-up. Therefore, in this study, a new heat-mixing model based ono the measurement of the heat distribution after an applied heat pulse, is proposed. The model was developed to predict mesomixing and support scale-up, scale-down, and design and optimisation of batch reactors. The proposed model considers the influences of rotational speed, stirrer type, solvent, stirrer-to-tank diameter, liquid-height-to-tank diameter, injection time, and pumping number. A strong correlation between the mixing time of the heat pulse method and the mass-transfer coefficient of the mixing-sensitive Bechamp reaction was observed.

Experimental study on oil supply efficiency of under-race lubrication based on radial oil scoop

Under-race lubrication is an efficient lubrication method of aeroengine bearings for achieving high DN values. In this paper, an experimental study on oil supply efficiency of under-race lubrication structure based on high rotation speed and small size radial oil scoop is carried out. The influence of rotation speed, nozzle diameter and oil temperature on oil supply efficiency are analysed. The research results can be used to guide the design of oil nozzle and under-race lubrication structure.

CHARACTERIZATION OF HEAT CONDUCTIVITY OF ECCENTRICALLY ROTATING HEAT PIPES USED FOR COOLING OF MOTOR SPINDLES

Heat losses within motor spindles lead to undesired effects such as machining inaccuracies and de-creasing lifetime of the motor and bearings. To reduce thermal loads, complex shaft cooling concepts with costly sealing techniques exist. For this reason, a novel, less costly cooling concept has been de-veloped based on heat pipes with high thermal conductivity and fin-shaped heat exchangers. The de-sign and integration of these heat exchanger elements into a motor spindle is carried out using the fi-nite element method. The aim is to optimize the efficiency of the heat pipes and heat exchangers for optimal shaft cooling performance. For a simulation-based development of a prototype spindle, un-known thermal characteristics of the heat transfer elements must be determined. In this paper, the de-termination of the thermal conductivity of the heat pipes is described. The determination of conductivi-ty is done experimentally. First, the developed test rig and the applied procedure for the determination of the conductivity are shown. Subsequently, the experimental results are presented and discussed. Two types of heat pipes were analyzed: Copper heat pipes with sintered wick structure and nickel-plated copper heat pipes with axial grooves. The influences of rotational speed, heat flow rates and the angle between the heat pipe and main axis of rotation were investigated. The results indicate a distinct dependency of the conductivity on the varied parameters. However, changes of parameter values have very different quantitative and qualitative effects on the determined conductivities de-pending on the type of heat pipe.

Nonlinear behaviors analysis of high-speed rotor system supported by aerostatic bearings

In the paper, the dynamic model of aerostatic bearing-rotor system combining rotor motion equation and transient Reynolds equation is established to study influences of rotational speed, unbalance, rotor mass and supply pressure on the nonlinear behaviors of rotor system. The results reveal abundant nonlinear phenomenon consisting of 3 T-periodic, 5 T-periodic and quasi-periodic motions. Furthermore, chosen proper unbalance, smaller rotor mass and larger supple pressure can control the nonlinear vibration and improve the system stability. The results provide a theoretical basis for a simple and feasible method to control the nonlinear vibration of rotor system by adjusting supply pressure.

Solid-state welding of ultrafine grained copper rods

The article focuses on the Direct Drive Rotary Friction Welding of ultrafine-grained copper rods, which feature increased mechanical properties and good electrical properties, yet are limited in size. The use of UFG metals is often limited by the too small dimensions of semi-finished elements produced by SPD methods. Therefore, the production of finished machine parts from UFG metals is currently economically unjustified. Dismissal of dimensional limitations can be done by introducing joining to technological processes. The proposed joining method does not lead to a melting of the material in the joining zone or excessive degradation of the UFG microstructure. To obtain the best results, the research used the method of low-energy welding of two kinds of specimens: with a flat or a conical contact surface. In the article, the authors present, by means of metallographic microsections and microhardness measurements, the influence of rotational speed, welding pressure and conical shape contact surface on the quality of the obtained joints. The conducted research made it possible to obtain good quality joints whose microhardness is reduced only by about 10% in comparison with the base material and the tensile strength dropped from only 397–358 MPa.

The effect of rotational speed on ankle-foot orthosis properties

Ankle–foot orthoses (AFOs) are devices that support ankle motion. An AFO’s sagittal plane rotational stiffness can affect gait kinematics. Because AFOs are often made from viscoelastic materials, their properties may vary at different walking speeds. The influence of rotational speed on AFO properties has not been thoroughly investigated. Therefore, the purpose of this study was to determine the impact of rotational speed on AFO stiffness about the ankle. We tested a sample of one thermoplastic off-the-shelf AFO and two 3-D printed carbon fiber enforced nylon AFOs. Each AFO’s dynamic resistance torque was measured as it was flexed at five speeds (5-100 °/s) using a custom-built measurement apparatus. We compared loading stiffness, neutral angle, and energy dissipation parameters for each AFO across speeds. Parameter values were generally greater at higher speeds. These effects were statistically significant for all AFOs (p≤0.002). However, differences in AFO stiffness and neutral angle across speeds were quite small (<0.6 Nm/° and <2.2 °). Changes in the thermoplastic AFO’s stiffness were lower than the minimum detectable difference. Energy dissipation, as indicated by hysteresis area, increased by up to 6.3 J (about 250%) at the highest speed. This demonstrates that AFO flexion speed can influence the properties of different AFOs over the range typically achieved in human walking. Future work should assess whether the observed small variations of stiffness and neutral angle have a clinically meaningful impact on user performance, as well as explore effects of angular speed on a variety of AFO materials and designs.

Contrast Research about Performance of PA1010 and HPb59-1 Isolator in Heavy Slewing Bearing

The performance of heavy slewing bearing isolator materials PA1010 and HPb59-1 mating for bearing steel GCr15 was investigated through experiments in this paper. The effects of applied load, sliding speed and lubricant on friction coefficient and wear loss of PA1010 and HPb59-1 were discussed. The damage mechanism and failure law of PA1010 and HPb59-1 isolators were analysed. The results show that the friction coefficient of PA1010 is lower than that of HPb59-1 and the wear loss of PA1010 is higher than HPb59-1. The influence of rotational speed on the tribological properties of HPb59-1 is obviously higher than that of PA1010. At the low sliding speed, the wear loss of these two materials changes more significantly with the change of load. The influence of coupling pair surface roughness on the tribological properties of PA1010 is significantly higher than that of HPb59-1. When the surface roughness of coupling steel ring increases from 0.2μm to 0.4μm, the growth rate of friction coefficient of PA1010 is 274.1% higher than that of HPb59-1, and the growth rate of wear loss is 25.5% higher than HPb59-1.

Temperature rise characteristics of high-speed water-lubricated hydrostatic thrust bearing

Hydrostatic thrust bearings have been widely adopted in machine tools. However, high level of temperature rise due to film shearing and hydraulic power of water pump leads to decrease of machining accuracy while operating at high speeds. This paper aims to investigate the temperature rise characteristics of a high-speed water-lubricated hydrostatic thrust bearing. Based on Newtonian law of viscosity, hydrostatic theory and first law of thermodynamic, considering the influence of pressure flow, shearing effect and centrifugal effect, the temperature rise of lubricating water has been deduced. The influence of rotational speed and eccentricity has been studied. Result shows that high-speed water-lubricated thrust bearing has good thermal performance.

Influence of Rotational Speed of an Inducer on the Propagation Velocity of Super-synchronous Rotating Cavitation

The phenomenon that a cavity rotates faster than the rotational speed of the pump in the direction of rotation is called super-synchronous rotating cavitation (super-S RC). It is known that super-S RC is often observed in rocket turbopumps, but that it is rare to be observed in industrial pumps. Therefore, we form a hypothesis that its occurrence is related to the rotational speed of pumps. In this study, experiments of an inducer were conducted at four rotational speed at Kakuda Space Center in the Japan Aerospace Exploration Agency. The pressure fluctuation and the rotor vibration were measured, and the propagation velocity ratio of super-S RC and the frequency of unsteady cavitation in the super–S RC were determined at each rotational speed. As a result, when the cavitation number is the same, the propagation velocity ratio is almost the same regardless of the rotational speed of the inducer. It means that the faster the rotational speed, the faster the unsteady cavitation oscillates in the inducer despite the condition of the same cavitation number. It indicates that rotating cavitation does not occur under a certain rotational speed because of the limitation of the frequency of unsteady cavitation, which is known in hydrofoil.

Measurement of Vibration on The Alternator Due to The Influence of Rotation Speed

The alternator or dynamo ampere is a device that functions as a generator that produces alternating current (AC) and converts it to direct current (DC). Signs of damage that often occur due to damage to the Alternator are the smell of burning, squeaking, dim spotlights, indicator lights, malfunction of the battery, and the supply of electricity. These signs will cause the vehicle to stop in the middle of the trip the electricity supply is very lacking. This requires that preventive maintenance checks on the alternator are a must in the automotive world. In this paper we research measuring the vibration of the alternator due to the influence of rotation speed (750 rpm and 1800 rpm), to predict damage to the alternator of the Daihatsu Luxio vehicle. The results of this study indicate that at the rotational speed of 750 rpm and 1800 rpm, were found 1x rpm the condition of the vibration amplitude on the alternator is smaller than the alternator in poor condition, this is due to the presence of an unbalanced alternator. Also, vibration due to misalignment is obtained because it has characteristics, among others: vibrations with a frequency of 1xRPM and/or accompanied by a relatively large 2xRPM, and relatively high vibration in the axial direction.

Simulation and Experimental Investigation of a Two-Stage Magnetic Precession Gear

Gears are common and important components of many types of propulsion systems applied in mechanical engineering. The aim of this paper is to present the mechanical design and performance analysis of a novel two-stage magnetic precession gear (MPG). The main advantage of the proposed design is the ability to obtain higher transmission ratios than other currently known magnetic gear types. A detailed analysis of the performance of the MPG was carried out employing a developed numerical model of the magnetic field in the proposed gear. The MPG model is based on the finite element method (FEM) and allows determining the relations between the torque acting on the main components of the gear, load angles, and air-gap lengths. To validate the developed FEM model, the prototype of an MPG with a 1/144 gear ratio was built and tested. The experiments were also focused on determining the mechanical efficiency as well as the influence of rotational speed and lengths of air gaps on the maximum load torque. The tests indicated that the maximum efficiency of the studied MPG is about 30%, which is comparable to the efficiency of mechanical two-stage precession gears with face meshing.

Ultra-high-speed TEHL characteristics of T-groove face seal under supercritical CO2 condition

Purpose The purpose of this paper is to acquire sealing properties of supercritical CO2 (S-CO2) T-groove seal under ultra-high-speed conditions by thermo-elastohydrodynamic lubrication (TEHL) analysis. Design/methodology/approach Considering the choked flow effect, the finite difference method is applied to solve the gas state equation, Reynolds equation and energy equation. The temperature, pressure and viscosity distributions of the lubricating film are analyzed, and sealing characteristics is also obtained. Findings The face distortions induced by increasing rotational speed leads to the convergent face seal gap. When the linear velocity of rotation exceeds 400 m/s, the maximum temperature difference of the sealing film is approximately 140 K, and the viscosity of CO2 is altered by 17.80%. Near the critical temperature point of CO2, while the seal temperature increases by 50 K, the opening force of the T-groove non-contact seal enhances by 20% and the leakage rate declines by 80%. Originality/value The TEHL characteristics of the T-groove non-contact seal are numerically analyzed under ultra-high-speed, considering the real gas effect and choked flow effect. In the supercritical conditions, the influence of rotational speed, seal temperature, seal pressure and film thickness on sealing performance and face distortions is analyzed.

An improved model for investigating the vibration characteristics of ball bearing owing to outer race waviness under high speed

In this study, an improved model for a ball bearing is established to investigate the vibration response characteristics owing to outer race waviness under an axial load and high speed. The mathematical ball bearing model involves the motions of the inner ring, outer ring, and rolling elements in the radial XY plane and axial z direction. The 2Nb + 5 nonlinear differential governing equations of the ball bearing are derived from Lagrange's equation. The influence of rotational speed and outer race waviness is considered. The outer race waviness is modeled as a superposition of sinusoidal function and affects both the contact deformation between the outer raceway and rolling elements and initial clearance. The MATLAB stiff solver ODE is utilized to solve the differential equations. The simulated results show that the axial vibration frequency occurred at l fc and the radial vibration frequencies appeared at l fc fc when the outer race waviness of the order (l) was the multiple of the number of rolling elements (k Nb) and that the principal vibration frequencies were observed at l fc fc in the radial x direction when the outer race waviness of the order (l) was one higher or one lower than the multiple of the number of rolling elements (k Nb 1). At last, the validity of the proposed ball bearing model was verified by the high-speed vibration measurement tests of ball bearings.

Research on Vibration Characteristics of Propulsion Shafting Under Unbalanced-misaligned Coupling Fault

Vibration characteristics under unbalanced-misaligned coupling fault of propeller shaft were studied. Firstly, the rigid-flexible mixing model of propeller shaft system test bench is established by using Solidworks and ADAMS. Then, the shafting vibration characteristics in time and frequency domain are obtained by simulation analysis under normal, unbalanced, misaligned and unbalanced-misaligned coupling faults. Finally, the influence of rotational speed on unbalanced-misaligned coupling fault shaft system is analysed. The simulation study shows that the vibration spectrum of shafting under unbalanced-misaligned coupling fault is mainly the superposition of the spectrum under each single fault, and the vibration caused by each fault is different in different locations. The increase of speed will aggravate the vibration of shafting.

Thermo-mechanical disturbances in a nonlocal rotating elastic material with temperature dependent properties

Purpose The purpose of this paper is to study two-dimensional deformations in a nonlocal, homogeneous, isotropic, rotating thermoelastic medium with temperature-dependent properties under the purview of the Green-Naghdi model II of generalized thermoelasticity. The formulation is subjected to a mechanical load. Design/methodology/approach The normal mode analysis technique is adopted to procure the exact solution of the problem. Findings For isothermal and insulated boundaries, discussions have been made to highlight the influences of rotational speed, nonlocality, temperature-dependent properties and time on the physical quantities. Originality/value The exact expressions for the displacement components, stresses and temperature field are obtained in the physical domain. These are also calculated numerically for a magnesium crystal-like material and depicted through graphs to observe the variations of the considered physical quantities. The present study is useful and valuable for the analysis of problems involving mechanical shock, rotational speed, nonlocal parameter, temperature-dependent properties and elastic deformation.

Development of New Particle Method Based on MPS and its Applicability for Friction Stir Welding of Dissimilar Joint

Friction stir welding (FSW) is one of the solid-state welding and it has been widely employed for joining aluminum alloys. In addition, as a result of R&amp;D efforts about FSW tool, this method is expected to join the steels and/or various dissimilar materials. In order to examine the thermal and mechanical behavior in FSW, many numerical studies have been conducted and the heat generation behavior near FSW tool is precisely demonstrated by using the moving particle semi-implicit (MPS) method which is one of the particle method. In this research, in order to reduce the computational time, a new parcel method based on MPS is developed and its applicability is examined for simulating the friction stir welded dissimilar joint between V-ally and austenite stainless steel SUS316L. From the serial computational results, it is revealed that the influence of rotational speed on the heat generation during FSW seems to be larger than that of traveling speed. Moreover, the numerical result indicates that the sound dissimilar joint might be fabricated when V-alloy is set to be the retreating side (RS), the FSW tool is inserted in RS and the rotational speed increased appropriately although the two materials have not been joined in this welding condition of FSW experimentally.

Influence of rotational speed and torque on meshing efficiency of double helical gear transmission system

The accuracy of gear meshing efficiency model is the key to study the influence factors of gear meshing efficiency. Experiment is an effective method to verify the theory model. Therefore, the acquisition of experimental value of gear meshing efficiency is particularly important. Taken double helical gears as the research object, on the analysis of a large number of experimental data, the experimental value of gear meshing efficiency for double helical gears are calculated and then the influence of rotational speed and torque on meshing efficiency of double helical gears is studied. Firstly, the calculation method of transmission efficiency for experimental value in different layout of gear test-rigs with closed power flow is summarized. Secondly, the calculation method of meshing efficiency for experimental value in gear test-rig with closed power flow is introduced. Thirdly, the calculation method of load-dependent bearing loss is given. Finally, the experimental value of meshing efficiency for double helical gears is calculated and the influence of rotational speed and torque on meshing efficiency of double helical gears is obtained, which lays a theoretical foundation for the further improvement of the transmission efficiency of double helical gears.

Influence of rotational speed, angle of impingement, concentration of slurry and exposure time on erosion performance of HVOF sprayed cermet coatings on 35CrMo steel

The efficient use of coal for power generation has been one of the country's largest challenges. The various investigators have been attempting for several years to substitute crude oil as a liquid fuel by coal slurries. Thus, significant material loss due to the wear of erosion is caused by the different mechanical elements, such as pipelines, pumps, bends, many others in mining, thermal and petroleum. Therefore to improve the lives of such materials, it is most important to research the effect of slurry erosion parameters that influence erosion rate. In this study, we propose the WC-10Co coatings coated by the High Velocity Oxy-Fuel (HVOF) technique on a 35CrMo steel substrate, commonly used in hydraulic turbines, have been examined for slurry erosion. The coating structures were examined using SEM and XRD methods. In addition, the slurry erosion experiments were performed on the coatings to explore the influence of rotational speed, angle of impingement, concentration of slurry and time on erosion behaviours. Findings indicate that the rotational speed was the most significant parameter determining the mass loss of the coatings followed by the angle of impingement, slurry composition, and time.