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Diagnostics of the rotor blades of aircraft gas turbine engines at pre-operational stage and later on during repairs is carried out by instrumental methods of non-destructive testing. The requirements for increasing operational reliability and safety of flights require a search for new solutions in assessing the strength of rotor blades at an early stage of damage development. For these purposes, one of the perspective directions is the development of acoustic emission methods. This article represents an experimental setup and a measuring-diagnostic system for assessing the operational reliability of rotor blades by the acoustic emission method. It also discusses the results of testing.

The sealing line between two conjugated rotors is a main leakage path in the vacuum pump, however, it is unable to be adjusted before the rotor profiles are determined in the traditional rotor profile generation method. Therefore, a generation method of rotor profiles for claw-type vacuum pumps based on the sealing line is proposed in this paper. The sealing line can be firstly specified as specific segments regarding the characteristics of claw-shaped rotor profiles. By applying the enveloping theory and the cubic spline curve fitting method, the rotor profile is able to be generated from the sealing line. Moreover, the adjustment method is proposed to segmentally correct the shape of sealing line using the quadratic functions by considering the geometric limitations to avoid interference and undercutting in rotor profiles. A three-lobe claw rotors profile is carried out to demonstrate the reasonability and stability of the proposed method.

The variable pitch twin-screw vacuum pump has more advantage than the uniform pitch twin-screw vacuum pump. Its energy efficiency and volumetric compression ratio are specifically high. Under the cyclic gas pressure and working temperature, the rotors of vacuum pump often deform and interfere that lead to noise, vibration and rotor abrasion. In this paper, a 3D model of the variable pitch rotor generating by CNC turning process is constructed to reasonably estimate the rotor load and deformation in operation. The contact force have been analyzed to show the advantages of variable pitch rotors.

The vibration of a generator in a power plant and the cause of rotor cracking wereanalyzed. The causes of generator rotor cracking were analyzed from the rotor raw material andheat treatment process. The results show that the brittleness and notch sensitivity of the rotormaterial are large due to the unreasonable heat treatment process of the rotor. When the stress isconcentrated, a cracking accident occurs. The generator rotor was returned to the manufacturingcompany for operation. At 3000 r•min-1, the generator's overhanging end vibrated greatly, and thefault was successfully eliminated by the dynamic balance test.

The paper is mainly focused on analysis characteristics of lobe pump with three different tooth profiles: Circular, Epi-cycloidal and Circular–Involute–Circular (CIC) rotor profiles. Based on the geometric analysis and mathematical model, the CIC rotor profile combined Circular–Involute–Circular is generated. In this paper, the CFD techniques are used to estimate the effects of tooth profile and lobe number to the pump performance. The simulation results obtained from FLUENT software illustrated that the rotor profile effects remarkably to the pump performance. The outlet pressure of CIC rotor profile is higher than that of the circular and epi-cycloidal rotor profiles. The numerical outcomes also showed that higher rotor’s speed is resulted in higher outlet pressure. Besides, the lobe number of rotor has effect slightly to the pump performance.

Finite element model based on a unit with cracks in the rotor of the exciter is set up. Andthen critical speed is calculated that compared to actual measured value to verify the rationality of themodel. Lastly response characteristics of the three-bearings supporting structure are studied when thefirst critical speed of the exciter with cracks is closed to the working speed. And the reliability ofconclusions is further verified by case analysis.

Flow over a rotating cylinder is a complicated phenomenon. Many researchers studied boundary layer, for both laminar and turbulent flow and reported instabilities. Because of the difficulty in the determination of skin friction coefficient for flow over a rotating cylinder, the experimental and computational values obtained by different researchers are also widely not in agreement. The flow over a rotating cylinder has many applications such as in ship propulsion using Flettner rotor, motion of a missile, etc. Flettner rotor can be used as an auxiliary power source for ship propulsion. In this paper, using four different empirical relations for skin friction coefficient, power developed/consumed by Flettner rotor on a ship is calculated for different values of wind speed and ship speed. It is found that though, these empirical relations are differently proposed by authors, the numerical values obtained for power generated by Flettner rotor for ship propulsion using these four different formulae didn’t have significant difference.

Screw rotor is a vital factor affecting the working efficiency of twin screw air compressor. Therefore, a type of twin screw air compressor in coal mine production process is taken as the research object. Firstly, the working principle and process of female and male rotor was introduced and analyzed. Then, according to the principle of parameter selection of the female and male rotor, the relevant design parameters of the female and male rotor are given. Finally, the vector equation and the tooth surface equation of the segmented line are deduced and established respectively for the end face profile and end face tooth surface of the rotor, the area and volume of the tooth are also calculated. The equation of the tooth surface is set up by rotation of rotor’s tooth direction, the inter-tooth area is composed of multi-section smooth curve and the top arc connected to form a circle, which can be obtained by means of analytical method. In order to better meet the requirements of the machining process, it is necessary to coordinate the female and male rotor profile on the coordinate axis when the end face of the rotor is non-symmetrical. This paper provides an important reference for selecting parameters of the rotor of the female and male and calculation of rotor profile.

Rotor axis orbit measurement of the spindle under cutting process is the important basis of cutting quality judgment and spindle fault diagnosis. In the cutting process, the non-stationary characteristics of vibration measurement signal of spindle rotor has been particularly outstanding, under such circumstances it is difficult to draw spindle rotor axis orbit accurately. To solve this problem, a new method using EEMD (Ensemble Empirical Mode Decomposition) and harmonic wavelet is put forward to realize non-stationary signal purification and rotor axis orbit feature extraction under machine tool spindle cutting process. In order to filter out the high frequency noise of the measurement, the EEMD method has been used, in addition that the characteristics of the original signal is preserved well. However the signal after EEMD filter still contains a variety of frequency components, in order to solve it, the harmonic wavelet method is used to decompose the signal into several signals according to the different frequency components, through the signal reconstruction achieve rotor axis orbit feature extraction. Using this method, the machined workpiece has been cut under the speed of 12000r/min, the vibration of spindle has been measured and processed. The experiment results show that the new method can effectively reduce the high frequency interference noise signal, and also apparently the rotor axis orbit obtained is more clearly than the original rotor axis orbit.

Steam turbine generator unit, water pump and other high speed revolution symmetric flexible rotor were regarded as research objects in this paper. According to variation characteristic of rotor shaft in rigid and flexible working mode, nine-reel high pressure water pump rotor was analyzed. The former four-order intrinsic frequency of flexible rotor was obtained by modal analysis and harmonic response analysis. The methods of reaction force response and unbalance response were been studied after first order and second order resonance region eliminating in different modes of simple harmonic exciting force. Based on above theoretical research results, trapezoid counterweight method was proposed for dynamic balance of flexible rotor. This method solved problem that rigid dynamic balance of low speed rotor was destroyed after first order and second order resonance region counter weight in dynamic balance of flexible rotor. The dynamic balancing techniques of flexible rotor could be improved the qualities of rotor and its relative products by this method, eliminating the vibration of unbalance mass of products radically.

The characteristics of the lateral nonlinear vibration in composite shaft-disk rotor system with nonlinear deformation are studied. Firstly, the equations of the kinetic energy of the composite shaft, the disk and the eccentric mass as well as the equations of the strain energy of the composite shaft are derived. Based on these equations, the nonlinear vibration equations are deduced by using the Lagrange equation. Then, the frequency response curves and time response curves of the system are obtained by using the IHB method and verified by the fourth order Runge-Kutta method. Experimental results show that the external damping coefficient, the size of eccentric mass only influences the nonlinear amplitude. Moreover, the ply-angle, thickness to diameter(T/D) ratio, length to diameter (L/D) ratio, and the position of disk in the shaft not only produce an effect on the nonlinear amplitude, but also influence the nonlinear vibration frequency.

The non-symmetrical rotor with mass imbalance and disk skew has been considered. For full description of the rotor motion dynamic and mathematical models of the machine have been developed. Expressions for Lagrangian functions and Rayleigh dissipative function are formed. The motion equations are written as the Lagrangian equations of the second kind. By separation of variables the expressions of amplitude and phase of vibrations have been determined. The special emphasis is placed to the joint effect of mass imbalance and disk skew on the rotor dynamics which is observed over the whole range of shaft speed. The amplitudes of the vibrations near the critical speeds and residual phase angle depending on the generalized imbalance and the relative distance to the disk are studied. Detection of the residual phase angle at low rotation speeds is of practical importance, it is extremely important at balancing the rotor, since for determination of the mass eccentricity line the results of measurements at low speeds are used. The main working expressions are presented in a compact and non-dimensional form.

Large unbalance in rotor-dynamic systems is typically responsible for high energy vibrations and the consequent decrease in machine life. This paper presents an analytical model developed using Lagrangian mechanics and partial differential equations (PDEs) for the purpose of early fault-detection in rotor-bearing systems. The model was validated through a Fortran based program, RDA99 developed by Adams (2010), by successfully quantifying the single-peak unbalance response of the simple 8 DOF and 12 DOF rotor-bearing mass stations over two cases. Case I uses bearings with symmetric stiffness and damping matrix. The critical speed for Case I occurred at 1690 rpm and orbital shapes of each mass station was found to be circular with forward-whirl orbits. In Case II asymmetrical bearing stiffness and damping coefficient matrices demonstrate an anisotropic system. Critical speed occurred at 1655 rpm and rotor, bearing and pedestal orbits were seen to be elliptical and changing with shaft speed. Both cases demonstrated a significant shaft bending contribution to the disk displacement.

This paper presents the flight dynamics simulation and analysis of a tilt-rotor vertical takeoff and landing (VTOL) aircraft on transition phase, that is conversion from vertical or hover to horizontal or level flight and vice versa. The model of the aircraft is derived from simplified equations of motion comprising the forces and moments working on the aircraft in the airplane's longitudinal plane of motion. This study focuses on the problem of the airplane's dynamic response during conversion phase, which gives an understanding about the flight characteristics of the vehicle. The understanding about the flight dynamics characteristics is important for the control system design phase. Some simulation results are given to provide better visualization about the behaviour of the tilt-rotor. The simulation results show that both transition phases are quite stable, although an improved stability can give better manoeuver and attitude handling. Improvement on the simulation model is also required to provide more accurate and realistic dynamic response of the vehicle.

Horizontal-axis wind turbines are sophisticated technical constructions that require modern design methods for further improvement and higher economic output. Thorough understanding of the whole turbine and its components is indispensable for this aim. The technological development in the last decades indicates the progress in this area and shows the potential of optimizations due to the improvement of rotor blade aerodynamics by additional aerodynamic devices. In this project the effect of an aeroelastic flap mounted on the trailing edge of a rotor blade on energy yield was investigated. For this purpose a flexible flap of fiberglass reinforced plastic for the profile at 70% of the rotor blade span has been designed for the trailing edge and analyzed using a 2-way fluid-structure-interaction simulation. In the first step the simulation is reduced to a two-dimensional investigation using the cross-section at 70% diameter of the rotor blade. Compared to an unmodified profile, the aeroelastic flap increases the lift-to-drag-ratio of the profile in an angle of attack range between 3.5° to 9.5°. The aeroelastic flap has a positive effect on the glide ratio, similar to a non-elastic, static flap.

H-Darrieus wind turbines, due to their simple design and relatively low manufacturing costs have recently received much attention particularly for standalone applications. However start-up issues associated with their operation restricted their operation in areas of low average wind speed and encourages engineers to develop novel design. Several design proposed in this way but in most cases design came up with complex sensing mechanisms and mechanical actuators or high cost manufacturing parts. A recent rotor design called double Darrieus rotor proposed as a German patent case bridged these complexities appropriately. The aim of present study is to investigate this innovative design from aerodynamic point of view by means of validated CFD techniques. A flow-driven simulation setup based on 6DOF calculations employed in order to study rotor operation from stand still until peak performance obtained. Results from these precise modeling reveal the superiority of the proposed double-stage design in compare with the original H-Darrieus rotors in terms of start-up behavior and optimum performance.

Studies conducted on axial flow hydraulic turbine by comparing the performance of turbines which use a single rotor and two rotors that rotate in opposite (contra-rotating). Both turbines are designed to generate energy utilizing a very low head water flow. Single rotor turbine consists of one row of guide vane and one row of rotor blade. Contra-rotating rotor turbine consists of one row of guide vane and two rows of rotor blade, which is the front rotor blade also serves as a guide vane for the rear rotor. Both of turbines are designed for the same flow and operating conditions. The results of numerical studies show that both of turbines can be applied with a fairly high efficiency, however the single rotor turbine is significantly higher. Especially for contra-rotating turbine, the total power that generated at the same operating conditions will increase because powers are resulted from both of rotors, but the effective head required will be significantly increase compare to the single-rotor turbine. These results may be used as a reference in the development of axial flow hydraulic turbine for very low head sites to expand the applications. Keywords: Single rotor, contra-rotating rotor, axial flow, very low head, hydraulic turbine.

This paper presents the new design of Hybrid Excitation Flux Switching Motor (HEFSM) using segmental rotor structure. HEFSMs are those that consist all the excitation flux sources at their stator with robust rotor structure. The rotor is designed as segmental due to the reason that segmental rotor has ability to yield the magnetic path for conveying the field flux to nearby stator armature coil with respect to the rotation of the rotor. This design gives the clear advantage of shorter end winding compared to the toothed rotor as there is no overlap winding between field excitation coil (FEC) and armature coil. In this paper the initial design of HEFSM with segmental rotor has been improved by changing segment span, FEC slot area and armature slot area until maximum torque and power of 33.633 Nm and 8.17 KW respectively have been achieved. Moreover coil test analysis, induced voltage, cogging torque, magnetic flux characteristics, torque vs. field current density and torque vs. power speed characteristics are examined on the basis of 2-D finite element analysis (FEA).

Blade fault is one of the most causes of failure in turbo machinery. This paper discussed the time frequency analysis for blade rubbing detection from casing vibration signal. Feasibility of Short Time Fourier Transform (STFT), Wigner-Ville distribution (WVD) and Choi-Williams distribution (CWD) were examined for blade rub detection in a multi stage blade system through an experimental data. Analysis results of the experimental data showed that these time frequency analysis methods have some inevitable deficiencies in segregating the blade passing frequency (BPF) components of the three rotor stage signals. However, CWD demonstrated a better time-frequency resolution in analyzing the multi stage rotor system signal.

The detection of rotor position plays an important role in the motor speed-adjustment system. By analyzing the back-EMF method and its improved methods, we know the amplitude of back-EMF is too small to be detected when the motor run at low speed. A new detection method of rotor position has been proposed in this paper. It detects the zero crossing point of line terminal voltage difference to acquire the rotor position signal after a 90 degrees mechanical angle delay. The amplitude of line terminal voltage difference is large in wide speed range, so the rotor position signal can be accurately acquired in most situations. Simulation results proved that the new method can obtain the rotor position signal exactly in both high and low speed. It meets the wide speed range of motor.

This paper studies the detection of twisted blade in a multi stages rotor system. Experimental study was undertaken to simulate twisted blade conditions in a three stages rotor system. The feasibility of vibration analysis as the technique to detect twisted blade based on the rotor operating frequency and its blade passing frequency was investigated in this study. Experimental results show that twisted blade can be easily detected by looking into the pattern of the vibration spectrum and its individual peaks.

Flux switching machines (FSMs), new type of electric machines with unique operating principles have been introduced and published recently. FSMs contain armature and excitation sources on the stator with robust rotor structure. According to rotor structure FSMs can be classified into two types namely salient pole rotor and segmental pole rotor. Various topologies have been studied and published using both rotor structures, however salient pole rotor has a demerit of less torque generation due to longer flux path resulting flux leakage surrounding the rotor. In this paper a new structure of hybrid excitation FSM (HEFSM) with segmental rotor is proposed and a comparative analysis with the invented field excitation FSM (FEFSM) and permanent magnet FSM (PMFSM) is presented. Initially, coil arrangement tests are examined to confirm the operating principle of HEFSM with segmental rotor. Moreover, the cogging torque, induced voltage, magnetic flux, torque at various armature current densities and power characteristics are observed based on 2D-finite element analysis (FEA).

Hybrid excitation flux switching machines (HEFSMs) have a several advantages such as robust rotor structure, high torque and power capabilities, and high efficiency suitable for light load and heavy industry applications. However, the general structure of HEFSMs employed with three main flux sources namely permanent magnet (PM), field excitation coil (FEC) and armature coil located on the stator body causes high manufacturing cost. Therefore, a new non-PM field excitation flux switching machine (FEFSM) consists of rugged rotor structure suitable for high-speed operation with capability to keep similar torque and power density of HEFSM is proposed and examined. In this paper, performances of both outer and inner rotor 12S-14P FEFSMs are analyzed and compared. As conclusion, the inner-rotor topology provides much higher torque and power when compared with outer rotor configuration.

The turbocharger is a unique example of the rotating machinery. Not only for its very high speed, but also because of its compact design and difficult operating conditions (i.e. high temperature, harsh vibrations, etc.). Moreover, measuring of most parameters characterizing the rotor dynamics is a very difficult task. Thus, it is advantageous to replace the real turbocharger by computational model and determine the turbocharger rotor dynamics using simulation tool. The development of such tool will be presented in this paper.

This article deals with experimental and numerical investigation of flow in an axial turbine stage with prismatic blades which are not equipped with the shroud.Main attention is paid to explain the influence of the radial clearance under the stator blade on the flow around the rotor blade.The experiment was performed on the test rig equipped with the water brake dynamometer, torque meter and rotatable stator together with the linear probe manipulator.Numerical modelling was carried out for the unsteady flow using the ``sliding mesh'' interface between the stator and rotor wheels.Results of the numerical simulation are compared with the experimental data.

The paper discusses the development procedure of a small direct drive wind turbine. Especially attention to the main rotor and to the wind blade design procedure is dedicated. Decisional technological steps are described, which makes the wind turbine design effective as environmental friendly product. All the design procedures are well documented by the clearly figures and by adequate descriptions as well. The starting conditions at different wind conditions are estimated and the interesting discussion about the necessity of the starting motor is given.

Critical speed rotor phenomenon characteristics at gas turbine generator is evaluated using finite element method. In this study, the critical speed is evaluated based on the over speed of 4500 rpm. The critical speed of the rotor is investigated in the Campbell diagram, which shows the relationship between natural frequency and rotational velocity of the system Dynamic characteristic in this paper simulated with ANSYS rotor dynamic software. The Finite Element simulation results will be known forms of vibration at each critical speed. Finally the results od simulation can be a reference for dynamic analysis and optimized the design of rotor generator.

The aim of this paper is the development and validation of an impulse excitation technique to determine static imbalance of a rotor. The experimental measurement of the vibroacustic response is carried out by using a condenser microphone. In determining the center of mass three measurements are needed: one in plane flexure, and other out of the plane flexure, to which is added a measurement for a balanced rotor. By the means of Finite Element Method (FEM), the natural frequencies and shape modes of two rotor specimens are determined. The analysis is carried out in balanced condition as well as unbalanced one, after artificially induced imbalance. The vibration responses of the specimens, in free-free conditions, are carried out using algorithms based on Fast Fourier Transform (FFT). To validate the results of the modal parameters estimated using Finite Element Analysis (FEA) these are compared with experimental ones.

The paper is presented the method of simulation of voltage on the stator winding terminals of induction motor with impaired short-circuit winding of rotor in the running-out mode. This method allows to simulate processes in induction motors with precision to satisfy the requirements of protection equipment.

A vertical takeoff and landing aircraft (VTOL) like a helicopter has come to be used in environmental investigations and inspections at dangerous places. However, there is a possibility that the VTOL like a helicopter crash if the rotor stopped. Then, computational simulation in the case that a six-rotor craft can safely continue to fly even though one of six rotors stop was carried out. Then the experimental six-rotor craft was developed and the validity of our control method was examined by the flying experiment.

The article presents the results of experimental investigations of rotor wheels supersonic microturbines with a large angle of rotation of the flow. The characteristics of the studied rotor wheels. The analysis of the results of the study ratio speed of rotor wheels, depending on the Mach number. Recommendations for the design working wheels microturbines operating at high supersonic gas flow rates.

The influence of dry friction damping on twin shaft model test rig vibration experimental investigation is presented. Experimental investigation method is devised and tested at the work. Dry and Coulomb friction damper is developed. The efficiency of damping is evaluated quantitatively via rotor shaft vibration displacements amplitude determining.

The hollow Be rotor is a spherical rotor with high accuracy, it has been grinded by the four-shaft-ball lapping machine. The rotor is a hollow sphere with non-uniform wall structure and there are errors between geometric center and mass center. Analyze the affect of eccentric distance and harmonic coefficients to the working condition of the rotor, establish the kinematic balance equation of rotor that is solved by Matlab software, and draw the rotor motion law with the change of time. The results indicate that with the decrease of eccentric distance of the rotor, the influence of damped motion decrease significantly. The influence on the damped motion of the rotor can be negligible when the eccentric distance is less than or equal to 0.051μm. The larger the harmonic coefficients, the faster the rotor attenuate.

This paper presents a method for determining the rotor temperature of an electric motor by observing the dq-axis flux linkage. A reference dq-axis flux linkage is obtained at a defined rotor temperature. The difference between calculated and reference flux in the d-axis is supposed to be caused by temperature, therefore the temperature can be back-calculated according to the permanent magnet temperature characteristic. The proposed method was confirmed to be correct and effective by the test results.

In order to study the impact of prestress and aqueous medium for axial pump flow rotor modal ，in this paper, with a axial flow model test of North Water Diversion Project, the flow of aqueous medium modal distribution of axial flow rotary mechanism was calculated through the coupling APDL command stream in ANSYS WORKBENCH with the basic idea of Fluid-structure interaction，and axial flow changes of impeller modal in aqueous medium and in the air was compared under prestressed case; the load of prestressed modal of the rotation for the entire organization was calculated through the one-way coupling method . The results show that the water medium has a significant decreases to the natural frequency of the impeller, while the impact of the prestress for modal is not obvious.

Vertical-Axis Wind Turbines (VAWTs) are known as the most suitable wind turbine for small-scale electrical generation. There are many types of VAWTs and each of it has different performances and efficiency. In this work, three types of VAWT systems (Savo-B2, Savo-B4 and Giro-B3) were designed, constructed and tested to investigate the amount of electrical power that could be generated under several constant wind speeds. The blade rotors were designed and built using 2 mm thickness of aluminum plate. The tip speed ratios, power coefficients, blade rotations for each blade rotor and the simplicity of the proposed designs were studied via an experimental setup. The experimental work demonstrates that Savo-B2 provides the highest power coefficient which is up to 0.32. Meanwhile, Giro-B3 offers the fastest rotational blade speed, up to 20.53 rad/s, among the three designs.

In this study, reduction of cogging torque and torque ripple for an exterior rotor type brushless dc (BLDC) motor for an automotive cooling device were proposed and a design concept for a fan motor for use in a battery pack mounted in an electric vehicle/hybrid electric vehicle (EV/HEV) was presented. Various pole/slot combinations and permanent magnet (PM) pole arc ratios were compared using finite element analysis (FEA), and the PM overhang ratio necessary to sufficiently increase the magnetic flux that enabled coil linkage was determined through 3D FEA. Based on the analysis results, an actual model was produced, experimentally verified, and used to validate the proposed design model.

Helicopter rotor aerodynamics is prognosticated to be one of the most perplexing and enigmatic affliction encountered by both researchers and aviators throughout the ages. The bewilderment of the flow field around the main rotor blade ceaselessly remains unrequited in tangible flight environments. Appalling calamities repeatedly befall owing to these unforeseen and equivocal instances. In order to extricate these impediments, one must go back to the brass tacks and apprehend the cause. However, it is every so often exceedingly disconcerting to obtain experimental data due to intricacy, perplexity and substantial price tag. Subsequently, computational simulation is progressively becoming more of a preferred choice in recent times. Bearing this in mind, this study intended to simulate and visualize the air flow configuration of the main rotor blade using symmetrical and transonic airfoils to demarcate their physiognomies and behavior. Results have revealed that the transonic airfoil has a higher lift coefficient (Cl) than the symmetrical airfoil. Contrariwise, if used in an actual rotorcraft, the transonic airfoil can cause stern apprehension in terms of stability and control.

A two-disk rotor system under the aero-engine support structure of typical 1-0-1 was established and the dynamical characteristics were analyzed. The two-disk rotor model was integrated to the Isight. The multi-objective design optimization of the transient process was then carried out with Evolutionary Optimization Algorithm. The optimum positions of the two-disk rotor system were obtained at the specified constraints. In order to verify the validity of the design optimization, the transient test was carried out on a high-speed flexible rotor mockup. The maximum amplitude of disk 1 cross the first critical rotation speed fell 50% and the maximum amplitude of disk 2 decreased by 20%. Experimental results indicated that the optimization method could obtain the position of the flexible rotor with the minimum amplitude and improve the design efficiency and quality, which had practical significance in the design of aero-engine rotor system.

A dual-rotor calculation model which can expand freely in the axial direction is established in this paper, and the effects of one-dimensional axial temperature distribution on critical speeds of the dual-rotor system are analyzed with finite element method. The temperature distribution of the dual-rotor system is given referring to that of similar aero-engine rotor system. Assuming that the left end temperature remains at 0 °C, and the highest temperature on the section of the high-pressure turbine disk is 0 °C, 200 °C, 400 °C, 600 °C, and 800 °C respectively, the critical speeds of the dual-rotor system are calculated, analyzed and compared. Calculation results show that, with the increase of the highest temperature of the dual-rotor system, the reduction percentage of the critical speeds increases, and the impact on the first critical speed is most obvious. When the highest temperature is 800 °C, the first critical speed of the rotor system excited by the low-pressure rotor reduces 13.13%, and that excited by the high-pressure rotor reduces 13.49%.

This paper studies the Jeffcott cracked rotor based on level set, considering the oil film oscillation effects on crack rotor, building the stiffness matrix of the cracked rotor in the fixed coordinate system and the moving coordinate, deriving the nonlinear differential equations of coupled vibration of a cracked rotor, and analysis of its dynamic characteristic combined with case. Analysis shows that: crack rotor can produce nonlinear vibration in the crack and Oil film oscillation can be coupled bending and torsional vibration of cracked rotor. The analysis results provides practical basis for diagnosing Resonance of the rotor system fault and the safe operation of rotor.

Linear finite element analysis model of the typical rotor system is established by the finite element method. Considering the gyroscopic effect of the rotor, critical speed in the rotor system is solved. Then the effect of the rotor system by the unbalanced force on dynamic characteristic is analyzed by frequency response curve. The result shows that support damping coefficient has a great effect on critical speed in the rotor system. With the support from rigid support to elastic support, the critical speed greatly reduces. Because of the unbalance exciting force, maximum resonance amplitude of the disk is near the critical speed of the rotor.

This paper describes the stability analysis of a flexible rotor supported by two horizontal identical plain circular bearings lubricated with Non-Newtonian fluid as micropolar fluid. The basic principles of hydrodynamic lubrication are also discussed here to study the dynamics of rotor bearing system. The mechanisms of hydrodynamic film generation and the effects of operating variables such as velocity, load, design parameters etc., on the performance of such films are outlined. The effects in hydrodynamic lubrication of rotor system using Non-Newtonian lubricant found some undesirable vibrations, undergoes periodic and quasi-periodic motion is described and their influence on bearing performance assessed. The numerical solution of modified Reynolds equation under micropolar lubrication with the usual lubrication assumptions is considered which yield the pressure distribution to find the couple of resulting forces in radial as well as in tangential direction.

Modern motor needs high power density and low rotary inertia,which can improve its dynamic characteristics.Traditional permanent magnet motor shows its limitations.A new structure of ironless rotor motor is proposed. Finite element analysis based on ANSYS proves that the new design not only can increase the motor air gap flux density, but can make the use of ironless rotor rotor become reality. From the relationship curve between air gap flux density and ironless material width, can easily find the ideal width of ironless material of the motor.

One method for diagnosis of faults with generator rotor is contrived by combining local wave method and blind source separation. Time-frequency image varies with local wave of different fault signals, and this feature is applied to identify different faults. In order to realize automatic classification of faults, blind source separation is employed for separation of independent components in time-frequency image of local wave of different fault signals, so as to derive projection coefficients for a set of source images. On the basis of this, automatic classification of faults is realized with probability nerve network. Taking fault signal of rotor as an example, this method is investigated, and the validity is proved by experimental results.

This paper proposes a rotor orientation control strategy on the large proportion of gyroscopic precession of a linear arc-shaped induction motor with multiple stators, applied to maglev bearings. A physical model of the rotor, considering gravitation, is established via analysis based on rotor dynamics: the kinematic model of the rotor, which is installed vertically, can be simplified as rigid body fixed-point rotation. To complete the dynamic formula, the equivalent circuit of a linear arc-shaped induction motor is transformed into dq0 model by Park transformation, in which the decoupling control of the tangential force and the normal force is determined. Moreover, to realize the control strategy combined air-gap cross feedback with damping method, parameter identification, including no-load test and locked rotor test, is modefied. Therefore, the control strategy, aiming at controlling the speed and guaranteeing the rotor rotating vertically around its axis simultaneously, by adjusting the current of the four stators, can be proved by simulation and experimental platform.

Many researchers dealt with single fault but in real life situations, combined action of two or more single faults are usually present. Multi-faults (two and three combinations) were studied by few researchers. Researchers have mostly studied the vibration behavior of a rotor with misalignment, unbalance and rub separately. This paper presents one such case, where multiple faults are considered together in a rotor system, i.e. misalignment, unbalance and rub. The objective of this paper is to experimentally investigate the vibration response of combined of three faults misalignment, unbalance and rub using Fast Fourier Transform (FFT). FFT spectrum of combination of three faults misalignment, unbalance and rub show 1 X and 2 X are predominant and many sub harmonics are generated.1X peak represent unbalance, 2X peak represents misalignment and sub harmonics shows rub fault.

The twin-screw vacuum pump is widely used in low and medium-low vacuum applications. Its core element consists of a pair of rotors rotating in opposite direction on parallel axes. Screw rotors with uniform pitch are usually finished by the form grinding method, but the rotors with variable pitch are not. In this paper, a manufacturing process for generating the tooth profile of the screw rotor with variable pitch by CNC lathe turning is proposed. The initial position of turning tool and normal profile error of the manufactured screw rotors are derived and verified numerically. Numerical examples are presented to validate the proposed method. The simulation results reveal that the proposed CNC turning process is feasible and flexible.

A variable value water resistor speed control system for rotor winding induction motor is introduced. On the basis of the structure about the water resistance and the governor principle, the steady-state mathematical model and the dynamic mathematical models are established. The effect of temperature changes on the resistance of the electrolyte solution is discussed, and temperature compensation is proposed. Simulation results show that the water resistance speed control system is feasible.

In high load-carrying bearing-rotor system, bearings’ places usually change for load distribution or in continual work. It influences the system’s stability, and brings out different vibration response in rotor system. This article puts forward mathematical model of bearing’s stiffness under load which is calculated from bearing displacement. Then through numerical integration it studies system’s rotating vibration with different bearing settings. The results of the analysis show that bearing displacement has a great effect on dynamic characteristics of the bearing-rotor system.