Papers by Keyword: Rotor

Abstract: The authors have developed a method of calculating the non-linear elastic force that arises in the clearance seal of a finite length. The authors have analysed the force impact on the dynamics of the rotor of a centrifugal machine.

Abstract: Cantilevered shaft-rotor systems consisting of multi disks and multi profiled shafts are considered. In this paper the procedures for the determination of the deflection, slope, shear force and bending moment at the extremities of the shaft are employed. Critical speeds or whirling frequency conditions are computed using transfer matrix method (TMM). For particular shaft-lengths, rotating speeds and shaft-profiles, the response of the system is determined for the establishment of the dynamic characteristics. A built-in shaft-rotor system consisting of two disks and two different profiled shafts is investigated for illustration purposes. Step response of the multi profiled shaft-rotor system is also found out.

Abstract: In order to improve the mechanics properties of the rotor components at ultra-high load steady acceleration conditions, the significant factors to the rotor mechanics properties, which include the ellipsoid axis length, minor axis length, rotor speed and gyration radius of holes, are taken as the optimizing objects, the extreme stress, strain extremes, moment of inertia of rotor are optimized as the targets. Then optimization models of the rotor mechanics parameters are established, and the multi-objective optimization method of rotor mechanics properties is proposed based on particle swarm. The results show that the mechanics properties of the rotor were significantly improved using the optimize method.

Abstract: The vertical shaft impact crusher the material is accelerated , while the rotor bear complex dynamic loads , finite element method for three-dimensional modeling of the rotor body and modal analysis , discussion and analysis of results. Won the first 20 natural frequencies and mode shapes , as well as the weak link parts may exist , making the crusher prone resonance attention away from the source at work , as well as designers kinetic design provides some guidance basis.

Abstract: Dynamic and static frequency of the rotor about diameter of 1.4m small horizontal axis wind turbine was tested by using PULSE16.1 structural vibration analysis system., through combining the data of static frequency to identify rotor Dynamic frequency using spectrum analysis method. The conclusions found that, at a yaw condition of constant rotor speed, vibration acceleration of axial movement, disc effect and first order vibration of rotor increased with the increase of the yaw angle. The reason was that yaw exciting force which generated by the yaw behavior increased with the increase of yaw angle. At a constant load yaw, vibration acceleration of axial float, disc effect increased with the increase of the yaw angle. At the yaw condition of constant load R=82Ω、R=118Ω and the yaw angle 25°,30°,the acceleration value sharp increased and occurred the machine resonance phenomenon due to the tower instability. First order symmetric and anti symmetric vibration acceleration of rotor decreased with the increase of the yaw angle. The reason was that after the wind turbine yaw, the speed decreased of rotor caused the centrifugal force of the blades decreased, the impact of the centrifugal load changed was far greater than yaw exciting force for the first order vibration acceleration. The study also found that vibration acceleration values of rotor first order anti symmetric was ​​greater than axial movement, disc effect and first order symmetric vibration acceleration values, which shows that stress concentration in root of blade was large and the blade fatigue damage was more serious. This paper related research results can provided a new analytical thinking for rotor fatigue damage or breakage occurred frequently in wind turbine operation process, and may provide a reference for the vibration characteristics of rotor in the process of yaw.

Abstract: Based on the finite element theory, an analysis about the changing of rotor vibration mode of the wind turbine with and without rudder at static state, and a research was carried out to study the impact of the rudder on wind turbine vibration frequency during operation condition of a small horizontal axis wind turbine by using Ansys Workbench. The result showed that, rudder vibration mode was the coupling of rudder vibration mode and first order anti-symmetric vibration mode of rotor. With the increasing of rotating speed, wind turbine vibration frequency increased because of the stiffening effect caused by centrifugal force, and the difference of first order anti-symmetric vibration frequency and symmetric vibration frequency was decrease which was caused by the aerodynamic force. At the same time, the changing of the external load had no effect on the vibration frequency of rudder, the reason of that was counterweight of the rudder. When the rotor speed was in the resonance region, rudder vibration frequency was equal to first order anti-symmetric vibration frequency at the rotating speed n=10.91Hz, an obviously resonance phenomenon occurred. The related research could provide some theoretical guidance for the design of small wind turbine rudder.

Abstract: Based on the structural and mechanics analysis of aero-engines rotor system, the dynamic model of the flexible rotor system with multi-supports are presented in order to solve the bearing misalignment problem of rotor system in aero-engines. The motion equations are derived through Lagrange method. The relationship between structural and mechanics characteristics parameters are built up. Finally, the dynamic influence of bearing misalignment on rotor system is divided into three kinds: additional rotor bending rigidity, additional bearing misalignment excitation force and additional imbalance. The equations suggest that additional imbalance excitation force activates the nonlinearity on rotor system and an additional 2× excitation force might appear.

Abstract: Performance of helicopters can be significantly influenced by rotor speed variation. A comprehensive model is built to exam the influences of rotating speed on performance and blade loads of a variable speed rotor. The results indicate that for a 2,200kg gross weight helicopter, power reduction is up to 30% at 100km/h by slowing the rotor properly. For lower gross weights, the reductions in rotor rotating speed and power savings are more apparent. The optimum rotating speed may cause a 20.5% increase in endurance and 8.5% in range by thoroughly consuming 400kg of fuel. Rotor RPM variation has an important effect on blade loads. For 100km/h and 2,200kg gross weight, amplitudes for most of the harmonic loads decrease with reduced rotor RPM.

Abstract: In the present study, mathematical modelling of different chamber profile of the vacuum pump to evaluate the evacuation time is developed. The validity of the developed mathematical modelling is demonstrated by performing an experiment on the vacuum pump with elliptical profile. The performance of the elliptical profile is also compared with that of the circular profile chamber of vacuum pump. It is shown that the evacuation time of vacuum pump with an elliptical chamber is lower than with a circular profile. Various parametric studies are also performed to investigate the effect of rotor eccentricity, ratio of minor and major axes of the elliptical profiles, air tank capacity on evacuation time of the vacuum pump.

Abstract: In general, aerostatic bearings are flat bearings and the stringent manufacturing tolerances in geometric dimensions and profile will make the bearing ideal for obtaining high stiffness during measurement. Aerostatic Spherical Bearing (ASB) on the contrary is a special bearing which provides a frictionless pivot and allows three degrees of rotational freedom. Methods involved in manufacturing and realizing a highly stiff ASB is discussed in this paper. ASB components viz. Stator and Rotor of hemi-spherical in geometry are the critical components to be machined, which are used in Mass properties and Dynamic Balancing Measurement machine (MaPDBM). MaPDBM is used to measure mass, center of gravity, moments of inertia and static & dynamic unbalance of spacecraft. An air film of 25-50 μm thickness separates the stator and rotor during measurement, thus forming an aerostatic bearing. Precise Machining, Thermal treatments to ensure crash-proof design, Special processes like lapping for profile correction, Geometrical and profile measurements during different stages in the sequence for controlling the bearing parameters using Coordinate Measurement Machine (CMM) are the challenges involved in the machining and realization of the ASB components and the same is discussed in this paper.