The Actuator Line/Navier-Stokes model is validated against wind tunnel measurements for flows past the yawed MEXICO rotor and past the yawed NREL Phase VI rotor. The MEXICO rotor is operated at a rotational speed of 4...The Actuator Line/Navier-Stokes model is validated against wind tunnel measurements for flows past the yawed MEXICO rotor and past the yawed NREL Phase VI rotor. The MEXICO rotor is operated at a rotational speed of 424 rpm, a pitch angle of ?2.3。, wind speeds of 10, 15, 24 m/s and yaw angles of 15。, 30。 and 45。. The computed loads as well as the velocity field behind the yawed MEXICO rotor are compared to the detailed pressure and PIV measurements which were carried out in the EU funded MEXICO project. For the NREL Phase VI rotor, computations were carried out at a rotational speed of 90.2 rpm, a pitch angle of 3。, a wind speed of 5 m/s and yaw angles of 10。and 30。. The computed loads are compared to the loads measured from pressure measurement.展开更多
The nonlinear properties of rotating machinery vibration signals are presented. The relationship between faults and quadratic phase coupling is discussed. The mechanism that gives rise to quadratic phase coupling is a...The nonlinear properties of rotating machinery vibration signals are presented. The relationship between faults and quadratic phase coupling is discussed. The mechanism that gives rise to quadratic phase coupling is analyzed, and the coupling models are summarized. As a result, higher order spectra analysis is introduced into fault diagnosis of rotors. A brief review of the properties of higher order spectra is presented. Furthermore, the bicoherence spectrum is employed to extract the features that signify the machinery condition. Experiments show that bicoherence spectrum patterns of different faults are quite different, so it is proposed to identify the faults in rotors.展开更多
Based on reconstructing the phase space and calculating the largest Lyapunov exponent, an improved method of detecting chaotic motion is presented for rotor-bearing systems. The method is an improvement to the Wolf me...Based on reconstructing the phase space and calculating the largest Lyapunov exponent, an improved method of detecting chaotic motion is presented for rotor-bearing systems. The method is an improvement to the Wolf method and the Rosenstein algorithm. The improved method introduces the correlation integral function method to estimate the embedding dimension and the reconstruction delay simultaneously, and it makes tracks for the evolutions of every pair of the nearest neighbors to improve the utilization of the reconstructed phase space. Numerical calculation and experimental verification show that the improved method can estimate the proper reconstruction parameters and detect chaotic motion of rotor-bearing systems accurately. In addition, the analytical results show that the current approach is robust to variations of the embedding dimension and the reconstruction delay, and it is applicable to small data sets.展开更多
Rotor-bearings systems applied widely in industry are nonlinear dynamic systems of multi-degree-of-freedom. Modem concepts on design and maintenance call for quantitative stability analysis. Using trajectory based sta...Rotor-bearings systems applied widely in industry are nonlinear dynamic systems of multi-degree-of-freedom. Modem concepts on design and maintenance call for quantitative stability analysis. Using trajectory based stability-preserving and dimensional-reduction, a quantitative stability analysis method for rotor systems is presented. At first, an n-dimensional nonlinear non-autonomous rotor system is decoupled into n subsystems after numerical integration. Each of them has only onedegree-of-freedom and contains time-varying parameters to represent all other state variables. In this way, n-dimensional trajectory is mapped into a set of one-dimensional trajectories. Dynamic central point （DCP） of a subsystem is then defined on the extended phase plane, namely, force-position plane. Characteristics of curves on the extended phase plane and the DCP＇s kinetic energy difference sequence for general motion in rotor systems are studied. The corresponding stability margins of trajectory are evaluated quantitatively. By means of the margin and its sensitivity analysis, the critical parameters of the period doubling bifurcation and the Hopf bifurcation in a flexible rotor supported by two short journal bearings with nonlinear suspensionare are determined.展开更多
针对集中绕组永磁电机中二倍频(2 f e)径向电磁力导致的空调压缩机振动与噪声问题,提出一种结合定子磁导偏置及转子谐波注入的抑振技术,实现低阶2 f e径向电磁力有效抑制。首先,基于电磁场理论和有限元分析方法,建立了永磁电机的2 f e...针对集中绕组永磁电机中二倍频(2 f e)径向电磁力导致的空调压缩机振动与噪声问题,提出一种结合定子磁导偏置及转子谐波注入的抑振技术,实现低阶2 f e径向电磁力有效抑制。首先,基于电磁场理论和有限元分析方法,建立了永磁电机的2 f e径向电磁力理论模型,分析了齿槽调制效应以及各阶力波对振动响应产生的影响。其次,提出定子旋转辅助槽创新结构,引入磁导偏置因子,显著降低了3阶2 f e径向电磁力幅值;同时提出了“上升楔形”转子结构,主动引入转子3次谐波,有效抑制了6阶2 f e径向电磁力。最后,通过电机振动测试、压缩机噪声测试以及空调系统噪声实验,分析了定子磁导偏置及转子谐波注入技术对振动噪声的抑制效果,验证了该技术对空调压缩机2 f e振动噪音改善的有效性。展开更多
文摘The Actuator Line/Navier-Stokes model is validated against wind tunnel measurements for flows past the yawed MEXICO rotor and past the yawed NREL Phase VI rotor. The MEXICO rotor is operated at a rotational speed of 424 rpm, a pitch angle of ?2.3。, wind speeds of 10, 15, 24 m/s and yaw angles of 15。, 30。 and 45。. The computed loads as well as the velocity field behind the yawed MEXICO rotor are compared to the detailed pressure and PIV measurements which were carried out in the EU funded MEXICO project. For the NREL Phase VI rotor, computations were carried out at a rotational speed of 90.2 rpm, a pitch angle of 3。, a wind speed of 5 m/s and yaw angles of 10。and 30。. The computed loads are compared to the loads measured from pressure measurement.
文摘The nonlinear properties of rotating machinery vibration signals are presented. The relationship between faults and quadratic phase coupling is discussed. The mechanism that gives rise to quadratic phase coupling is analyzed, and the coupling models are summarized. As a result, higher order spectra analysis is introduced into fault diagnosis of rotors. A brief review of the properties of higher order spectra is presented. Furthermore, the bicoherence spectrum is employed to extract the features that signify the machinery condition. Experiments show that bicoherence spectrum patterns of different faults are quite different, so it is proposed to identify the faults in rotors.
基金the National Basic Research Program (973) of China (No. 2009CB724302)
文摘Based on reconstructing the phase space and calculating the largest Lyapunov exponent, an improved method of detecting chaotic motion is presented for rotor-bearing systems. The method is an improvement to the Wolf method and the Rosenstein algorithm. The improved method introduces the correlation integral function method to estimate the embedding dimension and the reconstruction delay simultaneously, and it makes tracks for the evolutions of every pair of the nearest neighbors to improve the utilization of the reconstructed phase space. Numerical calculation and experimental verification show that the improved method can estimate the proper reconstruction parameters and detect chaotic motion of rotor-bearing systems accurately. In addition, the analytical results show that the current approach is robust to variations of the embedding dimension and the reconstruction delay, and it is applicable to small data sets.
文摘Rotor-bearings systems applied widely in industry are nonlinear dynamic systems of multi-degree-of-freedom. Modem concepts on design and maintenance call for quantitative stability analysis. Using trajectory based stability-preserving and dimensional-reduction, a quantitative stability analysis method for rotor systems is presented. At first, an n-dimensional nonlinear non-autonomous rotor system is decoupled into n subsystems after numerical integration. Each of them has only onedegree-of-freedom and contains time-varying parameters to represent all other state variables. In this way, n-dimensional trajectory is mapped into a set of one-dimensional trajectories. Dynamic central point （DCP） of a subsystem is then defined on the extended phase plane, namely, force-position plane. Characteristics of curves on the extended phase plane and the DCP＇s kinetic energy difference sequence for general motion in rotor systems are studied. The corresponding stability margins of trajectory are evaluated quantitatively. By means of the margin and its sensitivity analysis, the critical parameters of the period doubling bifurcation and the Hopf bifurcation in a flexible rotor supported by two short journal bearings with nonlinear suspensionare are determined.
文摘针对集中绕组永磁电机中二倍频(2 f e)径向电磁力导致的空调压缩机振动与噪声问题,提出一种结合定子磁导偏置及转子谐波注入的抑振技术,实现低阶2 f e径向电磁力有效抑制。首先,基于电磁场理论和有限元分析方法,建立了永磁电机的2 f e径向电磁力理论模型,分析了齿槽调制效应以及各阶力波对振动响应产生的影响。其次,提出定子旋转辅助槽创新结构,引入磁导偏置因子,显著降低了3阶2 f e径向电磁力幅值;同时提出了“上升楔形”转子结构,主动引入转子3次谐波,有效抑制了6阶2 f e径向电磁力。最后,通过电机振动测试、压缩机噪声测试以及空调系统噪声实验,分析了定子磁导偏置及转子谐波注入技术对振动噪声的抑制效果,验证了该技术对空调压缩机2 f e振动噪音改善的有效性。
