Search Results (19)

The consequent-pole interior permanent-magnet (CPM) motor is a promising alternative for minimizing rare-earth magnet usage while supporting high-speed operation. However, rotor flux asymmetry often leads to distorted back-electromotive force waveforms and increased torque ripple. This study investigated a flared-type CPM motor that employs ferrite magnets arranged in a flared configuration to enhance flux concentration within a compact rotor. To address waveform distortion, structural modifications such as bridge removal and an asymmetric air-gap design were implemented. Three rotor parameters—polar angle, asymmetric air-gap length, and rotor opening length—were optimized using Latin hypercube sampling combined with an evolutionary algorithm. Finite element method analyses conducted under no-load and rated-load conditions showed that the optimized model achieved a 77.8% reduction in torque ripple, a 43.4% decrease in cogging torque, and a 0.5% improvement in efficiency compared with the basic model. Stress analyses were performed to examine the structural bonding strength and rotor deformation of the optimized model under high-speed operation. The results revealed a 5.5× safety margin at four times the rated speed. The proposed approach offers a cost-effective and sustainable alternative to rare-earth magnet machines for high-efficiency household appliances, where vibration reduction, cost stability, and energy efficiency are critical. Full article

The cooling system is a core component for a vehicle’s powertrains to operate smoothly and maintain a satisfying noise, vibration, and harshness (NVH) performance. However, advances in new energy vehicles bring with them complex requirements for the cooling fan design due to new issues such as increased heat load, dynamic variations, and high-speed vibrations, which demand the optimization of fan dynamics over a wide range of parameters. In this paper, by thoroughly checking the effect of rigid–flexible coupling and the geometrically complex elastic frame of the fan, we propose a combined modeling approach to reduce the computational time of broad-range parameter variation analysis and examine the vibration problem in the cooling fans under various external excitations. First, the complicated frame of the fan is simplified through virtual prototyping based on an experiment. Then, modal transition is applied, reducing the complex kinetic expression, and a time-invariant system model is derived with multi-blade coordinate transformation. Stability and bifurcation analysis are performed regarding different excitation couplings from the rotor, powertrain, and road. The results of the simulation and experiment illustrate that the proposed methodology achieves a substantial reduction in computational time, and all degrees of freedom (DOFs) are divided into two groups including symmetrical and asymmetrical types. The results also imply the great potential for the optimization and control of the high-speed fan’s vibration for new energy cars. Full article

This paper comprehensively reports experimental proof of parity violation in the ground and photoexcited states of three mirror-symmetric Si–Si bond polymers in homogeneous solutions of achiral molecules under non-stirring conditions by analyzing 370 chiroptical datasets relating to multiple second-order helix–helix transitions in the circular dichroism (CD) of poly(di-i-butylsilane) (iBS), poly(di-i-pentylsilane) (iPS), and poly(di-i-hexylsilane) (iHS) in achiral alkanols and p-dioxane-h₈/-d₈. Particularly large (–)-CD of g_abs = −3.1 × 10⁻² at 290 nm was found for iBS in i-pentanol at 25 °C. Notably, iPS in n-propanol at −5 °C generated (–)-CD with g_abs = −0.48 × 10⁻² at 300 nm, but (+)-circularly polarized luminescence (CPL) with g_lum = +0.84 × 10⁻² at 326 nm. In contrast, iHS in n-octanol at 0 °C showed only very weak (–)-CD of g_abs ~−0.03 × 10⁻² at 310 nm. The H/D isotopes of p-dioxane-h₈/-d₈ weakly affected the helix–helix transition characteristics of iBS. (–)-Sign vibrational CD signals assigned to the handed symmetric and asymmetric bending modes of the CH₃ and CH₂ groups of the solvents and other achiral molecules were observed. We assumed (i) three ¹H nuclear-spin-1/2 induced handed motions of CH₃ rotors at i-alkyl side chains and achiral alkanols, and (ii) helical main-chain Si atoms (δ⁺) coordinated by handed lone pairs at oxygen (δ⁻) in gauche-containing n- and i-alkanols induced by the CH₃ rotors. A possible origin of biomolecular handedness is proposed based on the first observation of far-UV CD and UV spectra of zwitterionic glycine bearing H₃N⁺ rotor in neutral H₂O. Full article

This study addresses inlet flow distribution and pressure pulsation-induced vibration in LNG dual-pump parallel systems. We investigate an LNG dual-submerged pump tower system. Our approach combines computational fluid dynamics with vortex dynamics theory. We examine inlet flow characteristics under different flow conditions. Pressure pulsation propagation patterns are analyzed. System stability mechanisms are investigated. A 3D model incorporates inducers, impellers, guide vanes, outlet sections, and base structures. The SST k-ω turbulence model and Q-criterion vortex identification reveal key features. Results show minimal head differences during parallel operation. The inlet flow field remains uniform without significant vortices. However, local low-velocity zones beneath the base may cause flow separation at low flows. Pressure pulsations are governed by guide vane rotor–stator interactions. These disturbances propagate backward to impellers and inducers. Outlet sections show asymmetric pressure fluctuations. This asymmetry results from spatial positioning differences. Complex base geometries generate low-intensity vortices. Vortex intensity stabilizes at higher flows. These findings provide theoretical foundations for vibration suppression. Full article

Since the 1960s, theorists have claimed that the electroweak force, which unifies parity-conserving electromagnetic and parity-violating weak nuclear forces, induces tiny parity-violating energy differences (10⁻¹⁰–10⁻²¹ eV) between mirror-image molecules. This study reports the dual mirror-symmetry-breaking and second-order phase transition characteristics of mirror-symmetric 7₃-helical poly(di-n-butylsilane) in n-alkanes under static (non-stirring) conditions. In particular, n-dodecane-h₂₆ significantly enhances the circular dichroism (CD) and circularly polarized luminescence (CPL) spectra. A new (−)-CD band emerges at 299 nm below T_C1 ~ 105 °C, with a helix–helix transition at T_C2 ~ 28 °C, and exhibits g_abs = +1.3 × 10⁻² at −10 °C. Synchronously, the CPL band at 340 nm exhibiting g_lum = −0.7 × 10⁻² at 60 °C inverts to g_lum = +2.0 × 10⁻² at 0 °C. Interestingly, clockwise and counterclockwise stirring of the mixture induced non-mirror-image CD spectra. n-Dodecane-d₂₆ weakens the g_abs values by an order of magnitude, and oppositely signed CD and a lower T_C1 of ~45 °C are observed. The notable H/D isotope effect suggests that the CH₃ termini of the polysilane and n-dodecane-h₂₆, which comprise a three identical nuclear spin-1/2 system in a triple-well potential, effectively work as unidirectional hindered rotors due to the handedness of nuclear-spin-dependent parity-violating universal forces. This is supported by the (−)-sign vibrational CD bands in the symmetric and asymmetric bending modes of the CH₃ group in n-dodecane-h₂₆. Full article

The low specific speed centrifugal pump plays a crucial role in industrial applications, and ensuring its efficient and stable operation is extremely important for the safety of the whole system. The pump must operate with an extremely high head, an extremely low flow rate, and a very fast speed. The internal flow structure is complex and there is a strong interaction between dynamic and static components; consequently, the hydraulic excitation force produced becomes a significant factor that triggers abnormal vibrations in the pump. Therefore, this study focuses on a low specific speed centrifugal pump and uses a single-stage model pump to conduct PIV and pressure pulsation tests. The findings reveal that the PIV tests successfully captured the typical jet-wake structure at the outlet of the impeller, as well as the flow separation structure at the leading edge of the guide vanes and the suction surface. On the left side of the discharge pipe, large-scale flow separation and reverse flow happen as a result of the flow-through effect, producing a strong vortex zone. The flow field on the left side of the pressure chamber is relatively uniform, and the low-speed region on the suction surface of the guide vanes is reduced due to the reverse flow. The results of the pressure pulsation test showed that the energy of pressure pulsation in the flow passage of the guide vane occurs at the f_BPF and its harmonics, and the interaction between the rotor and stator is significant. Under the same operating condition, the RMS value distribution and amplitude at f_BPF of each measurement point are asymmetric in the circumferential direction. The amplitude of f_BPF near the discharge pipe is lower, while the RMS value is higher. A complex flow structure is shown by the larger amplitude and RMS value of the f_BPF on the left side of the pressure chamber. With the flow rate increasing, the energy at f_BPF of each measurement point increases first and then decreases, while the RMS value decreases, indicating a more uniform flow field inside the pump. Full article

The deposition of combustion residues in the nozzle ring (NR) of a turbocharger turbine stage changes the NR geometry significantly in a random manner. The resultant complex and highly asymmetric geometry induces low engine order (LEO) excitation, which may lead to resonance excitation of rotor blades and high cycle fatigue (HCF) failure. Therefore, a suitable prediction workflow is of great importance for the design and validation phases. The prediction of LEO excitation is, however, computationally expensive as high-fidelity, full annulus CFD models are required. Previous investigations showed that a steady-state computational model consisting of the volute, the NR, and a radial extension is suitable to reduce the computational costs massively and to qualitatively predict the level of LEO forced response. In the current paper, the aerodynamic excitation of 69 real contaminated NRs is analyzed using this simplified approach. The results obtained by the simplified simulation model are used to select 13 contaminated NR geometries, which are then simulated with a model of the entire turbine stage, including the rotor, in a transient time-marching manner to provide high-fidelity simulation results for the verification of the simplified approach. Furthermore, two contamination patterns are analyzed in a more detailed manner regarding their aerodynamic excitation. It is found that the simplified model can be used to identify and classify contamination patterns that lead to high blade vibration amplitudes. In cases where transient effects occurring in the rotor alter the harmonic pressure field significantly, the ability of the simplified approach to predict the LEO excitation is not sufficient. Full article

In this paper, we present research on a novel low-profile piezoelectric rotary motor with a triangle-shaped stator. The stator of the motor comprises three interconnected piezoelectric bimorph plates forming an equilateral triangle. Bimorph plates consist of a passive layer fabricated from stainless steel and four piezo ceramic plates glued to the upper and lower surfaces. Furthermore, spherical contacts are positioned on each bimorph plate at an offset from the plate’s center. Vibrations from the stator are induced by a single sawtooth-type electric signal while the frequency of the excitation signal is close to the resonant frequency of the second out-of-plane bending mode of the bimorph plate. The offset of the spherical contacts allows for a half-elliptical motion trajectory. By contrast, the forward and backward motion velocities of the contacts differ due to the asymmetrical excitation signal. The inertial principle of the motor and the angular motion of the rotor were obtained. Numerical and experimental investigations showed that the motor operates at a frequency of 21.18 kHz and achieves a maximum angular speed of 118 RPM at a voltage of 200 V_p-p. Additionally, an output torque of 18.3 mN·mm was obtained under the same voltage. The ratio between motor torque and weight is 36 mN·mm/g, while the ratio of angular speed and weight is 28.09 RPM/g. Full article

Crack is a common fault of rotor systems. The research on crack fault detection methods is mainly divided into numerical and experimental studies. In numerical research, the current fault detection algorithms based on deep learning are mostly applied to bearings and gearboxes, and there are few studies on rotor fault diagnosis. In experimental research, the rotors used in an experiment are mostly single-span rotors. However, there are complex structures such as multi-span rotor systems in the actual industrial field. Thus, the fault detection algorithms that have been successfully applied on single-span rotors have not been verified on complex rotor systems. To obtain a fault signal close to the actual asymmetric shaft system of an asymmetric rotor system and validate the fault detection method, the crack fault detection platform is designed and built independently. We measure the vibration signals of three channels under five working conditions and establish an intelligent detection method for crack location based on a residual network. The factors that influence fault detection performance are analyzed, and the influence laws are discussed. Results show that the accuracy and anti-noise performance of the proposed method are higher than those of the commonly used machine learning. The average accuracy is 100% when SNR (signal-to-noise ratio) is greater than or equal to −2 dB, and the average accuracy is 98.2% when SNR is −4 dB. Full article

Asymmetric vane pitch is a key technique to suppress the forced response of downstream rotor blades. To address the problem of low-engine-order (LEO) excitation with high amplitude under an asymmetric configuration (half-and-half layout) widely recognized in the previous literature, we first apply the in-house computational fluid dynamics code Hybrid Grid Aeroelasticity Environment to perform full-annulus unsteady aeroelasticity simulations of the turbine stage, comparing the resonance response of rotor blades on different asymmetric configurations and analyzing the flow field at the vane exit, as well as the excitation force, modal force, and maximum vibrational amplitude on the rotor blades. Second, we reveal that the potential field of the vane row is the main source of the LEO excitation caused by asymmetric configuration on rotor blades, the vane wake and potential field jointly determine the LEO excitation strength of rotor blades, and the vane pitch difference $\mathsf{\Delta }S$ can be used to regulate the strength of the LEO excitation. Finally, based on an in-depth understanding of flow physics under an asymmetric configuration, a more preferable and effective asymmetric configuration (non-half two-segment layout) is proposed. Our findings demonstrate that, with the proposed asymmetric configuration, the amplitude of the vane passing frequency was reduced by 48.32% compared to the uniform configuration; furthermore, the maximum vibrational amplitude of the three-nodal-diameter response of the rotor blade at the three-engine-order crossing decreased by 45.49% compared to the half-and-half layout. The non-half two-segment layout also significantly improves upon the half-and-half layout in terms of aerodynamic performance. The results presented in this paper provide a good theoretical basis for reducing blade vibration by applying asymmetric vane pitch in engineering practice. Full article

For periodic time-varying systems, a method of parameter identification based on the block-pulse function is presented. Firstly, the state-space equation of the system was expanded using the block-pulse function, then the recursion formula of the parameter identification of a time-varying system was obtained, according to the irrespective and orthogonal characteristics of the block-pulse function. This study provides a wide range of applications by saving time in calculation with a highly accurate method. The parameter identification was carried out by including the numerical simulation model of a three-degree freedom system and the vibration experiment results of an asymmetrical rotor system. The state space wavelet method and EMD method were compared cross-sectionally with the proposed method; this shows that the proposed method is accurate and effective, which makes it valuable in numerous applications. It also has a certain application value for several related projects. Full article

In recent years, large-capacity, high-head pump–turbine units have been developed for pumped storage power plants to effectively utilise water energy and store large amounts of electricity. Compared with the traditional Francis turbine unit, the radial distance between the trailing edge of the guide vanes and the leading edge of runner blades of high-head pump–turbine unit is smaller, so the rotor–stator interaction and the corresponding pressure fluctuations in the vaneless space of pumped storage units are more intense. The pressure fluctuations with high amplitudes and high frequencies induced by rotor–stator interaction (RSI) become the main hydraulic excitation source for the structures of the unit and may cause violent vibration and fatigue damage to structural components, and seriously affect the safe operation of the units. In this paper, the RSI of a high-head pump–turbine in turbine mode of operation is studied in detail by means of site measurement and full three-dimensional unsteady simulations. The results of RSI-induced pressure fluctuations in turbine mode are analysed experimentally and numerically. The accuracy of the numerical calculations is verified by comparing with the measured results, and the variation law of RSI is deeply analysed. The results show that the pressure fluctuations in the vaneless space are affected by the wake of the guide vane, the rotating excitation of the runner, the low-frequency excitation of the draft tube, and the asymmetric characteristics of the incoming flow of the spiral case, and shows significant differences in spatial position. The findings of the investigation are an important and valuable reference for the design and safe operation of the pumped storage power station. It is recommended to design the runner with inclined inlets to reduce the amplitudes of RSI-induced pressure fluctuations and to avoid operating the pump–turbine units under partial load for long periods of time to reduce the risk of pressure fluctuation induced severe vibration on the structures. Full article

Studies have substantiated that the vibration and noise produced by the iron core of an electromagnetic device are closely related to the magnetostriction of the iron core silicon steel sheet. Moreover, when the induction motor works under the condition of frequency conversion, the symmetry of the core silicon steel sheet will change, and the distribution of the vibration and noise field of the motor will be asymmetric, which will aggravate the vibration and noise. This paper completes the experimental measurement and analysis of the electromagnetic characteristics and magnetostrictive characteristics of silicon steel sheets. The magnetic field of a 1140 V/75 kW variable-frequency motor is calculated analytically based on the analytical method, and the stator/rotor magnetic induction intensity and permeance are calculated separately to obtain the air gap magnetic density and the radial electromagnetic force. The vibration and noise of the 1140 V/75 kW variable-frequency motor are analyzed by the finite element method, while the magnetization curve and magnetostrictive characteristic curve of a silicon steel sheet under different conditions are considered. An experimental platform is built to measure and analyze the vibration displacement and acceleration of the variable frequency motor, which verifies the correctness of the proposed scheme. Considering the influence of the magnetostrictive effect will make the result of calculating the vibration and noise of variable-frequency motors more accurate. Full article

The paper presents a numerical and experimental investigation of a novel two degrees of freedom (2-DOF) piezoelectric actuator that can generate rotary motion of the sphere-shaped rotor as well as induce planar motion of the flat stage. The actuator has a small size and simple design and can be integrated into a printed circuit board (PCB). The application field of the actuator is small-dimensional and high-precision positioning systems. The piezoelectric actuator comprises three rectangular bimorph plates joined with arcs and arranged by an angle of 120 degrees. A high-stiffness rod is glued on the top surface of each bimorph plate and is used to rotate the rotor or move flat stage employing contact friction force. Three U-shaped structures are used for the actuator clamping. 2-DOF rotational or planar movement is obtained by applying a harmonic or asymmetric electrical signal. The operation principle of the actuator is based on the superposition of the B₂₀ out-of-plane bending mode of the bimorph plates and the B₀₃ radial vibration mode of the ring. Design optimization has been performed to maximize amplitudes of contact point vibration. A prototype of the actuator was made, and a maximum rotation speed of 795.15 RPM was achieved while preload of 546.03 mN was applied. The linear velocity of 36.45 mm/s was obtained at the same preload force. Resolution measurement showed that the actuator can achieve an angular resolution of 17.48 µrad and a linear resolution of 2.75 µm. Full article

The unbalanced exciting force of high-speed rotary asymmetric rotor equipment is the main factor causing rotor vibration. In order to effectively suppress the vibration of the asymmetric rotor equipment, the paper establishes a multistage asymmetric rotor coaxial measurement stacking method that minimizes the exciting force. By analyzing the propagation process of the centroid of the multistage asymmetric rotor assembly and analyzing the relationship between the geometric center and the centroid of a single asymmetric rotor, a multistage asymmetric unbalanced rotor propagation model based on geometric center stacking is established. The genetic algorithm is used to optimize the unbalance of the multistage asymmetric rotors. Combined with the vibration principle under the exciting force, the vibration amplitude of the left bearing at different rotation speeds under the minimization of the exciting force and the random assembly phase is analyzed. Finally, the experimental asymmetric rotors are dynamically measured, combined with the asymmetric rotors’ geometric error measurement experiment. The experimental results confirm that the vibration amplitude of the assembly phase with the minimum exciting force is smaller than the vibration amplitude under the random assembly phase at three-speed modes, and the optimization rate reached 73.2% at 9000 rpm, which proves the effectiveness of the assembly method in minimizing the exciting force. Full article