Rotor Experiment Research Articles

A Novel Hybrid Approach to the Diagnosis of Simultaneous Imbalance and Shaft Bowing Faults in a Jeffcott Rotor-Bearing System

Ensuring optimal performance and reliability in rotor-bearing systems is crucial for industrial applications. Imbalances and shaft bowing in these systems can lead to decreased efficiency and increased vibrations. The early detection and mitigation of a rotor’s faults are essential, and model-based fault identification has gained much attention in the manufacturing industry over the years. Over the past two decades, however, the development of fault diagnosis rules with data-driven and artificial intelligence (AI) methods has become a trend, and in the foreseeable future the combination of AI with big data will become mainstream. Nevertheless, the critical role of rotating machinery in manufacturing introduces a challenge, as often insufficient fault data are available. This limitation renders the establishment of diagnostic rules using data-driven methods and AI technologies impractical. In light of these challenges, this study proposes a novel hybrid approach that combines a physical model with machine learning (ML) techniques for the diagnosis of multi-faults (imbalances and shaft bowing are demonstrated) in a Jeffcott rotor. To overcome the lack of real-world labeled fault datasets, a physics-based Jeffcott rotor model is first derived and then used to generate abundant fault datasets for ML. Subsequently, simulated data are employed for the training of an artificial neural network (ANN), enabling the network to learn from and analyze the vast array of generated data. The results prove that a well-trained feed-forward neural network (FNN) can accurately isolate and diagnose imbalance and shaft bowing faults using the simulated and real data from the Jeffcott rotor experiment. These physics-based and ML approaches prove effective particularly for multi-faults, offering new possibilities for advanced rotor system monitoring and maintenance strategies in industrial applications.

Experimental and numerical study of different wing number and flapping-rotation decomposition of a flapping wing rotor unmanned aerial vehicle

The flapping wing rotor (FWR) is a novel aerial vehicle that combines the aerodynamic benefits of both a flapping wing and a rotary wing. By utilizing the passive rotation effect resulting from the flexible deformation of the center symmetric flapping wing, the FWR can enhance its lift force. However, previous research has neglected to explore the mechanism behind the flapping-rotation motion of a flyable FWR, which elucidates its lift advantage compared to conventional flapping motion. Additionally, the impact of varying wing number on the flapping-rotation motion and performance of the FWR has not been taken into consideration. Therefore, it is imperative to conduct an experimental analysis to ascertain the impact of flapping-rotation decomposition and varying wing quantities on FWR. In this study, our prior vehicle design, which exhibited consistent stable hovering and maneuvering capabilities, is employed to construct the flapping wing rotor experiment system. Through this unique experimental system, the effects of flapping-rotation decomposition and different wing quantities on FWR are individually investigated. Additionally, computational fluid dynamics simulation is utilized as an auxiliary and supplementary approach to analyze the aerodynamic characteristics of the flapping-rotation motion. The result proves that the stable flapping-rotation motion does produce a more significant lift increase than the normal flapping motions. Under the premise of stable flapping-rotation motion, more wings will not only produce more lift but also require more driving power. The interactions between the wings also affect the flapping-rotation motion.

Study on enhanced performance of CuFe alloy's eddy current damping and its advantages in multi-mode vibration control of stay-cable

This study presents an innovative solution to address the performance degradation of eddy current dampers (ECD) at high speeds. It replaces the traditional copper conductor with a magnetically and electrically conductive CuFe alloy. The damping force equation for this CuFe alloy-based ECD (CuFe-ECD) is derived and validated through rotor experiments and a simplified finite element model. Results confirm that CuFe alloy enhances damping performance, with CuFe20 exhibiting outstanding quasi-bilinear characteristics, particularly at higher speeds. CuFe10, CuFe15, and CuFe30 also demonstrate similar behavior. The study explores the impact of CuFe alloy properties (conductivity, permeability, and thickness) on the bilinear damping curve. CuFe alloys notably reduce magnetic reluctance, especially in thicker conductors, mitigating skin effect and armature reaction in the electromagnetic field. Finally, the CuFe-ECD is utilized for multi-mode vibration control using the long cable of the Sutong Bridge. The results indicate that the modal damping ratios of modes 1st-20th can reach 5‰, which is superior to other schemes. In high-order modes, the damping ratio of the 35th-40th modes still stabilizes at 3.72–3.90‰. It can be concluded that the bilinear damper has significant advantages in multi-mode vibration control: compared with the single linear damper scheme, it can improve the vibration reduction effect of multi-mode control, and compared with the dual linear damper scheme, it can reduce the number of dampers and achieve better economic benefits.

Continuous daytime and nighttime forecast of atmospheric optical turbulence from numerical weather prediction models.

Future satellite-to-ground optical communication systems will benefit from accurate forecasts of atmospheric optical turbulence; namely for site selection, for the routing and the operation of optical links, and for the design of optical communication terminals. This work presents a numerical approach based on the Weather Research and Forecasting software that enables continuous forecast of the refractive index structure parameter, C n2, vertical profiles. Two different C n2 models are presented and compared. One is based on monitoring the turbulent kinetic energy, while the other is a hybrid model using the Tatarskii equation to depict the free atmosphere region, and the Monin-Obukhov similarity theory for describing the boundary layer. The validity of both models is assessed by using thermosonde measurements from the Terrain-induced Rotor Experiment campaign, and from day and night measurements of the coherence length collected during a six-day campaign at Paranal observatory by a Shack-Hartmann Image Motion Monitor. The novelty of this work is the ability of the presented approach to continuously predict optical turbulence both during daytime and nighttime, and its validation with measurements in day and night conditions.

Constrained layer damping for mitigating vibration of a rotating disk-drum coupled structure

Rotating disk-drum coupled structures are commonly employed in large rotating machines. They are prone to have vibration issues caused by their decreasing thickness to meet lightweight demands. Constrained layer damping (CLD) is a widely used technique to reduce vibrations, but no studies have yet investigated its application on rotating coupled structures. In this paper, a universal model is proposed and experiments are conducted to investigate the influence of CLD on a rotating cylindrical shell ended by an annular disk. This approach considers the rotating effects, and formulates the equations of motion using the Rayleigh-Ritz method with the help of the Sanders shell theory and Mindlin plate theory. Different sets of artificial springs are applied to model the coupling and boundary conditions. The proposed approach is validated by comparing the numerical results with those obtained from modal and rotor experiments. Then the modal parameters and vibration responses are evaluated for different rotational speeds, and the influences of the location and thickness ratio of the CLD patch and the coupling stiffness on the dynamic characteristics of the system are discussed.

Activation of HCA2 regulates microglial responses to alleviate neurodegeneration in LPS-induced in vivo and in vitro models

BackgroundPrevious studies have shown a close association between an altered immune system and Parkinson's disease (PD). Neuroinflammation inhibition may be an effective measure to prevent PD. Recently, numerous reports have highlighted the potential of hydroxy-carboxylic acid receptor 2 (HCA2) in inflammation-related diseases. Notably, the role of HCA2 in neurodegenerative diseases is also becoming more widely known. However, its role and exact mechanism in PD remain to be investigated. Nicotinic acid (NA) is one of the crucial ligands of HCA2, activating it. Based on such findings, this study aimed to examine the effect of HCA2 on neuroinflammation and the role of NA-activated HCA2 in PD and its underlying mechanisms.MethodsFor in vivo studies, 10-week-old male C57BL/6 and HCA2−/− mice were injected with LPS in the substantia nigra (SN) to construct a PD model. The motor behavior of mice was detected using open field, pole-climbing and rotor experiment. The damage to the mice's dopaminergic neurons was detected using immunohistochemical staining and western blotting methods. In vitro, inflammatory mediators (IL-6, TNF-α, iNOS and COX-2) and anti-inflammatory factors (Arg-1, Ym-1, CD206 and IL-10) were detected using RT-PCR, ELISA and immunofluorescence. Inflammatory pathways (AKT, PPARγ and NF-κB) were delineated by RT-PCR and western blotting. Neuronal damage was detected using CCK8, LDH, and flow cytometry assays.ResultsHCA2−/− increases mice susceptibility to dopaminergic neuronal injury, motor deficits, and inflammatory responses. Mechanistically, HCA2 activation in microglia promotes anti-inflammatory microglia and inhibits pro-inflammatory microglia by activating AKT/PPARγ and inhibiting NF-κB signaling pathways. Further, HCA2 activation in microglia attenuates microglial activation-mediated neuronal injury. Moreover, nicotinic acid (NA), a specific agonist of HCA2, alleviated dopaminergic neuronal injury and motor deficits in PD mice by activating HCA2 in microglia in vivo.ConclusionsNiacin receptor HCA2 modulates microglial phenotype to inhibit neurodegeneration in LPS-induced in vivo and in vitro models.

Analysis of the dry whirl and dry whip response in a vertical active magnetic bearing drop test rig

A horizontal rotor is usually the research subject of rotor drop failure in active magnetic bearing (AMB) test rigs. However, research shows, that a vertical rotor drop failure is not sufficiently understood at present. The experiments in other research studies show that the vertical rotor dynamic response is not simple whirl behavior after dropping on the touchdown bearing (TDB), which concludes dry whirl and dry whip processes, where the former is synchronous forward whirl, and the latter is subsynchronous forward whirl. To predict the dynamic response of a vertical rotor drop failure, theoretical research based on a rotor-TDB model system is developed in this paper, and the effectiveness of this model is validated by an AMB-TDB rotor experiment. The conclusion is that the natural whirl speed and the resulting critical speed clearly distinguish two states of forward whirl motion. When the rotation speed is less than the critical speed, the rotor is in a dry whirl state; otherwise, it behaves as in a dry whip. The rotor unbalance is introduced in the model, which explains the change in the whirl speed. Moreover, the influencing factors on the natural whirl speed are analyzed in depth. The result shows that parameters of the TDB, such as the friction coefficient and protective clearance, and the rotor unbalance have significant effects.

Simulations of Mesoscale Flow Systems around Dugway Proving Ground Using the WRF Modeling System

It is widely recognized that regions with complex heterogeneous topography and land-use properties produce a variety of diurnal mesoscale and microscale flows, which can be modified or even masked by significant large-scale synoptic forcing. These flows can be produced through both dynamic and thermal-forcing processes. Recent field programs such as the Terrain-induced Rotor Experiment (T-REX), Mountain Terrain Atmospheric Modeling and Observations Program (MATERHORN), and Perdigao have been used to observe and model flow behaviors under different topographical and large-scale meteorological conditions. Using the Advanced research version of the Weather Research and Forecast (WRF-ARW) model, we applied multi-nesting using an interactive one-way nesting approach to resolve to a sub-kilometer inner-grid spacing (0.452 km). Our interest was in the intensive observation period 6 (IOP6) of the Fall 2012 MATERHORN campaign conducted over Dugway Proving Ground (DPG) in Utah. An initial review of the IOP6 suggested that a range of diurnal flows were present, and that a relatively small subset of model setup configurations would be able to capture the general flows of this period. The review also led us to believe that this same subset would be able to capture differences due to variations in choice of model boundary-layer physics, land surface physics, land use/soil type specifications, and larger-scale meteorological conditions. A high model vertical resolution was used, with 90 vertical sigma levels applied. The IOP6 spanned the period of 2012 0800 UTC 14 October–0800 UTC 15 October. Based upon a lack of deep convection and moist microphysics throughout IOP6, we included comparison of planetary boundary layer (PBL) turbulence parameterization schemes even at the sub-kilometer grid spacing. We focused upon the gross model performance over our inner nest; therefore, a detailed comparison of the effects of model horizontal resolution are excluded. For surface parameters of wind and temperature, we compare mean absolute error and bias scores throughout the period at a number of surface meteorological observing sites. We found that despite attention given to the boundary layer turbulence physics, radiation physics and model vertical resolution, the results seemed to indicate more impact from the choices of thermal soil conductivity parameterization, land surface/soil texture category classification (and associated static property-parameter values), and large-scale forcing model. This finding lends support to what other researchers have found related to how these same forcings can exert a strong influence upon mesoscale flows around DPG. Our findings suggest that the two nights of IOP6 offer a pair of excellent consecutive nights to explore many of the forcing features important to local complex terrain flow. The flows of interest in this case included valley, anabatic/katabatic, and playa breeze systems. Subjective evidence was also found to support an influence provided by the modest synoptic northwesterly flow present within the lower troposphere (mainly on the night of 14 October). Follow-on research using the WRF-ARW capability to nest directly from mesoscale-to-LES can leverage IOP6 further. For example, to uncover more detailed and focused aspects of the dynamic and thermodynamic forcings contributing to the DPG diurnal flows.

Power fluctuation and wake characteristics of tidal stream turbine subjected to wave and current interaction

Turbulence and waves interactions are present in tidal streams ensuing the poorly comprehended unsteady state. To clarify several aspects of the wave influence on the flow and turbine power output, the 1:60 scale rotor experiments (Froude similarity) are carried out: current only and with parallel waves. Compared to steady predictions, the mean power in current and with waves against a range of rotor speeds are analogous. The power spectrum under wave conditions is almost a superposition of current and additional components, including wave frequency, rotation frequency, and their mixing frequency. The waves distort significantly the operating flow, by augmenting the turbulent intensity, wake rotation, anisotropy, and Reynold stresses, both in large proportion with the wave energy flux. The mean wake recovery was analogous, with deficits following symmetrical distributions of diminishing height longitudinally. Strikingly, the turbulence in the undisturbed flow resembles mostly near the pancake shape. This transitions towards the cigar-shaped in both most of the stream tube due to the turbine obstruction, and of the channel with the wave introduction. Further studies are required to validate these findings on non-isotropy and non-homogeneous effects in other wave conditions, such as a range of frequencies, heights and incident directions.

Assembly accuracy prediction and optimization of aero-engine rotor under the separation condition of assembly and measurement

The measurement and assembly of the aero-engine rotor are separated from each other, which makes it difficult to keep the assembly datum consistent with the measurement datum; the existence of the datum error will cause the characteristic matrix to fail to truly reflect the geometric state of the rotor itself and cause the assembly model to be inaccurate, then ultimately affect the assembly accuracy prediction. Combined with the fact that the geometric characteristics of parts/components are not related to the measurement datum, the datum error elimination method has been proposed which makes the rotor characteristic matrix and assembly model more accurate, thereby improving the prediction effect of assembly accuracy. At the same time, the proposed direct optimization strategy is more efficient than the traditional genetic algorithm. The assembly experiment of the aero-engine rotor shows that the model and method proposed in this paper can better reflect the geometric characteristics of the rotor itself and are beneficial to reduce the coaxiality of the front and rear fulcrum. The related research also has reference significance for other large-scale and high-precision mechanical product assemblies.

Perpendicularity Detection of Multistage Rotor Considering Compensation of Datum Error

Perpendicularity is an orientation tolerance, and the perpendicularity of end face can be utilized to assess the axial assembly precision of multistage rotor. The aim of this article is to detect the perpendicularity and parallelism of rotor using turntable-rotating approach. The misalignment between datum system of rotor and measurement datum of turntable will introduce the datum error, which is difficult to be thoroughly eliminated by the mechanical device of centering and leveling. To ensure that each measurement is carried out in the same datum system of rotor, the residual error of tilt and eccentricity between two datum systems is studied and compensated. The direction of assessment datum axis of rotor perpendicularity is determined by rotor axis rather than extrinsic measurement datum e.g. turntable axis. The experiment of rotor is performed to verify the effectiveness of the presented detection approach. The difference and relationship between rotor perpendicularity and parallelism are investigated and discussed. It is recommended that parallelism and perpendicularity should be considered together to fully reflect the axial geometric tolerance of rotor. The presented approach is general, which can also be conveniently utilized to detect axial geometric tolerances of other rotating components. For example, compressor rotor, motor rotor, gas turbine rotor, etc.

The Improvement of Performance through Minimizing Scallop Size in MEMS Based Micro Wind Turbine.

In this paper we report on the improvement of performance by minimizing scallop size through deep reactive-ion etching (DRIE) of rotors in micro-wind turbines based on micro-electro-mechanical systems (MEMS) technology. The surface profile of an MEMS rotor can be controlled by modifying the scallop size of the DRIE surface through changing the process recipe. The fabrication of a planar disk-type MEMS rotor through the MEMS fabrication process was carried out, and for the comparison of the improvements in the performance of each rotor, RPM testing and open circuit output voltage experiments of stators and permanent magnets were performed. We found that the smooth etching profile with a minimized scallop size formed using DRIE results in improved rotation properties in MEMS-based wind turbine rotors.

Doppler effect in rotating systems and Mössbauer rotor experiments

We address once more the problem of the physical interpretation of the Mössbauer effect in a rotating system in the view of the recently discovered extra energy shift (EES) between emitted and absorbed resonant radiation, which emerges in addition to the usual second order Doppler shift for an orbiting absorber. We highlight that both fractional components of the total energy shift have the same sign and correspond to the blueshift of the resonant radiation propagating from the rotational axis to the rotor rim. We indicate a possible way of understanding the origin of the EES in terms of combining metric effects in rotating systems with the quantum mechanical description of resonant nuclei confined in crystal cells by taking into account the recoil-free essence of the Mössbauer effect, where no energy is transmitted to the source (absorber) during the emission (absorption) of resonant radiation.

Investigation on the aerodynamic interaction between a rotor and ship with opened hangar door

Unsteady aerodynamic interference between a rotorcraft and a ship occurs during shipboard launch and recovery operations and has a negative impact on the safety. An experiment of a reduced-scale model rotor and a CFD analysis in hover was carried out to investigate the performance and flow field of a rotor approaching a ship. In this paper, the thrust and pitching moment of the rotor hovering above the ground, deck were tested, and the influence of hangar door on the thrust, pitching moment, and flow field was also measured. A CFD method based on RANS and overset technology was used to investigate the flow field of the rotor operating on the model-scale ship. As the rotor approaches the deck, its thrust first decreases induced by a recirculation near the deck, and then increases induced by the effect of deck, and finally obviously decreases caused by the recirculation near hangar door. The deck and hangar door also affects the flow field to yield an intensive nose-down pitching moment. The status of the hangar door has a significant influence on the rotor thrust and pitching moment. The recirculation is weakened with an opened hangar door resulting in recovery of the rotor thrust and decrease of the nosed down pitching moment.

Comparison of traditional and synchrotron beam methodologies in Mössbauer experiments in a rotating system.

Recent Mössbauer experiments in a rotating system reported by others in the literature have involved the application of synchrotron radiation onto a spinning semi-circular resonant absorber. Here, the physical interpretation of these methodologies, and their alleged performance improvement, is analyzed in the light of our own team's past experience based instead on the traditional laboratory setup. It is shown that a number of fundamental shortcomings in the approach reported in the literature deprives it of any practical significance with respect to the improvement of the technique of Mössbauer rotor experiments with a synchrotron source. It is concluded that, at present, only Mössbauer experiments relying on an ordinary compact source of resonant radiation and a resonant absorber both fixed on the rotor promise to provide crucial information with respect to the physical origin of the observed energy shift between emitted and absorbed resonant radiation in a rotating system.

Comment on “Analyses of Mössbauer Experiments in a Rotating System: Proper and Improper Approaches” [Annals of Physics Volume 418, July 2020, 168191

The notion of classical well localized trajectories of a single photon in Minkowski spacetime does not make any rigorous sense by the well-known existence of a proof that single photons cannot be well localized. This leads to principal difficultness when photodetection probability on relativistic non inertial frame of reference is considered. In order to resolve this tension, we extend canonical Minkowski geometry up to relevant point-free Minkowski geometry [Ann. Physics 423 (2020) 168329]. The photodetection probability density on uniformly rotating frame endrowed with point-free Lorentzian geometry is obtained. The result of S. A. Podosenov et al. [Ann. Physics 413 (2020) 168047] is obtained without any reference to unphysical notion of the classical trajectories of photon. The paper again shows the correctness of the remarkable result of Prof. C. Corda concerning the Mossbauer rotor experiment as new proof of general relativity, which has been awarded by the Gravity Research Foundation. In addition, the paper also shows various very elementary mistakes, misunderstandings and flaws by the self-called “YARK group”, which is a group of fringe researchers who attempts to promote wrong science, in particular, against the relativity theory.

Cuckoo Search Algorithm for Multi-Objective Optimization of Transient Starting Characteristics of a Self-Starting HVPMSM

The starting and synchronization process of high-voltage permanent magnetic synchronous motors (HVPMSM) is a complex electromechanical transient problem. This paper proposes a multi-objective five-dimensional optimization method for starting characteristics of HVPMSM based on quadratic response surface models (QRSM) combined with Cuckoo search algorithm. Eighty-nine sets of transient finite element models were developed. To obtain starting current, starting time, starting torque and torque ripple, the transient process of HVPMSM is calculated with different cage bar width, cage bar depth, cage bar conductivity, and slot wedge conductivity. Steady-state and locked rotor experiments are conducted to verify the accuracy of the FEA. Then, the Cuckoo search method is employed to optimize design parameters achieved by the finite element models to obtain the minimum starting current, the maximum starting torque, the shortest starting time, and the minimum torque ripple, while maintaining high output performance and low cost. The results demonstrate that QRSM combined with Cuckoo search algorithm accurately describe the non-linear relationship between the structural characteristics, material properties and output performance of the HVPMSM. The best solutions are consistent with the results of the finite element analysis. In addition, the theoretical method is verified by experiments.

Examining relationships between entrainment-driven scalar dissimilarity and surface energy balance underclosure in a semiarid valley

A surface energy budget underclosure, equivalent to an undersampling of sensible and latent heat fluxes at the surface, is commonly observed in the daytime convective boundary layer over land. The two mechanisms currently held responsible for such underclosure are, on one hand, entrainment-induced reduction of heat fluxes due to low-frequency circulations spanning the depth of the convective boundary layer, and on the other hand, horizontal advection effects induced by surface horizontal heterogeneity. Given the involvement of both heat fluxes in the budget equation, it is expected that the turbulent perturbations of variables involved in these fluxes (potential temperature θ′ and specific humidity q′) contain the signature of both mechanisms. Here, we assess to what extent non-local entrainment effects contribute to the budget underclosure in complex terrain using a quadrant analysis and multiresolution flux decomposition approach.We use data collected in the semi-arid Owens Valley, CA, USA, during the Terrain-Induced Rotor Experiment (T-REX) campaign. The budget components are sampled near the surface of the valley floor and the adjacent slope, with turbulence flux measurements, pyranometers, pyrgeometers, as well as ground heat flux measurements. We found that the budget underclosure was within the range of underclosures reported in past studies, with a systematically poorer closure over the valley slope. Although quadrant analysis revealed a dominance of scalar-similar events, associated with convective boundary layer overturning, a high degree of disagreement was found between the scalar-dissimilar quadrants which represent the counter-gradient motions. Specifically, those turbulent motions associated with entrainment of free tropospheric air to the surface, were found to be of minor importance in degrading scalar similarity. Instead, we postulate that local horizontal advection and hectometre-scale land-use heterogeneity in the vicinity of both the valley floor and slope sites, are the major factors in controlling the relationship between the budget underclosure and scalar similarity.

Iterative Blade Element Momentum Theory for Predicting Coaxial Rotor Performance in Hover

This paper presents a new blade element momentum theory (BEMT) for a coaxial rotor in hover. The new BEMT iteratively solves the upper and lower rotor induced velocities to account for the mutual rotor-to-rotor interaction. The upper rotor induced velocity is affected by the lower rotor thrust and induced velocity, whereas the lower rotor induced velocity is affected by the upper rotor thrust and induced velocity. Two empirical constants are included in each rotor calculation. This new BEMT provides the performance of each rotor as a function of the rotor separation distance. The new BEMT is validated with measurement data for two coaxial rotor experiments. The first experiment validates the thrust to power coefficients at a given separation distance. The second experiment validates each rotor's figure of merit, thrust, power, interference loss factors, etc. as a function of the rotor separation distance. It is shown that the BEMT captures the trends and magnitudes of the performance as a function of the rotor separation distance compared to the measurement data. Detailed radial distributions of aerodynamic properties are also presented at several separation distances.

The applications of POD method in dual rotor-bearing systems with coupling misalignment

In this paper, the proper orthogonal decomposition (POD) method is first time apply to the dimension reduction of dual rotor-bearing experiment rig which is similar to an aero-engine rotor. The basic theory of the POD method and the application in dynamical system are introduced. The supporting bearing nonlinearity and the coupling misalignment of high and low pressure rotors are considered, and the dynamical model is established by finite element method based on dual rotor experiment rig. The frequency behaviors of dual rotor-bearing coupling misalignment response are discussed via comparing the numerical and experiment results to verify the efficiency of the model. The POD method is used for dimension reduction of rotor-bearing system, and the dynamical behaviors of the reduced-order model (ROM) are compared with the full order system (FOM) and experiment to verify the higher computational efficiency and accuracy of the POD method. These results in this paper can provide engineering guidance to actual dual rotor-bearing system with coupling misalignment fault.