英国ROTORK电动执行器“MOTOR STALLED”故障原因探讨及在线更换方案

2020年,庐江公司#1、#2机组风机共发生3次风机动叶电动执行机构出现无法远控、就地电动操作现象。经检查,电动执行机构本体显示屏触发“MOTOR STALLED”电机堵转报警。本文针对以上问题对英国ROTORK电动执行机构“MOTOR STALLED”发生故障的原因进行分析并针对其在火力发电厂风机动叶电动执行机构在线更换提出可行性方案。

Unsteady Double Wake Model for the Simulation of Stalled Airfoils

In the present work, the recent developed Unsteady Double Wake Model, USDWM, is used to simulate separated flows past a wind turbine airfoil at high angles of attack. The solver is basically an unsteady two-dimensional panel method which uses the unsteady double wake technique to model flow separation and its dynamics. In this paper, the calculated integral forces have been successfully validated against wind tunnel measurements for the FFA-W3-211 airfoil. Furthermore, the computed highly unsteady flow field is analyzed in detail for a set of angles of attack ranging from light to deep stall conditions.

Beijing’s Stalled Traffic

Beijing authorities recently announced the extension of the city’s vehicle restrictions for another year, from April 11, 2009 to April 10, 2010, excluding legal holidays. According to the first round of auto restrictions designed for the Beijing Olympics, private vehicles were banned from roads from 6 a.m. to 9 p.m. daily,

Numerical Investigations on Dynamic Stall Characteristics of a Finite Wing

The paper examines the dynamic stall characteristics of a finite wing with an aspect ratio of eight in order to explore the 3D effects on flow topology,aerodynamic characteristics,and pitching damping.Firstly,CFD methods are developed to calculate the aerodynamic characteristics of wings.The URANS equations are solved using a finite volume method,and the two-equation k-ωshear stress transport(SST)turbulence model is employed to account for viscosity effects.Secondly,the CFD methods are used to simulate the aerodynamic characteristics of both a static,rectangular wing and a pitching,tapered wing to verify their effectiveness and accuracy.The numerical results show good agreement with experimental data.Subsequently,the static and dynamic characteristics of the finite wing are computed and discussed.The results reveal significant 3D flow structures during both static and dynamic stalls,including wing tip vortices,arch vortices,Ω-type vortices,and ring vortices.These phenomena lead to differences in the aerodynamic characteristics of the finite wing compared with a 2D airfoil.Specifically,the finite wing has a smaller lift slope during attached-flow stages,higher stall angles,and more gradual stall behavior.Flow separation initially occurs in the middle spanwise section and gradually spreads to both ends.Regarding aerodynamic damping,the inboard sections mainly generate unstable loading.Furthermore,sections experiencing light stall have a higher tendency to produce negative damping compared with sections experiencing deep dynamic stall.

EFFECT OF AXIAL SPACING ON COMPRESSOR STABILITY

Experimental studies are carried out at a low speed axial compressor with five different rotor/stator gaps. Analysis of the effect of axial spacing of two successive blade rows on the measured mean flow coefficient at stall inception and on the flow range of compressor under multi-cell rotating stall operating conditions proves that the stator can suppress the flow disturbance in the compressor and strengthen the stability of the compressor. Experimental data show that the stall flow coefficient decreases by reducing the axial spacing of successive blade rows. Moreover, by reducing the axial spacing, the stall pattern transition pace from multi-cell stall to single-cell stall can be shifted. And the compressor directly slips into single-cell stall at 21.0% CR axial spacing. By analyzing the pressure fluctuation closed to the surge line, it can be known that there exists an eigenfrequency where the amplitude of the oscillating pressure suddenly and dramatically increases as the compressor runs close to the surge line and this pressure disturbance is relevant to the compressor instability.

Flow Field Improvement by Bowed Stator Stages in a Compressor with Different Axial Gaps Under Near Stall Condition

The outlet flow fields of a low-speed repeating-stage compressor with bowed stator stages are measured with five-hole probe under the near stall condition when the rotor/stator axial gap varies. The performances of the straight stator stages are investigated and compared to those of the bowed stator stages. The results show that using bowed stator stages could alleviate the flow separation at both upper and low corners of the suction surface and the endwalls, and decrease the losses along the flow passage as well as the outlet flow angle. As the rotor/stator axial gap decreases, although the diffusion capacity of the compressor increases obviously, the outlet flow field in the straight stator stages deteriorates quickly. By contrast, little changes occur in the bowed stator stages, indicating that as the rotor/stator axial gap decreases, improved performance is achieved in the bowed stator stages.

Homologous recombination in DNA repair and DNA damage tolerance

Homologous recombination （HR） comprises a series of interrelated pathways that function in the repair of DNA double-stranded breaks （DSBs） and interstrand crosslinks （ICLs）. In addition, recombination provides critical support for DNA replication in the recovery of stalled or broken replication forks, contributing to tolerance of DNA damage. A central core of proteins, most critically the RecA homolog Rad51, catalyzes the key reactions that typify HR： homology search and DNA strand invasion. The diverse functions of recombination are reflected in the need for context-specific factors that perform supplemental functions in conjunction with the core proteins. The inability to properly repair complex DNA damage and resolve DNA replication stress leads to genomic instability and contributes to cancer etiology. Mutations in the BRCA2 recombination gene cause predisposition to breast and ovarian cancer as well as Fanconi anemia, a cancer predisposition syndrome characterized by a defect in the repair of DNA interstrand crosslinks. The cellular functions of recombination are also germane to DNA-based treatment modalities of cancer, which target replicating cells by the direct or indirect induction of DNA lesions that are substrates for recombination pathways. This review focuses on mechanistic aspects of HR relating to DSB and ICL repair as well as replication fork support.

CHARACTERISTICS OF FAN STALLING BASED ON CORRELATED DIMENSIONS

Different from the previous qualitative analysis of linear systems in time and frequency domains, the method for describing nonlinear systems quantitatively is proposed based on correlated dimensions. Nonlinear dynamics theory is used to analyze the pressure data of a contrarotating axial flow fan. The delay time is 18 and the embedded dimension varies from 1 to 25 through phase-space reconstruction. In addition, the correlated dimensions are calculated before and after stalling. The results show that the correlated dimensions drop from 1. 428 before stalling to 1. 198 after stalling, so they are sensitive to the stalling signal of the fan and can be used as a characteristic quantity for the judging of the fan stalling.

Study of future power interconnection scheme in ASEAN

The current energy supply trajectory in the Association of Southeast Asian Nations(ASEAN)region is not sustainable.Factors such as rising standards of living and demographic patterns,including population growth,lead to continuous increase in power demand,which is difficult to meet using limited fossil fuel resources.Thus,a transition toward clean energy sources is needed in the region.While ASEAN member countries are rich in clean energy resources,such resources are located far from demand centers;thus,allocation of clean energy is necessary to increase its utilization.In this study,power demand is forecasted using a combination of prediction methods.A model to evaluate the installed capacity and power exchange potential is proposed to deal with mismatch between the location of the clean energy base and the load center.Furthermore,the concept of cross-regional allocation of clean energy between the ASEAN region,China,and South Asia is presented.A power interconnection scheme among the ASEAN member countries as well as neighboring countries is proposed based on the power exchange potential.The proposed grid interconnection scheme contributes to the utilization of clean energy in the ASEAN region,increasing the proportion of clean energy in the generation mix,which ensures that the region becomes a sustainable and resilient society with a clean and low carbon development route.Furthermore,the proposed power interconnection scheme will generate valuable economic,social,environmental,and resource allocation benefits.

Experimental Study of the Pressure Fluctuations in a Pump Turbine at Large Partial Flow Conditions

Frequent shifts of output and operating mode require a pump turbine with excellent stability. Current researches show that large partial flow conditions in pump mode experience positive-slope phenomena with a large head drop. The pressure fluctuation at the positive slope is crucial to the pump turbine unit safety. The operating instabilities at large partial flow conditions for a pump turbine are analyzed. The hydraulic performance of a model pump turbine is tested with the pressure fluctuations measured at unstable operating points near a positive slope in the performance curve. The hydraulic performance tests show that there are two separated positive-slope regions for the pump turbine, with the flow discharge for the first positive slope from 0.85 to 0.91 times that at the maximum efficiency point. The amplitudes of the pressure fluctuations at these unstable large partial flow conditions near the first positive slope are much larger than those at stable operating condtions. A dominant frequency is measured at 0.2 times the impeller rotational frequency in the flow passage near the impeller exit, which is believed to be induced by the rotating stall in the flow passage of the wicket gates. The test results also show hysteresis with pressure fluctuations when the pump turbine is operated near the first positive slope. The hysteresis creates different pressure fluctuations for those operation points even though their flow rates and heads are similar respectively. The pressure fluctuation characteristics at large partial flow conditions obtained by the present study will be helpful for the safe operation of pumped storage units.

Self-Recirculating Casing Treatment for a Radial Compressor

Casing treatment is a widely employed technique to increase the stall margins of turbomachineries. In the last several decades, many researches on casing treatment have been carded out. However, the mechanism of its expanding stall margins is still not very clear. Till now, most casing teatment schemes are designed for axial compressors, while the investigations on casing treatments in centrifugal compressors are rarely reported. Moreover, current investigation methods mainly focus on experiments, and perfect theoretic al analysis is not yet feasible. In order to study the effectiveness and further the mechanism of casing treatments in centrifugal compressors, in this paper, a computationally based investigation of the impact of the self-recireulating casing treatment on the performance of a radial compressor is carried out. The results indicate that, by casing bleed and injection, the casing treatment with inclined blades in the cavity expands the stall margin most. At low mass flows, the reversed flow through the cavity with inclined blades develops the counter swirl flow in front of the impeller inlet, which is considered to benefit increasing the pressure rise from the injection port to the bleed port and thereby augment the recirculating flow. At 120% design speed, the stall margin is larger than that at the design speed. However, the cost of extending the stall margin is the reduction of isentropic efficiency. A mended casing treatment by shifting the bleed port upstream is also studied. It is demonstrated that, relative to the original casing treatment, this mend can improve the efficiency evidently notwithstanding a little narrowing of the flow range.

Rotor Vibratory Load Prediction Based on Generalized Forces

Three rigid-body-motion DOFs are introduced for the motion of the flap, laghinge and pitch bearing. The rotor blade is discretized using a five-nodes, 15 DOFs beam finiteelement. The dynamic coupling effect between the rigid motion of the blade and the nonlinear elasticdeflections is taken into account. Utilizing the constitutive law of the curvilinear coordinatesystem, the typical moderate deflection beam theory is reformulated. In addition, the Leishman andBeddoes unsteady and dynamic stall model is incorporated and the inflow is evaluated with the freewake analysis. The derived nonlinear ordinary differential equations with time - dependentcoefficients of the rotor blade are given in the sense of the generalized forces. The sectionalloads of the blade and the equations of motion are solved simultaneously in the physical space. Theblade vibratory loads predicted by present analysis show generally fair a-greement with the flighttest data of the SA349/2 Gazelle helicopter.

Lagrangian-based numerical investigation of aerodynamic performance of an oscillating foil

The dynamic stall problem for blades is related to the general performance of wind turbines,where a varying flow field is introduced with a rapid change of the effective angle of attack (AOA).The objective of this work is to study the aerodynamic performance of a sinusoidally oscillating NACA0012 airfoil.The coupled k-ω Menter's shear stress transport (SST) turbulence model and γ-Reθ transition model were used for turbulence closure.Lagrangian coherent structures (LCS) were utilized to analyze the dynamic behavior of the flow structures.The computational results were supported by the experiments.The results indicated that this numerical method can well describe the dynamic stall process.For the case with reduced frequency K =0.1,the lift and drag coefficients increase constantly with increasing angle prior to dynamic stall.When the AOA reaches the stall angle,the lift and drag coefficients decline suddenly due to the interplay between the first leading-and trailing-edge vortex.With further increase of the AOA,both the lift and drag coefficients experience a secondary rise and fall process because of formation and shedding of the secondary vortex.The results also reveal that the dynamic behavior of the flow structures can be effectively identified using the finite-time Lyapunov exponent (FTLE) field.The influence of the reduced frequency on the flow structures and energy extraction efficiency in the dynamic stall process is further discussed.When the reduced frequency increases,the dynamic stall is delayed and the total energy extraction efficiency is enhanced.With K =0.05,the amplitude of the dynamic coefficients fluctuates more significantly in the poststall process than in the case of K =0.1.

岩石电性参数频散特性对阿尔奇公式及Waxman-Smits模型的影响

在12Hz至100kHz频率范围内,测量不同矿化度的含水岩心和不同含水饱和度的含油岩心的电阻率,通常利用幂指数回归的方法,给出阿尔奇公式中的胶结指数m、岩性系数a、饱和度指数n、系数b的频散特性曲线;采用多矿化度方法,给出Waxman-Smits模型中的参数B的频散特性曲线。通过实验分析发现,阿尔奇公式和Waxman-Smits模型中的各参数都存在着不同程度的频散现象,从而使不同频率下的电阻率计算出的含水饱和度的值有所不同。因此在进行储层测井评价时,要根据电阻率测井所应用的测量频率,通过岩石电性参数频散特性的实验研究,选择相应的解释模型参数对岩石电性频散作用引起的差异进行校正。

Stall Flutter Analysis of High-Aspect-Ratio Composite Wing

The stall flutter characters of high-aspect-ratio composite wing are investigated, and the effects of structure geometric nonlinearity and stiffness couple created by composite anisotropy on them also are discussed. Firstly, the high-aspect-ratio wing is modeled as a composite thin-walled closed section Euler beam whose displacement and rotation both could be of finite value, and the nonlinear dynamic equations is build up on it with all the effects of geometric nonlinearity, aerodynamic nonlinearity and anisotropy of material being considered. Then vibration equations are deduced through perturbing the dynamic equations at wing＇s equilibrium position, and coupled with unsteady stall aerodynamic model and ONERA model, to obtain the nonlinear stall flutter analysis equations of wing. Finally, the flutter stabilities with various wind speeds are determined by the harmonic balance method. With several exampies, the validity of the stall flutter model is proved, and the significant effects of geometric nonlinearity on the stall flutter various characters as wall as the effects of ply angle on the stall flutter speed and frequency also are discussed.

A brief review on wind turbine aerodynamics

This article briefly reviews wind turbine aerodynamics, which follows an explanation of the aerodynamic complexity. The aerodynamic models including blade momentum theory, vortex wake model, dynamic stall and rotational effect, and their applications in wind turbine aerodynamic performance prediction are discussed and documented. Recent progress in computational fluid dynamics for wind turbine is addressed. Wind turbine aerodynamic experimental studies are also selectively introduced.

VIBRATION RESPONSE AND ITS CHARACTERISTICS OF CENTRIFUGAL COMPRESSOR WITH ROTATING STALL

Based on the beginning, propagating and ending mechanism of rotating-stallcell, the relation between the pressure history signal and the pressure distribution along rotorcircumference is proposed. The angular velocities of rotating-stall cell propagating are computedfrom time series picked by the pressure probes on a cross section. Self-relation calculatingfiltered the random noise of the pressure history data. The exciting load on rotor is computed byintegral of filtered pressure signal along rotor circumference. By Prohl-Myklestad method, dynamicalequations of rotor system are obtained. The dynamical response of rotor system is resolved by usingMatlab system. Further more, the situation of more than one of stall cells is discussed. Two casesrespectively from the natural gas compressor of some fertilizer plant and the CO_2 compressor ofsome nitrogenous fertilizer plant demonstrate that both methods of calculating the load exerted onrotor by pressure fluctuation and resolving the dynamic response of rotor are available and thecharacteristics of frequency spectrum of rotating stall are correct.

Wet Compression Performance of a Transonic Compressor Rotor at its Near Stall Point

In order to study the effects of wet compression on a transonic compressor,a full 3-D steady numerical simulation was carried out under varying conditions.Different injected water flow rates and droplet diameters were considered.The effect of wet compression on the shock,separated flow,pressure ratio,and efficiency was investigated.Additionally,the effect of wet compression on the tip clearance when the compressor runs in the near-stall and stall situations was emphasized.Analysis of the results shows that the range of stable operation is extended,and that the pressure ratio and inlet air flow rate are also increased at the near-stall point.In addition,it seems that there is an optimum size of the droplet diameter.

Dynamic stall control over an airfoil by NS-DBD actuation

The wind tunnel test was conducted with an NACA 0012 airfoil to explore the flow control effects on airfoil dynamic stall by NS-DBD plasma actuation. Firstly, light and deep dynamic stall states were set, based on the static stall characteristics of airfoil at a Reynolds number of 5.8 × 105. Then, the flow control effect of NS-DBD on dynamic stall was studied and the influence law of three typical reduced frequencies (k = 0.05, k = 0.05, and k = 0.15) was examined at various dimensionless actuation frequencies (F+ = 1, F+ = 2, and F+ = 3). For both light and deep dynamic stall states, NS-DBD had almost no effect on upstroke. However, the lift coefficients on downstroke were increased significantly and the flow control effect at F+ = 1 is the best. The flow control effect of the light stall state is more obvious than that of deep stall state under the same actuation conditions. For the same stall state, with the reduced frequency increasing, the control effect became worse. Based on the in being principles of flow separation control by NS-DBD, the mechanism of dynamic stall control was discussed and the influence of reduced frequency on the dynamic flow control was analyzed. Different from the static airfoil flow separation control, the separated angle of leading-edge shear layer for the airfoil in dynamic stall state is larger and flow control with dynamic oscillation is more difficult. The separated angle is closely related to the effective angle of attack, so the effect of dynamic stall control is greatly dependent on the history of angles of attack.

Experimental study on dynamic stall control based on AC-DBD actuation

To explore AC-DBD's ability in controlling dynamic stall,a practical SC-1095 airfoil of a helicopter was selected,and systematic wind tunnel experiments were carried out through direct aerodynamic measurements.The effectiveness of dynamic stall control under steady and unsteady actuation is verified.The influence of parameters such as constant actuation voltage,pulsed actuation voltage,pulsed actuation frequency and duty ratio on dynamic stall control effect is studied under the flow condition of k=0.15 above the airfoil,and the corresponding control mechanism is discussed.Steady actuation can effectively reduce the hysteresis loop area of dynamic lift,and control the peak drag and moment coefficient.For unsteady actuation,there is an optimal duty ratio DC=50%,which has the best effect in improving the lift and drag characteristics,and there is a threshold of pulsed actuation voltage in dynamic stall control.The optimal dimensionless frequency will not be found;different F+have different control advantages in different aerodynamic coefficients of different pitching stages.Unsteady actuation has obvious control advantages in improving the lift-drag characteristics and hysteresis,while steady actuation can better control the large nose-down moment.