Changes In Rotational Speed Research Articles

Numerical study of transmission shafts dynamics in motion modes when the rotation speed changes

Numerical study of transmission shafts dynamics in motion modes when the rotation speed changes

Study of Permanent Magnet Synchronous Motor With LQG Controller and Observer On The Hydraulic Pump System

In today's aircraft industry, the flight control system and landing gear system cannot be separated from the role of the hydraulic technology system. As the prime mover of the hydraulic pump or actuator hydraulic system, a permanent magnet synchronous motor (PMSM) is used. This PMSM is a substitute for the role of conventional combustion engines, and PMSM is considered to have several advantages in increasing performance and efficiency. This research will develop a system to find parameter values for Linear Quadratic Gaussian (LQG) controllers in a hydraulic pump system that is installed as a load from PMSM and then observe and analyze the performance of the response of the synchronous motor system, namely in the form of changes in rotor rotation speed, torque electric power, and stator current on the q-axis. The results of the research on the characteristics of the PMSM implemented in the hydraulic pump system show that the LQG controller is more optimal when compared to the observer controller. The LQG controller is known to have a faster transient response, which is indicated by the value of the settling time improvement at no load, namely 116.67% for the observer controller and 364.705% without the controller. Then when the synchronous motor serves the nominal load, the rotational speed of the rotor produced in the steady state becomes 8.29% faster than the observer controller and 74.49% without the controller. This rotor's rotational speed affects the time the actuator needs to extend and retract motion.

RESEARCH ON THE FLUID-INDUCED EXCITATION CHARACTERISTICS OF THE CENTRIFUGAL PUMP CONSIDERING THE COMPOUND WHIRL EFFECT

In order to study the correlation mechanism between the flow characteristics and the fluid-induced force under the compound whirl motion in the centrifugal pump, the RNG k-ε model is selected in this paper to simulate a low specific speed centrifugal pump with impeller eccentricity based on the N-S equation. The changes of fluid-induced force with impeller eccentricity and the unsteady flow characteristics of the internal flow field of centrifugal pump under different flow conditions and rotation speeds are investigated, and the relationship between the fluid-induced force of the impeller and the internal flow field characteristics is discussed. The results show that the trend of fluid-induced force and the pressure coefficient is similar. When the rotation speed changes and when the flow is similar, the pressure coefficient under different rotation speeds almost coincides. With the increase of impeller speed and impeller eccentricity, the dynamic and static interferences between the impeller and the volute tongue are more significant, the uneven distribution of the pressure around the impeller makes the internal flow of centrifugal pump more disordered and increases the fluid-induced force near the volute tongue. The research results can provide important reference value for accurately grasping the internal flow excitation principle of the centrifugal pump.

Varying rotational speeds and their effect on the mechanical properties of friction stir welded 6082-T651 aluminium alloy plates

The need to understand the effects of varying rotational speeds on the mechanical properties of Friction Stir Welded 6082-T6 aluminium alloy plates motivated this study. The rotational speeds used were influenced by the capabilities of the Friction Stir Welding machine used. The lowest rotational speed used on the machine was 680 rpm followed by 780 rpm and 900 rpm respectively. The rotational speed is the rate at which the welding tool rotates around its axis and is one of the most important parameters in Friction Stir Welding. Speeds are related to processing temperature which influences the underlying physical conditions of the material. The changes in rotational speeds had an influence on the resulting mechanical properties. The change in rotational speed affected heat distribution in the weld area causing changes in the ductility of the Heat Affected Zone (HAZ) which affected weld behavior during mechanical testing and how these failed during testing. The optimal welding rotational speed was obtained during the welding of 6082-T6 aluminium alloy plates used in this study. This observation is also backed by mechanical evaluation done on friction stir welded plates used and results compares to work of other researchers in the field. In terms of hardness, in the weld area, the optimum speed had a higher average hardness distribution in the weld area. Heat distribution in the weld area caused changes in the ductility of the Heat Affected Zone (HAZ) and this was proven during tensile testing. Vickers hardness across the weld area revealed changes in the hardness of the base metal and the weld area. Changes in tensile strength due to changes in rotational speed are also documented and reported on. The plunge depth, tilt angle and welding speed were kept constant throughout the duration of the welding procedure. This made it easier to analyze and compare the resulting changes in the properties of Friction Stir Welded 6082-T651 aluminum alloy plates.

Generator Out-of-Step protection using the trajectory of estimated relative speed

The condition where the load angle of a generator changes rapidly with respect to another generator or portion of a system is called Generator Out-of-Step (OOS). The traditional way of detecting an OOS condition is to analyze the trajectory of the impedance seen from the generator terminals. Therefore, setting calculations for these impedance-based methods become more challenging and time consuming. Detailed time domain simulations, which required both generator and system data, are necessary to set up these relays. This paper proposes a novel method to detect an OOS condition of a generator using its relative rotor speed. The inputs for the proposed algorithm are the terminal voltage, current and machine parameters which are readily available for typical synchronous generators. The proposed algorithm monitors the change of relative rotor speed following a fault and declares the OOS condition if the relative speed tends to increase during a swing cycle. This technique is computationally simple, easy to implement, and fast compared to impedance-based methods. The application of the proposed method is investigated using time domain simulations. Also, the sensitivity and security of the proposed method are analyzed under various power system conditions.

Nonlinear dynamics analysis of rotor system

In order to get the motion of the disc core and bearing in the rotor system, the nonlinear dynamic model was established. The influence of the disc core and bearing under the action of different rotor speeds and different bearing clearances is analyzed by numerical calculation. The results show that the change of rotor speed will not have a great impact on the disc center, will affect the movement cycle and amplitude, which will have a slight impact on the bearing. The increase of clearance will change the overall movement of the disc center, especially in the initial stage of the system, which will have a greater impact on the bearing.

Study on Segregation and Heat Transfer of Polydisperse Particles in a Three-Dimensional Rotating Drum by Using the DEM

The segregation and heat transfer of polydisperse particles in the rotating drum have an important impact on many industrial fields, and the theory is not completely clear. Based on the verified discrete element method model, the segregation and heat transfer of polydisperse particles in the rotating drum indirectly heated by the side wall are studied. The results show that the polydisperse particles form the segregation structure of the radial core and axial band in the rolling regime rotating drum. The comparison with monodisperse particles indicates that the heat transfer of polydisperse particles is influenced by the segregation structure. Small changes in rotation speed and filling level in the rolling regime do not alter the particle segregation and heat transfer structure. The addition of lifters is an effective means to reduce particle segregation and improve the heat transfer effect. This work provides a reference for revealing the segregation and heat transfer theory of polydisperse particles in the rotating drum.

Spatial and temporal features of cavitation in micropump by dynamic mode decomposing

This study investigates the spatial and temporal features of micropump cavitation. The numerical model is based on the k-Epsilon turbulence model and the Zwart cavitation model. Cases with different rotation speeds and flow volumes are carried out experimentally to validate the numerical model by changing rotation speed and flow rate separately. The periodic to chaos cavitation is observed by varying the cavitation number. Spatial modes of cavitation on the blade are identified by the dynamic mode decomposing. The frequencies of those modes are also obtained. The most energetic modes are presented and discussed. Cavitation of micropump on the suction side of the blade experiences growing, breaking, and shedding. With the decrease of cavitation number, the cavitation occurs at the leading-edge part, the middle part, and the entire blades. The leakage of cavitation can result in the interaction between cavitation between neighboring gaps of blades and the symmetrical distribution. The results also show that with the increase of cavitation number, there exists a downshift of frequency, and the bump point of the blade can influence the cavitation significantly.

DC Voltage Output Control of a Hybrid Synchronous Generator-based Wind Turbine

This article discusses regulating a Wind Turbine (WT) that uses a Hybrid Excitation Synchronous Generator (HESG) to power an isolated load via a diode bridge rectifier. The HESG acts as a DC generator and supplies power to the DC load. The primary objective of the suggested control strategy is to maintain a steady DC voltage output, even when there are changes in rotor speed and/or load. The entire system is simulated and modelled in Matlab/Simulink, and the simulation results prove the effectiveness of the proposed method in delivering power to an isolated location.

Optimasi Daya Generator Angin Melalui Pitch Angle Control dengan Particle Swarm Optimization dan Genetic Algortihm

In optimizing the power of the wind turbine generator (WTG) due to fluctuating wind speed, the pitch angle control is used on WTG. The pitch angle has a great influence towards the rotational speed change of the WTG. The pitch angle value is in the range of 0-90 degrees. The optimal value of the pitch angle can produce the maximum power output from the wind turbine generator. Because the pitch angle value changes with wind speed, the optimization method is carried out using Particle Swarm Optimization (PSO) method and Genetic Algorithm (GA) optimization method. By using these two methods optimally, the optimal pitch angle will be obtained dependant on changes in wind speed.

Direct Torque Control (DTC) Design With Fuzzy Sugeno-Proportional Derivative for 3-Phase Induction Motor Speed Control

In general, in the industrial world, induction motors are more widely used than direct current motors, due to the characteristics of induction motors that are sturdy, reliable, easy to maintain, and relatively inexpensive. The phenomenon of changing rotational speed when the load changes results in regulation of the speed of the induction motor, which risks slow response time, there is overshoot which should still be minimized, and there are disturbances caused by external environmental factors, so that a controller is needed that is able to work effectively to optimize performance. 3 phase induction motor. The purpose of this study is to design a sugeno-PD fuzzy DTC controller, where the DTC provides a fast and strong response mounted on an AC motor. Fuzzy Sugeno provides a short calculation time and its reasoning includes wide enough data and PD to speed up the response time results. So that the proposed method produces an induction motor rotating speed according to the given setpoint of 100 rad/s with a settling time of 0.45 seconds, a rise time of 0.2 seconds and no steady state error. From the state of the plan output response before being given the controller there is a steady state error of 5 rad/s, a maximum overshoot of 5.4111%, a settling time of 0.1554 seconds and a rise time of 0.1554 seconds

Study on gear meshing power loss calculation considering the coupling effect of friction and dynamic characteristics

Gear transmission system is widely used in many mechanical equipment to achieve power transmission and rotational speed changes. Meshing power loss is one key index to assess the performance of a gear system, which directly influences heat generation and lubrication, etc. Over the past decades, many computational models of gear meshing power loss have been proposed to support gear design and optimization. However, the coupling effect between the gear friction and dynamic characteristics are usually ignored, including time-varying meshing stiffness (TVMS) and dynamic meshing force (DMF), which are not conducive to accurate calculation and improvement of meshing power loss. Therefore, an improved gear meshing power loss calculation method is proposed to settle this problem in this paper. With the proposed method, the friction calculation model is established considering the effect of DMF and surface roughness based on mixed elastohydrodynamic lubrication (EHL). Then the TVMS is obtained with the friction force along the meshing line and DMF was taken into consideration. On the basis of modelling of friction and TVMS, a six degrees-of-freedom (DOF) gear dynamic model, as well as a power loss iteration calculation process are established and studied. The effects of gear surface manufacturing quality and loads on power loss are analyzed. Furthermore, a gear meshing power loss experimental setup is constructed to verify the effectiveness of the proposed method. The results show that this method is in better agreement with the experimental results than the traditional method which does not consider the coupling effects.

Leakage Flow Impact on Shrouded Stator Cavity Flow Topology and Associated High-Speed Axial Compressor Stage Performance

AbstractThis paper presents the investigation of realistic cavity leakage flow for the von Karman Institute for Fluid Dynamics H25 axial compressor stage, equipped with a shroud cavity of average Reynolds number Rer = 2.2 * 106 and average aspect ratio G = 0.06. On top of overall performance measurements, time averaged data from unprecedented experimental dataset are used to characterize the stator hub shroud cavity flow field and its interaction with the power stream. The sensitivity of the stage performance and stability as well as the cavity flow topology is evaluated against injection conditions, compressor throttling, and compressor speed. Parametric steady RANS simulations of the stage under injection are used to support the findings and state on the relevance of such approach in the preliminary design phase of axial compressor components. As an example, a stage efficiency reduction of 0.97% for a leakage fraction of 0.56% at design point is retrieved. This performance drop is attributed to the effect of cavity flow on: the blockage ratio, the boundary layer skewness, and total temperature increase at stator row inlet. It is also presented that there is a mutual interaction between the cavity geometry and the cavity flow field organization. The injection homogenizes the cavity flow field and the associated pressure gradient. The various operating conditions presented also demonstrate that the cavity flow studied is, on average (i.e., time), sensitive to changes in compressor rotation speed and changes in stage loading.

Research on the along-wind aerodynamic damping and its effect on vibration control of offshore wind turbine

The aerodynamic damping of the offshore wind turbine structure (OWT), which can be divided into along-wind aerodynamic damping and across-wind aerodynamic damping, is complex, changeable and closely related to the operation status of the wind turbine, the adopted control strategy and the wind speed. Further, the along-wind aerodynamic damping always plays a significant role in an operational OWT, which can effectively mitigate the dynamic response of the OWT structure. In this research, a new theoretical calculation method of the along-wind aerodynamic damping was firstly derived considering the contributions resulted from the changes in rotor speed with respect to wind speed. Then, this new proposed theoretical calculation process was verified by the simulation method in open-source software FAST and the parameters, which affect the along-wind aerodynamic damping such as wind speed, rotor speed and pitch angle, were also investigated. It is shown that the along-wind aerodynamic damping increases as the value of above influencing factors increases until the rotor speed approaches the rated rotor speed and the pitch angle is greater than the critical angle. Finally, the effect of aerodynamic damping on the performances of tuned mass damper (TMD) for an 5 MW OWT under operational condition was studied. The results demonstrate that the effectiveness of TMD is weakened with the increase of aerodynamic damping. Specifically, when the along-wind aerodynamic damping of the 5 MW OWT increases from 4.97% to 6.87%, the additional damping of the TMD decreases from 7.301% to 6.386%.

Performance Analysis of the Cylinder Gas Film Seal between Dual-Rotor Reverse Shafts Considering Lubrication and Centrifugal Expansion Effects

The cylinder gas film seal between dual-rotor reverse shafts is a new method for sealing aircraft engines that has excellent developmental prospects. We propose a novel method for determining if the sealing ring is fully fluid-lubricated using the average Reynolds equation. Considering surface roughness and centrifugal expansion, we calculated the dynamic pressure, gas film force and friction power consumption with and without inlet pressure differences for each of the four rotation modes. The gas film’s dynamic pressure effects were weakest when the dual rotors rotated in a reverse direction (Mode 3), with or without differences in inlet pressure, since solid contact is most likely to occur under counter-rotation. When the dual rotors were in counter-rotation with an inlet differential pressure of 80 kPa and fixed inner and outer rotor speeds (e.g., 3000 rpm), we calculated the minimum sealing ring film thickness, leakage rate, friction power consumption and gas film force. Changes in outer rotor speed greatly influenced the minimum film thickness and the sealing ring’s performance. Meanwhile, changes in the inner rotor speed had little influence on the minimum film thickness and sealing ring’s lubrication performance. When the speed difference was fixed and the sealing ring was fully fluid-lubricated, lubrication performance changes were mainly affected by changes in centrifugal expansion caused by the outer rotor speed. Given a fixed rotor speed and under dual-rotor counter-rotation, we calculated the effects of inlet differential pressure changes on minimum gas film thickness, leakage rate, friction power consumption, gas film force and other sealing performance variables. Leakage rate and the friction power consumption increase as inlet differential pressure increases. Our results provide a theoretical reference for avoiding solid contact of the cylinder seal between dual-rotor reverse shafts.

Non-linear dynamics and stability of rolling bearing–axle coupling system of a railway freight wagon with the change of axle rotating speed

PurposeThe purpose of this paper is to investigate the non-linear characteristics and stability of the rolling bearing–axle coupling system under the excitation of the axle/wheel speed of railway freight cars, so as to put forward a rationale for judging the vibration law and running stability of railway freight wagon.Design/methodology/approachConsidering the effects of eccentric force of the railway wagon axle, the non-linear resistance of the wagon and non-linear support forces of axle box rolling bearings, a centralized mass model of rolling bearing-axle coupling system of railway freight wagon is presented on the basis of the theory of rotor dynamics and non-linear dynamics. Then the Runge-Kutta method is adopted to solve the non-linear response of the proposed system, and numerical simulation including bifurcation diagrams, axis trajectory curves, phase plane plots, Poincaré sections and amplitude spectras are analysed when the axle rotating speed is changed. Meantime, the relation curve between Floquet multiplier and axle rotating speed, which affects the stability of coupling system, is plotted by numerical method based on the Floquet theory and method.FindingsThe simulation results of the dynamic model reveal the abundant dynamic behaviour of the coupling system when the axle rotating speed changes, including single period, quasi period, multi-period and chaotic motion, as well as the evolution law from multi-period motion to chaotic motion. And especially, the bearing–axle coupling system is in stable state with a single period motion when the axle rotating speed changes from 410 rpm to 510 rpm, in which the running speed of railway freight wagon is changed from 62 km/h to 80 km/h, the vibration displacement of the coupling system in X direction is between 1.2 mm and 1.8 mm, and the vibration displacement of the coupling system in Y direction is between 1.0 mm and 1.45 mm. Meanwhile, the influence law of axle rotating speed on the stability is obtained by comparing the bifurcation diagram and Floquet multiplier graph of the coupling system.Originality/valueThe numerical simulation data obtained in this study can provide a theoretical evidence for designing the running speed of railway freight wagon, utilizing or controlling the non-linear dynamic behaviours of the proposed coupling system, and ensuring the stability of railway freight wagons.

Experimental investigation of instability inception on a transonic compressor under various radial distributions of loading

The radial distribution of blade loading could be various due to the inlet distortion, the change of rotor speed or mismatching between stages, which is a key factor affecting the flow stability. In this paper, the instability inceptions under the various radial distribution of loading are experimentally investigated on a transonic compressor. The research subject is chosen as a 1.5-stage transonic axial flow compressor in which three types of instability inceptions were previously detected, including spike-type inception initiated at the rotor tip under the low speed, partial surge initiated at the stator hub under the high speed, and hub instability when the slot casing treatment was mounted. In order to facilitate the conversion of the compressor instability inception, the rotating speed is selected (17,160 r/min in this study) at which the blade loading at both the stator hub and rotor tip reach the critical value near the rotating stall. Furthermore, the variation of radial distribution of loading is induced by the radial non-uniformity of total pressure. Meanwhile, the high-response dynamic test points are mounted to measure static pressures at rotor tips and total pressures at stator trailing edges during the experiments. To detect the system response, an additional high response sensor is installed on the plenum inner wall. As demonstrated by the WFT and filtering methods, the results indicate that the instability evolution varies gradually with the radial distribution of loading at the inlet. The partial surge instability converts into the spike with the increase of tip loading intensity. With the increase of hub loading intensity, the partial surge instability converts into the hub instability. For the hub instability, a special process is that a sudden decrease of total pressure occurs at the stator hub. Furthermore, the short-length scale disturbance occurs at the rotor tip, and leads to the final compressor stall.

Nonlinear Modeling of an Automotive Air Conditioning System Considering Active Grille Shutters

This paper expands upon the state of the art in nonlinear modeling of automotive air conditioning systems. Prior models considered only the effects of the refrigerant compressor and the condenser fan. There are two new aspects included here. First, we create a mathematical model for front-end underhood airflow, considering vehicle speed, condenser fan rotational speed, and active grille shutter position. In addition, we present a new model for the power consumption of the vehicle associated with aerodynamic drag caused by underhood flow, as well as a fan power model which accounts not only for changes in rotational speed but also changes in flow rate. The models developed in this paper are coded in MATLAB/Simulink and assessed for various vehicle driving conditions against a higher-fidelity vehicle energy management model, showing good agreement. By including the active grille shutters as a controllable actuator and the impact of underhood flow on vehicle drag and fan power consumption, control schemes can be developed to holistically target reduced energy consumption for the air conditioning system and, thus, improve the overall vehicle energy efficiency.

Fault diagnosis of rolling bearing under multiple working conditions based on multi-scale kernel convolution neural network

As the key component of wind turbine, the rolling bearing of gearbox plays an important role in the running process of wind turbine. However, in real-world situations, the working environment and conditions of wind turbine are very bad, resulting in a high failure incidence probability of gearbox rolling bearings. As mechanical vibration signals are typically non-stable, non-linear, and non-periodic, failure mode and its mapping relation to the raw signal signs become very complex. This paper aims to design a convolutional neural network based on multi-scale kernel depth and angular domain re-sampling intelligent fault diagnosis model to accurately diagnose the rolling bearing fault of gearbox. The model can effectively reduce the difference of vibration signals caused by rotational speed changes, and the inception model is used to divide the deep convolutional neural network into multiple branches to extract the features of rolling bearings in uniform or variable rotational speed states. After extracting the features, information fusion and fault classification are carried out. This combination model has excellent feature learning ability and classification performance. Moreover, the proposed method can adapt to fault diagnosis under variable speeds and multiple working conditions, and the robustness and accuracy of fault diagnosis are greatly improved.

Modulation effect on rotor-stator interaction subjected to fluctuating rotation speed in a centrifugal pump

In the paper, the modulation effect of rotor-stator interaction subjected to fluctuating rotation speed is investigated numerically. A quasi-bivariate variable mode decomposition method for analyzing non-stationary flow fields is proposed for the first time. Different from the previous studies, this paper emphasizes the local features of the transient flow field at fluctuating rotation speed. The results show that the impact of fluctuating rotation speed on the impeller force is limited, but it significantly impacts the pressure pulsation at fluctuating frequency. The correlation between amplitude and fluctuation ratio is positive. Meanwhile, the fluctuating rotation speed also induces sidebands centered on the blade passing frequency and its harmonics. The periodic changes in rotational speed lead to frequency and amplitude modulation of pressure pulsations. The magnitude of the instantaneous frequency and amplitude increases as the fluctuation ratio grows. The change in pressure field is well synchronized with the rotational speed, while the change in velocity field lags behind the rotational speed. The variation of pressure field with rotational speed is mainly attributed to two aspects. One is the flow structure at the fluctuating frequency, and the other is the instantaneous component of the flow structure at blade passing frequency.