Numerical simulation and analysis of lithium plasma during low-pressure DC arc discharge

Alkali metal DC arc discharge has the characteristics of easy ionization,low power consumption,high plasma temperature and ionization degree,etc,which can be applied in aerospace vehicles in various ways.In this paper,we calculate the physical property parameters of lithium vapor,one of the major alkali metals,and analyze the discharge characteristics of lithium plasma with the magnetohydrodynamic(MHD)model.The discharge effects between constant current and voltage sources are also compared.It is shown that the lithium plasma of DC arc discharge has relatively high temperature and current density.The peak temperature can reach tens of thousands of K,and the current density reaches 6 x 107 A m 2.Under the same rated power,the plasma parameters of the constant voltage source discharge are much higher than those of the constant current source discharge,which can be used as the preferred discharge mode for aerospace applications.

Foreign Object Damage to Fan Rotor Blades of Aeroengine Part II: Numerical Simulation of Bird Impact

Bird impact is one of the most dangerous threats to flight safety. The consequences of bird impact can be severe and, therefore, the aircraft components have to be certified for a proven level of bird impact resistance before being put into service. The fan rotor blades of aeroengine are the components being easily impacted by birds. It is necessary to ensure that the fan rotor blades should have adequate resistance against the bird impact, to reduce the flying accidents caused by bird impacts. Using the contacting-impacting algorithm, the numerical simulation is carded out to simulate bird impact. A three-blade computational model is set up for the fan rotor blade having shrouds. The transient response curves of the points corresponding to measured points in experiments, displacements and equivalent stresses on the blades are obtained during the simulation. From the comparison of the transient response curves obtained from numerical simulation with that obtained from experiments, it can be found that the variations in measured points and the corresponding points of simulation are basically the same. The deforming process, the maximum displacements and the maximum equivalent stresses on blades are analyzed. The numerical simulation verifies and complements the experiment results.

NONLINEAR INVERSE SIMULATION FOR THE MANEUVERING FLIGHT OF COAXIAL ROTOR HELICOPTERS

The maneuvering flight governing equations for coaxial rotor helicopters are established. By introducing induced velocity interference factor analysis, the coaxial rotor aerodynamic interference can be taken into account. With the combination of coaxial rotor helicopter control features and nonlinear inverse solution technique, the governing equations for maneuvering flight can be solved so as to determine helicopter control input, control force and moment, and helicopter body attitudes which are needed for performing the defined maneuver. Finally, as an example of this methods engineering application, the calculated results with level turn, lateral jink maneuvers are presented and simply analyzed.

Numerical Simulation of Aerodynamic Characteristics of Helicopter Rotor with Tip Slots

Effects of tip slots on the aerodynamic characteristics of helicopter rotor were investigated numerically by solving three-dimensional Navier-Stokes equations based on unstructured overset grids algorithm.Improved delayed detached eddy simulation (IDDES) based on the Spalart-Allmaras turbulence model and adaptive grid refinement technique were employed.Several slots in the rotor blade tip were designed on the base of Caradonna-Tung rotor to study the effect of tip slots.Numerical results show that tip slots are able to introduce the airflow from the leading edge and turn it in the spanwise direction to be ejected out of the face at the rotor blade tip,which can reduce the strength of the rotor blade tip vortex and accelerate the dissipation process.Although tip slots may lead to the decrease of airfoils' lift coefficient at the root of the rotor blade,it can increase the lift coefficient of airfoils at the rotor blade tip,so the lift of the rotor with tip slots is almost the same as that of the rotor without tip slots.In addition,tip slots can also reduce the intensity of the tip shock wave,which is beneficial to reduce the wave drag of the rotor.

Parameter Modeling and Kinematical Simulation for Rotor and Stator of Screw Pump

The research object used in the dissertation was screw pump, which was widely applied in engineering field. The analysis of end face profile formation was completed on its main working components, i.e., rotor and stator. With the purpose of finding optimal parameters to improve the efficiency of screw pump design, the key technologies involved in the parametric modeling of rotor and stator were analyzed. The three-dimensional (3D) design software SolidWorks was used for the secondary development and parametric modeling of rotor and stator. After that the simulation models of different kinds of screw pumps were established based on the cycloid type, variation coefficient, and screw head number. Finally the COSMOSMotion was used to analyze the motion characteristics on the equidistant line of rotor, including velocity and acceleration. This design and modeling method has been used in screw pump enterprises for design and development, laying the foundation for finite element analysis and further optimization of screw pump.

Numerical Simulation of the Wake Generated by a Helicopter Rotor in Icing Conditions

The wake generated by the rotor of a helicopter can exert a strong interference effect on the fuselage and the horizontal/vertical tail.The occurrence of icing on the rotor can obviously make this interplay more complex.In the present study,numerical simulation is used to analyze the rotor wake in icing conditions.In order to validate the overall mathematical/numerical method,the results are compared with similar data relating to other tests;then,different simulations are conducted considering helicopter forward flight velocities of 0,10,20,50,and 80 knots and various conditions in terms of air temperature(atmospheric temperature degrading from−12°C to−20°C or from−20°C to−26°C).The results indicate that the rotor aerodynamic performance(i.e.,the lift-to-drag ratio distribution of the rotor disc)drops significantly once the rotor undergoes ice accretion.More importantly,the icing exerts a different influence of the wake dynamics depending on the atmospheric conditions.Interestingly,the rime-ice firstly occurs on the inner portion of rotor blades and then diffuses outward along the blade radial direction with the decrease in atmospheric temperature.

High-Order Discontinuous Galerkin Method for Hovering Rotor Simulations Based on a Rotating Reference Frame

An implicit higher ? order discontinuous Galerkin(DG) spatial discretization for the compressible Euler equations in a rotating frame of reference is presented and applied to a rotor in hover using hexahedral grids. Instead of auxiliary methods like grid adaptation,higher ? order simulations(fourth ? and fifth ? order accuracy) are adopted.Rigorous numerical experiments are carefully designed,conducted and analyzed. The results show generally excellent consistence with references and vigorously demonstrate the higher?order DG method's better performance in loading distribution computations and tip vortex capturing, with much fewer degrees of freedom(DoF). Detailed investigations on the outer boundary conditions for hovering rotors are presented as well. A simple but effective speed smooth procedure is developed specially for the DG method. Further results reveal that the rarely used pressure restriction for outlet speed has a considerable advantage over the extensively adopted vertical speed restriction.

Design and Analysis of a Dual Rotor Turbine with a Shroud Using Flow Simulations

This paper describes the flow simulation of a dual rotor, three-bladed wind turbine module with a shroud to determine its performance. The parameters that were evaluated are the effects of adding a second rotor, wind speed, distance between the two rotors, the size of the front rotor and the shroud. The results were obtained by using the Solid Works 2015 flow simulation program. Also, the benefits and cost issues for wind generating systems are illustrated.

Simulation and Optimization of a Double-Helical Rotor Wave Energy Converter

This paper presents a new type of double-helical rotor wave energy converter(WEC),which consists of two isolated sets of helical rotor structures(inner and outer).This device can generate electricity by using the rising and falling energy of a wave.The rotors are simulated and optimized by Fluent.Each rotor’s blades are simulated and analyzed,which are separately changed in terms of helix angle,shape,and thickness.The simulation result shows that,for both inner and outer helical rotors,the energy harvesting efficiency is the highest when the blade helix angle is 45°.Triangular blades have better hydrodynamic performance than square and circular blades.The energy harvesting efficiency of 15 mm thick blades is higher than that of 75 mm thick blades.

Optimization of the Gas Generator in Composite Power System with Tip-Jet Rotor

The key and bottleneck of research on the tip-jet rotor compound helicopter lies in the power system. Computational Fluid Dynamics (CFD) was used to numerically simulate the gas generator and rotor inner passage of the tip-jet rotor composite power system, studying the effects of intake mode, inner cavity structure, propellant components, and injection amount on the characteristics of the composite power system. The results show that when a single high-temperature exhaust gas enters, the gas generator outlet fluid is uneven and asymmetric;when two-way high-temperature exhaust gas enters, the outlet temperature of the gas generator with a tilted inlet is more uniform than that with a vertical inlet;adding an inner cavity improves the temperature and velocity distribution of the gas generator's internal flow field;increasing the energy of the propellant is beneficial for improving the available moment.

ROTOR FAULT DIAGNOSIS OF BRUSHLESS AC GENERATOR WITH ROTARY RECTIFIER

With a three-phase bridge type rectification, some typical rotor faults of a brushless AC generator with a rotary rectifier is analyzed in this paper by the help of computer digital simulation. It is also proPOsed that the rotor faults, whether exist or not, and the causes of the faults may be determined through the monitoring of the average value of the exciting current of the exciter and its principal harmonics.

异步电动机转子串电阻分级起动过程的SIMULINK仿真

利用 MATLAB/SIMULINK软件构造了绕线式异步电动机转子串电阻起动的仿真模型 。

矢量控制交流电动机调速系统的Simulink仿真

根据闭环控制和矢量控制的电气工作原理,基于模块化设计思想,利用Matlab/Simulink软件实现了按转子磁场定向的矢量控制异步电动机转速闭环调速系统的仿真建模,主要讨论异步电动机逆变器模块、矢量控制模块、三相/两相坐标系变换及其逆变换模块、转速调节模块、磁链计算模块、电流滞环脉宽调制(PWM)调节模块等的建模及其参数设置,并给出相应的仿真波形。仿真结果验证交流电动机矢量控制的优越性,使得学生对矢量控制复杂的理论知识有了更加直观的认识和理解,同时对矢量控制技术在运动控制系统领域的工程应用也具有一定的借鉴意义。

基于SIMULINK的双笼感应电动机的建模与仿真

论述了基于S IMUL INK的双笼转子三相感应电动机(DC IM)建模与仿真的方法。根据双笼感应电机在qd/qd旋转坐标系下的瞬态模型,结合必要的坐标变换,利用M ATLAB/S IMUL INK,通过编写M文件的S函数和构建坐标变换模块,建立了相应的仿真模型。并通过实例验证了仿真模型的有效性和实用性。

Combined Free Wake /CFD Methodology for Predicting Transonic Rotor Flow in Hover

A new combined wake /CFD methodology is used to include realistic wake effects in CFD solutions for the rotor flow in hover. The analytical method for predicting the hovering rotor wake is described to investigate the motion of the helical tip vortex. Beginning with the generalized wake model, a Semi Empirical Correction for the vortex core effect on the rotor wake is made. Then on the condition of circulation and wake geometry convergence, the free wake calculation is carried out. Finally, Euler equations are solved for transonic rotor flow employing Jameson’s finite volume explicit Runge Kutta time stepping scheme. The results are compared with the respective references and experimental data.

双笼感应电动机的SIMULINK建模与仿真分析

根据双笼感应电机在qd/qd旋转坐标系下的瞬态模型,结合必要的坐标变换,利用MATLAB/SIMULINK,通过编写M文件的S函数和构建坐标变换模块,建立了相应的仿真模型.通过实例验证了仿真模型的有效性和实用性.

Research on a combinatorial control method for coaxial rotor aircraft based on sliding mode

Aiming at the position and attitude tracking of coaxial rotor aircraft(CRA),this paper proposes a combinatorial control method of sliding mode control(SMC)coupled with proportional-integralderivative control(PIDC).Considering the complete description of flight dynamics,aerodynamics and airflow interference,the dynamical model of CRA is established.The dynamical model is simplified according to the actual flight,then the simplified dynamical model is divided into two subsystems:a fully-actuated subsystem and an under-actuated subsystem.The controller of the fully-actuated subsystem consists of a SMC controller coupled with a rate bounded PIDC controller,while the controller of the under-actuated subsystem is composed of a SMC controller.The sliding manifold is defined by combining the position and velocity tracking errors of the state variables for each subsystem.Lyapunov stability theory is used to verify the stability of the sliding mode controller,which ensures that all state trajectories of the system can reach and stay on the sliding mode surface,the uncertainty and external interference of the model are compensated.Simulation and experiment compared with the conventional PIDC are carried out,the results demonstrate the effectiveness and the robustness of the proposed control method of this paper.

Effectof Film Force Nonlinearity on Unbalance Responseof a Jeffcot RotorJournal Bearing System

The effect of oil film force nonlinearity on unbalance response of Jeffcot rotor elliptical bearing system is studied. Linear analysis is done by linearizing the bearing oil film dynamic forces and expressing them with stiffness and damping constants. Nonlinear dynamic simulation is done by taking the nonlinearity of bearing oil film dynamic force into full consideration, with the latter being expressed by a special database which is generated beforehand, and based on non stationary Reynolds equation and Reynolds boundary condition of film rupture. The linear and nonlinear unbalance responses of a Jeffcot rotor supported on a pair of elliptical bearings is studied. The resulting dynamic characteristics and rotor and journal whirling orbits are compared. While good consistancy between nonlinear and linear predictions is found under very small unbalance, significant or even drastic differences are found whenever the unbalance is not small, indicating the necessity of including the nonlinearity of oil film dynamic forces, especially when response to large unbalance is to be predicted.

Effects of Rotor Solidity on the Performance of Impulse Turbine for OWC Wave Energy Converter

Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column（OWC） wave energy converters, which can rotate in the same direction under the bi-directional air flows. A numerical model established in Fluent is validated by the corresponding experimental results. The flow fields, pressure distribution and dimensionless evaluating coefficients can be calculated and analyzed. Effects of the rotor solidity varying with the change of blade number are investigated and the suitable solidity value is recommended for different flow coefficients.

Intelligent Wind Power Unit with Tandem Wind Rotors and Armatures （Optimization of Front Blade Profile）

The authors have invented the superior wind power unit, which is composed of the tandem wind rotors and the double rotational armature type generator without the traditional stator. The large-sized front wind rotor and the small-sized rear wind rotor drive, as for the upwind type, the inner and the outer rotational armatures, respectively, in keeping the rotational torque counter-balanced between both wind rotors/armatures. The unique rotational behaviors of the tandem wind rotors and the fundamental performances of the unit have been discussed at the previous paper. Continuously, this paper investigates experimentally and numerically the flow condition around the wind rotors to know the flow interactions between the front and the rear wind rotors, and optimizes the blade profile in the front wind rotor. The front blade should work fruitfully at the larger radius and had better not work at the smaller radius for giving plenty of wind energy to the rear wind rotor, taking account of the flow interaction between both wind rotors.