Papers by Keyword: Transient Process

Abstract: Additive manufacturing (AM) is becoming one of the most discussed modern technologies. Significant achievements of the AM in metals today are mainly connected to the unprecedented freedom of component shapes this technology allows. But full potential of these methods lies in the development of new materials designed to be used specifically with AM. Proper understanding of the AM process will open up new possibilities, where material and component properties can be specifically tailored by controlling the parameters throughout the whole manufacturing process. Present paper discusses the issues related to the beam melting technologies AM and electron beam welding (EBW). We are speaking of new direction in material science that can be termed “non-stationary metallurgy”, using the examples from material and process development for EBW, electron beam melting (EBM^®) and other additive manufacturing methods.

Abstract: Safety membrane is a good mechanical device that can be applied in middle and small hydropower stations instead of a surge tank. This present study deals with the determination of three most important parameters of safety membrane, rupture pressure, diameter, and number. The mathematical model of transient process is established by introducing the method of characteristic, which is used for the simulation of the rupture behavior of safety membrane. Then the model is applied to a specific hydropower station that only can employ safety membrane as the regulating measurement, and it shows good performance. The achievements of the study can serve as a reference for similar projects.

Abstract: Taking a pumping station project with large scale centrifugal pumps as working example, an extreme transient flow in the pumping system caused by tripping pump due to electric supply failure was analyzed, and hydraulic disturbance or impulsion to the rest working running pumps were investigated by using the software of the Deltares WANDA 3.73. The results show that the rest running pumps in the system due to a sudden tripping pump disturbance are heavy disturbed when the tripping pump is suddenly failed from the pumping system. The flow rate and input power for the working pumps are greatly jumped shortly. The strongly transient impulsion to the pumping system is quite significant.

Abstract: In this paper, the circuit model and equation of uniform transmission line are analyzed theoretically. Because the equation of transmission line is a first-order differential equation, it is hard to carry on research on the transient process of transmission line in theory, In order to observe the reflection phenomenon and transmission delay phenomenon, the experimental device is set up in laboratory. Digital oscilloscope is used to capture the phenomenon of reflection and transmission delay. Different transient process is obtained by changing the material, distribution pattern of transmission line and signal frequency, the factors affecting the traveling wave of transmission line is obtained, which provide reliance of theory research of uniform transmission line.

Abstract: Manipulator dynamics is investigated on the basis of closed kinematic chain, in comparison to manipulator on the base of non-closed kinematic chain. Thereby the dynamic peculiarities of their driving actuators are considered. The solution of the task of program motion development was received as a solution of inverse task of kinematics. The modeling issues of investigated manipulators dynamics are resolved and the results were attained. The attained results demonstrate that the application of flat closed mechanisms as the operating device of manipulation robots is promising from the perspective of enhancement of their dynamical peculiarities.

Abstract: In this paper the auther made deep research on the principle and the transient process of resistance-capacitance over voltage protection circuit in different working condition during the electric locomotive running, and based on the analysis of the Circuit Transient Process, obtained the theoretic expressions of the voltage and the current of the resistance and the expression of the energy absorbed by the resistance during the working process. The research offers theoretical basis for design and improvement of the resistance-capacitance protection circuit.

Abstract: Optimization of closure law is the priority selection in solving the guaranteed regulation calculation problems due to its simplicity and economy. This present study deals with the optimization of two-stage closure law of wicket gates, which has more advantages in control pressure and speed rise. The mathematical model of transient process is established by introducing the method of characteristic, whose correctness is validated by the field test. Then the model is applied to a specific hydropower station that only can employ closure law optimization to coordinate the contradiction between pressure and speed rise, for two-stage closure optimization. The achievements of the study can serve as a reference for similar projects.

Abstract: Underwater environment is highly dynamic,presenting significant disturbances to the vehicle in the form of underwater currents.Additionally,the main difficulties associated with underwater control are the parametric uncertainties. The model-based controller need precise hydrodynamic coeffcients or the model of ROV,but in practice it is very hard or impossible.In order to avoid this problem,a model-free high order sliding mode controller is proposed,and design a reasonable transient process which make the controller have a good performance for any initial error condition.Performance of the proposed controller is verified using numerical simulations,implemented in a four freedom nonlinear underwater vehicle model. Simulation results show that exponential fast convergence of position and attitude,overshooting is very small,for any initial condition.And the controller is proposed needs few parameters to adjust. Algorithm is very easy to complie,could meet the engineering needs.

Abstract: Over-voltages happen when electric locomotive passes the neutral section, which has serious influence on safe operation of the traction power supply system. This paper builds the model of contact net and neutral section of traction power line and analyzes transient process of the electric locomotive passing the neutral section. This paper proposes automatic control system for electric locomotive passing neutral section. It is effective to avoid the over-voltages.

Abstract: In the large fluctuation transition process of hydropower unit, hydraulic turbine operating condition changes drastically, following the change, hydraulic-turbine transfer coefficients also change drastically, thus the mathematical model of hydro-turbine governing system is nonlinear. This paper establishes simulation model of large fluctuation transition process in SIMULINK software, puts forward a method of establishing simulation model of nonlinear hydro-turbine governing system.