Applied Mechanics and Materials Vols. 433-435

Abstract: In view of the shortcomings of band saw feeding system on position and micro-feeding speed tracking response characteristics, an electro-hydraulic servo feeding system of band saw is designed and its difference mathematical model is presented. Then, a new adaptive generalized predictive controller (AGPC) for the electro-hydraulic servo feeding system is provided. The controller identifies the parameters of the system model by system control input and output on line. Through minimizing performance evaluation function J which is based on j-step ahead predictive output of CARIMA model, system control variable can be got. The simulation and experiment application show that the proposed controller has better position precision and feeding tracking performances than the traditional PID controller and can well address feeding process of band saw.

Abstract: Considering that synchro-motion performance of four cylinders was influenced by flow allocation of one to more pipes, a nonlinear dynamics model of electro-hydraulic servo system with four cylinders was presented. Then a RSDA-PID synchro controller for electro-hydraulic servo system with four cylinders was provided with PID control, fuzzy control and RSDA(rough set data analysis) theory. This controller based on the equivalent synchro-motion control strategy. The simulation and factual applications show that the proposed control approach has better tracking and synchronization performance than that of conventional control strategy.

Abstract: Based on the establishment of the geometry and equations of non-contact vortex gripper, the numerical analysis of the internal flow field characteristics and the key parameters affecting the adsorption performance was carried out. The results showed that: for the single air-entrance gripper, the negative pressure center not coincides at the geometric center of the gripper. Besides, with the movement of swirling flow, the position of the negative pressure center transformed; When the geometric parameters and working conditions are fixed, there is the most suitable air gap making the maximum value of negative pressure and adsorption force; Compared to single air-entrance gripper, double air-entrance gripper have better adsorption stability.

Abstract: Hydrajet fracturing has the advantages which not only include perforating without compacted zone, creating fracture exactly, but also include controlling fracture height, shortening the working cycle, reducing operation risk and etc.^[. Through studying the optimization of nozzle materials and combination, string structure, operation pressure of surface casing and annular displacement, the hydraulic jet multistage fracturing technology is formed. This technology is successfully used and proves it has good popularization and application.

Abstract: Extraneous force is the main factor impacting the precision and dynamic characteristic of the electro-hydraulic load simulator. The structure and mathematical model of simulator is analyzed . then the improved compensation method based on the structure invariable principle is proposed to eliminate the extraneous force. The method use the velocity signal of the rudder servo system as the feed-forward compensation signal .and the speed signal is reproduced by integrating the given position signal of the rudder servo system. Then use the least square procedure for on-line identification to get tuning phase of the compensation signal. The experimental result show that improved compensation method is efficient obviously.

Abstract: The adiabatic flow process of gas or steam in a nozzle is not only widely used in steam turbines or other power equipment, but also applied to ejectors, impeller-type compressors, burners and other thermal devices in air conditioning, ventilation and gas engineering. In this paper we will describe steam flow in nozzle and the nozzle calculation, especially the relationship between the flow velocity and the flow area. We will describe the calculation on the velocity through a nozzle and the calculation on the area of the nozzle by an example.

Abstract: In this paper, viscous effects on hypersonic vehicle are investigated. Firstly, viscous aerodynamic is modeled based on reference temperature method, and viscous aerodynamic lift, drag and pitching moment are calculated by the model. And then, aerodynamic forces and elastic deformation are analyzed by comparing with viscous effects on/off. In final, considering the thermal choking condition, longitudinal velocity and attitude boundary values are discussed.

Abstract: At present, threshold pressure gradient method is usually used for describing fluid flow in low-permeability media. However, it is only an approximate approach. In this paper, a 2-D fractured-well model for numerical well-testing considering non-darcy mutative-permeability effect was established, and PSOR iterative algorithm was used for solving the sets of algebraic equations. Based on this model, the typical curves of pressure and pressure derivative were drawn with different sets of parameters. When considering mutative-permeability effect, the pressure derivative curves move upward in each flowing period compared with darcy flowing model. In addition, the range of upward movement is larger as the non-darcy effect is more notable.

Abstract: Through summary of multiphase flow coupling, considerate the conservation of mass and momentum conservation, used the gas phase as a continuous phase, liquid phase and solid phase as dispersed phase, CFB has been simulated with the help of Eulerian model. It show that the local gas holdup increases from the computational domain inlet to the outlet, the local solid holdup decreases from the computational domain inlet to the outlet, and the local liquid holdup decreases from the computational domain inlet to the outlet.

Abstract: The gas drilling mainly relies on the high speed air flow to carry the cuttings. The formation water or oil mixed with the cuttings and then stick together in clumps after the formation water or oil went into the hole annulus, the clumps stick on the drill string and the borehole. The clumps may block the hole annulus and cause the stick or bury the drill string and many other complex accident. It could stop the cuttings from sticking with the liquid through freezing the formation fluid with the liquid nitrogen. And the natural geotechnical becomes into the frozen soil, and forms the temporary solid which is intact, high strength and low-permeability. This technology could achieve the purpose of strengthening the formation and reducing the fluid flow of the formation, and it greatly broadens the scope of application of gas drilling.