Applied Mechanics and Materials Vol. 318

Abstract: The string is loaded by ground thermal stress, fluid squeeze pressure and gravity in horizontal wells in the process of fracturing. The fluid-solid heat coupling theory is used to make the theoretical feasibility analysis on the column simulation of the fracturing string. Fracturing string is analyzed on the suitable physical model which is set parameters, boundary conditions and constraints on the basis of actual condition by the finite element method. And it is made by different formation temperature load coupling analysis. The tubing analysis focuses on axial stress, axial deformation, and the relationship between axial stress and circumferential stress. So, it obtains the change rules of string in the process of fracturing which directly compared results of the theoretical calculation of the force produced by the axial deformation. It proves the feasibility of this method. So the paper provides a basis for guiding the production process of fracturing string, which can improve the effect of fracturing operation.

Abstract: This study reviews current researches on gas heat pumps (GHP) in which the gas engine and the compressor are connected with a single-stage or fixed transmission ratio (engine’s speed/compressor’s speed). A novel concept of gas heat pump with multi-stage transmission ratios is presented in this paper. Compared with conventional GHP with a fixed transmission ratio, the novel GHP renders its engine to operate with a higher efficiency under more heating/cooling operation conditions to enhance the primary energy ratio (PER) further. Advantages from multi-stage transmission ratio connection, such as PER improvement and running speed extension of compressor are theoretically analyzed. Results show that GHP with multi-stage transmission ratios has a higher PER and broader compressor speed range, and in particular, through transmission ratio switch under different load conditions, it is beneficial for engine to run with higher efficiency during a whole-year operation.

Abstract: In order to obtain the first 4 natural frequencies and vibration modals of ZJ70D drilling rig base. The experimental modal of the base is measured under the environment of uTekMa modal test system. Testing result shows it is identical to actual vibration condition. Comparing to the power frequency of engine, reducer, etc, it is found their working frequencies and frequency multiplications approach the drilling rig base natural frequencies, which are the main reason of drilling rig base vibration.

Abstract: Hydraulic control one-way valve as the retaining element of vertical hydraulic cylinder, often is due to improper application to produce large opening pressure, not unlocking, vibration, noise etc.fault. This paper analyses two vertical hydraulic balance circuit, one makes use of the one-way throttle valve and another is not,calculates the necessary condition and opening pressure of hydraulic control one-way valve reverse opening, obtains the opening characteristic of hydraulic control one-way valve in vertical balancing circuit, acquires the relationship of the reverse opening pressure with hydraulic cylinder balance pressure, hydraulic cylinder speed ratio, hydraulic control one-way valve structural parameters. Lastly, how to correctly use the hydraulic control one-way valve is discussed in the vertical hydraulic cylinder balanced circuit.

Abstract: According to the difficult question that how to calculate the productivity of coal mine underground extraction-CBM, introduced the method of wavelet neural network, for different pre-draining time, the productivity of CBM was calculated with dynamic fitting. Because wavelet neural network exists convergence speed slow and easy to fall into local minimum, therefore a parameter correction of the improved algorithm was put forward. The first neuron function of output layer used hyperbolic tangent function instead of traditional Sigmod function, Secondly used the way that added the momentum term in adjustment type of weights to select the learning step, in order to improve the efficiency of network learning. Using the proposed improvement method, the productivity prediction model of coal mine underground extraction-CBM was established. The results showed that: the improved wavelet neural network model can be good for accurate prediction of the productivity model of coal mine underground extraction-CBM, the prediction accuracy and generalization ability was better than the BP neural network and the wavelet neural network model, it had important guiding significance to CBM extraction engineering of deployment and mine gas management.

Abstract: Periodic noise is an important manifestation of the drill string vibration signal noise. In order to extract the characteristics of the signals which reflect the situation of the tools in drilling, the periodic components which influence the original drill string vibration signal in the well field were researched and the independent component analysis algorithm which is on the basis of negative entropy for periodic vibration noise separation was adopted. At the same time, the effect of algorithm demixing was improved where periodic noise components which existed in three directions of drill string vibration signals were used, combining with the improved particle swarm optimization algorithm to seek the optimal mixed matrix by which the multi-channel mixed-signal of independent component analysis algorithm could be structured. This method in operation was fast. And after separation each signal was of high similarity. Through the experimental simulation, the method was proven effective in the drill string vibration periodic noise signal separation.

Abstract: To reveal the static stiffness behavior of a 6-PTRT parallel robot and find out its change rule in order to provide the reasonable parameters for the structural design, the stiffness characteristics of this parallel mechanism was studied. Based on the influence coefficient method, a static stiffness model for 6-PTRT parallel robot was established. The proposed model considered not only the axis stiffness of actuator but also the stiffness of passive joints, and the change of Jacobian matrix and first-order influence coefficient brought about by tiny change of the parallel robot mechanism's configuration under external wrench. The static stiffness matrix of parallel robot in initial position and its stiffness distribution rules for a certain workspace were given by numerical calculation and finite element method, which comparatively verify the exactness of stiffness model.

Abstract: The framework is the main load bearing part of beam pumping unit. Its vibration performance has an important effect on the stability and reliability of beam pumping unit. This article takes the beam pumping unit (API C-228D-173-74) as an example, carries out the modal analysis in the environment of Solidworks Simulation, and obtains the first 6 orders of modal shapes and natural frequencies of the prestressed framework. This article clarifies the key technology of how to build the solid modal and how to apply load and constraints. The analysis result of the modal shows that the lowest frequency of the pumping unit framework (API C-228D-173-74) is 22.39Hz, which may be most likely resonant with the motor. We can adjust the rotate speed of the motor to avoid resonance. At the same time, the stiffness of the front legs is insufficient, suitable strengthen measures should be taken.

Abstract: Analysis external characteristic of hydraulic torque converter by modeling and numerical simulation on a type of YJ series. Using a leafy row whole runner geometric model and sliding grid method of multiple flow area coupling algorithm to realize real-time transmission of flow parameters between impellers .Getting values of moment of force from pump & turbine in each iteration step through UDF used in model ,then input that to text file. Judging whether the result tends to be stable or not by analysis and calculation changes of the text data. Result shows that the leafy row whole runner geometric model has high accuracy and reliability from comparing data under different conditions with measured moment data.