Journal of Engineering and Thermal Sciences
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Reducing the bottom-hole differential pressure by vortex and hydraulic jet methods
Get PDFReducing the bottom-hole differential pressure (BHDP) of a gas/oil well and so as to reduce the “chip hold-down effect” can significantly improve the rate of penetration (ROP). The fluid vortex and hydraulic jet methods are used to reduce the BHDP while the wellbore pressure is unchangeable to prevent wellbore instability. The depressurization theories of the two hydraulic pressure drawdown methods are studied. The structures, depressurization mechanism, depressurization capacity, and the current researches and developments of the hydraulic pressure drawdown tools, including the vortex tools and the jet hydraulic pressure drawdown tools (JHPDTs), are analyzed. Using field tests and flow field numerical calculation methods, the key factors which affect depressurization capacity of the vortex tools and the JHPDTs, and the design principles of the vortex bit and the jet pump bit are proposed. Different depressurization methods and structures are simulated, which shows the vortex and jet pump combination bit with 106 mm distance is preferable
Dynamic research of angle measurement comparator
Get PDFThe main aim of the research is to determine (by experiment) the dynamic characteristics of angle comparator carriage on which optical system is attached on it and to compare the experiment with the results obtained by theoretical calculations
The dynamic behavior and modal analysis of electric scooter
Get PDFThe main objective of this paper is to provide the methods and techniques to test and improve the design and manufacturing ability of electric scooter. This research study focuses on the steering mechanism, transmission mechanism and carrying structure parts. In this investigation, we will estimate the effects of flexibility of the flexible steering mechanism, transmission mechanism and carrying structure on the computation of the dynamic steering, transmission forces and responses. By using the computational ability and simulation of modern computers and CAE (Computer-Aided Engineering) softwares, the dynamic responses, dynamic stress distribution and modal tests can be calculated and performed. These data can be used as the design and manufacturing references of corresponding manufacturers. For the modal analysis, the impact hammer, data recorder, accelerometer, laser optical displacement sensor, spectrum analyzer and dynamic simulation software can be applied on the key parts of the electric scooter to perform the vibration modal and dynamic analysis
Experiment and simulation studies on sound insulation performance of the wooden component
Get PDFWooden component has been used extensively in industries and the sound insulation performance of these components will directly be associated with the noise problem. We used sound pressure method and sound intensity method separately to measure the transmission loss of wood component, their results were in good agreement through the entire frequency band and the differences between them are in reasonable engineering error range. Test failures have been avoided by this as well as providing some protection for the subsequent simulation validation. After that, the damping loss factor of wood component has been measured by pulse attenuation method and imported into AML model to calculate the transmission loss, compared to experiment results, they were in good agreement, which indicates this kind of simulation method is available in the prediction of the acoustic performance for wooden component. Various technique means have been used to optimize the sound insulation performance, such as changing the density, elastic modulus, thickness of wooden component and surface treatment and sound package, and the results show that all the optimization programs can be effective in the improvement of sound insulation performance. At last, all the optimization data was arranged and compiled into a database, through the operation of the database interface, it is easy to select any group of data to draw graphics. This database provides an effective way to develop the optimal program of wooden component which has the best sound insulation performance
The defect detection in glass materials by using discrete wavelet packet transform and artificial neural network
Get PDFIn this study, a method based on impact tests was designed in order to determine undamaged and broken glasses. By means of using an impact pendulum, impact was applied on glasses and the generated sounds were transferred to the computer using a microphone. The sound signals were decomposed into 128 components by using Discrete Wavelet Packet Transform (DWPT) at the seventh level. 16 of the 128 components that characterized the properties of undamaged and broken glasses were chosen as inputs for the designed Artificial Neural Network (ANN). The designed ANN model was tested with real-time simulation, and it was observed that the proposed method could determine undamaged and broken glasses with high precision. This method, which is based on analyzing the sounds generated after the impact, can detect defects that the conventional visual methods can detect; however, it can also be used as supplement to these methods
Computational considerations of 3-D finite element method models of railway vibration prediction in ballasted tracks
Get PDFThe study of vibrations induced by a passing train is of utmost importance to understand better this phenomenon and to design efficient mitigation measures. Within all the techniques used to model vibrations, finite element methods allow introducing in the model detailed characteristics of the real vehicle-train-soil system. However, the accuracy of the results is linked to how detailed the real elements implemented in the model are and consequently, with the computing time. In this paper a three-dimensional finite element method to predict vibrations is developed and validated with real field-measured data. Then, different scenarios are represented to assess the efficiency of the model linking the quality of the results obtained with the calculation time required in each case. Finally, a reflection regarding the constitutive model of the materials when working with finite element models is done
Design and analysis of a quasi-zero stiffness isolator using a slotted conical disk spring as negative stiffness structure
Get PDFThis paper concerns the characteristics of a novel quasi-zero stiffness (QZS) isolator developed by parallelly combining a slotted conical disk spring with a vertical linear spring. The static characteristics of the slotted conical disk spring as well as the QZS isolator are presented. The configurative parameters are optimized to achieve a wide displacement range around the equilibrium position for which the stiffness has a low value and changes slightly. The overload and underload conditions are taken into account, resulting in a Helmoholtz-Duffing equation. The primary resonance response of the nonlinear system composed by a loaded mass and the QZS isolator are determined by employing the Harmonic Balance Method (HBM) and confirmed with the results of numerical simulation. The frequency response curves (FRCs) are obtained for both force and displacement excitations. The force transmissibility, the absolute displacement and acceleration transmissibility are defined and investigated. The study shows that the overloaded or underloaded system can exhibit linear stiffness, softening stiffness, softening-hardening stiffness and hardening stiffness with the increasing excitation amplitude. The response and the resonance frequency of the system are affected by the excitation amplitude and the offset displacement to the position at which the dynamic stiffness is zero. To enlarge the isolation frequency range and improve the isolation performance, the loaded mass and the excitation amplitude should be suitably controlled
Analysis and implementation of adaptive filtered-X LMS algorithm based on reference signal self-extraction
Get PDFBy comparing conventional FXLMS (filtered-X least mean square) control algorithms, the present paper introduces an improved adaptive vibration control FXLMS algorithm based on reference signal self-extraction. It overcomes the problem of reference signal which correlated with external excitation signal is needed to be predicted in advance, namely, the reference signal is extracted from structural vibration in real time in the process of control algorithm. Its theoretical basis is: get an original vibration signal estimation using the error signal of the system and the estimation value is taken as the reference signal of adaptive filtering. In addition, to verify the feasibility and advantage of the proposed algorithm, we simulate solar panels with piezoelectric smart flexible plate and construct the corresponding experimental platform. Finally, the results presented in this paper demonstrate that the proposed algorithm is feasible, effective and achieve improvement with significantly faster convergence speed and better control effect compared with other algorithms
Diagnostic analysis of dynamic deflection for cracked asphalt pavements under FWD impulsive loading
Get PDFThe falling weight deflectometer (FWD) is a non-destructive testing technology used to calculate the stiffness-related parameters of pavement structures and has been widely used in the pavement engineering field. Deflection basin testing data have an obviously affecting effect on the modulus backcalculation of an asphalt pavement. Identifying effective data of dynamic deflection basins is an important task to perform modulus backcalculation. The objective of this paper is to study the distribution features of dynamic deflection basins of cracked asphalt pavements using a three dimension dynamic finite element method. Based on the systematic analysis, the criteria used to filter effective data of FWD deflection basins were presented and verified with an in-situ case study. The study results demonstrated that the crack width of 0.2 mm was a critical value to determine the existence of contact behavior between vertical crack surfaces. The distribution characteristics of dynamic deflection basins showed a significant difference between intact and cracked pavements. The established criteria, involving surface deflection indicator and surface modulus indicator, were verified to be reasonable and viable for filtering the FWD testing data
Nonlinear resonances of electrostatically actuated nano-beam
Get PDFNonlinear response of electrostatically actuated nano-beam near-half natural frequency is studied by considering the nonlinearities of the large deformation, electrostatic force and Casimir effect. A first-order fringe correction of the electrostatic force, large deformation, viscous damping, and Casimir effect are included in the dynamic model. The dynamics of the resonator are investigated by using the method of multiple scales in a direct approach to the problem. The sufficient conditions of guaranteeing the system stability and a saddle-node bifurcation are studied. The influences of large deformation, damping, actuation, and fringe effect on the resonator response are studied. The peak amplitude of the primary resonance is given in the paper. Numerical simulations are conducted for uniform nano-beam