Journal of Engineering and Thermal Sciences
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Multi-body dynamic simulation and vibration transmission characteristics of dual-rotor system for aeroengine with rubbing coupling faults
Get PDFIn this paper, a dual-rotor system multi-body dynamic model with rubbing coupling faults is established for practical aero-engine. In the model, the rubbing fault simulation method is introduced, the coupling effect between the internal and external rotor is considered. The numerical simulations of rotor vibration are accomplished by the utilization of multi-body dynamic platform, where the simulation model consists of discs unbalances and local rub-impact between discs and casing shells. The time-domain responses, the frequency spectra and the shaft-center trajectories of dual-rotor with different unbalance and different rubbing positions are obtained. The vibration and its transmission characteristics of the inner and outer rotors are calculated. Finally, the simulation results are compared with the measured vibration of a dual rotor tester with rubbing fault. The simulation results are consistent with the measured results, which confirms the feasibility of the established model and the multi-body dynamics simulation method in this paper. The application of multi-body dynamics simulation method in aero-engine can deepen the understanding of the internal operation nature and laws of aero-engine, reduce the repetition of physical tests, greatly improve the efficiency and quality of development, accelerate the research and manufacture process
Chaotic time series prediction using wavelet transform and multi-model hybrid method
Get PDFIn order to further improve the prediction accuracy of the chaotic time series and overcome the defects of the single model, a multi-model hybrid model of chaotic time series is proposed. First, the Discrete Wavelet Transform (DWT) is used to decompose the data and obtain the approximate coefficients (low-frequency sequence) and detailed coefficients (high-frequency sequence) of the sequence. Secondly, phase space reconstruction is performed on the decomposed data. Thirdly, the chaotic characteristics of each sequence are judged by correlation integral and Kolmogorov entropy. Fourthly, in order to explore the deeper features of the time series and improve the prediction accuracy, a sequence of Volterra adaptive prediction models is established for the components with chaotic characteristics according to the different characteristics of each component. For the components without chaotic characteristics, a JGPC prediction model without chaotic feature sequences is established. Finally, the multi-model fusion prediction of the above multiple sequences is carried out by the LSTM algorithm, and the final prediction result is obtained through calculation, which further improves the prediction accuracy. Experiments show that the multi-model hybrid method of Volterra-JGPC-LSTM is more accurate than other comparable models in predicting chaotic time series
Structural, shock and vibration analysis of special water filter
Get PDFThe present work is focused on the finite element analysis carried out on special water filter used in the marine application developed by CVRDE. This paper describes specifically on various type of analysis such as structural, shock analysis and modal analysis for the special water filter. The analysis is carried out using finite element method and compared it with the test results. It is observed that the shock test and sine sweep vibration test carried out is in line with the predicted finite element simulation. The filter assembly is designed in such a way that the natural frequency is away from resonance frequency. Thus, the special water filter has been validated through analysis using the finite element technique which help reduce the repeated testing of all the filters
Numerical simulation of vortex induced vibrations on a circular cylinder at different Reynold’s number
Get PDFThis research investigates the effect of vortex induced vibrations on flow past a circular cylinder for two-dimensional unsteady incompressible flow at different Reynold’s number. The pressure bases steady solver is used for computation along with standard k-ε turbulence model. The change in the lift and drag coefficient with respect to increase in Reynolds number is studied and contours of vorticity are plotted. The pressure distribution on the fixed cylinder for different Reynolds number is also presented. It is found that drag coefficient reduces with the increasing Re and lift coefficient increases up to Reynold’s number 104. Moreover, the pressure difference on the fixed cylinder increases with the increasing Reynold’s number
Vibration analysis of cantilever beam in time domain and frequency domain using Arduino platform
Get PDFIn this paper, analysis is made in the field of mechanical vibrations using Arduino and MATLAB code. Test was conducted on a cantilever beam to extract the first three natural frequencies. Two specimens made of Aluminium and Mild Steel were considered for the analysis. The frequencies were first determined using experimental setup utilizing Arduino and MATLAB, later verified with the help of two methods: (1) Traditional “strike method” using 8-channel FFT analyser with Data Acquisition System (2) Analytical solutions available in Robert D Blevins for idealized continuous beam model. The results obtained for both specimens through these methods were compared with Arduino MATLAB code and found to be in very good agreement. Hence, in this work an attempt is made with the use of Arduino to extract few frequencies for simple structures which is less expensive, fast and provides reasonably good results and can be a substitute for FFT analyser, which is very expensive and time consuming
Simulation on metro railway induced vibration. Part II: effect of corrugated rail
Get PDFThe deterioration of running surface, including out-of-round wheels and corrugated rails. The effect of out-of-round wheels on simulation of rail dynamic behavior was presented in a companion paper [1]. In this paper, the effect of corrugated rails was discussed. Considering a perfect round wheels moving on different irregularities rail surface, including perfect smooth rail, irregularities generated from a US PSD, measurement data from corrugated rails. Calculation result indicated that (1) the traditional used irregularity generated from US-PSD would not satisfy the requirement simulation on rolling noise and vibration generation in high frequency range; (2) corrugated rail plays the dominant role on the vibration which obviously related to its typical wavelength
Gear shift simulation by using virtual prototype
Get PDFThe presented paper is focused on the simulation of gear shift and prediction of whole gearbox dynamic behavior during gear shift. For this complex task the methodology for simplified gearbox was developed first. The whole methodology is divided into three different level of numerical model, where each of them was developed and validated by technical experiment. Afterwards the methodology was applied on more complex gearboxes, in presented case the heavy-duty gearbox concept. The virtual prototype was extended by gear shift option. The numerical sensitivity study of different gear shift time, which are simulated by different clutch activation and deactivation, was performed and the surface normal velocity and torque were evaluated and compared. The simulation was performed to find the optimal gear shift progress with minimal affects vehicle comfort. For this purpose, the surface normal velocity is evaluated, which is directly connected to emitted noise of whole gearbox
Path tracking with minimum time of vehicle handling inverse dynamics based on adaptive gauss pseudospectral method
Get PDFVehicle driving safety is the urgent key problem to be solved by an independent automobile development project. And it is also the premise and one of the necessary conditions for active vehicle safety. A new technique for path tracking with minimum time of vehicle handling inverse dynamics is proposed in this paper. Based on a new optimal control method – Adaptive Gauss Pseudospectral Method (AGPM), the optimal control for path tracking with minimum time problem was converted into a nonlinear programming problem which met the boundary condition and a series of path constraints including path constraint, state constraint, control constraint. And then the problem was solved using the sequential quadratic programming (SQP). The simulation results showed that the proposed method was not sensitive to the initial value and the optimization efficiency was higher compared with indirect methods and traditional direct methods. When solving the problem of path tracking with minimum time as per this method, boundary constraints and path constraints were well satisfied. The algorithm was not only precise but it could also shorten the evaluation period of vehicle handling stability and could reduce the tremendous cost for real vehicle testing. So the maneuverability of two different vehicles that complete the pylon course slalom test road with minimum time can be evaluated objectively by utilizing the method. The model correctness is verified through a real vehicle test
Mini review: interactions between antifungal azoles, neurological bladder and urinary problems
Get PDFThis review describes the importance of antifungal drugs in medicinal, pharmaceutical and agriculture fields because of their wide spectrum of biological activities in the recent years. Their chemical structure has expected considerable interest. Also, we focus on urinary problems and can be helpful to develop the ideas in neurological bladder for see the interactions and effect of antifungal drugs in system neurologic, because urinary tract infection is one of the most frequent diseases in medical practice. Some definitions are discussed and reported emphasizing microbiological, clinical and therapeutic aspects
Investigation and optimization of the cable force of a combined highway and railway steel truss cable-stayed bridge in completion state
Get PDFIn order to study the reasonable cable force of a highway and rail dual-purpose steel truss cable-stayed bridge in the completion state, this paper employs four methods, i.e. the rigid supported continuous beam method, bending minimum energy method, influence matrix method and BP neural network method combined with a genetic algorithm. The Baijusi Yangtze river bridge, with a main span of 660 m in the completion state, is chosen as the object of study. Through comparative analysis, it is found that the rigid supported continuous beam combined with the influence matrix method can determine the reasonable cable force of the highway and rail dual-purpose steel truss cable-stayed bridge more quickly and effectively