Journal of Engineering and Thermal Sciences
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Bearing fault detection of wind turbine using vibration and SPM
Get PDFRolling bearings are one of critical components in rotating machines. The importance of monitoring the bearings conditions to prevent the breakdown of system is becoming more and more obvious. Vibration and shock pulse method (SPM) are the two popular methods for detecting the bearings fault. Vibration method and theory have been comprehensively studied. SPM has gained a wide acceptance in industrial applications. But few studies have compared the superiority of the two methods, especially utilizing the industrial data. In order to solve this problem, a gearbox test rig of wind turbine is set up. Vibration device and SPM instrument are used to monitor and acquire the condition data of bearings respectively. Through analyzing the derived frequency spectrum, a conclusion that SPM is superior to vibration when detecting the bearings fault in industrial applications has been derived
The effect of vibration inside the Constantine’s tramway on the comfort of passengers
Get PDFNowadays the tramway is a means of transport that is frequently used in Constantine city, the tramway of Constantine took its place in the landscape and improved the offer of public transportation in Constantine city with its capacity to transporting 6000 travelers per hour. This means of transport is experiencing a gain of interest for its qualities: ability, comfort, speed, and improving accessibility to the city center. Despite these advantages there are some problems related to users’ comfort like the noise and vibration caused during the operation, track rail, engine blocks and other traction equipment are among the main sources of vibration. On this paper, we present the type of tram used and the level of vibration caused by the traction elements and by rail track inside the tramway Alstom Citadis 402. We also made a survey based on the opinion of users of the Constantine’s tramway about the discomfort level caused by the vibration and how it effects on the comfort of passengers, this is in order to improve furthermore the comfort in the conception of tram extensions to other urban areas in the city
Research into the characteristics of horizontal gaseous jets underwater
Get PDFThe gaseous jet of the solid rocket motor running under water is influenced by both gravity and buoyancy, which will have a significant influence on the flow field structure and thrust of the motor, especially in the initial period when vehicles are launching horizontally. The work in this paper consists of three parts: firstly, to understand the mechanism of the thrust oscillation characteristics and the jet structure of a solid rocket motor running under water, as affected by gravity and buoyancy, a 3-d numerical simulation using the volume of fluid (VOF) model was established. Compared with those results neglecting gravity and buoyancy, conclusions were obtained that the jet structure, considering gravity and buoyancy, are more consistent with the experimental results. Secondly, the principle of momentum was used to analyze the flow field structure and the thrust oscillating characteristics in the initial period of operation. Finally, after analyzing the density gradient along the axis of the motor, results indicated that the length of jets under the influence of gravity and buoyancy varies linearly and the slope of the line is related to the working conditions. Comparing the trajectories under different conditions, a common theme emerged. The laws of thermodynamics are also used to simulate the jets as gas-water-vapor, three-phase, systems. The effect of phase transitions on the structure of jets and the characteristics of their thrust form the key conclusions
New mixed adaptive detection algorithm for moving target with big data
Get PDFAiming at the troubles (such as complex background, illumination changes, shadows and others on traditional methods) for detecting of a walking person, we put forward a new adaptive detection algorithm through mixing Gaussian Mixture Model (GMM), edge detection algorithm and continuous frame difference algorithm in this paper. In time domain, the new algorithm uses GMM to model and updates the background. In spatial domain, it uses the hybrid detection algorithm which mixes the edge detection algorithm, continuous frame difference algorithm and GMM to get the initial contour of moving target with big data, and gets the ultimate moving target with big data. This algorithm not only can adapt to the illumination gradients and background disturbance occurred on scene, but also can solve some problems such as inaccurate target detection, incomplete edge detection, cavitation and ghost which usually appears in traditional algorithm. As experimental result showing, this algorithm holds better real-time and robustness. It is not only easily implemented, but also can accurately detect the moving target with big data
Bifurcation and chaos characteristic analysis of spur micro-segment gear pair
Get PDFCustomers call for better performance, such as miniaturization, low noise, and higher load capacity of gear system. The micro-segment gear is a new tooth form whose tooth profile curve is composed of many micro segments. This paper investigates the bifurcation and chaos characteristics of spur micro-segment gear pair. To improve the authenticity of the solution, the time-varying mesh stiffness is expressed in term of piecewise function, and the normal profile deviation is expressed in the form of Fourier series. The influence of damping coefficient, excitation frequency, internal and external excitation on bifurcation and chaos properties of the system are analyzed. The numerical results show that the dynamic system is very sensitive to damping coefficient. With the increasing of damping coefficient, the number of bifurcation and impressive jump tends to decrease; and the intervals of dimensionless frequency leading to unstable or chaotic motion have a trend to concentration. The influence of external and internal excitation on bifurcation characteristics are also investigated. Comparison results show that, internal excitation has a greater effect than external excitation based on corresponding amplitude-frequency diagrams and bifurcation diagrams
Stability and slow-fast oscillation in fractional-order Belousov-Zhabotinsky reaction with two time scales
Get PDFThe fractional-order Belousov-Zhabotinsky (BZ) reaction with different time scales is investigated in this paper. Based on the stability theory of fractional-order differential equation, the critical condition of Hopf bifurcation with two parameters in fractional-order BZ reaction is discussed. By comparison of the fractional-order and integer-order systems, it is found that they will behave in different stabilities under some parameter intervals, and the parameter intervals may become larger with the variation of fractional order. Furthermore, slow-fast effect is firstly studied in fractional-order BZ reaction with two time scales coupled, and the Fold/Fold type slow-fast oscillation with jumping behavior is found, whose generation mechanism is explained by using the slow-fast dynamical analysis method. The influences of different fractional orders on the slow-fast oscillation behavior as well as the internal mechanism are both analyzed
Assessment of dynamic parameters of heavy-duty gears
Get PDFThe article provides an analysis of use of heavy-duty gear trains in the mining industry. It was revealed that it is necessary to create a dynamic model to calculate the acting stresses and durability in order to assess the dynamic parameters of the gear train. The article provides the results of use of Nastran software shell in terms of stress-strain behavior of the girth gear
Residual useful life predictions for train’s rolling bearing based on proportional hazard model
Get PDFThis paper studies the rolling bearing of the train and it puts forward a method of predicting the residual useful life (RUL) of the train’s rolling bearing using the proportional hazard model (PHM). First, the problem of RUL predictions for the train’s rolling bearing is described. Secondly, PHM is introduced, including the basic form, sample data, parameter estimation and prediction. Then, the method of RUL predictions using PHM is put forward. Finally, PHM has been validated by the total life data of the train’s rolling bearing
Numerical simulation on ground vibration caused by the demolition of a 200 m high chimney
Get PDFA chimney-soil model was built using finite element method to simulate the demolition of a chimney and the subsequent ground vibration. The acceleration history of ground vibration at observed point was obtained. The simulated results were compared with on-site measured data and good agreement was found with errors of less than 2.88 % for maximum acceleration amplitudes. It was also demonstrated that the element disappearance in the model did not affect the vibration response
Engine remaining useful life prediction based on trajectory similarity
Get PDFThe traditional remaining useful life prediction methods need to study the mechanism failure of equipment and the vibration signals can easily be submerged by the noise in the actual operation, in order to solve these problems, the methods of Trajectory similarity based prediction (TSBP) and condition monitoring based on lubricant information are proposed in this paper. The gradient model of lubricant data information which is processed by principal component analysis (PCA) is used to monitor equipment status. Additionally, degradation trajectory abstraction procedure and similarity evaluation procedure are studied in detail. Finally, the both studies are combined for the research of engine remaining useful life prediction and case study proves the simplicity and effectiveness of this method