1,720,976 research outputs found
Fault diagnosis of wind turbine gearboxes through temperature and vibration data
No full textGearbox faults are one of the most common and severe causes of energy losses in large wind turbine technology. Further, degradation of gearboxes is an elusive phenomenon by the point of view of diagnostics. Yet, nowadays the widespread diffusion of Supervisory Control And Data Acquisition (SCADA) control systems is a keystone for fault prevention. It is desirable to conjugate accuracy of the outputs with intuitiveness and reasonable computational cost. The present work deals with these issues: some methods are proposed for data mining of SCADA gearbox temperature and vibration measurements. In particular, a model based on Artificial Neural Networks (ANN) is proposed and its performances are compared against similar approaches in the literature. It arises that vibration analysis at the time scale of SCADA data is not effective for fault diagnosis, even if powered by the artificial intelligence of the ANN, while the proposed ANN model for gearbox temperatures is useful for early fault diagnosis. The method is tested on the data sets of a wind farm in southern Italy and it is shown that it is useful for the diagnosis of incoming faults to three out of nine wind turbines of the site
Fault diagnosis of wind turbine gearboxes through temperature and vibration data
No full textGearbox faults are one of the most common and severe causes of energy losses in large wind turbine technology. Further, degradation of gearboxes is an elusive phenomenon by the point of view of diagnostics. Yet, nowadays the widespread diffusion of Supervisory Control And Data Acquisition (SCADA) control systems is a keystone for fault prevention. It is desirable to conjugate accuracy of the outputs with intuitiveness and reasonable computational cost. The present work deals with these issues: some methods are proposed for data mining of SCADA gearbox temperature and vibration measurements. In particular, a model based on Artificial Neural Networks (ANN) is proposed and its performances are compared against similar approaches in the literature. It arises that vibration analysis at the time scale of SCADA data is not effective for fault diagnosis, even if powered by the artificial intelligence of the ANN, while the proposed ANN model for gearbox temperatures is useful for early fault diagnosis. The method is tested on the data sets of a wind farm in southern Italy and it is shown that it is useful for the diagnosis of incoming faults to three out of nine wind turbines of the site
Dynamic effects of wind loads on a gravity damper
No full textThe gravity damper is safety device used for the air treatment that prevent overpressure inside the unit through the opening. It is a normally closed valve under the effect of the gravity force, which, under the action of the incident air flow, allows to manage any excess mass. Clearly, although the device is rather simple and therefore reliable, the operating conditions may prove burdensome, especially if the gravity dampers are applied to installations of energy transformation, such as the gas turbines; this is mainly due to the need to develop large masses of air at speeds rather incurred. This article describes an experiment carried out on a gravity damper designed to be installed in a gas turbine. The characterization has been performed in numerical (CFD-FEM), considering both the mode shapes and the natural frequencies of the device in working condition as well as any phenomenon of detachment of the fluid that can trigger vortex shedding and subsequently validated in the wind tunnel facilities of the University of Perugia. In particular, what is wanted to be highlighted is the fact that, after a preliminary analysis, it has been clearly evident that, under the operating conditions, the structure would be affected by phenomena of vortex shedding. The shedding frequency is next to some natural frequencies of the structure, with obvious repercussions on the integrity of the structure. An experimental vibration analysis performed in the wind tunnel at flow regime has in fact allowed to identify the phenomenon of lock-in
Numerical and experimental three-dimensional analysis of wakes in complex terrain
No full textThis work deals with wind energy exploitation in complex terrain. The topic in general poses several scientific challenges about the comprehension of wind flow on its own and of the interaction of the wind flow with the wind turbines. In particular, in this work the focus is about wake effects in complex terrain. The selected test case is a cluster of four 2.3 MW wind turbines sited in Italy a very complex terrain. Their behavior is analyzed through Supervisory Control And Data Acquisition (SCADA) data mining and the relevant role of the terrain in distorting the wake of the upstream turbines is observed. These experimental evidences stimulate a deeper comprehension through numerical modeling: Computational Fluid Dynamics (CFD) simulations are run, where the presence of the wind turbines is accounted for through the Actuator Disk (AD) model. A novel way of elaborating the output of the simulations is proposed in this work, providing insight into the three-dimensional evolution of the wake proceeding downstream. The main outcome of the numerical analysis is that the terrain distorts the wind flow so that the wake profile is severely asymmetric with respect to the lateral displacement. These results identify the selected test case as an ideal testing ground for further analysis about yawing, mechanical loads and fatigue behavior in complex terrai
An optimized method to evaluate the performance of trench isolation for railway-induced vibration
No full textDiagnosis of wind turbine misalignment through SCADA data
No full textOptimal alignment of wind turbines to the wind direction is a crucial condition for the quality of power output and for the health of the turbines. Actually, bad alignment can cause degraded performances and dangerous loads that can affect, on the long run, the mechanical safety of the wind turbine. Supervisory Control And Data Acquisition (SCADA) systems are becoming widespread in modern wind energy technology because of the appreciable costs – benefits ratio. The common time scale of SCADA, yet, usually is not effective for misalignment diagnosis because the wind varies too rapidly. For this reason, misalignment is often diagnosed using ad hoc techniques as LIDAR-based or spinner anemometers. In the present work, it is shown that very useful indications for the diagnosis of misalignment can be obtained also from the SCADA data, without invoking expensive supplementary control techniques. The method is validated on the data set of a wind farm sited in Italy
Numerical and experimental investigation of a monotube hydraulic shock absorber
No full textThis work is devoted to the dynamics of a hydraulic monotube shock absorber, whose design resembles racecar vehicles dampers, prototyped at the University of Perugia for scientific purposes. A physical approach is adopted for numerical modeling of the global operation of the device, and the model is validated against a comprehensive test bench experimental campaign, conducted at velocities and frequencies typical of racecar vehicles. The main peculiarity of the prototype is that it is built in Plexiglas, and therefore, it has transparent walls allowing experimental tests with optical acquisition through high-speed camera. This provides a completely novel perspective, because it is possible to observe the evolution of the internal behavior, through the optical access, jointly with standard experimental test approaches. These experimental techniques are especially fit for the analysis of the cavitation phenomenon: the influence of the main boundary conditions (compensation pressure, fluid temperature) on the onset and the evolution of cavitation is investigated. Further, the influence of cavitation, according to its evolution, on the performances of the device is investigated. In particular, it is further shown that the optical acquisition is fundamental to have insight on the incipient and evolving phases of cavitation, which cannot be observed through the common techniques found in the literatur
The Knocking Noise on Twin Tube Shock Absorbers: Individuation and Analysis of the Phenomenon
No full textOn the influence of the elastic characteristics of composite materials on the vibrating properties
Full text linkEconomical composite materials such as PA66GF35 (glass-fibre-reinforced polyamide matrix) are being increasingly used in the automotive industry. Their good mechanical characteristics combined with low density, very high workability, low production cost and high availability are attractive prerogatives that induce engineers to adopt it in complex technological challenges. Injection moulding is the most common production technology used to realize composite components. While in industrial design this type of material is considered as isotropic, it is well known that injection moulding process gives orientation to the reinforcing fibres, leading to anisotropic mechanical behaviour. Starting from these considerations, attention has been turned to the vibrating properties of such materials and to the comparison between vibration modes and mechanical properties. In fact, composite materials are also used to produce components in the automotive field significantly affected by noise problems. Since the noise derives from a fluid-structure interaction, the own frequencies and the vibrating modes cover an important role on the Noise, Vibration and Harshness performance of the components. A comparison of the vibration modes of a plate in PA66GF35, numerically modeled both as isotropic and anisotropic material according to Folgar and Tucker theory, was carried out and compared with experimental measurements. The anisotropy of the composite material is demonstrated by the variation of the mechanical characteristics obtained from the static tensile tests. Results show that injection moulding confers different mechanical properties to real components due to the intrinsic fluid-dynamic phenomena of the production process
Large Amplitude Oscillatory Shear From Viscoelastic Model With Stress Relaxation
No full textThe analytic response for the Cauchy extra stress in large amplitude oscillatory shear (LAOS) is computed from a constitutive model for isotropic incompressible materials, including viscoelastic contributions, and relaxation time. Three cases of frame invariant derivatives are considered: lower, upper, and Jaumann. In the first two cases, the shear stress at steady-state includes the first and third harmonics, and the difference of normal stresses includes the zeroth, second, and fourth harmonics. In the Jaumann case, the stress components are obtained in integral form and are approximated with a Fourier series. The behavior of the coefficients is studied parametrically, as a function of relaxation time and constitutive parameters. Further, the shear stress and the difference of normal stresses are studied as functions of shear strain and shear rate, and are visualized by means of the elastic and viscous Lissajous–Bowditch (LB) plots. Sample results in the Pipkin plane are reported, and the influence of the constitutive parameters in each case is discussed.</jats:p
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