•A microscopic machine learning based approach for predictive maintenance is presented.•Algorithms for concept drift detection and prediction in data streams are detailed.•Concept drift prediction ...outperforms drift detection on synthetic data sets.•An entire run-to-failure of a radial fan impeller was conducted in a case study.•The run-to-failure of a radial fan impeller could be detected and closely analyzed.
In this work we present a machine learning based approach for detecting drifting behavior – so-called concept drifts – in continuous data streams. The motivation for this contribution originates from the currently intensively investigated topic Predictive Maintenance (PdM), which refers to a proactive way of triggering servicing actions for industrial machinery. The aim of this maintenance strategy is to identify wear and tear, and consequent malfunctioning by analyzing condition monitoring data, recorded by sensor equipped machinery, in real-time. Recent developments in this area have shown potential to save time and material by preventing breakdowns and improving the overall predictability of industrial processes. However, due to the lack of high quality monitoring data and only little experience concerning the applicability of analysis methods, real-world implementations of Predictive Maintenance are still rare. Within this contribution, we present a method, to detect concept drift in data streams as potential indication for defective system behavior and depict initial tests on synthetic data sets. Further on, we present a real-world case study with industrial radial fans and discuss promising results gained from applying the detailed approach in this scope.
A low sound pressure level is a crucial quality feature for industrial and non-industrial radial fans. The scientific literature documents numerous mechanisms of flow-induced sound generation that ...can occur in a radial fan. Nevertheless, not all sound generation mechanisms are considered well-understood today and thus are still dealt with in ongoing research. This work develops an experimental setup to investigate the different mechanisms of flow-induced sound generation in radial fans. The aim is to close the existing gap between available experimental research on axial and radial fans. One critical factor for the experimental investigation of flow-induced sound generation in fans is the control of inflow. Due to the design of radial fans, the fluid flow deflects from the axial supply duct to the radial direction upstream of the impeller, generating a complex flow field with limited control possibilities. Hence, we designed a test rig that improves the control of inflow conditions, aiming to resolve the superposed sound generation mechanisms in acoustic measurements. This paper presents the key features of the test rig and some first experimental results. The investigation of the distinct sound generation mechanisms is left to future work based on the introduced test rig.
•A novel aeroacoustic test rig for centrifugal fans is presented.•The test rig allows for the variation of inlet conditions for centrifugal fans.•It has been possible to create a reference configuration with low sound emissions.•The inlet conditions to the centrifugal fan affect its noise emissions.•Correlation between pressure fluctuations on the blade and sound radiation.
Display omitted
•First realized SOFC system with steam-driven anode off-gas recirculation fan.•Design of a novel oil-free and durable recirculation fan with gas film bearings.•Propulsion with steam ...turbine leads to explosion-proof and efficient fan operation.•One of the smallest steam turbines tested with a tip diameter of 15 mm.•Reliable method of measuring recirculation ratios with a double Venturi nozzle.
While the global fuel utilization of solid oxide fuel cells (SOFCs) is limited by the stack aging rate, the fuel excess is typically used in a burner, and thus limiting the system electrical efficiency. Further, natural-gas-fueled SOFCs require treated water for the steam reforming process, which increases operational cost.
Here, we introduce a novel micro anode off-gas recirculation fan that is driven by a partial-admission (21%) and low-reaction (15%) steam turbine with a tip diameter of 15 mm. The 30 W turbine is propelled by pressurized steam, which is generated from the excess stack heat. The shaft runs on dynamic steam-lubricated bearings and rotates up to 175 krpm.
For a global fuel utilization of 75% and a constant fuel mass flow rate, the electrical gross DC efficiency based on the lower heating value was improved from 52 % to 57 % with the anode off-gas recirculation, while the local fuel utilization decreased from 75% to 61%, which is expected to significantly increase stack lifetime. For a global fuel utilization of 85%, gross efficiencies of 66% in part load (4.5 kWe) and 61% in full load (6.3 kWe) were achieved with the anode off-gas recirculation. The results suggest that the steam-driven anode off-gas recirculation can achieve a neutral water consumption.
The aeroacoustics of several configurations of a large complex radial fan module typical of ventilation systems used in building or large transportation systems has been directly simulated with a ...Lattice Boltzmann Method. For the reference configuration the available flow measurements are well captured by the simulation and excellent noise predictions are achieved for all microphones both in terms of levels and spectral shape. The inlet distortion and a flow separation at the fan blade foot are shown to cause the observed strong tonal noise at the blade passing frequency. The unsteadiness of the tonal noise is also traced to large “cucumber-like” coherent structures wandering on the fan hub and hitting the blade leading edge quite randomly. Fan hub contouring is shown to almost eliminate the flow detachment at the hub and improve fan performances. Yet it does not reduce the inlet distortion and has only a marginal effect on the noise. Adding a thin filter on the bellmouth removes the large turbulent structures ingested by the fan and improves the flow-field uniformity at the fan inlet. Significant noise reduction is then achieved eventhough additional pressure losses are introduced. A final tonal noise control with a rotating obstruction placed on the fan bellmouth has been successfully simulated yielding the expected sound modulation. All these flow and acoustic features compare remarkably well between the measurements and the simulations.
A series of liquid crystals (LCs) of bromine-terminated azobenzene were synthesised and characterised. The LCs were composed of an azobenzene core, an alkyl chain and a flexible spacer with a bromine ...atom at a remote position. Mesomorphic properties were dependent on both the alkyl chain length and the relative position of the bromine atom at the end of the spacer group. The nematic phase was favoured over the smectic A phase for alkyl chains with one and seven carbon atoms. However, the SmA mesophase was dominant for compounds with 10-carbon alkyl chains. The remote bromine atom in the spacer group favoured SmA for homologous with n-decyl chains and the nematic phase for n-heptyl and methyl groups. Molecular modelling showed that the azobenzene LCs tended to adopt the all trans-conformation in the gas phase as the number of carbon atoms increased. For short spacer groups, bent conformations contributed to the level population proportion of conformers. For the non-LC 5a, the gauche conformation became the most stable with a torsional angle of -68.9°. X-ray experiments showed a monolamellar SmA mesophase in an antiparallel arrangement. Absorption maxima at 360 and 440 nm were assigned to π-π* and n-π* transitions, respectively.
Aplikacija sredstava za zaštitu bilja na visoke voćke vrlo je zahtjevan rad, kod kojeg često dolazi i do velikog gubitka škropiva. U radu su prikazani strojevi koji se najčešće upotrebljavaju za ...zaštitu oraha i drugih visokih voćaka. Za visoke voćke aksijalni raspršivač mora imati crpku s većim protokom i ventilator većeg promjera, da škropivo dođe na pravo mjesto. Na području zaštite visokih voćaka na njemačkoj listi strojeva s redukcijom gubitaka škropiva nalaze se samo četiri raspršivača. Za zaštitu visokih voćaka upotrebljavaju se i raspršivači s usmjerivačkim topom, pa i leđni motorni raspršivači.
Hybrid noise predictions of a radial notebook blower Sanjose, Marlène; Moreau, Stéphane; Gullbrand, Jessica
European journal of mechanics, B, Fluids,
January-February 2017, 2017-01-00, Letnik:
61
Journal Article
Recenzirano
Odprti dostop
The tonal noise of a notebook radial blower in a free-field environment is investigated using an hybrid method based on unsteady Reynolds Averaged Navier–Stokes simulations and an Ffowcs Williams and ...Hawking’s analogy to compute the acoustic far-field from the wall-pressure fluctuations recorded in the simulations. Incompressible and compressible simulations have been performed to demonstrate the effect of the compressibility on the noise sources in the very constrained environment due to the casing specific design. The complex flow in the blower yields distributed noise sources. The tongue interaction with the blade wakes and the inlet flow distortions are major contributors at the blade passing frequency, while smaller structures in the clearance are important noise sources at higher harmonics. The influence of a daisy obstruction on one of the blower inlet is also investigated. The additional inlet distortion strongly affects the noise levels at the blade passing frequency. The acoustic predictions are compared to experimental measurements and provide good agreement within the variability of the acoustic level measured between blowers of the same conception batch. The compressible simulations provide the best agreement at higher frequency when the compactness limit is overpassed.
The lack of standards for industrial fan sizing forces companies to size its products under strong influence of precious experience, based, mostly, in empiric data. This can lead to the oversizing of ...the fans and, thus, increase the costs of the final product unnecessarily. The scope of the work is the computational fluid dynamics analysis of radial fans, using qualitative and quantitative results. The study was conducted in bench scale using a prototype. The characteristic data from the fan was collected and inserted in the ANSYS FLUENT software. The preliminary results, using the original geometry will enable the project optimization, increasing the product’s efficiency via the elimination of supersizing and assessing the feasibility of computational simulations in the industry.
PDF
