1,720,995 research outputs found
Study of tip clearance effects in centrifugal fans with unshrouded impellers using computational fluid dynamics
No full textPerformance of centrifugal fans with unshrouded impellers strongly depends upon complex configuration of the asymmetrical flowfield in the axial direction, which is highly unsteady. The flowfield, in turn, is considerably affected by the design parameters of both scroll and impeller geometry, for which tip clearance is of particular interest. This article presents a three-dimensional computational fluid dynamics (CFD) simulation of the flowfield in three different unshrouded centrifugal fan impellers with varying tip clearances. A commercial CFD code, namely, Fluent V6.2.16 with a k-epsilon two-equation turbulence model was utilized in order to study the effects of tip clearance on the overall performance of each fan with the tip clearances ranging from 5 to 30 mm. The numerical results were compared with the experimental data reported previously in the literature by the present author and his colleagues, and excellent agreements were observed for each fan
Modeling and testing of a field-controllable magnetorheological fluid damper
No full textIn this study, an experimental and a theoretical study were carried out to predict the dynamic performance of a linear magnetorheological (MR) fluid damper. After having designed and fabricated the MR damper, its dynamic testing was performed on a mechanical type shock machine under sinusoidal excitation. A theoretical flow analysis was done based on the Bingham plastic constitutive model to predict the behavior of the prototyped MR damper. The theoretical results were then validated by comparing them against experimental data, and it was shown that the flow model can accurately capture the dynamic force range of the MR damper. In addition to the flow model, a modified parametric algebraic model was proposed to capture the hysteretic behavior of the MR damper. The superiority of the proposed modified model was shown by comparing it with the Alg model as well as with a widely adopted modified Bouc-Wen model through an error analysis. It is observed that although all the three models are comparable at the excitation velocities of 0.05, 0.10, and 0.15 m/s, the mAlg model is remarkably successful at the highest excitation velocity of 0.2 m/s over the other two. The improvements in the predictions were found to be over 50%, relative to unmodified model especially at lower current inputs. Therefore, it was concluded that the present flow model can be successfully adopted to design and predict the dynamic behavior of MR dampers, while the mAlg model can be used to develop more effective control algorithms for such devices. (C) 2010 Elsevier Ltd. All rights reserved
Prediction of relative efficiency reduction of centrifugal slurry pumps: empirical- and artificial-neural network-based methods
No full textThis paper has focused on the predictive methods for relative efficiency reduction of centrifugal pumps handling slurries based on empirical- and artificial-neural network (ANN) approaches. A new correlation has been developed to predict the relative efficiency reduction of the centrifugal slurry pumps, and the range of validity of the present correlation has been verified using the data available in the literature. Then, the applicability of ANNs for the same purpose has been investigated using a total of 315 data. The comparisons of both methods showed that the present correlation produced the lowest deviation among some recent correlations in the literature, and, if properly constructed, ANNs could be used as a predictive tool with higher accuracy than the conventional empirical methods
Numerical simulation of laminar flow of water-based magneto-rheological fluids in microtubes with wall roughness effect
No full textFully developed laminar flows of water-based magneto-rheological (MR) fluids in microtubes at various Reynolds and Hedsrom numbers have been numerically simulated using finite difference method. The Bingham plastic constitutive model has been used to represent the flow behavior of MR fluids. The combined effects of wall roughness and shear yield stress on the flow characteristics of MR fluids, which are considered to be homogeneous by assuming the small particles with low concentration in the water, through microtubes have been numerically investigated. The effect of wall roughness on the flow behavior has been taken into account by incorporating a roughness-viscosity model based on the variation of the MR fluid apparent viscosity across the tube. Significant departures from the conventional laminar flow theory have been acquired for the microtube flows considered. (c) 2005 Elsevier Ltd. All rights reserved
Time-dependent CFD and quasi-static analysis of magnetorheological fluid dampers with experimental validation
No full textIn the study the non-Newtonian flow in the annular gap is investigated by a quasi-static analysis that enables to calculate plug thickness and damper force. Also CFD analysis of the MR damper is performed by using transient and deformed mesh to be able to simulate moving of piston head in the damper considering non-Newtonian regions. Results of the analyses have been compared to experimental data obtained from MR dampers manufactured for the study. Good agreement has been observed between experimental and analyses data. In addition, effects of stroke and velocity on the damper performance are examined in the study. (c) 2012 Elsevier Ltd. All rights reserved
Comparative evaluation of some existing correlations to predict head degradation of centrifugal slurry pumps
No full textIn order to optimally design a slurry transportation system, it is necessary to know how the presence of solids will change the performance of the slurry pump to be installed. This paper makes the comparison of some existing correlations available in the literature to predict the head reduction factors of such centrifugal pumps handling slurries. For this purpose, a large number of published data for various centrifugal slurry pump tests in the literature have been used to develop a new correlation and then this correlation and all others have been tested against the data. For the proposed correlation, the mean and average deviations between the calculated and measured head reduction factor is 8.378 and 0.620%, respectively, for all data of mostly handling commercial slurries. It also produces 12.441 % mean deviation in the prediction of efficiency ratio for 216 data points. Overall, the new correlation that can be applied to both metal and rubber lined pumps with impeller diameter up to 850 mm, gives remarkably closer fit to the published data of both head and efficiency ratios than all existing correlations
Energy auditing and recovery for dry type cement rotary kiln systems - A case study
No full textCement production has been one of the most energy intensive industries in the world. In order to produce clinker, rotary kilns are widely used in cement plants. This paper deals with the energy audit analysis of a dry type rotary kiln system working in a cement plant in Turkey. The kiln has a capacity of 600 ton-clinker per day. It was found that about 40% of the total input energy was being lost through hot flue gas (19.15%), cooler stack (5.61%) and kiln shell (15.11% convection plus radiation). Some possible ways to recover the heat losses are also introduced and discussed. Findings showed that approximately 15.6% of the total input energy (4 MW) could be recovered. (C) 2004 Elsevier Ltd. All rights reserved
PARAMETRIC INVESTIGATION OF A CENTRIFUGAL SLURRY PUMP WHILE HANDLING CLEAR WATER
No full textThe results show that the increase in blade number leads to an increase at head and shaft power. However, the hydraulic efficiency is variable and depends on flow rates. Around operation conditions of the studied pump, the impellers which have three and four blades are more efficient than impellers with two and five blades. Furthermore, by increasing of blade height from 30 mm to 50 mm, the performance of the slurry pump increases only at high flow rates. On the other hand with the decreases in blade thickness from 50 mm to 30 mm, the performance of centrifugal slurry pump increases at all flow range
Prediction of centrifugal slurry pump head reduction: An artificial neural networks approach.
No full textThe feasibility of using artificial neural networks (ANN) in the prediction of head reduction of centrifugal pumps handling slurries is examined. An ANN model is proposed and compared with the empirical correlation given by the present authors earlier The comparison showed that the ANN could successfully be used for the prediction of head reductions of centrifugal slurry pumps. The mean deviation between predicted and experimental values is 5.86% which is reasonable for slurry handling processes
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