Current Issue : July - September Volume : 2017 Issue Number : 3 Articles : 5 Articles
This paper concentrates on a new configuration for a wind turbine, named KIONAS.\nThe main purpose is to determine the performance and aerodynamic behavior of KIONAS, which\nis a vertical axis wind turbine with a stator over the rotor and a special feature in that it can consist\nof several stages. Notably, the stator is shaped in such a way that it increases the velocity of the air\nimpacting the rotor blades. Moreover, each stage�s performance can be increased with the increase of\nthe total number of stages. The effects of wind velocity, the various numbers of inclined rotor blades,\nthe rotor diameter, the stator�s shape and the number of stages on the performance of KIONAS\nwere studied. A FORTRAN code was developed in order to predict the power in several cases by\nsolving the equations of continuity and momentum. Subsequently, further knowledge on the flow\nfield was obtained by using a commercial Computational Fluid Dynamics code. Based on the results,\nit can be concluded that higher wind velocities and a greater number of blades produce more power.\nFurthermore, higher performance was found for a stator with curved guide vanes and for a KIONAS\nconfiguration with more stages....
By means of numerical simulation and experimental verification, this article investigates the hydraulic performance and\npressure fluctuation of a tank-style axial-flow pump device. With orthogonal test, 16 schemes are designed concerning\nthe different flow conditions of the inlet and outlet passages, and simulated calculations are done; then the non-steady\nnumerical simulation of pressure fluctuation is carried out for the optimized pump device; a model test finally verifies\nthe reliability of the simulated numerical values of the optimized scheme. The results show that using the orthogonal\ntest, an optimized scheme of the inlet and outlet passages can be obtained; compared with the initial scheme, the optimized\none reduces the hydraulic loss by 1.3 cm in the inlet passage and 7.96 cm in the outlet passage; numerical simulation\nwitnesses the highest pump operating efficiency of 70.04%, efficiency of 66.82% with the design head of 1.36m, and\nthe corresponding flow of 34.31m3/s; the model test verifies all the simulated values of the optimized scheme with the\nhighest pump operating efficiency reaching 71.5% and the test efficiency arriving at about 64% when the design head is\n1.36 m. Meanwhile, the highest pressure fluctuation appears at the entrance of the impeller; the main frequency of the\nimpeller and guide vane pressure fluctuation is 5Hz depending on the frequency of the blade. This study offers reference\nfor similar pump station project....
In the present work, the performance of oil-air two-phase flow under different\nlubricant oils was investigated. The simulation method was applied to study\nthe influence of the oil viscosity on the flow pattern, velocity distribution and\nRe number in oil-air lubrication by FLUENT software with VOF model to\nacquire the working performance of oil-air lubrication for high-speed ball\nbearing. This method was used to obtain the optimum lubrication conditions\nof high-speed ball bearing. The optimum operating conditions that produce\nthe optimum flow pattern were provided. The optimum annular flow was obtained\nby PAO6 oil with the low viscosity. Reynolds number influences the\nfluid shape and distribution of oil and air in pipe. The annular flow can be\nformed when Reynolds number is an appropriate value. The velocity distribution\nof oil-air two-phase flow at outlet was also discussed by different oil viscosities.\nThe simulating results show that due to the effect of the oil viscosity\nand flow pattern the velocity decreased and expanded gradually close to the\npipe wall, and the velocity increased close to the central pipe. The simulation\nresults provide the proposal for the design and operation of oil-air two-phase\nflow lubrication experiments in the present work. This work provides a useful\nmethod in designing oil-air lubrication with the optimum flow pattern and\nthe optimum operating conditions....
This research presents theoretical analysis and numerical simulation of combined valvesââ?¬â?¢ dynamic\ncharacteristics in reciprocating oilââ?¬â??gas multiphase pump. Based on the mathematical model describing\nvalvesââ?¬â?¢ motion, a geometric model of pump cavity and combined valves is put forward for\nnumerical simulation in multiphase pump. The simulation is conducted by computational fluid\ndynamics (CFD) method with its dynamic grid technique. The motion process of suction valve\nand discharge valve are obtained on the basis of boundary conditions and optimized numerical\napproaches. And the effects of gas volume fraction (0.1âË?¼0.9), suction pressure (0.20âË?¼0.40 MPa)\nand discharge pressure (1.0âË?¼3.0 MPa) on valvesââ?¬â?¢ motion are reported. The results of pressure distribution,\nand valvesââ?¬â?¢ lift and velocity show that valve platesmaycling or rebound and then vibrate after\nreaching the lift limiter, and the lag angle of one cycle remains 3Ã?° under different working conditions.\nThe study could lay theoretical foundation for the design of new type of multiphase pump....
The helical flows of couple-stress fluids in a straight circular cylinder are studied in the framework of the newly developed, fully\ndeterminate linear couple-stress theory. The fluid flow is generated by the helical motion of the cylinder with time-dependent\nvelocity. Also, the couple-stress vector is given on the cylindrical surface and the nonslip condition is considered. Using the integral\ntransformmethod, analytical solutions to the axial velocity, azimuthal velocity, nonsymmetric force-stress tensor, and couple-stress\nvector are obtained.The obtained solutions incorporate the characteristic material length scale, which is essential to understand the\nfluid behavior at microscales. If characteristic length of the couple-stress fluid is zero, the results to the classical fluid are recovered.\nThe influence of the scale parameter on the fluid velocity, axial flow rate, force-stress tensor, and couple-stress vector is analyzed by\nnumerical calculus and graphical illustrations. It is found that the small values of the scale parameter have a significant influence\non the flow parameters....
Loading....