Numerical Simulation And Design Study Of Water Driven Fan

With the continuous development of our marine industry, there are higher and higher requirements on the marine auxiliary equipment. The marine water driven fans should be not only fire prevention and smoke prevention, but also explosion-proof and lightweight. Most of domestic research on water driven fan adopt conventional design methods. One kind of marine portable water driven fan with high speed and large amount of smoke exhaust in the market was researched by adopting the method of numerical simulation and model test, which filled in the blank of the numerical simulation research on portable water driven fan. This paper carried out the following work:(1)CFD Model Research on the Water Driven FanAfter analysising the structure and working principles of the research object, the fluid domain was simplified reasonably and by using the software Gambit the3D Modeling and meshing of the water flow field and air flow field were completed; Based on the standard k-ε epsilon model of the Fluent software, the internal flow field of the hydraulic turbine and the fan were simulated, by comparing the results of numerical simulation date and experimental data, the relative error range between the calculated values for the flow rate of the hydraulic turbine and the measured values was0.9%-7.6%, and the relative error range between the calculated values for the total pressure of the fan and the measured values was4.7%-15.5%, which could basically meet the computing requirement. Thus the calculation model was basically reasonable.(2)Performance Prediction of the Water Driven Fan Based on Multi Field CouplingA multi field weak coupling calculation method was put forward:water flow field and air flow field are calculated at the same time by using Fluent UDF to program and control the process, and after the completion of calculation of each time step, data exchanges between the two flow field by reading and writing data files, until two flow field match and become steady. This method can not only complete the performance prediction of water driven fan, but also easily describes the relationship between different flow fields and provides reference for the transient calculation of the water driven fan.(3)The Flow Field Numerical Study and Structure Improvement of the Hydraulic Turbine The changes of the main hydraulic turbine performance parameters caused by the changes of the structure parameters of the turbine and nozzle which are the main parts of the hydraulic turbine were analyzed. The structure parameters discussed include the type line, the number and the height of hydraulic turbine blades, nozzle number, nozzle inner surface shape, oblique angle, as well as the cooperative relationship between the hydraulic turbine and nozzle. Simulation results show that:the hydrodynamic performance of the modified blade type line is a little less than that of the conventional line, but the processing performance can be improved obviously, so the modified blade type line can replace the conventional line; the blade number is available to choose in a wide range, and the turbine blade number of the original model is reasonable; By increasing height of the turbine blade simply cannot improve the performance; The addition of nozzle number can effectively increase the output; Conical nozzle can effectively reduce the pressure loss, increase the power and efficiency of the turbine; The smaller the nozzle oblique Angle is, the better the performance of the turbine will be, but considering the structure and the processing difficulty, oblique Angle should be in a certain range; By increasing the nozzle outlet diameter and blade height at the same time to decrease the diameter ratio, the flow capacity and power of the turbine can be obviously improved. According to the study, the structure of the turbine was improved. When the inlet pressure was0.2Mpa, the increasement and the grow rate of the turbine power were39.4W and24.7%, and when the inlet pressure was0.7Mpa, the increasement and the grow rate were330.2W and31.7%.(4)The Design Researches of the Potable Water Driven FanThe hydraulic design, structure design and aerodynamic design of the portable water driven fan were studied. When scaling coefficient k is0.9-1.2, the power range of different turbine is1000W-2200W, which provides wider power range for the design of the fan; Under the condition of meeting the structural strength requirement, the selection of the turbine and fan maximum size were completed; Combined with turbine performance curve, the way to predicting the design flow rate and total pressure of the fan was given. A design scheme of the water driven fan was proposed at last, and was verified through a design case.