Optimal adjustment of mine fan geometry and operation

Abstract

Mine fans consume significant electrical power, so it is important to ensure high efficiency of their operation. The aim of this study is to develop a method to determine the most economically efficient method to adjust axial fan geometry and operation at the maximum average efficiency in all operating modes. The method includes a developed mathematical model of the single-stage axial fan duty and a genetic algorithm for optimizing the fan parameters. The initial data for the mathematical model were the geometry of the fan blades of the average radius and the parameters of the fan operating mode. The result of the calculation was the fan efficiency in a preset operating mode. Two adjustment scenarios are modeled: fans with variable pitch blades and fans with variable rotation speed. The fan efficiency was determined by calculating the total pressure loss at the unit stage at the middle radius with regard to the loss at the blade tips. Since the mathematical model contains a large number of independent parameters, and there exists the possibility of local extrema, the optimization is performed using the genetic algorithm. The mathematical model of the fan with variable pitch blades was tested using experimental data. The error of the mathematical model in continuous modes at high efficiency (>75%) never exceeds 1.5%. As a case-study, the optimal fan parameters are determined for two preset operating modes and for two adjustment scenarios of fans with variable pitch blades and with variable rotation speed. On the basis of the obtained geometric parameters at the average radius of blades, using the constant circulation law, the fan designs were developed and then investigated by numerical simulation in CFX program. It is shown that if the air flow rate in operating modes differs significantly and the pressure is not, it is advisable to use fans with variable pitch blades.