Aerodynamic analysis of a windmill water pump using blade element momentum theory

Abstract

A windmill water pump has been designed based on simulation data using the Blade Element Momentum Theory (BEMT) method. According to the simulation data, a 10-blade configuration with an incidence angle of 7 degrees is predicted to produce an output torque of 40 Nm. To simplify the turbine manufacturing process, a turbine cross-sectional profile with a bent flat plate-based airfoil was selected. The simulation results indicate that providing an incidence angle of 7 degrees compensates for the resulting decrease in aerodynamic performance compared to using a cambered airfoil. Furthermore, a dynamic analysis was conducted to predict the turbine's rotational speed. With a 10-blade configuration and a blade material density of 2900 kg/m³ at a wind speed of 5 m/s, it is predicted to rotate at a steady speed of 167 rpm. When the material density is increased to 3500 kg/m3, the rotor's predicted rotational speed is 160 RPM. While the difference in rotational speed due to the increase in material density is not very significant, the time to reach steady-state conditions varies considerably. Specifically, a turbine with a material density of 2900 kg/m3 requires a settling time of 168 seconds, while a turbine with a density of 3500 kg/m3 requires a settling time of 310 seconds. This notable difference suggests that mass inertia primarily influences the dynamic response of the turbine in achieving a steady rotational speed without significantly affecting the turbine's aerodynamic performance.