Modelling and Simulation of Fan Performance using CFD Group

Abstract: Performance of vacuum cleaners are affected by factors such static pressure, airflow rate and efficiency. In this thesis work, attempt has been made to design a fan to meet the requirements of suction static pressure and air flow rate and in the process understand the fan design parameters that affect these performance parameters. Parametric study has been conducted for the same, by choosing six fan design parameters. Additionally, ways to increase the fan efficiency has been investigated during the parametric study. Computational Fluid Dynamics is used to visualize the flow inside the fan casing and further to simulate fan performance at an operational point. Steady state RANS and moving reference frames was used to model the turbulence in the fluid flow and rotation of the fan, respectively. Performance curve showing the relation between static suction pressure and mass flow rate is plotted for the base model is in proximity to the required performance. Parametric study was conducted on the six fan design parameters: Fan diameter, number of impeller blades, blade outlet angle, radius of the curve connecting inlet to outlet section of the fan, diffuser exit length and splitter blade length. The range for each parameter analysis was restricted so that static pressure values are around the required performance. Greater performance variation was found with design parameters: fan diameter, blade outlet angle, radius of the curve connecting inlet to outlet section of the fan and diffuser exit length. This variation at low mass flow rate can be majorly attributed to the randomness in the flow captured by entropy contours. At high mass flow rate, blockage in the flow visualized by pressure contours reasoned for the performance variation. Greater performance variation was not when design parameters such as number of blades and splitter blade length were varied. Larger variation of these parameters is required to see better variation.