Design and Development of Three-Bladed Propeller for Micro Air Vehicles

Abstract

CSIR-National Aerospace Laboratories (CSIR-NAL) is having a major program on development of Micro Air Vehicles (MAV) for civil, surveillance, and defense use. Under this program, MAV components development has been undertaken in various divisions of NAL. Propulsion system for one of the configurations of NAL MAV having fixed wing is battery-driven miniature motor and mini propellers. Efficient propulsion system plays a major role in deciding the endurance, payload, and maneuverability of MAV’s. Design of efficient propellers for these classes of vehicles is a challenging task because of their lower operating Reynolds number as well as conservative power utilization to enhance the endurance. Earlier, 2-bladed, fixed pitch, variable speed, 6-inch diameter propellers with different plan form has been carried out and reported. The present requirement is for 3-bladed, fixed pitch, variable speed mini propellers to augment thrust within the geometrical constraints as envisaged in the design of two-bladed propellers. To meet the mission requirements, design of three-bladed, fixed pitch, variable speed mini propellers were carried out using minimum induced loss method, and Eppler-193 airfoil is used in the design in view of its higher lift to drag ratios at low Reynolds numbers. This resulted in slight penalty on weight as well as power consumption and reduced noise level. Propeller CAD model is generated using SOLID WORKS and used for analysis as well as for fabrication. Performance estimation for this propeller is carried out using blade element momentum theory and ANSYS FLUENT. Fabrication of this propeller is carried out using three methods namely rapid prototype (RPT) using poly carbonate and conventional vacuum casting using poly urethane material and CFRP material with conventional casting using aluminum mold. The overall performance parameters like thrust, propulsive efficiency and motor power are evaluated for CFRP propeller and tested at uninstalled condition. Overall performance of the propellers is evaluated at MAV Aerodynamics Research Tunnel (MART), CSIR-NAL for different wind velocities and propeller rotational speeds in uninstalled conditions. This paper brings out the work carried out on design, development and testing of three-bladed miniature propeller for MAVs and its analysis using computational tools at propulsion division, CSIR-NAL.