Experimental Investigation of Lift Enhancement and Drag Reduction of Discrete Co-Flow Jet Rotor Airfoil

Shunlei Zhang,Bifeng Song,Zhuoyuan Li,Xudong Yang,Bo Wang

doi:10.3390/app11209561

Abstract

Rotor airfoil design involves multi-point and multi-objective complex constraints. How to significantly improve the maximum lift coefficient and lift-to-drag ratio of rotor airfoil is a fundamental problem, which should be solved urgently in the development of high-performance helicopter rotor blades. To address this, discrete co-flow jet (DCFJ) technology is one methods with the most potential that can be harnessed to improve the performance of the rotor airfoil. In this study, wind tunnel experiments are conducted to study the effect of DCFJ technology on lift enhancement and drag reduction of OA312 airfoil. Furthermore, the performance improvement effects of the open co-flow jet (CFJ) and DCFJ technologies are studied. In addition, the influence of fundamental parameters, such as the obstruction factor and relative unit length, are analyzed. Results demonstrate that DCFJ technology is better than CFJ technology on the performance enhancement of the OA312 airfoil. Moreover, the DCFJ rotor airfoil can significantly reduce the drag coefficient and increase the maximum lift coefficient and the stall angle of attack. The maximum lift coefficient can be increased by nearly 67.3%, and the stall angle of attack can be delayed by about 12°. The DCFJ rotor airfoil can achieve the optimal performance when the obstruction factor is 1/2 and the relative unit length is 0.025.

Highlights

The rotor is the major component of a helicopter to generate lift and operating force, which should satisfy the requirements of the helicopter for hovering, forward flight and maneuvering
As the basic component of the rotor blade, the performance of a rotor airfoil is crucial in terms of high maximum lift coefficient, high lift-to-drag ratio, high stall angle of attack and low zero-lift pitch moment
Existing airfoil design and optimization technologies have limited improvements in airfoil performance, while active flow control technology can significantly improve the aerodynamic characteristics of the rotor airfoil

Summary

Introduction

The rotor is the major component of a helicopter to generate lift and operating force, which should satisfy the requirements of the helicopter for hovering, forward flight and maneuvering. When the helicopter is hovering, its performance is limited by the maximum lift of the rotor. The low stall angle of attack and flow separation seriously restrict the flight performance of the helicopter. As the basic component of the rotor blade, the performance of a rotor airfoil is crucial in terms of high maximum lift coefficient, high lift-to-drag ratio, high stall angle of attack and low zero-lift pitch moment. The essential issue is how to improve the lift-drag characteristics and stall characteristics of the rotor airfoil to enhance the aerodynamic characteristics of the rotor and the flight performance of the helicopter. Existing airfoil design and optimization technologies have limited improvements in airfoil performance, while active flow control technology can significantly improve the aerodynamic characteristics of the rotor airfoil

Methods

Results

Conclusion