A Novel Approach to Design Reversible Counter Rotating Propeller Fans

Because of their high performance and unique abilities like producing none-rotating wake, Counter Rotating Propellers (C.R.P.) are being used in many advanced propulsion or ventilation systems. But due to complicated design procedure of C.R.P. fans up to now it was not possible to apply the concept in reversible systems. For the first time in this research, a new method presented to design a reversible counter rotating propeller system. This method is based on designing a basic C.R.P. by a reliable edition of blade element theory to achieve maximum performance in main rotating course and then to optimize it in order to have almost same performance in reverse rotating course. After expressing concepts of the method, a basic model is designed to ensure the capability of the presented scheme. Design outcome was a Reversible C.R.P. (R.C.R.P) system with 0.5 meter in diameter and cross section of NACA2412 airfoil. This model is evaluated by using R.S.M. turbulence method through ANSYS Fluent commercial software package. Evaluation results showed that system has efficiency of 0.85 in main course and 0.78 in reverse course by which a good performance for a small size reversible system can be captured.