Computational fluid dynamics of helicopter engine exhaust outflow

• Main Author: Chan, Kenneth Mun Chew
• Other Authors: Martin Skote
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/71481
• Institution: Nanyang Technological University

This paper reviews the computational study of the flow of exhaust gases in a helicopter’s Lobed Mixer Ejector or simply, an exhaust tailpipe. This study was done to investigate the directional flow of these multi-species fluids, when mixed with the entrained ambient air introduced by the rotor downwash. On top of that, the paper will highlight the heat dissipation from the ejector’s outlet, due to the significant amount of energy produced by the turboshaft’s combustion process. ANSYS Fluent was used in this analysis by simulating the theoretical fluid flow with hypothetical flight condition parameters. Contributing factors that affect a helicopter exhaust’s outflow and thus heat dissipation, would include the magnitude of the rotor’s downwash, the traveling speed of the helicopter and the orientation of the ejector. For simplicity, however, this study is limited to the conditions experienced by a hovering helicopter. In the simulation, the Shear Stress Transport (SST) K-Omega model was adopted, with a consideration of multiple gas species involved in the air-exhaust mixture. With effective simulation setup including accurate 3D CAD models of the Lobed Mixer Ejector & suitable mesh generation, a reliable solution provided by ANSYS Fluent was possible. The results proved to be as accurate as a previous study, conducted by Nanjing University of Aeronautics & Astronautics (NUAA). Illustrations and graphical methods were generated to offer a comprehensive presentation of the temperature distribution, velocity magnitudes and streamlines of the exhaust gas mixture. Additionally, having examined these plots and data, the report concludes with a discussion and interpretation of the findings.