CFD Investigation of Supersonic Scramjet Exhaust Geometry for Emission Reduction and Sustainable Hypersonic Propulsion

¹ *Department of Mechanical Engineering, Mailam Engineering College-Mailam, Villupuram 604304, Tamil Nadu, India, This email address is being protected from spambots. You need JavaScript enabled to view it.
² School of Engineering and Technology, Jaipur National University, Jagatpura, Jaipur, Rajasthan- 302017
³ Department of Mechanical Engineering, Mohan Babu University, Rangampeta, Tirupathi, Andhra Pradesh, Pincode-517501
⁴ Department of Autotronics, Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai- 602105, Tamil Nadu, India
⁵ Department of Mechanical Engineering, SRM Institute of Science & Technology, Vadapalani Campus, Chennai- 600026, Tamil Nadu, India
⁶ School of Mechanical Engineering, Sathyabama Institute of Science and Technology, Chennai- 600119, India
^7,9a Department of Mechanical Engineering, Vels Institute of Science, Technology & Advanced Studies, Chennai- 600117, Tamil Nadu, India
⁸ Faculty of Business and Communications, INTI International University, Putra Nilai- 71800, Malaysia
^9b Research Fellow, INTI International University, Putra Nilai- 71800, Malaysia

Published online: 16 April 2026

Abstract

This study employs CFD analysis to optimize the scramjet exhaust divergent angle with the aim of improving propulsion efficiency and reducing environmental impact in hypersonic flight. The work uses the computational fluid dynamics software ANSYS Fluent to simulate the supersonic flow inside the Scramjet engine. CATIA V5 to make the model and by using ANSYS to check and design analysis. The performance and efficiency of a supersonic nozzle under different divergent angles (10, 15, and 18 degrees) by using a symmetric axis in the two-dimensional model. Then the scramjet engine's exhaust by changing the angles in different ways. The degree of the divergent shock wave is coming from the exhaust. These are generally used to work at a higher speed, typically through the rocket that uses hydrogen as fuel. The CFD results show that the 15° divergent angle had the highest outlet velocity (about 720 m/s) and the best pressure expansion ratio (about 1.32) compared to the 10° and 18° angles. This means that the nozzle worked better and the flow was more stable.