Chapter 8 Study of Regression Rate in Hybrid Rockets Using Vortex Injector P. K. Dash and G. Ram Vishal Nomenclature a Regression rate coefficient ˙ m Mass flow rate per unit length B Mass transfer number C p Specific heat of gas D Diameter f m Fuel-air rate G Free stream mass flux h Enthalpy H Heat of combustion k Thermal conductivity K ox Oxidizer mass fraction L Length of fuel grain Le Lewis number n Flux index P. K. Dash (B ) · G. Ram Vishal Department of Aeronautical Engineering, Nitte Meenakshi Institute of Technology, Bengaluru, Karnataka, India e-mail: pramodkumar.dash@nmit.ac.in G. Ram Vishal e-mail: ramvishal.g@nmit.ac.in © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 S. Narendranth et al. (eds.), Recent Advances in Mechanical Engineering, Lecture Notes in Mechanical Engineering, https://doi.org/10.1007/978-981-19-1388-4_8 75