The wall profile of the swirl chamber greatly impacts the internal flow structures and separation efficiency of a liquid-liquid separation hydrocyclone. The objective of this study is to examine the effects of parabolic and hyperbolic wall profiles of hydrocyclone swirl chamber on the internal flow structures and separation efficiency based on the numerical simulations. The internal flow structures observed for the different wall profiles of swirl chamber motivates the redesign of hydrocyclone geometry to achieve enhanced separation efficiency. Results show that, for a dilute system (oil concentration less than 1%), the hyperbolic and parabolic swirl chambers without a tail pipe yield, respectively, 16.5% and 25% higher separation efficiency for a droplet size of 30 pm when compared with a conical swirl chamber without tail pipe. However, the hyperbolic swirl chamber has a greater potential for the reduction of effective length of hydrocyclone with maintaining high separation efficiency. In addition, a hydrocyclone with truncated hyperbolic swirl chamber and tail pipe provides very long reverse flow core and yields 17% and 33% higher efficiency than that of full hyperbolic and conical swirl chambers without tail pipe, respectively. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.