Semnan University Press Journal of Heat and Mass Transfer Research 2345-508X Articles in Press 2026 01 04 The Impact of Vortex Finder Changing on Gas-Oil Separator Performance اثرات تغییرات لوله خروجی روی عملکرد جداسازی گاز-روغن 10406 10.22075/jhmtr.2026.38518.1794 EN Farzad Parvaz Department of Mechanical Engineering, Semnan University, P.O. Box 35131-191, Semnan, Iran and Behbahan Khatam Alanbia University of Technology, Department of Mechanical Engineering, P.O. Box 63616-47189, Behbahan, Iran Sadegh Nikbakht Naserabad Energy Engineering Department, Faculty of Gas & Petroleum, Yasouj University, Gachsaran, Iran. Ehsan Dehdarinejad Department of Mechanical Engineering, Shahrekord University, Shahrekord, Iran Masoud Dorfeshan Behbahan Khatam Alanbia University of Technology, Department of Mechanical Engineering, P.O. Box 63616-47189, Behbahan, Iran Journal Article 2025 07 31 This study employed the Reynolds stress turbulence model (RSM) to numerically investigate the influence of vortex finder shape on the hydrodynamic and collection efficiency within three cylinder-shaped oil-gas cyclone separators, a type commonly used in compressor systems. The simulations were based on realistic operating conditions. The computational simulations revealed that alterations to the outlet pipe configuration in cylindrical cyclones significantly affect the gas-phase hydrodynamics. Case 1 is characterized by the highest tangential velocity, which achieves 2.8 times the inlet velocity. However, Case 3 demonstrates the lowest maximum tangential velocity among the investigated configurations, approximately 1.1 times the inlet velocity. Furthermore, deformation of the cyclone, particularly through a reduction in the outlet diameter, enhances the pressure drop adjacent to the cyclone walls. Nevertheless, the resulting complex flow patterns give rise to a counter-rotating flow, which compromises the overall separation performance. Conversely, the region surrounding the outlet pipe is characterized by heightened turbulence kinetic energy (TKE) and more intense rotational vortices compared to other sections of the cyclone. Therefore, the separation efficiency of gas-oil cylindrical cyclones is positively correlated with increasing flow velocity.