Using computational fluid dynamics to explore new hydrokinetic fluid coupling design for industrial applications

This study presents the initial design and computational investigation of a traction-type hydrokinetic fluid coupling for industrial applications. The problem addressed is the limited availability of validated mathematical and computational models for optimizing impeller–runner design and oil selection in fluid couplings. The objective is to establish an empirical–computational framework that combines dimensional analysis with CFD simulations to accurately predict operating behavior. The impeller and runner were designed using dimensional analysis–based empirical relations, supported by assumptions of incompressible flow, constant density, and steady-state operating conditions with a slip of 2–3 %. The theoretical oil mass required for power transmission was calculated using Rolfe's hydrodynamic equations, and validated against actual industry data. For a 420-size coupling operating at 1500 rpm impeller speed and 1450 rpm runner speed, the predicted oil requirement was 9.33 L versus the actual 10.05 L. CFD analysis employing a moving mesh and k–ω turbulence model revealed a maximum dynamic pressure of 5.4 bar and tangential velocity of 34 m/s, which produced a torque of 507.3 Nm and transmitted power of 79.9 kW, matching the rated 80 kW within 0.13 %. These results confirm that the proposed empirical–CFD framework accurately captures pressure distribution, vortex dynamics, and slip characteristics, thereby validating the mathematical assumptions.