2025S-GS4-1 Effect of Torque Limiter on Propulsion Engine Responses and Steady-State Operating Point Shift

National Maritime Research Institute Environment and Power System 1, National Maritime Research Institute Ship Hydrodynamics Performance Evaluation

Abstract

The behaviour of ship propulsion systems under wave-induced disturbances is crucial for operational efficiency and safety, particularly for modern vessels with reduced propulsion power. This study investigates the effect of torque limiters on propulsion engine responses and the steady-state operating point shift. A digital twin framework is employed to model the dynamics of the propulsion system, incorporating a state-space representation. The nonlinear saturation effect of the torque limiter is approximated using harmonic linearisation and a describing function method, enabling frequency-domain analysis. Numerical simulations compare the response of the nonlinear digital twin system with that of its linearised counterpart, demonstrating that the torque limiter significantly influences propulsion system performance. The results highlight the steady-state shift in operating conditions due to the dynamic limitation imposed by the torque constraint. This approach provides a computationally efficient means of assessing the behaviour of propulsion systems in waves, contributing to improved design and operational strategies.