Marine gas turbine propulsion system simulation: comparison of different approaches

Abstract: The paper presents a comparison of two different mathematical models for the LM 2500 gas turbine, prime mover widely used on board of Italian Navy ships and selected for the propulsion plant of the new aircraft carrier ‘Cavour’. In the first gas turbine model, developed by the authors and based on physical laws, each gas turbine component (i.e. compressor, turbine, combustor) is modelled in a specific module, which combines available performance maps with the solution of time dependent momentum, energy and mass equations. In the second model, the overall gas turbine performance is described more simply by performance tables, but, in order to take into account the dynamic effects typical of transient situations, the calculation results are corrected by means of time constants. Both models, validated by comparison with manufacturer data, have been used, alternatively, for the simulation of the mentioned ship propulsion system, whose main characteristics and performance capabilities are analysed and discussed. The paper presents the simulation results of two different ship manoeuvres (slam start and crash stop), obtained by using each of the different considered approaches. The comparison of the results puts into evidence the influence of the adopted gas turbine model on the ship simulation results from the point of view of reliability and computer time.