Digital simulation of gas turbine steady-state and transient performance for current and advanced marine propulsion systems

Abstract

The research study focuses on the idea of simulation of an Integrated Full Electric Propulsion System. The simulation required the development of a gas turbine performance model that could predict the dynamic behaviour of the engine in response to a fluctuation of electrical load. For this purposes it was necessary to evaluate the thermodynamic working process of the gas turbine and a computer code was created. A design point model written in FORTRAN 77 had been transformed to predict the steady state and transient performance of a two-shaft gas turbine and single shaft gas turbine. The models were based on the thermodynamic law of conservation of mass. For the model of the two-shaft gas turbine controls system equations had been derived from off-design analysis and implemented as handles for operation. Both the models were then transformed to a direct link library for the SIMULINK® package. They were further implemented with an electrical network model to form a high-fidelity prime mover-electrical networkpropulsion drive interface with which a complete systems analysis was done to understand the response of the three systems in parallel. In a second part heat exchanger modelling had to be performed so as to create a gas turbine model of an intercooled-recuperated engine. This was done for the steady state behaviour and sizing problem of heat exchangers. The models were run parallel to the steady state code as a validation exercise. Due to time and project restraints the complete incorporation of the models with the gas turbine code was not performed and only a uni-directional system of heat exchanger was created. Over all the period of research parametric studies had been done for comparison of various aspects of performance. The high fidelity model of the prime mover-electrical network highlighted the reasons for studying the impact of the propulsion drive and electrical network load dynamics on the operation of the prime movers and vice versa. The loss-of-propulsion-load scenario case study has demonstrated the capabilities of the integrated model, showing clear interactions between the individual subsystems. The interface can now be used to analyse novel types of gas turbine engines in the future. The method adopted to simulate transient performance of gas turbines was useful in understanding the impact of bleed air on current and novel cycles. Finally the task of heat exchanger simulation emphasized the need to create better and accurate models to understand the impact of its behaviour on the gas turbine.