Thermodynamic Analysis and Comparison of Two Marine Steam Propulsion Turbines

This paper presents thermodynamic (energy and exergy) analysis and comparison of two diff erent marine propulsion steam turbines based on their operating parameters from exploitation. The fi rst turbine did not possess steam reheating and had only two cylinders (high-pressure and low-pressure cylinders), while the second turbine possesses steam reheating and has one additional cylinder (intermediate-pressure cylinder). In the literature at the moment, there cannot be found a direct and exact comparison of these two marine steam turbines and their cylinders based on real exploitation conditions. Along with energy and exergy analyses, the research it is investigated the sensitivity of exergy parameters to the ambient temperature change for both turbines and each cylinder. It is also presented the influence of the steam reheating process on the energy and exergy effi ciency of the entire power plant. For both observed turbines and their cylinders it is valid that relative losses and effi ciencies (both energy and exergy) are reverse proportional. The operation of an intermediate pressure cylinder from a steam turbine with reheating is the closest to optimal. Due to the diff erent origins of losses considered in energy and exergy analyses, each analysis detects diff erent turbine cylinders as the most problematic ones. The steam reheating process decreases losses and increases effi ciencies (both energy of each turbine cylinder and the whole turbine. The whole turbine with reheating has an energy effi ciency equal to 81.46% and an exergy effi ciency equal to 86.48%, while the whole turbine without reheating has energy and exergy effi ciencies equal to 76.47% and 80.94%, respectively. Exergy parameters of a steam turbine without reheating as well as its cylinders are much more infl uenced by the ambient temperature change in comparison to the steam turbine with reheating and its cylinders. The steam reheating process will increase the effi ciency of the whole power plant in real exploitation conditions between 10% and 12%.