A Concept for Safe and Less Expensive Acceleration of a Marine Steam Turbine Start-up

Abstract

This paper analyses the issue of accelerated start-up of a marine steam turbine, which is an important problem because the start-up of a steam machine involves the combustion of fuel that is not transformed into useful energy. To find novel technologies that offer improvements in this aspect is essential due to restrictions on reducing ship emissions. Thus, the shorter the start-up time, the better for the environment and economy. High-pressure (HP) part of the turbine originally located on the Queen Elizabeth II unit was analysed. Advanced numerical calculations by thermal fluid-solid-interaction (Thermal FSI) were carried out. A series of simulations were performed for the accelerated start-up with controlled steam injection. A description of the chosen calculation methodology and the results obtained by simulation are included in this paper. The stress occurring during the accelerated start-up are approximately 40 MPa higher than those during the reference start-up. The relative elongations between the rotor and the hull during accelerated start-up reach a maximum value of 0.89 mm (0.83 mm for ultra-fast start-up). Reducing the steam turbine start-up time by 75% results in a 36.7 tons reduction in fuel consumption for start-up, resulting in an annual savings of 5 372 USD. In conclusion, the concept proposed by the authors is safe, less expensive and does not affect the life of the turbine. In addition, results and applications from Siemens prove that additional injection of cooling steam is possible.

Keywords

Marine steam turbine start-up / Ultra-fast start-up / Thermal stress / Relative elongations / Fuel savings / Energy management