A study of thermodynamic cycle and system configurations of hydrogen combustion turbines

Abstract

A hydrogen combustion turbine is powered by steam generated from the internal combustion of hydrogen as a fuel mixed with stoichiometric oxygen. As it is possible to use a closed cycle system, benefits in cycle efficiency and a reduction of environmental pollution effects. Three different closed hydrogen combustion turbine cycles are evaluated. These are the Bottoming reheat cycle (A), the Topping extraction cycle (B) designed by Jericha and Ratzesberger, and the Rankine cycle (C). Calculations have been carried out to investigate the best cycle. This investigation consists of the comparison of thermodynamic efficiency, first stage turbine vane height of the high temperature, high pressure turbine, and maximum operating temperature of the heat exchangers. In these investigations, the component efficiencies are assumed to be the values which are expected to be achieved in the near future. As a result, the thermal efficiency of cycles (A) and (B) is the same value of 61.5%. That of cycle (C), which has the feed water heating with optimized pressure ratio of the intermediate turbine, is 58.8%. Cycle (B) has the largest first stage turbine vane height of the high temperature/high pressure turbine. The larger vane height has an advantage from the point of view of both the manufacturing of the complex cooling passage inside the vane and the turbine aerodynamic efficiency. The maximum operating temperature of the heat exchanger of cycles (A) and (B) is 870 °C, while that of cycle (C) is more than 1000 °C where some problems are anticipated in the feasibility of this heat exchanger. This investigation shows that the Topping extraction cycle (B) is considered to be the best cycle from the point of view of both the thermal efficiency and the feasibility of manufacturing.