Analysis of Maisotsenko open gas turbine power cycle with a detailed air saturator model

This paper investigates Maisotsenko gas turbine power plant configuration with a detailed air saturator model. Accordingly, a mathematical formulation is developed to investigate the significance of the air saturator on cycle performance. In addition, the effects of different design/operating variables such as inlet air temperature, compressor pressure ratio, combustion chamber outlet temperature, inlet water temperature and the air saturator degree of humidification on the overall cycle performance are studied. Air saturator degree of humidification is the ratio of the desired injected water mass flow rate over the maximum rate of water that can be added in the upper section of the air saturator. Moreover, a comparative analysis between a simple gas turbine cycle with recuperator and Maisotsenko gas turbine cycle is presented. Finally, Maisotsenko gas turbine cycle thermodynamic performance is assessed based on the more popular humid air turbine cycle (without intercooler) in order to better understand each cycle advantages and disadvantages.

This paper’s most notable contribution is the developed air saturator model which enabled us to investigate the effects of the rate of water injected in the air saturator on the plant thermal efficiency and net specific work output. Maximum efficiency is associated with the case that water addition in the upper section of the air saturator is only utilized to cool down the exhaust gas to its dew point temperature. Further water injection only reduces the air temperature leaving the saturator and does not have any positive influence on the plant thermal performance. It is important to mention that the optimum value for the air saturator degree of humidification gets smaller as the assigned combustion chamber outlet temperature increases. On the contrary, increasing the compressor pressure ratio results in a rise in the optimum value of the air saturator degree of humidification. Moreover, efficiency reduction of 0.05% points for each 1 K rise in the inlet air temperature can be reported. Furthermore, varying water temperature from 283 K to 333 K leads to an increase in the thermal efficiency by 0.35% points and the net specific work output by 12.9 kJ/kg.

Integrating an air saturator instead of a conventional heat exchanger can enhance the plant efficiency by 7% points and net specific work output by 44.4%. This improvement results in approximately 13,000 tonne of natural gas fuel savings per year. In addition, comparative analysis between humid air turbine cycle and Maisotsenko gas turbine cycle indicates that the humid air turbine cycle is a more suitable configuration for low pressure ratios whereas Maisotsenko gas turbine cycle achieves greater thermal efficiency at higher pressure ratios. Bearing in mind that Maisotsenko gas turbine cycle’s specific work output is continuously greater than humid air turbine cycle’s specific work output regardless of the compressor pressure ratio value. Based on the outcomes presented in this research work, Maisotsenko gas turbine cycles can challenge humid air turbine cycles as the optimal humidified gas turbine cycle configuration.