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

Significance Statement

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. 

About the author

Mohamed Gadalla is a full Professor in the Mechanical Engineering Department at American University of Sharjah. He has over 25 years of experience in industry and academia. He published more than 100 papers in refereed Journal and International conferences. He carried out many industrial researches and participated in many projects in different industrial sectors in the USA, UAE, GCC, and Egypt. He has given many training courses, keynote lectures and workshops to many industries and scientific organizations. He has chaired many national and international conference, symposium, and technical meetings. He is an active member of various international scientific organizations and societies, and serves in editorial board in various prestigious international journals and symposiums. His main area of interests is in renewable energy technologies, energy systems and energy management, thermal stability of polymeric/composite structures, systems, UAV systems, efficient building operations, Fuel cells, HVAC systems, energy systems and energy management. He is a recipient of several research, teaching and service awards.  

About the author

Mohammad Saghafifar is currently a master’s student and graduate research assistant in the Mechanical Engineering department of the American University of Sharjah. He is working under the supervision of Dr. Mohamed Gadalla on his research. He is currently investigating the feasibility of a 50 MWe hybrid (solar and natural gas) combined cycle power plant with a topping gas turbine cycle and four different bottoming cycles. Power plant hybridization is accomplished by employing Heliostat field collectors. His research interest includes concentrated solar power, Photovoltaic/Thermal, gas turbine inlet cooling, power generation, thermal energy storage, solar power generation, solar air conditioning, Desiccant air conditioning.  

 

Journal Reference

Applied Energy, Volume 149, 2015, Pages 338–353.

Mohammad Saghafifar, Mohamed Gadalla,

Department of Mechanical Engineering, College of Engineering, American University of Sharjah, PO Box 26666, Sharjah, United Arab Emirates

Abstract

With ever increasing cost of fossil fuels and natural gas, the improvement in gas turbine power cycle efficiency is needed due to the tremendous savings in fuel consumption. Water/steam injection is considered as one of the most popular power augmentation techniques because of its significant impact on the gas turbine performance. One of the recently suggested evaporative gas turbine cycles is the Maisotsenko open cycle for gas turbine power generation. In this paper, detailed thermodynamic analysis of this cycle is investigated with a thorough air saturator model. A comparative analysis is carried out to signify the advantages and disadvantages of Maisotsenko gas turbine cycle (MGTC) as compared with humid air gas turbine cycles. MGTC performance is evaluated based on a simple recuperated gas turbine cycle. In addition, sensitivity analysis is performed to investigate the effect of different operating parameters on the overall cycle performance. Finally, integrating an air saturator instead of a conventional heat exchanger in recuperated gas turbine cycles enhances the power plant performance such that an efficiency enhancement of 7% points and net specific work output augmentation of 44.4% are obtained.

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