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Modeling of the Wet Compression System in Transient Behavior of the Industrial Gas Turbine

Keshavarz Mohammadian, Poorya | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55324 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saeedi, Mohammad Hassan
  7. Abstract:
  8. In general, the output power of the gas turbines decreases as the ambient temperature increases. One of the ways to deal with such a performance loss is to use a wet compression system, which reduces the air temperature rise throughout the compressor. In this system, the water droplets are injected into the compressor inlet and evaporated throughout the stages. As a result, the work of the compressor decreases, and the power and efficiency of the whole engine increase. Most of the researchers in this field have tried to develop mathematical models to investigate the effects of this system on compressor and gas turbine performance in steady-state conditions. However, it is necessary to investigate the impacts of this system in the transient maneuver of the gas turbine. So, this work attempts to model and study the gas turbine transient maneuver having a wet compression system in operation. The required models are developed to simulate the transient behavior of an industrial gas turbine with the wet compression system. The results show that due to the high speed of the axial airflow in the studied compressor, droplets with a diameter of more than 5 micrometers cannot evaporate throughout the compressor completely. Also, the operation of the wet compression system changes the load distribution in the compressor stages and increases the workload of the rear stages. The results also show that at an ambient temperature of 45 degrees Celsius, with a water-to-air flow ratio of 2%, the output power of the gas turbine increases to about 30%. In this case, the efficiency of the gas turbine increases to about 3%, as well. However, the stability margin of the compressor's last stages decreases from 12% to about 4%. Consequently, the stability of the rear stages of the compressor is a limiting factor for the ratio of water to air sprayed in the wet compression system. Also, studies show that in addition to the gas turbine exit temperature, the rotational speed of the gas generator can also be the limiting factor of the gas turbine base-load value when the wet compression system is in operation
  9. Keywords:
  10. Gas Turbines ; Droplet Evaporation ; Transient Maneuver ; Compressor Mean-Line Model ; Wet Compression System ; Power Output

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