Nitrogen oxides reduction and performance enhancement of combustor with direct water injection and humidification of inlet air

  • Saeid Shahpouri
  • Ehsan Houshfar
Original Paper


In this study, nitrogen oxides emission reduction is investigated with humid combustion in a non-premixed combustion chamber of a gas turbine that burns natural gas using computational fluid dynamics. For humidification of the combustion chamber, two methods are studied: direct water injection into the combustion chamber and increasing the inlet air humidity. The mathematical model of combustion, governing equations, numerical method, and the combustion chamber properties are extensively discussed. The mathematical model is first validated. The two approaches are then simulated and compared for low water and steam flow rates. The results show that at the water to fuel ratio of about 1, direct water injection is 1.69 times more efficient than increasing inlet air humidity in reducing nitrogen oxide emission. Finally, it is concluded that direct water injection is appropriate at low flow rates (up to the fuel flow rate) and for situations where reducing nitrogen oxide emission is highly relevant. Furthermore, increasing the humidity of the inlet air up to 25% is suitable and increases the combustion efficiency and reduces pollutants, while the outlet temperature is not decreased too much.

Graphical abstract


Humid combustion Gas turbine NOx reduction Water injection Combustion efficiency 


Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.School of Mechanical Engineering, College of EngineeringUniversity of TehranTehranIran

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