Session: 04-21 Combustor Design III
Paper Number: 127653
127653 - Effect of Dilution Hole Diameter on the Outlet Temperature Distribution in a Centrally Staged Combustor
The temperature distribution at the combustor outlet is of paramount importance for the lifetime and operational reliability of the turbine. In light of previous investigations, the dilution hole diameter emerges as a significant design parameter that influences the outlet temperature distribution. In the present work, focusing on the effect of dilution hole diameter on the outlet temperature field, numerical simulations of the single-sector centrally staged model combustors with different dilution hole diameters are conducted. The axial direction of each dilution hole is perpendicular to the liner wall, which is equipped with effusion cooling holes at the inlet angle of 30°. Under consistent operating conditions, the influence of dilution hole diameters ranging from 8 to 16 mm on the flow characteristics inside the combustors are explored, while the flame morphology in the high-temperature zones and the formation of hot streaks at the outlets are analyzed. The results indicate that, with a consistent inlet mass flow rate, the dilution hole diameter affects both the length of recirculation zone and the depth of jet penetration inside the combustion flow field. In the current study, the axial length of primary recirculation zone (PRZ) is minimized with a 14 mm dilution hole diameter, whereas the radial depth of jet penetration reaches maximum value with a 16 mm diameter. As the dilution hole diameter increases, the equivalence ratio in the primary zone gradually approaches the stoichiometric ratio from lean fuel, resulting in an expansion of the high-temperature zone within the region. Meanwhile, the position of the high-temperature zone shifts towards the dome, ultimately causing the hot streak at the outlet of the combustor to shrink towards the center. Under the smaller dilution hole size, two obvious flame fronts are formed at both the PRZ and the interface between the dilution hole jet and the shear layer. As the diameter increases to 16 mm, the flame front is divided by the shear layer formed due to the pilot stage airflow, leading to flame separation. Furthermore, as the dilution hole diameter increases from 8 mm to 16 mm, the total pressure loss of the combustor decreases from 3.5% to 2.5%, while both the pattern factor and the radial pattern factor exhibit a trend of initially increasing and then decreasing, and the combustion efficiency decreases from 99.97% to 99.74%. Upon comprehensive consideration, the combustor with dilution holes of 14 mm diameter in the design scheme obtains uniform outlet temperature distribution and exhibits optimum performance.
Presenting Author: Honghao Xu Harbin Engineering University
Presenting Author Biography: Xu honghao is a PH.D student in Harbin Engineering University.
Authors:
Liyao Pang Harbin Engineering UniversityHonghao Xu Harbin Engineering University
Dr. Ningbo Zhao Harbin Engineering University
Zongfu Li Harbin Engineering University
Hongtao Zheng Harbin Engineering University
Effect of Dilution Hole Diameter on the Outlet Temperature Distribution in a Centrally Staged Combustor
Paper Type
Technical Paper Publication