Short Helical Combustor: Dynamic Flow Analysis in a Combustion System With Angular Air Supply

A novel gas turbine combustor is investigated by means of a global flow analysis. Its main feature is the helical arrangement of the burners, which allows the utilization of the high angular momentum of the flow from compressor, so that the length of the flame tube and the number of NGV can be reduced. The concept was studied in Ariatabar et al. (2016, “Short Helical Combustor: Concept Study of an Innovative Gas Turbine Combustor With Angular Air Supply,” ASME J. Eng. Gas Turbines Power, 138(3), p. 031503) based on similarity considerations and a kinematic assessment of the simulated flow in various combustor models. For the best configuration found in the previous work, the exit mean flow angle was lower than the half of its initial value at the combustor inlet. The reason for this unwanted decay of the initial high angular momentum flux was not clear. In the present work, the underlying physics of the strong reduction of the mean flow angle is elucidated by analysis of the integral balance equation of angular momentum. It is shown that the flow in the vicinity of the burners is governed by inertial forces associated with an asymmetric pressure distribution on the sidewall and the combustor dome. The friction and turbulent mixing phenomena are found to have marginal effects on the flow pattern. To compare mean flow quantities of different combustor designs, a physically consistent averaging method is introduced, which can also be applied to a conventional combustor to assess different swirl configurations regarding the resulting flow pattern, mixing performance, and total pressure loss.