A novel concentric annual swirl combustor: Flow, ignition, and temperature distribution

Traditional gas turbine engines use a full-annular combustor with independent swirl heads and separate recirculation areas. This study introduces a concentric annular swirl combustor (CASC) that employs a single concentric annular swirler. The combustion flow field of the CASC through experimental and numerical simulations are investigated. The results show that the CASC establishes a circumferentially rotating annular recirculation zone, promoting the transfer of high-temperature gases and achieving a uniform temperature distribution at the outlet. This circumferential flow also enhances ignition and flame spread. It achieves full ignition and flame spread within 90 ms. It also exhibits excellent outlet temperature distribution, particularly at higher equivalence ratios, with the outlet temperature distribution factor (OTDF) decreasing to 0.15 at an equivalence ratio of 0.43. However, the CASC lacks the design of multiple rings of independent swirl heads, each with its own fuel circuit, which reduces its capability to regulate thermoacoustic instabilities and its adaptability to engine load variations. In addition, due to the use of diffusion combustion, the CASC does not offer advantages in CO/NOx emissions control. For example, preliminary simulations show that NO emissions typically exceed 500 ppm. Overall, the CASC demonstrates superior combustion performance, including improved flame distribution.