Numerical study on similarity performance of geometric scaling of lean premixed swirl combustor

Abstract

This paper describes the use of experimentally validated computational fluid dynamics methods to study the similarity performance of various models scaled by the DaI criterion. First, the numerical method is validated by particle image velocimetry and CH* chemiluminescence data under the reaction state. Combustor prototypes and models are then simulated under different equivalence ratios (ERs) and swirl numbers (SWs) with the geometric scaling factor (Q) ranging from 0.1 to 1. When Q < 0.3, the reaction zone is obviously stretched. Changes in Q produce large deviations in the velocity distribution. Increasing either ER or SW increases the deviation in the velocity distribution in the outer shear region in front of the combustor but reduces that in the recirculation zone and jet zone at the back of the combustor. The scaling law changes with ER and SW. To distinguish whether the reaction flow field of a model maintains similarity with respect to the prototype, a novel concept called “degree of similarity” is proposed. The “non-similarity range” for geometric scaling factors under different conditions is further clarified. When ER = 0.55, the range of non-similarity of the combustion flow field is Q ≤ 0.3. As ER increases, the range of non-similar intervals decreases, and when ER reaches 0.95, the non-similarity range is Q ≤ 0.1. When SW = 0.42, the non-similarity range is Q ≤ 0.4, and when SW ≥ 0.42, the non-similarity range is Q ≤ 0.3.