Experimental and numerical prediction of LBO performance in a centrally staged combustor

Abstract

A new type of centrally staged combustor was proposed for an aeroengine combustor with a fuel–air ratio of 0.037. The combustor dome comprised a three-stage swirler, which included a pilot stage and main stage. The pilot stage was composed of Stage 1 and Stage 2 swirlers, and all swirlers were radial. The effects of different inlet Reynolds numbers and swirler structural parameters, including the installation angle of the first radial swirler, installation angle of the second radial swirler, installation angle of the main stage, and co– and counter-rotation of Stage 1 and Stage 2 swirlers on the lean blow-out (LBO) performance of the centrally staged combustor were examined at an atmospheric pressure and inlet temperature of 473 K. Experiments with single-dome rectangular test pieces and numerical methods were used. The results showed that the fuel–air ratio decreases with an increase in the inlet Reynolds number, indicating that the increase in inlet Reynolds number plays an important role with respect to the LBO. When the rotation directions of Stage 1 and Stage 2 swirlers were opposite, the fuel–air ratio of the LBO was smaller than that of Stage 1 and Stage 2 swirlers in the same rotation direction, indicating that the rotation directions of Stage 1 and Stage 2 swirlers significantly affect the LBO performance. Stage 1 and Stage 2 swirlers exhibited the best LBO performance when they rotated in opposite directions, and the rotation direction of the main stage slightly affected the LBO performance. The best combination of rotation directions is that the rotation directions of Stage 1 and Stage 2 swirlers should be opposite and rotation direction of Stage 2 swirler should be the same as that of the main stage. With the increase in the installation angle of Stage 1 and Stage 2 swirlers, the LBO fuel–air ratio decreased by nearly 4% and 9%, respectively, and the LBO performance improved. The prediction of the LBO limit of 0.00553, using the fuel steady-state successive approximation method, was less than 0.0066, which was measured in the test, indicating that the method should be improved. The flow field characteristics of the LBO process, which could not be obtained in the test process, were obtained via numerical simulation.