Effect of lobe number on aerothermodynamic performance of lobed S-shaped two-dimensional nozzle

Based on a lobed S-shaped two-dimensional nozzle of a turbofan engine, the length, inner divergence angle, outer divergence angle and ratio of high to width of lobed mixer were kept unchanged only with the lobe number fixed as 12, 14, 16, 18, 20. A group of lobed S-shaped two-dimensional nozzle models with different lobe number were built. By the use of validated CFD simulation, the effect of lobe number on aerothermodynamic performance of lobed S-shaped two-dimensional nozzle was investigated. The results show that within the flow field between the lobe trail cross section and the first S bend, the degree of mixing is highly affected by the lobe number and the thermal mixing efficiency increases as a response to the increment of lobe number. Within the flow field between the first S bend and the exit of the lobed S-shaped two-dimensional nozzle, the lobed S-shaped two-dimensional nozzle model with 16 lobes always has the lowest value of total pressure recovery coefficient and neither thermal mixing efficiency nor total pressure recovery coefficient has distinct change between other models. At the exit of lobed S-shaped two-dimensional nozzle, the lobed S-shaped two-dimensional nozzle model with 16 lobes has the highest thermal mixing efficiency of 0.850, while total pressure recovery coefficient of the model has dropped by 0.289% when compared with the model of the biggest total pressure recovery coefficient. Besides, the gradual narrowing flow passage of the lobed S-shaped two-dimensional nozzle can contribute to better mixing and more rapid consumption of stream-wise vortex.