Numerical Investigation of Lobe Structure on Performance of Lobed Forced Mixing Exhaust System

Abstract

Geometric models of lobed mixer nozzle with different lobe shapes are created. The Reynolds Averaged Navier-Stokes (RANS) equations with standard k-e turbulence model are selected as controlling equations to simulate the corresponding flow field, and they are discretized by the Arbitrary Lagrange Euler method. The simulation results are compared with the splitter mixer nozzle, and the comparison outcomes indicate that lobed mixer can not only greatly increase the mixing between the core and fan flow, but also reduce the noise of exhaust. Besides, although energy loss of lobed mixer is bigger than splitter mixer, the difference of total pressure recovery coefficient and thrust coefficient between lobed mixer nozzle and splitter mixer nozzle is small. Among different lobe shape models, the straight cut and elliptical cut at the lobe exit can enhance the mixing, and their energy loss is slightly bigger than the corresponding model without cut. When the guide lines of lobed mixer is modified, thermal mixing efficiency declines, but the total pressure recovery coefficient increases. In addition, as lobe shape changes, although thrust coefficient varies, the difference between maximum and minimum thrust coefficient is less than 1%.