Effect of the swirl intensity on the non-reacting flowfields and fuel-air premixing characteristics for lean premixed combustors

According to the tendency of incorporating fuel jet holes into swirler-vanes, as well as the advantages of wide operating boundary conditions and low NO_x emissions of low swirl injectors for land-based gas turbines, an original lean premixed injector with convergent outlet was proposed in this paper. Based on the lean premixed injector, this paper presented laser diagnostic experiments and numerical simulations of flowfields and fuel/air premixing uniformities of S30 and S40. The results show that the axial size and the radial size of main recirculation zone (MRZ) of S30 are both smaller than those of S40, which can decrease residence time and is beneficial to NO_x reduction for S30. Furthermore, the MRZ of S30 are far from the convergent outlet, which can produce detached flames and reduce the risk of flashback. The SMV at S40 and S30 convergent outlet are 0.0008 and 0.0002, respectively, both of which are lower than 0.001, which shows that both S30 and S40 obtain good fuel/air premixing uniformities. These results demonstrate that S30 (low swirl injectors) constitutes a promising technology for low emission gas turbine combustors.