Characteristics of the main stage exert important effects on the performances in a centrally staged LPP combustor. The experiments on flow fields, spray, and combustion were carried out on the combustors with different axial velocity at the main stage exit (Vm). The NOx emissions, combustion efficiency and lean blowout are all tested in a rectangular model combustor under elevated temperature and pressure conditions, while flow field and spray characteristics are measured in an optical combustor by Kerosene-PLIF and PIV under non-reacting elevated temperature and pressure conditions.
The results show that with the Vm of the main stage changing from 61 m/s to 80 m/s, the NOx emission and combustion efficiency decreases. Meanwhile, lean-blow out (LBO) performance becomes worse. CFD simulation is conducted to investigate the flow fields, spray, emissions and LBO performance of the combustor. The simulation results show the turbulent intensity between the pilot and main stage flows is stronger for the combustor with higher Vm. Besides, the recirculating flow in the recirculation zone also has an increasing trend. The two reasons cause the temperature in the combustion zone decrease, which is beneficial to the NOx reduction. In addition, the stronger turbulence intensity between the main and pilot stage make the quenching of pilot flame more severe, causing the combustion efficiency lower. Moreover, the increase of the inverse flow also worsens the LBO performance.