Experimental Study on the Combustion Performance of Concentric Staged Lean Direct Injection Combustor With Two Different Swirler Angles of the Pilot Stage

With the civil aviation engine now developing towards lower pollutant, and the lean direct injection (LDI) combustion proves excellent potential in reducing NOx emission, a concentric staged LDI combustor, both the main and pilot stages are based on LDI combustion concept, is proposed in this paper. It has great potential for an aero engine for a more straightforward structure and smaller size than the Multi-Point Lean Direct Injection (MPLDI) low emission combustor. Experimental research on the combustion and emission characteristics of the concentric staged LDI single-tube combustor with two swirl angles of the pilot stage (Case A: 35°, Case B: 45°) was carried out. The ignition performance was carried out at atmospheric pressure while the total pressure drop was 0.01–0.06, and the combustion and emission characteristics were carried out at different inlet conditions, fuel-air ratios (FAR), and fuel ratios of the main stage. The results indicate that the lowest ignition FAR of both two cases presents the trend of first decreasing and then increasing with the pressure drop, and Case B is lower than Case A at all conditions. The lean blowout FAR of Case B is 0.008, which is reduced by 11.11% than Case A. At the low condition, the inlet temperature is 540K, the NOx emission of the exit presents the trend of increasing with the increase of the FAR while the pilot stage works only. At the condition of the inlet temperature with 653K, both the main and pilot stages work together, and the fuel ratio has a distinct effect on the NOx emission of the combustor. However, when the inlet temperature is 737K, the EINOx of the combustor is almost the same at different fuel ratios. It is identical for both Case A and B. At all conditions, the EINOx of case B is lower than case A, and it is the same for the combustion efficiency. Overall consideration, though the combustion efficiency of Case B is lower than Case A, it is still not less than 99.9% when the main and pilot stages work simultaneously, 90% when the pilot stage works only. All the ignition, lean blowout, and NOx emission performances of Case B are better than A. Case B is better than Case A for a civil aviation engine.