Numerical Analysis On LPP Combustion Characteristics In Multi-Swirling Combustor

With the development of gas turbine engines towards high thrust-weight ratio and high power, pollutants discharged from turbine engines has increased steadily. On the other hand,based on the environmental requirements of gas turbine engine emissions (especially NOx), a more stringent restrictions are proposed. One of the important techniques for reducing NOx emissions is the use of high efficient combustion of LPP (Lean Premixed Pre-evaporation). The multi-swirling dump combustion is the main combustion mode which gas turbine combustion design usually use. Multi-swirling has effect of combustion with stable and high efficient, while the swirl number and the gas flow distribution are important operating parameters. Research of multi-swirl focused on the stability conditions of combustion In this paper, after analysis of multi-swiring combustion process, hold that the high temperature air from compressor with the fuel has an important process of LPP(pre-mixed pre-evaporation) in swirl cup. When the structure of swirler is fixed, the flow distribution has great impact on process of LPP.In this thesis, premix pre-evaporation characteristics, combustion characteristics of dual-stage swirl cup and LPP combustor were studied numerically and the generation of pollutants in the combustion chamber was predicted. The lean blow out symptoms in combustion chamber with double swirling were studied. Study found that the flow distribution has great influence on the effect of pre-mixed and pre-evaporation. Taking other experiments as reference, the investigation is conducted when total flow rate of the double swirling remains unchanged. The numerical simulation results agree with experimental results and indicate that the fuel premixed and pre-vaporized well when the air flow ratio of first-stage to second-stage is 1:5, which is an appropriate flow distribution ratio. The analysis shows that when the flow distribution ratio turns larger, combustible mixture and combustion flame concentrate at the back of combustion chamber with higher peak value of flame and NOx emissions in this situation. On the country, a small flow distribution ratio leads to combustible mixture and combustion assembling at the inside of swirl cup. On this basis, according to theory of lean blowout, and taking other experimental research as references, flame failure symptom was numerically predicted. The numerical results of this article are in good agreement with experimental studies.