交变波瓣喷管高效掺混机理

High Mixing Efficiency Mechanisms of Alternating Lobed Nozzles

关键词:  交变波瓣  射流掺混  掺混效率  流向涡  数值模拟

Key words:  Alternating lobes  Jet mixing  Mixing efficiency  Streamwise vortices  Numerical simulation

摘要:

结合现有交变波瓣的特点对基准波瓣喷管进行处理，设计了一种新型波瓣喷管——剑形深波谷交变波瓣喷管。采用数值方法对基准波瓣喷管、平端面交变波瓣喷管、斜切交变波瓣喷管、剑形深波谷交变波瓣喷管、斜切交变波瓣喷管扇形处理的射流掺混进行模拟，研究了交变波瓣喷管高效掺混的机理。结果表明，交变波瓣喷管除了深、浅波谷之间的尾流区和较小的核心区代替了基准波瓣喷管较大的核心区以外，在侧壁尾流区产生更饱满的流向涡，以及深波谷端次流前锋的刺入或在深波谷端产生流向涡，都对提高掺混效率起重要作用。交变波瓣喷管射流掺混中横向流动程度越大造成的流动损失越大，其关系为初始流向涡量每增加0.1，总压恢复系数将减小0.0001。

Abstract:

A novel lobed nozzle named sword-shaped alternating lobed nozzle was designed，according to the characteristics of the existing alternating lobes to modify the baseline lobed nozzle. The numerical simulation was conducted on the baseline lobed nozzle，the planed alternating lobed nozzle，the scarfed alternating lobed nozzle，the novel nozzle and the scalloped and scarfed alternating lobed nozzle to investigate high mixing efficiency mechanisms of alternating lobed nozzles. Results show that besides regions between the deep and the shallow troughs and the smaller central region replace the larger central region of the baseline lobed nozzle，more well-rounded streamwise vortices off the side walls，and penetration of the secondary flow front via the deep lobe trough gullies into the primary flow or streamwise vortices off the deep lobe troughs. All contributes to promote the mixing efficiency of alternating lobed nozzles. More aggressive transverse flow induces more flow loss in the mixing of alternating lobed nozzles，showing that total pressure recovery coefficient will decrease by 0.0001 when initial streamwise vorticities increase by 0.1.