Effects of swirl on the performance of lobe exhaust system from helicopter engine
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摘要:
基于计算流体力学方法研究了排气旋流角对波瓣排气系统的性能影响规律。使用民用直升机发动机排气系统为验证算例,计算获得的压力损失与试飞数据的良好符合性证明了仿真方法的可靠性;对无旋条件的排气系统气动特性进行了分析,波瓣高度0.55R的波瓣主喷管比圆柱主喷管引射比高71%,而总压损失系数仅增加17%。研究了旋流角对波瓣排气系统的性能影响,波瓣主喷管具有消旋作用,排气旋流增强了引射比和总压损失系数,旋流角小于10°时,总压损失系数和引射比增长较慢,旋流角15°后,总压损失系数和引射比均快速增加。与无旋流相比,25°旋流角下,波瓣排气系统的总压损失系数增加84%,引射比增加46%。
Abstract:The swirl effects on the performance of lobed exhaust system from a helicopter engine are studied based on computational fluid dynamics. Firstly, using the exhaust system of a civil helicopter engine as a verification example, the calculated pressure loss is in good agreement with the flight data, which proves the reliability of simulation method. Then, the aerodynamic characteristics of the exhaust system under non-swirl are analyzed. The ejection ratio of the lobed nozzle with a lobe height of 0.55R is 71% higher than the cylindrical nozzle, while the total pressure loss coefficient only increases by 17%. Finally, the effect of swirl on the performance of a lobed exhaust system is studied. The lobed nozzle has a counteract rotation effect, and the exhaust swirl enhances the ejection ratio and total pressure loss coefficient. When the swirl angle is less than 10°, the total pressure loss coefficient and ejection flow rate increase slowly. While when the swirl angle is larger than 15°, both the total pressure loss coefficient and ejection flow rate increase rapidly. Compared with non-swirl flow, the total pressure loss coefficient and ejection flow ratio of lobed exhaust system increase by 84% and 46%, respectively, at 25° swirl angle.
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Key words:
- lobed nozzle /
- exhaust system /
- total pressure loss /
- ejection ratio /
- swirl angle
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表 1 计算网格信息
Table 1. Details for computation grids
网格
编号喷管处网格
单元尺寸/mm边界层第1层
厚度/mm网格单元
总数网格1 5 0.1 1200 万网格2 5 0.05 1800 万网格3 2.5 0.05 2200 万表 2 排气状态详细参数表
Table 2. Condition details for exhaust
计算
状态排气流量/
kg/s排气总温/
K输出功率/
kW排气
旋流角/(°)1 5.23 810.7 1266 −17.6 2 4.89 784.3 1042 −8.2 3 4.69 777.0 936 −2.0 4 4.26 760.7 721 11.7 表 3 三套网格计算的引射率和压力损失系数对比
Table 3. Comparisons of ejection flow ratio and pressure loss coefficient among three grids
网格编号 η δp 网格1 0.260 0.0276 网格2 0.267 0.0281 网格3 0.268 0.0283 表 4 不同主喷管的性能对比
Table 4. Comparison of results from different nozzles
主喷管类型 η δp,0,n 圆柱 0.150 0.0215 收缩圆 0.178 0.0307 波瓣3 0.236 0.0253 -
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