中心锥对波瓣强迫混合排气系统气动热力性能的影响

Effect of central plug on performance of forced mixing exhaust system

在波瓣混合器几何结构不变的情况下,通过分别改变波瓣出口截面处中心锥半径以及波瓣长度建立了一系列几何模型,并采用数值模拟的方法,研究了中心锥关键结构参数对涡扇发动机波瓣混合排气系统气动热力性能的影响规律.结果表明:当中心锥长度不变时,随着波瓣出口处中心锥半径的增加,热混合效率先增加后减小,其中当波瓣出口处中心锥半径为0.55倍波瓣高度时,波瓣混合排气系统出口处热混合效率最大.此外,当中心锥长度不变时,波瓣混合排气系统总压恢复系数大体上不断减小;排气系统出口处推力系数则呈现出先增大后迅速减小.当波瓣出口处中心锥半径不变时,随着中心锥长度的增加,热混合效率和总压恢复系数变化极小,在排气系统出口处,推力系数则先迅速增大后略有降低.

Geometric models with respective changes of plug radius at lobe exit and plug length in the lobed forced mixing exhaust system were established. Then these models were numerically simulated based on Navier-Stokes equations. The results show that when plug length is constant, the thermal mixing efficiency increases at first and then declines with plug radius at the lobe exit augmenting, and when ratio of plug radius at lobe exit to lobe height is equal to 0. 55, the lobed mixing exhaust system has the biggest thermal mixing ef- ficiency at the nozzle exit among the models researched. Generally speaking, the total pres- sure recovery coefficient declines as radius increases. Moreover, the thrust coefficient at the nozzle exit firstly increases and then decreases sharply. When plug radius at lobe exit keeps constant, with plug length rising, the thermal mixing efficiency and total pressure recovery coefficient vary little and the thrust coefficient at the nozzle exit augments quickly in the be- ginning and then declines slowly.