后甲板长度对带后甲板双S弯喷管流动特性影响研究

Effects of Aft Deck Length on Flow Characteristics of Double S-Shaped Nozzle with Aft Deck

关键词:  航空发动机  喷管  流动特性  一体化设计  数值模拟

Key words:  Aero engine  Nozzle  Flow characteristics  Integrated design  Numerical simulation

摘要:

为了研究不同后甲板长度下带后甲板双S弯喷管的流动特性变化规律，在4种不同落压比工况下，开展了5种不同后甲板长度双S弯喷管的数值模拟研究。结果表明，完全膨胀工况下，后甲板上无波系结构，喷流未发生明显偏转。欠膨胀工况下，后甲板上超声速喷流内部出现一系列膨胀波、激波结构，沿流向静压上下波动。后甲板长度对推力矢量角影响较大，随后甲板长度增加，波段数量增加，使得喷流离板时所处的波段位置不同。当附面层在后甲板末未分离（喷管压比NPR=3）时，喷流经压缩波离板，推力矢量角为负；经膨胀波离板，推力矢量角为正。随落压比增加，第一道膨胀波入射角度减小，波段长度增加，激波发生位置后移。高落压比（NPR=4.5，6）下，推力轴线偏转角度受到喷流离板时波系状态和附面层分离程度共同影响，其变化幅度可达14°。

Abstract:

To investigate the flow characteristics of double S-shaped nozzle with aft deck under different aft deck lengths， numerical simulation studies of five double S-shaped nozzles with different aft deck lengths under four different drop pressure ratio conditions were conducted. The results show that under the fully expanded condition， there is no wave system structure on the aft deck， and the jet does not deflect significantly. Under incomplete expansion conditions， a series of expansion waves and shock waves appear in the jet on the aft deck， and the static pressure fluctuates up and down along the flow direction. The length of the aft deck has a greater influence on the thrust vector angle. As the length of the deck increases， the number of the wave section increases， which makes the wave mode at the end of the deck is different. When the boundary layer does not separate at the end of the deck （nozzle pressure ratio NPR=3）， the jet leaves the deck after the compression wave， and the thrust vector angle is negative. The jet leaves the deck after the expansion wave， and the thrust vector angle is positive. As the drop pressure ratio increases， the incident angle of the first expansion wave decreases， the wave length increases， and the shock wave position moves backward. Under high drop pressure ratio conditions （NPR=4.5， 6）， the deflection angle of the thrust line is affected by the expansion wave， the shock wave and the degree of separation of the boundary layer， and its variation range can reach 14°.