航空发动机“空-空-油”螺旋套管换热器夹层传热数值模拟

Numerical Simulation of Heat Transfer in Annular Space in Air-Air-Fuel Helical Annular Tube Heat Exchanger Used for Aero-engine

作为一种新开发的航空发动机涡轮叶片冷却装置,双层螺旋套管具有结构紧凑、传热高效、耐压和抗热冲的优异性能。对夹层特殊通道和内螺旋管的流动与传热进行了耦合数值模拟研究,获得了夹层通道的速度/温度分布及变化特点。结果表明,相较于螺旋结构,曲率与夹层厚度(以外内径之比表征)对传热有显著影响,螺距的影响可忽略不计。鉴于现有经验公式不足以预测螺旋夹层换热系数,根据模拟结果拟合得到了螺旋套管夹层的换热系数关联式,为螺旋套管热力设计提供了参考依据。

As a newly developed cooling device for turbine blade of aero-engine,helical double-pipe heat exchanger has the advantages of high heat transfer coefficient,compact structure,good mechanical properties and resistance of thermal shock.In this paper,coupling numerical studies of flowing and heat transfer between annular space and inner spiral tube were carried out.The distribution and characteristics of temperature/velocity in annular space were obtained.It was shown from the results that the curvature and annular space(expressed by ratio of external diameter to internal diameter)have significant influence to heat transfer compared with that of helical structural shape,and the influence of helical pitch can be neglected.Because current heat transfer empirical equations are still not suitable for predicting the heat transfer coefficient for tube-in-tube helical heat exchangers with annular space,new empirical correlations for annular space have been proposed,which is hoped for providing certain reference to double-pipe helical heat exchanger thermodynamic design.