Abstract: The effects of flight altitude and material elastic modulus on the performance of flexible-extendible nozzle are numerically studied to examine the nozzle altitude compensation ability. Analyses are conducted using bidirectional fluid-solid coupling method based on ANSYS platform. The simulations reveal that， with the increase of flight altitude， the flexible-extendible nozzle wall deformation aggravates. The nozzle inner flow takes on ‘expansion-shock-expansion’ wave pattern， the maximum deformation and maximum stress of the extendible section are amplified. With large elastic modulus （>100MPa）， the deformation at the flexible section plays a minor role in changing the inner flow field. It is found that， at low altitude， the flexible-extendible nozzle has a significant higher specific impulse than that of the traditional nozzle； at high altitude， it has merely a little lower specific impulse than the traditional nozzle. An increase in the height-integrated specific impulse of 1.462% is reached for the present nozzle than the traditional nozzle at their design altitude of 6km.

Key words: Rocket motor;Flexible-extendible nozzle;Altitude compensation;Bidirectional fluid-solid coupling;Nozzle performance

摘要： 为研究柔性变结构喷管的高度补偿潜力，利用ANSYS平台，基于双向流固耦合方法，对柔性变结构锥型喷管进行数值模拟，分析了飞行高度和柔性材料的弹性模量对喷管性能的影响。模拟结果表明，随着飞行高度的升高，柔性喷管变形加剧，喷管内部流场呈现出膨胀波-激波-膨胀波的波系特征，喷管柔性段壁面的最大变形量和最大应力逐渐增大。当材料弹性模量>100MPa时，喷管柔性段型面变形对流场的影响可以忽略。研究显示，该柔性喷管的低空比冲显著高于传统喷管，高空比冲仅略低于传统喷管，其6km设计高度下较传统喷管有1.462%的高度积分比冲增益。

关键词: 火箭发动机;柔性变结构喷管;高度补偿;双向流固耦合;喷管性能