基于动力冗余的液体火箭动力系统频率特性分析

Frequency Characteristic Analysis of Liquid Rocket Propulsion System with Redundant Design

关键词:  液体火箭推进  冗余设计  交叉输送  动力系统  有限元法  频率特性

Key words:  Liquid rocket propulsion  Redundant design  Crossfeed  Propulsion system  Finite element method  Frequency characteristic

摘要:

液体火箭在发射过程中，恶劣的动力学环境常常会引起发动机推力下降或提前关机等工作故障，引入动力冗余技术可以保证发动机故障后仍有足够动力保证火箭正常飞行，从而大幅度地提高系统的可靠性。针对动力冗余技术而提出的液体捆绑火箭推进剂交叉输送问题，以三种工作模式：芯级火箭与助推器独立工作（Mode 1）；一台助推发动机故障，该助推器将多余推进剂供给芯级发动机（Mode 2）；为使助推器提前分离，所有发动机均由助推器供给推进剂（Mode 3）为研究对象，利用有限元技术分别建立三种工作模式下液体火箭动力系统的动力学模型。利用数值方法进行的频率特性分析表明，动力系统每组相似频率在Mode 1模式下的分布较为集中，而在其他两种模式下的分布则较为分散。此外，比较三种工作模式下蓄压器能量值的变频效果发现，Mode 1模式的变频效果最好，而Mode 3的效果最差。

Abstract:

The rugged working environment in the flight course of liquid vehicle often causes engine thrust dropping or prematurely shutting down and other working faults. The introduction of redundant propulsion technology can ensure that the vehicle works normally after the engine has failed， which leads to great improvement in the reliability of liquid vehicle. The propellant crossfeed of liquid vehicle with redundant propulsion system was discussed. The dynamic models of propulsion system of liquid vehicle under three different working modes： independently working （Mode 1）； when one booster engine faults， tanks of the booster will supply the superfluous propellants to the engines of core circuit （Mode 2）； the propellants in all engines are supplied from the boosters for early separating boosters （Mode 3） were established by the finite element technology. The frequency characteristics were analyzed by the numerical method. The results show that the distribution of similar frequencies is more concentrated under Mode 1， and is more dispersed under two other modes. In addition， by comparing the capability of changing frequency for the accumulator energy value under the three working modes， the conclusion can be obtained that the capability under Mode 1 is the best， while it is the worst under Mode 3.