氧换热器在两相流条件下的压力脉动机理分析

氢氧液体火箭发动机氧换热器在研制过程中出现了压力脉动现象，影响了换热器的正常工作。以该型换热器为研究对象，将换热器分为燃气侧、汇总管、圆管等结构，进行了CFD仿真计算，与试验结果对比，修正了传热相关参数，建立了换热器理论计算模型用于参数计算；利用非线性方法分析试验数据，确定了该换热器为混沌系统；利用两相流分析与电路类比两种方法分别针对换热器进行了建模与计算，均捕捉到了相变下换热器内的压力脉动。结果表明：通过CFD仿真及试验修正后的参数用于计算换热器的稳态参数，具有较好的一致性；换热器出现压力脉动时，具有一定非线性特征，且压力脉动越大，非线性程度越高；该换热器出现压力脉动的原因为氧工况接近两相区，相变使得介质密度发生剧变。根据分析结果提出了提高换热器设计压力的改进措施，通过试验得到了有效验证。

Theoretical Studies on Pressure Pulsation of Oxygen Heat Exchanger in Two-Phase Flow Condition

Pressure pulsation in oxygen heat exchanger of a hydrogen-oxygen rocket engine is detected in development stage, which has an adverse influence on the performance of the exchanger. The heat exchanger is divided into gas side, collecting pipe, round tube and other structures, and CFD simulation calculation is carried out. Compared with the test results, the heat transfer related parameters are corrected, and theoretical calculation model is established for parameter calculation. The non-linear method is used to analyze the experimental data and the heat exchanger is determined to be a chaotic system; the two-phase flow analysis and circuit analogy are used to model and calculate the heat exchanger respectively. The pressure pulsation in the heat exchanger under the phase change is captured. The results show that the parameters corrected by CFD simulation and experiment are consistent to calculate the steady-state parameters of the heat exchanger; when the pressure pulsation of the heat exchanger occurs, it has certain non-linear characteristics, and the greater the pressure pulsation, the higher non-linearity; the reason for the pressure pulsation of the heat exchanger is that the oxygen condition is close to the two-phase region, and the phase change makes the density change drastically. According to the analysis results, the designed pressure of exchanger is increased as an improvement measure, which has been verified by test.