Numerical and experimental investigation of bowing in large diameter liquid oxygen feed lines

The Indian Space Research Organisation (ISRO) is developing a semi-cryogenic engine with a thrust of 2000 kN. Due to the engine’s high thrust, the required Liquid Oxygen (LOX) flow rates are substantial, necessitating the use of 290 mm diameter pipelines to convey LOX from the test facility to the engine. During the initial chill-down phase, the large diameter of the pipeline can lead to significant temperature gradients across the circumference, potentially resulting in thermal bowing, which poses concerns such as, pipeline bending and increased loads on the supports. To address this, detailed non-linear finite element simulations were conducted to predict the structural behavior of the feed lines. An acceptable thermal gradient was identified, ensuring that the stresses caused by thermal bowing remained within safe limits. Novel techniques were implemented to maintain these gradients during the chilling process. During the first chill-down test of the system, multiple temperature and displacement measurements were employed. All necessary conditions for engine start were met in the very first attempt, and thermal bowing remained well within acceptable limits. This paper presents both the numerical simulations and experimental results.