Experimental characterisation of transient flow phenomena in cryogenic Fluids

The objectives of the prosposed activity is to improve the understanding of flow phenomena occuring during transients, start-ups and shut-downs in propulsion systems with cryogenic fluids.  

The activity focuses in particular when considering multiple re-ignition of upperstages. This entails waterhammer effects or pre-combustion phenomena where propellants undergo drastic changes due to sudden exposure to near-vacuum conditions. To allow proper modelling, detailed experiments need to be created for typical multi-phase, multi-component flow. Following activities are foreseen: Evaluation of the liquid front behaviour during waterhammer prior, during and after impact for different operational conditions. Evaluation of the (flashing) evaporation front during priming/start-up. Evaluation of atomization processes in flashing conditions at different conditions. Evaluation of vaporization rates in flashing conditions at different conditions. Extension of correlations for flash atomization. Extension/validation of correlations for flash vaporization. The present activity is part integral of a strategy towards the acquisition of experimental data in order to understand the physics of cryogenic flows and by this means to provide with tools for the design of propulsion components like valves, tanks and propulsion feed lines, among others. Indeed, first experimental investigation for cryogenic flows through injectors have been carried out in the TRP activity ?Multi-phase aspects in propulsion systems?. Experimental characterisation of valves in multi-physics environment are being studied in the GSTP activity ?Multi-physics valve models?. A feasibility experimental study on propellant feed lines exposed to strong pressure gradients in millisecond time is being done in the TRP ?Waterhammer test with cryogenic fluids?. Finally, experimental test data for cryogenic flows with strong heat ex-change is planned in the approved GSTP activity ?Experimental Investigation of Cryogenic Two Phase Flow?. The results of all these activities allow to constitute an experimental DataBase for cryogenic propellant, a key element towards the validation of design tools for propulsion components.