New Method to Determine the Velocities of Particles on a Solid Propellant Surface in a Solid Rocket Motor

Abstract

Use of aluminized composite solid propellants and submerged nozzles are common in solid rocket motors (SRM). Due to the generation of slag, which injects into a combusted gas flow, a two-phase flow pattern is one of the main flow characteristics that need to be investigated in SRM. Validation of two-phase flow modeling in a solid rocket motor combustion chamber is the focus of this research. The particles’ boundary conditions constrain their trajectories, which affect both the two-phase flow calculations, and the evaluation of the slag accumulation. A harsh operation environment in the SRM with high temperatures and high pressure makes the measurement of the internal flow field quite difficult. The open literature includes only a few sets of experimental data that can be used to validate theoretical analyses and numerical calculations for the two-phase flow in a SRM. Therefore, mathematical models that calculate the trajectories of particles may reach different conclusions mainly because of the boundary conditions. A new method to determine the particle velocities on the solid propellant surface is developed in this study, which is based on the x-ray real-time radiography (RTR) technique, and is coupled with the two-phase flow numerical simulation. Other methods imitate the particle ejection from the propellant surface. The RTR high-speed motion analyzer measures the trajectory of the metal particles in a combustion chamber. An image processing software was developed for tracing a slug particle path with the RTR images in the combustion chamber, by which the trajectories of particles were successfully obtained.

Assessment of the Performance of Ablative Insulators Under Realistic Solid Rocket Motor Operating Conditions

“…Real-time X-ray radiography (RTR) has been utilized to great effect in SRMs because it allows the internal processes of an SRM to be observed without affecting those processes. RTR has been utilized in subscale and full-scale rocket motor firings to study alumina slag flow [44] [45], solid propellant regression rates [46], hybrid fuel regression rates [42], and graphite nozzle erosion [11]. Since the contrast of X-ray images is essentially supplied by density gradients within materials, it is an ideal technique for examining the decomposition of ablative materials.…”

Study of Liquid Breakup Processes in Solid Rocket Motors

“…Moreover, because of the geometry of the motor, molten alumina agglomerates can form, resulting in two-phase flow losses 6, 7 , 8 . These agglomerates lower the propulsive efficiency of the exhaust flow because the agglomerates do not expand in the nozzle and also create a drag force on the flow 9,10 . Depending on the alumina particle size and the alumina particle-gas mixture percentage, two-phase flow losses can reduce the propellant specific impulse by as much as 6% 11,12 .…”

Study of Alumina Flow in a propulsion Chamber

“…These agglomerates lower the propulsive efficiency of the exhaust flow because the agglomerates do not expand in the nozzle and also create a drag force on the flow. 8,9 Depending on the alumina particle size and the alumina particle-gas mixture percentage, two-phase flow losses can reduce the propellant specific impulse by as much as 6%. 10,11 The breakup mechanism of the liquid phase of liquid alumina is one of the factors of performance improvement.…”