Combustion Instability Phenomena of Importance to Liquid Propellant Engines

Abstract : A systematic study of the atomization of impinging liquid jets was performed. Effects of jet flow condition, orifice diameter, impingement angle, pre-impingement length, fabrication procedure, and jet velocity at steady and oscillating, and atmospheric- and high-pressure ambient conditions were investigated. Measurements of sheet breakup length, drop size and velocity distribution, and the length between sheet structures and detached ligaments were made. Results of the experiments were compared to theoretical predictions. It appears that primary breakup of the sheets formed by turbulent impinging jets is controlled by pressure and momentum fluctuations in the liquid that are accentuated near the impingement point and that have their origin in the jet prior to impingement. Based on these results, approaches to modeling impinging jet atomization should focus on pre-impingement jet conditions and the physics near the jet impingement point. Experimental results were also studied in the context of an empirical correlation used in industry for the prediction of combustion stability. The frequency with which the periodic disturbances that control primary breakup are formed has a marked similarity to the combustion instability frequency predicted by the stability correlation. Furthermore, an increase in predicted stability coincides with an increase in measured mean drop size and an increase in the polydispersity of the drop size distribution. Impinging jet injectors, Combustion instability, Atomization