Breakup Behaviour of Like-impinging Type Rocket Injectors
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Rocket (weapon)
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The breakup characteristics of liquid sheets formed by like-doublet injector were investigated in the cold-flow and atmospheric ambient pressure condition. The sheet breakup wavelength, which induces the sheet to be broken into ligaments, as well as the sheet breakup length, which is important for the flame location, was measured using a stroboscopic light. The liquid ligaments are formed intermittently after the breakup of sheet, and the wavelength of ligaments has been believed to have a relation to the combustion instability of liquid rocket engine. Therefore, the wavelength of ligaments and the breakup length of ligaments into fine drops were also measured. Since these spray characteristics are affected by the flow characteristics of two liquid jets before they impinge on each other, we focused on the effects of orifice internal flow such as the cavitation phenomenon that occurs inside the sharp-edged orifice. From the experimental results, we found that the liquid jet turbulence delays the sheet breakup and makes shorter wavelengths for both sheets and ligaments. Since the turbulent strength of sharp-edged orifice is stronger than that of round-edged orifice, the shape of orifice entrance results in large differences in the spray characteristics. Using these results, we proposed empirical models on the spray characteristics of the like-doublet injector, and these models are believed to provide some useful and actual data for designing liquid rocket combustors.
Sauter mean diameter
Weber number
Liquid-propellant rocket
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The breakup characteristics of liquid sheet formed by the liquid rocket injector has a close relation with the combustion instability. In this paper, basic characteristics of liquid sheet was measured with instantaneous image of the spray cone and PDPA for the Like Doublet Impinging Injector. Test variables were the angle of impact, the diameter of orifice and jet velocity. Water was used as test fluid. Experimental results show that the breakup length of liquid sheet is increased with increasing orifice diameter. For Impingement angle, breakup length is decreased up to , then is increased for Impingement angle more than . When jet velocity changes, there exist two conflicting field which depends on the inertial force and the balance of surface tension. It was also found that breakup frequency increased with decreasing angle of impact and with increasing jet velocity The liquid sheet velocity which is the most important parameter for the breakup frequency can be expressed as a function of half angle of fuel and oxidizer jet().
Weber number
Ligand cone angle
Spray characteristics
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Dimensionless quantity
Weber number
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The atomization process of uni-element like-doublet injector includes formation of liquid sheet, fragment into ligaments, and breakup into fine drops. During the processes, breakup characteristics of the liquid sheet such as breakup length and breakup frequency affect the combustion instability as well as the efficiency of liquid rocket combustor. In this paper we proposed spray models on the breakup characteristics of the liquid sheet based on empirical data. We focused on the effects of the orifice inner flow characteristics such as cavitation phenomenon inside the sharp-edged orifice. From our experimental results, we found that the effects of turbulence inside the sharp-edged orifice are significant for the breakup of liquid sheet, and the cavitation tends to increase the turbulence strength. Since the turbulence strength of jet at the orifice exit increases as the orifice length becomes short, we also considered the effects of orifice length. Our empirical formula for the beakup length and the breakup frequency of liquid sheets formed by like-doublet injectors are believed to give some useful and actual data for designing liquid rocket combustors.
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Spray characteristics
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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
Weber number
Momentum (technical analysis)
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Breakup characteristics of liquid sheets formed by the impingement of two water jets, such as a breakup length and a breakup wavelength of sheet, were investigated as increasing the injection velocity up to 30m/s and the ambient gas pressure up to 4.0MPa. While round edged orifices formed a laminar sheet which has no waves on the sheet when the injection velocity is low, sharp edged orifices formed a turbulent sheet which has impact waves irrespective of the injection velocity. Thus we compared the differences of breakup characteristics between them. The results showed that the aerodynamic force significantly affects the breakup of laminar sheet when the gas based Weber number is higher than unity, It was also found that the turbulent sheets have three breakup regimes, i.e. expansion regime, wave breakup regime and catastrophic breakup regime according to the gas based Weber number.
Weber number
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