Mathematical model for multivariate nonlinear prediction of SMD of X-type swirl pressure nozzles

A comprehensive numerical analysis has been conducted to explore the development of liquid-oxygen (LOX) flow in pressure swirl injectors operating at supercritical pressures. The model is based on full-conservation laws and accommodates real-fluid thermodynamics and transport phenomena over the entire range of fluid states of concern. Three different flow regimes with distinct characteristics, the developing, stationary, and accelerating regimes, are identified within the injector. Results are compared to predictions from classical hydrodynamics theories to acquire direct insight into the flow physics involved. In addition, various flow dynamics are investigated by means of the spectral and proper-orthogonal-decomposition techniques. The interactions between the hydrodynamic instabilities in the LOX film and acoustic oscillations in the gaseous core are clearly observed and studied. The influences of flow conditions (mass flowrate, swirl strength of the injected fluid, and ambient pressure) and injector g...

Cryogenic fluid dynamics of pressure swirl injectors at supercritical conditions

This study investigated the spray and Sauter mean diameter characteristics of gas-liquid swirl coaxial injectors by measuring and analyzing spray angles and mean drop sizes. Two different types of gas-liquid swirl coaxial injectors were designed and tested for this experiment: 1) a gas-centered swirl coaxial injector and 2) a liquid-centered swirl coaxial injector. The spray patterns were obtained for both types of injectors. The spray angles of these liquidcentered swirl coaxial injectors showed a decreasing trend as a function of the momentum flux ratio over the conditions studied. Good agreement was generally achieved between the predicted and measured spray angles. On the other hand, with increasing momentum flux ratio, the spray angle of the gas-centered swirl coaxial injector initially decreased when the momentum flux ratios were relatively low, but the trend reversed over the high momentum flux ratio range studied. The Sauter mean diameter data of these two types of injectors were also obtained using an image-processing method. Results showed that the Sauter mean diameter distribution of the liquid-centered swirl coaxial injector had a solid cone shape, whereas the gas-centered swirl coaxial injector exhibited two distinct Sauter mean diameter distribution regimes. The gas-centered swirl coaxial injector had a solid cone shape along the centerline, and it had a hollow cone shape at the periphery.

Comparative Study of Spray Characteristics of Gas-Centered and Liquid-Centered Swirl Coaxial Injectors

Breakup of a power-law liquid sheet formed by an impinging jet injector

Review on pressure swirl injector in liquid rocket engine

The spray and breakup characteristics of a swirling liquid sheet were investigated by measuring the spray angle and breakup length as the axial Weber number We l was increased up to 1554 and the ambient gas pressure up to 4.0 MPa. As the We l and ambient gas density p increased, the disturbances on the annular liquid sheet surface were amplified by the increase of the aerodynamic forces, and thus the liquid sheet disintegrated from the injector exit. The measured spray angles according to the ambient gas density differed before and after the sheet broke up. Before the liquid sheet broke up, the spray angle was almost constant; however, once the liquid sheet started to break up, the spray angle decreased. As the ambient gas density and We l increased, the increasing aerodynamic force caused the breakup length to decrease. Finally, the measured breakup lengths according to the ambient gas density and We l were compared with the results of the linear instability theory. Considering the attenuation of sheet thickness in the linear instability theory, the corrected breakup length relation agreed well with our experimental results.

Effect of ambient gas density on spray characteristics of swirling liquid sheets

Self-pulsation characteristics of a gas-liquid swirl coaxial injector

The effects of recess in a liquid-liquid swirl coaxial injector on the spray characteristics have been investigated by measuring the spray angle and breakup length in eight cases of recess length. The orifice recess, a geometric parameter, has a strong influence on the spray and mixing characteristics by varying the interaction point between two liquid sheets. The variation of the recess length resulted in three different injection regimes: external, tip, and internal mixing injection. The coaxial spray characteristics in the external mixing injection regime are found to be mainly governed by the merging phenomenon and momentum balance between two liquid sheets. In the internal mixing injection regime, an impact wave is generated by the impingement of the inner spray on the outer liquid film inside the injector. The amplitude of the impact wave is gradually attenuated due to the fluid viscosity, flowing along the outer injector wall after impingement. This attenuation of the impact wave according to the recess length could affect the stability of a liquid sheet; therefore, the breakup length is found to increase with the increase in recess number.

Effect of Recess on the Spray Characteristics of Liquid-Liquid Swirl Coaxial Injectors

The spray and acoustic characteristics of a gas/liquid swirl coaxial injector are studied experimentally. The self-pulsation is defined as a pressure and flow rate oscillations by a time-delayed feedback between liquid and gas phase. Self-pulsation has strong influences on atomization and mixing processes and accompanies painful screams. So, the spray and acoustic characteristics are investigated. Spray patterns are observed by shadow photography technique in order to determine the onset of self-pulsation. And self-pulsation boundary with injection conditions and recess length is get. To measure the frequency of the spray oscillation, oscillation of the laser intensity which passes through spray is analyzed by Fast Fourier Transform. For acoustic tests, a PULSE System was used. Acoustic characteristics of a swirl coaxial injector are investigated according to the injection conditions, such as the pressure drop of the liquid and gas phase, and injector geometries, such as recess length and gap size between the inner and outer injector. From the experimental results, the increase of recess length leads to the rapid increase of the sound pressure level. And as the pressure drop of the liquid phase increases, the frequency of the self- pulsation shifts to the higher frequency. The frequency of spray oscillation is the same as that of the acoustic fields by self-pulsation.

Ji-Hyuk Im

Papers

Effect of ambient gas density on spray characteristics of swirling liquid sheets

Comparative Study of Spray Characteristics of Gas-Centered and Liquid-Centered Swirl Coaxial Injectors

Self-pulsation characteristics of a gas-liquid swirl coaxial injector

Effect of Recess on the Spray Characteristics of Liquid-Liquid Swirl Coaxial Injectors

Self-pulsation characteristics of a swirl coaxial injector with various injection and geometric conditions