• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.322-326
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• 2005

The spray and acoustic characteristics of a swirl coaxial injector are studied experimentally. The spray and 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.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.4
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• pp.113-123
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• 2003

Both numerical analysis and experiment of cold and hot tests were performed to obtain basic design data for the swirl coaxial type Injector and to predict the combustion performance. Mass distribution, mixing distribution, mixing efficiency, characteristic velocity efficiency were measured by the cold tests and numerical analysis using the commercial thermo-hydraulic program. Test and analysis variables were recess, pressure drop, velocity ratio, mixing spray, mixture ratio. Hot tests were performed for the Uni-element injector to compare the performance with the cold test results, and, hot tests for Multi-element injector were performed to compare the performance with Uni-element injector. Designed thrust of the Uni-element injector liquid rocket was 35kgf at sea level and combustion chamber pressure, 20bar. Kerosene and Lox were used as a propellant.

• Journal of ILASS-Korea
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• v.28 no.2
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• pp.75-88
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• 2023

In this paper, the atomization characteristics of bi-swirl coaxial injectors for a 420 N-class bipropellant thruster were investigated. Three types of injectors, namely closed-type, open-type, and screw-type, were manufactured and designed to have the same spray angle and injection pressure drop. Water was used as a simulant, and cold-flow tests were conducted under ambient temperature and pressure conditions. Since the inner and outer injectors were designed to be the same type, only the inner fuel injectors that were easy to measure were used. Using a phase doppler particle analyzer, the velocity and diameter of atomized droplets were measured. Closed-type swirl injector exhibited droplet distributions with relatively high velocities and small SMD compared to the other two injectors. Open-type swirl injector formed droplets with reverse velocities in the center region and had a large recirculation zone. Screw-type swirl injector showed a sharp decrease in droplet velocity and size with radial distance from the liquid film breakup point. For the same design requirements, the closed-type swirl injector has superior atomization performance.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.148-151
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• 2007

We made two injectors that were equal to all design except for existence or nonexistence of swirl chamber of fuel part, because we want to find cooling characteristics at the injector face according to existence or non existence of swirl chamber of fuel part. And we set regenerative cooling channel in injector face for protecting injector face for prolonged combustion time. Two injectors were performed hot firing test, and then we compared cooling characteristics of two injectors. Also we compared O/F ratio effects on cooling characteristics and combustion characteristics.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.479-483
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• 2010

In this paper, a study for hybrid rocket combustion with cylindrical multi-port grain and swirl injector was performed to take advantage of regression rate. Change of the regression rate in the multi-port grain the placement of a swirl Injector experiments were performed. The results of multi-port grain using swirl injector were showed that the regression rate was increased compare with the shower head type injector.

• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.27-36
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• 2023

To understand the atomization performance in gas-liquid swirl-coaxial injector applied to a small rocket engine, a cold-flow test was performed by varying the design parameters and supply condition of propellants. As the swirl-chamber diameter and the angle of the convergent section, which are design parameters of injector increased, the spray performance of the injector improved by increasing the swirl strength. In addition, as the gas-liquid momentum-flux ratio increased, the gas flow separated some of the droplets from the liquid film, and a gas-droplet mixture core was formed in the center of the spray sheet.

• Journal of ILASS-Korea
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• v.10 no.4
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• pp.32-46
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• 2005

The breakup characteristics of liquid sheets formed by the impinging and swirl type injectors were studied as increasing the Weber number (or injection condition) and the ambient gas pressure to 4.0.MPa. In the case of impinging type injector. we compared the changes of breakup lengths between laminar and turbulent sheets. which are formed by the impingement of laminar and turbulent jets. respectively. The results showed that both sheets expand as increasing the injection velocity irrespective of the ambient gas density when the gas based Weber number is low. When the Weber number is high, however, the breakup of turbulent sheet depends on the hydraulic force of jets as well as the aerodynamic force of ambient gas which determines the breakup of laminar sheet. Using the experimental results. we could suggest empirical models on the breakup lengths of laminar and turbulent sheets. In the case of swirl type injector. as $We_l$, and ambient gas density increased, the disturbances on the annular liquid sheet surface were amplified by the increase of the aerodynamic forces. and thus the liquid sheet disintegrated near from the injector exit. Finally, the measured breakup length of swirl type injector according to the ambient gas density and $We_l$, was compared with the result by the linear instability theory. We found that the corrected breakup length relation derived from linear instability theory considering the attenuation of sheet thickness agrees well with our experimental results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.228-233
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• 2004

The spray and acoustic characteristics by the self-oscillation of a swirl coaxial injector were experimentally studied. The self-oscillation of a swirl coaxial injector is defined as pressure and flowrate oscillations by a time-delayed feedback between liquid and gas phase and has strong influences on atomization and mixing processes. Hence the occurrence and effect of the self-oscillation are measured using shadow photography technique, acoustic test and PDPA. The occurrence of self-oscillation largely depends on the injection conditions, such as pressure drop of liquid phase and relative momentum ratio. From the experimental results, self-oscillation occurs when the momentum of gas phase is enough large and the smaller the pressure drop of liquid phase is, the better self-oscillation occurs at the same momentum ratio. The self-oscillation is also affected by injector geometries, increasing the recess length results in the expansion of self-oscillation region and the increase of sound pressure level. The self-oscillation of a swirl coaxial injector accompanies a high intensity scream and this scream may provide harmful disturbances to combustion processes. Self-oscillation leads to strong changes in the drop size distribution and smoothly varies the slope of radial SMD distribution.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.4
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• pp.132-144
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• 2003

Numerical analysis of the spray angles of Dual swirl injector were investigated to obtain basic design data and to predict the combustion performance. Using the commercial thermal hydraulic program, discharge coefficients and spray angles were numerically analyzed with recess length, pressure drop, velocity ratio, mixture ratio and back hole length. Water was used as simulants for oxidizer and fuel, respectively to compare the experimental results. Swirl injectors were designed to inject oxidizer of 70.5g/s and fuel of 29.5g/s at the pressure drop of 1MPa and two recess lengths were considered. In addition, the effect of injector geometry coefficient and velocity ratio on the discharge coefficient was studied.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.153-156
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• 2003

Backhole, which is one of geometric parameters in swirl coaxial injectors, is found to affect the inner flow motion and the acoustic characteristics of the swirl injector. In order to analyze the effect of the backhole as a damping device such as acoustic cavities of the combustion chamber, it was regarded as a Helmholtz or Quarter-wave resonator. As a result, it is known that the swirl coaxial injector with the backhole may produce the resonant frequency coincided with the frequency of the combustion chamber.