• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.16-19
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• 2011

An experimental study on the spray characteristics of Gas-centered swirl coaxial injectors(GCSCI) for high-performance staged combustion rocket engines has been carried out using cold flow tests. In this study, water and gaseous nitrogen are used as working fluids and a back-lit photography technique with image processing for the measurements of spray characteristics. Our study is focused on the effect of injector geometries like as gap thickness of liquid nozzle and gas nozzle and momentum flux ratio for fundamental understanding of the injectors.

• Journal of ILASS-Korea
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• v.26 no.1
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• pp.9-17
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• 2021

Six shear coaxial injectors with different recess length and taper angle were manufactured. Cold-flow tests on the injectors were performed at room temperature and pressure using water and air as simulants. By changing the water mass flow rate and air mass flow rate, spray images were taken under single-injection and bi-injection. Breakup length and spray angle were analyzed from instantaneous and averaged spray images using image processing techniques. For all the injectors, the breakup length generally decreased as the momentum flux ratio increased at the same gas mass flow rate. The injectors with 7.5° taper angle usually had the longest breakup length and the smallest spray angle. When the taper angle was 15° or more, it hardly affected breakup length and spray angle. The recess length did not influence breakup length but its effect on spray angle depended on the taper angle.

• Journal of ILASS-Korea
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• v.27 no.3
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• pp.134-143
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• 2022

When a recess is applied to a swirl coaxial injector that uses liquid and gas propellants, a self-pulsation phenomenon in which the spray oscillates at regular intervals may occur. The phenomenon is caused by the interaction between the liquid and gas propellants inside the injector recess region. The propellants' kinetic energies are expected to affect significantly the spray oscillation. Therefore, cold-flow tests using helium as a gas-simulating propellant were conducted and compared with the results of the previous study using air. Dynamic pressure was measured in the injector manifold and frequency characteristics were investigated through the fast Fourier transform analysis. In the experimental environment, the helium density was about seven times lower than the air density. Accordingly, the intensity of pressure fluctuations was confirmed to be greater when air was used. At the same kinetic energy condition, the perturbation frequency was almost identical in the low flow rate conditions. However, as the flow rate increased, the self-pulsation frequency was higher when helium was used.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.26-33
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• 2014

The gas-centerd swirl injectors are widely used on the main combustor of large liquid propellant rocket engines. Since the gas-liquid propellants, such as kerosene and oxygen-rich gas combination, are mixed and burned in the high pressure condition over the critical pressure point, the cold-flow spray test in the atmospheric condition can not represent the actual spray pattern. To observe the near actual spray patterns of gas-centered swirl injector, the high pressure spray chamber and the control system were constructed. The operating sequence was controlled precisely to obtain clear visualization images.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.577-580
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• 2010

Coaxial injectors using GCH4/LOx as propellants was designed with shear(gas)/shear(liquid) type and shear(gas)/swirl(liquid) type. Spray characteristics were investigated by cold flow test. Spray patterns of the shear/shear and the shear/swirl type injectors were like a spout of water and hollow cone, respectively. Atomization efficiency of the shear/swirl type injector was better than atomization efficiency of the shear/shear type injector.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.221-230
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• 2011

The cold spray process is an emerging technology that utilizes high velocity metallic particles for surface coating. Metallic powder particles are injected into a converging-diverging de Laval nozzle and accelerated to a high velocity by a supersonic gas flow. The cold spray process normally uses a circular nozzle that has a rather narrow spraying range. To overcome this fault, a slit nozzle was considered in this study. The slit nozzle is anticipated to reduce the coating process time because it has a wider coating width than the circular nozzle. However, the slit nozzle can reduce the coating efficiency because it does not allow as much gas and particle velocity as the circular nozzle. To improve the coating efficiency of a slit nozzle, the shape of the slit nozzle was modified. And the results of gas flow and particle behaviour according to the nozzlers shape were compared by the a numerical analysis. As a results, as Expansion Ratio(ER) of 7.5 was found to be the most optimal condition for enhancing the spraying efficiency when the ER was changed by the variation of nozzle neck and exit size.

• 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 Powder Materials
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• v.19 no.4
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• pp.317-321
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• 2012

In this study, Cu-5Ni-10Sn(wt%) spinodal alloy was manufactured by gas atomization spray forming, and the microstructural features and mechanical properties of Cu-5Ni-10Sn alloy have been investigated during homogenization, cold working and age-hardening. The spray formed Cu-5Ni-10Sn alloy consisted of an equiaxed microstructure with a mixture of solid solution ${\alpha}$-(CuNiSn) grains and lamellar-structure grains. Homogenization at $800^{\circ}C$ and subsequent rapid quenching formed a uniform solid solution ${\alpha}$-(CuNiSn) phase. Direct aging at $350^{\circ}C$ from the homogenized Cu-5Ni-10Sn alloy promoted the precipitation of finely distributed ${\gamma}$' or ${\gamma}-(Cu,Ni)_3Sn$ phase throughout the matrix, resulting in a significant increase in microhardness and tensile strength. Cold working prior to aging was effective in strengthening Cu-5Ni-10Sn alloy, which gave rise to a maximum tensile strength of 1165 MPa. Subsequent aging treatment slightly reduced the tensile strength to 1000-1100 MPa due to annealing effects.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.246-247
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• 2003

Large Eddy Simulation(LES) of turbulent spray combustion flow was conducted. An experimental database for the laboratory spray combustor is chosen to validate the present numerical simulation. The governing equations for the gas phases are discretized in three-dimensional curvilinear boundary-fitted coordinate system, and the fuel droplet motion equations are described in Lagrangian representation. The numerical results are compared with the experiment for the gas-phase mean velocities and its fluctuation in cold flow condition. Three dimensional vortical structures are well visualized and droplet motion is well predicted.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.57-60
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• 2011

The spray characteristics according to the recess length of the GCSC injector and the change of momentum flux ratio(MFR) of the gas and the liquid have been examined through high pressure cold flow test using a high pressure chamber. The liquid in this experiment was water, and the gas was nitrogen. The spray images were taken by a back-lit strobe imaging technique. Results showed that the spray was a wide hollow cone at the lower MFR(liquid velocity was fixed) and the spray became a narrow solid cone as the MFR was increased. And the injector with short recess length produced a narrow solid cone at the higher MFR.