• Journal of the Korean Society of Propulsion Engineers
• /
• v.23 no.4
• /
• pp.70-80
• /
• 2019

Combustion tests using six bi-swirl coaxial injectors with different shapes and recess lengths were performed in a model combustion chamber capable of flame visualization. By utilizing gaseous methane and gaseous oxygen instead of actual propellants, the effects of injector design and experimental conditions on the flame structure and combustion stability were analyzed. It was found that not only the experimental conditions but also the injector geometry such as the recess length and orifice diameter had a considerable influence on the combustion stability. In addition, it was confirmed that the heat release pattern changed with the occurrence of combustion instability.

• Journal of ILASS-Korea
• /
• v.28 no.2
• /
• pp.75-88
• /
• 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
• /
• 2007.04a
• /
• pp.148-151
• /
• 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.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.8 no.1
• /
• pp.54-60
• /
• 2004

Experimental study on combustion characteristics of double swirl coaxial injectors has been conducted for the assessment of critical injector design parameters. A reusable, subscale thrust chamber has been fabricated with a water-cooled copper nozzle. Two different configurations of injectors have been tested for the understanding of the effects of recess length on high pressure combustion. Clearly, the recess length drastically affects the combustion efficiency and hydraulic characteristics of an injector. Internal mixing of propellants in an injector with recess number of two increases a combustion efficiency and reveals sound combustion although a pressure drop required for the same amount of mass flow rates increases compared with an injector of recess number of one.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.10 no.3
• /
• pp.1-8
• /
• 2006

The influences of injection conditions and recess configuration of liquid-liquid swirl coaxial injectors on spray characteristics were investigated. The characteristics of the coaxial spray in internal mixing injection region were mainly controlled by the merging phenomenon and momentum balance between two liquid sheets, but those in internal mixing injection region were influenced by the impingement phenomenon as well as momentum balance between two liquid sheets.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.125-130
• /
• 2004

Experimental study on combustion characteristics of double swirl coaxial injectors has been conducted for the assessment of critical injector design parameters. A reusable, unielement thrust chamber has been fabricated with a water-cooled copper nozzle. Two principle design parameters, a swirl angle and a recess length, have been investigated through hot firing tests for the understanding of their effects on high pressure combustion. Clearly, both parameters considerably affect the combustion efficiency, dynamics and hydraulic characteristics of an injector. Internal mixing of propellants in a recess region increases combustion efficiency along with the increase of a pressure drop required for flowing the same amount of mass flow rates. It is concluded that pressure buildup due to flame can be released by the increase of LOx flow axial momentum or the reduction of a recess length. Dynamic pressure measurements of the thrust chamber show varied dynamic behaviors depending on injector configurations.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.1
• /
• pp.17-26
• /
• 2005

Both numerical analysis and cold tests for the swirl coaxial type injector were performed to obtain the influence of spray angle, velocity ratio and liquid film thickness for pressure drop and recess. The basic experimental and numerical data obtained in this study can be applicable to the performance design of swirl coaxial type injector. Spray angle was not affected by the applied test pressure drop, but spray angle was affected by tangential velocity ratio and shape factors. Feasibility of numerical analysis for the liquid film thickness and spray angle was confirmed, and the change of liquid film thickness by tangential velocity ratio affected more seriously than pressure drop, and liquid film thickness was decreased with increasing tangential velocity ratio.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.11 no.5
• /
• pp.37-50
• /
• 2007

This study investigated the characteristics of spray generated by a liquid coaxial swirl injector used in a combustor of the liquid rocket engine. The linear stability analysis considered long and short wave was introduced in liquid sheet breakup. Through the hydrodynamic analysis the initial liquid sheet thickness spray angle and injection velocity were predicted. To evaluate the effect of turbulence model standard $k-{\varepsilon}$ and RNC $k-{\varepsilon}$ model were applied to numerical calculation and it was known that RNC $k-{\varepsilon}$ model was more applicable to predict spray characteristics. On the basis of this evaluation validation of the developed model was performed with swirl injector installed in LPRE and the predicted results of breakup length, spray angle, and SMD agreed well with experiments qualitatively and quantitatively.

• Journal of the Korean Society of Combustion
• /
• v.21 no.2
• /
• pp.15-21
• /
• 2016

Flame characteristics and combustion stability of a swirl coaxial injector are studied experimentally. Characteristics of flame and combustion instability are analyzed with the parameter of MFR (momentum flux ratio) using hexane instead of kerosene. Flame patterns of blue and yellow are changed with variable MFR. Combustion instabilities are measured and analyzed by adopting a model chamber. Combustion instability mapping is made by evaluating damping factor at the 2 L (second longitudinal) mode with variable MFR in 63 cases for operating condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.10a
• /
• pp.288-291
• /
• 2004

The spray characteristics of coaxial swirl injector under ambient high pressure conditions were investigated in this paper. Three injectors were used to study the effect of recess length and fuel injector type(open or closed). In this research, experimental conditions(ambient gas density) were calculated by Buckingham Pi-theory and spray characteristics of the injectors were represented by mass flow rate according to the injection pressure, the spray angle, mass distribution, and mean diameter of droplet.