• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.102-111
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• 2004

The procedure of design and manufacture of sub-scale combustor using bipropellant swirl injector with external mixing for a liquid rocket engine are described. The results of cold flow test, ignition test and combustion test of the sub-scale combustor are also given in this paper. The sub-scale combustor uses liquid oxygen(LOx) and kerosene as propellants and has a injector head, an ablative material combustor wall and a water cooled nozzle. The injector head has LOx manifold, fuel manifold, fire face plate, one center swirl injector and 18 main swirl injectors. The cold flow, ignition and combustion tests were successfully performed without damage of combustor. Results of hot firing tests show that combustion efficiency meets the target of design and operations of start and stop cyclogram are stable and high frequency combustion instability does not occur.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.438-445
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• 2007

A Helmholtz resonator as a stabilization device to control high-frequency combustion instabilities in liquid rocket engine is adopted and its damping capacity is verified by linear acoustic analysis and atmospheric acoustic tests. To compare the results of acoustic attenuation effect in accordance with uni-resonator's geometry, quantitative analyses were made in the cases of various orifice diameters and lengths. Next, in the experiments to compare the results of acoustic attenuation effect by a difference in the number of resonators, damping capacity of harmful resonant frequency was improved by the increase of the number of resonators. On the other hand, attenuation efficiency of the frequency tended rather to lower due to over damping from the point of view of absorption coefficient. As the result, tuning the suitable geometry for the resonator to the resonant frequency is required for the control using the resonator. Also, the design of resonator's geometry and the choice of its number are important to put up the optimal efficiency in consideration of restriction of its volume.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.35-38
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• 2011

Damping characteristic according to acoustic cavity's geometries was investigated to control the high frequency combustion instability occurring in the Liquid Rocket Combustion Chamber by experimental test and linear analysis. Its diameter was determined as a design parameter and its orifice length and diameter were appointed as fixed parameter in this study. Result shows that the damping capacity has been almost constant through all the experiments despite using the same orifice and helmholtz resonators which have different volume.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.608-613
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• 2019

NOx (Nitrogen oxide) in the exhaust gas from vehicle engines is considered one of the most harmful substances in air pollution problems. NOx is made when combustion occurs under high temperature conditions and EGR (exhaust gas recirculation) is normally used to lower the combustion temperature. As the EGR ratio increases, the NOx level becomes low, but a high EGR ratio makes the combustion unstable and causes further air pollution problems, such as CO and unburned hydrocarbon level increase. This study showed that fuel droplets could move more freely by the radiation of sonic wave for the stable combustion. In addition, the engine performance improved with increasing EGR ratio. As a basic study, the effect of sonic wave radiation on the velocity of fuel droplets was studied using CFD software. The results showed that the velocity of small droplets increased more under high frequency sonic wave conditions and the velocity of the large droplets increased at low frequency sonic wave conditions. In addition, an engine analysis model was used to study the effects of the increased combustion stability. These results showed that a 15% increase in EGR ratio in combustion resulted in a 45% decrease in NOx and a 10% increase in thermal efficiency.

• Aerospace Engineering and Technology
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• v.1 no.1
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• pp.147-152
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• 2002

In the preceding tests of Sub.(Ⅰ) engines, it was observed that the heat resistant capability of the engines was not enough, and the design of Sub.(Ⅰ) engines was modified to satisfy the mission requirement. Sub.(Ⅰ) Mod. engines have three major design parameters - the arrangement of main injectors, the impinging angle of main injectors and thermal barrier coating. More than 20 experiments were carried out to evaluate engine performance and heat resistance capability with respect to design parameters. Analysing the result of Sub.(Ⅰ) and Sub.(Ⅰ) Mod. engine tests, it is found that the decreased impinging angle, adopting the H-type arrangement(rather than radial type arrangement), and adopting the thermal barrier coating can increase heat resistance capacity substantially. The result show that the performance variation by design change is below 5 percents and the radial type arrangement of injectors has higher performance than H-type. However, the performance of 15°impinging angle engine is higher than that of 20°impinging angle engine, which is inconsistent to our expectation. High frequency instabilities may cause such phenomenon, which will be verified by a series of tests.