• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.2
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• pp.19-28
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• 2010

Generally, combustion instability is generated by the mutual coupling between the heat release and the acoustic pressure in the combustor. On the occasion, the acoustic pressure generates the oscillation of the mass flow rate of propellant injected from injector, and this oscillation again affects combustion in the combustor. So, the dynamic characteristics of the injector have been studied to control combustion instability using injector itself in Russia from 1970's. In order to study injector dynamics, a mechanical pulsator for forced pressure pulsation is produced and the method to quantify the mass flow rate of the propellant that is oscillating at the exit of the injector is developed. With the pulsator and the method, pulsating values of the mass flow rate, pressure, liquid film thickness, and axial velocity generated at the exit of the simplex swirl injector are measured in real time. And phase-amplitude characteristics of each parameter are analyzed using these pulsating values acquired at the exit of the simplex swirl injector.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.619-625
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• 2015

Swirl injectors are widely used for Liquid Rocket Engine(LRE) as fuel injection system and following researches are also being carried out throughout the world. Especially, solving combustion instability problem is essential for every type of LREs. In this study, cold test was carried out for open type swirl injector as a fundamental research to solve combustion instability problem. Pressure fluctuation was applied to the inlet flow coming into the injector and the following response characteristics were observed. The effect of swirl chamber geometry was also studied by changing both swirl chamber length and diameter.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.8-14
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• 2015

This study has been done as a preliminary work in the process of confirming the modeling and calculation results on the dynamic characteristics of closed-type swirl injector which were performed by Ismailov et al. in Purdue university. Closed-type swirl injectors with replaceable swirl chamber parts were designed and manufactured. The steady state spray characteristics of closed-type swirl injector with varying swirl chamber length and diameter were verified. Mass flow rate was measured with a mass flow meter installed in front of the injector, and liquid film thickness was measured by Lefebvre's method with electrodes installed at the orifice of the injector. Variation of spray cone angle and break-up length were investigated from the spray images captured under different manifold pressure conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.67-75
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• 2006

A fully nonlinear model accounting for swirling effect has been applied in analyzing the dynamic response for a classical swirl injector. The current work applied highly accurate Boundary Element Methods (BEMs) in assessing its static and dynamic characteristics. On the basis of moving surface treatment method and surface instability study, which are obtained from the previous static characteristics analysis in pressure-swirl injectors, this work was expanded for analyzing the dynamics of a classical swirl injector. The dynamic response through injector components for disturbed inflow condition was investigated. The modified code was validated from comparison with the theoretical result for a typical swirl injector. Clearly the simulated result shows the interesting characteristics of swirl injectors to provide either amplification or damping of the input disturbance through each component. These results give promise in applying the current model to nonlinear dynamic characteristics of swirl injectors.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.54-60
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• 2010

액체로켓엔진 시스템의 시동 및 정지 또는 추력 제어와 같은 천이 작동시 동특성을 예측하기 위한 선행 연구로서 추진제 공급 시스템의 구성품에 대한 동특성 모델링을 수행하였다. 연료 공급계통과 산화제 공급 계통의 구성품들은 재생냉각채널을 제외하고 같은 것으로 가정하였다. 동특성 모델링의 대상 구성품은 펌프, 관로, 오리피스, 제어 벨브, 재생냉각채널, 인젝터 등이며 실제 엔진 시스템의 축소모형에 대한 수력시험을 통해 각 구성품의 동특성 모델링을 검증하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.691-698
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• 2017

In this study, the injector transfer function (ITF) of a gas-gas coaxial jet-swirl injector is measured by applying excitation to jet or swirl flow using a loudspeaker. As a result of measuring the ITF according to the variation of feed system length, the ITF peak occurs at the resonance frequency of the space where the perturbed flow passes. When applying the excitation to the jet flow, as the jet flow increases up to 56 slpm, the magnitude of ITF decreases, and ITF increases thereafter. Therefore the larger the velocity difference between the jet and the swirl flow, the larger the ITF. In the case of the swirl excitation, the ITF decreases as the jet flow increases because of the decrease of the energy with respect to the constant flow at the downstream. This difference is caused by the location of the hot wire anemometer on the downstream of the injector center axis.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.1
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• pp.35-44
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• 2011

Mathematical modelling for liquid rocket engine(LRE) main components were conducted to predict the dynamic characteristics when the LRE operates at the transient condition, which include engine start up, shut down, or thrust control. Propellant feeding system is composed of fuel and oxidizer feeding components except for regenerative cooling channel for the fuel circuit. Components modeling of pump, pipe, orifice, control valve, regenerative cooling channel and injector was serially made. Hydraulic tests of scale down component were made in order to validate modelling components. The mathematical models of engine components were integrated into LRE transient simulation program in concomitant with experimental validation.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.164-173
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• 2006

In the electro-hydraulic injector for the common rail Diesel fuel injection system, the injection nozzle is being opened and closed by movement of a injector's needle which is balanced by pressure at the nozzle seat and at the needle control chamber, at the opposite end of the needle. In this study, the piezo actuator was considered as a prime movers in high pressure Diesel injector. Namely a piezo-driven Diesel injector, as a new method driven by piezoelectric energy, has been applied with a purpose to develop the analysis model of the piezo actuator to predict the dynamics characteristics of the hydraulic component(injector) by using the AMESim code. Aimed at simulating the hydraulic behavior of the piezo-driven injector, the circuit model has been developed and verified by comparison with the experimental results. As this research results, we found that the input voltage exerted on piezo stack is the dominant factor which affects on the initial needle behavior of piezo-driven injector than the hydraulic force generated by the constant injection pressure. Also we know the piezo-driven injector has more degrees of freedom in controlling the injection rate with the high pressure than a solenoid-driven injector.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.8-13
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• 2011

본 연구에서는 대형 로켓엔진시스템의 시동 시 안정적인 유량공급을 위한 제어기 설계가 이루어졌다. 펌프, 오리피스, 제어밸브, 파이프, 인젝터 및 재생 냉각채널과 같은 엔진시스템 구성품들에 대한 동특성 모델링을 수행하였고 유량공급 제어가 가능한 밸브의 구동신호를 조절 가능한 PID 제어기를 설계하였다. 시동 시 안정적인 유량공급을 위하여 실험을 통해 얻은 밸브의 적정 개도율을 적용시켰으며, 이를 기준으로 하여 제어밸브의 작동신호를 조절하여 유량비를 제어하였다. 시뮬레이션 한 결과 제어기를 통해 시동 시 정상추력까지 유량공급을 제어 하는 방법이 적절함을 확인하였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.6
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• pp.140-147
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• 2011

The injection nozzle of an electro-hydraulic injector for the common rail Diesel fuel injection system is being opened and closed by movement of a injector's needle which is balanced by pressure at the nozzle seat and at the needle control chamber, at the opposite end of the needle. In this study, the slenoid actuator was considered as a prime movers in high pressure Diesel injector. Namely a solenoid-driven Diesel injector with different driving current types, as a general method driven by solenoid coil energy, has been applied with a purpose to develop the analysis model of the solenoid actuator to predict the dynamics characteristics of the hydraulic component (injector) by using the AMESim code. Aimed at simulating the hydraulic behavior of the solenoid-driven injector, the circuit model has been developed as a unified approach to mechanical modeling in this study. As this analytic results, we know the suction force and first order time lag for driving force can be endowed in solenoid-driven injector in controlling the injection rate. Also it can predict that the input current wave exerted on solenoid coil is the dominant factor which affects on the initial needle behavior of solenoid-driven injector than the hydraulic force generated by the constant injection pressure.