• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.153-156
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• 2014

This study was aimed to assess combustion stability for coaxial swirl injector and FOOF impinging injector which would be candidates in liquid rocket engine combustors. Simulating combustion tests under atmospheric condition have been conducted by gaseous oxygen and the mixture of methane and propane, using two actual injectors. By analyzing the measured dynamic pressure signals, we have evaluated the combustion stability margin of both injectors by drawing a stability map.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.135-140
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• 2006

In the experimental study of $N_2$ purge cold flow test of impinging(FOOF) injector for determining of instability region, the whistling sound which has a specific frequency is generated. The frequency of whistling is proportional to the gas flow velocity in part of the oxidizer orifice and due to the coupling of the vibrating gas column and the natural frequency of pipe-orifice shape, the discontinuous jumping phenomena arises. The whistling phenomena have no effect on the combustion instability. Compared the damping factor of 1T1L mode with the hot fire test, the instability region of $N_2$ purge cold flow test is very much like that. It means that flow instability by impinging or mixing of jet is the main reason of combustion instability of impinging injector(FOOF) in the hot firing test.

• Journal of the Korean Society of Combustion
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• v.22 no.1
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• pp.46-52
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• 2017

High-frequency combustion instabilities may occur during the development of feasible engine combustors. These instabilities can result in irreparable damages to the wall of combustors or the degradation of engine performance. So, it is essential to identify injectors that have high stability characteristics during the early stages of development. The objective of present study was to assess the stability of coaxial injectors and an impinging injector with different recess lengths in order to develop stable injectors optimally. Stability margin was evaluated based on the distance from operating condition to the unstable regions. A simulating combustion test method was used to analyze the stability of injectors. A small-scale combustion chamber was designed to simulate the first tangential acoustic mode of the actual combustor. Gaseous oxygen and a mixture of methane and propane were used as simulant propellants to satisfy their flow similarity to the actual propellants of a combustor in a liquid rocket combustor. The results indicated that injectors having small recess lengths showed relatively large combustion stability margins. For the injectors of large recess lengths, instability regions with large and super-large amplitude oscillations were observed. Thus, injector with shorter recess lengths had a higher stability than that of longer one due to the different mixing processes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.718-724
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• 2000

A model for depicting the rocket engine combustion process is presented and several experiments near a design point are provided with a FOOF type of unlike impinging injector for a propellant combination of Jet A-1 fuel and liquid-oxygen. The model is based on the assumption that the vaporization is the rate-controlling combustion process. The effects of initial drop size and initial drop velocity are systematically shown and discussed. It is seen that in the midst of considered parameters the change of initial drop size is more sensitive to the performance. The proposed model describes qualitative trends of combustion process well despite of its simplicity.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.3
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• pp.1-8
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• 1999

Mixing efficiency of the unlike Impinging split triplet injector(FOOF type) were measured to investigate the effect of the momentum ratio variation. $H_2$O/kerosene were used as a propellant simulant. The maximum mixing efficiency occured at the momentum ratio 1.5 (total mixture ratio 1.89). Calculated mixing efficiency of real propellant LOX/Kerosene showed similar trend but maximum efficiency of characteristic velocity occurs at the momentum ratio 2.0(total mixture ratio 2.17). Although there exist a little discrepancy between calculated mixing efficiency based on simulant cold test and hot fire test results, this calculated mixing efficiency can be used to predict hot fire mixing efficiency.

• Journal of the Korean Society of Combustion
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• v.5 no.1
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• pp.43-53
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• 2000

Experimental studies on determination of the supply leading time of propellants to combustion chamber have been made to stably and efficiently guarantee the ignition process with liquid rocket engine. The propellant used is a Jet A-1 as fuel and a liquid oxygen as oxidizer. Unlike impinging FOOF type of injectors are arranged radially and the designed O/F ratio is 2.34. The present experiment program also includes the stability on the quadlet type of ignitor using the triethylalumimum as an ignition source and injector life tests. Experimental results clarifies that the propellant supply through LOx leading to combustion chamber is proper for stable ignition and combustion processes based on the fuel and oxidizer manifold pressures, combustion chamber pressure, and the variation of flame length from the nozzle exit with lapse time, and shows that the leading supply time of propellants affects the engine performance little. The effect of positioning cooling holes is remarkable to protect the injector face.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.209-217
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• 1999

A model for depicting the rocket engine combustion process is presented and basic experiments near a design point are provided with a FOOF type of unlike impinging injector for RP-I fuel and liquid-oxygen. The model is based on the assumption that the vaporization is the rate-controlling combustion process. The effects of initial drop size and initial drop velocity are systematically shown and discussed. It is seen that in the midst of considered parameters the change of initial drop size is more sensitive to the performance. The proposed model describes qualitative trends of combustion process well despite of its simplicity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1457-1463
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• 2000

Experimental studies on determination of the supply leading time of propellants to combustion chamber have been made to stably and efficiently guarantee the ignitions process with liquid rocket engine. The propellant used is a Kerosene as fuel and a liquid oxygen as oxidizer. FOOF type of three injectors are set with an angle of 135。 and the combustion chamber pressure is 200psi. The present experiment program also includes the stability on the quadlet type of ignitor using the triehylaluminum (TEAL) as an ignition source. Experimental results clarifies that the propellant supply through LOx leading to combustion chamber is proper for stable ignition and combustion processes based on the fuel and oxidizer manifold pressures, combustion chamber pressure, and the variation of flame length from the nozzle exit with lapse time, and shows that the leading supply time pf propellants effects the engine performance little.