• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.503-506
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• 2009

In this study, we presented the results of static firing tests on the PE/LN2O hybrid rocket motor, which has a thrust of 650 kgf level. Through the early tests, we found that the combustion chamber pressure and the thrust were lower than design values because an actual oxidizer flow rate was less than that expected. In order to complement this result, the methods of decrease of nozzle throat and the increase of oxidizer mass flow rate were conducted in the next experiment, and we studied the combustion phenomena with the experimental results. Also we compared and analyzed a difference of combustion characteristics on scale effect. It show that a sub-scale motor regression rate was a little less than that of a lab-scale motor with the same oxidizer mass flux. Results of this study might be used as a basic data for development of hybrid sounding rocket.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.2
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• pp.8-14
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• 2011

In this paper, the combustion characteristics of hybrid rocket fuel with tapered grain port were investigated experimentally. The charging efficiency of convergent and divergent port shape fuel with $1^{\circ}$ taper angle was 6.8% higher than that of cylindrical port shape fuel. The regression rate was increased about 17.5% by using the convergent port shape fuel. On the other hand, in case of divergent port shape fuel, no notable difference of regression rate was observed when compared to that of the cylindrical port shape fuel. In the case of convergent port shape fuel, characteristic velocity and its efficiency were notably increased with respect to cylindrical port fuel. It was found that convergent port shape of hybrid rocket fuel can lead to a better option compared to the conventional cylindrical port in terms of combustion efficiency and performance improvement.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.247-250
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• 2008

An experimental investigation was conducted to clarify the combustion characteristics and merge characteristics of PMMA-GOX and PE-GOX hybrid motor using multi-port fuel grain configuration. The regression rate of multi-port fuel grain is higher than the regression rate of single-port fuel grain by thermal conduction and chamber pressure. The merge of multi-port has an effect on hybrid rocket performance by change of a combustion area.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.53-56
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• 2005

Hybrid rocket had many advantage with compared to solid and liquid rockets. In this study, swirl flow hybrid motor was designed and manufactured. And the methods of regression rate improvement wire considered. Thrust was calculated with pressure of the combustion chamber and the regression rate was measured in low flow rate of oxidizer. Several problems and solutions of operating hybrid rocket was presented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.311-317
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• 2005

Hybrid rocket had many advantage with compared to solid and liquid rockets. In this study, swirl flow hybrid motor was designed and manufactured. And the methods of regression rate improvement were considered. Thrust was calculated with pressure of the combustion chamber and the regression rate was measured in low flow rate of oxidizer. Several problems and solutions of operating hybrid rocket was presented.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.7
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• pp.567-574
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• 2018

Swirl injection induces not only the increase in fuel regression rate but also the reduction of combustion pressure oscillation. This acts, in turn, to stabilize combustion process. Thus, this study primarily focuses on the change in flow structure in the main chamber by swirl injection. Then examining the change in flow structure was done to understand the physical process for stabilizing combustion. In the results, the application of swirl injection could suppress the generation of p' and q' in 500Hz band and could shift the phase difference and cross correlation. Further investigations with combustion visualization also show that the development of helical motion near surface region affects the small-sized vortex generation and shedding yielding combustion stabilization eventually.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.206-209
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• 2010

The visualization device for hybrid rocket is fabricated to investigate the combustion phenomena. Visualization device were composed with ignition system, oxidizer supply system, control system and data acquisition system, combustion visualization system. GOX as oxidizer and HDPE, Paraffin-LDPE Blending, Paraffin sd were used. As results, combustion phenomena and fuel droplet entrainment were observed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.5
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• pp.456-466
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• 2010

Typical combustion instability such as DC-Shift found in the hybrid rocket motor is characterized by non-linearity. DC-Shift can occur in two different realizations. One is so-called a positive shift of measured DC voltage where the pressure increase suddenly. The other is a negative shift where the pressure drops abruptly. In the present work, specifically the negative DC-Shift was investigated to analyze the effect of oxidizer flow condition and the resonance between fundamental frequency and other ones, such as Helmholtz frequency, and acoustic frequency. Results show a peak frequency of several hundreds HZ shifts as combustion proceeds. A negative DC-shift was found as the result of phase cancellation between two dominant frequency, combustion frequency and flow related frequency. Still is it required to study further to identify the change of dominance of frequency during the combustion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.10
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• pp.720-727
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• 2019

Resonating thermal lags of solid fuel with heat transfer oscillations generated by boundary layer oscillation is the primary mechanism of the occurrence of the LFI (Low Frequency Combustion Instability) in hybrid rocket combustion. This study was experimentally attempted to confirm that how the boundary layer was perturbed and led to the LFI. Special attention was also made on oxidizer swirl injection to investigate the contribution to combustion stabilization. Also the overall behavior of fluctuating boundary layer flow and the occurrence of the LFI was monitored as swirl intensity increased. Fluctuating boundary layer was successfully monitored by the captured image and POD (Proper Orthogonal Decomposition) analysis. In the results, oscillating boundary layer became stabilized as the swirl intensity increases. And the coupling strength between high frequency p', q' diminished and periodical amplification of RI (Rayleigh Index) with similar frequency band of thermal lag was also decreased. Thus, results confirmed that oscillating axial boundary layer triggered by periodic coupling of high frequency p', q' is the primary mechanism to excite thermal resonance with thermal lag characteristics of solid fuel.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.5
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• pp.19-26
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• 2019

Paraffin fuels usually have low combustion efficiency due to discharged unburnt droplets from the nozzle. Therefore, optimization of the post-chamber is becoming an important factor for performance. In this study, combustion experiments were conducted by changing either the length or diameter of the post-chamber to reveal the combustion behavior of paraffin fuel for hybrid rocket. As a result, the combustion efficiency improved due to the increase of the residence time as the post-chamber length increased. On the other hand, it is found that the influence of the diameter change was not significant compared with the case of variable post-chamber length.