• Journal of Aerospace System Engineering
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• 제2권4호
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• pp.1-6
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• 2008

In generally, the regression rate was expressed with average value and oxidizer mass flux in hybrid propulsion system. This can not represent the local value of regression rate along with oxidizer flow direction. In this study, experimental studies were performed with Separation method and Cutting method for measure local regression rate. In axial injection, the local regression rate decreases rapidly with axial location near entrance and increases with axial direction from the leading edge and the empirical formula for local regression rate with function of oxidizer mass flux and location was derived. Swirl injection regression rate has higher value at the leading edge of the fuel and comparatively uniform regression rate at the downstream. Overall regression rate of swirl injection is higher increased about 54 % than regression rate of axial injection.

• Journal of Mechanical Science and Technology
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• 제19권10호
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• pp.1939-1949
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• 2005

Many studies have been conducted to increase regression rate of solid fuel in hybrid rocket. One of them resorts to swirl flow since it can extend the residence time of oxidizer in the fuel grain. Also, metal wires may lead to increase the regression rate of solid fuel as shown in solid propellants. In this study, a series of experiments was designed to investigate the enhancement of regression rate of solid fuel by embedded metal wires and by fuel port grain. And fuel port was designed with a helical configuration to attempt to induce swirl flow. PMMA with gaseous oxygen is the solid fuel used for investigation. Test results showed that embedded metal wires turned out to be ineffective method because only $3-4\%$ increases in regression rate were observed. However, fuel port grain configuration yields higher burning performance of up to $50\%$ increase in regression rate. Also pitch number as well as total impulse was found to be a design variable.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.77-81
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• 2008

The local regression rate behavior of solid fuel in swirl injection hybrid rocket were studied. In generally, axial injection regression rate was tending to be decrease with axial distance, beyond which increased with increasing axial distance from the leading edge. On the other hand, swirl injection regression rate was high at the leading edge of the fuel and comparatively uniform regression rate at the downstream. Overall regression rate of swirl injection was increased about 54% for the overall regression rate of axial injection. Through this study, it was found that using swirl injector was useful in applying to the small sounding rocket.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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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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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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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 Preventive Medicine and Public Health
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• 제54권2호
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• pp.145-152
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• 2021

Objectives: This study aimed to identify regional differences in the high-risk drinking rate among yearly alcohol users in Korea and to identify relevant regional factors for each quintile using quantile regression. Methods: Data from 227 counties surveyed by the 2017 Korean Community Health Survey (KCHS) were analyzed. The analysis dataset included secondary data extracted from the Korean Statistical Information Service and data from the KCHS. To identify regional factors related to the high-risk drinking rate among yearly alcohol users, quantile regression was conducted by dividing the data into 10%, 30%, 50%, 70%, and 90% quantiles, and multiple linear regression was also performed. Results: The current smoking rate, perceived stress rate, crude divorce rate, and financial independence rate, as well as one's social network, were related to the high-risk drinking rate among yearly alcohol users. The quantile regression revealed that the perceived stress rate was related to all quantiles except for the 90% quantile, and the financial independence rate was related to the 50% to 90% quantiles. The crude divorce rate was related to the high-risk drinking rate among yearly alcohol users in all quantiles. Conclusions: The findings of this study suggest that local health programs for high-risk drinking are needed in areas with high local stress and high crude divorce rates.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.524-527
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• 2004

Hybrid rocket had many advantage with compared to solid and liquid rockets. However, the engines have not yet been used in practical rocket systems, due mainly to the disadvantage of hybrid combustion, such as low fuel regression rate. In this study, lab-scale hybrid motor was designed and manufactured. And the methods of regression rate improvement were considered. Test firings with thrusts up to 300 N were conducted with GOX and transparent PMMA. Thrust was calculated with the pressure of the combustion chamber and the regression rate was measured in with variation of oxidizer flow rate. The regression rates showed a strong dependency on GOX mass flux. The frequency analysis technique of the bulk-mode oscillation of motor was applied to a hybrid rocket motor and was based on the principle that this frequency was inversely proportional to the square root of the chamber volume. Several problems and solutions of operating hybrid rocket were presented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.126-130
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• 2003

Hybrid rocket had many advantage with compared to solid and liquid rockets. In this study, lab-scale 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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• 제34권4호
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• pp.63-69
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• 2006

Experimental tests have been done with swirl injector and helical grain configuration to increase the regression rate of hybrid rocket solid fuel. Two types of injector were designed to evaluate the swirl effect of oxidizer stream on the increase in the regression rate. Results showed Type II injector with swirl number of 3.61 induced the better regression rate than Type I injector. Meanwhile, fuels with two different pitch number of 6 and 100 were used to analyzes the flow characteristics on the enhancement of regression rate. Test with fuels of pitch 6 showed better increase in the regression rate than in the pitch 100 when no swirler was imposed. This is due to the generation of strong turbulences in the oxidizer stream along the pitch 6 configuration. However, the regression rate could be increased further in the fuel with pitch 100 than with pitch 6 when swirl flow was imposed by Type II injector. This result implied that the fuel with pitch 100 could take a role of sustainer of the imposed swirl by swirler II instead of turbulence generator.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.66-71
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• 2005

In this study the regression rate of hybrid rocket fuel has been investigated by two methods. First method is to use swirl injectors for enhancement of regression rate. And second method is the modification of the helical grain deriving improvement of combustion area and generating swirl flow. Tests have been done with PMMA and gaseous oxygen. In this paper the incline angle of the helical grain was varied to find the optimal condition to obtain the max regression rate for a given operational condition.