• Journal of ILASS-Korea
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• v.25 no.3
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• pp.126-131
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• 2020

Throttleable rocket engines are in high demand due to the diversification of space missions. Pintle injector is known to be suitable for throttleable rocket engines, because of its high efficiency in overall thrust zone. In this study, the relationship between spray angle of a throttleable pintle injector and total momentum ratio based on hot fire test conditions was investigated. As a result, the spray angle in 100% and 60% throttling level is higher than the spray angle obtained by the case which considers only propellant mass flow rate, owing to higher total momentum ratio (TMR). The results of this study may be useful for predicting spray angle in hot fire test.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.5
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• pp.66-71
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• 2011

The spray distribution at high pressure condition was measured by the Tomography method. The constructed spray distribution was compared with the images by Indirect Photography method so that the spray size confirmed and took the boundary of the distribution. It confirmed that the Tomography applies to construct the distribution at high pressure.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.39-44
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• 2011

This study constructed the spray distribution by the Tomography method at high pressure condition. The constructed spray distribution was compared with the images by Indirect Photography method so that the spray size was confirmed and took the boundary of the distribution. It was confirmed that the Tomography applies to construct the distribution at high pressure.

• Fire Science and Engineering
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• v.34 no.4
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• pp.7-12
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• 2020

A numerical study was conducted to investigate the effects of the spray characteristics of water mist on the attenuation of thermal radiation. The attenuation process of the thermal radiation, generated from a hot surface panel, passing through the water mist was calculated via Fire Dynamics Simulator (FDS), and the effects of the flow rate, droplet mean diameter, and spray injecting angle of the water mist were analyzed. The results indicated that the increase in flowrate and decrease in droplet size led to an increase in the attenuation of thermal radiation. As the thermal radiation passed through the spray droplets, the effect of the spatial distribution of spray droplets was verified by calculating the thermal radiation attenuation at different spray injecting angles. The results indicated that the radiation attenuation increases as the spray angle increases. This implies that a wider distribution of spray droplets, irrespective of the droplet size and flowrate, increases the attenuation effect on thermal radiation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.9
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• pp.658-664
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• 2019

In the development of the liquid rocket engine using the pintle injector, spray characteristics such as spray angle, droplet size, and distribution of the droplets are dominant parameters. Three different kind of multi hole type pintle tip and a continuous type pintle tip were designed. In the case of multi hole pintle tip, SMD result did not have a significant difference depending on the number of holes. In analysis with visualization images, however, the droplets were uniformly distributed as the number of holes increased. Liquid droplets from continuous type pintle tip were finely atomized and dispersed uniformly than those from multi-hole type pintle tip. In addition, the thrust control by adjusting the liquid injection area of the pintle is suitable for the continuous type, which is easier to face-shutoff rather than the multi hole type. The spray angle of each pintle tip according to TMR was measured to derive a specific tendency and corresponding empirical formula.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.5
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• pp.37-50
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• 2007

This study investigated the characteristics of spray generated by a liquid coaxial swirl injector used in a combustor of the liquid rocket engine. The linear stability analysis considered long and short wave was introduced in liquid sheet breakup. Through the hydrodynamic analysis the initial liquid sheet thickness spray angle and injection velocity were predicted. To evaluate the effect of turbulence model standard $k-{\varepsilon}$ and RNC $k-{\varepsilon}$ model were applied to numerical calculation and it was known that RNC $k-{\varepsilon}$ model was more applicable to predict spray characteristics. On the basis of this evaluation validation of the developed model was performed with swirl injector installed in LPRE and the predicted results of breakup length, spray angle, and SMD agreed well with experiments qualitatively and quantitatively.

• Journal of Biosystems Engineering
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• v.13 no.3
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• pp.11-19
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• 1988

분무량(噴霧量) 및 유량계수(流量係數)에 관(關)한 많은 연구(硏究)가 실험결과자료(實驗結果資料)에 기초하여 수행(遂行)되어졌다. 그러나 공시체(供試體)의 노즐의 특성(特性)에 따라서 유선(流線)의 특성(特性)이 다르므로 많은 실험결과(實驗結果) 및 해석(解析)이 서로 상치되는 점이 많다. 본(本) 연구(硏究)에서는 이론분석결과(理論分析結果)가 실험결과(實驗結果)와 다소 다르더라도 노즐 설계(設計)의 실제응용면(實際應用面)에서 필요(必要)한 노즐구조(構造)의 기본기능(基本機能)을 이론적(理論的)으로 분석(分析), 이해(理解)시키고저 한다. 이론분석(理論分析)의 결과(結果)는 다음과 같다. 공동면적(空洞面積)은 분구경(噴口徑), 와실경(渦室徑), 중자도구경(中子導溝徑) 및 중자도구각(中子導溝角)에 관계되고 있으며, 특히 중자도구각(中子導溝角)이 공동현상(空洞現象)에 큰 영향을 미친다. $$r_r{^6}-3r_o{^2}r_r{^4}+[3r_o{^4}+\frac{r_c{^4}r_o{^2}}{(r_c-r_g)^2\;tan^2{\theta}}]r_r{^2}-r_o{^6}=0$$ 반경방향(半徑方向) 힘의 요소(要素)로 인(因)한 유량계수(流量係數)($C_t$)는 산출식(算出式)은 아래와 같다. $$C_t=[1-(\frac{r_r}{r_o})^2]^{3/2}$$ 분무각(噴霧角)(${\alpha}$)은 공동반경(空洞半徑) 및 분구반경(噴口半徑)에 의(依)하여 변화(變化)된다. $${\alpha}=2\;tan^{-1}\(\frac{r^r}{\sqrt{r_o{^2}-r_r{^2}}}\)$$분무각(噴霧角)은 특히 와실유선각(渦室流線角)의 영향을 많이 받음을 시사하고 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.186-190
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• 2006

This study was performed to investigate the characteristics of a co-axial swirl injector. Especially to predict the initial liquid sheet thickness and spray cone angle of an outer orifice a concept of effective area was introduced from hydraulic analysis. In addition, the parameters determining the characteristics of a co-axial swirl injector were re-defined around outer orifice. The calculated results-SMD, spray cone angle, and spray thickness agreed well with the test results qualitatively.

• Journal of ILASS-Korea
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• v.4 no.4
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• pp.9-16
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• 1999

Spray angle, a parameter which is most commonly used to evaluate. spray distribution, is important because it affects the axial and radial distribution of the fuel. Spray angles were measured and compared for the pintle-type gasoline fuel injector with n-heptane as a test fuel with the three different measuring techniques, i.e. digital image processing, shadowgraphy and spray patternator, respectively. Fuel was injected with the injection pressures of 0.2-0.35MPa into the room temperature and atmospheric pressure environment. In digital image processing method, the transmittance level greatly influences the spray angle with the axial distance from the injector. From the experimental results by the shadowgraphy technique, it is obvious that the spray angle vary during the injection period. The results of spray angle from the spray patternator show that there exist the different spray angles in the different areas. The spray angles increase with the increase in the injection pressure for the three measurement techniques considered in this study. The spray angle is widely different, especially in the near region from the injector, according to the measurement techniques used in this experimental work.

• Journal of Power System Engineering
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• v.13 no.3
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• pp.20-26
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• 2009

디젤기관에서 배출되는 유해배출성분인 NOx(Nitrogen oxides)와 PM(Particulate matter)은 기관 실린더내의 혼합기 분포에 의해 그 생성이 지배된다. 이 때문에 그 유해배출물들을 저감하기 위해서는 연소의 전단계인 혼합기 분포 및 그 생성과정의 해석은 매우 중요하다. 디젤기관에서 노즐로부터 분사된 연료는 주위기체와 혼합기를 형성하는 과정에서 액체에서 기체로 상변화를 동반한다. 따라서 분무의 혼합기형성과정을 해석하기 위해서는 액상과 기상을 동시에 분리하여 계측하는 것이 필요하다. 그러므로 본 연구에서는 디젤분무를 대상으로 Melton 등이 제안한 엑시플렉스(Exciplex) 형광법을 이용하여, 분무의 액상과 기상을 동시에 2차원분리해서 가시화촬영을 행하였다. 그 엑시플렉스 형광법을 이용하여 획득한 이미지에 화상 응용해석을 실시하여 비정상증발디젤분무의 혼합기형성과정에 대한 정보를 얻고자 하였다. 엑시플렉스 형광법을 이용해서 증발분무의 거동측성을 해석한 결과 프랙틸해석을 이용한 분무 흐트러짐(Disturbance)의 평가에서 플랙틸차원은 분사압력의 변화에 관계없이 하나의 값, 약 1.1로 정리 할 수 있고, 그 결과 각 분사압력에 대한 분무 기상외곽곡선(외주)은 거의 동일한 정도의 요철형상을 갖는다.