• 한국분무공학회지
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• 제6권1호
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• pp.18-24
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• 2001

Liquid fossil fuel contaminated by water can cause trouble in the combustion processes and affect the endurance of a combustion system. Using an optical sensor to monitor the water content instantaneously in a fuel pipeline is an effective means of controlling the fuel quality in a combustion system. In two component liquid flows of oil and water, the flow pattern and characteristics of water droplets are changed with various flow conditions. Additionally, the light scattering of the optical sensor measuring the water content is also dependent on the flow patterns and droplet characteristics. Therefore, it is important to investigate the detailed behavior of water droplets in the pipeline of the fuel transportation system. In this study, the flow patterns and characteristics of water droplets in the turbulent pipe flow of two component liquids of gasoline and water were investigated using optical measurements. The dispersion of water droplets in the gasoline flow was visualized, and the size and velocity distributions of water droplets were simultaneously measured by the phase Doppler technique. The Reynolds number of the gasoline pipe flow varied in the range of $4{\times}10^{4}\;to\;1{\times}10^{3}$, and the water content varied in the range of 50 ppm to 300 ppm. The water droplets were spherical and dispersed homogeneously in all variables of this experiment. The velocity of water droplets was not dependent on the droplet size and the mean velocity of droplets was equal to that of the gasoline flow. The mean diameter of water droplets decreased and the number density increased with the Reynolds number of the gasoline flow.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.451-454
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• 2006

This paper describes the results of cold flow test and hot firing tests of an uni-element coaxial swirl injector and hot firing tests of a subscale combustor, as to the development effort of coaxial swirl injector for high performance liquid rocket engine combustor. A major design parameter for coaxial swirl injector is the recess number of a bi-swirl injector. The results of hot firing tests of the uni-element injector combustor and the sub-scale combustor are analyzed to investigate the effect of the recess number influencing on the combustion performance and pressure fluctuation. The test results of a cold flow test of the unielement combustor shows that it was shown that the change in recess number has significant effect on mixing characteristics and efficiency, while the effect of recess number on atomization characteristic is not The results of a series of firing tests using unielement and subscale combustor show that the recess length significantly affects the hydraulic characteristics, the combustion efficiency, and the dynamics of the liquid oxygen/kerosene bi-swirl injector. As a point of combustion performance, combustion efficiencies are 90% for unielement combustor and 95% for subscale combustor. The difference in the characteristic velocities between the unielement combustor and the subscale combustor may be caused by the difference in thermal loss to the combustor wall and the relative lengths of the combustion chamber. For a mixed type coaxial swirl combustor, the pressure drop across the injector increases as recess number becomes larger. The low frequency pressure fluctuation observed in unielement combustor can be related to the propellant mixing characteristics of the coaxial bi-swirl injector. The effect of the recess number on the pressure fluctuation inside the combustion chamber is more significant in un i-element combustor than the subscale combustor, of which the phenomena are also observed in time domain and frequency domain.

• 한국분무공학회지
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• 제28권1호
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• pp.1-9
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• 2023

In the cylinder of gasoline direct injection engines, the spray targeting from injectors is of great significance for fuel consumption and pollutant emissions. The automotive industry is putting a lot of effort into improving injector targeting accuracy. To improve the targeting accuracy of injectors, it is necessary to develop models that can predict the spray targeting positions. When developing spray targeting models, the most used technique is computational fluid dynamics (CFD). Recently, due to the superiority of machine learning in prediction accuracy, the application of machine learning in this field is also receiving constant attention. The purpose of this study is to build a machine learning model that can accurately predict spray targeting based on the design parameters of injectors. To achieve this goal, this study firstly used laser sheet beam visualization equipment to obtain many spray cross-sectional images of injectors with different parameters at different injection pressures and measurement planes. The spray images were processed by MATLAB code to get the targeting coordinates of sprays. A total of four models were used for the prediction of spray targeting coordinates, namely ANN, LSTM, Conv1D and Conv1D & LSTM. Features fed into the machine learning model include injector design parameters, injection conditions, and measurement planes. Labels to be output from the model are spray targeting coordinates. In addition, the spray data of 7 injectors were used for model training, and the spray data of the remaining one injector were used for model performance verification. Finally, the prediction performance of the model was evaluated by R² and RMSE. It is found that the Conv1D&LSTM model has the highest accuracy in predicting the spray targeting coordinates, which can reach 98%. In addition, the prediction bias of the model becomes larger as the distance from the injector tip increases.

• 한국식품과학회지
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• 제15권4호
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• pp.342-347
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• 1983

보리차 추출액(抽出被)의 분무(噴霧) 건조(乾燥) 장치(裝置)의 atomizer 로 페인트용(用) spray gun을 사용(使用)할 경우 보리차 추출액(抽出液)의 농도(濃度)와 송입(送入)되는 공기(空氣) 압력(壓力)이 미세액적(微細液滴)의 크기, 균일도(均一度) 및 그 분포(分布)에 미치는 영향(影響)을 조사(調査)하였다. 1. 분무(噴霧)된 미세액적(微細液滴)의 평균(平均)지름 (${\overline{D}}\;{\mu}m$) 은 보리차 추출액(抽出液)의 농도(濃度)(C, %) 증가(增加)에 따라서 직선적(直線的)으로 증가(增加)하였고 보리차 추출액(抽出液)의 농도(濃度)와 미세액적(微細液滴)의 평균(平均)지름 사이에는 다음과 같은 관계(關係)가 성립(成立)하였다. ${\overline{D}}={_{a}}C+{\beta}$ 이때 ${\alpha},\;{\beta}$는 각 농도(濃度)에 따라 결정(決定)되는 계수이다. 2. 공기(空氣) 송입(送入) 압력(壓力)의 증가(增加)에 따라 미세액적(微細液滴)의 평균(平均)지름은 감소(減少)하였으며 특정(特定) 압력(壓力) 이상(以上)에서는 더 이상 감소(減少)하지않는 한계평균(限界平均)지름을 보였는데 농도(濃度) 15.7%에서는 $35{\mu}m$ 의 한계평균(限界平均)지름을 나타내었다. 3. 공기(空氣) 송입(送入) 압력(壓力)이 증가(增加)할수록 미세액적(微細液滴)의 균일도(均一度)는 증가(增加)하였으나 보리차 추출액(抽出液)의 농도(濃度) 증가(曾加)에 따른 균일도(均一度)의 변화(變化)는 20%까지는 각 압력(壓力)에서 근사하였으나 20% 이상에서는 균일도(均一度)의 급격한 감소를 보였다. 4. 공기(空氣) 송입(送入) 압력(壓力)의 변화(變化)에 따른 미세액적(微細液滴)의 크기 (D) 와 누계(累計) 백분율(百分率) 분포(分布)($P_D$) 사이에는 다음과 같은 관계(關係)가 성립(成立)하였다. $P_D$= e1nD + f 식(式)에서 e, f 는 압력(壓力)과 농도(濃度)에 따라 결정(決定)되는 계수이다.