와류형 고압인젝터의 초기분무의 분열 과도현상

최동석,김덕줄,고장권,Choi, Dong-Seok,Kim, Duck-Jool,Ko, Chang-Kwon 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.8

The disintegration process of initial spray from high-pressure swirl injector was investigated at different injection pressures. The transient breakup phenomena that were difficult to observe at high injection pressure were easily observed at the low injection pressure of 0.4MPa. The effect of fuel remained inside a nozzle hole volume on the penetration of initial spray was also investigated. The disintegration process of initial spray could be classified four regions: the formation of mushroom shape, the first collision, the second collision, and the development of spray, The liquid film of cup shape was particularly found in the second collision region, and the growth ratio of its length and width at low and high injection pressures were compared.

액체의 물성치와 노즐의 형상 변화에 따른 압력스월 노즐의 분무 특성

최윤철,정지원,김덕줄,Choe, Yun-Cheol,Jeong, Ji-Won,Kim, Deok-Jul 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.12

The purpose of this study was to investigate the significant characteristics in atomization process of industrial etching spray fur the design or Precise pressure-swirl nozzles. The experiment was carried out with different viscosities and densities of the liquid. The macro characteristics of liquid spray, such as the spray angle and breakup process were captured by PMAS and the micro characteristics of liquid spray. such as droplet size and velocity measurements were obtained by PDA. The droplet axial and radial velocity and SMD were measured along axial and radial direction. The RMS of two velocities was measured along radial direction. It was found that the fluid with higher kinematic viscosity resulted in the larger SMD and the lower mean droplet velocity. And we could divide breakup processes into three regions that is atomization, non-dilution and dilution one in spray of pressure-swirl nozzle. The radial as well as axial velocity of droplet played an important role in the atomization process of higher kinematic viscosity fluid.

상변화를 동반한 충돌분무의 거동해석

송홍종,차건종,김덕줄,Song, Hong-Jong,Cha, Keun-Jong,Kim, Duck-Jool 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.6

The emission in the exhaust gas from diesel engine is effected by the fuel spray characteristics. The spray of D.I. diesel engine impinges on a piston cavity and a cylinder wall. It is very important to know exactly the distribution and behavior of the spray inside cylinder. The objective of this study is to develop more accurate evaporation model. The EPISO code was used to analyze the flow characteristics in the engine. The Wakil model and the Faeth model are applied to the EPISO code to analyze the behavior of impinging spray. And also experimental and numerical analysis were carried out. The spray behavior characteristics were investigated by changing injection pressure, ambient pressure and temperature. The behavior of impinging spray was strongly effected by the change of ambient pressure and temperature. The effects of evaporation and rebounding droplet should be considered.

충돌 분무의 성장에 미치는 분사압과 배압의 영향에 관한 연구

차건종,서경일,김덕줄,Cha, Geon-Jong,Seo, Gyeong-Il,Kim, Deok-Jul 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.11

This study investigated the effects of pressure on the growth of an impinging spray. We obtained the frozen images which were scattered by Nd ; YAG laser light (pulse width : 7 ns) using synchronization circuit made in the laboratory. For an impinging spray a growth of the penetration length was progressed with increase of the injection pressure but an ambient pressure restrained its growth. The effect of an ambient pressure on penetration was larger than that of an injection pressure. The pressure ratio had an effect on the penetration growth rate. The thickness growth rate depended on both the injection pressure and the ambient pressure compositively. A lower injection pressure or a higher ambient pressure was required for spatial distribution of impinging spray.

직접분사식 가솔린엔진에서 피스톤 캐비티 형상이 연료 분무의 충돌과 거동에 미치는 영향

김동욱(Dongwook Kim),최경민(Gyungmin Choi),김덕줄(Duckjool Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

This study was carried out to investigate the effects of piston cavity geometry on the spatial and temporal development of injected fuel sprays in a DI gasoline engine. The impingement and behavior of impinged spray is affected the stratification of fuel mixture. Thus, it is informative to understand in detail the behavior and distribution of fuel mixture after impingement in the cavity. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze the behavior and distribution of fuel mixtures inside cylinder by exciplex fluorescence method. To clarify the wall effect of the piston cavity, cavity wall angle were set to 30, 60 and 90 degrees, respectively. The results show that In the case of 30 degrees, the rolling-up moved from the impinging location to the round and fuel-rich mixture distributed at periphery of cylinder. In the case of 60 and 90 degrees, the rolling-up recircurated and accumulated in the cavity and fuel mixtures concentrated at center region. High concentrated fuel vapor phase was observed in the cavity with 90 degrees. From present study, it was found that the desirable piston geometry affected the fuel mixture stratification in a DI gasoline engine.

중앙 분사방식의 직분식 가솔린 기관에서 연료 혼합기 형성에 미치는 분사시기와 캐비티 형상의 영향

김태안(Taean Kim),강정중(Jeongjung Kang),김덕줄(Duckjool Kim) 한국자동차공학회 2004 한국 자동차공학회논문집 Vol.12 No.2

This study was performed to investigate the behavior of liquid and vapor phase of fuel mixtures with different piston cavity diameters in a optically accessible engine. The conventional engine was modified as Central Injected DI gasoline engine with swirl motion. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze spray behavior and fuel distribution inside of cylinder using exciplex fluorescence method. Piston cavity geometries were set by Type S, M and L. The results obtained are as follows. In the spray formation after SOI, the cone angle and width of the spray were decreased at late injection timing. With a fuel injection timing of BTDC 180˚ fuel was not greatly affected in a piston cavity but generally distributed as homogeneous mixture in the cylinder. With a fuel injection timings of BTDC 90˚ and 60˚ fuel mixture was widely distributed in near the cavity center. As a injection timing was late in the compression stroke, residual width of fuel mixture was narrow in proportion to piston cavity.

직분식 가솔린엔진에서 피스톤 형상이 연료 혼합기의 형성과 거동에 미치는 영향

김동욱(Dongwook Kim),강정중(Jeongjung Kang),최경민(Gyungmin Choi),김덕줄(Duckjool Kim) 한국자동차공학회 2005 한국 자동차공학회논문집 Vol.13 No.5

This study was performed to investigate the behavior and spatial distribution of fuel mixtures with different wall angle and diameter of piston cavity in a DI gasoline engine. The spatial distribution of fuel mixtures after impingement of the spray against a piston cavity is one of the most important factors for the stratification of fuel mixture. Thus, it is informative to understand in detail the behavior and spatial distribution of fuel mixtures after impingement in the cavity. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze the behavior and distribution of fuel mixtures inside cylinder by exciplex fluorescence method. The exciplex system of fluorobenzene / DEMA in non-fluorescing base fuel of hexane was employed. Cavity wall angle was defined as an exterior angle of piston cavity. Wall angles of the piston cavity were set to 30, 60 and 90 degrees, respectively. The spray impinges on the cavity and diffuses along the cavity wall by its momentum. In the case of 30 degrees, the rolling-up moved from the impinging location to the round and fuel-rich mixture distributed at periphery of cylinder. In the case of 60 and 90 degrees, the rolling-up recircurated in the cavity and fuel mixtures concentrated at center region. High concentrated fuel vapor phase was observed in the cavity with 90 degrees. From present study, it was found that the desirable cavity wall angle with cavity diameter for stratification in a DI gasoline engine was demonstrated.

혼합모델에 의한 GDI 분무예측의 비교

강동완,황순철,김덕줄,Kang, Dong-Wan,Hwang, Chul-Soon,Kim, Duck-Jool 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.12

The purpose of this study is to obtain the information about the development process of GDI spray. To acquire the characteristics of GDI spray, the computational study of hollow cone spray for high-pressure swirl injectors was performed. Several hybrid models using the modified KIVA code have been introduced and compared. WB model and LISA model were used for the primary breakup, and DDB and APTAB models were used for secondary breakup. To compare with the calculated results, the experimental results such as cross-sectional images and SMD distribution were acquired by laser Mie scattering technique and Phase Doppler Analyzer respectively. The results show that LISA+APTAB hybrid model has the best prediction for spray formation process.

직분식 가솔린기관 내에서 피스톤 형상이 연료혼합기 거동에 미치는 영향

황필수,강정중,김덕줄,Hwang, Pil-Su,Gang, Jeong-Jung,Kim, Deok-Jul 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.4

This study was performed to investigate the behavior of vapor phase of fuel mixtures with different piston bowl shapes(F, B and R-type) in a optically accessible engine. The images of liquid and vapor phases were captured in the motoring engine using exciplex fluorescence method. Fuel was injected into atmospheric nitrogen to prevent quenching phenomenon by oxygen. Injection pressure was 5.1MPa. Two dimensional spray fluorescence image of vapor phase was acquired to analyze spray behaviors and fuel distribution inside of cylinder. Four injection timings were set at BTDC 90$^{\circ}$, 80$^{\circ}$, 70$^{\circ}$, and 60$^{\circ}$. With a fuel injection timing of BTDC 90$^{\circ}$, fuel-rich mixture level in the center region was highest in a B-type piston. With a fuel injection timing of BTDC 60$^{\circ}$, R-type piston was best. R-type piston shape was suitable under enhanced swirl ratio and late injection condition and B-type piston shape was right in a weak swirl ratio. It was found that the piston bowl shape affected the mixture stratification inside of cylinder.

디젤연소실에서 새로운 충돌분무 형성에 대한 수치적 고찰

류성목,차건종,김덕줄,박권하,Ryoo, Sung-Mok,Cha, Keun-Jong,Kim, Duck-Jool,Park, Kweonha 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.11

The objective of this study is to establish geometric guidelines for design of impaction parts prepared for removing undesirable effects of fuel deposition on a wall in small direct-injection diesel engines. In order to get the guidelines a new wall geometry is introduced and assessed, which has a flat top and a slant edge. The size of the flat top and the angle of the slant edge are varied and tested in same chamber condition, then their effects on spray dispersions and drop sizes are discussed. The results show that the case of 3.0mm flat top and $60^{\circ}$ edge angle gives the best spray characteristics for a small combustion chamber in the test conditions chosen in this paper.