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LIMIT OF FUEL INJECTION RATE IN THE COMMON RAIL SYSTEM UNDER ULTRA-HIGH PRESSURES
Jianhui Zhao,Leonid Grekhov,Pengfei Yue 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.3
The common rail injection system with higher injection pressure can improve injection characteristics. However, relevant researches for injection characteristics under ultra-high pressures are insufficient. In this article, the results of experiments with a maximum injection pressure of 390 MPa for nine different injectors of four types are presented. The experiment showed the existence of supercritical pressure during injection. At pressures below the supercritical pressure, the injection quantity increases with increasing injection pressure, however, when the injection pressure is over supercritical pressure, the injection quantity does not increase. According to the experiment results, the supercritical injection pressure is about 300 ~ 350 MPa. Under ultra-high pressures, fuel is strongly heated and the local sound velocity decreases, and the adiabatic flow velocity reaches the sound velocity. Under supercritical pressure, the injection rate ceases to increase and even begins to fall. The traditional equations for calculating the injection rate cannot correctly describe the injection under ultrahigh pressures. A new mathematic model with considering the fuel heating for describing the injection quantity of compressible fluid was developed, this model is not only suitable for calculating the injection quantity under ultra-high pressures, but under traditional injection pressures.
박성욱,김희준,양승호 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.3
In this study, the spray collapse in a non-flash boiling condition was studied. Spray collapse can occur in a sidemount gasoline direct injection (GDI) injector because of its narrow hole distance. To investigate the spray collapse, a spray visualization system was constructed with a high speed camera and a metal halide lamp. Spray visualization was conducted at various injection pressures, ambient pressure, and fuel temperature conditions. Moreover, two injectors with a narrow or wide hole pattern were used to observe the effects of the nozzle hole pattern. The central spray developed by spray collapse overtook the plume jet. As the injection pressure increased, the central spray overtook the plume jet earlier; however, the distance from the nozzle tip was not related to the injection pressure. Higher ambient pressure significantly reduced to the time to overtaking by increasing the spray cone angle. Additionally, when the ambient pressure was high, the effect of fuel temperature was negligible; however, when the ambient pressure was close to or less than the fuel saturation pressure, the spray collapse was dramatically accelerated because of the high evaporation rate with flash boiling. The nozzle hole pattern also had a significant effect on the overtaking point. The narrower hole pattern promoted spray collapse by more effectively blocking air flow from the outside to inside spray, which led to changes in the spray tip penetration. However, the velocity at the plume development and central spray was nearly the same, regardless of nozzle hole pattern.
원종진,이종선,윤희중,김형철 한국공작기계학회 2002 한국공작기계학회 추계학술대회논문집 Vol.2002 No.-
This study is object to structural analysis of high pressure injection nozzle. The finite element model was developed to compute the stress, strain for high pressure injection nozzle. For structural analysis using result from FEM code. This structural analysis results, many variables such as internal pressure, boundary condition, constraint condition and load condition are considered.
이종선,김형철 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.2
This study makes to flow analysis of computational fluid dynamics(CFD) according to the basic theory of turbulent flow regarding high-pressure injection nozzle. It also makes structural analysis to find out the structural validity of the optimum shape of high-pressure injection nozzle. It divides to two areas such as plunger area and high-pressure injection nozzle area including plunger.
증발 조건에서 초고압 분사와 노즐 홀 직경이 디젤 유량 및 분무 특성에 미치는 영향에 대한 연구
조원규 ( Won Kyu Cho ),박영수 ( Young Soo Park ),배충식 ( Choong Sik Bae ),유준 ( Jun Yu ),김영호 ( Young Ho Kim ) 한국분무공학회 2015 한국액체미립화학회지 Vol.20 No.1
Experimental study was conducted to investigate the effects of ultra-high injection pressure and nozzle hole diameter on diesel flow and spray characteristics. Electronically controlled ultra-high pressure fuel injection system was made to supply the fuel of ultra-high pressure consistently. Three injection pressures, 80, 160, and 250MPa were applied. Four type of injec- tors with identical eight nozzle holes were used. The four injectors have nozzle hole diameters of 115, 105, 95, and 85μm respectively. Injection quantity and rate were measured to investigate flow characteristics according to injection pressures and nozzle hole diameters. Mie-scattering and shadowgraph were performed to visualize liquid and vapor phases of diesel spray in a constant volume combustion chamber (CVCC). Ambient conditions of high pressure and high temperature in a diesel engine were simulated by using CVCC.
박인강(In Gang Park),임영찬(Young Chan Lim),서현규(Hyn Kyu Suh),박수한(Suhan Park) 대한기계학회 2021 大韓機械學會論文集B Vol.45 No.5
본 논문은 연료의 분무 해석에 적용되는 모델의 주요 상수가 바이오디젤 분무 특성에 미치는 영향을 파악하기 위하여 수행되었다. 이를 위하여 실린더 형상인 정적 챔버 내에 다양한 세부 모델을 포함하는 solid-cone 인젝터 모델을 적용하였으며, methyl decanoate의 화학적 특성과 methyl oleate의 물리적 특성을 결합한 바이오디젤 모사 연료의 분무 해석을 수행하였다. 해석 결과 노즐 유동 모델의 주요 상수인 경험적 노즐 유량 계수(Cd) 증가는 sac volume 압력과 blob 분사 속도를 감소시키고, 노즐 출구의 유효 단면적(Aeff)을 증가시켰다. KH-RT 분열 모델의 시간 상수(CKH) 증가는 노즐 팁에서 분사된 blob의 1차 분열 발생 시기를 지연시켜 액적 개수를 감소시키는 대신 액적의 평균 질량, 운동 속도 크기 및 지름을 증가시켰다. This study was conducted to investigate the effect of the critical constants for the fuel spray simulation model of biodiesel spray characteristics. A solid-cone injector model including different detailed models of a cylindrical constant volume chamber was applied. Spray simulations of the biodiesel surrogate fuel were performed by combining the chemical properties of methyl decanoate and the physical properties of methyl oleate. Based on the analysis, an increase in the empirical nozzle discharge coefficient (Cd), a critical constant of the nozzle flow model, decreased the sac volume pressure and blob injection velocity and increased the effective flow exit area (Aeff). An increase in the time constant (CKH) of the Kelvin-Helmholtz breakup model delayed the primary breakup timing of the blobs sprayed from the nozzle tip, decreasing the number of parcels and increasing the average mass, velocity, and droplet diameter.