• 한국분무공학회지
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• 제26권3호
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• pp.111-119
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• 2021

Deteriorated agricultural diesel engines using mechanical fuel injection systems have low fuel injection pressures. And they are not equipped with an exhaust gas abatement device, so it produces a lot of exhaust gas. Remanufactured used injectors can reduce emissions because spray characteristics are improved. In addition, remanufacturing is environmentally friendly and economical compared to producing new parts. For efficient injector remanufacturing, it is necessary to conduct a comparison experiment on the spray characteristics of an used mechanical injector and a new injector of the same model. In this study, the spray characteristics of the two injectors were compared by performing an injection quantity measurement and a spray visualization experiment. As a result, the used injector had a larger injection quantity, a shorter spray tip penetration, a wider spray angle and a smaller spray area than the new injector.

• 한국분무공학회지
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• 제26권4호
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• pp.197-203
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• 2021

In gasoline direct injection injectors, cavitation can be generated inside the hole because of their high injection pressure. In this paper, the effects of cavitation development in injector were investigated depending on the various hole drilling angles were investigated by a numerical method. In order to verify the internal flow model, injection rate and injection quantity of individual holes were measured. The BOSCH long tube method was used to measure the injection rate. As a result, even if the hole diameters were the same, the discharge coefficient differed by up to 10% depending on the hole angle. Moreover, if the hole drilling angle became greater than 30°, the area coefficient and the discharge coefficient decreased as the nozzle outlet was blocked due to cavitation.

• 한국기계기술학회지
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• 제20권6호
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• pp.783-789
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• 2018

This paper investigates the relationship of voltage and current waveform between normal piezo injector and deterioration abnormal piezo injector. The experimental methods using Pico oscilloscope and GDS scan tool are employed to measure current and voltage waveform and fuel pressure of piezo injector. The experiment is carried out during no-load condition. A summary of the important results are as follows. 1) In case of normal injector, the fluctuation of duration time of piezo injector was linearly and regularly decreased with increasing engine speed, but the that of deterioration piezo injector was irregularly decreased with increasing engine speed. 2) In main injection, the peak value of the current waveform of abnormal injector was larger than that of normal injector, the duration time of deteriorated abnormal injector was less than that of normal injector at 800rpm and 1500rpm, but the duration time of deteriorated abnormal injector was larger than that of normal injector at 2000rpm and 3000rpm. This irregularity appears to be caused by the deterioration of the injector.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1138-1144
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• 2002

Recently GDI(Gasoline Direct Injection) engine is spot-lighted to achieve higher thermal efficiency under partial loads and better performance at full loads. To realize this system, it is essential to make both stratified combustion and homogeneous combustion. Spray pattern must be optimized according to injection timing because ambient pressure in combustion chamber is varied with crank angle. In this experimental study, two types of visualization system such as laser scattering method and schlieren method were developed to clarity the spray behavior during on intake stroke. As the ambient pressure increases, thepenetration length and spray angle show a tendancy to decrease due to rising resistance caused by the drag force of the ambient air. Distribution of injected fuel on intake stroke has a significant effect on homogeneous mixture in the cylinder. These results provide the information on macroscopic wall-wet growth in the cylinder and design factors for developing GDI injector.

• 대한기계학회논문집B
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• 제27권9호
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• pp.1309-1316
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• 2003

A premixed-compression-ignition engine has been studied to improve the efficiency and to decrease exhaust emissions. However those systems have some difficulties for controlling combustion process. Radical is an activated chemical species formed by a chemical chain reaction between reactant and product. When the chain reactions occur, the energy bond of species is broken easily by the released radicals. The combustion chamber of the premixed-compression-ingnition engine is consist of a main chamber with lean premixture and a subchamber with rich premixture. Those are connected by narrow cylinderical connections. With ignition start in the subchamber, many different kinds of radical is jetted into the main chamber. The premixed gas in main chamber is quickly burned up by the radical ignition in multi-pionts. In this paper, the combustion phenomena in a constant volume combustor having a radical injector are numerically analyzed. The some constants in the reaction rate equation are adjusted by the experimental results tested in the same geometrical chamber. The code is applied on the two combustors in a wide range of equivalence ratio. The results show that the burning time is much shorter in the combustor having radical injector.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.353-358
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• 2000

To achieve the requirement for high fuel economy and low emissions, the research for GDI engines is recently very brisk in the whole world. This study was performed to measure distribution of average particle size in non-evaporating spray. The 2-D fluorescence/scattering images of fuel spray were captured simultaneously by visualization system composed of a laser sheet, a doubling prism, optical filters, and an ICCD camera. Using the ratio of the two light intensities, particle size distribution was obtained. The SMD measured by fluorescence/scattering technique was compared with it obtained by PDA. The experimental results show that the spray structure of GDI injector and temporal SMD distribution.

• 한국항공우주학회지
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• 제33권1호
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• pp.54-61
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• 2005

기체와 액체 추진제를 사용하는 동축형 분사기의 분무특성을 조사하기 위하여 shadow graph와 mechanical patternator, PDPA를 이용한 실험을 수행하였다. 차원해석 방법을 도입하여 운동량 플럭스 비(M)와 레이놀즈 수(Re)를 기체/액체 동축형 분무의 주요 변수로 설정하였고, 실험을 통하여 전단 및 스월 동축형 분무의 특성을 거시적 및 미시적 관점에서 비교분석하였는데, 기체 추진제의 영향력이 커지는 분사조건에서 전단 및 스월 동축형 분무의 거시적 특성이 유사해짐을 확인할 수 있었다. 또한, 본 연구에서는 미시적 분무특성에 대한 분석 결과로서 분무액적 크기와 분사조건 사이의 관계식도 제시하였다.

• 대한기계학회논문집B
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• 제28권8호
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• pp.984-988
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• 2004

This study presents the process of the solenoid parameter estimation of an common-rail injector fer HSDI(High Speed Direct Injection) diesel engines. The EMF(Electromotive Force) and solenoid inductance are the major parameters for presenting the injector dynamics, and also these parameters are estimated by using a multi-layer feedforward artificial neural networks(ANN). The performances of parameter estimators are verified by the simulation with injector model. The feasibility of this methodology is closely examined through the simulation in the various operating points of injector. The simulation results have revealed that estimated parameters show favorable agreements with the common-rail injector model.

• 대한기계학회논문집B
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• 제26권7호
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• pp.1047-1054
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• 2002

To improve the fuel consumption and exhaust emission for gasoline engines, GDI(Gasoline Direct Injection) system was spotlighted to solve above requirements. Thus, many researchers have been studied to investigate the spray characteristics and the mixture formation of GDI injector. In this study, we tried to study the spray characteristics of a gasoline direct injector by using entropy analysis and PlV methods. The entropy analysis is based on the concept of statistical entropy, and it identifies the degree of homogeneity in the fuel concentration. The PlV method was adopted to determine the fluid dynamics information at the spray. From the applied results on a direct injection gasoline spray, we could find that the direct diffusion phenomena was a dominant factor in the formation of a homogeneous mixture at downstream of GDI spray especially under vaporizing ambient conditions, and mixing phenomena was also progressed by momentum exchange with induced air. In addition, the correlation between entropy and vorticity strength enabled to find their relation.

• 대한기계학회논문집B
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• 제34권5호
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• pp.491-498
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• 2010

연료전지 자동차는 성능과 수명 측면에서, 전해질막의 가습이 필요하며, 이를 위해 반응기체인 공기, 수소의 높은 가습이 요구된다. 본 연구에서는 내경 75 mm공기공급관 내에 직접 삽입된 인젝터(노즐)과 액적제거를 위한 사이클론을 통한 가습장치를 고안하여 실험을 수행하였다. 충돌형 노즐 3 종류를 이용하여 분사압력, 공기 유량, 분사방향각도를 달리하여 실험을 수행하였다. 가습 성능을 분석하기 위해, 가습효율이라는 개념을 정의하였다. 별도의 외부 열공급원 없이 분사되는 물과 공기의 엔탈피가 자체 기화열 공급원으로, 분사되는 물의 양이 가습에 가장 중요한 변수임을 볼 수 있었다. 사이클론은 높은 공기유량에서 재비산이 발생되는 것을 볼 수 있었다. 노즐타입 PJ24, 분사방향 각도 90도, 분사압력 1200 kPa, 공기 유량 6000 nlpm에서 절대습도 $21.29\;kJ/kg_{da}$, 가습 효율 86.57%를 얻을 수 있었다.