• 한국분무공학회지
• /
• 제15권2호
• /
• pp.67-73
• /
• 2010

The capability of pilot injection with small fuel quantity at all engine operating conditions is one of the main feature of the common rail direct injection system. The purpose of the pilot injection is to lower the engine noise and to reduce the NOx emissions. This study describes the pilot spray structure characteristics of the common-rail diesel injectors with different electric driving characteristics, including solenoid-driven and piezo-driven type. Namely three common-rail injectors with different electric current wave were investigated in this study. The pilot spray characteristics such as spray speed, spray tip penetration, and spray angle were obtained by spray images, which is measured by the back diffusion light illumination method with optical system for high-speed temporal photography. As this research results, it was found that pilot injection of common-rail system was effected by rate of injection with different electrical characteristic for injector driving.

• 한국자동차공학회논문집
• /
• 제15권5호
• /
• pp.78-85
• /
• 2007

Recently, diesel vehicles have been increased and their emission standards have been getting strict. The emission of diesel vehicles contains numerous dangerous compounds, especially particulate matters cause a serious environmental pollutant and affect to human health seriously. Thousands of studies have already reported that particulate matters are associated with respiratory and cardiovascular diseases, and death. Due to these, it is necessary to measure the soot concentration and soot particle size in laboratory flames or practical engines to recognize the soot formation, and develop the control strategies for soot emission. In this study, the characteristics of exhausted soot particle size and volume fraction from 2.0L CRDI diesel engine have been investigated as varying engine speed and load. Laser induced incandescence has been used to measure soot concentration. Time-resolved laser induced incandescence has been used to determine soot particle size in the engine. The soot volume fraction is increased as increasing engine load but soot volume fraction is decreased as increasing engine speed. The primary particle size is distributed about $35nm{\sim}60nm$ at each experimental conditions.

• 한국정밀공학회지
• /
• 제26권2호
• /
• pp.54-62
• /
• 2009

The purpose of this study is to develop a piezo injector driver for common-rail direct injection diesel engines. In this research, we analyzed the electrical and mechanical characteristics of the piezo actuator through experiments. Current flow and charging voltage of the piezo injector are controlled by the PWM signal of variable duty ratio in order to realize both fast response and low peak current. The optimal switching duty ratio was designed by modeling and analyzing of the piezo driver circuit. In order to avoid resonance and unacceptably long settling time, appropriate frequency range of the PWM signal was derived based on the driver circuit model. The developed injector driver was validated by experiments under various fuel rail pressure, injection duration, and charging voltage.

• 한국분무공학회지
• /
• 제20권2호
• /
• pp.88-94
• /
• 2015

Recently, exhaust gas regulation has been gradually strengthened due to depletion of fossil fuels and environmental problem like a global warming. Due to this global problem, the demand for eco-friendly vehicle development is rapidly increasing. A clean diesel vehicle is considered as a realistic alternative. The common-rail fuel injection system, which is the key technology of the clean diesel vehicle, has adopted injection strategies such as high pressure injection, multiple injection for better atomization of the fuel. In addition, the emission regulations in the future is expected to be more stringent, which a conventional engine is difficult to deal with. One of the way for actively proceeding is the study of alternative fuels. Among them, the bio-diesel has been attracted as an alternative of diesel. So, in this study, spray characteristics of bio-diesel was analyzed in the common-rail fuel injection system with three injectors driven by different operating mechanism.

• 한국자동차공학회논문집
• /
• 제21권4호
• /
• pp.89-95
• /
• 2013

In this work, the evaluation of swirl nozzle injector performance was conducted by investigating effective area ($A_{eff}$), injection mass ($m_{inj}$), injection rate ($Q_{inj}$), and injection delay ($t_{delay}$) under various test conditions. To achieve these, fuel injection analysis system which was composed of fuel supply system, injection system, and control system was installed. At the same time, the swirl nozzle that had 12 orifice hole with $120^{\circ}$ injection angle was used in this work. It was revealed that the difference of injection mass ($m_{inj}$) between base and swirl nozzle injector increased as the injection pressure ($P_{inj}$) and energizing duration ($t_{eng}$) decreased under the same test conditions. The maximum injection rate ($Q_{inj}$) of swirl nozzle injector was higher than base nozzle injector about 2~5%. The injection performance of swirl nozzle was better than base nozzle at low injection pressure ($P_{inj}$) and short energizing duration ($t_{eng}$) conditions.

• 한국자동차공학회논문집
• /
• 제22권5호
• /
• pp.108-115
• /
• 2014

In this study, experimental approaching method was applied under and single-cylinder engine to research the performance of direct needle-driven piezo injector (DPI) for CR direct-injection. As key-point factor of this DPI that relies on direct-acting operating of injector needle, unlike conventional hydraulic-servo, its nozzle needle can be directly driven by piezo actuator. Thus, effect of direct-acting injection of DPI on diesel combustion and emission characteristics was investigated under common-rail single-cylinder direct-injection engine, equipped with three different driving mechanism, including indirect-acting solenoid, piezo and DPI system. As main results, it found that a direct-acting piezo injector has higher of IMEP. And it has higher heat release rate during premixed combustion and mixing controlled combustion phase due to its higher heat release, even though nitrogen oxide (NOx) formations were increased slightly.

• 한국분무공학회지
• /
• 제18권2호
• /
• pp.87-93
• /
• 2013

In this paper, high-pressure injection characteristic of servo hydraulic injector as the key component of diesel CRDi system, which is driven by solenoid and piezo-actuator were examined by experimental analysis. High-pressure injection characteristic of standard diesel fuel injected at high pressure up to 160 MPa was investigated at high-pressure chamber by using a high-speed camera for spray visualization and quantitative analysis. By this study, we found that the piezo-driven injector has better performances in controlling the fuel injection with the high pressure, including fuel quantity, spray penetration length and spray velocity, than that of a solenoid-driven injector. In particular, the needle response time for start of injection in piezo-driven injector was faster of about $125{\mu}s$ than that of solenoid-driven injector. Consequently, it is known that the piezo-driven injector has more degrees of freedom in controlling the fuel injection with the high pressure than solenoid-driven injector.

• 한국분무공학회지
• /
• 제20권1호
• /
• pp.14-19
• /
• 2015

Recently, R&D demand for environmental friendly vehicle has rapidly increased due to its global environmental issues such as global warming, energy and economic crisis. Under this situation, the most realistic alternative way for environmental friendly vehicle is a clean diesel vehicle. The common-rail fuel injection system, as key technology of clean diesel vehicle, consists of a high pressure pump, common-rail, high pressure fuel line and electronic control injector. In common-rail high-pressure fuel injection system, high pressure wave of injection system and geometry of injector elements have a major effects on high-pressure fuel spray. Therefore, in this study, the numerical model was developed for analysis about the common-rail fuel pressure pulsation by using AMESim code. We could secure stability of common-rail high-pressure fuel injection system through optimal design of fuel line.

• 한국자동차공학회논문집
• /
• 제21권4호
• /
• pp.181-187
• /
• 2013

Performance of DI diesel engine with high fuel injection method is directly related to its emission characteristics and fuel consumption. In this study, numerical model of 3rd generation piezo-driven injector was designed to analyze the hydraulic performance. Also the injection response characteristics was investigated by using the AMESim simulation code. From this study, it was shown that 3rd generation piezo-driven injector had a faster response and had better control capability due to its hydraulic bypass-circuit that has potential to higher hydraulic characteristics and improved accuracy of injected fuel quantity.

• 대한기계학회논문집B
• /
• 제36권7호
• /
• pp.759-765
• /
• 2012

1.7L 커먼레일 직접분사 디젤 엔진을 이용하여 1500rpm 3.9bar BMEP 조건에서 세가지 연소 전략에 따른 배기가스 배출 특성 및 탄화수소 종 분석을 수행하였다. 첫째 전략은 EGR 을 사용하지 않고 연료 분할 분사를 이용하는 방법(split injection), 둘째는 적절한 EGR 적용 및 단일 연료분사 방법(single-1)이며 셋째는 다량의 EGR 및 레일 압력 증대 등을 통한 저온디젤연소(single-2)이다. 본 실험 조건으로부터 split injection 방법과 single-1 방법은 PM-NOx 상반 관계를 보였고, single-2 방법은 PM-NOx 상관관계에서 벗어나 PM 및 NOx 동시 저감이 가능하였다. 탄화수소 종 분석 결과, THC 배출 경향과 동일하게 탄소번호에 관계없이 split injection 이 가장 적은 배출을 보였고, single-1 그리고 single-2 의 순서로 많이 배출하였다. 메탄, 아세틸렌 및 CO 의 THC 에 대한 비율은 공연비가 농후해 짐에 따라서 증가하였고 이는 공연비가 농후에 따른 연소 영역에서 산소 농도 감소로 열해리가 증가하였기 때문이다.