In order to investigate the optimum condition of the autofrettage process for the diesel engine fuel injection pipe, different values of autofrettage pressure, pressure rising time, pressure holding time, and repetition of autofrettage process were applied. Autofrettage was performed by applying the hydrostatic internal pressures of 604MPa, 535MPa, 500MPa on the fuel injection pipe, corresponding to theoretical 50%, 30%, and 20% overstrain levels, respectively. The autofrettage residual stresses in the injection pipe were experimentally determined by using X-ray diffractometer. As the overstrain level increased, the magnitude of compressive residual stress at the bore increased. It was found that the rising time to reach the autofrettage pressure, holding time at the autofrettage pressure, and repeated application of the autofrettage pressure on the pipe had no significant influence on the residual stress distributions.

In this study, the effects of fuel injection pressure changed from 45 to 65 MPa on combustion and emission characteristics were investigated in a common rail direct injection (CRDI) diesel engine fueled with diesel and palm oil biodiesel blends. The engine speed and engine load were controlled at constant 1700rpm and 100Nm, respectively. The tested fuel were PBD20 (20 vol.% palm oil biodiesel blended with 80 vol.% diesel fuel). The main and pilot injection timing was fixed at 3.5°CA BTDC and 27°CA BTDC (before top dead center), respectively. The experimental results show that the combustion pressure and heat release rate increased. In addition, the indicated mean effective pressure (IMEP) and maximum combustion pressure increased with an increase of the fuel injection pressure. Hydrocarbon (HC), smoke opacity and carbon monoxide (CO) decreased, but oxides of nitrogen (NOx) emissions increased as fuel injection pressure increased.

In this study, the effect of various pilot injection timings on combustion and emission characteristics were investigated in a common-rail direct injection (CRDI) diesle engine fueled with diesel-ethanol blends. The engine speed and engine load were controlled at constant 1500rpm and 70Nm, respectively. The tested fuels were DE0 (pure diesel fuel), DE5 (5 vol.% ethanol blended with 95 vol.% diesel oil), DE10 (10 vol.% ethanol blended with 90 vol.% diesel oil) and DE15 (15 vol.% ethanol blended with 85 vol.% diesel oil). The main injection timing was fixed at 0°CA TDC (top dead center), while various pilot injection timings including 25°CA BTDC (before top dead center), 20°CA BTDC and 10°CA BTDC were selected as the experimental variable. The experimental results showed that various pilot injection timings had little effect on the peak value of cylinder pressure, but had great influence on the start of combustion. The peak value of heat release rate (HHR) increased with the increase of ethanol content. However, the peak value of HRR reduced as the pilot injection is delayed. The diesel fuel containing 10% ethanol had a highest peak value of combustion pressure compared with the others, while the pilot injection timing occurred at 25°CA BTDC. On the other hand, the exhaust emissions of DE10 was also the lowest compared with the others. In addition, with the increase of ethanol content in diesel the PM and NOx emissions reduced.

The spray characteristics of two working fluids operating with a bi-fuel injector were investigated. A bi-fuel injector simultaneously sprays two working fluids, both of which possess different properties. An effervescent atomizer containing two separated aerator tubes was employed as the bi-fuel injector. Vegetable oil and kerosene were the working fluids. The mixing ratio and ALR were the experimental parameters. The mixing ratio is the mass fraction of vegetable oil in the total amount of working fluids. The ALR represents the ratio of the atomizing gas to the working fluid mass flow ratio. In order to examine spray characteristics, the spray angle, droplet size distribution, cumulative volume fraction, Sauter Mean Diameter and span factor were measured using a high resolution video camera and a Laser Diffraction Particle Analyzer. From the experimental results, spray angle is decreased with as the ratio of kerosene to vegetable oil in working fluid is increased. Regardless of ALR, SMD was the smallest when the only working fluid was kerosene and uniformity was the most stable when the only working fluid was vegetable oil.

The spray characteristics of two working fluids operating with a bi-fuel injector were investigated. A bi-fuel injector simultaneously sprays two working fluids, both of which possess different properties. An effervescent atomizer containing two separated aerator tubes was employed as the bi-fuel injector. Vegetable oil and kerosene were the working fluids. The mixing ratio and ALR were the experimental parameters. The mixing ratio is the mass fraction of vegetable oil in the total amount of working fluids. The ALR represents the ratio of the atomizing gas to the working fluid mass flow ratio. In order to examine spray characteristics, the spray angle, droplet size distribution, cumulative volume fraction, Sauter Mean Diameter and span factor were measured using a high resolution video camera and a Laser Diffraction Particle Analyzer. From the experimental results, spray angle is decreased with as the ratio of kerosene to vegetable oil in working fluid is increased. Regardless of ALR, SMD was the smallest when the only working fluid was kerosene and uniformity was the most stable when the only working fluid was vegetable oil.

In this paper, 'Pico scope' was used to measure and analyze high voltage waveforms of 'Grade injector' and 'IQA injector' due to defective solenoid injector of CRDI diesel engine, and the following conclusions were obtained. In the case of the injector of 'Grade Injector' and 'IQA Injector', there was no change in the injection timing of the injector while the injector was installed. However, by controlling the operation time, It is judged that the injector control is insufficiently controlled when the number of revolutions of the engine is increased to 2000 rpm and 3000 rpm in the idling state in the idling state because the injector failure is precisely controlled in the idling state, When determining the fault injector, the waveform of the 'Grade injector' and 'IQA injector' can be detected by waveform analysis by comparing the injection control time by measuring the high voltage waveform of the injector control in idle idling state. Can be easily diagnosed and maintained. I hope this study will be handed to the mechanics to make diagnosis of CRDI injector convenient.

This paper investigates the relationship between the waveform area and fuel injection quantity. It is on developing on analysis method of waveform the effect of waveform area on fuel injection quantity of CRDI Diesel engine. The experimental methods using Pico oscilloscope and fuel injection tester are employed to measure current and voltage waveform and fuel injection quantity of solenoid injector. The one normal and two abnormal solenoid injectors are used. The experiment is carried out during no-load condition. A summary of the important results are as follows. 1) The area of the voltage and current waveform of the abnormal injector becomes larger than the that of normal injector, and the area of the current and voltage waveform is inversely proportional to the fuel injection quantity. 2) The area of the current waveform can be obtained more accurate results than that of voltage waveform. 3) It is possible to infer the fuel injection quantity by measuring the current waveform and calculating the area.

This research aims to analyze the potential possibility of the butyl ether (BE, oxygenates of di-ether group) as a fuel additives for a naturally aspirated direct injection diesel engine fuel. Compared with the diesel fuel, smoke emission decreased approximately 26% by applying the blended fuel(diesel fuel 80 vol-% + BE 20vol-%) at the engine speed of 2,500 rpm and with full engine load. There was none significant difference between the blended fuel and the diesel fuel on the power, torque, and brake specific energy consumption rate of the diesel engine. But, NOx emission from the blended fuel was higher than that of the commercial diesel fuel. As a counter plan, the EGR method was employed to reduce the NOx. We found the possible area where the simultaneous reduction of the smoke and the NOx emission from the diesel engine was achieved by applying the BE blended fuel and the cooled EGR method.

Biodiesel fuel (BDF) can be effectively used as an alternative fuel in diesel engines. The BDF, however, may affect performance and exhaust emissions of the diesel engine because it's physical and chemical properties are different with from the diesel fuel such as viscosity, compressibility and so on. To investigate an effect of injection timing on characteristics of performance and exhaust emissions with the BDF in an IDI diesel engine, this research applied the BDF derived from soybean oil in this study. The engine was operated with six different injection timings from TDC to BTDC 12 ˚CA and six different loads at the engine speed of 1500 and 2000 rpm. In less then the BDF 20, it showed the similar trend compare to the diesel fuel. But, the best injection timing was 2˚CA retarded compare to the diesel fuel with BDF 50.

디젤엔진에서는 2차 분사 시스템은 다양한 배기 시스템에 적용이 가능하고, 엔진 제어와 관계없이 독립적으로 제어가 가능하기 때문에 환원제 희석 면에서도 후분사 또는 다른 농후한 환원제 분위기 형성 방법 등에 비해 장점이 많다. 2차 분사 시스템에서는 환원제의 공급 방법에 따라서 촉매의 효율은 달라질 수밖에 없다. 환원제는 일정압력 이상으로 유지 및 최적화가 필요하고, 인젝터의 위치 및 각도의 선정은 매우 중요한 인자이다. 본 논문에서는 2차 분사 조건을 변화시켜 환원제의 농도와 양을 변화시켰다. De-NOx 촉매 시스템에서 최대의 NOx 정화 효율에 적합한 환원제 분사 조건들의 선정이 필요하고, 분무 도달거리, 분무 평균 입경, 분무각, 분사량 등의 분무 특성과 환원제의 균일 분포를 잘 파악하여야 한다. 이와 같은 목적을 위하여 2차 분사에서 충돌판 형상에 의한 분무 및 거동 특성은 가시화 방법과 디지털 화상 처리 기법을 사용하여 분석하였으며, 충돌판 형상의 영향성과 각 형상에 대한 최적 각도 범위를 도출하였다.

Injection rate characteristics of biodesel fuels according to the blending ratio was described in this work. The injection rate measuring system based on the Bosch's method was utilized to measure and compare the fuel injection rate characteristics. Three different types of biodiesel which were derived from seed, unpolished-rice, and soybean were blended with the diesel fuel in 20% and 40% of volumetric ratio. The fuel properties, injection mass, and injection rate characteristics were obtained and compared in various injection conditions. It is expected that this observations provide important insights into the effect of fuel properties on the biodiesel fuel injection rate performance in a CI engine