EFFECTS OF A SPLIT INJECTION ON SPRAY CHARACTERISTICS FOR A COMMON-RAIL TYPE DIESEL INJECTION SYSTEM

PARK S. W.,SUH H. K.,LEE C. S. The Korean Society of Automotive Engineers 2005 International journal of automotive technology Vol.6 No.4

This work was performed to investigate the effect of a split injection on spray characteristics of fuel sprays injected from a common rail system. In order to analyze the spray behavior and atomization characteristics at various rates of split injections, the injection durations of pilot and main injections were varied in experiments. The injection rate of split injection was measured to study the effect of the pilot injection on the main injection. By using a Nd:YAG laser and an ICCD camera, the development of the injected spray was visualized at various elapsed time from the start of injection. The microscopic characteristics such as SMD and axial velocity were analyzed by using a phase Doppler particle analyzer system. The results indicate that the ambient gas flow generated by the pilot injection affects the behavior of main spray, whereas the effect of pressure variation on the main spray is little. The spray tip penetration of a main spray with pilot injection is longer than that of the single injection by the effect of ambient gas flow. Also the main spray produces larger droplets than the pilot spray due to a small relative velocity between the droplets and ambient gas.

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.

The Incidence of Various Types of Systemic Reactions Related to Epidural Steroid Injections: A Prospective Observational Study

이근영,이준우,Jin S. Yeom,Ki-Jeong Kim,Hyung-Ik Shin,강흥식 대한영상의학회 2018 Korean Journal of Radiology Vol.19 No.2

Objective: To evaluate the incidence, types and association of systemic reactions after an epidural steroid injection (ESI) with patient demographics, ESI factors and repeated occurrence of an ESI. Materials and Methods: This prospective observational study was approved by the Institutional Review Board of our hospital, and written informed consent was obtained from all the participants. From October to December 2011, systemic reactions at 2 weeks after 960 ESIs among 885 patients were measured. Patients were evaluated by phone interviews to obtain the patients’ demographics, history of previous ESI, ESI factors, and ESI reoccurrence. Statistical analyses were performed using the chi-square tests, Fisher’s exact tests and a binary logistic regression analysis. Results: Overall, 557 types of systemic reactions occurred after 292 injections (30.4%) of a total of 960 ESIs in which facial flushing was most common (131/557, 23.5%) and 144 ESIs were followed by a mixed form of systemic reactions (49.3%). Age of 62 years or younger (odds ratio [OR], 2.361), female sex (OR, 1.674), and history of diabetes mellitus (OR, 1.681) were significant risk factors in the occurrence of systemic reactions after an ESI. In 73 patients with repeated ESI, 14 patients re-experienced systemic reactions (19.2%), of which twelve re-experienced the same systemic reaction as the previous one. Conclusion: Systemic reactions followed about 30% of ESIs, and more commonly occurred in patients 62 years of age or younger, women, and diabetic patients. Half of the patients experienced a mixed form of systemic reactions. Patients with recurring systemic reactions tend to re-experience the same systemic reaction as the prior one after an ESI.

Correction strategy of fuel injection quantity during pilot-main injection for common rail system

Yun Bai,Yuanqi Gu,Qi Lan,Liyun Fan,Xiuzhen Ma 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.6

Common rail system is a key technology of energy saving and emission reduction for modern diesel engines. Multiple injection, as one of the most interesting features of common rail system, allows both optimal fuel consumption and exhaust emissions. In order to explore the method for controlling the fluctuation of fuel injection quantity during multiple injection, experiments have been carried out in this paper, focusing on pilot-main injection. The high pressure fuel circuits of the system have been equivalent to a spring-mass vibration system. Comparison with the experiment shows that the proposed fluctuation equation can reasonably predict the fluctuation characteristics of main injection quantity with pilot-main injection interval. The correction control strategy for the main injection quantity fluctuation has been proposed, in which the relative damping coefficient, rail pressure, pilot-main injection interval and main injection pulse width are chosen as the input variables. The experimental results with different rail pressure and main injection quantity show that the fluctuation of injection quantity during pilotmain injection can be controlled effectively by the proposed correction strategy. The maximum average fluctuation of main injection quantity decreases by as much as 44.66 %.

Influence of steam injection through exhaust heat recovery on the design performance of solid oxide fuel cell – gas turbine hybrid systems

박성구,김동섭,손정락 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.2

This study analyzed the influence of steam injection on the performance of hybrid systems combining a solid oxide fuel cell and a gas turbine. Two different configurations (pressurized system and ambient pressure system) were examined and the effects of injecting steam, generated by recovering heat from the exhaust gas, on system performances were compared. Performance variations according to the design of different turbine inlet temperatures were examined. Two representative gas turbine pressure ratios were used. Without steam injection, the pressurized system generally exhibits higher system efficiency than the ambient pressure system. The steam injection augments gas turbine power, thus increasing the power capacity of the hybrid system. The power boost effect due to the steam injection is generally greater in the relatively higher pressure ratio design in both the pressurized and ambient pressure systems. The effect of the steam injection on system efficiency varies depending on system configurations and design conditions. The pressurized system hardly takes advantage of the steam injection in terms of system efficiency. On the other hand, the steam injection contributes to the efficiency improvement of the ambient pressure system in some design conditions. In particular, a higher pressure ratio provides a better chance of efficiency increase due to the steam injection.

다단분사를 사용한 경량 DME 엔진의 연소제어에 관한 연구

정수진(Soo-Jin Jeong),오세두(Se-Doo Oh),박정권(Jeong-Kwon Park) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5

Dimethyl-ether(DME) is one of the most promising alternative fuels for IC engines. In this study, the compression ignition combustion fueled with dimethyl-ether was investigated. Three-point split injection strategy was applied and evaluated its availability and performance in terms of emission(CO, HC, NOx, PM), fuel economy and power. Experiments were carried out in 4-cylinder 2.9 liter direct-injection diesel engine equipped with common-rail injection system, and the engine performance and emission characteristics were tested the various pre and pilot injection timings and quantities. Experiments were performed under the engine condition ranging from 1200rpm, 2bar to 3000rpm,4 bar. From the results of this study, three-point split injection strategy showed the possibility to overcome the disadvantages of DME engine such as high NOx and HC emissions due to long injection duration for attaining diesel equilibrium performance. By optimizing pre and pilot injection timing and quantities NOx emission could be reduced by maximum 68.5% for low speed and load conditions. Additional NOx reduction of could be obtain by retarding main injection timing. Torque could be improved by reducing injection dwell timing between pilot and main injection. In the range of medium and high load and speed conditions, main injection timing was retarded for reducing NOx emission with sacrificing torque. However, this torque reduction could be compensated by reducing pilot injection quantity and increasing the quantity of main injection.

포스터 전시회 : 다단분사를 적용한 2.9리터급 DME 엔진의 배기특성에 관한 연구

박정권 ( Jung Kwon Park ),김현철 ( Hyun Chul Kim ) 한국액체미립화학회 2013 한국액체미립화학회 학술강연회 논문집 Vol.2013 No.-

Dimethyl-ether(DME) is one of the most promising alternative fuels for IC engines. In this study, the compression ignition combustion fueled with dimethyl-ether was investigated. Three-point split injection strategy was applied and evaluated its availability and performance in terms of emission, fuel economy and power. Experiments were carried out in 4-cylinder 2.9 liter direct-injection diesel engine equipped with common-rail injection system, and the engine performance and emission characteristics were tested the various pre and pilot injection timings and quantities. Experiments were performed under the engine condition ranging from 1200rpm, 2bar to 3000rpm,4 bar. From the results of this study, three-point split injection strategy showed the possibility to overcome the disadvantages of DME engine such as high NOx and HC emissions due to long injection duration for attaining diesel equilibrium performance. By optimizing pre and pilot injection timing and quantities NOx emission could be reduced by maximum 74% for low speed and load conditions. Additional NOx reduction of maximum 40% could be obtain by retarding main injection timing. Torque could be improved by reducing injection dwell timing between pilot and main injection. In the range of medium and high load and speed conditions, main injection timing was retarded for reducing NOx emission with sacrificing torque.

피에조 인젝터의 연료 분사 특성 및 분무 거동에 관한 연구

서현규(Hyun Kyu Suh),박성욱(Sung Wook Park),김재욱(Jae Wook Kim),이창식(Chang Sik Lee) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

This study was conducted to figure out the injection characteristic and spray behavior injected by a piezo-driven injector and to compare with a solenoid-driven injector in common-rail injection system. The test conditions and design parameters piezo and solenoid driven injector have the same nozzles in a shape and number. The process of spray injection was visualized by using the spray visualization system composed of a Nd:YAG laser and an ICCD camera. To investigate the injection characteristics such as injection profile and injection delay, the injection rate was measured by using an injection rate meter. Compared with solenoid-driven injector, the piezo-driven injector has short injection delay and reach quickly to the maximum injection value. Spray tip penetration makes little difference, however, spray angle of piezo-driven injector is larger than that of solenoid-driven injector.

콘크리트 구조물의 균열보수를 위한 무기계 균열주입기술

이대경(Lee Dae-Kyung),배기선(Bae Kee-Sun),곽수정(Kwak Su-Jung),백종명(Baek Jong-Myeong) 한국구조물진단유지관리학회 2006 한국구조물진단학회 학술발표회논문집 Vol.10 No.2

본 논문은 터널 콘크리트 구조물의 보수를 위한 무기계 균열주입기술의 표준화에 관한 연구이다. 본 연구를 위하여 균열보수공사가 필요한 터널 라이닝 및 박스 구조물을 선정하여, 균열폭에 따른 주입량, 주입시간 및 주입압력, 주입압력과 주입시간, 구조물 규모에 따른 주입량, 구조물별 균열 위치에 따른 주입량, 균열폭 및 구조물 두께와 주입시간의 관계에 관하여, 현장 조사와 시험평가를 수행하여 구조물의 종류 및 균열의 크기에 따른 균열보수재의 주입압력, 주입량 및 주입시간 등을 명확히 파악하였다. This study is to establish a standardization of injection system by inorganic material for crack repair of tunnel concrete structures. For this various surveys and experiments were carried out as followed. The first we surveyed capability of injection and crack pattern of concrete structures in site, and second we analyzed the relationship between crack width and volume of injection, and decided pressure and volume of injection. Finally we evaluated the relationship between crack width and volume of injection with kind of concrete structures, and between required time for injection and crack width with thickness of structure. From these surveys and experiments, we cleared the relationship between crack patterns and injection technologies such as volume, pressure of injection and required time for injection with kind of structure.

콘크리트 구조물의 균열보수를 위한 무기계 균열주입기술

이대경 ( Lee Dae-kyung ),배기선 ( Bae Kee-sun ),곽수정 ( Kwak Su-jung ),백종명 ( Baek Jong-myeong ) 한국구조물진단유지관리공학회 2006 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.10 No.2

본 논문은 터널 콘크리트 구조물의 보수를 위한 무기계 균열주입기술의 표준화에 관한 연구이다. 본 연구를 위하여 균열보수공사가 필요한 터널 라이닝 및 박스 구조물을 선정하여, 균열폭에 따른 주입량, 주입시간 및 주입압력, 주입압력과 주입시간, 구조물 규모에 따른 주입량, 구조물별 균열 위치에 따른 주입량, 균열폭 및 구조물 두께와 주입시간의 관계에 관하여, 현장 조사와 시험평가를 수행하여 구조물의 종류 및 균열의 크기에 따른 균열보수재의 주입압력, 주입량 및 주입시간 등을 명확히 파악하였다. This study is to establish a standardization of injection system by inorganic material for crack repair of tunnel concrete structures. For this various surveys and experiments were carried out as followed. The first we surveyed capability of injection and crack pattern of concrete structures in site, and second we analyzed the relationship between crack width and volume of injection, and decided pressure and volume of injection. Finally we evaluated the relationship between crack width and volume of injection with kind of concrete structures, and between required time for injection and crack width with thickness of structure. From these surveys and experiments, we cleared the relationship between crack patterns and injection technologies such as volume, pressure of injection and required time for injection with kind of structure. 요 지