소형 디젤 엔진에서의 250 MPa 고압 분사의 분무 특성 이해

배충식 ( Choongsik Bae ),조원규 ( Wonkyu Cho ),강승우 ( Seungwoo Kang ),김영호 ( Youngho Kim ) 한국액체미립화학회 2016 한국액체미립화학회 학술강연회 논문집 Vol.2016 No.-

An experimental study was conducted to investigate the effects of ultra-high injection pressure on spray characteristics under light duty diesel engine operating conditions. An electronically-controlled ultra-high pressure fuel injection system was used to inject the diesel fuel. Six injection pressures were applied from 40 MPa to 250 MPa. The injection rate was measured by an injection rate meter using the Bosch tube method. Mie scattering and shadowgraph were performed to visualize the liquid and vapor phases of the diesel spray in a constant volume combustion chamber (CVCC) under evaporating conditions. The experimental results showed that the injection rate under high injection pressure of 250 MPa increased greater than 80%, compared to injection pressure of 80 MPa. Therefore, a large amount of fuel was able to be injected in a shorter time with higher injection pressure for high load operations. In the evaporating condition, liquid penetration and liquid spray area slightly decreased with higher injection pressures. It can be estimated that additional piston wetting would not occur at high injection pressure over 200MPa. Moreover, it seemed to increase the margin that can retard the injection timing for NOx reduction at higher injection pressure, because the time required to evaporate the liquid phase of the fuel and form a homogeneous mixture is shortened. At a higher injection pressure, vapor penetration increased sharply. At the same time (after the start of energizing), vapor/liquid area ratio increased with higher injection pressure. Based on these results, it is clear that high injection pressure can produce a more homogeneous air-fuel mixture in a shorter time. Further, this study also revealed correlations between spray development in a CVCC and the combustion process in a single-cylinder diesel engine.

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.

Studies on Injection and Mixture Characteristics of High Pressure H₂ and O₂ under Ar atmosphere

( Deng Jun ),( Gong Xuehai ),( Gong Yinchun ),( Li Liguang ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

Facing with the hydrogen energy era in future, the development of high-efficiency and zero-emissions of power system is a worldwide problem and challenge. As a potential way to achieve high-efficiency and zero-emissions, the main idea of argon cycled engine concept is to use hydrogen as fuel and pure oxygen as oxidant in the combustion cycle of traditional internal combustion engine, and use Ar (with the specific heat ratio of up to 1.67) as intake charge instead of N₂. Argon cycled engine can substantially increase the theoretical thermal efficiency of traditional combustion engine and meanwhile avoid NOx emissions problem. Since N₂ is replaced with Ar, the in-cylinder ambient density increases, which makes the in-cylinder mixture process of the direct injected gas an outstanding problem. In this paper, studies on penetration length, cone angle, entrainment rate, under-expanded region and other characteristics of H₂ and O₂ injection into the Ar environment were conducted based on experimental method. Based on the high background pressure constant volume chamber and the high-speed camera system, the shape of gas jets under different conditions was studied by shadowing method. Maximum injection pressure is 10MPa. Maximum environment pressure is 1.2MPa.The experimental results show that increase of the injection pressure or the decrease of the environmental pressure leads to significant increases of the gas penetration length. Jet penetration length of O₂ is slightly lower than H₂ by 0-6%. The cone angle of the gas jet increases slightly with the increase of the injection pressure and the ambient pressure. Under all the experimental pressure boundary conditions, the H₂ jet cone angles are between 32 ° and 38 ° and the cone angles of the O₂ jet are between 22 ° and 28 °; The entrainment rate of the gas jet increases with increment of the injection pressure, the ambient pressure and the injection duration. Jet entrainment rate of O₂ is 2.43 to 2.98 times higher than H₂ jet.

Effects of Ambient Pressure and Injection Pressure on Diesel and Natural Gas Dual Fuel Spray

( Changsheng Shao ),( Qian Wang ),( Xiaoqiang Tan ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

Dual fuel engines operating with direct injected natural gas (NG) and pilot diesel has been attracted by many engine researchers. With this system, small quantities of diesel auto-ignite, and NG is then ignited by the pilot diesel flame. This stratified combustion technique provides better fuel economy and more efficient combustion, maintaining the power output of an equivalently-sized conventional diesel engine. Comparatively lower emissions of NOx and particulate matter were also recorded. For the further understanding of dual fuel spray, effects of ambient pressure and injection pressure on diesel and NG dual fuel spray are investigated. Both NG and diesel are directly injected into an optical constant volume chamber by a dual fuel injector combiner for different injection pressure and ambient pressure. Schlieren photography is used to visualize the development of dual fuel spray. A Matlab processing script was developed to extract useful qualitative and quantitative information from each video frame. A comparison is made between NG jet characteristics in single fuel model (SFM) and dual fuel model (DFM). Results shows that in both SFM and DFM, the tip penetration decreased with the increase of the ambient pressure and the decrease of NG injection pressure, while the cone angle increased with the increase of the ambient pressure and the decrease of NG injection pressure. At different ambient pressure, the diesel spray has little influence on NG tip penetration, however it has impact on NG cone angle. The cone angle in DFM is higher than that in SFM. With the increase of ambient pressure, the diesel spray has less impact on NG cone angle. At different NG injection pressure, the diesel spray has influence on both NG tip penetration and cone angle. With the increase of NG injection pressure, diesel spray has less impact on NG cone angle.

An analytical FEM-based study of the drawing process of an ultra-high-pressure common-rail fuel tube

안서연,박정권,원종필,김현수,강인산,조용석,신석신 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.7

The strengthening of regulations on diesel-engine exhaust emission has demanded performance improvements, including those on the pressure-enhanced common-rail fuel-injection system. The common-rail fuel-injection tube must meet the extreme fatigue reliability requirements in this system to endure the pulsations caused by the high injection pressure and repeated injections, as well as vibrations from engine operation and vehicle driving. In this work, an analytical study was conducted to investigate the drawing process used to fabricate the common-rail ultra-high-pressure tube for application in the common-rail system with fuel injection pressures over 2200 bar. For the drawing-process analysis, the finite element method was used to compose the die, plug, and tube models critical to the drawing process of the fuel-injection tube. Results were further analyzed to determine the physical changes in the fuel-injection tube drawing process that occurred as a result of varying the die semi-angle and corresponding plug angle. Based on these analyses, a numerical analysis was performed to examine the effect of the die and plug on the fuel-injection tube drawing process. A tube drawing process solution was then obtained to ensure the optimum strength for the 2200 bar ultra-high-pressure common-rail fuel-injection tube.

연료분무 및 연소 3 : 에조 인젝터의 다단분사에 따른 분무특성

박희범 ( Hee Bum Park ),김영진 ( Yung Jin Kim ),이기형 ( Ki Hyung Lee ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-

Recently the trend of researching vehicle`s engine has focused on environmental aspects like an air pollution or high thermal efficiency. To meet strengthening emission regulations, a diesel engine has chosen due to its high efficiency. To reflect this trend a piezo type injector with common-rail was used for fast response and feasibility of multiple stage injection in short time instead of solenoid type injector. In this paper, spray image of multiple injections and injection rates are investigated which are important parameters of piezo type injector. The interval of injection has studied to identify interaction of each injection. With a high pressure visualization chamber, characteristics of multiple injection has researched. Also a method of RMS(Root Mean Square) process was conducted to find out the distribution of each injection easily. As a result various characteristics of piezo injector were identified

GDI 연료분사 시스템에서 분사압력이 분무발달과정과 미립화에미치는 영향 분석

송진근 ( Jin Geun Song ),김대식 ( Dae Sik Kim ),박성욱 ( Sung Wook Park ) 한국액체미립화학회 2014 한국액체미립화학회 학술강연회 논문집 Vol.2014 No.-

This study represents the spray development procedure and atomization regimes for a wide range of injection pressure for the Gasoline Direct Injection (GDI) system. To investigate the effect of injection pressure on the spray characteristics, injection pressure was swiped from 5MPa to 30MPa. Imaging method with a high-speed camera was used to take the spray sequential images, and the atomization regimes were predicted with dimensional analysis. The increase of injection pressure promoted spray atomization, which was supported by sequential spray images and the breakup regimes. However, the spray characteristics did not show significant differences for the injection pressure conditions over 20MPa.

FUEL RAIL PRESSURE CONTROL CHARACTERISTICS OF A GDI HIGH-PRESSURE FUEL PUMP USING A NEWLY DEVELOPED EXPERIMENTAL SYSTEM CONTROLLED WITH A MICROCONTROLLER

이병진,이충훈 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.2

An experimental system was developed to evaluate the fuel injection parts of a gasoline direct injection engine. An AC motor and an inverter were used to rotate the camshaft in the engine cylinder head. A single plunger high-pressure fuel pump (HPFP) driven by a square cam at the end of the camshaft was used in the gasoline direct injection engine. The rotation position of the square cam was measured by a rotary encoder. The developed system allows control of the camshaft rotation speed, the HPFP pressure control valve (PCV) opening and closing timing, and the fuel injection duration, which are three important factors affecting the fuel rail pressure (FRP). It is confirmed that the fuel rail pressure can be made to vary wit different combinations of these three factors. By using the experimental system developed in this study, the fuel rail pressure can be effectively controlled in the range of 3 MPa to 20 MPa. The most influential factor for control of the fuel rail pressure was the HPFP PCV opening and closing timings. With the proposed using the experimental system, the rail pressure, fuel rail pressure wave characteristics, and the injector drive characteristics can all be assessed under various fuel injection conditions.

극초고압영역에서의 디젤연료의 자유분무특성에 관한 연구

정대용 ( D. Y. Jeong ),이종태 ( J. T. Lee ),홍기배 ( G. B. Hong ) 한국분무공학회 2002 한국액체미립화학회지 Vol.7 No.4

N/A The characteristics of free spray with ultra injection pressure was analyzed to clear the limit pressure of diesel engine. To obtain final goal, ultra high pressure injection equipment was developed, spray patterns were visualized under various ultra injection pressures. Spray penetration and spray width, volume and entrained air mass were increased with the increase of injection pressure. Sauter mean diameter and injection durstion were decreased. But over 3,000bar of ultra injection pressure region the rates of increase show almost similar and finally the reversed tendencies at 4,140bar.

SPRAY COLLAPSE IN A SIDE-MOUNT GASOLINE DIRECT INJECTION INJECTOR WITH VARIOUS INJECTION CONDITIONS AND INJECTOR NOZZLE CONFIGURATIONS

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.