• 한국자동차공학회논문집
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• 제8권2호
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• pp.64-71
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• 2000

In order to clarify the characteristics of soot formation and oxidation in-cylinder of a diesel engine, it is necessary to diagnose accurately for combustion of in-cylinder. The past techniques for soot measurement have limitations in providing the characteristics of soot in a diesel engine, whereas, laser-based 2D imaging diagnostics have the potential to provide better temporally and spatially resolved measurements of the soot distribution. We rebuilt an optically accessible diesel engine which is similar to the conditions of a conventional engine and tried to measure soot distribution in a cylinder of the diesel engine using laser induced scattering(LIS) and laser induced incandescence(LII). Some results were acquired in this study. LIS and LII signal that show soot distribution of a in-cylinder were taken by ICCD properly. The signal of LIS was intenser than that of LII. Although they have some differences of signal intensity in early combusion period, both of signals show that they are generally similar in late combustion period, after ATDC 50 degree.

• 한국자동차공학회논문집
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• 제8권3호
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• pp.37-45
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• 2000

The technique of laser sheet beam has been applied to optically accessible diesel engine for the quantitative measurement of soot. The results provide the information for us for reduction of soot in diesel engine. We used both LIS nad LII techniques simultaneously in this study. LIS and LII images show the quantitative distribution of the soot concentration in an optically accessible diesel engine. In this study, several results were obtained by the simultaneous measurement of LIS and LII technique. The diameter and number density of soot in combustion chamber of the test engine were obtained from ATDC 20$^{\circ}$ to 110$^{\circ}$ . The increase rate of soot diameter was about 40$^{\circ}$ between ATDC 20$^{\circ}$and 110$^{\circ}$. And the number density of soot decreased significantly between ATDC 20$^{\circ}$and 40$^{\circ}$.

• Journal of Advanced Marine Engineering and Technology
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• 제19권3호
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• pp.9-23
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• 1995

To analyze the spray and flame in D.I. diesel engine, the visualizing methods by schlieren photograph and diffused background illumination photograph with high speed camera are applied to optically accessible D.I.diesel engine. Wcaporating spray, spray droplets and brightness flame are taken with high speed camera by visuallizing method in accordance with various suction air temperature and injection time. The spray and flame image on the film was analyzed by image analyzer. The optically accessible D.I. diesel engine had the similar pressure characteristic to the real D.I. diesel engine. Experimental results showed that shadow areas of the evaporating spray were extended at higher suction air temperature, spray droplets had a max. Penetration length and their penetrating patterns were dependent on the surrounding gas temperature, and flame size after ignition was largely governed by the evaporated fuel quantity at ignition point and by the surrounding gas condition due to piston motion.

• Journal of Advanced Marine Engineering and Technology
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• 제25권1호
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• pp.115-123
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• 2001

This study describes the combustion characteristics under various condition of air excess ratio and ignition timing in a 2-valve gasoline optically accessible engine with swirl control valve(SCV). It adapted three different types of SCA(open ration 72.5%, 78%, 89%) to strengthen a swirl flow. Pressure data were acquired using pressure sensor to investigate the effect of swirl flow on combustion, and from these pressure data, IMEP(indicated mean effective pressure) and MFB(mass fraction burnt)were calculated to explain burn rate and flame speed. From acquired flame images, inspected the flame propagation direction, flame area, and flame centroid, Flame propagation direction was shown different tendency between with/without SCV, and flame area with SCV was faster and larger than that of conventional engine. Finally, the representative flame image at each crank angle were acquired by PDF method to verify flame growth process. It is found that strengthened swirl flow is more beneficial for faster and stable combustion.

• 한국분무공학회지
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• 제5권1호
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• pp.23-29
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• 2000

Recently the laser sheet technique has been developed to improve our limited understanding of the in-cylinder diesel combustion. The technique is capable of high temporal and spatial resolution, so that it is proved to be an adequate combustion diagnostics to find out exhaust emission formation. The optical signals of LIS(Laser Induced Scattering) and LII(Laser Induced Incandescence) images show informations for soot concentration within the optically accessible diesel engine. The LIS and LII signal images of soot concentration provide new insight into where and when soot occurs in a diesel engine.

• 대한기계학회논문집B
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• 제25권12호
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• pp.1692-1701
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• 2001

This study describes the combustion characteristics under various condition of air excess ratio and ignition timing in a 2-valve SI optically accessible engine with swirl control valve(SCV). It adapted three different types of SCV(open ratio 72.5%, 78%, 59%) to strengthen a swirl flow. Pressure data were acquired using pressure sensor to investigate the effect of swirl flow on combustion, and from these pressure data, IMEP(indicated mean effective pressure) and MFB(mass fraction burnt) were calculated to explain burn rate and flame speed. From acquired flame images, we inspected the flame propagation direction, flame area, and flame centroid. Flame propagation direction showed different tendency between with/without SCV, and flame area with SCV was faster and larger than that of conventional engine. Finally, the representative flame images at each crank angle were acquired by PDF method to verify flame growth process. It is found that strengthened swirl flow is more beneficial for faster and stable combustion.

• International Journal of Automotive Technology
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• 제1권2호
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• pp.79-87
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• 2000

Analytical approach was followed in this work under both the steady state and transient operating conditions to find optimum boundary conditions, where the optically accessible quartz engine can run safely without breaking. Temperature and stress distribution was predicted by FEM analysis. In order to validate thermal boundary condition, model reliability and constraint, outside cylinder temperature was measured and previous study was also followed up numerically. To reduce thermal stress level, three types of outside cooling (natural, moderate forced and intensive forced convection) were considered. Effects of clamping force and combustion pressure were conducted to investigate mechanical stress level. Cylinder thickness, was changed to fine the optimum cylinder thickness. The versatile results achieved from this work can be basic indication, which is capable of causing a sudden quartz cylinder breaking during fired operation.

• Journal of Mechanical Science and Technology
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• 제15권9호
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• pp.1311-1318
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• 2001

It is necessary to diagnose accurately the characteristics of soot formation and oxidation in a diesel engine. Whereas past measurement techniques for soot concentration give limited information for soot, laser-based two-dimensional imaging diagnostics have a potential to provide temporally and spatially superior resolved measurements of the soot distribution. The technique using laser sheet beam has been applied to an optically accessible diesel engine for the quantitative measurement of soot. The results provided the information for reduction of soot from the diesel engine. Both LIS (Laser Induced Scattering) and LII (Laser Induced Incandescence) techniques were used simultaneously in this study. The images of LIS and LII showed the quantitative distribution of the soot concentration in the diesel engine. In this study, several results were obtained by the simultaneous measurements of LIS and LII technique. The diameter and number density of soot in combustion chamber of the test engine were obtained from ATDC 20 degree to 110 degree. The soot diameter increased about 37% between ATDC 20 degree and 110 degree. The number density of soot, however, decreased significantly between ATDC 40 degree and 70 degree.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.32-38
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• 2004

This study was performed to investigate the behavior of liquid and vapor phase of fuel mixtures with different piston cavity diameters in a optically accessible engine. The conventional engine was modified as Central Injected DI gasoline engine with swirl motion. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze spray behavior and fuel distribution inside of cylinder using exciplex fluorescence method. Piston cavity geometries were set by Type S, M and L. The results obtained are as follows. In the spray formation after SOI, the cone angle and width of the spray were decreased at late injection timing. With a fuel injection timing of BTDC $180^{\circ}C$, fuel was not greatly affected in a piston cavity but generally distributed as homogeneous mixture in the cylinder. With a fuel injection timings of BTDC $90{\circ}C$ and $60^{\circ}C$, fuel mixture was widely distributed in near the cavity center. As a injection timing was late in the compression stroke, residual width of fuel mixture was narrow in proportion to piston cavity.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.96-104
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• 2001

The present study experimentally investigates the concentration distribution of liquid and vapor phase with different injection timings in the in-cylinder flow field of a optically accessible engine. The conventional MPI, DOHC engine was modified into DI gasoline engine. The images of liquid and vapor phases in the motoring engine were captured by using exciplex fluorescence method. Dopants used in this study were 2% fluorobenzene and 9% DEMA(diethyl-methyl-amino) in 89% solution of hexane by volume respectively. Two dimensional spray fluorescence images of liquid and vapor phases were acquired to analyze spray behaviors and fuel distribution in the in-cylinder flow field. Measurements were carried out fur four different injection timings, namely BTDC 270$^{\circ}$, 180$^{\circ}$, 90$^{\circ}$, and 50$^{\circ}$. Experimental results indicate that behaviors and distribution of vapor phase were largely affected by in-cylinder tumble flow, and mixture formation process was also greatly affected by in-cylinder flow at early injection mode and by ambient pressure at late injection mode.