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엄인용,박찬준,이정만 서울産業大學校 2005 논문집 Vol.54 No.1
A system to measure the fuel concentration distribution in a steady flow rig on the basis of Rayleigh scattering is presented. The system can be employed to measure both the temporal and the spatial distribution. It is possible to calibrate the system for the measurement of accurate absolute concentration. The system was tested at a calibration chamber for the determination of scattering cross section from propane, butane, acetylene, Freon-12 and Genetron 143a. It was adapted to a steady flow rig to measure the temporal and spatial fuel concentration induced from a cylinder head, intake manifold and injector. To cope with the problem of Mie scattering interference, a software filter was developed with is based on the rise time and the time constant of the photomultiplier-amplifier system. With this developed system measurement were made which showed that LRS can provide useful informations about concentration related parameter. At the same time it was found that ensemble averaging can lead to large error if the flow is unstable.
연료 조성에 따른 공연비 산정 (II) -Eltinge 차트에서 미연 성분의 보상-
엄인용,박찬준,Ohm, In-Yong,Park, Chan-Jun 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.11
This paper is the second part of several companion papers which compare the method of Air-fuel ratio(AFR) determination. In the previous paper, Eltinge chart was applied to the arbitrary fuel composition and the charts for gasoline, diesel, methanol, M85, liquefied petroleum gas(LPG), natural gas(NG), propane and butane were illustrated. In Eltinge chart, however, unburned hydrocarbon (UHC) is not used for determination of AFR. For improving accuracy, Eltinge suggested UHC compensation after the AFR reading in the chart. This compensation reduced the difference between real and reading value. In the compensation, however, the correction of oxygen and carbon dioxide is uncertain and there might be a mistake in conversion of UHC reading value. Therefore, the error is overestimated comparing with Spindt one which is most widely used. In addition, there is no comparison of the value with other useful methods. In this paper, the compensation of unburned HC was performed in Eltinge chart and the compensated value was compared with Spindts formula over wide range of AFR. The objects of investigating fuel are gasoline, methanol, NG and LPG. The result shows that Eltinge and Spindt method is flawlessly compatible and the difference between the two methods is under 0.3% in a λrange from 0.9 to 1.7. The method fur debugging instrumentation error is also presented.
EFFECT OF FUEL STRATIFICATION ON INITIAL FLAME DEVELOPMENT: PART 3−HIGH SWIRL CONDITION
엄인용,C. J. PARK 한국자동차공학회 2011 International journal of automotive technology Vol.12 No.5
This paper discusses the final investigation into the effect of fuel stratification on flame propagation. In previous works, the characteristics under the no port-generated swirl condition and the low-swirl condition were considered. For this purpose, the initial flame development and propagation were visualized under different axially stratified states in a modified optical single-cylinder SI engine. The images were captured by an intensified CCD camera through the quartz window mounted in the piston. Stratification was controlled by the combination of the port swirl ratio and injection timing. These were averaged and processed to characterize the flame propagation. The flame stability was estimated by the weighted average of flame area and luminosity. The stability was also evaluated through the standard deviation of flame area and propagation distance and through the mean absolute deviation of the propagation direction. The results show that the LML is expanded remarkably under the high-swirl cases up to the highest relative AFRs of 1.71 and 1.75 between 140 and 160CA. In addition, similar to the low-swirl condition, the flame-flow interaction determines the direction of flame propagation, and the governing roles of the two factors vary according to the swirl level; the flow is more important at the higher swirl conditions, and the flame is more important at the lower swirl condition. Finally, fast and stable flame propagation can be achieved under the preferably stratified condition, which is induced by the suitable combination of the high swirl and injection timing.
EFFECT OF FUEL STRATIFICATION ON INITIAL FLAME DEVELOPMENT: PART 2-LOW SWIRL CONDITION
엄인용,박찬준 한국자동차공학회 2008 International journal of automotive technology Vol.9 No.6
This paper is the second invstigation on the effect of fuel stratification on flame propagation. In the previous work, the characteristics under the no port-generated swirl condition, i.e., the conventional case was studied. In this work, the flame development under the low swirl condition was considered. For this purpose, the initial flame development and propagation were visualized under different axially stratified states in a modified optical single cylinder SI engine. The images were captured by an intensified CCD camera through the quartz window mounted in the piston. Stratification was controlled by the combination of the port swirl ratio and injection timing. These were averaged and processed to characterize the flame propagation. The flame stability was estimated by the weighted average of flame area and luminosity. The stability was also evaluated through the standard deviation of flame area and propagation distance and through the mean absolute deviation of the propagating direction. The results show that the flame-flow interaction determines the direction of flame propagation and that the governing roles of the two factors vary according to the stratified state and the location in the cylinder. In addition, the flame development and the initial flame stability are strongly dependent on the stratified conditions, and the initial flame stability is closely related to the engine stability and lean misfire limit. Lastly, there is no essential difference in gasoline and CNG flame propagation characteristics.
EFFECTS OF INTAKE VALVE ANGLE ON COMBUSTION CHARACTERISTIC IN AN SI ENGINE
엄인용 한국자동차공학회 2013 International journal of automotive technology Vol.14 No.4
In this study, 2 different valve-angle engines, one is wide and the other is narrow, were prepared for investigating the effects of the angle on the combustion. For this purpose, the part load performances were evaluated and the pressures were measured for combustion analysis at an engine bench under 5 different operating conditions, varying the compression ratio. The results show that the combustion proceeds so faster in the small IVA engine that its MBT timings are retarded considerably compared with that of large one and result in lower NOx emission level; however, unburned HC is higher because of its geometrical feature. In addition, there is no substantial difference between 2 IVA engines in the timings of combustion initiation and completion as a crank-angle-position-base in spite of the considerable difference of spark timing,on the other hands, the ignition delay of the small IVA is shorter than that of large one. Also the phenomena that the flame propagation is faster and the instant heat release rate is more concentrated and higher in the small were observed. Also, the burn duration of small one is shorter and the combustion process is more accelerated up to the mid-combustion stage; however,the process of large one is faster as the combustion approaches the last stage and the differences of combustion duration reduce as the compression ratio increases. Finally, the engine runs more stable when the IVA is small without any exception because of its rapid burn at the initial combustion stage.