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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.
엄인용,유주현 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.23 No.-
This study was to structurally characterize solid residues obtained from sunflower stalks hydrothermally treated at 180 and 200℃ for 30 min, followed by enzymatic hydrolysis. Recovered solid residue were 25.3% and 24.1% of fresh biomass, respectively. Each ethanol soluble fraction could be obtained up to 30% of the solid residue. The fraction from the solid residue at 200℃ was composed of smaller-sized lignin macromolecules with higher phenolic hydroxyl group, but lower aliphatic hydroxyl due to enhanced cleavage reactions related to side chain and aryl ether linkages of lignin, compared to that of the solid residue at 180℃.
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.
엄인용,Min-Ji Jung 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.6
A fast and simple sampling and sample preparation device, (NTD) has been developed and applied to sample and analyze volatile components from ground coffee beans. Coffee fragrances and other volatile organic compounds (VOCs) were sampled by the NTD and then analyzed by gas chromatograph-mass spectrometry (GC/MS). Divinylbenzene (DVB) particles (80/100 mesh size) were the sorbent bed of the NTD. More than 150 volatile components were first identified based on the database of the mass library and then finally 30 fragrances including caffeine were further confirmed by comparing experimental retention indices (i.e. Kovat index) with literature retention indices. Total sampling time was 10 minutes and no extra solvent extraction and/ or reconstitution step need. Straight n-alkanes (C6-C20) were used as retention index probes for the calculation of experimental retention indices. In addition, this report suggests that an empty needle can be an alternative platform for analyzing polymers by pyrolysis-GC/MS.
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.