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- 저자 : 김병균 (검색결과 166 건)
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김병균,Mengzhao Chang,박수한 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.1
This study is to analyze the spray characteristics near the nozzle according to the cavitating flow and step-hole structure using a quartz nozzle simulating a gasoline direct injection (GDI) injector. Referring to the dimensions of the injector used in mass-produced vehicles, various step-hole and injection pressure conditions were used in this experiment. Based on the injector dimensions, the step-hole conditions were designed in the direction of decreasing the depth and diameter. The internal flow in nozzle and spray near the nozzle were visualized by the shadow graphic and Mie-scattering visualization technique. A solenoid valve was used to simulate fuel injection like injector. Basically, the tendency of cavitating flow and spray characteristics were analyzed under various step-hole conditions. In addition, the tip wetting of nozzle with different step-hole conditions was analyzed, and the nozzle tip wettings at initial injection and end of the injection were separated and compared in detail. It was found that the wetting intensity decreased reduced 44.9 % when reduce step-hole depth from 2.5 to 1.5 mm. Tip wetting mainly occurred at initial injection for most step-hole conditions, but the tip wetting at end of injection was dominant when both decreasing the step-hole depth and step-hole diameter.
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김병균,노승천,박수한,김영배,최병철,정승훈,이동원 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.1
This study aims to analyze effect of needle position inside nozzle on the internal and external flow characteristics. To visualize cavitating flow inside nozzle, the transparent acrylic nozzle was used. We tested five needle positions that simulated the needle movement of injector. The cross-section of test nozzle is rectangular with a very narrow width instead of circular shaped for a better visualization of cavitating flow. The inside of the nozzle was visualized by the shadowgraphic visualization using a high-speed camera and a metal-halide lamp. From the experiments, development of the cavitating flow according to the needle positions depends on the flow velocity and the cavitation number. The cavitation length, cavitation width, and spray angle are relatively symmetrically shown when the needle was at the center. However, they were asymmetrical when the needle position was biased. When the needle positions were in the same on the vertical line, the minimum cavitation length, minimum cavitation width, and minimum spray angle were larger when the upper level. The needle position affects the development timing and cavitation growth. When the needle position was located at the upper level, the hydraulic flip occurred at a higher injection pressure than the lower level.
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김병균,김지연,김동환,최한님,이원용 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.4
A highly sensitive electrochemical detection method for bisphenol A (BPA) has been developed by using multi-walled carbon nanotube (CNT)-doped titania-Nafion composite modified glassy carbon (GC) electrode. The CNT−titania−Nafion/GC electrode exhibited excellent electrocatalytic activity towards BPA. Therefore, the CNT−titania−Nafion/GC electrode showed improved voltammetric responses for BPA compared to that obtained with bare GC electrode. In addition, cetyltrimethylammonium bromide (CTAB), a cationic surfactant, was added into the BPA sample solution in order to accumulate BPA through hydrophobic interaction between CTAB and BPA. The CNT−titania−Nafion/GC electrode gave a linear response (r2 = 0.999) for BPA from 1.0 × 10−8 M to 5.0 × 10−6 M with a detection limit of 9.0 × 10−10 M (S/N = 3). The modified electrode showed good selectivity against interfering species and also exhibited good reproducibility. The present electrochemical sensor based on the CNT–titania–Nafion/GC electrode was applied to the determination of BPA in food package samples.
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