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최낙정,이창식 대한기계학회 1992 대한기계학회논문집 Vol.16 No.8
본 연구에서는 정상운전 중인 4사이클 6실린더 터보과급 디젤기관에 갑자기 큰 부하가 작용하였을 경우, 기관 및 과급기 관성 모멘트의 변화가 기관과 과급기의 실제 회전속도, 압축기 압력비, 실린더내 공기유량, 연소효율, 배기온도 등의 과도 응 답성능에 미치는 영향을 시뮬레이션해석과 실험을 통하여 규명하였다. This study describes the response performances of actual engine speed, turbocharger speed, air mass flow rate through engine, boost pressure ratio, exhaust temperature and combustion efficiency for a six-cylinder four-stroke turbocharged diesel engine during the change in operating conditions by using the computer simulation with test bed. In order to obtain the transient conditions, a suddenly large load was applied to the simulation engine with the several kinds of inertia moment in turbocharger and engine, and engine set speed. From the results of this study, the following conclusions were summarized The inferior response performances was mainly caused by turbocharger lag, and air mass flow rate and boost pressure ratio were closely related to the turbocharger speed. A reduced moment of turbocharger inertia resulted in less transient speed drop and much faster recovery to the steady state of the engine. The increase of moment of engine inertia reduced cyclic variation of engine speed. When a large load was applied to the engine at high speed, the engine could be fastly recovered. However, when the same load was applied to the engine at low speed, the engine was stalled.
최낙정,손효수,Hyun-Jun Choi,김경국,이성남 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.3
We comparatively investigated the crystal and the optical properties of nonpolar (10-10) ZnOfilms grown on m-plane sapphire substrates by using atomic layer deposition (ALD) and radiofrequency (RF) magnetron sputtering. From high-resolution X-ray !/2 scans, the (100) peak ofthe ALD-grown ZnO film was clearly developed at 15.9 while that of the RF sputter-grownZnO was broadly observed at 15.6 15.9, indicating that a nonpolar (10-10) ZnO film would bepreferentially grown on an m-plane sapphire substrate. The photoluminescence bandedge emissionintensity of the ALD-grown (10-10) ZnO film was ten times higher than that of the RF sputtergrownZnO film. In addition, the electroluminescence intensity of a semipolar (11-22) GaN-basedlight-emitting diode (LED) with an ALD-grown (10-10) ZnO film as a transparent conductive oxidematerial was much higher than that of a semipolar (11-22) GaN-based LED with RF sputter-grown(10-10) ZnO film.
압축기출구에 공기분사가 터보과급 디젤기관의 성능에 미치는 영향에 관한 연구
최낙정,이창식 대한기계학회 1995 대한기계학회논문집 Vol.19 No.3
For the purpose of improving performances of a turbocharged diesel engine at low speed, this study investigates the effects of the injected air for the performances and flow characteristics in the intake and exhaust pipes by using the computer simulation with test bed. In the theoretical analysis, the whole flow system, including engine cylinders and intake and exhaust pipes, is calculated numerically by the method of filling and emptying. From the results of this study, the following conclusions may be summarized. Increasing injected air pressure into the pipe of compressor exit brings about the improvement in a performance and flow characteristics of intake and exhaust pipes under full load operating conditions at 1000 rpm of the engine speed, but shows trends of the inferior performances under no load operating conditions at 2000 rpm of the engine speed.
최낙정 한국마린엔지니어링학회 1999 한국마린엔지니어링학회지 Vol.23 No.1
This study investigates the effects of different kind fuels on the flame structure by using the numerical simulation in triple flame made by a co-flowing fuels-air stream based on the elementary chemical reaction mechanism. Methane and Hydrogen were used as fuel for this study. In order to interpret the result of the study on numerical simulation Skeletal chemistry is employe as the elementary chemical reaction mechanism for methane Gutheil's as an offset ele-mentary chemical reaction mechanism for hydrogen. The result of this study is as follows. In com-parison between the apparent burning velocity change of triple flame and the one-dimensional pre-mixed flame hydrogen fuel flame is higher than methane fuel flame. The flame thrusts out for-ward in the down stream of the boundary between air-fuel mixture and air stream and a part of the flow is bent and forks out in this protruding flame so that a triple flame is originated.