• 제목/요약/키워드: Air injection

검색결과 1,200건 처리시간 0.021초

광섬유 고속인출공정용 유리섬유 냉각장치 내 공기유입에 의한 내부헬륨농도 저하현상 연구 (HELIUM CONCENTRATION DECREASE DUE TO AIR ENTRAINMENT INTO GLASS FIBER COOLING UNIT IN A HIGH SPEED OPTICAL FIBER DRAWING PROCESS)

  • 김경진;김동주;곽호상;박상희;송시호
    • 한국전산유체공학회지
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    • 제15권4호
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    • pp.92-98
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    • 2010
  • In a modern high speed drawing process of optical fibers, it is necessary to use helium as a cooling gas in a glass fiber cooling unit in order to sufficiently cool down the fast moving glass fiber freshly drawn from the heated silica preform in the furnace. Since the air is entrained unavoidably when the glass fiber passes through the cooling unit, the helium is needed to be injected constantly into the cooling unit. The present numerical study investigates and analyzes the air entrainment using an axisymmetric geometry of glass fiber cooling unit. The effects of helium injection rate and direction on the air entrainment rate are discussed in terms of helium purity of cooling gas inside the cooling unit. For a given rate of helium injection, it is found that there exists a certain drawing speed that results in sudden increase in the air entrainment rate, which leads to the decreasing helium purity and therefore the cooling performance of the glass fiber cooling unit. Also, the helium injection in aiding direction is found to be more advantageous than the injection in opposing direction.

가솔린 엔진의 비정상 상태에 대한 Map 구성과 공기 및 연료 모델 개선 (Construction of Map for Transient Condition of a Sl Engine and Refinement of Intake Air Model & Fuel Model)

  • 심연섭;강태성;강승표;고상근
    • 한국자동차공학회논문집
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    • 제10권5호
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    • pp.1-8
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    • 2002
  • For gasoline engines, a three-way catalytic converter that has the maximum efficiency at stoichiometric air/fuel ratio is used to clean up the exhaust gas. So a precise air/fuel ratio control is necessary to maximize the catalytic conversion efficiency, For a transient condition, a fred-forward air/fuel ratio control method that estimates the air mass inducted into a cylinder is being used. In this study, a fuel injection map that makes an accurate air/fuel ratio control possible was constructed for the very same transient condition. For the same condition above, intake air model and fuel model were refined so that fuel injection values based on air mass through a throttle valve and intake manifold pressure are equal to the map values.

직접분사식 LPG 엔진의 연소전략 및 공기과잉률 변화에 따른 연소특성 비교 (Comparison of Combustion Characteristics with Combustion Strategy and Excess Air Ratio Change in a Lean-burn LPG Direct Injection Engine)

  • 조시현;박철웅;오승묵;윤준규
    • 한국자동차공학회논문집
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    • 제22권6호
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    • pp.96-103
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    • 2014
  • Liquefied Petroleum Gas(LPG) has attracted attention as a alternative fuel. The lean-burn LPG direct injection engine is a promising technology because it has an advantage of lower harmful emissions. This study aims to investigate the effect of combustion strategy and excess air ratio on combustion and emission characteristics in lean-burn LPG direct injection engine. Fuel consumption and combustion stability were measured with change of the ignition timing and injection timing at various air/fuel ratio conditions. The lean combustion characteristics were evaluated as a function of the excess air ratio with the single injection and multiple injection strategy. Furthermore, the feasibility of lean operation with stratified mixture was assessed when comparing the combustion and emission characteristics with premixed lean combustion.

ANALYSIS OF IN-CYLINDER FUEL-AIR MIXTURE DISTRIBUTION IN A HEAVY DUTY CNG ENGINE

  • Lee, Seok-Y.;Huh, Kang-Y.;Kim, Y.M.;Lee, J.H.
    • International Journal of Automotive Technology
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    • 제2권3호
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    • pp.93-101
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    • 2001
  • Distribution of fuel-air mixture has a strong influence on performance and emissions of a compressed natural gas (CNG) engine. In this paper, parametric study is performed by KIVA-3V to investigate fuel-air mixture with respect to injection timing, cycle equivalence ratio and engine speed. With open-valve injection intensive mixing during intake and compression stroke results in relatively homogeneous mixture in the cylinder. Sequential induction of fuel-air mixture and fresh air results in stratification in the cylinder among the test cases at closed-valve injection. There is close similarity in the calculated distributions of the mixture in the cylinder with different cycle equivalence ratios and engine speeds. The results are compared against pressure traces and flame images obtained in a single cylinder engine converted from a 11L six-cylinder heavy duty diesel engine.

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상업용 소각로 연소실 성능예측을 위한 수치해석 연구 (Numerical Analysis for the Performance Prediction of Combustion Chamber of Commercial Incinerator)

  • 이진욱;박병수;윤용승;서정대;허일상
    • 한국연소학회지
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    • 제4권1호
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    • pp.141-153
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    • 1999
  • Numerical analysis for the combustion flow in the combustion chamber of incineration system has been carried out in order to acquire the basic design capability of incineration system. Established mathematical model was applied to the performance prediction of the pre-designed combustion chamber of commercial plant. Especially, combustion characteristics and the variation of flow pattern have been deeply discussed in accordance with secondary air injection. Secondary air injection was effective for the turbulent mixing between air and carbon monoxide/volatile matter resulting in considerably reduced CO content at the exit. Secondary air injection was found to be one of the key design parameters because the size of recirculation zone could be changed with the variation of injection characteristics.

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충진층식 세정집진기의 집진특성 실험 (An Experiment on the Particle Collection Characteristics in a Packed Wet Scrubber)

  • 유경훈;노희환;최은수;김종균
    • 설비공학논문집
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    • 제15권4호
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    • pp.305-311
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    • 2003
  • DOP aerosol particles with geometric mean diameter of 0.5-3.0 ${\mu}{\textrm}{m}$, geometric standard deviation of 1.1-1.3 and total number concentration of 1,500-8,000 Particles/㎤ were used to determine collection efficiencies of a packed wet scrubber with respect to particle size. The tested operating variables included air velocity and water injection rate. It was shown from the experimental results that the collection efficiencies increased with increasing water injection rate and decreasing air velocity. Meanwhile, as for the particle size variation, all of the collection efficiency curves increased rapidly between 0.57-1.41${\mu}{\textrm}{m}$ for the range of water injection rate above 30 L/min. It was also seen that the collection efficiency of a packed wet scrubber is mainly governed by the mechanism of inertial impaction.

경막외 Morphine 투여에 의한 극심한 호흡억제 및 두개강내 공기음영 (Severe Respiratory Depression and Intracranial Air after Epidural Morphine -Subdural or Epidural Injection?-)

  • 강미경;문동언;서재현
    • The Korean Journal of Pain
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    • 제6권2호
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    • pp.270-274
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    • 1993
  • Massive extradural spread, distinguished from subarachnoid injection that sometimes follows the introduction of small amounts of local anesthetics or narcotics during attempted epidural anesthesia or analgesia, has been attributed to subdural injection. A 64-year-old woman was admitted for partial radical hysterectomy under general anesthesia after insertion of lumbar epidural cathter by loss of resistance technique with 5 ml of air. In this case, we experienced severe respiratory depression and loss of consciousness after administration of 4 mg of morphine for postoperative pain control. We confirmed air shadows at right silvian and suprasella cisterna region by CT scanning. Patients was recovered without sequele after 2 days, As this case resembles a "massive epidural", it is suggested that subdural injection rather than epidural injection may explain the phenomenon.

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동축선회 확산연소기의 1차 및 보조공기유량 변화에 따른 연소배출특성 (Combustion Characteristics in Various Primary and Auxiliary Air Flux Conditions at a Coaxial Swirling Diffusion Combustor)

  • 이용후;오세원;배대석;이도형
    • 동력기계공학회지
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    • 제6권3호
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    • pp.17-23
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    • 2002
  • The purpose of this study is to investigate the combustion emission characteristics changing auxiliary air injection in combustion field of coaxial swirling diffusion combustor. For this purpose, mean temperature, CO, CO2, O2 and HC concentration were measured by changing excess air ratio and auxiliary air injection. As a result of this study, mean temperature, CO2 emission were increased and CO emission decreased by increasing auxiliary air. Therefore, this paper showed the auxiliary air injection effected strongly on flame structure and combustion emission characteristics.

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공기 보조 연료 분사 장치가 있는 가솔린 기관의 희박 연소에 관한 연구 (A Study on the Lean Combustion of the Gasoline Engine with Air Assisted Fuel Injection System)

  • 김세웅;김응서
    • 한국자동차공학회논문집
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    • 제2권2호
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    • pp.117-123
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    • 1994
  • This paper describes the effect of air assisted fuel injection system(AAI) using compressed air to improve the performance of lean combustion engine. AAI is designed to promote fuel atomization and intake flow. In order to investigate the performance of engine with AAl, experiments are conducted varying the engine revolution speed, lean air-fuel ratio and intake manifold pressure. Compared with the original engine, the performance of the engine with MI is improved as the air-fuel mixture becomes leaner or the engine load becomes lower. The descreasing rate of BSFC is propotional to the relative air-fuel ratio and the lean misfire limit extended more than 0.2 relative airfuel ratio.

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연소실내 분사식 수소연료기관의 특성에 관한 연구 (A Study on the In-Cylinder Injection Type Hydrogen Fueled S.I. Engine)

  • 조우흠;이형승;김응서
    • 대한기계학회논문집
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    • 제19권7호
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    • pp.1702-1708
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    • 1995
  • Owing to the serious problem of hydrocarbon fuel such as environmental pollution, the development of alternative fuel is very urgent. To adopt hydrogen to the internal combustion engine, a solenoid-drive type in-cylinder injection system was constructed. The injection system was installed to the single cylinder research engine, and the engine performance and the emission of citric oxide were tested upon the fuel-air equivalence ratio and the spark timing. In the case of in-cylinder injection system, hydrogen is injected after the intake valve is close, so it is possible to operate the engine without the back fire and the fall of its volumetric efficiency. In the region of the fuel-air equivalence ratio below 0.5, hydrogen and air aren't well mixed and the thermal efficiency is lowered, so the nozzle should be designed to inject hydrogen uniformly into the combustion chamber. In the region of the fuel-air equivalence ratio above 0.7,the fuel-air mixture burns very fast and the amount of citric oxide emission increases rapidly, so the spark timing should be retarded as compared with MBT.