• 제목/요약/키워드: Air injection rate

검색결과 323건 처리시간 0.024초

수직원관 외부 유하액막 열전달에 주변 기체유동이 미치는 영향 (The Effect of Surrounding Gas Flow on the Heat Transfer of the Falling Film Flowing Down the Outside of a Vertical Tube)

  • 권경민;정시영;김병주
    • 설비공학논문집
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    • 제14권12호
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    • pp.996-1003
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    • 2002
  • Heat transfer characteristics were investigated for the falling film flowing down the outside of an electrically heated vertical tube. Water was used for the falling film, and its Reynolds number was varied in the range of 70~500. Because water is heated and evaporated as it flows down, both sensible and latent heat transfer should be considered. The effect of the surrounding air movement was investigated by changing the direction of the air injection; without air injection, parallel-flow, and counter-flow. For all cases, sensible teat transfer rate was almost linearly increased with the increasing film flow rate. It was found that the film heat transfer coefficient was hardly influenced by the parallel air flow. However, the counter-flow of air reduced the heat transfer coefficient, which might be caused by the uneven distribution or flooding of the film. At high heat flux, a sudden change of the film heat transfer coefficient was detected as the film flow rate reached the transition value. It is supposed that this phenomenon was caused by the change in the film flow pattern.

CNG 직접분사식 연소기에서의 연소 라디칼 특성 (Characteristics of Combustion Radical in CNG Direct Injection Vessel)

  • 최승환;조승완;이석영;정동수;전충환;장영준
    • 한국자동차공학회논문집
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    • 제12권5호
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    • pp.58-65
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    • 2004
  • A cylindrical constant volume combustion chamber was used to investigate the combustion characteristics of stratified methane-air mixture under several initial charge conditions in the author's previous reports. The results showed that the improvement of thermal efficiency and reduction of heat loss was realized simultaneously by using 2-stage injection method. This paper deals with the reason why the stratified combustion has showed better combustion rate through the measurement and analysis of chemiluminescence of C $H^{*}$ and $C_{2}$$^{*}$ radicals. An optic fiber bundle is used to measure the local emission of C $H^{*}$ and $C_{2}$$^{*}$ radicals to map the relationship between the excess air ratio and local radical intensity ratio in the combustion vessel at 5 mm apart form the geometric center. The results show that there exist a relationship between the intensity ratio and the air-fuel ratio. It is revealed that the improvement of combustion rate in a lean-stratified mixture is realized through the 2-stage injection method. method.

정상.과도 분사 조건에서의 에어슈라우드 인젝터 분무의 입경.분사량 분포에 관한 연구 (A study on distribution of drop size and injection rate of air-shroud injector sprays under steady and transient injection condition)

  • 이충훈
    • 한국분무공학회지
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    • 제9권4호
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    • pp.17-23
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    • 2004
  • Spray characteristics of a twin-hole air shrouded nonle designed for gasoline injectors was investigated by using laser diffraction particle analyzer (LDPA) and tomography reconstruction- A confined spray chamber which is optically accessible through a pair of glass windows was made to simulate the fuel injection condition in intake manifold of gasoline engine. The measurement was applied to the twin hole injector with and without an air shroud. It demonstrates that for the case with an air shroud, fine atomization is achieved and there exists a large number of fine droplets between the region of the main spray streams, which conforms with the spray visualization. The drop size distribution was investigated as a function of elapse time after fuel injection. The distribution was greatly affected by the measurement position from the injector exit. Also, the spatially resolved spray volume fraction and Sauter Mean Diameter (SMD) from line-of-sight data of the LDPA are tomographically reconstructed by Convolution Fourier transformation under the steady injection condition.

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COMBUSTION CHARACTERISTICS OF INHOMOGENEOUS METHANE-AIR MIXTURE IN A CONSTANT VOLUME COMBUSTION CHAMBER

  • Choi, S.H.;Jeon, C.H.;Chang, Y.J.
    • International Journal of Automotive Technology
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    • 제5권3호
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    • pp.181-188
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    • 2004
  • A cylindrical constant-volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of an inhomogeneous charge methane-air mixture under several parameters such as stratified pattern, initial charge pressure, ignition time and the excess air ratio of the initial charge mixture. Flow characteristics including mean velocity and turbulence intensity were analyzed by a hot-wire anemometer. The combustion pressure development, measured by a piezo-electric pressure transducer, was used to investigate the effect of initial charge pressure, excess air ratio and ignition times on combustion pressure and combustion duration. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to near-zero value at 3000 ms. For the stratified patterns, the combustion rate under the rich injection (RI) condition was the fastest. Under the initial charge conditions, the second mixture was accompanied by an increase in the combustion rate, and that the higher the mass which is added in the second stage injection, the faster the combustion rate.

터보 과급 디젤 기관의 동특성에 관한 연구 (A Study on the Dynamic Characteristics of a Turbocharged Diesel Engine)

  • 최낙정;이창식
    • 한국자동차공학회논문집
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    • 제3권1호
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    • pp.143-154
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    • 1995
  • This study investigates the response characteristics of a four-cylinder four-stroke turbocharged diesel engine by using computer simulation and experiments when a rapid acceleration is applied to the fuelpump rack. In the theoretical analysis, linearization method is used to avoid the difficulty on the complex nonlinear functions. Comppressor exit pressure, pressure and temperature of turbine inlet, and turbocharger speed are chosen as the independent variables of transfer functions which represent the dynamic characteristics of the turbocharger system, and expressed as the functions with respect to the time. Experiments on the same eigine system are also carried out to prove the validity of theoretical study. Further, this study carried an experiment for improving transient response performance by injecting air into the inlet manifold under the rapid accelerating conditions. The effects of air injection on the response performances are also represented at varying conditions such as injection pressure, injection period, accelerating rate, accelerating time, engine speed and load.

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냉각 파일런 분사를 이용한 스크램제트 연소기 내 혼합증대 (Mixing Augmentation with Cooled Pylon Injection in Scramjet Combustor)

  • 이상현
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2009년도 제33회 추계학술대회논문집
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    • pp.594-597
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    • 2009
  • The mixing characteristics of pylon injection in a Scramjet combustor and effects of film cooling to protect pylon from air-heating. Three-dimensional Navier-Stokes equations with $k-{\omega}$ SST turbulence model were used. Fuel hydrogen and air were considered as coolants. There were remarkable improvements of penetration and mixing rate with the pylon injection. There also over-heating on the front surface of pylon without film cooling. The coolant injected parallel to the front surface of the pylon protect the pylon from over-heating.

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다단 축류압축기의 안정성 개선을 위한 실험적 연구 (Experimental Research of Multi-Stage Axial Compressor Stability Enhancement by Air Injection)

  • 임영천;임형수;송성진;강신형
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2009년도 제33회 추계학술대회논문집
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    • pp.378-381
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    • 2009
  • 압축기에 불안정한 특성인 선회실속(Rotating stall)이 발생하면 압력 및 효율이 저하되고, 기계적인 손상도 야기한다. 이러한 불안정성을 개선하고 안정 운전영역을 넓히기 위해 4단 저속 축류압축기에 공기 분사(Air injection) 방법을 적용하여 안정성 개선 실험을 실시하였다. 동익 팁에 축방향으로 공기를 분사할 수 있도록 하기 위해 코안다 효과를 적용한 노즐을 사용하였고, 8개의 인젝터를 1단 동익 상단에 등간격으로 설치하였다. 축류 압축기 80% speed로 운전하면서 선회실속이 발생하기 전에 공기 분사를 실시하였고, 모드(Mode) 발생 유량의 5.4%에 해당하는 공기를 분사하여 약 4%의 안정성 개선 효과를 얻었다.

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노즐 홀 직경에 따른 단공 GDI 인젝터의 분무 특성 연구 - (1) 분사 및 거시적 분무특성 비교 (Study on Spray Characteristics of Single-Hole GDI Injector according to Nozzle Hole Diameter - (1) Comparison of Injection and Macroscopic Spray Characteristics)

  • 박정현;노승천;상몽소;박수한
    • 한국분무공학회지
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    • 제25권4호
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    • pp.145-153
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    • 2020
  • The purpose of this study is to compare the injection and spray characteristics of single-hole GDI injectors using injection rate and mie-scattering spray images. Five types of single-hole injectors with different nozzle hole diameters were used, and the spray rate, spray tip penetration, spray area, and spray width were analyzed. As a result, the diameter of the nozzle hole had a direct effect on the injection and spray characteristics. It was confirmed that the larger the diameter of the nozzle hole, the higher the injection quantity, the spray tip penetration, the spray area, and the spray width. In addition, it was confirmed that the near-field spray, which has little influence of ambient air, has a great correlation with the injection rate.

공작기계용 고속주축계의 공기냉각특성에 관한 연구 (Air Cooling Characteristics of a High Speed Spindle System for Machine Tools)

  • 최대봉;김석일;송지복
    • 한국정밀공학회지
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    • 제11권1호
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    • pp.123-128
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    • 1994
  • A high speed spindle system for machine tools can be used to reduce the machining time, to improve the machining accuracy, to perform the machining of light metals and hard materials, and to unite the cutting and grinding processes. In this study, a high speed spindle system is developed by applying the oil-air lubrication method, angular contact ball bearings, injection nozzles with dual orifices, cooling jacket and so on. And an air cooling experiment for evaluating the performance of the spindle system is carried out. Especially, in ofder to establish the air cooling conditions related to the development of a high speed spindle system, the effects of cooling air pressure, oil supply rate, air supply rate and rotational spindle speed are studied and discussed on the bearing temperature rise and frictional torque. Also the effects of cooling air pressure, rotational spindle speed and spindle system structure is investigated on the bearing temperature distribution. The experiment on the test model reveals the usefulness of the air cooling method.

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열펌프 압축기의 내부 액분사 효과에 대한 수치해석적 연구 (A Numerical Study of Liquid Injection into the Compressor Cylinder of a Heat Pump)

  • 허재경;방광현
    • 설비공학논문집
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    • 제15권5호
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    • pp.397-405
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    • 2003
  • Heat and fluid flow in a compressor into which liquid refrigerant is injected for the purpose of reducing discharge gas temperature in a heat pump system has been numerically studied. A mechanistic approach encompassing liquid jet breakup and droplet evaporation has been performed to investigate the effects of liquid injection on the spacial and temporal variation of the gas temperature and pressure inside the compressor cylinder. Various parameters, such as liquid injection mass, time, duration and droplet size, are considered in the present study to elucidate the flow field inside the compressor. As the injection mass is increased, discharge gas temperature is decreased, while the pressure is increased due to the added mass of the injection. For the injected liquid mass corresponding to 15% of the total vapor mass in the cylinder, the discharge gas temperature drops by 22.4 K. It is observed that the droplet size plays a major role in the evaporation rate of the droplets that determines the degree of the discharge temperature drop.