• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.652-657
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• 2001

Computational work using the axisymmetric, compressible, Navier-Stokes Equations is carried out to predict the discharge coefficient of mass flow through a micro-critical nozzle. Several kinds of turbulence models and wall functions are employed to validate the computational predictions. The computed results are compared with the previous experimented ones. The present computations predict the experimental discharge coefficients with a reasonable accuracy. It is found that the standard $k-\varepsilon$ turbulence model with the standard wall function gives a best prediction of the discharge coefficients. The displacement thickness of the nozzle wall boundary layer is evaluated at the nozzle throat and is well compared to a prediction obtained by an empirical equation. The resulting displacement thickness of the wall boundary layer is about 2% to 0.6% of the diameter of the nozzle throat for the Reynolds numbers of 2000 to 20000.

• 한국추진공학회지
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• 제7권2호
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• pp.7-14
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• 2003

본 연구에서는 마이크로 임계노즐을 통한 유출계수를 예측하기 위하여, 축대칭, 압축성 Navier-Stokes 방정식을 사용한 수치계산을 수행하였다. 수치해의 적합성을 조사하기 위하여, 다양한 난류모델과 벽함수를 적용하였으며, 수치 결과들은 종래의 실험결과와 비교하였다. 그 결과 본 수치계산법은 임계노즐을 통한 유출계수를 적절하게 예측하였으며, 특히 표준 $\kappa$-$\varepsilon$난류모델과 표준 벽함수를 적용한 경우에 유출계수를 가장 잘 예측함을 알았다. 본 연구의 결과로부터 얻어진 임계노즐벽면의 난류경계층의 배제두께는 레이놀즈수가 2000에서 20000의 범위에서 임계노즐목 직경의 약 2%에서 0.6%까지 변화하였으며, 종래의 경험식과 잘 일치하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2366-2371
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• 2007

Spray combustion characteristics of a conducting fuel electrospray have been studied for clean combustion technology. The multiplexing system which can retain the characteristics of the cone-jet mode is inevitable for the electrospray application. Charged micro droplets can be obtained in almost uniform size during operating the electrospray in the cone-jet mode. This experiment device set up the multiplexed grooved nozzle system with the extractor. Using the grooved nozzle, the stable cone-jet mode can be achieved at the each groove in the grooved mode. This electrospray system was applied to the diffusion combustion. It is the first step to discover the diffusion combustion characteristics of the electrospray. In case of the single grooved nozzle electrospray, the diffusion flames are occurred at each jet of grooved mode and they are quite stable. The exhaust gas analysis was indicated that there is the critical point which can make very stable diffusion combustion.

• 대한기계학회논문집B
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• 제31권12호
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• pp.979-985
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• 2007

Spray combustion characteristics of the conducting fuel electrospray has been studied for clean combustion technology. The electrospraying multiplexed system which can maintain the characteristics of the cone-jet mode is able to obtain charged micro droplets with high flow rate. In addition, they have monodisperse distribution during operating the electrospray in the cone-jet mode. The multiplexed grooved nozzle system with the extractor was applied to this experimental device set up. The stable grooved mode can be generated by the grooved nozzle and this electrospray system was applied to the diffusion combustion. It is the first step to discover the diffusion combustion characteristics of the electrospray, In case of the single grooved nozzle electrospray the diffusion flames are occurred at each Jet of grooved mode and they are quite stable. The exhaust gas analysis was indicated that there is the critical point which can make very stable diffusion combustion