• 한국자동차공학회논문집
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• 제9권4호
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• pp.18-26
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• 2001

OSKA engine was developed to remove the dense core of injection sprays. The engine uses impinging spray on a small pip, which spray after impinging is broken into smaller drops and disperses into fee space in chamber. In this paper the pip size is analyzed to give more dispersion of spray and fuel vapor. The gas phase is modelled by the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction. The liquid phase is modelled following the discrete droplet model approach in Lagrangian form, and the droplet wall interaction is modelled as a function of the velocity normal to impaction lands. The droplet distributions, vapor fractions and gas flows are analyzed for various injection pressure cases. Numerical results indicate that the land diameter of 5.6mm has the best performance of spray dynamics and vaporization in the test sizes.

• 한국자동차공학회논문집
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• 제7권5호
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• pp.55-65
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• 1999

Many researches have been investigating small direct-injection diesel engines using the spray impacting on walls. Those systems have one or more raised pips to break-up the fuel and spread it widely toward a desired direction in a combustion chamber. In this study, the sizes and heights of the pips are determined by using a computational fluid dynamics code employing non-orthogonal grid systems. In order to find out the suitable pip-shape to a small chamber, the spray behaviors, occupied spary volumes and averaged droplets sizes are calculated with the variation of shape of the pip, such as, size and heights and inclined degree. The desired shape of the impinging land is proposed for the design of combustion system in small diesel engines.

• 한국항해항만학회지
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• 제28권4호
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• pp.305-309
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• 2004

The problem for parameters estimation of the received signals impinging on array sensors has long been of great research Interest in a great variety of applications, such as radar, sonar, and land mobile communications systems. Conventional subspace-based algorithms, such as MUSIC and ESPRIT, require an extensive computation of inverse matrix and eigen-decomposition In this paper, we propose a new parameters estimation algorithm via nonlinear minimization, which is simplified computationally and estimates signal parameters simultaneously.

• Wind and Structures
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• 제38권4호
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• pp.261-275
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• 2024

Before performing an experimental study on the downburst-generated wave, it is necessary to examine the scale effects and corresponding corrections or compensations. Analysis of similarity is conducted to conclude the non-dimensional force ratios that account for the dynamic similarity in the interaction of downburst with wave between the prototype and the scale model, along with the corresponding scale factors. The fractional volume of fluid (VOF) method in association with the impinging jet model is employed to explore the characteristics of the downburst-generated wave numerically, and the validity of the proposed scaling method is verified. The study shows that the location of the maximum radial wind velocity in a downburst-wave field is a little higher than that identified in a downburst over the land, which might be attributed to the presence of the wave which changes the roughness of the underlying surface of the downburst. The impinging airflow would generate a concavity in the free surface of the water around the stagnation point of the downburst, with a diameter of about two times the jet diameter (D_jet). The maximum wave height appears at the location of 1.5D_jet from the stagnation point. Reynolds number has an insignificant influence on the scale effects, in accordance with the numerical investigation of the 30 scale models with the Reynolds number varying from 3.85 × 10⁴ to 7.30 × 10⁹. The ratio of the inertial force of air to the gravitational force of water, which is denoted by G, is found to be the most significant factor that would affect the interaction of downburst with wave. For the correction or compensation of the scale effects, fitting curves for the measures of the downburst-wave field (e.g., wind profile, significant wave height), along with the corresponding equations, are presented as a function of the parameter G.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.305-309
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• 2004

레이더, 소나 및 육해상 통신시스템에 있어서, 어레이 센서에 입사하는 수신신호가 가지는 도래방향 및 신호전력과 같은 파라미터 추정문제는 수십년 동안 많은 연구관심이 되어 왔으며, 현재에도 다양한 응용영역에서 중요한 문제 중의 하나이다. 수신신호의 파라미터 추정방법으로서 종래의 MUSIC 또는 ESPRIT와 같은 방법은 역행렬 연산과 고유치 계산이 필요하므로 계산적 복잡성이 부가된다. 본 논문에서는 어레이 안테나의 기본 신호모델로부터 파라미터 추정의 문제를 비선형 최소화 문제로 정식화 하여 역행렬과 고유치 연산을 요구하지 않는 수신신호의 파라미터 동시추정 알고리즘을 제안하고 평가한다.