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소산율 방정식의 개선을 통한 저레이놀즈수 k-.epsilon. 모형의 개발
송경,유근종,조강래,Song, K.,Yoo, G.J.,Cho, K.R. 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.5
Series of recent k-.epsilon. model modification have been carried out with the aid of DNS data to include the effect of near wall. Though these methods opened new way of turbulence modelings, newly developed turbulence models of its kind had yet shortcomings in prediction for the turbulent flows with various Reynolds numbers and various geometric conditions. As a remedy for these shortcomings, a new k-.epsilon. model proposed here by improving the dissipation rate equation and the damping function for eddy viscosity model. The new dissipation rate equation was modeled based on the energy spectrum and magnitude analysis. The damping function for eddy viscosity was also formulated on the ground of distribution of dissipation rate length scales near a wall and the DNS data. The new k-.epsilon. model was applied to the fully developed turbulent flows in a channel and a pipe with a wide range of Reynolds numbers. Prediction results showed that the present model represents properly the turbulence properties in all turbulent regions over a wide range of Reynolds numbers.
添加劑-스로틀링 再生에 의한 디젤 粒子狀物質 濾過裝置 性能評價에 관한 硏究
조강래(K.R.Cho),엄명도(M.D.Eom),유최호(J.H.You) 한국자동차공학회 1994 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1994 No.11_1
This research has been proceeded from 1991 to 1993 to develop locally suitable trap system to fit Korean vehicle and characteristics by using fuel additive and throttling regeneration method. For this object diesel particulate trap with fuel additive and throttling technology was locally produced for which lab. test were carried out. For laboratory test the engine performance, gas emission, reduction rate of particulate, and regeneration performance including throttling and bypass rate were analyzed. And actual road performance and durability for locally produced sample are tested in vehicle road test On the results of lab. and on-road test no significant engine performance and fuel consumption has been varied and the smoke is reduced by maximum 92% after particulate trap system applied. Also fuel additive concentration of 150ppm is confirmed to be proper concentration for higher durability of trap system.<br/>
프로펠러 팬과 덕트와의 상대위치가 유동특성에 미치는 영향
심우찬,조강래,주원구,Sim, W.C.,Cho, K.R.,Joo, W.G. 대한설비공학회 1997 설비공학 논문집 Vol.9 No.1
The position of propeller fan from duct inlet is one of basic parameters for the design of propeller fan. To investigate the effect of its position on fan characteristics, the inlet flow fields and relative flow angles were measured by a 5-hole pitot tube. The experimental results indicate that the ratio of radial flow introduced from propeller circumference to total inlet flow increases with the increase of propeller distance from duct inlet. When fan operates without duct, the total flow rate and the radial flow ratio are higher than those of any other positions of propeller relative to duct inlet. The radial flow ratio decreases as a flow coefficient and the propeller distance decrease. Therefore the front flow fields can be adjusted in some extent by varying the propeller distance according to a fan loading. The inlet flow angles are decreasing a little as a rotational speed and the propeller distance decrease. In the present case it was judged that the deviation angle of outlet flow became negative owing to a flow separation near a trailing edge.
김종수,조강래,Kim, J.S.,Cho, K.R. 대한설비공학회 1995 설비공학 논문집 Vol.7 No.2
The effects of duct inlet conditions on fan characteristics and upper wind velocity fields were investigated for two kinds of impellers. As the duct inlet condition, the relative positions between duct inlet and fan impeller and the size of baffle plate mounted on a duct inlet were selected. The 3-dimensional velocity components in flow fields were measured by a 5-holes pitot tube. From the results of measurements, it was found that the size of baffle plate scarecely effect on upper wind flow fields and characteristics of fan. It was also confirmed that the upper wind velocity distributions can be estimated by the potential flow field with large baffle plate at duct inlet.
박재인(J.I.Park),조강래(K.R.Cho) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.11_1
When a internal flow of turbomachine is analysed by numerical calculation method, the accuracy of calculated results will depend on the establishment of inlet and outlet boundary conditions, assuming that governing equations and differencing scheme are proper. So far the widely-used techniques of flow analysis for ordinary turbomachine have been adopted in the flow analysis of torque converter, i. e. the flow of each element of torque converter is analysed separately and in turn considering each one as a blade row of turbomachine. But the flow in torque converter is quite different from the flow in ordinary turbomachine in that the torque converter is closed-loop machine containing the same oil circulating through its elements, hence some difficulties appear in establishing boundary conditions. In this paper, in order to analyse the flow by more reasonable method the interrow mixing planes will be introduced between each element to fit in with the working principle of torque converter and the calculated performances of torque converter will be compared with the experimental results.
박재인(J.I.Park),조강래(K.R.Cho) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_2
In the hydraulic design of torque converters, there exist many geometrical paramerters to be considered. Each paramerter affects the performance of the torque converter. Unfortunately, the effects of the paramerters on variations of the perfornlance have been rarely known. In this paper, several geometrical paramerters including the meridional configuration of pump and turbine, the edge configuration at pump inlet, the ditribution of angular momentum change, the offset angle of turbine, and the treatment for the trailing edge of stator were analyzed by numerical calculations. It was found that the geometrical variations are strongly related with the performaces and the internal flow field of torque converters.
박재인(J.I.Park),조강래(K.R.Cho) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_2
The situation frequently occurs in which the input torque capaciy of the torque converter should be changed. It is known that the modification of the outlet blade angles of the torque converter elements is suitable for such situation with the outer diameter of flow path of the converter maintained. But so far it has been difficult to predict correctly the converter characteristics as well as the effects of oulet angles on torque capacity in the past numerical methods. In the present numerical method introducing the interrow mixing planes, the torque capacity was satifactorily estimated and it was shown that the torque capacity could be effectively changed by modifying the oulet blade angles of pump and stator.