• Journal of Hydrogen and New Energy
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• v.26 no.5
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• pp.438-444
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• 2015

This study describes the effect of T branch shape on internal flow characteristics inside itself. Continuity and three-dimensional Reynolds-averaged Navier-Stokes equation have been used as governing equations for the numerical analysis. The T branch was modeled assuming that it is used for Alaska pipeline project which was planned to provide reliable transportation of natural gas from ANS to Alaska-Yukon border. Therefore the characteristics of T branch and operating condition of pipeline were from report of Alaska pipeline project. The nine T branch shapes were analyzed and the mass flow rate ratio between mainline and branch was assumed to be 0.95 : 0.05, 0.9 : 0.1, 0.85 : 0.15. The results shows that there are typical flow patterns in T branch and the shape of T branch makes some differences to the internal flow of branch rather than mainline.

• Journal of Hydrogen and New Energy
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• v.26 no.4
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• pp.386-392
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• 2015

Flow characteristics inside a 10 inch ball valve have been analyzed using three-dimensional numerical analysis and experiments. Continuity and three-dimensional Reynolds-averaged Navier-Stokes equations have been used as governing equations for the numerical analysis. The numerical model has been constructed through the grid dependency test and validation with the results of experiments to ensure reliability and numerical effectiveness. The shear stress transport (SST) model has been used as the turbulence closure. The experimental test-rig has been constructed to measure pressure, temperature and flow rate along the pipeline. Some valve opening angles have been tested to evaluate the flow characteristics inside the ball valve and pipeline. The results show that the rapid pressure variations is observed while the valve opening angle decreases, which caused by flow separation at the downstream of the ball valve.

• Journal of Hydrogen and New Energy
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• v.26 no.5
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• pp.463-468
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• 2015

This study describes the effect of upstream curved pipe on internal flow characteristics ball valve. Continuity and three-dimensional Reynolds-averaged Navier-Stokes equation have been used as governing equations for the numerical analysis. The upstream curved pipe - ball valve model was assumed that it is used for Alaska pipeline project which was planned to provide reliable transportation of natural gas from ANS to Alaska-Yukon border. Therefore the characteristics of pipe and operating condition of pipeline were from report of Alaska pipeline project. The three curvature and three location of upstream curved pipe were analyzed. The results shows that there are typical flow patterns at ball valve and the upstream curved pipe makes some differences to the internal flow of ball valve.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.85-93
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• 2001

Minimized canister flow restriction and maximized flow uniformity are desired to maximize a purge capability. With the impending ORVR(On Board Refueling Vapor Recovery) systems, the reduction of restriction and increase of flow uniformity in a carbon canister becomes even more critical to meet the stringent regulation. In this study, three-dimensional numerical simulations have been performed to investigate the three-dimensional internal flow patterns in a carbon canister during purge. The effects of the declined angle of the purge pipe and the number of partitions on the pressure drop and purge efficiency in a carbon packed bed are examined. Results show that the purge efficiency and space velocity distribution are affected in the upstream region of 40% of total canister bed by porosity of carbon granule and angle of purge pipe. It is also found that the purge efficiency decreases with increasing the number of partitions.

• Solar Energy
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• v.19 no.4
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• pp.21-31
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• 1999

This paper presents a quasi-three-dimensional calculation method considered a spanwise mixing effect in a diagonal flow impeller. The effect of this spanwise mixing caused by spanwise distribution of blade loading is evaluated by a secondary flow theory. In order to verify the validity of this method, it is applied to the analysis of a diagonal flow fan designed under a vortex type of constant circumferential velocity and that of a free vortex. The comparison of the calculated result with experimental data shows a good agreement except the regions near the casing where the flow field is affected by the tip leakage flow.

• International Journal of Fluid Machinery and Systems
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• v.4 no.3
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• pp.317-323
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• 2011

Mini centrifugal pumps having a diameter smaller than 100mm are employed in many fields; automobile radiator pump, ventricular assist pump, cooling pump for electric devices and so on. Further, the needs for mini centrifugal pumps would become larger with the increase of the application of it for electrical machines. It is desirable that the mini centrifugal pump design be as simple as possible as precise manufacturing is required. But the design method for the mini centrifugal pump is not established because the internal flow condition for these small-sized fluid machines is not clarified and conventional theory is not suitable for small-sized pumps. Therefore, we started research on the mini centrifugal pump for the purpose of development of high performance mini centrifugal pumps with simple structure. Three types of rotors with different outlet angles are prepared for an experiment. The performance tests are conducted with these rotors in order to investigate the effect of the outlet angle on performance and internal flow condition of mini centrifugal pumps. In addition to that, the blade thickness is changed because blockage effect in the mini centrifugal pump becomes relatively larger than that of conventional pumps. On the other hand, a three dimensional steady numerical flow analysis is conducted with the commercial code (ANSYS-Fluent) to investigate the internal flow condition. It is clarified from the experimental results that head of the mini centrifugal pump increases according to the increase of the blade outlet angle and the decrease of the blade thickness. In the present paper, the performance of the mini centrifugal pump is shown and the internal flow condition is clarified with the results of the experiment and the numerical flow analysis. Furthermore, the effects of the blade outlet angle and the blade thickness on the performance are investigated and the internal flow of each type of rotor is clarified by the numerical analysis results.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.244-254
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• 2002

To enhance the acceleration performance and fuel consumption rate of a vehicle, the torque converter is modified or newly-developed with reliable analysis model. Up to recently, the one dimensional performance model has been used for the analysis and design of torque converter. The model is described with constant parameters based on the concept of mean flow path. When it is used in practice, some experiential correction factors are needed to minimize tole estimated error. These factors have poor physical meaning and cannot be applied confidently to the other specification of torque converter. In this study, the detail dynamic model of torque converter is presented to establish the physical meaning of correction factors. To verify the validity of model, performance test was carried out with various input speed and oil temperature. The effect of oil temperature on the performance is analysed, and it is applied to the dynamic model. And, to obtain the internal flow pattern of torque converter, CFD(Computational Fluid Dyanmics) analysis is carried out on three-dimensional turbulent flow. Correction factors are determined from the internal flow pattern, and their variation is presented with the speed ratio of torque converter. Finally, the sensitivity of correction factors to the speed ratio is studied for the case of changing capacity factor with maintaining torque ratio.

• The KSFM Journal of Fluid Machinery
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• v.18 no.5
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• pp.19-25
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• 2015

As a core component of a hydropower station, hydro turbines play a vital role in the integration of a power station. Research on the technology of hydro turbine is continuously increasing with the development of water electricity. On the basis of one-dimensional loss analysis, for three-dimension design, there are a lot of dimension of the internal flow passage shapes that are determined by experience. Therefore, the effect of the internal flow passage shapes on the performance and internal flow characteristics of a Francis hydro turbine model is investigated in this study. In this study, the small curvature of runner blade trailing edge shape is good for improving the efficiency of Francis turbine. The straight stay vane leading edge is good for suppressing the secondary flow. Moreover, suitable tongue passage shape and stay vane number improve the performance of the turbine considerably.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.13-18
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• 2009

Flight vehicles such as wheel wells and bomb bays have many cavities. The flow around a cavity is characterized as an unsteady flow because of the formation and dissipation of vortices brought about by the interaction between the free stream shear layer and the internal flow of the cavity. The resonance phenomena can damage the structures around the cavity and negatively affect the aerodynamic performance and stability of the vehicle. In this study, a numerical analysis was performed for the cavity flows using the unsteady compressible three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equation with Wilcox's turbulence model. The Message Passing Interface (MPI) parallelized code was used for the calculations by PC-cluster. The cavity has aspect ratios (L/D) of 2.5 ~ 7.5 with width ratios (W/D) of 2 ~ 4. The Mach and Reynolds numbers are 0.4 ~ 0.6 and $1.6{\times}106$, respectively. The occurrence of oscillation is observed in the "shear layer and transient mode" with a feedback mechanism. Based on the Sound Pressure Level (SPL) analysis of the pressure variation at the cavity trailing edge, the dominant frequencies are analyzed and compared with the results of Rossiter's formula. The dominant frequencies are very similar to the result of Rossiter's formula and other experimental data in the low aspect ratio cavity (L/D = ~ 4.5). In the large aspect ratio cavity, however, there are other low dominant frequencies due to the leading edge shear layer with the dominant frequencies of the feedback mechanism. The characteristics of the acoustic wave propagation are analyzed using the Correlation of Pressure Distribution (CPD).

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.91-99
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• 2014

The common-rail injectors are the most critical component of the CRDI diesel engines that dominantly affect engine performances through high pressure injection with exact control. Thus, from now on the advanced combustion technologies for common-rail diesel injection engine require high performance fuel injectors. Accordingly, the previous studies on the numerical and experimental analysis of the diesel injector have focused on a optimum geometry to induce proper injection rate. In this study, computational predictions of performance of the diesel injector have been performed to evaluate internal flow characteristics for various needle lift and the spray pattern at the nozzle exit. To our knowledge, three-dimensional computational fluid dynamics (CFD) model of the internal flow passage of an entire injector duct including injection and return routes has never been studied. In this study, major design parameters concerning internal routes in the injector are optimized by using a CFD analysis and Response Surface Method (RSM). The computational prediction of the internal flow characteristics of the common-rail diesel injector was carried out by using STAR-CCM+7.06 code. In this work, computations were carried out under the assumption that the internal flow passage is a steady-state condition at the maximum needle lift. The design parameters are optimized by using the L16 orthogonal array and polynomial regression, local-approximation characteristics of RSM. Meanwhile, the optimum values are confirmed to be valid in 95% confidence and 5% significance level through analysis of variance (ANOVA). In addition, optimal design and prototype design were confirmed by calculating the injection quantities, resulting in the improvement of the injection performance by more than 54%.