• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.10
• /
• pp.1238-1246
• /
• 2004

Momentum exchange theory has been generally used for an analysis of the regenerative turbomachines due to its direct description of the complicate circulatory flow. However, because its application is limited only to linear region and its model equations are incomplete on three variables, it needs further refinements. In the present study it is improved by introducing a central pivot of circulatory flow. Also, by assuming linear circulatory velocity distribution, mean radii of inlet and outlet flows through the impeller are newly suggested. By applying control volume analysis to both linear region and the acceleration region, the governing equation on the circulatory velocity is derived. As a result, systematic performance analysis on the entire region of the incompressible regenerative turbomachines can be carried out based on the proposed model equations.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.10
• /
• pp.1247-1254
• /
• 2004

In momentum exchange theory the loss models for the circulatory flow is critically important. But because of lack of loss model on the circulatory flow, analysis model on regenerative turbomachines is not available in the open literature. In the present study circulatory loss is evaluated by combining bend's losses. Through the comparison with the previous experimental data on linear pressure gradient, a combination factor is suggested in terms of the aspect ratio of a channel. Applying this factor to two kinds of regenerative blowers the predicted results are found to be in good agreement with the experimental data of the overall performance and the head distribution along the rotational direction. Especially, the comparison with the head distribution demonstrates the accuracy of hydraulic model and loss model suggested in the present study. And the comparison with the overall performance confirms the validness of physical models as well as loss models suggested in the present study.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.1 s.244
• /
• pp.16-23
• /
• 2006

The present study aims at establishing the design procedure of regenerative pumps. It is based on the new momentum exchange theory proposed in Yoo, Park and Chung. Salient feature of the present design procedure is that it does not require input of any kinds of empirical design data. Using the design procedure, a prototype regenerative pump has been designed and manufactured to confirm its validity. Comparison between the predicted performance and the experimental measurement reveals that the prototype pump has its maximum efficiency at the design flow rate and that the proposed performance analysis method satisfactorily predicts the machine performance.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.341-344
• /
• 2008

The complicated helical flow formed in the regenerative turbomachines is usually decomposed into a peripheral component and a circulatory component. On the basis of the momentum exchange theory, the circulatory flow plays a critical role of imparting angular momentum to the peripheral flow. Therefore, the accuracy of performance prediction is dominated by the circulatory flow modeling. Until now the circulatory flow has been accounted of a standstill flow normal to the peripheral flow. However, the circulatory path from the impeller exit to the re-entrance inlet is exposed to the adverse pressure gradient, so it would be more realistic to describe that the circulatory flow is formed on the skewed plane not perpendicular to the peripheral flow. Present study suggests new circulatory flow loss model including the effect of adverse pressure gradient and modifies the effective circulatory flow rate and circulatory pivot which were previously published.

• Journal of Navigation and Port Research
• /
• v.32 no.5
• /
• pp.341-347
• /
• 2008

Recently, it has been widely recognized that water-front and coastal vegetations may have great value in supporting fisheries, protecting from wave attack, stabilizing the sea bed and maintaining good scenery. Hydrodynamic factors playa major role in the functions of water quality and ecosystems. However, the studies on numerical and analytical process of wave propagation are few and far behind compared to those on the hydrodynamic roles of water-front vegetations. In this study, in order to express wave attenuation into water-front vegetation, a numerical model based on the unsteady mild slope equation is developed. This result is compared with an analytical model for describing the wave attenuation by assumed simple long wave condition. Based on both the analytical and numerical results, the physical properties of the wave attenuation are examined under various wave, geometric and vegetation conditions. Through comparisons between the analytical and numerical results, the effects of the vegetation properties, wave properties and model parameters such as the momentum exchange coefficient have been clarified.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.5
• /
• pp.10-18
• /
• 2017

The problem of non-ideal detonation propagation velocities in heterogeneous hybrid mixtures is studied in the case of a high explosive with suspended fine aluminum (Al) particles. Since there exist difference in the time scales of the characteristic induction and combustion of High Explosives and solid particles, the process of energy release behind the leading shock front occurs over an extended period of time. The problem is analyzed by the theory of the mechanics of multiphase media with mass, momentum and heat exchanges between particles and gases. The numerical results match the available experimental results of heavily aluminized (5~25% Al weight) HMX explosive obtained previously.