Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Journal of Physics Conference Series  

Effective utilization of small hydropower is expected to contribute to the low carbonization of our society, but it is still dif□icult for small head sites due to low cost-effectiveness. Toward this issue, the authors have been studying a Darrieus-type hydroturbine, one of the cross-□low turbines with simple structure, in open channels. In the present study, toward an effective utilization of unused hydropower with low head but large □low capacity like in discharge □low channel of hydropower plant, numerical simulation and model experiment were carried out for the multiple turbines installed in parallel. Firstly, numerical simulation in two-dimensional con□iguration was conducted to estimate the possible power output. The effects of distance among turbines and rotational directions were investigated just to understand the performance characteristics qualitatively. Then, a typical experimental apparatus consisting of two parallel rectangular open channels as a model discharge □low channel was constructed, and two small Darriues-type hydroturbines were installed and experimented. The effects of □low rate and □low depth on the performance were investigated.

DOI： 10.1088/1742-6596/3150/1/012149

Scopus

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Journal of Physics Conference Series  

The backflow vortex cavitation is well known to occur at the inlet of axial impellers due to the roll up of shear layer between main flow and swirling backflow. Especially in inducers, the characteristics of vortices have been considerably investigated. On the other hand, the behaviour of backflow vortices in centrifugal pumps could be different from that in inducers due to structural differences. In this study, the observation of backflow vortex cavitation in a centrifugal pump was conducted using a high-speed camera. With the aid of the URANS simulation, the number, axial/radial position, and rotational speed of vortices were investigated. As a result, the vortex’s characteristics were found to be qualitatively similar to those in inducers, which well correlated with the flow rate normalized by the shockless flow rate. At the same time, a quantitative difference was confirmed probably originating from the difference of inlet structures between the present test pump and inducers.

DOI： 10.1088/1742-6596/3150/1/012092

Scopus

Language：Japanese   Publisher：Turbomachinery Society of Japan  

<p>The development of prediction methods for cavitation flow is an important research topic since the cavitation causes several severe problems in real applications. Multi-Process (MP) model we employ in the present study is a homogeneous model with four equations that can take account of main elementary processes in cavitation using the moment method for a size distribution function of cavitation bubbles. Therefore, it is expected to improve the prediction accuracy compared to typical one-equation models generally applied for hydraulic machines with acceptable computational costs. In this paper, unsteady RANS simulation using MP model as well as a typical one-equation model was carried out on the final stage model of multi-stage centrifugal pump and the results are compared between two models as well as with experiments. As a result, the present simulation using MP model was found to qualitatively simulate the degradation of pump suction performance and the change in axial thrust force under cavitation as similar to the other homogeneous model; Thrust forces acting on the impeller and the balance drum decreases with the degradation of the head. In comparison with visualization experiments, both the models predicted cavity growth qualitatively well, although the distribution of void fraction showed significant differences.</p>

DOI： 10.11458/tsj.52.2_83

CiNii Research

Repository Public URL： https://hdl.handle.net/2324/7357483

Language：English   Publisher：The Japan Society of Mechanical Engineers  

<p>In the present study, numerical simulation of cavitating flow using Multi-Process model, which is one of the homogeneous cavitation models and consists of multiple transport equations of bubbly flow characteristics defined on the basis of the moment method, is conducted for a centrifugal pump toward more accurate prediction. The experiment is also conducted for the same pump to obtain the hydraulic performance including the axial thrust force characteristics as well as the visual aspects of cavitation for the validation of numerical simulation. It is found that the present simulation can qualitatively reproduce the degradation of pump suction performance as well as the change in axial thrust force under cavitation at the design flow rate; thrust forces acting on the impeller and the balance drum decreases with the head drop. The cavity patterns leading to the head drop are also well reproduced; the cavitation on the suction surface extends into the blade passage. At a partial flow rate close to the design one, the simulated cavity patterns with the inception and moderate states of cavitation agree with the observation, but they are not well reproduced perhaps due to the insufficient mesh resolution at the deep partial flow rate where the most of cavitation occurs in the vortical structure, typically in the tip separation vortex.</p>

DOI： 10.1299/jfst.2024jfst0011

Web of Science

Scopus

CiNii Research

Repository Public URL： https://hdl.handle.net/2324/7357482

Publisher：Journal of Physics: Conference Series  

In this study, in order to understand the relation between the diffuser rotating stall and the fluctuating radial thrust, unsteady RANS simulation of a centrifugal pump was carried out. The rotating stall with single stall cell was qualitatively reproduced though the propagation speed was smaller than the experiment. The pressure amplitude caused by the rotating stall was comparable to the measured one, and the tendency that the propagation speed increases as the flow rate increases agreed with experiment. The radial thrust fluctuation due to the rotating stall was well evaluated by the simulation, and a considerable difference of phase angle between the stall cell position and the working direction of radial thrust was detected, which also agreed with experiment. On the basis of simulation result, the reason is found to be that the radial force acting on the impeller external wall at the liner ring section due to stall cell was not very small but comparable to that acting on the impeller blade and outer wall, while their working directions were roughly 100° different. This suggests that considering the leakage flow in numerical simulation is important to accurately predict the radial forces generated by rotating stall.

DOI： 10.1088/1742-6596/2217/1/012031

Scopus

Event date： 2025.8

Language：English   Presentation type：Oral presentation (general)  

DOI： 10.1088/1742-6596/3150/1/012092

Open data URL： https://iopscience.iop.org/article/10.1088/1742-6596/3150/1/012092

Event date： 2025.1

Language：English   Presentation type：Oral presentation (general)  

Venue：Kanagawa, Japan