Sumio SAITO’s research while affiliated with National Institute of Technology, Tokyo College and other places

Wind turbines with a propeller-type rotor on a horizontal axis employ turbine blades have a thickness ratio δ(the ratio of chord length C against maximum thickness T), which is small at the blade tip (thin blade), and is large at the blade root (thick blade). In this study, we focused on the effects of vortex generator on allowing a significant expansion of the operable range to a higher angle of attack that causes a stall. And the flow visualization and velocity distribution around the airfoil were measured and compared with without of vortex generator. This paper examines in detail around the blades affects flow separation from the blade surface and aerodvnamic characteristics associated with stalls.

Various blades are used for fluid machinery such as wind turbines and pumps. This report focuses attention on wind turbine blades. Wind turbine generator systems consisting of wind turbines with propeller-type rotors on a horizontal axis employ turbine blades to effectively catch aerodynamic forces commonly represented by lift and drag. The thickness ratio of the blade is small at the blade tip (thin blade) and is large at the blade root (thick blade). The previous paper proposed that placing a cylindrical rod in front of a blade as a simplified stall control method for controlling the flow around the blade and avoiding stall phenomena improved the flow on the upper surface of the blade and extended the operable range significantly until the angle of attack reached the high attack angle region where a stall occurred. In this paper, a cylindrical rod in front of the thick blade was placed to examine the behavior of flow aro und the blade by using experimental and studied the effect of the cylindrical rod on the control of stall phenomena.

Water hammer pumps can effectively use the water hammer phenomenon for water pumping. They are capable of providing an effective fluid transport method in regions without a well-developed social infrastructure. The results of experiments examining the effect of the geometric form of water hammer pumps by considering their major dimensions have been reported. However, these conventional studies have not fully evaluated pump performance in terms of pump head and flow rate, common measures of pump performance. The authors have focused on the effects on the pump performance of various geometric form factors in water hammer pumps. The previous study examined how the hydrodynamic characteristics was affected by the inner diameter ratio of the drive and lift pipes and the angle of the drive pipe, basic form factors of water hammer pumps. The previous papers also showed that the behavior of water hammer pump operation could be divided into four characteristic phases. The behavior of temporal changes in valve chamber and air chamber pressures according to the air volume in the air chamber located downstream of the lift valve was also clarified in connection with changes in water hammer pump performance. In addition, the effects on water hammer pump performance of the length of the spring attached to the drain valve and the drain pipe angle, form factors around the drain valve, were examined experimentally. This study focuses on the form of the lift valve, a major component of water hammer pumps, and examines the effects of the size of the lift valve opening area on water hammer pump performance. It also clarifies the behavior of flow in the valve chamber during water hammer pump operation.

Water hammer pumps can effectively use the water hammer phenomenon in long-distance pipeline networks that include pumps and allow fluid transport without drive sources, such as electric motors. The results of experiments that examined the effect of the geometric form of water hammer pumps by considering their major dimensions have been reported. In addition, a paper has also been published analyzing the water hammer phenomenon numerically by using the characteristic curve method for comparison with experimental results. However, these conventional studies have not fully evaluated the pump performance in terms of pump head and flow rate, common measures indicating the performance of pumps. Therefore, as a first stage for the understanding of water hammer pump performance in comparison with the characteristics of typical turbo pumps, the previous paper experimentally examined how the hydrodynamic characteristics were affected by the inner diameter ratio of the drive and lifting pipes, the form of the air chamber, and the angle of the drive pipe. To understand the behavior of the components attached to the valve chamber and the air chamber that affects the performance of water hammer pumps, the previous study also determined the relationship between the water hammer pump performance and temporal changes in valve chamber and air chamber pressures according to the air chamber capacity. For the geometry of components attached to the drain valve, which is another major component of water hammer pumps, this study experimentally examines how the water hammer pump performance is affected by the length of the spring and the angle of the drain pipe.

Recently, as global-scale problems, such as global warming and energy depletion, have attracted attention, the importance of future environmental preservation has been emphasized worldwide, and various measures have been proposed and implemented. This study focuses on water hammer pumps that can effectively use the water hammer phenomenon and allow fluid transport without drive sources, such as electric motors. An understanding of operating conditions of water hammer pumps and an evaluation of their basic hydrodynamic characteristics are significant for determining whether they can be widely used as an energy-saving device in the future. However, conventional studies have not described the pump performance in terms of pump head and flow rate, common measures indicating the performance of pumps. As a first stage for the understanding of water hammer pump performance in comparison to the characteristics of typical turbo pumps, the previous study focused on understanding the basic hydrodynamic characteristics of water hammer pumps and experimentally examined how the hydrodynamic characteristics were affected by the inner diameters of the drive and lift pipes and the angle of the drive pipe. This paper suggests the effect of the air volume in the air chamber that affects the hydrodynamic characteristics and operating conditions of the water hammer pump.

In recent years, public concern about environmental affair is growing at the same time, wind power generation systems have been common, it is required to improve the efficiency of wind turbine blades, leading to its operational stability and high efficiency. In this study, it is examined if the blade surface roughness affects the flow condition around the wind turbine blades to control the blade performance. Specifically, the flow velocity around blades are measured by using the hot-wire anemometer, so as to identify the flow behavior on the blade surface and behind the blades. As a result, flow separation is decreased because of contain roughness on the blade, and it is clarified that flow behavior on the blade surface and behind the blades is changed due to the blade surface roughness.

The relationship between pump performance and vibration generated by cavitation was investigated using an axial-flow impeller. By experiments on cavitation of an axial-flow pump, the growth of cavitation due to the change of the Net Positive Suction Head (NPSH) and the pump performance were clarified. Moreover, the frequencies of cavitaion were disclosed by conducting the wavelet analysis on pressure fluctuation and vibration fluctuation at the casing wall. It was made clear in this paper that the tip clearance cavitation is proven to have a specific frequency.

As wind power generation systems have been common in these days, it is required to improve the efficiency of wind turbine blades, leading to its operational stability and high efficiency. It is introduced in this paper control methods for flow separations with simple devices, by which some improvements of airfoil characteristics can be achieved. By discussing experimentally the effects of both vortex generator installed on the upper side of blade surface and cylindrical rod set in the upstream of the blade on the airfoil characteristic, there methods are effective for improvements of the airfoil performance due to suppressed stall. The aerodynamic characteristics of the device is also verified by measuring the flow velocity just after the blade and by flow visualization using tuft grid method.

The pump was investigated about the behaviors under cavitating conditions. Change in the pump head and the shaft power curves are closely related to the cavitation growth on the suction side of the blades. By experiments on cavitation aspects of an axial-flow pump, the growth of cavitation due to the change of the net positive suction head (NPSH) and the pump performance were clarified. Moreover, the frequencies of cavitaion were disclosed by conducting the wavelet analysis on pressure fluctuation at the casing wall. It was made clear in this paper that the tip clearance cavitation is proven to have a specific frequency.

This study focuses on water hammer pumps that can effectively use the water hammer phenomenon and allow fluid transients without drive sources, such as electric motors. An understanding of water hammer pumps' operating conditions and an evaluation of their basic hydrodynamic characteristics are significant for determining whether they can be widely used as an energy-saving device in the future. However, these conventional studies have not described the pump performance in terms of pump head and flow rate, common measures indicating the performance of pumps, and are not useful in fully evaluating the pump characteristics. As a first stage for the understanding of water hammer pump performance in comparison to the characteristics of typical turbo pumps, this study focuses on understanding the basic hydrodynamic characteristics of water hammer pumps and experimentally examines how the hydrodynamic characteristics are affected by the inner diameter of the drive and lifting pipes, the form and capacity of the air chamber, and the angle of the drive pipe, which are believed to be representative geometric form factors.