Yutaka Hasegawa

Unsteady Pressure Distributions on the Impeller Blades of a Centrifugal Pump-Impeller Operating Off-Design

Pressure distributions on the impeller blades of a centrifugal pump were examined experimentally. The periodic pressure change caused in the suction and delivery pipes by the interaction between the rotating impeller blades and the dividing ridge of the volute casing was small. However, a noticeable cyclic change in the pressure on the blade surface was measured and related to the nonuniform pressure distribution in the volute casing at off-design flow rates. In a lower than normal range of flow rates this pressure fluctuation was largely increased near the leading edge of the blade due to the turbulent fluctuations and the flow separation from the blade surfaces. These periodic pressure changes have a large effect upon cavitation inception along the impeller periphery.Copyright

Flapwise and Edgewise Blade Loads Analysis of HAWT Rotor by Using Fluid-Oscillation Coupled Calculation Model

A horizontal axis wind turbine suffers fluctuating aerodynamic loads, which result in oscillations of the rotor blades. Since the blade oscillation has considerable effects on the blade fatigue life, the influence on the fatigue loads from the interaction between the aerodynamic loads and the structural oscillations should be considered in the design process of the wind turbine rotor. The objective of this work is to analyze the aerodynamic effects on the fatigue loads of rotor blade due to structural oscillation and inflow conditions, by using numerical calculation method. This paper explains a calculation model which can estimate the aerodynamic loads on the rotor blade of the horizontal axis wind turbine in the inflow conditions with the turbulence and yawed misalignment. The fluid-oscillation coupled calculation has been performed for the geometry of the NREL test turbine. The calculated results are compared with the experimental results to evaluate the validity of the calculation model.Copyright

Fluid-Oscillation Coupled Analysis for HAWT Rotor Blade (One Degree of Freedom Weak Coupling Analysis with Hinge-Spring Model)

Since large-scale commercial wind turbine generator systems such as MW-class wind turbines are becoming widely operated, the vibration and distortion of the blade are becoming larger and larger. Therefore the soft structure design instead of the solid-design is one of the important concepts to reduce the structural load and the cost of the wind turbine rotors. The objectives of the study are development of the fluid-structure coupled analysis code and evaluation of soft rotor-blade design to reduce the unsteady structural blade load. In this paper, fluid-structure coupled analysis for the HAWT rotor blade is performed by free wake panel method coupled with hinge-spring blade model for the flapwise blade motion. In the model, the continuous deflection of the rotor blade is represented by flapping angle of the hinge with one degree of freedom. The calculation results are evaluated by comparison with the database of the NREL unsteady aerodynamic experiment. In the analysis the unsteady flapwise moments in yawed inflow conditions are compared for the blades with different flapwise eigen frequencies.

Heat Transfer and Pressure Drop Characteristics of Finned Tube Banks in Heat Exchanger for Gas Turbine

In recent years the requirement for reduction of energy consumption has been increasing to solve the problems of the global warming and the shortage of petroleum resources. For example in the power generation field, as the thermal power generation occupied 60% of the power generation demand, the improvement of the thermal efficiency is required considerably. This paper described the heat transfer and pressure drop characteristics of the finned tube banks used for the heat exchanger in the thermal power generation. The characteristics were clarified by testing the serrated finned tubes banks for improvement of higher heat transfer and the conventional spiral finned tube banks under the same test conditions. The equations to predict heat transfer coefficient and pressure drop which are necessary on design of the heat exchanger were proposed.© 2004 ASME

Analysis of Unsteady Flow Around Airfoil of a HAWT by Vortex Method

Vortex methods have features such as relatively simple algorithm, no grid-generation in flow field and lagrangian scheme which traces each vortex element concentrated in a tiny region. It is considered that the vortex methods are effective tools for the analysis of three-dimensional, incompressible and unsteady outer flow such as flow around wind turbines. Recently, vortex methods are employed as engineering tools for three-dimensional unsteady flow. In a flow simulation by vortex methods, accuracy of simulation depends chiefly on the vortex creation model on the wall and the viscous diffusion effects. However, it seems that the deterministic model to introduce the vortex element created on the wall into flow field has not yet been accomplished. In this paper, an introduction model of vortex elements from the wall into flow field is proposed. This model is based on the analogy of the consideration of boundary-layer. In this model, intensity of vortex elements created on the wall is determined by applying both no-through and no-slip boundary conditions and the diffusion height of each element created on the wall is determined dynamically. To investigate the applicability of the model, proposed method is applied to flow around impulsively started airfoil section.Copyright

Effects of Coriolis Force on Instability of Laminar Boundary Layer on a Concave Surface

Stability of laminar boundary layer having a mean velocity of Pohlhausen type was studied by solving numerically the perturbation equations when the boundary layer is subject to curvature and Coriolis force. When the channel rotates so that the Coriolis force acts toward the concave wall, the Taylor-Gortler vortices are generated on a concave surface with a weaker curvature than that in the stationary condition because of the instability effects of the Coriolis force. Vortices are suppressed and the critical Gortler number is increased when the Coriolis force acts opposite to the centrifugal force due to the wall curvature. Over a wide range of rotation rate, vortices with scales as large as the boundary layer thickness are easily generated.Copyright