In the past decade, high-pressure direct injection systems in petrol engines have widely penetrated in the market supported by the raising environmental consciousness. The essential component of a gasoline direct injection system is the high-pressure fuel pump, which pressurizes the petrol as high as 20MPa. High-pressure fuel pump commonly used is single-cylinder type driven mechanically by the cam-shaft. This typically generates inherent undesirable high pressure pulsation noise which renders the sound of the traditionally petrol engine similar to that of a common-rail diesel engine. In this paper, we will describe the method we deployed to mitigate the high pressure pulsation noise. We applied Taguchi methodology to search for the sensitive design parameters. As a result, by modifying design parameters of the outlet valve, we confirmed 48% reduction of pulsation noise.

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Closed-type centrifugal impellers with single-blade are widely used as sewage pumps. However, they are geometrically asymmetric, thus resulting in significant changes in the circumferential static pressure distribution of the impeller as it rotate, which is believed to drastically change the radial and axial thrusts. To improve pump reliability, it is therefore necessary to quantitatively understand unsteady hydrodynamic forces, and to clarify the behavior and mechanism of generated hydrodynamic forces. This study investigates the radial and axial thrusts acting on a single-blade centrifugal impeller by component analysis. As a result, the behavior of the components of the radial and axial thrusts was clarified. In the time-averaged value of the radial thrust of the hydraulic part, the pressure component is dominant and the momentum component acts in a direction that offsets the pressure component. Although the momentum component is dominant in the time-averaged value of the axial thrust of the hydraulic part, it is mostly offset by the pressure component.

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The wind turbines with a flanged-diffuser shroud -so called “wind-lens turbine”- are developed as one of high performance wind turbines by Ohya et al. The steady and unsteady wind turbine performances are investigated in the paper. The flow structure around the compact-type wind lens turbine is made clear by PIV and CFD in steady wind. Also, that turbine show higher efficiency than the conventional wind turbine. Furthermore, the performances of the conventional wind turbine and the compact-type wind-lens turbine in unsteady wind are experimentally and numerically investigated. Experimental and numerical examples are presented to demonstrate the dependence of frequency of the harmonic oscillating velocity wind on the power coefficients. Consequently, using the present designed rotor, the compact-type wind-lens turbine shows better performance than the only rotor one in sinusoidally oscillating velocity wind. Moreover, the numerical estimation can predict the power coefficients for the fluctuating flows in 94 to 102% of accuracy.

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Lift and drag characteristics of a symmetric airfoil with miniature electromagnetic actuators have been investigated when an angle of attack has been increased at a constant speed in a low Reynolds number range. It was revealed that the dynamic actuation of the miniature actuators was effective to delay the stall. A basic example of a feedback control, in which the time series lift was used as the input signal to detect the stall and had a role to start the actuation of the miniature actuators, was tried and it could achieve the increase of the lift, that is, it could delay the stall. Second example of a feedback control including the increase and decrease of the angle of attack of the airfoil was demonstrated to be effective not only to recover the lift after the stall but also to maintain the high lift situation.

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Numerical simulation method of High Intensity Focused Ultrasound (HIFU) propagation in bubbly fluid (microbubbles in liquid) is proposed for observing the ultrasound wave propagation, the bubble motion at focal area and the ultrasound power at the focal point in this paper. The governing equations are the acoustic wave equation derived from the equation of fluid and the Keller equation (bubble volume motion equation). These equations are discretized by the finite difference method. Additionally, the linear dispersion relation is derived from governing equations. First, the present method is validated on grid convergence and compared with experiment and theory. Second, HIFU in bubbly fluid is simulated for various initial void fraction and bubble radius to observe the difference of pressure field and difference of bubble motion.

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Flow around an in-line forced oscillating circular cylinder was simulated numerically by using OpenFOAM in order to clarify the mechanism of flow induced vibration. Immersed boundary Method is used to solve the moving boundary. Reynolds number is set to 1000 and the reduced velocity is set to the range from 0 to 10. In the first excitation region, it is shown that negative drag force which is a factor for an in-line oscillation of a circular cylinder comes from contacting between high pressure region and a circular cylinder. The present simulation shows that twin vortex has an important role on the contact phenomena. In the second excitation region, it is shown that time averaged lift drag doesn't become zero on some oscillating conditions. It is considered that a cross-flow oscillation comes from the phenomena.

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An accident scenario of Fukushima Daiichi Nuclear Power Plant, Unit 2 is analyzed from the data open to the public. Phase equilibrium process model was introduced that the vapor and water are at saturation point in the vessels. Proposed accident scenario agrees very well with the data of the plant parameters obtained just after the accident. The estimation describes that the rupture time of the reactor pressure vessel (RPV) was at 22:50 14/3/2011. The estimation shows that the rupture time of the pressure containment vessel (RCP) was at 7:40 15/3/2011. These estimations are different from the ones by TEPCO, however; many measured evidences show good accordance with the present scenario.

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In this paper, non-catalytic partial oxidation reaction (fuel-rich combustion) of methanol was investigated experimentally when the reaction was stabilized in the vicinity of the ceramic honeycomb as a porous material inserted in the reactor. The experiment was conducted under various conditions of the gaseous mixture flow rates and velocity profiles. Temperature distributions of combusting gas and honeycomb surface were measured and the flame shapes were observed to evaluate the reforming characteristics and the reaction stability. Better stability and higher conversion rate were achieved in a wide turn down ratio range when the conical flame was formed. However, in the considerably smaller flow rate conditions, the flame attached to the honeycomb and the methanol conversion was deteriorated due to the heat loss effect of the honeycomb. In too much high flow rate conditions, on the other hand, the flame was stretched asymmetrically and the reaction became unstable. By introducing the mixture gas as a central jet in the reforming chamber, the stability of the flame was improved without deteriorating the reforming efficiency since the smaller velocity gradient in the near-wall surrounding region enhanced the flame stability.

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Effect of gas temperature on NOx removal by using dielectric barrier discharge (DBD) was investigated experimentally. NO/O₂/N₂ system was used as the test gas. The initial NO concentration was set as 100ppm. The experiment was conducted under two conditions with and without oxygen. The gas temperature was changed in a range of T_g=20°C～260°C. As the result, in the case of NO removal in nitrogen atmosphere (O₂=0%), NO was mainly reduced by N radical and several ppm of NO₂ and N₂O were produced. NOx removal efficiency at T_g=20°C (room temperature) was slightly higher than that at T_g=60～260°C. On the other hand, in the case of NOx removal in oxidative atmosphere (O₂=10%), NO was mainly oxidized by O₃ and reduced by N radical at T_g=20°C. At higher gas temperature conditions (T_g=60～260°C), NO_X concentration exceeded the initial NO concentration of 100ppm. The oxidation of NO with O₃ was controlled because the amount of O₃ was deceased due to the thermal decomposition of O₃. Also, NO, NO₂ and N₂O were produced by corona discharge in oxidative atmosphere. Thus, it was considered that the increase of NO_X in high temperature condition was caused by the thermal decomposition of O₃ and the formation of NO, NO₂ and N₂O.

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