In the process of manufacturing aluminum heat exchangers, they are usually brazed in the furnace filled with nitrogen below 20 ppm oxygen concentration. This paper proposes another method to make the environment above and the effect was verified by a model experiment. Firstly, the chamber (as a model of the furnace) is evacuated to a certain pressure. Secondary, it is filled with nitrogen gas. And then, it is evacuated again to 20 ppm oxygen concentration. This method reduces both the amount of nitrogen gas consumption and the time until the oxygen concentration falls enough. Furthermore, this time is found to be the shortest when the initial degree of vacuum p₁ is the same as the secondary p₂.

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The experimental study to investigate the effect of the swirling annular airflow by swirler with guided vanes for flame behavior under the transitional regime on a double concentric bluff-body burner was conducted. Propane gas was employed as the fuel gas and the swirler of the five types was prepared. The result shows that the swirling component of airflow makes a grate contribution to improve the flame stability and suggests that the geometrical swirl number larger than 0.6 and airflow velocity which exceeds a certain value are need to improve the stability. However, the result of the visualization of the flames reveals that the spread airflow by centrifugal force, which is prevented from mixing with fuel, accompanies stabilized flame. The result gives a surmise that it is difficult for the present burner to combine the flame stability and the perfect combustion.

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An experimental study is performed for channel flow with the dielectric barrier discharge plasma actuator (DBD-PA). The plasma actuator consists of two metallic electrodes mounted on both sides of a dielectric plate. The actuator is installed on the bottom wall of a channel passage. The channel height H is changed 6mm and 9mm, and the Reynolds number based on the bulk velocity and hydraulic diameter is varied from 800 to 7000. The wall static pressure is measured at the upper wall of the channel, and the pipe friction factor is evaluated. The velocity profiles are measured by a PIV system at the Reynolds number of 2000 and 4000. The results show that the pipe friction factor decreases by the effect of induced flow with the plasma actuator. The effect is remarkable in the laminar flow region. At the same Reynolds number, the wall static pressure distribution and pipe friction factor remain unaffected by the channel height. When the wave form with voltage of 6 kV and frequency of 2 kHz is applied to the electrode, the friction factor reduction rate of 31% is confirmed in the laminar flow region.

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A new discretization scheme of a Cartesian grid method for flow with heat transfer is proposed. The energy transport equation is discretized directly even in the boundary cells involving either the Dirichlet (isothermal) or the Neumann (iso-heat-flux/adiabatic) boundary conditions in order to ensure the energy conservation in those cells. The basic idea of this discretization is the same as the discretization scheme which is previously proposed by the present authors for boundary forcing in incompressible flow simulations. Moreover, the temperature gradients in both the normal and tangential directions at boundaries are required in the present method for representing the Neumann boundary condition on the Cartesian grids which do not necessarily coincide with the body geometries. The tangential components of the temperature gradients at boundaries are calculated by the extrapolations from the surrounding temperature field. Accuracy evaluations are conducted in a convective heat transfer problem in a flow between concentric cylindrical walls under the several different types of thermal boundary conditions applied at the inner and outer walls. It is confirmed that the present method significantly improves the accuracy orders for the temperature as well as the error magnitudes under both types of thermal boundary conditions. In particular, because the temperature gradients are correctly considered at the boundary cells where the Neumann boundary conditions are enforced, the same level of accuracy order is also maintained even in cases of non-uniformly distributed temperature at those boundaries.

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Noise sources of a turbomachinery installed with a semi-opened scroll casing have been identified by experimental and numerical approaches. The dominant noise is derived from pressure fluctuation coming from motion of the blade because the sound intensity is proportional to 5.4 power of the blade speed. The blade passing frequency (BPF) and the broad band frequency (BBF) is remarkable on the power spectrum of the noise. The measured pressure fluctuation and the computational fluid dynamics (CFD) indicate that the BPF is composed of the interference sound and the rotation sound. Also the interference sound and the rotation sound are compared by the Lowson's equation of far field sound radiated from a rotating object. The BBF is identified by the visualization of Powell's vortex sound source using CFD. It indicates that the vortex sound develops at the leading edge and the bended portion of the blade. The low noise blade and casing have been developed based on the identified noise source. Reduction of BPF and BBF has been verified and enhanced pressure-flow rate performance has been accomplished.

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Steam control valves in power plants are operated under wide range of valve openings and pressure ratios during startup and shutdown transients of the plants. It has been clarified by several researchers that transonic flows and flow fluctuations occur on these valves at a certain range of the operation condition. The transonic flow fluctuation can cause intense pressure fluctuation in the valve and in associating piping. The pressure fluctuation on the valve head yields unsteady fluid forces which can cause forced or self-excited vibrations. In the present study, measurements of the fluid forces are carried out. Using a fixed and misaligned valve, the correlation between the fluid forces and the pressure fluctuations on the valve head surface is confirmed. The time mean fluid force acts as restoring force against the valve head misalignment. Using a valve head exciter, unsteady fluid forces associated with the valve head vibration are measured. The result shows that the unsteady fluid force can provide negative damping force which causes the self-excited vibration of the valve head.

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There is a strong demand for improving brake system performance of Japanese Shinkansen which is a high speed railway to shorten the stopping distance at the time of an emergency such as a huge earthquake. An emergency brake for conventional train is a wheel disk brake system that is affected by rail tread surface condition (dry or wet condition), because of using friction (adhesion) between a wheel and rail. In order to achieve a high deceleration at the time of over 300 km/h, another complementary brake system guaranteed a stable braking force without the friction is required. In addition, it has to be a lightweight and small equipment space so that a passenger cabin capacity may not be affected. In this study, we discussed a small-sized aerodynamic brake system using an air drag panel. From the computational fluid dynamics using turbulent flow model and the wind tunnel experiment, the suitable shape of air drag panel, arrangement and an opening-and-closing mechanism of the panel were developed. In addition, a full-scale prototype aerodynamic brake device was designed and manufactured. Its aerodynamic characteristics were examined on a large wind tunnel with high Reynolds number. It was proven that the target braking force can be obtained with the small-sized aerodynamic brake placed into a thick turbulent boundary layer around the train at a running speed of 300 km/h.

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Polymer solution shows complex behaviors, which are merits and demerits in industries. For a molding process, a fiber spinning process and a turbulent drag reduction system, concentrated or dilute polymer solutions are used. In these processes, characteristics of extensional viscosity should be important. For example, increments of extensional viscosities due to polymers are considered as one of the reasons for the drag reduction occurrence. In this study, we propose a simple technique to measure the extensional viscosity of Newtonian and non-Newtonian fluids in abrupt contraction flows. The abrupt contraction flow was realized by connecting a syringe and a thin glass tube under a polarizing microscope. The syringe was filled with Newtonian and non-Newtonian fluids, and a syringe driver control to push the fluids out. The force to push the syringe was measured by a load cell to calculate the pressure added to the flow. Extensional viscosity was calculated by considering the pressure losses in the abrupt contraction flows. Water was measured as a Newtonian fluid, and polymer solution was measured as a non-Newtonian fluid. Extensional viscosity of the polymer solution measured in this study qualitatively shows the reasonable characteristics.

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HCCI operating range can be expanded by using two fuels with different ignition characteristics. In this study, the effect of oxidation characteristics of main fuel on the operating range was investigated. Toluene and methane were used as main fuel, and DME as ignition trigger fuel. Engine experiments using a single cylinder research engine showed that methane/DME HCCI operating range extended to higher equivalence ratio compared with toluene/DME HCCI. This is explained by numerical analysis based on elementary chemical reaction model that steep heat release rate can be controlled when higher ignition temperature fuel is used, because time lag between the first stage of high temperature oxidation induced by decomposition of hydrogen peroxide (H₂O₂) and onset of chain-branching reaction of main fuel increases. It was also found that the higher the reactivity with OH, the more the trigger fuel requirement, because low temperature oxidation of the trigger fuel was suppressed.

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The effects of the large-scale structure in a channel flow on turbulent heat transfer were investigated by using the high resolution Direct Numerical Simulations (DNS) database. The configuration is a fully developed turbulent channel flow with the constant wall-temperature difference condition. DNS database are the Reynolds numbers based on the friction velocity and the channel half-width of 150, 400, and 1000 and the molecular Prandtl number of passive scalar is 25. Joint probability density function (JPDF) profiles of the Reynolds shear stress and the wall-normal turbulent heat flux are independent of Reynolds number, outside the extent of the impact of the channel center or thermal boundary conditions. Though, a larger contribution of sweep events to both of the Reynolds shear stress and the wall-normal turbulent heat flux on the quadrant analyses, and one of strong turbulent intensities on the JPDF analyses, are founded with increase of Reynolds number. Furthermore, at the buffer layer, contributions of ejection events only to the wall-normal turbulent heat flux are increased with increase of Reynolds number.

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A triangulated surface with rigid plates is investigated as a model of heterogeneous membranes by using the canonical Monte Carlo simulation technique. The small rigid plates are included on the triangle surfaces as an analogue of heterogeneous components such as membrane proteins in membranes. The size of plate is negligible compared to the surface size in the thermodynamic limit. We assume three different densities for the total number of rigid plates. By fixing two rigid plates, which are separated by the distance L, on the surface, we calculate the string tension σ between these two terminal plates. We find that the dependence of σ on L is considerably different from that of the model without the plates. The implication of this result is intuitively discussed.

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To increase load factor of nuclear power plants, it is necessary to decrease the number of days needed for periodic inspection and the number of days of unplanned outages. One of the countermeasures for these issues is to establish a prediction method for pipe wall thinning. There are two phenomena to be considered in pipe wall thinning. They are flow accelerated corrosion (FAC) and liquid droplet impingement erosion (LDI). In boiling water reactors (BWRs), LDI tends to influence pipe wall thinning more than FAC does. LDI is the wall thinning phenomena caused by droplet impingement. It is necessary to develop an appropriate method to predict the location of wall thinning. In this paper we compared measured data with computational analysis results for the location of wall thinning. By defining that the droplet frequency distribution had double peaks at the extrapolated location from the wall of an orifice toward downstream, we were able to predict the central location of the large reduction in thickness with a difference of less than about 0.2D[mm](D: pipe diameter) from the measured location in the flow direction at the elbow.

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To utilize coal ash slag as aggregate, coal ash has to be completely-fused and recovered as amorphous granulated slag, same as granulated blast furnace slag. We designed the new coal ash fusing furnace consisting of two chambers to increase ash load and to inhibit the recovery of incompletely-fused slag. The upper chamber is the existing vertical cylindrical furnace and the lower chamber is the new horizontal furnace. In the upper chamber, coal ash is transferred near the inner wall by centrifugal force, and is trapped at the surface of fused slag, and then flow down to the lower chamber. When the ash load of the upper chamber increased, the rate of amorphous slag content decreased because of increasing incompletely-fused slag. To enhance heating, the lower chamber which has some burners was installed just below the upper chamber. In the lower chamber, what is called slag-bed furnace, the incompletely fused slag is fused completely during flowing down onto the bottom of the furnace. Then, we designed the new coal ash fusing furnace, the inner diameter of upper chamber was 0.6 m and the length of lower chamber was 1.8 m. We verified that to recover 100 % amorphous slag content at the ash/coal (kg/kg) ratio 4.6, the necessary fuel quantity of the furnace was 30 kg/h coal and 5.87 m³N/h LPG. Accordingly, the effect of slag-bed furnace to increase ash load was confirmed.

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In many countries, stricter exhaust emissions regulations are being set, and diesel particulate filter (DPF) has been developed to reduce particulate matters (PM). So far, the experiments using engine test bench for the DPF development are conducted. It is expected that an engine test bench could be performed under nearly real condition, but it is affected by intake air, fuel properties, and engine condition. In this study, using carbon particles as model diesel particles, we evaluated the filtration and regeneration performances of SiC-DPF. In filtration test, we observed the transition between depth filtration to surface filtration. Based on the regeneration test, it is found that carbon particles are oxidized at 400 degree centigrade. At 600 degree centigrade, the filter regeneration is largely promoted, which is suitable temperature for practical purpose. Continuously regeneration is achieved at 550 degree centigrade, which is a balance point where the oxidation rate is equal to the inflow rate of the carbon particle.

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This study is a numerical analysis on propagation behavior of a three dimensional detonation in a square tube and, influence on motion trajectories of high pressure region (shock triple points) due to the change of tube width was solved by a finite difference method which consists of the semi-implicit MacCormack method and TVD scheme in order to prevent numerical stiffness and Gibb's phenomena. Gas utilized in this computational study is the stoichiometric hydrogen and oxygen gas mixture composing 19 elementary reactions with 8 chemical species. It was found from numerical results that the behavior of shock triple points was classificated in three kind of modes. Furthermore, it was seen that the aspect ratio of the detonation cell became nearly constant value for each mode.

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Bessel beam has been gaining strong attention from various applications. In this study, a new concept for generating zero-order Bessel beams was studied theoretically and experimentally. The principle of the generation of a Bessel-like beam is discussed based on Fourier optics. A preliminary model is proposed that accounts for heat conduction and diffraction effect. Analytical modeling results indicated that Bessel beam can be generated by using a thermal lens and a convergent lens. A simple and flexible method to convert a Gaussian laser beam into a Bessel-like beam with a long and narrow focal line by using a thermal lens effect is demonstrated experimentally. Experimental and calculated results show a good agreement for generation and characteristics of Bessel-like beam. Experimental results also show that the focal depth of the Bessel beam can be controlled by adjusting some parameters in the thermal lens system. The paper concludes with suggestions for further research and potential applications for the work.

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The new type of heat exchanger, in which fuel gas flows inside thin tubes and water is shell-side, was proposed to develop the performance and compactness of shell & tube type heat exchanger for latent heat recovery from flue gas. The effects of tube diameter (1.0～5.0 mm) and heat exchanging length (7～100 mm) on the heat transfer characteristics of a single tube were systematically investigated by measuring the gas outlet temperature, the pressure loss of the gas, and the condensation rate for moist air. It was shown that the usage of thinner tubes was remarkably effective to achieve the high performance. That is, the rapid temperature drop near inlet occurred and high heat transfer rate was realized for thinner tubes of 1.0mm and 2.0mm in inner diameter compared with thicker tubes because of small heat capacity flow rate and high heat transfer coefficient. In addition, the increase in the volumetric heat transfer area in thin tube type heat exchanger contributed to the compactness. Furthermore, although the pressure drop increased with decreasing tube diameter, it was possible to keep it within the tolerance level for the heat exchanger of domestic hot water supply for practical use because of shorter length of thin tubes. It was shown that one twentieth of heat exchanging volume was possible to be downsized by changing small tubes of 1.0mm from 5.0mm.

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The melting furnace of a municipal solid waste gasification and melting system must have a high slag recovery rate and low dioxin emission. In this study, we developed a vertical swirling melting furnace with multistage air nozzles which can be used in the gasification and melting system. Three stage nozzles for feeding air and fuel are installed on a cylindrical furnace. Each nozzle is arranged in a tangential direction to generate swirling flow. The fuel is supplied by the primary nozzle which is located at the lowest level among the nozzles. Combustion air is supplied by the secondary and tertiary stage nozzles. The flow pattern of this furnace is similar to that of a cyclone separator. Most of the fuel goes down to the bottom of the furnace and burns in the swirl flow. The furnace design was done using a one-dimensional heat balance simulation tool. In this simulation, distribution of air mass flow in the furnace was determined by an air flow model experiment. The simulation results were compared with measured data from a 20t/day demonstration plant, and accuracy of the developed design tool was verified. The temperature prediction error was less than 40 degC. In the demonstration plant, the slag recovery rate of the melting furnace was higher than 90%, and the dioxin concentration in the flue gas at the chimney was lower than the government regulation value.

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We performed two-dimensional unsteady calculations of reactive flows, based on the compressible N-S equation, to study the effects of unburned-gas temperature on the instability of flame fronts. As the unburned-gas temperature became lower, the growth rate decreased and the unstable range narrowed. This was due mainly to the reduction of the burning velocity of a planar flame. The normalized growth rate increased with a decrease of the unburned-gas temperature, and the normalized unstable range widened at Lewis numbers smaller than unity. This was because that the thermal-expansion effects became stronger owing to the increase of the temperature ratio of burned and unburned gases, and that the diffusive-thermal effects strengthened at Lewis numbers smaller than unity owing to the increase of the Zeldovich number. Moreover, the cellular shape of flame fronts formed, which was due to intrinsic instability. The normalized burning velocity of a cellular flame increased as the unburned-gas temperature became lower, especially in premixed flames with small Lewis numbers.

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