In order to reduce measurement errors and fill missing data points, we have already proposed the cost function method (CFM) in which governing equations are applied to the correction and interpolation of measured data. In this paper, in order to study the applicability to the unsteady flow fields, we compare the properties of CFM with those of the four-dimensional data assimilation (FDDA), which is a method that is conventionally applied to unsteady flow fields in the field of numerical weather prediction. It was found that CFM produces a more suitable solution that does FDDA, according to our evaluation criteria. Then we applied PIV to a Karman vortex flow behind a plate and applied CFM to the data obtained. Furthermore, we examined the effect of the number of measured data points on the CFM results. It was found that the CFM is effective in correcting errors in the data, and also in filling missing data points smoothly both spatially and temporally. It is difficult to model a complicated flow field correctly using PIV or CFD separately. However, we can conclude from the results of this study that for the estimation of flow fields, CFM may be an effective technique also for unsteady flow.

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The effects of the different thermal wall boundary conditions on the turbulence statistics are investigated using direct numerical simulation (DNS) of the incompressible turbulent channel flow with passive scalar transport. The flow between isothermal walls with same temperature (Case 1), the flow between isothermal walls with a temperature difference (Case 2), and the flow between isothermal and adiabatic walls (Case 3) are considered. The simulations are carried out on the flow with Reynolds numbers based on the channel half-width and wall friction velocity of 150 and 300, and with Prandtl number of 0.72. The present DNS shows that the absolute value of correlation coefficient between velocity and temperature fluctuations near the adiabatic wall (Case 3) is much smaller than those of Cases 1 and 2. It is shown that turbulent Prandtl number varies linearly with the square of wall unit very close to the adiabatic wall. In addition, the budgets with respect to the temperature variance, its dissipation rate, and turbulent heat fluxes near the adiabatic wall are clarified.

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Full three-dimensional unsteady dynamic simulations of forced liquid jets flowing into and pinching off in ambient of another liquid have been performed using the level set method for tracking the interface between the immiscible materials. Two different viscosity ratios between the inner and outer fluids chosen are 0.17 and 1.7 while the density ratios are about unity. The jets have been forced at Strouhal number of 4.0. The Reynolds, Froud, and Bond numbers based on the conditions at the nozzle exit are 34-35, 0.2, and 6.1, for both cases. The results are compared with the experimental data with reasonable satisfaction. The comparisons are for flow images of one complete pinch-off cycle and axial and radial profiles of the instantaneous velocities around the region of jet disintegration. Although the level set method has shown its promising feature, due to the surface tension model, it requires very fine grid resolution (20 mesh cells for the diameter of a droplet, the Weber number based on the grid spacing is smaller than 1.0×10^-2) even for capturing such laminar surface phenomena.

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Lift forces on both clean and contaminated spherical gas bubbles rising near a vertical wall were determined experimentally below Reynolds number (Re) of 60. We developed an experimental apparatus in which a CCD camera with a microscope follows the rising bubble. We used it to precisely measure the bubble radius, the rising speed and the distance between the bubble and the wall and then estimate the lift force for Re<60. The results show that the lift coefficient of the fully contaminated bubble is always positive due to the viscous effect and the predicting equation for the lift coefficient which was proposed for Re<20 can be applied for Re<60. On the other hand, the lift coefficient of the clean bubble is positive for Re<30. However, the coefficient becomes negative for Re>45 and the attractive force acts on the bubble due to the inertia effect. Consequently, it is found that the surface condition affects on the lift force acting on the bubble rising near the vertical wall.

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In this study, a voxel Cartesian grid method combined with cut cells has been developed for simulating two-dimensional unsteady, viscous, and incompressible flows with arbitrary boundaries. The volume of fluid (VOF) approach based on finite volume method (FVM) is employed to accurately discretize the governing equation in Cartesian cells that are cut by irregular boundaries. The Cartesian grid cells and their faces are managed using a volume computer aided design (V-CAD) data system but not additional grid generation. The precision of the solution in the cut cells is ensured by special discretizations near the embedded boundaries. The accuracy and robustness of the method developed are validated by simulating a number of canonical viscous flows, and the ability of this method to simulate flows with complex geometry boundaries is also demonstrated by some numerical examples. Overall, extensive practical applications of the numerical analysis method proposed in this study could be expected.

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A high-lift system is a crucial part of aircraft design because it influences takeoff and landing performance. Computational fluid dynamics as well as wind tunnel test has been recently incorporated into high-lift design and a multi-element airfoil is used to optimize high-lift performance. To estimate the high-lift aerodynamics of multi-element airfoils, two-dimensional compressible unstructured Navier-Stokes code with Spalart-Allmaras one-equation turbulence model is presented. For this validation, subsonic flows over a two-element configuration, NASA Model-B airfoil, and a three-element configuration, RAE 2815 airfoil, are computed. On surface pressure coefficient distributions and boundary-layer velocity profiles, the present computed results show good agreement with the wind-tunnel testing data. Also performed are the computations of subsonic flows over a five-element configuration, NASA Model-D airfoil, to demonstrate the possibility for more complex geometry. The present code is expected to be powerful tool for high-lift design.

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Stratified turbulence is analyzed using the rapid distortion theory (RDT) in the Craya-Herring frame, in which the wave components and the vortex components are separated automatically and the difference in the behaviors of two modes is shown more clearly than the previous analysis which utilized the usual Cartesian frame. In this study we have explicitly calculated the time development of the energy partition among the wave, vortex and potential energy components which clearly represents the oscillatory behaviour due to the buoyancy force or the steady behavior unaffected by the buoyancy force. We have verified the equi-partition between the wave component of kinetic energy (E_w) and the potential energy (PE) in the long-time asymptotics, which has been observed in the previous DNS. This occurs quite generally irrespective of the initial conditions such as the isotropy of turbulence or the initial energy partition.

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Numerical simulation of velocity and stress fields for flowing powder comprised of an infinite number of particles presents a most difficult problem in powder technology. The Distinct Element Method (DEM) is useful for determining each particle trajectory which involves multi-body interactions. However, total particle can not be computed using DEM. The particle number which can be calculated for a three-dimensional spherical system would be in the hundreds of thousands. A description of flow characteristics for a small amount of powder would not be paractical. Simulation within a tank would thus be virtually impossible. The authors have conducted numerical simulation of flowing powder using the smoothed particle hydrodynamics (SPH) through application of continuum dynamics. Glass beads (particle diameter : 100 μm) were used in the present study as test powder stored in a tank and discharged by gravitational force. Calculated velocity distribution, free surface in the tank and the rate of discharge were compared with experimental data and a good agreement was noted. Based on the results of this study, SPH in conjunction with the model equation for yield stress appears quite useful for simulating the flow of fine powder.

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In order to consider the rotating source-sink flow which is applicable to an accurate wet-type centrifugal classification system, we numerically studied the structure of through-flow within a rotating axisymmetric container, focussing on the almost rigidly rotating flow developing with decreasing Ekman number for a very small Rossby number. Consequently, in the almost rigidly rotating flow in a rotating squarish doughnut-shaped container with the source and sink at corners of outer and inner walls, an axial velocity component was found to singularly increase in magnitude near the source and sink. Also, the axial-transport thickness defined by an axial velocity component and the displacement thickness defined by an angular momentum were found to correspond to E^1/3- and E^1/4-Stewartson layers, respectively. Next, we numerically studied particle motions in the almost rigidly rotating flow in a radially-inward-expanding axisymmetric container, and obtained the result that the cut size can be controlled by angles of walls with hardly decreasing the classification accuracy in this flow field.

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Measuring techniques such as Laser Doppler Anemometry (LDA), Particle Image Velocimetry (PIV), Particle Tracking Velocimetry (PTV) and Holographic Particle Image Velocimetry (HPIV) depend on the velocity information obtained from a micron-sized particle traveling in a fluid. The traceability of these particles to any velocity changes in a flow field is one of the key assumptions, in applying such techniques. However, in the flow field with large velocity gradient, this assumption would become improper. This paper shows a numerical investigation for the motion of tracer particles in the presence of steep velocity gradient across a steady shock wave. Various particles with different radius and density are taken into account. The particle motions are simulated by using Basset-Boussinesq-Oseen (BBO) equation. The contribution of each term in the equation to particle behaviour is investigated. The results indicate that the non-dimensional settling length can be estimated only from the particle diameter.

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An anemometry using tracer particle, such as PIV and LDV, has some errors related to the deviation of particles from the stream, particularly around the large velocity gradient. But the reasonable correcting procedure has never been established. For a notable example, we have investigated the behavior of particle when it passes through a shock wave. In the first report, the effects of particle density and size are clarified by carrying out the simulation with the weak shock theory to the flow field and the BBO equation to the traveling particle. In the present paper, shock wave oscillation and nonuniforme particle size are taken into account, to realize the more exact experimental conditions. The results suggest that the turbulence detected in measurement contains the considerably large amount of errors concerning with the particle property used. In particular, the dispersion of particle diameter is more serious.

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We present a new numerical method to simulate unsteady fluid flows under a wide range of Mach number conditions : supersonic to natural convection. This method titled QCAM is based on a quasi-conservative formulation for momentum and energy advection. The TVD scheme extended for the present formulation is used to suppress spurious oscillations of the primitive variables (v and E) arising near shock front and contact discontinuity. The Newton iteration is applied to solve coupled equations of mass, EOS, and energy evolution with the div (pv) term, thus accurate mass conservation and the implicit relationship among the status variables are preserved. Some representative calculations (Mach number 2 to 5×10^-5) show that this method sounds good. In particular the QCAM produced as accurate solution as strictly conservative AUSM code for high speed flow regime, and also has high potential to reduce CPU time and memory requirement due to its simple structure.

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Blade stresses of 3-bladed inducer were measured under various cavitation numbers. At the transition point from asymmetric cavitation to cavitation surge, the pattern of the cavity on each blade changes irregularly with keeping the asymmetric cavitation pattern. The blade stress fluctuates between zero and a value observed under the non-cavitating condition. Under the firing test of LE-7 A engine for H-IIA rocket, the same phenomenon was observed through the measurement of shaft vibration. The result of that firing test is also shown for comparison.

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This paper concerns the secondary flow due to pulsating flows with various frequencies in a U-shaped pipe, solved by a finite difference method with CIP and fractional step methods in a general coordinate system. The streamwise velocity distributions obtained are confirmed with experimental results. The resultant secondary flow is complicatedly changed by the induced secondary and third vortex cores. The intensity of the secondary flow does change throughout the curved pipe, indicating the flow is still developing even at the exit. The overall intensity of the secondary flow within the pipe increases with an increase in the pulsating frequency.

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The response characteristics and suppression of flow-induced vibration of rectangular prisms with various width-to-height ratios were experimentally investigated. The present study focused on rotary oscillation, which is one of flow-induced vibrations generated in a rectangular prism. In this paper, the response characteristics on elastically supported prisms were first examined in detail by free-vibration test. Next, flow-induced vibrations obtained by the free-vibration test were reproduced by forced-vibration test, and then the generation mechanism of flow-induced vibrations was examined on the basis of the visualized flow patterns, fluctuating pressure distributions of the surface of prism and characteristics of flow-induced vibrations by the flow control. The main findings were that (i) there are three types of flow-induced vibrations, i. e., vortex excitation, low-speed torsion flutter and high-speed torsion flutter, (ii) flow-induced vibrations can be classified into six patterns depending on the width-to-height ratio, (iii) flow-induced vibrations occur due to change in fluctuating pressure on the surface of the prism based on the difference of the behavior of the shear layer separating from the leading edge, the impinging leading-edge vortex, and the wake vortices, and (iv) generation of low-speed torsion flutter and vortex excitation is completely suppressed by adopting large values of the reduced mass-damping factor, however, high-speed torsion flutter occurs regardless of the reduced mass-damping factor.

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Discrete frequency noise of a cross flow fan is generated by periodic flow fluctuation according to the rotation of an impeller. The interference of an impeller and a stabilizer is known as the main noise source. In this work, the discrete frequency noise source and the characteristics of the sound propagation of a cross flow fan were visualized according to operation points. The time sequential propagation of the sound wave was reconstructed by using an acoustic holography method. From the visualization of the discrete frequency noise, the following results were obtained. When the flow rate coefficient is large, the dominant discrete frequency noise source was observed at the contiguous area of an impeller and a stabilizer. And it shifts to the contiguously point of an impeller and a casing wall according to the decrease of the flow rate coefficient.

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In the present paper, presented are experimental results of observation of liquid-solid contact and bubble behaviors around the critical heat flux of saturated and subcooled pool boiling on a plate of single crystal sapphire. The observation is conducted from the backside of a rectangular boiling surface and also from the side and backside of a boiling surface with a narrow width. The main results obtained are summarized as follows. The bubble base area is almost dry and lateral coalescence of bubbles forms coalescent dry areas. As the wall superheat increases, liquid-solid contact becomes like a canal meandering through dry areas. The dependency on the surface superheat of the contact-line length density (CLLD) which is defined as the total length of the boundary between wetted and dry areas in a unit area is almost the same as the boiling curve, and the value of CLLD at CHF is not strongly dependent on boiling liquid and subcooling. The relation of the number density of dry areas and their equivalent diameter in the large dry area region at CHF is not dependent on boiling liquid and subcooling, and it is similar to that of dropwise condensation.

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An experimental investigation of the effect of concentration of inversely soluble polymer solutions on minimum film boiling temperature T_min has been performed. The vapor film thickness was determined by analyzing digitalized photographs using a computer. The minimum film boiling temperature has been investigated experimentally in order to clarify the mechanism of vapor explosion suppression. Polymeric solutions, Poly (ethylene oxide : PEO), of concentrations ranging from 0 to 600 wppm are used. A 30 mm diameter, hemispherically-ended, stainless steel (SUS 304) rod was heated by gas tourch and was quenched in PEO solutions of various concentrations at temperatures ranging from 30°C to 90°C. The measured results for T_min decrease with increasing PEO concentration. The vapor film thickness around the heat transfer surface in PEO 600 wppm solution is larger than that in water for the same temperature. These results suggest that the dilute PEO solution suppresses vapor explosions.

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Motion of silicone-oil and water droplets induced by the Marangoni force was numerically simulated by using the two- and three-dimensional second order finite difference methods with the CIP and the level set methods. The surface tension was introduced by using the continuum surface force (CSF) method. The results clearly showed the flow induced by the Marangoni force and the dependence of droplet motion velocity on droplet size, contact angle, temperature gradient, and fluid properties. The Marangoni force balanced with the viscous force in the small contact angle case ; on the other hand, in the large contact angle case, it balanced with the normal component of the surface tension. As for the effect of the fluid properties on the droplet motion, the temperature coefficient of the surface tension had much larger effect than viscosity, thermal diffusivity, and surface tension.

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Thermal striping tests in mixing tees with same pipe diameters were conducted in order to construct databases for establishment of an evaluation method for high-cycle thermal fatigue of piping systems. The flow patterns were visualized and fluid temperature distributions near the pipe wall were measured to clarify the temperature fluctuation characteristics. The velocity ratio, which is the ratio of the velocity in the branch pipe to that in the main pipe, was changed from 0.1 to 5. Temperature difference of incoming flows was about 40 degrees Celsius. Large temperature fluctuations more than 90% of the incoming flow temperature difference occurred near the mixing tees and frequency characteristics were random. The temperature fluctuation characteristics depended on the velocity ratio. The effects of the upstream and downstream piping elements such as a diffuser, valve, and elbow on the temperature fluctuation were small.

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Surface tension of alcohol/water mixtures has been measured over the whole fraction range and then it has been measured when a surface-active agent was added into the mixtures. The effect of the concentration of alcohol and the surface-active agent on surface tension was experimentally clarified, in order to gain base data related to enhancement of a heat transfer coefficient in the mixtures and water. The experiment has also been carried out to enhance the boiling heat transfer coefficients of water and alcohol/water mixtures on a horizontal heated fine wire at pressure of 0.1 Mpa by adding the surface-active agent into the tested liquid. As a result, the coefficients were enhanced in lower alcohol concentration (C≤O.5) and low heat flux range which is just after onset of boiling. It was also found that the enhancement effect by the surfactant disappears in concentrations over 1000 ppm. Finally, we clarified that the surface tension remarkably affects the heat transfer coefficients in nucleate pool boiling.

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Thermocapillary-driven convection in a half-zone liquid bridge of high-Prandtl-number fluid was investigated experimentally. It is widely known that the flow field in the liquid bridge exhibits a transition from two-dimensional steady flow to three-dimensional 'oscillatory' one at a critical temperature difference. In this study, special attention was paid upon the flow structures far beyond the critical condition. Types of the induced flows were categorized into several regimes mainly according to the suspended particle motion in the bridge and the surface temperature variation. Chaotic and turbulent flows were realized in this configuration. The flow regimes were analyzed by applying the pseudo-phase-space reconstruction from the time series of the surface temperature, and the evaluations of the correlation dimension and the maximum Lyapunov exponent.

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Critical power experiments using the test section with an axially uniformly-heated tight-lattice rod bundle have been carried out. One of the aims of the experiments is to propose the critical power correlation. Critical power in tight-lattice rod bundles is very important on the thermal-hydraulic design of the Reduced-Moderation Water Reactor (RMWR). Many parameter effects on critical power such as flow and configuration parameters, axial and radial power distributions, bundle size etc. have to be considered. In this investigation, we focused on the fundamental parameter effects such as flow and configuration parameter and radial power distribution on critical power as the first step. Test section was an axially uniformly-heated 7-rod bundle with gap between rods of 1.0 mm, rod diameter of 12.3mm and heated length of 1.8m. Critical power correlation for the axially uniformly-heated tight rod bundles was derived based on the present and BAPL databases. An excellent agreement was obtained between the developed correlation and data (371 points) within an error of ±4.6%.

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A Weavless Aluminum Fiber Layer (WAFL) is a wool made of Aluminum fibers with the diameater of about 120 μm, which are used as an air filter of cooking room's ventilators and also sound absorption materials. This paper is concerned with the experimental study of the effective thermal conductivity of WAFL, λ_e. The effective thermal conductivity in this paper is evaluated for the heat transfers in the direction of perpendiclar to the WAFL placed horizontally. As the results, it is seen that the thermal conductivity of WAFL is comparatively low notwithstanding to have a very high thermal conductivity of Aluminum base material, and also that the effective thermal conductivity increases monotonically with increasing the compression on WAFL.

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This paper describes a response of solid-liquid interface in a water-saturated porous medium to the time-varying cooling temperature. Spherical soda glass beads with an average diameter 5 mm constituted the porous medium. A lower boundary is kept at 8°C at all time during experiments. First, the upper plate was set at an optional temperature lower than the solidifying point, and then growth of solidified layer was measured. The cooling temperature was then varied periodically with a fixed amplitude of 4°C. The solid-liquid interface position has a characteristic amplitude and phase delay to the upper plate cooling temperature. It is found that the amplitude of interface position is proportional to a period of the cooling temperature variation. The thicker solid layer causes the bigger phase delay in the interface movement. The proposed one-dimensional model is found appropreate to characterize the response of solid-liquid interface.

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Heat and fluid flow in a layer heated from the bottom and the side walls simulating underground LNG tank is experimentally studied under high Rayleigh number (7.5×10¹⁰<Ra<1.5×10¹³) conditions by electrochemical mass transfer technique. From the experiment, following results are obtained. When side walls are heated, the heat transfer along the bottom surface is reduced. Heat transfer along sidewalls is independent of bottom heating, and is modeled by an equation for laminar natural convection flow even for Ra>10⁹. And convective flow pattern in the tank is visualized by Schlieren technique. The results, combined with local mass transfer measurement, show that Sh is reduced in the area of the bottom surface impinging downward flow. It is caused by the suppression of plume formation by the downward flow.

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Single-walled carbon nanotubes (SWNTs) are the fascinating material for their unique mechanical, physical, electrical and chemical properties based on their specially elongated fullerene structure. Macroscopic SWNTs have been generated by laser-oven techniques, arc-discharge techniques, and recently by catalytic chemical vapor deposition (CCVD) techniques. Furthermore, we have developed a simple, high-quality and relatively low-temperature CCVD technique using alcohol as the carbon source. These synthesis techniques and the characterization technique by resonant Raman scattering are discussed. Finally, the formation mechanism of SWNTs is briefly discussed.

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Microexplosions of light oil-water emulsified fuel droplets were successfully documented using a high speed video camera with laser illumination. The temperature profile and the local frequency of explosion occurrence were estimated in open spray flames of water-in-oil type emulsion formed using an air-assist atomizer with a set of ring pilot burners. The estimates of the local frequency of the explosion occurrence were made in the upstream region of spray flames, since their temperature profiles indicated that the heat release was accelerated in the upstream region from the nozzle tip up to the height of 80 mm. Microexplosions were frequently observed in the upstream region where no microexplosion phenomenon was observed in the former study. In addition, all of those had very small spatial and temporal scales. It is probable that the principal factor having effects on the heat release of emulsion spray flame is not the microexplosions of larger droplets, as former theories predicted, but those of smaller ones. We, furthermore, observed the microexplosions of smaller droplets using an ultra high speed video camera, the frame rate of which was 10₆ frames/s. It was observed that the smaller droplets, whose diameter were less than 50 μm, exploded in the spray flame and their temporal and spatial scales were around 10 μs and 300 μm, respectively.

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Flame structure of a spark ignition engine under the conditions of lean burn limit was investigated. The experiment was performed with propane air mixture of equivalence ratios of 0.50 and 0.55. The flames had a small structure that the unburned gas was entrained into the burned gas, or were obstructed by turbulence and the partial quenching was observed. Fractal analysis was performed for the flame boundaries of the obtained images. The values of the fractal dimension under lean limit conditions reached 1.45 larger than that of non-reaction turbulence.

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Flame propagation into the lean area of the stratified mixture was investigated numerically by simulating the counterflow flames of the lean mixture. The propagating flame into the lean mixture and the burned gas behind it were linked to the counterflow flame configuration of the lean mixture and the opposing gas. Nitrogen and burned gas were opposed to the lean mixture varying their temperature and composition. And the stoichiometry of the lean mixture was also varied widely. The results show that the gas temperature and composition affect the reaction of the lean flame. Fuel reaction of the lean mixture far below the lower flammability limit was supported by the transport of heat and species such as CO and H₂ from the opposing gas. Property of CO production in the supported flame was different from that of self-propagating flame.

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Fuel atomization is known as one of the most effective way to reduce both exhaust emission and fuel consumption of spark ignition engines. Authors have studied an influence of turbulence upstream of a nozzle on the fuel atomization, which is effective for improving the fuel atomization. This paper discusses an experimental investigation of the turbulence on the fuel atomization using a silicon plate nozzle (SPN) with a sharp edge inlet and aperture size of 100 μm or less. Here, the basic configurations of the SPN, that is, its aperture size and sharpness of the edge were changed so as to investigate characteristics of the fuel atomization for the respective cases. The characteristics of the fuel atomization were also investigated in case of superposing two SPNs and combining the SPN with a needle valve. As a result, it is clarified that the fuel atomization cannot be improved by merely reducing the orifice aperture size, and the turbulence upstream of the nozzle is also effective for the SPN with a small aperture.

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In order to clarify the thermal decomposition behavior of typical solid wastes (urethane RDF, wood chips and rubber chips), pyrolysis experiments were performed under two isothermal conditions, which are 500°C and 600°C respectively, employing a bench scale facility. Effects of steam injection were also investigated at the temperature of 600°C. The time change of the pyrolysis gas composition was measured continuously and the total weight of generated tar components and char were measured. Based on these measurements, mass and energy balances of pyrolysis products were determined. The effects of pyrolysis temperature and steam injection on pyrolysis behavior were quite different for each solid waste. It was found that the heating value of pyrolysis gas increases with the rise of pyrolysis temperature, and the peak value appears at the early stage of the pyrolysis process. It was also demonstrated that steam injection can significantly facilitate cracking of high molecular compounds and decompose char into H₂, CO and C0₂, especially in the case of wood chips, where about twice gas yields was successfully obtained by steam injection.

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The control of ignition timing, the suppression of rapid combustion, and the expansion of stable operating range upto higher load maintaining ultra low NO_x and smokeless combustion were achieved by direct methanol injection in a premixed charge compression ignition engine. The combustion suppression effect increased with advancing methanol injection timing as the methanol widely distributed in combustion chamber. With increasing in methanol injection amount, the onset of low temperature oxidation delayed and the heat release in the low temperature oxidation decreased. This reduction of low temperature oxidation resulted in suppression of the temperature rise before the onset of high temperature oxidation, then delayed the onset of high temperature oxidation, and suppressed the rapid combustion. At high load the fraction of methanol injection amount have to be more than 50% to achieve normal combustion without too early ignition and knocking. Flame luminosities during the low and high temperature oxidations decreased with methanol injection.

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To make full use of cold heat of LNG, a heat exchanger that exchange heat between air and combustible LNG was experimentally studied. It is called Double Tube type because channels of each fluid are separated by a double tube to improve the safety. Heat transfer characteristics of the heat exchanger were measured, using a test section of 1 m long and 110 mm in diameter. The sum of thermal contact resistance between the outer tube and the plate fin and between the outer tube and the inner tube was 3.9 m²K/кW when air was cooled down to 230 K. The sum is the upper limit value or safety-side value because the other degradation factors such as flow maldistribution or bypass flow between the baffle plate and the shell were not considered. The calculated shell-side pressure loss was in good agreement with the experiment when pressure loss around the window of a baffle plate was estimated by using semi-empirical formula for 90° elbow pipe.

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The flame temperature of oxygen-blown medium-Btu gasified coal fuel is higher and so NO_x production from nitrogen fixation is expected to increase significantly. We have started to develop low NO_x and stable combustion technology using medium-Btu gasified coal fuel. In this paper, based on the fundamental combustion tests using the small diffusion burner, we have through out the new combustion technique which injects nitrogen directly into the high temperature region in the combustor for low NO_x and stable combustion. A gas turbine combustor with a swirling nitrogen injection function designed with new combustion technique was constructed and the performance of this combustor was evaluated under atmospheric pressure conditions and operational conditions. From the test results, it is confirmed that : (1) This new combustion technique with nitrogen direct injection results in a significant reduction in NO_x production from nitrogen fixation, 8 ppm or less (corrected at 16% O₂) in the gas turbine operational conditions for IGCC ; and (2) CO emission concentration decreased to a significant level, as low as 10 ppm, under operational conditions, or combustion efficiency was almost always 100%. From the above results, this combustor has an excellent performance under the operational conditions in IGCC, and bright prospects of low NO_x and stable combustion technology of the medium calorific fuel are obtained.

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