Buoyancy-driven helium-air exchange flow throgh double small openings was investigated. The double openings with rectangular cross section were settled side by side, in order to evaluate the interaction between the flows through the double openings. In the exchange flow experiment, the exchange flow rate and the flow pattern around the openings were simultaneously measured. Two flow patterns were formed even in the same boundary condition, i.e., (a)uncaptured flow pattern with larger exchange flow rate, and(b) captured flow pattern with smaller exchange flow rate. The entrainment effect caused the two flow patterns. In order to clarify the mechanism, characteristics of the entrainment were evaluated in the forced flow experiment. Only the flow pattern(b)was observed in the forced flow experiment. The relationship between the entrainment ratio α and flow rate q was measured for the flow pattern(b), resulting in the entrainment characteristic curve. A new correlation for the exchange flow rate was proposed with considering the entrainment. With applying the obtained entrainment characteristic curve to the correlation, the exchange flow rate was predicted. It agreed with the measured value better than the conventional prediction without consideration of the entrainment.

View full abstract

This study investigated the mechanism of a large vortex formed behind a wedge under three angles of attack(α=0°, 22.5°and 45°)which have different separation conditions. Velocity field was visualized using LDV measurement and the FFT spectrum processing technique. It was found that the large vortex grows fully at the end of the vortex formation region defined by the authors. A flow saddle point corresponding to a stagnation point exists on the boundary of the region and almost coincides with the point where the large vortex is about to cut a separated shear layer. Especially in the case of α=22.5°, a separation bubble forms and stays on the upper surface of the wedge. Consequently, the mechanism of the vortex formation shows unique features, such as a flat and long vortex formation region, fluctuating velocities with high frequency over the separated shear layers near the separation points, and a large unibersal Strouhal number defined by Griffin.

View full abstract

The forces acting on and the flow patterns around a rigid bluff body submerged in an oscilatory flow were studied. The force coefficients on a circular cylinder were measured and compared with those from other studies using a U-tube water tank to verify the experimental setup. Then, measurements of both in-line and transverse forces of a square cylinder at an angle of attack of 0° were made in a relatively wide range of Keulegan-Capenter(KC) numbers from 1 to 90. For both circular and square cylinders, the force signals were analyzed spectrally to obtain major frequencies. Flow visualization was also employed to confirm the relationship between flow patterns and force coefficients. It is evident that several classes of flow patterns appear within the measured KC range, and that variations of the in-line and transverse forces are related closely to vortex motions.

View full abstract

The 3-D flow field relative to a rotating paddle blade is obtained by synchronizing LDV measurements with the output of a shaft-mounted encoder, thus making it possible to determine the impeller stream velocity field, including details of the discharge flow region behind the blades. Mean velocities, ensemble-averaged between a specific impeller blade pair(over 90°)show the extent determinde from both the passage and structure of the discharge flow region. Pumping capacities are consequence of fluid entrainment into the discharge flow region. Mean velocities taken in a rotating frame of reference reveal a significant periodic variation near to those taken in a fixed frame.

View full abstract

Experimental studies on weak shock wave attenuation in high-speed train tunnels were conducted using a 1 / 250-scaled train tunnel simulator and a shock tube. Three kinds of porous / perforated walls installed in the test section of the simulator near its exit were examined. Installing aluminum foam or porous plastic on the wall clearly decreased the pressure gradient of the wave front. The processes of the shock wave attenuation were visualized by holographic interferometer. A significant decrease in the overpressure was obtained by installing perforations along the simulator wall. However, with the short perforation section of 0.5m, the pressure gradient of the shock wave remained steep. Through the series of the experiment and theoretical consideration, it is found that the length of the perforated / porous section is one of the most essential parameters to effectively attenuate the shock wave.

View full abstract

Study on control of vibration of a spring-mass system by using a magnetic fluid is conducted. The system consists of a cylinder filled with a magnetic fluid, a piston immersed in the magnetic fluid and a weight attached to the piston. The cylinder connected to the weight by a spring is excited to vibrate. The magnetic field necessary for stopping vibration of the mass is predicted. Validity of the prediction is proved by numerical experiments, where the equation of motion for the spring-mass system and the axisymmetric flow of the magnetic fluid are simultaneously solved. The magnetic field generated by a couple of coils can effectively damp the transient vibration and control the steady vibration to be extremely small.

View full abstract

To apply the direct numerical simulation(DNS) and the large-eddy simulation(LES) of turbulence to flow fields of complicated geometry, a higher-order finite-difference method(FDM) has been developed for the body-fitted coordinate system. The consistency and the conservation property of FDMs are discussed for the collocated grid. As numerical examples, DNS results of decaying isotropic turbulence and DNS / LES results for plane channel flow are shown and the influence of variable arrangement is examined. The results by the consistent 'interpolation'method for gradient from on the collocated grid agree well with those by other proper FDMs and the spectral method.

View full abstract

Active control of jets emitted into a two-dimensional channel with insulated suction near the wall during monitoring with a neural network is described. The aim of this work is to simulate the possibility of controlling the flow pattern with a flip-flop phenomenon by suitable suction. In this case, the output of a neural network is estimated satisfactorily based on 3 flow patterns of teaching data. The periodic flow pattern at the Reynolds number Re=1.0×10³ is reduced by a suction rate of less than 10% for primary jets. Then flow becomes stable as a result of feedback gain of the neural network. Since the control with suction need not be continuous, the power cost is reduced. The nonperiodic case at Re=1.0×10⁴ is difficult to control, but we achieved good control by with the use of a suitable suction rate with the neural network.

View full abstract

In this study, a steady, three-dimensional incompressible turbulent flow within a torque converter was numerically analyzed by introducing an interrow mixing model. Mixing planes were introduced to exchange the flow information between two adjacent elements of a torque converter. By installing the mixing planes among the three elements of a torque converter, the flow field within the torque converter could be calculated without any assumptions concerning circulating flow rates or any upstream and / or downstream extension of boundaries for each element. The numerically calculated performances of the torque converter were in good agreement with the experimental results, and the complex flow patterns could be observed according to the given working conditions. It was concluded that the present numerical method was ver effective in the steady flow analysis of torque converters.

View full abstract

The author describes the effect of deformation of a liquid droplet on its displacement due to airstreams. Experiments are conducted using a 60mm×150mm crosssectional and 500-mm-long horizontal air-suction wind tunnel. Uniformly sized liquid droplets produced by the longitudinal vibration of a nozzle are used. The liquid droplets exposed to airstreams are deformed;that is, their size normal to the airstream direction is changed. The projection area of a droplet in relation to airstream direction is expected to greatly influence the displacement of a droplet and the drag;therfore, the longitudinal droplet diameter is measured precisely. The author formulated an equation that quantifies dimensionless droplet displacement with dimensionless exposure time. The equation can be used to predict displacement of droplets with slight deformation. Therefore, the appropriate deformation rate of the droplet applicable to the equation is investigated in detail. The relationship between Weber number and maximum / minimum dimensionless longitudinal droplet diameter is also surveyed.

View full abstract

This paper presents a correlative mapping method for measuring individual phase flow rates in an air-water two-phase flow. The method consists of the extraction of stochastic features from differential pressure waveforms, construction of a data base by making contour maps of the feature vectors, and flow rate identification based on a pattern recognition technique using the data base and measured pressure waveforms. To enable the metering device to be portable, pressure is detected by a Venturi tube installed just downstream of an offset elbow, by which the mixture is forcibly mixed, and which brings about a definite flow state depending on a pair of phase flow rates. Experiments in an air-water loop showed that individual phase flow rates can be measured with an accuracy of 4.7% for the air phase and 4.0% for the water phase, and that the method appears to be applicable for measuring production rates at well heads in offshore oil fields.

View full abstract

Pressure drop and heat transfer for flow-boiling of water in small-diameter tubes under atmospheric pressure were discussed. The results of experiments were compared with those of several existing correlations and models. The experiments were carried out using atmospheric-pressure water in tubes with inner diameter D ranging from 2.0 to 6.0mm, heated length L from 4.0 to 680.0mm, inlet water subcooling ΔT_in from 70 to 90 K, and mass velocity G from 100 to 10170kg / (m²s). The highest heat flux q attained was 33 MW / m². Interesting phenomena were observed in small-diameter tubes with a very short heated length. The most suitable correlations for predicting the pressure drop and heat transfer in small-diameter tubes were also discussed.

View full abstract

Long wave analysis of downward liquid film stability in a countercurrent two-phase flow is theoretically studied in terms of a finite-amplitude for a base harmonic and a harmonics of interfacial wave until just befor flooding. We use a method of integral relations of the Navier-Stokes equation in gas and liquid phases to analyze the stability of the interface between the phases. The unstable interfacial wave of the harmonics appears in two different wave number regions, and both regions are included in the unstable regions of the base harmonic. The one region appears in the conditions of a high wave number and a low gas velocity and the other in which the most dangerous wave is indicated appears in a low wave number and high gas velocity. In the former region increase of gas velocity gives a stable liquid film and in the latter region increase of gas velocity induces an unstable interfacial wave.

View full abstract

A numerical study of radiative heat transfer in silicon floating zone crystal growth furnace with the needle-eye technique has been carried out. Both diffuse and specular reflections are considered on the concave surface of the silicon melt. The radiation element method is employed to solve the radiative heat transfer, in which the ray tracing method is adopted to calculate the view factors among curved diffuse and specular surfaces. The accuracy of the method is verified by good agreement with the analytical solution in a simple concave configuration system. The effects of view factors and the specular reflection of the surfaces of the melt, the crystal and the inductor on radiative heat transfer of a floating zone furnace are discussed. It is found that the specular reflection on the surfaces of melt and inductor tends to increase the heat flux or decrease the temperature gradient on the silicon melt surface. The view factors are changed remarkably with the variation of the concave surface shape, and consequently, affect strongly the radiative heat transfer.

View full abstract

A general mathematical model for forced air precooling of spherical food products in bulk is developed. The food products are arranged inline to form a rectangular parallelepiped. Chilled air is blown along the height of the package. The governing equations for the transient two-dimensional conduction with internal heat generation in the product, simultaneous heat and mass transfer at the product-air interface and one-dimensional transient energy and species conservation equations for the moist air are solved numerically using finite difference methods. Results are presented in the form of time-temperature histories. Experiments are conducted with model foods in a laboratory scale air precooling tunnel. The agreement between the theoretical and experimental results is found to be good. In general, a single product analysis fails to predict the precooling characteristics of bulk loads of food products. In the range of values investigated, the respiration heat is found to have a negligible effect.

View full abstract

The velocity field associated with a nozzle flow emanating into a co-flowing stream was measured using a Laser Doppler Velocimetry(LDV) technique. The present work concentrates on the effect of small tabs introduced at the nozzle exit plane on mixing of the jet. The effect of tab geometry on mixing rate has been studied. The principal objective of the present measurements was to study the effect of introducing a 3-D shape to the tab geometry, rather than plain 2-D tabs of small thickness. Three different 3-D shape tabs were studied. The mixing improvement for all 3-D shape tabs was found to be substantially reduced compared to the plain 2-D tab results for the same projected area. Therefore, attempts to reduce the drag and performance loss penalty of the tabs were accompanied by significant reductions in tab mixing effectiveness.

View full abstract

In this paper a power generation system is proposed for electricity generaton and desalinated freshwater production by an indirect hot He reactor by burning up Pu partitioned from spent fuel from Light Water Reactors(LWR), in order to extinct Pu as an energy resourse and prevent it from being converted to nuclear weapons. Heat released in burning up Pu fuel decreases with time, and, therefore, unlike the performance of a conventional LWR power plant, thermal energy is produced from new Pu fuels by properly pulling out control rods from them. A new system, using 950°C He at the reactor exit, generates electricity by He turbine and produces desalinated freshwater using turbine exhaust heat in the secondary loop. When Pu partitioned from the spent fuel of LWR of 1000 MWe is burned up, it is shown that the GT-PuHHR having 316 MWt generates 137 MWe with 43.7% thermal efficiency, produces 6275 ton / day freshwater and attains about 90% total plant thermal efficiency.

View full abstract

In a compact closed two-phase loop thermosyphon which consists of a multiradiator and a refrigerant bath with multiple power modules mounted vertically, the heat radiation performance deteriorates as the refrigerant bath becomes thinner. We have found that this is because the return condensate is blocked by the back flow of the bubble in the return path when the heat load decreases and increases sharply. We have also improved the heat radiation performance by providing an adiabatic path between the boiling area and the return path.

View full abstract

When a Shinkansen(Japanese bullet train) passes through a tunnel, the pressure changes due to the pressure wave in the tunnel penetrate the cars. This gives rise to aural discomfort in passengers, which becomes severe when two trains pass each other in the tunnel. In this paper, a new ventilation system for alleviating this aural discomfort is described. A method of numerical simulation of the pressure change outside and inside the train is also presented. A field test has been carried out to confirm the fundamental performance of the system using Shinkansen electric cars Series 300 and the results are compared with those of the numerical simulation. Moreover, the applicability of the system to a superhigh-speed train traveling at 350 km / h is ascertained by numerical simulation.

View full abstract

The hot surface ignition of methane-air mixtures in microgravity has been studied experimentally and numerically. Experiments on the ignition of the mixtures with electrically heated nickel wires and platinum wires in microgravity have been performed. Numerical calculations, including the catalytic reaction rate for platinum, have been performed to understand the experimental results obtained in microgravity. The ignition delays and ignition temperatures for a wide range of equivalence ratios were investigated. experimental results show that the ignition temperatures with platinum wires have a maximum near the stoichiometric mixture ratio, while those with nickel wires increase as the equivalence ratio increases. Ignition temperatures with platinum wires are higher than those with nickel wires. Numerical results show that reactants next to platinum wires are consumed by the catalytic reaction. Therefore, a higher temperature is required to ignite mixtures with platinum wires. The catalytic inhibition of hot surface ignition is simulated successfully by the numerical model.

View full abstract

A series of experiments regarding the ignition of H₂-O₂-O₃ / H₂-O₂-O₃-Ar mixture with KrF excimer laser has been carried out. We investigated the influences of some factors upon the Minimum Incident Laser Energy Intensity(MILEI) for the ignition, and took schlieren photographs with an image converter camera to observe the photolysis and ignition process. The results of these works showed that ozone was a strong and unique absorber for the focused KrF laser light and suggested that the photolysis of ozone induced the ignition. In our experimental range, the MILEI decreased with the increase of ozone concentration, dilution with argon and preheating of the mixture. However, a weak dependence of MILEI on the equivalence ratie of H₂-O₂-O₃ mixtures was measured. From the schlieren photographs, we observed the rapid growth of the initial ignition kernel and the formation of shock wave. These observations suggested that the ignition process was considerably faster than the one induced by the photolysis of O₂ with ArF laser.

View full abstract

The effect of initial CO₂ concentraion on NO destruction and regeneration was investigated as part of our ongoing research on NO emission from CO₂ recycled coal combustion, which could realize easy CO₂ recovery and drastic NO reduction simultaneously. Experiments were carried out in a flat flame burner for CH₄ / O₂ / Ar / NO / CO₂ flame at various excess oxygen ratios(from 0.6 to 1.2) and CO₂ concentrations(from 0% to 48%). It was found that CO₂ has a pronounced negative effect on the destruction of NO under fuel-rich condition. In contrast, under fuel-lean condition, the effect of CO₂ becomes smaller even at high CO₂ concentration. Kinetic Modeling showed that a large part of NO is regenerated through the reaction N+CO₂=NO+CO at high CO₂ concentrations. The effect of CO₂ is not so significant under fuel-lean condition because this reaction is no longer competitive with other NO formation reactions in this case.

View full abstract

The flow and optical fields of a supersonic flow chemical oxygen-iodine laser are simulated by solving the three-dimensional Navier-Stokes equations as well as the paraxial wave equation, and the laser power extraction characteristics are studied. The present results show that considerable flow nonuniformity remains in the optical resonator. Therefore, the effects of refraction caused by flow nonuniformity on the near-field and far-field patterns of radiative flux, and the laser power are evaluated using an actual nonuniform flow and an equivalent uniform flow. The mixing between O₂(¹Δ)and I₂ in the present condition is fairly satisfactory from the viewpoint of power extraction characteristics. It is also shown that the present simulation overestimates the small signal gain coefficient and the output laser power to some extent. It is thought, however, that the calculation predicts the extremely complicated phenomenon in S-COIL fairly well in spite of the many assumptions used in the present study.

View full abstract

This paper describes the application of a stratified fuel / water injection system for diesel engines. This system makes it possible to inject water during fuel injection from the same nozzle hole without mixing the liquids. First, it was confirmed that NO_x reduction and improvement of thermal efficiency and smoke density could be achieved using this system. The reason for such improvement of combustion with water was investigated in detail using a special test engine with which burning flames could be visualized by taking high speed photographs. Moreover, the distribution of the water vapor in the fuel spray was estimated through calculations using the software KIVA. Based on these studies, this system may soon be put into practical use.

View full abstract

Transient temporal and spatial spray characteristics have been investigated. A kind of practical fuel injector with swirl nozzle was examined under variable injection duration within the range of 0.25 to 4.0 ms and injection pressure 5.0 and 7.0 MPa. The fuel spray was injected at a cycling frequency of 50 Hz in a room under normal atmospheric condition. Considered details of sub-millisecond transient dynamics were observed by using a high-speed video camera with temporal resolution of 24.69 μs(40500 frames / s). The results indicate that investigated spray consists of two incorporated flow fractions that are a core jet and a quasi-umbrella droplets spray simultaneously moving down and swirling in local cross-axis domains. Instantaneous transient values of axial and radial penetration were accurately evaluated and analyzed. It was observed that after actual injection a post-injection of fuel droplets occurs and the time-delay and lifetime of these droplets were systematically estimated.

View full abstract

Measurements of the instantaneous in-cylinder flow fields were carried out in a water analog engine simulation rig using a state of the art 3-D Particle Tracking Velocimetry(3-D PTV).Raw images for the 3-D PTV measurements were acquired at the end of intake stroke (Bottom Dead Center, BDC) for a simulated idle condition using a pair of high speed video cameras. Efforts were made to maximize the particle seeding density(and the resulting number of 3-D velocity vectors)to yield approximately 500 to 600 instantaneous vectors at each cycle. Using an appropriately designed spatial filter, large scale(low pass filtered) 3-D instantaneous velocity fields were reconstucted for each cycle as well as the ensemble averaged flow fields over large number of cycles. Based on these cycle-resolved(low pass filtered)flow fields and the ensemble averaged flow field, cycle-to-cycle variations were computed. Furthermore, the deviations of the instantaneous flow fields from the corresponding cycle-resolved large scale motions were computed to estimate the root mean square(rms)levels of the "in-cycle"turbulence. This paper presents the unique application of the 3-D PTV and the water analog engine simulation approach not only to measure the ensemble averaged mean 3-D flow patterns, but also to study the cycle-to-cycle stability of such flow patterns and ultimately to gain a better understanding of the combustion stability characteristics.

View full abstract

As a countermeasure for global warming, the development of CO₂ recovery technology from fossil fuel power plant flue gas has continued. MEA processes are widely used for CO₂ recovery from combustion flue gas in beverage use, etc. However, if we consider power plant scale CO₂ recovery, the biggest theme is the reduction of energy needed to recover CO₂. Our presentation focuses in sterically hindered amines and a new absorber packing. Also, the result of optimum steam system analysis are indicated. CO₂ disposal method is needed with the combination of CO₂ recovery, therefor CO₂ subterranean disposal method is also discussed as the practical way.

View full abstract

With the greenhouse effect in mind, we have been studying the CO₂ recovery thermal power generation system. In this system, it is necessary to recover CO₂ from LNG reformed fuel gas using a high temperature gas separation system. By a trial calculation of the efficiency of a power generation plant with CO₂ recovery system, it is appeared that membrane separation offered low power and low cost. A homogeneous silica-base membrane was obtained by the advanced sol-gel method with a polymer-hybrid. The gas separation factor of H₂ to CO₂ and the factor of N₂ to CO₂ was larger than 100 at 673K. H₂ permeability was on the order of 10^-7mol / m²·s·Pa order. This performance remained almost constant for 720 hours.

View full abstract

The system of oxygen / recycled flue gas combustion for the removal of carbon dioxide from pulverized-coal fired power plants, the combustion characteristics of pulverized coal, and the trial designing of a 1000 MWe pulverized-coal power plant were studied. The flame propagation speed of pulverized-coal cloud was measured in a microgravity combustion chamber at O₂ / CO₂, O₂ / N₂ and O₂ / Ar atmosphere. NO_x and SO₂ emissions from the system were investigated in the industrial-scale combustion test facilities. Based on these results and the previous works, the trial designing of a 1000 MWe pulverized-coal fired power plant applying this combustion system was also studied. As for the heat absorption performance of the boiler furnace, a 3-dimensional numerical analysis was applied to a large utility boiler furnace. It was compared with another promising system CO₂-recovery, pulverized-coal power plant combined with amine absorption process.

View full abstract

The IHI flue gas desulfurization system was completed for a new 700 MW coalfired boiler in December 1995. The system is now operating very smoothly, achieving a removal efficiency of more than 90% for SO₂ and more than 85% for particulates. 100% availability has been maintained so far. Special features of the system are as follows: 1.A simultaneous SO₂ and particulates removal absorber with a forced oxidation system is used, which is the largest spray tower ever built in Japan. 2.Two variable pitch axial flow fans are positioned downstream of the absorber(C-Position). 3.Optimum FGD control system is installed to minimize the operating cost for AFC(automatic frequency control) operation of the power plant.

View full abstract

The development of a Fixed Bed Type Hot Gas Cleanup system for coal gasification combined cycle power plant had been newly succeeded with the achievement of 765 hours stable and continuous operation of the 20t / d pilot plant during March-April, 1995. This hot gas cleanup system, composed of the dust removal unit with a porous ceramic filter and the sulfur compounds(H₂S, COS)removal unit with honeycomb desulfurizers enables highly efficient and stable performance under a wide range of gasifier operation. Moreover, in the sulfur recovery system, not only elemental sulfur but also gypsum was proved to be obtainable with high yield and purity. The Fixed Bed Type Hot Gas Cleanup Process is thus found to be suitable for the IGCC. In case of the fixed bed type, the scaling up for the demonstration plant is easy, since it can be designed with demensions proportional to the treated capacity.

View full abstract

From the viewpoint of reducing power generation costs and saving energy resources, improved efficiency of thermal power plants is a critical issue. Steam turbines, which are the main plant equipment, have been developed which provide a high level in blade performance. Further enhancement of blade performance, however, requires refinement of the blade shape and the control flow pattern in the radial direction. Recently, development of three-dimensionally designed blades has been active, with goals of raising the internal efficiency and being able to the control flow pattern in the radial direction not only for stationary blades, but also for moving blades^(1)-(3). In order to improve the flow pattern through the blade rows, the authors have proposed three-dimensionally designed stationary blades^(4)-(7), which can be used in low pressure(LP) and high and intermediate pressure(HIP)turbines. This paper describes the development of three-dimensionally designed blades, in which performance of turbine stages including moving blades has been improved. The new blades reduce the end-wall losses in the HIP stages where there is a serious problem with secondary flow.

View full abstract

Advansed High-Pressure(HP) / Intermediate-Pressure(IP) and Low-Pressure(LP)stages, with three-dimensionally-optimized flow patterns, have been developed in order to further improve steam tubine efficiency. The HP / IP advanced flow pattern stages were designed to provide optimized mass flow distributions and reduced secondary flow losses for short- and medium-height passages. Two new types of stage were numerically and experimentally investigated, and shown to have an efficiency gain of 1-2% over the conventional stage. Applying this concept to the LP section, an advanced flow pattern last-stage nozzle and moving blades have been designed to reduce the secondary losses in the root and tip of the nozzle, and prevent flow separation along the tip wall. The effectiveness of the new stage was verified in a low-pressure test turbine and by numerical calculations.

View full abstract

In response to recent demands for effective use of energy and increased awareness of environmental protection, MHI has developed a new CUF boiler capable of ensuring a low NO_x emission and burning coal stably at a low air ratio. In the CUF type boiler, its burner is installed at the four surrounding walls having high radiative intensity and the fuel and the air are injected slightly downwards to be fired while they are made to swirl over the entire furnace. Becauce this boiler type is excellent in fuel ignitability and can maintain a sufficient fuel residence time in its reduction zone, its development has always been oriented towards combustion of hard-to-burn coals such as anthracite. In the CUF boiler newly developed, those features have been adopted towards low NO_x and high efficiency. For further decrease of the NO_x level, optinum conditions of the burner location and the fuel injection direction were found out using a 1 / 15 scale cold model test, which made it possible to achieve coal firing at a lower NO_x and higher effeciency than ever. Based on these results, a CUF boiler of evaporation 350t / h was made and this boiler has successfully been operating. Combustion state in the furnace has been found very stable and operation of this boiler using a low air ratio of excess O₂ obout 1% is made available. Comparison with the conventional boiler of the same scale shows that there is the effect of NO_x decrease by about 30% on a basis of the same unburned carbon ratio in ash.

View full abstract

An experimental study on the combustion of extra heavy oil has been performed using a cylindrical test furnace. Recently, light oil such as gasoline is almost exclusively demanded as liquid fuel made from petroleum. In order to produce light oil in a high yield, extra heavy oil, which is called as VR(Vacuum Residue), remains after refinement under reduced pressure. VR features extremely high viscosity, as well as high percentages of sulfur, nitrogen, heavy metals, and resident carbon in fuel. Regarding the use of VR as a fuel for actual commerical boilers, a number of serious problems must be overcome. These include high- and low-temperatue corrosion of metal materials, and the need to meet environmental regulations calling for low NO_x and a low unburned carbon ratio in exhaust gas. In the present study, accordingly, a firing test has been conducted to accumulate the basic characteristics of VR combustion. From the test results, stable ignitability was ascertained, and both NO_x emission and the unburned carbon ratio in exhaust gas were found to be at the same level as for bituminous coal combustion. Also, the reactivity and the carbon structure of the sampled soot and char were chemically examined in detail, and the reaction rate with oxygen was formulated. Furthermore, numerical simulation of combustion in onedimensional furnace was conducted, and the calculated results were compared with the experimental data.

View full abstract

The Integrated Gasification Combined Cycle(IGCC) is regarded as a prospective winner of thermal power system in the next decade. Ishikawajima-Harima Heavy Industries CO., Ltd.(IHI) has been developing gasification technology and dry gas desulfurization technology. These are key technologies for IGCC commercialization. IHI has constructed Texaco Type coal gasification test facility and has been carrying out various tests since 1987. Also at the Japanese national IGCC development project, IHI has been in charge of a dry gas desulfurization pilot plant development for 200 coal tons / day gasification plant. This worldly largest desulfurization unit has performed successfully and concluded in February 1996. With these test results, IHI has continued to improve IGCC system through various feasibility studies with Toshiba who designed the combined cycle. We also carried out parameter survey that focused on the influence of fuel properties. These results made clear some useful features for IGCC development.

View full abstract

Ishikawajima-Harima Heavy Industries Co., Ltd.(IHI) have been developing the Gasification and the Hot Gas Cleanup technology for Integrated Gasification Combined Cycle(IGCC). Gasification tests have been carried out in corporation of Tokyo Electric Power Company and Kansai Electric Power Co., Inc., with a 6 ton(coal) / day Texaco process gasification pilot plant(CGT project), which is located at IHI's Aioi Works in Hyogo Prefecture. This project has started in 1986 gasifying various kind of coal, and by the end of November 1996, 15 kinds of coal are gasified and cumulative operation time of 7000 hours have been achieved. From 1994 in order to diversify availability of fuels for gasification, several kinds of heavy oil had been gasified in this plant. Through these tests the relationship between process variables and the performances of heavy oil gasification became clear. This paper describes the process of the heavy oil gasification and the results of the heavy oil gasification tests which were carried out at the CGT project.

View full abstract

The combustion technology whih carries out both low NO_x emission and low load stable combustion is desired in pulverized coal-fired power plants. A new advanced low NO_x burner which can reduce NO_x concentration and unburned carbon concentration in fly ash to 100 ppm and 3% respectively, had already been developed. To improve the combustion stability of this burner at lower loads, an adjustment method to raise the local concentration of coal by placing a ring in the primary air nozzle was invented. The combustion stability and the emission characteristics of NO_x and unburned carbon in fly ash were investigated with a test furnace having a coal feed rate of 100 kg / h. The burner equipped with a ring achieves stable combustion at 20% load as like an oil burner by the adjustment of the local coal concentration. At higher load, the burner equipped with a ring maintains the same emission characteristics of NO_x and unburned carbon in fly ash with the new advanced low NO_x burner.

View full abstract

Combustion using combustion air with the condition of 1010°C and 3.0% oxygen content diluted air, has shown unique characteristics. A high flame stability, flame volume enlargement, greenich flame color and low NO_x emissions were the characteristics of the combustion named here as high temperature air combustion. Flame with an enlarged volume having low flame luminosity was one of the important findings which implies a heat release rate in unit space of the flame decreased. The flame temperature profile thus became more homogeneous than ordinary flames. This potential that the high temperature air conbustion may improve thermal field uniformity can cause a revolution of combustion technology on the high performance industrial furnace design.

View full abstract

Three-dimensional numerical simulation was made for the hydrogen flame injected into the wake of a bluff-body type flameholder placed in an air stream. This analysis of the flame structure was aimed at designing the optimum combustion system of high performance. The velocity and pressure field were numerically solved using the SIMPLER algorithm. Turbulence model was based on Myong-Kasagi's low Reynolds number type k-ε model. The turbulent combustion was simulated by using Magnussen's eddy dissipation model. The simulated results showed a reasonable agreement with the species concentration profile observed in the wake.

View full abstract

Samples of two Cr and / or Al-containing Fe-base alloys were exposed to gas mixtures with oxygen and chlorine activities similar to those expected to be established in the heat-recovery-boiler section of a coal gasification plant under development. Alloy samples were prepared by either SiC-paper grinding, diamond-paste polishing, shot-peening or electropolishing. Analyses of the oxidized samples showed that sample mass changes, morphology and composition of the product scales depended on sample surface preparation and the nature of gas mixtures. Physical properties of sample surfaces which affected scale formation and evaporation of metal chlorides from the alloy matrix were proposed as possible reasons for the observed dependency. The results indicated that sample preparations that produce rough surfaces may be effective in reducing the adverse effect of HCl gas on high temperature corrosion of alloys by promoting the development of protective Cr-or Al-rich corrosion product scales.

View full abstract

Both of the newly developed tungsten strengthened ferritic steels considered here, i.e., 2.25Cr-1.6W-V-Nb(HCM2S) steel and 12Cr-0.4Mo-2W-1Cu-V-Nb(HCM12A) steel, have the practical capability to be used for steam enerator tubing due to their excellent fabricability and very high creep strength. These steels have already been approved by the ASME Boiler and Pressure Vessel Code Committee for use in Section I construction. A field service test putting these steel tubes in service along with comparative materials in the tertiary superheater and secondary reheater of a 156 MW utility power boiler has been conducted since April 1993, and the tubes were removed to confirm their material properties and corrosion / steam oxidation behaviors after one-year and 3-year periods of service. The investigation results showed that the practical performances of HCM2S and HCM12A steel tubes were good, demonstrating superior corrosion resistance and less material degradation than the comparative materials. This paper deals with the practical properties and examination results of these newly developed steels compared with conventional boiler steels.

View full abstract

Cavitation erosion of control valves is one of serious problems frequently arisen in industrial plants dealing with high pressure liquid flows. Nevertheless, there have been only slight empirical data helpful in estimating the valve life and diagnosing the valve performance deterioration in relation to the erosion development. A needle-type contoured plug inserted in a low C_v-value globe valve has been subjected to erosion tests using a 20 MPa high pressure water facility. Several factors affecting the erosion development are obtained by the present experiment. On materials of plug metal, the rate of mass loss by the erosion decreases in the order of brass, Stainless Steel-316, Stainless Steel-630, Stainless Steel-440C and Stellite#6. The loss rate is found to take an extremely high level as the valve is opened at its full lift. The erosion feature is largely altered by a slight change in the plug geometry, oxygen amount of the water and also level of the outlet pressure. These effects are compared in terms of the eroded mass rate data. Cavitation pictures obtained by a low pressure facility at a level of 1MPa are also presented as supplementary data to specify the erosion part on the plug depending on the cavitation bubble behaviors.

View full abstract