The Monte Carlo method is applied to study the effects of nongray gas and anisotropic scattering on the temperature profiles of particle-gas mixture between parallel black cold walls. The gas is nongray combustion gas and the particle is assumed to have gray surface and behaves as an absorber, emitter and anisotropic scatterer of radiative energy. The analysis is based on radiative transfer in a medium which is internally heated uniformly. For comparison, analyses with gray gas and with isotropic scattering particles are also carried out. The results obtained show that within the particle number density region where radiation-heat-transfer enhancement is expected, the gray gas assumption presents a flatter temperature profi1e than that of the nongray gas. When the particle density is increased, the layer temperature at the center first decreases and then, for greater particle density, it increases. But the temperature of the mixture adjacent to the wall, after being decreased, approaches a certain value when the particle density is increased. In the higher particle density region, the anisotropic scattering effect causes layer temperature higher than that of isotropic scattering.

View full abstract

Light scattering effects by ash polydispersion on spectral emission from coal-fired MHD combustion gas are predicted numerically by means of the first (P₁) and third (P₃) spherical harmonics approximations of a radiative transfer equation in a rectangular cross section of the MHD channel, with consideration of variation in optical properties across a boundary layer, particle diameter distribution of ash polydispersion and wavelength change of ash complex refractive index. Results of P₁ approximation agree well with those of P₃ approximation when optical thickness is greater than about 2. Scattering effects can be neglected for a large optical thickness and a small scattering albedo, but precise calculation is needed when the absorption coefficient of the combustion gas is of the same order of magnitude as the scattering or absorption coefficient of the ash polydispersion.

View full abstract

Touhoku Electric Power Company and Mitsubishi Heavy Industries, Ltd. are now jointly developing key technologies of a next generation high temperature gas turbine. The gas turbine operates at a 1500°C firing temperature and a thermal efficiency of a combined cycle plant which consists of the gas turbine and a steam turbine cycle is expected over 55% (LHV). The key of the gas turbine are dry low NO_x combustion system technology, an innovative blade cooling and advanced heat resistant materials. The selected technologies for the purpose are a premixed dry low NO_x combustion system, a full coverage film cooling and a directional solidified blade. The program consists of two phases. The first phase is the evaluation of the candidate technologies and the second phase is the improvement of the technologies for practical application. The paper describes an outline of the joint development program.

View full abstract

This paper describes the results of feasibility study on an Integrated Coal Gasification Combined Cycle (IGCC) Power Plant of 350 MW unit output. The purpose of this study is to achieve higher thermal efficiency by composing the proven and high reliable components. The selected IGCC process in this study consists of a coal dry feed oxygen-blown pressurized entrained flow gasifier, a wet low temperature cleanup system, a high temperature gas turbine, a reheat steam cycle and a cryogenic air separation unit. In this study, steam cycle conditions and performances of main components based on the latest technologies are surveyed and evaluated, furthermore this study also evaluates the highly integrated system which integrates an air separation unit and a gas turbine. As a result of this study, more than 43% (HHV) net efficiency is expected.

View full abstract

Municipal waste is incinerated at the rate of 35 million tons a year in Japan. However, the generation of electricity from the combustion heat is quite limited because of the irregular supply of the waste, fuel caused by (1) the difficulty in handling, (2) difficulty in steady collection of an adequate quantity and (3) fluctuation in the properties and quantity. Recently, a technique was developed to mix municipal waste with calcium oxide and to pelletize the material into dry, hard RDF, which can be stored biologically stably for a long period of time. This paper reports that the RDF can be burned completely without any difficulty, in a circulating fluidized bed combustor, and the emission of air pollutants such as NO, N₂O, SO₂, HCl and dioxines is quite low.

View full abstract

A new concept of the coal combustion system with very high molten slag removal efficiency is proposed, wherein a cyclone-type combustor and a pebble bed filter are combined. The major part of the molten slag is deposited on the wall of the cyclone-type combustor by centrifugal force, and the carried-over smaller-size molten slag particles are caught in the pebble bed filter by inertia. To demonstrate the feasibility of such a pebble bed filter, cold model experiments of minute particle filtration are carried out under conditions similar to those in commercial-scale coal combustion systems. From the experimental results, a new empirical equation is derived which is applicable for predicting the filtration effciency of the pebble bed filter. Based on this equation, a trade-off calculation is carried out between the slag removal efficiency and the pressure loss of the commercialscale pebble bed filter, which shows that very high slag removal efficiency can be expected with reasonable pressure loss.

View full abstract

Renewable energy technologies are expected to be capable of contributing significantly to solution of the global warming problem because of their inherent advantages : resources can be considered as virtually inexhaustible and no carbon dioxide release will occur during the energy conversion process. On the other hand, their generally high energy cost due to low availability inevitably makes it difficult, under the prevailing decision-making process based on conventional performance indices, to exploit their advantages on the large scale of substitution for conventional energy technologies such as fossil fuel or nuclear power. In the present paper, we introduce a methodology based on indices derived from net energy analysis to assess the significance of renewable energy technologies as an option to mitigate global warming as well as to satisfy future energy demand, and discuss the effectiveness of some new carbon-free energy technologies, including the proposed Hydrogen-Based Global Renewable Energy Network System.

View full abstract

If the compression process of a regenerative gas turbine cycle is replaced by an isothermal process, higher thermal efficiency can be expected. This combination of Brayton and Ericsson cycles has a potentially higher efficiency. Isothermal compression can be achieved using a hydraulic air compressor, which converts hydraulic energy into the energy of compressed air. It can be used as the compressor of the gas turbine system. The performance of the system was analyzed by assuming conventional operating conditions and component characteristics. As a result, the higher thermal efficiency of the system was proven, and an output larger than that of a conventional hydropower plant was obtained.

View full abstract

The development of an energy-supply system which is considerably efficient and does little harm to the environment is desirable. Adsorption heat pumps satisfy these two requirements because they use low-level thermal energy as a driving force, and use safe and natural substances ; silica gels or zeolites as adsorbents and water as the refrigerant. A tube plate reactor in which adsorption and desorption take place is proposed here to make the system compact, to enhance heat transfer, and to provide heat storage capacity. As a simple measure to evaluate heat and mass transfer in adsorbent beds, the concept of equivalent thermal conductivity was defined and identified through fundamental heat and mass transfer experiments and simulations. However, the equivalent thermal conductivity obtained is so small that fins must be adopted. In this paper, thermal design of the adsorption reactor is developed through simulations using the equivalent thermal conductivity of adsorbent beds, and as a result, the relationship between heat storage capacity, COP, and required area for the adsorption reactor is quantitatively evaluated.

View full abstract

For protection of the global environment, suppression of CO₂ gas emission from power systems is required. In the present paper, separation of CO₂ gas from fossil fuel with a combined SOFC and turbine system is proposed to satisfy this requirement. The results from a model calculation of the system indicate that the total thermal efficiency of the system is higher than 60% (LHV) and increases with increase in fuel utilization and also with decreases in excess air factor, steam carbon ratio, air recirculation ratio and system pressure. Furthermore, CO₂ concentration in the exhaust gas from the present system is 1/10 or less of that from existing heat engines. In addition, CO₂ concentration supply to a CO₂ separator in the system is 10 times as high. This means that the present CO₂ separator can be minimized in volume to about 1/10 of the volume of separators applied to existing systems.

View full abstract

Design requirements for the next-generation LWR have been investigated by many organization. In summary, these investigations suggest that improvement in plant safety is required through the evaluation of system simplification, reliability enhancement and preclusion of human factors. Hybrid safety systems, which are combinations of passive safety systems and active safety systems, have the possibility to satisfy the design requirements for next-generation LWR. This article shows the configuration of hybrid safety systems by describing the system selection process and then shows the results of system simplification.

View full abstract

In order to predict the critical power of a BWR rod bundle by calculation, we have developed a fuel rod spacer effect model for quantitative estimation of the spacer effect on film flow on a fuel rod surface. Unknown parameters introduced in the spacer effect model are determined, based on critical power test data conducted at the Toshiba 4×4 bundle test loop. In this parameter estimation procedure, a boiling transition (BT) rod position effect is included, using critical power test data in which BT is expected to occur at different rod positions. The spacer model developed in the present program has been implemented in the film flow model subchannel analysis code CRIP version 2, and the calculated critical power is compared with the 4×4 bundle test data. The results of measurement and analysis show good agreement.

View full abstract

The present study is concerned with the prediction of gas entrainment onset conditions for free surface flow in the vessel of a fast-breeder reactor. The scale effect on the gas entrainment onset was examined by conducting water experiments using 4 scaled models, while the effects of fluid properties were studied by changing the viscosity and the surface tension coefficient of working fluids. The experimental results have indicated that the critical Froude number decreased in proportion to the -0.5th power of scale. The results have also shown that gas is likely to be entrained with a decrease in viscosity and surface tension coefficient. Furthermore, applicability of a computational method to gas entrainment prediction is studied by means of a finite difference analysis.

View full abstract

A sodium-immersed electromagnetic pump (EMP) has special features of high reliability, high maintainability and norestrictions for installation, in comparison with a mechanical pump. This type of EMP has the potential to simplify the FBR plant system by its application to the primary system. In this paper, a study on practical EMP application focusing on an EMP system and the structural concept, and a development of a coil under high temperature focusing on the electrical insulation system of a large coil are described. For practical EMP application, the system components and the structural concept for the modular double pool reactor are established. For development of a coil, heat cycle testing from the point of view of mechanical and electrical characteristics under high temperature is first carried out. It is confirmed that the electrical insulation characteristics for the first-step heat cycle test are adequate.

View full abstract

The objectives of the experimental program of research were to study the behavior a pressure-driven, three-dimensional turbulent boundary layer with embedded streamwise vortices. Two different vortex orientation were examined. Case 1, the vortex rotation is opposite to the direction of the near-wall vorticity of the three-dimensional boundary layer. Case 2 is the opposite rotation. The downstream devolopment of the vortex and the boundary layer were examined. The axial velocity contours for Case 2 show a far greater distortion than for Case 1. The stray vortex sweeps low momentum fluid away from the wall. The peak vorticity decays very rapidly in the three-dimensional boundary layer compared with two-dimensional boundary layer.

View full abstract

The paper presents the Reynolds stress data for the two cases. Case 1 in which the vortex sign is opposite that of the near-wall vorticity of the three-dimensional boundary layer and Case 2 in which the vortex sign is the same as the near-wall vorticity. The value of U² is initially large in the vortex core region but decays rapidly for both Cases through the third measurement slot. Regions of high U² develop on upwash side of the vortex and above the vortex center, in Case 2. The first region is the vicinity of the cross-flow separation point. The contours of V² and W² show an elliptic shape centered on the peak vorticity point. The difference between the vertical and spanwise normal stress component shows increasing distortion going downstream, in Case 2.

View full abstract

The present research is undertaken to further the physical understanding of the behavior of an embedded vortex in a three-dimensional turbulent boundary layer. The vectors of instantaneous transport of turbulent kinetic energy are large above the vortex and in the downwash region, in Case 2. The production terms are mainly contributed to the values of V² and W². Then these profiles show an elliptic shape centered on the peak vorticity point. Both the production and advection terms of turbulent kinetic energy fall rapidly between the first and second measurement stations. In Case 2, a region of high production develops in the upwash region. The contribution of production and advection results in a uniform high value of turbulent kinetic energy in the entire region above the vortex.

View full abstract

A two-dimensional jet impinging on a body generates an aerodynamic sound. Although frequency of the sound is predicted on the basis of the feedback mechanism, the sound level cannot the-oretically be obtained, partly because the effect of vortices separated from the surface on the feedback mechanismis not understood yet. In this paper, the sound and structure of the jet vortices impinging on the surface were experimentally studied by changing the shape of the body to realize different flow separation from the surface. The body was a circular cylinder and an aerofoil whose leading edge was a semicircle with the same radius as the cylinder. Phase-averaged vorticity and surface-pressure distibutions were presented. The sound level was generally higher, the jet vortices impinging on the surface were more compact, and the rms surface pressure was much higher for the circular cylinder than for the aerofoil.

View full abstract

An experimental study is carried out on a fully developed turbulent channel flow with uniform injection through a porous wall at five injection rates. Attention is mainly paid to a self-preserving region of such flows. The fluctuations of streamwise velocity, as well as the mean velocity profiles, are measured by means of a hot-wire anemometer. Mean velocity decreases in the region of y/h< 0.15 and increases in the core region. A similarity of the velocity defect profile is observed when the velocity defect is normalized with the outer scales. Turbulence intensity increases with increasing injection rate except very near the wall. Moreover, the relationship between van Driest's damping factor and nondimensional injection velocity, and the method of determining the friction velocity are clarified.

View full abstract

The boundary layer transition caused by the disturbance generated by a circular cylinder placed in the free stream is experimentally investigated. The cylinder is located dwnstream of the leading edge where the Reynolds number is above the critical value, although the boundary layer is laminar to this point. The distance between the cylinder and the wall is chosen so that the cylinder wake gradually merges with the boundary layer downstream. In contrast to the case of small free-stream disturbance, the transition process in this case starts with the appearance of "streaks." For large cylinder-wall distances, the streaks are followed by turbulent spots, while for the small distances, they directly generate turbulence downstream. A geometrical parameter is newly defined, with which the spanwise spacings of the streaks are correlated, and the observed flow patterns are easily classified.

View full abstract

A new pressure-strain-rate correlation model in a Reynolds stress equation is proposed. When a Reynolds stress equation is written in other than Cartesian coordinates, source-like terms arise in convection terms. The present model incorporates the effect of isotropization on the source-like terms. New model constants are determined to satisfy four basic criteria simultaneously : (1) the effect of streamline curvature, (2) measured stress levels in homogeneous free shear flow, (3) analytical results for rapid distortion theory and (4) return to isotropy in grid turbulence decay.

View full abstract

Numerical predictions employing three types of stress equation models, which are those of Launder et al., Gibson-Younis and the authors' are conducted and compared with an experiment of turbulent decaying swirling flow in a long circular pipe. The accuracy of the prediction with the authors' model is demonstrated as compared with those of Launder et al. and Gibson-Younis. Characteristic momentum transport induced by swirl is interpreted with respect to the interaction between production and pressure-strain-rate terms. In particular, it is stressed that it is important to consider the effect of isotropization on source-like terms which appear in convection terms.

View full abstract

This paper describes the yield stress of a water-based magnetic fluid having typical concentration and magnetization. Yield stress was estimated from the relationship between shear rate and shear stress in a two-dimensional channel in a low-shear-rate region. When the interaction between magnetic field and flow vorticity is the greatest, yield stress was clearly observed. On the contrary, when the interaction disappeared, yield stress was not observed. Based on these test results, yield stress due to structures of solid particles formed in a magnetic fluid is considered to be very small and the apparent yield stress mentioned above is considered to be due mainly to the interaction between magnetic field and flow vorticity. This idea was verified through a flow resistance test in a circular channel.

View full abstract

This paper deals with anomalous shapes of viscoelastic fluid extruded from circular nozzles. The working fluid employed was prepared by mixing nine kinds of low-density polyethylene sold by several makers. The extrudate picked up consists of two distinct regions, wavy smooth and melt fracture, which are arrayed alternately. Their period and ratio were studied. The data were rather scattered but mean values were arranged well. It was elucidated that the frequency of the period was in direct proportion to the shear rate, and the ratio gradually approached the fixed value with increasing shear rate.

View full abstract

The issue of open, or outflow, boundary conditions is important in the numerical simulation of incompressible viscous flows. However, there are few studies of this problem because it is very difficult to give exact mathematical conditions for finite and artificial boundaries. In this paper, four types of open boundary conditions are compared numerically in a two-dimensional flow past a square cylinder using a finite difference method. They are a free outflow condition and three kinds of Sommerfeld radiation conditions based on the free stream velocity at infinity, Halpern's analysis, and the local velocity. The free outflow condition deforms velocity and pressure fields, while the Sommerfeld radiation condition utilizing the free stream velocity has the least influence on the flow.

View full abstract

This paper gives a detailed investigation of the fractal feature of sets of isoconcentration points taken from data on an axisymmetric point source plume which is evolved in grid-generated turbulence and distorted by a sphere. The following points are clarified in this paper : (1) The fractal dimensions of sets of isoconcentration points, D_f1, are valued at approximately 0.3, and are likely to be independent of the threshold level of a wide range of concentration : (2) Although there is no clear range of the -5/3 power law in the spectra of the turbulence and the concentration fluctuation, sets of isoconcentration points appear to be fractal-like, and the fractal dimension is close to the value of 0.36±0.05, found in high Reynolds number flows : (3) The distortion of flow due to a sphere has almost no effect on the magnitude of the fractal dimension of a set of isoconcentration points, but merely gives rise to the change of the boxsize range within which the fractality holds.

View full abstract

A large cabinet model(812 by 812 by 1856 mm) containing a heater was fabricated. Experiments were conducted using this cabinet model for free convection cooling and for forced convection cooling by a fan. The measured internal temperature distribution of the cabinet model was compared with the prediction on the basis of flow network method. This calculation method assumes the flow to be one-dimensional, while friction, buoyancy and radiation effects are taken into account. The results of calculation agree well with the experimental data in the case of forced convection cooling, however a discrepancy of about 5% between the experiment and the prediction was observed in the case of free convection cooling.

View full abstract

The effect of compressibility on the two-dimensional large-scale structures in a single shear layer was investigated for the temporally developing case. Each eddy is elongated by compressibility through (i) the formation of volumetric source and sink distribution and (ii) the emergence of unstable travelling waves under the condition that the Mach number of free streams, M, exceeds unity. The dilatation accelerates the streamwise velocity and decelerates the transverse velocity, so that the convection of vorticity makes the resulting eddy elongated in the streamwise direction and reduces its own angular velocity of rigid-body rotation. The eddy formed at M>1 takes an airfoil-like shape and has almost the same thickness as the original shear layer, due to an existing phase velocity different from the mean value of the two free stream velocities. Each eddy can propagate by itself in such a way that its leading edge rolls up the tail of the preceding eddy.

View full abstract

We performed numerical simulations of supersonic conical nozzle flows and supersonic flow past wedge-shaped test pieces. We used the point-implicit MacCormac scheme to solve the governing equations. Chemical source terms were calculated using the Park model. The equation of Millikan was used to calculate relaxation time of vibrational energy of diatomic molecules. We consider two reservoir conditions : design and experimental. From these numerical simulations, the following conclusions are obtained. (1) Due to the effect of the boundary layer in the nozzle flow, the Mach number at the exit becomes smaller compared with the inviscid one-dimensional result. (2) The flow field can be considered as chemically frozen downstream from the shock wave. (3) The behavior of vibrational energy downstream from the shock wave in the experimental conditions on the ground is different from that in flight conditions at high altitude.

View full abstract

In this paper, the vortex method presented in the previous report is used to analyze the separated unsteady flow in a centrifugal impeller for various discharge coefficients C_e=Q/Q_n (C_e=0.6, 1.0, 1.5). From the results of the numerical analysis, the unsteady phenomena of the flow between the blades are clearly shown and are seen to be changed with both the formation of a reversed flow area and the emission of separated vortices from the outlet of the impeller as time elapses. Moreover, the characteristics and the slip factor of the centrifugal impeller are also discussed qualitatively.

View full abstract

The effects of diffuser outlet blockage using a damper ring on rotating stall in a vaneless radial diffuser were experimentally investigated. The main results are as follows. As the outlet area decreases, the flow rate of stall onset moves to the lower flow rate side. The suppression effect on rotating stall by restricting the outlet area is not caused by changing the mean time values in the diffuser such as static pressure ratio and flow angle distribution in the range of 1≤r/r_i≤1.61. The magnitude of rotating stall under the restricted condition becomes weak with decreasing amplitude and the frequency of its fluctuation decreases under the outlet condition BR≥0.5.

View full abstract

Detailed measurements of flow velocity and pressure field were undertaken in a radial vaneless diffuser. The unsteady flow pattern at critical flow rates for rotating stall was investigated, using a transient data recorder which can store the velocity and/or pressure signals prior to the stall onset. The results show the existence of prestall symptoms that can be characterized by velocity/pressure oscillation with a frequency of 1.45 times that detected during the succeeding rotating stall. The measurements of velocity field using an X-wire probe confirm that this velocity fluctuation is associated with the reversed flow region, and transfers in tangential direction at an angular velocity of about 15% of the impeller revolution. Although the duration of this prestall phenomena diminishes with the decreasing flow rate at which the stall takes place, it is confirmed that its occurence is commonly observed for the conditions covered by the present study.

View full abstract

Oil hydraulic gear pumps are well known for yielding a pulsating flowrate which is theoretically determined by the geometry of gears. In the present paper, we aim to measure actual waveforms of a gear pump output with high-frequency pulsation. The measurement is based on detecting pressure differences kinetically induced by the motion of an oil column, and the accuracy of the method has proven satisfactory in advance of actual use. The findings are as follows : (1) Whether the pulsation impedance for the 1st harmonic at the pump outport is larger or smaller than that for the 2nd harmonic mainly dominates the waveforms of flowrate pulsation. (2) According to whether the impedance for the 1st harmonic is larger or smaller than that for the 2nd harmonic, the 2nd harmonic of pump output becomes larger and the 1st one smaller than the theoretical predictions, or vice versa. (3) This tendency becomes more marked as the line pressure increases.

View full abstract

The high-pitched noise emitted by a regenerative pump is mostly generated by the impact of the recirculating flow against the partition between the discharge port and the suction port. The recirculating flow between the impeller and the flow passage in the pump is the basic mechanism for the pumping action. In a test pump, 87% of the noise energy was generated by this factor under nominal operating conditions. By tilting the surface of the partition on the discharge port side, the energy of the impact noise was reduced as much as 57%, and the noise level of the pump was decreased by 3 dB. An analytical model of noise generation by impact of the recirculating flow was developed, and the predicted noise levels of the pump with the partition tilted at four different angles agreed with experimental data within 0.3 dB.

View full abstract

This paper proposes a new type of nozzle which generates a high-speed two-phase water jet as a propulsion device for a ship. The high-pressure gas accelerates the two-phase jet by temporal and local pressure gradients ; therefore, the principle of accelerating water flow is different from that of jet pumps. A two-dimensional nozzle was set in a towing tank, and the thrust was measured for various parameters such as pressure of the injection gas, towing speed, air injection angle, and front and/or near opening angle. The thrust increases monotonically as the gas pressure increases for all flow velocities, but it converges to a maximum value. The propulsion effeciency increases as the flow velocity increases, but it is higher when the gas pressure is lower. It was proven that the proposed device is applicable to ship propulsion by operation of a model ship using this device.

View full abstract

In radiation heat transfer evaluation, the hemispherical emittance spectrum is the most important characteristic quantity. This emittance is directly related to the hemispherical reflectance R_HH for perfect-diffuse hemispherical irradiation. However, there has been no proper technique for measuring R_HH of real surfaces which reflect radiation imperfect-diffusely. In this paper, we present a new reflectometer system for measuring a spectrum of R_HH in a wavelength region of 0.35-1.10μm. This system has two ellipsoidal mirrors and a beam splitter to realize the perfect-diffuse irradiation and the hemispherical reflection detection. This system also measures the spectra of normal- and obliqueincident hemispherical reflectances. We apply this technique to the investigation of the spectral and angular characteristics of reflection from rough surfaces of mild steel, and demonstrate the capability of the system in a fundamental study of radiation characteristics of materials.

View full abstract

This paper deals with thermal properties of oil (tetradecane, C₁₄H₃₀, melting point of 278.9K) / water emulsion as a latent heat storage material having a low melting point. The measured results of the physical properties of the test emulsion, i.e., thermal conductivity, specific heat, latent heat and density, were discussed for the temperature region of solid and liquid phases of the dispersion material (tetradecane). It was clarified that Eucken's equation could be applied to the estimation of thermal conductivity of the emulsion. Moreover it was established that tetradecane as the dispersion material exhibited a supercooling phenomenon which influenced the thermal properties. Useful correlation equations of thermal properties for the emulsion were proposed in terms of temperature and concentration ratio of the emulsion constituents.

View full abstract

The horizontal continuous casting process was simulated. In the model, heat transfer of the whole system including the casting machine was considered. Temperature distribution and heat flux under normal operating condition were presented and the heat transfer characteristics were clarified. Conditions in the calculation, such as thermal resistance of mold section, and of carbon liner, inlet temperature of cooling water, its flow rate and withdrawal speed, were varied and the thermal effect on the forming process of steel was studied. Furthermore, a guide to optimize the size of the casting machine to improve the efficiency of manufacturing was proposed.

View full abstract

There have been many experiments to characterize Diesel fuel spray under steady-state conditions. However, the appropriate number of holes and the hole position on the sac to be used in the experiment are not clear. To address this subject, we investigate Diesel type spray flows using a laser Doppler anemometer (LDA) and a phase Doppler anemometer (PDA). Spray flow characteristics such as mean and fluctuating two-component velocities, two-dimensional distribution of particle diameter and the variation of three parameters at the log-hyperbolic fitting for particle size distribution are given from measured data. Spray jets from four varieties of Diesel nozzle are compared with each other to clarity the differences in spray characteristics between them. The results show that the spray from the single-hole nozzle on top of the sac is distinct from the others.

View full abstract

A pulse response test of an aircraft turbofan engine has been conducted in ground-level static conditions in order to obtain dynamical characteristics of the engine in the linear operating range and to develop a high-fidelity mathematical simulation model. The engine test results have been compared with the simulation results in regard to frequency characteristics of rotor speed for fuel flow perturbations. By taking the heat capacity of the combustion chamber into account, we have improved the phase lag characteristics of the model. Examination of other characteristics such as time constants of high-pressure rotor speed at various operating points has verified the high fidelity of the modified simulation model.

View full abstract

Experimental and analytical investigations on the catalytic oxidation of formaldehyde were carried out. Experiments were conducted in the catalytic reactor by changing parameters such as the concentration of coexisting NO, the type of noble metal and the amount of loaded noble metal. The experimental results showed that the presence of NO in the reaction gas affects the formaldehyde oxidation characterisics and the phenomenon of physical adsorption strongly appears in the low-temperature region. By consideration of this physical adsorption, formaldehyde removal rates in a catalytic reactor were predicted. The evaluation indicated that a satisfactory agreement between the predicted and experimental data is obtained when physical adsorption is considered.

View full abstract

Three low NO_x combustors, i.e., a lean premixing combustor, a rich-lean two-stage combustor and a lean diffusion flame combustor are tested in order to determine a suitable combustion design for an automotive ceramic gas turbine combustor. The prevaporization-premixing lean combustion is proposed as the most promising candidate to meet the Japanese l0·15 mode regulation for gasoline passenger cars. Droplet size for the atomizer, air-ratio range, air loading and other dimensional criteria in the lean primary combustion zone are proposed.

View full abstract

The coming shortage of crude oil supply and the demand for environmental conservation has resulted in an increased interest in introducing alternative fuels for internal combustion engines. The objective of the present work is to identify the role of the properties of various liquid fuels in the performance of a spark ignition engine. Fuels tested were methanol, ethanol, isooctane, benzene and regular gasoline. Attention was focused mainly on the chemical aspect of the fuel properties, while the influence of physical parameters was minimized. A test engine was devised so as to allow the liquid fuel to vaporize well and to mix with fresh air prior to being charged inside the combustion chamber. The mixtures were observed by means of the laser light scattering method. The cylinder pressure, rate of heat release, combustion duration, thermal efficiency and NO emissions were measured.

View full abstract