The corrosion fatigue crack growth rate of a high tensile strength steel HT55 has been measured in 1% NaCl solution at various stress cycle frequencies and stress ratios to elucidate the corrosion product-induced wedge effect and dominating mechanical parameters for crack growth. The wedge effect is greatest at R = 0.1, whereas it is less great in the order of R = -1 and R = 0.5. At R = -3, however, the wedge effect disappears, and the growth rate is higher in 1% NaCl solution, the load-strain hysteresis loop traces different paths during loading and unloading periods, resulting from viscosity of the corrosive solution remaining within cracks, but the load sharing capacity of the viscosity is negligibly small. Regions I and II in the hysteresis loop must be taken into consideration to explain uniquely the corrosion fatigue crack growth characteristics under various conditions, and a contributory stress intensity factor range ΔKcontis proposed as a difference between ΔK and ΔK<ret>, deduced from the load range shared by regions I and II.
The effects of specimen geometry, specimen thickness, stress ratio and frequency on the fatigue crack growth rate of structural steels were examined at 123 K to clarify the formation mechanism of a cleavage during fatigue crack growth, and the condition of the final fracture. Fatigue crack growth rate at 123 K was found to be sensitive to the stress ratio, and to be considerably increased by the occurrence of a cleavage during striation formation. The value of Kci at which the first cleavage appears was about 20 MPa√m regardless of specimen configuration of the material caused by cyclic straining ahead of the crack tip. The value of Kfc at which final fracture occurs is fond to increase as the specimen thickness does not satisfy the size requirement for small scale yielding.
A series of creep-fatigue interaction tests were conducted in order to evaluate a criterion for failure taking into account the detrimental effect caused by the time dependent process. From the test data on commonly used high temperature materials for gas turbine and diesel engine in air, hydrogen gas and corrosive ash, we proposed a life estimation method under the combined creep-fatigue loadings. This method based on linear cummulative creep damage expressed by the equivalent hold time is stress dependent and independent of loading modes. We confirm by this method that the correlation between experimental data or available data in literatures and estimation is quite good for several types of loadings. Our experiments need no complicate testing to obtaining the material constants but require only the conventional simple low cycle fatigue tests with the effects of hole time considered at peak strain or stress and creep rupture tests.
In the previous reports, theoretical results about cutting resistance of cutting surface were considered through experiments. In the experiments soft polymers were cut by applying low frequency harmonic vibration to a knife-blade in the longitudinal direction (X direction). The present paper treats the method of elliptical vibration cutting which utilizes effective reduction of both the solid friction and the cutting resistance which occur in the cutting and non-cutting processes in one cycle of vibration. In this method, it is clear that not only is the cutting resistance in the V direction less than half of the previous results, but also the cutting resistance in the X direction has an equivalent nagative value. And in addition, the cutting surface of elliptical vibration cutting is as high in quality as in rectilinear vibration cutting. That the theoretical results agree well with the experimental results has been confirmed.
Notch tensile tests are performed to evaluate the effects of stress triaxiality at the net section and uniaxial tensile properties on the notch strength ratio. Notched cylindrical specimens with a U-shaped circumferential notch are employed. These specimens are made of eight kinds of materials chosen for providing a wide variety of deformation characteristics. The notch strength ratio increases with stress triaxiality factor proportional to the ratio of hydrostatic to equivalent stress, and with the ratio of local to total elongation in an engineering stress-strain curve. The notch strength ratio is determined by the multiplication effect of these two factors. Notch strengthening occurs owing to the strong multiplication effect. The value of the notch strength ratio can be obtained by an empirical equation expressed in terms of these two factors. The notch strength ratio is independent of the absolute quantity of ductilities of a material.
As a basic study for the establishment of an accuracy estimation method in the finite element method, this report deals with the problems of transverse bending of thin flat plates. From numerical experiments for uniform mesh divisions, the following relation was deduced; ε∝(h/a)k, k≥1, whereεis the error of the value by the finite element method relative to the exact value and h/a is a dimensionless mesh diameter. Combining this relation with the results obtained by error analysis for local mesh refinement, an accuracy estimation method based on the recursive simulation method was presented. A computer program using this accuracy estimation method was developed and applied to nineteen problems of various plate shapes. The usefulness of this accuracy estimation method was illustrated by these application results.
Hardness is influenced by mechanical properties of a spherical indenter in the elastic-plastic transient indenting process. To clarify that point, we indented steel and tungsten carbide spherical indenters into several standard blocks for hardness. In order to experimentally establish the relations of the elastic-plastic transient indenting process. we related the hardness Pm (mean contact pressure) with the true profile coefficient of a permanent indentation (d/Dp), not with an apparent profile coefficient (d/D) used traditionally, and formulated as follows; Pm=Pup(d/Dp)xp We can calculate the hardness affected by the different mechanical properties of the spherical indenter using this formula for arbitrary conditions. Further, we compared the Brinell hardness obtained by Yoshizawa with our calculated values, and found good coincidence between them.
In this paper, fundamental experiments are carried out to examine the occurrence of slip bands (flecks) in a copper electroplating foil under variable stresses. The following conclusions are drawn: (1) Miner's rule holds for the occurrence of slip bands under two-level single block stressing; (2) the appearance of slip bands is dominated by the amplitude of the plating foil, cumulative fatigue damage that causes the slip initiation and the grain growth in the foil is not dominated by Miner's rule; and (4) both overstressing and under stressing reduce the heating duration for recrystallization of the copper plating foil and then promote the occurrence of slip bands.
In the pressure vessel of a reactor which is subjected to some kinds of thermal loading, the J integral for an assumed crack is evaluated using the finite element method. By considering the effect of the stainless steel cladding, the J integral is extended to the multi-phase material. First, a two dimensional crack is treated. Two cases, one a surface crack and the other an embedded one, are analyzed and the effect of the cladding on the J value is studied. It is shown that the cladding effect appears in a complicated form and it changes with the position of the crack and the cladding. Second, a athree dimensional embedded crack is analyzed. Thre three dimensional J integral is evaluated around a crescent type crack, and the result is compared with that of a two dimensional analysis. It is concluded that two dimensional modelling is enough to discuss the cladding effect in the case considered in this paper.
To investigate the effect of hydrostatic pressure on the fracture toughness of boron steel and aluminum alloy, a compact tension test based on ASTM Standard is carried out under pressure up to 400 MPa. The displacement at the crack initiation is detected by an electric potential difference method under pressure. The elastic-plastic fracture toughness JIC increases with an increasing increasing pressure. The phenomenon of the increase of fracture toughness due to pressure is confirmed by measuring a critical stretch zone width of boron steel. The experimental JIC values are compared with the J-integral values analyzed by FEM.
In the present paper, replacing similar adherends and an adhesive by finite strips, stress distributions in adhesive joints are analyzed strictly using the two-dimensional theory of elasticity in the case where adhesive butt joints are subjected to tensile loads. The effects of stiffness and thickness of adhesive on the stress distributions are shown by numerical computations. For verification, an experiment is performed, and the analytical result is in fairly good agreement with the experimental one. Furthermore, the analytical result and the result obtained by F. E. M., are in fairly good agreement.
A plane elastostatic problem of two bonded elastic half planes consisting of isotropic and anisotropic materials is considered. It is assumed that the isotropic half plane contains a straight crack normal to the bimaterial inter face, and the bonded plane is subjected to a constant strain away from, and perpendicular, to the crack. Two cases of the crack fully embedded into the isotropic half plane and terminating at the interface are investigated. The problems are formulated as singular integral equations with Cauchy and generalized Cauchy kernels, using the method of continuous distribution of dislocations. Numerical results are presented for the order of stress singularities and stress intensity factors, and for typical material combinations.
The effects of interaction between crack-like defects in fiber reinforced composite materials on the local stress concentrations in their neighbourhoods are theoretically investigated from the macro and micro and micromechanical points of view. The most simple models consisting of homogeneous and heterogeneous anisotropic elastic plates with two collinear or parallel cracks are assumed, and the mathematical formulations are made in terms of the Cauchy-type singular integral equations of the first kind by the methods of harmonic-type stress functions and Fourier transforms. Numerical calculations are carried out for the stress intensity factors, and the results thus obtained from these models are compared with each other.
This paper describes a new approach to bending problems of circular plates with uniform or a concentrated load under mixed boundary conditions. The cases are considered when circular plates have boundary portions of two kinds, i.e. clamped portions and simply supported portions. A method proposed in this study is an iterative method, and by comparing the results obtained by this method with ones by other investigators its validity is proved.
The deformation and strength of single lap joints having adherends of dissimilar materials were investigated both analytically and experimentally. The strain distributions under tensile shear loads of the joints of carbon steel and aluminum alloy bonded with epoxy resin were analyzed using the finite element method. The analytical result was shown to coincide approximately with the experimental one. The analyzed strength was less than the experimental one probably because the former predicted the initial cracking loads whereas the latter predicted the fracturing loads which were different from the former. Young's moduli of adherends and the adhesive length had great effect on the joint strength. The strength of joints of carbon steel and aluminum alloy had valued intermediate between the strengths of joints having carbon steel adherends and aluminum alloy adherends. The curing process of the adhesive resin improved the joint strength overcoming the difference in thermal properties of the adherends.
Errors included in solutions obtained by the boundary element method analysis are generally larger than those by the finite element method analysis in the case that the number of discretized elements is small. One of the reasons is supposed to be attributable to the error which will be produced in the numerical integration of the singular functions of the type (1/γ)n in a two dimensional elastic problem. In this report the distance r between a load point and an observation point on a boundary element was represented graphically by two parameters. Then the functions composing the fundamental solutions could be classified into seven basic ones and their tendencies along an element were characterized. The following results were obtained: (1) Errors of the numerical integration of the functions are small enough in the region γd/L>0.5 even if four points are chosen in the Gaussian quadrature formulas. (2) The higher the exponent, the more increase the errors in the integration of the functions γi<, x>γj<, y>ξk/γl. Then, the methods to reduce computing time and to decrease errors of the numerical integrations are proposed.
A descriptive model for rate-dependent behavior in cyclic plasticity, based on the random barriers theory, was presented by considering the velocity of a moving dislocation which was one of the movable dislocations and named a"free dislocation"in this paper. Each of the stress- and strain-rate sensitivities on the stress-rate relation in each half cycle could be fairly well estimated on the basis of an equilibrium equation derived in this study as a function of the stress-rate and the strain-rate at any stress level. Moreover, several types of transient behaviors caused by a sudden change in the stress- or strain-rate might be uniformly expressed by each analysis of the processes in which a deficient or excess quantity of the free dislocations in this period came close to the moderate quantity decided by the stress and stress-rate.
Experimental results concerning the forming limit of in-plane stretching of brass, copper and aluminum sheet alloys are presented. Theoretical curves of limit strains are calculated on the basis of the modified M-K (Marciniak and Kuc'zynski) analysis in which M-K analysis is applied to the post-diffuse necking (post-instability) condition. The imperfection is represented by the apparent initial inhomogeneity factor, f, as estimated from the ratio of the minimum to maximum thickness of the sheet at the instability condition, which is equal to unity at plane-strain condition and then decreases with an increase of strain ratio. It can be concluded that the predicted limit strains depend on the work hardening law equations applied and, when best fit work hardening law equations for the materials, namely Voce, Swift, and Hollomon law equations for brass, copper, and aluminum, respectively, are applied, the predicted limit strains are in food agreement with the experimental data plots. These results are explained in terms of the work hardening behavior.
Some finite-difference methods, which use primitive variables, are proposed to analyze an incompressible fluid flow. Especially, two methods are developed: one is to calculate the accurate pressure field immediately after the fluid starts to flow (two-step method); the other allows a larger time-step than the corresponding explicit method (non-iterative implicit method). As a numerical example, the two-dimensional transient Womersley flow, and the non-iterative implicit method requires less computer time compared with the explicit method.
Flow in a two-dimensional square cavity was investigated primarily by visualization using white starch powder or aluminium powder suspended in water; the flow was generated by sliding the cavity model itself on a stationary flat plate. Experimental flow patterns at Reynolds numbers up to 1000 were compared with those obtained by numerical calculations. It was found that the experimental location of the center of vortices agrees well with the calculated one. On the other hand the sizes of secondary vortices in the experiment were somewhat smaller than those in the numerical calculations. A velocity profile along a vertical line through the center of primary vortex was experimentally obtained by using the digital image processing technique and it showed fairly good agreement with the calculated profile.
Motion of small particles in a viscous flow past many square cylinders spaced regularly is investigated theoretically. In a steady flow past regularly spaced cylinders found by numerically solving the Navier-Stokes equations, trajectories of small particles are numerically found under the assumption that particles are subjected to Stokes' drag force and the viscous flow is not affected by the presence of small particles. As a result, a critical condition that particles always collide with the square cylinders spaced regularly is found as a function of the mass ratio, the Reynolds number and the situation of cylinders. When the particles do not collide with the cylinders, trajectories of particles which are started from arbitrary positions with arbitrary velocities are found to tend to become only one particular trajectory after a sufficiently long time. There theoretical results are confirmed qualitatively by an experiment undertaken in a slow flow of water.
This paper describes an experimental study on the flow with swirl in a circular duct. The swirl flow is very important for gas turbine combustors, furnaces, etc. In the present study, the velocity and turbulence of the swirl flow in a circular duct was measured using a Laser Doppler Velocimeter (LDV), when the swirl number was varied from 0.45 to 1.35 by the axial flow type swirler. The present study clarified the characteristics of the turbulent intensity, Reynolds stress, turbulent energy and turbulent dissipation ratio for the swirl numbers.
It is known that a swirling flow in a diverging pipe breaks down more easily than a flow in a converging one. In this report, experiments are made using a divergent pipe, a convergent pipe and a straight pipe, in order to clarify the relation between the shape of pipes and the occurrence of the breakdown. A swirling flow field, which is induced in a rotating conical-pipe, is measured by a laser-Doppler-velocimeter. When each pipe rotates faster than a certain critical value, a stationary internal wave occurs. The vortex breakdown phenomenon is ascribed to the internal waves in swirling flows, as pointed out in preceding reports. In the diverging pipe, the amplitude of the wave is smaller than that in the converging pipe; but the average flow near the axis is fairly retarded, so that the flow reverses at the trough of the superposed wave component, and a bubble type breakdown appears. A mathematical model is presented to give a qualitative explanation for the effect of a sectional area variation.
The Savonius rotor was proposed in the early 1920's. Until now, there has been no systematic work on the optimum design configuration of Savonius rotors. In the present work, various model tests were carried out in a wind tunnel, in order to determine the optimum design configuration of Savonius rotors. The effects of seven design parameters on the aerodynamic performance of the rotors were experimentally determined. The parameters were the rotor aspect ratio, the overlap and the gap between rotor buckets, the profile of the bucket cross-section, the number of the buckets, the presence or absence of rotor endplates, and the influence of the stack of buckets. In addition, the flow around the rotor was investigated by the flow-visualization method. In this study, the influence of important design parameters of the Savonius rotor has been investigated and the rotor configuration giving the maximum torque and power has been determined.
The design problems of scroll compressors are discussed in this paper. The critical machine element in a scroll compressor is the thrust bearing when the compressor is employed for air conditioning and refrigeration, over a long period of operation. Not only the thrust, but also the moment acts on the thrust bearing. The theory of Rumbarger is applied to describe the load condition of the thrust bearing. How to optimize the geometric shape of the spiral elements is also of prime interest to the designers. We explain in this paper how the spiral geometry can be optimized when the stability condition, weight, thrust, and outer diameter of the orbiting scroll are taken into account. This optimum design would minimize the overturning moment of an orbiting scroll when the outer diameter of the thrust bearing is predetermined.
A study has been made of the fluidborne vibration (noise) generated by a closed circuit hydrostatic power transmission consisting of a swash plate type axial piston pump, a motor and a connecting pipe. First the mathematical models for flow ripples and source impedances of the test pump and motor have been derived on the basis of the results in the authors' previous studies, and their appropriateness and applicable limits have been examined by making a comparison with the measured pressure ripples carried out on the"high impedance pipe method". Next, the mathematical model for pressure ripple in a hydrostatic transmission has been developed on the basis of the above four characteristic values and the known wave propagation theory for the fluid (oil) column in a connecting pipe. Experimental values of pressure ripple almost agree, up to harmonic frequencies of some 2500Hz. with predicted values from the proposed mathematical model, regardless of the values of system parameters such as working pressure, pump speed, pipe length, etc.
This paper presents the theoretical and experimental results obtained by a study of cylindrical capsules traveled concentrically in pipeline. Considering the total pressure loss of a capsule flow to be established by friction drag and pressure drag, the authors make them clear respectively from both a theoretical and an experimental study. In particular, the flow in the annular section of a capsule is approximated by the flow through annular pipes when the inner pipe moves. Then a general formula, concerned with the pressure loss due to friction drag in a turbulent flow regime for the moving concentric annuli, is derived by taking account of the one-seventh power law for an axial velocity profile and the boundary-layer characteristics on pipe walls. In conclusion, it is confirmed that the capsule velocity as well as the total pressure loss can be estimated with reasonable accuracy.
Fluid flow and heat transfer in a two-dimensional miter-bend were examined in connection with a corrugated wall channel as a means of augmenting a forced-convection heat transfer with a single-phase flow in a heat exchanger. Pressure losses, distributions of mean velocities and velocity fluctuations, streaklines, power spectra of velocity fluctuation and local Nusselt number distributions were compared with those of numerical analysis. It is shown that the effect of heat transfer augmentation is remarkable on the Reynolds number of the order of 2000, where the laminar flow is maintained in the straight channel.
In this paper, firstly it is revealed that straight acoustic streaming generates in the progressive sound field in front of a loud-speaker, by visualizing the thermal field around a heated cylinder. Secondly the influence of the acoustic streaming on the heat transfer from a horizontal isothermal cylinder in a progressive sound field is investigated. The results show the heat transfer of the cylinder in a progressive sound field increases mainly at the speaker side, and the effect depends on the velocity of the streaming rather than on the sound pressure level. Consequently, it is clarified that we should note the straight acoustic streaming, which has been ignored in previous research works, on heat transfer augmentation in a sound field.
An improvement of the principle for measuring thermophysical properties by the direct heating method has been done. In this report, an improved method for measuring thermal conductivity, k, and total hemispherical emittance, ε, is presented. Theoretical evaluations of accuracy in these measurements using a circular rod sample are also conducted. From the results of experiments on silver (99.99% pure), it becomes clear that this is an advantageous method for measuring precise thermophysical properties, such as k andε, of an electrically conductive solid. The results of analysis have been verified by those of experiments. By using the theoretical evaluation of accuracy, the optimum sample size can be determined.
Fluid flow and heat transfer in a plate-fin and tube heat exchanger were studied, using a fundamental model consisting of a pair of parallel plates and a square cylinder passing perpendicularly through the plates, which simulated plate-fins and a tube, respectively. The analytical results were reported about the heat transfer in a laminar region for Reynolds number Re=200 and Prandtl number Pr=0.71. Heat transfer characteristics under a constant wall heat flux condition were show in terms of distributions of temperatures and local Nusselt numbers, and the heat transfer mechanism was investigated in detail.
Analytical expressions of the scattering and extinction efficiency factors, the phase function and the asymmetry factor of a spherical particle embedded in an absorbing medium are derived and then the characteristics of the near-field scattering of a particle are examined in some details.
Pressure oscillation may be induced in liquid when steam is injected into subcooled liquid through a submerged pipe. Theoretical and experimental considerations have been made on mechanism of the pressure oscillation in the case that an oscillatory condensation interface exists at the pipe exit. The pressure oscillation is triggered by a physical process in a vapor phase, being strongly affected by the type of condensation heat transfer at the vapor-liquid interface. A heat-transfer mechanism proposed here well explains parametric effects on various characteristics of the pressure oscillation. A new dimensionless parameter of subcooling is proposed which correlatees water and freon data better than Jacob number. Operational ranges for the onset of pressure oscillation as well as its frequency and amplitude are obtained in analytical forms which are verified by experiments in a wide range of parameters.
The disadvantage of rotary type compressors for automotive air-conditioners is that the refrigerating capacity increases linearly in proportion to the increase in engine speed, and so in the present research, attention was focused upon the phenomenon of the refrigerating flow in the suction stroke, and the conditions for construction of capacity self-controllable type compressors by selecting suitable parameters were established, In this report, the basic equations which represent all stages of the vane's position in suction passage during the suction stroke are introduced. By theoretical analysis of the equations, it is found that the capacity self-control characteristics by choosing the area of the suction port and suction groove can be calculated. These results are confirmed by the experiments.
Recently, the lithium-bromide/water absorption refrigerating machine has begun to be used for the air-conditioning of large buildings. However, more improvement of the absorber, one of its main components, is needed to achieve a better coefficient of performance and also to reduce the whole size and the installation space, In this paper, an analysis of the absorption process is made for the simplified cooling surface geometry of a vertical flat plate instead of the horizontal tubes used in real machines. An analytical model is formulated by assuming that the flow is laminar and that the absorbent is thermodynamically in equilibrium at the surface. The governing equations are solved by the finite difference method and the profile method. Calculation examples of both methods are given for a standard condition. Near the entrance region, the calculated temperature profiles differ slightly, but becomes equal rapidly as flow length increases. The average concentrations agree well.
This paper describes a simulation model used to predict the transient temperature rise in multichip packages. The model was designed to consider not only heat conduction but also thermal radiation and natural convection as well as simplicity. The calculations were made with the designed model (MODEL 1), in addition to only a heat conduction model (MODEL 2). The experiments were performed for a ceramic substrate, which had capacitor chips. It had a 36 cm2 surface area -32 watts heat flow rate. The calculation results with MODEL are in good agreement with the experimental data. However, the results with MODEL 2 are 10 percent higher than those with MODEL 1. It was found that MODEL 1 is very useful for high density multichip package thermal design.
In order to clarify the mechanisms of transition from dropwise to filmwise condensation heat transfer, dropwise condensation curves on a copper surface adsorbing a common monolayer type promoter, trilauryl trithiophosphite, were measured precisely for the substances having various physical properties, i.e. propylene glycol, ethylene glycol and glycerol vapors, at several reduced pressures and vapors, at several reduced pressures and vapor forces. As the condensing surface subcooling increases in steady states, an abrupt change from drop type to film type occurs and the dropwise condensation curves of all the vapors become discontinuous at comparatively high vapor pressures, although the curves are continuous for propylene glycol and glycerol vapors at low vapor pressures. The surface subcoolings at the points, where these discontinuities start, are also shown and discussed.
Characteristics of shock phenomena in a one-component two-phase bubbly flow induced by a sudden valve closure at the downstream end of a test section are investigated. An experiment was conducted for a two-phase flow in a horizontal stainless tube of 21.4mm Id and 16.17m length with a surge tank having a gas chamber at the upstream end, using Freon-113 as the working fluid. The pressure transients are presented and discussed qualitatively. They are different from those of a two-component two-phase flow due to the mass transfer between the vapor and the liquid. The effect of factors such as the initial void fraction, the liquid velocity, the initial pressure, and the valve closing time on the profiles of the transient pressure are shown. Also, the behaviors of the vapor bubbles after the valve closure are sketched and explained, comparing with the profiles of transient pressure.
We studied the behavior of air-water interface in a horizontal tube caused by a step change of air flow above still water. As to the critical condition of wave generation, the experimental results are well explained by the theory of Kelvin-Helmholtz instability. This tendency remains true also in case of different surface tension. The lower limit of air velocity for slugging in a short time (1.75 sec) after the staring of the flow is about 3m/s greater than the results of Wallis which correspond to the transition from the steady wavy flow.
The experiments were carried out to investigate qualitatively the effects of emulsion internal phase structure such as the size distribution of water droplets on the micro-explosion phenomena of water-in-'A' heavy oil emulsified droplets vaporizing on the hot surface. The results confirm that the size distribution of water droplets in the emulsified fuels plays a very important role in the boiling phenomena, in spite of the same water content included in the fuels. That is, Emulsified fuel 1 with fine- and uniform-size distribution of the internal water droplets has a longer life time than the neat fuel ('A' heavy oil) on account of a distinctive feature such as 'two stage vaporization'. In contrast, Emulsified fuel 2 with some coarse sizes of them has a life time less than a half of vaporization was caused by the destruction of the vapor film due to the 'violent micro explosion' of coarse-coalescent water droplets.
To explore the formation of polycyclic aromatic hydrocarbons (PAH) and soot during combustion, equilibrium compositions of fuel-rich mixture at elevated temperatures have been obtained based on thermodynamic considerations. In the calculations, only gaseous intermediates have been included, while solid carbon has been excluded on the assumption that the formation of carbon particles is much slower than that of other species. It has been shown that major intermediates before sooting are PAH and acetylene. At the atmospheric pressure, a maximum PAH concentration appears at about 1400K, while the acetylene concentration increases with temperatures above 1200K. A comparison with the experimental results of a heated flow reactor suggests that the present prediction explains the formation of SOF and dry soot during thermal decomposition. Further, a discussion is made of the effects of the C/H ratio and enthalpy of formation of fuel on PAH and soot.
In the previous report, space difference and numerical methods were proposed for simulating a three-dimensional laminar flame development after the mixture was ignited in a closed vessel. This report aims to raise this method to a level applicable to the actual problems involving a pressure drop, therefore, heat transfer from gas to wall. The previous analysing method has been combined with those of the change of average quantities of states in both burnt and unburnt regions. It has become feasible to evaluate the change of heat transfer rate and simulate more precisely the combustion process from ignition, maximum pressure, via burn-out of mixture to the time of slow decrease in pressure. The measured and calculated results have been compared with each other for laminar flames in a spherical and cylindrical vessel, and the effects of the point of ignition on the heat loss and pressure change have been examined.
In the first report the experimental results of the flow patterns and the concentration distribution of tracer fluid in a two-dimensional model on which perforated plates were instead of a tube bundle were reported. In thee present report, in order to evaluate these characteristics quantitatively, numericalcalculations of the flow pattern and the transient concentration distribution based on the turbulent energy model (one equation model) have been conducted. The effects of the magnitude of flow resistance of the tube bundle on the flow pattern and mixing performance were clarified quantitatively referring the comparisons with the experimental results.
A method for calculating the three-dimensional gas flows during intake stroke in the cylinders of four-stroke cycle engines has been examined using simplified model engines. The process of induction swirl generation in a model engine with an off-center intake valve has been simulated numerically. The results show that the flow pattern in the cylinder varies in many ways with the distribution of inflow velocities around the intake valve. The effects of the differences in inflow velocity distribution (helical-port and directional-port type) on the generation of swirl are predicted.
This paper describes a method for estimating the induction swirl intensity by means of numerical simulation of the gas flow in the intake ports of four-cycle engines. Three-dimensional flow of compressible viscous gas in the intake port has been calculated for intake stroke in order to predict the effect of the configuration of the intake port, especially the configuration of the helical port, on the induction swirl intensity. Cartesian coordinates are used to simulate the unsteady flow field in the model passage of the intake port. The results show that the present method is applicable to the investigation of the flow in the intake ports, and that the volumetric efficiency and induction swirl intensity can be estimated from the distribution of the calculated outflow velocity around the intake valve.
The catalytic reduction of NOx by NH3 generated from NOx has been applied to methanol engine exhaust system. In an automotive three-way catalyst (Pt-Rh coated) a large amount of NOx is converted to NH3 in a temperature range of 500-550K and an excess air ratio of 0.9-1.0. On the other hand, NOx reduction by NH3 in methanol engine exhaust gas is efficiently performed under the condition of O2= 2-4%, gas temperature= 450-500K, and NH3 ≥ the stoichiometry of NOx. Finally, about half an amount of NOx is converted to NH3 in a three-way catalyst and the formed NH3 ratio is around 55%. On the basis of these results, some systems using the application of NOx-NH3 reactions to practical engines are proposed and their potential is discussed.
This paper presents expressions and computational graphs to determine the optimum tuning and damping parameters for a linear system with two degrees of freedom. The mass m1 is connected to an immovable foundation through a spring k1 and a dashpot c1. An impressed harmonic force acts on the sass m2. Either of the masses (named main mass) should be isolated from the vibration originating from the impressed force; whereas, the other mass functions as a dynamic absorber, The optimization criterion is minimizing the maximum displacement of the main mass. The optimum design parameters can be formulated when c1=0. If c1≠0, and tested on a vibratory model. The experiment makes it clear that the theory is very useful for the isolation of actual mechanical vibrations.
A method is presented for solving free vibrations of conical shells with variable thickness. Three components of displacements are assumed to have quadratic expressions of thickness. The characteristic equations are solved by a new method. Frequencies and distributions of displacements and stresses are presented and the new method is compared with Mirsky method and a linear approximation one.
This paper is concerned with the dynamic response of a plane curved bar with varying cross-sections under a dynamic load working perpendicular to the plane comprising the center line. As numerical examples, time responses of displacement and bending moment are found for a symmetric semi-elliptic arc bar having varying cross-sections and clamped ends subjected to a step concentrated impact load. The behaviors of responses due to variations of the cross-sections and the load point are clarified.
Although much research work has been performed on the liquid sloshing inside simple cylindrical vessels, with free surface at the time of an earthquake, few reports are published about the sloshing in intricate structures with inner structures. This paper deals with an analysis of liquid sloshing in the annular region of more intricate coaxial circular cylinders. In this analysis, by utilizing the velocity potential theory, the transient response is formulated as a boundary value problem in axisymmetrical vessels when the sine wave in resonance with the sloshing of the primary mode is applied which is known to be a convenient method to evaluate the seismic response of sloshing. These analytical results show very good agreement with the experimental results. Further, by utilizing this anlytical method and FEM, the sloshings in more complicated structures are investigated.
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