LES of turbulent premixed flame stabilized by the bluff body is developed by using subgrid scale combustion model based on the G-equation describing the flame front propagation. The basic idea of LES modeling is to evaluate the filtered-front speed, which should be enhanced in the grid scale by the subgrid scale fluctuations of the flame surface. The dynamic subgrid scale models newly introduced into the G-equation are validated by the premixed combustion flow behind the triangle flame holder. The calculated results can predict the velocity and temperature of the combustion flow in good agreement with the experiment data.

抄録全体を表示

DNS results performed at a few different Reynolds numbers indicate that the pressure gradient in the wall normal direction is much smaller than those in tangential directions within about 10 viscous units of the wall. This near-wall constant pressure property that is related to the blocking effects of solid walls, is made use of in developing an efficient numerical simulation technique for Navier-Stokes equations. Calculations have been performed with different mesh sizes for channel flow test case and results are seen to agree very well with the conventional DNS results and yet the technique leads to maximum computational saving of 80% compared with the conventional DNS.

抄録全体を表示

This paper describes the two-dimensional unsteady low-Reynolds-number flow past an impulslvely started rotating and translating circular cylinder. Invoking the vorticity equation, we first derive a system of two coupled integral equations that govern the stream function and a modified vorticity function. This system, singular in the low-Reynolds-number, is then asymptotically solved by using a singular perturbation method and introducing five regions in the space-time domain. The first-order solutions are found to linearly depend on the translating and rotating motions within each region. Because of its importance for applications, a special attention is paid to the lift coefficient C_L which results here from intricate interactions between rotation and translation. The obtained initial asymptotic behavior of C_L actually exhibits a t^-1/2 singularity and thereby differs from the prediction of Badr & Dennis⁽¹⁾ at moderate Reynolds numbers.

抄録全体を表示

In the first report, the Cartesian grid approach with virtual boundary method was validated for applying to the DNSs of the incompressible flows around a circular cylinder. The aims of this report are to introduce the solution-adaptive mesh refinement and to develop the more effective scheme. The computational Cartesian grid is generated by using the Adaptive Mesh Refinement (AMR) approach. The DNSs of the steady and unsteady incompressible flows around a circular cylinder are considered in order to compare with the results in the first reporrt. The present solution-adaptive mesh refinement approach gives the reliable solutions and we can achieve successfully that both number of total grid points and computational time are reduced to 2/3 of the original Cartesian grid approach with the virtual boundary method.

抄録全体を表示

Steady and unsteady cascade flow characteristics of thin arc airfoil is numerically investigated. In comparison with thick airfoil, flow field around thin airfoil is quite sensitive to its leading edge configuration. In this study, new type of leading edge configuration is proposed, and two types of thin arc airfoil are calculated to investigate the improvement by our design. We tested thin arc airfoil (TA) and front-thicken airfoil (FA) having thickened leading edge. Since fluctuation of drag coefficient becomes smaller in FA cascade, aerodynamic characteristic of FA cascade is robust with respect to the change in attack angle. Although existence of periodic separation bubble are observed in both cascades in high attack angle cases, the hysteretic excursion on a map of reattachment point vs. downstream separation point of suction side surface revealed that thickness of leading edge suppresses the interaction between separaion bubble and wake from downstream separation point.

抄録全体を表示

Guide vanes and impellers of turbomachinery operate in boundary layer due to the walls of casing and boss, and further operate in cavitating condition in high speed flow. From these circumstances, hydrodynamic characteristics are analyzed about a partially cavitating hydrofoil which is placed in boundary layer between parallel plane walls. By separation of variables for disturbance pressure, the governing equation is transformed into two problems, of which the one is that of wing sectional plane, the other that of spanwise direction. In the problem of the sectional plane, a simultaneous integral equation is derived and solved by series expansion method. The problem of spanwise direction is reduced to the eigenvalue problem of Sturm-Liouville type which is numerically solved by finite difference method. These two kinds of solution are linearly combined in order to obtain the hydrodynamic characteristics.

抄録全体を表示

The lattice gas automata method was used to simulate fluid motion. In two-dimensional simulation, it was shown that the 9-velocity ILG model was effective for the numerical simulation of the immiscible two component flow including energy transport. However, three-dimensional simulation was requested for the actual engineering application. In the present paper, the three-dimensional ILG model was proposed based on the 9-velocity model. The proposed model was applied to the numerical simulation of droplet atomization. It was clarified that the three-dimensional ILG model not only satisfied Laplace's formula but also dealt with the compex behavior of two-component surface as well as the 9-velocity ILG model.

抄録全体を表示

We analyze the numerical stability of Finite Difference Lattice Boltzmann Method (FDLBM) by means of von Neumann stability analysis. A FDLBM is proposed to ensure the numerical stability by relaxing the Lagragian particle convection and by satlsfylng CFL condition. The stability boundary of FDLBM depends on the BGK relaxation time, the CFL number, the mean flow velocity, and the wavenumber. We show that stability regions, as a function of the relaxation time and of the CFL number, drastically change as varying the difference method, which discretizes the kinetic equation. With the centerered difference, FDLBM has characteristics opposite to the conventional LBM, that is, as the BGK relaxation time is increased, stability region of the FDLBM is decreased. We also analyze the numerical stability of FDLBM capable of simulating multi-phase flow by additional fictitious forcing terms. The use of semi-implicit schemes improves numerical stability. With semi-implicit upwind difference, though CFL number equals to unity, we can simulate phase transition without encountering any numerical stability problem.

抄録全体を表示

Hydrogen gas is not only clean but also renewable. That is, it can mitigate NO_x and SO_x emissions and cope with the eventual depletion of fossil energy resources. Therefore, it is considered a hopeful candidate for next energy resource. On the other hand, with the recent development of an aircraft, the propulsion system is required to be lighter and lower emissions. If the combustion chamber is eliminated, combustion process is handled within turbine blade passages, and hydrogen is used as the fuel, we can satisfy these requirements. In the present study, we investigate the idea of new jet engine without combustion chamber. The computations of turbulent flow field with hydrogen-fueled combustion within turbine blade passage are performed. Reynolds-averaged Navier-Stokes equations are solved with incorporating a k-εturbulence model and a reduced chemical mechanism. Visualizing the hydrogen combustion in the passage, the possibility to realize our concept is investigated.

抄録全体を表示

Experiments are carried out to investigate behavior of shock wave diffraction from a safety-engineering point of view. Because, once the shock wave is released into an ambience, high pressure and negative pressure lasting for relatively long period have possibility to cause serious damages against human bodies as well as general buildings. Therefore, it should be one of the most significant subjects to attenuate the shock wave efficiently within a short distance from the source. In this report, a cavity is installed at an open end of a shock tube and flow-fields behind diffracted shock wave are visualized using schlieren photography. In addition, piezo-electric pressure transducer is flush mounted on the surface of reflector, which is installed at test section, and pressure histories are recorded with wide frequency response. Lastly, numerical simulation using the TVD finite difference scheme is performed to compare with the experimental results. As a result, (i) the pressure histories on the reflector coincides well between the numerical and experimental results, (ii) flow-fields behind the shock wave are clarified, (iii) maximum pressure behind reflected shock wave can be attenuated by installing several cavities inside the open end of the shock tube.

抄録全体を表示

We proposed a new LGA model for simulation of immiscible two-phase flow with wide difference in density. We used two types of particles, whose difference is only color, to represent different two phases, and we introduced long-range interparticle forces into the model to simulate density difference between these two phases. Using this model, some phase separation simulations were made and we found that two-phase stable interfaces are made spontaneously without explicitly described correlation equations. Two-phase interfaces of particle density distribution coincided with those of particle color distribution. We measured the growth rate of the bubble during the phase separation. Comparing the results with those of another microscopic models such as molecular dynamics, we found the results look the same as those of another models. We also investigated surface tension of the model and found it to be applicable to two-phase flow simulation.

抄録全体を表示

Effects of ion concentration distribution at a bubble surface on rising speed of a carbon dioxide bubble in strong alkaline solution was investigated experimentally and numerically. We developed an experimental system that use a CCD camera coupled with a microscope to track the rising bubble and precisely estimated the drag coefficients when a CO, bubble dissolves in sodium hydroxide solution. We also numerically estimated the drag coefficients of the "Stagnant Cap Model". The results reveal that we observed that the behavior of the bubble returns to that of a fluid sphere after it is closed to that of a solid particle when the concentration of sodium hydroxide is high. And by comparing the numerical results, the ion concentration distribution at the surface changes the position of the stagnant cap angle and the flow around the bubble.

抄録全体を表示

Experimental studies are carried out to clarify the structures and erosive properties of rectangular cavitating jets. The jet is supplied from a high pressure pump and injected through a rectangular nozzle of aspect ratio of two or four. It discharges into a test cell at specified constant pressure and impinges against a test specimen of aluminum alloy. The structures of the jets are observed by instantaneous photographs and high-speed movies. The erosion tests are conducted at the injection pressure of 18 MPa and the cavitation number of 0.01, 0.02, and 0.03. It is shown that the structures of the cavitating jets issuing from the rectangular nozzles are completely different from those of circular cavitating jets. Corresponding to the jet structures, the erosive properties of the rectangular cavitating jets are different from those of the circular cavitating jets.

抄録全体を表示

This study experimentally examines the sloshing behavior In a pool by a jet flow injected from free surface into the pool. The effect of parameters : pool geometry, jet injection angle and jet injection location, are investigated. The experiment is conducted in a simplified two-dimensional rectangular pool having a free surface and the free jet injected from above the surface. Observed free surface oscillations are classified into five regimes : (1) Standing wave, (2) Transition wave, (3) Vortex, (4) Hydraulic jump and (5) Stable or ripples. The standing wave and the transition wave indicate several frequencies dependent on pool geometry. The frequencies of the standing wave almost agree with the theoretical sloshing frequencies. In the transition wave, unstable surface behavior with a progressive wave is observed on the standing wave, and includes two predominant frequencies. Those frequencies also agree with the theoretical frequencies of n-th and (n+1)-th mode of the standing wave. The free surface oscillation depends on the pool size and the jet injection location. It is noted that the pool length affects the frequency of the surface oscillation and the jet injection location affects the mode. A simplified resonance model can predict the transition mechanism of the standing wave mode.

抄録全体を表示

Numerical solutions are presented of an oscillatory laminar flow In the inlet region of a circular tube perpendicularly installed in the wall of a large reservoir. The velocity profiles and the distributions of the wall shear stress are obtained for a wide range of the nondimensional parameters, in which the Womersley numbers a range from 2 to 20 and the Reynolds numbers are Re=100∼500. Entrance-flow phenomena are discussed mainly for the flow at the Reynolds number of 500 and the influences of the Womersley number on the development of the velocity field are made clear. In the vicinity of the tube entrance, the flow in the outflow term assumes a velocity feature similar to that for a fully developed region. On the other hand, the flow in the inflow term shows a complicated behavior with the Womersley number and its aspect is greatly related to a stream caused in the reservoir in the preceding outflow term. The change of the velocity profile along the axial direction is rather large in the section of about 10 percent of Re/a² from the entrance. The inlet length based on the amplitude value of the axial velocity is noticeably shorter than that for a steady flow at the same Reynolds number and is roughly, excluding a case of appreciably higher a, proportional to Re/a².

抄録全体を表示

This paper describes the effect of spacing of circular cylinder row on vortex exciting vibration. The experiment was carried out in an N. P. L. blow-down type wind-tunnel with a working section of 500 mm×500 mm×2000 mm, and with the Reynolds number of 9.4×10³. The test cylinder was supported by the elastic wires. The power spectrum in the wake behind circular cylinders, displacement of the oscillating circular cylinder, and the time-mean and fluctuating surface pressure distributions on the circular cylinder were measured. Consequently It was found that (i) vortex shedding from circular cylinders occurs in the range of spacing ratio S/D≥1.5, while there Is two patterns regarding the existence of vortex shedding from circular cylinders in the range of 1.5≤S/D≤2.0, (ii) the displacement of oscillating cylinder due to the shedding vortices attains maximum at S/D= 2.3, (iii) the fluctuating pressure distribution on the surface and fluctuating lift by frequency of shedding vortices become largest at S/D=2.3.

抄録全体を表示

When circular cylinders are moved in still water, it is known that fluctuating lift exhibits nonrepeatable characteristics even if the cylinders are repeatedly towed or swung under the same conditions. In this study, asymmetric wake is produced by control of boundary layer separation with placing tripping wire on the surface of circular cylinders in towed or swung motion to suppress the nonrepeatability of fluctuating lift. The effectiveness of the suppression was evaluated by standard deviation of ensembly collected lift data at each towed distances or swung angles and flow visualizations. The results obtained by this study will be applied to the development of manipulator arms operated in water where effects of mechanical vibrations are insignificant in comparison of that of fluctuating fluid forces associated with vortex formation.

抄録全体を表示

Hypothetical method for reducing separation noise of a two-dimensional airfoil with a high angle of attack was investigated numerically. The method was based on suppression of local surface-pressure fluctuations in a small area in a cordwise direction. The area in which the pressure fluctuations were suppressed was regarded as a working area of an imaginary actuator. The effect of the actuator on reduction of the separation noise was investigated. The sound pressure level of the separation noise was found to be sensitive to the setting position of the actuator. The separation point near the leading edge on the suction side and the separation point near the trailing edge on the pressure side were found to be the effective positions of the actuator for reducing the separation noise.

抄録全体を表示

A new computational model is developed here to analyze the influence of entrapped air on free-surface-pressurized flows. A virtual slot with ceiling on the top of the pipe is introduced to treat a separated gas-liquid flow. This model is a modified model of Preissmann's and is applicable not only to open channel flow and closed conduit flow but also pressurized flow with entrapped air. Compared to experimental results using the model of 1/50 scale, the calculation results show that the entrapped air in horizontal pipe advances the time of pressure rising and makes the maximum value of pressure higher. The escape flow of entrapped air at dropshaft is caused by surface waves pushing the air in the horizontal pipe, and then the pipe slope affects the flow rate of air. The air compressibility has less effect on the transient separated air-water flow in the pipe.

抄録全体を表示

One of the important factors affecting the diffuser performance is the shape of the inlet velocity profiles. Experiments have been performed systematically to investigate the performance for a wide range of mixed-flow-type conical walled annular diffusers having asymmetric uniform shear velocity profiles in the inlet core region except for a thin inlet boundary layer. The configuration of this type of diffusers consists of a circular inlet cross-sectional portion and conically diverging inner and outer walls having the same cone angle. Pressure recovery of diffusers reduces markedly with an increase in the inlet shear ratio. Systematic data on pressure recovery coefficients are presented comprehensively on the performance charts together with optimum geometry lines of diffusers both at constant diffuser length and at constant diverging area ratio for four degrees of the inlet shear ratio.

抄録全体を表示

We developed the twist-type rubber-tube pump which discharges its inner liquid according to the twist angle of the tube one side of which is fixed and the other is connected to the motor axis. The rubber's volume does not change when it is stretched. And the tube is fixed on both sides. Discharge volume ΔV of the pump is therefore approximated by the formula ΔV=[1-L₀{L₀²+r_e²(θ-α)²}^<1/2]S₀L₀, where S₀ is cross-section area of the tube, L₀ is length, θis twist angle, r_e is typical radius, and α is delay angle of discharge. We designed and made a prototype (tube inner radius : φ4 mm, outer radius : φ8 mm, length : 50 mm). The prototype can discharge 50 μL of liquid at a twist angle of 270°and has a long life, that is the discharge pattern changes little after 2 million repetitions.

抄録全体を表示

In the Earth's atmosphere, zonal currents with a vertical velocity gradient are induced under the action of rotation and horizontal temperature gradient. These currents satisfying the so-called "thermal wind equation" generate the cyclones and anticyclones through the baroclinic instability, and hence have serious effects on the global circulation. In this study, the generation and development mechanisms of vertical vortices associated with the cyclones and anticyclones are investigated by using direct numerical simulation of the thermal wind. By imposing the stable density stratification in the vertical direction, the effects of the stable stratification and the Reynolds number are studied in detail. As a result, we have found the distinct effects of stable stratification on the anisotropy of the flow field and the generation of the vortical structure. It is also found that the cyclone becomes dominant in comparison to the anticyclone at a relatively low Reynolds number under the weak stable stratification. At a higher Reynolds number, both cyclonic and anticyclonic vortices are enhanced by the nonlinear vortex stretching term, and hence the asymmetry between them becomes negligible. The intensive stable stratification attenuates the nonlinear vortex stretching and contributes to the occurrence of the asymmetry in the vortices even at the higher Reynolds numbers

抄録全体を表示

Experiments have been performed for a turbulent channel flow over a backward-facing step. The backward-facing step flow is passively controlled by equipping the slit in upstream of the step, and deducing the high-speed fluid from the slit in the recirculating region. Angle of the slit is changed 30°and 45°, and the width of the slit are changed in several steps in ranging 2 mm∼12 mm. The local heat transfer coefficient and the wall static pressure are measured behind the backward-facing step. The total performance between heat transfer and pressure drop is estimated under the conditions of equal pumping power. In addition, the velocity profiles are measured by the split hot film probe. When angle of the slit is 30°and width of the slit is 10 mm, the highest performance is obtained.

抄録全体を表示

This paper is concerned with the double diffusive convention due to the melting of a horizontal square ice bar into a calcium chloride aqueous solution inside a insulated square cavity. The temperature in the ice bar suddenly decreases just after the melting begins, however, the temperature gently decreases during the melting process. The concentration induced convection appears above in the liquid, and the temperature induced convection appears below in the liquid. The present ideal numerical model predicts approximately the temperature decrease in the ice bar, the mean melting mass and the mean melting Nusselt number.

抄録全体を表示

The distribution of normal alcohol (n-alcohol) on water and the stability of the alcohol distribution were investigated using molecular dynamics simulation for three types of 72-alcohol (n-propanol, C₃H₇OH ; n-heptanol. C₇H₁₅OH ; and n-undecanol, C₁₁H₂₃OH), four of five concentrations of alcohol. The simulation results reveal the following. The distribution of n-propanol on water is homogeneous at all n-alcohol concentrations studied here and the distribution of n-heptanol and n-undecanol on water is heterogeneous. The n-alcohol concentration at which fluctuations in the alcohol distribution begin to increase depends on the length of the hydrocarbon chain of the n-alcohol.

抄録全体を表示

The residual bubble or liquid drop formed while the three-phase contact line moves on the solid surface with steep roughness has an important effect on the contact angle hysteresis. Based on the condition of system equilibrium proposed in the preceding report, the energy change is theoretically calculated for the movement of the three-phase contact line on a surface with two-dimensional saw-tooth roughness. The energy change is contributed from the wetting of the surface and also from the formation of liquid-gas interface of residual bubble or drop. The result shows that the macroscopic contact angle ; i. e., the advancing and receding contact angles, are determined by the same condition as those when the residual bubble or drop are not formed. The maximum inclination of the roughness influences the hysteresis of the contact angle. The numerical calculation of the energy change for the roughness with arbitrary shape gives the same result as stated above.

抄録全体を表示

Heat and mass transfer characteristics in a reforming catalyst bed have been experimentally investigated. Experiments were carried out with a single bench-scaled reforming tube, which was filled with reforming catalyst. The tube wall was uniformly heated, and a mixture between steam and methane or propane was reformed through the catalyst bed. Most part of the reaction was completed in the upper part of the tube. The effects of space velocity, steam carbon molar ratio, wall temperature, bed temperature, and catalyst particle diameter on the transport phenomena with chemical reactions were determined. A correlation for heat transfer coefficient was determined by Nu, Re_p, Pr, d_p/d_i, and Da. The prediction of overall methane conversion rate was also presented.

抄録全体を表示

In recent years, calorific power of computer chip has been increasing. So more compact cooling unit compared with air-forced aluminum fin and heat pipe is desired. It is the problem that establishment of boiling part structure can correspond to high heat flux in size reduction. In this paper, thermal resistance in boiling part is remarkably reduced by proposal of original boiling part structure which consists of optimum porous structure and vapor path.

抄録全体を表示

This paper proposes an optimum method for combining a Solid Oxide Fuel Cell and Gas Turbine Combined Cycle by high fuel/air utilization. The proposed system is projected to significantly increase efficiency by ACT (Advanced Cooling Technology) model of the SOFC as compared with a simple cycle GT/CC combined with a Fuel Cell. This ACT improves the air consumption of the SOFC by controlling It to minimum and makes the hybrid gas turbine and fuel cell system attain over 65% (HHV) of power generation efficiency whether with combustor or not, while the generation efficiency of the conventional SOFC/GT/CC is less than 55% (HHV).

抄録全体を表示

In order to promote active and wide application of the pulse combustion systems for commercial and industrial use, experimental and numerical investigations on the acoustic resonance characteristics of a pulse combustor are made using the soap-bubble method. A soap bubble of propane-air mixture having a small diameter of 15mm is ignited in the open space and in the model pulse combustor and sound pressure and CH-emission intensity are then measured. A simplified numerical simulation on the acoustic properties in the pulse combustor is carried out, by assuming a quasi-one-dimensional, inviscid, and isentropic flow. The time history of pressure fluctuation calculated agrees very well to that measured experimentally in the initial stage of acoustic resonance in the pulse combustor. It is found that measurements of the acoustic pressure profiles in the model combustor having the same construction and dimensions as those of the real pulse combustor are necessary for predicting pressure amplitude characteristics in the pulse combustor. The assumption of inviscid flow, however, gives the limit of application to the long term description of the resonant behavior.

抄録全体を表示

Shredder dust of disposed vehicles can be converted into low calorific flammable gas with a pyrolysis gasification system. The stationary electric power generation using internal combustion engines fueled with the gas is one of hopeful methods to reuse wastes. The shredder dust pyrolysis gas mainly consists of H₂, CO, CO₂, and N₂. Composition and heating value of the gas depends on conversion system and property of waste. Characteristics of combustion and exhaust emissions in a premixed combustion spark ignition engine fueled with the shredder dust converted gas were analyzed in this research. Influences of heating value, CO/H₂ ratio, and inert gas were analyzed parametrically. Observations of combustion flame were also done with a bottom view type optical engine.

抄録全体を表示

A natural gas direct injection test engine equipped with a newly developed natural gas injector was built. The high THC emission at part-load condition and the high NO_x emission at high-load condition are left as the problems for a direct injection natural gas engine. The THC reduction and combustion improvement by throttling and the NO_x reduction by EGR were investigated. The following results were obtained : (1) The combustion at light- and medium-load conditions is improved by throttling. It is possible to improve the thermal efficiency at light-load condition in spite of pumping loss by throttling. The concentration of THC emission is greatly decreased in this condition ; (2) The great NO_x reduction can be obtained without combustion deterioration by appropriate EGR at high-load condition ; and (3) It is possible to decrease both THC and NO_x emissions by both throttling and EGR at part-load condition.

抄録全体を表示

In this study, effects of internal EGR ratio on the ignition and the combustion of homogeneous charge compression ignition (HCCI) engine are investigated experimentally. At first, using single cylinder test engine, relation between exhaust valve close timing and internal EGR (Exhaust Gas Re -circulation) ratio is clarified. Effects of an internal EGR gas on autoignition timing, combustion duration and knocking limits are discussed. As a result of an experiment, it became clear the following facts ; with advancing exhaust valve close timing, i) internal EGR ratio is increasing, ii) both knocking limits at high load and misfiring limits at low load are expanding, iii) ignition timing is advancing, iv) combustion duration is decreasing and v) combustion efficiency is increasing.

抄録全体を表示

The hydrocarbon composition in the exhaust of a dimethyl ether (DME) fueled CI engine and sensitivity correction techniques for a THC analyzer were discussed. The formation process of unburned hydrocarbon species was also investigated by in-cylinder gas sampling. The results showed that since HC emissions in the exhaust consist of DME and a small amount of lower hydrocarbons, a constant correction factor could be applied for THC analyzer, within an error of ±5%. The gas sampling results indicated that high levels of C₂ components, such as C₂H₂, C₂H₄, C₂H₆ were formed during combustion process, and were mostly oxidized before the exhaust valve opened.

抄録全体を表示

Unburnt HC and its components including 1, 3 butadiene and benzene from a DI diesel engine during both start up to warm up" and "increasing load" operations were investigated. At start-up with a high equivalence ratio the THC gradually increased with elapsed cycles, and then decreased sharply with a rapid decrease in equivalence ratio at warm-up operation. Coolant temperature strongly influenced on the THC concentrations and the THC with lower coolant temperature are remarkably higher throughout the "start-up to warm-up". Reducing the equivalence ratio and shortening the duration of high equivalence ratio operation at start-up are effective to reduce THC emission. The lower hydrocarbon components determined the THC behavior for both "start-up to warm-up" and "increasing load" operations, while the proportion of each HC component was not significantly changed. Of the components, ethylene comprised the larger portion of the low hydrocarbon components, 1, 3 butadiene and benzene are slightly detected for both transient operations.

抄録全体を表示

A key technology to realize the gasoline direct injection combustion is to control the in-cylinder gas motion. The effect of the shroud attached on intake valves and the cam profile for intake valves on the flow characteristics such as the swirl and tumble are examined from a theoretical viewpoint. As a result, it is found that the shroud affects not only the swirl flow but also tumble flow, and that the spatial stratification of swirl intensity in the axial direction, which can control the in-cylinder gas motion during the compression stroke, is difficult only by a modification of the valve timing

抄録全体を表示