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Viewing 1 to 30 of 76
Technical Paper
2010-10-25
Hajime Fujimoto
The premixed charge compression ignition (PCCI) combustion in a compression ignition (Cl) engine is one of countermeasures against the very much severe regulation for exhaust gas of engine out. The authors have been proposed to use the fuel mixed with high volatility component and low volatility component to actualize PCCI combustion. This kind of fuel injected forms a fine and lean spray by the flash boiling phenomena which depends on the pressure and the temperature. The role of the former fuel is to decrease in the generation of particulate matters (PM) and that of the latter one is to break out the ignition. Thus, it is very much significant to find the distribution of vapor concentration of both fuels in a spray. This paper describes both distributions in a single diesel spray by use of the technique of laser induced fluorescence (LIF) in a constant volume chamber with high temperature at high pressure as the fundamental research.
Technical Paper
2009-09-13
Hajime FUJIMOTO, Tsukasa HORI, Jiro SENDA
LES of non-evaporative diesel spray have been performed to investigate the effects of breakup models of Modified TAB, WAVE and KHRT model on computational results. KIVALES that is LES version of KIVA code was used for base code. In our KIVALES, CIP scheme was incorporated in order to suppress the numerical diffusion. Results showed that the breakup model is significantly affected on the calculated spray shape, because the droplet diameter determined by breakup models affects on the transmittance of the droplet momentum into the ambient gas, the evolution of the vortex structure in the gas phase and the droplet dispersion by the vortex structure.
Technical Paper
2008-10-06
Hajime Fujimoto, T. Hori, J. Senda, H. Nakagawa, S. Kamata, K. Katsuta
It is very much necessary for researchers and engineers whose work is the field of combustion in a CI engine to find the information of droplets in a diesel spray. The information is strongly required to construct the model of spray built in the numerical code for its simulation and to be used for the verification of the accuracy of the calculation. This paper describes the photographing system with high spatial resolution, the distribution of droplet size and the vortex scale caused by the droplets motion by means of this system.
Technical Paper
2008-04-14
Tsukasa Hori, Takahiro Kuge, Jiro Senda, Hajime Fujimoto
In this study, a numerical experiment using a 2D convective equation and LES of an evaporative diesel spray for different convective schemes has been performed to examine effects of convective schemes on a fuel-air mixture formation of the diesel spray simulation and to determine the convective scheme used in KIVALES. In addition to KIVALES original schemes, such as QSOU, PDC and IDC, CIP was incorporated into KIVALES in order to calculate the convective terms with low numerical diffusion. The numerical experiment using the 2D convective equation showed that the numerical diffusion of CIP scheme was lowest in the convective schemes used in present study. However CIP scheme used was not a monotone scheme completely due to the overshoot and the undershoot of the scalar provided near the boundary. Hence, CIP scheme was employed for only the convective term of the LES momentum equation, while the other convective schemes were calculated using QSOU, which is a monotone scheme. The LES spray simulation showed that the sensitivity for convective schemes was significant high in the diesel spray simulation with LES approach.
Technical Paper
2007-10-29
Hajime Fujimoto, J. Senda, T. Yamashita, T. Hori, M. Oshima, H. Tanaka
The particulate matters (PM) containing in the exhaust gas through a CI engine affects strongly the human health. Thus, it is very significant to measure the mechanism of PM itself generation for actualization of a clean CI engine. On the standpoint mentioned above, the authors carried out the experiments of the characteristics of PM generated from a small high speed DI CI engine with a single cylinder. The variables were the equivalence ratio, the injection timing, the EGR rate and the sort of fuel. As a result, the effect of experimental condition on the distribution of PM is clear through experiments.
Technical Paper
2007-07-23
Shuji Kamata, Hiroki Nakagawa, Tsukasa Hori, Jiro Senda, Hajime Fujimoto
Instantaneous and statistical spray structures of diesel sprays are examined with numerical simulation and experiment. KIVALES, which is LES version of KIVA code, is used as the computational code. Injection velocity profiles measured by momentum method are employed for the initial condition of the calculation. In the experiment, shadowgraph photography is performed to measure macroscopic spray structure. LES approach predicts the instantaneous structure, which are the heterogeneity and intermittency in the periphery of the spray and the cyclic variability of each injection event. Moreover, LES can predict both the instantaneous and statistical spray structures.
Technical Paper
2007-04-16
Tsukasa Hori, Takahiro Kuge, Jiro Senda, Hajime Fujimoto
Three-dimensional large eddy simulation (LES) has been conducted for a diesel spray flame using KIVALES which is LES version of KIVA code. Modified TAB model, velocity interpolation model and rigid sphere model are used to improve the prediction of the fuel-mixture process in the diesel spray. Combustion is simulated using the Eddy-Dissipation model. CIP method was incorporated into the KIVALES in order to suppress the numerical instability on the combustible flow. The formation of soot and NO was simulated using Hiroyasu model and KIVA original model. Three different grid resolutions were used to examine the grid dependency. The result shows that the LES approach with 0.5 mm grid size is able to resolve the instantaneous spray with the intermittency in the spray periphery, the axi-symmetric shape and meandering flow after the end of injection as shown in the experimental results. Furthermore, the cyclic variability at each injection is evaluated from the results of the five computations.
Technical Paper
2007-04-16
Taku Tsujimura, Yoshihiko Ueda, Keita Mitsushima, Jiro Senda, Hajime Fujimoto, Yoshiroh Tokunaga
It is thought that the synthetic gas, including hydrogen and carbon monoxide, has a potential to be an alternative fuel for internal combustion engines, because a heating value of the synthetic gas is higher than one of hydrogen or natural gas. A purpose of this study is to acquire stable auto-ignition and combustion of the synthetic gas which is supposed to be applied into a direct-injection compression ignition engine. In this study, the effects of ambient gas temperatures and oxygen concentrations on auto-ignition characteristics of the synthetic gas with changing percentage of hydrogen (H2) or carbon monoxide (CO) concentrations in the synthetic gas. An electronically-controlled, hydraulically-actuated gas injector was used to control a precise injection timing and period of gaseous fuels, and the experiments were conducted in an optically accessible, constant-volume combustion chamber under simulated quiescent diesel engine conditions. Results obtained in this study are that the ambient gas temperature has a significant effect on the auto-ignition delays of the synthetic gas, and that the higher a percentage of CO in the synthetic gas results in the greater temperature dependency of the auto-ignition delay.
Technical Paper
2007-04-16
Jiro Senda, Tomoki Ikeda, Teruaki Haibara, Sho Sakurai, Yoshimitsu Wada, Hajime Fujimoto
Authors propose the reformulation technique of physical properties of Biodiesel Fuel (BDF) by mixing lower boiling point fuels. In this study, waste cooking oil methyl ester (B100), which have been produced in Kyoto city, is used in behalf of BDF. N-Heptane (C7H16) and n-Dodecane (C12H26) are used as low and medium boiling point fuel. Mixed fuel of BDF with lower boiling point fuels have lighter quality as compared with neat BDF. This result is based on the chemical-thermo dynamical liquid-vapor equilibrium theory. This paper describes fundamental spray and combustion characteristics of mixed fuel of B100 with lower boiling point fuels as well as the reformulation technique. By mixing lower boiling point fuel, lighter quality fuels can be refined. Thus, mixed fuels have higher volatility and lower viscosity. Therefore, vaporization of mixed fuel spray is promoted and liquid phase penetration of mixed fuel shortens as compared with that of neat BDF. For combustion characteristics, although oxygen content in fuel decreases by mixing lower boiling point fuel, soot formation can be suppressed due to the promotion of the spray evaporation.
Technical Paper
2007-04-16
Yoshimitsu Wada, Yuji Nishimura, Akihiro Yamaguchi, Noriyuki Magara, Jiro Senda, Hajime Fujimoto
A diesel engine operating in premixed charge compression ignition (PCCI) mode promises the reduction of engine-out emissions of NOx and particulate matter. A serious issue for PCCI operation with the early injection timing during the compression stroke is the difficulty of controlling the mixture formation process. In this study, a mixed fuel consisting of high volatility fuel and high ignitability one is applied in order to develop a control technique for the mixture preparation. In particular, we focuses on a flash boiling phenomenon of mixed fuel. For pure substance, the quality of flashing spray is dominated by the degree of superheat. In contrast, that of mixed fuel is affected much by low boiling point fuel. Therefore, the present study defined a new variable making it possible to distinguish the flashing atomization regime of mixed fuel and, then, investigated both the effects of it and ambient condition on the behavior of flashing spray of mixed fuel in a constant volume vessel.
Technical Paper
2007-01-23
Yoshimitsu Wada, Kazuki Okimoto, Naoki Kitamura, Keisuke Ueda, Jiro Senda, Hajime Fujimoto
A single cylinder engine has been run with direct-injection premixed charge compression ignition (PCCI) operation. The operation is fueled with primary reference fuels for a wide variety of injection timing and equivalence ratio to investigate the effect of charge stratification and octane rating on PCCI combustion. The test results showed that although the change of the injection timing can gain the high combustion efficiency for a wide range of equivalence ratio, the combustion phasing where the high combustion efficiency is accomplished is not varied only by changing the injection timings. Therefore, the only change of injection timings does not improve the thermal efficiency which is influenced by the combustion phasing. On the other hand, at the fixed compression ratio, inlet air temperature and so on, the octane rating is useful in altering the combustion phasing. The experiments in which the octane rating was changed demonstrated that for the lean air-fuel mixture which produces low NOx emission without EGR, the combustion phasing must be advanced to gain the better combustion efficiency at low load.
Technical Paper
2006-10-16
Yoshimitsu Wada, Yoshiaki Kitta, Akihiro Yamaguchi, Yuji Nishimura, Jiro Senda, Hajime Fujimoto
The authors have explored the potential of fuel to control spray and its combustion processes in a diesel engine. Fuel has some potential for low emission and high thermal efficiency because its volatility and ignitability are one of the ultimate performing factors of the engines. In present study, the ignition process of mixed fuel spray was investigated in a constant volume combustion vessel and in a rapid compression and expansion machine, The ignition delay based on the diagram of rate of the heat release, the imaging of natural flame emissions and the numerical simulation were carried out to clarify the effect of the physical and chemical properties of mixed fuel on ignition characteristics.
Technical Paper
2006-10-16
Tsukasa Hori, Jiro Senda, Takahiro Kuge, Hajime Fujimoto
Large Eddy Simulation (LES) is applied to non-evaporative and evaporative diesel spray simulations. KIVALES, which is LES version of KIVA code, is used as the LES computational code. Modified TAB model is used as breakup model, and interpolated donor cell differencing scheme is employed to calculate convective terms. To validity LES simulation, LES results using KIVALES are compared with experimental results and simulated results with conventional RANS approach using KIVA3V res.2. The results show that the LES simulation of non-evaporative spray depends on the grid size in comparison with RANS simulation, and good agreement is obtained between experimental results and the LES results with fine grid (720,000 cells). Furthermore, asymmetric non-evaporative spray which has intermittency at the outer edge of sprays is simulated, since instantaneous turbulent flow field can be predicted directly in LES case. In evaporative spray simulation, although symmetric spray shape simulated by use of RANS, LES case shows the asymmetric shape and instantaneous structure of diesel spray, which has intermittency at the outer region of spray, and fluctuating distribution of gas velocity, equivalence ratio and gas temperature.
Technical Paper
2006-10-16
Hajime Fujimoto, J. Senda, Y. Komemushi, T. Kuge
One of the effective ways to cope with the very severe future regulation of soot exhausted through a CI engine is the use of oxygenated fuel. This paper describes the experimental results of the soot generation of six kinds of oxygenated fuel and n-heptane whose cetane number is the almost the same as that of the gas oil by means of time resolved LII (TIRE-LII) and the classical two color method. The experiments were carried out in a constant volume chamber. The main result is that the oxygen content of the fuel is the much significant factor to decrease in the soot.
Technical Paper
2005-10-24
Hajime Fujimoto, K.- J. Myong, H. Suzuki, K. Ueda, J. Senda
Almost all the researches relating to the characteristics of transient spray have carried out by using the fuel with only single component. However, the actual fuel oil supplying to a reciprocating engine has multiple components. Thus, this paper describes the experimental results on the characteristics of a transient spray formed by the mixed fuel with three kinds of pure fuel. The state of periphery of non evaporating spray near the nozzle outlet was arranged by the dimensionless number. And the technique of laser Induced fluorescence (LIF) was applied to an evaporating spray to find the state of mixing.
Technical Paper
2005-09-11
Hajime Fujimoto, K. Higashi, T. Yamashita, J. Senda
This paper describes the soot behavior in a diesel flame. The experiments were carried out in a constant volume chamber with quiescent atmosphere. Parameters were the ambient temperature and the oxygen concentration. The integrated image of flame was taken, the natural emission of flame was detected and the KL factor was found by means of classical technique of laser light extinction. The results were discussed by use of the apparent rate of heat release. As a result, the ignition delay and the vortex with large scale generated in a diesel spray affect the soot behavior in a diesel flame.
Technical Paper
2004-10-25
Hajime Fujimoto, J. Senda, T. Ito, S. Asao, K. Higashi
It is very significant to take the intermediate products in diesel combustion for understanding the generation of exhaust emissions like SOF, dry soot and so on. The products generated in a constant volume combustion chamber were sampled by pricking a sheet of polyester film installed in the chamber to freeze the chemical reaction. The gas was analyzed by a gas chromatography. The fuel used was n-heptane. It is able to explain the generation of exhaust emissions by the experimental results. The other objective is to simulate the intermediate products. It is capable of explaining the relation between the simulated and experimental results.
Technical Paper
2004-06-08
Hajime Fujimoto, J. Senda, D. Kawano, Y. Wada
The mixed fuel composed of two kinds of fuel oil whose boiling temperature is different each other forms the fine spray with minute droplets when its condition crosses over the two-phase region. It is expected that the fuel with low volatility dominates the ignition delay and that with high volatility does the generation of particulate matter. The experiments were carried out in a rapid compression and expansion machine and in an actual high-speed small sized diesel engine by use of this kind of fuel. The experimental results prove this expectation.
Technical Paper
2004-03-08
Takayuki Ito, Tomofumi Hosaka, Masato Ueda, Jiro Senda, Hajime Fujimoto
This work investigates the soot formation process in diesel jet flame using a detailed kinetic soot model implemented into the KIVA-3V multidimensional CFD code and 2D imaging by use of time-resolved laser induced incandescence (LII). The numerical model is based on the KIVA code which is modified to use CHEMKIN as the chemistry solver using Message Passing Interface (MPI). This allows for the chemical reactions to be simulated in parallel on multiple CPUs. The detailed soot model used is based on the method of moments, which begins with fuel pyrolysis, followed by the formation of polycyclic aromatic hydrocarbons, their growth and coagulation into spherical particles, and finally, surface growth and oxidation of the particles. The model can describe the spatial and temporal characteristics of soot formation processes such as soot precursors distributions, nucleation rate and surface reaction rate. The experiments by use of laser induced incandescence were conducted using a constant volume combustion vessel which simulated diesel engine conditions.
Technical Paper
2004-03-08
Kwangjae Myong, Motoyuki Arai, Hirotaka Suzuki, Jiro Senda, Hajime Fujimoto
The maximum liquid-phase penetration and vaporization behavior was investigated by using simultaneous measurement for mie-scattered light images and shadowgraph ones. The objective of this study was to analyze effect of variant parameters (injection pressure, ambient gas condition and fuel temperature) and fuel properties on vaporization behavior, and to investigate liquid phase penetration for the single- and multi-component fuels. The experiments were conducted in a constant-volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector. It was observed that: • Liquid phase length is influenced by fuel properties, boiling point temperature, density and viscosity, etc. • The injection pressure has a little effect on the liquid phase length. • High-boiling point fuel within the multi-component fuel controls liquid phase length. • The difference in vaporization rate among the multi-component fuels with a different mass fraction gradually grow smaller with rising fuel temperature and ambient gas one. • Batch distillation characteristics of multi-component fuel are more apparent at low ambient temperature.
Technical Paper
2004-03-08
Jiro Senda, Nobunori Okui, Tokihiro Tsukamoto, Hajime Fujimoto
This paper describes the results of on-board measurement of engine performance and emissions in diesel vehicle operated with bio-diesel fuels. Here, two waste-cooking oils were investigated. One fuel is a waste-cooking oil methyl esters. This fuel is actually applied to a garbage collection vehicle with DI diesel engine (B100) and the city bus (B20; 80% gas oil is mixed into B100 in volume) as an alternative fuel of gas oil in Kyoto City. Another one is a fuel with ozone treatment by removing impurities from raw waste-cooking oils. Here, in order to improve the fuel properties, kerosene is mixed 70% volume in this fuel. This mixed fuel (i-BDF) is applied into several tracks and buses in Wakayama City. Then, these 3 bio-diesel fuels were applied to the on-board experiments and the results were compared with gas oil operation case. Small size SUV with IDI diesel engine of 2.0 liter in engine displacement was utilized to conduct on-board experiments of vehicle performance and exhaust emissions.
Technical Paper
2004-03-08
Jiro Senda, Nobunori Okui, Teppei Suzuki, Hajime Fujimoto
The Flame structure and combustion characteristics for two waste-cooking oils were investigated in detail. One fuel is the waste-cooking oil methyl esters. This fuel is actually applied to the garbage collection vehicle with DI diesel engine (B100) and the city bus (B20; 80% gas oil is mixed into B100 in volume) as an alternative fuel of gas oil in Kyoto City. Another one is the fuel with ozone treatment by removing impurities from raw waste-cooking oils. Here, in order to improve the fuel properties, kerosene is mixed 70% volume in this fuel. This mixed fuel (i-BDF) is applied into several tracks and buses in Wakayama City. In the experiments, the used fuels were gas oil, i-BDF, B100 and B20. Spray characteristics and basic combustion properties were measured inside a rapid compression and an expansion machine (RCEM). And, the combustion performance including the exhaust-gas emissions were revealed in a single-cylinder, direct injection diesel engine with toroidal type chamber, 4-hole nozzle and bosch type injection system.
Technical Paper
2003-05-19
Daisuke Kawano, Jiro Senda, Yoshimitsu Wada, Hajime Fujimoto, Yuichi Goto, Matsuo Odaka, Hajime Ishii, Hisakazu Suzuki
Fuel design for internal combustion engines has been proposed in our study. In this concept, the multicomponent fuel with high and low volatility fuels are used in order to control the spray and combustion processes in internal combustion engine. Therefore, it is necessary to understand the spray and combustion characteristics of the multicomponent fuels in detail. In the present study, the modeling of multicomponent spray vaporization was conducted using KIVA3V code. The physical fuel properties of multicomponent fuel were estimated using the source code of NIST Mixture Property Database. Peng-Robinson equation of state and fugacity calculation were applied to the estimation of liquid-vapor equilibrium in order to take account for non-ideal vaporization process. Two-zone model in which fuel droplet was divided into droplet surface and inner core was introduced in order to simply consider the temperature distribution in fuel droplet. Furthermore, droplet diameter after breakup was optimized by changing the parameters in original TAB model, because original TAB model underestimated a droplet diameter.
Technical Paper
2003-05-19
Takayuki Ito, Masato Ueda, Takeo Matsumoto, Takaaki Kitamura, Jiro Senda, Hajime Fujimoto
This work presents the ignition delay time characteristics of oxygenated fuel sprays under simulated diesel engine conditions. A constant volume combustion vessel is used for the experiments. The fuels used in the experiments were three oxygenated fuels: diethylene glycol dibutyl ether, diethylene glycol diethyl ether, and diethylene glycol dimethyl ether. JIS 2nd class gas oil was used as the reference fuel. The ambient gas temperature and oxygen concentration were ranging from 700 to 1100K and from 21 to 9%, respectively. The results show that the ignition delay of each oxygenated fuel tested in this experiments exhibits shorter than that of gas oil fuel for the wide range of ambient gas conditions. Also, NTC (negative temperature coefficient) behavior which appears under shock tube experiment for homogenous fuel-air mixture was observed on low ambient gas oxygen concentration for each fuel. And at the condition, the ignition behavior exhibits two-stage phase.
Technical Paper
2003-05-19
Takaaki Kitamura, Takayuki Ito, Yasutaka Kitamura, Masato Ueda, Jiro Senda, Hajime Fujimoto
This paper provides new insights on the mechanism of the smokeless diesel combustion with oxygenated fuels, based on a combination of soot kinetic modeling and optical diagnostics. The chemical effects of fuel compositions, including aromatics - paraffins blend, neat oxygenated fuels and oxygenate additives, on sooting equivalence ratio ‘ϕ’ - temperature ‘T’ dependence were numerically examined using a detailed soot kinetic model. To better understand the physical factors affecting soot formation in oxygenated fuel sprays, the effects of injection pressure and ambient gas temperature on the flame lift-off length and relative soot concentration in oxygenated fuel jets were experimentally investigated. The computational results show that the leaner mixture side of soot formation peninsula on the ϕ - T map, rather than the lower temperature one, should be utilized to suppress the formation of PAHs and ultra-fine particles together with the large reduction in particulate mass. Especially for highly oxygenated fuels, the smokeless ϕ - T region on the leaner mixture side of soot formation peninsula can be enlarged effectively due to the notable reduction in production of PAHs.
Technical Paper
2003-03-03
Taku Tsujimura, Shohei Mikami, Norihisa Achiha, Yoshiroh Tokunaga, Jiro Senda, Hajime Fujimoto
In this study, characteristics of the development and auto-ignition/combustion of hydrogen jets were investigated in a constant-volume vessel. The authors focused on the effects of the jet developing process and thermodynamic states of the ambient gas on auto-ignition delays of hydrogen jets. The results show that the ambient gas temperature and nozzle-hole diameter are significantly effective parameters. By contrast, it is clarified that the ambient gas oxygen concentration has a weak effect on the auto-ignition/combustion of hydrogen jets. Consequently, it is supposed that the mixture formation process is capable of improving the auto-ignition/combustion of hydrogen jets.
Technical Paper
2003-03-03
Daisuke Kawano, Jiro Senda, Yoshimitsu Wada, Hajime Fujimoto
In this study, the novel fuel design concept has been proposed in order to realize the low emission and combustion control in engine systems. In this fuel design concept, the mixed fuels with a high volatility fuel (gasoline or gaseous fuel components) and a low volatility fuel (gas oil or fuel oil components) are used in order to improve the spray characteristics by flash boiling. In our previous papers on this study, the fundamental characteristics of spray and its combustion of mixed fuel were reported. In this paper, heat release and exhaust emission (smoke, NOx and THC) characteristics of single cylinder diesel engine operated with the mixed fuels were investigated under each load. The exhaust performance of diesel engine could be improved using mixed fuel, because fuel properties and spray characteristics were controlled by changing mixing fraction of the mixed fuel. Moreover, in this exhaust gas concentration measurement, initial fuel temperature was employed for experimental parameter in order to control flash boiling process in mixed fuel spray, for flash boiling can be easily occurred by increasing initial fuel temperature.
Technical Paper
2003-03-03
Takayuki Ito, Takaaki Kitamura, Masato Ueda, Takeo Matsumoto, Jiro Senda, Hajime Fujimoto
Considering the bell-shaped temperature dependence of soot particle formation, the control of flame temperature has a possibility to drastically suppress of soot formation. Furthermore, oxygenated fuels are very effective on soot reduction, and the use of these kinds of fuels has a potentiality for smokeless diesel combustion. In this paper, the effects of flame lift-off and flame temperature on soot formation in oxygenated fuel sprays were experimentally investigated using a constant volume combustion vessel which simulated diesel engine conditions. The diffusion flame lift-off length was measured in order to estimate the amount of the oxygen entrained upstream of the flame lift-off length in the fuel jet. This was determined from time-averaged OH chemiluminescence imaging technique. Also, the flame temperature and soot concentration were simultaneously evaluated by means of two-color method. Measurements were obtained at various ambient gas temperatures, oxygen concentrations and injection pressure drops across nozzle orifice.
Technical Paper
2002-10-21
Hajime Fujimoto, Jiro Senda, M. Sora, N. Yoshida
In an SI engine with direct injection of gasoline (DGI), many small droplets disperse in premixed gas in the cylinder. In a CI engine, diesel spray is injected a cylinder, thus, the situation at the spray periphery is almost the same as that of DGI SI engine. From the standpoint it is useful for understanding the combustion phenomena in both engines to experiment the combined combustion of premixed gas where many small droplets exist. This paper describes this kind of combustion and it seems to be able to apply the results to the simulation of combustion in these engines.
Technical Paper
2002-03-04
Jeong-Kuk Yeom, Tomoyuki Tanaka, Jiro Senda, Hajime Fujimoto
This paper analyzes heterogeneous distribution of branch-like structure at downstream region of the diesel spray. The liquid and vapor phase of the spray are obtained by a 35mm still camera and CCD camera in order to investigate spray structure of evaporative diesel spray. The many previous studies about diesel spray structure have yet stayed in the analyses of 2-D structure, and there is little information which is concerned with 3-D structure analysis of evaporative spray. The heterogeneous distribution of droplets in inner spray affects the mixture formation of diesel spray, and the combustion characteristics of the diesel engines. In this study, the laser beam of 2-D plane was used in order to investigate 3-D structure of evaporative spray. The incident laser beam was offset on central axis of the spray. From the analysis of images taken by offset of the laser beam, we examine formation mechanism of heterogeneous distribution of the diesel spray by vortex flow at the downstream of the spray.
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