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Technical Paper

Vizualization of Evaporative Diesel Spray Impinging Upon Wall Surface by Exciplex Fluorescence Method

A single diesel spray of n-decane which was miscible with a small quantity of exciplex dopants was injected from a hole nozzle into a quiescent high-temperature and high-pressure atmosphere of nitrogen, and was impinged in a normaldirection upon a flat wall with elevated temperature. This experiment was to serve as a simplified model of the actual state in a combustion chamber of diesel engines. When a thin sheet of laser light from Nd:YAG laser is passing through the cross section of this spray containing its central axis, it is able to generate fluorescent emissions from vapor and liquid phases in this evaporating spray. Then, clear 2-dimensional images concerning the concentration distributions of vapor and liquid phases were obtained simultaneously, by an exciplex fluorescence method using an image-intensifier and a CCD camera system. The dispersion processes of vapor and liquid phases in this impinging spray near the wall were analyzed with an image analyzer.
Technical Paper

Visualization of Micro Structure in a Diesel Spray by Use of Photography with High Spatial Resolution

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

Vaporization Characteristics and Liquid-Phase Penetration for Multi-Component Fuels

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.
Technical Paper

The structure analysis of diesel free spray with phase change~(Effect of viscosity change of vapor-phase fuel on the structure of diesel free spray)

In this study, the purpose is placed in analysis the structure of diesel spray and, especially, making clear the mixture formation process in the evaporative diesel spray. The liquid fuel was injected from a single-hole nozzle (1/d = 1.0 mm/0.2 mm) into a constant-volume vessel possessing phenomena visualization under high pressure and temperature field. As for measurement method, in order to investigate liquid and vapor-phase of injected spray, exciplex fluorescence method was applied in the evaporative fuel spray. And the interested view region in injected spray is the downstream spray. For the minute investigation of spray flow, the liquid and vapor-phase region is taken with 35 mm still camera and CCD camera, respectively.
Technical Paper

The Structure Analysis of Evaporative Diesel Spray

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.
Technical Paper

The Effect of Fuel-Vapor Concentration on the Process of Initial Combustion and Soot Formation in a DI Diesel Engine Using LII and LIEF

A phenomenological or empirical model based on experimental results obtained from various optical measurements is critical for the understanding of DI diesel combustion phenomena as well as for the improvement of its emission characteristics. Such a model could be realized by the application of advanced optical measurement, which is able to isolate a particular phenomenon amongst complicated physical and chemical interactions, to a DI diesel combustion field. The authors have conducted experimental studies to clarify the combustion characteristics of unsteady turbulent diffusion flames in relation to the soot formation and oxidation process in a small-sized DI diesel engine. In the present study, the effect of fuel vapor concentration on the process of early combustion and soot formation has been investigated using several optical measurements.
Technical Paper

Study on Characteristics of Auto-Ignition and Combustion of Unsteady Synthetic Gas Jet

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.
Technical Paper

Soot formation/oxidation and fuel-vapor concentration in a DI diesel engine using laser-sheet imaging method

Four kinds of optical measurements were performed to investigate the process of soot formation and oxidation in a direct-injection (DI) diesel engine. Measurements were carried out in an optically accessible DI diesel engine that allows planar laser sheet for combustion diagnostics to enter the combustion chamber either horizontally or along the axis of the fuel jet. The temporal and spatial distribution of soot particles has been investigated using the laser- induced incandescence (LII) and high-speed direct photography. Fuel vapor concentration, which is directly linked to the soot formation process in diesel combustion, has been deduced from the images obtained by the measurements of laser shadowgraph and elastic Mie scattering. According to the experimental results, soot formation begins to occur near the injector nozzle in which a fuel-rich mixture is distributed with a homogeneous condition. LII signal is dominated by the fuel vapor concentration in initial combustion period.
Technical Paper

Soot Generation in Spray of Oxygenated Fuel

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

Similarity Law of Entrainment into Diesel Spray and Steady Spray

The surroundings around the diesel spray are entrained during the growth of the spray. The mixing process between the evaporated fuel oil and the entrained surroundings, that is, the entrainment, has a significant meaning for the combustion diesel engine. It is difficult to detect the movement of the entrainment because the diesel spray is the gas-liquid two-phase flow and the unsteady phenomenon within a few milliseconds. Then, in order to clarify and to generalize the movement of entrainment, following three experiments were done. 1)Two-dimensional steady water spray -flat spray- injected into the ambient atmosphere, using tuft and hot wire method. 2) Unsteady water jet injected into water, using tracer. 3)single diesel spray injected into the atmosphere with high pressure at room temperature, using smoke wire.
Technical Paper

Quantitative Analysis of Fuel Vapor Concentration in Diesel Spray by Exciplex Fluorescence Method

An unsteady single spray of n-tridecane which was mixed with a small quantity of exciplex - forming dopants, that is naphthalene and TMPD, was impinged on a flat wall surface with high temperature of 550 K at a normal angle. These experiments were carried out in a quiescent N2 atmosphere with high temperature of 700 K and high pressure of 2.5 MPa. It was possible to generate the fluorescence emissions from the vapor and liquid phases in this spray, when a laser light sheet from a Nd:YAG laser was passing through the cross section of the spray containing its central axis. Then, clear 2 - D images of vapor and liquid phases in the spray were acquired simultaneously by this method. And, the vapor concentration was analyzed quantitatively by applying Lambert - Beer's law to the measured TMPD monomer fluorescence intensity from vapor phase, and by correcting the intensity for the effect of the quenching process due to the ambient temperature and fuel concentration.
Technical Paper

On-Board Measurement of Engine Performance and Emissions in Diesel Vehicle Operated with Bio-diesel Fuel

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.
Technical Paper

OH Radical Generation and Soot Formation/Oxidation in DI Diesel Engine

OH radical generated in a DI diesel engine has a close relationship to soot oxidation. To clarify this fact, the distribution of the natural emission of OH radical was captured by means of an interference filter system and that of soot was detected by the simultaneous application of a laser induced incandescence (LB) and a laser induced scattering (LIS). The experiments were carried out in a small sized high-speed DI diesel engine installed with an optical access view. The generation of OH radical and the formation/oxidation of soot are discussed by using both images.
Technical Paper

New Concept on Lower Exhaust Emission of Diesel Engine

One of countermeasures for exhaust emissions from a diesel engine, especially, DI diesel engine, is the use of a super high pressure injection system with a small hole diameter. However, the system needs greater driving force than that with normal injection pressure, and its demerit is increase in NOx, although soot is decreasing. Then, authors propose the new concept on the simultaneous reduction of NOx and soot. The concept is that the utilization of flash boiling phenomenon in a diesel engine. The phenomenon can be realized by use of the injection of fuel oil with CO2 gas dissolved. Flash boiling facilitates the distinguished atomization of fuel oil and CO2 gas contributes to realizes the internal EGR during combustion. Fundamental information on the characteristics of a flash boiling spray of n-tridecane with CO2 gas dissolved is described in this paper, as a first step.
Technical Paper

NO Formation in Transient Premixed Combustion Field by LIF

In the internal combustion engines, combustion characteristics relating to HC & NO emission are affected remarkably by the spatial distribution of fuel concentration, temperature and turbulence properties. Especially, No formation process inside the combustion chamber affected by the mixture concentration field should be focused relating to the flame field temperature distribution. As the first step of NO formation study in premixed combustion field, NO formation process in the chamber was examined by considering OH radical property and flame temperature in homogeneous mixture conditions. In this study, in order to clarify NO formation process inside the transient premixed combustion field, relative concentration fields of OH radical and NO and temperature fields were measured by laser induced fluorescence technique(LIF) in the constant volume vessel for methane-air homogeneous mixture with the variation of equivalent ratio of the mixture.
Technical Paper

Multicomponent Fuel Consideration for Spray Evaporation Field and Spray-Wall Interaction

It is expected that the analysis of the evaporation process for multicomponent fuels such as actual fuels like gasoline and diesel gas oil could be performed to assess more accurately the mixture preparation field inside the cylinder of D.I.S.I engines and diesel engines. In this paper, we suggested the importance of this multicomponent fuel consideration relating to the mixture formation and combustion characteristics from the basis of their own fuel physical and chemical properties. Then, we introduce a treatment for the phase change of a multicomponent solution through the formation of two-phase regions with the basis of chemical-thermodymical liquid-vapor equilibrium. Next, we analyze the distillation properties of a multicomponent fuel as well as the evaporation process of a multicomponent single droplet by use of the chemical-thermodymical analysis.
Technical Paper

Modelling of Atomization Process in Flash Boiling Spray

This paper presents the analysis of atomization and vaporization processes in a flash boiling spray based on experimental results obtained from injection systems in the suction manifold of a gasoline engine. Two kinds of liquid fuel, n-Pentane and n-Hexane, were injected into quiescent atmosphere at room-temperature and low-pressure through a pintle type injector with electronic control. The spray characteristics of both fuels below various atmospheric pressures were investigated in detail by taking photography. Then, in the region of flash boiling, where the back pressure was below the saturated vapor pressure of fuel, the bubble nucleation process due to the flash boiling was modelled by both the measurement results of bubble and the nucleation rate equation using the degree of superheat of the liquid fuel.
Technical Paper

Modeling of Diesel Spray Impingement on a Flat Wall

This paper presents an analysis using a model of the dispersion process of a Diesel spray impinging on a flat wall. The objective is to simulate the spray / wall interaction process inside Diesel engines. This analysis has two parts: one for non - evaporative spray and the other for evaporative spray. For the non - evaporative spray analysis, a single spray of n - tridecane was injected at high - pressure from a single hole nozzle into a quiescent atmosphere at room - temperature. The spray impinged vertically on the wall at room temperature. Thus, the wall temperature Tw was less than the saturation temperature Tsat of the fuel, that is the boiling temperature. A new submodel including fuel film formation on the wall, its breakup process due to droplet impingement and the dispersion process of breakup - droplets was developed. Also, the droplet density distribution was measured experimentally by the laser light extinction method.
Technical Paper

Modeling and Measurement on Evaporation Process of Multicomponent Fuels

In previous multi-dimensional modeling on spray dynamics and vapor formation, single component fuel with pure substance has been analyzed to assess the mixture formation. Then it should be expected that the evaporation process could be performed for the multicomponent fuel such as actual Gasoline and Diesel gas oil. In this study, vapor-liquid equilibrium prediction was conducted for multicomponent fuels such as 3 and 10 components mixed solution with ideal solution analysis and non-ideal solution analysis. And the computation of distillation characteristics was conducted for the steady state fuel condition fuel condition to understand the evaporation process. As a result, calculated distillation characteristics are consistent well with experiment results. And the evaporation process of a multicomponent droplet in the combustion chamber has been calculated with the variation of ambient pressure and temperature.
Technical Paper

Mechanism of Combined Combustion of Premixed Gas and Droplets

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.