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Diesel sprays injected into a combustion chamber of a small sized high-speed CI engine impinge surely on a piston surface and a cylinder wall. As a consequence, their vaporization, mixture formation and combustion processes are affected by impingement phenomena. And the other important factors affecting on the processes is the injection pressure. Then, the distribution of the vapor concentration in a single diesel spray impinging on a flat and hot wall was experimented by the exciplex fluorescence method, as a simple case. The injection pressure was varied in the range from 55 MPa to 120 MPa. It is found that the distribution of the vapor concentration in this case is much leaner than that in the case of the low injection pressure of 17.8MPa.

CNG is one of the future fuel for a CI engine. Recently, the general tendency is the use of the high pressure injection system over 100 MPa in a CI engine for the near future severe regulation. Combustion phenomenon in a CI engine with such injection system is like a transient gas diffusion flame. The flow in a gas diffusion flame was investigated by the particle image velocimetry on its 2-D images, the relative soot concentration, the temperature and the relative CO2 concentration was detected in the experiments. And the model of transient gas diffusion flame was constructed by use of experimental data.

The applicability of several popular diesel particulate matter (PM) measurement techniques to low temperature combustion is examined. The instruments' performance in measuring low levels of PM from advanced diesel combustion is evaluated. Preliminary emissions optimization of a high-speed light-duty diesel engine was performed for two conventional and two advanced low temperature combustion engine cases. A low PM (<0.2 g/kg_fuel) and NOx (<0.07 g/kg_fuel) advanced low temperature combustion (LTC) condition with high levels of exhaust gas recirculation (EGR) and early injection timing was chosen as a baseline. The three other cases were selected by varying engine load, injection timing, injection pressure, and EGR mass fraction. All engine conditions were run with ultra-low sulfur diesel fuel. An extensive characterization of PM from these engine operating conditions is presented.

An experimental study was performed to investigate diesel particulate filter (DPF) performance during filtration with the use of real-time measurement equipment. Three operating conditions of a single-cylinder 2.3-liter D.I. heavy-duty diesel engine were selected to generate distinct types of diesel particulate matter (PM) in terms of chemical composition, concentration, and size distribution. Four substrates, with a range of geometric and physical parameters, were studied to observe the effect on filtration characteristics. Real-time filtration performance indicators such as pressure drop and filtration efficiency were investigated using real-time PM size distribution and a mass analyzer. Types of filtration efficiency included: mass-based, number-based, and fractional (based on particle diameter). In addition, time integrated measurements were taken with a Rupprecht & Patashnick Tapered Element Oscillating Microbalance (TEOM), Teflon and quartz filters.

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.

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.

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.

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.

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.

Fuel formulation for premixed charge compression ignition (PCCI) combustion has been attempted based on the mixture formation and auto-ignition behavior of normal paraffin fuels. Different pure and mixed fuels with different blending ratios are tested. The mixture formation behavior is investigated photographically in a constant volume combustion chamber (CVCC) at elevated temperature and pressure. Auto-ignition behavior is tested in a Fuel Ignition Analyzer under different test conditions. It is found that the evaporation rate of pure n-paraffin fuel increases and the ignition delay becomes longer with decreases in the chain length. In the range of test condition used in this study, the flash-boiling phenomenon affects the fuel evaporation rate and ignition delay to some extent. Based on the experimental results a mixture of a very light mixture promoting component (MPC) and a moderately dense igniting component (IC) at a ratio of 3:1 is found to be optimum for PCCI combustion.

Soot formation process inside the combustion chamber of an DI diesel engine is focused as a phenomenological basic scheme by using several optical diagnostics technique for the improvement of diesel exhaust emission. We have conducted the series of optical measurement research for the clarification of combustion field in an DI diesel engine. Then, this paper is a kind of review by adding the fuel vapor properties and particle image velocimetry (PIV) analysis with focusing the soot formation process. The experiments were carried out in a small sized high-speed DI diesel engine installed with an optical access view. The spray characteristics and its flow field in 2-D field were measured by laser sheet scattering (LIS) method and PIV scheme.

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.

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.

It is unavoidable that a DI diesel engine exhausts a blue and white smoke at starting, especially in the cold atmosphere. In the experiments presented here, a small DI diesel engine started under the conditions of coolant and suction air whose minimum temperatures were 255 K and 268 K, respectively. The flame was photographed by high-speed photography, the temperature of flame and the soot concentration were measured by two-color method, and CO2 concentration was detected by luminous method. The engine cannot be started over several cycles when the coolant temperature is 255 K and suction air temperature is 268 K. As the temperature of coolant and suction air are decreasing, the maxima of the cylinder pressure, the flame temperature, the soot concentration and CO2 concentration are decreasing. Luminous small dots or small lumps of flame become scattered in the piston cavity.

There is a concept that the increase in the temperature of charge in a combustion chamber and the shield of heat transferred through a chamber wall can facilitate the oxidation of soot and reduce the discharge of soot from the engine. In the experiments presented here in, an IDI diesel engine was used to inspect the concept. The engine was installed a bigger sized cylindrical swirl chamber which was equipped with two flat quarts windows, in order to observe the combustion phenomena and to apply the optical measurement. The experiments were carried out using two types of divided chambers, that is, the swirl chamber made of ceramics and that made of steel, to examine the the effects mentioned above.

In this study, a rapid compression and expansion machine(RCEM) with a pancake combustion chamber was designed to investigate fundamentally on the knocking phenomena in spark ignition(S.I) engines. This RCEM is intended to simulate combustion in an actual engine. The homogeneous pre-mixture of n-pentane and air was charged into a quiescent atmosphere of the chamber. Then, the combustion field become simpler in this machine than it in a real S.I. engine. Also, the combustion phenomena, that is a cylinder pressure history, the behavior of flame propagation and so on, with high reproducibility are realized in this machine. The phenomena caught in this experiment were so-called low speed knocking. And, this knocking characteristics such as a knock intensity and a knock mass fraction were revealed by the cylinder pressure analysis varying the charge pressure and the equivalence ratio of the mixture, a compression ratio and an ignition timing.

This paper presents an atomization mechanism of a spray injected into the low-pressure field, as the subject of injection system in a suction manifold of gasoline engine. Pure liquid fuel, which is n-Pentane or n-Hexane is injected into quiescent gaseous atmosphere at room-temperature and low- pressure through pintle type electronic control injector. Fuel sprays are observed by taking photographs for variation of the back pressure and the changes in spray characteristics with the back pressure below atmospheric pressure are examined in detail. In particular, in the case of the back pressure below the saturated vapor pressure of fuel, the atomization mechanism is discussed from a viewpoint of flash boiling phenomena, those are bubble growth rate and so on.

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.

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.

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.