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This study was visualized by experimental and numerical analysis for the unknown injected droplet phenomena with the multi-phase flow in the Urea-SCR dosing system. Visualization experiments were conducted on the droplet behavior inside the pipe with simulated urea SCR injection system. Although the total number of droplets decreases at gas temperatures of 150°C and 200°C, a significant number of injected droplets remained at the position corresponding to the SCR catalyst. That is physical kinetic energy was found to dominate over thermal evaporation. However, the impingement of droplets into the pipe wall had occurred complex behavior by physical/thermal evaporation, and these droplets weren't on gas airflow at the lower part of the pipe. Furthermore, these actual phenomena were reflected in experimental coefficients for new reduction model analysis instead of CFD.

In recent years, the automotive industry has been clearly moving toward carbon neutrality, and internal combustion engines that use fossil fuels are becoming unsustainable. On the other hand, hydrogen engines do not emit CO2 during operation, and if the working gas of a hydrogen engine is replaced with argon and oxygen (by removing the produced water and circulating argon), the thermal efficiency can be dramatically improved. However, when the high adiabatic compression temperature of argon is added to the inherent knocking problems of hydrogen engines, the knocking problem becomes even more pronounced, and no effective solution to avoid knocking has been found to date. In this study, the effects of argon, oxygen, and hydrogen concentrations on combustion and power, respectively, were investigated to determine the effects of working gas composition on combustion and knocking, and the control effects of oxygen rich or hydrogen rich on knocking was investigated.

To explore the production and oxidation characteristics of soot in the flame of diesel jet under the condition equivalent to the direct injection diesel engine condition, the effect of three different important parameters (including injection pressure, injection duration, and oxygen concentration) are experimentally examined. For these purposes, a small CVCC (constant volume combustion chamber) with the volume of 60cc equivalent to the volume of combustion chamber of automotive diesel engine is used. To obtain the experimental data of soot production and oxidation, in experiments, the ambient condition of temperature, pressure and oxygen concentration before injection timing are prepared by the combustion of lean hydrogen mixture (with help of 8 spark plugs) at a high temperature and pressure condition around 1000K and 4.5MPa. The common rail type injector with 8 injection holes for modern diesel engine is attached to this vessel.

Effect of the ambient O2 concentration and pressure on the spray combustion characteristics of diesel fuel was experimentally examined using a high-temperature, high-pressure combustion vessel. The sequential images were captured by using a high-speed color video camera and were analyzed using the two color method to quantify the temporal variation of the soot temperature and KL factor. Based on a series of systematic experiments, it is confirmed that O2 concentration is the dominant factor affecting both the ignition delay and combustion period. The volumetric fraction of O2 in ambient air has great effect on flame temperature and NOx emission, however ambient pressure has little effect on both values. On the contrary both of the volumetric fraction of O2 in ambient air and the ambient pressure have large effect on soot production.

The objective of this study is to understand the fundamental spray combustion characteristics of FAME mixed with diesel oil. To examine the phenomena in detail, diesel spray flame formed in a constant volume high pressure vessel was visualized and the flame temperature and the KL factor were analyzed by two color method of luminous flame. The FAMEs examined in this study are PME, RME and CME, and compared with the combustion characteristics of diesel oil. From the systematic experiments, it is confirmed that the ignition delay and combustion period of bio diesel fuels are almost equivalent with those of diesel oil. The flame temperature decreased slightly with the bio fuel. Furthermore the total KL factor, a measure of the amount of soot in flame, decreased drastically by using the bio diesel fuel in the order of the mass fraction of oxygen in the molecule.

The effects of CO2 and N2 mixing and the effect of O2 concentration on intermittent spray combustion were examined experimentally under the same condition of ambient temperature and pressure, and the same injection pressure. Through the systematic experiments, it was confirmed that the O2 concentration is the dominant factor affecting ignition delay and combustion duration. The flame temperature becomes lower with the decrease of O2 concentration mainly due to the dilution effect. The decrease of flame temperature due to the dilution effect and that due to the thermal/chemical effect of CO2 was quantified. Concerning the soot production, with the decrease of O2 concentration, it is suppressed during the early stage of combustion, however it becomes higher in the middle to later stage of combustion.

This study investigates the mechanisms of solubility, ignition, combustion and emission of ethanol diesel blend fuel for the prospect of using ethanol diesel blend in a Premixed Compression Ignition (PCI) engine. Ethanol diesel blend fuel of ethanol blend ratio 20vol% (E20) does not solubilize in atmospheric temperature, though will solubilize when heated to 323K. When applying ethanol diesel blend fuel to a PCI engine, combustion characteristics changes, which increases ignition delay and decreases the rate-of-pressure-rise. We speculated that the above combustion characteristics were shown as a result of the following three reasons: a leaner mixture caused by increase in ignition delay, fuel adhesion to cavity wall by ethanol and diesel fuels evaporation characteristics, and a decrease in combustion rate by adding ethanol.

In order to study the effects of EGR on diesel combustion fundamentally, the effects of CO2 and N2 mixing into ambient air on intermittent spray combustion were examined experimentally. Under the same condition of ambient temperature and pressure, and the same injection pressure, the rates of CO2 or N2 mixing were changed from 0 to 15% and the combustion characteristics of diesel spray were examined. Through the systematic experiments, it was explored that the ignition delay and the combustion period became longer with the increase of CO2 and N2 mixing, and the effect was larger in the case of CO2 mixing. The flame temperature became lower with the N2 mixing mainly due to the dilution effect. In the case of CO2 mixing, the flame temperature decreased notably, and the flame region with higher temperature became very small. The reason of this tendency was attributed to the dilution effect, the higher heat capacity of CO2 and the chemical effect of CO2.

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.

Homogeneous charge compression ignition (HCCI) combustion of methane was performed using dimethyl ether (DME) as an ignition improver. The ignition mechanisms of the methane/DME/air HCCI process were investigated on the basis of the chemical kinetics. The engine test was also conducted to verify the calculation results, and to determine the operation range. Analysis of the results showed that DME was an excellent ignition improver for methane, having two functions of temperature rise and OH radical supply. It was also shown that the operation range was extended to an overall equivalence ratio of 0.54 without knocking, by controlling DME quantity.

The effects of aromatic components in fuel on ignition and combustion of intermittent spray were examined experimentally. Four types of fuel with different aromatic components, and with similar cetane number and calorific value were used in this study. Fuels were injected into the high-temperature and high-pressure vessel with the injection pressures of 100 MPa and 60 MPa using an electronically controlled fuel injection system developed by the authors. Injection rate shaping applied to the experiments was rectangular, which is a typical injection rate shaping of a common rail type injection system. Images of spray flames were captured using an ICCD camera under ambient conditions corresponding to a turbo-charged diesel engine, 6.1 MPa and 1030 K. A two-color pyrometry technique was applied to the images of spray flame to quantify two-dimensional distributions of flame temperature and soot in flame.

To investigate the ignition process in a diesel spray, the ignition in a transient fuel spray is analyzed numerically by a discrete droplet spray model (DDM) coupled with the Shell kinetics model at various operating conditions. Predicted results show that the fuel mixture injected at the start of injection, which travels along midway between the spray axis and the spray periphery, contributes heavily to the first ignition in a spray. The equivalence ratio and temperature of the first ignited mixture are kept nearly constant until the start of hot ignition. The temperature of the first ignited mixture is kept at a constant value of higher temperature than the thermodynamic equilibrium temperature of the mixture before the hot ignition starts. The equivalence ratio of the first ignited mixture is around 1.6 at initial gas temperatures between 750 K and 850 K.

To make clear the influence of a torch jet flow on the combustion process, a laser Doppler anemometer (LDA) is used to measure the mean velocity and turbulence intensity in a spark ignition engine with an unscavenged prechamber connected to a main chamber by a torch nozzle of different area sizes. The test engine is operated at a constant speed of 16.7 rps (1000 rpm), a constant volumetric efficiency of 80±2% and MBT for each torch nozzle area under firing as well as motored conditions. The LDA system is a dual beam forward scatter type, and its signals are acquired quickly and stored in a memory through a frequency tracking system. The LDA measurements are made at several locations in the main chamber. In the present paper, the turbulence is defined as the high frequency component of velocity above a cut-off frequency (0.75 kHz), and a cycle resolved analysis is performed to obtain the mean velocity and turbulence from individual cycle.