Akihiko Azetsu

Effects of N2 and CO2 mixing on ignition and combustion in a homogeneous charge compression ignition engine operated on dimethyl ether

Abstract The control of ignition timing and combustion duration over a wide range of engine speeds and loads in a homogeneous charge compression ignition (HCCI) engine is one of the barriers to the realization of this type of engine. Application of exhaust gas recirculation (EGR) is a promising option to control ignition timing, extend combustion duration, and suppress knock-like combustion. In this study, the effects of the mixing of N2 and CO2, major components of exhaust gas, with the fuel-air mixture on the heat release of the cool flames and the emission characteristics of CO were investigated by experiment and computation. The heat release of the cool flames was reduced with N2 mixing; however, it increased with CO2 mixing. From the systematic experiments and chemical kinetic computations, it was confirmed that the amount of heat release from the cool flames depends strongly on the concentration of O2 at the onset of cool flame. The dominant pathway for CO oxidation is the reaction of CO + OH = CO2 + H, where the H atoms produced react with O2 molecules and produce OH + O or HO2. The CO oxidation becomes active as the branching rate to OH + O is increasing. However, the branching rate to HO2 was increased with the addition of CO2 into the mixture, resulting in higher CO emission. Though the mixing of CO2 is effective in suppressing knock-like combustion owing to its small specific heat ratio and large heat capacity, it has an inferior effect on CO emission.

Effects of Aromatic Components in Fuel on Flame Temperature and Soot Formation in Intermittent Spray Combustion

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. Through systematic experiments, it was explored that the aromatic components have little effects on ignition delay and combustion period. However, the aromatic components have significant effects on flame temperature and soot formation. The flame temperature and the amount of soot in flame become higher as the aromatic components in fuel increase. The injection pressure has a great effect on spray combustion, i.e., shorter combustion period and rapid soot oxidization with high injection pressure. However the effects of aromatic components on combustion were not changed qualitatively by the increased injection pressure.

A study on development of a velocity time measuring system for motorcycles using wireless connection

This paper presents the development of velocity - time measuring system for motorcycles and the potential of proposing a driving cycle for motorcycles in Ho Chi Minh City. Motorcycles are the major mean of transport, but they are also the main source of air pollution in the biggest cities in Vietnam. Nowadays, the high levels of fuel consumption and air pollution are the most important problems that characterized the urban areas of both developed and developing countries. In this work, a velocity time measuring system is developed for tracking the change of velocity as a function of time. This system is studied using (1) Velocity sensor: magnetic type converted analog signal to digital/pulse signal sending to Arduino circuit; (2) Accelerator sensor: measured accelerator for three axis (x, y, z) and sending to Arduino via standard of I2C; (3) Arduino: receiving and processing the measured signal and communicating smart phone via Bluetooth; (4) Smart phone/receiver using android operating system: receiving the signal via Bluetooth and estimating the concerned parameters and monitoring the measured/estimated results. The preliminary results are useful to evaluate for better understanding the current status and further development for driving cycle for motorcycle.

Combustion Characteristics of Diesel Spray Under Low O2Concentration Condition

The spray combustion of diesel fuel under conditions of very low ambient O2 concentrations was examined in this study. The detailed combustion characteristics were evaluated using two different sets of experimental apparatuses. A high-temperature, high-pressure combustion vessel with dual observation windows was employed to visualize the spray flame. The sequential images were obtained by using a high-speed color video camera and were analyzed using the two color method to quantify the temporal variation of the two dimensional distribution of soot temperature and KL factor. Both the ambient O2 concentration and the CO2 mixing ratio were varied as experimental parameters. A second constant volume vessel with a smaller internal volume was also employed as an experimental apparatus to conduct analyses of heat release rates based on temporal variations of pressure.Based on a series of systematic experiments, we confirmed that O2 concentration is the primary factor affecting both the ignition delay and combustion period, while the level of CO2 mixing has little effect. Decreasing O2 concentrations were associated with delays in the appearance of the luminous flame following the onset of light emission from OH radicals. The heat release rate study showed the possibility of the existence of endothermic reactions during this period. The flame temperature was observed to decrease as the O2 concentration decreased and as the CO2 ratio increased, resulting in reduced NOx emissions. The amount of soot inside the flame initially increased with decreasing O2 concentrations, but then decreased starting at an O2 concentration of approximately 11%, such that minimal amounts of soot were generated at very low O2 levels. Both visual observations and emissions measurements confirmed that the simultaneous reduction of NOx, soot and CO can be successfully achieved under very low O2 concentrations.Copyright