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Compression ignition engines provide superior thermal efficiency over other internal combustion engines. Unfortunately the combustion process is diffusive combustion, meaning a lot of fuel is impinged the on the piston and cylinder wall. This creates cooling loss coupled with smoke, CO and THC. Minimization of the nozzle orifice diameter is a simple method widely used to shorten spray penetration. However, decreasing the nozzle orifice diameter also decreases fuel flow rate resulting in a prolonged injection and combustion process and reducing thermal efficiency. An offset orifice nozzle causes less fuel impingement by shorter fuel spray penetration without significant reduction of fuel flow rate. The offset orifice nozzle was made by shifting its alignment from the center of the sac to the edge of the sac following the swirl direction. A counterbore design was applied to maintain constant orifice length.

In order to investigate the mechanism of heat transfer on the chamber wall of direct-injection diesel engines, 2-D temperature imaging and heat flux measurement in the flame impinging region on the chamber wall were conducted using laser-induced phosphorescence technique. The temperature of the chamber wall surface was measured by the calibrated intensity variation of the 355nm-excited laser-induced phosphorescence from an electrophoretically deposited thin layer of La2O2S:Eu phosphor on a quartz glass plate placed in a rapid compression and expansion machine (RCEM). Instantaneous 2-D images of wall temperature at different timings after start of injection and time-resolved (10kHz) heat flux near the flame impinging region were obtained for combusting and non-combusting diesel sprays with impinging distance of 23.4mm at different injection pressures (80 and 120MPa).

In this study, the combustion characteristics of diesel flame achieved in a rapid compression and expansion machine (RCEM) at various patterns of oxygen distribution in the chamber are investigated in order to clarify the effect of heterogeneity of oxygen distribution in diesel engines induced by EGR on the soot and NOx emissions. To make the heterogeneous distribution of oxygen in a combustion chamber, the mixtures with different oxygen concentrations are injected through the each different port located on the cylinder wall. Results indicate that the amount of oxygen entrained into the spray upstream the luminous flame region affects the NO emission from diesel flame strongly.

The relation between the characteristics of a non-evaporating spray and those of a corresponding frame achieved in a rapid compression machine was investigated experimentally. The fuel injection pressure was changed in a range of 55 to 260 MPa and the other injection parameters such as orifice diameter and injection duration were changed systematically. The characteristics of the non-evaporating spray such as the Sauter mean diameter and the mean excess air ratio of the spray were measured by an image analysis technique. The time required for a pressure rise due to combustion was taken as an index to characterize the flame. It was concluded that the mean excess air ratio of a spray is the major factor which controls the burning rate and that the high injection pressure is effective in shortening the combustion duration and reducing soot formation.

In order to investigate the combustion phenomena in a combustion chamber of the diesel engine at transient operations, the simultaneous measurements of temperatures of flame and wall surface in a combustion chamber were conducted. The new technique for simultaneous measurements of flame temperature and wall surface was developed. Laser-Induced phosphorescence was used for the measurement of wall surface temperature which was coupled with the flame temperature measurement by a two-color pyrometry. The NOx and soot emissions were also measured simultaneously in transient operations. The relation between the temporal changes of emissions and temperatures of flame and surface wall are discussed. The results show that the temporal change of NOx emission during transient operation is similar to that of the average gas temperature in a chamber. On the other hand, the temporal change of soot emission is similar to neither that of flame temperature nor that of average gas temperature.

This work investigates the effects of ignition improvers on the ignition and combustion characteristics of hydrous ethanol with 5% by weight water and 1% by weight Lauric acid (Eh95) under simulated diesel engine conditions using the rapid compression and expansion machine (RCEM). Results indicate that hydrous ethanol with commercial additive (ED95) and hydrous ethanol with 5% by weight glycerol ethoxylate in hydrous ethanol exhibit a near identical rate-of-pressure-rise and heat release rate. Ignition delay of hydrous ethanol with 5% by weight glycerol ethoxylate is shorter, but hydrous ethanol with 1% by weight glycerol ethoxylate has longer ignition delay time and different combustion characteristics compared with hydrous ethanol with commercial additive (ED95). Hydrous ethanol with 1% by weight glycerol ethoxylate and hydrous ethanol with 5% by weight glycerol ethoxylate are considered suitable fuels for high compression-ratio diesel engines.

The increase of air pollution and global warming is a threat for human life. Besides, the price of petroleum is increasing rapidly and the resources are diminishing. This obliged scientists and engineers to look for alternative sources of energy, which are cleaner and more sustainable. Biodiesel, defined as mono-alkyls of esters from vegetable oils and animals fat, is a cleaner renewable fuel and has been considered as the best alternative for petroleum based diesel fuel hence it can be used in any compression ignition engines without any significant modification. The main advantages of using biodiesel are its renewability and better quality of exhaust gas emissions due to their higher content of oxygen. The produce less soot and hence the feed stuck is plant it will regenerate the CO2 by the photosynthesis which ensures the renewability and reduces global warming.

To understand further the mixing process between the injected fuel and air in the combustion chamber of a diesel engine, the turbulent mixing process in a one-phase, two-dimensional transient jet was theoretically studied using the discrete vortex simulation. First, the simulation model was evaluated by comparisons between calculated and experimental data on two-dimensional turbulent jets. Second, the trajectories of the injected fluid elements marked with different colors were graphically demonstrated. Also the process of entrainment of the surrounding fluid into the jet was visually presented using colored tracers.

A rapid compression-expansion machine was developed, which can simulate intake, compression, expansion and exhaust strokes in a single Diesel cycle by an electrically controlled and hydraulically actuated driving system. The whole system which is composed of a hydraulic actuator, fuel injector and a valve driving device, is sequentially controlled by a micro-computer. The machine features; 1) accurate control of piston position at TDC, 2) no effect of lubricant on HC emission due to the use of dry piston rings; 3) independent control of local wall temperature; and 4) high power output to drive heavy piston at high frequency. The single cycle operation permits Diesel combustion experiments under a wide range of operating conditions and easy access of optical diagnostics with minimized amount of test fuel. The performance test showed that the machine can drive a DI Diesel type piston with a 100 mm bore at a maximum frequency of 16.7 Hz at a maximum compression pressure of 15 MPa.

In an attempt to achieve lean combustion in Diesel engines which has a potential for simultaneous reduction in no and soot, the authors developed a micro-hole nozzle which has orifices with a diameter as small as 0.06 mm. Combustion tests were carried out using a rapid compression-expansion machine which has a DI Diesel type combustion chamber equipped with the micro-hole nozzle. A comparison with the result of a conventional nozzle experiment revealed that the ignition delay was shortened by 30 %, and in spite of that, both peaks of initial premixed combustion and diffusion combustion increased significantly. The combustion in the case of the micro-hole nozzle experiment was accompanied with a decrease in soot emission, whereas an increase in NO emission.

A new technique was proposed for measuring instantaneous distributions of flame temperature and KL factor of luminous flames. Here the principle of the two-color method was used to calculate flame temperature and KL factor from the two-color densities of a film image taken on a nega-color film. We applied this technique to the high speed nega-color photographs of flames in a D. I. diesel engine operated with varying swirl ratios, and discussed the measured results of instantaneous distributions of flame temperature and KL factors.

The concentrations of soot, NO and the other combustion products were measured by incylinder gas sampling in a DI diesel engine. The effects of injection timing, swirl ratio, and combustion chamber geometry on the formation and emission processes of soot and NO were studied. The following results were obtained: (1) Soot is promptly formed in the flame during the early combustion period where the equivalence ratio in the flame is high over 1.0. Thereafter almost all the formed soot is swiftly burnd up by oxidation during the middle combustion period. This process mainly determines the exhaust soot concentration. (2) NO is formed in the flame during the early and middle combustion period where the flame temperature is high over 2000 K. The highest NO concentration is observed at the flame tip swept by the air swirl. Though the concentration of the formed NO decreases by dilusion it nearly constant during the later combustion period.

Experiments on the effects of temperature T and equivalence ratio ϕ on soot formation at high pressures up to 5 MPa were conducted. The soot formation region is mapped on ϕ-T diagram using the results obtained in the experiments and the published data. NO formation region is also determined by the Zeldovich equations and is plotted on the same diagram. The time histories of ϕ and T of the flame in a DI diesel engine which was obtained by a gas sampling study, are plotted on the ϕ-T diagram to form a trajectory. Discussion of the trajectory in relation to both soot and NO formation region gives suggestion of a possibility of high temperature - rich mixture combustion to reduce particulate formation in diesel engines.

A rapid compression-expansion machine which can simulate the combustion processes in diesel engines is developed. The configuration of the combustion chamber is a 100 mm bore and a 90 mm stroke, and the compression ratio is 15. The piston is driven by an electro-hydraulic system with a thrust of 90 kN and the maximum frequency of 20 Hz. The whole system composed of a hydraulic actuator, a fuel injection system, and a valve driving unit is sequentially controlled by a computer. The reproducibility of the stop position of the piston at the end of compression is achieved with an accuracy of ±0.1 mm by employing a hydraulic-mechanical brake mechanism. The experiment shows that the combustion in the expansion stroke is achieved, and that the combustion characteristics such as the rate of heat release and indicated output as well as the exhaust emission can be measured.

Multi-step water splitting with Mn-ferrite(MnFe2O4)/sodium carbonate(Na2CO3) system accompanying endothermic reaction was investigated for converting solar energy into chemical energy. This water splitting is caused by the oxidation-reduction of manganese ion in the Mn-ferrite. Multi-water splitting with MnFe2O4/Na2CO3 system was consisted of three steps. The first step was hydrogen generation at 1073K. The second step was oxygen release at 1273K. The third step was Na2CO3 reproduction at 873K. The mechanism of multi-water splitting has been considered by XRD, chemical analysis of colorimetry and back titration. The temperature range 873 to 1273K is quite lower than those studied on the solar furnace reaction (O2 releasing step) in two-step water splitting (1500-2300K). This lower temperature range would permit further progress in converting the direct solar energy into chemical energy.

Diesel engine is one the effective solutions for reducing CO2 and recognized as a leading candidate for mitigating global warming. To comply with increasingly stringent emission standards, all diesel engines require some sort of NOx control systems such as selective catalytic reduction (SCR) systems. The SCR catalyst for reducing NOx from diesel engines is classified into two groups, urea-SCR and HC-SCR catalyst, respectively. Although the urea-SCR catalyst is widely recognized as promising de-NOx technology in respect to the NOx conversion efficiency, it have some outstanding issues such as ammonia slip, urea injection, storage space, freezing and some infrastructures for supplying urea water solutions. In an attempt to overcome the inherent shortcoming of existing urea-SCR catalyst, hydrocarbons have been considered as alternative reducing agents for SCR process, instead of NH3.

Physicochemical characteristics of particulate matters which are influenced by engine oil additives from engine combustion of diesel and synthetic biodiesel: hydrotreated vegetable oil (HVO) were successfully investigated using electron microscopy, electron dispersive x-ray spectroscopy and thermogravimetric analysis. The agglomerate structure of diesel PM, HVO PM and diesel blending lubricant PM are similar in micro-scales. However, nanostructure of soot is a spherical shape composed of curve line crystallites while the metal oxide ash nanostructure is composed of parallel straight line hatch patterns. The oxidation kinetics of fuel blending lubricant PMs are higher than neat fuel PMs due to catalytic effect of incombustible metal additives from engine lubricating oil.

Nanostructures of diesel and biodiesel engine particulate matters (PMs) were investigated by using a Transmission Electron Microscopy (TEM). The average single particle sizes of biodiesel and diesel PMs are approximately 30-40 nm and 50-60 nm, respectively. Image processing process was used to estimate each carbon platelet length by using TEM image. The average carbon platelet length of biodiesel and diesel PMs are in the range of 0.1-7.0 nm. Moreover, carbon atoms per cubic volume of PMs are approximately 500-900. The result shows that engine load and fuel property are strongly impact on the size of single particle and carbon atom density of particle. This is one of interesting behaviors need to be investigated for better understanding. The results of this research would be used as basic information for design and develop removing process of PM emitted from engine combustion which using in diesel and biodiesel fuels.

The increasing of global energy demand and stringent pollution regulations have promoted research on alternative fuels. In Thailand, ethanol, can be produced from many sources of national agriculture products as renewable fuel, which was strongly promoted by government due to its many merits for use in transportation field. In this study, combustion characteristics of ethanol-gasoline blend (20%, 85%, and 100%) as well as pure gasoline (E0) were investigated by using a swirl-generated constant volume combustion chamber. Flame propagations of different fuel blends were observed by high speed Schlieren photography technique while pressure history data were recorded for detailed combustion analysis. Combustion behavior, combustion duration and rate of pressure rise of all tested fuels were investigated in various swirl intensities and equivalence ratios. In addition, effect of swirl intensities and ethanol concentration on lean misfire limit were also discussed.

The present study aims to investigate the parameters affecting cold start characteristics of ethanol at low temperature, and suggest a solution to avoid cold starting problem without the installation of second fuel tank. The testing engine is a 125cc volume displacement, single-cylinder four strokes SI engine with fuel injection and ignition timing system controlled by ECU (electronic control unit). The cold starting performance tests were extensively conducted with different percentages of ethanol blends, surrounding temperatures, heating inside combustion chamber, heater injector, pre-cranking without fuel injection, and amount of fuel injection. From the experimental results, when using ethanol fuel in conventional engine, the problem of cold starting was observed at surrounding temperature lower than 20°C for ethanol. Increasing of injection duration can lower the possible cold start temperature of neat ethanol.