| This work is an investigation of the combustion characteristics of neat ethanol and blends of ethanol and diesel fuel No. 2 (DF2) in a direct-injection, single-cyclinder, research-type diesel engine.; The theoretical part includes the analysis of the preignition processes and the formation of the combustible mixture. Both the physical factors and the chemical factors are discussed. Physical ignition delay is calculated using a transient model.; The experimental work was conducted on a direct-injection, single-cylinder, research-type diesel engine. The tests covered the whole range of ethanol-diesel blends; from 100% ethanol to 100 DF2. The test parameters were: the fuel type, the intake air properties, and the fuel-air ratio. The ignition delay was measured by detecting the beginning of injection and the occurrence of a detectable pressure rise. The cycle-to-cycle variations in ignition delay were determined from the superimposed pressure traces for 112 consecutive cycles. The effects of ethanol-diesel fuel blends on engine performance were investigated.; The present results show that, for ethanol-DF2 blends, the pressure-rise delay and its cycle-to-cycle variations decrease by increasing both the intake-air pressure and the intake-air temperature, and increase by increasing the ethanol content in the blend. Three important findings of this study are: (1) Developing ignition delay correlations for ethanol-DF2 blends. (2) Determining the global activation energy for ethanol-DF2 blends. (3) Determining the cetane numbers for ethanol-DF2 blends.; The present work shows that the ignition delay period becomes more chemically controlled as the ethanol content is increased in an ethanol-DF2 blend. Increasing the ethanol content reduces smoke emissions. On the other hand, the increase in the ethanol content causes a delay in the dynamic injection timing and an increase in materials wear. |
