| In recent years, the automobile output increase brings with energy and environment problems that are drawing more and more attentions. As oil price increase and global warming as well as other environmental problems become more and more seriously, the automobile structure should be modified and fuel properties be improved to meet the requirements of energy and environment. We conducted numerous tests by means of DMCC and DECC at diesel engine test bench tests and vehicle road tests, and obtained quite good results.However, However, how alcohol fuels affects diesel's mechanisms is not clearThis study presented in the thesis investigated in the combustion characteristics of N-heptane, N-heptane added to ethanol, methanol, ethanol and Dimethyl Ether(DME) and ethanol and their effect from the angle of combustion science combined by means of chemical analysis and optical measurements. And we hope that the study can improve alcohol fuel and DME blending mechanism for the purpose of better usage as an alternative fuels and additives fuel in engines.Compared the advantages and disadvantages of in situ optical spectroscopic probes and extractive sampling method, it was introduced that the synchrotron radiation combined with molecular beam sampling and time-of-flight mass spectrometry, including its principle, development and characteristic, and compared with other common combustion diagnostics methods.A constant volume combustion bomb for experiment was designed and manufactured to conduct some related basic researches about diffuse flames of diesel with adding alcohol fuels. The structures of the test devices are very simple, and thermal parameters (including fuel air ratios, residual gas, pressure and temperature) and turbulent parameters can be easily changed. These make us easily study the effects to combustion at the condition of changing single parameter. The results show that temperature and gas composition have great influences on diesel's ignition characteristics. With temperature increasing, the diesel's ignition delay period and flame lift-off length will be shorter no matter under the condition of air or air mixture with alcohols. However, the diesel's ignition delay period and flame lift-off length at air conditions are smaller than that's at mixture gas with alcohol. These results suggest that air with adding alcohol has influence on diesel spontaneous combustion period. All these can gain more time for air fuel mixture and create favorable conditions for HCCI. With methanol content of mixture being higher, the diesel's ignition delay period and flame lift-off increase. Flame brightness first enhances then weaks. Flame lift-off length increases at methanol content's of mixture gas elevating.Low pressure premixed ethanol with higher octane number and DME burning in oxygen were studied and flame intermediates were identified by molecular-beam sampling mass spectrometry (MBMS) combining with tunable synchrotron radiation photoionization technique. And the flames of N-heptane with ethanol burning in oxygen were measured via synchrotron radiation single-photon ionization combined with molecular beam sampling technical. It is shown that although ethanol and DME are isomers, their properties have great differences. The octane number of ethanol is up to 111, however its cetane number is only eight. And the cetane number of DME reached 60. The results from tunable synchrotron radiation showed that the pyrolyzing rate of ethanol is obviously faster than that of DME. Flame burning rate of N-heptane is faster than that of N-heptane with ethanol. This illustrated that N-Heptane is suppressed by ethanol. The ethanol addition increased the mole fraction of acetaldehyde and ketones, and this indicated that N-heptane's some oxidation reaction was strengthened after ethanol addition, affect its consumption routes and soot precursor's producing ways.
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