Use of the molecular beam mass spectrometry to study the low-temperature combustion chemistry.

With the aim to reduce the global pollution caused by the increasing levels of NOx, CO and CO2 emitted by internal combustion engines, the study of low-temperature chemistry (LTC) of the combustion process has been greatly enhanced. The goal of this thesis work is to evaluate the performances of the time-of-flight Molecular Beam Mass Spectrometry (TOF-MBMS) in the analysis of the oxidation of propane at low temperature with strong interest in the detection of fleeting species to verify the low-temperature oxidation mechanism. To do that we performed two different experiments: propane oxidation in jet stirred reactor and ozone activated cool diffusion flame in a counterflow setup. The first was carried out flowing a mixture of C3H8/O2/Ar with molar fraction 2/13/85%, respectively, corresponding to a equals to 0.77, in the temperature range 750-1100 K and residence time τ=1 s. To support the results obtained from MBMS, we analyzed the propane oxidation in the same conditions with the gas chromatograph (GC) technique. The results have been compared with the MBMS ones showing good agreement for most of the analysed species. Numerical simulations of the molar fraction of all species were performed and compared with experimental data. The results indicate that the model well predicts the trends of the molar fraction of the species, except for C2H2 and the allyl radical. The onset of the reaction is predicted at a lower temperature than in the experiment. In cool flame experiments the fuel/N2 and O2/O3 streams are facing each other and both propane and n-butane were used as fuel. In propane experiments a 50/50% C3H8/N2 mixture has been used with O2 flow rate of 5 dm3/min, which corresponds to an ozone concentration of 5.94%. For n-butane tests the mixture used was 45/55% for C4H10/N2, O2 flow rate 7 dm3/min and ozone concentration of 5.02%. Numerical analysis was performed showing a good prediction of flame position and species profiles through the reaction zone.