Yoshiaki Hidaka

Shock-tube and modeling study of acetylene pyrolysis and oxidation

Abstract Pyrolysis and oxidation of acetylene were studied behind reflected shock waves in the temperature range 1100–2000 K at pressures of 1.1–2.6 atm analyzing the reacted gas mixtures. The progress of the oxidation reaction was also observed with real-time spectroscopy. Main products in the pyrolysis with H 2 or without H 2 were vinylacetylene, diacetylene, and triacetylene. In the oxidation with fuel-rich mixtures, it was found that CO was the main product, and C 1 and C 3 carbon species appeared. The pyrolysis and oxidation of acetylene were modeled using a kinetic reaction mechanism, including the most recent mechanism for formaldehyde and ketene oxidations. The present and earlier shock tube data were reproduced by a proposed mechanism with 103 reaction steps and 38 species. It was found that reactions C 2 H 2 + O 2 → CHO + CHO or C 2 H 2 + O 2 → CHCO + OH and C 2 H 2 + CH 2 → C 3 H 4 were important to predict our data in a wide range of mixtures from acetylene pyrolysis to acetylene-lean oxidation.

Shock-tube and modeling study of ethylene pyrolysis and oxidation

Abstract Pyrolysis and oxidation of ethylene were studied behind reflected shock waves in the temperature range 1100–2100 K at pressures of 1.5–4.5 atm. Ethylene decay in both the pyrolysis and oxidation reactions was measured by using both time-resolved IR-laser absorption at 3.39 μm and time-resolved IR-emission at 3.48 μm. CO 2 production in the oxidation was also measured by time-resolved IR-emission at 4.24 μm. The production yields were also studied using a single-pulse method. The pyrolysis and oxidation of ethylene were modeled using a kinetic reaction mechanism including the most recent mechanism for formaldehyde, ketene, methane, ethane, and acetylene oxidations. The present and some earlier shock tube data was reproduced using the proposed mechanism with 161 reaction steps and 51 species. The reactions and the rate constants in the mechanism were discussed in detail. It was found that reactions C 2 H 4 + M → C 2 H 2 + H 2 + M, C 2 H 4 + M → C 2 H 3 + H + M, C 2 H 4 + C 2 H 4 → C 2 H 3 + C 2 H 5 , C 2 H 4 + H → C 2 H 3 + H 2 , C 2 H 4 + C 2 H 3 → 1, 3-C 4 H 6 + H, C 2 H 4 + O → products and C 2 H 3 + O 2 → products were important to predict our data, which was with mixtures of wide composition from ethylene-rich to ethylene-lean.

Shock-tube and modeling study of acetone pyrolysis and oxidation

Abstract Pyrolysis and oxidation of acetone were studied behind reflected shock waves in the temperature range 1050–1650 K at total pressures between 1.2 and 3.2 atm. The study was carried out using the following methods, (1) time-resolved IR-laser absorption at 3.39 μm for acetone decay and CH-compound formation rates, (2) time-resolved UV absorption at 200 nm for acetone decay and product formation rates, (3) time-resolved UV absorption at 306.7 nm for the OH radical formation rate, (4) time-resolved IR emission at 4.24 μm for the CO 2 formation rate, and (5) a single-pulse technique for product yields. From a computer simulation, a 164-reaction mechanism that could satisfactorily model all of our data was constructed that includes the most recent submechanisms for methane, acetylene, ethylene, ethane, formaldehyde, and ketene oxidation. The rate constants of , were evaluated as k 1 = 1.13 × 10 16 exp(−81.7 kcal/ RT ) s −1 and k 2 = 2.30 × 10 7 T 2.0 exp(−5.00 kcal/ RT ) cm 3 mol −1 s −1 . (CH 3 ) 2 CO → CH 3 CO + CH 3 ,(1) (CH 3 ) 2 CO + H → CH 3 COCH 2 + H 2 .(2) The submechanisms of methane, ethylene, ethane, formaldehyde, and ketene were found to play an important role in acetone oxidation.

Shock-tube and modeling study of methane pyrolysis and oxidation

Abstract Methane pyrolysis and oxidation were studied behind reflected shock waves in the temperature range 1350–2400 K at pressures of 1.6 to 4.4 atm. Methane decay in both the pyrolysis and oxidation reactions was measured by using time-resolved infrared (IR) laser absorption at 3.39 μm. CO2 production was also measured by time-resolved IR emission at 4.24 μm. The production yields were also studied using a single-pulse method. The pyrolysis and oxidation of methane were modeled using a kinetic reaction mechanism including the most recent mechanism for formaldehyde, ketene, acetylene, ethylene, and ethane oxidations. The present and earlier shock tube data is reproduced by the proposed mechanism with 157 reaction steps and 48 species. The reactions and the rate constants, which were important to predict our and earlier shock tube data for methane pyrolysis and the oxidation with mixtures of wide composition from methane-rich to methane-lean, are discussed in detail.

A Multiple Shock Tube and Chemical Kinetic Modeling Study of Diethyl Ether Pyrolysis and Oxidation

The pyrolysis and oxidation of diethyl ether (DEE) has been studied at pressures from 1 to 4 atm and temperatures of 900-1900 K behind reflected shock waves. A variety of spectroscopic diagnostics have been used, including time-resolved infrared absorption at 3.39 mum and time-resolved ultraviolet emission at 431 nm and absorption at 306.7 nm. In addition, a single-pulse shock tube was used to measure reactant, intermediate, and product species profiles by GC samplings at different reaction times varying from 1.2 to 1.8 ms. A detailed chemical kinetic model comprising 751 reactions involving 148 species was assembled and tested against the experiments with generally good agreement. In the early stages of reaction the unimolecular decomposition and hydrogen atom abstraction of DEE and the decomposition of the ethoxy radical have the largest influence. In separate experiments at 1.9 atm and 1340 K, it is shown that DEE inhibits the reactivity of an equimolar mixture of hydrogen and oxygen (1% of each).

Shock-tube study of CH2O pyrolysis and oxidation

Pyrolysis and oxidation of formaldehyde were studied behind reflected shock waves in the temperature range 1,160-1,890 K at total pressures between 1.4 and 2.5 atm. Formaldehyde decay was followed by using time-resolved IR-laser absorption and IR-emission. The consumption of CH[sub 2]O was promoted by addition of O[sub 2] and the increase in CH[sub 2]O concentration also brought about a promotion of the CH[sub 2]O consumption in the oxidation reaction. A mechanism that can explain the profiles obtained under the experimental conditions was examined by simulation. The present and earlier shock tube data were satisfactorily modeled with a 34-reaction mechanism. The CH[sub 2]O decay rate was very sensitive to the rate constants of the reactions 6, 9, and 25, shown below. Reaction 9 played a very important role in the CH[sub 2]O oxidation under the experimental conditions. New values of the rate constants of these reactions were derived. Reaction 6= CH[sub 2]O + O[sub 2] [r arrow] CHO + HO[sub 2]; Reaction 9= CH[sub 2]O + HO[sub 2] [r arrow] CHO + H[sub 2]O[sub 2]; and Reaction 25= H + HO[sub 2] [r arrow] H[sub 2] + O[sub 2].

Shock-tube and modeling study of ethane pyrolysis and oxidation

Abstract Pyrolysis and oxidation of ethane were studied behind reflected shock waves in the temperature range 950–1900 K at pressures of 1.2–4.0 atm. Ethane decay rates in both pyrolysis and oxidation were measured using time-resolved infrared (IR) laser absorption at 3.39 μm, and CO2 production rates in oxidation were measured by time-resolved thermal IR emission at 4.24 μm. The product yields were also determined using a single-pulse method. The pyrolysis and oxidation of ethane were modeled using a reaction mechanism with 157 reaction steps and 48 species including the most recent submechanisms for formaldehyde, ketene, methane, acetylene, and ethylene oxidation. The present and previously reported shock tube data were reproduced using this mechanism. The rate constants of the reactions C2H6 → CH3 + CH3, C2H5 + H → C2H4 + H2 and C2H5 + O2 → C2H4 + HO2 were evaluated. These reactions were important in predicting the previously reported and the present data, which were for mixture compositions ranging from ethane-rich (including ethane pyrolysis) to ethane-lean. The evaluated rate constants of the reactions C2H5 + H → C2H4 + H2 and C2H5 + O2 → C2H4 + HO2 were found to be significantly different from currently accepted values.

Shock tube and modeling study of 1,3‐butadiene pyrolysis

1,3-Butadiene (1,3-C4H6) was heated behind reflected shock waves over the temperature range of 1200–1700 K and the total density range of 1.3 × 10−5 −2.9 × 10−5 mol/cm3. Reaction products were analyzed by gas-chromatography. The concentration change of 1,3-butadiene was followed by UV kinetic absorption spectroscopy at 230 nm and by quadrupole mass spectrometry. The major products were C2H2, C2H4, C4H4, and CH4. The yield of CH4 for a 0.5% 1,3-C4H6 in Ar mixture was more than 10% of the initial 1.3-C4H6 concentration above 1500 K. In order to interpret the formation of CH4 successfully, it was necessary to include the isomerization of 1,3-C4H6 to 1,2-butadiene (1,2-C4H6) and to include subsequent decomposition of the 1,2-C4H6 to C3H3 and CH3. The present data and other shock tube data reported over a wide pressure range were qualitatively modeled with a 89 reaction mechanism, which included the isomerizations of 1,3-C4H6 to 1,2-C4H6 and 2-butyne (2-C4H6).

High-temperature pyrolysis of dimethyl ether in shock waves

Abstract The high-temperature pyrolysis of dimethyl ether (DME) was studied behind reflected shock waves using single-pulse (reaction time between 1.3 and 2.9 ms), time-resolved IR absorption (3.39 μm), IR emission (4.24 μm), and UV absorption (216 nm) methods. The studies were done using DME-Ar, DME-H 2 -Ar, DME-CO-Ar, and DME-CH 2 O-Ar mixtures in the temperature range 900–1900 K at pressures in the range 0.83–2.9 atm. From a computer simulation, a 94-reaction mechanism that could explain all our data was constructed. The rate constant expressions of the following five reactions at high temperatures are discussed in detail: CH 3 OCH 3 + M → CH 3 O + CH 3 + M, H + CH 3 OCH 3 → CH 3 OCH 2 + H 2 , CH 3 + CH 3 OCH 3 → CH 3 OCH 2 + CH 4 , CH 3 O + CO → CH 3 + CO 2 , CH 2 O + CH 3 → CHO + CH 4 . We found that in the pyrolysis of DME there is an extremely low tendency to form higher hydrocarbons at high temperatures.

Shock tube and modeling study of ketene oxidation

Ketene (CH{sub 2}CO) and ketyl radicals (CHCO) are produced in acetylene combustion. Ketene oxidation was studied behind reflected shock waves in the temperature range 1,050--2,050 K at total pressures between 1.1 and 3.0 atm using ketene-O{sub 2} and ketene-N{sub 2}O mixtures diluted with Ar. Ketene decay and carbon dioxide production were followed using time-resolved UV-absorption at 200 nm and time-resolved IR-emission at 4.24 {micro}m, respectively. Production yields for reaction times between 1.7 and 2.1 ms were also studied using a single-pulse method. From a computer-simulation study with a 85-reaction mechanism, rate-constant expressions that could explain all the data were derived.