In order to clarify the chemical suppression mechanisms of CF3H, experimental and theoretical studies were conducted respectively in this paper. Firstly, the combustion species in low pressure laminar premixed flat me...In order to clarify the chemical suppression mechanisms of CF3H, experimental and theoretical studies were conducted respectively in this paper. Firstly, the combustion species in low pressure laminar premixed flat methane flames with CF3H addition is measured by synchrotron radiation molecular beam mass spectrometry （SR-MBMS） experimentally. Fire suppression chemistry of CF3H is investigated by selective detection of combustion radicals and intermediates in experimental process. Secondly, quantum chemistry calculations are performed to calculate the potential energy surfaces （PES） for the CF3H unimolecular dissociation reaction and reactions of CF3H with free radical OH and H at the B3LYP/6-311-F ＋G＊＊ and QCISD（T）/6-311＋＋G＊＊ levels. Finally, the chemical suppression mechanism of CF3H was discussed by comparing the theoretical calculation with experimental measurement.展开更多
The normal pressure decomposition of CF 2Cl 2 and CF 2ClBr in air by non equilibrium plasma was studied. The pressure of CF 2Cl 2 and CF 2ClBr was 2.67×10 3Pa, added the dry air to 1.01×10 5 Pa, dis...The normal pressure decomposition of CF 2Cl 2 and CF 2ClBr in air by non equilibrium plasma was studied. The pressure of CF 2Cl 2 and CF 2ClBr was 2.67×10 3Pa, added the dry air to 1.01×10 5 Pa, discharged by corona or DBD, 11.5% of CF 2ClBr was decomposed by corona after 120s discharge, more than 85% of CF 2Cl 2 and 95% of CF 2ClBr were decomposed by DBD after 10s discharge respectively. The main products were CF 2O, Cl 2 and Br 2.展开更多
1,1,2,2,3,3,4-Heptafluorocyclopentane(F7A)has considerable potential to be a new halon replacement due to its environmental friendliness and low-toxicity.However,the reaction processes of F7A with hydroxyl and hydroge...1,1,2,2,3,3,4-Heptafluorocyclopentane(F7A)has considerable potential to be a new halon replacement due to its environmental friendliness and low-toxicity.However,the reaction processes of F7A with hydroxyl and hydrogen free radicals,which are of great importance for investigating its fire suppression mechanisms,are still unclear.In this paper,ab inito and density functional theory are used to deduce the possible reaction pathways for the reactions of F7A with hydroxyl and hydrogen free radicals at the CCSD/cc-pVDZ//B3LYP/6-311++G(d,p)level of theory.Two distinct reaction pathways including ten elementary reaction channels for F7A with hydroxyl free radical,and five distinct reaction pathways including twenty elementary reaction channels for F7A with hydrogen free radical are investigated.The geometries,vibrational frequencies and reaction energy barriers are also determined.Based on the calculated results,the possible reaction mechanisms are proposed and discussed.The most feasible reaction channel for F7A with hydroxyl free radical is that leads to CH(OH)CH_(2)(CF_(2))_(3)+•F,and the most feasible reaction channel for F7A with hydrogen free radical is that leads to(CF_(2))_(3)CH_(2)CH•+HF.The study is helpful to further study its fire suppression mechanisms and promote it to be a new generation of halon replacement.展开更多
基金Project supported by the National Natural Science Foundation of China （No. 50706018） and Tianjin Research Program of Application Foundation and Advanced Technology （No. 08JCYBJC10700）.
文摘In order to clarify the chemical suppression mechanisms of CF3H, experimental and theoretical studies were conducted respectively in this paper. Firstly, the combustion species in low pressure laminar premixed flat methane flames with CF3H addition is measured by synchrotron radiation molecular beam mass spectrometry （SR-MBMS） experimentally. Fire suppression chemistry of CF3H is investigated by selective detection of combustion radicals and intermediates in experimental process. Secondly, quantum chemistry calculations are performed to calculate the potential energy surfaces （PES） for the CF3H unimolecular dissociation reaction and reactions of CF3H with free radical OH and H at the B3LYP/6-311-F ＋G＊＊ and QCISD（T）/6-311＋＋G＊＊ levels. Finally, the chemical suppression mechanism of CF3H was discussed by comparing the theoretical calculation with experimental measurement.
文摘The normal pressure decomposition of CF 2Cl 2 and CF 2ClBr in air by non equilibrium plasma was studied. The pressure of CF 2Cl 2 and CF 2ClBr was 2.67×10 3Pa, added the dry air to 1.01×10 5 Pa, discharged by corona or DBD, 11.5% of CF 2ClBr was decomposed by corona after 120s discharge, more than 85% of CF 2Cl 2 and 95% of CF 2ClBr were decomposed by DBD after 10s discharge respectively. The main products were CF 2O, Cl 2 and Br 2.
基金This work was supported by the National Natural Science Foundation of China(Grant no.51176078).
文摘1,1,2,2,3,3,4-Heptafluorocyclopentane(F7A)has considerable potential to be a new halon replacement due to its environmental friendliness and low-toxicity.However,the reaction processes of F7A with hydroxyl and hydrogen free radicals,which are of great importance for investigating its fire suppression mechanisms,are still unclear.In this paper,ab inito and density functional theory are used to deduce the possible reaction pathways for the reactions of F7A with hydroxyl and hydrogen free radicals at the CCSD/cc-pVDZ//B3LYP/6-311++G(d,p)level of theory.Two distinct reaction pathways including ten elementary reaction channels for F7A with hydroxyl free radical,and five distinct reaction pathways including twenty elementary reaction channels for F7A with hydrogen free radical are investigated.The geometries,vibrational frequencies and reaction energy barriers are also determined.Based on the calculated results,the possible reaction mechanisms are proposed and discussed.The most feasible reaction channel for F7A with hydroxyl free radical is that leads to CH(OH)CH_(2)(CF_(2))_(3)+•F,and the most feasible reaction channel for F7A with hydrogen free radical is that leads to(CF_(2))_(3)CH_(2)CH•+HF.The study is helpful to further study its fire suppression mechanisms and promote it to be a new generation of halon replacement.
