Annealing of carbon nanotubes (CNTs) by the hydrogen flame in air was investigated in this study. Raman spectroscopy and scanning electron microscopy were used to characterize the products. The peak width of Raman spe...Annealing of carbon nanotubes (CNTs) by the hydrogen flame in air was investigated in this study. Raman spectroscopy and scanning electron microscopy were used to characterize the products. The peak width of Raman spectra decreased with the increase in the annealing time. The CNTs were not stable in the hydrogen flame and the etching rate of the CNTs by hydrogen flame was very high. The hydrogen flame annealing had some effects on improving the crystallinity of CNTs.展开更多
Swirl-premixed combustion systems exhibit potential to meet future regulations on pollution emissions. However, combustion induced vortex breakdown(CIVB) flashback is frequently observed in these systems, especially f...Swirl-premixed combustion systems exhibit potential to meet future regulations on pollution emissions. However, combustion induced vortex breakdown(CIVB) flashback is frequently observed in these systems, especially for high hydrogen content fuel. In this study, a swirl-premixed burner with diverging centerbody was used to investigate CIVB flashback based on azimuthal vorticity at mixing zone exit. Through 2D axisymmetric model, it was found that there was a maximal azimuthal vorticity at mixing zone exit for each equivalence ratio. The physical meaning of these maximal azimuthal vorticity values was the minimally required azimuthal vorticity to trigger CIVB flashback. At the same time, the required azimuthal vorticity declined with the increase of equivalence ratio since turbulent burning velocity started to control flashback. Nevertheless, azimuthal vorticity offered by heat release increased with the increase of equivalence ratio, which promoted flame propagating upstream continually.展开更多
A modal interferometer is experimentally demonstrated based on tapering a single-mode-multimode-single- mode （SMS） fiber structure heated by hydrogen flame. The interference fringe begins to form when tapering lengt...A modal interferometer is experimentally demonstrated based on tapering a single-mode-multimode-single- mode （SMS） fiber structure heated by hydrogen flame. The interference fringe begins to form when tapering length is 19.8 mm, and becomes regular and clear when the tapering length is longer and the tapered waist diameter is smaller. Annealing process is undertaken to achieve a high extension ratio of approximately 17 dB with free spectral range of 1.5 nm when the tapering length is 33 mm and the tapered waist diameter is approximately 5 μm. The temperature and axial strain dependences of the tapered SMS structure are characterized, and the measured temperature and strain coefficients are ＋7 pm/℃ and -9.536 pm/με, respectively.展开更多
文摘Annealing of carbon nanotubes (CNTs) by the hydrogen flame in air was investigated in this study. Raman spectroscopy and scanning electron microscopy were used to characterize the products. The peak width of Raman spectra decreased with the increase in the annealing time. The CNTs were not stable in the hydrogen flame and the etching rate of the CNTs by hydrogen flame was very high. The hydrogen flame annealing had some effects on improving the crystallinity of CNTs.
基金supported by the National Natural Science Foundation of China(Grant Nos.51306180 and 51406203)
文摘Swirl-premixed combustion systems exhibit potential to meet future regulations on pollution emissions. However, combustion induced vortex breakdown(CIVB) flashback is frequently observed in these systems, especially for high hydrogen content fuel. In this study, a swirl-premixed burner with diverging centerbody was used to investigate CIVB flashback based on azimuthal vorticity at mixing zone exit. Through 2D axisymmetric model, it was found that there was a maximal azimuthal vorticity at mixing zone exit for each equivalence ratio. The physical meaning of these maximal azimuthal vorticity values was the minimally required azimuthal vorticity to trigger CIVB flashback. At the same time, the required azimuthal vorticity declined with the increase of equivalence ratio since turbulent burning velocity started to control flashback. Nevertheless, azimuthal vorticity offered by heat release increased with the increase of equivalence ratio, which promoted flame propagating upstream continually.
基金supported in part by the National "973" Program of China(No.2011CB301700)the National Natural Science Foundation of China(Nos.61007052, 61071011,61107041,61127016)+3 种基金the International Cooperation Project from the Ministry of Science and Technology of China(No.2011FDA11780)the STCSM Project(Nos.09JC1408100,10DJ1400402)the "SMC Young Star" Scientist Program of Shanghai Jiao Tong Universitythe National Key Lab Projects(No. GKZD030021)
文摘A modal interferometer is experimentally demonstrated based on tapering a single-mode-multimode-single- mode （SMS） fiber structure heated by hydrogen flame. The interference fringe begins to form when tapering length is 19.8 mm, and becomes regular and clear when the tapering length is longer and the tapered waist diameter is smaller. Annealing process is undertaken to achieve a high extension ratio of approximately 17 dB with free spectral range of 1.5 nm when the tapering length is 33 mm and the tapered waist diameter is approximately 5 μm. The temperature and axial strain dependences of the tapered SMS structure are characterized, and the measured temperature and strain coefficients are ＋7 pm/℃ and -9.536 pm/με, respectively.
