当前医院对生产环境的业务可用性要求越来越高,随着医院的业务量越来越大,医院电子病历使用的Oracle数据库的数据量也越来越大,基于Oracle Data Guard和Oracle Flashback的恢复技术,可以在Oracle数据库的部分表数据被误删除后,快速将表...当前医院对生产环境的业务可用性要求越来越高,随着医院的业务量越来越大,医院电子病历使用的Oracle数据库的数据量也越来越大,基于Oracle Data Guard和Oracle Flashback的恢复技术,可以在Oracle数据库的部分表数据被误删除后,快速将表数据恢复到数据被删除前的任意一个时间点。展开更多
In this study,the measurement object is a flame propagating in a premixed burner with swirling flow in order to investigate unsteady flame behavior in a gas turbine premixer.During flashback,the flame propagating upst...In this study,the measurement object is a flame propagating in a premixed burner with swirling flow in order to investigate unsteady flame behavior in a gas turbine premixer.During flashback,the flame propagating upstream was visualized with a high-speed camera.Moreover,we established the technique to measure the instantaneous flow fields of unburned fuel-air mixture in a swirling premixed burner using particle image velocimetry(PIV).As a result,the characteristics of flame behavior propagating upstream were examined.And it was found that a low velocity region existed in the vicinity of the flame tip.The relationship between low velocity region and flame behavior was discussed in detail.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
文摘当前医院对生产环境的业务可用性要求越来越高,随着医院的业务量越来越大,医院电子病历使用的Oracle数据库的数据量也越来越大,基于Oracle Data Guard和Oracle Flashback的恢复技术,可以在Oracle数据库的部分表数据被误删除后,快速将表数据恢复到数据被删除前的任意一个时间点。
文摘In this study,the measurement object is a flame propagating in a premixed burner with swirling flow in order to investigate unsteady flame behavior in a gas turbine premixer.During flashback,the flame propagating upstream was visualized with a high-speed camera.Moreover,we established the technique to measure the instantaneous flow fields of unburned fuel-air mixture in a swirling premixed burner using particle image velocimetry(PIV).As a result,the characteristics of flame behavior propagating upstream were examined.And it was found that a low velocity region existed in the vicinity of the flame tip.The relationship between low velocity region and flame behavior was discussed in detail.
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.
