Research On Performance Of Flame Ignition And Extinction Of Can Annular Combustor

Gas turbine is often working at the condition of rich fuel in ignition process and there islots of smoke at the combustor exit. To solve this problem, it is hoped that the ignition can besuccessfully achieved at lean condition. But the combustor lean ignition limit is extremelynarrow, so people try all their best to improve the ignition limit. The ignition location,ignition energy, ignition continuance, and flame core diameter play a very importantinfluence on ignition characteristic. So, the investigation on ignition property and itsinfluence take a very important role in combustor design and alteration.In practice, gas turbine will always deviate from the design point. While working at thelow operation condition, combustor is easy to be extinction. It is hoped that combustor LeanBlowout Limits (LBO) could be predicted exactly and improved greatly. If the combustorLBO or extinction portent could be predicted both in terms of experiment and theoreticaltreatment, on one hand, the corresponding operation may be carried out to avoid extinction,on the other hand, the combustor LBO could be improved by combustor structureoptimization and to provide a guideline for combustor design.The paper investigated a can annular gas turbine combustor, established the combustionconservation equations, and researched combustor ignition and extinction characteristic bynumerical simulation. And the conclustions provide a theoretical guideline for combustordesign. The main contents are as follows:(1) The numerical simulation on the antetype combustor working with oil fuel wascarried out at the combustor design condition. According to this numerical result, combustorgeometry model was simplified.(2) The numerical research on combustor ignition performance has been carried out inthe present work, including ignition location, ignition energy, ignition power, ignitioncontinuance and flame core diameter. The paper also analyzed the reason for unsuccessfulignition and the influence of air temperature, oil temperature and oil velocity on ingnitionproperty. The resuls show that, the optimal ignition location, the minimum ignition energy,the shortest ignition continuance, and the smallest flame core diameter can be found bynumerical simulation. The research can provide a guideline for igniter design and its layout. (3) The paper researched ignition process and flame propagation characteristic, analyzedthe influence of crossfirer location on propagation time and the role of crossfirer in ignitionphase. The numerical results show that, there will be an optimal crossfirer location which canminimize the flame propagation time. The whole ignition time and the turbulent flamepropagation velocity are abtained. The present work found that the second recirculation zonetakes a very important role in ignition process, oil evaporation delays the ignition process,and crossfirers can effectively improve the combustor stability.(4) The paper investigated the combustion flow field at different species, and analyzedthe characteristic of flame frontier and flame root. Extinction portent was gained bynumerical simulation. The conclution of the results provide a guideline for combustor controlto avoid extinction. According to extinction portent property, an extinction criterion named"Characteristic Point Method"(CPM) has been put forward in the end of the paper. Thismethod was used to predict one type of dual-swirls combustor, and the numerical results arein good agreement with the experiment data. The conclusion confirmed the precision of thismethod. The paper also analyzed the influence of air temperature, oil temperature, oil velocity,and oil droplet average-diameters on combustor LBO.Innovations of this dissertation are as follows:(1) A systematic study has been carried out on combustor ignition performance,including igniter location, energy, power, and continuance.The present work abtained theinfluence of igniter property on ignition characteristic. The conclusion would provide apractical guideline for igniter design and layout.(2) The numerical simulation on can-annular combustor ignition process has beencarried out in the paper. The flme propagation characteristic of can-annular combustor hasbeen summarized. The present work provides a guideline for combustor and crossfirer design.(3) A new extinction criterion named "Characteristic Point Method" has been putforward in the present work. And it has been used to investigate the influence of operationparameters on combustor Lean Blowout Limits. The criterion improves the prediction ofcombustor Lean Blowout Limits and it also provides an estimate for extinction portent.