Numerical Research On Combustion Stability And NO_x Reduction Of Gas Turbine Firing Syngas

With the development of our country's economy,environmental pollution problem has drawn more and more people's attention.Integrated gasification combined cycle?IGCC?is regarded as the most potential clean power generation technology.However,NO_x produced from combustion process of syngas will pollute environment.Adding diluents will lower maximum temperature in combustion process and effectively reduce NO_x emission.But adding diluents also influences combustion process of syngas,such as ignition delay time,laminar flame speed,etc.So this thesis researches influences of adding H₂O,CO₂ and N₂ on ignition delay time,laminar flame speed and NO_x reduction.Firstly,this thesis analyzes effects of three diluents above on ignition delay of syngas.In high temperature region,adding H₂O and CO₂ can significantly increase ignition delay of syngas,because as third body,they have higher collision efficiency in reaction H + O₂?+ M?= HO₂?+ M?.While in low temperature range,adding H₂O can promote reactivity of syngas,especially in high pressure conditions.In the research region of this thesis,adding N₂ mainly affects temperature rising process,thus influencing ignition delay time.At lean premixed condition,increasing equivalence ratio can increase reactivity of syngas,because less air needs to be heated.Secondly,this thesis analyzes effects of three diluents above on laminar flame speed of syngas.Under conditions of this thesis,flame speed of syngas varies parabolically with equivalence ratio.On one hand,adding diluents will influence temperature rise;on the other hand,it will change reaction rate of some important elementary reactions.Comparing three diluents chosen in this thesis,adding CO₂ shows the most significant ability to decrease flame speed because of its highest specific heat,followed by H₂O and CO₂,which indicates that flame speed is mainly influenced by temperature rise in combustion progress.Finally,this thesis researches influences of adding diluents above on NO_x reduction of syngas under premixed and diffusive conditions.Under premixed condition,each parameters are distributed symmetrically while under diffusive condition,they no longer follow the law.For syngas and research conditions in this thesis,NNH mechanism is the dominant way to generate NO_x.For premixed flame,adding H₂O shows lowest NO_x emission,while adding CO₂ produces more O radical,which helps NNH and NH translate into NO_x.However,for diffusion flame,adding H₂O and CO₂ have equal effects and this is the contribution of both O radical and temperature rise in combustion process.