| Advanced vortex combustor (AVC) is presented as a new kind of concept on thebasis of trapped vortex combustor. With the characteristics of having a special way offlame stabilization, a high combustion efficiency and low pollutant emission, AVChas been paid attention to widely. But the research on AVC is still focused on the coldflow field, thus the flow property of turbulent combustion and the mechanism ofcavity’s flame stability is still unclear.In this thesis the numerical simulation of turbulent flow under the cold andcombustion condition have been carried out, and the characteristic of cavity’ flamestability is analyzed.To determine the mathematical relationship of bluff-body structural parameters,the influences of bluff-body structural parameters on the cold flow field of AVC hasbeen studied, and the results show that the vortex in cavity can be the most stable andthe pressure loss can be the least when structural parameter is H1/H2=0.7、S/H1=0.6.At the same time the mechanism of transverse injection is introduced to study themutual influence law between transverse injection and cavity. The result indicates thatthe transverse injection is very useful at enhancing the mixing efficiency of fuel andair, and the jet parameters can affect the formation and distribution of the vortex incavity.The characteristics of turbulent combustion under the premixed and non-premixedconditions are numerically simulated. And the study finds that premixed combustionwill be helpful for vortex stability in cavity and can also maintain the AVCperformance even in the lean combustion condition. The acceleration of mainstreamwill increase the temperature of cavity, and the increase of inlet temperature ofmainstream will raise the outlet temperature of AVC.Non-premixed combustion can also influence the cavity flow, with the jet angleincreases, the vortex flow field tends to be more stable and the cavity temperature getshigher. In addition, the formation of high temperature region relies on a certainvelocity ratio, but the inlet temperature of injection will not be an important effect forthe high temperature formation. In this thesis, two schemes have been put forward to enhance the turbulentcombustion flow of cavity. One scheme is central jet of cavity wall, and the other isstructure improvement of after bluff-body. The results show that both of the twoschemes can be efficient in heightening the cavity’s temperature and makingtemperature distribution more homogeneous in premixed combustor. At the same time,it will enhance the momentum of vortex in cavity to make the vortex structure steadier.The schemes about central jet of cavity wall will influence a lot on the cavity’stemperature and flow in non-premixed combustor, when the jet velocity increases, thetemperature will fall down, in addition, the vortex flow fields will be tend to besymmetrical, but it’s structure is not stable. The schemes about structure improvementof after bluff-body has less effects on the cavity’s temperature in non-premixed AVC,however, due to reducing the weight of combustor, this scheme has a certainadvantage in practical engineering technology applications... |
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