Numerical Study On Swirl Lean Fuel Injection TVC

As a novel trapped vortex combustor(TVC), swirl lean fuel injection TVC combines part characteristics of LDI and RQL. The purpose of this thesis is to reveal the combustion flow phenomena and its evolution under the interaction of swirl, recirculation and combustion, have better understanding of the combustion turbulence flow mechanism and seek the structural optimization matching law of high efficiency combustor performance and low NOx emission. This thesis studies three-dimensional non-reacting and reacting flow with non-swirl and swirl respectively by numerical simulation method. The results suggest both major structural parameters and pneumatic parameters affect combustor performance and NOx emission in different degrees. Overall total pressure loss is influenced limited, single swirl mode achieves good emission performance under different pneumatic conditions. Swirl and combustion affect turbulence flow field characteristics significantly. Main conclusions include:(1) Non-all-confined guide vane is better(La/Bc=0.47). Swirl aisle structure mainly affects combustion efficiency(Zs/Lc=0.47,BR=0.6), swirl exit premixed structure is better. In single swirl mode Ri/Ro mainly affects combustion efficiency(Ri/Ro=0.888,LR=14.98), increasing Ri/Ro makes emission increase only when Ro is moderate. In dual swirl mode increasing Ri/Ro improves combustion efficiency and emission performance(Ri/Ro=0.72,LR=14.98). There exists a reasonable matching(Ds/W=0.5) which makes emission performance best. Co-swirl structure achieves better comprehensive performance due to counter-swirl’s downstream high temperature gradient though counter-swirl has better combustion efficiency. Generally single swirl mode has more advantage in low NOx emission.(2) Non-reacting flow: swirl mainly affects recirculation intensity, interaction between swirls mainly affects recirculation form. Swirl expands scope of intense turbulent pulsation region and weakens dual vortex greatly. Moderate velocity and swirler are better to maintain dual vortex. Reacting flow: swirl mainly affects recirculation intensity and blunt-body-effect recirculation. Single swirl increases cavity turbulent pulsation greatly, however, dual swirl makes it suppressed. Swirl mainly affects temperature distribution of swirl aisle downstream. Combustion changes cavity recirculation and swirl recirculation form apparently. It declines recirculation intensity and scale, strengthens swirl recirculation intensity but reduces its scale. Combustion reduces both cavity recirculation scale and intensity obviously, improves dual vortices structure, makes axial attenuation characteristics of airstream stronger than turbulent pulsation’s. Combustion strongly affects liner downstream field instead of swirl feature in cavity mixing flow.(3) Generally, lower jet equivalence ratio, jet velocity and jet temperature are conducive to improve combustor performance, as well as lower swirl temperature and larger swirl velocity. Enhancing swirl number(S) interferes dual vortices structure at strong swirl stage, while dual vortices are totally destroyed at super strong swirl stage. At strong swirl stage, increasing S mainly enhances combustion intensity of swirl recirculation and nearby. Combustion efficiency is influenced manifestly only at super strong swirl stage. There exists a value for S as an inflection point where NOx emission increases then declines, as predicted by the numerical simulation results, the inflection point S is about 0.8.