Combustion Characteristics And Field Synergy Analysis Of Advanced Vortex Combustor

To meet the performance requirements of high temperature rise and low-pollution for the modern gas turbine, the Ramgen company presented the concept of Advanced Vortex Combustor(AVC). Stable combustion is achieved by the use of low velocity recirculation zones in cavity to provide continuous source of ignition mixing hot products with the incoming fuel and air. AVC receives extensive attention both at home and abroad because its overall performance is better than the conventional swirl combustor significantly. And it is a very potential and promising new concept combustor. AVC has become one of the most important candidates for the future high temperature rise combustor of military aero engine. It is hence of great theoretical and practical significance to make an intensive study of AVC.The turbulent flow and combustion characteristics of AVC with a slot in the rear blunt body were numerically calculated in this thesis. An analysis of field synergy has been carried out to evaluate the flow and heat transfer characteristics of AVC comprehensively.The effect of different combustion conditions on combustion characteristics of AVC with a slot in the rear blunt body was numerically calculated. The results show that it can achieve stable combustion with different conditions. As incoming velocity increases, the total pressure loss increases, the combustion efficiency reduces, the temperature in cavity increases and the temperature distribution in cavity becomes more uniform. With the increase of incoming temperature, the total pressure loss firstly reduces then remains constant, the combustion efficiency increases. As wall temperature increases, the temperature in cavity increases and the temperature distribution in cavity becomes more uniform, the total pressure loss increases, the combustion efficiency reduces. As equivalent ratio increases, the total pressure loss firstly increases then reduces, the combustion efficiency reduces.To improve gas mixing ratio and to improve the combustion performance, the principle of Vortex Generator is adopted to AVC. The numerical simulation has been carried out to investigate the combustion and flow characteristics of AVC based on Vortex Generator by controlling anteversion angle(α), sloping angle(β), diameter of the injection hole(D) and the ratio of injection velocity to mainstream velocity(R). The results show that AVC based on Vortex Generator has better performance than traditional injection AVC. It can improve gas mixing ratio, increase cavity center turbulence, and transform more thermal energy into kinetic energy of the outlet when increasing α and β, while it increases the total pressure loss significantly. Cavity can achieve more uniform temperature distribution with increasing β. With increasing D and R, the overall temperature distribution of AVC is firstly increased and then decreased. Stable combustion with higher temperature, lower total pressure loss and lower pollution emission can be achieved under lean conditions when α=60°, β=60°.To form a desirable dual-vortex structure without any cavity air injection, placing two flow guide vanes at the leading edge of the front-body. To investigate the combustion and flow characteristics of AVC with flow guide vanes, the effect of different structural parameters on AVC were numerically studied. The results show that AVC with flow guide vanes has better performance than formal AVC. It can form a desirable dual-vortex structure even without any cavity air injection, which can enhance the stability of flame and the mixing of gas, improve combustion efficiency greatly, improve exit temperature distribution, and reduce pollutant emission. Structural parameters of flow guide vanes have certain significant effects on the combustor characteristics. Stable combustion with lower total pressure loss, lower pollution can be achieved when a/B=0.2, b/H=0.4, c/L=0.1~0.2(where a is defined as the length of vane inside the cavity, b is defined as the distance from vane to the upper surface of the front-body, c is the distance from vane to the rear surface of the front-body, B is the front-body height, H is height of the inlet, L is the cavity length) under lean conditions, and the combustor exit temperature distribution became more uniform.To investigate the flow and heat transfer characteristics of AVC, the velocity field, temperature field and the field synergy angle between velocity field and temperature field were numerically calculated. The results show that the smaller synergy angle areas are mainly located in the rear side of the rear blunt body, the cavity and the horizontal central section of the intake passage. Vortex area can enhance heat transfer. The field synergy performance is the best in the center section of AVC. The volume-average synergy angles between velocity field and temperature field are larger than the area-average synergy angles. With the increase of the incoming velocity and the incoming temperature, the average synergy angle reduces. As the thermostatic wall temperature increases, the average synergy angle increases. When equivalent ratio is less than 1.0, as the equivalent ratio increases, the average synergy angle increases. However, when equivalent ratio is larger than 1.0, the change of synergy angle is not obvious.An analysis of multi-field synergy on velocity field, temperature field and pressure field has been carried out to evaluate the flow and heat transfer characteristics of AVC comprehensively. The results show that as the increase of the incoming velocity, the synergy angle α between velocity and velocity gradient, the synergy angle β between velocity and temperature gradient, the synergy angle θ between velocity and pressure gradient decrease, the synergy angle γ between temperature gradient and velocity gradient, the synergy angle φ between pressure gradient and velocity gradient increase. With the increase of the incoming temperature, α and θ increase, while β, γ and φ decrease. With the increase of the thermostatic wall temperature, α and θ decrease, while β, γ and φ increase. For turbulent flow field of heat transfer enhancement in AVC, increasing the incoming velocity and incoming temperature, reducing thermostatic wall temperature can enhance flow and heat transfer; increasing the incoming velocity and thermostatic wall temperature, reducing incoming temperature can reduce the flow resistance; increasing the incoming velocity and thermostatic wall temperature, reducing incoming temperature can raise the overall performance of heat transfer enhanced.