Single Cavity Trapped Vortex Combustor Dynamics – Part-2: Simulations

• Main Authors: Atul Singhal, R. V. Ravikrishna
• Format: Article
• Language: English
• Published: SAGE Publishing 2011-03-01
• Series: International Journal of Spray and Combustion Dynamics
• Online Access: https://doi.org/10.1260/1756-8277.3.1.45

The first part described a versatile TVC test rig capable of a continuously variable length-to-depth ratio (L/D) of the cavity and optical access through quartz plates provided on three sides for visualization. Flame stabilization in the single cavity TVC was successfully achieved with methane as fuel and the range of flow conditions for stable operation were identified. From these, a few cases were selected for detailed experimentation, the results of which were presented in part-1. The results indicated that reducing L/D ratio and increasing cavity-air velocity favour stable combustion. In the present paper, numerical simulations are performed to ascertain reasons for some of the trends. The predicted temperatures at the exit showed reasonably good agreement with measured values. The experiments are also performed for different flow conditions to ascertain stability limits of the combustor. Insight from these set of experiments along with simulations has highlighted the importance of air and fuel injection strategies in the cavity. It was observed in the experiments that for certain cases involving moderate cavity-air velocity, the flame tend to blowout whereas at higher and lower cavity-air velocities, the flame was observed to be stable. This observation could be explained based on understanding obtained from simulations. From a mixing and combustion efficiency standpoint, it is desirable to have a cavity vortex that is anti-clockwise. However, natural tendency for flow over a cavity is to form a vortex that is clockwise. The tendency to blowout at higher inlet flow velocities is thought to be because of these two opposing effects. This basic understating of cavity flow dynamics can be used for further design improvements in future to improve flame stability at higher inlet flow velocities.