| Description |
This paper aims at increasing the flow velocity in the flare stack by decreasing the flow diameter to solve the issue of low flow operation in the flares. A new air assisted flare design of 1m height and 15cm diameter has been tested using CFD simulation in this work. The design includes injecting air at different velocities (0.6m/s, 0.8m/s and 1m/s) from small pipes added near the tip of the flare to produce thrust to increase the stack cross velocity like in aircrafts during the takeoff. Moreover, to produce homogenous distribution of air from pipes and direct it toward the cross flow in the stack, a curved surface has been added to the design in front of pipes' exit to produce Coanda effect and to ensure a homogenous mixing with cross flow in the stack. Furthermore, a cone has been added to the design above the small pipes to ensure the flow will be directed to the tip of the flare. In this work, C3D CFD code based on LES has been used to study the effect of Coanda principle using cold flow approach in three different cases. In this simulation, the total number of hexahedral cells were 1222100 (110*110*101), with aspect ratio and growth ratio of 1. Three cases have been applied in this work, injecting air through the slots at three different velocities in each case; 0.6m/s, 0.8m/s and 1m/s while keeping the injection velocity of the air through the stack constant at each case at 0.78m/s. Ten vertical locations at the centre of the stack have been chosen to measure the cross flow velocity in the stack. The results showed that as the pipes' flow velocity increase, the cross velocity increases due to decreasing flow diameter. Highest velocity of the cross flow measured equal to 1.83m/s, during 1m/s injection from each slot above the tip at 1.05m. finally, at the same location, cross flow velocity measured to be 1.25m/s in case of 0.6m/s injection from each slot, and 1.51m/s in case of 0.8m/s injection from each slot. |
