Help with combustion simulation in rocket nozzle
 

Hi folks,
Ive been trying to simulate combustion happening in a rocket nozzle. Im using the

• SST K-w model, with SDES.
• EDC kerosene air species transport
• density based solver
• pressure inlet and pressure outlet, for nozzle with domain, operating pressure set to zero, inlet being chamber pressure and outlet pressure boundary which is at end of the domain to atmospheric conditions

but ive not been able to get any solution to converge, initially I had errors due to ISAT convergence, which was resolved by relaxation. Now for some reason im getting divergence due to temperature going below 0 K and pressure below 0 Pa.

Can anyone tell me what the issue could be, mesh is not an issue since it is proper without any negative elements and has a parameter of 0.9 orthogonal quality and 1.2 aspect ratio, Ive skipped the boundary layer for now.