Problem of PDF about density

Wu

Hi, all. In my case, my fuel inlet supply the mixture of fuel and air, and air inlet supply pure air. Originally, I think that I give it a reference pressure and velocity, so the density and mass flux will be calculated. And then I start to analysis its diffusion flame. For a PDF model, 1...do my case suit to be applied by PDF model? 2...if ok, is it necessary that density as defining boundary regions is correctly specified? 3...ignition isn't been needed? Wu