Hey everyone, I'm pretty new to Star-CD and am having some problems with a model that I have been trying to get running for quite a while now.

Basically what I am trying to do it to inject some fuel into a constant volume chamber. This is the starting point and then I will introduce a porous medium but this basic setup isn't working. I have run some models using es-ice in which I have sprayed fuel into the moving cylinder and they worked fine but now I am just trying to simulate fuel spray at one set crank angle (i.e. just a fixed volume) but I get an error that says: "Error 076: Negative densities at more than 100 cells" after only a few iterations. The fuels starts injecting before the error and everything seems to be as expected at these iterations.

If anyone know what the problem might be, I would really appreciate it.

Thanks

I have got the same error"Error 076: Negative densities at more than 100 cells" when I simulate the diesel engine,and the soft Engineers sometimes have not idea to deal with it except for asking for "reduce the time step,or uder-relaxation factor,etc".But this is no useful.

try to locate your injector a little deeper into the domain (not on the surface of the domain)

Hi,

Thanks for the tip. I have located the injector 1.5mm radially the edge and 1.3mm in the z-direction. The other thing is that it gets the negative densities much before the fuel injection starts. Any other ideas?

You can try checking your reference pressure or relax very heavily on temperature and density or if you have a pressure outlet make sure that the pressure on it is realistic.

allam

you should change your time step and then your problem will be solved