Thrust value, positive or negative?

Emmanuel

I am using Force-->Report-->wall, to obtain the induced thrust on an ejector in a jet and ejector combination. I know the experimental result of the induced thrust to be about 50N, and the jet thrust is about 180N. I do not know the experimental values of the jet total pressure.

My question is when I use different pressures at the jet, I obtain different values of induced thrust, but some cases gives me positive thrust values, while others gives me negative thrust values, which is correct?