Do you have the "Irregular" Shape in a model??
If it's inside a tank you could split the tank, just add a configuration and a cut extrude, cut up towards the nozzle. From the tip of the nozzle project the spray pattern onto the shape and use a Split Line Curve, add a surface and then measure the area of that surface..
SDRC Ideas has a project-to-point capability (focused projection). I used it only very occasionally when I ran that program, but it was handy as all get out when I needed it. I don't think there is any way to do it in SolidWorks. It is not the same as parallel projection or the same as draft.