When planar converging flow channels are used as nozzles for polymer based additive manufacturing machines, the extensional rate imposed by the polymer flow can be used for dispersive mixing of a suspended phase. We study such a nozzle whose spanwise width varies inversely as the streamwise coordinate along the flow direction. Application of lubrication approximation for the flow shows that the extensional rate is approximately constant along the centerline. We validate this prediction using experiments and show the effect of such a flow on suspended solid and immiscible fluid particles. The degree of deformation of the immiscible fluid particles, under the constant extensional rate, is closely related to the difference between the particle velocity and the background flow velocity at the same point. This result helps understand the apparent effect of the flow on a suspended phase when it is incorporated into conventional polymer based additive manufacturing.