The intake opening, the propulsion device, and the conduit define a flow path for the flow of air and particulates and in one embodiment, the flow path has {HEAD ~ an approximately constant flow area} from {TAIL ~ the intake opening} to the propulsion device 
The intake opening , the propulsion device , and the conduit define a flow path for the flow of air and particulates and in one embodiment , the flow path has { HEAD ~ an approximately constant flow area } from { TAIL ~ the intake opening } to the propulsion device
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH