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