a filter pack disposed in {TAIL ~ the combustion chamber} along {HEAD ~ an inner diameter} of the outer wall 
a filter pack disposed in { TAIL ~ the combustion chamber } along { HEAD ~ an inner diameter } of the outer wall
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH