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